The effects of loading frequency, tensile overload and compressive underload on the fatigue crack propagation behaviour of polymethyl methacrylate

摘要

An experimental investigation into the fatigue crack propagation in polymethyl methacrylate (PMMA) was performed to determine the effects of loading frequency, tensile overload and compressive underload in an otherwise constant amplitude loading scenario. It was found that contrary to what was observed for ductile materials, the loading frequency had little or no influence on the fatigue behaviour of PMMA at room temperature in air. A single tensile overload produced a small amount of fatigue crack growth retardation in PMMA. The amount of retardation decreased with higher overload level. In addition, an overload applied at shorter crack length produced more retardation than one applied at longer crack length. Furthermore, there was also more retardation when multiple overloads were applied, compared to a single overload. However, a single compressive overload produced an insignificant amount of fatigue crack growth retardation or acceleration in PMMA that showed no apparent relationship between the underload level and the amount of retardation or acceleration. (C) 2003 Elsevier Ltd. All rights reserved.