An investigation into the dynamic indentation response of metallic materials

Abstract

The dynamic indentation response of several ductile metallic materials [Al(111), polycrystalline copper, Fe, and Ti6Al4V] has been investigated using a pendulum-based nano-impact test. The impact process involves repetitive contact cycles until finally coming to rest in the material. Each cycle includes four phases: acceleration, indentation, rebound, and deceleration. The dynamic indentation resistance of the metallic materials scales with their hardness determined under quasi-static conditions. However, through a one-dimensional analytical model, it has been shown that the relationship between the dynamic resistance and the depth during indentation cannot be adequately described using the quadratic relationship commonly found under quasi-static conditions. A power law relationship with a reduced index was proposed and it is found the index is around 1 when the quasi-static and dynamic compliance are similar. A linear relationship between impact resistance and depth has been found during rebound, where the released elastic energy is much higher than that produced by quasi-static nanoindentation.

Dynamic fracture of CrN coating by highly-resolved nano-impact

“…It should be noted, the impact velocity decreased rapidly when the indenter contacted with the surface of the hard coating. This is a little different with our previous study by using a shaper Berkovich indenter to impact the soft materials of Al, Cu, Fe and Ti6Al4V, where the contact velocity changed slowly [34]. This phenomenon may be attributed to high hardness of CrN coating and larger contact area with blunt cube corner.…”

“…7f, a well-developed circumferential cracking was generated on the surface of CrN coatings at 50mN acceleration load, and the parameters are summarized in Table 1. Based upon the analysis of first impact contact cycle, the total impacting energy (Wt) can be divided into four parts as [44]:…”

High-velocity micro-projectile impact testing

“…The dynamic impact hardness of metals has mainly been measured over the past two decades through impact indentation using pendulum-based dynamic micro-indenters (PDMI) (143). PDMI has allowed fundamental studies on materials properties, despite experimental calibration complications and debate over hardness calculations procedure (140,144,145). For example, Trelewicz and Schuh demonstrated the breakdown of the Hall-Petch strength scaling in nanocrystalline Ni-W alloys and subsequent emergence of an inverse Hall-Petch weakening regime (146).…”

A new method for the dynamic deformation characterization of thin-film stacked structures

“…[6] Investigators have recently developed the nano-impact indentation method to study micro-and nanoscale specimens at high strain rates. [7][8][9] The strain rates swept rapidly from a high value (10 4 -10 5 s -1 ) at the moment of contact to zero at the maximum penetration depth, where the indenter stopped and bounced back. [10] However, since the strain rates cannot be controlled or monitored in the impact process, the varied stain rates corresponding to the deformation measured in this method were not defined.…”