tailieunhanh - The gauge block handbook Episode 10

Tham khảo tài liệu 'the gauge block handbook episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | hl -1 0 0 0 0 0 24 0 6 3 3 0 24 11 0 3 6 3 0 24 124 J 0 3 3 6 0 24 0 0 0 0 2 0 24 24 24 24 0 0 A. 11 Using S as the restraint the solution to the equations is S L C 1 8 -2y1 y2 2y4 y5 - y6 - y7 y8 - y9 - y10 y11 L X 1 8 -y1 y2 y3 y4 - y5 - 2y7 - y9 y10 2y11 - y12 L Y 1 8 -y1 2y2 - y3 y4 y6 - y7 - y8 - 2y9 y11 y12 L A -1 12 y1 y2 y3 y4 y5 y6 y7 y8 y9 Ỵ10 Ỵ11 Y12 The deviations d1 d2 . d12 can be determined from the equations above or can be calculated directly using matrix methods. For example These deviations provide the information needed to obtain a value s which is the experiment s value for the short term process standard deviation or within standard deviation ơw. n m s2 E Yi - E ArX Xtr 2 n - m 1 i 0 r 0 The number of degrees of freedom results from taking the number of observations n 12 less the number of unknowns m 5 S C X Y A and then adding one for the restraint. Because of the complete block structure all 12 possible combinations measured all of the standard deviations are the same ơw 4BiS 1 2 s 127 Process Control F - Test Continued monitoring of the measurement process is required to assure that predictions based on the accepted values for process parameters are still valid. For gauge block calibration at NIST the process is monitored for precision by comparison of the observed standard deviation ơw to the average of previous values. For this purpose the value of ow is recorded for every calibration done and is periodically analyzed to provide an updated value of the accepted process ow for each gauge block size. The comparison is made using the F distribution which governs the comparison of variances. The ratio of the variances s2 derived from the model fit to each calibration and ow2 derived from the history is compared to the critical value F 8 OT a which is the a probability point of the F distribution for degrees of freedom 8 and OTŨ. For calibrations at NIST a is chosen as to give F 8 ot .01 . F s2 .