Study Of X-Ray Stress Test System Based On 6-DOF Robot

The residual stress generally has a potential damaging effect on the properties of the object material and the lifecycle of the material.Therefore,the residual stress measurement on the surface of the workpiece is of great significance for the practical research and application of the engineering.The result obtained by calculating the residual stress on the surface of the workpiece to be tested is accurate and reliable by using the X-ray diffraction method.The traditional X-ray stress analyzer’s design and method are different based on material,size,and precision of the measured object.But these devices have some common shortcomings: low DOF made the measurement very limited,the lack of the detection of flexibility which means it cannot be used to test workpiece with the complex shape and large size and also cannot provide a variety of measurement methods,The process of stress testing have higher requirements and he structure design of mechanism have high complexity,so the configuration process is relatively cumbersome.In order to solve these problems,an X-ray stress analyzer system based on 6-DOF robot is proposed and the methods of detection points’ localization as well as calculating motion path of measurement based on robots are studied.The hardware design: according to the specific configuration of robot and research of existed stress testing device,the hardware platform of 6-DOF robot stress analyzer system was proposed.It uses the robot and goniometer to cooperate with each other,not only to meet the measurement of different measured material requirements;but also to improve flexibility of the stress measurement.Secondly,according to the requirement of high precision stress detection,two kinds of teleoperation positioning strategy was proposed,which including absolute speed control positioning method and absolute position control positioning method.Both of them can meet the requirement of speed and precision.After that,the height positioning method based on PID controller with help of laser range finder was studied to improve the accuracy of height positioning.Thirdly,the accuracy of robot measurement motion directly affects the precision of the results of residual stress,according to the principle of the stress test method,the 6-DOF kinematics was modeled and mathematical calculation of several method of stress test was proposed,and derived the trajectory of the robot motion by the polynomial interpolation method.In order to improve the motion accuracy of the robot,multi-point calibration method based on fixed base was adopted to calibrate tool coordinate system.An experiment to test the accuracy of the robot motion was carried out to verify the correctness of the calculation of robot measurement trajectory and accuracy of calibration.Finally,the software platform of this an X-ray stress analyzer system was proposed using Modular design method and calculation methods and calculation steps of residual stress was then proposed.After that,a stress test experimental platform was built to test the stress of the reduced iron powder using four methods.The result verifies the feasibility and accuracy of this X-ray stress analyzer system.