ИСТИНА

Selective Laser Melting (SLM) is a promising technology for manufacturing 3D metal parts with complicate shape and specified inhomogeneity. The main theme is that the part is being created sequentially, piece by piece, due to melting and fusing metallic powders together in precise geometric shape. There are, nonetheless, a number of challenges that hamper the practical application of SLM. One of them is the following. The metallic powder are heated to the melting temperature and then cooled when they are already attached to the part, which causes distortion of its geometric shape and the accumulation of residual stresses in it. Up to now a variety of ways to reduce residual stresses in SLM manufactured parts are known. Most use the modulation of melting beam or overall heating of the part during additive process. These allow to reduce the inhomogeneity of temperature field and, consequently, to reduce residual stresses. In present work we propose to take a further step: to heat the part during SLM process in specific non-uniform manner which upon the technological (melting) heating results in almost constant temperature profiles and hence in low residual stresses. In order to generate such specific heating an induction with high frequency current modulated in time can be used. One may observe here the similarity with skin-effect induced by alternating current. To make this technological idea a reality it is necessary to develop a mathematical model of SLM process accompanied by selective heating and evolution of residual stresses emerging in a part. To this end the mechanics of growing solids is proposed to use. In present work, by way of illustration, the mathematical model for thermoelastic conducting growing cylinder is developed. It is based on the idea of the sequence of boundary-value problems which describe elementary step of the process. Metal melt occurs on the cylindrical surface while the distribution of the temperature is controlled by modulated alternating current. The process of growth is considered as a sequence of thin cylindrical layers which are added one by one to the body, whose temperature is close to the melting degree, the initial data for the boundary value problem for each time of adding a layer are determined by the values of the corresponding fields at the final time moment of adding the previous layer. A closed-form solution is constructed for this problem and the temperature field on the growing surface is analyzed numerically for various accretion scenarios.