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AR Monthly Archives: May 2020
Improve Mining Procedures With Microindendation
MICROINDENTATION RESEARCH AND QUALITY CONTROL
Rock mechanics is the study of the mechanical behavior of rock masses and is applied in mining, drilling, reservoir production, and civil construction industries. Advanced instrumentation with precise measurement of mechanical properties allows for part and procedure improvement within these industries. Successful quality control procedures are ensured by understanding rock mechanics at the micro scale.
Microindentation is a crucial tool used for rock mechanics related studies. These techniques advance excavation techniques by providing further understanding of rock mass properties. Microindentation is used to improve drill heads which improve mining procedures. Microindentation has been used to study chalk and powder formation from minerals. Microindentation studies can include hardness, Young’s modulus, creep, stress-strain, fracture toughness, and compression with a single instrument.
MEASUREMENT OBJECTIVE
In this application the Nanovea mechanical tester measures the Vickers hardness (Hv), Young’s modulus, and fracture toughness of a mineral rock sample. The rock is made up of biotite, feldspar and quartz which form the standard granite composite. Each is tested separately.
RESULTS AND DISCUSSION
This section includes a summary table that compares the main numerical results for the different samples, followed by the full result listings, including each indentation performed, accompanied by micrographs of the indentation, when available. These full results present the measured values of Hardness and Young’s modulus as the penetration depth (Δd) with their averages and standard deviations. It should be considered that large variation in the results can occur in the case that the surface roughness is in the same size range as the indentation.
Summary table of main numerical results for Hardness and Fracture Toughness
CONCLUSION
The Nanovea mechanical tester demonstrates reproducibility and precise indentation results on the hard surface of mineral rock. Hardness and Young’s modulus of each material forming the granite was measured directly from depth versus load curves. The rough surface meant testing at higher loads that may have caused micro cracking. Micro cracking would explain some of the variations seen in measurements. Cracks were not perceivable through standard microscopy observation because of a rough sample surface. Therefore, it is not possible to calculate traditional fracture toughness numbers that requires cracks length measurements. Instead, we used the system to detect initiation of cracks through the dislocations in the depth versus load curves while increasing loads.
Fracture threshold loads were reported at loads where failures occurred. Unlike traditional fracture toughness tests that simply measure crack length, a load is obtained at which threshold fracture starts. Additionally, the controlled and closely monitored environment allows the measurement of hardness to use as a quantitative value for comparing a variety of samples.
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In-line Roughness Inspection
Instant Error Detection With In-Line Profilers
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IMPORTANCE OF NON-CONTACT PROFILER FOR IN-LINE ROUGHNESS INSPECTION
Surface defects derive from materials processing and product manufacturing. In-line surface quality inspection ensures the tightest quality control of the end products. The Nanovea 3D Non-Contact Profilometers utilize chromatic confocal technology with a unique capability to determine the roughness of a sample with-out contact. Multiple profiler sensors can be installed to monitor the roughness and texture of different areas of the product at the same time. The roughness threshold calculated in real-time by the analysis software serves as a fast and reliable pass/fail tool.
MEASUREMENT OBJECTIVE
In this study, the Nanovea roughness inspection conveyor system equipped with a point sensor is used to inspect the surface roughness of the acrylic and sandpaper samples. We showcase the capacity of Nanovea non-contact profilometer in providing fast and reliable in-line roughness inspection in a production line in real-time.
RESULTS AND DISCUSSION
The conveyor profilometer system can operate in two modes, namely Trigger Mode and Continuous Mode. As illustrated in Figure 2, the surface roughness of the samples are measured when they are passing under the optical profiler heads under the Trigger Mode. In comparison, Continuous Mode provides non-stop measurement of the surface roughness on the continuous sample, such as metal sheet and fabric. Multiple optical profiler sensors can be installed to monitor and record the roughness of different sample areas.
During the real-time roughness inspection measurement, the pass and fail alerts are displayed on the software windows as shown in Figure 4 and Figure 5. When the roughness value is within the given thresholds, the measured roughness is highlighted in green color. However, the highlight turns red when the measured surface roughness is out of the range of the set threshold values. This provides a tool for the user to determine the quality of a product’s surface finish.
In the following sections, two types of samples, e.g. Acrylic and Sandpaper are used to demonstrate the Trigger and Continuous Modes of the Inspection system.
Trigger Mode: Surface inspection of the Acrylic Sample
A series of Acrylic samples are aligned on the conveyor belt and move under the optical profiler head as shown in Figure 1. The false color view in Figure 6 shows the change of the surface height. Some of the mirror-like finished Acrylic samples had been sanded to create a rough surface texture as shown in Figure 6b.
As the Acrylic samples move at a constant speed under the optical profiler head, the surface profile is measured as shown in Figure 7 and Figure 8. The roughness value of the measured profile is calculated at the same time and compared to the threshold values. The red fail alert is launched when the roughness value is over the set threshold, allowing users to immediately detect and locate the defective product on the production line.
Continuous Mode: Surface Inspection of the sandpaper sample
Surface Height Map, Roughness Distribution Map, and Pass / Fail Roughness Threshold Map of the sandpaper sample surface as shown in Figure 9. The sandpaper sample has a couple of higher peaks in the used part as shown in the surface height map. The different colors in the pallet of Figure 9C represent the roughness value of the local surface. The Roughness Map exhibits a homogeneous roughness in the intact area of the sandpaper sample, while the used area is highlighted in dark blue color, indicating the reduced roughness value in this region. A Pass/Fail roughness threshold can be set up to locate such regions as shown in Figure 9D.
As the sandpaper continuously passes under the in-line profiler sensor, the real-time local roughness value is calculated and recorded as plotted in Figure 10. The pass/fail alerts are displayed on the software screen based on the set roughness threshold values, serving as a fast and reliable tool for quality control. The product surface quality in the production line is inspected in situ to discover defective areas in time.
CONCLUSION
In this application, we have shown the Nanovea Conveyor Profilometer equipped with an optical non-contact profiler sensor works as a reliable in-line quality control tool effectively and efficiently.
The inspection system can be installed in the production line to monitor the surface quality of the products in situ. The roughness threshold works as a dependable criteria to determine the surface quality of the products, allowing users to notice the defective products in time. Two inspection modes, namely Trigger Mode and Continuous Mode, are provided to meet the requirement for inspection on different types of products.
The data shown here represent only a portion of the calculations available in the analysis software. Nanovea Profilometers measure virtually any surface in fields including Semiconductor, Microelectronics, Solar, Fiber, Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.
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Block-On-Ring Wear Test
IMPORTANCE OF BLOCK-ON-RING WEAR EVALUATION
Sliding wear is the progressive loss of material that results from two materials sliding against each other at the contact area under load. It occurs inevitably in a wide variety of industries where machines and engines are in operation, including automotive, aerospace, oil & gas and many others. Such sliding motion causes serious mechanical wear and material transfer at the surface, which may lead to reduced production efficiency, machine performance or even damage to the machine.
Sliding wear often involves complex wear mechanisms taking place at the contact surface, such as adhesion wear, two-body abrasion, three-body abrasion and fatigue wear. The wear behavior of materials is significantly influenced by the work environment, such as normal loading, speed, corrosion and lubrication. A versatile tribometer that can simulate the different realistic work conditions will be ideal for wear evaluation.
Block-on-Ring (ASTM G77) test is a widely used technique that evaluates the sliding wear behaviors of materials in different simulated conditions, allows reliable ranking of material couples for specific tribological applications.
Block-on-Ring (ASTM G77) test is a widely used technique that evaluates the sliding wear behaviors of materials in different simulated conditions, allows reliable ranking of material couples for specific tribological applications.
MEASUREMENT OBJECTIVE
In this application, the Nanovea Mechanical Tester measures the YS and UTS of stainless steel SS304 and aluminum Al6061 metal alloy samples. The samples were chosen for their commonly recognized YS and UTS values showing the reliability of Nanovea’s indentation methods.
The sliding wear behavior of an H-30 block on an S-10 ring was evaluated by Nanovea’s tribometer using the Block-on-Ring module. The H-30 block is made of 01 tool steel of 30HRC hardness, while the S-10 ring is steel type 4620 of surface hardness 58 to 63 HRC and ring diameter of ~34.98 mm. Block-on-Ring tests were performed in dry and lubricated environments to investigate the effect on wear behavior. Lubrication tests were performed in USP heavy mineral oil. The wear track was examined using Nanovea’s 3D non-contact profilometer. Test parameters are summarized in Table 1. The wear rate (K), was evaluated using the formula K=V/(F×s), where V is the worn volume, F is the normal load, s is the sliding distance.
RESULTS AND DISCUSSION
Figure 2 compares the coefficient of friction (COF) of the Block-on-Ring tests in dry and lubricated environments. The block has significantly more friction in a dry environment than a lubricated environment. COF
fluctuates during the run-in period in the first 50-revolution and reaches a constant COF of ~0.8 for the rest of the 200-revolution wear test. In comparison, the Block-on-Ring test performed in the USP heavy mineral oil lubrication exhibits constant low COF of 0.09 throughout the 500,000-revolution wear test. The lubricant significantly reduces the COF between the surfaces by ~90 times.
Figures 3 and 4 show the optical images and cross-section 2D profiles of the wear scars on the blocks after dry and lubricated wear tests. The wear track volumes and wear rates are listed in Table 2. The steel block after the dry wear test at a lower rotational speed of 72 rpm for 200 revolutions exhibits a large wear scar volume of 9.45 mm˙. In comparison, the wear test carried out at a higher speed of 197 rpm for 500,000 revolutions in the mineral oil lubricant creates a substantially smaller wear track volume of 0.03 mm˙.
The images in ÿgure 3 show severe wear takes place during tests in the dry conditions compared to the mild wear from the lubricated wear test. High heat and intense vibrations generated during the dry wear test promotes oxidation of metallic debris resulting in severe three-body abrasion. In the lubricated test the mineral oil reduces friction and cools the contact face as well as transporting abrasive debris created during wear away. This leads to signiÿcant reduction of wear rate by a factor of ~8×10ˆ. Such a substantial di˛erence in wear resistance in di˛erent environments shows the importance of proper sliding wear simulation in realistic service conditions.
Wear behavior can change drastically when small changes in test conditions are introduced. The versatility of Nanovea’s tribometer allows wear measurement in high temperature, lubrication, and tribocorrosion conditions. The accurate speed and position control by the advanced motor enables wear tests to be performed at speeds ranging from 0.001 to 5000 rpm, making it an ideal tool for research/testing labs to investigate the wear in di˛erent tribological conditions.
The surface condition of the samples was examined by Nanovea’s non-contact optical proÿlometer. Figure 5 shows the surface morphology of the rings after the wear tests. The cylinder form is removed to better present the surface morphology and roughness created by the sliding wear process. Signiÿcant surface roughening took place due to the three-body abrasion process during the dry wear test of 200 revolutions. The block and ring after the dry wear test exhibit a roughness Ra of 14.1 and 18.1 µm, respectively, compared to 5.7 and 9.1 µm for the long-term 500,000 – revolution lubricated wear test at a higher speed. This test demonstrates the importance of proper lubrication of piston ring-cylinder contact. Severe wear quickly damages the contact surface without lubrication and leads to irreversible deterioration of the service quality and even breakage of the engine.
CONCLUSION
In this study we showcase how Nanovea’s Tribometer is used to evaluate the sliding wear behavior of a steel metal couple using the Block-on-Ring module following the ASTM G77 Standard. The lubricant plays a critical role in the wear properties of the material couple. The mineral oil reduces the wear rate of the H-30 block by a factor of ~8×10ˆ and the COF by ~90 times. The versatility of Nanovea’s Tribometer makes it an ideal tool for measuring wear behavior under various lubrication, high temperature, and tribocorrosion conditions.
Nanovea’s Tribometer o˛ers 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 tribological properties of thin or thick, soft, or hard coatings, ÿlms, and substrates.
