Applicability of Strain Gauge Methods for Experimental Determination of Operating Stress of Construction, Road and Agricultural Machines Attached to Tractors

The operating stress of construction, road and agricultural machines is determined during experimental and factory tests using force sensors. The aim of the research is to improve the methods of experimental determination of horizontal forces transferred by mobile implements using strain gauges combined with the elements of fastening of technological machines. The stress-strain state and deformations of measuring strain gauges at their different arrangements on strain gauge pins of circular cross-section are considered. When determining the horizontal load on the vehicle with the use of pre-calibrated strain gauge pins, it was experimentally established that the mentioned strain gauges can additionally react to the vertical load, which leads to the emergence of systematic errors in estimating the horizontal load. To eliminate this, it is proposed that before the main calibration of the horizontal force sensors, it is necessary to pre-determine the position at which the calibrated strain gauge will not respond to the vertical force, by rotating it relative to the longitudinal axis and then ensuring fixation in this position. The influence of axial forces on strain gauge pins, picked up by the strain gauges, can also lead to distortion of the stress field in the body of the strain gauge. Taking into account this influence on the strain gauge pins requires additional experimental studies.