Approximate creep analysis for thermoplastic beams and struts

Abstract

Abstract

Creep deformation up to 10⁶ s has been measured for beams subjected to pure and three-point bending and for buckling struts made from polymethyl methacrylate, polyvinyl chloride and polypropylene. Of the analytical methods considered for predicting creep, the most accurate was that in which the isochronous stress-strain curves in tension and compression were used in conjunction with equilibrium and strain displacement equations. However, this involved more computation than the other two methods which simply substituted a secant-modulus value from the isochronous curves (1) at the expected maximum stress and (2) at a limit of 1 per cent strain in the established linear elastic formulae for the components. In (1) there was only slight over-estimation of experimental deformations but in (2) there were quite serious differences, particularly at longer times, and small strains.