Experimental investigation of the effects of stress rate and stress level on fracture in polystyrene |
| |
Authors: | B L Gregory J Botsis |
| |
Affiliation: | (1) Department of Civil Engineering, Mechanics and Metallurgy, University of Illinois at Chicago, Box 4348, 60680 Chicago, Illinois, USA |
| |
Abstract: | The effects of stress rate and stress level on fatigue crack propagation in compression-moulded single-edge notched specimens (0.25 mm in thickness) of polystyrene are reported. Values of the stress rate
are obtained from the formula
= 2v( max – max),, wherev is the frequency and max, min are the maximum and minimum stresses of the fatigue cycle. Different levels of
are achieved by changing the frequency while keeping max, min at fixed values. The effect of the stress level is investigated by keeping
and min constant and varying max andv. The results show that when the kinetic data are plotted as l/ t against the energy release rateG
1, a relatively small effect of the stress rate is observed. If the same data are treated as l/ N againstG
1, a decrease in l/ N with test frequency is seen. The increase in the level of max results in a higher crack speed. The critical crack length is found to be practically the same for all stress-rate experiments. A decrease in the critical crack length is observed with the increase in stress level. Analysis of craze distribution around the crack path shows that the extent of crazing decreases with the increase in stress rate and increases with the increase in stress level. For all experimental conditions, the ratio of the second moment to the square root of the fourth moment of the histograms of craze density along directions normal to the crack path is found to be constant throughout the slow phase of crack propagation. This result supports a self-similarity hypothesis of damage evolution proposed in the crack layer model. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|