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The gauge block handbook Episode 11

Tham khảo tài liệu 'the gauge block handbook episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Appendix D. Deformation Corrections Whenever two materials are forced into contact there is an elastic deformation. For gauge block comparators the contact is between a spherical probe and the flat gauge block surface. The following formula from a CSIRO Technical Note D1 has been found to be identical to the earlier NBS nomographs D2 . The nomographs were developed to avoid the cumbersome calculations needed for deformation corrections. However microcomputers have made the formula easier to use than nomographs and we therefore give only the deformation formula. 2 2 1 a 2.231 P3 V1 V2 3 D 3 D.1 a is the deformation in millimeters P is the force in NEWTONS D is the diameter of the probe in MILLIMETERS Vi is a number characteristic of the probe or block material from the table below Material V 10-8 Steel Chrome Carbide Tungsten Carbide Ceramic Diamond 139 86 40 139 43 Example 1 A steel gauge block is measured with a two point probe system each with a spherical diamond contact of 6 mm diameter. The top force is 1 N and the bottom force is 1 3 N. Top Contact D 6 mm F 1 N V1 139 x 10-8 V2 43 x 10-8 steel block diamond sphere a 2.231 1 2 3 139 x 10-8 43 x 10-8 2 3 6 -1 3 D.2 141 0.000181 mm 0.181 gm Bottom Contact D 6 mm F 1 3 N V1 139 x 10-8 steel block V2 43 x 10-8 diamond sphere a 2.231 1 3 2 3 139 x 10 8 43 x 10-8 2 3 6 1 3 D.3 0.000087 mm 0.087 gm Thus the total deformation is 0.00027 mm or 0.27 gm. Example 2 Same apparatus but measuring a chrome carbide gauge block Top Contact D 6 mm F 1 N V1 86 x 10 8 chrome carbide block V2 43 x 10-8 diamond sphere a 2.231 1 2 3 86 x 10 8 43 x 10 8 2 3 6 1 3 D.4 0.000145 mm 0.145 gm Bottom Contact D 6 mm F 1 3 N V1 86 x 10-8 chrome carbide block V2 43 x 10-8 diamond sphere a 2.231 1 3 2 3 86 x 10 8 43 x 10 8 2 3 6 1 3 D.5 0.000070 mm 0.070 gm Thus the total deformation is 0.00022 mm or 0.22 gm. 142 If we were to use a steel master block to calibrate a chrome carbide block under the above conditions we see that the penetration .