Mechanical Engineering Research
Faculty are engaged in various research projects. Following are some of the current research activities and contacts.
Fatigue improvement process development for resistance spot welds
In automotive industry, resistance spot welding (RSW), or spot-welding, has been and continues to be an important process in body structure assembly. Fatigue is a frequent cause of failure in sheet steel joined by spot welds and resistance spot welds are prominent sites for origination of defects and cracks. Even though there is a great amount of interest in achieving high durability and fatigue resistance for resistance spot-welded sheets, there is no open literature in regards to developing a process to improve the fatigue strength of RSW low carbon steel joints. In order to improve fatigue strength of low carbon steel and aluminum RSWs, a post-weld cold working process has been recently introduced. The cold working process generates uniform and consistent large zones of compressive residual stresses in resistance spot-welded low carbon steel structures using a specially designed indentation device. To achieve the proper magnitude of compressive residual stresses, indenting process parameters have been developed for a range of sheet thicknesses and weld sizes. This innovative technology can minimize the cost needed to improve the fatigue life of the resistance spot weld in metal structures.
For research opportunity at the undergraduate and graduate level, please visit Dr. Kim's web site or contact Dr. Kim.
Traditional and non-traditional manufacturing of advanced engineering materials
Today, advanced engineering materials such as composites are being used extensively in the aerospace industry as well as other types of industries due to their advantages including better durability, reduced maintenance requirements and increased potential for future developments. The machining processes of composites are essential to finish the majority of the post-mold manufactured composite parts. Even though importance of composite materials is emerging recently, very limited studies on machining of composite materials were reported. The field of manufacturing processes of composite materials and their performances is the focus of this research.
For research opportunity at the undergraduate and graduate level, please visit Dr. Kim's web site or contact Dr. Kim.
Micro-Electrical-Discharge-Machining of Engineering Materials
Machining of materials on micrometer or nanometer scales is considered to be a key future technology. Aside from the well-known lithographic processes used in the fabrication of micro-electro mechanical system (MEMS) devices, micromachining technologies play an increasing role in the miniaturization of complete machines ranging from biological and medical applications to electro-mechanical sensors and actuators. Currently, research in micromachining focuses only on semiconductor or metal fabrications. Micromachining technology using photolithography on silicon substrate is without a doubt the best known because it is one of the key processes used to fabricate micro-structures in industry. However, there are some limitations in this process due to its quasi-three-dimensional structure, its low aspect ratio, and limitation of the working material. Micro- Electrical Discharge Machining (micro-EDM) is a new technology and has established itself as one of the major alternatives to the conventional methods of machining difficult-to-cut materials and/or generating complex contours. Micro-EDM can offer the possibility of making three-dimensional structures in micro- or nano- scales.
For research opportunity at the undergraduate and graduate level, please visit Dr. Kim's web site or contact Dr. Kim.
Simulation of micro-electro-mechanical systems (MEMS)
Micro-electro-mechanical System is a rapidly growing research area that may ultimately rival integrated circuit in importance. The past few decades have seen innovative MEMS applications in biomedical, telecommunication, electronic, automotive, aerospace and other industries. Microfabrication technologies now allow development of highly miniaturized structures of unprecedented level of functionality on small-scale devices such as biochips, optical switch arrays, airbag sensors and other critical applications across diverse fields.
Experimentation at small scales is quite challenging and expensive. This leads to a strong need for high fidelity simulation to effectively predict the performance of micro-electro-mechanical systems. Our interest in this area is to develop computational tools to simulate complicated physical behaviors of MEMS by accounting for multiphysics interactions between coupled fields.
For research opportunity at the undergraduate and graduate level, please visit Dr. Chen's web site or contact Dr. Chen.
Computer-aided tissue engineering
Tissue engineering is a multidisciplinary field to develop strategies for regenerating biological tissues. Current surgical practice in treating diseased or damaged tissues through transplantation is constantly facing the risk of immune rejection and limited donor supply. This leads to emerging research areas in tissue engineering that has the potential to revolutionize traditional ways of health care treatment.
A particular challenge in addressing material issues in tissue engineering is to design biocompatible materials to guide the growth of the seeded cells in the process of forming functional tissues. Desirable biomaterials should not only match properties of the healthy tissue but also have an interconnected porous microstructure to allow cell proliferation.
Computational simulations can play an important role to augment experimental techniques in the design of emerging biomaterials. Our research interest in this area is to approach clinical challenges by applying and developing simulation tools in the modeling and characterization of biomaterials.
For research opportunity at the undergraduate and graduate level, please visit Dr. Chen's web site or contact Dr. Chen.
MR-Glove: A force feedback device for virtual reality
Virtual reality (VR) is an interactive technology that places the user in an artificial, computer generated world. A typical application achieves this effect through the use of a graphics workstation with advanced input and output devices such as head-mounted audio/visual displays, position/orientation sensors, instrumented gloves, etc. The rich and real-time sensorial interaction provided in a virtual environment makes the user feel immersed in the simulation. Unlike looking at the computer screen, the user feels surrounded by the synthetic world. To provide sufficient realism, the simulation must include physical characteristics such as object rigidity, weight, friction, dynamics, surface texture, etc. This is accomplished by using force feedback devices known as haptic interfaces.
Our research goal is to explore development of a passive actuator using a magnetorheological fluid to design a haptic glove (MR-Glove). A user wearing the MR-Glove is able to hold and manipulate virtual objects (computer generated graphical objects). Using a VR system with haptic interfaces, new products can be quickly designed and tested without a need for making physical prototypes.
For research opportunity at the undergraduate and graduate level, please visit Dr. Gurocak's web site or contact Dr. Gurocak.
Haptic interface for AFM microscope to manipulate carbon nanotubes
In order to manipulate materials at the nanometer scale, we are developing a force-feedback interface for an atomic-force-microscope (AFM). With the aid of this interface, direct positioning of the AFM probe will be possible. In addition, the interface enables the user to feel tip-sample force interactions in real-time.
For research opportunity at the undergraduate and graduate level, please visit Dr. Gurocak's web site or contact Dr. Gurocak.
Micro-channels two-phase flow
Two-phase flow analysis for the evaporation and condensation of refrigerants within the micro-channels is an area of ongoing research. The two-phase flow characteristics in micro-channels may be more sophisticated than conventional macro-channels, and the theories and empirical correlations for one scale may not work for the other one. The objective of this research topic is to investigate the parameters that affect the two-phase heat transfer within the micro-channels, and to utilize the dimensional analysis technique to develop appropriate correlations for specific geometries.
For research opportunity at the undergraduate and graduate level, please visit Dr. Jokar's web site or contact Dr. Jokar.
Mini-channels compact heat exchangers
The single-phase flow analysis of the mini-channel air-liquid heat exchangers has continuously been under investigation. Many reports proved that the transport phenomena of the mini-size heat exchangers are different from the classical theories which have been established for the conventional macro-size heat exchangers. However, several experimental researches observed this difference only for the heat transfer correlations, while the pressure drop can still be estimated as the same. An example of this research study is the heat transfer and fluid flow of cooling fluids in mini-channel compact heat exchangers.
For research opportunity at the undergraduate and graduate level, please visit Dr. Jokar's web site or contact Dr. Jokar.
Micro-channel enhancement for thermal management
The rapid increase in power dissipation from electronic devices has led to challenging thermal management issues. With heat fluxes approaching hundreds of watts per square centimeter, even aggressive techniques such as single-phase micro-channel cooling are being stretched to their limits. Fortunately, micro-scale enhancement methods could extend traditional micro-channels beyond their current regime to meet future thermal loads. Passive techniques can include micro-fabricated versions of macro-enhancement methods, such as turbulators, dimples, and pin fins. Further, the unique flow physics observed in microfluidics permit unconventional enhancement methods involving electrical, surface tension, and viscous effects. Active flow control devices, such as micro-scale jets, can also be developed to augment local heat transfer at hot spots. Our laboratory investigates enhancement methods to determine their efficacy and potential applicability in electronics devices, using advanced experimental techniques, such as micro-PIV, as well as computational tools incorporating the micro-scale physics.
For research opportunities at the undergraduate and graduate level, please visit Dr. Solovitz's web site or contact Dr. Solovitz.
Micro-actuator flow control
Modern engineering devices require careful control in order to function appropriately and efficiently. Although many control methods involve large-scale actuators, such as airplane flaps, smaller micro- and meso-scale devices can also produce macro-scale flow control and enhancement benefits. By applying low-energy driving forces at key locations in a flow system, substantial improvements can be made to the entire structure. Unfortunately, many traditional macro-scale actuators do not function properly at the micro-scale due to decreased efficiency and manufacturability, so new technology must be employed. Our laboratory develops and applies micro-flow control and enhancement devices that use the flow physics of micro- and meso-scale systems to produce large-scale effects. These can include mechanical devices, such as synthetic jets and piezo-electric actuators, as well as more non-traditional microfluidic devices using electrical, magnetic, or other drivers. We apply theoretical analysis, computational simulation, and experimental validation to examine the full performance range of these actuation methods in order to develop a better fundamental understanding of the micro-scale physics.
For research opportunities at the undergraduate and graduate level, please visit Dr. Solovitz's web site or contact Dr. Solovitz.