基于循环载荷试验的聚乙烯管材寿命预测研究

Lifetime prediction of polyethylene pipe based on cyclic load

采用循环载荷裂纹圆棒(CRB)试验,测试了A~C 3种聚乙烯(PE)材料在载荷比(R)分别为0.1、0.3和0.5时,缺口圆柱棒试样的裂纹扩展速率(da/dt)与应强度因子(KI)的对应关系。通过结合聚合物材料线弹性断裂力学理论,外推至R=1(静载)条件,得到含缺陷PE管材的使用寿命(tf),并与全缺口蠕变试验(FNCT)评价结果进行了对比分析。结果表明,当A~C 3种PE管材内壁存在a_(ini)=0.4 mm的初始裂纹缺陷时,CRB试验外推得的管材的tf分别为44、53和65年;FNCT外推结果分别为53、59和79年;CRB和FNCT的寿命预测结果具有较好的正相关性,寿命预测结果偏差较小,试验结果证实了该方法的有效性。

In this paper,a cyclic loading circular bar(CRB)test was conducted to measure the corresponding relationship between the crack growth rate da/dt and stress factor KIof three types of PE materials A,B and C at loading ratios of R=0.1,0.3 and 0.5,respectively.Through using the theory of linear elastic fracture mechanics of polymer materials in the condition by extrapolating to R=1(static load),the failure time tfof PE pipes with defects was obtained.The results were compared with those obtained form full notch creep test(FNCT).When there was an initial crack defect at a_(ini)=0.4 mm on the inner wall of the three PE pipes,the failure lifetimes of extrapolated tubes obtained from the CRB test were 44,53 and 65 years for the PE pipe A,B and C,respectively.The extrapolating results of FNCT were 53,59and 79 years for the PE pipe A,B and C,respectively.The test results indicated that the lifetime prediction results of CRB and FNCT had a good positive correlation,and their deviation was small.The experimental results confirmed the availability of the method.