Indentation technique for estimating the fracture toughness of 7050 aluminum alloy with the Berkovich indenter

A nondestructive and convenient technique was proposed to estimate the fracture toughness for 7050 aluminum alloy using an indentation system equipped with a Berkovich indenter based on the continuum damage mechanics. With the increase of indentation loads P, the material damage was exhibited on the effective elastic modulus E^-. It was found that natural logarithms of the effective elastic modulus E^- versus them of plastic indentation depth h_p approximated great linear relationship, the critical effective elastic modulus Ec* can be obtained based on the basic concepts of continuum damage mechanics using the elongation δ of the standard uniaxial tensile tests, subsequently the critical plastic indentation depth hp* can be obtained using the extrapolation method. Consequently the critical indentation energy per unit area γ^- can be obtained based on the quadratic polynomial fitting between the indentation load P and the plastic indentation depth h_p, and then the value of the fracture toughness K_c can be obtained. Both indentation tests and conventional compact tensile tests were conducted to verify the agreement of the results.