Research of Materials Science June 2015, Volume 4, Issue 2, PP.50-53
Experimental Research on the Size Measurement of the High Temperature Forging Based on Multicolor CCD Technology Zhonghui Yin, Ling Lin School of Mechanical Engineering, Anhui University of Science and Technology, Anhui Huainan 232001, China
Abstract In order to determine the size measurement accuracy of the high temperature forging’s multicolor CCD image by using computer programs, this paper obtained the high temperature forging’s CCD image by multicolor CCD camera and its fact size by the vernier caliper on the forging field, and then measured the size of the high temperature forging from its CCD image, compared the size from the CCD image and the size from the vernier caliper, the result shows that the measurement accuracy satisfied the industrial production. Keywords: High Temperature Forging; Multicolor CCD Image; Size Measurement; Measurement Accuracy
1. INTRODUCTION Size measurement of the high temperature forging is very difficult because of its bad production environment. The original manual measurement is with great errors, great labour intensity for worker and low utility of materials. Industry statistical shows that the utilization ratio of forging materials is only 50~55 percent in China, 60 ~65 percent in Korea and 70~75 percent in Japan [1]. The author studies on a method which discriminate the high temperature forging from its background and then measure the size of high temperature forging’s image based on CCD technology. The present research shows the above method is feasible in theory[2-3]. This paper would verify the practical feasibility of the method by experiments.
2. EXPERIMENTAL EQUIPMENTS AND METHOD 2.1 Experimental Samples In order to get the comparatively exact measurement result, small rough hot forgings for bearings of Qianchao Bearing Factory were chosen as experimental samples, as shown in Fig.1.
FIG.1 EXPERIMENTAL SAMPLE
2.2 Experimental Equipment Digital Single Lens Reflex Cameras Nikon D80 was used to obtain the multicolor CCD image of the forging, and the vernier caliper was used to measure the fact size of the forging. - 50 http://www.ivypub.org/rms
2.3 Experimental Process On-Site On the testing field, clipped the hot forging with a vernier caliper and then captured its image by multicolor CCD camera. Three different hot forging samples were tested as shown in Fig.2.
(a) Sample 1 (b) Sample 2 (c) Sample 3 FIG.2 SCHEMATIC DIAGRAM OF CAPTURING IMAGE ON THE TESTING FIELD
2.4 Calibration of the Image Size Input image Fig.2 (a) to CAD software. Take the graduation line near the center O of the image as graduation line AO’ as shown in Fig.3. The coordinate value of the datum mark O’ is (x0, y0,). Along x direction take point i ( i=1,2,3,4,5) which horizontal distances to the point O’ are 10mm, 20mm, 30mm, 50mm and 70mm respectively, as shown in Fig.4.
FIG.3 SCHEMATIC DIAGRAM OF THE CALIBRATION DATUM MARK
FIG.4 SCHEMATIC DIAGRAM OF THE IMAGE CALIBRATION
TABLE.1 CALIBRATION COEFFICIENT OF THE EXPERIMENT FOR SAMPLE 1 Measurement Points num Measurement Serial num 1 2 1 3 Average 1 2 2 3 Average 1 2 3 3 Average 1 2 4 3 Average 1 2 5 3 Average
Coordinate of the image measurement(mm) x0
y0
xi
yi
-1.571 -1.266 -1.494
131.943 131.943 131.889
63.772 63.195 63.525
132.719 132.595 132.606
-1.571 -1.266 -1.494
131.943 131.943 131.889
128.514 128.029 128.371
133.351 133.321 133.336
-1.571 -1.266 -1.494
131.943 131.943 131.889
193.453 193.000 193.321
134.228 134.076 134.180
-1.571 -1.266 -1.494
131.943 131.943 131.889
324.012 323.579 323.784
135.445 135.240 135.424
-1.571 -1.266 -1.494
131.943 131.943 131.889
455.780 455.404 455.258
137.260 137.099 137.223
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image measurement distance Lc/(mm) 65.348 64.464 65.024 64.945 130.093 129.303 129.874 129.756 195.038 194.278 194.828 194.715 325.602 324.862 325.298 325.254 457.383 456.699 456.783 456.955
standard distance Lb/(mm)
average of calibration calibration coefficient coefficient Ki K
10.000
0.154
20.000
0.154
30.000
0.154
50.000
0.154
70.000
0.153
0.154
Take the point O’ as the starting point and the point i (i=1,2,3,4,5)as the ending point respectively. Measure the coordinate values of the starting point and every ending points three times. To improve measurement accuracy, the local amplification of the image can be used. Image measurement distance between two points can be calculated according to their coordinate values. Set calibration coefficient K as the ratio of image measurement distance Lc and standard distance Lb between Point O’ and Point i. K is different and should be calibrated respectively because of the different measuring position. The experimental results and calculation of image 2(a) is shown in Table.1.
2.5 Size Measurement of the high Temperature Forging’S Image In image 2(a), the distance between two claws of the vernier caliper is the rough hot forging’s fact diameter and its value is 46.6mm, as shown in Fig.5. Set B,C as the two points of intersection of the two claws of the vernier caliper and the rough hot forging. Measured the coordinate values of Point B and Point C and the distance between two points can be calculated by the way above. The rough hot forging’s image diameter is shown in Table. 2. The measurement results of the experiments for Sample 2 and Sample 3 were obtained as shown in Table.3 and Table.4 by the same method above.
FIG.5 SCHEMATIC DIAGRAM OF THE IMAGE’S DIAMETER MEASUREMENT
TABLE.2 MEASUREMENT RESULT OF THE EXPERIMENT FOR SAMPLE 1 measurement serial num
1 2 3 Average
coordinate of point B
coordinate of point C
Image standard calibration measurement distance of distance of coefficient distance of B, B, C B, C x1 y1 x2 y2 C Lc(mm) K Lt(mm) Lb(mm) -174.363 -62.432 128.445 -64.059 302.813 0.154 46.578 46.6 -175.701 -64.219 128.075 -64.059 303.775 0.154 46.726 46.6 -174.005 -63.736 128.155 -63.928 302.161 0.154 46.478 46.6
absolute error △(mm)
relative error
-0.0217 0.1264 -0.1219
-0.0005 0.0027 -0.0026
absolute error △(mm)
relative error
-0.0217 0.1264 -0.1219
-0.0005 0.0027 -0.0026
absolute error △(mm)
relative error
-0.0217 0.1264 -0.1219
-0.0005 0.0027 -0.0026
TABLE.3 MEASUREMENT RESULT OF THE EXPERIMENT FOR SAMPLE 2 measurement serial num
coordinate of point B x1
1 2 3 Average
y1
-174.363 -62.432 -175.701 -64.219 -174.005 -63.736
coordinate of point C
Image standard calibration measurement distance of distance of coefficient distance of B, B, C B, C x2 y2 C Lc(mm) K Lt(mm) Lb(mm) 128.445 -64.059 302.813 0.154 46.578 46.6 128.075 -64.059 303.775 0.154 46.726 46.6 128.155 -63.928 302.161 0.154 46.478 46.6
TABLE.4 MEASUREMENT RESULT OF THE EXPERIMENT FOR SAMPLE 3 measurement serial num
coordinate of point B x1
1 2 3 Average
y1
-174.363 -62.432 -175.701 -64.219 -174.005 -63.736
coordinate of point C
Image standard calibration measurement distance of distance of coefficient distance of B, B, C B, C x2 y2 C Lc(mm) K Lt(mm) Lb(mm) 128.445 -64.059 302.813 0.154 46.578 46.6 128.075 -64.059 303.775 0.154 46.726 46.6 128.155 -63.928 302.161 0.154 46.478 46.6
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3. THE EXPERIMENTAL RESULTS AND THE ERROR ANALYSIS 1) It is feasible in practice to measure the size of the high temperature forging on-site by the multicolor CCD image measurement method. 2) The CCD image experimental measured values of the rough hot forging’s diameter fluctuates around its fact value. The relative error is 0.27%~0.32% and the maximum relative error is 0.32% by the method. The results show the measurement precision by the method above can satisfy the requirement of the high temperature forging blank.
REFERENCES [1]
R.M. Wu: Large Size and High Temperature Forging Binocular Stereo Vision Measurement Method (MS, Dalian University of Technology, China 2008), p.2. (In Chinese)
[2]
Cong, Hexi and Wang, Shutao and Li, Yuanyuan and Wang, Yutian. Online thickness measurement technology for high temperature glass based on light reflection. Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2011, 40 (7): 1356-1359
[3]
Zhonghui Yin, Chun Li, The Principle and Conditions of Discriminating High Temperature Forgings in Multicolor CCD Image [J]. Research of Materials Science, 2014.12
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