bluuebunny/crossref_metadata_2025 huggingface dataset:
How the Ageing Population Contributes to UK Economic Activity: A Microsimulation Analysis
Authors: Lawson Tony
Published: February 2016

In the United Kingdom, as in several other countries, increasing life expectancy is leading to a shift in the age distribution of the population. Meanwhile, at the level of individuals, spending patterns change as people age. This paper investigates the extent to which demographic change is likely to affect household spending patterns by combining the techniques of dynamic microsimulation with an imputation method known as random assignment. While there has been significant concern about the economic cost of the ageing population, this paper finds a potentially beneficial effect in the form of an increase in total spending for most expenditure categories.
Union decline in Britain: does gender have anything to do with it?
Authors: Haile Getinet Astatike
Published: February 2016

The paper examines if workplace gender diversity offers some explanation for the decline of unions in Britain. Using the WERS2004 linked employer–employee data and alternative econometric estimators it reports an inverse relationship between workplace union density and gender diversity. Gender and ownership status based sub‐group analyses suggest the inverse relationship to be stronger for male union members and those in the private sector. Gender group size‐based analysis reveals a positive link between workplace union density and gender diversity in workplaces with a female majority. The findings in this paper may mean that unions may need to embrace the changing workplace demography genuinely to improve their fate.
Factors Associated with Suicidality Among a National Sample of Transgender Veterans
Authors: Lehavot Keren , Simpson Tracy L. , Shipherd Jillian C.
Published: February 2016

Correlates of past‐year suicidal ideation and lifetime suicide risk among a national sample of transgender veterans were examined. An online, convenience sample of 212 U.S. transgender veterans participated in a cross‐sectional survey in February–May 2014. We evaluated associations between sociodemographic characteristics, stigma, mental health, and psychosocial resources with past‐year suicidal ideation and lifetime suicide plans and attempts. Participants reported high rates of past‐year suicidal ideation (57%) as well as history of suicide plan or attempt (66%). Transgender‐related felt stigma during military service and current posttraumatic stress disorder and depressive symptoms were associated with suicide outcomes as were economic and demographic factors.
An association between systemic cyclosporine administration and development of acute bullous keratopathy in cats
Authors: Pierce Kenneth E. , Wilkie David A. , Gemensky‐Metzler Anne J. , Curran Paul G. , Townsend Wendy M. , Petersen‐Jones Simon M. , Bartoe Joshua T.
Published: February 2016

Objective

To determine whether any association exists between the onset of feline acute bullous keratopathy (ABK) and administration of systemic corticosteroid or immunosuppressive therapy.

Animals studied

Medical records of cats diagnosed with ABK between the years of 2000 and 2008 were retrospectively reviewed. Breed, age at diagnosis, weight, systemic disease status, eye affected, ophthalmic examination findings, systemic and topical therapy instituted, dosage and duration of therapy, visual outcome and histopathological analyses were recorded in cases meeting the inclusion criteria.

Results

A total of 12 cats of a surveyed population of 70 167 met the inclusion criteria with 17/24 eyes affected by ABK. Medical and/or surgical therapy was utilized for management of ABK with 13/17 eyes remaining sighted at the time of last follow‐up. In a subset of cases corneal cytology, aerobic bacterial culture, FHV‐1 PCR, virus isolation and/or histopathology were performed; no infectious organisms were identified. A rupture in Descemet's membrane of the cornea was identified histologically in two globes. A total of 10 of 12 cats had been previously diagnosed with ongoing systemic disease. A total of 10 of 12 cats were receiving systemic therapy, and a significant association (P < 0.001) was noted between systemic administration of corticosteroids and/or cyclosporine A and the development of ABK. A total of 8 of 10 cats were administered oral prednisolone at doses between 1–2 mg/kg every 12–24 h. A total of 5 of 8 cats receiving oral prednisolone were concurrently administered oral cyclosporine at doses of 1.5–7 mg/kg every 12–24 h. Systemic cyclosporine therapy was found to be a significant risk factor (P < 0.001) for ABK development, while systemic prednisolone was not significant (P = 0.10).

Conclusions

Systemic cyclosporine administration appears to be a risk factor for development of ABK in the population of cats studied.
OUTCOMES AND PROGNOSTIC FACTORS ASSOCIATED WITH CANINE SINONASAL TUMORS TREATED WITH CURATIVE INTENT CONE‐BASED STEREOTACTIC RADIOSURGERY (1999–2013)
Authors: Kubicek Lyndsay , Milner Rowan , An Qi , Kow Kelvin , Chang Myron , Cooke Kristen , Fox Leslie , Farese James , Bacon Nicholas , Lurie David
Published: February 2016

Stereotactic radiosurgery (SRS) is a relatively new therapeutic option in veterinary oncology. The role of this modality has not been extensively evaluated for the use in canine nasal tumors. The objective of this retrospective, observational study was to describe the clinical outcome and prognostic factors associated with survival times in a sample of canine patients treated with SRS for sinonasal tumors. Fifty‐seven dogs with sinonasal tumors met inclusion criteria. Histologic diagnoses included sarcoma (SA) (n= 9), carcinoma (CA) (n= 40), osteosarcoma (OSA) (n= 7), and round cell (n= 1). Four of 57 cases were treated twice with SRS. For these, the median and mean doses delivered were 30Gy and 33Gy, respectively (range 18.75Gy–56Gy). Late effects occurred in 23 cases and ranged from grades I–III. The median overall survival time was 8.5 months. The median overall survival times in dogs with tumor type of CA, SA, and OSA were 10.4, 10.7, and 3.1 months, respectively. Dogs with the tumor type of OSA had shorter overall survival time than that in dogs with tumor type of CA and SA. Findings from this retrospective study indicated that SRS may be beneficial for canine patients with sinonasal tumors, however a controlled clinical trial would be needed to confirm this. Prospective studies are also needed to better define the role of SRS as palliative or curative, and to further investigate the risk of clinically significant toxicity.
Rotordynamic Force Prediction of a Shrouded Centrifugal Pump Impeller—Part I: Numerical Analysis
Authors: Kim Eunseok , Palazzolo Alan
Published: February 2016

Computational fluid dynamics (CFD) is employed to calculate the fluid-induced forces in the leakage path of an incompressible shrouded centrifugal impeller. Numerical solutions of the whirling shrouded impeller at the centered position provide the radial and tangential impedances that can be modeled as a quadratic function of whirl frequency. Calculated impedance results on a face-seal impeller can be modeled with a second-order function of whirl frequency and the predicted rotordynamic coefficients show reasonable agreement with the test results by Bolleter et al. (1989, “Hydraulic Interaction and Excitation Forces of High Head Pump Impellers,”Pumping Machinery: Third Joint ASCE/ASME Mechanics Conference, La Jolla, CA, pp. 187–194). However, the present analysis shows that the calculated impedance curves for a conventional wear-ring seal impeller using three-dimensional (3D) numerical approach have “bumps” and “dips” which can be observed in the bulk flow analysis of impeller models by Childs (1989, “Fluid-Structure Interaction Forces at Pump Impeller-Shroud Surfaces for Rotordynamic Calculations,” J. Vib., Acoust., Stress, Reliab. Des., 111(3), pp. 216–225). After reviewing previous predictions and experiments that showed the bump and dip in the computed and measured forces, the current study focuses on the estimation of the possible sources causing the peaks. The selected possible sources are inlet tangential velocity at the shroud entrance, flow rate of primary passage, shape of the shroud leakage path, and seal clearance. The fluid-induced forces of the conventional wear-ring seal impeller are calculated and analyses on the effects of these variables are provided.
Comprehensive Study of Steam Reforming of Methane in Membrane Reactors
Authors: Yücel Özgün , Hastaoglu Mehmet Alaittin
Published: February 2016

A 2D model and heat transfer mechanism are proposed to analyze and study oxidative steam reforming of methane (OSRM) in a membrane reactor. The model describes mass and thermal dispersions for gas and solid phases. It also accounts for transport through the membrane. The effects of operating parameters on methane conversion and H2 yield are analyzed. The parameters considered are the bed temperature (800–1100 K), molar oxygen-to-carbon ratio (0.0–0.5), and steam-to-carbon ratio (1–4). The results show that our model prevents overestimation and provides valuable additional information about temperature and concentration gradients in membrane reactor which is not available in a simple one-dimensional approach. Simulation results show that large temperature and concentration gradients cannot be avoided. The particle properties and the bed diameter have a considerable effect on the extent of gas mixing. Effective gas mixing coefficient also increases with increasing gas and solid velocity. In membrane reactor, simulation results show that mixing which depends on operational and design parameters has a strong effect on the hydrogen conversion. Also, the removal of hydrogen with membranes breaks equilibrium barrier leading to efficient production of hydrogen, reduced reactor size, and tube lengths. The model can be used in real-time simulation of industrial reactors for control and optimization purposes.
Rotational Flow in Centrifugal Pump Meridian Using Curvilinear Coordinates
Authors: Pochylý František , Stejskal Jiří
Published: February 2016

A new model for calculation of the velocity field in a pump meridian is presented in this paper. It is a parameterized rotational flow model providing the pump designer with an option to simulate various flow conditions at the blade leading edge using a single parameter, which leads to different blade designs. Despite being rotational, this flow model does not allow for creation of helical swirl structures, a feature that is usually sought to be suppressed in a pump impeller. A condition for a flow pattern suitable for a pump hydraulic design is derived using curvilinear coordinates. The variation of the meridional velocity for different choices of the parameter is demonstrated, and the meridional flow field is compared against the turbulent flow. The resulting velocity field is easy to obtain and provides a unified approach to determine the distribution of the blade inlet angles along the leading edge for a range of design requirements.
Micro Flat End Milling Simulation Model With Instantaneous Plowing Area Prediction
Authors: Bayesteh Abdolreza , Ko Junghyuk , Jun Martin Byung-Guk
Published: February 2016

There is an increasing demand for product miniaturization and parts with features as low as few microns. Micromilling is one of the promising methods to fabricate miniature parts in a wide range of sectors including biomedical, electronic, and aerospace. Due to the large edge radius relative to uncut chip thickness, plowing is a dominant cutting mechanism in micromilling for low feed rates and has adverse effects on the surface quality, and thus, for a given tool path, it is important to be able to predict the amount of plowing. This paper presents a new method to calculate plowing volume for a given tool path in micromilling. For an incremental feed rate movement of a micro end mill along a given tool path, the uncut chip thickness at a given feed rate is determined, and based on the minimum chip thickness value compared to the uncut chip thickness, the areas of plowing and shearing are calculated. The workpiece is represented by a dual-Dexel model, and the simulation properties are initialized with real cutting parameters. During real-time simulation, the plowed volume is calculated using the algorithm developed. The simulated chip area results are qualitatively compared with measured resultant forces for verification of the model and using the model, effects of cutting conditions such as feed rate, edge radius, and radial depth of cut on the amount of shearing and plowing are investigated.
Effects of Heat Loss/Gain on the Transient Testing of Heat Wheels
Authors: Fathieh Farhad , Besant Robert W. , Evitts Richard W. , Simonson Carey J.
Published: February 2016

Heat wheels are used in ventilation systems to provide indoor thermal comfort by recovering considerable amount of sensible energy from exhaust airstream. The transient single step test is a new testing method developed to determine the sensible effectiveness of heat wheels. In practice, heat loss/gain may create large uncertainty in the sensible effectiveness obtained through the transient testing. In this study, the transient analytical model in the literature is extended to account for heat loss/gain effects in the transient testing. The results state that in particular operating conditions, the sensible effectiveness can be affected by more than 10% due to heat loss/gain. A new testing facility is developed to investigate the effects of heat loss/gain on the sensible effectiveness through transient testing of a small-scale heat exchanger. After decoupling heat loss/gain effects from transient test data, less than 2% difference was observed in the sensible effectiveness while supply and exhaust flow rate was small (Re < 209) and the temperature difference between them was ΔTst < 7.0 °C. However, the sensible effectiveness decreased more than 9% while ΔTst > 37.5 °C or Re > 600. An empirical correlation was proposed based on the transient test data that correlates the sensible effectiveness with the heat capacity rate ratio. Comparing the results of proposed correlation with literature, less than 2% difference was observed at the heat capacity rate ratio of greater than 0.5 after the heat loss/gain effects were decoupled from transient test data.
Performance of High-Temperature Materials for Efficient Power Plants: The Waterside Challenge
Authors: Auerkari Pertti , Yli-Olli Sanni , Penttilä Sami , Tuurna Satu , Pohja Rami
Published: February 2016

Supercritical (SC) service at high operating values aims for good plant efficiency, but the waterside oxidation resistance can then become life-limiting. In this paper, selected materials and modeling options are compared for life assessment under waterside SC oxidation, particularly for thermal power plants that increasingly need to accommodate cyclic service, fast ramping, and low minimum loads to an extent to which the conventional design practices and materials solutions only partially accounted. For example, the life reduction by high-temperature oxidation and corrosion via lost load-bearing wall thickness is more easily accommodated than the impact on crack growth or material ductility.
Effect of Weber Number on Disintegration of Liquid Sheet With Co-Flowing Gas
Authors: Ali Mohammad , Mayeed Mohammed S. , Islam A. K. M. Sadrul , Islam M. Quamrul
Published: February 2016

The disturbances on the surface of a moving liquid sheet in a moving gaseous medium are studied to analyze the dynamics and breakup of the liquid sheet with co-flowing gas. The problem, composed of the Navier-Stokes systems associated with surface tension forces, is solved by the Volume of Fluid (VOF) technique with a Continuum Surface Force (CSF) manner artificially smoothing the discontinuity present at the interface. The investigation provides the insights into the dynamics and breakup processes. The inlet velocities of liquid and gas are determined by liquid and gas Weber number, respectively. It is found that the disturbances occurred by the gas Weber number controls the instability process for the liquid sheet breakup. The results show that there is a range of gas Weber number for the occurrence of droplet. In this range, the gas Weber number causes an aerodynamic normal force at the tip of the liquid sheet which is able to form a droplet from the tip of the liquid sheet. Below that range of gas Weber number, the aerodynamic normal force at the tip of the sheet is too low to produce a droplet and above the range, the aerodynamic normal force stretches the liquid sheet too much and no droplet occurs.
Effective Finite Element Modeling of Mode III Failure in Composites
Authors: Suryan Levi J. , Atanasov Atanas A. , Daniels Mitchell A. , Parmigiani John P.
Published: February 2016

The ever increasing use of composite materials in today’s society has created a drastic demand for better modeling of their behavior. The difficulty arises in that many modern composite structures are unique in shape and are exposed to a variety of loading situations. More specifically, loading scenarios which cause out-of-plane shear (Mode III) or mixed mode (Mode I + Mode II + Mode III) failure are of greatest challenge to model. This study investigates the capabilities of Simulation Composite Analysis (SCA), a composites software by Autodesk, in modeling failure in notched carbon-fiber composite panels loaded in Mode III. SCA was used with the finite element modeling software Abaqus/Standard (Dassault Systèmes) to model six different laminate stacking sequences. Three of the layups featured 40 plies through the thickness and the other three had 20 plies, with each containing either 10, 30, or 50 percent zero degree plies. The modeled panels were displaced as to create for a Mode III loading condition and the resulting maximum loads, load-displacement plots, and damage propagation outputs were compared to experimental results. It was found that SCA can determine the maximum failure load of the panels with an average of 11.6 percent deviation from experimental values. For one laminate stacking sequence in particular, the software determined maximum loads that deviated less than 1 percent from the experimental data. The load-displacement plots showed good correlations with experimental data in the linear region; however, the load-displacement behavior after damage was well modeled for only certain layups. The damage propagation paths for all the panel models were similar to the experimental panels in general, though self-similar damage propagation was not captured by the FEA models. Overall, Mode III failure in the notched carbon fiber panels was satisfactorily modeled for maximum load, but continued development is needed for predicting damage propagation paths. Modeling Mode III failure in composites is a difficult task; therefore, determining accurate methods in which to model such failure will be a substantial benefit to the composites engineering community. If low cost computer models can be established which accurately capture material damage and failure, the need for expensive and time-intensive experiments may be greatly reduced.
Four Points Bending Tests on Large Scale Welded Pipes Containing a Through-Wall Defect: Fatigue and Fracture Analysis
Authors: Bourgeois M. , Le Grasse T. , Kayser Y.
Published: February 2016

Within the framework of European project STYLE (Structural integrity for lifetime management), fracture tests on two large scale pipes containing a through wall crack have been performed. Two Mock-ups have been tested: MU1 is a narrow gap Inconel Dissimilar Metals, provided and designed by AREVA France, and MU2 is a an austenitic steel butt-weld with a thermally aged weld repair austenitic weld, provided by EDF British Energy.

The four-points bending tests were carried out by the French Alternative Energies and Atomic Energy Commission (CEA), in order to study the mechanical properties and integrity of component such as welding pipes. A through wall crack was machined in the both pipes. After a fatigue pre-cracking step carried out at RT, the monotonic fracture test was performed (at 300°C on MU1). Optical camera and Electrical Potential Drop Method have allowed following the crack growth during fatigue and final fracture stages. The observations made post-mortem showed ductile tearing of a few millimeters in those pipes.

The first part of this paper is devoted to the four-points bending tests. The second part of this paper deals with first numerical analysis related to the Mock-up-1. Previous results concerning the mechanical characterizations of the constitutive materials are discussed. Fracture mechanics small scale specimens are interpreted using FE Analysis to obtain the fracture parameters used in global approaches. First computation is shown on the Mock-up-1 in order to predict the behavior of the large scale test mechanical and fracture behavior.
Unsteady Stokes Flow for a Vibrating Cantilever Under a Free-Surface
Authors: Ilio Giovanni Di , Sahin Iskender , Tafuni Angelantonio
Published: February 2016

Vibration of a thin, rectangular-cross-section beam submerged in a viscous, quiescent fluid undergoing small amplitude oscillations is studied using a Boundary Element (BE) approach in which the free-surface is modeled through a stress-free boundary condition. The Stokes approximation is used where nonlinear convective terms are negligible and the problem is formulated in Fourier and Laplace transform space when appropriate. Results are expressed in terms of non-dimensional hydrodynamic force and its components, namely added mass and damping coefficients. Several parametric studies are conducted to evaluate the effects of depth of submergence, frequency and the amplitude of oscillations on the hydrodynamic functions. The results are compared with the classical solution for a vibrating lamina in an infinite fluid as the limit case and with a recent study using Smoothed Particle Hydrodynamics (SPH) analysis in the presence of a free-surface.
Modeling of Twinning Based Plasticity Phenomenon in Austenite Dominated Steels Under Combined Loading
Authors: Khan Rashid , Pervez Tasneem , Al-Abri Omar S. , Al-Maharbi Majid
Published: February 2016

Advanced high strength steels cover a vast range of applications more specifically in aerospace and oil industry where large deformation of a material is desired in order to attain a specified shape and geometry of the product. The main reason behind their successful implementation is having an optimum combination of strength and formability. Austenite based twinning induced plasticity steel lies in the second generation and has excellent strength-cum-formability combination among the group of advanced high strength steels. The stress assisted phase transformation from austenite to martensite, which is known as twinning, found to be principal reason behind an enhancement of these properties. This work is aimed to investigate an elastic-plastic behavior of an austenite dominated steel, which undergoes slip and mechanical twinning modes of deformation. Initially, a micromechanical model of twining induced plasticity phenomenon is developed using crystal plasticity theory. Then, the developed model is numerically implemented into finite element software ABAQUS through a user-defined material sub-routine. Finally, finite element simulations are done for single and poly-crystal austenite subjected to combined load. This replicates the complex loading condition which exists in material forming processes like pipe expansion, extrusion, rolling. The variation in stress-strain response, magnitude of shear strain, and volume fraction of twinned martensite are plotted and analyzed.
Processing of Hybrid Nanocomposite High Performance Fibers (UHMWPE+Nylon 6+CNT+MAH) Using Solution Spinning Technique
Authors: Absar Saheem , Khan Mujibur , Edwards Kyle
Published: February 2016

Ultrahigh molecular weight polyethylene (UHMWPE) fiber blends with Nylon-6 and reinforced with single-walled carbon nanotubes (SWCNT) were produced using a solution spinning process. Polyethylene-graft-Maleic Anhydride (PE-g-MAH) was used as a compatibilizer to enhance the interfacial bonding between the polymer phases. The loading of Nylon-6, MAH, and SWCNTs with respect to UHMWPE was 20 wt.%, 10 wt.% and 2 wt.% respectively. The development of morphological characteristics due to the inclusion of a compatibilizer in an immiscible hybrid polymer nanocomposite fiber is hereby discussed. Characterization studies of the hybrid fibers were performed using scanning electron microscopy (SEM), Energy-dispersive X-Ray Spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR).
Experimental and Numerical Study on the Fretting Fatigue Mechanism of the V Type Engine
Authors: Li Xin , Zuo Zhengxing , Qin Wenjie
Published: February 2016

Fretting fatigue is one of the typical failure forms of engine block. The aim of this study is to investigate the fretting fatigue mechanism of the V type engine and guide engine design. An experiential system was developed to simulate fretting fatigue failure under typical engine working condition. And a submodel was used in the finite element calculation to analyze contact status and stress distribution of the structural model. Through the fretting fatigue experimental observations and finite element analysis, it can be concluded that the additional rotate torque caused by bearing load and the bolt pretension load are the two main factors which affect the fretting fatigue mechanism of the V type engine. Appropriate increasing of the bolt pretension load and using extended skirt block with cross-bolted main bearings design will restrain the oscillation of the main bearing cap can be beneficial to fretting fatigue lives of the engine block.
Analysis of Contact Area Between an Elasto-Plastic Rough Body and a Flat Body Under Different Working Mode
Authors: Huang Jianmeng , Gao Chenghui , Lin Youxi , Lin Xiezhao
Published: February 2016

A thermo-mechanical coupling contact model between a fractal rough body and a flat body is established. In the model, the heat flux coupling between the sliding surfaces and the effect of elasto-plastic deformation of the rough body are considered. To obtain the transient microcontact process between the rough body and the flat body during rotating sliding friction, the thermo-mechanical problem under this three-dimensional model is solved by the nonlinear finite element multi-physical methods. The comparisons of the real contact area are analyzed under two different working modes, including loading processes with and without frictional rotating. During the loading and rotating process, the shear stress and the total frictional force on the frictional rough interface, and the equivalent plastic strain of the contact asperity are larger. All these including the thermal expansion make the real contact area increase with the applied normal load much faster under the working mode of loading and rotating than it does under the only loading mode.
Modeling and Experimental Studies of Spalling Process in Silicon Wafers
Authors: Alhomoudi Ibrahim A.
Published: February 2016

Analyses involving both modeling and experimental measurements for the residual stresses evaluation in Ni thin films on silicon wafers have been studied with focus on determining the optimum condition that leads to spallation. Different thicknesses of stressor thin films (Ni in our case) have been electroplated on Si(100) and Si(111) wafers to predict the critical residual stress in the Ni/Si system that are required for steady-state crack depth. The Ni film thicknesses and the total critical stresses in the Ni films required for steady state spalling processes were specified for different crack depth in Si(100) and Si(111) wafers.
Behavior of NPS30 Pipe Subject to Denting Load
Authors: Ghaednia Hossein , Gerard Kyle , Bhattacharjee Sudip , Das Sreekanta
Published: February 2016

Pipeline is the common mode for transporting oil, gas, and various petroleum products. Structural integrity of oil and gas transmission pipelines is often threatened by external interferences such as concentrated lateral loads and as a result, a failure of the pipeline may occur due to “mechanical damages”. Sometime, this load may not cause immediate rupture of pipes; rather form a dent which can reduce the pressure capacity of the pipeline. A dent is a localized defect in the pipe wall in the form of a permanent inward plastic deformation. This kind of defect is a matter of serious concern for the pipeline operator since a rupture or a leak may occur. Accordingly, an extensive experimental study is currently underway at the Centre for Engineering Research in Pipelines (CERP), University of Windsor on 30 inch (762 mm) diameter and X70 grade pipes with D/t of 90. The aim of this research is to examine the influence of various parameters such as dent shape and service pressure on strain distributions of dented pipe. Also, three-dimensional finite element models were developed and validated for determining strains underneath the indenter. The load-deformation behavior of pipes subject to this type of lateral denting load obtained from experimental study and finite element analysis is discussed in this paper. In addition, distributions of important strains in and around the dent obtained from the study are also discussed.
A New Paper Tube Laminated by Plastics
Authors: Suda Mitsunori , Zhao Defang , Kitamura Takanori , Ito Kanta , Wada Kenji , Zhang Zhiyuan , Yang Yuqiu , Hamada Hiroyuki
Published: February 2016

Recycled paper and plastics are widely used in current society. Recycled paper is very helpful to reduce waste emissions and energy consumption, saving resource and cost and environment protection. Recycled paper tube is one of the most successful cases in application of recycled paper. Plastics and Recycled paper are excellent choices for packing materials. They are also used to construct temporary structures for both exhibition spaces or for rapid-recovery shelters in emergency operations. As paper tubes are laminated composite materials composited of paperboard which is inherent anisotropy materials, the research on mechanical property and fracture behavior becomes more complicated. In order to analyze deformation and fracture behavior of paper tube and paper tube laminated combined with polymer under lateral compressive load, both the paper tube and hybrid paper tube which was dipped in to the thermosets resin were tested and compared. The energy analysis was also conducted here.
Demystifying Lifshitz’ Theory of van der Waals Adhesion
Authors: Narayanaswamy Arvind , Zheng Yi
Published: February 2016

Adhesion and cohesion of materials are of importance in many different areas of science and engineering, such as friction between objects, flow of liquids on solids or other liquid surfaces, and phase change heat transfer. One contribution to adhesive energy, irrespective of the type of material(s), is from van der Waals interactions, which arise from alteration of the quantum and thermal fluctuations of the electrodynamic field due to the presence of interfaces. Despite its importance, the theory of van der Waals interactions between macroscopic bodies, which is mainly due to Lifshitz, Dzyaloshinskii, and Pitaevskii, remains shrouded in relatively complicated language of quantum statistical physics. In this paper, we will present an alternate derivation which skirts quantum statistical physics (for most part) and relies primarily on a combination of classical electrodynamics and energy conservation.
Adhesion of Elastic Pre-Stressed Tapes
Authors: Putignano Carmine , Afferrante Luciano , Gentile Angelo , Carbone Giuseppe
Published: February 2016

In this paper, we discuss the mechanism of detachment of thin pre-stressed films from a flat smooth rigid substrate. Indeed, we develop an analytical solution in closed form which shows how the critical value of the pull-off force strongly depends on the press-stress P0. In detail, the critical pull-off force needed to detachment is shown to be higher for pre-stressed tapes. Furthermore, we notice that, when a high pre-stress is present, tapes may behave in different manner and spontaneously detach from the rigid substrate.
The Influence of Multiple Inclusions on the Cauchy Stress of a Spherical Particle-Reinforced Composite Under Uniaxial Loading
Authors: Niu Ke , Abedini Armin , Chen Zengtao
Published: February 2016

This paper investigates the influence of multiple inclusions on the Cauchy stress of a spherical particle-reinforced metal matrix composite (MMC) under uniaxial tensile loading condition. The approach of three-dimensional cubic multi-particle unit cell is used to investigate the 15 non-overlapping identical spherical particles which are randomly distributed in the unit cell. The coordinates of the center of each particle are calculated by using the Random Sequential Adsorption algorithm (RSA) to ensure its periodicity. The models with reinforcement volume fractions of 10%, 15%, 20% and 25% are evaluated by using the finite element method. The behaviour of Cauchy stress for each model is analyzed at a far-field strain of 5%. For each reinforcement volume fraction, four models with different particle spatial distributions are evaluated and averaged to achieve a more accurate result. At the same time, single-particle unit cell and analytical model were developed. The stress-strain curves of multi-particle unit cells are compared with single-particle unit cells and the tangent homogenization model coupled with the Mori-Tanaka method. Only little scatters were found between unit cells with the same particle volume fractions. Multi-particle unit cells predict higher response than single particle unit cells. As the volume fraction of reinforcements increases, the Cauchy stress of MMCs increases.
A Novel Method for the Implementation of Contact Including Energy Dissipation in Finite Element Methods
Authors: Grudzinski J. J. , Gosz M.
Published: February 2016

A new method for implementing contact/impact in an implicit finite element formulation has recently been developed. The method uses the idea of buoyancy and fluid drag forces to enforce the contact constraint as well as provide a method of dissipating energy due to the contact. Additionally, the method provides a simplified means for accounting for contact friction. The method has potential usefulness in a certain class of problems such as contact with bodies having soft and viscous foundations as well as problems with sliding. In this work, we introduce the method and illustrate it with an example that shows the benefits and utility of the method.
Analysis of the Residual Stress and Deformation in a Steel Tube due to Quenching Process Using Different Media
Authors: Sarker Pratik , Chakravarty Uttam K.
Published: February 2016

Steel tubes are widely used in industries as machine components and are most common in heavily loaded mechanisms subjected to high dynamic torsional and compressive stress. Hence, they should have higher strength than that of the conventional mechanisms to resist failure. Quenching, an industrial heat treatment process, can improve the microstructure, hardness, toughness, and corrosion and wear resistance of materials. Steel tubes, if quenched, would have desired properties to serve the purposes. However, besides improving material properties, quenching generates some residual stress and deformation in the material due to rapid temperature drop and phase transformation. Therefore, to estimate the temperature distribution, residual stress, and deformation computationally; a three-dimensional fluid-structure interaction model is developed for the steel tube with different quenchants. The quenching characteristics by water, brine, and propylene glycol are estimated and compared with each other. The time-varying nodal temperature distributions in the tube are observed and the critical regions are identified having maximum residual stress and deformation. The time-varying residual stress and deformation at a particular point and along the axial and radial directions of the tube are studied. The convergence of the model is checked and validation of the model is done.
Effects of Moisture Absorption on the Dielectric Properties of Nanoclay-Reinforced Epoxy for Radome Applications
Authors: Garcia Carla , Chesley Christine , Cohn Joshua L. , Grace Landon
Published: February 2016

The relative permittivity and loss tangent at 10 GHz of a nanoclay-reinforced epoxy is investigated as a function of nanoclay loading percentage and moisture content. The energy dissipation associated with frictional and inertial losses during the reorientation of absorbed dipole water molecules exposed to an oscillating electromagnetic field has a significant impact on the relative permittivity and loss tangent of moisture-contaminated polymer materials. This can damage the performance of polymer-based radar-protecting structures (radomes) designed to protect sensitive radar equipment. Thus, prevention or minimization of water absorption in these materials is critical to mitigating this effect. The moisture barrier properties of nanoclay reinforcement are well known, and are targeted in this study as a potential method to reduce the moisture absorption rate and therefore improve the performance of polymer-based radomes exposed to precipitation and humid air. The ability of a water molecule to rotate freely in the presence of an EM field is dependent on its physical and chemical state; whether it be bound and unable to rotate, or unbound and able to dissipate energy through unrestricted rotation. Therefore, any potential dielectric property changes associated with the physical and chemical interaction of water and nanoclay must be quantified prior to exploiting prospective moisture-barrier benefits. In this study, the relative permittivity and loss tangent of an epoxy system reinforced with nanoclay up to 5% content by weight are assessed using a resonant cavity technique at 10 GHz during moisture uptake due to immersion in distilled water at 25°C. Variations in moisture diffusion behavior are observed due to the nanoclay loading percentage. Although deviations in the dielectric properties due solely to nanoclay loading percentage are minimal, effects due to moisture absorption are much more prominent. In the most extreme case, a nearly 15% increase in relative permittivity is observed at 5% moisture content by weight, with a direct correlation between diffusion behavior and degradation of relative permittivity observed for all samples. Likewise, an increase in the loss tangent of approximately 220% is observed at 5% moisture content by weight.
Effect of Hygrothermal Aging on Glass Transition Temperature of a Bismaleimide/Quartz Laminate
Authors: Rodriguez Luis A. , Fittipaldi Mauro , Grace Landon R.
Published: February 2016

The effect of different hygrothermal aging conditions on the glass transition temperature of a six-ply quartz-fiber-reinforced bismaleimide composite is investigated via dynamic mechanical analysis. Bismaleimide is a polymer matrix material suitable for high-temperature structural and electrical applications such as the radar-protecting structure on supersonic aircraft. This particular material is usually subjected to water absorption due to humid air, precipitation, condensation, and accumulation of water in the interior of its constituent structure. In the fully dry, un-aged condition, the glass transition temperature of the laminate is approximately 380°C. Hygrothermal aging conditions are simulated by full-immersion of laminate specimens in distilled water ranging from 30 to 200 days at 25, 40, 60, 75, and 90°C. Specimens immersed at 40°C for 200 days showed the largest depression in glass transition temperature, to approximately 365°C. A subtle, secondary transition marked by a depression and recovery in storage modulus is consistently present in specimens exposed to 75 and 90°C conditions, independent of total immersion time, near 260°C. However, the specimens aged at 75 and 90°C did not exhibit a significant decrease in glass transition temperature as expected. Results indicate variations in glass transition temperature as a result of water absorption in BMI/quartz laminates are dependent on hygrothermal aging history, rather than solely a function of moisture content.
Directional Evaluation of Surface Topography Parameters and Dry Friction
Authors: Wangenheim Matthias
Published: February 2016

Surface topography parameters commonly used do not give information on directional structures on a technical surface, that originate e.g. from manufacturing and finishing processes. On the other hand these sturctures might show large influence on the friction behaviour of these surfaces. A numerical study is performed with an unlubricated dynamic sealing contact, which is e.g. utilized in vacuum applications: These results are compared to directional evaluation of surface parameters. It is shown, that surface roughness parameters commonly used are neither appropriate to predict the level of friction on technical surfaces nor can they give information on directional properties of a counter surface.
Application of Load Transfer Index (U*) in Structural Analysis in Comparison With Conventional Stress Analysis
Authors: Pejhan Khashayar , Wu Christine Q. , Telichev Igor
Published: February 2016

The U* index has been used for load transfer analysis to show its capability in giving general awareness regarding performance of structure. Although U* index and stress values have been proven to be useful indexes as structure design criteria, a thorough comparison between conventional stress analysis and loads transfer analysis (based on U* index) is lacking. In this study, we evaluate load transfer behaviors of a parcel rack of multiple passenger vehicles under different loading conditions using the U* index. Then by demonstrating the unique capabilities of U* as an index for stiffness, it is shown that the load path concept can be combined with the stress analysis results to provide comprehensive information about the structure responses to loading. In addition to the agreement between stress analysis and the U* analysis, it is shown that U* can provide additional information about the structure response that stress analysis fails. Such information includes: interpreting high and complicated stress distributions in structure and detection of questionable stiffness in certain parts of structure. More importantly, the load path index U* can detect the area where significant changes in the structure stiffness occurs. Such information can be used as a guideline for structure design with the goal to reduce the weight while still keeping the structure integrity.
Analysis of Effective Mechanical Properties and Anisotropy of Structured Porous Materials
Authors: De la Rosa Dávila Efrain , de Lange Dirk F. , Medellín Castillo Hugo I. , Rodríguez Gilberto Mejía
Published: February 2016

Many natural and modern man-made materials are porous materials. In many cases, for practical applications and for the proper design of products it is necessary to understand the effective mechanical properties of the porous structure. Even though some general applicable theories exist to estimate the mechanical properties in function of the porosity fraction, or apparent density, the relation between the pore structure and size distribution is not clear. In particular, in case of structured porosity the mechanical properties demonstrate anisotropic behavior. For specialized applications there is an interest to be able to design materials with specified anisotropic properties or with properties varying in space.

In order to design and optimize porous structures with specific anisotropic properties, a flexible simulation model is developed and tested to predict and understand the mechanical anisotropic properties of a large variety of porous structures. In order to be able to change the geometric pore structure without recreating a new model, the pore structure is implemented into a space dependent smoothed binary function.

A comparison is made between results obtained with FEM models with a fully defined geometry and the FEM model with the porosity function to describe the pore structure in order to evaluate and quantify the error that is introduced by the latter implementation and investigate the possibility to mitigate the error.

The model results are also compared with experimental en numerical results reported in literature.
Insights Into the Mechanics of Cytokinetic Ring Assembly Using 3D Modeling
Authors: Bidone Tamara Carla , Tang Haosu , Vavylonis Dimitrios
Published: February 2016

During fission yeast cytokinesis, actin filaments nucleated by cortical formin Cdc12 are captured by myosin motors bound to a band of cortical nodes. The myosin motors exert forces that pull nodes together into a contractile ring. Cross-linking interactions help align actin filaments and nodes into a single bundle. Mutations in the myosin motor domain and changes in the concentration of cross-linkers alpha-actinin and fimbrin alter the morphology of the condensing network, leading to clumps, rings or extended meshworks. How the contractile tension developing during ring formation depends on the interplay between network morphology, myosin motor activity, cross-linking and actin filament turnover remains to be elucidated. We addressed this question using a 3D computational model in which semiflexible actin filaments (represented as beads connected by springs) grow from formins, can be captured by myosin in neighboring nodes, and get cross-linked with one another through an attractive interaction. We identify regimes of tension generation between connected nodes under a wide set of conditions regarding myosin dynamics and strength of cross-linking between actin filaments. We find conditions that maximize circumferential tension, correlate them with network morphology and propose experiments to test these predictions. This work addresses “Morphogenesis of soft and living matter” using computational modeling to simulate cytokinetic ring assembly from the key molecular mechanisms of viscoelastic cross-linked actin networks that include active molecular motors.
A Study on Structural Safety Evaluation Technology for Lead Support Structure in Transformer With Considerations on Short-Circuit Failure
Authors: Yun Minok , Kim Changwook , Choi Myungjun , Kim Youngchul
Published: February 2016

Recently, the importance of lead support structure design has been growing. This is due to very large electromagnetic forces generated by high current flow in short-circuit failure of a transformer. In this paper, a coupled electromagnetic-structural analysis based on numerical method was conducted in order to calculate electromagnetic force which is difficult to calculate analytically. Then, an analysis on change of stress generated from lead support structure was carried out to evaluate structural safety in fault current conditions. A Structural analysis was performed on two types of domains (between leads and bolts, between leads and supports) considering nonlinear contact conditions because these two domains initially have gaps or can be separated. As a result, the arrangement of lead support structures considering their allowable stress was derived to secure the structural safety against the short-circuit force. The proposed arrangement of lead support structure was applied to the structures was applied to the initial designs and this led to improvement of lead support structures designs. Through this process, the evaluation technology suggested in this paper was validated.
Planar and Cylindrical Electrostatic Separators for Enhanced Separation of Fine Liquid Particles From High Velocity Air Stream
Authors: Yang Ning , Shooshtari Amir , Dessiatoun Serguei , Ohadi Michael M.
Published: February 2016

Recently, separation of fine liquid droplets from gaseous flow medium has become an important subject for process and aerospace industry. The aim of this work is to study collection efficiency of high concentration droplets from high velocity air stream using electrostatic separators. To improve the separation efficiency, different designs of separator were studied experimentally including wire-to-plate and wire-to-cylinder designs. The results demonstrated that two-stage planar and cylindrical separators, if designed properly, could provide high collection efficiencies for both small and large particle sizes at high concentration conditions.