===6.4.7 Contact Spring Calculations===
[[File:One side fixed contact bending spring.jpg|right|thumb|One side fixed contact bending spring]]
Fig. 6.20:
One side fixed contact bending spring<br />
L = Length of spring<br />
E = Modulus of elasticity<br />
B = Width of spring<br />
F = Spring force<br />
D = Thickness of spring<br />
x = Deflection<br />
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:
<math>F =
\frac {3 x E x J}{L^3} x</math>
where J is the momentum of inertia of the rectangular cross section of the beam
<math>J =
\frac {B x D^3}{12}</math>
For springs with a circular cross-sectional area the momentum of inertia is
<math>J=\piD^4/64</math><br />
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==
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]]
