SHOT PEEN FORMING OF DOUBLE CURVATURE SKINS USING A CONTACT TYPE CNC SHOTBLASTING MACHINES

The PURPOSE of the paper is to improve the production efficiency of long-size double curvature skins of aircrafts based on the control of the stress-strain state under automated technological process of shot peening. The following steps are required in order to achieve the set purpose: to improve the calculation accuracy of the internal force factors of the shot blasting process that directly depend on the processing modes and determine the deformation of the processed part; to develop a methodology for process parameters calculation that will allow to increase the degree of conformity to the theoretical contour of the part shape resulting from the rough forming; to provide the conditions for the automation of part final shaping operations; to develop technological methods aimed at increasing the shaping performance of double-curvature sections; solve a number of technical issues on the automation of auxiliary operations that are responsible for significant raise in labour intensity; take measures to ensure the stability of the shot blasting process under the implementation of the control program. The METHODS applied include modeling using nonlinear finite element analysis, study of the machined surface micro-relief using a 3D optical profilometer, measurement of the curvature of samples using electronic indicating devices. RESULTS AND THEIR DISCUSSION. The procedure is proposed to determine internal force factors of shot peening by the finite-element modeling of the process of multiple indentation of shots with different speeds and trajectory inclination angles in the machined part material. The methods have been developed to determine the conditions of the technological process of shot blasting on contact type installations in the automated control mode taking into account the effect of the stress-strain state of the workpiece and the control results of the intermediate shape of the part. The design and software solutions aimed at ensuring the implementation of the automated process of shot blasting forming are proposed. Based on the performed theoretical and experimental researches the calculation methods of technological parameters of shot peening operations for rough forming of double curvature parts have been developed. They take into consideration the influence of the stress-strain state and control of the workpiece shape under forming and finishing treatment on the basis of the results of control of the workpiece intermediate shape.

skin, shot peening, internal force, residual and initial stresses, diagram, shot blasting machine of the contact type

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