CONTACT US

Category: Mechanical Testing

 

High Temperature Scratch Hardness using a Tribometer

HIGH TEMPERATURE SCRATCH HARDNESS

USING A TRIBOMETER

Prepared by

DUANJIE, PhD

INTRODUCTION

Hardness measures the resistance of materials to permanent or plastic deformation. Originally developed by a German mineralogist Friedrich Mohs in 1820, scratch hardness test determines the hardness of a material to scratches and abrasion due to friction from a sharp object1. The Mohs’ scale is a comparative index rather than a linear scale, therefore a more accurate and qualitative scratch hardness measurement was developed as described in ASTM standard G171-032. It measures the average width of the scratch created by a diamond stylus and calculates the scratch hardness number (HSP).

IMPORTANCE OF SCRATCH HARDNESS MEASUREMENT AT HIGH TEMPERATURES

Materials are selected based on the service requirements. For applications involving significant temperature changes and thermal gradients, it is critical to investigate the mechanical properties of materials at high temperatures to be fully aware of the mechanical limits. Materials, especially polymers, usually soften at high temperatures. A lot of mechanical failures are caused by creep deformation and thermal fatigue taking place only at elevated temperatures. Therefore, a reliable technique for measuring hardness at high temperatures is in need to ensure proper selection of the materials for high temperature applications.

MEASUREMENT OBJECTIVE

In this study, the NANOVEA T50 Tribometer measures scratch hardness of a Teflon sample at different temperatures from room temperature to 300ºC. The capability of performing high temperature scratch hardness measurement makes the NANOVEA Tribometer a versatile system for tribological and mechanical evaluations of materials for high temperature applications.

NANOVEA

T50

TEST CONDITIONS

The NANOVEA T50 Free Weight Standard Tribometer was used to perform the scratch hardness tests on a Teflon sample at temperatures ranging from room temperature (RT) to 300°C. Teflon has a melting point of 326.8°C. A conical diamond stylus of apex angle 120° with tip radius of 200 µm was used. The Teflon sample was fixed on the rotative sample stage with a distance of 10 mm to the stage center. The sample was heated up by an oven and tested at temperatures of RT, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C.

TEST PARAMETERS

of the high temperature scratch hardness measurement

NORMAL FORCE 2 N
SLIDING SPEED 1 mm/s
SLIDING DISTANCE 8mm per temp
ATMOSPHERE Air
TEMPERATURE RT, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C.

RESULTS & DISCUSSION

The scratch track profiles of the Teflon sample at different temperatures are shown in FIGURE 1 in order to compare the scratch hardness at different elevated temperatures. The material pile-up on the scratch track edges forms as the stylus travels at a constant load of 2 N and ploughs into the Teflon sample, pushing and deforming the material in the scratch track to the side.

The scratch tracks were examined under the optical microscope as shown in FIGURE 2. The measured scratch track widths and calculated scratch hardness numbers (HSP) are summarized and compared in FIGURE 3. The scratch track width measured by the microscope is in agreement with that measured using the NANOVEA Profiler – the Teflon sample exhibits a wider scratch width at higher temperatures. Its scratch track width increases from 281 to 539 µm as the temperature elevates from RT to 300oC, resulting in decreased HSP from 65 to 18 MPa.

The scratch hardness at elevated temperatures can be measured with high precision and repeatability using the NANOVEA T50 Tribometer. It provides an alternative solution from other hardness measurements and makes NANOVEA Tribometers a more complete system for comprehensive high-temperature tribo-mechanical evaluations.

FIGURE 1: Scratch track profiles after the scratch hardness tests at different temperatures.

FIGURE 2: Scratch tracks under the microscope after the measurements at different temperatures.

FIGURE 3: Evolution of the scratch track width and scratch hardness vs. the temperature.

CONCLUSION

In this study, we showcase how the NANOVEA Tribometer measures the scratch hardness at elevated temperatures in compliance to ASTM G171-03. The scratch hardness test at a constant load provides an alternative simple solution for comparing the hardness of materials using the tribometer. The capacity of performing scratch hardness measurements at elevated temperatures makes the NANOVEA Tribometer an ideal tool for evaluating the high temperature tribo-mechanical properties of materials.

The NANOVEA Tribometer also offers precise and repeatable wear and friction testing using ISO and ASTM compliant rotative and linear modes, with optional high temperature wear, lubrication and tribo-corrosion modules available in one pre-integrated system. Optional 3D non-contact profiler is available for high resolution 3D imaging of wear tracks in addition to other surface measurements such as roughness.

1 Wredenberg, Fredrik; PL Larsson (2009). “Scratch testing of metals and polymers: Experiments and numerics”. Wear 266 (1–2): 76
2 ASTM G171-03 (2009), “Standard Test Method for Scratch Hardness of Materials Using a Diamond Stylus”

NOW, LET'S TALK ABOUT YOUR APPLICATION

Weld Surface Inspection Using a Portable 3D Profilometer

WELd surface inspection

using a portable 3d profilometer

Prepared by

CRAIG LEISING

INTRODUCTION

It may become critical for a particular weld, typically done by visual inspection, to be investigated with an extreme level of precision. Specific areas of interest for precise analysis include surface cracks, porosity and unfilled craters, regardless of subsequent inspection procedures. Weld characteristics such as dimension/shape, volume, roughness, size etc. can all be measured for critical evaluation.

IMPORTANCE OF 3D NON-CONTACT PROFILOMETER FOR WELD SURFACE INSPECTION

Unlike other techniques such as touch probes or interferometry, the NANOVEA 3D Non-Contact Profilometer, using axial chromatism, can measure nearly any surface, sample sizes can vary widely due to open staging and there is no sample preparation needed. Nano through macro range is obtained during surface profile measurement with zero influence from sample reflectivity or absorption, has advanced ability to measure high surface angles and there is no software manipulation of results. Easily measure any material: transparent, opaque, specular, diffusive, polished, rough etc. The 2D and 2D capabilities of the NANOVEA Portable Profilometers make them ideal instruments for full complete weld surface inspection both in the lab and in the field.

MEASUREMENT OBJECTIVE

In this application, the NANOVEA JR25 Portable Profiler is used to measure the surface roughness, shape and volume of a weld, as well as the surrounding area. This information can provide critical information to properly investigate the quality of the weld and weld process.

NANOVEA

JR25

TEST RESULTS

The image below shows the full 3D view of the weld and the surrounding area along with the surface parameters of the weld only. The 2D cross section profile is shown below.

the sample

With the above 2D cross section profile removed from the 3D, dimensional information of the weld is calculated below. Surface area and volume of material calculated for the weld only below.

 HOLEPEAK
SURFACE1.01 mm214.0 mm2
VOLUME8.799e-5 mm323.27 mm3
MAX DEPTH/HEIGHT0.0276 mm0.6195 mm
MEAN DEPTH/HEIGHT 0.004024 mm 0.2298 mm

CONCLUSION

In this application, we have shown how the NANOVEA 3D Non-Contact Profiler can precisely characterize critical characteristics of a weld and the surrounding surface area. From the roughness, dimensions and volume, a quantitative method for quality and repeatability can be determined and or further investigated. Sample welds, such as the example in this app note, can be easily analyzed, with a standard tabletop or portable NANOVEA Profiler for in-house or field testing

NOW, LET'S TALK ABOUT YOUR APPLICATION

Industrial Coatings Scratch and Wear Evaluation

INDUSTRIAL COATING

SCRATCH AND WEAR EVALUATION USING A TRIBOMETER

Prepared by

DUANJIE LI, PhD & ANDREA HERRMANN

INTRODUCTION

Acrylic urethane paint is a type of fast-dry protective coating widely used in a variety of industrial applications, such as floor paint, auto paint, and others. When used as floor paint, it can serve areas with heavy foot and rubber-wheel traffic, such as walkways, curbs and parking lots.

IMPORTANCE OF SCRATCH AND WEAR TESTING FOR QUALITY CONTROL

Traditionally, Taber abrasion tests were carried out to evaluate the wear resistance of acrylic urethane floor paint according to the ASTM D4060 standard. However, as mentioned in the standard, “For some materials, abrasion tests utilizing the Taber Abraser may be subject to variation due to changes in the abrasive characteristics of the wheel during testing.”1 This may result in poor reproducibility of test results and create difficulty in comparing values reported from different laboratories. Moreover, in Taber abrasion tests, abrasion resistance is calculated as loss in weight at a specified number of abrasion cycles. However, acrylic urethane floor paints have a recommended dry film thickness of 37.5-50 μm2.

The aggressive abrasion process by Taber Abraser can quickly wear through the acrylic urethane coating and create mass loss to the substrate leading to substantial errors in the calculation of the paint weight loss. The implant of abrasive particles in the paint during the abrasion test also contributes to errors. Therefore, a well-controlled quantifiable and reliable measurement is crucial to ensure reproducible wear evaluation of the paint. In addition, the scratch test allows users to detect premature adhesive/cohesive failures in real-life applications.

MEASUREMENT OBJECTIVE

In this study, we showcase that NANOVEA Tribometers and Mechanical Testers are ideal for evaluation and quality control of industrial coatings.

The wear process of acrylic urethane floor paints with different topcoats is simulated in a controlled and monitored manner using the NANOVEA Tribometer. Micro scratch testing is used to measure the load required to cause cohesive or adhesive failure to the paint.

NANOVEA T100

The Compact Pneumatic Tribometer

NANOVEA PB1000

The Large Platform Mechanical Tester

TEST PROCEDURE

This study evaluates four commercially available water-based acrylic floor coatings that have the same primer (basecoat) and different topcoats of the same formula with a small alternation in the additive blends for the purpose of enhancing durability. These four coatings are identified as Samples A, B, C and D.

WEAR TEST

The NANOVEA Tribometer was applied to evaluate the tribological behavior, e.g. coefficient of friction, COF, and wear resistance. A SS440 ball tip (6 mm dia., Grade 100) was applied against the tested paints. The COF was recorded in situ. The wear rate, K, was evaluated using the formula K=V/(F×s)=A/(F×n), where V is the worn volume, F is the normal load, s is the sliding distance, A is the cross-sectional area of the wear track, and n is the number of revolution. Surface roughness and wear track profiles were evaluated by the NANOVEA Optical Profilometer, and the wear track morphology was examined using optical microscope.

WEAR TEST PARAMETERS

NORMAL FORCE

20 N

SPEED

15 m/min

DURATION OF TEST

100, 150, 300 & 800 cycles

SCRATCH TEST

The NANOVEA Mechanical Tester equipped with a Rockwell C diamond stylus (200 μm radius) was used to perform progressive load scratch tests on the paint samples using the Micro Scratch Tester Mode. Two final loads were used: 5 N final load for investigating paint delamination from the primer, and 35 N for investigating primer delamination from the metal substrates. Three tests were repeated at the same testing conditions on each sample to ensure reproducibility of the results.

Panoramic images of the whole scratch lengths were automatically generated and their critical failure locations were correlated with the applied loads by the system software. This software feature facilitates users to perform analysis on the scratch tracks any time, rather than having to determine the critical load under the microscope immediately after the scratch tests.

SCRATCH TEST PARAMETERS

LOAD TYPEProgressive
INITIAL LOAD0.01 mN
FINAL LOAD5 N / 35 N
LOADING RATE10 / 70 N/min
SCRATCH LENGTH3 mm
SCRATCHING SPEED, dx/dt6.0 mm/min
INDENTER GEOMETRY120º cone
INDENTER MATERIAL (tip)Diamond
INDENTER TIP RADIUS200 μm

WEAR TEST RESULTS

Four pin-on-disk wear tests at different number of revolutions (100, 150, 300 and 800 cycles) were performed on each sample in order to monitor the evolution of wear. The surface morphology of the samples were measured with a NANOVEA 3D Non-Contact Profiler to quantify the surface roughness prior to conducting wear testing. All samples had a comparable surface roughness of approximately 1 μm as displayed in FIGURE 1. The COF was recorded in situ during the wear tests as shown in FIGURE 2. FIGURE 4 presents the evolution of wear tracks after 100, 150, 300 and 800 cycles, and FIGURE 3 summarized the average wear rate of different samples at different stages of the wear process.

 

Compared with a COF value of ~0.07 for the other three samples, Sample A exhibits a much higher COF of ~0.15 at the beginning, which gradually increases and gets stable at ~0.3 after 300 wear cycles. Such a high COF accelerates the wear process and creates a substantial amount of paint debris as indicated in FIGURE 4 – the topcoat of Sample A has started to be removed in the first 100 revolutions. As shown in FIGURE 3, Sample A exhibits the highest wear rate of ~5 μm2/N in the first 300 cycles, which slightly decreases to ~3.5 μm2/N due to the better wear resistance of the metal substrate. The topcoat of Sample C starts to fail after 150 wear cycles as shown in FIGURE 4, which is also indicated by the increase of COF in FIGURE 2.

 

In comparison, Sample B and Sample D show enhanced tribological properties. Sample B maintains a low COF throughout the whole test – the COF slightly increases from~0.05 to ~0.1. Such a lubricating effect substantially enhances its wear resistance – the topcoat still provides superior protection to the primer underneath after 800 wear cycles. The lowest average wear rate of only ~0.77 μm2/N is measured for Sample B at 800 cycles. The topcoat of Sample D starts to delaminate after 375 cycles, as reflected by the abrupt increase of COF in FIGURE 2. The average wear rate of Sample D is ~1.1 μm2/N at 800 cycles.

 

Compared to the conventional Taber abrasion measurements, NANOVEA Tribometer provides well-controlled quantifiable and reliable wear assessments that ensure reproducible evaluations and quality control of commercial floor/auto paints. Moreover, the capacity of in situ COF measurements allow users to correlate the different stages of a wear process with the evolution of COF, which is critical in improving fundamental understanding of the wear mechanism and tribological characteristics of various paint coatings.

FIGURE 1: 3D morphology and roughness of the paint samples.

FIGURE 2: COF during pin-on-disk tests.

FIGURE 3: Evolution of wear rate of different paints.

FIGURE 4: Evolution of wear tracks during the pin-on-disk tests.

WEAR TEST RESULTS

FIGURE 5 shows the plot of normal force, frictional force and true depth as a function of scratch length for Sample A as an example. An optional acoustic emission module can be installed to provide more information. As the normal load linearly increases, the indentation tip gradually sinks into the tested sample as reflected by the progressive increase of true depth. The variation in the slopes of frictional force and true depth curves can be used as one of the implications that coating failures start to occur.

FIGURE 5: Normal force, frictional force and true depth as a function of scratch length for scratch test of Sample A with a maximum load of 5 N.

FIGURE 6 and FIGURE 7 show the full scratches of all four paint samples tested with a maximum load of 5 N and 35 N, respectively. Sample D required a higher load of 50 N to delaminate the primer. Scratch tests at 5 N final load (FIGURE 6) evaluate the cohesive/adhesive failure of the top paint, while the ones at 35 N (FIGURE 7) assess the delamination of the primer. The arrows in the micrographs indicate the point at which the top coating or the primer start to be completely removed from the primer or the substrate. The load at this point, so called Critical Load, Lc, is used to compare the cohesive or adhesive properties of the paint as summarized in Table 1.

 

It is evident that the paint Sample D has the best interfacial adhesion – exhibiting the highest Lc values of 4.04 N at paint delamination and 36.61 N at primer delamination. Sample B shows the second best scratch resistance. From the scratch analysis, we show that optimization of the paint formula is critical to the mechanical behaviors, or more specifically, scratch resistance and adhesion property of acrylic floor paints.

Table 1: Summary of critical loads.

FIGURE 6: Micrographs of full scratch with 5 N maximum load.

FIGURE 7: Micrographs of full scratch with 35 N maximum load.

CONCLUSION

Compared to the conventional Taber abrasion measurements, the NANOVEA Mechanical Tester and Tribometer are superior tools for evaluation and quality control of commercial floor and automotive coatings. The NANOVEA Mechanical Tester in Scratch mode can detect adhesion/cohesion problems in a coating system. The NANOVEA Tribometer provides well-controlled quantifiable and repeatable tribological analysis on wear resistance and coefficient of friction of the paints.

 

Based on the comprehensive tribological and mechanical analyses on the water based acrylic floor coatings tested in this study, we show that Sample B possesses the lowest COF and wear rate and the second best scratch resistance, while Sample D exhibits the best scratch resistance and second best wear resistance. This assessment allows us to evaluate and select the best candidate targeting the needs in different application environments.

 

The Nano and Micro modules of the NANOVEA Mechanical Tester all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest range of testing available for paint evaluation on a single module. The NANOVEA Tribometer offers precise and repeatable wear and friction testing using ISO and ASTM compliant rotative and linear modes, with optional high temperature wear, lubrication and tribo-corrosion modules available in one pre-integrated system. NANOVEA’s unmatched range is an ideal solution for determining the full range of mechanical/tribological properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others. Optional NANOVEA Non-Contact Optical Profilers are available for high resolution 3D imaging of scratchs and wear tracks in addition to other surface measurements such as roughness.

NOW, LET'S TALK ABOUT YOUR APPLICATION

Scratch Hardness Measurement using Mechanical Tester

SCRATCH HARDNESS MEASUREMENT

USING A MECHANICAL TESTER

Prepared by

DUANJIE LI, PhD

INTRODUCTION

In general, hardness tests measure the resistance of materials to permanent or plastic deformation. There are three types of hardness measurements: scratch hardness, indentation hardness and rebound hardness. A scratch hardness test measures a material’s resistance to scratch and abrasion due to friction from a sharp object1. It was originally developed by German mineralogist Friedrich Mohs in 1820 and is still widely used to rank the physical properties of minerals2. This test method is also applicable to metals, ceramics, polymers, and coated surfaces.

During a scratch hardness measurement, a diamond stylus of specified geometry scratches into a material’s surface along a linear path under a constant normal force with a constant speed. The average width of the scratch is measured and used to calculate the scratch hardness number (HSP). This technique provides a simple solution for scaling the hardness of different materials.

MEASUREMENT OBJECTIVE

In this study, the NANOVEA PB1000 Mechanical Tester is used to measure the scratch hardness of different metals in compliance with ASTM G171-03.

Simultaneously, this study showcases the capacity of the NANOVEA Mechanical Tester in performing scratch hardness measurement with high precision and reproducibility.

NANOVEA

PB1000

TEST CONDITIONS

The NANOVEA PB1000 Mechanical Tester performed scratch hardness tests on three polished metals (Cu110, Al6061 and SS304). A conical diamond stylus of apex angle 120° with tip radius of 200 µm was used. Each sample was scratched three times with the same test parameters to ensure reproducibility of the results. The test parameters are summarized below. A profile scan at a low normal load of 10 mN was performed before and after the scratch test to measure the change in the surface profile of the scratch.

TEST PARAMETERS

NORMAL FORCE

10 N

TEMPERATURE

24°C (RT)

SLIDING SPEED

20 mm/min

SLIDING DISTANCE

10 mm

ATMOSPHERE

Air

RESULTS & DISCUSSION

The images of the scratch tracks of three metals (Cu110, Al6061 and SS304) after the tests are shown in FIGURE 1 in order to compare the scratch hardness of different materials. The mapping function of the NANOVEA Mechanical Software was used to create three parallel scratches tested under the same condition in an automated protocol. The measured scratch track width and calculated scratch hardness number (HSP) are summarized and compared in TABLE 1. The metals show different wear track widths of 174, 220 and 89 µm for Al6061, Cu110 and SS304, respectively, resulting in a calculated HSP of 0.84, 0.52 and 3.2 GPa.

In addition to the scratch hardness computed from the scratch track width, the evolution of coefficient of friction (COF), true depth and acoustic emission were recorded in situ during the scratch hardness test. Here, the true depth is the depth difference between the penetration depth of the stylus during the scratch test and the surface profile measured in the pre-scan. The COF, true depth and acoustic emission of Cu110 are shown in FIGURE 2 as an example. Such information provides insight into mechanical failures taking place during scratching, enabling users to detect mechanical defects and further investigate the scratch behavior of the tested material.

The scratch hardness tests can be finished within a couple of minutes with high precision and repeatability. Compared to conventional indentation procedures, the scratch hardness test in this study provides an alternative solution for hardness measurements, which is useful for quality control and the development of new materials.

Al6061

Cu110

SS304

FIGURE 1: Microscope image of the scratch tracks post test (100x magnification).

 Scratch track width (μm)HSp (GPa)
Al6061174±110.84
Cu110220±10.52
SS30489±53.20

TABLE 1: Summary of scratch track width and scratch hardness number.

FIGURE 2: The evolution of coefficient of friction, true depth and acoustic emissions during the scratch hardness test on Cu110.

CONCLUSION

In this study, we showcased the capacity of the NANOVEA Mechanical Tester in performing scratch hardness tests in compliance to ASTM G171-03. In addition to coating adhesion and scratch resistance, the scratch test at a constant load provides an alternative simple solution for comparing the hardness of materials. In contrast to conventional scratch hardness testers, NANOVEA Mechanical Testers offer optional modules for monitoring the evolution of coefficient of friction, acoustic emission and true depth in situ.

The Nano and Micro modules of a NANOVEA Mechanical Tester include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user-friendly range of testing available in a single system. NANOVEA’s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others.

NOW, LET'S TALK ABOUT YOUR APPLICATION

Titanium Nitride Coating Scratch Test

TITANIUM NITRIDE COATING SCRATCH TEST

QUALITY CONTROL INSPECTION

Prepared by

DUANJIE LI, PhD

INTRODUCTION

The combination of high hardness, excellent wear resistance, corrosion resistance and inertness makes titanium nitride (TiN) an ideal protective coating for metal components in various industries. For example, the edge retention and corrosion resistance of a TiN coating can substantially increase the work efficiency and extend the service life of machine tooling such as razor blades, metal cutters, injection molds and saws. Its high hardness, inertness and non-toxicity make TiN a great candidate for applications in medical devices including implants and surgical instruments.

IMPORTANCE OF TiN COATING SCRATCH TESTING

Residual stress in protective PVD/CVD coatings plays a critical role in the performance and mechanical integrity of the coated component. The residual stress derives from several major sources, including growth stress, thermal gradients, geometric constraints and service stress¹. The thermal expansion mismatch between the coating and the substrate created during coating deposition at elevated temperatures leads to high thermal residual stress. Moreover, TiN coated tools are often used under very high concentrated stresses, e.g. drill bits and bearings. It is critical to developing a reliable quality control process to quantitatively inspect the cohesive and adhesive strength of protective functional coatings.

[1] V. Teixeira, Vacuum 64 (2002) 393–399.

MEASUREMENT OBJECTIVE

In this study, we showcase that the NANOVEA Mechanical Testers in Scratch Mode are ideal for assessing the cohesive/adhesive strength of protective TiN coatings in a controlled and quantitative manner.

NANOVEA

PB1000

TEST CONDITIONS

The NANOVEA PB1000 Mechanical Tester was used to perform coating scratch tests on three TiN coatings using the same test parameters as summarized below:

LOADING MODE: Progressive Linear

INITIAL LOAD

0.02 N

FINAL LOAD

10 N

LOADING RATE

20 N/min

SCRATCH LENGTH

5 mm

INDENTER TYPE

Sphero-Conical

Diamond, 20 μm radius

RESULTS & DISCUSSION

FIGURE 1 shows the recorded evolution of penetration depth, coefficient of friction (COF) and acoustic emission during the test. The full micro scratch tracks on the TiN samples are shown in FIGURE 2. The failure behaviors at different critical loads are displayed in FIGURE 3, where critical load Lc1 is defined as the load at which the first sign of cohesive crack occurs in the scratch track, Lc2 is the load after which repeated spallation failures take place, and Lc3 is the load at which the coating is completely removed from the substrate. The critical load (Lc) values for the TiN coatings are summarized in FIGURE 4.

The evolution of penetration depth, COF and acoustic emission provides insight into the mechanism of the coating failure at different stages, which are represented by the critical loads in this study. It can be observed that Sample A and Sample B exhibit comparable behavior during the scratch test. The stylus progressively penetrates into the sample to a depth of ~0.06 mm and the COF gradually increases to ~0.3 as the normal load increases linearly at the beginning of the coating scratch test. When the Lc1 of ~3.3 N is reached, the first sign of chipping failure occurs. This is also reflected in the first large spikes in the plot of penetration depth, COF and acoustic emission. As the load continues to increase to Lc2 of ~3.8 N, further fluctuation of the penetration depth, COF and acoustic emission takes place. We can observe continuous spallation failure present on both sides of the scratch track. At the Lc3, the coating completely delaminates from the metal substrate under the high pressure applied by the stylus, leaving the substrate exposed and unprotected.

In comparison, Sample C exhibits lower critical loads at different stages of the coating scratch tests, which is also reflected in the evolution of penetration depth, coefficient of friction (COF) and acoustic emission during the coating scratch test. Sample C possesses an adhesion interlayer with lower hardness and higher stress at the interface between the top TiN coating and the metal substrate compared to Sample A and Sample B.

This study demonstrates the importance of proper substrate support and coating architecture to the quality of the coating system. A stronger interlayer can better resist deformation under a high external load and concentration stress, and thus enhance the cohesive and adhesive strength of the coating/substrate system.

FIGURE 1: Evolution of penetration depth, COF and acoustic emission of the TiN samples.

FIGURE 2: Full scratch track of the TiN coatings after the tests.

FIGURE 3: TiN coating failures under different critical loads, Lc.

FIGURE 4: Summary of critical load (Lc) values for the TiN coatings.

CONCLUSION

In this study, we showcased that the NANOVEA PB1000 Mechanical Tester performs reliable and accurate scratch tests on TiN-coated samples in a controlled and closely monitored manner. Scratch measurements allow users to quickly identify the critical load at which typical cohesive and adhesive coating failures occur. Our instruments are superior quality control tools that can quantitatively inspect and compare the intrinsic quality of a coating and the interfacial integrity of a coating/substrate system. A coating with a proper interlayer can resist large deformation under a high external load and concentration stress, and enhance the cohesive and adhesive strength of a coating/substrate system.

The Nano and Micro modules of a NANOVEA Mechanical Tester all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user-friendly range of testing available in a single system. NANOVEA’s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear-resistance and many others.

NOW, LET'S TALK ABOUT YOUR APPLICATION

Adhesion Properties of Gold Coating on Quartz Crystal Substrate

 

Adhesion Properties of Gold Coating

on Quartz Crystal Substrate

Prepared by

DUANJIE LI, PhD

INTRODUCTION

The Quartz Crystal Microbalance (QCM) is an extremely sensitive mass sensor capable of making precise measurements of small mass in the nanogram range. QCM measures the mass change on the surface through detecting variations in resonance frequency of the quartz crystal with two electrodes affixed to each side of the plate. The capacity of measuring extreme small weight makes it a key component in a variety of research and industrial instruments to detect and monitor the variation of mass, adsorption, density, and corrosion, etc.

IMPORTANCE OF SCRATCH TEST FOR QCM

As an extremely accurate device, the QCM measures the mass change down to 0.1 nanogram. Any mass loss or delamination of the electrodes on the quartz plate will be detected by the quartz crystal and cause significant measurement errors. As a result, the intrinsic quality of the electrode coating and the interfacial integrity of the coating/substrate system play an essential role in performing accurate and repeatable mass measurement. The Micro scratch test is a widely used comparative measurement to evaluate the relative cohesion or adhesion properties of coatings based on comparison of the critical loads at which failures appear. It is a superior tool for reliable quality control of QCMs.

MEASUREMENT OBJECTIVE

In this application, the NANOVEA Mechanical Tester, in Micro Scratch Mode, is used to evaluate the cohesive & adhesive strength of the gold coating on the quartz substrate of a QCM sample. We would like to showcase the capacity of the NANOVEA Mechanical Tester in performing micro scratch tests on a delicate sample with high precision and repeatability.

NANOVEA

PB1000

TEST CONDITIONS

The NANOVEA PB1000 Mechanical Tester was used to perform the micro scratch tests on a QCM sample using the test parameters summarized below. Three scratches were performed to ensure reproducibility of the results.

LOAD TYPE: Progressive

INITIAL LOAD

0.01 N

FINAL LOAD

30 N

ATMOSPHERE: Air 24°C

SLIDING SPEED

2 mm/min

SLIDING DISTANCE

2 mm

RESULTS & DISCUSSION

The full micro scratch track on the QCM sample is shown in FIGURE 1. The failure behaviors at different critical loads are displayed in FIGURE 2, where critical load, LC1 is defined as the load at which the first sign of adhesive failure occurs in the scratch track, LC2 is the load after which repetitive adhesive failures take place, and LC3 is the load at which the coating is completely removed from the substrate. It can be observed that little chipping takes place at LC1 of 11.15 N, the first sign of coating failure. 

As the normal load continues to increase during the micro scratch test, repetitive adhesive failures occur after LC2 of 16.29 N. When LC3 of 19.09 N is reached, the coating completely delaminates from the quartz substrate. Such critical loads can be used to quantitatively compare the cohesive and adhesive strength of the coating and select the best candidate for targeted applications.

FIGURE 1: Full micro scratch track on the QCM sample.

FIGURE 2: Micro scratch track at different critical loads.

FIGURE 3 plots the evolution of friction coefficient and depth that may provide more insight in the progression of coating failures during the micro scratch test.

FIGURE 3: Evolution of COF and Depth during the micro scratch test.

CONCLUSION

In this study, we showcased that the NANOVEA Mechanical Tester performs reliable and accurate micro scratch tests on a QCM sample. By applying linearly increased loads in a controlled and closely monitored fashion, the scratch measurement allows users to identify the critical load at which typical cohesive and adhesive coating failure occurs. It provides a superior tool to quantitatively evaluate and compare the intrinsic quality of the coating and the interfacial integrity of the coating/substrate system for QCM.

The Nano, Micro or Macro modules of the NANOVEA Mechanical Tester all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user friendly range of testing available in a single system. NANOVEA‘s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others.

In addition, an optional 3D non-contact profiler and AFM module are available for high resolution 3D imaging of indentation, scratch and wear track in addition to other surface measurements, such as roughness and warpage.

NOW, LET'S TALK ABOUT YOUR APPLICATION

The World’s Leading Micro Mechanical Tester

 

NOW THE WORLD'S LEADING

MICRO MECHANICAL TESTING

Prepared by

PIERRE LEROUX & DUANJIE LI, PhD

INTRODUCTION

Standard Vickers Micro Hardness Testers have usable load ranges from 10 to 2000 gram force (gf). Standard Vickers Macro Hardness Testers load from 1 to 50 Kgf. These instruments are not only very limited in range of loads but they are also inaccurate when dealing with rougher surfaces or low loads when indents become too small to be measured visually. These limitations are intrinsic to older technology and as a result, instrumented indentation is becoming the standard choice due to the higher accuracy and performance it brings.

With NANOVEA’s world leading micro mechanical testing systems, Vickers hardness is automatically calculated from depth versus load data with the widest load range on a single module ever available (0.3 grams to 2 Kg or 6 grams to 40 Kg). Because it measures hardness from depth versus load curves, the NANOVEA Micro Module can measure any type of materials including very elastic ones. It also can provide not only Vickers hardness but also accurate elastic modulus and creep data in addition to other types of test such as scratch adhesion testing, wear, fatigue testing, yield strength and fracture toughness for a complete range of quality control data.

NOW THE WORLD'S LEADING MICRO MECHANICAL TESTING

In this applications note, it will be explained how the Micro Module has been designed to offer the world’s leading instrumented indentation and scratch testing. The Micro Module’s wide range testing capability is ideal for many applications. For example, the load range allows for accurate hardness and elastic modulus measurements of thin hard coatings and can then apply much higher loads to measure the adhesion of these same coatings.

MEASUREMENT OBJECTIVE

The capacity of the Micro Module is showcased with the NANOVEA CB500 Mechanical Tester by
performing both indentation and scratch tests with superior precision and reliability using a wide load range from 0.03 to 200 N.

NANOVEA

CB500

TEST CONDITIONS

A series (3×4, 12 indents in total) of Microindentations were performed on a standard steel sample using a Vickers indenter. The load and depth were measured and recorded for the complete indentation test cycle. The indentations were performed to different maximum loads ranging from 0.03 N to 200 N (0.0031 to 20.4 kgf) to showcase the capacity of the micro module in performing accurate indentation tests at different loads. It is worth noting that an optional load cell of 20 N is also available to provide 10 times higher resolution for tests in the lower load range from 0.3 gf up to 2 kgf.

Two scratch tests were performed using the Micro Module with linearly increased load from 0.01 N to 200 N and from 0.01 N to 0.5 N, respectively, using conico-spherical diamond stylus with tip radius of 500 μm and 20 μm.

Twenty Microindentation tests were carried out on the steel standard sample at 4 N showcasing the superior repeatability of the Micro Module’s results that contrast the performance of conventional Vickers hardness testers.

*microindenter on the steel sample

TEST PARAMETERS

of the Indentation Mapping

MAPPING: 3 BY 4 INDENTS

RESULTS AND DISCUSSION

The new Micro Module has a unique combination of Z-motor, high-force load cell and a high precision capacitive depth sensor. The unique utilization of independent depth and load sensors ensures high accuracy under all conditions.

Conventional Vickers hardness tests use diamond square-based pyramid indenter tips that create square shaped indents. By measuring the average length of the diagonal, d, the Vickers hardness can be calculated.

In comparison, the instrumented indentation technique used by NANOVEA‘s Micro Module directly measures the mechanical properties from indentation load & displacement measurements. No visual observation of the indent is required. This eliminates user or computer image processing errors in determining the d values of the indentation. The high accuracy capacitor depth sensor with a very low noise level of 0.3 nm can accurately measure the depth of indents that are difficult or impossible to be measured visually under a microscope with traditional Vickers hardness testers.

In addition, the cantilever technique used by competitors applies the normal load on a cantilever beam by a spring, and this load is in turn applied on the indenter. Such a design has a flaw in case a high load is applied – the cantilever beam cannot provide sufficient structural stiffness, leading to deformation of the cantilever beam and in turn misalignment of the indenter. In comparison, the Micro Module applies the normal load via the Z-motor acting on the load cell and then the indenter for direct load application. All the elements are vertically aligned for maximum stiffness, ensuring repeatable and accurate indentation and scratch measurements in the full load range.

Close-up view of the new Micro Module

INDENTATION FROM 0.03 TO 200 N

The image of the indentation map is displayed in FIGURE 1. The distance between the two adjacent indents above 10 N is 0.5 mm, while the one at lower loads is 0.25 mm. The high-precision position control of the sample stage allows users to select the target location for mechanical properties mapping. Thanks to the excellent stiffness of the micro module due to the vertical alignment of its components, the Vickers indenter keeps a perfect vertical orientation as it penetrates into the steel sample under a load of up to 200 N (400 N optional). This creates impressions of a symmetric square shape on the sample surface at different loads.

The individual indentations at different loads under the microscope are displayed alongside of the two scratches as shown in FIGURE 2, to showcase the capacity of the new micro module in performing both indentation and scratch tests in a wide load range with a high precision. As shown in the Normal Load vs. Scratch Length plots, the normal load increases linearly as the conico-spherical diamond stylus slides on the steel sample surface. It creates a smooth straight scratch track of progressively increased width and depth.

FIGURE 1: Indentation Map

Two scratch tests were performed using the Micro Module with linearly increased load from 0.01 N to 200 N and from 0.01 N to 0.5 N, respectively, using conico-spherical diamond stylus with tip radius of 500 μm and 20 μm.

Twenty Microindentation tests were carried out on the steel standard sample at 4 N showcasing the superior repeatability of the Micro Module’s results that contrast the performance of conventional Vickers hardness testers.

A: INDENTATION AND SCRATCH UNDER THE MICROSCOPE (360X)

B: INDENTATION AND SCRATCH UNDER THE MICROSCOPE (3000X)

FIGURE 2: Load vs Displacement plots at different maximum loads.

The load-displacement curves during the indentation at different maximum loads are shown in FIGURE 3. The hardness and elastic modulus are summarized and compared in FIGURE 4. The steel sample exhibits a constant elastic modulus throughout the test load ranging from 0.03 to 200 N (possible range 0.003 to 400 N), resulting in an average value of ~211 GPa. The hardness exhibits a relatively constant value of ~6.5 GPa measured under a maximum load above 100 N. As the load decreases to a range of 2 to 10 N, an average hardness of ~9 GPa is measured.

FIGURE 3: Load vs Displacement plots at different maximum loads.

FIGURE 4: Hardness and Young’s modulus of the steel sample measured by different maximum loads.

INDENTATION FROM 0.03 TO 200 N

Twenty Microindentation tests were performed at 4N maximum load. The load-displacement curves are displayed in FIGURE 5 and the resulting Vickers hardness and Young’s modulus are shown in FIGURE 6.

FIGURE 5: Load-displacement curves for microindentation tests at 4 N.

FIGURE 6: Vickers hardness and Young’s Modulus for 20 microindentations at 4 N.

The load-displacement curves demonstrate the superior repeatability of the new Micro Module. The steel standard possesses a Vickers hardness of 842±11 HV measured by the new Micro Module, compared to 817±18 HV as measured using the conventional Vickers hardness tester. The small standard deviation of the hardness measurement ensures reliable and reproducible characterization of mechanical properties in the R&D and quality control of materials in both the industrial sector and academia research.

In addition, a Young’s Modulus of 208±5 GPa is calculated from the load-displacement curve, which is not available for conventional Vickers hardness tester due to the missing depth measurement during the indentation. As load decrease and the size of the indent decreases, the NANOVEA Micro Module advantages in terms of repeatability compare to Vickers Hardness Testers increase until it is no longer possible to measure the indent through visual inspection.

The advantage of measuring depth to calculate hardness also becomes evident when dealing with rougher or when samples are more difficult to observe under standard microscopes provided on Vickers Hardness Testers.

CONCLUSION

In this study, we have shown how the new world leading NANOVEA Micro Module (200 N range) performs unmatched reproducible and precise indentation and scratch measurements under a wide load range from 0.03 to 200 N (3 gf to 20.4 kgf). An optional lower range Micro Module can provide testing from 0.003 to 20 N (0.3 gf to 2 kgf). The unique vertical alignment of the Z-motor, high-force load cell and depth sensor ensures maximum structural stiffness during measurements. The indentations measured at different loads all possess a symmetric square shape on the sample surface. A straight scratch track of progressively increased width and depth is created in the scratch test of a 200 N maximum load.

The new Micro Module can be configured on the PB1000 (150 x 200 mm) or the CB500 (100 x 50 mm) mechanical base with a z motorization (50 mm range). Combined with a powerful camera system (position accuracy of 0.2 microns) the systems provide the best automation and mapping capabilities on the market. NANOVEA also offers a unique patented function (EP No. 30761530) which allows verification and calibration of Vickers indenters by performing a single indent across the full range of loads. In contrast, standard Vickers Hardness Testers can only provide calibration at one load.

Additionally, the NANOVEA software enables a user to measure the Vickers hardness via the traditional method of measuring the indent diagonals if needed (for ASTM E92 & E384). As shown, in this document, depth versus load hardness testing (ASTM E2546 and ISO 14577) performed by a NANOVEA Micro Module is precise and reproducible compared to Traditional Hardness Testers. Especially for samples that cannot be observed/measured with a microscope.

In conclusion, the higher accuracy and repeatability of the Micro Module design with its broad range of loads and tests, high automation and mapping options renders the traditional Vickers hardness testers obsolete. But likewise with scratch and micro scratch testers still currently offered but designed with flaws in the 1980’s.

The continuous development and improvement of this technology makes NANOVEA a world leader in micro mechanical testing.

NOW, LET'S TALK ABOUT YOUR APPLICATION

Creep Deformation of Polymers using Nanoindentation

Creep Deformation of Polymers using Nanoindentation

Learn more

 

CREEP DEFORMATION

OF POLYMERS USING NANOINDENTATION

Prepared by

DUANJIE LI, PhD

INTRODUCTION

As viscoelastic materials, polymers often undergo a time-dependent deformation under a certain applied load, also known as creep. Creep becomes a critical factor when the polymeric parts are designed to be exposed to continuous stress, such as structural components, joins and fittings, and hydrostatic pressure vessels.

IMPORTANCE OF CREEP MEASUREMENT FOR POLYMERS

The inherent nature of viscoelasticity plays a vital role in the performance of polymers and directly influences their service reliability. The environmental conditions such as loading and temperature affect the creep behavior of the polymers. Creep failures often occur due to the lack of alertness of the time-dependent creep behavior of the polymer materials used under specific service conditions. As a result, it is important to develop a reliable and quantitative test of the viscoelastic mechanical behaviors of the polymers. The Nano module of the NANOVEA Mechanical Testers applies the load with a high-precision piezo and directly measures the evolution of force and displacement in situ. The combination of accuracy and repeatability makes it an ideal tool for creep measurement.

MEASUREMENT OBJECTIVE

In this application, we showcased that
the NANOVEA PB1000 Mechanical Tester
in Nanoindentation mode is an ideal tool
for studying viscoelastic mechanical properties
including hardness, Young’s modulus
and creep of polymeric materials.

NANOVEA

PB1000

TEST CONDITIONS

Eight different polymer samples were tested by nanoindentation technique using the NANOVEA PB1000 Mechanical Tester. As the load linearly increased from 0 to 40 mN, the depth progressively increased during the loading stage. The creep was then measured by the change of indentation depth at the maximum load of 40 mN for 30 s.

MAXIMUM LOAD 40 mN
LOADING RATE
80 mN/min
UNLOADING RATE 80 mN/min
CREEP TIME
30 s

INDENTER TYPE

Berkovich

Diamond

*setup of the nanoindentation test

RESULTS & DISCUSSION

The load vs displacement plot of the nanoindentation tests on different polymer samples is shown in FIGURE 1 and the creep curves are compared in FIGURE 2. The hardness and Young’s modulus are summarized in  FIGURE 3, and the creep depth is shown in FIGURE 4. As an examples in FIGURE 1, the AB, BC and CD portions of the load-displacement curve for the nanoindentation measurement represent the loading, creep and unloading processes, respectively.

Delrin and PVC exhibit the highest hardness of 0.23 and 0.22 GPa, respectively, while LDPE possesses the lowest hardness of 0.026 GPa among the tested polymers. In general, the harder polymers show lower creep rates. The softest LDPE has the highest creep depth of 798 nm, compared to ~120 nm for Delrin.

The creep properties of the polymers are critical when they are used in structural parts. By precisely measuring the hardness and creep of the polymers, a better understanding of the time-dependent reliability of the polymers can be obtained. The creep, change of the displacement at a given load, can also be measured at different elevated temperatures and humidity using the NANOVEA PB1000 Mechanical Tester, providing an ideal tool to quantitatively and reliably measure the viscoelastic mechanical behaviors of polymers
in the simulated realistic application environment.

FIGURE 1: The load vs displacement plots
of different polymers.

FIGURE 2: Creeping at a maximum load of 40 mN for 30 s.

FIGURE 3: Hardness and Young’s modulus of the polymers.

FIGURE 4: Creep depth of the polymers.

CONCLUSION

In this study, we showcased that the NANOVEA PB1000
Mechanical Tester measures the mechanical properties of different polymers, including hardness, Young’s modulus and creep. Such mechanical properties are essential in selecting the proper polymer material for intended applications. Derlin and PVC exhibit the highest hardness of 0.23 and 0.22 GPa, respectively, while LDPE possesses the lowest hardness of 0.026 GPa among the tested polymers. In general, the harder polymers exhibit lower creep rates. The softest LDPE shows the highest creep depth of 798 nm, compared to ~120 nm for Derlin.

The NANOVEA Mechanical Testers provide unmatched multi-function Nano and Micro modules on a single platform. Both the Nano and Micro modules include scratch tester, hardness tester and wear tester modes, providing the wildest and most user-friendly range of testing available on a single system.

NOW, LET'S TALK ABOUT YOUR APPLICATION

Multiphase Material using Nanoindentation NANOVEA

Multiphase Metal Nanoindentation

Metallurgy Study of Multiphase Material using Nanoindentation

Learn more

 

METALLURGY STUDY
OF MULTIPHASE MATERIAL

USING NANOINDENTATION

Prepared by

DUANJIE LI, PhD & ALEXIS CELESTIN

INTRODUCTION

Metallurgy studies the physical and chemical behavior of metallic elements, as well as their intermetallic compounds and alloys. Metals that undergo working processes, such as casting, forging, rolling, extrusion and machining, experience changes in their phases, microstructure and texture. These changes result in varied physical properties including hardness, strength, toughness, ductility, and wear resistance of the material. Metallography is often applied to learn the formation mechanism of such specific phases, microstructure and texture.

IMPORTANCE OF LOCAL MECHANICAL PROPERTIES FOR MATERIALS DESIGN

Advanced materials often have multiple phases in a special microstructure and texture to achieve desired mechanical properties for target applications in industrial practice. Nanoindentation is widely applied to measure the mechanical behaviors of materials at small scales i ii. However, it is challenging and time-consuming to precisely select specific locations for indentation in a very small area. A reliable and user-friendly procedure of nanoindentation testing is in demand to determine the mechanical properties of different phases of a material with high precision and timely measurements.

MEASUREMENT OBJECTIVE

In this application, we measure mechanical properties of a multiphase metallurgical sample using the Most Powerful Mechanical Tester: the NANOVEA PB1000.

Here, we showcase the capacity of the PB1000 in performing nanoindentation measurements on multiple phases (grains) of a large sample surface with high precision and user friendliness using our Advanced Position Controller.

NANOVEA

PB1000

TEST CONDITIONS

In this study, we use a metallurgical sample with multiple phases. The sample had been polished to a mirror-like surface finish before the indentation tests. Four phases have been identified in the sample, namely PHASE 1, PHASE 2, PHASE 3 and PHASE 4 as shown below.

The Advanced Stage Controller is an intuitive sample navigation tool which automatically adjusts the speed of sample movement under the optical microscope based on position of the mouse. The further the mouse is away from the center of field of view, the faster the stage moves toward the mouse’s direction. This provides a user-friendly method to navigate the entire sample surface and select the intended location for mechanical testing. The coordinates of the test locations are saved and numbered, along with their individual test setups, such as loads, loading/unloading rate, number of tests in a map, etc. Such a test procedure allows users to examine a large sample surface for specific areas of interest for indentation and perform all the indentation tests at different locations in one time, making it an ideal tool for mechanical testing of metallurgical samples with multiple phases.

In this study, we located the specific phases of the sample under the optical microscope integrated in the NANOVEA Mechanical Tester as numbered on FIGURE 1. The coordinates of the selected locations are saved, followed by automatic nanoindentation tests all at once under the test conditions summarized below

FIGURE 1: SELECTING NANOINDENTATION LOCATION ON THE SAMPLE SURFACE.
RESULTS: NANOINDENTATIONS ON DIFFERENT PHASES

The indentations at the different phases of the sample are displayed below. We demonstrate that the excellent position control of the sample stage in the NANOVEA Mechanical Tester allows users to precisely pinpoint the target location for mechanical properties testing.

The representative load-displacement curves of the indentations are shown in FIGURE 2, and the corresponding hardness and Young’s Modulus calculated using Oliver and Pharr Methodiii are summarized and compared in FIGURE 3.


The
PHASES 1, 2, 3 and 4 possess an average hardness of ~5.4, 19.6, 16.2 and 7.2 GPa, respectively. The relatively small size for PHASES 2 contributes to its higher standard deviation of the hardness and Young’s Modulus values.

FIGURE 2: LOAD-DISPLACEMENT CURVES
OF THE NANOINDENTATIONS

FIGURE 3: HARDNESS & YOUNG’S MODULUS OF DIFFERENT PHASES

CONCLUSION

In this study, we showcased the NANOVEA Mechanical Tester performing nanoindentation measurements on multiple phases of a large metallurgical sample using the Advanced Stage Controller. The precise position control allows users to easily navigate a large sample surface and directly select the areas of interest for nanoindentation measurements.

The location coordinates of all the indentations are saved and then performed consecutively. Such a test procedure makes measurement of the local mechanical properties at small scales, e.g. the multi-phase metal sample in this study, substantially less time-consuming and more user friendly. The hard PHASES 2, 3 and 4 improve the mechanical properties of the sample, possessing an average hardness of ~19.6, 16.2 and 7.2 GPa, respectively, compared to ~5.4 GPa for PHASE 1.

The Nano, Micro or Macro modules of the instrument all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user friendly range of testing available in a single system. NANOVEA’s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others.

i Oliver, W. C.; Pharr, G. M., Journal of Materials Research., Volume 19, Issue 1, Jan 2004, pp.3-20
ii Schuh, C.A., Materials Today, Volume 9, Issue 5, May 2006, pp. 32–40
iii Oliver, W. C.; Pharr, G. M., Journal of Materials Research, Volume 7, Issue 6, June 1992, pp.1564-1583

NOW, LET'S TALK ABOUT YOUR APPLICATION

Dynamic Mechanical Analysis (DMA) Frequency Sweep on Polymer

 

DMA FREQUENCY SWEEP

ON POLYMER USING NANOINDENTATION

Prepared by

Duanjie Li, PhD

INTRODUCTION

IMPORTANCE OF DYNAMIC MECHANICAL ANALYSIS FREQUENCY SWEEP TEST

The changing frequency of the stress often leads to variations in the complex modulus, which is a critical mechanical property of polymers. For example, tires are subjected to cyclical high deformations when vehicles are running on the road. The frequency of the pressure and deformation changes as the car accelerates to higher speeds. Such a change can result in variation in the viscoelastic properties of the tire, which are important factors in the car performance. A reliable and repeatable test of the viscoelastic behavior of polymers at different frequencies is in need. The Nano module of the NANOVEA Mechanical Tester generates sinusoidal load by a high precision piezo actuator and directly measures the evolution of force and displacement using ultrasensitive load cell and capacitor. The combination of easy setup and high accuracy makes it an ideal tool for Dynamic Mechanical Analysis frequency sweep.

Viscoelastic materials exhibit both viscous and elastic characteristics when undergoing deformation. Long molecular chains in polymer materials contribute to their unique viscoelastic properties, i.e. a combination of the characteristics of both elastic solids and Newtonian fluids. Stress, temperature, frequency and other factors all play roles in the viscoelastic properties. Dynamic Mechanical Analysis, also known as DMA, studies the viscoelastic behavior and complex modulus of the material by applying a sinusoidal stress and measuring the change of strain.

MEASUREMENT OBJECTIVE

In this application, we study viscoelastic properties of a polished tire sample at different DMA frequencies using the Most Powerful Mechanical Tester, NANOVEA PB1000, in Nanoindentation mode.

NANOVEA

PB1000

TEST CONDITIONS

FREQUENCIES (Hz):

0.1, 1.5, 10, 20

CREEP TIME AT EACH FREQ.

50 sec

OSCILLATION VOLTAGE

0.1 V

LOADING VOLTAGE

1 V

indenter type

Spherical

Diamond | 100 μm

RESULTS & DISCUSSION

The Dynamic Mechanical Analysis frequency sweep at the maximum load allows a fast and simple measurement on the viscoelastic characteristics of the sample at different loading frequencies in one test. The phase shift and the amplitudes of the load and displacement waves at different frequencies can be used to calculate a variety of fundamental material viscoelastic properties, including Storage Modulus, Loss Modulus and Tan (δ) as summarized in the following graphs. 

Frequencies of 1, 5, 10 and 20 Hz in this study, correspond to speeds of about 7, 33, 67 and 134 km per hour. As the test frequency increases from 0.1 to 20 Hz, it can be observed that both Storage Modulus and Loss Modulus progressively increase. Tan (δ) decreases from ~0.27 to 0.18 as the frequency increases from 0.1 to 1 Hz, and then it gradually increases to ~0.55 when the frequency of 20 Hz is reached. DMA frequency sweep allows measuring the trends of Storage Modulus, Loss Modulus and Tan (δ), which provide information on the movement of the monomers and cross-linking as well as the glass transition of polymers. By raising the temperature using a heating plate during the frequency sweep, a more complete picture of the nature of the molecular motion under different test conditions can be obtained.

EVOLUTION OF LOAD & DEPTH

OF THE FULL DMA FREQUENCY SWEEP

LOAD & DEPTH vs TIME AT DIFFERENT FREQUENCIES

STORAGE MODULUS

AT DIFFERENT FREQUENCIES

LOSS MODULUS

AT DIFFERENT FREQUENCIES

TAN (δ)

AT DIFFERENT FREQUENCIES

CONCLUSION

In this study, we showcased the capacity of the NANOVEA Mechanical Tester in performing the Dynamic Mechanical Analysis frequency sweep test on a tire sample. This test measures the viscoelastic properties of the tire at different frequencies of stress. The tire shows increased storage and loss modulus as the loading frequency increases from 0.1 to 20 Hz. It provides useful information on the viscoelastic behaviors of the tire running at different speeds, which is essential in improving the performance of tires for smoother and safer rides. The DMA frequency sweep test can be performed at various temperatures to mimic the realistic working environment of the tire under different weather.

In the Nano Module of the NANOVEA Mechanical Tester, the load application with the fast piezo is independent from the load measurement done by a separate high sensitivity strain gage. This gives a distinct advantage during Dynamic Mechanical Analysis since the phase between depth and load is measured directly from the data collected from the sensor. The calculation of phase is direct and does not need mathematical modeling that adds inaccuracy to the resulting loss and storage modulus. This is not the case for a coil-based system.

In conclusion, DMA measures loss and storage modulus, complex modulus and Tan (δ) as a function of contact depth, time and frequency. Optional heating stage allows determination of materials phase transition temperature during DMA. The NANOVEA Mechanical Testers provide unmatched multi-function Nano and Micro modules on a single platform. Both the Nano and Micro modules include scratch tester, hardness tester and wear tester modes, providing the widest and most user friendly range of testing available on a single module.

NOW, LET'S TALK ABOUT YOUR APPLICATION