Comparison of metals in their steadiness to pulse-periodic microwave heating fatigue

If a metal is heated by a high power microwave pulse, a mechanical stress arises in a near-surface layer. After a number of pulses, cracks may appear at the surface, which is fraught with degradation of the microwave structure parameters. The fatigue effect (dangerous for pulse repetitive HPM generators and linear electron accelerators) depends on the rf pulse power and duration as well as on the conductivity and mechanical properties of the metal. We submit a simplified approach applicable to compare stresses in various metals at various rf heating modes.