Deformation Of Panel Research Articles

Experimental study on seismic performance of low-yield point steel plate shear walls

This paper studies the seismic performance of the low-yield point steel plate shear wall (LSPSW) by conducting cyclic loading tests on three single-story single-span steel plate shear wall (SPSW) specimens, including a non-stiffened LSPSW (LYP) and a non-stiffened normal strength SPSW (NW). A new LSPSW with steel tube stiffeners (HSS) is then proposed to restrain the out-of-plane deformation of the infill panel. The failure modes, strain development, bearing capacity, stiffness, ductility, energy dissipation capacity, degradation characteristics, and deformation performance of the above three SPSWs are compared and analyzed. Afterwards, the corresponding numerical modeling approaches are developed and verified by the test results. Furthermore, supplementary analyses of the plate-frame interaction in terms of the shear distribution, energy dissipation behavior, and plastic damage performance are performed, and relevant suggestions are provided for the design of SPSW. The experimental and numerical results show that compared with the NW specimen, the use of low-yield point steel in the LYP specimen significantly improves the ductility and energy dissipation capacity of the SPSW, delays the tearing of the infill panels, reduces the residual deformation of the infill panels with higher ability of recovery, and achieves a more uniform distribution of cumulative plastic deformation. The application of steel tube stiffeners in the HSS specimen further enhances the energy dissipation capacity of LSPSW, effectively restrains the out-of-plane deformation of the infill panels, and reduces the impact of the tension strips on the edge columns. The analyses of the plate-frame interaction show that the boundary frame has more contribution to the shear resistance and energy dissipation after using the low-yield point steels for the infill panel. The proportion of shear force borne by the boundary frame is up to 65%–70%, which should be considered in the design procedure to optimize the geometrical dimensions of the infill panel and the boundary frame, allowing to optimize the structural performance and material utilization.

Operating effect of filler on filling roll bending of integral panel

A filling roll bending process of a 2A12 aluminum alloy integral panel with polypropylene as filler was studied. The operating effect of filler was revealed, based on analytical, numerical, and experimental methods. The results show that the position difference of the neutral layer between the ribs and the web of the integral panel leads to the error of generatrix straightness, and the filler can reduce this difference. A certain range of the width gap (1–3 mm) between filler and rib can avoid the instability of the rib and the curl of the filler. The height gap between filler and rib determines the compression degree of filler. The best pressure transmission effect can be achieved as the filler is still higher than the rib (1 mm) after compression. The elastic modulus of filler slightly affects the forming accuracy of the integral panel within a certain range (450–1300 MPa). Still, the filler transfers insufficient pressure under lower elastic modulus (50 MPa) and limits the deformation of the integral panel under higher elastic modulus (20 GPa). Experimentally measured generatrix straightness verified the operating effect of filler.

Coupling numerical and experimental methods to characterise the mechanical behaviour of the Mona Lisa: a method to enhance the conservation of panel paintings

A numerical FEM (Finite Element Method) model was implemented to represent the mechanical state of the wooden panel of the Mona Lisa, as it is conserved in its exhibition case, and constrained in its auxiliary frame. The model is based on the integration of advanced numerical analysis and various experimental examinations carried out non-invasively on the artwork by the authors during over 15 years. This includes visual, microscopic and X-ray observations together with mechanical measurements and monitoring of panel deformations and constraining external forces. In addition to the development of non-invasive techniques to characterise the mechanical properties of the panel, the FEM model reliably evaluated the strains and stresses generated in the panel by the various actions it experiences. The paper consists of the following parts: (i) a short summary of the experimental measurements and other observations, (ii) a detailed description of the FEM numerical model, of the hypotheses it is based on, and of its advantages and limits, (iii) the main results obtained by running the model. This includes the identification of local strains and stresses, the location of most critical areas, an evaluation of the risk that the existing ancient crack may propagate, and an evaluation of safe ranges for the forces acting on the wooden panel, (iv) the validation criteria for such results, and (v) a discussion about the significance of the mechanical model.

Shear resistance and deflection prediction of steel–concrete–steel sandwich panel with headed stud connectors

Bending tests were conducted on eight specimens to investigate the mechanical behavior of steel–concrete-steel (SCS) sandwich panels with headed studs, taking into account the effects including loading mode, steel plate thickness, concrete core thickness and connectors spacing, and one sandwich panel was used as a control specimen. The failure characteristics and crack patterns of the specimens were recorded and the vertical displacement in the span was measured. The test results were used for the validation of the finite element model (FEM). Further parametric studies of the FEM yielded the effect of steel plates on the load-bearing capacity of the sandwich structure. Analytical models applicable to the initial stiffness and shear resistance of specimens with headed studs were proposed. The shear strength considered the effect of steel plate and pin action. The deflection calculation models of the sandwich panel were obtained based on the energy method and were in good agreement with the load–displacement response curves obtained by FEM results. The research results of this paper will have an impact on the large deformation and ultimate strength prediction of sandwich protective panels.

Experimental investigation of the air blast performance of hybrid composite skinned sandwich panels with X-ray micro-CT damage assessment

This research investigates the performance of interlaminar hybrid composites as the skins of composite sandwich panels under blast loading with the aim of promoting delamination between dissimilar plies for energy absorption. The deformation of the composite panels was captured using high-speed digital image correlation (DIC). High-speed full-field DIC enables failure to be captured at the moment it occurs across the entire panel. X-ray micro-CT imaging was used to assess the post-blast damage sustained by particular areas of interest from each panel, which were selected based on DIC results. The combination of full-field DIC and detailed X-ray micro-CT scanning enabled a unique comparison of both the global and localised blast resilience of hybrid and conventional composite sandwich panels to be performed.Following a single blast load, the extent of damage to the Hybrid-3B skinned sandwich panel was found to lie between that of GFRP and CFRP skinned sandwich panels. X-ray micro-CT scanning of these panels reveals that there is no continuous damage path through the skin thickness of Hybrid-3B, whereas the GFRP and CFRP panels sustain damage in every ply.Following repeat blast loading, the Hybrid-4 skinned sandwich panel suffered from a front skin crack spanning the length of the panel. Post-blast compressive strength testing reveals that this skin crack and resulting core crack acted as a stress relief, limiting the damage sustained elsewhere in the panel.It was concluded that Hybrid-3B results in a good trade-off between strength and stiffness and is advantageous over conventional CFRP and GFRP panels under a single blast load. Under repeated loading Hybrid-4 offers advantages over Hybrid-3B. Finally, the design of the support structure can significantly aid in blast resilience, and, a holistic approach considering both panels and support should be taken when designing for blast resilience.

Experimental and numerical studies on shear behavior of lattice-web reinforced PET foam sandwich panels

To solve the problem that traditional lightweight core sandwich structure is prone to core brittle failure and interface debonding, innovative sandwich panels with fiber reinforced polymer (FRP) as facings and lattice-webs, and polyethylene terephthalate (PET) structural foam as the core were designed. Five composite sandwich panels with different thicknesses of cores and facings were fabricated by vacuum infusion molding process. Three-point bending test was carried out to survey the shear properties of panels, such as failure modes and load–deflection variation laws, which disclosed that the ultimate shear loads of the sandwich panels could be increased by 96.1% and 25.5% by heightening the thickness of the foam core from 40 mm to 80 mm and adding (0,90°)/(±45o) layers. Theoretical formulas were then put forward to calculate the ultimate loads, and the error between theoretical and test values was within 10%. Finally, the shear mechanical characteristics of the sandwich panels under the three-point bending test were simulated with the finite element software ANSYS, and the change rules of the bearing capacity and deformation of the sandwich panels under various test parameters were obtained. Parametric analysis proved that increasing the lattice-webs thickness by one factor can heighten the ultimate shear value of sandwich panels by 95.9%, and longitudinal lattice-webs spacing greatly influenced the ductility performance of panels.

Energy absorption analysis of origami structures based on small number of samples using conditional GAN

Origami-inspired metamaterials are increasingly being applied to the fields of science and engineering owing to their unique mechanical characteristics. Geometric and material arrangements of the panels and creases can lead to different mechanical properties of origami structures, such as energy absorption and multi-stability. The actual folding processes of the origami structures usually include crease rotation and panel deformation. However, the traditional analytical or empirical solutions based on rigid folding assumptions cannot sufficiently reflect the folding process precisely. Finite element analysis can provide detailed origami folding information, but it is a highly time-consuming cycle, including modeling and computing. Typically, conventional data-driven approaches necessitate a considerable amount of data samples to analyze the energy absorption of origami structures. The unavailability of extensive datasets poses a major impediment in employing data-driven methods to explore the authentic behavior of origami structures. Based on the situations above, a new data-driven framework with conditional generative adversarial networks with tabular data (CTGAN) is proposed in this study. To verify the feasibility of the framework, two study cases are presented herein: a Miura-ori structure in-plane quasi-static compression and the square-twist (Type 1) folding process. Energy absorption properties are predicted accurately and efficiently by the framework based on small number of samples, which are highly consistent with predicted results based on a large dataset. The framework not only provides a promising solution for energy absorption analysis of origami structures but also overcomes the bottlenecks (small number of sample datasets and a mixture of data types) associated with machine learning methods in origami structure area.

Development of a Cubic Core Lightweight Panel Using Origami-Kirigami Engineering

Honeycomb core panels are commonly used in industry as lightweight structures. However, because the bond between the face plate and the regular hexagonal core is weak, there are strength problems, such as heat and shear loads. In this study, a new cubic core panel was developed as an alternative to a honeycomb core panel. Unlike conventional honeycomb core panels, cubic cores can be processed from a single flat plate by punching and bending. Through the square contact area between the face plate and the cubic core, a double-bond integral panel structure was assembled using glue and rebates. The cubic core panel had a higher bending stiffness and bonding strength than the conventional honeycomb panel. A three-point bending test was performed on the processed cubic core panel. The relationship between the bending load and the deformation of the cubic core panel was determined. The curved part of the cubic core panel can be easily processed by cutting out a part of the material on one side of the cubic core panel in accordance with the lightweight structure of the curved part. A design formula for the curved part of the cubic core panel was derived using the curvature radius and curvature angle of the actual curved structure. A cubic core molding system was investigated using the parallel movement characteristics of the four-bar link mechanism for future mass production. An important design factor for practical use was obtained by deriving the relational expression between the bending load and plastic displacement.

Mechanical Properties of Shear Key in Composite Segment for Shield Tunnel under High Temperature Welding

With the increasing requirements of shield tunnel construction, the demand for the development and application of high-performance lining segments continues to rise. During the manufacture and forming process of high-performance composite segments, large-scale shear key welding is an important factor affecting the mechanical performance of segments. This paper aims to study the effect of shear key welding on the mechanical properties of composite segments. In this study, the algorithm transformation of the welding heat source model was first conducted. Then, a comprehensive analysis of the shear key was presented using the finite-element method, and a welding experiment was conducted to verify the reliability of the adopted numerical model. It was found that the temperature of the welding point changes with the movement of the heat source in the shear key welding, in which the maximum temperature peak can reach 2,236 K. The welding residual stress was mainly concentrated in the range of about 30 mm from the welding point, and then the value decreased gradually. In the welding of multiple shear keys, the residual stress at the central axis of adjacent shear keys will be superimposed, and the mutual influence of adjacent shear keys during welding should be avoided. Through a key-panel welding experiment, the numerical simulation results of the shear key-panel model were verified. The panel deformation at the edge position was also affected by the boundary conditions.

Thermal Deformation Measurement of Aerospace Honeycomb Panel Based on Fusion of 3D-Digital Image Correlation and Finite Element Method

Aiming to solve the problem of the high-precision deformation measurement of large-scale satellite structures in manufacturing and testing environments, this paper proposes a measurement method based on the idea of fusing actual measurements with finite element analysis. The digital image correlation (DIC) method is used to obtain the high-precision deformation of the honeycomb panel, and the finite element method (FEM) model is introduced to remove the limitations of existing pure measurement methods. Data fusion based on a machine learning neural network is proposed to fuse high-precision deformation and physical information such as temperature to conduct multi-level training on FEM parameters. Through an interpolation of the analysis and calculation results after training, not only can the accuracy of the finite element be improved, but difference and extrapolation of the digital image correlation measurement results can be performed. In the experiments, the satellite on-orbit temperature data are substituted into the modified finite element model. The testing results shows that the prediction accuracy of the model under different temperature loads can be controlled within 10 μm under an 840 mm × 640 mm scale. A high predictive accuracy can be achieved for the revised model for the complete deformation of large structural sections.

Process-based deep learning model: 3D prediction method for shot peen forming of an aircraft panel

Shot peen-forming is a more precise method of forming aircraft panels than conventional methods. The traditional method of acquiring the process parameters relies mainly on prior theoretical knowledge and trial-and-error. Despite the finite element method's ability to replace some experimentation, it still cannot realize the design of shot peen forming processes parameters of an aircraft panel based on a known contour. This study uses an innovative model-based deep learning approach to predict aircraft panel deformation and active design the shot peening parameters. The prediction time is less than 1 second, resulting in a significant reduction in computational time. The shot peen forming process parameters and the geometric structure characteristics of the aircraft panel are divided into independent channels to establish a high-dimensional feature map, which are used to train the deep learning model. The forming contours of the 2024-T351 high-strength aluminum alloy panel are predicted under different shot peening processes. In addition, the process parameters are designed according to the known contour of the forming process. To verify the precision of the proposed method, the designed shot peen forming process is used to manufacture a single curvature aircraft panel with a curvature radius of 3500 mm. There is good agreement between the forming contour and the theoretical design contour. The maximum deformation error is less than 1 mm and its mean error is 7.8%. The mean curvature radius error is 5.668%. The proposed method provides a new and practical reference to the precise design of the shot peen-forming process.

Effect of cavity pressure on shock train behavior and panel aeroelasticity in an isolator

The flow characteristics of shock train in the isolator play an important role in the overall performance of the scramjet. Although several studies have concentrated on understanding this phenomenon in rigid isolators, few works have focused on methods to control it. The current study proposes a new concept shock train control strategy based on the aeroelastic effect of the flexible panel. An in-house developed code was used to solve the compressible Navier–Stokes equations and the geometric nonlinear equations of the panel, where the conventional serial staggered algorithm was adopted for the two-way fluid–structure interaction. Then, we numerically investigated the effect of cavity pressure on the dynamic behavior of the panel, location, and structure of the shock train, separation zone, and performance of the isolator. The results show that the dynamic response of the panel subjected to the different cavity pressure can be characterized into three states: static stability state, high-frequency second-order limit cycle flutter state, and multi-frequency periodic flutter state. The panel flutter mainly presents an approximately second-mode pattern for the limit cycle flutter state and a first-order vibration mode for the periodic flutter state. With increasing cavity pressure, the average value of shock-train head location moves downstream significantly, while the general trend of separation zone length on top and bottom walls becomes smaller. The flexible panel with the high-frequency second-order limit cycle flutter state can increase the total pressure recovery coefficient with the smaller side load and outlet flow distortion, reduce the averaged separation length, and make the shock-train head move downstream. This is due to the isentropic compression and expansion waves induced by the vibration and deformation of the flexible panel.

Simulation and experiment of thermal deformation behavior of reflector panels with honeycomb sandwich structure

The honeycomb sandwich structure reflector panel is a multilayer structure formed by three-layer aluminum plate and two-layer honeycomb bonded by epoxy resin adhesive, and its thermal deformation behavior is complicated. In this study, the thermal deformation behavior of the reflector panel is studied by a combination of experiment and finite element simulation.Firstly, the thermal deformation analysis finite element model of reflector panels with honeycomb sandwich structure is established. The three-layer aluminum plate is modeled according to actual geometric parameters and adopts shell element model. The honeycomb core is equivalent to a homogeneous orthotropic layer with a constant thickness. The elastic modulus of the equivalent model of the honeycomb core with adhesive are obtained through the tensile and compressive mechanical performance tests. Then, the temperature deformation experiment of the honeycomb sandwich structure panel is carried out. Combined with the experimental results and the thermal deformation simulation analysis model, the multi-island genetic algorithm is used to modify the thermal expansion coefficient of the honeycomb core layer.Finally, the thermal deformation behavior of the reflector is verified by finite element simulation and experiment. The results show that the profile error distribution caused by the panel thermal deformation has continuous symmetry. From the error distribution trend and numerical deviation, the established simulation model can be used to predict the thermal deformation of sandwich panels.

The impact responses and failure mechanism of composite gradient reentrant honeycomb structure

The carbon fiber reinforced composite reentrant honeycomb structures with different gradient distributions of wall thickness were manufactured by mold hot pressing and bonding technology. The dynamic responses of composite gradient reentrant honeycomb structures under local impact load were investigated. The impact process and failure behavior of composite gradient reentrant honeycomb structures under local impact load were obtained through the foam aluminum projectile impact experiment. The influence of wall thickness gradient form on the impact resistance of composite reentrant honeycomb structure was analyzed. The results showed that the wall thickness gradient setting of the reentrant honeycomb structure could reduce the maximum transverse deformation of the rear panel, and improve the anti-impact ability of the structure compared with homogeneous reentrant honeycomb structure. In addition, compared with the positive gradient reentrant honeycomb structure, the negative reentrant honeycomb structure had better impact resistance, and the impact resistance advantage became more obvious with the increase of the impact strength. The finite element model of composite gradient reentrant honeycomb structure under local impact load was presented, and the dynamic responses and failure modes of the numerical simulation results were compared with that of the experimental results.

Development and experimental verification of a modified constitutive model for 3D orthogonal woven composite under bird impact

Three-dimensional (3D) orthogonal woven composites have potential application as a material for aeroengine blades, which are required to withstand the impact of a bird strike. In the current research, quasi-static and dynamic tensile tests were conducted on a 3D orthogonal woven composite in the warp and weft directions. The results indicate that the ultimate strength increased while the failure strain decreased with an increase of the strain rate. The effects of strain rate on the ultimate strength in the warp and weft directions are different. Therefore, a modified constitutive model that accounts for the different effects of the strain rate in different directions was established. The corresponding parameters were obtained from the test results. Bird impact tests and numerical simulations using the developed constitutive model were carried out with 3D orthogonal woven composite panels. These panels resisted the impact of high-speed bird strikes through an overall deformation. As the impact speed increased, the maximum deformation of the target panel in the thickness direction increased and the residual deformation after the impact also increased significantly. The simulation results are in good agreement with the test results, demonstrating the effectiveness of the modified model.

Large deformation of sandwich wide panel

This work addresses the general nonlinear static and dynamic formulations of sandwich panels with compressible cores under large deformation, within the framework of Extended High-order Sandwich Panel Theory. The commonly-used assumption named large displacement with moderate rotation, is assessed. Within a total Lagrange manner, the weak form of the nonlinear equation of equilibrium is derived via the principle of virtual work and further linearized through the Newton-Raphson iteration. Both the static and dynamic governing equations are acquired with respect to the nodal degrees of freedom. Numerical techniques involving Newton-Raphson method for the static analysis, and Newmark-Beta method for the time domain integration are employed to get the solutions. The static and transient mechanical response of simply supported sandwich panels under static pressure and dynamic blast is conducted respectively. The closed linear solutions and finite element models are accomplished to validate. Conclusions are drawn that the deformation gradient, as well as the displacement and rotation, critically determines the structural stiffness and internal force, and their relationship is originally provided in this paper. The structural stiffness at large deformation is stronger than that at small deformation. The assumption of large displacement with moderate rotation is inadequate for sandwich structure in large deformation.

An immersed boundary-material point method for shock-structure interaction and dynamic fracture

As a class of extreme fluid-structure interaction (FSI), shock-structure interaction problems are always accompanied with dynamic fracture phenomena in solid structure. During the dynamic fracture process, small fragments of thin geometry and fresh FSI interfaces will be generated, which makes the FSI interface difficult to be reconstructed. An immersed boundary-material point method (IBMPM) is proposed in this paper for simultaneous simulations of shock-structure interaction and accompanied dynamic fracture. The finite volume method (FVM) is employed as fluid solver and specifically a TVD Riemann solver is adopted for shock simulation, while the material point method (MPM) is employed as solid solver for simulation of extreme deformation problem. The FVM and MPM are then coupled by our improved immersed boundary method (IBM) which is named as Lagrangian continuous-forcing IBM (lg-CFIBM). The lg-CFIBM is proposed in the frame of continuous forcing approach with a compact support area for the immersed boundary conditions. It can guarantee the boundary velocity conditions strictly at each time step and has no need to reconstruct FSI interfaces. Several numerical examples, including shock-cylinder obstacle interaction, flexible panel deformation induced by shock wave and fragmentation driven by detonation, are studied to verify and validate the proposed method, and numerical results are in good agreement with experiments.

Experimental and numerical study on seismic performance of a novel type of cold-formed steel shear wall with built-in sandwich panels

The purpose of this paper is to study the seismic behavior of the cold-formed thin-walled steel composite wall with built-in honeycomb sandwich and analyze its failure mechanism. A total of 13 monotonic and cyclic loading tests of wall specimens were completed in this paper, including four for observing the force and failure mode of the built-in sandwich of cold-formed steel (CFS) frame specimens, and nine specimens sheathed with double-sided oriented strand board (OSB). The mechanical performance indicators such as shear bearing capacity, stiffness, ductility, energy dissipation capacity and stiffness degradation of the honeycomb sandwich and other sandwich CFS shear walls were compared and analyzed. The experimental results demonstrate that the failure mode of the wall specimens is mainly ductile failure, including chord stud buckling or tearing, screw tilted, sank into the panel, or cut off at the connection between the honeycomb sandwich and the track. The built-in honeycomb sandwich can play a better role as a skin, which can significantly improve the shear bearing capacity and stiffness of the composite wall, but reduce the ductility. The sheathing and studs can effectively limit the out-of-plane buckling deformation of the sandwich panel and give full play to the properties of the sandwich material, thereby improving the shear bearing capacity, stiffness and energy dissipation capacity of the wall, as well as improving the ductility. The effects of wall aspect ratio and sandwich thickness on the seismic behavior for the built-in honeycomb sandwich CFS shear wall were analyzed by finite element analysis (FEA) and compared with the flat steel plate sandwich and OSB plate sandwich wall. And the nonlinear simplified analysis model of the composite wall under cyclic loading was established by SAP2000.

Design and Analysis of Multi-Layered Composite Panels for In-Plane Loadings

Composites have a wide range of applications in the field of robotics, aerospace, aviation, sports, and automotive engineering. They have appealing properties such as high strength to weight ratio, good mechanical and electrical properties, and durability. Multilayered composites are prepared by stacking different layers of composites along different directions. This research focuses on the compression and tension response of multilayered composite panels without interference of bending by using in-plane loading. The aim of this research is to develop a generalized MATLAB code for a number of layers, to solve a model composite through analytical and MATLAB computations, to analyze the stress behavior in ANSYS (ACP) and finally to compare the results. For carrying out the analysis, a multi-layered, symmetric composite panel is modelled under in-plane loading. First, a mathematical model is formulized to solve the multi-layered composite panel under in-plane loading and analytical results are obtained. Next, a generic MATLAB code is developed, followed by simulations and computational study using ANSYS (ACP) module. The results of MATLAB and the solution of the mathematical model are found to be identical. Further, the results obtained from ANSYS (ACP) have shown the stresses in each layer and overall deformation of the composite panel. The overall results from three methods have shown that the stresses produced in a composite panel are symmetric across mirrored layers. However, there is a significant difference between the analytical and ANSYS (ACP) results, this is due to the limitations of the Classical Laminate Theory (CLT) which has been used in the analytical study. CLT does not take into effect the out-of-plane stresses. However, in real life scenarios, out-of-plane stresses exist under the in-plane loadings and have a significant effect around the edges and corners of the panel. If 10 percent of the edges are removed on both sides, the analytical results and simulations are found to be in good agreement. Further, after the ANSYS (ACP) analysis has been obtained for the panel, a sandwiched composite panel has been modelled by adding a core material of foam and polyethylene at the center of the composite. The thickness of the core material is varied to observe the change in the stress behavior. The results have shown that there is an increased stress behavior when a softer core is used or the thickness of the core material is increased.

Cylindrical Panel Like Response of Fully Surface Parallel Restrained Simply Supported Hyperbolic Paraboloidal Thick General Cross-ply Panels

An analytical (exact in the limit) solution to the boundary-value problem of deformation of a finite-dimensional general cross-ply thick hyperbolic-paraboloidal panel, modeled using a third order shear deformation theory, is presented. Of special interest is the issue of cylindrical panel-like response, in the presence of full surface-parallel constraints at all four edges of a thick antisymmetric cross-ply panel of negative Gaussian curvature.