Digital Commons Network^™

Design Charts For Circular Fins Of Arbitrary Profile Subject To Radiation And Convection With Wall Resistances, G. Zhang, Benjamin T.F. Chung

Mechanical Engineering Faculty Research

In this work, the optimization for a radiative-convective annular fin of arbitrary profile with base wall thermal resistances is considered. A fourth order Runge-Kutta method is used to solve the associated non-linear governing equa-tions. Further differentiations yield the optimum heat transfer and the optimum fin dimensions. To facilitate the thermal design, design charts for optimum dimensions are proposed. Furthermore, the fin effectiveness for the optimal annular ra-diative-convective fins is presented to check the practicality of the design.

http://dx.doi.org/10.2174/1874396X01206010015

Progressive Damage In Stitched Composites Under Impact Loading, Kwek Tze Tan, N. Watanabe, A. Yoshimura, Y. Iwahori, T. Ishikawa

Mechanical Engineering Faculty Research

Damage in carbon fibre reinforced plastics (CFRP) due to impact loading is an extremely complex phenomenon that comprises of multiple failure mechanisms like intra-laminar matrix cracks, interlaminar delamination, fibre pull-out and fibre fracture. In stitched composites, impact damage behavior is further complicated by the presence of through-thickness stitching [1, 2], which not only favorably increases mode I/II interlaminar strength [3, 4], but also inevitably creates geometrical defects like weak resin-rich pockets around stitch threads and misalignment of in-plane fibres. Computational modeling has been used to simulate progressive damage effectively [5]. However, the complexity of impact damage progression in stitched composites …

Enabling And Understanding Failure Of Engineering Structures Using The Technique Of Cohesive Elements, H. Jiang, Xiaosheng Gao, T. S. Srivatsan

Mechanical Engineering Faculty Research

In this paper, we describe a cohesive zone model for the prediction of failure of engineering solids and/or structures. A damage evolution law is incorporated into a three-dimensional, exponential cohesive law to account for material degradation under the influence of cyclic loading. This cohesive zone model is implemented in the finite element software ABAQUS through a user defined subroutine. The irreversibility of the cohesive zone model is first verified and subsequently applied for studying cyclic crack growth in specimens experiencing different modes of fracture and/or failure. The crack growth behavior to include both crack initiation and crack propagation becomes a …

Influence Of Stitch Density And Stitch Thread Thickness On Compression After Impact Strength Of Stitched Composites, Kwek Tze Tan, N. Watanabe, Y. Iwahori, T. Ishikawa

Mechanical Engineering Faculty Research

This study aims to investigate the influence of stitch density and stitch thread thickness on compression after impact (CAI) strength of stitched composites. Unstitched laminated composites and specimens stitched with varying stitch density and stitch thread thickness are subjected to impact damage and then compressive loading. It is shown that stitched composites have higher CAI strength than unstitched counterpart due to smaller impact-induced delamination area, where local buckling occurs during compressive failure. However, it is revealed that the effectiveness of stitching in suppressing delamination growth and inhibiting sublaminate buckling under compressive loading is intimately related to stitch density. It is …

Atomic Friction Studied By Modeling The Buried Inteface, Yalin Dong, Ashlie Martini, Qunyang Li, Robert W. Carpick

Mechanical Engineering Faculty Research

Molecular dynamics simulation is carried out to model the single-asperity friction in atomic force microscope experiments. Superlubricity is achieved through misalignment between the AFM tip and substrate. Direct observation of the buried interface reveals that incommensurability-induced inhomogeneous shear stress can cause ultra-low atomic scale friction.

A New Look At Optimum Design For Convecting-Radiating Annular Fins Of Trapezoidal Profile, Benjamin T.F. Chung

Mechanical Engineering Faculty Research

This paper deals with a controversial problem in answering the question “Does the optimum fin design always exist? If not, what are the optimization ranges and limitations?” These authors employ a general example of convecting-radiating trapezoidal annular fin with heat transfer at the tip and wall resistance at the interface. The present results indicate that the answer to the above first question is negative. The ranges of fin optimum design under different thermal and physical conditions are proposed. The effects of Biot number, radiation number, the heat loss at the tip, fin profile and overall wall resistance on fin optimization …

Development Of A Multi-Material Stereolithography System, Ho-Chan Kim, Jae-Won Choi, Ryan B. Wicker

Mechanical Engineering Faculty Research

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats …

High School Bridge Program: A Multidisciplinary Stem Research Program, Jiang Zhe, Dennis Doverspike, Julie Zhao, Paul C. Lam, Craig C. Menzemer

Mechanical Engineering Faculty Research

A Science, Technology, Engineering and Math (STEM) summer Bridge Program was developed for high school students. The program was designed to encourage students to consider choosing an engineering major in college and to explore STEM as a future career. This was accomplished through a 10-week program involving multidisciplinary research activities. The participants in the program included 33 high school students. Among former participants in position to make a choice in terms of attending college, 100% had chosen to continue on in college, and 86% had chosen to major in a STEM area. The results indicated that that the program had …

Study Of Take-Up Velocity In Enhancing Tensile Properties Of Aligned Electrospun Nylon 6 Fibers, Johnny F. Najem

Mechanical Engineering Faculty Research

The variation of both the tensile properties and thermal properties of aligned electrospun fibers with the take-up velocity (TUV) of disc collector has not been widely investigated due to the difficulty of handling aligned nanofibers and measuring low loads. In this thesis, 25% of nylon 6 was dissolved in formic acid and then electrospun into fibers and the fibers were aligned using a rotating disc collector. We evaluated the tensile and thermal properties, average fiber diameter, crystallinity, crystalline morphology, molecular and crystalline orientation of aligned electrospun nylon 6 nanofibers as a function of TUV based on a disc collector. It …

Static And Dynamic Responsive Behavior Of Polyelectrolyte Brushes Under External Electrical Field, Hui Ouyang, Zhenhai Xia, Jiang Zhe

Mechanical Engineering Faculty Research

The static and dynamic behaviors of partially charged and end-grafted polyelectrolyte brushes in response to electric fields were investigated by means of molecular dynamics simulation. The results show that the polymer brushes can be partially or fully stretched by applying an external electric field. Moreover, the brushes can switch reversibly from collapsed to stretched states, fully responding to the AC electric stimuli, and the gating response frequency can reach a few hundred MHz. The effects of the grafting density, the charge fraction of the brushes and the strength of the electric field on the average height of the polymer brushes …

Particle Swarm Optimization Approach For Maximizing The Yield Of A Coal Preparation Plant, Vishal Gupta, Hussain Unjawala, Ajay Mohan Mahajan, Manoj Mohanty

Mechanical Engineering Faculty Research

This paper presents the use of particle swarm optimization to maximize the clean coal yield of a coal preparation plant that typically has multiple cleaning circuits that produce the same product quality so that the blend of clean coal meets the targeted product quality contraints. Particle swarm is used for the yield optimization while satisfying multiple product quality restraints. The results show a 2.73% increase in the yield can be achieved leading to additional revenue of $5,460,000 per annum for a plant producing 10 million tons of clean coal per year without significantly adding to the implementation/operation cost.

Material Selection Of Z-Fibre In Stitched Composites - Experimental And Analytical Comparison Approach, Kwek Tze Tan, N. Watanabe, M. Sano, M. Takase, Y. Iwahori, H. Hoshi

Mechanical Engineering Faculty Research

Strain energy release rates are measured and compared for laminated composites stitched with different fibre materials – Carbon, Kevlar and Vectran. DCB test and FE simulation are performed to evaluate the interlaminar toughness. It is proven that Vectran provides the toughest interlaminar reinforcement and is most suitable for Zfibre application.

Numerical Modeling Of The Constraint Effects On Cleavage Fracture Toughness, Sunil Prakash, Xiaosheng Gao, T. S. Srivatsan

Mechanical Engineering Faculty Research

Cleavage fracture has been an important subject for engineers primarily because of its catastrophic nature and consequences. Experimental studies of cleavage fracture did reveal a considerable amount of scatter and provided evidence of noticeable constraint effects. This did provide the motivation for the development of statistical-based and micromechanics-based methods in order to both study and analyze the problem. The Weibull stress model, which is based on the weakest link statistics, uses two parameters (m and σ u) to effectively describe the inherent distribution of the micro-scale cracks once plastic deformation has occurred and to concurrently define the relationship between the …

A Study Aimed At Characterizing The Interfacial Structure In A Tin-Silver Solder On Nickel-Coated Copper Plate During Aging, D. C. Lin, R. Kovacevic, T. S. Srivatsan, Guo-Xiang Wang

Mechanical Engineering Faculty Research

This paper highlights the interfacial structure of tin-silver (Sn-3·5Ag) solder on nickel-coated copper pads during aging performance studies at a temperature of 150°C for up to 96 h. Experimental results revealed the as-solidified solder bump made from using the lead-free solder (Sn-3·5Ag) exhibited or showed a thin layer of the tin-nickel-copper intermetallic compound (IMC) at the solder/substrate interface. This includes a sub-layer having a planar structure immediately adjacent to the Ni-coating and a blocky structure on the inside of the solder. Aging performance studies revealed the thickness of both the IMC layer and the sub-layer, having a planar structure, to …

Implementing High-Speed String Matching Hardware For Network Intrusion Detection Systems, Ajay Mahajan, Benfano Soewito, Sai K. Parsi, Ning Weng, Haibo Wang

Mechanical Engineering Faculty Research

This paper presents high-throughput techniques for implementing FSM based string matching hardware on FPGAs. By taking advantage of the fact that string matching operations for different packets are independent, a novel multi-threading FSM design is presented, which dramatically increases the FSM frequency and the throughput of string matching operations. In addition, design techniques for high-speed interconnect and interface circuits for the proposed FSM are also presented. Experimental results conducted on FPGA platforms are presented to study the effectiveness of the proposed techniques and explore the trade-offs between system performance, strings partition granularity and hardware resource cost.

High Ppeed Circuit Techniques For Network Intrusion Detection Systems (Nids), Ajay Mohan Mahajan

Mechanical Engineering Faculty Research

No abstract provided.

Fabrication Of Complex 3d Micro-Scale Scaffolds And Drug Delivery Devices Using Dynamic Mask Projection Microstereolithography, Jae-Won Choi, In-Baek Park, Ryan B. Wicker, Seok-Hee Lee, Ho-Chan Kim

Mechanical Engineering Faculty Research

Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue engineered scaffolds with controlled biochemical and mechanical micro-architectures. A μSL system for tissue engineering was developed using a Digital Micromirror Device (DMDTM) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking the photoreactive polymer solution. The μSL system was designed with x-y resolution of ~2 μm and a vertical (z) resolution of ~1 μm. To demonstrate the use of μSL in tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight of ~1200 Da. The viscosity of the PPF was reduced to ~150 cP (at …

A Simulation-Based Approach For Dock Allocation In A Food Distribution Center, Balagopal Gopakumar, Suvarna Sundaram, Shengyong Wang

Mechanical Engineering Faculty Research

This research endeavor focused on the warehouse receiving process at a large food distribution center, which comprises of trucks with goods reaching the destination warehouse, unloading and finally putting away the contents to the specific aisles. Discrete event simulation was used to model the current system’s functioning and to identify operational inefficiencies which were quantified through a detailed value stream mapping exercise. Inspired by ‘lean’ philosophy, a dock allocation algorithm was designed to take into account the relationship between the dock location and the destination aisle to ‘optimally’ assign the trucks to the docks. After validating the baseline, new scenarios …

An Evaluation Of A Stem Program For Middle School Students On Learning Disability Related Ieps, Paul C. Lam, Dennis Doverspike, Julie Zhao, Jiang Zhe, Craig C. Menzemer

Mechanical Engineering Faculty Research

A year long Science, Technology, Engineering and Math (STEM) program was developed for middle schools students on Individualized Education Programs (IEPs) involving learning disabilities. The workshops were designed to encourage students both on IEPs and not on IEPs to explore STEM as a future career choice by building their knowledge and confidence. The participants in the workshops included 11 students on IEPs and 15 students not on IEPs. Parents also provided feedback regarding their attitudes toward the program. The results indicated that there were increases in student participant knowledge and career interest for both the students not on IEPs and …

Fiber-Optic Strain Gauge With High Resolution And Update Rate, Fernando Figueroa, Ajay Mohan Mahajan, Mohammad Sayeh, Bradley Regez

Mechanical Engineering Faculty Research

An improved fiber-optic strain gauge is capable of measuring strains in the approximate range of 0 to 50 microstrains with a resolution of 0.1 microstrain. (To some extent, the resolution of the strain gauge can be tailored and may be extensible to 0.01 microstrain.) The total cost of the hardware components of this strain gauge is less than $100 at 2006 prices. In comparison with prior strain gauges capable of measurement of such low strains, this strain gauge is more accurate, more economical, and more robust, and it operates at a higher update rate. Strain gauges like this one are …

"Smart" Sensor Module, Ajay Mohan Mahajan

Mechanical Engineering Faculty Research

An assembly that contains a sensor, sensor-signal-conditioning circuitry, a sensor-readout analog-to-digital converter (ADC), data-storage circuitry, and a microprocessor that runs special-purpose software and communicates with one or more external computer(s) has been developed as a prototype of "smart" sensor modules for monitoring the integrity and functionality (the "health") of engineering systems. Although these modules are now being designed specifically for use on rocket-engine test stands, it is anticipated that they could also readily be designed to be incorporated into health-monitoring subsystems of such diverse engineering systems as spacecraft, aircraft, land vehicles, bridges, buildings, power plants, oilrigs, and defense installations. The …

Local Material Properties Meausrement Using Ultrasonic C-Scan Techniques, Dooheon Kim, Tsuchin P. Chu, Ajay Mohan Mahajan

Mechanical Engineering Faculty Research

Mechanical material properties of concrete specimen are evaluated locally and non-destructively using an ultrasonic C-scan system. The time of flight of the sound wave between front surface and back surface for test samples was measured. Local Young's modulus at scanning point and average Young's modulus of entire specimen are calculated. Testing techniques are developed by calibrating the transducer not only to compensate for the time delay but also to control the measurement of properties of interest, such as true density and local thickness. In order to obtain additional mechanical property, such as Poisson's ratio, the transverse velocities of the wave …

Improvement Of Mechanical Properties Of Uv-Curable Resin For High-Aspect Ratio Microstructures Fabricated In Microstereolithography, Su-Do Lee, Jae-Won Choi, In-Baek Park, Chang-Sik Ha, Seok-Hee Lee

Mechanical Engineering Faculty Research

Recently, microstructures fabricated using microstereolithography technology have been used in the biological, medical and mechanical fields. Microstereolithography can fabricate real 3D microstructures with fine features, although there is presently a limited number of materials available for use in the process. Deformation of the fine features on a fabricated microstructure remains a critical issue for successful part fabrication, and part deformation can occur during rinsing or during fabrication as a result of fluid flow forces that occur during movement of mechanical parts of the system. Deformation can result in failure to fabricate a particular feature by breaking the feature completely, spatial …

Fabrication Of Microstructure Array Using The Projection Microstereolithography System, Jae-Won Choi, Young-Myoung Ha, Seok-Hee Lee

Mechanical Engineering Faculty Research

Microstereolithography technology is similar to the conventional stereolithography process and enables to fabricate a complex 3D microstructure. This is divided into scanning and projection type according to aiming at precision and fabrication speed. The scanning MSL fabricates each layer using position control of laser spot on the resin surface, whereas the projection MSL fabricates one layer with one exposure using a mask. In the projection MSL, DMD used to generate dynamic pattern consists of micromirrors which have per side. The fabrication range and resolution are determined by the field of view of the DMD and the magnification of the projection …

Pneumatic Tire, Alan Neville Gent, Joseph D. Walter

Mechanical Engineering Faculty Research

For many years, tire engineers relied on the monograph, 'Mechanics of Pneumatic Tires', for detailed information about the principles of tire design and use. Published originally by the National Bureau of Standards, U.S. Department of Commerce, in 1971, and a later (1981) edition by the National Highway Traffic Safety Administration (NHTSA), U.S. Department of Transportation, it has long been out of print. No textbook or monograph of comparable range and depth has appeared since. While many chapters of the two editions contain authoritative reviews that are still relevant today, they were prepared in an era when bias ply and belted-bias …

Dielectric Properties Of Graphite Nanocomposites, Shing Chung Josh Wong, Erwin M. Wouterson, Eric M. Sutherland

Mechanical Engineering Faculty Research

Polymer nanocomposites are an emerging class of multifunctional materials that have not been optimized for their functional potential. In this study, the dielectric properties of graphite polymer nanocomposites were evaluated. The objective was to develop for composite applications, an alternative cost-effective nanoscale carbon material with properties comparable to those of carbon nanotubes.

Recent Development In The Weibull Stress Model For Prediction Of Cleavage Fracture In Ferritic Steels, Xiaosheng Gao, Robert H. Dodds Jr.

Mechanical Engineering Faculty Research

This paper reviews recent developments in the Weibull stress model for prediction of cleavage fracture in ferritic steels. The procedure to calibrate the Weibull stress parameters builds upon the toughness scaling model between two crack configurations having different constraint levels and eliminates the recently discovered non-uniqueness that arises in calibrations using only fracture toughness data obtained under small scale yielding (SSY) conditions. The introduction of a non-zero threshold value for Weibull stress in the expression for cumulative failure probability is consistent with the experimental observations that there exists a minimum toughness value for cleavage fracture in ferritic steels, and brings …

Intelligent Sensors: An Integrated Systems Approach, Ajay Mahajan, Sanjeevi Chitikeshi, Pavan Bandhil, Lucas Utterback, Fernando Figueroa

Mechanical Engineering Faculty Research

The need for intelligent sensors as a critical component for Integrated System Health Management (ISHM) is fairly well recognized by now. Even the definition of what constitutes an intelligent sensor (or smart sensor) is well documented and stems from an intuitive desire to get the best quality measurement data that forms the basis of any complex health monitoring and/or management system. If the sensors, i.e. the elements closest to the measurand, are unreliable then the whole system works with a tremendous handicap. Hence, there has always been a desire to distribute intelligence down to the sensor level, and give it …

Physical Intelligent Sensors, Pavan Bandhil, Sanjeevi Chitikeshi, Ajay Mohan Mahajan, Fernando Figueroa

Mechanical Engineering Faculty Research

This paper proposes the development of intelligent sensors as part of an integrated systems approach, i.e. one treats the sensors as a complete system with its own sensing hardware (the traditional sensor), A/D converters, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow them to get better with time. Under a project being undertaken at the NASA s Stennis Space Center, an integrated framework is being developed for the intelligent monitoring of smart elements. These smart elements can be sensors, actuators or other devices. The immediate application is the monitoring of the rocket test …

Analysis Of Loading Rate Effects On Cleavage Fracture Toughness Of Ferritic Steels, Xiaosheng Gao, Robert H. Dodds Jr.

Mechanical Engineering Faculty Research

No abstract provided.