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The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained. [ABSTRACT FROM AUTHOR]

This article describes a new method for evaluation of radial crush strength of paper cores. Based on the theory of multilayered composites, a mathematical model has been developed to calculate the value of destructive force during radial crushing of spirally shaped paper cores whose layers are made of different materials. To start calculations, it is necessary to have geometry parameters of the cores, Young's modulus and SCT of an individual component layers. [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]

It is difficult for the existing Burgers model to accurately depict the off-axis cyclic drawing process of woven coatings. In this paper, the mechanical deformation of woven PVC (polyvinyl chloride)-coated film at different temperatures is investigated. One-dimensional (1D) and two-dimensional (2D) constitutive models were established to characterize cyclic deformation processes. The 1D model is an improved Burgers model. The effects of the time dependence of the viscosity coefficient and the ratio of elastic to viscous deformation are considered simultaneously. The accuracy of the 1D model for predicting the cyclic nonlinear deformation at different temperatures and loading rates is improved. The 2D model is a nonlinear orthotropic model using polynomials. On the basis of the single-objective genetic algorithm, the inverse algorithm is used to obtain the shear polynomial coefficients in the tension phase and the shear modulus in the unloading phase, which circumvents performing the difficult shear test. UMAT subroutines of off-axis stretching and off-axis cyclic stretching are written separately. The intelligent inverse algorithm program consists of a single-objective genetic algorithm program, a finite element parametric modelling program, and a UMAT subroutine. The simulation results are compared with the off-axis cyclic tensile test data to validate the effectiveness and accuracy of the proposed 2D model for the analysis of the woven PVC-coated films in the tension–shear coupling state. [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]

Lifting is to use lifting equipment to lift components and install them to the designated position. On the main structure, lifting equipment is used to transport the flue and transport the sectional flue to the designated position. Certain deformation will occur during the lifting operation of the flue due to its force condition, but it is not known whether it is elastic deformation or plastic deformation. Therefore, this paper analyzes the stress and strain of the flue during operation by finite element method, and observes and analyzes the influence of plastic deformation on the whole flue. [ABSTRACT FROM AUTHOR]

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: 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]

A simple analytical model for calculating the nonlinear deformations of a corrugated core (fluting) during out-of-plane compression is developed. The results from the analytical model are compared to a more comprehensive finite-element model and to experiments. A connection between the boundary conditions and the damage state of the corrugated board is discussed. Including a modified set of boundary conditions gives an almost perfect match of the initial stiffness to the experimental results, indicating that the core might be significantly damaged as a result of the manufacturing process. Possibly, the strength of corrugated boards might be increased about 20% if one could avoid damaging the fluting during the manufacturing process. [ABSTRACT FROM AUTHOR]

Cutting toolholders, with designed in-built compliant mechanisms, are frequently used for machining microfeatures. In this paper, compliant structures are designed using trusses as they exhibit a superior strength-to-weight ratio. Systematically stacked two-stage truss structures along with flexure hinges are designed to yield the desired precise cutting motion. The materially reduced efficient design amplifies the output force and greatly assists in overcoming cutting resistance during machining. The characteristics of the designed compliant tool holder are analysed by considering the output force and displacement for a given input. Both mathematical modelling to determine the force and finite element analysis to identify the critical stress regions when subjected to a prescribed input displacement are presented. As part of dynamic analysis, modal analysis and harmonic response studies were performed to determine how the trussed compliant structure deforms when subjected to dynamic loadings. The designed tool holder was additively manufactured using functionally rigid polyamide-12-glass-bead (PA12-GB) material. The performance of the developed cutting tool holder is then verified by machining radially graded surfaces following which, the machining results are presented in this paper. [ABSTRACT FROM AUTHOR]

The expansion process of the base pipe of the expanded screen pipe includes large displacement elastic-plastic deformation problems such as geometric nonlinearity, material nonlinearity and contact nonlinearity. In this paper, based on the elastic-plastic deformation mechanism of the base pipe of expanded screen pipe, finite element equations are established and numerical simulation is used to construct a finite element simulation model to study the mechanical behavior and deformation law of F203.2 mm base pipe of the expanded screen pipe expansion process. The results show that the expansion rate has no effect on the increase of wall thickness, and the decrease is proportional to the expansion rate. The greater the expansion rate, the greater the residual stress at both ends of the slot. [ABSTRACT FROM AUTHOR]

• A complex variable EFG method for hyperelastic large deformation under non-conservative loads was proposed. • Deformation and stress of hyperelastic materials under non-conservative loads were analysed. • The approximation function of the displacement field was established by the complex variable moving least-squares method. • The complex variable EFG method has a great advantage in efficiency and accuracy than other methods. The finite element method is extremely popular in almost all fields of engineering and scientific research due to its powerful and accessible industrial software for computational modelling. However, alternatives including the meshless methods, have received increasing attention on the large deformation problems of hyperelastic materials that need to avoid mesh distortion. In this paper, based on the complex variable moving least-squares approximation, the complex variable element-free Galerkin (CVEFG) method for the large deformation problem of hyperelastic materials under non-conservative loads is established. In the present method, the Newton-Raphson method is used for solving the nonlinear equations. The algorithm for hyperelastic large deformation problems under non-conservative loads are established. Three numerical examples are used to verify the effectiveness of the CVEFG method in this paper. Numerical results show that the solution obtained using the CVEFG method is closer to that obtained by ABAQUS and is more efficient than the element-free Galerkin method. [ABSTRACT FROM AUTHOR]

This paper presents the analysis by the finite element method of the tensions and deformations produced in the mechanized support beams. The finite element method allows the analysis of physical phenomena that can be described with the help of mathematical models made up of systems of differential equations with initial and boundary conditions. From the results obtained in this paper, it was observed that the asymmetries with the greatest influence are those with respect to the vertical-longitudinal plane of the mechanized support [ABSTRACT FROM AUTHOR]

This paper addresses the problems of easy deformation, difficult dimensional control and difficult accuracy assurance during the production of thin-walled gears for helicopter spoke cutting. It uses finite element simulation technology, metal cutting principles, process optimization and other design and manufacturing technologies to reveal the causes of cutting deformation, effectively predict the deformation of parts during cutting, and develop reasonable deformation control strategies. This study explores the effects of cutting force, residual stress and clamping method on gear machining deformation. The deformation of the spoke plate is analysed by finite element simulation. Abaqus software is adopted to establish a finite element model for 2D turning simulation to predict the machining residual stresses and cutting forces during gear turning machining with different cutting parameters. The simulated cutting forces are compared with the residual stresses and experimentally measured values to verify the accuracy of the finite element model and provide a theoretical basis for model construction in the next simulation study. With Abaqus software, the effect of different cutting forces on the deformation of the spoke plate is simulated, and the effect of the superposition of cutting and clamping forces on the deformation of the spoke plate is simulated using life and death cell technology to simulate the machining of the workpiece. Then, a corresponding fixture is designed to realise the corresponding clamping position for machining experiments, and the deformation of the spoke plate is measured by CMM (coordinate measuring machine) to verify the realism of the simulation. This research provides scientific theoretical guidance and process support for aerospace thin-walled gear spoke plate turning. [ABSTRACT FROM AUTHOR]

Due to the fast growth of urban areas worldwide, the demand for tunnels in developed areas is increasing. The design and construction of those tunnels are complex because of their shallow depths and their interaction with existing aboveground and buried structures, which results in rather limited allowable ground deformations induced by the tunnel excavation and support. In tropical regions, residual porous soils near the surface are common. Those soils are highly deformable; thus, tunneling may induce large ground deformations that may damage nearby structures. The new Austrian tunneling method (NATM) and the sprayed concrete lining (SCL) technique are being widely employed in several big cities in tropical regions, but little research has been conducted to assess the induced ground deformations in residual soils, common in tropical areas. This paper provides insight into this issue. A well-documented metro tunnel in São Paulo, Brazil, in a residual red porous clay, was analyzed using 3D finite element method (FEM). The behavior of the residual red porous clay was approximated by an advanced constitutive soil model calibrated with triaxial tests on intact samples extracted at the site. Predictions of the tunnel deformations during construction matched the field data. The calibrated model was then used to explore the tunnel performance under different construction strategies. The influence of partial face excavation, unsupported span length, support stiffness and pipe roof umbrella were assessed. The numerical results showed that partial face excavation was effective to reduce ground deformations ahead of the face of the tunnel and to improve face stability; however, the settlements behind the face increased because of the delay in closing the primary lining. The installation of a stiffer liner closer to the face reduced the ground deformations significantly. The pipe roof umbrella was the most effective technique to reduce the ground deformations around the tunnel; however, the numerical results did not consider deformations that could be induced by the drilling and grouting operations. The results shown in this paper provide both qualitative and quantitative information about the ground deformations induced by NATM tunneling in residual porous soils, that could help designers and contractors choose the optimum support and construction methods to minimize ground deformations. [ABSTRACT FROM AUTHOR]

During the operational period, unexpected upstream deformation has been observed in several super-high arch dams located in the alpine and gorge regions. In addition, the phenomenon of the downstream dam deformation monitoring values being apparently smaller than the numerical simulation results appears in some super-high arch dams. This paper focuses on the genetic mechanism of a super-high arch dam's special deformation characteristics. The finite element method (FEM) was used to analyze the effects of solar radiation, valley contraction, and overhanging on super-high arch dam's deformation behavior. First, the influences of solar radiation on the temperature field and deformation characteristics of the super-high arch dam under the shading effects of the mountain and the dam body were investigated. Second, the impacts of valley contraction on the deformation characteristics of the super-high arch dam during the storage period were studied. Subsequently, the impact of the overhanging effect on the super-high arch dam's deformation was explored. Finally, a case study was conducted on the basis of the Jinping I super-high arch dam to evaluate the effectiveness of the proposed analytical method. It is indicated that the dam's special deformation can be explained reasonably. Above all, in order to accurately analyze and predict the deformation characteristics of super high-arch dams in the alpine and gorge regions of Southwest China, solar radiation, valley contraction, and the dam-overhanging effect need to be considered as influencing factors of dam deformation. [ABSTRACT FROM AUTHOR]

As the first waterproof component of the immersed tunnel, it is very important to ensure the remaining compression of the GINA gasket to resist external water intrusion. This paper proposed a method for determining warning thresholds for the remaining compression of the GINA gasket based on a material-to-mechanical analysis. In terms of material analysis, two factors that affect the GINA gasket are investigated: rubber hardness and cross-sectional shape, and they are adopted as the basis for subsequent mechanical analysis. In terms of mechanical analysis, uneven settlement during the operation period is considered to be the major cause of joint deformation, which is further divided into four modes: bending, shear, expansion, and torsion, with the computation model of the GINA gasket established to obtain the warning threshold. After that, a graded early warning method is adopted, and corresponding thresholds are given after an investigation of previous studies, which are validated by a three-dimensional finite element analysis. The deformation monitoring data between the E28 and E29 elements of the Hong Kong–Zhuhai–Macao Bridge Immersed Tunnel are used to verify the proposed method. The results show that the GINA gasket of the Hong Kong–Zhuhai–Macao Bridge Immersed Tunnel is currently in a safe state, and its deformation is much lower than the minimum warning level. [ABSTRACT FROM AUTHOR]

In order to reduce the machining deformation of thin-walled parts during milling, a non-uniform allowance planning method for thin-walled parts based on the workpiece deformation constraint with the idea of adding materials in reverse material removal sequence is proposed in this paper. This method does not require accurate deformation prediction and extensive experiments compared to traditional error compensation methods. It strives to maximize the allowance to enhance the stiffness of the in-process workpiece. First, a cutting force threshold calculation method is proposed according to the finite element method. The cutting force threshold at different positions is calculated by obtaining the local stiffness characteristics at the cutter-contact point under the constraint of allowable deformation. And then, the maximum machining allowance at the cutter-contact point is calculated depending on the cutting force model. Considering that the stiffness of the workpiece is position-dependent and affected by material removal, the stiffness of the workpiece is updated by adding elements in the reverse cutting direction, and the finishing stock is obtained by surface fitting. Experimental results show that compared with the traditional uniform allowance method, the error of the proposed method is reduced by about 83%, which can effectively reduce the deformation and improve the machining accuracy. [ABSTRACT FROM AUTHOR]

The tooth width and length of face gear limit control the strength of face gear, and heat treatments are often used to improve the hardness and strength of face gear. However, heat treatments will often cause additional deformations, which will affect the dimensional accuracy of the face gear. In this paper, to effectively control the deformation and ensure the accuracy of the face gear, the finite element method was used to establish the calculation model of the face gear die quenching method, and thus, the influence of die on the gear quenching deformation was analyzed. Next, the accuracy of the calculation model was verified by the pressure quenching experiment. The results demonstrated that the inconsistent phase transformation between the surface and the center of the face gear was the key factor affecting the deformation due to the influence of the carbon content. Compared with die-less quenching, the inner hole-die can effectively limit the radial shrinkage deformation of the face gear. With the increase of the upper-die pressure, the axial and radial deformations of the face gear gradually became stable. In the actual production, the load of dies should be reasonably selected based on the gear accuracy requirements. [ABSTRACT FROM AUTHOR]

Filament-wound flexible pipes are widely used to transport fluid in pipeline systems, proved extremely useful in marine engineering. The hyperbolic flexible pipes have good vibration suppression performance, but they are easily deformed under internal pressure. This paper focuses on the stability of hyperbolic flexible pipes based on the composite Reissner shell theory and the transfer-matrix method. The nonlinear stretch of the reinforced filament and the fiber bridge effect are considered in the model. The calculation results show that a large winding angle reduces the deformation and the meridional stress. The available initial winding angle is limited by the geometry and the slippage coefficient of flexible pipe. The reinforced filament of high tensile modulus will reduce the deformation of the pipe. Compared with the geodesic winding trajectory, non-geodesic winding trajectories improves the stability of the pipe. The theoretical result is verified by the finite element analysis. The investigation method and results present in this paper will guide the design and optimization of more novel flexible pipes in the future. [ABSTRACT FROM AUTHOR]

Curing deformation prediction plays an important role in guiding the tools, curing process design, etc. Analytical methods can provide a rapid prediction and in-depth understanding of the curing deformation mechanism. In this paper, an analytical model is presented to study the cure-induced deformation of composite laminates. Based on the classical laminate theory, the thermal stress and deformation of composites during the curing process are calculated by considering the evolution of the mechanical properties of resin. Additionally, the coupling stiffness of the laminate is taken into consideration in the analytical model. An interface layer between the tool and the part is developed to simulate the variation of the tool–part interaction with the degree of resin cure. The maximum curing deformations and deformation profiles of different lay-up composite parts predicted by the proposed model are compared with the results of the finite element method and previous literature reports. Then, a comprehensive parametric study is carried out to investigate the influence of curing cycle, geometry, tool thermal expansion, and resin characteristics on the curing deformation of composite parts. The results reveal that geometry has a significant influence on the curing deformation of composite parts, but for dimensionally determined parts, curing deformation is mainly attributable to their own anisotropy in macro and micro aspects, as well as the stretching effect of the tool on the part. The percentage contribution of different factors to curing deformation composites with different lay-ups and geometries is also discussed. [ABSTRACT FROM AUTHOR]

The segmental joints are the weak parts of the immersed tunnel structure, and their deformation characteristics are closely correlated with the waterproof behavior and structural safety of the whole tunnel. In order to study the deformation characteristics of the segmental joints of immersed structure, in this paper, the E13 pipe section in the natural foundation section of an immersed tunnel in the Hong Kong-Zhuhai-Macao Bridge is taken as the research object, and the model test of the immersed tunnel is carried out. The similarity ratio of the model to the prototype is determined according to the actual engineering scale and the capability of the model test system, and the plexiglass is selected as the model material of the immersed tunnel according to the similarity of elastic modulus and density. In the test, various working conditions, including back-silting load and different prestress control values, are analyzed, and the influence of settlement and opening of the immersed tunnel is obtained, along with the stress-strain characteristics of the segment joints. Results show that the increase of the back-silting load will increase the element settlement and the expansion of the segment joints, but the application of prestress increases the overall stiffness of the element, which can effectively restrain the settlement of element and the expansion of joints. Furthermore, based on the model test conditions, a finite element model is established to simulate the mechanical behavior of the immersed tunnel. The settlement curve and stress-strain curve of the numerical analysis are found to be similar to those obtained from the model test, which verifies the reliability of the model test. [ABSTRACT FROM AUTHOR]

Aiming at the problems of a large amount of material cutting waste or large forming load when large gear profile forming adopts overall cutting or precision forging process, this paper proposed a three-roller bending process (TRBP) for large gear teeth profile, and analyzed the deformation mechanism of the rack bending, meanwhile the gear chain for roll forming was designed. Finite element analysis (FEA) was carried out to numerically simulate the load effects of both the precision forging process and the TRBP for the large gear teeth profile in 17CrNiMo6. The effects of deformation force and strain of TRBP for large gear teeth profile were analyzed. The results showed that as the deformation temperature and speed increase, the deformation force and strain required by the gear profile gradually change. And the reasonable parameter of TRBP is around 750 ∘ C of deformation temperature and 0.5 mm · s - 1 of speed. Compared with the precision forging process under the same boundary conditions, the deformation force of the gear profile TRBP has decreased by about 99 % which could significantly reduce the tonnage requirement of deforming equipment. [ABSTRACT FROM AUTHOR]

In this paper, a low-cycle-fatigue (LCF) crack initiation life prediction approach that explicitly distinguishes nucleation and small crack propagation regimes is presented for ultrafine-grained (UFG) aluminum alloy by introducing two fatigue indicator parameters (FIPs) at the grain level. These two characterization parameters, the deformation inhomogeneity measured by the standard deviation of the dot product of normal stress and longitudinal strain and the microscale multiaxial strain considering the non-proportional cyclic additional hardening and mean strain effect, were proposed and respectively regarded as the driving forces for fatigue nucleation and small crack propagation. Then, the nucleation and small crack propagation lives were predicted by correlating these FIPs with statistical variables and cyclic J-integrals, respectively. By constructing a microstructure-based 3D polycrystalline finite element model with a free surface, a crystal plasticity finite element-based numerical simulation was carried out to quantify FIPs and clarify the role of crystallographic anisotropy in fatigue crack initiation. The numerical results reveal the following: (1) Nucleation is prone to occur on the surface of a material as a result of it having a higher inhomogeneous deformation than the interior of the material. (2) Compared with the experimental data, the LCF initiation life of UFG 6061 aluminum alloy could be predicted using the new parameters as FIPs. (3) The predicted results confirm the importance of considering the fatigue behavior of nucleation and small crack propagation with different deformation mechanisms for improving the fatigue crack initiation life prediction accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes a new sheet forming method that combines electromagnetic forming (EMF) with hydraulic forming called electromagnetic hydroforming (EMHF). Finite element models of both the EMF and EMHF processes were established using ANSYS and ABAQUS. Then, dynamic free bulging deformation of 5052 aluminum alloy during the forming processes was analyzed. The EMF process results in a deformed sheet profile with an uneven conical shape, whereas EMHF leads to a deformed profile with a regular circular shape. This is because during the EMHF process, electromagnetic impact energy is transformed into liquid pressure that is evenly distributed on the sheet surface. When the discharge voltage is 4.5 kV, the maximum deformation speed and strain rate reached 70.6 m/s and 2176.8 s−1, respectively. Thus, EMHF can be considered a high-speed forming method. The simulation results for both EMF and EMHF were verified by experiment at two different discharge voltages. The maximum error was less than 7.4%. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for removing out-of-plane deformation in stretched metal interconnects by adding a fractal structure to the original meander shape and using an optimized fabrication stack. In thermoformed electronics, in cases where copper is used as conductor, the twisting of meander-shaped structures caused by excessive mechanical stress can cause a non-uniform surface, delamination of the metal interconnect from the substrate, and in some cases, a short circuit to the adjacent tracks. Typically, designers of stretchable electronics use various shapes and widths of the copper interconnect to tackle this issue. Using conventional meander shapes such as horseshoes and U-shapes is not universally practical, especially when stretching is higher than 30 percent leading to significant out-of-plane buckling. Limiting this out-of-plane buckling by reducing the track width is not always applicable, as a minimum width is needed from a technology and conductivity perspective. The presented approach is inspired by computational and experimental studies of multiple meander shapes and fabrication methods. A geometry- and fabrication-based approach is presented, reducing the mechanical stress of almost all possible meander shapes by increasing the meander's path length to accommodate the metal track's produced torque during stretching. An analytical approach is provided for calculating the optimal meander parameters and the optimal fabrication stack is achieved based on simulation results. Experiments and finite element modeling for a case study show the improvement in the stress distribution and reduction of out-of-plane buckling. [ABSTRACT FROM AUTHOR]

Due to the unique low rigidity of thin-walled parts, significant machining deformation may occur in the milling process. A deformation prediction model is presented in this paper while considering the effect of the removed material on the global stiffness matrix. Aiming at reducing the scale of the global stiffness matrix, the super-element method is firstly used and the scale of the stiffness matrix is significantly reduced about 30%. And then, the stiffness matrix of the in-process workpiece (IPW) is directly obtained by eliminating the contribution of the removed nodes in the global stiffness matrix. This method can avoid re-building the geometric model or re-meshing the finite element (FE) model in the machining process. To improve the inverse calculation efficiency of the stiffness matrix, a novel nodes re-sorting method is proposed based on the calculation order of the matrix blocks in LU decomposition and inverse calculation. Furthermore, the optimal stiffness direction is discussed and applying the cutting force in this direction can minimize the machining deformation. The simulation results verified the existence of the optimal stiffness direction. Finally, the simulation and experiment are carried out to validate the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

Large deformation analyses of structures are of great importance to the evaluation of structural performance under extreme environmental loads, but currently available methods are time-consuming because of the requirement of factorizing large-scale matrices. The inelasticity-separated finite-element method (IS FEM), which can keep the global stiffness matrix unchanged and uses the Woodbury formula as the solver, was presented recently to provide a highly efficient tool for local material nonlinear analysis. To extend the high efficiency advantage of the IS FEM to large deformation analyses, in which the material nonlinearity may be nonlocal and the geometric nonlinearity should be considered, this paper proposes a novel numerical solution scheme by incorporating the updated Lagrangian (UL) formulation into the IS FEM framework. Within this scheme, a Woodbury approximation method (WAM) is introduced as an efficient solver, in which the changing global stiffness matrix is approximated as a constant matrix within a short time period, and a linear equation related to the Schur complement matrix is solved by the combined approximations (CA) method. To eliminate the additional error induced by the approximation, an adaptive iteration strategy (AIS) is presented, in which the approximation error involved in WAM solution is evaluated based on energy norm concept, and the global stiffness matrix is required to be updated adaptively according to the calculated error. The high efficiency and accuracy of the proposed method are finally demonstrated by the time complexity analysis and numerical examples. [ABSTRACT FROM AUTHOR]

The paper deals with the numerical investigation and implementation of the two-surface plasticity model (or bounding surface model). This plasticity theory allows to describe the deformation behavior under large strain cyclic plasticity and the material stress-strain responses at small-scale re-yielding after large pre-straining. A novel strategy to model the isotropic hardening stagnation is developed within a fully implicit integration scheme in order to speed up the computation and to improve the material description. [ABSTRACT FROM AUTHOR]

The paper focuses on the design of the metal tower for the sinking of Netiș deventilating shaft in Râul Mare Retezat hydro-energetic setup. The analytical calculation of sizing and verification of the metal structure is doubled by the graphic simulation with speciality software, in view of obtaining results as close as possible to the real exploitation conditions of the tower. The tower of the deventilating shaft is considered to be a temporary construction, and its component parts will be decommissioned once the sinking is finalized. The tower is made up of metal structures in four transoms, 3 being mounted with junction plates and screws, the fourth being the roof. [ABSTRACT FROM AUTHOR]

Shot peening is widely used in the aeronautical industry to enhance the fatigue life of the parts and form large, thin, and complex components, such as wing and fuselage skins. Previous research on peen forming simulation has rarely considered the influence of the shot peening sequence on the resulting deformed shape. In particular, the study on the mechanics mechanism of asymmetry in double-sided sequential (un-simultaneous) shot peening is not enough. In this study, therefore, experiments based on symmetrical plane strips (Almen-sized Al7075 strip and Almen strip) show that the final deformation is often asymmetrical with the same shot peening parameters in sequence. As the symmetrical surfaces are peened in sequence, the final bending direction is always consistent with the later shot peening effect. To explain this interesting phenomenon, the double-sided symmetrical sequential shot peening process was simulated by finite element method (FEM). The simulation and experiment results verified the universality of asymmetric deformation in double-sided symmetrical sequential shot peening process. A theory analytical model of the stiffness reduction proposed in this paper was used to explain the asymmetric deformation mechanism, and it is verified by three-point bending tests. Some new results obtained by the experiment and simulation are presented. The influences of the strip thicknesses and shot peening pressures on the asymmetric deformation are discussed in double-sided symmetrical sequential shot peening. [ABSTRACT FROM AUTHOR]

The real-time estimation of structural deformations using discrete strain data, known as shape sensing, is critical to the health monitoring of structures such as bridges. An innovative methodology called the inverse finite-element method (iFEM) is proposed to solve this issue. In this paper, a novel two-node inverse beam element, iBeam3, is developed for two-dimensional deformation monitoring of beam type structures. The present iFEM formulation is derived based on the least-squares variational principle involving section strains of Euler-Bernoulli beam theory for stretching and bending. The iBeam3 element is able to reconstruct deformed shapes without any prior material and/or loading information because only the strain-displacement relationship is used in the formulation. Static and dynamic validation cases regarding steel beams with different boundary conditions subjected to transverse force are discussed in detail. In the tests, different discretization strategies are used to perform the iFEM analysis, and the effects of sensor positions, number of sensors, and measurement errors are evaluated with respect to iFEM-predicted accuracy. The experimental results demonstrate that the iBeam3 element is accurate, robust, and highly efficient. The present methodology provides promising potential in the real-time shape sensing of civil infrastructures. [ABSTRACT FROM AUTHOR]

Abstract Terrestrial laser scanning is extensively adopted in the area of high-precision monitoring and three-dimensional measurement. Architectural structures today are increasingly complex and health monitoring plays an important role in guaranteeing their safety. Therefore, how reliability deformation monitoring can be improved is one of the key problems in the field of engineering. This paper combines the three-dimensional laser scanning technology and finite element method (FEM) to investigate the deformation mechanism of arched structures. Within this paper, we simulated arched structures using the FEM, which is consistent with the result of terrestrial laser scanner (TLS) measurement. We aimed at constructing an intelligent and efficient FEM model which can be extensively applied in the monitoring of many constructs, such as bridges and ancient architecture. The focus in this research lies mainly on deformation analysis, which is based on FEM model simulation with the calibration of TLS measurement. [ABSTRACT FROM AUTHOR]

Abstract Intelligent morphing wings have become a research hotspot due to their potential value. This paper is also an innovative basic research work to study it. The deformation performances of the GFRP(glass fiber reinforced polymer) composite beams embedded different pre-strained indented SMA wires were experimentally and numerically studied. The indentation SMA wire made by mechanical indentation method has better interface bonding strength than normal SMA wire. In this paper, the indented SMA wires acting as actuators, were embedded in a symmetrically GFRP laminated composite beam and located at the eccentric position of the laminate. The layering scheme of the laminated plate is as follows: [90°(4:1 fabric)/SMA/0°/0°/90°(4:1)]. The 0° direction is consistent with the direction of the axis of the SMA wire. The Finite element method is adopted to simulate the deformation of the beam with indented SMA wire in which the linear constitutive model of fully constrained SMA wires, together with considering their thermally-induced strain response, is used to describe the recoverable properties of SMA. The prediction from the numerical simulation agrees well with experimental measurements. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Heterogeneous self-sensing materials that respond electrically to mechanical strains enable real time health monitoring of structures. To facilitate design and applicability of such smart materials with piezo-resistivity, a finite element-based numerical framework is being proposed in this paper for evaluation of electro-mechanical response and strain-sensing ability. Intrinsic heterogeneous nature of such composites warrants the need for microstructure-based study to have an insight into the effect of microstructural configuration on the macro-scale response. The microstructure-guided simulation framework, presented in this paper, implements interfacial debonding at the matrix-inclusion interface using a coupled interface damage-cohesive zone model and incorporates an isotropic damage model in the matrix under applied strain in the post-peak regime to obtain the deformed/damaged microstructure which is subjected to an electrical potential to simulate change in resistance due to applied strain. The applicability of the simulation framework is confirmed through its successful implementation on a smart structural material containing nano-engineered conductive coating at the inclusion-matrix interfaces. The predicted electro-mechanical responses correspond very well with the experimental observations and thus, the model has the potential to help develop design strategies to tailor the microstructure in these self-sensing materials for efficient performance. [ABSTRACT FROM AUTHOR]

Foil-winding transformers with high currents in low voltage winding normally have copper/aluminum bars as leads of the coils. A practical solution for locating bar leads without increasing the size of the active part is to flatten the coil in the leads zone causing a deformation. Abnormalities in the leakage reactance have been identified in this type of transformers. In order to take this effect into account, this paper proposes a correction to the mathematical formulation for calculating the leakage reactance in transformers with deformations in the low voltage winding. Three methods for calculating the leakage reactance have been compared for four real case studies: the proposed formulation, the commonly used formulation, and detailed simulations with the finite element method in three-dimension (FEM3D). The leakage reactance calculated with the proposed method has been found to have an improved accuracy compared with the one calculated using the formulation without correction in all case studies. The main contribution of this paper is that the proposed correction in the formulation makes it possible to increase the accuracy in the calculation of leakage reactance, avoiding the need to resort to detailed simulations with FEM3D. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The effect of preloading on strengthening efficiency of CFRP prestressed beams was investigated. • An uncoupled concrete-to-laminate interface model was developed. • Very good agreement between experiments and numerical simulations was obtained. • Supplementary parametric study includes material and structural features not examined in tests. Abstract The paper presents the research on reinforced concrete beams strengthened with pre-tensioned CFRP laminates under self-weigh only and self-weight and external preload. In the first part the results of experimental campaign (Kotynia et al., 2013) are briefly described and discussed. Next a two-dimensional plane stress model of beams was developed on the basis of experimental observation. The model takes into account the nonlinear behaviour of concrete, steel bars and the concrete-to-laminate interface. A new uncoupled interface model was developed and programmed in order to properly describe the concrete-to-laminate connection for severely cracked structures. Numerical simulations performed for the calibrated material parameters exhibit very good convergence with the experimental results. The analysis confirmed suitability of the model to predict behaviour of RC members strengthened in flexure with CFRP materials in the whole range of loading. Moreover, in this part of the paper the numerically obtained effectiveness of active strengthening in relation to general passive methods of strengthening RC members in flexure was analysed. The calculations show that prestressing increases load bearing capacity in comparison with passively strengthened elements. The second part of the paper contains parametric study of the effect of concrete class, steel ratio, CFRP laminate width and stiffness, maximum concrete-to-laminate bond strength, loading configuration and preloading on load-deflection behaviour and load capacity of actively strengthened beams. The performed parametric study considerably broadened the scope of the experimentally investigated cases by Kotynia et al. (2013). [ABSTRACT FROM AUTHOR]

Modeling deformation processes of materials under high strain rate and impact conditions in which the strain rates vary spatiotemporally over several orders of magnitude is challenging, especially in terms of constitutive description. Visco-plastic power-law flow rule, commonly used within crystal plasticity constitutive models, usually introduces superfluous strain rate effects, entering numerically via the slip activation criterion, which result in artificially high flow stress predictions under high strain rate deformation conditions. This paper presents a novel, implicit finite element implementation of a visco-plastic self-consistent polycrystal model that is implicit in dislocation-based hardening with removed strain rate sensitivity introduced by the power-law flow rule. In the model, the strain rate dependence of the flow stress is defined solely by the rate sensitivity of Peierls stress and the evolution of dislocation density within the hardening law, enabling the prediction of high strain rate and impact deformation. As a result, the predicted flow stress is accurate in its magnitude. The physically based strain rate and temperature sensitive model also features, in addition to Schmid, the non-Schmid activation contribution for slip, which is necessary for understanding and modeling the plastic deformation of body-centered cubic metals. The model is calibrated to simulate the strain rate- and temperature-sensitive monotonic deformation of tantalum and is subsequently applied to a Taylor impact test of the same material. Since the impact simulation required remeshing and interpolation of state variables, the spherical linear interpolation algorithm in the space of quaternions is implemented to facilitate the interpolation of texture. Predictions of the simulation were found to compare favorably with experimental measurements of post-test geometrical changes and texture evolution. The implementation and insights from these predictions are presented and discussed in the paper. [ABSTRACT FROM AUTHOR]

For testing a conductive pipeline, remote field eddy current testing (RFECT) is used, which is composed of solenoidal exciter coil and receiving sensor coils. In RFECT, there is remote field zone where the eddy current distributions are concentrated on the external surface of the pipe wall. Therefore, it is possible to detect a defect that occurs on the external surface of the pipe wall even if the receiving coils are located inside the pipe. From the measured coil signals, it is necessary to decompose background offset and predict the pattern of defect signal in order to estimate the defect size for the maintenance of underground pipelines eventually. In the process, the amplitude variations of the induced magnetic field at sensor coils are closely related to defect depth. Therefore, it is important to analyze and eliminate distortions of measured RFECT signals. This paper analyzes the effects of the induced magnetic field on the sensing signals with respect to different depth sizes in the RFECT system. The amplitude and the distribution pattern of defect signals are computed by a 3-D finite-element method and the method to eliminate the signal distortions caused by induced magnetic fields are presented. Simulated results in this paper agreed well with measuring ones. [ABSTRACT FROM AUTHOR]

Adhesive joints are increasingly employed for bonding critical parts of industrial structures. Therefore, adhesive joints become a key element in design, and their mechanical characterization is of the utmost importance. Significant advancement has been realized for their characterization under quasi-static loadings; however characterization techniques are rather limited for dynamic loadings. Indeed, due to the complex paths of waves through structures, existing dynamic characterization techniques will not characterize only the adhesive joint, but instead will characterize the complete assembly containing the joint and the adherents. Moreover, multiaxiality control of the loading on the adhesive joint is difficult to achieve. This paper proposes an innovative experimental technique for the characterization of adhesive joints under dynamic multiaxial loadings. The experimental method relies on three main components: i) a conventional split Hopkinson pressure bar (SHPB) apparatus, ii) a novel specimen, denoted as DODECA, which enables testing of three distinct multiaxial loadings using the same method and iii) local strain and stress measurements performed by digital image correlation (DIC). The paper describes all steps of the experimental procedure, including the underlying preparation of the specimen and the measuring methods. The stress and strain in the adhesive joint are estimated directly from the experimental data both during loading and at the failure point. Finally, the dynamic material behavior of the adhesive joint is identified from the data. [ABSTRACT FROM AUTHOR]

The Taylor-Hopkinson test is widely used in predicting the dynamic strength of materials. For low-density foam materials, the output bar in the Taylor-Hopkinson test is often made from much weaker materials like polymethylmethacrylate (PMMA) to reduce the wave impedance mismatch between the foam sample and the output bar. These low impedance materials exhibit viscoelastic properties and may affect the dynamic stress prediction of foam samples. In this paper, the shock wave theory for the foam sample in conjunction with the viscoelastic wave propagation in the output bar is employed to illustrate the influence of the viscoelastic output bar on the dynamic response of foam samples in the Taylor-Hopkinson impact. The theoretical model presented in this paper can be degenerated into previous elastic target bar model and rigid target bar model. Finite element simulations are further performed to verify the proposed theory. The influence of material parameters on the final deformation of the foam sample, impact duration and residual velocity of the foam sample are investigated. The results in this paper not only help in understanding the effect of the viscoelastic bar on the dynamic response of foam samples, but also set up guidelines to perform the Taylor-Hopkinson test more precisely. [ABSTRACT FROM AUTHOR]

[Display omitted] • A quantitative criterion for determining the deformation mode of tubes under oblique loads is proposed. • A method for fast judging the deformation mode of multi-cell tubes under oblique loads is proposed based on the SVM, with the accuracy above 91%. • The cross-section length and structure height are showed as the main sensitive parameters affecting the oblique load stability of multi-cell tubes. • An optimal method to increase the critical load angle of tube is proposed according to the instability hyperplanes. This paper aims at oblique load stability of multi-cell tubes and proposes a fast prediction method for fast judging the deformation mode of multi-cell tubes under oblique loads based on support vector machines (SVM). Firstly, the finite element model of multi-cell tubes under oblique load is established and verified by the compression experiments. According to the mechanical response and deformation characteristics of multi-cell tubes under oblique loads, a quantitative criterion for determining the deformation of tubes is proposed. Through the combination of finite element data and SVM, the prediction models of four types multi-cell tubes with oblique crushing is established, with the accuracy above 91%. A fast prediction method of critical load angle of tubes is proposed. The analysis of the critical load angle instability hyperplane shows that the cross-section length and structure height are the main sensitive parameters, and the response of the critical load angle is nonlinear. The prediction model proposed in this paper can quickly predict the stability of the multi-cell tubes and provide directions for the optimization of the stability of the multi-cell tubes. [ABSTRACT FROM AUTHOR]

Thin-walled curved box beam structures especially rectangular members are widely used in mechanical and architectural structures and other engineering fields because of their high strength-to-weight ratios. In this paper, we present experimental and theoretical analysis methods for the static analysis of thin-walled curved rectangular-box beams under in-plane bending based on 11 feature deformation modes. As to the numerical investigations, we explored the convergence and accuracy analysis by normal finite element analysis, higher-order assumed strain plane element, deep collocation method element, and inverse finite element method, respectively. The out-of-plane and in-plane characteristic deformation vector modes derived by the theoretical formula are superimposed by transforming the axial, tangential, and the normal deformation values into scalar tensile and compression amounts. A one-dimensional deformation experimental test theory is first proposed, formulating the specific contributions of various deformation modes. In this way, the magnitude and trend of the influence of each low-order deformation mode on the distortion and warping in the actual deformation are determined, and the significance of distortion and warping in the actual curved beams subjected to the in-plane loads is verified. This study strengthens the deformation theory of rectangular box-type thin-walled curved beams under in-plane bending, thus providing a reference for analyzing the mechanical properties of curved-beam structures. [ABSTRACT FROM AUTHOR]

The current paper focuses on numerical simulation peculiarities of offset welded rectangular hollow section joints. Understanding the modelling techniques can result in easier and faster and above all correct outcomes from FEA for future use. The steel joints under discussion are composed from cold-formed regular rectangular hollow sections where RHS brace members are laterally shifted from chord axis. Joints work under monotonically increasing compression load applied to a brace top. Numerical models were developed in FE programme Abaqus. FE-models is composed of C3D8R 8-noded solid linear brick elements with an emphasis on mesh size effect and modelling of a weld seam. FE advanced model were compiled considering both material and geometric nonlinearities. For validation purposes, the full-scale laboratory tests were conducted. Proposed FE models reliably predict the structural behaviour of welded offset T-joints thanks to good agreement achieved on deformation limit 3 % b0 with the maximum deviation 10.3 %. [ABSTRACT FROM AUTHOR]

The time-dependent behavior of concrete members with uniform cross-section subjected to symmetric drying can be predicted with one of many models anchored in the design codes. Since these models use the cross-sectional approach, only the average quantities can be obtained. More complex phenomena can be investigated by means of a coupled hygro-mechanical finite element analysis. Owing to insufficient or missing experimental data, the input parameters for the moisture transport model are often tuned to match the development of axial shrinkage or moisture loss measured on small-scale laboratory specimens. In this paper it is assessed whether this approach leads to a unique set of parameters of the Bažant-Najjar model for moisture diffusion. Additionally, for the selected sets of parameters the analysis is repeated with modified size and/or boundary conditions leading to asymmetric drying and the results are discussed. [ABSTRACT FROM AUTHOR]

The magnitude and time evolution of shrinkage are influenced by numerous factors which are implemented in the design codes often in a different way. The time-dependent behavior of concrete in structures sensitive to creep and shrinkage should be verified by means of short-term laboratory measurements. Extrapolation of drying shrinkage from short-term measurements is an illposed problem. The process is extremely slow but can be accelerated by reducing the specimen size. The knowledge of the size-effect on drying shrinkage is a necessity to establish the transition from the laboratory to the structural size. In the literature, the experimental data on such size-effect are insufficient. For this reason a new experiment was developed to study this phenomenon on small-scale specimens made of cement mortar and the results from the first year are summarized in this paper. The measured data are validated by coupled FEM hygro-mechanical simulations. [ABSTRACT FROM AUTHOR]

This paper studies the mechanical behavior of a polymeric degradable vessel subjected to internal pulsatile pressure, external pressure, and axial elongation. Two deformation-induced evolution laws are selected to investigate time-position-dependent material properties of the polymeric vessel. The vessel is subjected to the neo-Hookean constitutive model and an axisymmetric condition. To simulate finite deformation in the degradable vessel, FlexPDE commercial software is invoked in which the governing equations are solved by Standard Galerkin Finite Element Method (SGFEM). Results show that stresses pulsationally increase during degradation. Deformation response of the degradable vessel against time reveals the creep-like behavior of degradable polymers. Degradation rate begins from an initial peak value and decreases over time. The impact of degradation on invariants of the deformation tensor versus time and the vessel radius is discussed. Degradation evolution is higher in the outer radius of the vessel because of higher deformation in this region. [ABSTRACT FROM AUTHOR]

Research on the equivalent deformation parameters of grouted arch dam abutment rock masses has recently emerged as a key in the design, construction and stability assessment of arch dams. With the aim of synthetically considering scale effects and anisotropy of the rock mass equivalent deformation parameters after grouting, in this paper, a practical numerical calculation method is developed. First, the Latin hypercube sampling method is introduced to generate a network of fractures of the arch dam abutment rock mass. Subsequently, the finite element models of the rock masses with different sizes in various directions are constructed. On this basis, equivalent continuum theory and cohesive element model are applied for numerical calculation of grouting fractured rock masses. Then, the scale effect and anisotropy of the deformation modulus of rock mass under different grouting conditions are investigated. Finally, the Jinping super-high arch dam is taken as an example to validate the theoretical significance and application effect of the proposed method. The analysis results indicate that the process of fracture and fragmentation of grouted rock masses is characterized precisely, and the deformation of material units can be described as fully as possible to calculate more realistic equivalent deformation parameters of the fractured rock masses. [ABSTRACT FROM AUTHOR]

Deformation directly reflects the behavior of arch dams, and deformation behavior models have been widely used for structural health monitoring (SHM) in accordance with monitoring data. The deformation field brings advantages to the SHM of arch dams in terms of the spatiotemporal scale. In this paper, a spatiotemporal deformation field behavior model based on a convolutional neural network (CNN) was proposed. The temperature field of the dam fusing the climatological data, including air temperature, weather conditions, and solar radiation, was introduced. Furthermore, the water pressure and constraint fields were also input into the CNN-based model. The physical law and structural continuity were considered, and the parameters of the CNN-based model were general and uniform for each predicted location. The accuracy and extrapolation ability of the proposed model were evaluated. The results illustrate that the CNN-based model predicts accurate deformation at the spatiotemporal scale of the arch dam. The accuracy of the prediction of single-point deformation time series from the CNN-based model is close to that from the traditional hydraulic-seasonal-time (HST) model and finite element model (FEM). For the prediction of the spatial deformation field, the mean MAE of the CNN-based model is 2.68 mm, while it is 5.66 mm for the FEM model, showing much higher prediction accuracy of the CNN-based model. The proposed globally uniform CNN-based model can derive a high-precision and high-density deformation field of arch dams with sparse monitoring data. It can also be continuously updated in real-time according to the latest monitoring data without inverse analysis and parameter adjustment like the FEM model. [ABSTRACT FROM AUTHOR]