Numerical simulation of construction 3D printing process. Problems and solution methods

The numerical modeling methods of the construction 3D-printing process with concrete are analyzed from the point of view of the variable geometry printed objects stability numerical simulation possibilities. The method of computational fluid dynamics (finite volume method) implemented in CFD-complexes (ANSYS Fluent, OpenFOAM, COMSOL) was found effective for modeling and process control. The method and CFD tools applicability to solve the printing process modeling and controlling problem is determined by the numerical simulation possibility of concrete mixture flow during extrusion and layers formation, geometric conformity and structures stability prediction, taking into account the mixture rheological properties (viscosity, yield strength and thixotropy) and their change in time. A distinctive feature of the developed generalized approach and the 3D printing process numerical model is the mixture rheological parameters usage. The requirements for the nomenclature and range of its values have been determined experimentally. As part of this approach implementation experimental studies of rheological behavior by shear rheometry were carried out for three types of mixtures. During the model elements 3D printing their quality and stability in dependence with the mixtures type and technological characteristics were assessed. As a result, the rheological behavior rational model of and the values range of visco-plastic mixture parameters ensuring its suitability for extrusion and layering is substantiated. These include effective viscosity and Bingham yield strength, which determine the mixture extrusion quality; static viscosity and plastic strength, static yield strength, on which the layer shape, preservation and the printed structure stability are depended.