bluuebunny/crossref_metadata_2025 huggingface dataset:
Transformation of the State and Political Economy of the Governance
Authors: Yıldırım Emek
Published: December 2019

By the 1980s and 1990s, neoliberal policies such as privatizations and deregulations transforming the minimal state model to regulative state model from the Keynesian social welfare state system made some structural and functional changes in the state mechanism, and the public administration has been in the first place due to the changing relationship between the state and the market. In fact, within this context, the new institutional economics (NIE) had a remarkable influence upon the debates upon the altering role of the state. Hence, the transformation of the state in this regard also revealed the argumentations on the governance paradigm along with the doctrinaire contributions of the new institutional economics. Therefore, this chapter will discuss the transformation of the state and the political economy of the governance together with a critical assessment of the new institutional economics in the public administration.
Hybrid Equilibrium Finite Element Formulation for Cohesive Crack Propagation
Authors: Parrinello Francesco
Published: December 2019

Equilibrium elements have been developed in hybrid formulation with independent equilibrated stress fields on each element. Traction equilibrium condition, at sides between adjacent elements and at sides of free boundary, is enforced by use of independent displacement laws at each side, assumed as Lagrangian parameters. The displacement degrees of freedom belongs to the element side, where an extrinsic interface can be embedded. The embedded interface is defined by the same stress fields of the hybrid equilibrium element and it does not require any additional degrees of freedom. The extrinsic interface is developed in the consistent thermodynamic framework of damage mechanics with internal variable and produces a bilinear response in a traction separation diagram. The proposed extrinsic interface can be modelled on every single element side or can be modelled only on a set of predefined element sides.
Mechanical Properties and Fracture Surface Analysis of Vinyl Ester Resins Reinforced with Recycled Carbon Fibres
Authors: Zattini Giorgio , Mazzocchetti Laura , Benelli Tiziana , Maccaferri Emanuele , Brancolini Gianluca , Giorgini Loris
Published: December 2019

This work is focused on the mechanical characterization and fracture surfaces analysis of thermosetting polymers reinforced with short, randomly oriented, recycled carbon fibres (rCFs). This work aims at evaluating fibre/matrix adhesion between recycled CFs - reclaimed via pyrolysis followed by controlled oxidation of the pyrolytic char - and different polymer matrices, namely epoxy and vinyl ester resins. The latter is the main focus in this work, being amongst the most widely used thermosetting resins in SMC processes, which are the typical target for short rCFs. The evaluation of the properties of this new recycled carbon fibre reinforced polymer (rCFRP) has been via thermogravimetric analysis, dynamic mechanical analysis, stress/strain tests in tensile mode, and a subsequent analysis of the fracture surfaces by means of images analysis obtained by macrophotography, Optical Microscopy and Scanning Electron Microscopy. The comparison amongst the results allowed to evaluate the influence of the polymer nature and of the adhesion quality between fibres and polymeric matrix, mainly on the mechanical properties of the rCFRPs.
Optimization Methodology for Continuous Heterogeneous Structures: A Preliminary Design of an Engine Mounting Bracket
Authors: Campo G.A. , Vettorello A. , Giacalone M.
Published: December 2019

A numerical methodology is presented which is based on Topology Optimization (TO) approach for designing continuous heterogeneous structures. This method is then exploited to reduce weight and to increase stiffness in mechanical components. Useful guidelines for the evaluation of equivalent material properties of metallic cellular structures are discussed, and they are applied for the optimization process of an engine mounting bracket under realistic loading and boundary conditions. The outcome of TO, which is related to the material density distribution into the design space, is critically reviewed for the definition of bulk, lattice and void regions within the component.
Fibreglass Reinforced Polymer Structure Response under Different Impact Scenarios
Authors: Lamanna Giuseppe , Greco Alessandro , Manzo M. , Armentani Enrico , Opran Constantin Gheorghe
Published: December 2019

Composite materials are increasingly used in those fields where it is necessary to achieve the requirements of lightweight and high mechanical properties. Even though their high specific strength which get these materials very attractive, especially for the transport field, there are several critical issues that still limit their application in primary structures. Among these, dynamic loading conditions play a critical role because they can significantly lower their residual strength. This paper aims to investigate experimentally the structural response of a 25 mm thick Omega composite structure under different impact loading conditions. The investigated test article consists of E-glass fibres (40% volume fraction) reinforced polyester matrix. The structure is covered by a HELIOPOL 1401 M AGC W 11 gelcoat layer and it has been impacted through a drop mass of 3.94 kg, dropped from heights of 50 mm, 75 mm, 100 mm, 150 mm, 200 mm, 250 mm, 350 mm and 500 mm.
A Model for Low-Cycle Fatigue in Micro-Structured Materials
Authors: Parrinello Francesco , Gulizzi Vincenzo , Benedetti Ivano
Published: December 2019

A microscale formulation for low-cycle fatigue degradation in heterogeneous materials is presented. The interface traction-separation law is modelled by a cohesive zone model for low-cycle fatigue analysis, which is developed in a consistent thermodynamic framework of elastic-plastic-damage mechanics with internal variables. A specific fatigue activation condition allows to model the material degradation related to the elastic-plastic cyclic loading conditions, with tractions levels lower than the static failure condition. A moving endurance surface, in the classic framework of kinematic hardening, enables a pure elastic behaviour without any fatigue degradation for low levels of cyclic traction. The developed model is then applied to micro-structured materials whose micro-mechanics is analysed using a boundary integral formulation. Preliminary results demonstrate the potential of the developed cohesive model. The future application of the proposed technique is discussed in the framework of multiscale modelling of engineering components and design of micro-electro-mechanical devices (MEMS).
Lifetime Calculation of Soil-Loaded Non-Pressure Polymer Pipes
Authors: Poduška Jan , Hutař Pavel , Frank Andreas , Pinter Gerald , Náhlík Luboš
Published: December 2019

Outstanding durability of plastic pressure and non-pressure pipes can cause difficulties, when a reasonable lifetime estimation is needed. It is impossible to prove the lifetime by testing, but there is a method of calculation that can provide a certain idea about the expected lifetime. The lifetime estimation is based on the assumption that the failure occurs as a result of the slow crack growth mechanism and it is calculated using the linear elastic fracture mechanics approach. Numerical simulations of crack growth in the pipe are necessary for this calculation. These simulations must consider various effects that can play a role in the lifetime. This paper deals with the lifetime calculations of a pressure and a non-pressure corrugated pipe considering the soil loads acting on pipes when they are buried. In the simulation of the pressure pipe, a combination of loads is applied that consists of internal pressure, residual stress and the soil loads. The influence of the loads is discussed. The non-pressure corrugated pipe is loaded by the soil loads only.
Size Dependent Thermo-Piezoelectricity for In-Plane Cracks
Authors: Sladek Jan , Sladek Vladimir , Repka M. , Tan Choon Lai
Published: December 2019

The finite element method (FEM) is developed to analyse the size effect (flexoeletricity) for 2-D crack problems in thermo-piezoelectricity. Flexoelectricity is observed in micro/nanoelectronic structures, where large strain gradients destroy the symmetric structure of atoms in crystals and thereby causing polarization, even in dielectric materials. In contrast to using classical Fourier heat conduction theory, a finite speed of the thermal wave is considered in the higher order transport equation. The variational principle is applied to derive the FEM equations and C1-continuous elements are employed in the implementation of the FEM. An example is presented to demonstrate the effect of the characteristic time parameter on the crack opening displacement and temperature distribution.
Evaluation of Residual Stresses in Laser Welded High-Pressure Vessels Steels by X-Ray Diffraction
Authors: Čapek Jiří , Ganev Nikolaj
Published: December 2019

This paper contains results of a comprehensive experimental programme aimed at an evaluation of residuals stresses in and near laser welds of pressure vessels steels using X-ray diffraction method. Welds were prepared by the company RAPTECH s.r.o., where two types of steel plates, namely P355 and P460 of the thickness 5, 8 and 10 mm, were welded by a laser beam with specific parameters. Surface transversal and longitudinal stresses were analysed on both sides of the welds, namely upper and downside. The results, important for further applications of the used technology, are discussed particularly from the viewpoint of possible critical areas near the welds and their impact on fatigue loading.
Influence of Unsizing and Carbon Nanotube Grafting of Carbon Fibre on Fibre Matrix Interfacial Shear Strength of Carbon Fibre and Polyamide 6
Authors: Tanaka Kazuto , Yamada Kanako , Hinoue Yoshitake , Katayama Tsutao
Published: December 2019

Carbon Fibre Reinforced Thermoplastics (CFRTP) are expected to be applied to the automotive industry instead of CFRP which require curing time, due to the expected short production cycle time of CFRTP, which is using thermoplastic as a matrix. We reported that the grafting of carbon nanotubes (CNTs) on the carbon fibre improves the fibre matrix interfacial shear strength. In our process to graft CNTs on carbon fibre, chemical vapour deposition (CVD) method was used and Ni, which was used as the catalyst, was electrically plated onto carbon fibres. Since commercially available carbon fibre was sized, which may affect the plating behaviour of Ni, the effects of sizing agents on CNT deposition have to be clarified. In this study, Ni for catalytic metal was plated by electrolytic plating using a watt bath on spread PAN-based carbon fibre and unsized carbon fibre, and the influence of the sizing agent to the distribution of Ni was evaluated. The morphological observation of carbon fibre and single fibre pull-out test were conducted to clarify the influence of sizing agent on the CNT deposition and the interfacial shear strength between the CNT grafted carbon fibre and Polyamide 6 (PA6). Uniform distribution of small sized Ni particles can be obtained on unsized carbon fibre and uniform Ni particles results in uniform CNT distribution. The CNT grafted unsized carbon fibre showed higher interfacial shear strength with PA6 than that of sized carbon fibre.
Influence of Magnetite Dispersion on Tensile Properties
Authors: Tanaka Kazuto , Ishii Yuta , Katayama Tsutao
Published: December 2019

Nanofibers have high cell affinity due to their fine structure and surface roughness, and are expected to be used as biomaterials. In particular, magnetic nanofibers containing magnetic particles are expected to be used for magnetically induced drug delivery systems and hyperthermia. However, due to the aggregation of the magnetic particles contained in the nanofibers, there is a problem that the aggregation location becomes a starting point of fracture and causes a decrease in tensile strength. In this study, to improve the dispersibility of magnetic particles in Magnetite/PLA nanofiber nonwoven fabrics for suppressing the decrease in tensile strength, magnetite is subjected to surface treatment with oleic acid or stearic acid and ultrasonic agitation. Magnetite/PLA nanofiber nonwoven fabric was prepared by the electrospinning method, and dispersion of magnetite in PLA nanofiber nonwoven fabric and tensile strength were evaluated. Magnetite dispersion was improved by the surface treatment and increasing the ultrasonic agitation time. In particular, by performing the stearic acid treatment and prolonging the ultrasonic agitation time, the magnetite dispersion tended to be improved. This treated Magnetite/PLA nanofiber nonwoven fabric showed higher tensile strength.
Utilization of Williams’ Power Series for Estimation of Crack Behavior under Mixed-Mode Loading
Authors: Malíková Lucie , Miarka Petr , Šimonová Hana
Published: December 2019

Multi-parameter fracture mechanics concept has been applied to investigate crack behavior under mixed-mode loading, particularly in a semi-circular bending disc. The so-called Williams’ series expansion is used for the crack-tip stress field approximation. It has been shown that application of the generalized fracture mechanics concept can be crucial for materials with specific fracture behavior, such as elastic-plastic or quasi-brittle one, when fracture occurs not only in the very vicinity of the crack tip, but also in a more distant surrounding. Then, considering the higher-order terms of the Williams’ expansion in fracture criteria can be helpful. The attention is devoted to the analysis of the influence of various distances between the supports during the three-point bending test on the results of the further crack propagation direction.
Growth Rate of Small Surface-Cracks in Age Hardening Cu-Ni-Si Alloy under Cyclic Stressing
Authors: Goto Masahiro , Yamamoto Takaei , Kitamura Junichi , Han S.Z. , Takanami R. , Yakushiji Terutoshi , Lee J.H.
Published: December 2019

Stress-controlled fatigue tests were conducted on round-bar specimens to understand the fatigue behavior of precipitate-strengthened Cu–6Ni–1.5Si alloy. The cracks were initiated at the grain boundaries, followed by growth along the crystallographic slip planes in the adjacent grains. The crack growth data of plain specimens exhibited a large scatter, resulting in a difficulty of the measurement of crack growth rate. To evaluate the small-crack growth rate of the alloy, the plain specimens with a small blind hole as the crack starter were fatigued. The crack growth rate of small cracks from the hole was uniquely determined by a term σanl and the material constant, n, was 5.3. The term σanl with n = 5.3 was applied to the plain specimen, showing good applicability of the term to small cracks in the plain specimen.
Numerical Studies of the Correlation between Inclusion Shape and Effective Elastic Properties of the Particle Reinforced Composites
Authors: Piat Romana , Happ Pascal A.
Published: December 2019

In present paper the effect of inclusions with irregular shapes on the elastic material properties of two-phase composites is studied. The irregular shapes of the real inclusions were approximated using smooth three-dimensional structures. For this needs the images of the microscopic particles were numerically approximated through smooth structures using methods of the computer algebra and were used for the following FE studies. The reference elements with typical inclusions with irregular shapes were determined and used for calculation of the effective material properties.
High-Temperature Creep Tests of Two Creep-Resistant Materials at Constant Stress and Constant Load
Authors: Sklenička Václav , Kuchařová Květa , Kvapilová Marie , Kloc Luboš , Dvořák Jiří , Král Petr
Published: December 2019

Creep is defined as a time dependent component of plastic deformation. Creep tests can be performed either at constant load or at constant applied stress. Engineering creep tests carried out at constant load are aimed at determination of the creep strength or creep fracture strength, i.e. the data needed for design. The constant stress tests are important as a data source for fundamental investigations of creep deformation and fracture mechanisms and for finite element modelling of more complex stress situations. For some materials, the difference between the two type of testing can be very small, while for other materials is large, depending on the creep plasticity of the material under testing. The paper aims to compare the creep results of two different creep-resistant materials: the advanced 9%Cr martensitic steel (ASME Grade P91) and a Zr1%Nb alloy obtained by both testing methods and to clarify the decisive factors causing observed differences in their creep behaviour.
Hierarchical Reinforcing Fibers for Energy Harvesting Applications - A Strength Study
Authors: Karalis George , Mytafides Christos , Polymerou Anastasia , Tsirka Kyriaki , Tzounis Lazaros , Gergidis Leonidas N. , Paipetis Alkiviadis S.
Published: December 2019

This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more detail, glass fibers were coated with an efficient thermoelectric (TE) ink in order to create multifunctional reinforcing fibers for advanced composite structural applications. The main scope is to evaluate the fracture properties of the TE-enabled hierarchical glass fibers. The hybrid nanocrystal TE ink was synthesized via a solvothermal reaction and further fully characterized in coating form. The morphology and wetting properties of the TE ink deposition onto glass fibers were evaluated via SEM and contact angle measurements. Enhanced values by 19.4% in tensile strength for the coated glass fibers compared to the reference are being reported, measured at single fiber level. The evaluated multifunctional glass fiber strength will be utilised during ongoing research for the interfacial shear strength determination.
Recovery of Fracture Toughness on Self-Healing Epoxies Using Ternary Nanomodified Microcapsules: A Parametric Study
Authors: Kosarli Maria , Tsirka Kyriaki , Chalari Stella , Palantza Antigoni , Paipetis Alkiviadis S.
Published: December 2019

This study is focused on the effect of the nanomodification of the microcapsules healing agent on the healing efficiency. In detail, nanomodified epoxy resin with both carbon nanotubes (CNTs) and carbon black (CB) diluted with a non-toxic solvent was encapsulated into UF capsules. The morphology of the external surface and the mean diameter was investigated via Scanning Electron Microscopy (SEM). In addition, the thermal stability was estimated with Thermogravimetric analysis and healing efficiency was evaluated for the polymer epoxy matrix. A parametric study was performed at various solvent percentages and catalyst percentages. Results indicated an increase of the healing efficiency with nanomodified capsules against of the use of conventional microcapsules.
Water Effect on the Deformation Behavior of Nafion Membrane
Authors: Riku Isamu , Mimura Koji
Published: December 2019

The water channels inside the Nafion membrane are considered as the elastic particles and the effect of the elastic modulus of the particles on the deformation behavior of the membrane is discussed with a particle-contained composite model, which is constituted based on the homogenization method. The results show that the deformation resistance of the membrane is quite dependent on the elastic modulus of the particles, whereas the strain softening behavior after the yielding of the membrane is almost derived from the onset and the propagation of the localized shear band in the matrix, which also leads to the dramatic disappearance of the entanglement points in the molecular chain network of the matrix.
A Finite Element Numerical Methodology for the Fatigue Analysis of Cylinder Liners of a High Performance Internal Combustion Engine
Authors: Barbieri Saverio Giulio , Mangeruga V. , Giacopini Matteo , Laurino Carlo , Lorenzini Mariano
Published: December 2019

In this paper a numerical methodology is proposed, which aims at predicting the fatigue behaviour of engine cylinder liners in an eight-cylinder V-type four-stroke turbocharged engine. A preliminary kinematic and dynamic study of the crank mechanism is fulfilled in order to properly identify the load cycle that involves the cylinder liner. Finite Element analyses, both thermal and thermo-mechanical, are performed to evaluate the stress and the strain of the component. In particular, non-linear models are developed to mimic the piston-liner interaction when subjected to different loading conditions. A simplified approach is proposed in order to reduce the computational effort of the simulations. FEM results are then processed employing the multiaxial Dang Van fatigue criterion.
TEM Study of Junctions between Martensite Laths and Changes in Microstructure of Low-Carbon Steel before LCF II
Authors: Eterashvili Tamaz , Vardosanidze M. , Dzigrashvili T.
Published: December 2019

The joining points between martensite packets (laths) and their microstructure in low-carbon martensitic steel were TEM studied. In order to determine the real microstructure of the packet, martensite examinations were conducted before low-cycle fatigue (LCF) tests, considering the structure of the packets and types of their joining. The changes in microstructure occurred in the above places after austenite-martensite transformation were also analyzed. It was shown that after jointing some packets initiate arch-like contours in the laths, exhibiting a presence of local stresses. Several types of joints are considered, including the penetration of laths of one packet into that of neighboring one. It was revealed that the microstructure changes are exhibited in joining points without any external deformation, and result in the localized plastic deformation at LCF. It is assumed that microcrack initiation and commencement of fatigue failure of the material should be expected to happen just in these areas. All the above is explained from point of view of the peculiarities of martensitic transformation.
TEM Study of Martensite Microstructure in the Junctions of Laths in Low-Carbon Chromium Steel after LCF III
Authors: Eterashvili Tamaz , Dzigrashvili T. , Vardosanidze M.
Published: December 2019

TEM study of junctions between martensite packets (laths) and their microstructure in low-carbon martensitic steel were studied. It was revealed that formation of slip bands commences at junctions between laths. Heavy changes in microstructure occur at junctions of packets and in the near-boundary laths because of plastic deformation of martensite. A number of typical junctions between the laths after LCF are considered. Deformation process within the individual packet occurs inhomogeneously, some of the laths deform more heavily than the others. The coarser slip bands group within large laths and run along their whole lengths. It was shown that the above microstructure changes strongly affect the cyclic fracture of the steel. Some concrete sites of microcrack initiation are indicated.
Ultrasonic Damage Detection of Impacted Long and Short Fibre Composite Specimens
Authors: Sellitto Andrea , Riccio Aniello , Russo A. , Napolitano Carmine , Zarrelli Mauro , Meo Michele
Published: December 2019

Composite materials structures are particularly susceptible to the damages induced by low-velocity impacts that may result in Barely Visible Impact Damages (BVIDs), which can hardly be identified through visual inspection. These damages are particularly dangerous, since they can critically reduce the mechanical properties of the impacted structures. In this work, the damage induced in impacted long and short fibre composite specimens has been experimentally evaluated by means of Non-Destructive Technique (NDT) inspections. The damages size and location have been evaluated by means of ultrasonic testing to assess the influence of fibres aspect ratio (long and short fibres), fibres material (carbon and glass), volume fraction, and impact energy for low velocity impacts on composite specimens. Considerations about the failure mechanisms arising as a consequence of the impact event and their interactions have been finally introduced.
On the Crack Quasi-Static Growth
Authors: Pavelko Vitalijs
Published: December 2019

The theoretical model of quasi-static crack growth in the elastic-plastic material under load variation in a wide range. Small-scale yielding is principal assumption and main restriction of proposed theory. The model of crack growth provides for continues and interrelated both the crack propagation and plastic deformation development. The nonlinear first-order differential equation describes the quasi-static process of crack growth. In dimensionless form this equation invariant in respect to geometrical configuration and material. The critical size of the plastic zone is proposed as the characteristics of material resistance which is directly connected with the fracture toughness, but more convenient in practical applications of invariant equation. The demonstration of solution is performed for the double cantilever beam that widely used as the standard (DCB) sample for measurement of the mode-I interlaminar fracture toughness. he short analysis of some properties of solution of the invariant equation and its application is done.
The Role of Replicated Service Atmosphere on Deformation and Fracture Behaviour of Carburised AISI Type 316H Steel
Authors: Warren Xander , Heard P.J. , Flewitt P.E.J. , Martin T.L.
Published: December 2019

The UK Advanced Gas Cooled nuclear reactor fleet adopted CO2 gas as the heat transfer medium. Over the plant service life carbon diffuses into the stainless steel components as part of the overall oxidation process. This carbon enrichment promotes carbide precipitation and changes overall microstructure, thereby altering temperature deformation and fracture behaviour. Due to difficulties of replicating the high temperature/high pressure CO2 service environment, many tests are conducted under simulated CO2 conditions. We compare the role of a range of surrogate atmospheres on steel test specimens to one which failed in service to establish the influence of testing atmosphere on creep deformation and fracture characteristics.
Comprehensive Numerical Simulation on Thermally Grown Oxide and Internal Stress Evolutions in Thermal Barrier Coatings
Authors: Nakajima Ryuta , Katori Hiroaki , Arai Masayuki , Ito Kiyohiro
Published: December 2019

TBCs (Thermal Barrier Coatings) is deposited on gas turbine blades to protect the substrate from a combustion gas flow. One of the serious problems occurred in gas turbine is TBC delamination which is caused by startup, steady and stop operation in service. TBC delamination results from subjecting to both cyclic thermal stress and evolution of internal stress due to thermally grown oxide (TGO). In this study, the finite element code which can simulate thermal and internal stress fields generated in TBC was developed. The developed code involves the follows: inelastic constitutive equation for ceramic coating, bilinear-type constitutive equation for bond coating and Chaboche-type inelastic constitutive equation for the substrate, and mass transfer equation in consideration of oxygen diffusion and chemical reaction with aluminum. Thermal cycling simulation was conducted using the developed code. It was confirmed that maximum stress and its location in the ceramic coating/bond coating interface were matched with the associated experimental results.
Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere
Authors: Ito Kiyohiro , Gao Fei , Arai Masayuki
Published: December 2019

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.
Optimum Design of Damage Resistant Reinforced Composite Panels
Authors: Sellitto Andrea
Published: December 2019

In this work, an optimization procedure able to determine the optimum design of a stiffened aeronautical panel subjected to low velocity impacts is presented. As design variables, the number of plies and the stacking sequence of the panel have been considered. The optimization is based on a genetic algorithm, while the onset of the impact induced damage is predicted by means of an approach based on the critical impact force threshold. A multi-objective optimization has been carried out to determine, among the configurations able to withstand the low velocity impacts, the ones characterized by the maximum buckling load and the minimum weight.
An Approach for Predicting the Initiation of Ductile Fracture in Plane Strain Rolling
Authors: Lyamina Elena , Pirumov Alexander , Hwang Yeong Maw
Published: December 2019

The paper extends Orowan’s method to the prediction of ductile fracture in plane strain rolling. In general, any uncoupled ductile fracture criterion can be used in conjunction with the solution found. However, the present paper focuses on a ductile fracture criterion based on the workability diagram. It is assumed that the initiation of fracture occurs at the axis of symmetry.
Analysis of 3-Dimensional Creased Cracks
Authors: Sonobe Yohei , Ino Takuichiro , Koyama Atsuhiro , Saimoto Akihide
Published: December 2019

A method of analysis for calculating a precise distribution of a stress intensity factor alonga front of 3D crack was improved by introducing a closed-form integral. In the present study, the crackface is discretized with number of triangular boundary elements on which the weighting function ofbody force doublet varies linearly with coordinate variables. A closed form solution of a resultant forceover an arbitrary planar-triangular area due to a presence of an isolated point force was derived andused to satisfy a stress boundary condition of a creased crack problem. In principle, arbitrary shaped3D cracks which may contain asperities and multiple creased lines in its face can be solved by presentapproach.
Rupture and Damage at Dilatant Geological Interfaces
Authors: Selvadurai A.P.S.
Published: December 2019

The work discusses the processes that can be present at fractures and defects at geological interfaces. The introductory comment clearly indicates that the computational approaches offer the most appropriate methods for examining complex contact problems at geomaterial interfaces. There are, however, certain types of contact problems that are amenable to analytical treatment. The paper examines the problem of a circular dilatant-frictional patch located at an otherwise frictionless interface. The dilatancy processes are induced at the circular patch by the relative shear of the elastic regions. The paper presents a mathematical approach for the study of the problem where results from the solution of integral equations applicable for the internal indentation of a penny-shaped crack by a rigid inclusion and the internal pressurization of an annular crack are combined with a work-dissipation relationship to examine the mechanics of the interactions at the dilatant zone.
Thermoelastic Rolling Contact Problem of an FGM Layered Elastic Solid
Authors: Alinia Y. , Aali A. , Guler M.A.
Published: December 2019

This study focuses on the thermo-elastic rolling contact problem of a graded coating/substrate system. The problem is formulated under the plane thermoelasticity framework. Assuming an exponential variation of the shear modulus within the coating, the governing singular integral equations are extracted by means of the Fourier transform. The solution to problem is provided via the Gauss-Chebyshev integration method. The sensitivity of the contact stresses as well as the surface temperature rise to the stiffness ratio, the coating thickness and the non-dimensional speed is investigated. The results indicate that the thermal expansion ratio substantially affects the contact stresses. Also, the softening coatings will result in maximum surface temperature rise. The coating thickness can alter the surface temperature rise such that an increase of the coating by a factor of 1.6 may result in 50% reduction of the maximum surface temperature.
Dynamic Fracture Analysis of Plates Loaded in Tension and Bending Using the Dual Boundary Element Method
Authors: Li Jun , Sharif Khodaei Zahra , Aliabadi M.H.
Published: December 2019

The purpose of this paper is to solve dynamic fracture problems of plates under both tension and bending using the boundary element method (BEM). The dynamic problems were solved in the Laplace-transform domain, which avoided the calculation of the domain integrals resulting from the inertial terms. The dual boundary element method, in which both displacement and traction boundary integral equations are utilized, was applied to the modelling of cracks. The dynamic fracture analysis of a plate under combined tension and bending loads was conducted using the BEM formulations for the generalized plane stress theory and Mindlin plate bending theory. Dynamic stress intensity factors were estimated based on the crack opening displacements.
Effect of Resin Layer Thickness on Mode II Delamination Growth Property of CFRTP Laminates under Static Loadings
Authors: Tanaka Kazuto , Ishida Kosuke , Takemoto Keisuke , Katayama Tsutao
Published: December 2019

Carbon Fibre Reinforced Thermoplastics (CFRTP) are expected to be used in various fields for the point of their superior mechanical properties. CFRP laminates with continuous fibres tend to be damaged by microcracks in the layer and interlaminar delamination. Especially, it is necessary to evaluate the mode II delamination growth property, which is correlated with compression after impact (CAI) strength. It is reported that CF/Epoxy laminates with a thicker interlaminar resin layer show higher toughness. By applying an extra thick interlaminar resin layer to CFRTP in which thermoplastic resin with relatively higher fracture toughness is used for the matrix, CFRTP with higher interlaminar fracture toughness can be developed. In this study, the mode II delamination growth property of CFRTP laminates under static loading was evaluated for the specimens with various layer thicknesses of polyamide (PA) resin in the middle layer of the laminates. Their moldability and damage propagation properties were evaluated by three-point bending tests and end notched flexure (ENF) tests. CF/PA laminated composites with a thicker PA layer showed superior mode II delamination growth property under static loading since they had more ductile fracture due to a thicker PA layer.
On the Use of Carbon Nanotubes to Develop Durable Structural Electrodes for Self-Sensing Applications
Authors: Grammatikos Sotirios A. , Dahl Morten Melby , Brøndbo Vegar Salin , La Rosa Angela Daniela
Published: December 2019

This paper reports an experimental investigation on embedded polyurethane (PUR) electrodes into a carbon fibre reinforced polymer (CFRP) composite to enable the dependable use of composites as a piezoresistive sensors, among other uses, and pave the way towards advanced structural health monitoring (SHM). To be able to use polyurethane as electrodes, multi-walled carbon nanotubes (MWCNTs) were used as fillers in PUR to increase its electrical conductivity. Various concentrations of MWCNTs in PUR were tested to reveal the optimum synthesis. This was conducted by performing mechanical and electrical property tests of the electrodes, studying the adhesion capabilities between composite matrix and polyurethane electrode and carrying out load-unload testing where the composite acts as a strain sensor.
Production and Characterization of Boride Coatings on Steels
Authors: Anthymidis Konstantinos , Trakali Afroditi , Tsipas Dimitrios N.
Published: December 2019

Boride coatings on steels have an excellent combination of properties. They can significantly improve the hardness, the wear and corrosion resistance of steels. Boronizing of steels has been achieved using different methods such as pack cementation and paste boriding. On the other hand, fluidized bed technology has been successfully used in many surface engineering applications in the deposition of hard and / or corrosion resistant layers e.g. carburizing, aluminizing and chromizing. This method is simple, efficient and environmental friendly and is characterized by excellent heat and mass transfer, which results to improve quality of the as-produced coatings. As a result, fluidized bed technology can be considered as a useful alternative method for the production of boride coatings on steel substrates. In the present paper we used this method to deposit boride coatings on steels. The as-produced coatings were examined by means of optical microscopy, X-Rays diffraction, Vickers microhardness and pin on disk in terms of coatings thickness and morphology, phase formation and mechanical properties. It was found that they are characterized by good adherence and uniformity all over the substrate and showed improved tribological properties under dry wear conditions.
Fracture Surface of a Ti-6Al-4V Specimen with EDM Notches Tested under Quasi-Static Loading in Methanol
Authors: Baragetti Sergio , Borzini Emanuele , Arcieri Emanuele Vincenzo
Published: December 2019

Ti-6Al-4V titanium alloy is a high strength-to-mass ratio material common in a lot of engineering fields. Its surface oxide can guarantee the protection of the substrate from various corrosive media. Unluckily, this film can be scratched in presence of mechanical and chemical loads and for this reason the corrosion resistance can decrease. The Structural Mechanics Laboratory (SM-Lab) is carrying out a characterization of the alloy in different environments under quasi-static loading. In this paper, a summary of the outcomes of the investigation and the description of the fracture surface of a specimen with EDM notches quasi-statically tested in methanol is provided
Bypassing primary healthcare institutions: Reasons identified by patients’ attending the out-patient department
Authors: Karunaratne N. P. , Kumara G. S. P. , Karunathilake K. T. G. S. , Karunathilake G. V. K. M. , Kaushalya P. G. M. , Kavinda H. W. I. , Keshala A. A. M. , Ponnamperuma T.
Published: December 2019

IntroductionSri Lanka has a hierarchy of health services, from health care units with fewer facilities to hospitals with specialized care. Due to the absence of well demarcated draining areas and lack of clear referral policies, patients tend to bypass the primary health care units and attend much superior health care institutions without referrals. This practice has caused congestion in hospitals and deterioration of efficacy and quality of care provided to needy patients. This study was designed to identify the reasons for bypassing primary health care institutions by patients. MethodA cross sectional study was done among conveniently selected sample of patients attending outpatient department of Teaching Hospital Karapitiya (THK). Data were collected by an interviewer administered questionnaire that assessed their socio demographic status and reasons for bypassing their nearest hospital. Patients whose nearest hospital are THK and referred patients were excluded from the study. ResultsAmong 344 patients, 60.2% were females, mean age was 41 years. Most were educated up to GCE O/L, unemployed, and had an average income<Rs 30,000. More than half (52%) of the patients had a primary health care unit less than 5km from their residence. In average, patients spent nearly 1 & 1/2 hours for traveling and paid Rs. 186 to reach tertiary care hospital.   According to the participants’ understanding, most of their nearest hospitals had adequate supply of medicine (72%) and staff (79%), but not the laboratory facilities (48%).Poor quality of service represented by of doctors, delayed service, lack of essential facilities and lack of laboratory facilities and specialized services were reported as main reasons for by passing their nearest health care institutions. ConclusionsFindings confirmed that averagely educated people with low middle-income avoid primary health care services due to unavailability of specialized care, inadequate facilities and poor quality of service. Improving facilities and building trust on primary care service will therefore improve utilization of primary health care institutions in the country.
Self-Antigens Displayed on Liposomal Nanoparticles above a Threshold of Epitope Density Elicit Class-Switched Autoreactive Antibodies Independent of T Cell Help
Authors: Chen Zhilin , Wholey Wei-Yun , Hassani Najafabadi Alireza , Moon James J. , Grigorova Irina , Chackerian Bryce , Cheng Wei
Published: December 2019

Epitope density has a profound impact on B cell responses to particulate Ags, the molecular mechanisms of which remain to be explored. To dissect the role of epitope density in this process, we have synthesized a series of liposomal particles, similar to the size of viruses, that display a model self-antigen peptide at defined surface densities. Immunization of C57BL/6J mice using these particles elicited both IgM and class-switched IgG1, IgG2b, and IgG3 autoreactive Abs that depended on the epitope density. In C57BL/6 gene knockout mice lacking either functional TCRs or MHC class II molecules on B cells, the liposomal particles also elicited IgM, IgG1, IgG2b, and IgG3 responses that were comparable in magnitudes to wild-type mice, suggesting that this B cell response was independent of cognate T cell help. Notably, the titer of the IgG in wild-type animals could be increased by more than 200-fold upon replacement of liposomes with bacteriophage Qβ virus-like particles that displayed the same self-antigen peptide at comparable epitope densities. This enhancement was lost almost completely in gene knockout mice lacking either TCRs or MHC class II molecules on B cells. In conclusion, epitope density above a threshold on particulate Ags can serve as a stand-alone signal to trigger secretion of autoreactive and class-switched IgG in vivo in the absence of cognate T cell help or any adjuvants. The extraordinary immunogenicity of Qβ viral-like particles relies, in large part, on their ability to effectively recruit T cell help after B cell activation.
Real-World Experience on the Effectiveness and Tolerability of Apremilast in Patients with Plaque Psoriasis in India
Authors: Parasramani Shrichand , Thomas Jayakar , Budamakuntla Leelavathy , Dhoot Dhiraj , Barkate Hanmant
Published: December 2019

Introduction:

Apremilast, a phosphodiesterase-4 inhibitor, has been recently approved for the management of plaque psoriasis in India in 2017. However, no real-world experience pertaining to apremilast has been documented.

Materials and Methods:

A retrospective review of medical records was conducted of all patients across India who were prescribed apremilast for an entire 16 weeks. The primary endpoint was the percentage of patients achieving the Psoriasis Area and Severity Index (PASI) 75 at 16 weeks. The secondary endpoints were as follows: (i) change in mean PASI; (ii) change in mean body surface area (BSA); (iii) percentage of patients who achieved PASI 50, 90, and 100; and (iv) adverse events (AEs) reported.

Results:

We analyzed the records of 105 patients. Mean age was 41 years and mean disease duration was 6.75 years. All the patients had previously received some forms of systemic treatment. Forty-three patients (41%) achieved ≥ PASI 75 of which four patients (3.8%) and five patients (4.76%) achieved PASI 100 and PASI 90, respectively at week 16. Moreover, 28 patients (26.7%) demonstrated PASI 50 response. Baseline mean PASI score of 14.78 reduced to 4.5 (−69.55%), whereas mean BSA score of 24.4 reduced to 8.24 (−66.3%). Nine patients discontinued apremilast due to adverse effects. Thirty-five patients (33.3%) had one or more AEs, diarrhea being the most common (30.5%) followed by nausea (20.3%). Most AEs were mild to moderate in severity.

Conclusion:

These results, from a real-world setting in India, confirm the effectiveness and tolerability of apremilast as seen in clinical trials.
Assessment of Knowledge and Attitude Towards Sun Exposure and Photoprotection Measures Among Indian Patients Attending Dermatology Clinic
Authors: Dey Vivek Kumar
Published: December 2019

Background:

Many skin diseases are known to be either initiated or aggravated by excessive ultraviolet (UV) exposure. High cumulative levels of UV radiation may lead to tanning, burning, photoaging, photoallergic and phototoxic reactions, immunosuppression, and even skin cancers. Many international studies have found that the level of knowledge, attitudes, and practices of the general public toward sun exposure and sun protection measures is good in the Western countries, especially in countries with high incidence of skin cancers compared to Asian countries and Middle East. In India, the incidence of skin cancer is not very high, but UV exposure has definitely increased in the past few decades. Little is known about the knowledge and attitude of Indians toward sun exposure and sun protection due to the paucity of research in this arena.

Aims and Objectives:

This study was aimed at exploring the knowledge and attitudes of Indians toward sun exposure and sun protection measures.

Materials and Methods:

A cross-sectional survey was conducted using a predesigned questionnaire related to the knowledge, behavior, and attitudes toward sun exposure and sun protection of the participants visiting a dermatology outpatient clinic for various dermatological problems.

Results:

A total of 324 patients were studied. Participants were divided into five age groups of equal number of male and female participants. Mean age was 37.7 ± 13.15. Overall awareness and knowledge was poor and only 14% were using regular sunscreen. Females had better knowledge and attitude toward sun exposure and protection. The most commonly used sun protection measure was avoiding sun during peak hours of the day.

Conclusion:

The level of knowledge regarding sun exposure hazards was very low among the study population, and sun prevention behaviors were also very poor. Regular use of sunscreen was practiced only by a small fraction of our population. Knowledge of sun exposure and photoprotection was better in urban, young participants, female gender, and also positively associated with higher education and socioeconomic status. Participants from urban background, females, and middle-aged participants had better attitude toward photoprotection.
Inverse Psoriasis with Pityriasis Amiantacea Treated Successfully with Dapsone
Authors: Lunge Snehal Balavant , Swamy Manjunathswamy Basavapurad , Tatawati Ashiwini Shivashankar
Published: December 2019

Inverse psoriasis, also known as intertriginous psoriasis, presents itself as erythematous plaques with poor or nondesquamation in skin flexion folds. Inverse psoriasis is a rare form of psoriasis associated with pityriasis amiantacea. This condition affects the intertriginous areas, making it difficult to diagnose and treat. Here, we report a case with lesions in the intertriginous area with pityriasis amiantacea in a patient of achondroplasia, who showed improvement with dapsone.