Strength of bcc crystals under combined shear and axial loading from first principles

► We study (ab initio) bcc crystals under combined shear and normal stresses. ► The 〈1 1 1〉{1 1 0} shear strength is lowered by tensile normal stress. ► Impact of normal stress to shear strength is higher in {1 1 0} planes than in {1 1 2}. ► In 〈1 1 0〉 compression, bcc crystals transform via fco and fct back to bcc structure. ► Maximum 〈1 1 0〉 stresses in compression are lower than those in tension.