Deformation Of Panel Research Articles

Simulation and theoretical studies on the influence of removable panel deformation on the seal characteristics of ceramic wafer seal

Purpose The purpose of this study is to investigate the influence of geometric parameters of removable panels on the sealing characteristics of ceramic wafer seal structure subjected to high-temperature gas flow. Design/methodology/approach Based on the laminar flow Reynolds equation, the theoretical and numerical calculation models were constructed to investigate the influence of external convex deformation of removable panel on leakage rate. The theoretical formula for leakage rate after deformation of the removable panel was derived, and the flow field and leakage characteristics of ceramic wafer seal under different operating parameters were studied. Findings The leakage rate exhibits consistent trends between theoretical calculation, numerical simulation and experimental value, with a maximum discrepancy of 8.9%. This validates the accuracy of both the theoretical model and numerical simulation. As the deformation angle of the removable panel increases, the sealing gap gradually widens, resulting in a compromised sealing effect. Moreover, the leakage rate in the central region of the sealing area is lower compared to that at both ends. Originality/value The leakage of the ceramic wafer seal structure under the removable panel with different deformation angles can be monitored based on Reynolds equation. The pseudo-transient numerical calculation method can be used to determine the leakage value of the micro-state ceramic wafer seal structure. These research findings provide a theoretical foundation and numerical investigation approach for studying ceramic wafer seal structures.

Dynamic behaviour and failure mechanism of bamboo scrimber panels under single and repeated impacts: Experimental tests

Bamboo scrimber, as a renewable and sustainable material engineered from bamboo, is inevitably subjected to impact loadings in engineering applications. To study the dynamic behaviour and failure mechanism of bamboo scrimber panels under low-velocity impact, a series of drop hammer impact tests were conducted on 36 panels. The peak force, deformation and energy absorption of bamboo scrimber panels were obtained and analysed. The influence of impact energy, impactor shape and impact angle on the dynamic behaviour of panels was quantitatively characterised. Besides, based on test observations and microscopic views, the failure mechanism of bamboo scrimber panels under different impact types was revealed, including the energy absorption mechanism through fibre fracture, fibre debonding, fibre pull-out and matrix failure. Test results showed that with increasing impact energy, the peak force of panels impacted by the spherical and flat impactors increased, while that of panels impacted by the wedge impactor did not vary significantly. The deformation and energy absorption of panels also increased with increasing impact energy. Notably, the impactor shape obviously influenced the dynamic behaviour of panels, causing a higher peak force of panels impacted by the flat impactor and a larger deformation of panels impacted by the wedge impactor. The failure mechanism of panels depended highly on the impact energy and the impactor shape. Finally, a comparative study of single versus repeated impacts revealed that the deformation of bamboo scrimber panels under repeated impacts was less than that of panels under a single impact when the same amount of energy was imposed to the panel. This study provided a basis for the use of bamboo scrimber to resist impact loadings.

Elastic mode expansion in smoothed particle hydrodynamics framework for hydroelasticity and validation with 3D hydroelastic wedge impact experiments

To perform an efficient hydroelastic simulation with violent free surface interactions, we extend δ+ SPH to elastic modes of a floating structure through GPU parallelization, which includes the correction of velocity divergence with the deformation and computation of the structure's strain. Free surface interaction is supplemented with a segmented particle shifting and tensile instability correction. We validate the developed hydroelastic simulation for experiments of elastic wedge impacts with aluminum and composite panels. Through comparative analysis with different deadrise angles and impact velocities, we find that the improved free surface interactions reduce early separation from the deforming panels, leading to better prediction of the wedge acceleration and reasonably well-matched profiles of the free surface and panel deformation. The marginal difference is attributable to the water passing through the gaps of the physical test model built in three dimensions, which is absent in the simulation setup. Comparing strain time series, measured at two locations on the elastic panels, through three sets of simulations in different dimensions of the simulation set-up and mode shapes, we see that three-dimensional simulation with correct mode shapes in three dimensions accurately predicts the strain time series at both locations as well as the wedge acceleration. The hydroelastic simulation through the modal expansion in GPU parallelization can be utilized to efficiently predict various hydroelastic phenomena with violent free surface interactions.

Investigation into the effect of impact damage on compression behavior of the omega-stiffened composite panels

Abstract With superior performance and weight-saving potential, composite structures have been increasingly applied in the aerospace industry. The damage process and post-buckling deformation of composite panels under compressive load have been proven to limit the application of composite structures. For the purpose of utilizing the full potentiality of thin-walled composite structures, an experimental investigation was employed to explore the influence of impact damage on the buckling behavior and the load-carrying capacity of omega-stiffened composite panels. Pristine panels and impact-damaged panels were under compressive load until failure. The results showed that the pristine panels had higher compressive stability and ultimate strength, and the existence of impact damage led to a decline in the buckling load and the carrying capacity, which were up to 16% and 27%, respectively. Additionally, the complex stress state caused by the introduced impact damage influenced the buckling response and the damage patterns of the omega-stiffened panels. The pristine panels exhibited typical compression failure mode, with matrix crack and fiber breakage in the stringer and the skin. However, the collapse of the pre-damaged panels was dominated by the debonding of the skin-stiffener interface and the out-of-plane deformation of the skin.

Fluid-Structure Interactions of a Fin over a Compliant Panel in Supersonic Flow

The fluid-structure interactions of a blunt fin mounted over a compliant panel in Mach 2 flow were investigated. The test geometry consisted of a thin, flexible panel fixed on all edges with a blunt fin with a hemispherically rounded leading edge mounted in a manner that the leading edge of the fin overhung the panel. The blunt fin was also pivoted to several angles of attack with respect to the oncoming flow. This allowed for the study of the dynamic system created by the interactions between the compliant panel and the blunt fin geometries. Both rigid and compliant panel models were used in order to provide a comparison between the flow with and without the dynamics of the compliant panel. High-speed schlieren and surface oil flow visualizations showed that the time-averaged flow remained almost entirely unchanged between the rigid and compliant panels. The instantaneous flow fields, however, showed a highly dynamic system where the compliant panel induced oscillatory shock waves that were both stationary and freely moving. Simultaneous high-speed schlieren visualization and stereo digital-image correlation showed a strong linkage between the motion of the shock waves and the deformation of the panel. This was demonstrated through frequency analysis and modal decomposition of the panel deformation and shock motions.

Aeroelastic Effects in Supersonic Shock-Turbulent Boundary Layer Interaction over Flexible Panels

The dynamic coupling between a Mach 1.94 shock wave/turbulent boundary layer interaction (SBLI) and a flexible panel is investigated. High-order numerical simulations are performed for distinctly different dynamic panel motions and rigid snapshots of their maximum deflected shape. They are compared with a baseline interaction over a rigid planar wall. The panel’s dynamic surface motions were obtained from the Air Force Research Laboratory (AFRL) wind tunnel experiments. The primary aim of the study was to determine whether there were any differences in the flow pressure loading on the compliant panel due to the various rigid and dynamic deformations considered. The results show that the examined panel deformations increase the SBLI size near the panel midpoint, where the deformation amplitude tends to be the largest. Relative to the rigid planar case, the examined surface deformations cause the mean-flow high-pressure surface loading caused by the impinging shock wave to shift downstream along the compliant panel midspan, albeit by a small amount. The spectrogram of the dynamic deformation and the flow surface pressure response suggests that the two are strongly coupled at the dominant (primary) mode but less so at the secondary modes. Although the primary mode frequencies overlap, they do not exactly match, with the pressure response frequency always being slightly higher in all three cases. The rigid deformations did not enhance the pressure power content at the SBLI. However, pre-SBLI and near the panel leading edge, the pressure power spectrum weakly increased throughout the resolved frequency range and overlapped with the onset of the amplification found in the dynamic deformation cases. Post-SBLI, the rigid deformations cause a weak enhancement at frequencies below 1 kHz, which closely match the dominant and secondary pressure response frequencies obtained in the dynamic cases.

Technologies for Increasing the Control Efficiency of Small Spacecraft with Solar Panels by Taking into Account Temperature Shock

The problem of the effective control of a small spacecraft is very relevant for solving a number of target tasks. Such tasks include, for example, remote sensing of the Earth or the implementation of gravity-sensitive processes. Therefore, it is necessary to develop new technologies for controlling small spacecraft. These technologies must take into account a number of disturbing factors that have not been taken into account previously. Temperature shock is one such factor for small spacecraft with solar panels. Therefore, the goal of the work is to create a new technology for controlling a small spacecraft based on a mathematical model of the stressed/deformed state of a solar panel during a temperature shock. The main methods for solving the problem are mathematical methods for solving initial/boundary value problems, in particular, the initial/boundary value problem of the third kind. As a result, an approximate solution for the deformation of a solar panel during a temperature shock was obtained. This solution is more general than those obtained previously. In particular, it satisfies the symmetrical condition of the solar panel. This could not be achieved by the previous solutions. We also observe an improvement (as compared to the previous solutions) in the fulfillment of the boundary conditions for the whole duration of the temperature shock. Based on this, a new technology for controlling a small spacecraft was created and its effectiveness was demonstrated. Application of the developed technology will improve the performance of the target tasks such as remote sensing of the Earth or the implementation of gravity-sensitive processes.

High-fidelity landing modeling of small-body probes: Considering solar panel deformation and soil properties

A high-fidelity dynamical model that can depict the touchdown of a probe on a small body is fundamental for precise control and is critical to the success of a landing mission. However, such models are lacking in the literature, and existing models fail to adequately account for soil properties on the small body or flexible parts (solar panels) on the probe. In this study, we develop a dynamical model with dynamics, contact, and control modules to simulate a legged probe with solar panels landing on a small body with weak gravity, unknown soil properties, and rugged terrain. The dynamical equations for the probe landing are derived by considering the solar panel deformation. A valid method for calculating the penetration depth is proposed to address the contact between the probe and soft soil based on Polygonal Contact Model (PCM). Theories of terra-mechanics and Coulomb friction are introduced to characterize the physical properties of the soil. Numerical examples illustrate the natural/controlled landing sequence and demonstrate the validity of the dynamical model. Compared to the rigid-body dynamical model, flexible solar panels increase energy dissipation and thus make the controlled-landing probe less prone to bounce repeatedly on a small body. In the natural landing mode, the solar panels cause the probe to fluctuate continuously. For the physical properties of the soil, both larger friction moduli and smaller internal friction angles are detrimental to the stable landing of the probe on a small body.

An immersed multi-material arbitrary Lagrangian–Eulerian finite element method for fluid–structure-interaction problems

Fluid–structure-interaction (FSI) phenomena are widely concerned in engineering practice and challenge current numerical methods. In this article, the finite element method is strongly coupled with the multi-material arbitrary Lagrangian–Eulerian (MMALE) method to develop a monolithic FSI method named the immersed multi-material arbitrary Lagrangian–Eulerian finite element method (IALEFEM). By immersing the finite elements in the MMALE computational grid, the fluid–solid interface is directly tracked by the element boundary with accurate normal directions. The fluid–structure-interaction is implicitly implemented by assembling the nodal variables and updating the Lagrangian momentum equation on the MMALE grid. Combining the advantages of both MMALE and FEM with the immersed boundary method, the IALEFEM is effective for solving complicated FSI problems with multi-material fluid flow. A slip fluid–structure-interaction method is also proposed to enhance the computational accuracy in simulating FSI problems with significantly different velocity fields. The accuracy and effectiveness of the IALEFEM are verified and validated by several benchmark numerical examples including the shock-cylinder obstacle interaction, flexible panel deformation induced by shock wave, dam break problem with large structural deformation, water entry of a wedge, fragmentation of a cylinder shell induced by blast, response of elastic plate subjected to spherical near-field explosion and structural damage of open-frame building under blast loading.

Flow Response of a Laminar Shock–Boundary Layer Interaction to Prescribed Surface Motions

The response of an impinging laminar shock–boundary layer interaction (SBLI) to prescribed surface motions is investigated numerically at M∞=2, Rea=120,000, and a shock-associated pressure ratio of 1.5. Parametric sweeps over classical standing and traveling mode shapes are considered at low-, moderate-, and high-frequency conditions for fluid–structure interaction. The specific values are chosen based on compliant panel deformations and frequencies reported in the literature. At low surface oscillation frequencies, the SBLI responds to the deformations in a quasi-steady fashion, with standing wave forcing displaying both breathing and sloshing of the separated region depending on structural mode shape. As the oscillation frequency is increased, the flow transitions to an unsteady response with pronounced separation bubble undulations in time. Higher-order modes and frequencies lead to the largest reductions in the time-mean separation bubble size, more so with traveling surface waves. Modal decompositions show that pressure fluctuations, which arise due to dynamic interaction with the surface, persist downstream and increase in amplitude with the surface oscillation frequency.

A coupled smoothed particle hydrodynamics–peridynamics model for two-dimensional hydroelastic water entry

In this paper, a numerical model coupling the smoothed particle hydrodynamics (SPH) with peridynamics (PD) is developed to solve the problem of the hydroelastic water entry. By combining the geometric nonlinear peridynamics with the weakly compressible SPH, the proposed model can efficiently simulate the nonlinear deformation of the structure and the deformation of a fluid free surface. The transmission of information between the fluid and solid phases is implemented by a dummy particle boundary treatment method. By simulating benchmark tests, the ability of the proposed model to solve nonlinear fluid–structure coupling problems is verified. In order to improve the computational efficiency, the graphics processing unit parallel acceleration scheme is applied to the SPH-PD model. Compared with the serial scheme, the speedup effect of the parallel scheme in large-scale computation is verified. As an application of the numerical model, the water entry of the flexible panel at a constant entry velocity is studied. The mechanism of hydroelastic effect is explained by analyzing the variations in the fluid pressure field, slamming force, and panel deformation during water entry. In addition, the influences of plate rigidity, impact velocity, and deadrise angle on the hydroelastic effect are investigated.

Quasi-static bending analysis of composite laminated cylindrical panels under hygrothermal conditions

The combined effects of temperature and humidity, termed hygrothermal, are included in the deformation analysis of laminated composite cylindrical panels based on first-order shear deformation theory (FSDT). The panel is under transverse mechanical load, and both steady-state and transient hygrothermal loads are considered. The problem is solved using the minimum potential energy theorem for different boundary conditions. The moisture profile through the thickness is obtained by analytical solution of Fick diffusion equation. The dependency of moisture diffusion coefficient on temperature is considered and the material temperature is assumed to be the same as the environmental temperature. Using a semi-analytical approach, displacement field of the panel subjected to evaluated profile of moisture in a specific time and thermo-mechanical loads is obtained. The accuracy and validation of the present solution are demonstrated by solving numerical examples and comparing them with the results available in the literature. Furthermore, new results are presented and effects of various important parameters such as panel geometry, edge boundary conditions, lamination layups and imposed moisture conditions on the deformation of the composite cylindrical panel are studied. Solved examples demonstrate that higher length-to-arc and radius-to-thickness ratios result in increased deflection and amplify the influence of mechanical load compared to hygrothermal effects on the overall deformation of the panel. In most case studies, the hygroscopic deformation observed at one-tenth of the saturation time exceeded half of the deformation observed after the saturation time, which shows the importance of transient hygroscopic analysis.

Study on prefabricated composite shear wall cladding anti-shedding connection structure

Fabricated steel structure systems have undergone significant advancements. However, problems associated with exterior wall panel systems have become increasingly prominent, particularly the issue of exterior wall panel shedding. Three full-scale fabricated composite shear wall exterior panel components were designed and tested under quasi-static conditions. The failure sequence and characteristics of the exterior wall panels at different displacement angles, including their out-of-plane displacement and stiffness degradation, were evaluated to assess their seismic and connection performance in different building construction methods. The results indicated that drilling holes near the centre of autoclaved lightweight concrete (ALC) boards improved the seismic performance of wall panels. Long round holes in the ALC boards allowed the dissipation of sliding energy during the initial deformation of wall panels. Furthermore, wall panels with bonded anchorage connections for rockwool boards exhibited better seismic performance than those with pure anchorage connections. To verify the accuracy of the findings, a structural finite element model was established, and the influences of various parameters, such as the position of ALC board connecting bolts, length of ALC board holes, and bonding rate of rockwool boards, on the stress and deformation of the exterior wall panel system were analyzed. Based on the test results and finite element simulation analysis, an anti-shedding connection construction method was proposed.

Out-of-plane interactive behavior and design of novel T-hooked buckling-restrained steel plate shear walls

To eliminate the use of a large number of connecting bolts for the cover panels in conventional buckling-restrained steel plate shear walls (BRSPSWs), T-hooked BRSPSW was proposed by using T-sectional stiffeners for restraining the out-of-plane deformation of the cover panels. With larger-sized flexural cover panels that provide confinement effects to the infilled steel plate, the out-of-plane interactive behavior between the infilled steel plate and each cover panel is greatly concerned for safe designs of the T-hooked BRSPSW. In this paper, a refined finite element (FE) model was established for evaluating the out-of-plane restraining effects in the T-hooked BRSPSW. The key parameters affecting the high-order buckling modes of the infilled steel plate were analyzed. The average spacing between adjacent buckling half-waves varied from 0.15 to 0.7 times the height of the steel sub-plate across common parameter ranges. Furthermore, a formula that estimates the total extrusion force produced by the buckled steel plate was corrected. By simplifying the cover panels into one-way flexural plates under uniform force, a flexural moment amplification coefficient in the range of 1.11 − 9.74 was defined to consider the difference between the actual strip-shaped interaction forces and the simplified model. Finally, a formula to calculate the bending moment of cover panels was proposed to safely design the T-hooked BRSPSWs.

Mechanical analysis of a stitched sandwich structure and its SiO2f/SiO2 panels: Experimental and numerical investigation on compression and shear performances

The compression and shear performances of the stitched sandwich thermal protection structure (SSTPS) was systematically investigated through experimental and simulation methods in this study. Compression and shear testing methods were designed, and macroscopic performance data for SiO2f/SiO2 thin panels and SSTPS were successfully obtained, thereby validating the rationality of the experimental approach. By establishing mechanical experimental methods, the correlation between microscopic structural features and macroscopic mechanical performance was revealed, and mechanical modeling and analysis work was conducted. The experimental and numerical results indicate that compression and shear failure of thin panels mainly occur at the intersections of fiber bundles, exhibiting non-brittle failure. The delamination of sandwich materials or the buckling deformation of panels is identified as the primary cause of the nonlinear response in SSTPS. Elevated temperatures induce an increase in the modulus and strength of SSTPS and a decrease in toughness, correlated with the high-temperature densification of the matrix structure. Finite element simulations reveal the critical role of component and interface damage in macroscopic nonlinear mechanical responses. The research demonstrates that, the compressive and shear failure mechanisms of SiO2f/SiO2 thin panels and SSTPS were successfully elucidated through the implementation of an innovative experimental methodology.

A coupled FD-SPH method for shock-structure interaction and dynamic fracture propagation modeling

Shock wave propagation and their damage to solid structures, which involve complex multiphase and multiphysics phenomena, are difficult problems to address. In this paper, a three-dimensional graphics processing unit (GPU)-accelerated finite difference-smoothed particle hydrodynamics (FD-SPH) method was developed for the prediction of strongly compressible fluid flow and strong fluid-structure interactions. The conventional mesh-based finite difference method was used to simulate shock wave propagation, while the smoothed particle hydrodynamics method was employed to predict the dynamic behavior of solid materials. In addition, the immersed boundary method (IBM) was implemented in the GPU-accelerated FD-SPH solver for the boundary treatment of the interface between solid and fluid materials. Four numerical cases, namely shock-cylinder obstacle interaction, elastic panel deformation induced by shock wave propagation, the response of stainless steel tubes under internal blast loading, and the damage of blast loading on reinforced concrete slab, were conducted for verification of the GPU-accelerated FD-SPH solver. The numerical results were compared against the available experimental data, which shows that the GPU-accelerated FD-SPH solver is capable of capturing the shock wave propagation and its damage to structures very well.

Residual Stress‐Driven Non‐Euclidean Morphing in Origami Structures

Morphing origami has numerous potential engineering applications owing to its intrinsic morphing features from 2D planes to 3D surfaces. However, the current 1D hinge deformation‐driven transformation of foldable origami with rigid or slightly deformable panels cannot achieve a 3D complex and large curvilinear morphing. Moreover, most active origami structures use thin hinges with soft materials on their creases, thus resulting in a lower load capability. This study proposes a novel origami morphing method demonstrating large free‐form surface morphing, such as Euclidean to non‐Euclidean surface morphing with shape‐locking. Tensorial anisotropic stress in origami panels is embedded during the extrusion‐based 3D printing of shape memory polymers. The extrusion‐based 3D printing of isotropic SMPs can produce tensorial anisotropic stress in origami panels during fabrication, which can realize significant non‐Euclidean surface morphing with multiple deformation modes. The connecting topology of the origami unit cells influences the global morphing behavior owing to the interaction of the deformation of adjacent panels. Non‐Euclidean morphing integrated with 4D printing can provide multimodal shape locking at material and structural levels.

Study on Calculation Method of Bending Performance of Concrete Sandwich Composite Slab.

In order to explore the flexural behavior of a concrete sandwich panel under concentrated boundary conditions, based on Kirachhoff's elastic thin plate theory in this paper, the geometric deformation, physical conditions, and equilibrium relationship of a sandwich panel are deduced by constructing the layered analysis model of the sandwich panel, the basic differential equation of the flexural deformation of the concrete sandwich thin plate is obtained, and the mathematical expression of the internal force and displacement under the boundary condition of concentrated support is given. Combined with an engineering example, the proposed calculation method is verified. The results show that, in the arrangement of reliable connectors for concrete sandwich panels, the concrete wythes bear the load while the contribution of the core layer to the bending capacity of the structure can be ignored. When subjected to a laterally distributed load, the sandwich panel mainly experiences out-of-plane bending deformation, and the bending normal stress in the concrete panel layer shows a linear non-uniform distribution along the thickness direction of the panel. The bending deformation performance and bearing efficiency of a concrete sandwich slab with the change in concentrated support position have significant effects, and the load transfer efficiency can be improved by optimizing the arrangement of supports. Except for small local areas near the supports, the bending stress distribution and deformation behavior of the concrete sandwich panel can be accurately analyzed by the calculation method established in this paper.

Repeated impact response of honeycomb sandwich panels based on the failure parameters of adhesive layer and material

Honeycomb sandwich structure has been widely used in lightweight and impact protection of rail vehicle structures due to its excellent mechanical properties. In this paper, the plastic deformation, failure response and energy absorption characteristics of honeycomb sandwich panels for rail vehicles under repeated impact loads were studied. The three-point bending tests and low-speed impact tests of honeycomb sandwich panels were carried out, and a three-dimensional numerical model considering the detailed structure of the honeycomb core and the failure of the adhesive layer was established. The model can reasonably simulate honeycomb sandwich panels’ stiffness, strength, and structural failure. The effects of impact times and impact angle on the performance indexes of the honeycomb sandwich panel were studied. The results show that when the impact energy is the same, the impact times will affect the energy absorption distribution of honeycomb sandwich panels. With the increase in impact times, the panel’s absorption energy decreases, the core’s absorption energy increases, and the total absorption energy decreases. For multiple impact conditions, with the increase of impact times, the single energy absorption of the upper panel and core decreases, and the single energy absorption of the lower panel increases. When the impact energy is the same, the rise in impact angle will increase the damage to the honeycomb sandwich panel, and the energy absorption of each part will increase. In addition, the influence of impact times on the energy absorption efficiency of honeycomb sandwich panels is related to the impact angle.

Energy quantification framework for underwater explosive loading into PVC foam cladded composite plates

This paper presents a novel approach for analyzing the effects of near-field underwater blast loading on composite marine structures. The operational requirements of these structures often expose them to blast or shock loading, which can lead to significant damage. The study focuses on the propagation of spherical blast waves and the subsequent secondary bubble collapse pulse that affects the structure under near-field underwater blast loading events. An analytical framework is developed to calculate the blast energies and structural energies during this complex loading event. The study further investigates the effect of applying a sacrificial cladding made of low-density closed-cell foam to the loading face of a composite panel. Experiments were conducted in a specialized facility to characterize the explosive-driven blast-loading and the subsequent interaction between the shock pressure front and the structure. Dynamic pressure measurements and high-speed imaging were utilized to capture the behavior of the composite panel under these extreme conditions. 3D digital image correlation was employed to analyze strain and deformation of the composite panel, while high-speed side view cameras captured the fluid-structure interaction during the blast and bubble collapse loading event. The results strongly indicate that the collapse of the explosion bubble is the dominant failure source in near-field underwater blast loadings. The analytical quantification of energy further corroborates the significant damaging effects of bubble collapse due to the buildup of after-flow energies during the bubble collapse duration. Furthermore, the inclusion of low-impedance elastic-plastic PVC foam cladding is shown to significantly mitigate the effect of blast loading on the composite structure.