Properties at Small Deformations

There is an important qualitative difference between the mechanical properties at small deformations and those at large deformations. The modulus, for example, truly is a material property. However, most ultimate properties are functions of the measurement conditions, including sample orientation and preparation, and as such are very much sample specific. Failure invariably takes place at a defect or stress concentrator. Every value reported must be regarded as an average that is meaningless... 

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