How is creep behavior characterized and used in design for high-temperature applications?

Creep is time-dependent deformation under constant stress at elevated temperature. Stages: Primary (decreasing rate), Secondary (steady-state), and Tertiary (accelerating to failure). Characterization: Constant load or stress tests at multiple temperatures, Measure strain vs. time, Extract creep rate, time to rupture. Modeling: Larson-Miller parameter - Correlates temperature and time for rupture: LMP = T(C + log(t)); Creep rate equations - Norton law: rate = A*sigma^n*exp(-Q/RT). Design use: Creep rupture data for life prediction, Creep strain limits for dimensional stability, Stress relaxation for bolted joints, and Temperature-stress-life trade-offs. Superalloy design: Minimize diffusion paths (single crystal), Precipitate stability (gamma prime coarsening), and Coating degradation effects. Analysis: Larson-Miller curves for material comparison, Creep-fatigue interaction for cyclic high-temperature service. Allowable stresses based on minimum creep rate or rupture life with appropriate safety factors.