This manual provides a complete background to MSC Nastran Implicit Nonlinear (SOL 400) and describes using SOL 400 within the MSC Nastran environment. The theoretical aspects of nonlinear analysis methods, types, and techniques are included as well as thorough descriptions for nonlinear material models, properties, and loads and constraints. The goal is to provide material relevant to this subject in such a manner that this book can be used both as a learning tool and as a reference text.