Failure Modes of Perforated Material Under Finite Deformation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Xinjian Duan ◽  
Arnaud Weck ◽  
David S. Wilkinson ◽  
Don R. Metzger
Keyword(s):  
Failure Modes ◽  
Structural Model ◽  
Cell Model ◽  
Local Deformation ◽  
Fracture Pattern ◽  
Plastic Strain Rate ◽  
Small Scale ◽  
Engineering Strain ◽  
Failure Path ◽  
Local Cell

Local deformation due to the interaction of small scale features such as voids or hard particles is expected to have a significant influence on the failure mode of a material. To this end, the fracture pattern of a perforated aluminum sheet is studied experimentally and numerically using finite element models on two different length scales: a full-scale structural model and a local cell model based on large deformation theory. Through the appropriate application of boundary conditions, the more efficient local cell model is shown to produce almost the same results as the full structural model. It is also found that the failure path is significantly affected by the loading conditions (uniaxial versus biaxial) and the hole distribution pattern. By plotting the instantaneous contours of the plastic strain rate, the fracture path can clearly be distinguished by the time that the overall engineering strain reaches approximately 3%. This model developed here has great potential to assess the integrity of high pressure components such as tubesheet.

Plastic Limit Analysis of Perforated Material Under Finite Deformation

2005 ◽  
Author(s):  
Xinjian Duan ◽  
Arnaud Weck ◽  
David S. Wilkinson ◽  
Don R. Metzger
Keyword(s):  
Deformation Theory ◽  
Structural Model ◽  
Cell Model ◽  
Fracture Pattern ◽  
Plastic Strain Rate ◽  
Finite Element Models ◽  
Engineering Strain ◽  
Failure Path ◽  
Plastic Limit Analysis ◽  
Local Cell

In this paper, the fracture pattern of a perforated aluminum sheet is studied experimentally and numerically using finite element models on two different length scales: a full-scale structural and a local cell models based on the large deformation theory. Through appropriate application of boundary conditions, the more efficient local cell model is shown to produce almost the same results as the full structural model. It is also found that the failure path is significantly affected by the loading conditions (uniaxial vs. biaxial) and the hole distribution pattern. By plotting the instantaneous contour of plastic strain rate, the fracture path could clearly be distinguished by the time that the overall engineering strain had reached 3%.

Failure Analysis of Composite Structures Using Multiscale Technique

2020 ◽  
Vol 995 ◽  
pp. 209-213
Author(s):  
Young W. Kwon
Keyword(s):  
Composite Structures ◽  
Failure Modes ◽  
Cell Model ◽  
Fibrous Composite ◽  
Failure Criteria ◽  
Multiscale Approach ◽  
Interface Failure ◽  
Fiber Failure ◽  
Strain Rate Effects ◽  
Constituent Material

Failure analyses of laminated fibrous composite structures were conducted using the failure criteria based on a multiscale approach. The failure criteria used the stresses and strains in the fiber and matrix materials, respectively, rather than those smeared values at the lamina level. The failure modes and their respective failure criteria consist of fiber failure, matrix failure and their interface failure explicitly. In order to determine the stresses and strains at the constituent material level (i.e. fiber and matrix materials), analytical expressions were derived using a unit-cell model. This model was used for the multiscale approach for both upscaling and downscaling processes. The failure criteria are applicable to both quasi-static loading as well as dynamic loading with strain rate effects.

Nonlinear Mechanics of Solids Containing Isolated Voids

2006 ◽  
Vol 59 (4) ◽  
pp. 210-229 ◽  
Author(s):  
Z. P. Huang ◽  
J. Wang
Keyword(s):  
Critical Review ◽  
Cell Model ◽  
Extreme Case ◽  
Local Deformation ◽  
Mechanics Of Solids ◽  
Nonlinear Mechanics ◽  
Theoretical Frameworks ◽  
Nonlinear Materials ◽  
A Cell ◽  
Nonlinear Composite

The ductile fracture of many materials is related to the nucleation, growth, and coalescence of voids. Also, a material containing voids represents an extreme case of heterogeneous materials. In the last few decades, numerous studies have been devoted to the local deformation mechanisms and macroscopic overall properties of nonlinear materials containing voids. This article presents a critical review of the studies in three interconnected topics in nonlinear mechanics of materials containing isolated voids, namely, the growth of an isolated void in an infinite medium under a remote stress; the macroscopic mechanical behavior of these materials predicted by using a cell model; and bounds and estimates of the overall properties of these materials as a special case of nonlinear composite materials. Emphasis are placed upon analytical and semianalytical approaches for static loading conditions. Both the classical methods and more recent approaches are examined, and some inadequacies in the existing methods are pointed out. In addition to the critical review of the existing methods and results, some new results, including a power-law stress potential for compressible nonlinear materials, are presented and integrated into the pertinent theoretical frameworks. This review article contains 118 references.

scholarly journals Edgewise Compressive Behavior of Composite Structural Insulated Panels with Magnesium Oxide Board Facings

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3030
Author(s):  
Łukasz Smakosz ◽  
Ireneusz Kreja ◽  
Zbigniew Pozorski
Keyword(s):  
Magnesium Oxide ◽  
Sandwich Panel ◽  
Failure Modes ◽  
Small Scale ◽  
Fe Model ◽  
Compressive Behavior ◽  
Axial Loads ◽  
Reliable Prediction ◽  
Structural Insulated Panels ◽  
Prediction Capability

Edgewise compression response of a composite structural insulated panel (CSIP) with magnesium oxide board facings was investigated. The discussed CSIP is a novel multifunctional sandwich panel introduced to the housing industry as a part of the wall, floor, and roof assemblies. The study aims to propose a computational tool for reliable prediction of failure modes of CSIPs subjected to concentric and eccentric axial loads. An advanced numerical model was proposed that includes geometrical and material nonlinearity as well as incorporates the material bimodularity effect to achieve accurate and versatile failure mode prediction capability. Laboratory tests on small-scale CSIP samples of three different slenderness ratios and full-scale panels loaded with three different eccentricity values were carried out, and the test data were compared with numerical results for validation. The finite element (FE) model successfully captured CSIP’s inelastic response in uniaxial compression and when flexural action was introduced by eccentric loads or buckling and predicted all failure modes correctly. The comprehensive validation showed that the proposed approach could be considered a robust and versatile aid in CSIP design.

Influence of Human Error on Structural Reliability

2017 ◽  
Author(s):  
Eric Brehm ◽  
Robert Hertle ◽  
Markus Wetzel
Keyword(s):  
Human Error ◽  
Structural Reliability ◽  
Failure Modes ◽  
Structural Model ◽  
Limit State ◽  
Design Procedure ◽  
Material Strength ◽  
Limit States ◽  
The Impact

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

Benchmark of a Novel Aero-Elastic Simulation Code for Small Scale VAWT Analysis

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
David Marten ◽  
Matthew Lennie ◽  
George Pechlivanoglou ◽  
Christian Oliver Paschereit ◽  
Alessandro Bianchini ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Open Source ◽  
Structural Model ◽  
Element Model ◽  
Small Scale ◽  
Elastic Model ◽  
Element Analysis ◽  
Simulation Code ◽  
Highly Nonlinear

After almost 20 years of absence from research agendas, interest in the vertical axis wind turbine (VAWT) technology is presently increasing again, after the research stalled in the mid 90's in favor of horizontal axis wind turbines (HAWTs). However, due to the lack of research in past years, there are a significantly lower number of design and certification tools available, many of which are underdeveloped if compared to the corresponding tools for HAWTs. To partially fulfill this gap, a structural finite element analysis (FEA) model, based on the Open Source multiphysics library PROJECT::CHRONO, was recently integrated with the lifting line free vortex wake (LLFVW) method inside the Open Source wind turbine simulation code QBlade and validated against numerical and experimental data of the SANDIA 34 m rotor. In this work, some details about the newly implemented nonlinear structural model and its coupling to the aerodynamic solver are first given. Then, in a continuous effort to assess its accuracy, the code capabilities were here tested on a small-scale, fast-spinning (up to 450 rpm) VAWT. The study turbine is a helix shaped, 1 kW Darrieus turbine, for which other numerical analyses were available from a previous study, including the results coming from both a one-dimensional beam element model and a more sophisticated shell element model. The resulting data represented an excellent basis for comparison and validation of the new aero-elastic coupling in QBlade. Based on the structural and aerodynamic data of the study turbine, an aero-elastic model was then constructed. A purely aerodynamic comparison to experimental data and a blade element momentum (BEM) simulation represented the benchmark for QBlade aerodynamic performance. Then, a purely structural analysis was carried out and compared to the numerical results from the former. After the code validation, an aero-elastically coupled simulation of a rotor self-start has been performed to demonstrate the capabilities of the newly developed model to predict the highly nonlinear transient aerodynamic and structural rotor response.

On the effect of electrode finiteness in small-scale electrical resistivity imaging

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. EN39-EN52 ◽  
Author(s):  
Cécile Verdet ◽  
Yannick Anguy ◽  
Colette Sirieix ◽  
Rémi Clément ◽  
Cécile Gaborieau
Keyword(s):  
Electrical Resistivity ◽  
Point Source ◽  
Cell Model ◽  
Characteristic Size ◽  
Electrode Spacing ◽  
Small Scale ◽  
Electrode Effect ◽  
Point Approximation ◽  
Electrode Length ◽  
The Impact

Electrical resistivity tomography (ERT) profiles including finite steel-rod electrodes have been widely used in assuming a surface-node current injection for inversion. This hypothesis was shown by others to be safe for ratios of electrode embedment to electrode spacing smaller than 20%. Relying on the conductive cell model (CCM), we took into account the complete electrodes in the DC forward problem. We found that an electrode effect is included in resistivity sections inverted with a surface point electrode model. Several synthetic examples indicated that this unwanted effect is particularly developed when the electrode spacing does not meet a double constraint from the characteristic size of a shallow heterogeneity and from the electrode embedment. This effect deserved correction. A point approximation for a finite electrode referred to as the equivalent electrode point (EEP) was sought by placing a point-source current in the ground along the electrode length. The appropriate EEP depth was the one for which the CCM and a buried point source minimized a systematic geometric error; i.e., the relative change of the geometric factors obtained with the CCM and with an EEP. An EEP placed at 73% of the electrode length was declared as a suitable point approximation for an electrode. Use of this point assumption for inversion remedied efficiently the electrode effect subject to conditions. More precisely, the electrode spacing should stay within a lower bound equal to twice the electrode embedment and an upper bound equal to the shallow heterogeneity characteristic size divided by 0.75. The interest of such a metrological appraisal of the suitable acquisition layout to be used on the field was illustrated by a small-scale ERT field survey. This case study permitted us to understand more reliably the impact from fires upon a centimetric shallow layer in a calcareous wall.

scholarly journals Flax, Basalt, E-Glass FRP and Their Hybrid FRP Strengthened Wood Beams: An Experimental Study

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1255 ◽  
Author(s):  
Wang ◽  
Bachtiar ◽  
Yan ◽  
Kasal ◽  
Fiore
Keyword(s):  
Failure Modes ◽  
Maximum Load ◽  
Tensile Failure ◽  
Flexural Behavior ◽  
Single Type ◽  
Small Scale ◽  
Frp Composites ◽  
Bending Load ◽  
Wood Beams ◽  
Glass Frp

In this study, the structural behavior of small-scale wood beams externally strengthened with various fiber strengthened polymer (FRP) composites (i.e., flax FRP (FFRP), basalt FRP (BFRP), E-glass FRP (“E” stands for electrical resistance, GFRP) and their hybrid FRP composites (HFRP) with different fiber configurations) were investigated. FRP strengthened wood specimens were tested under bending and the effects of different fiber materials, thicknesses and the layer arrangements of the FRP on the flexural behavior of strengthened wood beams were discussed. The beams strengthened with flax FRP showed a higher flexural loading capacity in comparison to the beams with basalt FRP. Flax FRP provided a comparable enhancement in the maximum load with beams strengthened with glass FRP at the same number of FRP layers. In addition, all the hybrid FRPs (i.e., a combination of flax, basalt and E-glass FRP) in this study exhibited no significant enhancement in load carrying capacity but larger maximum deflection than the single type of FRP composite. It was also found that the failure modes of FRP strengthened beams changed from tensile failure to FRP debonding as their maximum bending load increased.

scholarly journals Limitations of a dynamic shear-frame model based in a small-scale experimental steel structure

2018 ◽  
Vol 211 ◽  
pp. 14005
Author(s):  
Augusto de S. Pippi ◽  
Pedro L. Bernardes Júnior ◽  
Suzana M. Avila ◽  
Marcus V. G. de Morais ◽  
Graciela Doz
Keyword(s):  
Dynamic Behavior ◽  
Geometric Modeling ◽  
Structural Model ◽  
Natural Frequencies ◽  
Numerical Models ◽  
Steel Structure ◽  
Small Scale ◽  
The Real ◽  
Frame Model ◽  
Shear Frame

Many engineering problems require geometric modeling and mechanical simulation of structures. Through the structural models, engineers try to simulate the real behavior of these structures. It is important that a model contain all the necessary parameters that describe the structure and its behavior during its useful life. In the field of dynamics, one of the most used models is the shear-frame, in which the stiffness of the structure is given by the stiffness of the columns and the whole mass is concentrated in the floor levels, which are considered with infinite stiffness. In some cases, this simplification offers more conservative results, which can lead to considerable errors, especially in the case of natural frequencies. Knowing that the quality of a structural model depends on the simplifications considered, an experimental 3D steel frame, constructed to typify the dynamic behavior of a tall building, was tested with a data acquisition system and accelerometers, in order to obtain its natural frequencies. In addition, a numerical model was developed in order to ascertain the results. These values of natural frequencies are compared with an idealized shear-frame model obtained from the experimental model. This comparison allows a critical analysis of the numerical models that can be employed to represent the real dynamic behavior of structures. The aim of the investigation is to show the results of the modal analysis for each model, comparing them with the experimental results and commenting their advantages and the limitations.

scholarly journals Uniaxial Cyclic Tests on Reinforced Concrete Members with Lap Splices

2019 ◽  
Vol 35 (2) ◽  
pp. 1023-1043 ◽  
Author(s):  
Danilo Tarquini ◽  
João P. Almeida ◽  
Katrin Beyer
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Local Deformation ◽  
Experimental Program ◽  
Loading History ◽  
Cyclic Tests ◽  
Continuous Reinforcement ◽  
Lap Splices ◽  
Lap Splice ◽  
Concrete Members

This data paper presents the quasi-static uniaxial cyclic tests of 24 reinforced concrete members, of which 22 feature lap splices and 2 are reference units with continuous reinforcement. The objective of the experimental program is to investigate the influence of lap splice length ( ls), confining reinforcement, and loading history on the behavior of lap splices. Particular attention is placed on the measurement of local deformation quantities, such as lap splice strains and rebar-concrete slip. Details of the geometry and reinforcement layout of the specimens as well as the employed test setup, instrumentation, and loading protocols are provided. The global behavior of the test units, including the observed crack pattern and failure modes, are discussed. The organization of the experimental data, which are made available for public use under DOI: 10.5281/zenodo.1205887, is outlined in detail.

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