How do you design vehicle body structure for fatigue durability?

Body fatigue design involves: Defining road load spectra from customer usage studies, identifying critical joints and load path nodes, analyzing stress distribution using CAE with representative load cases, evaluating fatigue life using SN curves and rainflow counting, addressing stress concentrations through design optimization, specifying weld and joint quality requirements, and validating through proving ground and lab durability testing. Critical areas include suspension attachment points, door hinges, and closure latches. Design targets typically include 100,000+ miles of equivalent customer driving. Multi-scale analysis addresses global body flex through local joint details.