We study theoretically the yielding of sheared amorphous materials as a function of increasing levels of initial sample annealing prior to shear, in three widely used constitutive models and three widely studied annealing protocols. In thermal systems we find a gradual progression, with increasing annealing, from smoothly “ductile” yielding, in which the sample remains homogeneous, to abruptly “brittle” yielding, in which it becomes strongly shear banded. This progression arises from an increase with annealing in the size of an overshoot in the underlying stress-strain curve for homogeneous shear, which causes a shear banding instability that becomes more severe with increasing annealing. Ductile and brittle yielding thereby emerge as two limiting cases of a continuum of yielding transitions, from gradual to catastrophic. In contrast, athermal systems with a stress overshoot always show brittle yielding at low shear rates, however small the overshoot.

中文翻译：

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热和非热非晶态材料的延性和脆性屈服

我们在三个被广泛使用的本构模型和三个被广泛研究的退火方案中，从理论上研究了被剪切的非晶态材料的屈服与剪切之前初始样品退火水平提高的函数。在热系统中，随着退火的增加，我们发现了一个渐进的过程，从平稳的“延性”屈服（使样品保持均匀）到突然的“脆性”屈服（使它成为强剪切带）。这种进展是由于退火引起的，对于均匀剪切而言，基础应力-应变曲线中的过冲量随退火量的增加而增加，这导致剪切带不稳定性随着退火量的增加而变得更加严重。因此，韧性和脆性屈服作为连续屈服过渡（从渐进到灾难性转变）的两个极限情况出现。相反，