Elastomers and Composites

The Rubber Society of Korea (한국고무학회)
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A Study on the Stress Measurement in a Plastic Product using Chemical Cracking Method

케미칼 크랙킹 방법을 이용한 플라스틱 제품의 응력측정에 관한 연구

  • Won, S.T. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Kim, T.B. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Lee, S. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Won, J.M. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Cha, K.H. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Lyu, M.Y. (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology)
  • 원시태 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 김태범 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 이실 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 원정민 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 차규호 (서울과학기술대학교 기계시스템디자인공학과) ;
  • 류민영 (서울과학기술대학교 기계시스템디자인공학과)
  • Received : 2012.10.11
  • Accepted : 2012.11.27
  • Published : 2012.12.31
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Abstract

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

사출성형품에서 잔류응력은 성형공정 중 열과 전단응력에 의해 형성된다. 잔류응력을 평가하는 방법은 여러 가지가 있는데, 불투명한 제품에서의 잔류응력은 케미칼 크랙킹 테스트 방법으로 측정 할 수 있다. 이 방법은 시편과 솔벤트가 반응하게 하여 측정하는 방법이다. 크랙은 응력의 크기에 따라 형성되기 때문에 크랙의 크기나 수를 측정하여 응력을 정량적으로 측정한다. 본 연구에서는 케미칼 크랙킹 방법으로 잔류응력을 측정하기 위한 기초자료인 응력과 크랙과의 관계를 규명하기 위한 실험을 수행하였다. 시편을 제작하기 위한 재료는 PC/PBT와 PC/ABS사용하였으며 지그를 이용하여 시편을 변형을 주고 이를 솔벤트에 담궈서 크랙을 유도하였다. 솔벤트는 tetrahydrofuran과 methyl alchol을 이용하여 제조하였다. 두 재료 모두 응력이 어느 정도 이상에서만 크랙이 형성되었으며, 크랙은 응력이 증가함에 따라 대략 2차함수로 증가하였다.

Keywords

References

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