Indentation

About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.

High temperature nanoscale mechanical property measurements

Abstract: A depth sensing indentation instrument widely used for measuring the small scale mechanical properties of thin films and surfaces has been modified for operation at elevated temperatures. The essential feature permitting this development is the vertical orientation of the specimen, which allows the heated zone to be placed above the high sensitivity displacement transducer. In the present work, small scale hardness and elastic modulus measurements were performed on glass, gold, and single crystal silicon at room temperature and 200°C. The results show that at 200°C the hardness and elastic modulus of soda lime glass and gold are lower than at room temperature, as anticipated. In contrast, indentation testing of Si(100) at 200°C produced a similar hardness value to that obtained at room temperature, although the modulus was again reduced, from 140·3 to 66·0 GPa. In addition, the well known ‘pop out’ event, which is observed during unloading of a silicon indentation at room temperature, disappeared ...

Young's modulus measurements on ultra-thin coatings

Abstract: The determination of the mechanical properties of ultra-thin coatings has become more and more important because of the increasing number of applications using such films. However, an accurate mechanical testing of coatings with a thickness down to some nanometers is still a challenge, despite the improvements of existing measurement techniques. Nanoindentation is an often used mechanical nanoprobe. Using the conventional test method with a sharp Berkovich indenter, the problem of the influence of the substrate on the results arises with decreasing film thickness. Therefore, it is nearly impossible to measure the modulus of films with a thickness less than 100–200 nm. The problem can be overcome by using spherical indenters in combination with an analytical solution for the Hertzian contact of coated systems. It allows a separation of film and substrate properties from the load–displacement curve of the compound. Indentation measurements were done at a 44 nm TiN film and at diamondlike carbon coatings in the thickness range between 4.3 nm and 125 nm on Si substrates. Several corrections were applied to obtain wholly elastic force–displacement curves with high accuracy. It is shown in more detail how zero point and thermal drift corrections are used to obtain statistical depth errors below 0.2 nm. Laser-acoustic measurements based on ultrasonic surface waves were chosen as a second method, which also measures the Young’s modulus in this thickness range. Although the indentation technique is a local probe and the laser-acoustic technique gives an integrated value for a surface range of some millimeters, the results agree well for the investigated samples. In contrast, it was impossible to get the correct Young’s modulus results by conventional indentation measurements with Berkovich indenter, even for ultra-low loads.

Experimental Measurement of Residual Stress Field around Sharp Indentation in Glass

Abstract: A new technique is developed to measure the residual stress field around Vickers indentations in glass and ceramics. This technique uses a small indentation as a microprobe to measure the residual stress at a specific position near a large indentation. The approach is based on the observation that the crack lengths of the small indentation are changed under the influence of the residual stress field created by the large indentation. A simple fracture mechanics model is derived to calculate the residual stress from the measurement of the changes of the crack lengths of the small indentation. The results show that the residual stress around Vickers indentations is a nonequal biaxial field; both tensile and compressive stresses exist around a sharp indentation and decrease as the distance from the center of indentation increases. This technique can be easily extended to many other cases of residual stress in ceramics and composites.