Sensitivity Analysis of Ball Punch Geometry for Small Punch Testing

Abstract

The ball punch is an important component for the small punch test. The results of the small punch tests can be affected by the accuracy of the ball punch. Hence, the sensitivity of the ball punch to the specimen deformation should be investigated. Combined with Kachanov-Robatnov constitutive model, finite element simulation is performed for small punch method. Both of the dimensional and shape error for the ball are considered. It shows that the results of small punch tests are sensitive to the ball punch. To solve this problem, a novel small punch beam creep testing method is proposed. A flat punch with semi-circular cross-section and rectangular specimen are adopted. Compared to small punch method, the small punch beam method is non-sensitive to the variation of the punch dimension. To reduce the ball punch effect, it is recommended to evaluate the materials creep properties by the small punch beam method.