Strain gauge pin based force measurement

In this article authors present force measurement method based on strain gauge measuring system installed inside pin, which is a part of light helicopter Main Landing Gear Shock Absorber. Strain gauges in full bridge configuration were installed inside the mounting pin (upper one – fuselage side). Placement and type of strain gauges were selected during the preliminary tests, which verified the validity and conditions of the force measurement. Preliminary tests allowed verification and selection of an optimal measurement system by testing two types of them. The impact on force according to the angle of force vector direction was also verified. Preliminary tests of the strain gauges equipped pin were performed using quasistatic tests stand – 40 T hydraulic press for applying force acting on shock absorber and pin. Whole measuring system is planned to be used in real time analysis of shock absorber force acting on fuselage mounting node. The strain gauges allows measurement of force in any place of the structure, the article presents the advantages of the system located inside pin. Additionally, the installation technologies of strain gauges in hard-to-reach places are presented. The article is summed up with an analysis of the problems, which arise during the installation and measurement process using strain gauges installed in such a specific place.