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AR Blog Archives
Progressive Tribology Mapping of Flooring
The traffic of human movement, movement of furniture, and other daily activities imposes constant degradation onto flooring. Flooring, usually comprised of wood, ceramic, or stone, must be able to handle the wear and tear they are designed for, whether residential or commercial applications. For this reason, most flooring have a layer that is supposed to be resistant to wear called a wear layer. The thickness and durability of the wear layer will depend on the type of flooring and the amount of foot traffic it will be receiving. Since flooring can have multiple layers (e.g. UV-coating, wear layer, decorative layer, glaze, and etc.), the wear rate through each layer can be very different. With Nanovea T2000 Tribometer with a 3D Non-Contact Line Sensor attachment, the progression of wear on a stone and wood flooring is closely observed.
Adhesiveness of Tape via Nanoindentation
The effectiveness of tape is determined by its cohesive and adhesive abilities. Cohesion is defined as the tape’s internal strength while adhesion is the tape’s ability to bond to its interacting surface. The adhesion of tape is influenced by numerous factors, such as exerted pressure, surface energy, molecular forces, and surface texture [1]. To quantify adhesion of tapes, nanoindentation with the Nanovea Mechanical Tester’s Nano Module can be conducted to measure the work required to separate the indenter from the tape.
Fatigue Testing of Wire with Electrical Conductance Apparatus
Electrical wires are the most common form of interconnects between electrical devices. Wires are usually made of copper (and sometimes aluminum) due to copper’s ability to conduct electricity very well, ability to bend, and its cheap cost. Outside of material, wires can also be assembled in different ways. Wires can come be obtained in different sizes, usually denoted by gauges. As the wire diameter increases, the wire gauge decreases. Longevity of the wire will change with wire gauge. The difference in longevity can be compared by conducting a reciprocating linear test with the Nanovea Tribometer to simulate fatigue.
Fatigue Testing of Wire with Electrical Conductance Apparatus
Scratch Testing on Multi-Layered Thin Film
Coatings used extensively throughout multiple industries to preserve the underlying layers, to create electronic devices, or to improve surface properties of materials. Due to their numerous uses coatings are extensively studied, but their mechanical properties can be difficult to understand. Failure of coatings can occur in the micro/nanometer range from surface-atmosphere interaction, cohesive failure, and poor substrate-interface adhesion. A consistent method to test for coating failures is scratch testing. By applying a progressively increasing load, cohesive (e.g. cracking) and adhesive (e.g. delamination) failures of coatings can be quantitatively compared.
Cyclical Nanoindentation Stress-Strain Measurement
Cyclical Nanoindentation Stress-Strain Measurement
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Importance of Nanoindentation
Continuous stiffness measurements (CSM) obtained by nanoindentation reveals the stress-strain relationship of materials with minimally invasive methods. Unlike traditional tensile testing methods, nanoindentation provides stress-strain data at the nanoscale without the need of a large instrument. The stress-strain curve provides crucial information on the threshold between elastic and plastic behavior as the sample is subject to increasing loads. CSM gives the capability to determine the yield stress of a material without dangerous equipment.
Nanoindentation provides a reliable and user-friendly method to quickly investigate stress-strain data. Furthermore, measuring stress-strain behavior on the nanoscale makes it possible to study important properties on small coatings and particles in materials as they get more advanced. Nanoindentation provides information on elastic limit and yield strength in addition to hardness, elastic modulus, creep, fracture toughness, etc. making it a versatile metrology instrument.
The stress-strain data provided by nanoindentation in this study identifies the elastic limit of the material while only going 1.2 microns into the surface. We use CSM to determine how mechanical properties of materials develop as an indenter travels deeper into the surface. This is especially useful in thin film applications where properties can be depth dependent. Nanoindentation is a minimally invasive method of confirming material properties in test samples.
The CSM test is useful in measuring material properties versus depth. Cyclical tests can be performed at constant loads to determine more complex material properties. This can be useful to study fatigue or eliminate the effect of porosity to obtain true elastic modulus.
Measurement Objective
In this application, the Nanovea mechanical tester uses CSM to study hardness and elastic modulus versus depth and stress-strain data on a standard steel sample. Steel was chosen for its commonly recognized characteristics to display the control and accuracy of the nanoscale stress-strain data. A spherical tip with a 5-micron radius was used to reach high enough stresses beyond the elastic limit for steel.
Test Conditions & Procedures
The following indentation parameters were used:
Results:
Increase in load during oscillations provide the following depth versus load curve. Over 100 oscillations were conducted during loading to find the stress-strain data as the indenter penetrates the material.
We determined stress and strain from the information obtained at each cycle. The maximum load and depth at each cycle allows us to calculate the maximum stress applied in each cycle to the material. Strain is calculated from the residual depth at each cycle from the partial unloading. This allows us to calculate the radius of the residual imprint by dividing the radius of the tip to give the strain factor. Plotting stress versus strain for the material shows the elastic and plastic zones with the corresponding elastic limit stress. Our tests determined the transition between the elastic and plastic zones of the material to be around 0.076 strain with an elastic limit of 1.45 GPa.
Each cycle acts as a single indent so as we increase load, we run tests at various controlled depths in the steel. So, hardness and elastic modulus versus depth can be plotted directly from the data obtained for each cycle.
As the indenter travels into the material we see hardness increase and elastic modulus decrease.
Conclusion
We have shown the Nanovea mechanical tester provides reliable stress-strain data. Using a spherical tip with CSM indentation allows for material property measurement under increased stress. Load and indenter radius can be changed to test various materials at controlled depths. Nanovea mechanical testers provide these indentation tests from the sub mN range to 400N.
