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===<!--6.4.7-->Contact Spring Calculations===<figure id="fig:Oneside_fixed_contact_bending_spring">[[File:One side fixed contact bending spring.jpg|right|thumb|One side fixed contact bending spring]]</figure>The influence of the dimensions can be illustrated best by using the single side fixed beam model <xr id="fig:Oneside_fixed_contact_bending_spring"/><!--(Fig. 6.20)-->. For small deflections the following equation is valid::$<math>F = \frac{3 \cdot E \cdot J}{L^3} $</math> where J is the momentum of inertia of the rectangular cross section of the beam :<math>J = \frac{B \cdot D^3}{12}</math> For springs with a circular cross-sectional area the momentum of inertia is :<math>J=\pi D^4/64</math> :<math>D= Durchmesser</math> To avoid plastic deformation of the spring the max bending force σ_max cannot be exceeded :<math>\sigma_{max} = \frac{3 \cdot E \cdot D}{2L^2}\cdot_{max}</math> The stress limit is defined through the fatigue limit and the 0.2% elongation limit resp. :<math>\times_{max} = \frac{2 \cdot L^2}{3 \cdot D \cdot E}R_{p0,2}</math> <br />and/or<br /> :<math>F_{max} = \frac{B \cdot D^2}{6L}R_{p0,2}</math> <li>'''Special Spring Shapes'''</li> <ul> <li>'''Triangular spring'''</li> Deflection :<math> \times = \frac{F}{2 \cdot E \cdot J}L^3</math> :<math>= \frac{6 \cdot F}{E \cdot B}\cdot \frac{L^3}{D^3}</math> Max. bending force :<math>\sigma_{max}= \frac{18 \cdot F \cdot L}{B \cdot D^2}</math> <li>'''Trapezoidal spring'''</li> Deflection :<math> \times = \frac{F}{(2 + B_{min} /B_{max})}\times \frac{L^3}{E \cdot J}</math> :<math>\times= \frac{12 \cdot F}{(2 + B_{min} /B_{max})}\cdot \frac{L^3}{E \cdot B \cdot D^3}</math> Max. bending force :<math>\sigma_{max}= \frac{18 \cdot F \cdot L}{(2 + B_{min} /B_{max}) \cdot B_{max} \cdot D^2 }</math> </ul> ==References== [[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]] [[de:Berechnung_von_Kontaktfedern]]