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Earlier issues

Research Article

ScienceAsia 18 (1992): 053-065 |doi: 10.2306/scienceasia1513-1874.1992.18.053





ABSTRACT: PVC pipe is the major application of PVC in Thailand, utilising the mechanical properties and low cost of the material. However, unstable failure at low stresses is a problem that can occur in material that has been approved by standard quality control tests. This paper demonstrates the fracture of PVC pipe under creep deformation. Fracture mechanics concepts have been utilised to assess the stability of artificial cracks in tested samples and thus establishing criteria of failure in PVC and design data for long term predictions. The value of fracture toughness of materials can provide an understanding of the time-dependent failure mechanisms in PVC and can be used to rank the quality of different grades of PVC with respect to the processing conditions, thus providing a means of optimising the manufacturing process. In long term testing at 20oC in air, the fracture toughness of the PVC decreased from a value of 4.7 to 2.0 MPa M over two years, highlighting the marked time-dependence. The experimental data can be described by a simple Power Law, the index value was found to be in excellent agreement with the indices from the modulus and yield stress data.

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Department of Mechanical Engineering, Imperial College of Science and Technology, Exhibition Road, London SW1, U.K.
* present address: Drycolor-Hoechst Ltd., 31 Rama 3 Road, Chongnonsri, Yannawa, Bangkok 10120, Thailand.

Received April 3, 1992