MECHENG 382 Lecture Notes - Solid Solution, Directional Solidification, Thermal Expansion

• School: U of M
• Department: Mechanical Engineering
• Course: MECHENG 382
• Professor: All

Document Summary

Deformation mechanism maps: for steady-state creep (ignores microstructural changes, cavitation and elasticity, different mechanisms can operate simultaneously, fastest mechanism will dominate, deformation-mechanism map dominant mechanisms for stress & temperature. Low-temperature power-law creep is core-diffusion power-law creep: boundary-diffusion creep d-3; lattice-diffusion creep d-2. Lecture 32 - deformation mechanisms maps & creep-resistant materials: with small grain sizes, boundary diffusion may dominate for all temperatures, lattice diffusion may dominate at higher temperatures with large grains (because ql > qb) Increase in grain size reduces diffusional creep rate, but not power-law creep. Example: cylindrical pressure vessel of pure nickel with grain size of 0. 01 mm. Average radius of cylinder = 200 mm; wall thickness = 1 mm; internal pressure of 0. 1 mpa. What is life time at 860 c if failure occurs at an effective strain of 0. 01. = pr/t; zz = pr/2t; rr = 0 . H = 3pr/2t = 17. 3 mpa. H = / 3.