Prediction of the Ceramic Foam Structure Failure Using a Detailed Finite Element Model

2019 ◽  
Vol 827 ◽  
pp. 222-227
Author(s):  
Oldřich Ševeček ◽  
Jiří Hanák ◽  
Zdeněk Majer ◽  
Daniel Drdlík ◽  
Zdeněk Chlup ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Crack Initiation ◽  
Energy Condition ◽  
Energy Criterion ◽  
Element Model ◽  
Ceramic Foam ◽  
Fe Model ◽  
Stress Concentrations ◽  
Foam Structure ◽  
3D Volume

The contribution deals with modelling and prediction of failure of mechanically loaded open cell ceramic foam structures by using 3D volume FE models constructed from CT scans of real foam specimens. The condition for crack initiation in particular struts comes from the coupled stress-energy criterion which combines two fracture-mechanics parameters of the investigated material – tensile strength and its fracture toughness. By combining of both stress and energy condition one obtains information about the crack initiation length which is later used (together with the tensile strength) for determination of the strut failure in the complex 3D FE model of the ceramic foam structure. The crack onset is considered in the critical location at the moment when the (tensile) principal stress under the strut surface (in a depth corresponding to the crack initiation length) exceeded the tensile strength of the strut. Such approach enables us to define failure also on relatively coarse meshes of the FE models where potential stress concentrations are not described precisely and therefore it is not possible to decide about the failure just based upon the value of tensile stress on the strut surface.

A Finite Element Model of a Surgical Knot

2017 ◽  
Author(s):  
Arz Y. Qwam Alden ◽  
Andrew G. Geeslin ◽  
Jeffrey C. King ◽  
Peter A. Gustafson
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Computational Models ◽  
Mechanical Performance ◽  
Surgical Techniques ◽  
Element Model ◽  
Fe Model ◽  
Stress Concentrations ◽  
Suture Materials ◽  
Surgical Suture

Background Surgical knots are one of several structures which can fail during surgical repair. However, there is no universal agreement on the superiority (best/safest) of one particular surgical knot technique. Tensile testing of repaired soft tissue has been used to assess the efficacy of surgical knot tying techniques, however, few computational models exist. The purpose of this study was to create a validated biomechanical model to evaluate the effect of knot configuration on the mechanical performance of surgical sutures. Methods Two sutures were tested experimentally to find the mechanical properties and strength. Single throw knots were also tested for strength. Finite element models were constructed of each configuration and correlation was established. Results The finite element results are quantitatively and qualitatively consistent with experimental findings. The FE model stress concentrations are also consistent with published strength reductions. Model and experimental results are presented using as-manufactured No. 2 FiberWire as well as its core and jacket constituents separately. Clinical Relevance This paper describes a model which can evaluate the effect of knot topology on the mechanics of surgical suture. In the future, the model may be used to evaluate the mechanical differences between surgical techniques and suture materials. The findings may impact choices for suture and knot types selected for soft tissue repairs.

Anisometry Anterior Cruciate Ligament Sport Injury Mechanism Study: A Finite Element Model with Optimization Method

2014 ◽  
Vol 543-547 ◽  
pp. 173-180
Author(s):  
Na Li ◽  
Song Wu ◽  
Wei Wang ◽  
Bin Ye
Keyword(s):  
Sports Medicine ◽  
Cruciate Ligament ◽  
Elevation Angle ◽  
Knee Injuries ◽  
Element Model ◽  
Optimization Method ◽  
Fe Model ◽  
Mechanism Study ◽  
Stress Concentrations ◽  
Combined Movements

ACL damage is one the most frequent causes of knee injuries and thus has long been the focus of research in biomechanics and sports medicine. Due to the anisometric geometry and functional complexity of the ACL in the knee joint, it is usually difficult to experimentally study the biomechanics of ACLs. Anatomically ACL geometry was obtained from both MR images and anatomical observations. The optimal material parameters of the ACL were obtained by using an optimization-based material identification method that minimized the differences between experimental results from ACL specimens and FE simulations. The optimal FE model simulated biomechanical responses of the ACL during complex combined injury-causing knee movements, it predicted stress concentrations on the top and middle side of the posterolateral (PL) bundles. This model was further validated by a clinical case of ACL injury diagnosed by MRI and arthroscope, it demonstrated that the locations of rupture in the patients knee corresponded to those where the stresses and moments were predicted to be concentrated. The result implies that varus rotation played a contributing but secondary role in injury under combined movements, the ACL elevation angle, is positive correlated with the tensional loading tolerance of the ACL.

Influence of corrosion on fatigue behaviour of old crane runway steel

2019 ◽  
Vol 54 (7-8) ◽  
pp. 416-423
Author(s):  
Stanislav Seitl ◽  
Petr Miarka ◽  
Pavel Pokorný ◽  
Jan Klusák
Keyword(s):  
Crack Initiation ◽  
Cross Sections ◽  
Fatigue Cracks ◽  
Element Model ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Experimental Measurements ◽  
Stress Concentrations ◽  
The Finite Element Model ◽  
Surface Crack Initiation

Experimental measurements of fatigue properties of old steel used for a crane runway were performed to capture the influence of corrosion on fatigue life of the material. Basquin’s law was used to quantify the fatigue properties of old steel with different cross sections and with different surface of specimens (polished and corroded). The finite element model was prepared to assess and quantify the various stress distribution in specimens with circular and rectangular cross sections. Fracture surfaces of the three kinds of specimens (circular polished, rectangular polished and rectangular corroded) were studied and they showed the surface crack initiation. The following fatigue cracks developed from the surface and expanded into specimen with radiation pattern. Observed crack initiation areas confirmed the ones expected according to stress concentrations.

Mechanical testing and fracture analyses of miniaturized ZnO-based multilayer components

2015 ◽  
Vol 2015 (1) ◽  
pp. 000163-000168 ◽  
Author(s):  
K. Macurova ◽  
M. Gruber ◽  
M. Pletz ◽  
P. Supancic ◽  
R. Danzer ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Mechanical Testing ◽  
Tape Casting ◽  
Casting Process ◽  
Element Model ◽  
Internal Stresses ◽  
Fe Model ◽  
Stress Concentrations ◽  
Numerical Predictions ◽  
Functional Components

Functional components are commonly fabricated combining a ceramic substrate with external and/or internal metallization (e.g. metal electrodes, vias, contact pads, etc.) using a tape casting process. Different layers are printed and/or fired (e.g. up to 800°C) onto the ceramic part to provide the component with a (certain) functionality. As a result of the combination of different materials (e.g. ceramic, glass, metal alloys) with different coefficients of thermal expansion, internal stresses may arise during the different fabrication steps. Although some of these tensile residual stresses may relax due to plastic deformation of metallic materials, stress concentrations generated in material junctions or terminations (imposed by geometrical constrains) may lead to cracks and/or reduce the component strength. In this work different architectures combining metal and glass layers on the surface of ZnO substrates were investigated experimentally and numerically in order to identify weak points in commercial components. Mechanical testing using three-point-bending was performed on samples taken after different steps. A FE model was developed to (i) calculate residual stresses generated during the manufacturing process, and (ii) simulate the propagation of initial crack/defect during manufacturing. Experimental results were compared with numerical predictions. These results in combination with fractographic analyses were used to validate the finite element model in order to assess location of failure.

Computational Analysis of Crack-Like Defects Influence on the Open Cell Ceramic Foam Tensile Strength

2018 ◽  
Vol 774 ◽  
pp. 271-276 ◽  
Author(s):  
Oldřich Ševeček ◽  
Zdeněk Majer ◽  
Petr Marcián ◽  
Luca Bertolla ◽  
Michal Kotoul
Keyword(s):  
Tensile Strength ◽  
Computational Analysis ◽  
Fe Simulation ◽  
Voronoi Tessellation ◽  
Microscopic Analysis ◽  
Operating Conditions ◽  
Ceramic Foam ◽  
Foam Structure ◽  
Open Cell ◽  
Fast Estimation

This work deals with a computational analysis and quantification of the influence of processing (primarily crack-like) defects of various amount on the (tensile) strength of open cell ceramic foam structures. This information is essential e.g. for application of these materials in the mechanically loaded application, where a design with certain reliability to operating conditions is required. The analysed ceramic foam structures are composed of both regular and irregular cells and crack-like defects (pre-cracked struts) are simulated inside them. The foam structure is modelled using a 3D FE beam element based model created by utilization of the Voronoi tessellation technique. The tensile strength upon presence of various amount of pre-cracked struts is analysed based upon an iterative FE simulation on whose base the critical failure force leading to specimen fracture is determined. The performed parametric study relates the tensile strength of the foam structure to the amount of initial defects. With increasing amount of these defects, the foam strength decreases by approximately 30% with every 10% of broken struts. This information can be directly used for a fast estimation of the foam tensile strength if the fraction of broken struts to the intact ones is known (e.g. from a microscopic analysis).

Influence of the Ceramic Foam Structure Irregularity on the Tensile Response

2016 ◽  
Vol 258 ◽  
pp. 161-164 ◽  
Author(s):  
Oldřich Ševeček ◽  
Petr Navrátil ◽  
Roman Papšík ◽  
Petr Skalka ◽  
Michal Kotoul
Keyword(s):  
Point Of View ◽  
Ceramic Foam ◽  
Fe Model ◽  
Foam Structure ◽  
The Real ◽  
Tensile Response ◽  
Real Cell ◽  
Cell Shapes ◽  
Definition Of ◽  
Computational Resources

To better understand response or fracture conditions of the ceramic foam materials to the mechanical loading, a finite element (FE) analysis of these structures has to be employed. The cellular structure of foams can be modelled either using a detailed realistic FE model based on the computer tomography scans or by using of simplified, beam element based, models. Nevertheless a main drawback of the realistic foam modelling consists in its high demandingness on computational resources. Therefore, simplified models are welcome substitutions (at least for analysis of the global mechanical foam response). The regular foam structure, based e.g. on Kelvin cells, is simple from the modelling point of view, but it doesn´t exactly capture the fully random character of the real foam structures and corresponding response to the external load. Definition of the random beam foam structure (respecting the real cell shapes and their distribution within volume), can thus improve this deficiency. The main aim of this work is thus to compare these different modelling approaches and quantify the influence of the foam irregularity on the response of ceramic foams to external (tensile) loading for various model sizes.

µCT/HR-pQCT Image Based Plate-Rod Microstructural Finite Element Model Efficiently Predicts the Elastic Moduli and Yield Strength of Human Trabecular Bone

2010 ◽  
Author(s):  
X. Sherry Liu ◽  
Aaron J. Fields ◽  
Tony M. Keaveny ◽  
Elizabeth Shane ◽  
X. Edward Guo
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Shell Element ◽  
Element Model ◽  
Fe Model ◽  
Human Trabecular Bone ◽  
Age Related ◽  
The Individual ◽  
3D Volume

Osteoporosis is an age-related disease characterized by low bone mass and architectural deterioration, which affects primarily the trabecular sites and causes millions of fractures. High-resolution image voxel-based finite element (FE) models with the detailed 3D microstructure have been widely utilized to assess the mechanical properties of trabecular bone [1, 2]. However, the very large size of the voxel-based FE model, in general, limits its application to linear elastic cases. Despite the great potential it has shown in studying trabecular bone failure, iterative nonlinear analysis is still hard to be performed efficiently. Therefore, there is an apparent need for an alternative approach, which maintains the advantages of the voxel-based FE models in capturing details of trabecular microstructure, while allowing faster computation. Based on the individual trabeculae segmentation (ITS) technique [3], a specimen-specific plate-rod (P-R) microstructural FE model was developed by substituting the individual beam/shell element for 3D volume of trabecular plate/rod of μCT images of trabecular bone (21 μm resolution) (Fig. 1). The first goal of this study is to validate both linear and nonlinear predictions based on the P-R models for in vitro μCT images of human trabecular bone samples. The prediction accuracy and computational speed of the P-R model were examined by comparing with those of the voxel-based FE model.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

scholarly journals Bond Behaviour of Near-Surface Mounted Strips in RC Beams—Experimental Investigation and Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4362
Author(s):  
Renata Kotynia ◽  
Hussien Abdel Baky ◽  
Kenneth W. Neale
Keyword(s):  
Concrete Strength ◽  
Element Model ◽  
Steel Reinforcement ◽  
Reinforcement Ratio ◽  
Experimental Program ◽  
Fe Model ◽  
Bond Behaviour ◽  
Near Surface ◽  
Cfrp Laminates ◽  
Near Surface Mounted

This paper presents an investigation of the bond mechanism between carbon fibre reinforced polymer (CFRP) laminates, concrete and steel in the near-surface mounted (NSM) CFRP-strengthened reinforced concrete (RC) beam-bond tests. The experimental program consisting of thirty modified concrete beams flexurally strengthened with NSM CFRP strips was published in. The effects of five parameters and their interactions on the ultimate load carrying capacities and the associated bond mechanisms of the beams are investigated in this paper with consideration of the following investigated parameters: beam span, beam depth, longitudinal tensile steel reinforcement ratio, the bond length of the CFRP strips and compressive concrete strength. The longitudinal steel reinforcement was cut at the beam mid-span in four beams to investigate a better assessment of the influence of the steel reinforcement ratio on the bond behaviour of CFRP to concrete bond behaviour. The numerical analysis implemented in this paper is based on a nonlinear micromechanical finite element model (FEM) that was used for investigation of the flexural behaviour of NSM CFRP-strengthened members. The 3D model based on advanced CFRP to concrete bond responses was introduced to modelling of tested specimens. The FEM procedure presents the orthotropic behaviour of the CFRP strips and the bond response between the CFRP and concrete. Comparison of the experimental and numerical results revealed an excellent agreement that confirms the suitability of the proposed FE model.

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