The lifetime of thermoplastic polyurethane (TPU) encapsulants used in underwater acoustic sensor (UAS) was predicted using accelerated life testing (ALT). The TPU specimens for tensile and tear strength tests were aged at six different temperatures, and the strengths of the aged specimens were then measured. The measured tensile and tear strengths as a function of aging temperature were used as ALT data for the analysis of the TPU encapsulant lifetime using ReliaSoft’s ALTA software. For the analysis of ALT data, the acceleration models and the life distribution models in the ALTA software were combined. The maximum likelihood estimation (MLE) method was used to find the most reliable acceleration-life distribution model when interpreting ALT data for tensile and tear strengths. It reveals that the Arrhenius-Weibull distribution model best fits the ALT data of the TPU encapsulant. The lifetime of the TPU encapsulant for tensile and tear strength was estimated using the Arrhenius-Weibull distribution model. The estimated results exhibited that the lifetime for tear stress was much shorter than that for tensile stress at 25 °C. Tensile and tear stresses are applied simultaneously to the TPU encapsulant during UAS operation. Thus, its replacement time should be determined by its tear strength lifetime.

中文翻译：

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水下声学传感器中使用的热塑性聚氨酯密封胶的加速寿命测试

使用加速寿命测试（ALT）预测了用于水下声传感器（UAS）的热塑性聚氨酯（TPU）密封剂的寿命。将用于拉伸和撕裂强度测试的TPU样品在六个不同的温度下进行时效，然后测量时效后的样品的强度。使用ReliaSoft的ALTA软件，将测得的拉伸强度和撕裂强度作为老化温度的函数用作ALT数据，以分析TPU密封胶的寿命。为了分析ALT数据，结合了ALTA软件中的加速度模型和寿命分布模型。当解释抗张强度和撕裂强度的ALT数据时，最大似然估计（MLE）方法用于找到最可靠的加速寿命分布模型。它表明Arrhenius-Weibull分布模型最适合TPU密封剂的ALT数据。使用Arrhenius-Weibull分布模型估算了TPU密封剂的抗张强度和抗撕强度的寿命。估计结果表明，在25°C下，撕裂应力的寿命比拉伸应力的寿命短得多。在UAS操作期间，拉伸应力和撕裂应力同时施加到TPU密封剂上。因此，其更换时间应由其抗撕强度寿命决定。在UAS操作期间，拉伸应力和撕裂应力同时施加到TPU密封剂上。因此，其更换时间应由其抗撕强度寿命决定。在UAS操作期间，拉伸应力和撕裂应力同时施加到TPU密封剂上。因此，其更换时间应由其抗撕强度寿命决定。