Small punch testing technology is used for quantifying the mechanical properties of bulk materials with greatly reduced volume. However, as the volume decrease, the ductile to brittle transition region of the specimen will move to lower temperature. That means a small punch specimen and a bulk specimen may fracture under different regime. For this case, it’s difficult to obtain fracture toughness of bulk materials from the small punch tests. In this paper, a new approach, which is based on Beremin local approach, to evaluate the Weibull parameters of bulk materials in the ductile to brittle transition region by small punch tests has been proposed.
This paper focuses on the choice of specimen types of small punch test based on Beremin model. Four different types of specimens were tested at ductile to brittle transition region. i.e. ( a ) two kinds of linear notched small punch test specimen (LNSP), (b) two kinds of center holed small punch test specimen (CHSP). All notches of the specimens were machined by electric discharge method, and both sides of the specimens were grinded and polished.
The results showed that 0.5mm CHSP (center holed small punch test specimen) is the best choice for small punch test based on Beremin model according to experimental curves, SEM (scanning electron microscope) analysis, and result of finite element simulation. Furthermore, the cumulative failure probability in ductile-to-brittle transition region by small punch tests was obtained and the method of calculating Weibull parameters (m,σu) is analyzed.
Evaluation of ductile-brittle transition temperature of anisotropy material by small punch test with U-shaped notch
