Abstract: The automotive air spring rubber bellows is made of a rubber-double-layer cord composite material, featuring mechanical properties such as hysteresis nonlinearity, anisotropy, and rate dependence under large deformation conditions. To accurately describe the material mechanical behaviour of the bellows, the strain energy function per unit volume is ingeniously decoupled into four parts: rubber hyperelastic strain energy, cord stretching strain energy, rubber-cord angular shear strain energy, and rubber viscoelastic strain energy, based on the hierarchical structure of the bellows. A mapping relationship between engineering strain and engineering stress for the rubber bellows is established, and an anisotropic hyper-viscoelastic constitutive model for the air spring rubber bellows made of rubber-dual-layer cord composite is proposed. The result show that this model can effectively predict the hysteresis nonlinearity, anisotropy, and rate dependence of the rubber bellows, with the maximum relative error between the predicted and experimental data not exceeding 5.78%. The established model can effectively characterize the hyperelastic and viscoelastic mechanical behaviors of the air spring rubber bellows made of rubber-dual-layer cord composite, and the model has the characteristics of simplicity, ease of parameter determination, and accurate prediction. The research results provide a theoretical basis for the precise design and matching of the delayed nonlinearity mechanical properties of automotive air springs.

Key words: rubber bellows, double-layer cord reinforced, hyper-viscoelasticity, constitutive model, air spring