In-situ Decoupling and Stiffness Optimization of Resiliently Coupled Assemblies Using FRF-Based Substructuring

Road shake remains one of the most critical NVH challenges in light- and heavy-duty body-on-frame trucks, directly shaping ride comfort and perceived vehicle quality. At the heart of this issue are the body mounts, which govern the transfer of vibration between frame and body. Optimizing these mounts for improved road shake performance is therefore a key objective in NVH engineering. Traditionally, such optimization has relied on finite element analysis (FEA). While highly accurate, FEA—especially when performed with commercial solvers such as NASTRAN—demands enormous computational resources, with complete simulations often requiring hundreds of hours. Each design iteration multiplies this cost, restricting the pace and efficiency of NVH development. Recent methods such as response surface modeling (RSM) and machine learning (ML) have aimed to reduce the burden, yet they remain dependent on large libraries of pre-computed FEA data, inheriting much of the same expense and inflexibility. To move beyond these limitations, this paper introduces a novel approach: Frequency Response Function Substructuring (FBS). By decomposing the system into smaller substructures and characterizing each through FRFs, FBS dramatically reduces computational load without sacrificing accuracy. This enables faster, leaner, and more cost-effective optimization of body mounts for road shake. A unique challenge addressed here is that subsystem FRFs are not directly available; only the overall system FRF, already shaped by the mounts, is provided. We propose a methodology to extract these hidden subsystem FRFs and apply FBS to optimize the bushings—offering a game-changing framework for NVH innovation in body-on-frame trucks.