An engine mount pad is a single rubber layer

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Solid continuum mechanics and complex fluids · Solid continuum mechanics and complex fluids

Bending, Ringing, Breaking and Flowing, Ch Hooke's law for an isotropic solid

Problem

An engine mount pad is a single rubber layer,

200\,\mathrm{mm}

square and

10\,\mathrm{mm}

thick, bonded between two rigid steel plates, carrying a compressive load of

50\,\mathrm{kN}

spread uniformly over the pad. The rubber has

G = 0.4\,\mathrm{MPa}

and

K = 2.0\,\mathrm{GPa}

. ((a)) Estimate the compressive strain of a free (unbonded) block of the same rubber under the same compressive stress, using

E \approx 3G

, and comment on what this implies. ((b)) Estimate the pad's compression using the confined modulus

M = K + \tfrac43G

(perfect bonded confinement). ((c)) The bonded pad's edges are free to bulge, giving a shape factor

S = (\text{loaded area})/(\text{total free edge area}) = 5

. Using the quoted result

E_c \approx 6GS^2

for the bonded-layer compression modulus and combining it with the bulk compliance as

1/E_{\rm eff} = 1/E_c + 1/K

, estimate the pad's compression.

Browse the problem library