AA7150-T7751 LCF Ni-base superalloy Probabilistic modeling René80 Sanicro 25 X-ray micro computer tomography activation volume aluminum cast aluminum-silicon cylinder head anisotropy bcc constitutive modelling constitutive models crack growth models crack-tip blunting and sharpening crack-tip cyclic plasticity creep creep fatigue cyclic plasticity defects economy elevated temperature engineering design environmentally-assisted cracking experimental set-ups fatigue criterion fatigue strength flow stress hardening/softening