Comparative Analysis between National and Industry Standard Testing Methods and the Instrument for Longitudinal Stiffness of Shanks

The test method of the longitudinal stiffness for shanks has been changed from an industry standard to a national standard, and certain changes have occurred in testing method and instrument. A systematic comparison of the differences between these two standards can help laboratories better understand the influencing factors and their changes in the test, so as to better control the testing quality. Based on the longitudinal stiffness calculation formula, this study thoroughly compares the differences between national and industry standards in terms of longitudinal load, lever arm length, and longitudinal displacement, etc. The analysis reveals that manual testing instrument, compared to automated instrument, exhibits smaller allowable deviations of instrument. However, the measurement structure of manual instrument is more complex, which may lead to more system error accumulation, so the two have their own advantages and disadvantages in system error. In terms of the control of random errors, the automatic instrument is simple to operate, has little human influence, so its stability and accuracy are superior. By using manual and automatic instrument to carry out repetitive tests on the same shank, it was finally found that the error of the test results of the manual instrument was indeed greater. Therefore, it is recommended that laboratories use automatic equipment to carry out the longitudinal stiffness of shanks, or implement targeted technical improvements to manual instrument to ensure testing quality, additionally, propose systematic technical recommendations in response to revisions of national standards.