Loading...

Nonlinear Dynamic Analysis of PDMS Micro Sensors based on Strain Gradient Theory

Taheran, Farshad | 2020

384 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53134 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Ahmadian, Mohammad Taghi; Firoozbakhsh, Keikhosrow
  7. Abstract:
  8. In this research, a viscoelastic microcantilever beam is analytically analyzed based on the modified strain gradient theory and the results are used in order to study micro pillar shear stress sensors. The abstract of this research can be divided to three sections:In the first section, applying Euler-Bernoulli inextensibility of the centerline condition via Hamilton’s principle, the nonlinear equation of motion and related boundary conditions are derived based on shortening effect theory and discretized by Galerkin method. Inner damping, nonlinear curvature effect, and nonlinear inertia terms are applied. First mode nonlinear frequency and time response of the viscoelastic microcantilever beam are analytically evaluated utilizing multiple time scale method and validated by numerical findings. Outcomes clarify the importance of size effects in analyzing of the mechanical behavior of small scale structures.Next, analytical frequency analysis of a nonlinear viscoelastic microcantilever under harmonic force is performed based on strain gradient theory. Implying Steady-state condition the nonlinear relation between detuning parameter and amplitude of the vibration of a nonlinear viscoelastic microcantilever in the framework of the strain gradient theory is developed, and stability and bifurcation criteria near primary resonance is analytically evaluated. Results show that the damping nonlinearities causes the microcantilever to be softer while size effects via geometric and inertia nonlinearities have the opposite effect. It is also found that utilizing strain gradient theory have a considerable effect on natural frequency, stability criteria, the amplitude of oscillation, force, and frequency bandwidth, in comparison with classical and modified coupled stress theory,Finally, sensitivity of micro pillar shear stress sensors are studied. Then, Effects of different parameters such as damping, nonlinear terms and non-classical theories on the sensitivity are investigated. The results prove the importance of non-classical analysis on sensitivity of micro sensors
  9. Keywords:
  10. Nonlinear Vibration ; Strain Gradient Theory ; Frequency Analysis ; Viscoelastic Damping ; Cantilever Beam ; Viscoelastic Beam ; Microbeam

 Digital Object List

 Bookmark

No TOC