bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small Cracks and High-Cycle Fatigue
Authors: Ritchie R. O. 
Published: July 2023

Abstract
The problem of high-cycle fatigue (HCF) failures that has recently plagued the aircraft jet-engine industry is associated with the rapid growth of small defects under the action of high-frequency vibrational or resonant loading; such defects have been associated with regions of microstructural damage attributed to such processes as foreign object damage, surface fretting and low-cycle fatigue. Since the size of these defects is generally below characteristic inspection limits, traditional design and life-prediction procedures do not specifically address this problem. Moreover, from a fracture-mechanics perspective, small fatigue cracks, of dimensions less than ∼500 μm, often behave in an apparently anomalous fashion, compared to conventional results on through-thickness large cracks, of dimensions greater than ∼5 mm (e.g., in compact-tension specimens). Such “anomalous” small-crack behavior is not limited to metallic alloys but is also seen in ceramics and intermetallics. It is the intent of this paper to briefly review what a small crack is and how its behavior may differ from that of long cracks. Indeed, there are several definitions of small cracks which relate to their size in comparison to the dimensions of the microstructure, the local inelastic zones (e.g., plastic-zone size) ahead of the crack tip, and the zone of crack-tip shielding (e.g., from crack closure) behind the tip. The relevance of this to the HCF problem and more broadly to fatigue life prediction in general will also be discussed.
Force-Deflection Behavior of Individual Unimorph Piezoceramic C-Block Actuators
Authors: Moskalik Andrew J. , Brei Diann 
Published: July 2023

Abstract
Most piezoelectric actuators used in smart structure applications are either stiff stacks which produce high forces and small deflections, or compliant benders which produce large deflections and small forces. This leaves a mid-range gap in actuator performance in which many applications operate. A new class of solid state piezoceramic actuators, known as C-blocks, has been developed as a mid-range actuator. A C-block is a semicircular composite bender. It can be combined in series and/or parallel to increase actuator deflection and/or force. A simple analytical model for the steady-state force-deflection behavior of an individual unimorph piezoceramic C-block was derived and experimentally verified with two case studies. The results demonstrate that the stiffness of an individual C-block is six times more than that of a comparable straight bender.
Nonlinear Analysis of Piezothermoelastic Laminated Composite Beams
Authors: Bao Y. , Tzou H. S. 
Published: July 2023

Abstract
Conventional analyses of piezoelectric laminated structures are based on the linear theories. Investigations of nonlinear characteristics are still relatively scarce in recent years. In this paper, static, dynamic, and control effects of a piezothermoelastic laminated beam with an initial nonlinear large static deflection (the von Karman type geometric nonlinear deformation) and temperature and electric inputs are studied. It is assumed that the piezoelectric layers are uniformly distributed on the top and bottom surfaces of the beam. Beam equations incorporating the nonlinear deflections, piezoelectric layers, temperature and electric effects are simplified from the generic piezothermoelastic shell equations. Analytical solutions of nonlinear static deflection and eigenvalue problems of the nonlinearly deformed beam including temperature and electric effects are derived. Active control effects on nonlinear static deflections and natural frequencies imposed by the piezoelectric actuators via high control voltages are investigated. A numerical example is provided and response behavior discussed.
A Theoretical Modeling of Wave Localization due to Material Damping: Results
Authors: Esteban Jaime , Lalande Frederic , Rogers Craig A. 
Published: July 2023

Abstract
In the first part of this paper (Esteban, et al., 1996a), a methodology to study the effects of material damping in the phenomena of sensing localization, as well as a quantification of the damping in a structure, were derived. The results obtained using this analytical procedure supported with experiments will be here presented. Since damping in structures cannot be predicted, but experimentally measured, numerical and experimental analysis are carried out jointly in order to obtain the damping in the structure and the energy losses that occur. A long beam structure, butt bolted at the middle, is analytically and experimentally investigated: The beam is longitudinally and transversely excited, and the response is measured before the mid-span connection, calculating the phase speed of the wave and reconstructing the dispersion curve relation for the system. A measurement of the viscoelastic material properties of the beam structure is obtained with the use of this procedure. These values are inserted into the equations describing the dynamics of the system to further investigate its damping, through measurements of the specific damping capacity of the structure. The effect on the localization of the energy of vibration to a region close to the wave generating source is observed by comparing the energy dissipation due to material damping to that due to structural joints.
On-Board Truck Computers and Accident Risk
Authors: Ayres T. J. , Donelson A. , Brown S. , Bjelajac V. M. , Van Selow W. 
Published: July 2023

Abstract
On-board trip computers facilitate record-keeping in trucks, but some models permit drivers to enter data manually while driving. Three approaches were taken to investigate the potential risk associated with such devices. A review of studies involving other in-vehicle devices revealed that drivers can safely time-share visual attention between the road and a display. An experiment conducted in a controlled driving environment found that head and eye movements while using an on-board truck computer were similar to those for common devices and activities such as operating a radio or checking the odometer. Analysis of accident reports from North Carolina and the Fatal Accident Reporting System showed that in-vehicle devices were only rarely cited as distracters in accidents. Based on these findings and on the safety benefits provided by truck computers, it is expected that these will have a net positive impact on truck fleet safety.
Predicted Thermally Induced Stresses in an Epoxy Molding Compound at the Chip Corner
Authors: Uschitsky M. , Suhir E. 
Published: July 2023

Abstract
Mechanical reliability of epoxy molding compounds in plastic packages depends on the stress level at the chip corners. In this analysis we evaluate the effect of radii of curvature at the corners and the interfacial delamination on the thermally induced stresses caused by the thermal contraction mismatch of the epoxy and silicon. We found that, in the case of perfect adhesion, the calculated stresses are in the range of 5,000–10,000 psi, depending on the fillet radius. The role of the delamination at the chip/epoxy interface was assessed using Fracture Mechanics approach. We showed that delamination leads to a substantial increase in the stress level at the delamination tip. The predicted stresses are in the range of 20,000–100,000 psi, depending on the delamination length and the fillet radius. We showed also that the stress intensity factor KI for the local stresses is proportional to the stress level at the chip corner and the square root of the delamination length. The combined action of the thermally and delamination induced stresses can lead to crack (delamination) propagation. The initiated crack can be stopped (“arrested”) if this stress reaches a “critical” level. We conclude that the propensity of the molding compound to a thermo-mechanical failure can be reduced by employing compounds with high adhesion strength, and that increased radii of curvature at the chip corners might result in appreciable reduction of the induced stresses. The obtained results can be helpful in reliability analyses and physical design of plastic packages.
“Thick” Plastic Packages With “Small” Chips vs “Thin” Packages With “Large” Chips: How Different Is Their Propensity to Moisture-Induced Failures?
Authors: Suhir E. , Ilyas Q. S. M. 
Published: July 2023

Abstract
We suggest a simple geometrical parameter reflecting the combined effect of the chip width, the pad width, and the underchip thickness of the molding compound on the propensity of a plastic electronic package to a moisture-induced failure. We use this parameter to analyze the experimental data for the moisture level leading to such a failure. We show that “thick” packages (such as PLCC, MQFP, etc) with “small” (4–5mm wide) chips are less prone to moisture induced failures, than “thin” packages (such as TQFP) with “large” (8–10mm wide) chips. “Thick” packages are also less sensitive to the change in the moisture content. We show also that, from the standpoint of structural analysis, the distinction between “thick” and “thin” packages is due primarily to the level of the in-plane (“membrane”) stresses in the underchip portion of the molding compound: in “thick” packages bending stresses only should be considered, while in “thin” packages both the bending and the in-plane (“membrane”) stresses should be accounted for. The obtained results are intended to be used in the development of guidelines (“figures of merit”) that would enable one to separate packages that need to be “baked” and “bagged” (or “rebaked” and “rebagged”) from those that supposedly do not.
Impact of Polymerization on Warpage Prediction of Molded Plastic Packages
Authors: Teng Sue Y. , Sarihan Vijay , Thomas Ron , Adhihetty Indira 
Published: July 2023

Abstract
Warpage determination and minimization in molded plastic packages is critical to package reliability, especially for large plastic packages. Power modules with exposed heat sinks fall in this category. Seamless contact of these power modules with the external heat sink, or cold plate, is also required for effective thermal dissipation. Hence, accurate prediction of warpage is very important for reducing the design cycle time for this class of packages.
Conventional modeling methodologies maintain the assumption that the package is stress-free and undeformed at the molding temperature. Warpage prediction is typically based solely on the differential thermal expansion of the package materials during cool down from the mold temperature. These assumptions, however, result in a large discrepancy between the predicted warpage and the actual measured warpage. This study resolves this disparity by proposing a methodology which accounts for the impact of polymerization of the mold compound on package warpage after the package is removed from the mold.
A hybrid FEM and experimental methodology has been developed which determines the impact on package warpage prediction due to polymerization, in addition to the differential thermal contractions of the various materials in the package during the cool down process after mold release.
A Comparison of Viscoplastic and Plastic Constitutive Models for Pb/Sn Solder Alloys
Authors: Basaran Cemal 
Published: July 2023

Abstract
In the literature there has been a number of constitutive models proposed for modeling thermomechanical behavior of Pb/Sn solder alloys. Some of these models are based on the plasticity (using time independent irreversible deformations), and some are based on the viscoplasticity (using time dependent irreversible deformations). In this paper it is demonstrated that Pb/Sn solder alloys are highly viscous materials, and that their behavior cannot accurately be modeled with a plasticity based model.
Evaluation of Minimum Zone Straightness by Nonlinear Optimization Method
Authors: Orady Elsayed A. , Li Songnian , Chen Yubao 
Published: July 2023

Abstract
Fitting algorithm is considered one of the significant uncertainty factors to the measurement results using CMM. In this paper, a new algorithm, named Nonlinear Optimization Method (NOM) has been developed for the evaluation of straightness error. To improve the accuracy, efficiency and robustness of NOM, data filtering and rebuilding are incorporated in the method. The algorithm, Least Squares Method (LSM) and Convex Hull Method (CVH) are applied to data sets obtained with CMM measurements on the surfaces machined with different processes such as milling, planning, grinding and hand-finishing. Practically valuable results have been obtained and the algorithm has proven to guarantee Minimum Zone Evaluation (MZE) of straightness.
Point-to-Point Probe Performance Test of Kinematic Touch Trigger Probes on Coordinate Measuring Machines
Authors: Shen Yin-Lin , Moon Sung-Ho 
Published: July 2023

Abstract
The default 49-point sampling plan specified in the ANSI B89 standard when applied to kinematic touch trigger probes is investigated in this paper. The default sampling plan was tested by using experimental data and research findings indicate that a systematic bias in the Z coordinate of the best-fit center of the reference ball exists when testing performances of kinematic touch trigger probes. A two-latitude sampling plan synthesis method based on a pretravel model for touch trigger probes is proposed in this paper. It is shown that the proposed method can be used to synthesize sampling plans resulting in a near-unbiased reference ball center in probing tests even when noise is included in the probing data. The proposed method is not to replace the three-dimensional (3D) probe testing procedure, but to be used together with the 3D probe testing method, to reveal the actual probe performance or roundness of the measurements.
Thermal Management in Direct Chip Attach Assemblies
Authors: Baldwin Daniel F. , Beerensson James T. , Sitaraman Suresh K. 
Published: July 2023

Abstract
Direct chip attach packaging technologies are finding increasing application in electronics manufacturing particularly in telecommunications and consumer electronics. In these systems, bare die with bumped interconnect bond pads are assembled in a flip chip configuration (i.e., active face down) directly to low-cost organic substrates. In this work, the thermal management of three direct chip attach technologies is investigated. Experimental measurements are conducted exploring the junction-to-ambient thermal resistance and thermal dissipation path for the three interconnect technologies which include solder attach, anisotropic adhesive attach, and isotropic adhesive attach. A first order chip-scale thermal design model is developed for flip chip assemblies exhibiting good agreement with the experimental measurements.
Anisothermal Fatigue Analysis of Solder Joints in a Convective CBGA Package Under Power Cycling
Authors: Hong Bor Zen , Yuan Tsorng-Dih , Burrell Lloyd G. 
Published: July 2023

Abstract
This paper presents the use of an integrated flow-thermo-mechanical analysis method and tools for numerically studying the effect of local heat transfer coefficient on anisothermal cyclic fatigue behavior of solder joints in a CBGA (ceramic ball grid array) package under power cycling. A cyclic chip power load of 1 watt to 10 watts at a frequency of 5 cph (cycles per hour) with an air flow speed of 0.5 m/s was used to simulate a typical field condition for a 32mm CBGA air cooled package. Temperature dependent viscoplastic properties of Pb-Sn (lead-tin) alloys were used to model the solder joint behavior in the package. An approach using the Δϵeqin-modified Coffin-Manson Law was applied to estimate the fatigue life of the solder joint. The Δϵeqin represents a saturated equivalent inelastic strain range as determined by the finite element model. The results of anisothermal deformation and fatigue response of solder joint are compared to that of a condition of constant temperature cycling.
A Multi-Axial Thermo-Mechanical Fatigue Tester for Electronic Packaging Materials
Authors: Lu Minfu , Liu Sheng 
Published: July 2023

Abstract
A multi-axial thermo-mechanical mini-fatigue tester has been developed at Wayne State University for investigating the behaviors of small specimens, particularly in the field of electronic packaging materials and structures. The testing and calibration of machine is described in this paper. Materials tested include a copper wire, two kinds of polyimide films, a lead-free solder alloy.
Fluid Compressibility Effects in Semiactive Vibration Absorbers (SAVA)
Authors: Mo C. , Lee J. , Khaw C. , Kuehn J. , Patten W. N. 
Published: July 2023

Abstract
Recent past work by this research team has demonstrated that semiactive hydraulic vibration absorbers hold the promise of providing an ideal means of mitigating structural vibration. This paper examines an issue that must be treated when designing a semiactive vibration absorbers (SAVA) system for application to a full scale structure; fluid compressibility. An expanded and consistent dynamic model of the flow process is first established. A laboratory experiment is then presented to identify pertinent parameters. A simple feedback control is then tested on a single degree of freedom laboratory structure to verify the findings.
Development of a Neural Network Flush Airdata Sensing System
Authors: Rohloff Thomas J. , Catton Ivan 
Published: July 2023

Abstract
Neural network techniques have been successfully applied in the development of flush airdata aviation instrumentation. Current flush airdata sensing (FADS) systems use a matrix of pressure measurements from the vehicle nose to infer airdata states. The objective of this investigation was to use flight data available from the NASA Dreyden Flight Research Center to train a multi-layered, feed-forward neural network to solve the FADS airdata estimation problem. Using a modified back propagation training algorithm, a neural network was developed to represent the mapping between the pressure-matrix-input and the airdata-output vector spaces. The resulting FADS neural network allows for accurate airdata estimation over the range of flight conditions considered. The results of this investigation demonstrate that neural networks can be applied to flush airdata systems, and can be as robust as the existing semi-empirical model.
Servo Performance of Actuator Bearing Greases
Authors: Prater Walter L. , Stone Garvin J. , Tierney Kevin W. , Karis Tom E. 
Published: July 2023

Abstract
The hysteresis properties of a magnetic recording disk drive rotary actuator servo were measured for bearings lubricated with three different types of grease. The three types of grease tested were: 1) mineral oil with a polyurea thickener, 2) polyol ester oil with a polyurea thickener, and 3) perfluorinated polyether (PFPE) oil with a polytetrafluoroethelyne (PTFE) particle thickener.
The grease dynamic viscosity and yield stress were measured to characterize the grease flow properties.
Actuator bias current was measured on files to quantify changes in the hysteresis and linearity. Head settle times were measured following a random seek pattern.
Actuators made with the mineral oil and polyol ester oil polyurea thickened greases had acceptable actuator bias current and head settle times. Actuators made with the PFPE grease exhibited large bias hysteresis, significant non-linearity, and the head settle time was significantly longer than for those actuators made with mineral oil grease.
The reasons for the increased hysteresis and settle time observed with the PFPE grease were investigated. It was found that the PTFE grease particles get shredded and deposited in the raceway and they also form large agglomerates that impede the smooth rolling of the bearing.
Shear Mechanical Behavior of the Human Lumbar Anulus Fibrosus and the Effects of Degeneration
Authors: Iatridis James C. , Kumar Sanjay , Krishnan Leena , Rawlins Bernard A. , Weidenbaum Mark , Mow Van C. 
Published: July 2023

Abstract
Clinically, it is observed that a correlation may exist between low back pain and activities associated with torsional loading of the lumbar intervertebral discs (IVD). Analysis of the localized mechanical response of the IVD under different loading conditions is necessary for evaluation of internal stresses and strains within the disc which are responsible for successful performance or failure of the IVD. An understanding of the localized shear mechanical properties of the IVD is an important step toward the development of a precise mathematical model of the entire IVD and motion segments. While some information is available on the shear mechanical behavior of the nucleus pulposus [2] and anulus fibrosus (AF) [3], more information is required to completely characterize their material behaviors. The objective of this study was to investigate the shear mechanical behavior of the AF with attention to frequency of loading, axial compressive stress, and degree of degeneration.
Local Gas Transport Rate in Oscillatory Flow in a Model Human Central Airways
Authors: Tanaka Gaku , Ito Jin , Oka Kotaro , Tanishita Kazuo 
Published: July 2023

Abstract
The rate of local axial gas transport in oscillatory flow through a model human central airways was measured to evaluate the gas exchange during high-frequency oscillation. A rigid model of human airways consists of asymmetrical bifurcations up to third generation, of which geometries were determined by the study of Horsfield et al. (1971). A bolus of CO2 tracer was injected into the trachea, and effective diffusivities as a function of location in the airways were obtained by CO2 washout profiles. The rate of increase of effective diffusivity depends on the local flow conditions and differs with branches. The effective diffusivity in the left main bronchus becomes 3 times greater than that in the straight tube, whereas no significant effect is observed in the right main bronchus.
Sinusoidal Oscillating Flow Through Asymmetrical Bifurcation
Authors: Yamaguchi Ryuhei , Okada Kazuki , Ikeda Tomohiko 
Published: July 2023

Abstract
The respiratory system is characterized by many bifurcations. The bronchi are composed of symmetrical and asymmetrical bifurcations. It is generally considered that the gas mixing during the respiration are induced by the flow through the bronchi.
In the present study, the axial and the transverse velocity components have been measured in the asymmetrical bifurcation by LDV. Consequently, the asymmetry of axial flow and the secondary flow around the flow divider have been clarified experimentally.
The Zero-Tension Hypothesis for the Mechanism of Atherogenesis and the Wall Shear Stress Gradient (WSSG) Predictor Equation
Authors: Lei Ming , Kleinstreuer Clement , Truskey George A. , Archie Joseph P. 
Published: July 2023

Abstract
Non-uniform hemodynamic factors are believed to play important roles in the onset and development of atherosclerotic lesions in branching blood vessels and intimal hyperplasia at graft-artery bypass junctions. At present, a variety of theories regarding the hemodynamic aspects of atherogenesis have been proposed, which include almost all hemodynamic factors, such as high and low shear stresses, oscillatory shear index (OSI), temporal and spatial variations of wall shear stresses, flow separation, long particle residence time, and secondary flow, etc.[1–4] However, the underlying mechanism of endothelial cell (EC) response to hemodynamic forces leading to atherosclerosis is still not well understood.