Modeling, identification and simulation of dynamics of structures with joints and interfaces

Mechanical joints can cause local stiffness change and become the primary source of energy dissipation in assembled structures. Micro-impact and micro-/macro-slip occurring along the joint interface are two mechanisms for joint mechanics. The lack of efficacious joint models hinders accurate response prediction of jointed structures. The goal of this work is to understand the underlying physical mechanisms of joint mechanics, and to develop physics-based analytical and numerical joint models that are capable of replicating the effects of joints on vibrating structures.; A distributed-parameter joint model with non-uniformly distributed interfacial pressures is developed to study the constitutive relation and energy dissipation of a shear lap joint under lateral loading. Investigations indicate that efficacious friction models that can accurately describe interfacial friction taking placing in a joint need to be developed. Pressure distribution at joint interfaces plays a central role in the joint properties. The postulated cubic relation between the energy dissipation and the magnitude of applied force on a joint is a special case for uniformly distributed interfacial pressure.; As a modeling endeavor, two and three-dimensional adjusted Iwan beam elements (2-D/3-D AIBE) are developed to simulate the 2-D and 3-D nonlinear behavior of shear lap joints due to friction in finite element dynamic analyses of jointed structures. Multi-layer feed-forward (MLFF) neural networks are employed to extract the parameters of the 2-D/3-D AIBE from experimentally-obtained structural responses. Dynamic response simulations were implemented on a 2-D jointed beam and a 3-D jointed frame. The efficacy of the AIBE and the parameter identification procedure were established through comparisons of numerical solutions and experimental measurements.; To account for both dynamic impact and friction, a general joint interface element is also developed. Here, segment-to-segment contact (SSC) is considered, and contact effects are accounted for along continuous edges of the elements. Thus, micro-scale stick-slip behavior along the joint interfaces can be captured even with a relatively coarse mesh. Numerical examples demonstrate that the general joint interface element is capable of accounting for the friction and impact damping in joint interfaces, capturing the transformation of vibration energy from low frequency to high due to impact, and effectively describing the transient relation between the varying normal pressure and tangential traction.