Development Of Phased Array Nondestructive Testing Platform For Railway Vehicle Drive Shaft

The axle is one of the important parts of the railway vehicle.Timely detection and treatment of its defects is an important foundation to ensure the safe operation.At present,the manual testing method which is mainly used domestically relies on artificial experiences.Many drawbacks are brought out.And the domestic large-scale automated ultrasonic testing equipment is blamed for complex structure,cumbersome control,poor versatility and other defects.This paper developed a phased array ultrasonic flaw detection platform for railway vehicle axle to achieve the automatic flaw detection,high precision inspection,a variety use of active axles.The mechanical structure of railway vehicle axle automation Ultrasonic testing platform includes bed,axle clamping mechanism,spindle drive transmission mechanism,detection mechanism,and coupling agent spraying device.Axle clamping mechanism meets the requirements of China’s various axle sizes.A 45SL001 spindle motor and CW series cylindrical worm reducer are adopted according to the accuracy of ultrasonic flaw detection requirements.Detection mechanism takes the transmission method of servo motor driving ball screw moving on the training platform.The 60CB020C-010000 AC servo motor is selected according to the detection speed and the load torque.A flexible phased array ultrasonic transducer probe is used,and a flexible bracket is designed to detect a variety size of axles only by one probe.The probe structure and testing movement control process is simplified to a large extent.The bracket can protect the transducer from being pulled severely as the traditional probe holder,which extends the life of the transducer.The detection platform needs to control four movements: the spindle motor driving the axle rotation,the axial servo motor driving probe bracket movement,the radial servo motor driving probe bracket movement and water pump’s action.The system hardware adopts the control structure combined with the host computer and the lower parts.The host computer adopts the SIMATIC Rack PC 347 E IPC.The lower parts adopt the DMC2410 B four-axis motion control card,the servo drive,three servo motors,a water pump,a photoelectric encoder and a laser ranging sensor acting as the speed feedback element and the position feedback element.In this paper,a dynamic model of the ball screw mechanical transmission and that of the servo motor drive are established.A mathematical model of the motion control system of the axial detection mechanism is constructed.The system transfer function under the condition of speed closed-loop and position closed-loop is given.The stability of the system is analyzed by the Routh criterion and the amplitude and phase frequency curves of Bode plot.The system control block diagram is established in Simulink and the closed-loop step response curve is given.The system performance is improved by adding proportional-integral control and the response speed of the system is improved.System performance is optimized.