Выражение встречается в следующем контексте:
As an integrated objective of the CRASURV project, the development and implementation of enhanced composite material models was achieved into the commercial F.E. RADIOSS crash code (MECALOG company) [5]. The new orthotopic composite material law is based on a visco-elasto-plastic modelling of composites non-linear and strain rate dependant behaviours. The plastic flow threshold F(a) is formulated as a Tsai-Wu quadratic function of the stress tensor

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