In this work, we deal with the design, manufacture, calibration and testing of a test bench, design for determination of spring constant of helical compression springs with a specific geometry. Based on literature review, we designed a horizontal test bench, which utilizes a pneumatic cylinder as the actuator for spring compression. On the test bench, we installed a load cell for force measurement and a potentiometric linear displacement sensor for distance measurement. Sensors were calibrated prior to the installation and the measurement uncertainty of force and displacement measurements was calculated based on calibration results. Both of these parameters were used to calculate the spring constant of (non-)linear helical compression springs. We determined that our test bench provides good repeatability of measurements with the measurement uncertainty comparable to that of industrial test benches. Based on the measurements performed on six springs we confirmed the existence of a loading and unloading hysteresis and found that the characteristic curve of a spring can be approximated using a third-degree polynomial with the first derivative of the latter representing the spring coefficient as a function.
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