Elastic-Plastic Analysis of Crack Opening, Stable Growth and Instability Behavior in Flawed 304 SS Piping

1983 ◽  
Vol 105 (4) ◽  
pp. 290-298 ◽  
Author(s):  
M. D. German ◽  
V. Kumar
Keyword(s):  
Applied Load ◽  
Failure Load ◽  
Crack Opening ◽  
Stress Criterion ◽  
Applied Loading ◽  
Area Of Interest ◽  
Bending Effect ◽  
Stable Growth ◽  
Flaw Type ◽  
Growing Cracks

Crack initiation, stable growth, instability and crack opening behavior in flawed 304 SS piping has been examined within the framework of the engineering approach developed by Kumar, German and Shih [1]. Crack geometries considered include part-through, complete circumferentially cracked pipe subjected to remote tension, and through-wall flawed pipe in tension and in bending. Effect of flaw type and size, pipe diameter and length, and applied loading on the failure load and mechanism is investigated. Results are employed to assess the net section stress criterion based on plastic collapse. Crack opening area of interest in leak rate evaluations is calculated as a function of applied load or pipe end deflection for stationary as well as growing cracks.

A Fundamental Study of the Interaction of Residual Stress and Applied Loading on Fracture

2010 ◽  
Author(s):  
C. J. Aird ◽  
M. J. Pavier ◽  
D. J. Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Crack Closure ◽  
Applied Load ◽  
Element Model ◽  
Residual Stress Field ◽  
Fundamental Study ◽  
Analytical Expression ◽  
Applied Loading

This paper presents the results of a fundamental finite-element based study of the crack-closure effects associated with combined residual and applied loading. First, an analytical expression for a representative two-dimensional residual stress field is derived. This residual stress field contains a central compressive region surrounded by an equilibrating tensile region. The analytical expression allows the size and shape of the field to be varied along with the magnitude of the residual stress. The residual stress field is then used as a prescribed initial stress field in a finite element model, in addition to a far field applied load. By introducing cracks of increasing length into these models, charts of stress-intensity-factor versus crack length are produced for different relative magnitudes of residual stress and applied load and for different sizes and shape of the residual stress field. These charts provide insight into the way in which crack-tip conditions evolve with crack growth under conditions of combined residual and applied loading and also enable conditions of crack closure and partial closure to be identified.

Study on Weld Fatigue Evaluation Incorporating Welding Induced Residual Stress Effect

2016 ◽  
Author(s):  
Jeong K. Hong
Keyword(s):  
Residual Stress ◽  
Applied Load ◽  
Fatigue Behavior ◽  
Load Ratio ◽  
Stress Effect ◽  
Structural Stress ◽  
Applied Loading ◽  
Welded Structure ◽  
Residual Stress Effect ◽  
Weld Fatigue

For fatigue assessment of a welded structure, an important characteristic is the failure location. The fatigue crack begins from the pre-existing crack-like flaw which is an inherent feature of a weld toe or root. Residual stress in the welded joints is another important characteristic. It is also well known that tensile residual stress in welded structures can be as high as the material yield strength level and so the fatigue strength of the welded joint is governed by the applied stress range regardless of the applied load ratio. However, when the presumed conditions with high tensile residual stress in the weld regime are not satisfied, the fatigue behavior in welded structure deviates from the general weld fatigue behavior. In this paper, firstly the applied load ratio effect on fatigue behavior is investigated for two different residual stress levels of welds, i.e., as-welded and stress relieved. It has been observed that stress-relieving effect of welds is apparent when the applied loading introduces stress fluctuations in compressive loading. When the load ratio effect is considered in Battelle structural stress based fatigue parameter, the stress relieved weld fatigue data was consolidated within the master S-N curve. Based on this investigation, the Battelle structural stress based effective load ratio considering both applied loading and detailed residual stress is introduced for the weld fatigue behavior. The two-stage crack growth model is reformulated with the structural stress based effective load ratio, which is a function of crack length. Lastly, a fatigue life prediction procedure incorporating residual stress effect is proposed and validated using the existing fatigue test results. The proposed procedure clearly shows that the compressive residual stress distributions at the weld prone to crack provide great benefits for fatigue life improvement.

Fracture mechanics in design and service: ‘living with defects’ - Assessment of defects: the c.o.d. approach

1981 ◽  
Vol 299 (1446) ◽  
pp. 155-167 ◽  
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Opening ◽  
Local Stress ◽  
Concentration Effects ◽  
Opening Displacement ◽  
Widespread Application ◽  
Linear Elastic ◽  
Applied Loading ◽  
Displacement Approach

In welded construction particular problems arise with the application of fracture mechanics for the assessment of the effect of defects on structural performance. In many practical cases the use of plane strain linear elastic fracture mechanics methods is invalidated by the actual material thicknesses of interest, by residual stresses or by local stress concentration effects, and by local yielding. The crack opening displacement approach was originally devised as a means of extending linear elastic methods to more widespread application to welded structures. This required the development of a means of assessing fracture toughness, and a means of relating this fracture toughness to the applied loading conditions, and to sizes and types of defects which might be present. The success of this method of assessing defects over a period of some 10-12 years will be illustrated, together with a discussion of the inherent limitations of the approach and possible improvements resulting from recent research into slow tearing and design curve relationships.

A Novel Robust Remeshing Finite Element Technique for Fracture Propagation

2020 ◽  
pp. 2050040
Author(s):  
L. D. C. Ramalho ◽  
J. Belinha ◽  
R. D. S. G. Campilho
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Opening ◽  
Crack Tip ◽  
Weighted Average ◽  
Fixed Number ◽  
Stress Criterion ◽  
Maximum Tangential Stress Criterion ◽  
Maximum Crack ◽  
Element Technique

In this work, a novel and robust remeshing algorithm for crack opening problems is proposed, combined with triangular plane stress finite elements. In the proposed algorithm, the crack tip efficiently propagates until a pre-established maximum crack length is achieved and the crack propagation direction is defined considering the maximum tangential stress criterion. The stress state at the crack tip is obtained using a weighted average of the stresses of the integration points adjacent to the crack tip, to smoothen the stress field near the crack tip. In order to achieve accurate stress fields in the vicinity of the singularity, the proposed algorithm establishes that there is always a fixed number of nodes and elements surrounding the crack tip. To verify the accuracy of the algorithm, three benchmark tests were analyzed and the solutions were compared with results available in the literature. It was observed that the proposed technique allows to maintain the meshes regular during the propagation process, significantly reducing the number of distorted elements, which solves one of the main problems when simulating crack propagation with the finite element method (FEM). Additionally, the obtained results allowed to understand that this algorithm generally leads to accurate crack paths.

Failure Analysis of Bolted Composite Joint Based on Extended Finite Element

2011 ◽  
Vol 488-489 ◽  
pp. 771-774
Author(s):  
Zhen Qing Wang ◽  
Song Zhou ◽  
Jian Sheng Zhou ◽  
Xiao Di Wu
Keyword(s):  
Finite Element ◽  
Failure Analysis ◽  
Failure Load ◽  
High Strength ◽  
Maximum Principal Stress ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Geometrical Parameters ◽  
Stress Criterion ◽  
Composite Joint

In this paper, the influence of geometrical parameters on failure load of bolted single-lap composite joint was investigated. The composite laminate was manufactured from HTA/6376, a high-strength carbon fiber–epoxy material currently used in primary structures in the European aircraft industry. Two geometrical parameters which were plate width-to-hole diameter ratio (W/D), and the edge-to-hole diameter ratio (E/D) were analyzed. To avoid modeling each ply of the laminates discretely, the laminates were modeled using equivalent linear elastic properties. the failure analysis was modeled by Extend Finite Element Method (XFEM) in ABAQUS. Maximum principal stress criterion (Maxps) was used to determine the failure load.

Determining the Remaining Prestress Force in a Prestressed Concrete Railroad Tie Through Loading in Direct Tension

2018 ◽  
Author(s):  
James D. Scott ◽  
Robert J. Peterman ◽  
B. Terry Beck ◽  
Aaron A. Robertson ◽  
Kyle A. Riding ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Prestressed Concrete ◽  
Applied Load ◽  
Crack Opening ◽  
Previous Method ◽  
Opening Displacement ◽  
Cross Sectional ◽  
Prestressing Steel ◽  
Prestressing Force ◽  
The Cross

Extensive research has been conducted by the research team in recent years to determine the prestressing steel and concrete properties that must be provided to ensure that the transfer length of a prestressed concrete railroad tie is shorter than the distance from the edge of the tie to the rail seat. In addition, a significant of amount of data has been collected that indicates high bonding stresses can produce longitudinal splitting cracks along the reinforcement. In a study of how prestressing steel and concrete properties relate to a ties propensity for longitudinal cracking, existing ties that have performed well in track for over 25 years without issues are being evaluated. One parameter of interest that affects the bonding stress is the amount of prestress force in a railroad tie, which is unknown for the existing ties being evaluated. The current paper focuses on a new method that was developed for determining the remaining prestress force in a tie. In a previous method for determining the prestress force, ties were first loaded in four-point bending to initiate flexural cracking. The crack opening displacement was measured in order to determine the applied load required to reopen the crack. Using this load and the cross-sectional parameters at the location of the crack, the prestress force in the tie can be calculated using static equilibrium. The issue with this method is that as a tie is being loaded and the crack propagates, there is a continuous change in the stiffness of the cross-section. This results in the load versus crack opening displacment curve being overly rounded. This increases the error when determining the load required to reopen the crack, and increases the uncertainty of the calculated prestress force. The new test method eliminates the problems associated with flexural testing by loading the ties longitudinally in tension. In the new proposed experimental method, ties that have been pre-cracked in the center are pulled in tension. Similar to the previous method, the crack opening displacement is measured while the tie is loaded. For the crack to fully open, the applied load must exceed the prestress force holding the crack closed. Prior to the crack opening, the applied load is resisted by the composite section of concrete and prestressing tendons. Once the crack as fully opened, the applied load is resisted by the prestessing tendons only. This creates two distinctly linear portions of the load versus crack opening displacement curve, one prior to the crack opening, and one after. The beginning of the linear portion post-crack opening marks a very clear upper bound for the amount of prestressing force in a tie. This method can estimate the remaining prestress force in a tie with much greater accuracy than the previous method, and eliminates the need of the cross-sectional parameters at the crack location. To verify this method, tests were first conducted on a smaller scale with prismatic beams with a known initial prestressing force. Then the method was applied to a full scale existing tie to determine the remaining prestress force. Results are presented for testing of both the prismatic beams, and the full scale tie.

A Two-Parameter Description of the Behaviour of a Process Zone at a Crack Tip: Part II — Determination of the Parameters

2004 ◽  
Author(s):  
E. Smith
Keyword(s):  
Process Zone ◽  
Crack Opening ◽  
Crack Tip ◽  
Relative Displacement ◽  
Zone Model ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Face ◽  
Applied Loading ◽  
Crack Tip Opening

An earlier paper (Part I) has shown how key parameters associated with the uniform stress process zone model of a crack: crack tip opening displacement, process zone size, crack opening area and the effective opening area of the process zone, depend upon parameters that are associated with the relevant terms in the expansion of the expression, for the purely elastic situation, for the relative displacement of the crack faces or the stress ahead of an elastic crack. The earlier paper focussed upon the case where the non-linear (with regards to applied stress) contributions to the crack-process zone parameters were determined to the first two terms in increasing powers of the applied loading stress parameter. These terms depend upon the first two terms in the expressions for the crack face relative displacement on the stress ahead of the crack in the elastic situation. The first of these terms is related to the stress intensity factor. In this paper we show how the parameter g0, which defines the second term, can be determined for some idealised situations.

Direct observation of crack opening as a function of applied load in the interior of a notched tensile sample of AlLi 2090

1997 ◽  
Vol 45 (5) ◽  
pp. 1977-1987 ◽  
Author(s):  
A. Guvenilir ◽  
T.M. Breunig ◽  
J.H. Kinney ◽  
S.R. Stock
Keyword(s):  
Direct Observation ◽  
Applied Load ◽  
Crack Opening ◽  
Tensile Sample

Boundary element analysis of cracked panels with mechanically fastened repair patches

2002 ◽  
Vol 37 (3) ◽  
pp. 223-238 ◽  
Author(s):  
P. H Wen ◽  
M H Aliabadi ◽  
A Young
Keyword(s):  
Stress Intensity ◽  
Boundary Element ◽  
Crack Opening ◽  
Lap Joints ◽  
Boundary Integral ◽  
Element Analysis ◽  
Bending Effect ◽  
Mechanically Fastened ◽  
Membrane Problem ◽  
Shear Deformable

In this paper, lap joints and mechanically attached repairs containing cracks are analysed by the boundary element method. A coupled boundary integral formulation of shear deformable plate and two-dimensional plane stress elasticity is utilized to allow the modelling of bending and membrane forces. Stress intensity factors, three for the bending problem and two for the membrane problem, are evaluated from crack-opening displacements. Several examples are presented to demonstrate the accuracy and robustness of the proposed method. The stress intensity factor solutions are shown to be dominated by the bending effect.

Sign in / Sign up

Export Citation Format

Share Document