Investigation of Torsional Stress Intensification Factors and Stress Indices for Girth Butt Welds in Straight Pipe

2002 ◽  
Author(s):  
Edward A. Wais ◽  
E. C. Rodabaugh ◽  
R. Carter
Keyword(s):  
Carbon Steel ◽  
Test Data ◽  
Straight Pipe ◽  
Butt Weld ◽  
Bending Tests ◽  
Butt Welds ◽  
Stress Indices ◽  
Stress Intensification Factor ◽  
Torsional Test ◽  
Fatigue Evaluation

The basis for fatigue evaluation of ASME Section III Class 2, 3 and B31.1 piping is the girth butt weld where the Stress Intensification Factor (SIF) is defined to be 1.0. The SIFs for other components are based on comparison to the butt welds. This SIF of 1.0 for butt welds is based on extensive bending tests on carbon steel straight pipe which are reviewed and summarized in this study. The results of new test data, including torsional test data, are presented. The authors are unaware of any previous torsional tests on carbon steel straight pipe. This new data leads to suggested changes in the codes taking into account the directionality of the loading.

Stress Intensification Factor for Large Diameter Welding Tee Connections

2015 ◽  
Author(s):  
Sadjad Ranjbaran ◽  
Akbar Daneshvar Ghalelar
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Large Diameter ◽  
Piping System ◽  
Bending Moments ◽  
Straight Pipe ◽  
Butt Welds ◽  
Beam Elements ◽  
Stress Intensification Factor ◽  
Fatigue Characteristics

Stress Intensification Factors (SIFs) are factors relating to fatigue characteristics of piping components. SIF is fatigue correlation which compares fatigue life of a typical piping component such as a tee and elbow to the reference fatigue life, that is girth butt welds in straight pipe subjected to bending moments. In order to calculate localized stress of such piping component, above mentioned figured out SIF shall be multiplied by nominal stress. ASME B31 contains several formulas for stress intensification factors considering limitation that those formulas are valid only for D/T≤100 (diameter to thickness). Extending the valid range mentioned in ASME B31 this paper is dedicated to SIF calculation for D/T≤100 and also for D/T>100 by utilizing Finite Element Analyzing (FEA) for welding tee. The computed SIF for D/T>100 welding tee can now be placed to typical pipe stressing program which analyzes piping system using beam elements. In addition, this paper investigates the effect of Rx (the magnitude of corner radius of shoulder at branch) on SIF of Welding Tee Connections.

scholarly journals Determination of Constraint-Modified J-R Curves for Carbon Steel Storage Tanks

2002 ◽  
Author(s):  
P.-S. Lam ◽  
Y. J. Chao ◽  
X.-K. Zhu ◽  
Y. Kim ◽  
R. L. Sindelar
Keyword(s):  
Carbon Steel ◽  
Test Data ◽  
Storage Tank ◽  
Closed Form Solution ◽  
Crack Tip ◽  
Form Solution ◽  
Fracture Parameter ◽  
Element Analysis ◽  
Crack Tip Constraint ◽  
Senb Specimen

Mechanical testing of A285 carbon steel, a storage tank material, was performed to develop fracture properties based on the constraint theory of fracture mechanics. A series of single edge-notched bend (SENB) specimen designs with various levels of crack tip constraint were used. The variation of crack tip constraint was achieved by changing the ratio of the initial crack length to the specimen depth. The test data show that the J-R curves are specimen-design-dependent, which is known as the constraint effect. A two-parameter fracture methodology is adopted to construct a constraint-modified J-R curve, which is a function of the constraint parameter, A2, while J remains the loading parameter. This additional fracture parameter is derived from a closed form solution and can be extracted from the finite element analysis for a specific crack configuration. Using this set of SENB test data, a mathematical expression representing a family of the J-R curves for A285 carbon steel can be developed. It is shown that the predicted J-R curves match well with the SENB data over an extensive amount of crack growth. In addition, this expression is used to predict the J-R curve of a compact tension specimen (CT), and reasonable agreement to the actual test data is achieved. To demonstrate its application in a flaw stability evaluation, a generic A285 storage tank with a postulated axial flaw is used. For a flaw length of 10% of the tank height, the predicted J-R curve is found to be similar to that for a SENB specimen with a short notch, which is in a state of low constraint. This implies that the use of a J-R curve from the ASTM (American Society for Testing and Materials) standard designs, which typically are high constraint specimens, may be overly conservative for analysis of fracture resistance of large structures.

Four Points Bending Tests on Large Scale Welded Pipes Containing a Through-Wall Defect: Fatigue and Fracture Analysis

2014 ◽  
Author(s):  
M. Bourgeois ◽  
T. Le Grasse ◽  
Y. Kayser
Keyword(s):  
Large Scale ◽  
Structural Integrity ◽  
Atomic Energy Commission ◽  
Electrical Potential ◽  
Potential Drop ◽  
Small Scale ◽  
Butt Weld ◽  
Bending Tests ◽  
Scale Test ◽  
Fracture Tests

Within the framework of European project STYLE (Structural integrity for lifetime management), fracture tests on two large scale pipes containing a through wall crack have been performed. Two Mock-ups have been tested: MU1 is a narrow gap Inconel Dissimilar Metals, provided and designed by AREVA France, and MU2 is a an austenitic steel butt-weld with a thermally aged weld repair austenitic weld, provided by EDF British Energy. The four-points bending tests were carried out by the French Alternative Energies and Atomic Energy Commission (CEA), in order to study the mechanical properties and integrity of component such as welding pipes. A through wall crack was machined in the both pipes. After a fatigue pre-cracking step carried out at RT, the monotonic fracture test was performed (at 300°C on MU1). Optical camera and Electrical Potential Drop Method have allowed following the crack growth during fatigue and final fracture stages. The observations made post-mortem showed ductile tearing of a few millimeters in those pipes. The first part of this paper is devoted to the four-points bending tests. The second part of this paper deals with first numerical analysis related to the Mock-up-1. Previous results concerning the mechanical characterizations of the constitutive materials are discussed. Fracture mechanics small scale specimens are interpreted using FE Analysis to obtain the fracture parameters used in global approaches. First computation is shown on the Mock-up-1 in order to predict the behavior of the large scale test mechanical and fracture behavior.

Development and Preliminary Validation of a 50th Percentile Pedestrian Finite Element Model

2015 ◽  
Author(s):  
Costin D. Untaroiu ◽  
Jacob B. Putnam ◽  
Jeremy Schap ◽  
Matt L. Davis ◽  
F. Scott Gayzik
Keyword(s):  
Finite Element ◽  
Lumbar Spine ◽  
Test Data ◽  
Element Model ◽  
Human Model ◽  
Whole Body ◽  
Fe Model ◽  
Pedestrian Protection ◽  
Bending Tests ◽  
Impact Tests

Pedestrians represent one of the most vulnerable road users and comprise nearly 22% of the road crash related fatalities in the world. Therefore, protection of pedestrians in the car-to-pedestrian collisions (CPC) has recently generated increased attention with regulations which involve three subsystem tests for adult pedestrian protection (leg, thigh and head impact tests). The development of a finite element (FE) pedestrian model could be a better alternative that characterizes the whole-body response of vehicle–pedestrian interactions and assesses the pedestrian injuries. The main goal of this study was to develop and to preliminarily validate a FE model corresponding to a 50th male pedestrian in standing posture. The FE model mesh and defined material properties are based on the Global Human Body Modeling (GHBMC) 50th percentile male occupant model. The lower limb-pelvis and lumbar spine regions of the human model were preliminarily validated against the post mortem human surrogate (PMHS) test data recorded in four-point lateral knee bending tests, pelvic impact tests, and lumbar spine bending tests. Then, pedestrian-to-vehicle impact simulations were performed using the whole pedestrian model and the results were compared to corresponding pedestrian PMHS tests. Overall, the preliminary simulation results showed that lower leg response is close to the upper boundaries of PMHS corridors. The pedestrian kinematics predicted by the model was also in the overall range of test data obtained with PMHS with various anthropometries. In addition, the model shows capability to predict the most common injuries observed in pedestrian accidents. Generally, the validated pedestrian model may be used by safety researchers in the design of front ends of new vehicles in order to increase pedestrian protection.

On the Decrease of Fatigue Limit Due to Small Prestrain

1992 ◽  
Vol 114 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Y. Nagase ◽  
S. Suzuki
Keyword(s):  
Growth Rate ◽  
Carbon Steel ◽  
Fatigue Limit ◽  
Surface Crack ◽  
Fatigue Behavior ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Small Surface ◽  
Bending Tests ◽  
Rotating Bending

Fatigue behavior of plain specimens of low carbon steel subjected to small tensile prestrain is investigated through rotating bending tests and the mechanism of the decrease of fatigue limit due to the prestrain is discussed. It is found that 3 percent prestraining causes the acceleration of both slip and crack initiations, and increases the growth rate of a small surface crack of less than 0.3 mm. It also decreases the fatigue limit. If prestrained material is aged, the fatigue limit increases. These effects of the small prestrain are explained based on the unpinning of locked dislocations due to the prestrain.

Investigation of Stress Indices and Directional Loading of Eccentric Reducers

2003 ◽  
Author(s):  
Edward A. Wais ◽  
E. C. Rodabaugh ◽  
R. Carter
Keyword(s):  
Test Data ◽  
Stress Indices ◽  
Piping Systems ◽  
Class 1

Stress indices and stress intensification factors are used in the design of piping systems that must meet the requirements of ASME Section III for Class 1 and Class 2 systems. This study reviews the present values for eccentric reducers and provides new test data for comparison, which takes into account the directionality of the loading. Suggestions are presented which significantly improve the evaluation of reducers.

Low-Cycle Fatigue Evaluation Using the Weld Master S-N Curve

2006 ◽  
Author(s):  
P. Dong ◽  
Z. Cao ◽  
J. K. Hong
Keyword(s):  
Test Data ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Structural Stress ◽  
Stress Strain ◽  
Strain Behavior ◽  
Scale Test ◽  
Stress Estimation ◽  
Fatigue Evaluation

In the context of fatigue evaluation in the low-cycle regime, the use of the master S-N curve in conjunction with elastic FE-based structural stress calculations is presented. An elastic pseudo structural stress estimation is introduced by assuming that Neuber’s rule applies in relating structural stress and strain concentration at a weld to the material’s cyclic stress-strain behavior. With the pseudo structural stress procedure, recent sources of recent full scale test data on pipe and vessel welds were analyzed as a validation of the proposed procedure. The estimated fatigue lives versus actual test lives show a reasonable agreement. Finally, the feasibility of using monotonic stress-strain curves as a first approximation is also examined for applications when cyclic stress-strain curve may not be readily found. The analysis results indicate that the life estimations using monotonic stress-strain curves are reasonable, with the recent test data falling within mean ± 2σ, where σ represents the standard deviation of the master S-N curve.

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