After calculating the residual standard deviation, it can be seen that the linear relationship between the load and the deformation of the spring is very good. According to the calculation of 2:, the test point with more than 95% probability falls within the range shown. It should be pointed out that the fitting of the straight line needs to have enough test points. The better the linear relationship is (r is close to 1), the number of test points can be reduced, but generally not less than 5 points; the worse the correlation, the test points need to be increased appropriately, otherwise The fitted line is invalid.
The linear fitting calculation content requires a higher accuracy test. When reporting, it should indicate the true value range (confidence interval) and the probability that the true value falls within this range (confidence level) to indicate its true value. The degree of reliability. The confidence interval is a measure of the reliability of a small number of averages, that is, the average value within the confidence interval, which can be accepted as a reasonable value, and the data outside the interval is discarded. Calculate the relationship between the load and displacement of the project l and the disperse belt two art 2, one machine Liliwei three two art mothers 2 a fisherman's fishing. 5 games Iu Yiyi ie-1 Yingba two plastic 845555kN set the standard deviation is S, after The average value obtained from n trials is a fork, and it is safe to believe that the true value (overall average) T of the measured object will be a desire. Within the scope of the hair, the following formula is used to represent n50.5nlll 2 5 = person LPaLP-b0.972kN is 11nl5.914kNL help r one ring Wangonglei one production case 0.999991kN where: T-total average, equivalent The interval where the true value is; the fork - the average of the measured data; t - the correction factor, which represents the confidence factor at a certain confidence probability. Generally, T can be expressed as another. The fitted straight line is generally only suitable for the original data range, and the application range cannot be expanded arbitrarily. If it is necessary to expand the application range, further test data is required. In addition to the straight line fitting method used above, the trend data analysis method in EXCEL can be used to fit the test data to obtain the linear equation and the correlation coefficient. EXCEL operation is convenient and can meet the needs of general data processing, but some parameters such as residual standard deviation: additional calculations are needed. The confidence interval for tensile strength is shown. The confidence factor t confidence factor t50%1 of the test of the second SA Shidu 22 into a 2-10 test. For example, the average value of the four measurements is the fork, the standard deviation is S, and the selected confidence probability is 95%. The t is 3.182, so we have 95% confidence that the true value is in the following range and the standard deviation is +3182 bang>T>"One 3182 is S 2 Shanghai is not a drift one 76 if selected The confidence probability is 90%, t=2.353, there is 90°, t% is sure that the true value is in the following range. If the probability of confidence is 90%, then we can see that the number of trials is reduced. When the value of t increases, because n decreases, the data of the estimated population mean is also reduced, and the increase of t value just compensates for the decrease. For the safety valve spring, we measure the tensile strength by sampling test. The tensile strength of each sample is 798, 813, 818, 820, 802 MPa, and the resistance of the spring is calculated. Pull strength. The average value is again used as an estimate of the average tensile strength of 5. 2 10] soil 9.3MPa Therefore, we have 90% confidence that the tensile strength of the batch of springs is 810MPa 9.3MPa, the test data beyond this range can be discarded. In conclusion, the load and deformation test data of the spring are fitted by the least squares method to obtain the linear equation, and the stiffness of the spring is obtained. The full test is replaced by sampling, and the tensile strength of the spring is given by statistical analysis. Confidence intervals, compared with the past, while ensuring product quality, reducing test workload and improving work efficiency.
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