Yield Criterion According to Drucker-Prager

σ_{v} = \frac{m - 1}{2} (σ_{1} + σ_{2} + σ_{3}) + \frac{m + 1}{2} \sqrt{\frac{1}{2} [(^{σ_{1} - σ_{2}) 2} + (^{σ_{2} - σ_{3}) 2} + (^{σ_{3} - σ_{1}) 2})]}

m = \frac{σ_{c}}{σ_{t}}

σ_c	Limit stress for compression
σ_t	Limit stress for tension

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