scholarly journals Effect of Cavity Design on the Strength of Direct Posterior Composite Restorations: An Empirical and FEM Analysis

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
V. Susila Anand ◽  
C. Kavitha ◽  
C. V. Subbarao
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Compressive Strength ◽  
Material Properties ◽  
Null Hypothesis ◽  
Fem Analysis ◽  
Empirical Testing ◽  
Composite Restorations ◽  
Concave Shape ◽  
Cavity Design

The aim of the present study was to verify the hypothesis that cavity design does not affect the strength of direct composite restorations as do material properties. Finite element modeling (FEM) and empirical testing were done for two cavity designs: a box shape (cube) and a concave shape (U). Two microhybrid composites were used to prepare the samples with the help of split stainless steel moulds. Compressive strength was tested. The results were statistically analyzed. Both FEA and empirical testing were complementary to each other in that the concave shape showed a significantly higher strength than box. Material properties affected the values only when box shape was used. The null hypothesis is thus rejected, and it is concluded that design significantly affects the strength of direct composite restorations.

scholarly journals Probability Study on the Thermal Stress Distribution in Thick HK40 Stainless Steel Pipe Using Finite Element Method

Designs ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 9
Author(s):  
Sujith Bobba ◽  
Shaik Abrar ◽  
Shaik Mujeebur Rehman
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
High Temperature ◽  
Material Properties ◽  
Thermal Stresses ◽  
Steel Pipe ◽  
Stress Distributions ◽  
Stainless Steel Pipe ◽  
Deterministic Solution ◽  
Analytical Expressions

The present work deals with the development of a finite element methodology for obtaining the stress distributions in thick cylindrical HK40 stainless steel pipe that carries high-temperature fluids. The material properties and loading were assumed to be random variables. Thermal stresses that are generated along radial, axial, and tangential directions are generally computed using very complex analytical expressions. To circumvent such an issue, probability theory and mathematical statistics have been applied to many engineering problems, which allows determination of the safety both quantitatively and objectively based on the concepts of reliability. Monte Carlo simulation methodology is used to study the probabilistic characteristics of thermal stresses, and was implemented to estimate the probabilistic distributions of stresses against the variations arising due to material properties and load. A 2-D probabilistic finite element code was developed in MATLAB, and the deterministic solution was compared with ABAQUS solutions. The values of stresses obtained from the variation of elastic modulus were found to be low compared to the case where the load alone was varying. The probability of failure of the pipe structure was predicted against the variations in internal pressure and thermal gradient. These finite element framework developments are useful for the life estimation of piping structures in high-temperature applications and for the subsequent quantification of the uncertainties in loading and material properties.

A Determination of Material Properties of Flexible Structures Using EMA and FEM Analysis

2014 ◽  
Vol 693 ◽  
pp. 293-298 ◽  
Author(s):  
Rastislav Duris
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Low Cost ◽  
Flexible Structures ◽  
Fem Analysis ◽  
Element Analysis ◽  
Structural Dynamic ◽  
Vibration Data ◽  
Complex Interactions ◽  
Applied Forces

Dynamic behavior of mechanical structures results from complex interactions between applied forces and the stiffness properties of the structure. Currently, many problems of structural dynamic analysis are solved using Finite Element Method (FEM). However, in recent years, the implementation of the Fast Fourier Transform (FFT) in low cost computer-based signal analyzers has provided a powerful tool for acquisition and analysis of vibration data. This article discusses combination of two approaches to structural dynamics testing; the experimental part which is referred to as Experimental Modal Analysis (EMA), respectively the analytical part, which is realized by Finite Element Analysis (FEA). Main goal of the paper is calculation of material properties from experimentally determined modal frequencies.

scholarly journals Probability Study on the Thermal Stress Distribution in the Thick HK40 Stainless Steel Pipe Using Finite Element Method

2018 ◽  
Author(s):  
Shaik Abrar ◽  
Sujith Bobba ◽  
Shaik Mujeebur Rehman
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
High Temperature ◽  
Material Properties ◽  
Thermal Stresses ◽  
Steel Pipe ◽  
Stress Distributions ◽  
Stainless Steel Pipe ◽  
Deterministic Solution ◽  
Analytical Expressions

The present work deals with the development of finite element methodology for obtaining the stress distributions in thick cylindrical HK40 stainless steel pipe that carry high temperature fluids. The material properties and loading are assumed to be random variables. Thermal stresses that are generated along radial, axial and tangential directions are computed generally using analytical expressions which are very complex. To circumvent such an issue, the probability theory and mathematical statistics have been applied to many engineering problems which allows to determine the safety both quantitatively and objectively based on the concepts of reliability. Monte Carlo simulation methodology is used to study the probabilistic characteristics of thermal stresses which is used for estimating the probabilistic distributions of stresses against the variations arising due to material properties and load. A 2-D Probabilistic finite element code is developed in MATLAB and the deterministic solution is compared with ABAQUS solutions.  The values of stresses that are obtained from the variation of elastic modulus are found to be low as compared to the case where the load alone is varying. The probability of failure of the pipe structure is predicted against the variations in internal pressure and thermal gradient. These finite element framework developments are useful for the life estimation of piping structures in high temperature applications and subsequently quantifying the uncertainties in loading and material properties.

Plasticity as a Lifesaver in the Design of Cardiovascular Stents

2007 ◽  
Vol 340-341 ◽  
pp. 841-846 ◽  
Author(s):  
Matthieu De Beule ◽  
Peter Mortier ◽  
Jan Belis ◽  
Rudy Van Impe ◽  
Benedict Verhegghe ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stainless Steel ◽  
Yield Stress ◽  
Material Properties ◽  
Failure Strain ◽  
The Finite Element Method ◽  
Size Dependency ◽  
Stent Expansion ◽  
Nominal Strain

A common treatment to restore normal blood flow in an obstructed artery is the deployment of a stent (i.e. small tube-like structure). The vast majority of stents are crimped on a folded balloon and laser cut from 316L stainless steel tubes. Although, several numerical studies (exploiting the Finite Element Method) are dedicated to the mechanical behaviour of balloon expandable stents, there seems to be no consensus regarding the mechanical properties to describe the inelastic material behaviour of SS316L. Moreover, as the typical dimensions of stent struts (e.g. 100 μm for coronary stents) are of a similar order of magnitude as the average grain size in stainless steel (i.e. 25 μm), continuum approaches relying on macroscopic material properties may be questionable. In addition, an experimental study on stainless steel stent strut specimens showed a size-dependency of the failure strain. In this study the impact of the magnitude of the yield stress on the stent expansion behavior is examined. An increase in the yield stress (from 205 N/mm² to 375 N/mm²) results in an increase of the pressure (from about 0.3 N/mm² to approximately 0.4 N/mm²) which the clinician needs to exert for the balloon to unfold and to reach its cylindrical expanded shape. Furthermore, the effect of the size dependency behavior of the material is studied by monitoring the nominal strain during stent expansion. The maximum value of the nominal strain in the expanded stent (e.g. εn = 23 %) does not exceed the critical value of the failure strain, (i.e. εn = 33 %), moreover the critical values are nowhere exceeded in the whole stent during the expansion. Our numerical results - accounting for the presence of the balloon in its actual folded shape - correspond very well with pressure/diameter data supplied by the manufacturer. Consequently, this study shows that the free expansion of new generation balloon-expandable stents can be studied accurately with computational analysis based on the Finite Element Method (FEM) and relying on macroscopic material properties. In this context, there is no need to implement a size-based constitutive material model, but before accepting the results of the study, one should check in any case the maximum strain against the limit as shown above.

scholarly journals DETERMINATION OF THE PROPERTIES OF BAMBUSA BLUMEANA USING FULL-CULM COMPRESSION TESTS AND LAYERED TENSILE TESTS FOR FINITE ELEMENT MODEL SIMULATION USING ORTHOTROPIC MATERIAL MODELING

2019 ◽  
Vol 9 (1) ◽  
pp. 54-71
Author(s):  
Ma. Doreen Esplana Candelaria ◽  
Jaime Yabut Hernandez, Jr.
Keyword(s):  
Finite Element ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Material Properties ◽  
Orthotropic Material ◽  
Building Materials ◽  
Material Model ◽  
Tensile Tests ◽  
Concentrated Load ◽  
Bamboo Culm

Construction materials are selected based on two factors: structural integrity and economy. However, there is an emerging issue with regards to building materials, and that is sustainability, which considers the environmental load of a construction material. Bamboo’s lightweight and flexibility make it a good alternative for residential construction in seismic. In this study, bamboo was tested for its material properties. Layered tensile tests and full-culm compressive tests were done to get the material properties of the bamboo. The top part of the bamboo culm recorded the highest tensile strength per layer, with its outer layers having tensile strength as high as 600 MPa. The tensile strength of its middle and inner layers, on the other hand, were approximately 450 MPa and 180 MPa, respectively. As for the compressive strength, the top part of the bamboo culm recorded the highest compressive strength with an average of 76.84 MPa. The middle part of the bamboo culm recorded the lowest compressive strength with an average of 62.55 MPa. The bottom part of the bamboo culm recorded an average compressive strength of 69.49 MPa. These properties were then used to construct an orthotropic material model and simulate the stresses using finite element modeling. The FEM model of a simply-supported beam with a concentrated load at midspan was made. To validate the orthotropic material model for bamboo, three-point bending tests of bamboo beams were conducted and compared with the simulation results. The results show that in modeling the material properties of the bamboo to check for deflections, the orthotropic model gives more accurate results.

Analytical Evaluation of Weld Residual Stress Distribution for BWR Pipings

2008 ◽  
Author(s):  
M. Ando ◽  
K. Nakata ◽  
R. Sumiya ◽  
M. Itow ◽  
N. Tanaka
Keyword(s):  
Heat Transfer ◽  
Residual Stress ◽  
Stainless Steel ◽  
Material Properties ◽  
Fem Analysis ◽  
Residual Stress Distribution ◽  
Temperature History ◽  
Stress Distributions ◽  
Weld Residual Stress ◽  
Stress Analyses

SCC (stress corrosion cracking) of low-carbon stainless steel piping has been found in Japanese BWR plants since 2002. According to JSME Fitness-for-Service Code, flaw evaluations are required to verify the life-time of piping if SCC is detected. In order to evaluate the SCC propagation behavior, it is necessary to obtain the residual stress distribution through the thickness of piping. In this study, the mock-up PLR (Primary Loop Recirculation system) piping weld joints made of L-grade Type 316 stainless steel with 300 mm and 600 mm diameter were fabricated and residual stress analyses were performed in order to obtain stress distributions. Material properties (specific heat, thermal conductivity, Young’s modulus, stress-strain curve, etc.) were obtained and temperature history during welding and weld residual stress were measured using these mock-ups. Material properties were used in the heat transfer and stress analyses. Measured temperature history and residual stress were compared with the results of heat transfer and stress analyses, respectively. Residual stress analysis of the pipe weld joint is commonly performed using axisymmetric element. In some cases of the combination of pipe diameter and thickness, residual stress obtained by the conventional method might differ from the experimental result owing to the difference of heating and constraint conditions between the axisymmetric model and the actual condition. In order to obtain more precise results, heat transfer and stress analyses were performed, taking into account the adjustment of the boundary condition in the weld passes of the last layer and the constraint condition using a spring element, respectively. On the outer and inner surfaces, almost the same residual stress distributions were obtained for the FEM analysis and the measurement. The residual stress distributions for PLR piping with different diameters, thicknesses, welding processes and groove angles were obtained by FEM analysis. Based on the results of the analyses, the influences of these parameters on residual stress were evaluated.

scholarly journals Model for in-vivo estimation of stiffness of tibiofemoral joint using MR imaging and FEM analysis

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Sandeep Panwar Jogi ◽  
Rafeek Thaha ◽  
Sriram Rajan ◽  
Vidur Mahajan ◽  
Vasantha Kumar Venugopal ◽  
...  
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Knee Joint ◽  
Material Properties ◽  
Weight Bearing ◽  
Fem Analysis ◽  
Implant Design ◽  
Tibiofemoral Joint ◽  
Specific Stiffness ◽  
Subject Specific

Abstract Background Appropriate structural and material properties are essential for finite-element-modeling (FEM). In knee FEM, structural information could extract through 3D-imaging, but the individual subject’s tissue material properties are inaccessible. Purpose The current study's purpose was to develop a methodology to estimate the subject-specific stiffness of the tibiofemoral joint using finite-element-analysis (FEA) and MRI data of knee joint with and without load. Methods In this study, six Magnetic Resonance Imaging (MRI) datasets were acquired from 3 healthy volunteers with axially loaded and unloaded knee joint. The strain was computed from the tibiofemoral bone gap difference (ΔmBGFT) using the knee MR images with and without load. The knee FEM study was conducted using a subject-specific knee joint 3D-model and various soft-tissue stiffness values (1 to 50 MPa) to develop subject-specific stiffness versus strain models. Results Less than 1.02% absolute convergence error was observed during the simulation. Subject-specific combined stiffness of weight-bearing tibiofemoral soft-tissue was estimated with mean values as 2.40 ± 0.17 MPa. Intra-subject variability has been observed during the repeat scan in 3 subjects as 0.27, 0.12, and 0.15 MPa, respectively. All subject-specific stiffness-strain relationship data was fitted well with power function (R2 = 0.997). Conclusion The current study proposed a generalized mathematical model and a methodology to estimate subject-specific stiffness of the tibiofemoral joint for FEM analysis. Such a method might enhance the efficacy of FEM in implant design optimization and biomechanics for subject-specific studies. Trial registration The institutional ethics committee (IEC), Indian Institute of Technology, Delhi, India, approved the study on 20th September 2017, with reference number P-019; it was a pilot study, no clinical trail registration was recommended.

Precision Laser Deburring

1999 ◽  
Vol 123 (4) ◽  
pp. 601-608 ◽  
Author(s):  
Seoung Hwan Lee ◽  
David A. Dornfeld
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stainless Steel ◽  
Carbon Steel ◽  
Fem Analysis ◽  
Experimental Results ◽  
High Power Laser ◽  
Power Laser ◽  
Complex Part ◽  
Thermal Affected Zone

The purpose of this study is to develop an effective way of automated deburring of precision components. A high power laser is proposed as a deburring tool for complex part edges and burrs. Experimental results for carbon steel and stainless steel are presented. Also, the prediction of the HAZ and cutting profile of laser-deburred parts using finite element method is presented and compared with the experimental results. This study shows that FEM analysis can effectively predict the thermal affected zone of the material and that the technique can be applied to precision components.

scholarly journals Propagation of a Crack in a Composite Plate

2018 ◽  
Vol 55 (2) ◽  
pp. 179-183
Author(s):  
Ionel Iacob ◽  
Ionel Chirica ◽  
Elena Felicia Beznea
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Material Properties ◽  
Composite Plate ◽  
Extended Finite Element Method ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Extended Finite Element ◽  
Time Step ◽  
Element Method

In this paper, a model of a composite plate with a central elliptical cut-out and with an initial fissure was subjected to a tension load in the finite element method (FEM) software Abaqus to observe the propagation of that crack during a certain amount of time that elapsed in the FEM analysis. Due to symmetry, only half of the plate was modeled, as a shell, and the extended finite element method (XFEM) was used for the crack. The material properties that were assigned to the plate were taken from the database of the Ansys Mechanical software. In the vicinity of the crack a finer mesh was applied to be able to better observe the evolution of the fissure and the changes of the Von Misses stress graphs for each time step of the analysis.

The Effects of Material Degradation on Sealing Performances of O-Rings

2013 ◽  
Vol 328 ◽  
pp. 1004-1008 ◽  
Author(s):  
Zhi Guo Zeng ◽  
Yun Xia Chen ◽  
Rui Kang
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Failure Mechanisms ◽  
Mechanical Systems ◽  
Fem Analysis ◽  
Time Dependent ◽  
Material Degradation ◽  
Degradation Of Materials

O-rings are seal structures widely applied in a variety of mechanical systems. In this paper, the time-dependent performances of O-rings are investigated with the aid of finite element (FEM) analysis. The investigation starts with a discussion on the failure mechanisms of O-ring seals and FEM models are built to establish relations between O-ring failures and the material properties. Since the material properties will degrade with time, we further investigate the influence of the degradation on the sealing performances of O-rings. The results show that the degradation of materials might be one reason for the time-dependent O-ring leakages and can be used to prevent O-rings from field failures.

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