The TATB-based explosives undergo irreversible volume growth upon a series of cyclic thermal loading known as ratchet growth and have been extensively studied. In the past, experimental elucidation of this phenomenon has focused on irreversible expansion as a function of the number of thermal excursions over a given temperature range, where growth is asymptotic with increasing cycle number. In this paper, we find that the ratchet growth of TATB-based charge evolves associated with its dimension, and demonstrate that the growth can be modeled by a force-thermal coupled calculation method. We have measured the strain response of four various size specimens, and the results show that irreversible strain on the smaller specimen grows more significantly and rapidly. Based on the equivalent relaxation model in which the relaxation stresses are regarded as functions of temperature and temperature gradient, we develop a force-thermal coupled method for calculating the irreversible deformation. The relaxation model parameters were calibrated by comparing the calculations with the experimental measurements. We propose that it is the thermal expansion effect rather than thermal stress, which plays a dominant role in irreversible deformation. Further analysis indicated that the size effect of ratchet growth was not caused by temperature gradient, but was positively correlated with thermal excursions. The size effect of temperature distribution in the process of equivalent stress relaxation may be responsible for the size effect ratchet growth of TATB-based charges. Such tests and analytical models should help to understand and predict the ratchet growth response for TATB-based charges.

中文翻译：

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热循环下基于 TATB 的电荷的棘轮生长建模

基于 TATB 的炸药在一系列称为棘轮增长的循环热载荷下经历不可逆的体积增长，并已被广泛研究。过去，对这种现象的实验阐明集中在不可逆膨胀上，它是给定温度范围内热偏移次数的函数，其中随着循环次数的增加，增长是渐近的。在本文中，我们发现基于 TATB 的电荷的棘轮生长与其尺寸相关联，并证明该生长可以通过力-热耦合计算方法进行建模。我们测量了四个不同尺寸试样的应变响应，结果表明，较小试样上的不可逆应变增长得更显着和更快。基于等效松弛模型，其中松弛应力被视为温度和温度梯度的函数，我们开发了一种计算不可逆变形的力-热耦合方法。通过将计算结果与实验测量值进行比较来校准松弛模型参数。我们提出，在不可逆变形中起主导作用的是热膨胀效应而不是热应力。进一步分析表明，棘轮生长的尺寸效应不是由温度梯度引起的，而是与热偏移呈正相关。等效应力松弛过程中温度分布的尺寸效应可能是导致 TATB 基电荷的尺寸效应棘轮增长的原因。