Article
  • Residual Stresses in Plastic Pipes and Fittings Ⅳ.Effect of Annealing on Deformation and Fracture Properties
  • Choi SW, Broutman LJ
  • 플라스틱 파이프의 잔류응력에 관한 연구; Ⅳ. 아닐링에 따른 변형 및 파괴성질의 변화
  • 최선웅, Broutman LJ
Abstract
The effect of thermal annealing on deformation and fracture behavior of residually stressed polyethylene pipes was investigated. Thermal annealing of she pipes simultaneously caused a change in material density and the relaxation of residual stresses. The residual stress relaxation was more sensitive to annealing temperature than annealing time. Annealing at 120℃ for 1 hour removed the residual stresses effectively. While the large deformation properties such as the spilt ring tensile yield strength and the pipe burst strength were affected primarily by the change of crystallinity, the fracture related properties were predominantly affected by the residual stress relaxation. Sustained long term strength and slow crack growth were such properties. It was demonstrated that both of these properties were sensitive to residual stress change and that 100% increase in fracture times was observed as a result of tensile residual stress relaxation. Although the environmental stress cracking resistance (ESCR) test was also conducted to measure the relative clacking behavior the test was not suitable for determining the residual stress effect, as large deformation applied on rung sample effectively removed title residual stresses.

잔류응력 상태의 폴리에틸렌 파이프를 아닐링하여 이에 따른 변형 및 파괴거동을 고찰하였다. 일반적으로 아닐링은 잔류응력을 완화 또는 제거함과 동시에 폴리에틸렌의 밀도를 증가시키므로 이들 각각이 큰 변형 및 파괴 거동에 미치는 영향을 split 링 인장, 단시간 파이프 파열, 환경응력균열, 긴 시간 파이프 압력-파괴 및 정적균열 파괴실험을 통해 분리하였다. 잔류응력의 완화는 아닐링 시간보다, 아닐링 온도에 더욱 민감하였고, 120℃에서 1시간의 아닐링은 파이프내의 잔류응력을 완전히 제거하였다. 아닐링은 큰 변형 성질인 인장강도 및 단시간 파열강도를 아닐링전과 비해 각각 약 20% 증가시켰고, 파괴성질인 긴 시간 압력-파괴 강도와 정적균열 성장속도를 각각 약 100% 증가시켰다. 이 결과들로부커 큰 변형거동은 밀도, 그리고 파괴거동은 잔류응력상태에 의존함을 알 수 있었고, 환경응력균열 실험은 큰 변형이 가해진 상태에서 진행되는데 이로 인해 잔류응력이 완화 또는 제거되므로 잔류응력에 의한 파괴거동을 가리는데 있어 효과적인 방법이 될 수 없었다.

Keywords: plastic pipes; residual stress and distribution; annealing; large deformation behavior; fracture behavior

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  • Polymer(Korea) 폴리머
  • Frequency : Bimonthly(odd)
    ISSN 0379-153X(Print)
    ISSN 2234-8077(Online)
    Abbr. Polym. Korea
  • 2022 Impact Factor : 0.4
  • Indexed in SCIE

This Article

  • 1997; 21(1): 93-102

    Published online Jan 25, 1997