EXPERIMENTAL INVESTIGATIONS ON THE EFFECT OF HEAT ON THE PERFORMANCE OF HSL WASHERS

This work studies the effect of higher temperatures on the Load Deflection Characteristics of helical spring lock (HSL) washers. The reaction force at the elastic point and loss of helix height due to the locking of HSL washers at higher temperatures are determined to ensure the reusability of these washers in the nut-bolt assembly. M10 size HSL washers made of spring steel (EN42J) material were used. To study the effect of preheating temperature, the samples are exposed to higher temperatures (50 to 200°C) for various time periods. After heating the washer samples were used to determine the load-deflection characteristic curves using an automatic test-rig. The preheating of HSL washers at 200°C shows a significant improvement in its performance. Additionally, the HSL washers were locked in the nut-bolt assembly at the desired tightening torque and exposed to higher temperatures (50 to 200°C) for various time periods. After dismantling these washers, the dimensions were measured and a significant loss in helix height was observed and further used to determine their characteristic curves. The noticeable loss in reaction load at an elastic point is observed around 57.58% at 200°C temperature for 200 hours of locking duration compared to ambient temperature conditions.