As a matter of safety, the reliable prediction of the structural failure of materials is the most important key issue for various types of engineered structures. Traditional theories of material strength mainly rely on empirical formulas. Although there are a variety of strength theories available in the literature, they are largely limited by the materials and working conditions of their application. To ensure safety, engineering structures are often designed with large safety factors, resulting in a significant use of material resources. However, this still cannot eliminate the occurrence of catastrophic accidents. Recently, the author developed a thermodynamic framework, referred to as the thermodynamic strength theory (TST) [Eng. Fract. Mech., 2021, 254: 107936; Adv. in Mech., 2023, 53: 693–712.], to accurately predict the failure strength of engineering material structures. In this paper, the principle of virtual energy (PVE) is established based on the modern thermodynamics for the practical application in engineering. For a given imaginary small change in the key state variables of a material system, one can establish a failure strength criterion for the loaded material structure by investigating the induced change in the free energy. Some examples are presented to show the universality and feasibility of the principle, which demonstrates its excellent prospects for all engineering applications.

中文翻译：

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预测材料结构强度的虚拟能量原理

就安全性而言，材料结构失效的可靠预测是各类工程结构最重要的关键问题。传统的材料强度理论主要依赖于经验公式。尽管文献中存在多种强度理论，但它们在很大程度上受到其应用的材料和工作条件的限制。为了确保安全，工程结构往往设计有较大的安全系数，导致材料资源的大量使用。然而，这仍然不能杜绝灾难性事故的发生。最近，作者开发了一个热力学框架，称为热力学强度理论（TST）[Eng.分形。机械，2021，254：107936；副词。 in Mech., 2023, 53: 693–712.]，准确预测工程材料结构的失效强度。本文基于现代热力学建立了虚拟能量（PVE）原理，供工程实际应用。对于材料系统关键状态变量的给定假想小变化，可以通过研究自由能的诱发变化来建立负载材料结构的失效强度准则。举例说明了该原理的普适性和可行性，展示了其在工程应用中的良好前景。