Author : Gajanan S. Rao and R. R. Deshmukh

The horn switch has a helical compression spring at the base within the assembly to restore the position of the horn switch once used. The spring is subjected to cyclic loading with a maximum expected frequency of usage at about 150 cycles a day. Considering the design life of a two-wheeler at about 15 years, the spring should withstand a cyclic compression loading for about 0.8 million times. With a room for safety, the life of the spring is expected to be about a 0.3million cycles. This dissertation report gives the brief look on the life enhancement of compression spring used in two wheeler horn using fatigue analysis. The objective of the present work is to calculate the fatigue life and reduce the incidence of fatigue failure for the working life of compression spring in two wheeler horn. Hence the present spring (AISI 1065 : Co 45%, Mn 0.6-1.3%, Hardness- 42 HRC) is analysed using MSC fatigue software, which shows the maximum stress is developed at the inner side of the spring. Its experimentation shows hair cracks with permanent set, which proves fatigue failure occurs before 3,00,000 cycles. Considering factors affecting fatigue life, material properties are changed (AISI 302/304 : Cr 17-19%, Ni 8-10%, Hardness- 45 HRC) and same is analysed using MSC fatigue software, which shows infinite life. And experimental test proved no any failure for 3,00,000 cycles.

Keywords: Fatigue analysis, Geometric modeling, Helical compression spring, Life analysis, Two-wheeler horn.

Article published in International Journal of Current  Engineering  and Technology, Vol.4,No.3 (June- 2014)