Experimental inflation tests, conducted on 90 pig corneas before and after corneal collagen crosslinking (CXL) treatment, are simulated with the finite element method. The experimental sample consists of five groups of corneas treated with different UV-A irradiation times (2.5, 5, 10, 15, and 20 min) at constant irradiance 9 mW/cm2. The linear elastic shell theory is used to estimate the equivalent material stiffness of the corneas, revealing that it increases with the exposure time in CXL corneas. In the view of numerical simulations, a simple mechanical model assuming piecewise constant elastic modulus across the corneal thickness is introduced, to estimate the effective increment of the material stiffness in the anterior stroma and the effective depth of the stiffness increment. The two effective quantities are used in the finite element models to simulate the post-CXL tests. Numerical models are able to describe the mechanical effects of CXL in the cornea. The increment of equivalent material stiffness has to be ascribed to a localized increment of the material stiffness in the anterior layers of the cornea, while the posterior layers preserve the original material stiffness. According to the simplified model, the increment of the material stiffness of the anterior cornea increases with the irradiation dose, while the effective reinforcement depth decreases with the irradiation dose. This trend, predicted by a simple mechanical model by imposing equilibrium and compatibility, has been verified by the numerical calculations that captured the global mechanical response of the corneas in untreated and post-CXL conditions.

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Mechanical damages in structures, in structural components of plants and in industrial products usually imply changes of parameters which have central roles in computational modelling apt to assess safety margins with respect to service loading. Such parameters may depend also on the production processes in industrial environments. In this chapter, the parameter identification methodology by inverse analyses is dealt with under the following limitations: experiments at macroscale level, deterministic approaches, statical external actions and time independence in material behaviours. Semiempirical approaches frequently adopted in codes of practice are not dealt with here. The inverse analysis methods outlined here are centered on computational simulations of tests (namely, direct analyses), sensitivity analyses for the optimal design of experiments, model reduction procedures and other provisions apt to make fast and economical the parameter estimation in engineering practice. The applications summarized here as examples concern structural diagnoses based on indentation tests, in situ diagnostic experiments on concrete dams and laboratory mechanical characterization of membranes and laminates

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