Measurement Of Key Parameters In Forging And Welding Process Based On Laser Ranging Principle

The measurement of key parameters such as the size and position of forgings during forging and friction stir welding is very important.It can play a role in guiding processing and correcting processing errors in a timely manner and improving processing quality.In this paper,for the measurement of the posture forgings and the plunge depth of shoulder in the forging and friction stir welding process,the distance from the sensor to the surface of the workpiece is measured using a laser rangefinder,the required key parameters are solved by a series of data algorithms.Aiming at the problem of the concentricity of the contact surface between the forging billets and upsetting rod during the upsetting process,a concentricity measurement method based on the principle of laser ranging is proposed.The distance value of all measurement points on a cross section is obtained using a laser rangefinder.The distance values are transformed into the coordinate value corresponding to the phenomenon with the coordinate transformation method,and then use the least squares fitting method to fit the circumferential curve.Since the workpiece cross-section is circular,the fitting curve equation used in the concentricity measurement the is circle curve equation,and the circle center coordinates can be solved represent the position of the measured piece in the measurement system.Finally,the coordinates of the two measured pieces can obtained.In order to reduce the influence of measurement accuracy,an improved Kalman filtering method is proposed.In order to eliminate the influence of discrete points,a weighted least squares fitting method is proposed to fit discrete points,which reduces the weight of outliers in the fitting process.To ensure the processing effect of outliers,the Kalman filter algorithm also adds the processing function of outliers.The experimental results show that the workpiece center coordinate value obtained by the improved Kalman filtering and weighted least squares fitting method has the smallest measurement error,and the result of concentricity measurement error is less than 0.5mm.Aiming at the problem that the piercing rod is not parallel to the central axis of the forging billets during the piercing process.Based on the laser rangefinder surround measurement method,multiple cross-sectional centers are obtained by increasing the measured cross-section in the vertical direction.The oblique cross-section is elliptical.The method of direct least squares fitting is used to calculate the center coordinate of the cross-section from the fitted elliptic curve equation.Finally,the three-dimensional straight-line equation is fitted with the mid-points of the cross-sections to obtain the inclination angle of the axis.In order to eliminate the influence of outliers on the fitting results,the outlier detection method based on regression analysis is used process the distance data.Foreign objects of different shapes and sizes are used in the experiment to verify the accuracy of the algorithm to judge outliers.To compensate for system errors,set a continuously varying tilt angle in the XY direction,and establish a compensation formula based on measured and theoretical values.After system error compensation,the tilt angle measurement error is less than 0.1 °Aiming at the problem of measuring the plunge depth of shoulder in friction stir welding,since the plunge depth of shoulder during welding is closely related to the quality of the weld,monitoring the plunge depth of shoulder during welding can improve the quality of the weld.Firstly,a real-time measuring device with a laser displacement sensor as the main body was designed.During the welding process,the measurement of the plunge depth of shoulder was measured,and the measurement performance of the plunge depth of shoulder measurement device was tested.Then,welding plates are partitioned to study the relationship between the upset force and plunge depth by setting different depth,the temperature of the weld and the plunge depth.From the analysis of experimental data,it can be concluded that the relationship between upset force and plunge depth meets different linear functions in different ranges.The temperature rises with the increase of the contact area between the shoulder and the plate.The research on the plunge depth shows that monitoring the change of the plunge depth during the welding process helps to improve the quality of the weld.