scholarly journals Impact of Boundary Conditions on the Behavior of Thin-Walled Laminated Angle Column under Uniform Shortening

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2732
Author(s):  
Jarosław Gawryluk
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Testing Machine ◽  
Experimental Tests ◽  
Quantitative Agreement ◽  
Actual Behavior ◽  
The Real ◽  
Damage Initiation ◽  
Thin Walled ◽  
The Impact

Determining the appropriate boundary conditions of a structure is a very important aspect in the failure analysis. In experimental tests, the method of compressing composite samples significantly influences the obtained results. In numerical studies, there is a problem of correctly defining the boundary conditions applied in real object. Therefore, many numerical tests on samples should be undertaken to observe their behavior and to determine ultimate load. The present work includes study to determine the impact of boundary conditions on the thin-walled laminated angle column under compression. The phenomenon of buckling and the post-buckling bahavior of columns were investigated experimentally and numerically. First, the real simply supported angle columns subjected to uniform shortening are tested. Due to the stress concentration between the real sample and the grips, a flexible pads were used. Experimental tests are carried out on the universal testing machine. The deformations of columns were measured using the non-contact Aramis System. The composite material condition was monitored by acoustic emission using the Vallen Systeme with piezoelectric sensors. Next, the numerical calculations in Abaqus software based on the finite element method are performed to validate the empirical results. To determine the influence of the boundary conditions, two numerical models of the system with and without flexible pads are developed. To estimate damage initiation load in numerical models a different damage criteria ( Tsai-Hill, Tsai-Wu, Azzi-Tsai-Hill, Hashin) are used. Based on the results specified that the model with elastic pads more accurately reflects the actual behavior of the L-profile element under compression. It was supported, i.e. by good agreement of flanges deflection (the equilibrium paths) with experimental results. Furthermore, a qualitative and quantitative agreement of damage initiation load were obtained using Hashin criteria (error 4.61%).

The Effect of the Impactor Diameter and Boundary Conditions on Low Velocity Impact Composites Behaviour

2007 ◽  
Vol 7-8 ◽  
pp. 217-222 ◽  
Author(s):  
Ana M. Amaro ◽  
Paulo N.B. Reis ◽  
A.G. Magalhães ◽  
Marcelo F.S.F. de Moura
Keyword(s):  
Boundary Conditions ◽  
Damage Model ◽  
Testing Machine ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
Impact Energies ◽  
The Impact

The aim of present work is to study the influence of the impactor diameter and boundary conditions on low velocity impact on carbon-fibre-reinforced epoxy laminates. Experimental tests were performed on [04,904]s laminates, using a drop weight-testing machine. Circular plates were tested under low velocity impacts for two diameters of the hemispherical impactor, 12.7 mm and 20 mm, and considering similar impact energies, 2.6 J for the first impactor and 3 J for the second one. Rectangular and square plates were analysed under low velocity impacts with different boundary conditions. The impacted plates were inspected by X-radiography. Numerical simulations were also performed considering interface finite elements compatible with three-dimensional solid elements including a cohesive mixed-mode damage model, which allows to model delamination between layers. The impact tests showed that both the impactor’s diameter and boundary conditions have influence on the delaminated area. Good agreement between experimental and numerical analysis for shape, orientation and size of damage was obtained.

scholarly journals Sandwich Panels with Polymeric Foam Cores Exposed to Blast Loading: An Experimental and Numerical Investigation

2020 ◽  
Vol 10 (24) ◽  
pp. 9061
Author(s):  
Kristoffer Aune Brekken ◽  
Aase Reyes ◽  
Torodd Berstad ◽  
Magnus Langseth ◽  
Tore Børvik
Keyword(s):  
Shock Tube ◽  
Numerical Models ◽  
Sandwich Panels ◽  
Blast Loading ◽  
Experimental Tests ◽  
Quantitative Agreement ◽  
Low Velocity Impact ◽  
Blast Load ◽  
Low Velocity ◽  
Skin Deformation

Sandwich panels have proven to be excellent energy absorbents. Such panels may be used as a protective structure in, for example, façades subjected to explosions. In this study, the dynamic response of sandwich structures subjected to blast loading has been investigated both experimentally and numerically, utilizing a shock tube facility. Sandwich panels made of aluminium skins and a core of extruded polystyrene (XPS) with different densities were subjected to various blast load intensities. Low-velocity impact tests on XPS samples were also conducted for validation and calibration of a viscoplastic extension of the Deshpande-Fleck crushable foam model. The experimental results revealed a significant increase in blast load mitigation for sandwich panels compared to skins without a foam core, and that the back-skin deformation and the core compression correlated with the foam density. Numerical models of the shock tube tests were created using LS-DYNA, incorporating the new viscoplastic formulation of the foam material. The numerical models were able to capture the trends observed in the experimental tests, and good quantitative agreement between the experimental and predicted responses was in general obtained. One aim of this study is to provide high-precision experimental data, combined with a validated numerical modelling strategy, that can be used in simulation-based optimisation of sandwich panels exposed to blast loading.

scholarly journals Experimental Nondestructive Test for Estimation of Buckling Load on Unstiffened Cylindrical Shells Using Vibration Correlation Technique

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Kaspars Kalnins ◽  
Mariano A. Arbelo ◽  
Olgerts Ozolins ◽  
Eduards Skukis ◽  
Saullo G. P. Castro ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Cylindrical Shells ◽  
Laser Scanner ◽  
Experimental Tests ◽  
Buckling Load ◽  
Correlation Technique ◽  
Thin Walled Structures ◽  
Instability Point ◽  
Thin Walled

Nondestructive methods, to calculate the buckling load of imperfection sensitive thin-walled structures, such as large-scale aerospace structures, are one of the most important techniques for the evaluation of new structures and validation of numerical models. The vibration correlation technique (VCT) allows determining the buckling load for several types of structures without reaching the instability point, but this technique is still under development for thin-walled plates and shells. This paper presents and discusses an experimental verification of a novel approach using vibration correlation technique for the prediction of realistic buckling loads of unstiffened cylindrical shells loaded under axial compression. Four different test structures were manufactured and loaded up to buckling: two composite laminated cylindrical shells and two stainless steel cylinders. In order to characterize a relationship with the applied load, the first natural frequency of vibration and mode shape is measured during testing using a 3D laser scanner. The proposed vibration correlation technique allows one to predict the experimental buckling load with a very good approximation without actually reaching the instability point. Additional experimental tests and numerical models are currently under development to further validate the proposed approach for composite and metallic conical structures.

scholarly journals Influence of boundary conditions in FEM model on structural behaviour of thin-walled steel beams strengthened by CFRP tapes

2020 ◽  
Vol 19 (2) ◽  
pp. 073-086
Author(s):  
Katarzyna Rzeszut ◽  
Ilona Szewczak ◽  
Patryk Rozylo
Keyword(s):  
Boundary Conditions ◽  
Laboratory Tests ◽  
Numerical Models ◽  
Load Capacity ◽  
Steel Beams ◽  
Structural Behaviour ◽  
Fem Model ◽  
Mesh Density ◽  
Newton Raphson ◽  
Thin Walled

The main aim of the study is verification and validation of FEM numerical model of beams made of thin-walled steel profiles retrofitted by CFRP tapes Sika CarboDur S. Validation is are carried out based on own laboratory tests conducted on “Blachy Pruszyński” S-type beams. The CFRP tape are bonded to the beam at compressed or tensioned flange. The most important part of this study is focused on investigation of boundary conditions influence in FEM model developed in Abaqus program. Moreover the numerical models are also tested in terms of different mesh density and types of finite elements. Numerical analyses are carried out using Newton-Raphson iterative method to solve non-linear equilibrium equation. In the paper special attention is paid to the evaluation of the possibility to increase the load capacity of the beams by appropriate localisation of CFRP tape.

scholarly journals Laboratory and Numerical Analysis of Steel Cold-Formed Sigma Beams Retrofitted by Bonded CFRP Tapes—Extended Research

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4960
Author(s):  
Ilona Szewczak ◽  
Katarzyna Rzeszut ◽  
Patryk Rozylo ◽  
Malgorzata Snela
Keyword(s):  
Laboratory Tests ◽  
Numerical Models ◽  
Main Idea ◽  
Steel Beams ◽  
Bottom Flange ◽  
Large Rotation ◽  
Thin Walled Structures ◽  
Four Point Bending ◽  
Thin Walled ◽  
The Impact

The presented research is a part of a broader study of strengthening methods closely associated with cold-formed sigma steel beams with tapes made of Carbon Fiber Reinforcement Polymer/Plastic (CFRP). The presented results are a continuation and extension of the tests described in previous work by the authors and refer to high-slenderness thin-walled steel sigma beams subjected to a significant large rotation. The main idea of this expanded study was to identify the effectiveness of CFRP tapes with respect to different locations, namely at a bottom-tensioned or upper-compressed flange. Six beams with a cross-section of an Σ140 × 70 × 2.5 profile by “Blachy Pruszyński” and made of S350GD steel with a span of L = 270 cm were tested in the four-point bending scheme. Two beams, taken as reference, were tested without reinforcement. The remaining beams were reinforced with the use of a 50-mm wide and 1.2-mm thick Sika CarboDur S512 CFRP tape, with two beams reinforced by placing the tape on the upper flange and two with tape located on the bottom flange. The CFRP tape was bonded directly to the beams (by SikaDur®-30 adhesive). Laboratory tests were aimed at determining the impact of the use of composite tapes on the limitation of displacements and deformations of thin-walled structures. In order to perform a precise measurement of displacement, which is, in the case of beams subjected to large rotations, a very difficult issue in itself, the Tritop system and two coupled lenses of the Aramis system were used. Electrofusion strain gauges were used to measure the deformation. In the next step, numerical models of the analyzed beams were developed in the Abaqus program. Good compliance of the results of laboratory tests and numerical analyses was achieved. The obtained results confirm the beneficial effect of the use of tapes (CFRP) on the reduction in displacements and deformations of steel cold-formed elements.

scholarly journals Analysis of the Impact Dynamics of Shape Memory Alloy Hybrid Composites for Advanced Applications

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 153 ◽  
Author(s):  
Michele Guida ◽  
Andrea Sellitto ◽  
Francesco Marulo ◽  
Aniello Riccio
Keyword(s):  
Shape Memory Alloy ◽  
Carbon Fibre ◽  
Shape Memory ◽  
Hybrid Composites ◽  
Numerical Models ◽  
Experimental Tests ◽  
Lower Velocity ◽  
Reinforced Plastic ◽  
Carbon Fibre Reinforced Plastic ◽  
The Impact

In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites (SMAHCs) for aeronautical applications is analysed and compared by means of findings from numerical analyses and experimental tests. At first, experimental tests are performed by using a drop tower facility on both carbon fibre reinforced plastic samples and Carbon Fibre Reinforced Plastic (CFRP) samples hybridized with shape memory alloy materials. The materials properties and the different lower velocity impacts behaviours are simulated and validated by means of numerical models discretized in LS-Dyna explicit solver. For both configurations, the deformation mechanism for low intensity impacts, the absorbed energy, and the effect of rebounding upon the velocity change, and hence the amount of force, are investigated. Then, a configuration is prepared to withstand higher-energy impacts. Finally, the numerical analysis is extended for an innovative layup adapted on an aeronautical structure, which is subjected to the bird-strike phenomenon at 180 m/s and with an impacting mass of 1.8 kg according to the airworthiness requirements. In this study, SMAHCs are used to improve the composite impact response and energy absorption thanks to the superelastic effect.

scholarly journals Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

2019 ◽  
Vol 9 (20) ◽  
pp. 4334 ◽  
Author(s):  
José Henrique Nazzi Ehms ◽  
Rejane De Césaro Oliveski ◽  
Luiz Alberto Oliveira Rocha ◽  
Cesare Biserni ◽  
Massimo Garai
Keyword(s):  
Numerical Model ◽  
Boundary Conditions ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Source Term ◽  
Numerical Models ◽  
Fixed Grid ◽  
Numerical Studies ◽  
The Impact

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

scholarly journals Improving Blast Performance of Reinforced Concrete Panels Using Sacrificial Cladding with Hybrid-Multi Cell Tubes

Modelling ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 149-165
Author(s):  
Mahmoud Abada ◽  
Ahmed Ibrahim ◽  
S.J. Jung
Keyword(s):  
Reinforced Concrete ◽  
Numerical Models ◽  
Plate Thickness ◽  
Core Layer ◽  
Engineering Structures ◽  
Finite Element Program ◽  
Explicit Finite Element ◽  
Element Program ◽  
Thin Walled ◽  
The Impact

The utilization of sacrificial layers to strengthen civilian structures against terrorist attacks is of great interest to engineering experts in structural retrofitting. The sacrificial cladding structures are designed to be attached to the façade of structures to absorb the impact of the explosion through the facing plate and the core layer progressive plastic deformation. Therefore, blast load striking the non-sacrificial structure could be attenuated. The idea of this study is to construct a sacrificial cladding structure from multicellular hybrid tubes to protect the prominent bearing members of civil engineering structures from blast hazard. The hybrid multi-cell tubes utilized in this study were out of staking composite layers (CFRP) around thin-walled tubes; single, double, and quadruple (AL) thin-walled tubes formed a hybrid single cell tube (H-SCT), a hybrid double cell tube (H-DCT), and a hybrid quadruple cell tube (H-QCT). An unprotected reinforced concrete (RC) panel under the impact of close-range free air blast detonation was selected to highlight the effectiveness of fortifying structural elements with sacrificial cladding layers. To investigate the proposed problem, Eulerian–Lagrangian coupled analyses were conducted using the explicit finite element program (Autodyn/ANSYS). The numerical models’ accuracy was validated with available blast testing data reported in the literature. Numerical simulations showed a decent agreement with the field blast test. The proposed cladding structures with different core topologies were applied to the unprotected RC slabs as an effective technique for blast loading mitigation. Mid-span deflection and damage patterns of the RC panels were used to evaluate the blast behavior of the structures. Cladding structure achieved a desired protection for the RC panel as the mid-span deflection decreased by 62%, 78%, and 87% for H-SCT, H-DCT, and H-QCT cores, respectively, compared to the unprotected panels. Additionally, the influence of the skin plate thickness on the behavior of the cladding structure was investigated.

scholarly journals Experimental and Numerical Assessment of Supporting Road Signs Masts Family for Compliance with the Standard EN 12767

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5999
Author(s):  
Michał Stopel ◽  
Artur Cichański ◽  
Nathalie Yague ◽  
Grzegorz Kończalski
Keyword(s):  
Numerical Models ◽  
Product Family ◽  
Experimental Tests ◽  
Severity Index ◽  
Point Of View ◽  
Passive Safety ◽  
Road Signs ◽  
Numerical Assessment ◽  
The Impact ◽  
Crash Tests

The analysis aimed to assess the passive safety of supporting masts for road signs in accordance with EN 12767. Experimental tests were carried out based on the requirements of the standard for the smallest and the largest constructions within the product family. Numerical models of crash tests were prepared for whole product family using the Finite Element Method in the LS-Dyna environment. Based on the comparison of the experimental tests and the numerical calculations, the usefulness of the numerical model for estimating the actual value of the Acceleration Severity Index (ASI) and the Theoretical Head Impact Velocity (THIV) was assessed. With the use of these relationships the values of ASI and THIV for masts not tested experimentally were estimated. It was confirmed that the analyzed masts met the requirements for the passive safety of structures set out in the standard EN 12767. It was possible since as a result of the impact, the mast column detached from the base, allowing the vehicle to continue moving. The behavior of the masts was primarily influenced by the destruction of the safety connectors. The paper presents the most important elements from the point of view of designing such solutions.

scholarly journals DIC in Validation of Boundary Conditions of Numerical Model of Reinforced Concrete Beams Under Torsion

2018 ◽  
Vol 64 (4) ◽  
pp. 31-48 ◽  
Author(s):  
B. Turoń ◽  
D. Ziaja ◽  
L. Buda-Ożóg ◽  
B. Miller
Keyword(s):  
Reinforced Concrete ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Experimental Research ◽  
Concrete Beams ◽  
Numerical Models ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Image Correlation

AbstractThe paper presents the experimental research and numerical simulations of reinforced concrete beams under torsional load. In the experimental tests Digital Image Correlation System (DIC System) Q-450 were used. DIC is a non-contact full-field image analysis method, based on grey value digital images that can determine displacements and strains of an object under load. Numerical simulations of the investigated beams were performed by using the ATENA 3D – Studio program. Creation of numerical models of reinforced concrete elements under torsion was complicated due to difficulties in modelling of real boundary conditions of these elements. The experimental research using DIC can be extremely useful in creating correct numerical models of investigated elements. High accuracy and a wide spectrum of results obtained from experimental tests allow for the modification of the boundary conditions assumed in the numerical model, so that these conditions correspond to the real fixing of the element during the tests.

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