Оценка точности и прочности модульной системы вспомогательного инструмента на основе профильных соединений

Abstract

The purpose of the paper is to determine the values of elastic movements of mandrels when assessing the stress-strain state of modular constructions of a spindle-instrumental mandrel designed on the basis of conical detachable profile joints under static loading, and to estimate the accuracy and durability of a conical detachable profile joint designed for torque transmitting and featuring an equiaxial contour with a number of faces equal to three spindle-instrumental mandrel assemblies. The methods of numerical solution of elasticity theory problems including the finite-element method (FEM) as well as the methods of mathematical statistics and computer technology are used to study the stress-strain state of the modular system of an auxiliary tool based on profile joints. The paper provides the results of a complex research, the stress-strain state of modular structures of the multi-purpose machine-tool spindle assembly, namely: a modular system of an auxiliary tool based on profile joints with the equiaxial contour. The article analyzes the influence of design parameters of a conical profile joint, retaining pressure (with the fixation method by the magnitude of the assembly force), values of limiting external loads and friction forces on the accuracy and strength of spindle-instrumental mandrel joint with a profile mounting surface of the shank for actual dimensions of the modular design of the assembly. The values of elastic displacements of instrumental mandrel sections along the mounting length of the profile joint are determined with the use of the mathematical apparatus of the finite-element method based on spline approximation and a variation-energy principle of the displacement method of the elasticity theory. The calculation is performed of the values of elastic displacements of a mandrel and stresses in radial, normal and circumferential directions by the volume of the instrumental mandrel and spindle. Software in FEMAP 11.1 environment with NX NASTRAN has been applied for calculations. It has been determined that the values of elastic displacements of instrumental mandrel sections change nonlinearly and their value at the end face does not exceed 1.8 µm under the limiting external loads of the joint. Accordingly, the maximum values of the normal contact stresses in the extreme sections of the spindle do not exceed 7.71 MPa.