On determination of elastic modulus and indentation hardness by instrumented spherical indentation: influence of surface roughness and correction method

Abstract

Although, surface roughness can influence the determination of elastic moduli and indentation hardness to some extent by instrumented spherical indentation test, limited work has been done to quantitatively reveal and minimize these influences. In the present work, through a large number of finite element (FE) simulations and analyses, we clarified the evolution trend of determined elastic moduli and indentation hardness corresponding to different normalized indentation depths (h/R) and normalized roughness (Sq/R). On this basis, an area correction method was proposed to improve the measurement accuracy in the elastic moduli and indentation hardness. The FE results show that, with the newly proposed correction method, the maximum relative error in determined elastic moduli is reduced from about ±7% to ±2%, and that in the determined indentation hardness is reduced from about ±13% to ±5%, when Sq/R ≤ 2.2 × 10-3 and h/R = 5%. Applications were then illustrated on four typical metallic materials (i.e., AA 7075, AA 2014, steel 316L, and copper T2). The experimental results demonstrate that the proposed correction method is able to mitigate the effects of surface roughness on the determination of elastic moduli and indentation hardness to obtain more correct results.

Estimation of Mechanical Properties of Aluminum Alloy Based on Indentation Curve and Projection Area of Contact Zone

“…This opened up new possibilities in the field of indentation techniques. With the continuous advancement of technology, there is a growing demand for understanding the mechanical properties of materials, such as hardness [3][4][5][6][7], Young's modulus [8][9][10][11][12], residual stress [13][14][15][16][17], and plasticity [18][19][20][21][22]. These studies have demonstrated that the mechanical properties of materials can be extracted by comparing the load-displacement curves obtained from finite element simulations with those obtained from experimental measurements when the data are in good agreement.…”