Influence of degradation of structure on the behaviour of a full-scale embankment

2012 ◽  
Vol 49 (3) ◽  
pp. 344-356 ◽  
Author(s):  
S. Panayides ◽  
M. Rouainia ◽  
D. Muir Wood
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Pore Water ◽  
Model Comparison ◽  
Field Measurements ◽  
Full Scale ◽  
Numerical Predictions ◽  
Pore Water Pressures ◽  
Finite Element Procedure ◽  
Degradation Of Structure

The advanced constitutive model KHSM for structured clays, which incorporates the effects of loss of structure within an elastoplastic framework, has been implemented in a finite element procedure and used to investigate the failure height and pore-water pressures of embankment A constructed at Saint Alban, Quebec. For the purpose of model comparison, simulations were also performed using the standard bubble model (KHM) without destructuration. The numerical predictions of pore-water pressures and settlements are also compared with field measurements. The results clearly demonstrate the importance of including the effects of loss of structure in the analysis.

Infiltration characteristics of two instrumented residual soil slopes

2003 ◽  
Vol 40 (5) ◽  
pp. 1012-1032 ◽  
Author(s):  
Illias Tsaparas ◽  
Harianto Rahardjo ◽  
David G Toll ◽  
Eng-Choon Leong
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Field Measurements ◽  
Residual Soil ◽  
Rainfall Runoff ◽  
Rainfall Events ◽  
Pore Water Pressures ◽  
Soil Slopes ◽  
Pressure Changes

This paper presents the analysis of a 12 month long field study of the infiltration characteristics of two residual soil slopes in Singapore. The field measurements consist of rainfall data, runoff data of natural and simulated rainfall events, and pore-water pressure changes during infiltration at several depths and at several locations on the two slopes. The analysis of the field measurements identifies the total rainfall and the initial pore-water pressures within the two slopes as the controlling parameters for the changes in the pore-water pressures within the slopes during infiltration.Key words: infiltration, rainfall, runoff, pore-water pressure, field measurements.

Field measurement of anchor forces, ground temperatures, and pore-water pressures behind a retaining structure in northwestern Ontario

1992 ◽  
Vol 29 (1) ◽  
pp. 112-116
Author(s):  
K. D. Eigenbrod ◽  
J. P. Burak
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Retaining Wall ◽  
Field Measurements ◽  
Strain Gauges ◽  
Ground Temperatures ◽  
Northwestern Ontario ◽  
Pore Water Pressures ◽  
Load Increase

Anchor forces, ground temperatures, and piezometric pressures were measured at a retaining wall in northwestern Ontario over a period of 2 years. The anchor forces were measured with strain gauges attached in pairs directly to the anchor rods. This method appeared practical in the field for time periods of less than 2 years as long as the strain gauges were carefully protected against moisture. The anchor forces increased from an average of 5 kN initially up to values of 50 kN during the winter periods and dropped during the summer periods back to the same values measured initially. The anchor forces were largely independent of pore-water pressure variations behind the wall. Rapid drawdown conditions, however, which were experienced during the second summer, were reflected in a load increase that was equivalent to the associated unloading effect in front of the wall. The pore-water pressures behind the wall were not noticeably affected by rapid drawdown, possibly due to the restraining effect of the anchors and the high rigidity of the low sheet pile wall. Ground temperatures at or below the groundwater table never dropped below 0 °C thus restricting the depth of frost penetration. Key words : anchor loads, freezing pressure, retaining walls, pore-water pressures, ground temperatures, field measurements.

scholarly journals Probabilistic analysis of pore water pressures of an earth dam using a random finite element approach based on field data

2019 ◽  
Vol 259 ◽  
pp. 105190 ◽  
Author(s):  
Anthony Mouyeaux ◽  
Claudio Carvajal ◽  
Philippe Bressolette ◽  
Laurent Peyras ◽  
Pierre Breul ◽  
...  
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Probabilistic Analysis ◽  
Field Data ◽  
Earth Dam ◽  
Finite Element Approach ◽  
Pore Water Pressures ◽  
Element Approach ◽  
Random Finite Element

Significance of material constitutive model and forming parameters on the crashworthiness performance of capped cylindrical tubular structures

2019 ◽  
Vol 234 (2) ◽  
pp. 320-334
Author(s):  
Praveen Kumar A ◽  
Afdhal Akbar ◽  
Annisa Jusuf ◽  
Leonardo Gunawan
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Performance Indicators ◽  
Thickness Distribution ◽  
Material Constitutive Model ◽  
Numerical Predictions ◽  
Forming Parameters ◽  
Crushing Force ◽  
Cylindrical Tubes ◽  
Energy Absorbing

An accuracy of crushing performance indicators is critical to evaluate in finite element crushing simulations particularly for the press-formed capped tubular energy absorbing structures. It is essential to select the appropriate material constitutive model and to incorporate the forming parameters into the finite element crushing model as a vital input. Hence in the present article, the influence of various material constitutive models and forming (multi-stage deep drawing) parameters on the axial crashworthiness characteristics of thin-walled capped cylindrical tubes were investigated numerically. Both forming and crushing simulations were executed by nonlinear finite element LS-DYNA® code. The forming parameters such as thickness distribution, residual stress, and effective plastic strain were mapped to a finite element crushing model of the tube. The numerical predictions of the thickness distribution and final deformed profiles of the capped cylindrical tubes are correlated with the experiments. The results revealed that the forming parameters have a substantial effect on the crushing performance of the deep drawn capped cylindrical tubes. As a result of these analyses, the thickness and strain predictions strengthens the tube and significantly influenced the crushing performance indicators such as initial peak crushing force, mean crushing force, and the energy absorbing capacity.

Finite element simulation of ferromagnetic shape memory alloys using a revised constitutive model

2017 ◽  
Vol 28 (19) ◽  
pp. 2853-2871 ◽  
Author(s):  
Siavash Jafarzadeh ◽  
Mahmoud Kadkhodaei
Keyword(s):  
Finite Element ◽  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Model Parameters ◽  
Ferromagnetic Shape Memory Alloy ◽  
Ferromagnetic Shape Memory Alloys ◽  
Numerical Predictions ◽  
Ferromagnetic Shape Memory

In this article, a previously developed constitutive model for ferromagnetic shape memory alloys is phenomenologically enhanced using experimental observations. A modified phase diagram along with a method for calibration of the required model parameters is further presented. The model is implemented into a user material subroutine to equip commercial finite element software ABAQUS with the capability of simulating magneto-mechanical behaviors of ferromagnetic shape memory alloys. A combined convergence scheme is employed to solve the implicit equations. The proposed model together with the presented numerical solution is shown to be able to study shape memory effect and pseudoelasticity at different constant magnetic fields. The simulated magnetic loading/unloading cycles at different constant stresses are found to be well-fitted to the experimental findings. As a practical application of the ferromagnetic shape memory alloy coupled magneto-mechanical response, a spring actuator (a bias spring serially connected to one ferromagnetic shape memory alloy element) is investigated, and the numerical predictions are shown to be in a good agreement with available experimental results. As a novel case, geometrically graded NiMnGa elements are also introduced and are simulated with the use of this approach.

Evaluating Pressure Integrity of Polymer Ring Seals for Threaded Connections in HP/HT Wells and Expandable Casing

SPE Journal ◽  
2008 ◽  
Vol 13 (01) ◽  
pp. 123-132 ◽  
Author(s):  
Lawrence B. Hilbert ◽  
Jorgen Bergstrom
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
New Technology ◽  
Full Scale ◽  
Seal Integrity ◽  
Seal Design ◽  
Threaded Connections ◽  
Metal Seal ◽  
Physical Testing ◽  
Ring Seal

Summary This paper presents new technology for evaluating high-pressure gas-seal integrity of polymer ring seals used as secondary or backup pressure seals in casing and tubing threaded connections. This new technology may also enable the further consideration of API connections with ring seals, as an alternative to premium connections, for appropriate applications. A nonlinear elasto-viscoplastic constitutive model for the behavior of polymers and elastomers has been developed and extended to the specific application of analysis of casing and tubing connections with fiberglass-filled polytetrafluoroethylene (PTFE) ring seals. Procedures for modeling makeup of a connection including a fiberglass-filled PTFE ring seal have been developed using a finite-element model (FEM) of 10¾-in. OD, 45.5 lb/ft, P-110 API buttress thread casing-seal ring groove (BTC-SRG). The results of finite-element analysis (FEA) of makeup, followed by the application of thermal, axial, and internal pressure loads are presented in this paper. In addition, based on the interest in the development of gas-tight threaded connections for expandable casing, the FEM was subjected to a radial expansion of a 20% increase in the outside diameter. In this paper, the theory of the constitutive model is summarized and calibration of the model with experimental test and published data are presented. The focus of the FEA results is on the contact pressures between the ring seal, coupling groove, and pin threads. Historical Perspective FEA of threaded connections has been used for overcoming challenging well-design problems for many years (Crose et al. 1976). FEA has become an important part of the validation and service evaluation process of API and proprietary casing and tubing threaded connection designs, along with the physical testing procedures documented in API RP 5C5 (1996) and ISO 13679: 2002 (2002). Major advances have been achieved in design of premium connections through analysis of metal-to-metal seal contact stresses computed from FEM (Hilbert and Kalil 1992). Analysis and verification of the performance of threaded connections that include polymeric or elastomeric ring seals has been limited to full-scale physical testing (Payne 1988). Until now, only costly full-scale gas pressure tests have been used to evaluate ring seal integrity. Ring-seal design has been a trial and error process, with new ring-seal or pin and coupling dimensions prescribed only after failure of the seal in a proof test. In some cases, ring design or the effects of ring dimensions have been based on analytical calculations, relying on the bulk modulus of the material. When more advanced design tools, such as FEA, have been used, the pressure generated by entrapment of the ring seal has been estimated and then these pressures have been applied to the groove and pin thread surfaces to simulate the effect of the actual ring seal. The developments in the paper were motivated by a need to reduce the cost of connection qualification by reducing the number of tests and to improve the process of ring-seal design. Properties of PTFE PTFE is a thermoplastic fluorocarbon derived from the monomer tetrafluoroethylene (TFE). PTFE is a semi-crystalline polymer composed of crystalline and amorphous regions. Its molecular structure, shown in Fig. 1, consists of long chains of carbon atoms symmetrically surrounded by fluorine atoms. This structure imbues PTFE with unique mechanical and chemical properties. The straight "backbone" of carbon atoms provides PTFE with a high degree of chemical inertness, stability, and one of the lowest coefficients of friction of any commonly used material. PTFE is more commonly known by the trade name Teflon. In a moment of pure serendipity, in 1938 Roy Plunckett of DuPont discovered TFE when he was conducting experiments to develop nonflammable, nontoxic, colorless, and odorless refrigerants (Ebnesajjad 2000).

A Constitutive Model for Casting Magnesium Alloy Based on the Analysis of a Spherical Void Model

2007 ◽  
Vol 546-549 ◽  
pp. 221-224
Author(s):  
Bin Chen ◽  
X. Peng ◽  
Xiang Guo Zeng ◽  
X. Wu ◽  
S. Chen
Keyword(s):  
Finite Element ◽  
Magnesium Alloy ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Void Nucleation ◽  
Spherical Void ◽  
Evolution Rule ◽  
Void Evolution ◽  
Finite Element Procedure ◽  
Elastoplastic Constitutive Model

Casting magnesium alloys are heterogeneous materials containing numerous voids. Assuming the voids are spherical, in the present investigation, the evolution equations of the growth and nucleation of the voids have been presented. Combining the evolution equation of the void growth with that of the void nucleation, the evolution rule of the voids was obtained. Based on the void evolution rule a nonclassical elastoplastic constitutive model involving void evolution was developed. The corresponding numerical algorithm and finite element procedure were developed and applied to the analyses of the elastoplastic response and the porosity of casting magnesium alloy. The calculated results show the satisfactory agreement with experiments.

Thermomechanical Analysis of Solder Joints Under Thermal and Vibrational Loading

2001 ◽  
Vol 124 (1) ◽  
pp. 60-66 ◽  
Author(s):  
Cemal Basaran ◽  
Rumpa Chandaroy
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Constitutive Model ◽  
Solder Joints ◽  
Cycle Fatigue ◽  
Simultaneous Application ◽  
Short Cycle ◽  
Finite Element Procedure ◽  
Life Predictions

Due to the coefficient of thermal expansion (CTE) mismatch between the bonded layers, the solder joint experiences cycling shear strain, which leads to short cycle fatigue. When semiconductor devices are used in a vibrating environment, additional strains shorten the fatigue life of a solder joint. Reliability of these joints in new packages is determined by laboratory tests. In order to use the FEM to replace these expensive reliability tests a unified constitutive model for Pb40/Sn60 solder joints has been developed and implemented in a thermo-viscoplastic-dynamic finite element procedure. The model incorporates thermal-elastic-viscoplastic and damage capabilities in a unified manner. The constitutive model has been verified extensively against laboratory test data. The finite element procedure was used for coupled thermo-viscoplastic-dynamic analyses for fatigue life predictions. The results indicate that using Miner’s rule to calculate accumulative damage by means of two separate analyses, namely dynamic and thermo-mechanical, significantly underestimates the accumulative total damage. It is also shown that a simultaneous application of thermal and dynamic loads significantly shortens the fatigue life of the solder joint. In the microelectronic packaging industry it is common practice to ignore the contribution of vibrations to short cycle fatigue life predictions. The results of this study indicate that damage induced in the solder joints by vibrations have to be included in fatigue life predictions to accurately estimate their reliability.

Thermomechanical Finite Element Analysis of Problems in Electronic Packaging Using the Disturbed State Concept: Part 1—Theory and Formulation

1998 ◽  
Vol 120 (1) ◽  
pp. 41-47 ◽  
Author(s):  
C. Basaran ◽  
C. S. Desai ◽  
T. Kundu
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Electronic Packaging ◽  
Constitutive Models ◽  
Cyclic Behavior ◽  
Element Analysis ◽  
Theoretical Formulation ◽  
Finite Element Procedure ◽  
Reliable Design ◽  
Number Of Cycles

Accurate prediction of the thermomechanical cyclic behavior of joints and interfaces in semiconductor devices is essential for their reliable design. In order to understand and predict the behavior of such interfaces there is a need for improved and unified constitutive models that can include elastic, inelastic, viscous, and temperature dependent microstructural behavior. Furthermore, such unified material models should be implemented in finite element procedures so as to yield accurate and reliable predictions of stresses, strains, deformations, microcracking, damage, and number of cycles to failure due to thermomechanical loading. The main objective of this paper is to present implementation of such an unified constitutive model in a finite element procedure and its application to typical problems in electronic packaging; details of the constitutive model are given by Desai et al. (1995). Details of the theoretical formulation is presented in this Part 1, while its applications and validations are presented in Part 2, Basaran et al. (1998).

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