bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Coupler Height Mismatch on Tank Car Stub Sills
Authors: Prabhakaran Anand , Sharma Vinaya , Peña Jose S. 
Published: November 2021

Abstract
Revenue service tests of tank cars conducted by the Association of American Railroads (AAR) as part of the ‘Freight Equipment Environmental Sampling Tests’ (FEEST) program have measured high coupler vertical loads. It is believed that such high vertical loads can cause significant damage to the structural integrity of tank car stubsills, thereby seriously affecting operational safety. Also, it is suspected that coupler height mismatches are a major source of these vertical forces, and thereby contribute to stubsill failures. The focus of this paper is the study of the effect of coupler height mismatches on stub sill integrity. As part of this study a tank car loaded to 266,200 lb. was instrumented and tested, in static conditions and during impact. The static tests consisted of a series of longitudinal load (squeeze) tests conducted at three different coupler heights, and vertical load tests with forces being applied at the coupler shank. The impact tests consisted of a series of impacts at speeds ranging from 2 mph to 8.5 mph for the following coupler mismatch levels: a) Struck and striking car at the same level, b) Struck car 2″ higher, and c) Struck car 2″ lower. In addition to the testing, finite element models were developed to help in studying additional operating conditions. These models were validated using the test results. The results from the testing indicate that coupler height mismatches have a significant effect on the vertical force levels and the stress levels seen at critical car locations. The stresses in critical areas are generally higher when the struck car is lower. Differences over 50% (compared to when the cars are level) were noted at the head brace, when the struck car was 2″ lower than the hammer car. The tests also established the criticality of vertical forces on the structural integrity of the stubsill. On average, a 50,000 lb. vertical force can generate as much stress as a 680,000 lb. longitudinal force. This work is being funded by the Office of Research & Development of the Federal Railroad Administration (FRA).
Damage Modeling and Detection in Smart Composites
Authors: Chattopadhyay Aditi , Dragomir-Daescu Dan 
Published: November 2021

Abstract
The presence of damage in structures made out of composite and/or piezoelectric materials can cause significant degradation in structural performance. In the present paper, damage indices based on two-dimensional gapped smoothing technique and model strains are developed in order to enhance the accuracy in predicting the location and extent of damage in composite structures. Structural analysis is performed based on a refined higher order theory, which can capture the transverse shear effects in anisotropic laminates. An approach using the developed damage indices and the laminate model of the higher order theory is employed to model and identify delaminations in composite laminates. It is also used in the delamination analysis of composite laminates with piezoelectric actuators. The proposed modal strain based damage indexes are used to perform delamination analysis. Comparison study is performed to illustrate that the reliability and robustness of the new proposed damage indices in locating delaminations in composite and smart composite structures. The effects on modal strain and damage indices due to the presence of surface bounded piezoelectric actuators are also presented and discussed.
Analysis of Fatigue Damage Mechanisms and Residual Properties of Polymer Matrix Composites
Authors: Soutis Costas , Kashtalyan Maria 
Published: November 2021

Abstract
Resin dominated damage modes such as matrix cracking in the off-axis plies and matrix crack-induced local and edge delaminations are common failure mechanisms in composite laminates under tensile or thermal fatigue. Accurate prediction of the laminate stiffness and strength must consider all the above-mentioned damage modes. In the present paper, an approach is developed for the analysis of cross-ply laminates damaged by transverse and longitudinal cracks and transverse and longitudinal delaminations that initiate and grow along these cracks. It is based on the Equivalent Constraint Model (ECM) of the damaged ply and employs an improved 2-D shear lag method to determine the stress field in the cracked and locally delaminated ply. The method is applied to predict residual stiffness properties of cross-ply graphite/epoxy laminates using experimentally observed damage patterns.
Role of Frozen Water on the Fracture Growth of Composite Materials
Authors: Dutta Piyush K. 
Published: November 2021

Abstract
Delamination of composites is a fairly common failure mechanism. Its sensitivity to the interference of environmental parameters e.g. temperature and moisture is generally well known. Accelerated delamination induced by moisture at high temperature, which lowers the Tg (the glass transition temperature of the matrix), has been studied for decades. Also, predictive tests for durability of composite materials suggest boiling of composites as a technique to develop the predictive index for lifecycle prediction (Dewimille and Burnsell, 1983). However, these approaches ignore the dramatic degradation process of composites at subzero temperatures, and are based probably on the misleading but general concept that low temperature improves performance of materials. Of course, at subzero temperatures, there is a drastic increase in strengths (shear and tension), and hygroelasticity, (Ip, Dutta and Hui, 1996), but a sequence of processes conducive to fracture growth are also set in, especially when there are frequent incursions between the sub-zero and above-zero temperatures in moist environment. First, the thermal expansivity mismatch of the constituents induce mechanical stresses as high as 50% of the matrix strength (Lord and Dutta 1988), leading eventually, or under accelerative action of thermal cycling, to thermal cracking (Figure 1) (Dutta and Hui, 1996), which, in turn facilitates moisture penetration into the structure. Second, the liquid phase transport of moisture by capillary flow or microcracks (and to a lesser degree by diffusion) involves both flow and storage of water in microvoids, which lead to further degradation by chemical (e.g. hydrolysis), and physical (e.g. swelling strains) processes in an auto-accelerated manner. And the third, which has been least studied in literature, is the dramatic effect of expanded frozen water on interlaminar or interfacial crack extension at the sub-zero temperature.
Free Vibration of Spinning Stepped Timoshenko Beams Using Finite Element Method
Authors: Wang Z. C. , Cleghorn W. L. , Yu S. D. 
Published: November 2021

Abstract
Free lateral vibration of stepped shafts is investigated in this paper using the Timoshenko beam theory and the finite element method. Beam finite elements having two nodes and 16 degrees of freedom were employed to model flexural vibration of a stepped shaft for a total four field variables — two lateral displacements and two bending angles. Within each uniform segment, the stepped shaft is modeled as a substructure for which a system of equations of motion may be easily formulated using the Galerkin method. The global equations of motion for the entire stepped shaft are subsequently formulated by enforcing the displacement continuity and force equilibrium conditions across the interfaces between two adjacent substructures. The second order governing differential equations for a non self-adjoint dynamic system are then reduced to the equivalent first order differential equations for which eigenvalue problem is formulated and solved using the Matlab® program. Values of natural frequencies are in excellent agreement with those available in the literature. Effects of rotational springs attached to the end of a stepped shaft, used to simulate the non-classical boundary constraints of chuck on a work piece in a typical turning process, are also investigated. The bi-orthogonal conditions for modal vectors, which are useful in chatter analysis during turning processes, are given in this paper.
Visualization of Finite Element Automobile Crash Simulation Using Virtual Reality Technology
Authors: Moraes Ricardo , Nicholson David , Divo Eduardo 
Published: November 2021

Abstract
A prototype system is described for visualization of automotive crash. The system is based on integrating two tools: (a) Finite Element Analysis (FEA) and (b) Virtual Reality Visualization (VRV).
The prototype VRV system, recently developed by DUAL Incorporated of Lake Mary, FL in partnership with the University of Central Florida (UCF), consists of a PC-level graphics workstation, a head mounted display, motion trackers, a multi-degree of freedom mouse, drivers and a software toolkit, all of which have been established at DUAL and UCF.
Modeling and Prediction of Acoustic Resonance for Round Supersonic Jets
Authors: Cary A. W. , Bower W. W. , Cain A. B. , Kershen E. J. 
Published: November 2021

Abstract
A computationally rapid analysis tool has been developed to compute the acoustic resonance of off-design supersonic jets known as “screech”. For the case of round jets, the computational model is described which is based on coupling analytical representations of each of the four components of the resonance: 1) the shear layer instability; 2) the vortex/shock interaction; 3) the upstream-propagating acoustic radiation; and 4) the receptive coupling of scattered acoustic waves and instability waves at the nozzle lip. Comparisons among predicted and measured sound pressure levels and frequencies of the resonance are presented for a range of jet operating conditions.
The Effect of Temperature on the Viability of Deformed Cells
Authors: Takamatsu Hiroshi , Kumagae Norihiko , Rubinsky Boris 
Published: November 2021

Abstract
Recent studies show that during slow freezing of cells, in addition to chemical damage, the cells may be also injured by mechanical damage induced by ice crystal compression. A new experimental procedure is employed to develop a quantitative understanding of cell destruction by deformation with two parallel surfaces. The viability of deformed cells (prostatic carcinoma cells, 17.5 μm in mean diameter) is measured at 0 °C, 23 °C and 37 °C, and six different nominal gap sizes between 32 μm and 3.5 μm. The relation between measured viability and gap size at 0 °C and 23 °C are identical but the viability decreases at 37 °C. This may suggest that deformation damage is not related to the mechanical properties of the lipid membrane but the deformation of the cytoskeleton.
2-D Thermal Dose Optimization in High Intensity Focused Ultrasound Treatments Using the Adjoint Method
Authors: Loulou Tahar , Scott Elaine P. 
Published: November 2021

Abstract
A previously reported numerical technique, which uses adjoint method when optimizing 1D space variation of thermal dose in hyperthermia treatment is extended to the case of 2D problems [1]. Using a 2D transient computational model in the Penne’s bio-heat equation, optimization of thermal treatment during hyperthermia is shown to be effective and accurate. Numerical simulations are carried out with the 2D computational method to retrieve the prescribed thermal dose from the solution of an inverse thermal problem. The non-continuity of the temperature variation of thermal dose around the reference temperature is linearized over a small temperature interval. The adjoint method in conjunction with the conjugate gradient algorithm are employed to perform the optimization of the objective function. The results are obtained in terms of the computed thermal dose and the heat source to be applied. The numerical results, obtained for a simple treatment case show a good agreement between the estimated and desired thermal dose. However, the non-uniqueness of the obtained solution (the control function: heat source to be applied) is still under investigation and supports the need for further fundamental research.
Comparison of Drug Distribution Between Intravitreal Injection and a Controlled–Release Implant in a Rabbit Eye
Authors: Banerjee Rupak K. , Lutz Robert J. , Keyhani Keyvan , Dedrick Robert L. , King Brian , Robinson Michael 
Published: November 2021

Abstract
Due to physiological barriers within the eye, which limit penetration of many drugs from the systemic circulation into the vitreous, the most common method of treating retinal disease is direct intravitreal injection. However, this common procedure may be inappropriate for a wide range of drugs as it may lead to highly variable concentrations potentially causing higher toxicity for tissues inside the eye and limiting therapeutic effect.
A recent procedure is to use surgically implanted drug release device, called implant here, in the vitreous of the eye that allow controlled release of drug over a sustained period of time. For constant release of drug over 15 hours, a substantial reduction in peak drug concentration is predicted near the retina. When compared with the implant, a doubling of drug concentration would be expected for more than 3 hours near the retina for the intravitreal injection.
Experimentally Validated Vibration Fatigue Life Prediction Model for Ball Grid Array Solder Joint
Authors: Wong T. E. , Palmieri F. W. , Kachatorian L. A. 
Published: November 2021

Abstract
A newly developed methodology is used to support test validation of ball grid array (BGA) solder joint vibration fatigue life prediction model. This model is evolved from an empirical formula of universal slopes, which is derived from high-cycle fatigue test data using a curve fitting technique over 29 different materials of metals.
To develop the BGA solder joint vibration fatigue life prediction model, a test vehicles (TV), on which various sizes of BGA daisy-chained packages are soldered, is first designed, fabricated and subjected to random vibration tests with continuously monitoring the solder joint integrity. Based on the measurement results, a destructive physical analysis is then conducted to further verify the failure locations and crack paths of the solder joints. Next, a method to determine the stresses/strains of BGA solder joints resulting from exposure of the TV to random vibration environments is developed. In this method, a 3-D modeling technique is used to simulate the vibration responses of the BGA packages. Linear static and dynamic finite element analyses with MSC/NASTRAN™ computer code, combined with a volume-weighted average technique, are conducted to calculate the effective strains of the solder joints. In the calculation process, several in-house developed Fortran programs, in conjunction with the outputs obtained from MSC/NASTRAN™ static and frequency response analyses, are used to perform the required computations. Finally, a vibration fatigue life model is established with two unknown parameters, which can be determined by correlating the derived solder effective strains to the test data. This test-calibrated model is then recommended to serve as an effective tool to determine the integrity of the BGA solder joints during vibration. Selecting more study cases with various package sizes, solder ball configurations, vibration profiles to further calibrate this model is also recommended. An example of a 313-pin plastic and 304-pin ceramic BGAs is illustrated in the present study.
Thermal Aging Effect on the Ball Shear Strength of Pb-Free Solders on a Ceramic Substrate With Pd/Ag Surface Metallization
Authors: Huang Xing Jia , Lee Shi-Wei Ricky , Tse Wan Sze 
Published: November 2021

Abstract
In the present study, solder balls of two Pb-free solder alloys, 95.5Sn-3.8Ag-0.7Cu and 91.8Sn-3.4Ag-4.8Bi, were reflowed on a ceramic substrate with the surface metallization of Pd/Ag. The specimens were subjected to thermal aging for 250 hours at the temperatures of 85°C, 125°C and 150°C, respectively. For comparison, specimens with 63Sn-37Pb solder were also fabricated and tested. Ball shear tests were performed to evaluate the effect of thermal aging on various solders. In general, the testing results indicated that the shear strength of solder balls decreased gradually with respect to the increase of thermal aging temperature. The shear strength of 95.5Sn-3.8Ag-0.7Cu solder balls was found to be least sensitive to the thermal aging. Besides, it was identified that the predominant failure mode in the ball shear tests was the fracture at the interface between the Pd/Ag metallization and the ceramic substrate.
Free Vibration Analysis for Thin Wire of Modern Wiresaw Between Sliced Wafers in Wafer Manufacturing Processes
Authors: Wei Songbin , Kao Imin 
Published: November 2021

Abstract
In wiresaw manufacturing process where thin wire moving at high speed is pushed onto ingot to produce slices of wafer, the wire is constrained by two wafer walls as it slices into the ingot. In this paper, we investigate the vibration of such wire under the constraints of wafer walls. To address this problem, the model for wire vibration with impact to wafer walls is developed. The equation of motion is discretized using the Galerkin’s method. The principle of impulse and momentum is utilized to solve the impact problem. The results of analysis and simulation indicate that the response under a pointwise sinusoidal excitation is neither periodical nor symmetric with respect to the horizontal axis, due to the excitation from the impact. The wire vibration behavior is affected dramatically by the wafer wall constraints.
Analysis of the Interaction Between Thin-Film Fluid Hydrodynamics and Wire Vibration in Wafer Manufacturing Using Wiresaw
Authors: Zhu Liqun , Bhagavat Milind , Kao Imin 
Published: November 2021

Abstract
In free abrasive wafer slicing process (FAM) using wiresaw, hydrodynamic pressure exerted by the thin slurry film is crucial to the process of cutting and material removal from substrate surface. It affects the process quality by introducing viscous damping effect to the transverse motion of the wire. The pressure distribution in the slurry film is subjected to the interaction of multi-physical phenomena induced in the wire-saw cutting process, including the axially moving wire transverse vibration under high tension (20N to 35N), as well as the hydrodynamic lubrication behavior of the thin slurry film. In this paper, the interaction between thin-film hydrodynamics and wire vibration is modeled using the coupling of basic Reynold’s equation for fluid lubrication and the dynamic equation describing the transverse vibration of the translating wire. The time-variant hydrodynamic pressure field is used to obtain the dynamic damping force exerted on the wire by the thin slurry film. A computational model is constructed and typical parametric studies are conducted based on the simulation results. Numerical scheme of semi-discretization is carried out to simulate the dynamic multi-disciplinary model. Galerkin method of weighted residual is used to carry out the spatial finite element discretization of the governing non-linear partial differential equations of the system with certain boundary conditions. In addition, Newmark method is applied to perform the time integration of the semi-discretized computational model from initial conditions. The direct numerical simulation dynamically yields the profile of the slurry hydrodynamic pressure distribution and the wire vibration response as functions of process parameters, such as the static film thickness of the slurry flow, wire translating speed and wire tension. From the simulation results, it is shown that the presence of the slurry film in the wiresaw process is important in eliminating the undesirable vibration modes and reducing the amplitude of wire vibration.
Stress Analysis of Wiresaw Slicing Piezoelectric Materials
Authors: Yang Fuqian 
Published: November 2021

Abstract
Using linear piezoelectricity theory, the stress and electric potential fields in a half infinite piezoelectric material under anti-plane mechanical loading in wiresaw slicing process has been studied by using appropriate boundary conditions and contact mechanics. Both electric field and electric displacement field are singular at the edges of the contact zone between wire and workpiece. The singularity of electric displacement arises from the electric loading and electro-mechanical interaction. Similar to the conventional contact mechanics, stress singularity occurs due to the contribution of both mechanical and electric loading. At a given mechanical loading, electric loading can either increase or decrease the stress applied to the piezoelectric half space in the slicing process, which depends on the relative direction of the electric field to that of mechanical loading.
Cooling of a PWB With Irregular Populated Chips
Authors: Ding Yiwu , Agonafer Dereje , Short Elliott 
Published: November 2021

Abstract
A simple analysis and series of 3-D CFD simulations are carried out to estimate the temperature for the 208-pin QFP chips on a PWB. The main feature of the problem is the low primary velocity (0.09∼0.36 m/s), which implies that 3D effects, buoyancy force, PWB thermal conductivity and radiation will have a big impact on the temperature profile. This is verified by using commercial CFD simulation codes. The results show CFD tools are ideally suited for these classes of problems.
For the PWB under study, the worst case consists of an inlet air velocity of 0.09 m/s, no conduction in the board, and the board is laid horizontally, for which the buoyancy force is not well utilized). The resulting highest case temperature will be 110∼120C, which is close to the allowable case temperature 125C. Several heat spreader (heat sink) configurations are studied. One of them reduces the highest case temperature below 100C.
However, if the board conductivity is not too low (&gt;0.5 W/mK), or if. the board is laid vertically and air is blown from bottom to top, there is no need for extra heat spreaders.
A Biomechanical Model of Lumbar Spine
Authors: Uppala Subramanya , Gao Robert X. , Cowan Scott , Lee K. Francis 
Published: November 2021

Abstract
The strength and stability of the lumbar spine are determined not only by the bone and muscles, but also by the visco-elastic structures and the interplay between the different components of the spine, such as ligaments, capsules, annulus fibrosis, and articular cartilage. In this paper we present a non-linear three-dimensional Finite Element model of the lumbar spine. Specifically, a three-dimensional FE model of the L4-5 one-motion segment/2 vertebrae was developed. The cortical shell and the cancellous bone of the vertebral body were modeled as 3D isoparametric eight-nodal elements. Finite element models of spinal injuries with fixation devices are also developed. The deformations across the different sections of the spine are observed under the application of axial compression, flexion/extension, and lateral bending. The developed FE models provided input to both the fixture design and experimental studies.