The intrinsic nature of materials failure and the global non-equilibrium energy criterion
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cember 2020 Vol. 63 No. 12: 124611 https://doi.org/10.1007/s11433-020-1610-8
The intrinsic nature of materials failure and the global non-equilibrium energy criterion *
Biao Wang
School of Physics and Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China Received July 28, 2020; accepted August 10, 2020; published online October 23, 2020
Materials failure under some sort of loading is a well-known natural phenomenon, and the reliable prediction of materials failure is the most important key issue for many different kinds of engineering structures based on their safety considerations. In this research, instead of establishing empirical models, the material failure process was modeled as a nonequilibrium process based on the microstructural mechanism. Then, the evolution equations were established and the stability analysis was carried out to obtain the critical conditions for the materials failure. It was found that the material strength was a global property in nature, and the commonly used local criteria based on the most dangerous point failure were not the rational assumption. Based on the idea, some examples were considered, such as the size effect of the material strength, the strength of the polycrystalline metals, the stress-strain relationship of the ultrafine crystalline metal with nanoscale growth twins, the strength of lithium niobite crystal specimens with notches. All of the theoretical predictions gave reasonable results compared with the experimental data. strength theory, nonequilibrium thermodynamics, stability analysis, size effect, nanomaterials PACS number(s): 46.05.+b, 62.20.Mk, 62.20.Fe, 05.70.Ln Citation:
B. Wang, The intrinsic nature of materials failure and the global non-equilibrium energy criterion, Sci. China-Phys. Mech. Astron. 63, 124611 (2020), https://doi.org/10.1007/s11433-020-1610-8
1 Introduction Material breakages or failures under loading are very common natural phenomena, and how to establish the criterion of material breakdown has attracted much attention from physicists, material scientists, earth scientists, and mechanical and civil engineers in particular, for a very long time. In essence, the strength theory of materials is the failure criterion of a material. da Vinci (1452-1519) and Galilei (15621642) may be the earliest researchers of the problem. They performed tensile and bending tests of wires and stones to determine their strength. da Vinci believed that the strength of an iron wire depended significantly on its length, while Galilei believed that fracturing occurred when a critical *Corresponding author (email: [email protected])
stress was reached. To satisfy widespread engineering needs, various strength theories have been established for different materials. A general common characteristic of all the strength theories is that when some stresses or stress combinations at some point in a material specimen reach a critical value, the material sample will break. The critical values for different mate
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