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1. Strain rate concentration factor for flat notched specimen to predict impact strength for polymeric materials

Author

Noda, Nao-Aki, Takaki, Rei, Shen, Yunong, Inoue, Akane, Sano, Yoshikazu, Akagi, Daichi, Takase, Yasushi, and Galveza, Pedro

Subjects
Strain rate concentration factor, Dynamic stress, Stress concentration factor, Notched specimen, Polycarbonate, Time-temperature superposition principle, Impact strength
Abstract

In this study, the impact strength of notched specimens of polymeric materials was studied by using high speed tensile test. Focusing on the strain rate at the notch root, the final fracture elongation was expressed in terms of the time-temperature superposition principle. Fracture behavior under various impact speed and temperature can be predicted by mean of the obtained master curves. The validity of the elastic strain rate concentration factor was confirmed through elastic-plastic analyses for both polycarbonate and polydimethylsiloxane copolymerized polycarbonate. It is found that the strain rate concentration factor can be estimated from the stress concentration factor for flat test specimens.

Published
2019

2. Relationship between strain rate concentration factor and stress concentration factor

Author

Department of Mechanical Engineering, Kyushu Institute of Technology, Noda, Nao-Aki, Shen, Yunong, Takaki, Rei, Akagi, Daichi, Ikeda, Tomohiro, Sano, Yoshikazu, Takase, Yasushi, Department of Mechanical Engineering, Kyushu Institute of Technology, Noda, Nao-Aki, Shen, Yunong, Takaki, Rei, Akagi, Daichi, Ikeda, Tomohiro, Sano, Yoshikazu, and Takase, Yasushi

Abstract

type:Journal Article, In this study, the strain rate concentration is considered for high speed tensile test, which is now being recognized as a standard testing method. To evaluate the impact strength of engineering materials under high impact speed, Izod and Charpy tests are unsuitable since they cannot control the impact speeds and therefore do not coincide with the real failure of real products. For smooth specimens, the strain rate can be determined from the tensile speed u/t and specimen length l as ̇smooth =u/tl. For notched specimens, however, the strain rate at the notch root enotch should be analyzed accurately. In this study, therefore, the strain rate concentration factor defined as Kte=enotch/esmooth is studied with varying the notch geometry and specimen length. It is found that the strain concentration factor Kte can be estimated from stress concentration factor Kt.

Published
2019

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