Study On Measuring The Residual Stress Of Pre-stretched Aluminum Alloy Plates And Developing The System For Predicting Machining Deformation

High strength aluminum alloys have been widely used as the key materials of aircraft structures due to their high strength-weight ratio, excellent corrosion resistance, and high fracture resistance. Monolithic components are being widely used for aerospace applications because of their combination of lower height, higher assembly quality and higher structural efficiency. However, these components are large in size, complex in structure, and thin-walled. In the milling process, more than90%of the materials would be removed which results in low rigidity. Therefore, the large machining deformation of the monolithic components is often observed. The efficient, precise measurement procedures of residual stress and emergency response mechanism are discussed based on the crack compliance method. The data-processing system is developed to analyze the stress uncertainties and calculate the residual stress automatically. The finite element simulation system for predicting machining deformation is developed to realize the engineering application.The standard and systematic measurement procedure and the compliance function modelling procedure are established based on the crack compliance method. An optimal expansion order is obtained based on minimizing the total stress uncertainty which is evaluated by considering the two main sources in calculation of stress uncertainty:the random errors in strain data and model error. Then the residual stress depth profiles in pre-stretched aluminum alloy plate7050-T7451and2124-T851are determined.The finite element simulation system for compliance function is developed based on the secondary development of ABAQUS in which the "element birth and death","Load Case" techniques and the subroutine written by FORTRAN are embedded to solve problems. The data-processing module is developed to analyze the stress uncertainty and calculate the residual stress based on the GUI of MATLAB. The finite element simulation system for predicting machining deformation is developed by customizing applications of secondary development of ABAQUS, in which several typical monolithic components are modeled considering the relationship between the machining stress and process parameters, structure parameters of tools.In order to prove the accuracy of the predicting system, the milling experiment is operated to machine a three-box structural component with certain process parameters and tool. The relevant deformation data is collected to contrast to simulation results.