Issue 51

A. A. Lakhdari et alii, Frattura ed Integrità Strutturale, 51 (2020) 236-253; DOI: 10.3221/IGF-ESIS.51.19 240 - the parameters of the initial mechanical properties of the material (modulus of elasticity, transverse deformation coefficient, diffusion coefficient, density, stress diagram, etc.); - the parameters of the finite element model which determine the quality of the mesh; - the massive parameters, containing the mechanical properties of the material that vary in time and space. There are also massive-parameters for storing the results of calculations. In Tab. 1, the names and dimensions of the massifs used are presented. Name of the massif Content Dimension psy_func values of the function Ψ(ε i , C, S) for each FE at each time step _ n el amount  nu_func values of the function ν(ε i , C, S) for each FE at each time step _ n el amount  teta_func values of the function θ(C, S) for each FE at each time step _ n el amount  strain_stress Values of deformations and corresponding stresses under the influence of hydrogen _ n el amount  s_factor Parameter values, characterizing the rigidity of the constraint state diagram for each EF at each time step _ n el amount  d_factor Diffusion coefficient values for each FE at each time step _ n el amount  strain_int Deformation intensity values for each FE at each time step _ n el amount  stress_int Constraint intensity values for each FE at each time step _ point el amount n   stress_avg Values of the average stress for each FE at each time step _ n el amount  concentr Hydrogen concentration values for each FE at each time step _ n el amount  Table 1 : Names and dimensions used in mass calculations In Tab. 1: n - number of time steps needed to solve the problem; _ el amount - total number of finite elements of the model; point - number of points by which the deformation diagram is constructed. The massive strain_stress is three-dimensional. It is therefore possible to save a deformation diagram for each FE at each time step. The solution of the problem is conveniently divided into several stages: Step 1: Construction of the geometric model of the structural element . At this stage, the construction of a geometric model of a fragment of the long hollow cylinder. The construction of the geometric model was carried out according to the bottom-up principle, that is to say, first, the key points are defined, and then the lines passing through these points are drawn. According to the lines, was built the axial section of the cylinder. Then, by rotating the section around the OZ axis, at a 90 degree angle, is built a volume - cylinder fragment (in order to save the memory of the computer). The section could be rotated 360 degrees, to obtain the entire cylinder. For the construction of the geometric model, the cylindrical coordinate system was chosen. Step 2: Construction of the finite element model As is known, the use of an ordered mesh makes it possible to obtain more precise solutions, with respect to a disordered mesh. To build an ordered mesh, you have to prepare a model. For this, each line forming part of the volume must be