Abstract
Charpy impact toughness values show large statistical scatter, particularly in the ductile-to-brittle transition temperature (DBTT) range. Although the statistical distribution of Charpy absorbed energy has not been clarified, critical values of the stress intensity factor, J-integral and crack-tip opening displacement (CTOD) at brittle fracture generally show the Weibull distribution with two or three parameters. This study proposes a brittle fracture model, based on the weakest link theory, for evaluating the scatter in Charpy absorbed energy KV. The numerical results show that the amplitude of the opening stress fields ahead of the V-notch at varying amounts of KV are uniquely characterized as the square of the applied load. With these numerical results, the Weibull shape parameter of the statistical distribution of KV is almost equal to 2. The proposed statistical model is verified through experimental results. It is found that the statistical distribution of KV is characterized by a two-parameter Weibull distribution with the shape parameter of 2 under the condition of pure brittle fracture.
Highlights
The Charpy V-notch impact test is widely used for evaluating material toughness
It is well known that Charpy impact toughness values show large scatter, in the ductile-to-brittle transition temperature (DBTT) range
The shape parameter value for the KV distribution is almost equal to 2 under the condition of pure brittle fracture. This finding leads to the statistical evaluation of the material toughness
Summary
The Charpy V-notch impact test is widely used for evaluating material toughness. A brittle fracture model is proposed, based on the weakest link theory, for evaluating the statistical scatter in KV. The theoretical value for the Weibull slope in the case of the Charpy V-notch impact test is evaluated with the proposed model. The validity of this statistical model is discussed according to the experimental results obtained for structural steels and welds in other studies [2, 6]. Under the impact loading condition, high-speed straining generates heat adiabatically It was assumed in the FE analysis that 90% of the plastic work is transferred to heat.
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