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首页> 外文期刊>Journal of Materials Science >A fatigue-to-creep correlation in air for application to environmental stress cracking of polyethylene
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A fatigue-to-creep correlation in air for application to environmental stress cracking of polyethylene

机译：空气中疲劳与蠕变的相关性，用于聚乙烯的环境应力开裂

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The present study was undertaken to determine whether the correlation between fatigue and creep established for polyethylene in air could be extended to environmental liquids. Fatigue and creep tests under various conditions of stress, R-ratio (defined as the ratio of minimum to maximum load in the fatigue loading cycle), and frequency were performed in air and in Igepal solutions. The load-displacement curves indicated that stepwise fatigue crack growth in air was preserved in Igepal solutions at 50 degrees C, the temperature specified for the ASTM standard. In air, systematically decreasing the dynamic component of fatigue loading by increasing the R-ratio to R = 1 (creep) steadily increased the lifetime. In contrast, the lifetime in Igepal was affected to a much smaller extent. The fatigue to creep correlation in air was previously established primarily for tests at 21 degrees C. Before testing the correlation in Igepal, it was necessary to establish the correlation in air at 50 degrees C. Microscopic methods were used to verify stepwise crack growth by the sequential formation and breakdown of a craze zone, and to confirm the fatigue to creep correlation. The crack growth rate under various loading conditions was related to the maximum stress and R-ratio by a power law relationship. Alternatively, a strain rate approach, which considered a creep contribution and a fatigue acceleration factor that depended only on strain rate, reliably correlated fatigue and creep in air at 50 degrees C under most loading conditions of stress, R-ratio and frequency. The exceptions were fatigue loading under conditions of R = 0.1 and frequency less than 1 Hz. It was speculated that compression and bending of highly extended craze fibrils were responsible for unexpectedly high crack speeds.
机译：进行本研究以确定在空气中聚乙烯所建立的疲劳与蠕变之间的关系是否可以扩展到环境液体。在空气和Igepal解决方案中，在各种应力​​，R比率（定义为疲劳载荷循环中最小载荷与最大载荷的比率）和频率的各种条件下进行了疲劳和蠕变测试。载荷-位移曲线表明，在Igepal溶液中，在50摄氏度（ASTM标准规定的温度）下，空气中的疲劳裂纹逐步生长。在空气中，通过将R比率提高到R = 1（蠕变）来系统地降低疲劳载荷的动态分量，从而稳定地增加了使用寿命。相反，伊格帕尔（Igepal）的生命受到的影响要小得多。先前主要在21°C的测试中建立了空气中疲劳到蠕变的相关性。在Igepal中测试该相关性之前，有必要在50°C的空气中建立该相关性。依次形成和破坏裂纹区域，并确认疲劳与蠕变的相关性。通过幂律关系，各种载荷条件下的裂纹扩展速率与最大应力和R-比有关。可替代地，考虑了蠕变贡献和仅取决于应变速率的疲劳加速因子的应变速率方法，在大多数应力，R比率和频率的载荷条件下，可靠地关联了50摄氏度空气中的疲劳和蠕变。例外是在R = 0.1和频率小于1 Hz的条件下的疲劳载荷。据推测，高度延伸的裂纹原纤维的压缩和弯曲导致了意外的高裂纹速度。

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