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122                               Chapter 7  Vibration Analysis



                                                                  2 w
                                                           Ez
                                                                  x   2

                                         2D Plate
                                                                   ,
                                         The  stress  components       of  the  plate  are
                                                                       ,
                                                                         xy
                                                                  x
                                                                      y
                              determined at any  z  coordinate from the computed deflection  w
                              as,
                                                          E       2  w    2  w 
                                                                       z
                                                x
                                                        1      2  x   2  y   2  
                                                          E         2  w    2  w 
                                                                       z
                                                y
                                                        1      2  x   2  y   2  
                                                          E    2 w 
                                               xy                z
                                                        1       xy   

                                         3D Solid

                                                                                   ,
                                         The  three  normal  stress  components       and
                                                                                ,
                                                                                  y
                                                                               x
                                                                                      z
                              three shearing stress components   xy , xz ,   are determined from
                                                                      yz
                                                                       ,
                              the computed displacement components  ,u v w as,
                                                    E             u    v     w 
                                                           (1     )          
                                        x
                                               (1     )(1 2 )       x   y   z   
                                                    E         u        v     w 
                                                               (1     )      
                                        y
                                               (1     )(1 2 )       x   y   z   
                                                    E          u    v        w 
                                        z    (1     )(1 2 )           x       y     (1     )  z     
                                                 E       u  v  
                                                           
                                       xy
                                               2(1      )   y  x   
                                                 E       u   w 
                                                           
                                       xz
                                               2(1      )   z  x   
                                                 E      v    w 
                                                           
                                       yz
                                               2(1      )   z  y   
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