A Procedure for Verifying the Structural Integrity of an Existing Pressurized Wind Tunnel

1974 ◽  
Vol 96 (4) ◽  
pp. 283-291
Author(s):  
J. T. Taylor ◽  
P. E. Lewis ◽  
J. W. Ramsey
Keyword(s):  
Wind Tunnel ◽  
Fracture Mechanics ◽  
Fatigue Fracture ◽  
Structural Integrity ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Cyclic Life ◽  
Working Pressure ◽  
Test Pressure ◽  
Non Destructive

This paper describes the application of material test, stress-fatigue-fracture mechanics analyses, nondestructive examinations and repairs to verify the structural integrity and the remaining cyclic life in a large pressurized wind tunnel (65,000 ft3) (1840 m3). The tunnel with pressures up to 135 psig (0.93 MPa) was constructed in 1940 and has been in service to the present date. The only record of a non-destructive examination conducted on the vessel prior to this evaluation was a hydrostatic test-pressure at 1 1/2 times the maximum working pressure. The material tests were performed on a sample of material (A-70 steel) cut from the tunnel shell. These tests included fracture toughness (R-curve, Kc) as determined from a compact tension specimen, crack growth rate (da/dn vs ΔK), Charpy V-notch, dynamic tear (from which the nil-ductility temperature was determined), and tensile and chemical tests. The results and applications are presented and discussed. Stress analyses include computer programs based on finite element and numerical integration techniques. Fatigue analyses incorporating a fatigue reduction or stress amplification factor to account for a small flaw existing in a weld are presented. Fracture mechanics analyses of the tunnel shell were performed for (1) the general membrane regions, (2) regions of high bending stress, and (3) areas at tunnel penetrations. The critical flaw sizes at each location are determined. The use of the “leak before break” criterion is discussed. The non-destructive examinations (radiograph, ultrasonic, sonic, and magnetic particle) to verify the assumptions of fatigue-fracture mechanics analyses and ASME Code applications are documented. Penetrations in the tunnel shell that were fatigue limited are shown “before” and “after” repair. The remaining cyclic life as obtained by the fatigue-fracture mechanics analyses and the operating envelope which resulted from these studies for metal temperature vs pressure was determined to be approximately 10 years.

Neutron Diffraction Measurement of the Stress Field During Fatigue Cycling of a Cracked Test Specimen

1989 ◽  
Vol 166 ◽  
Author(s):  
M.T. Hutchings ◽  
C.A. Hippsley ◽  
V. Rainey
Keyword(s):  
Fracture Mechanics ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Test Specimen ◽  
Maximum Stress ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Diffraction Measurement ◽  
Tension Specimen ◽  
Neutron Diffraction Measurement

ABSTRACTThe triaxial stress field has been measured along the centre line of a compact tension specimen in the direction of cracking. The specimen had been subjected to ∼60,000 cycles at δK=31 and Kmax = 34 MPa mm½ and was bolted open at maximum stress. The field was remeasured after the stress had been fully relaxed. The results are discussed in terms of expectations from fracture mechanics calculations.

scholarly journals Fracture Toughness Evaluation of S355 Steel Using Circumferentially Notched Round Bars

2018 ◽  
Vol 47 (2) ◽  
pp. 91-95 ◽  
Author(s):  
Fatih Bozkurt ◽  
Eva Schmidová
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Fracture Load ◽  
Alternative Methods ◽  
Test Procedures ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation

In engineering applications, steels are commonly used in various areas. The mechanical members are exposed to different loading conditions and this subject can be investigated in fracture mechanics. Fracture toughness (KIC) is the important material property for fracture mechanics. Determination of this properties is possible using a compact tension specimen, a single edge notched bend or three-point loaded bend specimen, which are standardized by different institutions. Researchers underline that these standardized methods are complex, the manufacturing process is difficult, they require special fixtures for loading during the experiment and the test procedures are time consuming. Alternative methods are always being sought by researchers. In this work, two different approaches are investigated for S355 steels. In the first method, a circumferentially cracked round bar was loaded in tensile mode and pulled till failure. Using suitable equations, fracture toughness can be calculated. In the second method, a circumferentially notched bar specimen without fatigue pre-cracking was loaded in a tensile machine. By means of fracture load values, fracture toughness was determined by the proposed equations. It can be stated that these two different approaches for calculating fracture toughness are simple, fast and economical.

Structural Evaluation for Repaired J-Weld Portion of Reactor Vessel Head Penetration

2006 ◽  
Author(s):  
Seiji Asada ◽  
Kiminobu Hojo ◽  
Mayumi Ochi ◽  
Itaru Muroya ◽  
Hajime Ito
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Reactor Vessel ◽  
Nuclear Power Generation ◽  
Head Penetration ◽  
Structural Evaluation ◽  
Non Destructive

Leakage was found in a Reactor Vessel (RV) Head Penetration of Ohi unit 3 of the Kansai Electric Power Co., Inc. in May 4, 2004. Non-destructive examinations identified flaws in a J-weld portion of the Head Penetration. The J-weld portion was repaired by using Embedded Flaw Repair Technique [1] that performs welding of 52 weld metal on the J-weld surface remaining the flaws. In order to show the structural integrity of the J-weld portion, a fracture mechanics evaluation was performed in accordance with the Rules on Fitness-for-Service for Nuclear Power Plants of the JSME Codes for Nuclear Power Generation Facilities, JSME S NA1-2002 [2] (hereafter, the JSME Fitness-for-Service Rules) and literatures related. The flaw was characterized as both case of an embedded flaw and a surface flaw and KI for each flaw was directly calculated by using FE analysis. Fatigue crack growth analysis using KI calculated showed the amount of the crack growth was quite small. The fracture mechanics evaluation followed confirmed that the result satisfied the criteria. This paper explains the method and results for evaluation of the structural integrity of the J-weld portion.

Non-Linear Fatigue Fracture Analysis of Composite Laminates

2009 ◽  
Vol 17 (6) ◽  
pp. 371-377 ◽  
Author(s):  
V. Rizov
Keyword(s):  
Crack Growth ◽  
Fatigue Fracture ◽  
Composite Laminates ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Damage Analysis ◽  
J Integral ◽  
Tension Specimen ◽  
Linear Deformation ◽  
Non Linear

In this paper, results of an experimental and numerical investigation of the effects of non-linear deformation on the fatigue crack growth in composite laminates are presented and discussed. Mode I fatigue fracture experiments are carried out on extended compact tension specimens under sinusoidal load control at a frequency of 4 Hz. The fatigue fracture test data are analysed using a power law relationship between the crack growth rates and the range of the path-independent J-integral. A two- dimensional finite element model of the extended compact tension specimen is set up in order to compute the J-integral values. The model is coupled with damage analysis in order to study the effect of non-linear deformation on the fatigue fracture performance. The damage analysis is based on the Tsai-Wu failure criterion. The non-linear model is verified by carrying out comparisons between the simulated mechanical behaviour of the extended compact tension specimen and the measured one. The damage distribution within the specimen is analyzed. The J-integral is computed over paths surrounding the crack tip and not crossing the damage zone. It is shown that taking into account the damage behaviour improves the fatigue fracture resistance, which is attributed to increased strain energy dissipation as a result of non-linear deformation.

scholarly journals NUMERICAL MODELLING SOFTWARE COMPARISON IN CASE OF LINEAR FRACTURE MECHANICS

2015 ◽  
Vol 2 ◽  
pp. 207
Author(s):  
Inga Vanaga ◽  
Andris Siliņš ◽  
Normunds Jēkabsons
Keyword(s):  
Fracture Mechanics ◽  
Numerical Modelling ◽  
Solid Mechanics ◽  
Linear Models ◽  
Mesh Size ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen ◽  
Software Comparison ◽  
Linear Fracture

The paper deals with the accordance's comparison of resources and results of several commercial and solid mechanics numerical modelling software. One of the most common fracture mechanics example is Compact Tension Specimen (CTS) which is used in this paper for testing and comparing the results of commercial solid mechanics numerical modelling software (for instance SolidWorks module CosmosWorks, Unigraphics NX technical analysis module, etc.) using nontrivial examinations to their possibility margins. Standard Griffith (A.A.Griffith) model of energy balance is used in linear models which explores the mesh size influence to the precision of results. Achieved results have been compared mutually and with the examples found in the literature.

Fracture Mechanics and Non-Destructive Testing for Structural Integrity Assessment

2008 ◽  
Vol 399 ◽  
pp. 27-36 ◽  
Author(s):  
Stojan Sedmak ◽  
Aleksandar Sedmak
Keyword(s):  
Fracture Mechanics ◽  
Structural Integrity ◽  
Strain Analysis ◽  
Destructive Testing ◽  
Testing Procedures ◽  
Integrity Assessment ◽  
Loaded Component ◽  
Analysis Of Failures ◽  
Non Destructive

Fracture mechanics parameters can be applied for the analysis of failures of structures, and also for prevention of failures when defects in a structure are detected and defined. The approach is presented through stages: detection of defects, stress-strain analysis of loaded component, characterization of material properties required for structural integrity assessment and application of convenient procedure. In this way the decision about next use of defective component can be made (to continue the operation, increased care by inspection, exclusion the component from next service, with eventual repair, if possible). Special attention is paid to the most popular testing procedures for crack resistance parameters.

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