We propose a novel strength-constrained topology optimization approach based on isogeometric analysis (IGA) aimed at achieving structural lightweight design while enhancing both static and fatigue strength. This approach integrates static stress constraint under static loading and fatigue constraint under cyclic loading within a unified volume minimization framework, and it is decoupled as a multiple load cases problem by introducing a safety factor that assumes the fatigue loading is \(20\%\sim 60\%\) of the static loading. The fatigue constraint is explicitly formulated based on the modified Goodman criterion. The stress-life method under proportional and constant amplitude mechanical loading is applied for high-cycle fatigue analysis, where the mean stress and stress amplitude remains constant throughout the loading cycle. This allows the dynamic fatigue loading to be transformed into an equivalent static loading through equivalent static analysis. IGA is employed to ensure high-order continuity, enhance the representation of refined topology, and achieve more precise stress field calculations and more accurate fatigue strength evaluations. The clustering p-norm functions are independently utilized to approximate the maximum values of stress and fatigue. An adaptive scaling scheme is introduced to improve convergence stability by dynamically adjusting constraint scaling factors. This approach mitigates the nonlinearity introduced by large values of \(P\) , thereby reducing the sensitivity to the aggregation parameter. Numerical examples are presented to illustrate the effectiveness of the proposed approach in avoiding yielding under static loading and preventing fatigue failure under cyclic loading. The results demonstrate that IGA enables precise evaluation, yielding feasible optimal solutions and pushing the limits of alternating load resistance, whereas FEA may be more prone to premature convergence or constraint violations.
