Fracture Initiation in Compact Tension Specimens of Hydrided Irradiated Zr-2.5Nb Materials With Split Circumferential Hydrides

2017 ◽  
Author(s):  
Shin-Jang Sung ◽  
Jwo Pan ◽  
Poh-Sang Lam ◽  
Douglas A. Scarth
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Tensile Tests ◽  
Compact Tension ◽  
Transverse Tensile ◽  
Stress Strain Relation ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Fracture initiation in compact tension (CT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is examined by conducting three-dimensional finite element analyses with submodeling. The stress-strain relation for the irradiated Zr-2.5Nb materials is based on the experimental results of transverse tensile tests. For CT specimens with split circumferential hydrides, plastic strain concentration is observed in the middle of the ligaments ahead of the crack front. With a strain-based failure criterion with consideration of stress triaxiality, the necessary fraction of the load for crack initiation is about 0.55 to 0.70 to fracture the ligaments when compared to that for a CT specimen without split circumferential hydrides. The computational results can be used to explain the near 40% reduction of the fracture toughness at room temperature obtained from hydrided irradiated curved compact tension specimens (CCTSs) when compared with that from unhydrided irradiated ones.

Fracture Initiation in Pressure Tube Specimens of Hydrided Irradiated Zr-2.5Nb Materials With Split Circumferential Hydrides

2017 ◽  
Author(s):  
Shin-Jang Sung ◽  
Jwo Pan ◽  
Poh-Sang Lam ◽  
Douglas A. Scarth
Keyword(s):  
Crack Initiation ◽  
Crack Front ◽  
Room Temperature ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Pressure Tube ◽  
Computational Results ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Fracture initiation for axial cracks in pressure tube (PT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides at room temperature is examined by conducting three-dimensional finite element analyses. With a strain-based fracture criterion with consideration of stress triaxiality, the location for the earliest crack initiation is determined near the middle of the axial crack front. For PT specimens with split circumferential hydrides, three types of strain concentration are observed in the ligaments ahead of the crack front. The computational results suggest that the internal pressure for crack initiation of hydrided irradiated PT specimens with many randomly distributed split circumferential hydrides needs only 55% to 70% of that for unhydrided irradiated PT specimens. The computational results can be used to explain the near 40% reduction of the fracture toughness at room temperature obtained from hydrided irradiated PT specimens when compared with that from unhydrided irradiated ones.

Comparative Study of Predictive Finite Element Methods for Mechanical Properties in 2D Woven Carbon/Carbon Composites

2008 ◽  
Vol 59 ◽  
pp. 116-119
Author(s):  
Joshim Ali ◽  
Derek Buckthorpe ◽  
Allister Cheyne ◽  
Johar Farooqi ◽  
Paul M. Mummery
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Unit Cell ◽  
Carbon Composites ◽  
Fe Model ◽  
Dimensional Finite Element ◽  
Composite Microstructure ◽  
Tomographic Data ◽  
Three Dimensional Finite Element

Three-dimensional finite element (FE) methods are used to predict the Young’s modulus of two types of 2D woven carbon/carbon composites. Tensile tests are performed to validate the predictions. The results indicate that a novel image-based route in generating FE meshes gave strong agreement with experimental data, while a comparative unit cell FE model of the structure was found to be poorer. The differences between the image-based and unit cell methodologies were the consideration of the finer architectures of the composites and their porosity. The image-based approach highlighted true porosity in the structure due to meshes forming directly from X-ray tomographic data. However, the finer fibre architectures of the composites were compromised because of limitations in the pixel resolutions employed during the initial scanning process. In comparison, the unit cell models were based solely on idealisations of the composite microstructure, in which porosity was neglected.

Fatigue Behavior and Deformation of Aluminum and Steel HVOF Sprayed with WC-Co Coatings

1997 ◽  
Author(s):  
A. Ibrahim ◽  
C.C. Berndt
Keyword(s):  
Fatigue Life ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Element Model ◽  
Fatigue Tests ◽  
Dimensional Finite Element ◽  
Life Distributions ◽  
Three Dimensional Finite Element ◽  
Good Agreement

Abstract The effect of WC-Co coating on the high cycle fatigue (HCF) behavior of SAE 12L14 steel and 2024-T4 aluminum was investigated. The fatigue tests were performed at room temperature and 370°C. The fatigue life distributions of specimens in the polished, grit blasted, peened, and coated conditions are presented as a function of the probability of failure. HVOF sprayed WC-Co coating has influenced the fatigue life of aluminum and steel. Factors contributing to this influence, which include grit blasting, elastic modulus, and residual stress, are discussed. A three-dimensional finite-element model (FEM) of the coated specimen was used to calculate the stress distribution across the coating and the substrate. The results of the analytical model are in good agreement with fatigue lives observed experimentally.

scholarly journals Interaction of void spacing and material size effect on inter-void flow localisation

2020 ◽  
pp. 1-13
Author(s):  
Ingrid Holte ◽  
Ankit Srivastava ◽  
Emilio Martínez-Pañeda ◽  
Christian F. Niordson ◽  
Kim L. Nielsen
Keyword(s):  
Size Effect ◽  
Strain Gradient ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Void Coalescence ◽  
Porous Metals ◽  
Dimensional Finite Element ◽  
Stress States ◽  
Three Dimensional Finite Element ◽  
Ligament Size

Abstract The ductile fracture process in porous metals due to growth and coalescence of micron scale voids is not only affected by the imposed stress state but also by the distribution of the voids and the material size effect. The objective of this work is to understand the interaction of the inter-void spacing (or ligaments) and the resultant gradient induced material size effect on void coalescence for a range of imposed stress states. To this end, three dimensional finite element calculations of unit cell models with a discrete void embedded in a strain gradient enhanced material matrix are performed. The calculations are carried out for a range of initial inter-void ligament sizes and imposed stress states characterised by fixed values of the stress triaxiality and the Lode parameter. Our results show that in the absence of strain gradient effects on the material response, decreasing the inter-void ligament size results in an increase in the propensity for void coalescence. However, in a strain gradient enhanced material matrix, the strain gradients harden the material in the inter-void ligament and decrease the effect of inter-void ligament size on the propensity for void coalescence.

Three-Dimensional Finite Element Analyses of Thin-Sliced Compact Tension Specimens of Irradiated Zr-2.5Nb Materials With Consideration of Split Circumferential Hydrides

2016 ◽  
Author(s):  
Shin-Jang Sung ◽  
Jwo Pan ◽  
Poh-Sang Lam ◽  
Douglas A. Scarth
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
Three Dimensional ◽  
Compact Tension ◽  
Finite Element Analyses ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Unit Thickness ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, the low energy mode associated with split circumferential hydrides is examined by conducting three-dimensional finite element analyses of thin-sliced compact tension (CT) specimens of irradiated Zr-2.5Nb materials with split circumferential hydrides. Finite element models of thin-sliced CT specimens with split circumferential hydrides and various slice thicknesses are developed with the assumption of the plane strain condition in the thickness direction except in the split circumferential hydride regions. The computational results indicate that with split circumferential hydrides, the crack tip opening displacement (CTOD) can increase 50% for thinner thin-sliced specimens under the same load per unit thickness. With the use of a strain-based failure criterion with split circumferential hydrides, the load per unit thickness for thinner thin-sliced specimens can reduce by at most 70% to meet the failure criterion.

Influences of Thermo-Mechanical Properties of Polymeric Cords on Tires with and without Post-Cure Inflation

2002 ◽  
Vol 30 (3) ◽  
pp. 156-179 ◽  
Author(s):  
B. Chen
Keyword(s):  
Material Characterization ◽  
Room Temperature ◽  
Three Dimensional ◽  
Dimensional Change ◽  
Element Model ◽  
Thermal Shrinkage ◽  
Cooling Process ◽  
Dimensional Finite Element ◽  
Overall Performance ◽  
Three Dimensional Finite Element

Abstract During manufacturing, tires are naturally cooled to room temperature after release from their molds. The manner in which the post-cure cooling process is performed can greatly influence a tires overall performance. As an effective procedure, post-cure inflation (PCI) had been commonly used during the post-cure cooling process to control dimensions and shapes of tires. However, since the introduction of dimensionally stable polyester as tire carcass cord material, PCI has been considered an unnecessary step and has been eliminated from some tire manufacturer's lines. By convention, tires manufactured with PCI are designated as PCI tires whereas tires manufactured without PCI are designated as no-PCI tires. As a result of the different loading histories experienced during the post-cure cooling process, PCI and no-PCI tires exhibit different behavioral aspects including dimensions and footprint shape. More specifically, when the same mold is used, the most prominent difference between PCI and no-PCI tires is the profile. No-PCI tires have smaller section widths and inflated crown radii than PCI tires due to the thermal shrinkage occurring in the cords during the post-cure cooling process. On the other hand, no-PCI tires exhibit more dimensional change than PCI tires when subjected to exercise. In this study, experimental passenger tires (235/75/R15) with and without PCI are built using the same curing mold, and a series of tests are conducted to establish the differences between these two kinds of tires. Meanwhile, material characterizations of the polyester tire cords used in the tire construction are conducted with various thermal-mechanical loading histories, and the influences of the post-cure cooling process on the cord properties are determined. Then an axisymmetric and a three-dimensional finite element model are constructed and the post-cure cooling processes with and without PCI are simulated. With the input of the cord material properties obtained through the material characterization, the numerical analyses successfully predict the tire dimensions, profile, and footprints for both PCI and no-PCI tires. The analytical results obtained are in agreement with the experimental measurements obtained from the experimental tires.

Three-dimensional finite element analysis and strength evaluation of link chains in chain hoists subjected to impact loads

1996 ◽  
Vol 31 (1) ◽  
pp. 43-51 ◽  
Author(s):  
T Hiroshima ◽  
T Sawa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Chain Elongation ◽  
Impact Loads ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Von Mises ◽  
Three Dimensional Finite Element

Elastoplastic stresses in link chains subjected to impact loads are analysed using a finite element method. The code employed is ‘DYNA3D’. Chain strength is predicted by using the von Mises criterion. The effects of chain dimensions on the stress distribution, a location where rupture occurs, and on the chain strength are examined. Measurement of the strains in link chain and impact tensile tests were also performed when impact loads were applied to a link. Fairly good agreement is seen between the numerical and the experimental results. It was found that chain strength can be predicted by using the relationship between chain elongation and impact energy. The chain strength can be improved by optimizing the chain geometry (pitch, width and compressed depth) using finite element analysis.

Three-Dimensional Finite Element Analyses of Compact Tension Specimens of Irradiated Zr-2.5Nb Materials Using Submodeling

2016 ◽  
Author(s):  
Shin-Jang Sung ◽  
Jwo Pan ◽  
Poh-Sang Lam ◽  
Douglas A. Scarth
Keyword(s):  
Finite Element ◽  
Plastic Zone ◽  
Crack Front ◽  
Three Dimensional ◽  
Crack Tip ◽  
Compact Tension ◽  
Finite Element Analyses ◽  
Middle Portion ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, the crack tip stresses along the front of a crack in a compact tension (CT) specimen of irradiated Zr-2.5Nb material are investigated by three-dimensional finite element analyses using the submodeling technique. A parametric study on two-dimensional submodeling of a CT specimen was first conducted to determine the appropriate mesh near the crack tip of a global model and the appropriate size of a submodel. The results show that the collapsed elements should be used near the crack tip in a global model and the region of a submodel should at least enclose the plastic zone to achieve acceptable results. With the submodeling strategy, a three-dimensional finite element analysis of the CT specimen is conducted. The distributions of the opening stress and out-of-plane normal stress ahead of the front of a crack in the CT specimen are obtained. Based on the computational results with the hydride fracture stress of 750 MPa for both radial and circumferential hydrides, all radial hydrides ahead of the crack front and the circumferential hydrides in the middle portion of the specimen should fracture at the specimen load of 3,000 N. Circumferential hydrides near the free surfaces do not fracture and the size of the zone without fractured circumferential hydrides increases with the increasing radial distance to the crack front. The computational results also show the three-dimensional effects on the variation of the plastic zone size and shape along the crack front, that is different from the conventional understanding of a dog-bone shape where the plastic zone on the free surface follows that under plane stress conditions and the plastic zone near the middle portion of the crack front follows that under plane strain conditions.

scholarly journals Characteristics of selected measures of stress triaxiality near the crack tip for 145Cr6 steel - 3D issues for stationary cracks

2020 ◽  
Vol 10 (1) ◽  
pp. 571-585
Author(s):  
Marcin Graba
Keyword(s):  
Finite Element Method ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Fem Analysis ◽  
Material Constant ◽  
Stress Fields ◽  
Material Characteristic ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

AbstractIn the paper the numerical analysis of the stress fields for 145Cr6 steel, near crack tip is presented, based on three-dimensional finite element method (FEM) analysis. The FEM analysis is focused on SEN(B) specimens with relative crack length a/W ≈ 0.30. In addition to the presentation of the normal components of the stress tensor, the paper presents selected measures of stress triaxiality parameters, measured for the value of the J-integral, corresponding to the experimentally determined fracture toughness, denoted as JIC, which is considered to be a material constant or material characteristic [1, 2]. Presented topic is a continuation of papers [3, 4],whichwere based on experimental analysis, presented in [5].

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