Stress Concentration Factor Evolution
Critical Time (τ_crit) [s]
—
Residual Kₜ (steady-state)
—
Analysis: The fillet radius creates a geometric discontinuity that amplifies thermal stress.
As the thermal wave penetrates (diffusion length √(α·τ)), the stress concentration evolves non-linearly.
Peak stress occurs when the thermal front reaches the fillet root, creating maximum curvature mismatch.
For r/t = —, the theoretical static Kₜ ≈ —.
However, under dynamic loading at — °C/s, the transient amplification factor reaches —x.
This is why the frozen brisket cracks: the thermal shock exceeds the yield strength before the core can equilibrate.
Grounded in: Timoshenko & Goodier (Theory of Elasticity, Ch.12) · NASA SP-8007 (Thermal Stress in Composite Structures)