On the Influence of Clamping Force and Contact Friction in Small Punch Test

Small punch (SP) test is a relatively new method used to predict the mechanical properties of the materials at cryogenic, room, or even elevated temperatures. Accurate modelling of small punch tests, considering several factors, leads to a better understanding of how the materials behave under these load conditions. This paper discusses the influence of clamping force and friction in the contact surface between puncher and specimen on force–displacement behaviour in Grade 91 steel subjected to a small punch load at room temperature. The small punch test is modelled in Abaqus finite element (FE) software as an axis-symmetric model, and the friction coefficient between puncher and specimen is varied between 0 (frictionless) and 0.7. In the range of 500–5000 N, the effect of clamping force on the force–displacement curve is insignificant. In contrast, it is observed that the friction force affects the maximum punch load up to μ = 0.5. Beyond this value, the maximum load is found to be insignificantly changed. Furthermore, the FE results show that the maximum von-Mises stress occurs at the center of the specimen when the contact between die and specimen is frictionless. As the μ increases, the maximum stress location shifts at the distance offset from the center of the specimen and closer to the puncher edge. In conclusion, the friction between puncher and specimen appears to influence the force–displacement behaviour during the small punch test. Attempts made in the future to model the SP test need to accurately calibrate the friction coefficient value.