Development And Application Of Torque Calibration Device For High-strength Bolt Torsion Testing Machine

Torque calibration device is a device for calibrating torque measuring instruments such as torsion testing machine and torque sensor based on standard load and standard lever.Torque data can be measured more accurately in engineering application through calibrated measuring instruments,which plays a vital role in the safe use of torque in engineering application.There are many problems in the calibration process of torque calibration devices currently used in largescale torsion testing machines(such as high-strength bolt torsion testing machines which are widely used in engineering testing): the measuring range of the calibration devices can not meet the requirements,the calibration period is too long,and there are potential safety hazards during transportation,etc.As a result,the large-scale high-strength bolt torsion testing machines of many testing institutions,especially in remote areas,cannot guarantee the engineering quality during engineering testing.Therefore,developing a lightweight,efficient and portable calibration device for high-strength bolt torsion testing machine has important engineering application value and significance.In this paper,a new and practical calibration system is developed by analyzing and studying the traditional calibration devices.The system includes 1.A torque sensor with large range,2.A calibration device(including calibration lever and force applying device)for transmitting the torque sensor,and then the calibrated torque sensor with large range is applied to the calibration research of high-strength bolt torsion testing machine in engineering practice.Specifically:Firstly,the traditional device is analyzed.Through theoretical calculation and numerical simulation,a light and safe calibration lever is optimally designed and manufactured.The lever is designed with equal-strength beam and truss support,which finally makes the structure light and high-strength.The force application system at the end of lever is optimized,and the traditional code loading form is replaced by mechanical jack plus pressure sensor,which improves the safety and operation convenience when using the device.The contact system of the application point is optimized,and the method of sliding track and fixing steel ball to the loading device is adopted to reduce the error caused by the rotation of the lever during the test and improve the accuracy of the test results.Secondly,the stress of the lever is measured by strain electrical measurement,and compared with the results of numerical simulation.The results show that the mechanical behavior of the structure is good under the maximum design load,and the test results are in good agreement with the simulation results.Then,according to the uncertainty theory,the uncertainty of the lever is analyzed,and the performance of the device is evaluated.The main sources of uncertainty are the loading force value and the distance of the force arm.The results show that the device has high accuracy and can meet the requirements,and the factor causing the highest uncertainty is the accuracy of loading instruments.Finally,through theoretical calculation and numerical simulation design,a torque sensor with a large range is manufactured,and the sensor is calibrated by a calibration lever,and its linearity,sensitivity coefficient,repeatability and hysteresis are obtained.The results show that each index of the torque sensor meets the accuracy requirement.The torque sensor is applied to the calibration of a 10000N·m high-strength bolt torsion test,which realizes the transmission of torque value and ensures the accuracy and reliability of the test results of the torsion testing machine.