Three classes of inverse coefficient problems arising in engineering mechanics and computational material science are considered. Mathematical models of all considered problems are proposed within the J2-deformation theory of plasticity. The first class is related to determination of unknown elastoplastic properties of a beam from a limited number of torsional experiments. The inverse problem here consists of identifying the unknown coefficient g(ξ2) (plasticity function) in the nonlinear differential equation of torsional creep-(g(|∇u|2)ux1)x1 - (g(|∇u|2)ux2)x2 = 2φ, x ∈ Ω ⊂ R2 , from the torque (or torsional rigidity) τ (φ), given experimentally. The second class of inverse problems is related to identification of elastoplastic properties of a 3D body from spherical indentation tests. In this case one needs to determine unknown Lame coefficients in the system of PDEs of nonlinear elasticity, from the measured spherical indentation loading curve
, obtained during the quasi-static indentation test. The third model an inverse problem of identifying the unknown coefficient g(ξ2(u)) in the nonlinear bending equation is analyzed. The boundary measured data here is assumed to be the deflections wi[τk] := w(λi;τk), measured during the quasistatic bending process, given by the parameter τk,
, at some points
,
, of a plate. An existence of weak solutions of all direct problems are derived in appropriate Sobolev spaces, by using monotone potential operator theory. Then monotone iteration schemes for all the linearized direct problems are proposed. Strong convergence of solutions of the linearized problems, as well as rates of convergence are proved. Based on obtained continuity property of the direct problem solution with respect to coefficients, and compactness of the set of admissible coefficients, an existence of quasi-solutions of all considered inverse problems are proved. Some numerical results, useful from the poins of view engineering mechanics and computational material science, are demonstrated.