Чисельне моделювання термо-напружено-деформованого стану елементів у процесі 3D друку

The paper is devoted to the assessment of the thermo-stress-strain state of elements of structures obtained by 3D printing using FDM (Fusing Deposition Modeling) technology. Three stages of solving this problem are considered: (1) - mathematical formulation of the problem, that includes universal balance relations, constitutive equations of mechanical behavior of the material and is based on the model of growing bodies; (2) the technique of finite-element solution with increasing mesh due to the addition of new elements; (3) - study of a specific problem of growing plate-like element by polymer PLA (polylactide) with temperature-dependent physical properties. Options of deposed layers of different thickness are considered. The residual stress-strain state of the body has a two-scale structure, which reflects the change of state characteristics in the scale of body size, as well as the thickness of the layers. As the thickness of the layers increases, the average values of the residual stresses decrease, but the amplitude of the stress fluctuations along the thickness of the layer slightly increase. Pages of the article in the issue: 70 - 75 Language of the article: UkrainianРобота присвячена оцінці термо-напружено-деформованого стану виробів, отриманих методом 3D друку за технологією FDM (Fusing Deposition Modeling). Розглянуто три стадії розв‘язання цієї задачі: (1) – математична постановка задачі, що базується на моделі тіл, що ростуть; (2) методика скінченно-елементного розв‘язку задачі; (3) – дослідження конкретної задачі з метою виявлення закономірностей термомеханічних процесів при 3D друку

Unsteady processes in stiffened by thin shell viscoelastic cylinder under pulse loading

Solid propellant rocket motor is considered as hollow viscoelastic cylinder inserted in multilayered elastic shell-like case. The material of propellant is considered to be compressible. An estimation of maximum unsteady stresses on cylinder-shell boundary and shell under growing pressure on interior or external cylindrical surface were calculated by FEM. Four corner isoparametric finite element is utilized. Numark method to integrate by time the dynamic equations is used. The problem of linear viscoelasticity have been employing of the Schapery method. `In the case of internal pressure, the possibility of tensile radial stresses on the contact surface of the propellant-shell during the transition process has been established. The dependence of the maximum contact stresses as well as circumferential stresses in the shell on the shell thickness is established. In the case of external pressure pulse, the presence of significant tensile radial stresses on the propellant-shell interface is shown. Insignificant tensile circumferential stresses in the transient wave process are possible in the shell.Key words: viscoelastic cylinder, pulse loading, maximum dynamical stresses.Pages of the article in the issue: 202-205Language of the article: Russia