This book methodically details the formulations and approaches to solve boundary value problems, which are essential for determining the stress-strain states in three-layer rods and plates subjected to both single and quasi-static variable loads in thermal radiation and force fields. It duly considers the complex influences on the physically nonlinear properties of the materials in each layer. The book offers several innovative analytical solutions and a numerical parametric analysis of the stress-strain scenarios in these structures. It describes the deformation of physically nonlinear media in thermoradiational fields within the small elastic-plastic deformations theory framework. The work explores variational problem-solving methods and the elastic solution method. It presents a formula for calculating the temperature within a three-layer assembly, derived by averaging the thermophysical properties of the materials across the layers' thickness. Additionally, the book includes an analysis of the attenuation of neutron flux as it passes through a three-layer element.