Contact Spring Calculations

6.4.7 Contact Spring Calculations

Fig. 6.20: One side fixed contact bending spring L = Length of spring E = Modulus of elasticity B = Width of spring F = Spring force D = Thickness of spring x = Deflection max = maximum bending force

The influence of the dimensions can be illustrated best by using the single side fixed beam model (Fig. 6.20). For small deflections the following equation is valid:

F= x 3 x E x J L³

where J is the momentum of inertia of the rectangular cross section of the beam

J= B x D³ 12

For springs with a circular cross-sectional area the momentum of inertia is

J=BD4/64 D= Durchmesser

To avoid plastic deformation of the spring the max bending force σ cannot be max exceeded

Fmax= 3 x E x D xmax 2L²

The stress limit is defined through the fatigue limit and the 0.2% elongation limit resp.

xmax= 2 x L ² Rp0,2 3 x D x E

and/or

Fmax= B x D ² Rp0,2 6L

• Special Spring Shapes

• Triangular spring

Deflection x= L³ F 2 x E x J

= x L³ D³ 6 x F E x B

Max. bending force Fmax= 1 8 x F x L B x D²

• Trapezoidal spring

Deflection x= x L³ E x J F (2 + B /B )

x= x L³ E x B x D³ 12 x F (2 + B /B ) min ma

Max. bending force

Fmax= 1 8 x F x L (2 + B /B ) x B x D² min max max

References

References