Papers by Keyword: IIT

Abstract: The instrumented indentation technique (IIT) is a powerful method for evaluating mechanical properties of materials such as elastic modulus, tensile strength, fracture toughness and residual stress. Especially, IIT is a promising alternative to conventional methods of residual stress measurement such as hole drilling, saw cutting, X-ray/neutron diffraction, and ultrasonic methods because of its various advantages of nondestructive specimen preparation, easy process, characterization of material properties on local scales and measurement of in-service structures. Evaluation of residual stress using IIT is based on the key concepts that the deviatoric-stress part of the residual stress affects the indentation load-depth curve and that the quantitative residual stress in a target region can be evaluated by analyzing the difference between the residual stress-induced indentation curve and residual stress-free curve. To verify the applicability of the suggested technique, indentation tests were performed on the welded zone.

Abstract: The Johnson-Kendall-Roberts (JKR) theory was combined with the instrumented indentation technique to evaluate the work of adhesion and modulus of an elastomeric polymer. An indentation test was used to obtain the load-displacement data for contacts between a diamond indenter and poly(dimethylsiloxane), PDMS. The JKR theory, modified to avoid the effect of ambiguous contact radius and depth for nanocontact, was applied to take into account surface adhesion and viscoelastic effects of the compliant polymer. Future work will include experimental verification that polymer stiffness in JKR contact is a time-dependent function.