A New Dynamic Indentation Tool for Rapid Mechanical Properties Profiling and Mapping

Surface measurements are used extensively in many industries and research disciplines to characterize a material's mechanical properties and strength without the need for traditional, time consuming, and expensive laboratory tests, or for large volumes of sample material. This paper briefly reviews indentation methodologies for index and physical properties measurements and then focuses on the implementation of a method of using the measured force versus time of an impact to infer mechanical properties. By relying only on the measurement of force versus time, the method greatly simplifies the measurement process and thus allows for applications requiring rapid and automated measurements of both elastic stiffness and/or inelastic deformation during indentation. The indenter tip geometry, free-fall height, and the mechanical model used to describe the interaction of the contact between the indenter and material are investigated through the analysis of measurements performed on a wide variety of materials including plastics, rocks, ceramics, and asphalt. It is shown that using a spherical tip the method can be used to provide measurements of the elastic stiffness by fitting the measured force versus time curves to predictions of quasi static elastic theory. We then show how conversion of the force-time data into force-displacement curves realizes a direct connection with the already established static indentation interpretation framework. Through the use of force-displacement interpretation, the method becomes applicable to arbitrary tip geometries and inelastic mechanical properties. Through illustrative examples, we show how the force-displacement data from an impact can be interrogated for critical parameters such as loading and unloading characteristics, and maximum, residual, and elastic displacement.