bluuebunny/crossref_metadata_2025_split huggingface dataset:
Femtosecond Pulsed Laser-Induced Micromachining of Difficult-to-Machine Materials: Diamond a Case Study
Authors: Malshe A. P. , Ozkan A. M. , Railkar T. A. , Adhi K. P. , Brown W. D. , Molian P. A. 
Published: November 2021

Abstract
Meso and micro scale machining is an important and emerging area of research. Various non-traditional and novel tools are being explored for meso and micro machining of non-silicon materials. In this paper, we report etching, micro machining and related phenomena of commercially available single and polycrystalline diamond using a femtosecond pulsed excimer laser (λ = 248 nm, tp ∼ 380 fs). Surface modifications due to single pulse and multiple pulse irradiation of diamond samples, at different energy densities, have been analyzed using Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Etching rate of single crystal type IIA diamond by femtosecond pulsed excimer laser is also studied. Raman spectroscopy study of the single shot irradiation of diamond with a femto second laser shows the formation of a non-diamond disordered (sp2 bonded) phase on the surface. However, subsequent micro machining of this non-diamond disordered surface, by delivering several shots from the femtosecond laser, results in the removal of the non-diamond disordered layer and the restoration of the diamond surface. It is experimentally shown that the periodicity of the 2-dimensional corrugations written on diamond surface is shorter than the laser wavelength used. 3-dimensional writing on diamond globules during laser etching is also discussed. Further, micro machining of diamond tips is shown to be precise, and without mechanical and chemical damages. Femto second laser is demonstrated as a next-generation tool for mechanical and chemical damage free precision micro machining of the hardest material, diamond.
A Design Methodology to Replicate the Sub-Micron Land-Groove Structure in DVD-RAM Substrates by Injection-Compression Molding
Authors: Seong Kibyung , Moon Su-dong , Kim Hyun , Kang Shinill , Lee Jun-Seok , Lee Dongcheol 
Published: November 2021

Abstract
Recently, the sub-micron structured substrates of 0.74 μm track pitch and 800 Å groove depth are required for DVD-RAM, and the track pitch is expected to be narrower as the storage density for optical disk is getting higher. For the accurate replication of the land-groove structure in the stamper to the plastic substrates, it is important to control the injection-compression molding process such that the integrity of the replication for the land-groove structure is maximized. However, the determination of the processing conditions has been relied on experience or trial-and-error. In the present study, polycarbonate substrates were fabricated by injection compression molding and the land-groove structure regarded as one of the most important geometrical properties for DVD-RAM substrates was measured. The effects of the mold temperature and the compression pressure on the integrity of the replication were examined experimentally. An efficient design methodology using the response surface method (RSM) and the central composite design (CCD) technique was developed to obtain the optimum processing conditions which maximize the integrity of the replication with a limited number of experiments. The model used in this study was verified using the analysis-of-variance (ANOVA), and it was found to be adequate within the confidence limit.
On the Role of Continuum Models in Mechanobiology
Authors: Kamm R. D. , McVittie A. K. , Bathe M. 
Published: November 2021

Abstract
Models of cellular and subcellular mechanics are essential in gaining an understanding of the link between forces applied to a cell and its biological response. Various approaches can be used to construct these models, but one that holds considerable promise is through the use of continuum solid and fluid mechanics, coupled when necessary with molecular dynamic simulations. Here we present a continuum mechanics model of the effects of normal stress applied to a layer of airway epithelial cells. The model predicts widely differing stress distributions associated with basolateral membrane deformation, intercellular flow, or mechanical forcing by other methods such as in the use of adherent beads. When coupled with experimental results obtained from cell culture, these simulations can help to identify the site and possibly the underlying mechanisms of mechanotransduction. We also present some hypotheses concerning the nature of mechanotransduction at the molecular scale.
Flow in the Atherosclerotic Carotid Artery
Authors: Berger Stanley A. , Stroud Jennifer S. 
Published: November 2021

Abstract
The carotid artery bifurcation is vulnerable to the buildup of atherosclerotic plaque. This buildup may lead to vessel occlusion or to embolism or plaque rupture. Numerical simulations of blood flow in severely stenotic vessels, when considered in conjunction with experimental and in vivo data, can contribute to the understanding of plaque rupture. The Navier-Stokes equations are solved in their finite-volume formulation for carotid bifurcation geometries based on surgically removed specimens. Aspects of plaque morphology are isolated so that their effect on flow patterns and fluid mechanical stresses may be independently evaluated; results suggest that a measure of such features as plaque asymmetry and surface irregularity may usefully complement percent stenosis in the diagnosis of vulnerable plaques. The resulting flows contain large recirculation zones and high spatial variations in wall shear. Even steady flows exhibit unsteadiness (e.g. vortex shedding) due to the complex plaque morphology. The computed flow patterns and fluid stresses in different atherosclerotic vessels may be compared to identify critical features of plaque geometry and “risk factors” for plaque rupture. In this way, numerical simulations can help determine the risk of plaque rupture posed by a particular plaque deposit.
Damage Behavior of Trabecular Bone
Authors: Yeh Oscar C. , Niebur Glen L. , Jaasma Michael J. , Keaveny Tony M. 
Published: November 2021

Abstract
In trabecular bone, damage refers to both the physical microstructural changes which can occur in the tissue due to mechanical loads as well as to the degradations in mechanical properties which may result from such morphological changes. One hypothesis to explain age-related increases in osteoporotic fracture risk is that a history of overloads or falls can cause damage to accumulate in trabecular bone and ultimately lead to a catastrophic fracture. The purpose of this paper is to review what is known about the complex damage behavior of trabecular bone and to suggest further avenues of research.
Hydrostatic Pressurization and Depletion of Trapped Lubricant Pool During Creep and Sliding Contact of a Rippled Indenter Against a Biphasic Articular Cartilage Layer
Authors: Soltz Michael A. , Ateshian Gerard A. 
Published: November 2021

Abstract
This study presents an analysis of the contact of a rippled rigid impermeable indenter against a cartilage layer, which represents a first simulation of the contact of rough cartilage surfaces with lubricant entrapment. Cartilage was modeled with the biphasic theory for hydrated soft tissues, to account for fluid flow into or out of the lubricant pool. The findings of this study demonstrate that under contact creep, the trapped lubricant pool gets depleted within a time period on the order of seconds as a result of lubricant flow into the articular cartilage, while for steady state sliding contact a lubricant pool cannot be sustained. These results suggest that the classical cartilage lubrication models of weeping and boosted lubrication may have to be revised. More recent mixture-based models described in the literature are able to predict the frictional response of articular cartilage without necessarily assuming or requiring entrapment of lubricant pools at the articular contact interface.
High Velocity Coating: Effect of the Air Entrapped on the Contact Line Temporal Stability
Authors: Woehl Pierre , Bourgin Patrick 
Published: November 2021

Abstract
Getting and maintaining stable conditions is one key challenge in high speed coating, like in many other processes. The temporal stability of the contact line, i.e. the three-phase junction between the moving substrate, the liquid sheet and the surrounding air, is investigated. The model exhibits a sub-critical instability which is consistent with the observations of the man-of-the-art. It is then tempting to assimilate the transition from stable to unstable regime to the onset of air entrainment. Further investigations, namely experiments, are to be carried out in order to confirm this theoretical prediction.
X-Ray Microtomography of Microcellular Polymers
Authors: Pyrz Ryszard 
Published: November 2021

Abstract
Among modern measuring techniques, which are designed to reconstruct and to measure three-dimensional aspects of microstructure on mesoscopic scale lengths, the X-ray microtomography seems to be very well suited to yield this information. Generally, X-ray microtomography is the X-ray based non-destructive testing method that was first developed for medical purposes and only recently applied to materials characterization. Monitoring materials’ microstructure using X-ray microtomography allows reconstructing a three-dimensional image of the specimen from non-destructive, serial sections and processing it in order to visualize and measure three-dimensional features. Thus valuable information can be deduced from the correlation of measured stress and strain values with a number of internal geometrical parameters which cannot be measured at the specimen surface.
Effect of Gas Type on Microcellular Foam Process Using Atmospheric Gases as a Blowing Agent
Authors: Chen Lee , Straff Rich , Wang Xiang 
Published: November 2021

Abstract
This work concerns the effects of gas type on the microcellular foam process when using atmospheric gases as a blowing agent. Three gases were investigated, CO2, N2 and argon. Gas absorption, viscosity reduction and cell formation were tested with these gases using the foaming process simulator (2) and an extruder with a capillary die. Significant differences were observed among these gases. The gas absorption of N2 and argon in polymers was much lower than CO2. The diffusion rate also seems to be lower with N2 and argon. The viscosity reduction was also lower with N2 and argon. Cell nucleation density was similar for all the three gases at high saturation pressures, but it was significantly lower with N2 or argon when the saturation pressure is low. The cell size is smaller with N2 and argon at a high saturation pressure, especially with N2. As a result, the foam density is higher with these two gases at the same foaming conditions compared to CO2.
Energy Absorption of Braided Glass Fiber Reinforced Composite Tubes
Authors: Quek Shu Ching , Waas Anthony M. 
Published: November 2021

Abstract
Results from an experimental and analytical study on the behavior of braided glass fiber composite tubes under quasi-static crush conditions are presented. The composite tubes have an initiator plug introduced at one open end (chamfered) while the other end is clamped. This procedure causes the tube to ‘flare’ outwards into fronds and results in the progressive failure of the tube in the axial and hoop direction without global tube buckling. Axial force and axial displacements are measured during these tests in order to assess energy absorption. In addition, readings from strain gages that are placed at critical locations on the tube walls are used to assess the state of strain on the tube walls away from the crush end. During a crush test, the axial load ascended to a maximum value and subsequently settled to a plateau value about which the load oscillated during the progressive crushing of the tube. The oscillations exhibited distinct periodicity. Results from an analytical model that best simulates the failure of these tubes are presented. The model is based on an axisymmetric formulation of the cylindrical shell equations in conjunction with ideas from classical fracture mechanics and continuum damage mechanics.
The Improved Volumetric-Efficiency of an Axial-Piston Pump Utilizing a Trapped-Volume Design
Authors: Manring N. D. , Zhang Y. 
Published: November 2021

Abstract
In this research, the volumetric efficiency of the axial-piston pump is examined as it relates to the compressibility losses of the fluid. In particular, two valve-plate geometries are compared to show that alterations in the valve-plate design can cause differences in the operating efficiency of the pump. In this paper, a standard valve-plate design which utilizes slots is compared to a trapped-volume design which eliminates the slots altogether. In the analytical result of this paper, it maybe shown that the standard valve-plate design introduces a volumetric loss which may be accounted for by the uncontrolled expansion and compression of the fluid that occurs through the slots themselves. By eliminating these slots, and utilizing a trapped volume design, it may be shown that improvements in the operating efficiency can be achieved. Though this paper does not claim to provide the ideal valve-plate design for all pump applications, it does provide the theoretical reason for utilizing trapped volumes and lends general insight into the overall problem of valve-plate design.
Model Identification of a High Performance Hydrostatic Actuation System
Authors: Habibi S. R. , Pastrakuljic V. , Goldenberg A. A. 
Published: November 2021

Abstract
An advanced hydrostatic actuation system referred to as the Electro Hydraulic Actuator (EHA) has been designed and prototyped. The prototype of EHA exhibits a very high level of dynamic performance and positional accuracy. EHA’s positional accuracy with a simple outer-loop proportional controller equals its optical position-encoder resolution of 10 Micron. In this paper, a linearized mathematical model of EHA is derived and used as a basis for model identification. Open loop experiments and numerical optimization are used for tuning some of the unknown model parameters and for quantifying their influence. The resulting model is validated and matches closely the measured response.
Deformation Twinning During Impact of a Titanium Cylinder: Numerical Investigation
Authors: Lapczyk I. , Rajagopal K. R. , Srinivasa A. R. 
Published: November 2021

Abstract
It is well known that polycrystalline metals (especially those with bcc or hcp structures), when subjected to impact, undergo two inelastic processes — slip and twinning. Since the work of Taylor (1948) the former one has been studied extensively; while more recently, deformation twinning has attracted attention of some researchers, e.g. Bolling & Richman (1965), Armstrong & Worthington (1974) and Zerilli & Armstrong (1988). Zerilli and Armstrong (1988) suggested that the major effect of twinning is a refinement of the grain size. Based on this assumption, they proposed a model for twinning and showed that much better agreement with experiments can be obtained if, in addition to deformation by slip, deformation twinning is also considered. Similar conclusions were reached by Holt, Mock, Zerilli and Clark (1994) who analyzed the Taylor impact of a titanium specimen.
In this study, we model the Taylor impact of a titanium cylinder. We assume that the problem is axisymmetric and solve the full dynamic equations by using the Galerkin finite element method. Our results show that the energy absorbed during twinning and the deformation due to twinning are relatively small. We also demonstrate the dependence of the results on the initial grain size of the material. Specifically, by modeling two materials of widely differing grain sizes, we show that the long-grained material twins substantially more than the small-grained material.
Mechanics of Random Fiber Networks
Authors: Ostoja-Starzewski M. , Stahl D. C. 
Published: November 2021

Abstract
Paper has a multiscale structure, including a spectrum of features: macro-fluctuations (scale of tens, hundreds, thousands … of meters), streaks (scale of meters), flocs (scale of centimeters), single cellulose fibers (scale of millimeters), cellulose fiber being a composite helically wound from fibrils (scale of tens of microns), fibrils (submicron scale), and molecular chains (tens through thousands of Angstroms). This complexity is the root cause of various size-scale effects in mechanics (elasticity and strength) of paper. We outline a micromechanics model of paper which provides a bridge from the scale of interacting fibers to a statistical continuum approximation. The model accounts for a 3-D random geometry of fiber networks with any degree of fiber flocculation, and employs a Timoshenko beam with torsion for each fiber segment (between two contiguous fiber-fiber bonds). The fiber-fiber bonds are treated as either rigid or flexible. The model involves a computational mechanics of thousands of fibers, in which global failure occurs on microscale through fracture of a fiber segment and/or fracture of a fiber-fiber bond. We also report on the scale effects and statistics of effective mechanical (elastic and strength) responses due to a nonuniform paper formation.
Active Control of Translating Media With an Arbitrarily Varying Length
Authors: Zhu W. D. , Ni J. , Huang J. 
Published: November 2021

Abstract
In this paper we determine the general control laws for point-wise controllers that dissipate energies of vibration of translating strings and beams with an arbitrarily varying length. Special domain and boundary control laws that can be easily implemented result as a special case. Sufficient conditions for uniform and uniform exponential stability of controlled systems are established via Lyapunov stability criteria. Numerical simulations demonstrate the effectiveness of active controllers in stabilizing translating media during both extension and retraction. Optimal gains leading to the fastest rates of decay of energies of vibration of controlled systems are identified. It is shown that under the optimal control gains, translating media can be completely stabilized during extension and retraction.
Failure Modes in Sandwich Beams With Composite Face-Sheets and PVC Foam Cores
Authors: Steeves Craig A. , Fleck Norman A. 
Published: November 2021

Abstract
Sandwich beams with glass-fibre reinforced plastic faces and PVC foam cores were manufactured and tested in three point bending. The experiments were compared with analytical predictions of beam behaviour for three failure modes: face microbuckling, core shear collapse, and local indentation. A new model for indentation failure was developed which gives accurate predictions for ultimate strengths of sandwich beams that fail due to indentation.
Real Time Experimental Investigation of Dynamic Failure Mode Selection in Sandwich Structures
Authors: Xu Luoyu R. , Rosakis Ares J. 
Published: November 2021

Abstract
Past studies of dynamic failure in sandwich structures have mostly been concerned with post-mortem investigations of failure patterns resulting from the dynamic loading of such structures through projectile impact. The final fracture patterns have typically been very complex and their time sequence, interdependence, and detailed nature (opening versus shear) were unclear. In the present work we concentrated on the real-time investigation of the generation and the subsequent evolution of dynamic failure that occurred within microseconds after impact. Model sandwich structures involving a combination of transparent polymers and metals (typically tri-layers bonded together by weak or strong adhesives) were designed and subjected to impact loadings to study the failure evolution mechanism. High-speed photography and dynamic photoelasticity were utilized to study the nature and the sequence of failure modes. A series of complex failure modes was observed. In most cases, interfacial cracks (dynamic delamination) appeared first. These cracks were shear dominated and were often intersonic. Thus, initial delamination was found to be shear driven and happen at extremely short time scales even at moderate impact speeds ranging between 20 to 50 m/s. The transition behavior between interlayer crack growth and intralayer crack formation was also observed. Opening (subsonic) intralayer cracks kinking from the dynamic shear delamination propagated into the core layer of the model sandwich structure and eventually branched as they reached a high enough growth speed.
Effect of Implanted Delamination and Core Density on the Buckling Behavior of Sandwich Composites
Authors: Mahfuz Hassan , Islam Syful , Carlsson Leif , Atkins Makeba , Jeelani Shaik 
Published: November 2021

Abstract
Foam core sandwich composites have been fabricated using innovative co-injection resin infusion technique and tested under in-plane compression. The sandwich construction consisted of Klegcell foam as core materials and S2-Glass/Vinyl ester composites as face sheets. Tests were conducted with various foam densities and also with implanted delamination between the core and the face sheet. The intent was to investigate the effect of core density, and the effect of core-skin debonds on the overall buckling behavior of the sandwich. Analytical and finite element calculations were also performed to augment the experimental observations. It has been observed that core density has direct influence on the global buckling of the sandwich panel, while embedded delamination seem to have minimal effect on both global as well as local buckling. Detailed description of the experimental work, finite element modeling and analytical calculations are presented in this paper.
Elasticity Solutions for a Sandwich Orthotropic Cylindrical Shell Under External/Internal Pressure, and Axial Load
Authors: Kardomateas George A. 
Published: November 2021

Abstract
The elasticity solution is constructed for a cylindrical sandwich shell under external and/or internal pressure and for the same shell under axial load. The solution is an extension of the one for a homogeneous, monolithic shell and is provided in closed form. All three phases, i.e., the two face-sheets and the core are assumed to be orthotropic. Moreover, there are no restrictions as far as the individual thicknesses of the face-sheets and the sandwich construction may even be asymmetric. These solutions can be used as benchmarks for assessing the performance of various sandwich shell theories. Illustrative results are provided in comparison to the sandwich shell theory.
Sandwich Shell Model With Woven Fabric Facings for Nonlinear Finite Element Simulation
Authors: Tabiei Ala , Tanov Romil 
Published: November 2021

Abstract
This paper presents a micromechanical model for analysis of woven fabric composites. The micro model is coupled with a shell element developed for the analysis of sandwich structures. Starting with the average strains in the representative volume cell and based on continuity requirements at the sub-cell interfaces, the strains and stresses in the composite constituents are determined as well as the average stresses in the lamina. In their formulation the developed micromechanical models take into consideration all components of the 3-D strain and stress tensors. The formulation is implemented in the explicit nonlinear finite element code DYNA3D. The performance of the model is assessed through couple of examples. The simplicity of formulation makes this model attractive for the nonlinear finite element analysis of sandwich composite structures with woven facings.