scholarly journals A Simple and Efficient Method for Obtaining the Whole-Range Uniaxial Tensile Properties of Pipeline Steel

Metals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 555
Author(s):  
Lingzhen Kong ◽  
Lingbo Su ◽  
Xiayi Zhou ◽  
Liqiong Chen ◽  
Jie Chen ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Pipeline Steel ◽  
True Strain ◽  
Strain Curve ◽  
Element Model ◽  
True Stress ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Output Data

To obtain the whole-range true stress-true strain curves of API X65, a method is proposed based on the equal proportion principle and digital images. The tensile elongation was obtained by tracing the gauge points on the specimen surface, and the true strain and true stress of API X65 were calculated according to the formulae. The obtained true stress-true strain curves were validated by a 3-D finite element model. The true stress-true strain curve was set as the input data, while the engineering stress-engineering strain curve was set as the output data. The output data of the finite element model was the same as that of the experiment test. The findings imply that the proposed method could acquire reliable, whole-range true stress-true stain curves. These curves, which depict the material behavior of pipeline steel from initial elongation to fracture, could provide basic data for pipeline defect tolerance limit analysis and fracture assessment.

A FINITE ELEMENT MODEL FOR COMPRESSIVE ICE LOADS BASED ON A MOHR-COULOMB MATERIAL AND THE NODE SPLITTING TECHNIQUE

2021 ◽  
pp. 1-33
Author(s):  
Hauke Herrnring ◽  
Søren Ehlers
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Material Behavior ◽  
Double Pendulum ◽  
Strain Rates ◽  
Splitting Technique ◽  
Structure Interaction ◽  
Node Splitting ◽  
Brittle Mode

Abstract This paper presents a finite element model for the simulation of ice-structure interaction problems, which are dominated by crushing. The failure mode of ice depends significantly on the strain rate. At low strain rates the ice behaves ductile, whereas at high strain rates ice reacts in brittle mode. This paper focuses on the brittle mode, which is the dominating mode for ship-ice interactions. A multitude of numerical approaches for the simulation of ice can be found in the literature. Nevertheless, the literature approaches do not seem suitable for the simulation of continuous ice-structure interaction processes at low and high confinement ratios in brittle mode. Therefore, this paper seeks to simulate the ice-structure interaction with the finite element method (FEM). The objective of the here introduced Mohr-Coulomb Nodal Split (MCNS) model is to represent the essential material behavior of ice in an efficient formulation. To preserve mass and energy as much as possible, the node splitting technique is applied, instead of the frequently used element erosion technique. The intention of the presented model is not to reproduce individual cracks with high accuracy, because this is not possible with a reasonable element size, due to the large number of crack fronts forming during the ice-structure interaction process. To validate the findings of the model, the simulated maximum ice forces and contact pressures are compared with ice-extrusion and double pendulum tests. During validation, the MCNS model shows a very good agreement with these experimental values.

A Three-Dimensional Coupled Finite Element Model for the Simulation of Stress Corrosion on Pipeline Steel

2019 ◽  
Author(s):  
Dongxu Sun ◽  
Ming Wu ◽  
Fei Xie ◽  
Ke Gong
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Stress Corrosion ◽  
Corrosion Behavior ◽  
Pipeline Steel ◽  
Three Dimensional ◽  
Element Model ◽  
Circumferential Direction ◽  
The Self ◽  
Corrosion Defect

Abstract In this study, a three-dimensional finite element model was constructed to study the stress corrosion behavior of pipeline steel. Stress analysis and electrochemical calculation were incorporated into the model through multiphysics field coupling technique. Tensile property and electrochemical corrosion behavior of X70 pipeline steel were measured by experiments to formulate the model. The modeling results show that the corrosion is accelerated on the surface of corrosion defect where the stress tends to concentrate because of mechanoelectrochemical effect. The effect of elastic strain on corrosion enhancement is not obvious. The plastic deformation on defect bottom increases the corrosion rate significantly, especially for the conditions with high operating pressure or large defect depth. The corrosion current distribution indicated that the “self-acceleration effect” exists on corrosion defect. This effect makes the corrosion develop to depth and the shape of corrosion defects is more likely to cause stress concentration, and finally induces corrosion perforation or cracking. The two directions, i.e. axial and circumferential direction, have the different stress corrosion behaviors. The “self-acceleration effect” is more obvious on circumferential direction than that on axial direction, which can explain the phenomenon that there are mostly axial stress corrosion cracks on the pipeline in field.

scholarly journals 4414 Collagen Dermal Replacement Scaffold Mechanobiology in Treatment of Difficult-to-Heal Wounds

2020 ◽  
Vol 4 (s1) ◽  
pp. 4-4
Author(s):  
David Oleh Sohutskay ◽  
Adrian Buganza Tepole ◽  
Sherry Voytik-Harbin
Keyword(s):  
Wound Healing ◽  
Finite Element ◽  
Finite Element Model ◽  
Animal Experiments ◽  
Element Model ◽  
Constitutive Law ◽  
Wound Contraction ◽  
Uniaxial Tensile ◽  
Scanning Electron Micrographs ◽  
Histological Image

OBJECTIVES/GOALS: Difficult-to-heal wounds of the skin are a common and costly medical problem. Dermal replacement strategies have emerged as a solution, but a challenge is identification of optimal scaffold parameters. We present a model for assessment of clinical potential of collagen scaffolds for wound healing. METHODS/STUDY POPULATION: In previous animal experiments, we evaluated dermal replacement scaffolds custom-fabricated from fibril-forming collagen oligomer with controlled fibril density (4, 20, 40mg/cm3) and spatial gradients in rat excisional wounds. Wound contraction and cellularization were monitored by gross and histological image analysis for comparison with model outcomes. We now parameterize the scaffold parameters for use in the mathematical model of wound healing with nonlinear curve fitting. A preliminary chemo-bio-mechanical finite element model including collagen, cells, and an inflammatory signal was adapted to simulate wound healing results. RESULTS/ANTICIPATED RESULTS: Collagen oligomer microstructure was quantified from scanning electron micrographs. A constitutive law for collagen mechanics was fit to experimental uniaxial tensile tests. We have conducted preliminary three-dimensional finite element model simulations to be validated against experimental wound contraction, recellularization, and collagen remodeling data collected from each experimental group. We show the effects of collagen density and stiffness on wound contraction by altering early wound mechanical properties. We anticipate future work to further improve the model of mechanotransduction, inflammation, and recellularization. DISCUSSION/SIGNIFICANCE OF IMPACT: This work represents the first step towards a computational model of wounds treated with collagen scaffold dermal replacements. In turn, the model will be used to explore cell-scaffold interactions for purposes of prediction and optimization of tissue regeneration outcomes.

Miniature Test Technique for Acquiring True Stress–Strain Curves for a Large Range of Strains Using a Tensile Test and Inverse Finite Element Method

2011 ◽  
Vol 110-116 ◽  
pp. 4204-4211 ◽  
Author(s):  
Hafeez Farrukh ◽  
M.N. Desmukh ◽  
Husain Asif ◽  
D.K. Sehgal
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
True Strain ◽  
Element Model ◽  
Conventional Technique ◽  
True Stress ◽  
Constitutive Behavior ◽  
Test Technique ◽  
Miniature Specimen ◽  
Strain Relationship

The paper presents a non conventional technique to predict the constitutive behavior of materials by assessing the true stress–true strain relationship through miniature specimen tests. The miniature test was conducted on two different types of steel ring specimens (outer diameter14mm, inner diameter 8mm, thickeness 0.5mm) with V-notch (1mm depth) added diametrically to it. A finite element model was developed and validated to calculate the load–deflection curve obtained from the miniature specimen experiment. The constitutive behavior assigned to the specimen for the calculations was determined from the standard tensile test. Using an inverse methodology, it was possible to show that the constitutive behavior from the miniature tests using inverse FE procedure, and that from the conventional standard ASTM test bears close resemblance.

Crystallographic effects during micromachining — A finite-element model

2015 ◽  
Vol 29 (22) ◽  
pp. 1550119
Author(s):  
Shin-Hyung Song ◽  
Woo Chun Choi
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Chip Formation ◽  
Orthogonal Cutting ◽  
Element Model ◽  
Material Behavior ◽  
Face Centered Cubic ◽  
Work Material ◽  
User Material Subroutine ◽  
Crystallographic Orientations

Mechanical micromachining is a powerful and effective way for manufacturing small sized machine parts. Even though the micromachining process is similar to the traditional machining, the material behavior during the process is much different. In particular, many researchers report that the basic mechanics of the work material is affected by microstructures and their crystallographic orientations. For example, crystallographic orientations of the work material have significant influence on force response, chip formation and surface finish. In order to thoroughly understand the effect of crystallographic orientations on the micromachining process, finite-element model (FEM) simulating orthogonal cutting process of single crystallographic material was presented. For modeling the work material, rate sensitive single crystal plasticity of face-centered cubic (FCC) crystal was implemented. For the chip formation during the simulation, element deletion technique was used. The simulation model is developed using ABAQUS/explicit with user material subroutine via user material subroutine (VUMAT). Simulations showed that variation of the specific cutting energy at different crystallographic orientations of work material shows significant anisotropy. The developed FEM model can be a useful prediction tool of micromachining of crystalline materials.

Bodner-Partom Constitutive Model and Nonlinear Finite Element Analysis

1990 ◽  
Vol 112 (3) ◽  
pp. 287-291 ◽  
Author(s):  
F. A. Kolkailah ◽  
A. J. McPhate
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Finite Element Model ◽  
Numerical Technique ◽  
Element Model ◽  
Material Behavior ◽  
Model Parameters ◽  
Elastic Plastic

In this paper, results from an elastic-plastic finite-element model incorporating the Bodner-Partom model of nonlinear time-dependent material behavior are presented. The parameters in the constitutive model are computed from a leastsquare fit to experimental data obtained from uniaxial stress-strain and creep tests at 650°C. The finite element model of a double-notched specimen is employed to determine the value of the elastic-plastic strain and is compared to experimental data. The constitutive model parameters evaluated in this paper are found to be in good agreement with those obtained by the other investigators. However, the parameters determined by the numerical technique tend to give response that agree with the data better than do graphically determined parameters previously used. The calculated elastic-plastic strain from the model agreed well with the experimental strain.

Strength Analyses of Sandwich Pipes for Ultra Deepwaters

2004 ◽  
Vol 72 (4) ◽  
pp. 599-608 ◽  
Author(s):  
Segen Farid Estefen ◽  
Theodoro Antoun Netto ◽  
Ilson Paranhos Pasqualino
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Ultimate Strength ◽  
Thermal Insulation ◽  
Research Work ◽  
Element Model ◽  
Material Behavior ◽  
Core Material ◽  
Small Scale ◽  
Mechanical Resistance

Design requirements for pipelines regarding both ultimate strength and flow assurance in ultra deepwater scenarios motivated the development of a new sandwich pipe which is able to combine high structural and thermal insulation properties. In this concept, the annulus is filled with low cost materials with adequate thermal insulation properties and good mechanical resistance. The aim of this research work is to perform small-scale laboratorial tests and to develop a finite element model to evaluate the structural performance of such sandwich pipes with two different options of core material. After calibrated in view of the experimental results, a three-dimensional finite element model incorporating nonlinear geometric and material behavior is employed to perform strength analyses of sandwich pipes under combined external pressure and longitudinal bending. Ultimate strength envelopes for sandwich pipes are compared with those generated for single-wall steel pipes with equivalent collapse pressures. The study shows that sandwich pipe systems with either cement or polypropylene cores are feasible options for ultra deepwater applications.

scholarly journals Finite Element Analysis and Experimental Characterisation of SMC Composite Car Hood Specimens under Complex Loadings

2018 ◽  
Vol 2 (3) ◽  
pp. 53
Author(s):  
Josh Kelly ◽  
Edward Cyr ◽  
Mohsen Mohammadi
Keyword(s):  
Finite Element ◽  
Composite Materials ◽  
Finite Element Model ◽  
Volume Fraction ◽  
Failure Strain ◽  
Fibre Volume Fraction ◽  
Element Model ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
Structural Applications

Composite materials have recently been of particular interest to the automotive industry due to their high strength-to-weight ratio and versatility. Among the different composite materials used in mass-produced vehicles are sheet moulded compound (SMC) composites, which consist of random fibres, making them inexpensive candidates for non-structural applications in future vehicles. In this work, SMC composite materials were prepared with varying fibre orientations and volume fractions (25% and 45%) and subjected to a series of uniaxial tensile and flexural bending tests at a strain rate of 3 × 10−3 s−1. Tensile strength as well as failure strain increased with the increasing fibre volume fraction for the uniaxial tests. Flexural strength was found to also increase with increasing fibre percentage; however, failure displacement was found to decrease. The two material directions studied—longitudinal and transverse—showed superior strength and failure strain/displacement in the transverse direction. The experimental results were then used to create a finite element model to describe the deformation behaviour of SMC composites. Tensile results were first used to create and calibrate the model; then, the model was validated with flexural experimental results. The finite element model closely predicted both SMC volume fraction samples, predicting the failure force and displacement with less than 3.5% error in the lower volume fraction tests, and 6.6% error in the higher volume fraction tests.

Investigation of the Mechanical Properties of a Stitched Triaxial Fabric

2014 ◽  
Vol 611-612 ◽  
pp. 332-338 ◽  
Author(s):  
Cynthia J. Mitchell ◽  
James A. Sherwood ◽  
Lisa M. Dangora ◽  
Jennifer L. Gorczyca
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Material Behavior ◽  
Composite Forming ◽  
Experimental Deformation ◽  
Shear Frame ◽  
The Finite Element Model ◽  
The Ideal

A traxial fabric was investigated for use in composite forming applications. Three stitched layers of fibers, originally oriented at [-60o/0o/60o], comprise the fabric architecture. The mechanical properties of the material are characterized by testing the tensile, shear, and frictional behavior. Conventional shear frame testing methodology assumes that the yarns are originally oriented perpendicular to one another; however, such an assumption is not valid for this particular fabric geometry and must be adjusted. The material behavior is implemented into a discrete mesoscopic finite element model that can predict the response of the material during deformation. Different element types will be investigated to represent the fabric and used to determine the ideal mesh configuration that best captures the fabric behavior. Different modes of deformation will also be studied, and the observed experimental deformation will be compared to the deformation predicted by the finite element model.

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