Influence of bushing flexibility and its constitutive behavior on the performance of suspension system

Abstract

We study the effect of strut top mount bushing flexibility and its constitutive law on the ride comfort performance of a quarter car suspension model. A fractional Kelvin–Voigt model has been employed to capture the viscoelastic behavior of the top mount bushings. To study the effectiveness of the suspension system, we have considered sinusoidal and standard (motion over bumps) road inputs. For the sinusoidal input, the frequency response function for both the traditional and fractional Kelvin–Voigt models has been obtained using the harmonic balance method. However, we have resorted to numerical simulations for the standard base inputs for which a reduced-order system of ODEs has approximated the fractional derivative term. Convergence of the reduced system of ODEs is established by comparing the numerical results for sinusoidal forcing with those obtained analytically. We find that the bushing modeled as a traditional Kelvin–Voigt element increases the response amplitude in the resonance zone, while for higher frequencies, the response reduces. Hence, the inclusion of bushing flexibility is equivalent to decreasing the damping in the suspension. These observations also remain valid for the fractional Kelvin–Voigt model, but the effect is less pronounced than in the traditional model. Ride comfort for standard road profile is studied in terms of performance indices which suggests that a fractional Kelvin–Voigt bushing improves the ride comfort. Accordingly, bushing flexibility with an appropriate constitutive law should be accounted in the design of a suspension system for ride comfort. • Effect of strut top mount bushing (STMB) flexibility on ride comfort is studied. • Fractional Kelvin–Voigt model is employed for the viscoelastic behavior of the STMB. • Studied the suspension system response on sinusoidal and standard road inputs. • Ride comfort has been studied in terms of transmissibility and performance indices. • We find that STMB flexibility improves ride comfort especially during transient loads.