Research On Control Of Three-dimensional Stress Tube Testing Machine

Exploring yield behavior of the material in a complex stress state, which make an important guidance for the prediction of the forming process and defect analysis of the material. For example, the tube is loaded under compressive stress in axial direction and tensile stress in ring direction in hydroforming process. In order to achieve multiple complex stress loading test, the author adopted electro-hydraulic servo system, achieved the purpose of loading the tube in axial stress, hoop stress and radial stress to a certain relationship, achieved the thick-walled tube yield behavior research.This paper presented a three-dimensional stress loading scheme,and design a three-dimensional stress testing machine and its control system. It can be used for aluminum, stainless steel pipes of different materials for yield behavior. In order to achieve different tubing sizes testing, only prepare some standard sized molds and accessories according to the needs.The paper deduced initial loading phase of the three-way tube stress intermediate position(axial stress, hoop stress, radial stress) formula, forecasted the deformation trends of the tube under different loading conditions by finite element analysis software ABAQUS. Then corrected the formula in different deformation state, during the experiment, to ensure a proportional relationship between the stress in all directions by these formulas.According to the requirements of the testing, build the mathematical modeling of the testing machine’s physical model, and valve controlled asymmetrical cylinder system modeling, deduce the loading system transfer function model, simulation analysis with AMESim and Simulink, separately analysis the system’s capability in both frequency domain and time-domain angle. Design PID controller and neural network adaptive controller, where PID is traditional algorithm, neural network algorithm is intelligent algorithms. Finally according to the control effects of the debugged, choose one of a controller used for the actual test.According to testing system, design hardware of the control system, as well as its procurement and installation work, program the control system Software by C++ Builder, to achieve real-time data acquisition, real-time monitoring of calculated stress, and three servo valve control, etc. Optimize the control system interface to improved color scheme, ensure that the system is easy to use, debugging the entire system finally. Solve the various problems encountered in the experiment, Final completion of a stable, convenient and practical three-dimensional stress testing machine.