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The Proton Exchange Membrane Fuel Cell (PEMFC) performances are strongly impacted by the compression of the Gas Diffusion Layer (GDL). Despite its fibrous microstructure, this material is usually considered as a continuous medium and characterized with uniform loading. However, the GDL is subjected to a heterogeneous compression onto rib/channel patterns in the fuel cell assembly. In the present study, a complex behavior of the GDL response is experimentally revealed when the material is loaded with a rib/channel pattern, compared to uniform compression. The tests are simulated by finite element modeling using a classical strain-dependent elastic law, using parameters fitted from uniform compression experiments. It is shown that the numerical results do not reproduce the effect of pattern observed experimentally. Hypotheses to interpret these results involve mechanisms at the fiber microscale including fiber fracture, cross-link breakage and fiber rearrangement, which are exacerbated by larger material deformation caused by the heterogeneous loading. • Unexpected impact of rib/channel patterns on GDL compression. • Experimental investigation of the effect of rib/channel width on GDL deformation. • Numerical study with classical model unable to reproduce experimental results. • Interpretations based on mechanisms at the fiber microscale. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

• Elasticity and failure behaviors of the resin-coated aramid paper are analysed. • A novel segmented equivalent mechanical model of the material is proposed. • Equivalent mechanical parameters of multi-layer structure are derived theoretically. • Proposed model performs well in ultrasonic cutting simulation of Nomex honeycomb. • Difficulty of modelling and CPU time of simulation are reduced significantly. Nomex honeycomb, as the core part of sandwich structure, has been widely used in the aviation and aerospace industries. Ultrasonic cutting, as a technology that can reduce machining defects, has been highlighted in recent years, but some problems in the cutting process still need to be investigated significantly. Finite element method (FEM) offers an alternative way of in-depth understanding of the problems. However, the multi-layer structure of the Nomex honeycomb cell wall, which is the resin-coated aramid paper, makes it difficult to establish a detailed multi-layered finite element (FE) model at a macro-scale level. Therefore, a novel segmented material mechanical model, which is applicable to the equivalent single-layer model, is proposed based on the analysis of the mechanical behaviour of the multi-layer structure of the resin-coated aramid paper. Moreover, the calculating method of equivalent mechanical parameters of the multi-layer structure are proposed theoretically. The proposed method is first verified by FE models at a micro-scale level in both single-layer and multi-layer approaches. Additionally, simulations and experiments are performed to verify that the proposed method performs well in the simulation of ultrasonic cutting for Nomex honeycomb, and the difficulty of modelling and CPU time of simulation are reduced significantly. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Coating blades are used in the paper industry to meter off the excess coating applied to the paper. They are essential in attaining high-quality coating films with minimum operating cost. During the coating process, the blades are worn down at the tip and are replaced when the coating quality degrades. The objectives of this study are to predict the wear rate of the blades and examine the hypothesis that the blades wear into a quasi-steady-state wear profile, despite both low- and high-angle particle impact. Experimental data and results from finite element simulations are presented for a series of blade materials and suspensions. The approach taken differs considerably from earlier studies, in that it treats blade wear as erosion from the action of the impacting slurry particles rather than abrasion, thus explaining the enhanced wear around the heel. The current approach relies on computer experiments to solve the equations for the liquid flow field, the individual particle motion, the substrate deformation and the eroded volume of the blade, rather than employing empirical relations between wear rates and average fluid velocity. The shear thinning behavior of the coating suspension was properly taken into account. To validate the calculations, blade samples from both a pilot and an off-machine coater were collected at a variety of time intervals. The blade samples aided not only in the establishment of the wear rates and the identification of the wear patterns, but also in the confirmation of the steady-state wear hypothesis that is correctly predicted by the simulations. [Copyright &y& Elsevier]

A computationally efficient method to study the in-plane and out-of-plane dimensional instability of thin paper sheets under the influence of moisture changes is presented. The method explicitly resolves the bonded and the free segments of fibers in the sheet, capturing the effect of anisotropic hygroexpansion at the fiber level. The method is verified against a volumetric model. The importance of longitudinal fiber hygroexpansion is demonstrated in spite of the absolute value of longitudinal hygroexpansion being an order of magnitude lower than the transverse hygroexpansion component. Finally, the method is used to demonstrate the formation of macroscopic sheet curl due to a moisture gradient in structurally uniform sheets in the absence of viscoelastic or plastic constitutive behavior and through-thickness residual stress profiles. [ABSTRACT FROM AUTHOR]

In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid–solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called “edge-flutter” is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension. [Copyright &y& Elsevier]

A fully printed piezoelectric based touch sensor device has been successfully fabricated on flexible polyethylene terephthalate (PET) and paper substrates using screen printing technique. The device, consisting of a 4 × 4 array of printed sensors and interconnect lines, was fabricated using silver (Ag) ink. Screen printed polyvinylidene fluoride (PVDF), as a piezoelectric layer, was sandwiched between the printed Ag top and bottom electrode metallization layers. A linear relationship between the sensor response and varying applied forces to the device was obtained through finite element analysis (FEA) method simulation. X-ray diffraction (XRD) analysis was performed to verify the formation of the β-phase crystals in the PVDF layer during the curing process. The effective polarization of the printed piezoelectric layer was analyzed using capacitance-voltage analysis. A sensitivity of 1.2 V/N and 0.3 V/N, with correlation coefficient of 0.9954 and 0.9859, was obtained for the PET and paper based printed touch sensors, respectively. The piezoelectric-voltage analysis demonstrated that the printed sensors can be used for both touch and force based applications. [ABSTRACT FROM AUTHOR]

• Numerical model for solution of heat diffusion equation. • Thermographic investigation in optically semi-transparent materials. • Non-destructive detection of graphic features buried in cultural heritage artefacts. • Selective configurations for optical and thermal properties investigation in paper. In this paper, infrared thermography is applied to the quantitative characterization of optically semi-transparent media by using a newly introduced mathematical model. The method is specifically aimed to the detection and evaluations in graphic features buried beneath the surface of some particular kind of cultural heritage artefacts, such as books and documents. A numerical approach based on the finite element method, is proposed for solving the model equations. The computed thermographic signal depends on different inspected material physical properties, which have been selectively evaluated by comparing the theoretical results with the experimental ones in specifically designed test samples. Thereafter, the model is applied to the analysis of the results obtained in the case of graphic elements buried within samples constituted by the same previously characterized materials. [ABSTRACT FROM AUTHOR]

Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko–Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young’s modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko–Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose. [ABSTRACT FROM AUTHOR]

Orthodontic archwire rotation around its long axis, known as third-order torque, is utilised to correct tooth rotational misalignments moving the tooth root closer to or away from the cheek through engagement with an orthodontic bracket. Studying the behaviour of archwire and brackets during an applied rotation can aid in better understanding and appreciating the mechanics of third-order torque, potentially allowing for more effective orthodontic treatment protocols. Mechanically characterising archwire behaviour during third-order torque application is a complex task due to their physical scale and geometries. An advanced measurement technique was needed to address these constraints. A three-dimensional (3D) non-contact optical method using a digital image correlation (DIC) system was developed. An orthodontic torque simulator (OTS) was used to apply and measure third-order torque with 0.483 × 0.635 mm (0.019″ x 0.025″) rectangular archwires in tandem with a 3D DIC system, whereby surface deformations and strains could be computed using correlation algorithms. The 3D DIC system was implemented to enable third-order torque experimentation with the OTS while imaging the archwire and bracket surfaces. The 3D DIC system's ability to measure 3D archwire deformations and strains was verified using a finite element model, where comparisons between 3D DIC measurements and calculated results from the model were made to ensure the measurement capabilities of 3D DIC in the context of third-order torque. The 3D DIC system was then used to compare archwire behaviour between stainless steel (SS) and titanium molybdenum alloy (TMA) archwires to study potential clinical differences in archwire behaviour, in which the archwires were rotated with a custom SS rigid dowel (RD) as well as commercial Damon Q orthodontic brackets. The quantification of third-order torque and archwire deformations and strains led to the conclusion that SS archwires led to larger torque magnitudes compared to TMA archwires. The RD resulted in larger archwire strains compared to Damon Q brackets. The 3D DIC system provides a non-contact measurement technique that can further be used with third-order torque experimentation with the OTS. Image 1 • Isolated orthodontic archwire response to torsion is studied. • Finite element analysis is used to verify optical measurements. • Three-dimensional digital image correlation strain measurement method is validated. • Stainless steel and titanium molybdenum alloy archwire responses are compared. • Three-dimensional orthodontic archwire and bracket strain measurements are obtained. [ABSTRACT FROM AUTHOR]

In order to satisfy the demands for both safety and global warming reduction, a high-strength seismic reinforced steel bar is required in the structural steel market. Recent developments in computational thermodynamics and related application software have made it possible to design a suitable material as well as support engineers of steel manufacturing companies in the production of the designed material with minimum benchmarks in practical operations. This paper reports our recent success in developing grade 600 MPa reinforced steel bars for seismic safety in South Korea. First, conventional alloy design based on CALPHAD-type computational thermodynamics was carried out. For this purpose, a typical alloy system of Fe-0.30C-0.23Si-1.37Mn-0.14V-0.22Cu (in wt%) was selected, and thermodynamic and kinetic calculations were carried out using MatCalc and JMatPro software. Second, in order to reduce V content in the steel for economic reasons, a cooling process designed using finite element (FE) simulation based on the thermodynamic database was performed. For this application, Fe-0.34C-0.22Si-1.34Mn-0.04 V (in wt%) alloy was chosen, and the FE software ABAQUS was applied for modeling the TempCore process. The mechanical properties of the steel products with a diameter of 32 mm produced based on the simulated results satisfy the required properties for grade 600 MPa seismic reinforced steel bars. [ABSTRACT FROM AUTHOR]

The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic–plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent. [ABSTRACT FROM AUTHOR]

The tensile response of dense fiber-based materials like paper or paperboard is mainly dependent of the properties of the fibers, which store most of the elastic energy. In this paper, we investigate the influence of geometrical and material parameters on the mechanical response of the pulp fibers used in paper manufacturing. We developed a three-dimensional finite element model of the fiber, which accounts for microfibril orientation of cellulose fibril, and the presence of lignin in the secondary cell wall. The results showed that the change in the microfibril orientation upon axial straining is mainly a geometrical effect, and is independent of the material properties of the fiber, as long as the deformations are elastic. Plastic strain accelerates the change in microfibril orientation and thus makes it material-dependent. The results also showed that the elastic modulus of the fiber has a non-linear dependency on microfibril angle, with elastic modulus being more sensitive to the change of microfibril angle around small initial values of microfibril angles. Based on numerical results acquired from a 3D fiber model supported by available experimental evidence, we propose an anisotropic-kinematic hardening plasticity model for a fiber within a beam framework. The proposed fiber model is capable of reproducing the main features of the cyclic tensile response of a pulp fiber, such as stiffening due to changing microfibril angle. The constitutive model of the fiber was implemented in a finite-element model of the fiber network. By using the fiber network model, we estimated the level of strain that fiber segments accumulate before the typical failure strain of the entire network is reached. [ABSTRACT FROM AUTHOR]

In fibrous paper materials, an exposure to a variation in moisture content causes changes in the geometrical and mechanical properties. Such changes are strongly affected by the inter-fibre bonds, which are responsible for the transfer of the hygro-mechanical response from one fibre to its neighbours in the network, resulting in sheet-scale deformation. Most models developed in literature assume perfect bonding between fibres. In the 3D reality, there is some flexibility in the bond region, even for the perfectly bonded fibres, because of the possibility of deformation gradients through the fibre thickness. In earlier 2D idealizations, perfectly bonded fibres were assumed, implying full kinematic constraint through the entire thickness of the sheet. The purpose of the present study is to assess the effect of this assumption. Using a homogenization approach, a random network of fibres is generated with different coverages and modelled using finite elements. In order to understand the role of bonding between fibres on the hygro-expansive behaviour of a network, a bond model is developed. In this model, the fibres are modelled using 2D regular bulk finite elements and the bonds are represented by interfacial elements of finite stiffness, which are introduced between each pair of fibres bonded in the network. These embedded interfacial elements form a connection between two respective fibres, allowing relative displacements between their mid-planes. The hygro-elastic response of networks obtained with this bond model is investigated by varying the bond stiffness and the network coverage under the application of mechanical loading and changes in moisture content. Furthermore, the bond model is used to analyse the influence of inter-fibre bonds on the anisotropic response of the paper fibre network. [ABSTRACT FROM AUTHOR]

Abstract: Depending on unique operation characteristics for voltage applied on valve side winding of the converter transformers, it is extraordinarily significant to study the partial discharge (PD) behavior with oil-paper insulation under combined AC–DC voltage. Therefore, this paper investigated PD inception characteristics by pulse current methods with needle-plate electrode system under combined AC–DC voltage. Furthermore, 3D electric field distributions versus combined AC–DC voltage in different ratios were calculated by Finite Element Analysis (FEA). An experimental conclusion was drew that AC partial discharge inception voltage (PDIV) in pure oil would decrease linearly with the DC component increasing but the inception voltage with oil-paper insulation appeared to be independent of DC voltage and dependent of AC voltage. And 3D electric field distribution deduced from simulation provided a supplementary proof on the experimental results. Moreover, high speed photography was used to capture emitted light produced by discharge, estimate streamer velocity (1.8 km/s) and record streamer initiation and propagation process in oil gap. Previous studies have shown that the prebreakdown phenomena involving the generation and propagation of vapor channels through the oil could be divided into a three-stage process. [Copyright &y& Elsevier]

Poly-(meta-phenylene isophthal-amide) (PMIA) is regarded as an ideal insulating medium for electronic devices owing to its excellent chemical stability and breakdown strength. However, the poor thermal conductivity limited the application under complex electrical-thermal environment. In this work, the size-graded AlN/PMIA composite papers were fabricated, with a multi-scale structure of matrix and fillers, and maintain qualified stability, mechanical strength and electrical insulation properties. With doping 40 wt% of 10 μm AlN and 10 wt% of 200 nm AlN, the optimum paper with in-plane (λ ∥) and out-of-plane (λ ⊥) of optimal paper reached thermal conductivity of 17.3 W/(mK) and 1.96 W/(mK) is obtained, and the breakdown strength increased to 69 kV/mm. The improvement mechanism brought by size-graded fillers was further revealed by the co-simulation of finite element method and loop nesting algorithm. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Continuum damage mechanics (CDM) is used to describe the post-elastic behavior of low-basis-weight paper. The relevance of undertaking studies of the mechanical behavior of low-basis-weight paper is that it enables characterization, optimization and quality control. In accordance with a CDM theory, an internal variable is introduced that represent the degree to which the material has degraded in a continuum sense and details inherent in a damage evolution law contain information about the rupture mechanism. To account for long ranging micro-structural effects, because of the fiber structure in the paper material, a non-local formulation of the constitutive law is considered. Of particular interest is the fracture toughness of the material, i.e. the ability to resist further crack propagation, as it is often a good measure of flaw tolerance and durability in the context of paper. The constitutive model discussed is verified against tensile tests on rectangular paper specimens containing pre-fabricated cracks. Acoustic emission was used to study the damage evolution in paper specimens during tensile loading. An orthotropic material description has been utilized. The model is contrasted with a purely isotropic formulation. It seems that for the type of problem analyzed in this work, an orthotropic material description does not significantly improve the predictive capability as compared to an isotropic formulation. It is concluded that the model can be used to evaluate the influence of arbitrary defect geometries, defect size and loading conditions and can easily be incorporated into a finite element code. [Copyright &y& Elsevier]

The mechanical behavior of two packaging paper materials subjected to tensile loading up to complete breakage has been investigated. A model for isotropic strain hardening elastic anisotropic plasticity, coupled to anisotropic damage, is discussed. The constitutive relations, including a gradient enhanced damage model, are developed within a thermodynamical framework. The Helmholtz free energy in the continuum is assumed to depend not only on the strain and stress components but also on the damage in the material.The model has been analyzed in a non-linear finite element procedure. The capability of the model to properly capture and simulate the failure of a paper material subjected to tensile loading is demonstrated by means of several numerical examples that are compared to, and verified with, experiments on packaging paper specimens of varying geometry. [Copyright &y& Elsevier]

Abstract: A finite element procedure, developed in order to account for the effect of high anisotropy at folding of coated papers, is presented. The anisotropic behaviour (with very low stiffness in the thickness direction) is modelled using stiff structural elements (trusses and beams). The numerical results indicate that high elastic anisotropy leads to lower strain levels at folding than reported in previous analyses where this effect was not accounted for. High plastic anisotropy, on the other hand, will contradict this result. [Copyright &y& Elsevier]

Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the numerical analysis, the basepaper is modelled as an anisotropic elastic–plastic material (both elastic and plastic anisotropy is accounted for) while the constitutive behaviour of the coating layers are approximated by classical (Mises) elastoplasticity. The numerical results suggest, among other things, that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. It is also shown that delamination buckling, in the present circumstances, will have a very small influence on the strain levels in the coating layer subjected to high tensile loading. [Copyright &y& Elsevier]

Carbon nanotube buckypaper has been considered as one of the promising candidates for chemiresistive sensor applications, especially with environmental monitoring purpose due to large surface area, device flexibility, and the broad spectrum of responsive chemical vapor molecules. However, one of typical drawbacks in carbon-based sensors is incomplete recovery to their initial state after chemical reactions with analytes, degrading sensing reproducibility. In this work, we present a thermally stable and robust boron nitride nanotube/carbon nanotube (BNCNT) hybrid paper for self-enhanced chemiresistive sensing with full reversibility. Boron nitride nanotube (BNNT) plays an essential role in long-term reliability (33 days) at the operating temperature of 200 °C. In addition, a finite-element method was applied to understand the thermal behavior of the BNCNT network structure. The BNCNT paper-based chemiresisitve sensor exhibited highly sensitive, selective, and fully reversible responses to NO 2 without external heating. Also, the sensor demonstrated the detection limit of parts per billion (ppb)-levels under strain with high reliability. With these remarkable strengths, significantly facile and cost-effective fabrication processes provide an environmental sensing platform for use in smart clothing with wearable electronics. • Boron nitride nanotube/carbon nanotube (BNCNT)-based chemiresistive sensor with full reversibility was developed. • The BNCNT paper exhibits a highly sensitive detection to NO 2 at room temperature. • The detection limit (DL) is 3.41 parts per billion (ppb) even under strained conditions with high reliability. • The BNCNT papers maintained its self-enhanced temperature of 200 °C during a long-term stability test for 33 days. • The BNNT plays a major role in the long-term reliability of maintaining a temperature of CNT networks. [ABSTRACT FROM AUTHOR]

Paper-like electronics with thin multi-layer structures, which can be repeatedly bent and twisted like paper, are promising for diverse innovation application. Employing surface-mounted flexible strain sensors is a general way to monitor the bending characteristics of each layer inside paper-like electronics, however, the deviation of measured strain will reach up to 15% on account of the layer-to-layer interface sliding, neutral axes offset resulted from the extra effect of the flexible strain sensor. Here, we proposed a precise measurement method to evaluate the surface bending strain of paper-like electronics by using flexible sensors. In combination with the effects of the thickness, length, etc, a strain compensation model has been established to compensate the measurement deviation. Meanwhile, a slip failure model has been developed to guide the design of the sensitivity unit within the non-sliding area of the flexible sensor. Validated by finite element analysis and experiment, the bending strain of paper-like electronics (eg., ∼50 μm) can be evaluated much more accurate compared to the frequent access one. The newly-proposed method provides a powerful basis for further research of paper-like electronics. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a method to predict the through-thickness moisture content distribution and associated induced deformations of paper and cardboard sheets as they are subjected to relative humidity changes. The transient moisture diffusion problem is solved using a “natural” analytic approach that has previously been applied for solving transient heat conduction in multi-layer solids. The deformation behaviour of the sheet during the moisture diffusion process is predicted using a semi-analytical approach based on a Rayleigh–Ritz minimization of the total potential energy. Geometrically nonlinear effects are taken into account. Curvatures of the originally flat sheet are predicted as a function of time, as are the shapes of the sheet for steady-state condition. As multiple solutions exist, stability is studied. The developed model was used to study the deformation behaviour of one paper and two cardboard sheets. Comparisons with finite-element results demonstrate that the developed model provides accurate results. The displacements obtained for steady-state conditions are within +6%. Comparisons with previous steady-state analyses reveal important differences in the shape of one cardboard sheet. This suggests that the moisture diffusion process may influence the configuration assumed by the sheet at steady-state equilibrium. Hence, it may be necessary to take the moisture diffusion into account in the analysis to accurately predict the hygro-mechanical behaviour of paper or cardboard sheets. [Copyright &y& Elsevier]

Abstract: An anisotropic elasto-plastic constitutive model of paper material is presented. It is formulated in a spatial setting in which anisotropic properties are accounted for by use of structural variables. A multiplicative split of the deformation gradient is employed to introduce plasticity. A similar approach is used to model the plastic deformation of the substructure. The yield surface adopted is based on the Tsai–Wu failure criterion, used previously to model failure of paper material. A non-associated plasticity theory is employed to calibrate the model to experimental data. It turns out that a multi-axial loading situation is needed to calibrate the model and here a biaxial tension test is audited. The model was implemented into a finite element environment and the creasing process of a corrugated board panel is investigated. [Copyright &y& Elsevier]

Abstract: A new paper separation and feed mechanism is proposed to realize a highly reliable paper handling system for printers and copiers. The paper-separation system consisted of a pair of parallel electrodes and a paper pile between the electrodes. Electrostatic separation of a piece of paper was possible from the top of the pile when the applied voltage exceeded the threshold needed to generate an electrostatic force larger than the weight of the paper. The threshold voltage was on the order of several kilovolts, and it agreed with the numerical value calculated using the finite element method (FEM) for the electrostatic field. Based on these basic investigations, a prototype mechanism for paper separation and feeding was constructed. It consisted of a roller-type separation electrode coated with an insulating film, a biased charger roller in contact with the separation roller to charge the insulating film on the separation roller, a ground electrode, and a paper pile situated between the electrodes. When an electrostatic field was applied between the biased charger roller and the ground electrode on which the paper pile was mounted, only the top sheet of paper separated, adhering electrostatically to the roller. The sheet was then fed rotating the separation roller. Using this system, reliable paper separation and feed was realized and a feed speed over 600mm/s was demonstrated. [Copyright &y& Elsevier]

Abstract: The rolling of a cylindrical drum on a stack of separate paper sheets is studied using the finite element method. A two-dimensional model under plane strain conditions is considered. The material of the sheets is modelled by a linearly elastic orthotropic constitutive law. The friction between the various contacting surfaces is modelled by the conventional Coulomb''s law. As a result of the FEM-calculations, the time development of the displacements, stresses and strains of the paper layers is obtained. The slip behaviour at the various contacting surfaces is presented. The micro-slip pattern of the contacting surfaces in the nip area and, particularly, at the trailing edge of the nip, seems to be the main reason for the tightening effect of the nip. The results are compared to the corresponding results for a solid elastic block under the rolling cylinder. [Copyright &y& Elsevier]

Abstract: This paper presents analysis of a 3-dimensional engineered structural panel (3DESP) having a tri-axial core structure made from phenolic impregnated laminated-paper composites with and without high-strength composite carbon-fiber fabric laminated to the outside of both faces. Both I-beam equations and finite element method were used to analyze four-point bending of the panels. Comparisons were made with experimental panels. In this study, four experimental panels were fabricated and analyzed to determine the influence of the carbon-fiber on bending performance. The materials properties for finite element analyses (FEA) and I-beam equations were obtained from either the manufacturer or in-house material tensile tests. The results of the FEA and I-beam equations were used to compare with the experimental 3DESP four-point bending tests. The maximum load, face stresses, shear stresses, and apparent modulus of elasticity were determined. For the I-beam equations, failure was based on maximum stress values. For FEA, the Tsai-Wu strength failure criterion was used to determine structural materials failure. The I-beam equations underestimated the performance of the experimental panels. The FEA-estimated load values were generally higher than the experimental panels exhibiting slightly higher panel properties and load capacity. The addition of carbon-fiber fabric to the face of the panels influenced the failure mechanism from face buckling to panel shear at the face–rib interface. FEA provided the best comparison with the experimental bending results for 3DESP. [Copyright &y& Elsevier]

Paper is a complex material consisting of a network of cellulose fibres at the micro-level. During manufacturing, the network is dried under restraint conditions due to tension in the paper web in machine direction. This gives rise to internal strains that are stored in the produced sheet. Upon exposure to a moisture cycle, these strains may be released. This results in permanent shrinkage that may cause instabilities such as curl or waviness of the sheet. The prime objective of this paper is to model this irreversible shrinkage and to link its magnitude to the properties of the fibres and of the network. For this purpose, randomly generated fibrous networks of different coverages (i.e. ratio of the area occupied by fibres and that of the sheet) are modeled by means of a periodic representative volume element (RVE). Within such RVEs, a finite element method combined with a kinematic hardening plasticity model at the scale of the fibres is used to capture the irreversible response. The computational results obtained demonstrate that the magnitude of the irreversible strains increases with coverage until a certain coverage and beyond that coverage decreases in magnitude. This phenomenon is explained by considering the area fraction of free-standing fibre segments relative to bonded fibre segments in the network. A structure–property dependency of irreversible strains at the sheet-level on the micro-structural parameters of the network is thereby established. [ABSTRACT FROM AUTHOR]

Abstract: Strains, computed by the finite element method, are evaluated and compared to an experimentally determined strain field. The analyzed low-density paper has been designed to ensure bond–breakage as the dominating damage mechanism and the paper material is approximately in-plane isotropic. An optical non-contact displacement measuring system has been used in fracture tests to determine the strain field in the crack-tip region of a pre-fabricated crack. Additionally, acoustic emission monitored tensile tests have been conducted to determine onset and evolution of damage processes and thereby enabling calibration of required constitutive parameters. The results suggest that the investigated paper material can tolerate significantly higher strains than what is predicted by a classic elastic–plastic J 2-flow theory. Immediately before onset of the final fracture (i.e., localization), the experimental measured normal strain in the near-tip region is around 60% higher than the computed strain when using exclusively an elastic–plastic theory for the corresponding load while the strain computed utilizing a non-local damage theory is of the same order of magnitude as the experimentally measured strain. Hence, it seems essential to include a non-local continuum theory to describe strains in the near-tip region quantitatively correct for paper materials. It is demonstrated that path independence of the well-known J-integral does not prevail for this class of material models. Only for the special situation of a homogenous damage field in the crack-tip region may the stress and strain fields be described by the well-known HRR-solutions. [Copyright &y& Elsevier]

Abstract: We present a model for the laminated composite plate problem based on the Reissner–Mindlin model and first-order lamination theory. The weak problem based on this model is solved with the finite element method using stabilized MITC (mixed interpolation of tensorial components) finite elements. Detailed a priori estimates are given for the mixed finite element formulation of the problem. Explicit bounds for the continuity and coercivity constants of the coupling terms are presented, thus refining earlier results. Furthermore, we present an application of the theory to the paper cockling problem and investigate the effect of boundary conditions on the small-scale deformation of the solution numerically. [Copyright &y& Elsevier]

Abstract: Out-of-plane deformations of paper, such as fluting, significantly deteriorate the quality of a printed product. There are several explanations of fluting presented in the literature but there is no unanimously accepted theory regarding fluting formation and retention which is consistent with all field observations. This paper first reviews the existing theories and proposes a mechanism that might give an answer to most of the questions regarding fluting. The fluting formation has been considered as a post-buckling phenomenon which has been analysed with the help of the finite element method. Fluting retention has been modelled by introducing an ink layer over the paper surface with the ink stiffness estimated from experimental results. The impact of fast drying on fluting has been assessed numerically and experimentally. The result of the study suggests that fluting occurs due to small-scale hygro-strain variations, which in turn are caused by the moisture variations created during fast convection (through-air) drying. The result also showed that ink stiffening alone cannot explain the fluting amplitudes observed in practice, but that high drying temperatures promote inelastic (irreversible) deformations in paper and this may itself preserve fluting. [Copyright &y& Elsevier]

Abstract: A model, using the finite element method (FEM), was developed for the analysis of the time and humidity-dependent stresses of paper webs at offset printing press conditions. The offset press was simplified to a flat thin moving web and its unit process steps were described by combinations of prescribed displacements, tractions and moisture ratios. Based on previous modelling and experimental findings, a convective hygro-viscoelastic model of the paper web was derived. The constitutive law and some of the boundary conditions were implemented as user-defined subroutines into commercial FEM software in a displacement-based framework. Some simulation examples were used to study the applicability of the proposed formulation in the analysis of web-fed offset printing at stationary conditions. The numerical stationary solutions converged rapidly and the model was robust for the investigated conditions. Incorporating effects from moisture, the numerical results show web tension profiles along the analysed model press comparable to those found by others from full-scale newsprint printing press trials. Effects of altered levels of the peripheral velocities of rollers, friction, web velocity, moisture and web properties on in-plane stresses and strains are presented. In order to exemplify the practical use of the model for runnability investigations, different analysed quantities obtained from the numerical solutions were related to web tension, web widening, misregister in multi-colour printing, sheet size analysis, conditions for web stability and traction conditions at drag rollers. [Copyright &y& Elsevier]

Abstract: The creep of paper is accelerated by moisture cycling. This effect is known as mechano-sorptive creep. It is assumed that this is an effect of transient stresses produced during moisture content changes in combination with non-linear creep behaviour of the fibres. The stresses produced by the moisture content changes are often much larger than the applied mechanical loads. If this is the case, the mechanical loads are only a perturbation to the internal stress state, and it will appear as if the mechano-sorptive creep is linear in stress. It is possible to take advantage of this feature. In the present report the pure moisture problem is first solved. The mechanical load is then treated as a perturbation of the solution to the moisture problem. Using this strategy, it is possible to linearize a non-linear network model for mechano-sorptive creep and to formulate a continuum model. As a result, the number of variables in the model is reduced. This is a significant improvement as it will be possible to use the linearized model to describe the material in a finite element program and solve problems with complicated geometries. [Copyright &y& Elsevier]

Abstract: The fundamentals of a new radiation model are described in this paper. The spatial and angular dependence of the radiation intensity are split in such a way that the radiation intensity is approximated by a linear combination of basis functions dependent only on the angular direction. The coefficients of the approximation are functions of the spatial coordinates. The spatial discretization is performed using the finite volume method and the angular discretization is based on the finite element method. This means that the basis functions are defined according to the criteria used in the finite element method. The step scheme was employed in the spatial discretization and bilinear basis functions were chosen for the angular discretization. The method may be applied to both grey and non-grey media, non-scattering and scattering media, simple and complex geometries. However, it is still in an early stage of development, and therefore it is applied in this paper to simple one-dimensional problems of radiative transfer in enclosures with grey, emitting-absorbing and scattering media. The results obtained show that the method gives good results for several benchmark problems with available analytical solutions, and converges to the exact solution as the grid is refined and the number of terms in the approximation increases. [Copyright &y& Elsevier]

Finite element analysis of the hip implant is conducted in this paper for representative femoral cross-section geometries and development of stress in the presence of bone cement is elucidated. Differences in cement stresses generated by varying implant cross-sections were compared with conventional features derived from representative implants. The analysis was performed under idealized implant assemblies by constraining the implant movement in the assembly. The cross-sections and implant geometries used are generic and intended to be representative of available geometries. This paper is a part of student research projects, prepared from a series of activities in biomedical implant research currently underway at Ohio Northern and Arkansas Tech Universities. [Copyright &y& Elsevier]

Abstract: In order to improve fixture reliability of paper honeycomb during high speed machining process, a new technique and method based on magnetic field and friction force principle is put forward. In this method, the pressures, vertical to honeycomb walls and the clamping plane, are produced because of the gravity of the iron powder injected into the honeycomb and the magnetic force induced by the additional magnetic field. Two kinds of friction force, between iron powder and honeycomb walls, honeycomb and clamping plane, are both controllable by adjusting the parameters, such as electric current intensity, height of iron powder and air gap. The finite element analysis and experiments have validated the feasibility in technique. In addition, a prototype clamping equipment is designed and put into production. [Copyright &y& Elsevier]

Folding of coated papers is examined numerically using the finite element method. The analysis is focused on the influence from dynamic effects on the folding process. In particular, the behaviour of field variables relevant for cracking of the coating layers are studied in some detail. The results presented indicate that dynamic effects are of little importance as regards maximum strain levels in the coating but will influence the stress and strain distributions. Accordingly, a quasi-static analysis of the problem will be sufficient in order to describe many of the important features related to cracking. [Copyright &y& Elsevier]

The effect of geometric parameters has been studied in this paper on the development of stress in hip implants. The parameters include: head diameter, neck diameter, and neck angle. Two three-dimensional models were drawn, one modular and one integrated implant. These models were then altered geometrically one variable at a time, and finite element analysis (FEA) was performed on the models. In total, twenty assemblies of implant/bone cement/bone were tested. Stress spectrum was drawn for each case under a combination of hip dimensions. It is shown that as the head diameter increases, the stress at a given location reduces, however, as the surface area from increased head diameter increases, the wear rate increases. Neck angle has been found to concentrate stresses in the select regions of the hip implant. In that an angle of 40° showed low stress combinations. Therefore, a particular combination offering the best performance has not been identified and constitutes a part of an on going research activity in Mechanical Engineering Department at Ohio Northern University. [Copyright &y& Elsevier]

Owing to overheating of electronic components during work, more and more attention has been paid to the research of high thermal conductivity polymer composites in recent years. However, traditional way to improve the thermal conductivity of polymer is not ideal. Here, a high-performance polyline-folded graphite paper (PFGP)/epoxy resin (EP) composite was prepared by using polyline-folded graphite paper and liquid epoxy resin as fillers and matrix, respectively. Its out-of-plane thermal conductivity and the improvement efficiency per 1 wt% are as high as 24.19 Wm −1 K −1 and 349%, respectively. Most importantly, this approach is very simple and can be industrialized compared to traditional polymer compounding methods. The thermodynamic finite element analysis in this work simulated the thermal conductivity of PFGP/EP composite at different mass fractions, which can verify the accuracy of the experimental values. These results indicate that the PFGP/EP composites have great prospects in the field of thermal interface materials. • Polyline-Folded graphene paper can create ultra-efficient heat transfer paths. • The prepared composite has an extremely high thermal conductivity. (24.19 Wm−1K−1). • The prepared composite is an excellent candidate for CPU heat dissipation. • The prepared composite can be initially industrialized. [ABSTRACT FROM AUTHOR]

Abstract: Objective: This brief review essay was triggered by the discovery of two errors that have been perpetuated in the dental literature for the last quarter century and is intended to alert the research community. Methods: An extensive search of the published literature, using PubMed and Web of Science search engines, electronic journal resources, and several trips to the library for manual retrievals of articles were used to retrieve hundreds of articles reporting on finite element modeling – finite element analysis (FEM/FEA) involving periodontal ligament (PDL) and gutta percha (GP). Results: The literature search revealed that erroneous values for the modulus of elasticity of PDL and GP were introduced in 1980 and in 1983, respectively. The identified errors range between two to three orders of magnitude and have been used in hundreds of FEM/FEA papers. Significance: The finding casts serious doubts regarding the validity of the results published in hundreds of papers and highlights the importance of checking the references cited and citing, or at least confirming, primary sources rather than citing citations. [Copyright &y& Elsevier]

Abstract: A multisymplectic integrator for the periodic nonlinear Schrödinger equation is presented in this paper. Its accuracy is proved. By introducing a norm, we investigate its nonlinear stability. We also discuss the relationship between this multisymplectic integrator and two variational integrators which are derived by using the discrete multisymplectic field theory and the finite element method. [Copyright &y& Elsevier]

In this paper, we use a prevalent finite element analysis software, MARC, to simulate the process for a subject material undergoing equal channel angular extrusion (ECAE), as well as calculating the strain conditions. For a single ECAE pass, the transversal strain distribution in the deformed body will be analyzed to investigate the influences from channel angle, friction between die and pressed material, and curved joining channels. Simulations involving double passes of the subject material were also conducted, something that has not been previously pursued much elsewhere. [Copyright &y& Elsevier]

In this paper, we focus on some aspects of the finite element simulations of robotic paper folding and the reconstruction of models from the origami crease patterns by the robot arms. The paper highlights the simulation problems, which should be solved in developing our recent study in mechanical and geometrical design of the origami-performing robot. The basic premise underlying the study is that folding operations with the origami crease patterns are considered as the functions of the mechanical systems such as a robot. Manipulations with the foldable objects, such as a sheet of paper (the origami crease pattern), by the robot arms in the simulation environment lead to understanding the design of the origami-performing robot without testing physical prototypes at each design stage. In this case, dynamic and kinematic behavior of the robot arms in forming the 3D origami objects is modelled by using the finite element method (FEM) in LS-DYNA solver. For simulating, two forms of origami are considered: flexible, if bending is used for paper folding, and rigid, if origami patterns are considered as the kinematic systems. Results of the simulation are presented and provided by the illustrations. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe electrophoresis of charged particles in a thin layer of a nonpolar liquid between two insulating substrates because this configuration is common in recently developed in-plane electronic paper. In the in-plane electrophoresis experiments a model system of charged inverse micelles in dodecane has been used which is well understood from studies of out-of-plane electrophoresis. The transient current due to drift and diffusion of charged inverse micelles is measured in thin in-plane devices upon application of a voltage step. For the modelling of the transient dynamics of charged inverse micelles without chemical reactions or convection a 1-dimensional approximation of the Poisson–Nernst–Planck (PNP) equations is developed. This approximation is valid for a sufficiently thin in-plane device and allows much faster calculations. Firstly, it is verified in the case of a sufficiently thin in-plane device and high applied voltage that the 1-dimensional approximation is in good agreement with the solution of the full 2-dimensional PNP equations with finite elements implementation. Then, the 1-dimensional approximation is used to study the transient current and trajectories of trace amounts of charged colloidal particles in different regimes depending on the screening of the electric field. Also a comparison is made to the well-studied case of out-of-plane electrophoresis. Finally, it is verified that for voltages much larger than the thermal voltage the experimental results are in good agreement with the 1-dimensional approximation, indicating that the charge transport dynamics of charged inverse micelles in the bulk are described well by the model. [Copyright &y& Elsevier]

This paper designs, analyzes, and implements a finite element analysis for the simulation of the nonlinear advection-diffusion model. The key feature of the proposed work is to provide novel a priori error estimates in Bôchner norms L 2 (0 , T ; H 0 1 (Ω)) and L ∞ (0 , T ; H 0 1 (Ω)) simultaneously. To achieve the desired error estimates for both semidiscrete and fully discrete schemes, our idea is to introduce the Ritz projection operator that allows us to enforce the known estimates for P 1 and P 2 finite elements in the formulation of the desired results. Further, this paper establishes the stability, existence, and uniqueness in the precise normed spaces. Finally, we prove the fully discrete error estimates using the Backward Euler and Crank-Nicolson's schemes which are corroborated by numerical experiments to validate the developed theory on various domains for both schemes. To the best of author's knowledge, this is the first finite element simulation that provides the estimates in the L 2 Bôchner norm for any such types of time-dependent problems. [ABSTRACT FROM AUTHOR]

This paper summarizes the effective components of computer-aided design and computer-aided manufacturing (CAD-CAM) resin composites that contribute to achieving greater mechanical properties and further development. In silico multi-scale analysis, in silico nonlinear dynamic finite element analysis (FEA), and artificial intelligence (AI) were used to explore the effective components of CAD-CAM resin composites. The effects of the filler diameter and silane coupling ratio on the mechanical properties of CAD-CAM resin composites have been clarified through multi-scale analysis. The effects of the filler contents, and filler and monomer compositions have been investigated by AI algorithms. The fracture behavior of CAD-CAM composite crown was analyzed using in silico non-linear dynamic FEA. The longevity of CAD-CAM composite crown was assessed through step-stress accelerating life testing (SSALT). As the filler diameter decreases, there is an increase in elastic moduli and compressive strengths at the macroscale. At the nanoscale, a decrease in the filler diameter results in a decrease in the maximum value of the maximum principal strain. When the silane coupling ratio decreases, there is a decrease in the elastic modulus and compressive strength. According to the exhaustive search and feature importance analysis based on the AI algorithm, the combination of certain components was narrowed down to achieve a flexural strength of 269.5 MPa. The in silico non-linear FEA successfully detected the sign of the initial crack of the CAD-CAM composite molar crown. The SSALT revealed that CAD-CAM resin composite molar crowns containing nanofillers with a high fraction of resin matrix demonstrated great longevity. This paper summarized the effective components of CAD-CAM resin composites for their further development. The integration of in vitro and in silico approaches will expedite the advancement of CAD-CAM resin composites, offering benefits such as time efficiency and reduction of material waste for researchers and manufacturers. • The effective components of CAD-CAM resin composites (RC) have been summarized. • A smaller filler and a high silane coupling ratio enhance the mechanical properties of CAD-CAM RC. • Non-linear FEA has detected the sign of the initial crack in the CAD-CAM composite crown. • AI has been utilized to narrow down the effective components that achieve high flexural strength. • CAD-CAM composite crowns with a high fraction of resin matrix demonstrate remarkable longevity. [ABSTRACT FROM AUTHOR]

In order to solve the deficiencies of traditional board-level assembly CubeSat, such as low modularity, complex assembly process and poor scalability, a sandwich module assembly structure and method with no drive components is proposed, which can achieve quick connection and flexible assembly between modules. First, the proposed CubeSat standard module can be compatible with the standard interface of traditional CubeSat. The 4-in-1 interface of Mechanical-Electrical-Thermal-Data does not occupy the internal space of the standard module, and the electrical and thermal interfaces meet the requirements of CubeSat in-orbit work. Secondly, in order to improve the reliability of the connection between the modules, a plug-in connection scheme of the mechanical interface was designed. Finally, a genetic algorithm was used to optimize the interface size, so that it has better plug-in performance. The simulation results show that the performance of the male interface of titanium alloy material is the best, and the error between the finite element analysis and genetic algorithm results is less than 4.8 %, which is consistent with the actual tensile test results of the optimized prototype, and meets the mechanical requirements of the launch process and space orbit operation for CubeSat. The test results can guide production and provide a reference for subsequent engineering applications of CubeSat modular assembly. • In this paper, a standardized modular assembly method of CubeSat sandwich structure is designed. The assembly structure does not include driving parts, is simple in form, can be quickly connected, is flexible in assembly mode, and does not occupy the internal space of the standard module. • A standard 4-in-1 connection device was designed in this paper, including four interfaces: mechanical, electrical, thermal and data, which can achieve "plug and play". • This paper uses genetic algorithm to optimize the structure of the mechanical connection male joint, and obtains the optimal configuration of the male joint. This ensures the reliability, firmness and stability of mechanical connections, and meets the mechanical requirements of CubeSats during launch and in orbit. [ABSTRACT FROM AUTHOR]

Grinding damage of hard and brittle materials has a direct impact on part strength and subsequent polishing efficiency. Damage suppression is one of the key research issues in hard and brittle material processing. Due to the uncertain damage evolution law, there is still a lack of optimization methods for the multi-step grinding process under given damage constraints. In this paper, the extended finite element method is used to establish a model between the prefabricated crack depth and final crack depth, which reveals the influence of various existing subsurface damages on crack propagation. It is found that only when the prefabricated crack depth is close to the indentation crack depth on the perfect surface, the final crack depth will be affected to some extent. To optimize the grinding process to achieve low damage, a semi-empirical model for predicting grinding damage is proposed which is suitable for process optimization and does not rely on some difficult-to-obtain parameters. Finally, based on the damage evolution law and prediction model, the core content of this paper is proposed, that is, a multi-step grinding process optimization method with variable grinding depth. This method can minimize the damage while ensuring the same processing efficiency, the damage depth is reduced by 25 %. The effectiveness of the optimization method and the correctness of the damage evolution law are proved by experiments. This method is suitable for engineering applications and has practical significance for understanding the damage evolution mechanism, which is helpful for the suppression of grinding damage and the optimization of the grinding process. • Reveal the evolution mechanism of various existing subsurface damage on crack propagation by XFEM. • Propose a semi-empirical model for grinding damage prediction suitable for process optimization. • Propose a multi-step grinding process optimization method for hard brittle materials with variable grinding depth. • Prove the effectiveness of the optimization method and the evolutionary model through experiments. [ABSTRACT FROM AUTHOR]