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A Study on the Prediction of Thermally-Induced Residual Stress and Birefringence in Quenched Polystyrene Plate Including Free Volume Theory

자유 체적이론을 고려한 급냉 폴리스티렌판에 발생하는 잔류응력과 복굴절 형성에 관한 연구

  • 김종선 (단국대학교 대학원 기계공학과) ;
  • 윤경환 (단국대학교 기계공학과)
  • Published : 2003.01.01

Abstract

The residual stress and birefringence in injection-molded plastic parts can be divided into the flow-induced residual stress and birefringence produced in flowing stage, the thermally-induced residual stress and birefringence produced in cooling stage. However, the physics involved in the generation of the thermally-induced residual stress and birefringence still remains to be understood. Because polymer experiences viscoelastic history near the glass-transition temperature it is hard to model the entire process. Volume relaxation phenomenon was included to predict the final thermally-induced residual stress and birefringence in quenched plastic parts more accurately. The present study focused on comparing the predicted values far thermally-induced residual stress and birefringence with and without volume relaxation behavior (or free volume theory) under free and constrained quenching conditions. As a result, tile residual stress remained as a tensile stress at the center and as a compressible stress near the surface for the free quenching cases. In contract the residual stress remained as a compressible stress at the center and as a tensile stress near the surface fur the constrained quenching cases. The residual birefringence remained as minus values at the center and as plus values near the surface for the free quenching cases. Interestingly the residual birefringence showed minus values in entire zone for the constrained quenching cases. In the prediction of birefringence only the case including free volume theory showed the correct result for the distribution of birefringence in thickness direction.

Keywords

Residual Stress;Birefrigence;Volume Relaxation;Free Volume Theory;Constrained Quenching;Free Quenching;Injection Molding

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