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9 Contact Stresses

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TABLE 9-2 Formulas for <strong>Contact</strong> <strong>Stresses</strong> 439<br />

TABLE 9-2 FORMULAS FOR CONTACT STRESSES, DIMENSIONS, AND CONTACT AREAS, AND RIGID-BODY<br />

APPROACHES a<br />

Notation<br />

γ = (1 − ν 2 1 )/E1 + (1 − ν 2 2 )/E2<br />

a, b = semimajor axis and semiminor axis of contact ellipse, respectively<br />

d = rigid distance of approach of contacting bodies or surface deformation<br />

Ei = modulus of elasticity of object i, i = 1or2<br />

F = force<br />

p = pressure<br />

q = distributed line load<br />

σc = maximum compressive stress of contact area, = (σc)max<br />

νi = Poisson’s ratio of object i, i = 1or2<br />

τ = shear stress<br />

Case Formulas<br />

1a.<br />

Sphere on sphere<br />

K = D1 D2<br />

D1+D2<br />

a = b = 0.721(FKγ) 1/3<br />

σc = 0.918[F/(K 2 γ 2 )] 1/3<br />

d = 1.040(F 2 γ 2 /K ) 1/3<br />

Spheres

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