Mr. Shishay Amare Gebremeskel

Research

Design Customization and Development of Split Hopkinson Pressure Bar for Light and Soft Armour Materials

Article October 31, 2014

In order to face the grand challenge of characterizing soft and light armour material system shaving polymers and shear thickening fluids under impacts at high strain rates lead to design and development of this particular SHPB set up. The developed set up is designed for a maximum firing pressure of 300 bar of nitrogen gas and it comprises automated gas filling and firing, striker bar velocity recording and data acquisition system. Pressure bars are made of titanium alloy due to its high yield strength and reasonably lower density which could protect plastic deformation, wave dispersion and reduces impedance mismatch with the intended soft specimens, unlike maraging steel bars. The maximum stresses on the critical parts of the setup are crosschecked with simulation results and compared with corresponding yield strengths. Velocitypressure calibration of the developed setup shows higher velocities can be achieved at any particular pressure, when it is compared with the existing public domain velocity calibration of SHPB setup.

Design, Simulation, and Prototyping of Single Composite Leaf Spring for Light Weight Vehicle

Article January 8, 2013

Reducing weight while increasing or maintaining strength of products is getting to be highly important research issue in this modern world. Composite materials are one of the material families which are attracting researchers and being solutions of such issue. In this project reducing weight of vehicles and increasing or maintaining the strength of their spare parts is considered. As leaf spring contributes considerable amount of weight to the vehicle and needs to be strong enough, a single E-glass/Epoxy leaf spring is designed and simulated following the design rules of the composite materials considering static loading only. The constant cross section design of leaf springs is employed to take advantages of ease of design analysis and its manufacturing process. And it is shown that the resulting design and simulation stresses are much below the strength properties of the material, satisfying the maximum stress failure criterion. The designed composite leaf spring has also achieved its acceptable fatigue life. This particular design is made specifically for light weight three wheeler vehicles. Its prototype is also produced using hand lay-up method.