http://hdl.handle.net/10057/260 http://soar.wichita.edu:8080/dspace/retrieve/180 http://hdl.handle.net/10057/260 Search the Channel s http://soar.wichita.edu:8080/dspace/simple-search http://hdl.handle.net/10057/2341 title: Study of wave shaping techniques of split Hopkinson pressure bar using finite element analysis authors: Tasneem, Nazia <br>abstract: The split Hopkinson pressure bar (SHPB) continues to be one of the most common methods of testing materials at high rates of strain. Elevated rates of strain, such as those found in impact and explosive applications, have been shown to induce phenomena such as strain hardening and phase transitions that can significantly affect the strength of most materials. Due to its relative simplicity and robustness, the SHPB remains one of the preferred platforms for evaluating mechanical properties of materials at rates of strain approaching 10 4 in/in-s (s -1 ). At the National Institute for Aviation Research (NIAR), research has been conducted to study the wave shaping techniques of SHPB using finite element analysis. The SHPB consists of two long, slender cylindrical bars, denoted input and output bars that "sandwich" a cylindrical test specimen. Utilizing a high-pressure gas gun, a third cylindrical steel bar, known as the striker bar, is fired at the input bar, causing a compressive stress wave to travel through the input bar to the input bar - test specimen interface. At this interface, a portion of the stress wave propagates through the test specimen while the remainder of the pulse reflects back through the input bar as a tensile stress wave. <br>description: Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering. <br> Mon, 28 Nov 2005 22:58:59 GMT http://hdl.handle.net/10057/2105 title: Numerical investigation of self-piercing riveted dual layer joint authors: Krishnappa, Uma Shankar <br>abstract: Self-piercing riveting (SPR) is a high-speed mechanical fastening technique for point joining of sheet-material components. SPR is becoming important in automotive applications for aluminium vehicle body assembly. However, compared with current sheet-metal joining processes in the automotive industry, the effects of various parameters such as mechanical properties, rivet setting methods and systems, methods of removing self-piercing rivets, etc. A study examining the effect of specimen configuration on the mechanical behavior of self-piercing riveted, dual-layer joints in aluminium alloys was conducted. It has observed that the specimen configuration had a significant effect on the strength and failure mechanism of a self-piercing riveted dual-layer joint. The basic aspects of SPR process forming by conducting both explicit and implicit analysis have been investigated in this thesis. It was found that the operating force-deformation curve of SPR process was determined by the rivet deformation force and its displacement. Under certain process conditions, an increase in inertia effect due to high velocity of metal forming process results was not significant to an extent. In this research, the springback characteristic parameters of the SPR process were also studied. The springback analysis carried out at the end of the forming process showed that the dimensional change in the part due to springback was not significant. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical Engineering <br> Fri, 28 Nov 2008 22:58:59 GMT http://hdl.handle.net/10057/2103 title: Fatigue behavior of plasma spray coatings on polymer matrix composite materials authors: Haqu, Ziaul <br>abstract: The majority of coated structural components are subjected to fluctuating internal and/or applied stress because of oscillating mechanical loads. The fatigue behavior of coatings and the overall cyclic failure response of coated structures have remained relatively unexplored. This study was an effort to investigate the fatigue behavior of plasma spray coatings on polymer matrix composite materials. Since no ASTM standard is available, we designed our own experiment to determine coatings suitability under cyclic loading, response in dynamic loading conditions, fatigue failure modes and fatigue life. Coatings were tested at different stress levels and frequencies. The stresses versus number of cycles (S-N) curves for the coatings were generated. The results indicate that the plasma spay coatings on polymer matrix composite materials are suitable for dynamic loading conditions. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical Engineering <br> Fri, 28 Nov 2008 22:58:59 GMT http://hdl.handle.net/10057/2100 title: Guiding nonmagnetic particles by external magnetic field in a microfluidic device authors: Zhang, Bangwei <br>abstract: This report presents the fabrication of a micro fluidic device using the UV lithography method in order to separate nonmagnetic fluoresbrite carboxy microspheres from the mixed ferrofluids in microchannels. The microfluidic device is fabricated using a SU8-50 negative photoresist that is exposed to the UV lights with a mask (Y shape) on the top of the photoresist. By applying the external magnet from a side of the microchannel, the fluoresbrite carboxy microspheres and ferrofluids are separated into different channels because of the magnetic force acted on the nonmagnetic spheres. During the fabrication, a number of different parameters, such as UV exposure times, UV power, photoresist thickness, etc. were conducted and optimized for our needs. In addition, in the magnetic field testing, different pumping speeds, and particle concentrations associated with the different distances between the magnet and the microfluidic system were studied for an efficient separation. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical Engineering <br> Fri, 28 Nov 2008 22:58:59 GMT