Study of fatigue crack growth retardation due to overloads in polymethylmethacrylate

Overload effect on the fatigue crack propagation of PC/ABS alloy

“…This is also supported by the measurement of crack tip stress given in Ref. [27]. It was found that the maximum stress would reduce just after removing the overload.…”

“…They are generally more than 50,000 depending on the value of overload ratio P peak /P max for PC/ABS alloy. Reference to literature [27,28]: P peak /P max value of 1.18 is used in the experiment given in Ref. [27], which gives a retardation of about 60 cycles.…”

“…Reference to literature [27,28]: P peak /P max value of 1.18 is used in the experiment given in Ref. [27], which gives a retardation of about 60 cycles. P peak /P max values of 1.7 and 1.95 are used in the experiment in Ref.…”

“…However, quantitative correlation between the crack increment and the damage state cannot be given yet. Although, the damage accumulation processes were discussed microscopically for some kinds of polymers in literature [1,15,18,27], no proper parameters were used to describe the damage accumulation state at the fatigue crack tip.…”

“…Mai [25] suggested that the crack retardation was due primarily to the formation of crazes thus blunting the crack tip after the overload. Imai et al [27] experimentally studied the retardation of fatigue crack growth due to overload in polymethylmethacrylate (PMMA) by measuring the optical interference fringes from the crack and craze during the fatigue loading with a very low cyclic fatigue frequency, and concluded that the reduction of the stress at the crack tip after removing the overload was one of the main reasons that caused the retardation of crack growth. Yuen et al [28] studied the effects of loading frequency, tensile overload and compressive underload on the fatigue crack propagation of PMMA.…”