Design and analysis of a quasi-zero stiffness vibration isolation system with load adaptability

• A mechanically adjustable quasi-zero stiffness isolator with load adaptability is proposed. • Nonlinear stiffness characteristics of disc springs are modeled and analyzed in detail. • Static and dynamic performance under varying design parameters are thoroughly investigated. • The Harmonic Balance Method is used to derive amplitude–frequency and transmissibility curves. • Experiments validate the isolator’s improved performance and 23% bandwidth expansion. This study proposes a mechanically adjustable quasi-zero stiffness (QZS) vibration isolation system, consisting of multiple combined disc springs in parallel with helical springs, to address the degradation in vibration isolation performance of conventional QZS systems due to stiffness mismatch under varying loads. The nonlinear and combined stiffness characteristics of the disc springs are analyzed, and the relationship between the deformation of positive and negative stiffness elements and the applied vertical force is derived. Through static modeling, the influence of key parameters on the static characteristics and overall vibration isolation performance is investigated. A nonlinear dynamic model is established, and the dynamic differential equations are simplified using the Harmonic Balance Method (HBM). The amplitude–frequency and force transmissibility curves are analytically derived and numerically validated. The influence of nonlinear terms, damping, and excitation amplitude on dynamic performance is comprehensively analyzed. Comparative analysis of force transmissibility under stiffness-matched and mismatched states demonstrates the effectiveness of the proposed load adaptability mechanism. Experimental validation shows that the adjusted system significantly improves isolation performance and expands the vibration isolation bandwidth by 23%. The proposed system maintains its quasi-zero stiffness characteristics across different loads, effectively addressing the stiffness mismatch issue and offering a reliable solution for low-frequency vibration isolation in engineering applications.