| AVS 57th International Symposium & Exhibition | |
| MEMS and NEMS | Friday Sessions |
| Session MN-FrM |
| Session: | Characterization for MEMS and NEMS |
| Presenter: | A. Mousavi, University of New Mexico |
| Authors: | A. Mousavi, University of New Mexico Z.C. Leseman, University of New Mexico |
| Correspondent: | Click to Email |
The highly nonlinear nature of the crack propagation is studied using a completely nonlinear beam theory model. A model is described that is highly accurate for various deflections of microcantilevers and agrees with the experimental data with nanometer accuracy. The micro cantilever beams used are fabricated by SUMMiT V technology and the dimensions of the beams are 500 x 20 x 2 microns. A nonlinear method is also proposed to calculate the strain energy release rate of stiction failed micro cantilever beams. It is shown that at higher deflections the previous methods fail to accurately determine the stored strain energy and the strain energy release rate. The proposed method is used to accurately determine the beam’s profile and strain energy release rate at higher deflections, and it is in good agreement with the other methods at small deflections.
The method developed here is completely applicable to both Mode I and mixed mode I & II crack development problems. It is shown that when it comes to micro cantilevers the so called Mode I crack propagation turns out to be a mixture of Mode I and Mode II. Longitudinal stresses developed inside the cantilevers increases rapidly as the beam gets nonlinear and starts to play a more important role in the crack length and strain energy release rate. The strain energy release rate can be formulated both using the elastic energy stored in the beam and also using the definition of stress intensity. In this paper, the two common methods for calculation strain energy release rate are discussed and stress intensity factors determined. The obtained stress intensity factors once again verify the fact that there is some Mode II component present during the crack propagation. These results also show that the strain energy release rate is not a constant value and increases as the crack develops. A highly linear relationship is observed between stress intensity components which are in good agreement with the analytical models of the phase angle. It is observed that the phase angle is almost a constant value for all crack heights.