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5. Static response of MEMS                                        327













                    Figure 5.60  Equivalent  loading of the pinned-pinned bent beam

         The deformation  produced through  bending by  the  action of the  force  can
         simply be found by integrating the following differential equations:









          and by using the appropriate boundary conditions that are zero deflections at
          points 1 and 3‚ as well as equal deflections and equal slopes at point 2. It can
          be shown that the total offset of the deformed beam is:







          where:





          By using Eqs.  (5.171) and (5.181)‚  it is found that the strain energy is equal
          to:





          The work done by the axial force is:





          By equating  the  strain energy  U  to the work W‚  according to  the energy
          principle‚ gives the expression of the critical force:
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