bluuebunny/crossref_metadata_2025 huggingface dataset:
Linking Student Achievement to Learning Outcomes Assessment
Authors: Ainane Sami , Thamire Chandrasekhar
Published: April 2008

In 2005, the undergraduate program offered by the Department of Mechanical Engineering at the University of Maryland, College Park, will be undergoing the ABET accreditation review process. In view of the recent changes in the EAC criteria, the Department is currently implementing a reformed assessment program. Direct assessment practices are now being utilized to assess the outcomes, along with the other assessment tools and methodologies used during the previous years. As part of this process, individual courses in the curriculum are identified to target selected learning outcomes, related student work is collected and examined by individual faculty and faculty committees, and the results are used to evaluate the outcomes and identify deficiencies. In this paper we present the outcomes assessment process developed for this purpose, which includes a description of the direct measures of student achievement in engineering courses and the traditional tools such as course and program evaluation surveys and inputs from various constituencies and committees. Specific student work targeted to achieve different learning outcomes is identified for selected outcomes.
Shock and Vibration Survivability Prediction Using Failure Envelopes for Electronic and MEMS Packaging
Authors: Lall Pradeep , Panchagade Dhananjay , Choudhary Prakriti , Suhling Jeff , Gupte Sameep
Published: April 2008

Product level assessment of drop and shock reliability relies heavily on experimental test methods. Prediction of drop and shock survivability is largely beyond the state-of-art. However, the use of experimental approach to test out every possible design variation, and identify the one that gives the maximum design margin is often not feasible because of product development cycle time and cost constraints. Presently, one of the primary methodologies for evaluating shock and vibration survivability of electronic packaging is the JEDEC drop test method, JESD22-B111 which tests board-level reliability of packaging. However, packages in electronic products may be subjected to a wide-array of boundary conditions beyond those targeted in the test method. In this paper, a failure-envelope approach based on wavelet transforms and damage proxies has been developed to model drop and shock survivability of electronic packaging. Data on damage progression under transient-shock and vibration in both 95.5Sn4.0Ag0.5Cu and 63Sn37Pb ball-grid arrays has been presented. Component types examined include — flex-substrate and rigid substrate ball-grid arrays. Dynamic measurements like acceleration, strain and resistance are measured and analyzed using high-speed data acquisition system capable of capturing in-situ strain, continuity and acceleration data in excess of 5 million samples per second. Ultra high-speed video at 150,000 fps per second has been used to capture the deformation kinematics. The concept of relative damage index has been used to both evaluate and predict damage progression during transient shock. The failure-envelope provides a fundamental basis for development of component integration guidelines to ensure survivability in shock and vibration environments at a user-specified confidence level. The approach is scalable to application at system-level. Explicit finite-element models have been developed for prediction of shock survivability based on the failure envelope. Model predictions have been correlated with experimental data for both leaded and leadfree ball-grid arrays.
Methodologies for Prognostication and Health Monitoring of Leaded and Lead Free Electronics and MEMS Packages in Harsh Environments
Authors: Lall Pradeep , Islam Nokibul , Choudhary Prakriti , Suhling Jeff
Published: April 2008

In this paper, a methodology for prognostication-of-electronics has been developed for accurate assessment of residual life in a deployed electronic components, and determination of damage-state in absence of macro-indicators of failure. Proxies for leading indicators-of-failure have been identified and correlated with damage progression under thermo-mechanical loads. Examples of proxies include — micro-structural evolution characterized by average phase size and intermetallic growth rate in solder interconnects. Validity of damage proxies has been investigated for both 63Sn37Pb leaded and SnAgCu leadfree electronics. Structures examined include — plastic ball grid array format electronic and MEMS Packages and discrete devices assembled with FR4-06 laminates. Focus of the research presented in this paper is on interrogation of the aged material’s damage state and enhancing the understanding of damage progression. The research is aimed at development of damage relationships for determination of residual life of aged electronics and assessment of design margins instead of life prediction of new components. The prognostic indicators presented in this paper, can be used for health monitoring of electronic assemblies.
Experimental Investigation of Natural Convection Heat Transfer From a Horizontal Array of Three Heated Cylinders
Authors: Chatha Asim , Fakheri Ahmad
Published: April 2008

An experimental study was performed to determine the natural convection heat transfer characteristics of a row of three horizontal heated cylinders of two different diameters (0.625 in. and 1.50 in.) with various cylinder-spacing arrangements. As a result, it was found that the heat transfer characteristics are strongly dependent on the spacing between the cylinders and the Rayleigh number Ra. The results of this study show that as the inter-cylinder spacing between a single row of three horizontal heated cylinders is reduced, the natural convection heat transfer coefficient and the heat transfer from each cylinder initially increase and then decrease beyond those for infinitely apart cylinders. Therefore, the array’s total rate of heat transfer increases because of two factors: the enhanced heat transfer coefficient, and the ability to add more cylinders in a fixed volume. This type of behavior has not been reported before experimentally and should be useful in the design of heat exchangers to reduce their sizes.
An Yield Model for Electronics Assembly
Authors: Gnanasambandam N. , Munikrishnan M. , Poyyapakkam V. , Borgesen P. , Srihari K.
Published: April 2008

Managing assembly yield in the Printed Circuit Board (PCB) assembly process is crucial in reducing the overall manufacturing cost of a product. Being faced with electronic components that have high interconnect (pin or solder bump) count, density, and complexity, it is extremely important to streamline the manufacturing losses arising from misplaced or poorly assembled components. In order to achieve this goal, yield models are utilized to anticipate and evaluate problems and their causes. This activity could be potentially implemented at the design stage or at least much before the product reaches the manufacturing floor. This research examines some important factors that affect area array (BGA, CSP, flip chip) assembly yields, taking a two-pronged approach to modeling. Achievable yield is classified into placement and assembly components and is estimated using a simulation model.
A Multi-Fingered Micromechanism for Coordinated Micro/Nano Manipulation
Authors: Krishnan Sandeep , Saggere Laxman
Published: April 2008

Micromanipulators for coordinated manipulation of micro- and nano-scale objects are critical for advancing several emerging applications such as microassembly and manipulation of biological cells. Most of existing designs for micromanipulators accomplish either primarily microgripping or primarily micropositioning tasks, and relatively, only a very few are capable of accomplishing both microgripping and micropositioning, however, they are generally bulky. This paper presents conceptualization, design, fabrication and experimental characterization a novel micromanipulation station for coordinated planar manipulation combining both gripping and positioning of micro- and nano-scale objects. Conceptually, the micromanipulation station is comprised of multiple, independently actuated, fingers capable of coordinating with each other to accomplish the manipulation and assembly of micron-scale objects within a small workspace. A baseline design is accomplished through a systematic design optimization of each finger maximizing the workspace area of the manipulation station using the optimization toolbox in MATLAB. The device is micromachined on a SOI (silicon-on-insulator) wafer using the DRIE (Deep Reactive Ion Etching) process. The device prototype is experimentally characterized for the output displacement characteristics of each finger for known input displacements applied through manual probing. An excellent correlation between the experimental results and the theoretical results obtained through a finite element analysis in ANSYS software, which validates both the design and the fabrication of the proof-of-the-concept, is demonstrated.
Picoliter Fluidic Flow Characterization Using Ion-Selective Measurement
Authors: Cavallaro Alberto , Saggere Laxman
Published: April 2008

Techniques for accurate measurement of liquid flows involving volumes on the order of nanoliters and picoliters are critical for advancement of microfluidics applications. Although several techniques for measurement of microfluidic flows where a liquid is dispensed on to a target are available today, no proven techniques currently exist for measurement of microfluidic flows where a liquid is injected into a liquid media. Motivated by such a measurement need in a current project, this paper presents a novel experimental technique to measure bulk-flow of a liquid dispensed into another liquid medium with sensitivity down to picoliter range. This technique is based on the principle of titration of two liquids and measurement of hydrogen ions in the resulting solution. The critical components of the system that enable the proposed technique are: A highly sensitive hydrogen ion concentration (pH) sensor and a device to dispense very small, calibrated, volumes of liquid. Since commercially available hydrogen ion sensors are bulky for use in the proposed technique, a hydrogen ion sensor element that provides a sensing tip dimension on the order of a few microns is fabricated from a glass capillary for the current study. Dispensing of calibrated volumes of liquid is accomplished by means of a calibrated syringe for volumes in nanoliter range and a glass capillary for volumes in picoliter range, the latter serving as a dispensing port of a diameter of about 2 μm. The paper includes details of experiments where the proposed technique is first applied to precisely predict injections of 20 and 40 nL volumes and then extended to demonstrate the sensitivity of the sensor element to injections of volumes in the picoliter range. The preliminary experimental results presented generally validate the principle involved in this technique and suggest that the technique is virtually scalable to any volume flows typically encountered in the microfluidics applications.
Structural Reliability of SU-8 Material for MEMS Application
Authors: Park S. B. , Chung Soonwan , Makhar Sandeep , Ackler Harold , Lin Pinyen
Published: April 2008

Mechanical properties of SU-8 over the range of temperature, −50 to 250 °C, were measured. Traditional tension test is performed with the dog-bone specimens using microfabrication techniques. The bulk properties such as elastic modulus, Poisson’s ratio and tensile strength are obtained in various temperatures. Bulge test is performed using SU-8 membrane constrained by silicon wafer. Pressure is applied to the membrane, and by analyzing the deflection of membrane, the elastic modulus and residual stress of SU-8 thin film are acquired. The relationship between applied pressure and deflection is obtained by changing some geometric parameters such as membrane thickness and diameter. The interfacial fracture toughness between SU-8 and silicon will measured using the membrane structure. The interfacial toughness obtained from the experiments will be compared with the strain energy release rate from finite element analysis, and the failure analysis at the interface under the actual thermal fatigue environment will be investigated using a numerical model.
Effects of Heat Transfer From a Scroll Compressor Using Heat Pipes
Authors: Dinh Khiem , Lear William
Published: April 2008

A scroll air compressor was experimentally tested in three configurations: stock, integrated with a heat pipe rejecting heat by free convection to the ambient atmosphere, and integrated with a heat pipe rejecting heat by forced convection to the ambient atmosphere. Each configuration was tested over a range of motor speeds. Parameters of interest included mass flow rate, pressure ratio, scroll compressor component temperatures, discharge air temperature, and power consumption. Furthermore, a simple computer model was developed in Excel and used to further analyze the experimental data.
Fatigue Strength Evaluation of Defects Embedded in Large-Sized Stud Bolt of Marine Engine
Authors: Kim Kukbin , Kim Byung-Joo , Park Jinsoo , Yoon Young-Cheol , Park Deukjin
Published: April 2008

Millimeter-sized defects are often found during inspection near the centerline of the shank of large-sized stud bolts. Determination of allowable defect size is practically required in view of safety. An experimental investigation on the fatigue strength of the stud bolt has been carried out in order to evaluate the effect of defects embedded in the stud bolt on the fatigue strength. Fatigue testing was conducted for stress ratios of 0.0, 0.4 and 0.7 using plain specimens and defected specimens having a defect embedded inside to examine the fatigue limit according to the stress ratio. Macroscopic and microscopic analyses were also conducted in order to determine initial defect size, crack initiation site and propagation rate from beach marks on the fracture surface. Existing small defect evaluation methods currently available were used for the strength evaluation. Allowable internal defect size was determined based on the high mean and high cycle stress states of the bolt by linear elastic fracture mechanics.
An Evaluation of the Mechanical Behaviour of Imperfect Aluminium Tubes
Authors: Henning Pieter F. J. , Pretorius Leon , Laubscher Rudolph F.
Published: April 2008

In this research the effect of geometric changes introduced on Al 6063-T6 circular tubes in the form of horizontal and spiral grooves, (Fig. 2 and Fig. 3) is assessed. The horizontal and spiral grooves were cut into the tube to a depth of half the wall thickness of the tubes, while the pitch was varied for both the horizontal and spiral grooves, and the cut width was kept constant. These tubes were axially compressed, and load vs. displacement and Energy vs. displacement graphs were generated from the captured experimental data for the tubes. A Finite Element Method model is presented for each of the experimentally tested tubes. 2D models for the uncut and horizontally grooved tubes and a 3D model for the spiral cut tube were generated and analyzed. Reaction force vs. displacement and energy vs. displacement graphs are presented for the different analyses. A comparison is made between the numerically and experimentally determined gradients of the energy vs. displacement graphs for each of the tubes analyzed. This forms the basis for an energy absorber design with application in the transport industry currently under consideration.
Using Objective-Driven Heat Transfer Lab Experiences to Simultaneously Teach Critical Thinking Skills and Technical Content
Authors: Bruno Bradford A. , Anderson Ann M.
Published: April 2008

The heat transfer course at Union College has been redesigned to improve critical thinking and problem solving skills, provide an understanding of the origin of the data and parameters used in heat transfer analysis, and familiarize students with modern experimental and computer analysis tools. The course is taught in the junior year and combines a 4-hr/wk lecture with a 3-hr/wk integrated lab component during a 10 week term. The lecture covers the traditional conduction, convection and radiation heat transfer material whereas in the lab students combine hands on experimental measurements with the use of sophisticated design tools. Our method for achieving the course goals is to use objective-driven lab exercises. Students are asked directed questions about a concrete problem involving heat transfer and are required to develop an experimental/numerical plan to answer the questions. Initial labs are more directed and are designed to introduce experimental / numerical analysis techniques which students may then use in the end of term design project which is more open ended. We have focused on the use of small scale inexpensive equipment which allows us to use multiple set-ups and have students work in small (2-3 person) groups. In this paper we present the weekly lab exercises and discuss how they contribute to the pedagogical goals for the lab, course, and curriculum.
Self Adapting Mechanical Step Bearings for Variations in Load
Authors: Jackson Robert L.
Published: April 2008

As the application of small-scale and precision technologies increases, the need will grow for bearings which are able to provide precision control of their location. At the micro and nano-scale there is a need for new bearing technologies to reduce friction and wear, and provide precision control of bearing motion. This control can be provided by electronically controlled actuators and sensors, but then the system is dependant on the reliability of the electronics. This work uses numerical methods to research the design and behavior of self adapting smart step bearings. These step bearings are designed to change their surface profiles to achieve an optimal or controlled behavior, without the use electronics or external control. The bearing changes its profile to control the film height of the bearing to a near constant value for different loads. The result is a self adapting step bearing design that may be applied at multiple scales for use in a wide variety of machine components. The numerical simulation shows that the self adapting step bearing is able to autonomously adapt in real time to dynamic loads and maintain a desired film thickness with a relatively small amount of deviation. The self adapting step bearing also exhibits smaller dynamic responses to transient loads in comparison to a conventional static geometry step bearing.
Micromechanics of Longitudinal Mechanical Properties for Active Fiber Composites With Embedded Metal-Core Piezoelectric Fibers
Authors: Ghasemi Nejhad Mehrdad N. , Askari Davood
Published: April 2008

An analytical micromechanics approach is presented to model the effective longitudinal mechanical properties of Metal-Core Piezoelectric Fibers (MPF). The model assumes general orthotropic material properties for the piezoelectric as well as the core material. Next, the general orthotropic solution is reduced to transversely isotropic for the piezoelectric fiber and isotropic for the metal-core. This MPF system is also modeled using finite element analysis (FEA) and the results from the analytical solution and FEA are compared for verification purpose. Next, the Metal-Core Piezoelectric Fiber (MPF) is embedded inside a metal or a polymer and the resulting longitudinal mechanical properties of these Active Fiber Composite (AFC) systems are given analytically.
Influence of Sensor Substrate Geometry on the Sensitivity of MEMS Micro-Extensometers
Authors: Azevedo R. G. , Chen I. , O’Reilly O. M. , Pisano A. P.
Published: April 2008

In order to determine the influence of the silicon chip substrate on measurement fidelity in a silicon MEMS micro-extensometer, finite element modeling of strain transfer efficiency from a steel beam through a bond layer and silicon chip is investigated over a range of chip and steel beam geometries under both axial and pure bending load conditions. The finite element model results are verified against experimental data. An analytical model that incorporates both influence of the bonded substrate on the effective load and shear-lag phenomenon in the bond is developed and is shown to compare favorably to the finite element model over a wide range of chip and beam geometries. Based on these results, a partially-trenched silicon chip is also investigated as an alternate means of locally enhancing the strain transfer to the micro-extensometer without compromising the ability of the substrate to act as part of the encapsulation of moving elements of the micro-extensometer from the environment. The partially-trenched substrate in bending is experimentally shown to generate strains that are 118% of the strain applied to the substrate—a 23% percent improvement over the equivalent unpatterned substrate geometry.
Numerical Simulation in a Multiple Flow Control Valve System of Polymer Melt During Injection Molding Processes
Authors: Layser Gregory S. , Coulter John P.
Published: April 2008

Process control is an important factor for improving the performance and consistency of thermoplastic parts manufactured by injection molding processes. A critical process parameter for manufacturing of high quality plastic parts is cavity pressure. This paper presents a continuation of a numerical based study of flow control utilized during multi-cavity injection molding processes and focuses in more detail on multiple flow control valve systems, since the valves are coupled with one injection source. The capabilities of the current system design are limited by multiple valve interactions, which may produce undesirable effects in regards to flow modulation and pressure distribution in multiple cavities and should be studied further. Understanding the flow modeling details through a single valve system is essential, thereby reducing the computational work involved with a multiple valve system.
Asymptotic Solutions of Effective Thermal Conductivity of Particle-Laden Polymers
Authors: Karayacoubian P. , Bahrami M. , Culham J. R.
Published: April 2008

A general predictive model for the effective thermal conductivity of mixtures is developed. In the limit of very small particle volume fractions, a limiting case is approached where the effective medium theory of Maxwell holds. At higher solid fractions, an analytical model for the conductivity of a packed bed of spheres is developed. These two limiting asymptotic solutions are then combined using a blending procedure. The result is a semi-analytical model that is valid over the full range of solid fractions. The model shows that in addition to the conductivities of the particle/matrix and the solid fraction, the degree of wetting of the particles by the matrix is an important parameter in estimating the effective thermal conductivity of the mixture. In addition, the effect of entrapped air is captured through the definition of an effective volume fraction in Maxwell’s model. The model shows good agreement with experimental data.
Techno-Economic Analysis of an Earth-Air Heat Exchanger for Cooling and Heating of a Building
Authors: Shukla Ashish , Tiwari G. N. , Sodha M. S.
Published: April 2008

In this communication a quasi-steady state mathematical model is developed to predict the air temperature at the outlet of an earth-air heat exchanger and seasonal heating and cooling potential, associated with the use of the exchanger. Seasonal values of heating and cooling potential are estimated theoretically and validated by experiments in two distinct seasons, i.e. winter and summer, corresponding to composite climate of New Delhi (28° 35′ N, 77° 12′ E) India. It is observed that there is significant saving of energy and money by reducing cooling and heating loads on air-conditioners, if earth air heat exchanger is used. There is fair agreement between theoretical values and experimentally observed values of the seasonal values of heating and cooling potentials for each season (i.e. winter and summer).
An Implicit Model for Snake Robot Locomotion and Gait Optimization
Authors: Nirakh Appa Rao , Brennan Sean N. , Gandhi Farhan S.
Published: April 2008

The present study aims to develop dynamic models suitable for the analysis and design of robotic snakes. Specifically, this research presents an implicit model with a high degree of design flexibility, namely the ability to change the number of links and to vary friction in the model formulation. The implicit model is validated numerically by comparison to an explicit model with small number of links. The validated implicit model is then used to establish the optimal gait for a six-link snake robot to achieve locomotion with minimal power consumption. An iterative search is conducted over a range of operational parameters — amplitude of angular displacement inputs at each joint, relative phase lag between the sinusoidal displacement inputs at the joints, and frequency of sine-wave input — to determine the optimally efficient gait. Results indicate that, for a particular forward velocity, an optimal gait exists that minimizes power consumption. This optimal solution is validated experimentally via tests performed on a six-link snake robot.
A Crush Zone Design for an Existing Passenger Rail Cab Car
Authors: Martinez Eloy , Tyrell David , Rancatore Robert , Stringfellow Richard , Amar Gabriel
Published: April 2008

A Crash Energy Management (CEM) cab car crush zone design has been developed for retrofit onto an existing Budd M1 cab car. This design is to be used in the upcoming full-scale train-to-train test of a CEM consist impacting a standing freight consist of comparable weight. The cab car crush zone design is based upon the coach car crush zone design that has been previously developed and tested. The integrated system was developed after existing national and international CEM systems were reviewed. A detailed set of design requirements was then drafted, and preliminary designs of sub-assemblies were developed. The preliminary designs were analyzed using detailed large deformation finite element software. Performance of the cab car crush zone under ideal and non-ideal loading conditions was analyzed prior to development of the final design. The key components of the design include: a long stroke push-back coupler capable of accommodating the colliding locomotive coupler, a deformable anti-climber to manage the colliding interface interaction, an integrated end frame on which the deformable anti-climber is attached, a set of primary energy absorbers designed to crush in a controlled manner while absorbing the majority of the collision energy, and a survivable space for the operator which pushes back into an electrical closet. The cab car crush zone is designed to control both lateral and vertical vehicle motions that can promote lateral buckling of the train and override of the impacting equipment. The design is capable of managing the colliding interface interaction with a freight locomotive and passing crush back to successive crush zones. Detailed fabrication drawings have been developed and submitted to a fabrication shop. In addition, existing Budd M1 cars are being prepared to receive the retrofit components.
Bi-Directional Actuation of a Piston Using MR Valves and a Piezoelectric Pump
Authors: John Shaju , Yoo Jin-Hyeong , Sirohi Jayant , Wereley Norman M.
Published: April 2008

There is a demand for hybrid actuation systems which combine actuation and valving systems in a compact package. MR fluids can be used in valves to control the motion of an output cylinder. Such a valving system will have no moving parts and thus can be used in applications where there is high centrifugal loading. In the current setup, MR valves are configured in the form of a Wheatstone bridge where the two arms form the high and low pressure sides of the output cylinder. The actuation is performed using a compact piezoelectric stack driven actuator. The frequency rectification of the piezo stack motion is done using reed valves. This actuator and valve configuration form a compact hydraulic system with electro-mechanical valves. The advantages of such systems are that part count is low, fewer moving parts and the ability to control the motion of the output cylinder by controlling the fluid flow through the MR valves. By the application of different magnetic fields in the arms of the bridge (by applying different currents to the magnetic circuits), we can control the differential pressure seen by the output cylinder. This allows us to design different controllers for the system. The two systems in this configuration have been separately evaluated. The piezo pump system was first tested for its performance and efficiency with conventional hydraulic fluid and MR fluid. At this stage, the MR valve setup has not been added to isolate the actuating system from the valve system and the MR fluid acts merely as a transmission fluid. The Wheatstone bridge setup was then added and the efficiency of the MR valve was tested against a dummy mechanical valve. The modeling of the valve was done on the basis of standard rheological models like Bingham Plastic and bi-viscous models. Data for bi-directional actuation of the output cylinder is presented and assessed analytically.
Finite Element Analysis of Functionally Graded Shell Panels Under Thermal Loading
Authors: Cooley W. Glenn , Palazotto Anthony
Published: April 2008

Functionally Graded Materials (FGM) have continuous variation of material properties from one surface to another unlike a composite which has stepped (or discontinuous) material properties. The gradation of properties in an FGM reduces the thermal stresses, residual stresses, and stress concentrations found in traditional composites. An FGM’s gradation in material properties allows the designer to tailor material response to meet design criteria. For example, the Space Shuttle utilizes ceramic tiles as thermal protection from heat generated during re-entry into the Earth’s atmosphere. However, these tiles are prone to cracking at the tile / superstructure interface due to differences in thermal expansion coefficients. An FGM made of ceramic and metal can provide the thermal protection and load carrying capability in one material thus eliminating the problem of cracked tiles found on the Space Shuttle. This paper will explore analysis of shell panels under thermal loading and compare performance of traditional homogeneous materials to FGMs using ABAQUS [1] finite element software. First, theoretical development of FGMs is presented. Second, finite element modeling technique for FGMs is discussed for a thermal stress analysis. Third, homogeneous curved panels made of ceramic and metal are analyzed under thermal loading. Finally, FGM curved panels created from a mixture of ceramic and metal are analyzed. FGM performance is compared to the homogeneous materials in order to explore the effect continuously grading material properties has on structural performance.
Development of Virtual Assembly Application With Haptics, Assembly Modification and Statistical Output Measures
Authors: Mandiak Matthew A. , Kesavadas Thenkurussi
Published: April 2008

The concept of virtual assembly offers endless possibilities to a designer in a manufacturing setting. Various assembly measures such as clearance, assembly planning, force and alternate designs can be examined without the need to waste resources through manufacturing. This paper investigates the possibility of using force feedback through haptics in a virtual environment as a way of understanding the intricacy of simple assembly. This allows a designer to further understand what will, and will not, work during the design phase. The study of certain characteristics, including lubrication, is also examined to see what impact it has on the ease of assembly. A user, or designer, can then get an actual feel to see what characteristics change the likelihood for a proper fit. In addition, the creation of a virtual part run is also examined to fully understand what constitutes a defect. Statistical output is provided so a user can analyze a run of parts for quality control and be able to pinpoint possible causes for error in a process. Virtual parts can then be assembled from the run to see how each differs from the others and to emphasize the undesirability of a defect for assembly purposes.
Development of a Dynamic Failure Prediction Tool for Marine Composite Structures
Authors: Lua Jim , Gregory William
Published: April 2008

Composite ship structures are subjected to both the low and high velocity impact during their service life. The dynamic impact can generate fiber, matrix and/or delamination damage inside a woven fabric composite laminate, which may significantly reduce its stiffness and strength. Both the structural mechanics and fracture mechanics based models cannot fully capture the impact damage evolution due to coexistence of continuum and discrete damage. The stress and strain at the element level cannot be directly used to predict the constituent damage and the resulting mechanism driven stiffness degradation. In this paper, a hybrid discrete and continuum damage model is developed and numerically implemented within the LS-DYNA environment via a user-defined material model. The continuum damage progression and its associated stiffness degradation are predicted based on the constituent stress/strain and their associated failure criteria while the delamination damage is numerically captured via a cohesive interface model.
Mathematical Modeling and Numerical Simulation of Flame Spread Over Water-in-Oil Emulsions
Authors: Thatte Azam M. , Kulkarni Anil K.
Published: April 2008

Flame spread characteristics are studied for water-in-oil emulsion layers floating on top of a water body — similar to a scenario in which an accidental oil spill occurs in open, rough sea. A comprehensive mathematical model is developed and numerical solution is obtained for the ignition and flame spread process which takes into account the emulsion break up into oil and water due to heating, oil vaporization, combustion of oil vapor mixed with air in open atmosphere, radiative and convective heat feed back from flames to the condensed phase (consisting of emulsion, oil, and water), and continuation of the emulsion breaking resulting in flame spread till the oil is consumed. Numerical results are compared with experiments conducted on Arabian Medium Crude oil emulsions made with up to 20% weathered oil (light fraction evaporated, by volume), having up to 50% water content in the emulsions. The flame spread rate decreased as the water content and the weathering level increased, with a reasonable agreement between experiments and model. The long term objective of this work is to assist the application of in situ burning as a measure for the cleanup of weathered and emulsified oils.
Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control
Authors: Gautam Ashwini , Fuller Chris , Carneal James
Published: April 2008

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.
Delivering an International Experience to Students in an Intercultural Engineering Course
Authors: Ciocci Richard C.
Published: April 2008

At Penn State, Engineering Technology (ET) 420W, Design for Society, is an interdisciplinary study of the engineering design process and the influences of society and culture on design. Students explore sustainability in various countries, examine and describe connections between technological and cultural development, learn and apply the engineering design process in societal and cultural contexts, and focus analytical skills on societal and cross-cultural issues. In 2005, the university’s Capital College offered ET 420W with an option for students to participate in an international study tour of London during spring break. This international experience was designed to provide out-of-classroom activities that would supplement course material. Penn State chose London as a destination since UK industry and government act as leaders in moving the European Union (EU) towards a sustainable society. This paper describes the study tour experience, provides descriptions of its activities, and examines its benefit to both students and the instructor.
Comparative Study of Unprotected vs. Protected Surfaces Using an Innovative Process for Applying Solid Lubricants to Reduce Friction and Wear
Authors: Buehler Jane E. , Bowles K. Dean
Published: April 2008

Two tribocouples were compared neat vs. treated with Induratec™. The tribocouples, tested under dry sliding conditions via a pin-on-disc tribometer, were 52100 steel ball on 52100 steel disc and 8620 steel pin on C67300 bronze disc. Comparisons of coefficient of friction and wear coefficient, K (mm3/N m) are presented. For the 52100 tribocouple two test conditions were completed, a 9.8 N load at 0.75 m/s and a 29.4 N load at 2.0 m/s. The coefficient of friction, for the treated samples compared to the untreated samples, was reduced by 74% for the lower load and speed condition and by 79% for the higher load and speed condition. For the lower load and speed test condition, the wear coefficient was reduced by a factor of 55 and for the higher load and speed condition the wear coefficient was reduced by a factor of 887. For the 8620 steel pin on C67300 bronze disc, two test conditions were completed, a 9.8 N load at 2.5 m/s sliding speed and a 19.6 N load also at 2.5 m/s sliding speed. The treated surface had a 42% lower coefficient of friction at the 9.8 N load and a 57% lower coefficient of friction at the 19.6 N load. The treated tribocouple wear coefficient was reduced by a factor of 600 for the 9.8 N load and by a factor of 1733 for the 19.6 N load.
Stress Analysis of a Novel MEMS Microphone Chip Using Finite Element Analysis
Authors: Gao Jia , Miles Ronald N. , Cui Weili
Published: April 2008

Residual stress produces major challenges in the fabrication of MEMS devices. This is particularly true in the development of MEMS microphones since the response of the thin sound-sensitive diaphragm is strongly affected by stress. It is important to predict the effects of fabrication stress on the microphone chip and identify the failure modes to ensure a satisfactory fabrication yield. In this study, a finite element model of the microphone chip is developed to analyze the laminated structure under different fabrication stresses. The model of the microphone chip includes the diaphragm, backplate and sacrificial oxide layers on top of the silicon substrate. Fabrication stresses are included through the use of an equivalent thermal stress. The stresses in the different layers have been estimated based on measurements performed on fabricated test structures. The estimated stresses are simulated in the finite element model. An important factor in determining the process reliability is the compressive stress of the low temperature sacrificial oxide layer (LTO). A variety of stress combinations between different layers with the low temperature oxide layer are investigated. It is found that an adequate level of tensile stress in the backplate is crucial to ensure the fabrication yield. In the designs considered here, silicon nitride in combination with a thin conductive layer is identified as a favorable material for the backplate considering its high modulus and tensile stress in ‘as deposited’ film. In addition, the presence of a LTO layer on the backside of the wafer turns out to be very helpful in reducing the deflection of the unreleased chip and the stress in the diaphragm. In the case where there is a net compressive stress in the laminate, the failure mode is identified by nonlinear analysis. This analysis provides a guideline to select robust materials and tune the fabrication process to ensure a satisfactory fabrication yield.
Discontinuous Finite Element Modeling of Grain Growth Behavior in Various Anisotropy of Surface Energy and Interface Mobility
Authors: Shu Y. , Ai X. , Li B. Q.
Published: April 2008

In this paper, a discontinuous finite element solution to the phase-field equations for the microstructure evolution of polycrystalline material is presented. The mathematical formulation and numerical implementation are discussed. Numerical studies are conducted on the interactions between multiple grain seeds with different orientations during solidification. The discontinuous numerical scheme is validated by the results reported in literature. The combined impacts from free surface energy and interface mobility on the microstructure formation of interface are investigated using the presented model. Results show that the anisotropy of surface energy and mobility play dominant roles in the growth rate of grains with different orientation, and hence determine the final interface morphology of crystals.
Low-Velocity Impact Response Characterization of a Hybrid Titanium Composite Laminate
Authors: Bernhardt S. , Ramulu M. , Kobayashi A. S.
Published: April 2008

The low-velocity impact response of a hybrid titanium composite laminate (HTCL), known as TiGr, was compared to that of graphite/epoxy composite. The TiGr material comprised of two outer plies of titanium foil surrounding a composite core. The composite core was PIXA-M (a high temperature thermoplastic) reinforced by IM-6 graphite fibers and consolidated by an induction heating process. The impact response of TiGr was characterized by two modes of failure which differed by failure or non-failure in tension of the bottom titanium ply. The ductility of titanium caused buckling by yielding whereas the brittle adjacent composite ply lead to fracture. The maximum failure force of the material correlated well with the previously reported static flexural data, and the material outperformed the commonly used graphite/epoxy.
The Effect of Matrix Type on Self-Assembly of Nanoparticles for Mechanical and Magnetic Applications
Authors: Abiade Jeremiah T. , Neralla Sudhir , Bradley Jermaine , Viswanathan Sundara , Gupta Alok , Paige Adero , Kumar Dhananjay
Published: April 2008

The controlled synthesis of nanostructured particles with uniform size, shape, composition, and preferred orientation is a formidable task. Some conventional techniques have been demonstrated with limited success; however, reproducible processing schemes for heterogeneous multifunctional materials are still not satisfactory. To realize the advantageous technical applications of nanostructured materials, self-assembly or self-organizing methods are currently under investigation. Our results show that the matrix or template used for directed growth of nanoparticles (Fe, Ni) significantly affects the resultant mechanical properties of the multilayered structure. For example, a crystalline material like TiN, which grows epitaxially on silicon, results in embedded epitaxial nanoparticles. Conversely, an amorphous template like Al2O3 results in polycrystalline magnetic particles. In this work, we will discuss the effect of matrix type, specifically yttria stabilized zirconia (YSZ), on the orientation of nanoparticle assemblies. The resultant mechanical and magnetic properties of the multilayer structures will be discussed in the oral presentation.
Nonlinear System Identification of a MEMS Dual-Backplate Capacitance Microphone by Harmonic Balance Method
Authors: Liu Jian , Martin David T. , Kadirvel Karthik , Nishida Toshikazu , Cattafesta Louis N. , Sheplak Mark , Mann Brian P.
Published: April 2008

This paper presents the nonlinear identification of system parameters for a capacitive dual-backplate MEMS microphone. First, the microphone is modeled by a single-degree-of-freedom (SDOF) second order differential equation with electrostatic and cubic mechanical nonlinearities. A harmonic balance nonlinear identification approach is then applied to the governing equation to obtain a set of algebraic equations that relate the unknown system parameters to the steady-state response of the microphone under the harmonic excitation. The microphone is experimentally characterized and a nonlinear least-squares technique is implemented to identify the system parameters from experimental data. The experimentally extracted bandwidth of the microphone is over 218 kHz. Finally, numerical simulations of the governing equation are performed, using the identified system parameters, to validate the accuracy of the approximate solution. The differences between the properties of the integrated measured center velocity and simulated center displacement responses in the steady state are less than 1%.
Effect of Settlement on Dense Slurry Flow in a Horizontal Channel
Authors: Yang R. , Sun D. C. , Park Seungbae
Published: April 2008

The flow of a dense slurry where the filling particles are heavier than the liquid carrier is analyzed by considering the particle-particle and particle-wall interactions, which were derived from fluid film lubrication theory. The effect of settlement causes the flow behavior to depart from that of slug flow (described in [1], also submitted to this Congress). It is found that steady flow is still possible, and, for a few representative packing patterns considered, somewhat modified patterns exist. An ongoing under-fill flow experiment aimed at validating the above theoretical results is described.
Non-Invasive Method for Velocity and Slug Length Measurements in Gas/Liquid Flow in Horizontal Pipes
Authors: Al-Lababidi S. , Sanderson M. L.
Published: April 2008

A method was developed for the measurement of slug frequency, slug velocity and slug length of two-phase gas/liquid flow under slug conditions in 2-inch horizontal pipe. The method consists of two pairs of ultrasonic transducers with 1MHz frequency. Non-invasive detection for slugs was achieved over a range of (0.1–1 ms−1) superficial liquid velocity and (0.1–3 ms−1) superficial gas velocity. The slug translational velocity was measured using a cross correlation technique for the modulated ultrasonic signals received. The slug length was measured after measuring the slug time t(slug) and slug translational velocity. The slug parameters measured were extensively compared with conductivity probes measurements and experimental correlations.