bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Temperature Wafer Bonding in Medium Vacuum
Authors: Yu W. B. , Wei J. , Tan C. M. , Deng S. S.
Published: April 2008

Direct wafer bonding was performed under medium vacuum condition. The effect of the sequence of wafers contact and vacuum application, plasma treatment, and annealing temperature on the bonding quality was investigated. From the comparison of the bonding efficiency, contacting two wafers in air rather than in vacuum produces much less bubbles. Besides, it was also found that ex-situ plasma treatment degrades the bonding quality. It is believed that the degradation is caused by contamination and damage induced by the plasma treatment before vacuum wafer bonding. For vacuum bonding without plasma treatment, good bonding can be achieved at temperature as low as 300 °C.
Low Temperature Wafer Bonding Process Using Sol-Gel Intermediate Layer
Authors: Deng S. S. , Wei J. , Tan C. M. , Yu W. B. , Nai S. M. L. , Wong C. K.
Published: April 2008

Silicon-to-silicon wafer bonding has been successful prepared using sol-gel intermediate layer, which is deposited by spinning acid catalyzed tetraethylthosilicate (TEOS) solution on both two silicon wafer surfaces. To investigate the effects of the process parameters, Draper-Lin small composite design is used, as it requires the minimum runs in the design of experiments. Four process parameters, bonding temperature, solution PH value, solution concentration and solution aging time, have been considered to influence the bond quality, including bond efficiency and bond strength. The bond efficiency is in the range of 40%–90% and bond strength is up to 35 MPa. Statistic analysis shows that the bonding temperature is the dominant factor for the bond quality, while the interaction between temperature and concentration is significant on bond strength. Various characterization techniques, including differential thermal analysis (DTA), atomic force microscopy (AFM), scanning electron microscope (SEM), contact angle measurement and ellipsometry, have been used to study the surface and interface properties. The residual organic species inside the sol-gel coating may be the origin of the significant effect of bonding temperature on the bond efficiency. The interaction effect on bond strength is attributed to the surface hydrophilicity and porosity of sol-gel coating. Higher concentration solution can form lower hydrophilic wafer surface, which results in lower bond strength when bonding temperature is at low level. Whereas, at high bonding temperatures, the increase of porosity of the sol-gel coating prepared by higher sol concentration can absorb more undesired hydrocarbon gas molecules and lead to higher bond strength. The bonding mechanism for the low temperature sol-gel intermediate layer bonding technique is related to the smooth coating surface, porous intermediate layer and water-absent bonding groups.
Enhancing the Performance of Sn-Ag-Cu Solder With the Addition of Titanium Diboride Particulates
Authors: Nai S. M. L. , Wei J. , Wong C. K. , Gupta M.
Published: April 2008

In this study, varying volume percentage of titanium diboride particulates were successfully incorporated into Sn-Ag-Cu solder, to synthesize lead-free composite solders. The composite solders were synthesized via the powder metallurgy route of: blending, compaction, sintering and extrusion. The extruded materials were then characterized for their microstructural development, thermal and mechanical properties. With increasing volume percentage of titanium diboride particulates, the composite solders experienced a corresponding decrease in density values but porosity levels were observed to increase. Microstructural characterization using scanning electron microscopy revealed uniform distribution of reinforcement particulates and a fairly good interfacial integrity between the particulates and the solder matrix. Thermomechanical analysis showed that presence of titanium diboride particulates as reinforcements, decreased the average coefficient of thermal expansion of the solder composites. A change in the mechanical properties was also observed with the presence of increasing particulates. An attempt is made, to correlate the increasing presence of titanium diboride particulates with the microstructural development, as well as the mechanical and thermal properties of solder matrix.
Characterization of Magnesium/Carbon Nanotubes Composites Synthesized Using an Innovative Solidification Method
Authors: Goh C. S. , Gupta M. , Wei J. , Lee L. C. , Lim K. W.
Published: April 2008

In the study reported in this paper, carbon nanotubes of up to two per cent by weight were added as reinforcement to the pure magnesium. A disintegrated melt deposition technology was employed as the solidification method and the ingots produced were subsequently hot extruded at a temperature of 350 °C and extrusion ratio of 20:1. The thermo-mechanical analysis showed a reduction in the coefficient of thermal expansion due to the presence of the carbon nanotubes. Examination of the mechanical properties indicated that with increasing amount of carbon nanotubes reinforcement added, there was a significant improvement in the performance of pure magnesium. An attempt is made to correlate the weight fraction of the carbon nanotubes with the properties of the resulting magnesium nanocomposite material.
The Fundraising “DREAM” Come True
Authors: Foroudastan Saeed D. , Saxby Dyani
Published: April 2008

In times of perpetual budget cuts, project fundraising can be a difficult feat for many mechanical engineering technology departments. This is especially true for smaller departments. In fact, it is a problem that has plagued the department of Engineering Technology and Industrial Studies (ETIS) at Middle Tennessee State University (MTSU) for many years. Recently, however, the faculty of the ETIS department at MTSU has been able to overcome this difficulty through a series of five carefully prepared and executed steps that MTSU has entitled “DREAM.” The five steps that will be discussed in this paper are as follows: 1. Do well in one prestigious, national competition. 2. Request additional funding after success. 3. Establish relationships with industry. 4. Additional projects. 5. Make the most of the learning experience. This paper was written to document the experiences of the ETIS department at MTSU with the hopes of giving other mechanical engineering technology departments additional insight into fundraising techniques. The beauty of the DREAM plan is that it makes fundraising much easier because industries are usually willing to support successful teams that do well in national competitions. The DREAM plan has greatly enhanced the learning experience of the students at MTSU in several ways. First, it gives them hands-on experience that will benefit them in the real world. Next, it allows them to apply knowledge from classroom lectures and labs to an actual project from the first sketch to the competition. Finally, it gives them valuable contacts with potential future employers. These are opportunities that MTSU’s students might not be able to experience otherwise. With internal funding in such short supply, perhaps other departments could benefit from the DREAM plan as well.
Process Modeling: Lost-Foam Pattern Filling
Authors: Blaser Peter J. , Snider Dale M. , Williams Ken A. , Cook Alan E. , Hoover Mark
Published: April 2008

A transient, three-dimensional, multi-phase particle-in-cell approach is used to solve for the flow of polystyrene beads in complex three dimensional geometries which represent patterns used for lost-foam casting. The numerical method solves the gas conservation equations on an Eulerian grid and the motion of polystyrene beads is calculated in a Lagrangian frame of reference. The true particle size distribution is modeled, and the particle flow ranges from dilute to close-pack. Predicted fill behavior is compared to experimentally blown patterns using colored beads and to the measured transient filling of a pattern. The colored beads show a complex fill pattern which is calculated well by the numerical method. The transient calculation compares very well with measured video data, and the particle motion has unique particle behavior unlike a fluid. Because of uncertainties in boundary conditions in production lost-foam tooling, the sensitivity of lost-foam pattern filling to boundary conditions is examined.
An Investigation of the Lead-Free Surface Mount Soldering Process: Solder Joint Evaluation and Process Optimisation
Authors: Ryan Claire , Punch Jeff M. , Rodgers Bryan , Heaslip Greg , O’Neill Shane , Murphy Eamonn
Published: April 2008

A European Union ban on lead in most electrical and electronic equipment will be imposed as of July 1st 2006. The ban, along with market pressures, means that manufacturers must transfer from a tin-lead soldering process to a lead-free process. In this paper the implications on the surface mount (SMT) soldering process are presented. A set of experiments was conducted to investigate the screen-printing and reflow steps of the SMT process using a tin-silver-copper (95.5Sn3.8Ag0.7Cu) solder and a baseline of standard tin-lead (63Sn37Pb). 10×10 arrays of micro Ball Grid Array (micro-BGA) components mounted on 8-layer FR4 printed wiring boards (PWBs) were used. The screen-printing experiment addressed the deposition of the solder paste on the board. The parameters used in the investigation were print speed, squeegee pressure, snap-off distance, separation speed and cleaning interval, with the responses being measurements of paste height and volume. Optimum screen-printer settings were determined which give adequate paste volume and height and a good print definition. The reflow experiment investigated the following parameters of the temperature profile: preheat, soak, peak and cool down temperatures, and conveyor speed. The resulting solder joints were evaluated using cross-section analysis and x-ray techniques in order to determine the presence of defects. A mechanical fatigue test was also carried out in order to compare the strength of the solder joints. The overall quality of the lead-free solder joints was determined from these tests and compared to that of tin-lead. The outcome is a set of manufacturing guidelines for transferring to lead-free solder including optimum screen-printer and reflow oven settings for use with an SnAgCu solder.
Genetic Q-Fuzzy Based Intelligent Control for Mobile Robot Navigation
Authors: Parimi V. Ram Mohan , Garg Devendra P.
Published: April 2008

This paper deals with the design and optimization of a Fuzzy Logic Controller that is used in the obstacle avoidance and path tracking problems of mobile robot navigation. The Fuzzy Logic controller is tuned using reinforcement learning controlled Genetic Algorithm. The operator probabilities of the Genetic Algorithm are adapted using reinforcement learning technique. The reinforcement learning algorithm used in this paper is Q-learning, a recently developed reinforcement learning algorithm. The performance of the Fuzzy-Logic Controller tuned with reinforcement controlled Genetic Algorithm is then compared with the one tuned with uncontrolled Genetic Algorithm. The theory is applied to a two-wheeled mobile robot’s path tracking problem. It is shown that the performance of the Fuzzy-Logic controller tuned by Genetic Algorithm controlled via reinforcement learning is better than the performance of the Fuzzy-Logic controller tuned via uncontrolled Genetic Algorithm.
Identification of Cardiovascular Dynamics From Peripheral Circulatory Waveforms Using Laguerre Model Blind System ID
Authors: McCombie Devin , Asada H. Harry , Reisner Andrew
Published: April 2008

A new tool has been developed for characterizing both the global and local dynamic behavior exhibited by peripheral circulatory waveforms. The signals representing these waveforms can be derived from a variety of different cardiovascular sensor modalities measuring changes in pressure, flow, or volume. The correlation that exists between two peripheral circulatory waveform measurements taken at different locations allows this new signal-processing algorithm to identify two compact, low order dynamic models in real-time. These models identify the distinct dynamic behavior of the circulatory paths traveled by the pulsatile waveforms using output measurements alone. This new algorithm is based on a multi-channel blind system identification technique that has been reformulated to use a Laguerre basis function series expansion. Additionally, a new deconvolution algorithm has been developed to allow estimation of the unknown common input using the identified Laguerre models, which are generally inversely unstable. This new approach has been shown to provide accurate identification of vascular hemodynamics when applied to experimental data derived from a swine.
Optimization of Heat Sink Design With Focus on Transient Thermal Response
Authors: Yazawa Kazuaki , Ishizuka Masaru
Published: April 2008

Transient heat flow in the heat sink base is modeled assuming hemispherical expansion of isotherms, and a closed form formula for temporal thermal resistance is derived. The objective of the study is to optimize the thickness of the heat sink base on a given mass for energy efficient design. Since the state-of-art VLSI generates a variety of temporal heat in short and long time duration, it is important and effective to model the solution of thermal response as an explicit and simple formula of time function. Stepwise input of heat from the heat source that spreads to a wider area rectangular heat sink base is used for model verification. The model assumes constant airflow though the fins. Numerical analysis was conducted to validate the model for a wide range of time scale, and the results were referred to explicate the modes of temperature propagation. The analytical model based on the stepwise input is extended to general time function of heat input based on the comparison. On the basis of the analytical model, the geometry of the base is discussed for a given mass. Various ratio of footprint to thickness is studied over the wide range of time response. It was found that the optimum shape for steady-state is also effective for dynamic. In addition, a recommendation was made for a small time response.
Product Tolerance Allocation in Compliant Multistation Assembly Through Variation Propagation and Analytical Target Cascading
Authors: Li Zhijun , Yue Jianpeng , Kokkolaras Michael , Camelio Jaime , Papalambros Panos Y. , Hu S. Jack
Published: April 2008

Compliant sheet metal assembly is a hierarchical manufacturing process that plays a significant role in automotive product development. Parts are joined in different stations to form the final product (e.g., the vehicle body structure). Dimensional variation is a product attribute of major importance that characterizes quality, and is mainly affected by the variability of parts, fixtures, and joining methods at each of the multiple stations. The propagation of dimensional variation through the multistation assembly system is modeled as a linear process, where all three aforementioned sources of variability are taken into account at each station using finite element models. In this article we apply the analytical target cascading process to the tolerance allocation problem in multistation assembly systems. Specifically, we translate final product variation targets to tolerance specifications for subassemblies and incoming parts. We demonstrate the methodology by means of a vehicle side frame assembly example.
The Conceptual Basis for Statics and Development of a Statics Concept Inventory
Authors: Steif Paul S.
Published: April 2008

This paper describes efforts to establish the fundamental concepts that underlie the solving of problems in Statics, and to devise means of measuring student understanding of these concepts. These efforts are aimed at providing a principled means for improving the quality of instruction in Statics, at least with respect to promoting conceptual understanding. A set of four concept clusters is proposed, together with a set of skills for implementing these concepts. Typical errors committed by students are categorized and shown to be related to these concept clusters. A testing instrument is presented to measure student ability to use the key concepts of Statics individually, with negligible mathematical analysis. This Statics Concept Inventory includes 27 multiple choice questions, focusing on 4 general concepts: free body diagrams, interchange of forces, couples and moments, the forces acting at connections and between bodies, and the conditions of equilibrium. Incorrect answer choices reflect typical student errors. Psychometric analyses of two administrations of this test are reported, one at the start and one just after the end of a sophomore mechanical engineering Statics course.
Design and Numerical Investigation of Advanced Radial Inlet for a Centrifugal Compressor Stage
Authors: Kim Yunbae , Koch Jay
Published: April 2008

The performance of a centrifugal compressor stage can be seriously affected by inlet flow distortions due to an unsatisfactory inlet configuration and the resulting flow structure. In this study, two radial inlets were designed for a centrifugal compressor stage and investigated numerically using a commercially available 3D viscous Navier-Stokes code. The intent of the design was to minimize the total pressure loss across the inlet while distributing the flow as equally and uniformly as possible to the impeller inlet. For each inlet model, the aerodynamic performance was calculated from the simulation results and then the results from both models were evaluated and compared. The second radial inlet design outperformed the initial design in terms of total pressure loss, flow distortion and uniformity at the impeller inlet. Furthermore, the aerodynamic performance of the second radial inlet was insensitive to a wide range of mass flow rates compared to the initial design due to the distinctive geometric features implemented for the second inlet design.
A General Method for the Modeling of High Speed Spindle Systems
Authors: Cao Yuzhong , Altintas Yusuf
Published: April 2008

This paper outlines a general method that can be used to model spindle assembly, which consists of spindle shaft, angular contact ball bearings and housing. The spindle shaft and housing are modeled as Timoshenko’s beam by including the centrifugal force and gyroscopic effects. The bearing is modeled as a standard nonlinear finite element based on Jones’ bearing model which includes the centrifugal force and gyroscopic effects from the rolling elements of bearings. By applying cutting forces to the spindle for a given preload, the stiffness of the bearings, contact forces on bearing balls, natural frequencies, time history response and frequency response functions of the spindle assembly can be evaluated. The paper provides details of the mathematical model supported by experimental results obtained from an instrumented test spindle.
A New High-Efficiency Error Compensation System for CNC Multi-Axis Machine Tools
Authors: Wang Shih-Ming , Yu Han-Jen , Liao Hung-Wei
Published: April 2008

To enhance the accuracy of CNC machines for the request of modern industry, an effective static/quasi-static error compensation system composing of an element-free interpolation algorithm based on the Galerkin method for error prediction, a recursive software compensation procedure, and an NC-code converting software, is developed. Through automatically analyzing the machining path, the new error prediction method taking into the consideration of the fact that machine structure is non-rigid, can efficiently on-line determine the position errors of the cutter for compensation without computing a complex error model. The predicted errors are then compensated based on a recursive compensation algorithm. Finally, a compensated NC program will be automatically generated by the NC-code converting software for the precision machining process. Because of the advantage of element-free theory, the error prediction method can flexibly and irregularly distributing nodal points for accurate error prediction for a machine with complex error distribution characteristics throughout the workspace. To verify the algorithm and the developed system, cutting experiments were conducted in this study, and the results have shown the success of the proposed error compensation system.
Interpreting Sensor Data Using Continuous Wavelet Transformations
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G.
Published: April 2008

Structural monitoring systems consist of a method to measure the structure’s performance at a given point in time to produce raw sensor data and the interpretation of this data in terms of presence and location of damage. This work focuses on the interpretation. The raw sensor data needs to be examined to indicate when further inspection is necessary, prior to the degradation of key structural performance parameters. Finding low levels of damage is critical to the development of a health monitoring system. This paper describes the use of the continuous wavelet transformation in the identification of damaged plates. Strain time histories are used in the algorithm. The strain histories are measured experimentally. In the past the authors have used finite element analysis to generate virtual sensor data. The authors track how the wavelet maximas change as damage accumulates. Various excitations are used to determine their affect.
Characterization of Indentation-Induced “Particle Crowding” in Metal Matrix Composites
Authors: Pereyra R. , Shen Y.-L.
Published: April 2008

A direct experimental characterization of reinforcement configuration in an indentation-deformed metal matrix composite is undertaken. The primary objective is to quantify the possible local increase in particle concentration, which has been proposed to cause inconsistency in the indentation hardness and the overall composite strength. Quantitative metallography on the post-indented material is carried out to measure the particle volume fraction. Multiple cross sections of an indentation are investigated with statistically significant results obtained. A distinct increase in particle concentration induced by the indentation is found. The spatial distribution of particle concentration is also examined in detail. The residual compressive stress field remained in the material upon unloading, as illustrated by the finite element analysis, is shown to be in qualitative agreement with the measurement.
Trabecular Bypass: Effect of Schlemm’s Canal and Collector Channel Dilation
Authors: Zhou Jianbo , Smedley Gregory T.
Published: April 2008

An ocular outflow model is proposed to theorize the effect of Schlemm’s canal (SC) and/or collector channel (CC) dilation combined with a trabecular bypass on elevated intraocular pressure (IOP) in glaucomatous eyes. The dilated height of the elliptic SC is largest at the bypass and linearly deceases to the non-dilated height over the dilated circumferential length. The CC dilation is modeled with a reduced outflow resistance of second order polynomial. Equations governing the pressure and flow in SC are solved numerically. The model predicts that the IOP is reduced substantially with moderate dilation from the normal 20 μm to 40 μm at the bypass. SC dilation is more effective for eyes with smaller SC. The dilation of CC can also significantly lower the IOP. With the trabecular bypass alone, the elevated IOP is expected to drop to the mid-to-high teens. The IOP can be further reduced by another 3 to 6 mmHg with moderate SC and CC dilation.
Capstone Senior Design: A Small Engineering Program Experience
Authors: Abu-Mulaweh H. I.
Published: April 2008

This paper presents the author’s experience in the development and coordination of capstone senior design at a small engineering program. The mechanical engineering program at Purdue University, Fort Wayne is relatively small and only undergraduate. The capstone senior design in the mechanical engineering program at Purdue University, Fort Wayne has gone through several modifications and upgrades over the last few years. Before these changes, the capstone senior design at our program was criticised by the ABET accrediting teams and was cited as weak. Because of this the faculty developed and implemented a new approach and new guidelines to strengthen the capstone senior design. This effort resulted in a much stronger capstone senior design and the mechanical engineering program was commended and praised in this area.
A Theoretical Approach to Dropwise Condensation Using Population Balance Concept
Authors: Vemuri S. , Kim K. J. , Wood B. D. , Bell T. W.
Published: April 2008

A model using the population balance concept is used to derive a theoretical formula to predict the drop-size distribution of small drops which grow mainly by direct condensation. All the important resistances to heat transfer such as the heat conduction through the drop, vapor-liquid interface are considered in developing this model. By knowing the contact angle of the drop made with the condensing surface and the maximum drop radius the sweeping effect of large falling drops could be calculated which is also incorporated into the model. This is combined with the well known size distribution for large drops proposed by Le Fevre and Rose (1966) which grow mainly by coalescence and with the growth rate of single drops to compute the heat flux during the process of dropwise condensation. The data obtained from this theoretical model is compared to that of the data obtained from our experimentation. There has been a satisfactory agreement between our experimental data and the present theoretical model.
Effective Automatic Recognition of Cultured Cells in Bright Field Images Using Fisher’s Linear Discriminant Preprocessing
Authors: Long Xi , Cleveland W. Louis , Yao Y. Lawrence
Published: April 2008

Recent progress in the development of methods for molecular genetic analysis (e.g. RT-PCR, microarrays) has brought sensitivities to the level where single cells can be analyzed [1]. To carry out single-cell-level assays on significant numbers of cells, high throughput robotic systems are needed. These systems require identification of cultured cells (often in bright field images) for micromanipulation and subsequent molecular analysis. Given the variability of cell size and morphology, the presence of “trash,” as well as variations in microscope parameters, such as focus and illumination, identification of cultured cells in bright field images is a difficult task that, traditionally, is done by an experienced human observer. However, the use of human observers represents a severe impediment to the development of high throughput robotic systems. Therefore, there is a major need for algorithms that permit automatic recognition of cells in bright field images.
Electrokinetic Behavior of Cylindrical Nanowires in Microfluidic Channels
Authors: Davidson Scott M. , Mayer Theresa S. , Sharp Kendra V.
Published: April 2008

Nanowires, literally wires with nanometer-scale diameters and lengths of several microns up to tens of microns, have recently garnered significant attention given their potential applications within the fields of electronics and sensing [1], among others. Nanowires can be fabricated from a diverse set of materials including metals and semiconductors, and functionalized or tailored for a range of applications (e.g. detection of specific biological or chemical species [2]). One of the key issues for integration of nanowires into electronic or sensing devices is the controlled separation, delivery, and placement of nanowires with a high degree of accuracy. Electrokinetic control of the motion of gold nanowires with both negligible and negative surface charge is demonstrated inside of fluid-filled glass microchannels. The electroosmotic and electrophoretic velocities of the nanowires are measured and compared to theoretical predictions for cylindrical particles in suspension.
The Effect of Flow Induced Coupling on Sound Radiation From Convected Fluid Loaded Plates
Authors: Frampton Kenneth D.
Published: April 2008

Recent investigations concerning the effects of fluid convection on structural acoustic radiation have noted that radiation efficiency increases with increasing flow speeds. However, most of these studies based this conclusion on simulations which neglected flow induced coupling between the structural modes. Yet, flow induced modal coupling is know to have dramatic effects on structural dynamics including static and dynamic instabilities, and should therefore be expected to significantly affect sound radiation. The purpose of this investigation is to quantify the effects that fluid flow has on the sound radiated from rectangular vibrating plates when flow-induced structural modal coupling is considered. The discussion includes a description of the fundamental physics associated with a simply supported, vibrating, rectangular plate imbedded in an infinite baffle and radiating into a semi-infinite, convected fluid. This is followed by a discussion of the effect that flow-induced coupling has on the structural dynamic behavior. Finally, numerical results are presented which demonstrate the effect that such coupling has on the sound power radiated from a plate.
An Investigation of Wall Curl Reduction Through Post-Stretch Forming
Authors: Xia Z. C. , Ren F.
Published: April 2008

When sheet metals go through drawbeads or die corners, stress differentials are generated across metal thickness. The draw wall will curl up upon release of stamping tools, resulting in so-called wall curl. It is a serious problem in the deep drawings of U-channel type of structures such as rails. Numerical modeling is conducted to investigate a post-stretch forming process for wall curl reduction. In this process a set of lockbeads in the binder activates just before the end of punch stroke, locking the remaining blank in the binder. The continuation of the punch stroke then creates a final increment of pure stretch. It is most effective for deep drawings of U-channel type of structures such as rails. This technique is also known as “post-stretch” or “shape set” in the automotive industry and in the literature. Finite element simulations for a straight channel are conducted in order to understand the wall curl reduction mechanism of the process and to determine its effectiveness. After an examination of deformation profile after drawing and wall curl as a result of springback, various magnitude of post-stretch amount is modeled and their deformation history is analyzed. It is found that a post-stretch strain around 2% almost completely eliminates wall curl. CAE investigations demonstrate that the technique is equally applicable to more complex 3D channel, where a step channel is examined. The effectiveness of this concept is demonstrated by laboratory experiment on the forming of a U-channel. Various implementation techniques for the process in an industrial environment are also suggested, together with a discussion on the associated benefits and costs for production use.
Ballistic Damage Evaluation of Thick-Section S-2 Glass/SC15 Composites With and Without Predefined Delaminations
Authors: Gama Bazle A. , Rahman Mostafezur , Hoppel Chris P. R. , Gillespie John W.
Published: April 2008

Thick-section composites made from plain weave (5×5) S-2 glass fabrics and toughened API epoxy SC15 resin are impacted with right circular cylinder projectiles at different impact velocities, and at support span of diameter 101.6-mm. The impact and residual velocity of the projectiles are measured using flash X-Ray. Ballistic energy dissipated in the composite plates is determined following an energy balance approach. The damage mechanisms under ballistic impact are evaluated by sectioning each composite plate through the impact axis. Composite damage mechanisms are presented as a function of dimensionless impact and residual velocity, VI/V50 and VR/V50, respectively. It has been identified that the damage mechanisms are significantly different in case of partial-penetration (VR/V50=0), than the case of complete-penetration (VR/V500). The effect of pre-defined delamination planes on the ballistic limit and damage is investigated.
Examination of Platform and Differentiating Elements in Product Design
Authors: Van Wie Michael J. , Stone Robert B. , Thevenot Henri , Simpson Timothy
Published: April 2008

The problems of mass customization, portfolio design, and platforming all pose a common challenge to the designer: knowing how to partition a set of product variants to maximize commonality and simultaneously achieve sufficient differentiation for purposes of customization. This research focuses on the particular issue of how differences between platform elements and differentiating elements are evidenced in the product layout or configuration. The premise of this research is that certain architectural properties, such as modularity, vary between platform and differentiating elements. In particular, certain measures of commonality offer an appropriate set of indices for evaluating these differences in a systematic and repeatable manner. Both function and physical solution commonality provide a descriptor with which to distinguish and rank platform and differentiating elements. By evaluating components of a product in terms of function commonality, physical solution commonality, and modularity, a comparison can be made between platforms and differentiating elements with respect to these indices. The hypothesis of this work is that platforms are integrated and the non-common differentiating elements are, relative to the platforms, more modular. While anecdotal evidence exists to support this idea, the purpose of this work is to evaluate two existing product families as a means for analyzing this hypothesized relation. The result of this research is a descriptive set of knowledge that illustrates the distinguishing factors between platform and differentiating elements. The data specifically demonstrate the differences in architecture between platforms and differentiating elements, thus suggesting how these design aspects can and should be addressed at the conceptual stage of design. While not the focus of this study, future research involving a more prescriptive approach to conceptual design can directly benefit from the results. The knowledge gained in this work serves as a foundation for addressing portfolio design where both customization and commonality are key issues.
Fuel Transfer Function Measurements in Modulated Liquid Jets
Authors: Stenzler Jacob N. , Lee Jong G. , Deepe J. Matthew , Santavicca Domenic A. , Lee Wonnam
Published: April 2008

Results are presented from an experimental study of the effect of operating conditions on the fuel transfer function of a modulated liquid jet injected into a high velocity crossflow. This injection configuration is commonly used in a variety of liquid-fueled gas turbine combustion systems. The transfer function relates the rate at which fuel is injected into the crossflow to the Mie scattering intensity of droplets at a given downstream location. The time-varying rate of liquid injection into the test section is measured using a high speed rotating patternator. From a spectral analysis of the input and output functions, correlations are developed to predict the phase and gain of the fuel transfer function. Experiments are conducted over a range of jet and crossflow conditions in order to determine the effect of operating conditions on the fuel transfer function.
A Parametric Study on Material Properties of Cortical Shell and Trabecular Core in an Osteoporotic, Lumbar Vertebral Bone Model
Authors: Sindall David R. , Langrana Noshir A. , Cuitino Alberto
Published: April 2008

This study is about understanding the biomechanical parameters in osteoporosis phenomena. Experimental data are available on intact cadaver normal and osteoporotic lumbar vertebrae. It was observed that there is inconsistency between the clinical DEXA measurements and the mechanical measurements such as failure strength. The vertebral bone parameters include geometry (height, width, curvature, and thickness of the cortical shell) and material properties of cortical and trabecular bone. A non-linear Micromodel Finite Element Analysis (MFEA) program has been developed to include these parameters and obtain the compressive load. Response surface methodology (RSM) was developed to relate BMD to failure strength and is used in this study to see how the mechanical properties of bone influence the failure load. (Sindall, 2003)
Experimental Investigation of Local Heat Transfer in a Square Duct With Continuous and Truncated Large Ribs
Authors: Wang Lei , Sunde´n Bengt
Published: April 2008

Repeated ribs are frequently employed to promote turbulence and to enhance heat transfer in various ducts. In the present study, liquid crystal thermography has applied to the study of heat transfer from a square channel having one surface heated at uniform heat flux and roughened by repeated ribs. The continuous and truncated ribs, having square sections, with height-to-hydraulic diameter ratio of 0.15, were deployed normal to the mainstream direction of flow. Detailed distributions of the local heat transfer coefficient were obtained at various Reynolds number within the turbulent flow regime. Averaged data were calculated in order to evaluate the augmentation of heat transfer by the presence of different ribs.
Computational Aspects of Three-Dimensional Crack Growth Simulations
Authors: Zuo Jianzheng , Deng Xiaomin , Sutton Michael A.
Published: April 2008

An important task in mixed-mode fracture analysis and prediction is the simulation of crack growth under mixed-mode conditions. To complete such a task, one must have (a) a computer code capable of handling the kinematics of general crack growth and determining the stress and deformation states during crack growth, and (b) a fracture criterion that can properly predict the onset and direction of crack growth. A current challenge is the simulation of mixed-mode crack growth under three-dimensional (3D) conditions, such as the growth of surface cracks, corner cracks, embedded cracks, and cracks with a curved crack surface and/or a curved crack front. This paper focuses on item (a) in the above discussion and describes the computational aspects of a simulation procedure, which can be used together with a given fracture criterion to simulate crack growth. For illustration purposes, a CTOD fracture criterion (e.g. [11]) will be used when needed. The associated algorithms for simulating arbitrary 3D crack growth under general loading conditions have been developed and successfully implemented by the authors in a custom, finite element based, crack growth analysis and simulation code—CRACK3D. In particular, this paper will present strategies for automatic re-meshing of regions around growing crack fronts in a 3D body, and will discuss verification examples.
Crack Tunneling: Effect of Stress Constraint
Authors: Zuo Jianzheng , Deng Xiaomin , Sutton Michael A. , Cheng C.-S.
Published: April 2008

Crack tunneling is a crack growth feature often seen in stable tearing crack growth tests on specimens made of ductile materials and containing through-thickness cracks with initially straight crack fronts. As a specimen is loaded monotonically, the mid-section of the crack front will advance first, which will be followed by crack growth along the rest of the crack front, leading to the formation of a thumb-nail shaped crack-front profile. From the viewpoint of fracture mechanics, crack tunneling will occur if the operating fracture criterion is met first in the mid-section of the crack front, which may be due to a higher fracture driving force and/or a lower fracture toughness in the mid-section. A proper understanding of this fracture behavior is important to the development of a three-dimensional fracture criterion for general stable tearing crack growth in ductile materials. In this paper, the phenomenon of crack tunneling during stable tearing crack growth in a single-edge crack specimen is investigated by considering the effect of stress constraint on the fracture toughness. Crack growth in the specimen under nominally Mode I loading conditions is considered. In this case, crack tunneling occurs while the initially flat crack surface (which is normal to the specimen’s lateral surfaces) evolves into a final slanted fracture surface. A mixed-mode CTOD fracture criterion and a custom three-dimensional fracture simulation code, CRACK3D, are used to analyze the tunneling and slanting process in the specimen. Results of this investigation suggest that the critical CTOD value (which is the fracture toughness) has a clear dependence on the crack front stress constraint (which is the ratio of the mean stress to the von Mises effective stress). This dependence seems to be linear within the range of stress constraint values found, with the toughness decreasing as the constraint increases. It is found that crack tunneling in this case is mainly the result of a higher stress constraint (hence a lower fracture toughness) in the midsection of the crack front. Details of the crack growth simulation and other findings of this study will also be presented.
Experimental Study on Performance Enhancement of Heat Pump With Screw Compressor
Authors: Huagen Wu , Pengcheng Shu , Yuanyang Zhao , Ziwen Xing
Published: April 2008

The air-source heat pump has been widely used in industrial refrigeration and central air-conditioning applications because of its unique superiority. An important consideration in the design of heat pump is improving its COP (coefficient of performance). In this paper, the results of experimental investigation on the effects of alternative refrigerants (R22, R134a, R404A and R407C) and economizer on the performance of heat pump are presented. The COP of the heat pump used R134a is up to 4.5% higher than R22, but its capacity got a 37.08% decrease. The refrigerant R407C applied in heat pump can improve the capacity up to 7.86% than R22, but its COP shows a decrease up to 5.92%. The refrigerant R404A used in heat pump will result in poor capacity and COP compared to R22. The economizer system used in heat pump will improve the COP, but as the superfeed pressure of the economizer increases, the system COP increases first, and then drops. So there exists an optimal superfeed pressure of the economizer for the best COP. Also, the effect of the economizer on the screw compressor performance is analyzed by recording the P-v indicator diagram.
Design Principles and Aerodynamics of Low Reynolds Number Multi-Stage Microturbomachinery
Authors: Lee Changgu , Arslan Selin , Fre´chette Luc G.
Published: April 2008

In this paper, the design process for multi-stage micro scale turbomachinery will be presented, along with CFD predictions of the key aerodynamic performance parameters required in this design process. This work focuses on the unique and unexplored design space defined by the small scale and planar geometries characteristic of MEMS turbopumps, compressors, gas turbines, steam turbines, or other turbomachinery-based microsystems. Correlations are proposed for the loss coefficient, based on laminar flow theory. A critical Reynolds number is also identified (Recrit = 200–300), below which adjacent boundary layers merge, inducing a sharp increase in loss and deviation. This imposes practical limits on the miniaturization of such microturbomachinery.
Developing an Efficient Multigrid Strategy for Solving Incompressible Flow
Authors: Darbandi Masoud , Schneider Gerry E. , Taheri Arash
Published: April 2008

In this work, a multigrid acceleration technique is suitably developed for solving the two-dimensional incompressible Navier-Stokes equations using an implicit finite element volume method. In this regard, the solution domain is broken into a huge number of quadrilateral finite elements. The accurate numerical solution of a flow field can be achieved if very fine grid resolutions are utilized. Unfortunately, the standard implicit solvers need more computational time to solve larger size of algebraic set of equations which normally arise if fine grid distributions are used. Past experience has shown that the convergence of classical relaxation schemes perform an initial rapid decrease of residuals followed by a slower rate of decrease. This point indicates that a relaxation procedure is efficient for eliminating only the high frequency components of the residuals. This problem can be overcome using multigrid method, i.e., carrying out the relaxation procedure on a series of different grid sizes. There are different prolongation operators to establish a multigrid procedure. A new prolongation expression is suitably developed in this work. It needs constructing data during refining and coarsening stages which is fulfilled using suitable finite element interpolators. The extended formulations are finally used to test several different problems with available benchmark solutions. The results indicate that the current multigrid strategy effectively improves the bandit solver performance.
Investigation on High Energy Density Materials Utilizing Biological Transport Mechanisms
Authors: Sundaresan Vishnu Baba , Tan Honghui , Leo Donald J. , Cuppoletti John
Published: April 2008

Biological systems such as plants produce large deformations due to the conversion of chemical energy to mechanical energy. These chemomechanical energy conversions are controlled by the transport of charge and fluid across permeable membranes within the cellular structure of the biological system. In this paper we analyze the potential for using biological transport mechanisms to produce materials with controllable actuation properties. An energetics analysis is performed to quantify the relationship between the introduction of chemical energy in the form of ATP to the resulting osmotic pressure variation within an enclosed membrane. Our analysis demonstrates that pressure variations of between 5 and 15 MPa are achievable. The pressure variations are then coupled to a finite element analysis to determine the ability of organized arrays to produce extensional and bending actuation in thin membranes. Our analysis demonstrates that internal pressure variations on the order of 10 MPa can produce actuation materials with extensional energy density on the order of 100 kJ/m3 and bending energy density on the order of 10 kJ/m3.
A Morphing-Based Surface Blending Operator for Footwear CAD
Authors: Li Guo , Joneja Ajay
Published: April 2008

A new operator to interpolate a smooth surface between two given disjoint surfaces is presented in this paper. The method uses a modified form of shape morphing to generate interpolation points in the region of the gap. An energy minimization formulation is used to enhance transition smoothness. The work is motivated by a practical problem in footwear CAD, although the operator will find use in other applications. Some preliminary results from our implementation are presented.
On the Possible Application of a Microscale Thermocouple to Measure Intercellular Ice Formation in Cells Embedded in an Extracellular Matrix
Authors: Kandra Deepak , Devireddy Ram V.
Published: April 2008

To optimize a freezing protocol for tissue systems, knowledge of intercellular ice formation and water transport is essential. Water transport during freezing can be measured using low temperature microscopy technique [1] and/or by differential scanning calorimetry method [2]. To study the formation of intracellular ice in cells embedded in an extracellular matrix we propose to design and develop an array of microscale thermocouples using microfabrication techniques [3]. The microfabricated thermocouples will be required to accurately measure the small temperature fluctuations in an embedded cell due to the formation of intracellular ice.