Thesis supervisor: Szabolcs Berezvai
Location of studies (in Hungarian): BME Department of Applied Mechanics Abbreviation of location of studies: MM
Description of the research topic:
a.) Preliminaries:
Nowadays, MEMS (Micro-electromechanical system) sensors are used in small everyday devices, like smartphones, watches, earbuds, and are also utilized in automotive applications, as part of the safety systems, the engine or the power train. There are many situations in which these sensors encounter impact: e.g., falling from the production line, being dropped when inside the smartphone, or during a car crash. At the same time, as manufacturing technology advances, smaller and more sensitive devices are made.
b.) Aim of research:
Because of the reduction in size, MEMS sensors become less robust and more prone to fracturing when exposed to the sudden, high forces of an impact. This necessitates the development of a reliable method to simulate the impact shock and determine the probability of fracture.
The goal of the research is to investigate the fracturing of MEMS sensors and develop a suitable simulation process for predicting and avoiding failure. Furthermore, the research also aims to characterize the fracture properties of the materials applied in polysilicon MEMS sensors and to develop and implement failure models in the numerical simulation environment.
c.) Tasks, main items, necessary time:
Literature review: Study of available impact simulations and brittle fracture models of polysilicon, summary of the state-of-the-art solutions, summary of material models. (6 month)
Mechanical tests: Investigation of shock propagation through the sensor package and the MEMS structure under different impact conditions (12 month)
Material modelling: Determination of microscopic fracture mechanism types occurring in polysilicon MEMS structures and applicability analysis of fracture criterions to the case of impact loads in silicon microstructures (12 months)
Numerical simulations: Develop a simulation procedure, possibly employing statistical principles, based on which reliable predictions on the probability of fracture can be made (18 months)
Publication work: 1st year - national and international conferences; 2nd year - impact factor (IF) paper and international conference; 3rd year - IF papers and international conferences; 4th year - IF papers and thesis.
d.) Required equipment:
Material testing devices (uniaxial and biaxial material testing machines, high-speed camera, microscope), laboratory equipment for specimen preparation (3D printer, drying oven, microcontrollers), software (Abaqus, Mathematica, Ansys, Matlab).
The experimental tests on silicon MEMS sensors (drop test, fracture tests, microscope measurements and the MEMS signal analysis) will be performed at Robert Bosch Hungary Kft.
The equipment needed for research is provided by the Department of Mechanical Engineering and Robert Bosch Hungary Kft.
e.) Expected scientific results:
The research outcome is expected to be a simulation method, which can be used for making reliable predictions regarding the fracture of the silicon sensor structures. Furthermore, the experimental, numerical and analytical characterization of silicon MEMS fracture will be provided.
f.) References:
[1] O.N. Pierron, C.L. Muhlstein: The critical role of environment in fatigue damage accumulation in deepreactive ion-etched single-crystal silicon structural films. Journal of Microelectromechanical Systems,
15(1):111–119, February 2006.
[2] Robert Boroch: Mechanical Properties and Fatigue of Polycrystalline Silicon under Static and High Frequency Cyclic Loading, PhD Dissertation, Technischen Universitat Karlsruhe, 2008
[3] T.L. Anderson. Fracture Mechanics - Fundamentals and Applications, CRC Press, 3rd edition, 2005
[4] Berezvai Szabolcs, Kossa Attila, Bachrathy Dániel, Stépán Gábor: Numerical and experimental investigation of the applicability of pellet impacts for impulse excitation, International Journal of Impact
Engineering 115: pp. 19-31., 2018
[5] Kwon Younghoon, Seo Soyoung E., Lee Jaejun, Berezvai Szabolcs, Read de Alaniz Javier, Eisenbach Claus D., McMeeking Robert M., Hawker Craig J., Valentine Megan T.: 3D-printed polymer foams
maintain stiffness and energy dissipation under repeated loading, Composite Communications 37: p. 101453., 2023
[6] Takács Donát M., Berezvai Szabolcs, Kovács László: A general method for numerical identifiability
and sensitivity analysis of failure criteria for continuous fibre-reinforced plastics, European Journal of Solid Mechanics A-Solids 100: 104976, 2023
Required language skills: English Number of students who can be accepted: 1
Deadline for application: 2024-04-23
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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