The Research Of Nondestructive Measurement System Based On The Depth Of Surface Damage

In the running process or periodic maintenance of EMU, the surface of the parts is easy to be scratched, use the pinion shaft on the bogie as an example, when the surface damage is serious, will make the CRH train not work in normal operation. The scratches depth on the surface is the main factor to determine if it can be used, according to industry standards, when scratches depth is greater than 0.2 mm, pinion shaft will not be used sequentially.This article first investigates and summarizes the pinion shaft damage situation and measurement requirements, using a variety of methods to survey and analyze the depth of the scratches. Contact measurement don’t meet the requirements of nondestructive measuring; the laser phase method and pulse method measuring largely but low in measurement precision; the laser interferometer meet the measuring accuracy but demanding on the environment; laser triangulation method has advantages of simple principle, fast dynamic response and high precision, so satisfy the requirement of the shaft surface scratch depth measurement.Based on the principle of laser triangulation measurement system, this paper establishes the mathematical model of oblique type system structure and direct type system structure, according to the surface characteristics and measurement requirement of measured object, this paper selects the direct type system structure based on its low measurement error and compact structure. In order to guarantee the accuracy optical information in the measurement process, this paper has carried on the demonstration to Scheimpflug condition.Using MATLAB software to optimize and analysis the parameters of the optical element and the positions of each other, according to the influence of receiving lens focal length, working distance, beam Angle and other parameters on the measuring range、accuracy of measurement and the system, acquire the specific parameters meet the actual requirements(ranging range is 0.05-0.5 mm, the measuring accuracy is higher than 0.02 mm): focal length f = 30 mm、distance H = 35 mm、beam Angle m = 33 °. Select optical components on the basis of structural model parameter, design 3 d structure model of the system, build a measurement system experimental platform, on the basis of the experimental results accord with theoretical value, this paper designs the 3 d model structure on the EMU pinion shaft surface scratch measurement device.According to the working principle and the performance parameters of linear CCD- TCD1501 D, this paper designs the software and hardware drivers. In order to obtain visual measuring dynamic image information, this paper makes c++ as a programming language, makes MFC as a framework, makes the Visual Studio as a developing environment, to write the basic image interface; to write Scratches depth algorithm based on the distance model parameters; put the algorithm into interface program and achieved the scratch depth of real-time display.Finally, the main factors in the system which influencing the measurement precision are analyzed in detail, acquire the relation between measuring error and the incline, and provide the method to eliminate the tilt error, provides direction for obtaining more perfect triangulation measurement system.