scholarly journals A Quantitative Index Representing Crack Shapes and Corresponding Techniques

2022 ◽  
Vol 2148 (1) ◽  
pp. 012022
Author(s):  
Junhua Wu ◽  
Tangliang Kuang ◽  
Fangyuan Fu ◽  
Jiahao Li
Keyword(s):  
Crack Propagation ◽  
Information Entropy ◽  
Physical Significance ◽  
Crack Development ◽  
Gray Level ◽  
Grayscale Image ◽  
Test Results ◽  
Quantitative Index ◽  
Program Test ◽  
Soil Cracks

Abstract In order to quantificationally describe the soil cracks due to dry-wet cycles, the concept of gray level entropy is applied according to the physical significance of the information entropy to represent various shapes of cracks. Then a piece of simple and easy-to-use equipment for taking photos is used to monitor and record the crack propagation. A grayscale image and the corresponding gray level entropy are obtained automatically by a program. Test results showed that gray level entropy can quantificationally describe the shape of cracks reasonably well and evaluate the degree of crack development effectively.

Test Stand for Analysis of Fatigue Crack Propagation under Bending with Torsion

2008 ◽  
Vol 144 ◽  
pp. 90-93 ◽  
Author(s):  
Grzegorz Gasiak ◽  
Grzegorz Robak
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Digital Camera ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Test Stand ◽  
Crack Development ◽  
Fatigue Crack Propagation Rate ◽  
Fatigue Crack Development

The paper presents a test stand for measurements of fatigue crack propagation. The stand includes a fatigue machine MZGS–100 and a device for registration of the crack length. The test stand is equipped with a stereoscopic microscope with fluent magnification of 7× – 67.5×. The microscope can be applied for observation of fatigue crack development. The microscope is also equipped with a digital camera, which enables continuous observation of fatigue crack development on the computer monitor and it is not necessary to stop the machine. The test results obtained at this stand can be used for determination of fatigue life and fatigue crack propagation rate.

Crack Propagation Versus Crack Initiation Lives of FPSO Weld Details

2010 ◽  
Author(s):  
Inge Lotsberg ◽  
Mamdouh M. Salama
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Testing ◽  
Fatigue Cracks ◽  
Full Scale ◽  
Test Results ◽  
Inspection Strategy ◽  
Scale Test ◽  
Crack Initiation Life

Documentation of a long crack propagation phase is important for planning a sound inspection program for fatigue cracks in FPSOs. Test results of full scale FPSO weld details have shown that fatigue lives of FPSO details are governed by crack propagation and that crack propagation lives are several times that of the crack initiation life. However, some analysis packages predict a short crack propagation life until failure compared to the crack initiation life. These predictions are not consistent with full scale test results and thus cannot be relied on in developing inspection strategy. The reason for this inconsistency in analysis as compared with test results may be due to limitations in the analysis program packages. The paper presents analysis of fatigue testing data on several full scale FPSO weld details. The paper also discusses the effect of “shake-down’ that is not simulated in the full scale constant amplitude testing and would even lead to longer crack propagation lives under the actual long term loading on FPSOs.

Analysis and Experimental Verification of SCC Characteristics of Typical Chinese Steels for Pressure Vessels Under Wet H2S Environment

2006 ◽  
Author(s):  
Xuedong Chen ◽  
Jialing Jiang ◽  
Tiecheng Yang ◽  
Jiushao Hu ◽  
Zhibin Ai ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Critical Concentration ◽  
Dynamic Control ◽  
Control Process ◽  
Critical Stress Intensity Factor ◽  
Pressure Vessels ◽  
Concentration Limit ◽  
Test Results ◽  
Hydrogen Induced Cracking ◽  
Chinese Standard

In this paper, the estimation expression of critical concentration for hydrogen-induced cracking and estimation expression of critical stress intensity factor KISCC for hydrogen-induced delayed brittle fracture of the three Chinese steels for pressure vessels — 16MnR, 15MnVR and 07MnCrMoVR in Chinese standard GB 6654 are derived first according to SCC mechanism and in combination with fracture mechanics techniques, and verified by comparison with test values. The estimation expressions of diffusion-dominated crack plateau growth rate da/dt of these three materials are derived using Gerberich model based on the analysis of dynamic control mechanism of hydrogen-induced crack propagation under wet H2S environment and the estimated values are verified with the test results for WOL specimens. And the effect of concentration limit and concentration of the medium at normal temperature on the dynamic control process of crack propagation is also discussed.

Investigation of Steam Turbine Nozzle and Blading Efficiency

1940 ◽  
Vol 144 (1) ◽  
pp. 147-164 ◽  
Author(s):  
F. Dollin
Keyword(s):  
Reynolds Number ◽  
Steam Turbine ◽  
High Efficiency ◽  
Dynamic Test ◽  
Mathematical Expression ◽  
Physical Significance ◽  
Dynamic Efficiency ◽  
Test Results ◽  
Turbine Efficiency ◽  
Dynamic Methods

The paper describes the essential characteristics of the passages forming the fixed and moving elements of multistage high-efficiency turbines, whether impulse or reaction. The problems of nozzle investigations by static and dynamic methods are discussed, and a new nozzle tester is described. Reference is made to the Reynolds number; its physical significance is explained, and experimental results are used to demonstrate its effectiveness as a correlative factor. The significance of the static (nozzle) efficiency and the dynamic (turbine) efficiency is discussed, and the essentially different way in which they are affected by the discharge angle is pointed out. A mathematical expression is derived for the relation between static and dynamic efficiency for 50 per cent reaction blading as a function of the discharge angle. This, in conjunction with the Reynolds number, is used to demonstrate the unity and consistency of static and dynamic test results which at first sight seem to be conflicting or unrelated.

Fatigue Crack Propagation in Clad RR58 Sheet to DTD 5070A: Analysis and Correlation of Test Results

1969 ◽  
Vol 73 (700) ◽  
pp. 335-339 ◽  
Author(s):  
D. P. Rooke ◽  
N. J. F. Gunn ◽  
J. T. Ballett ◽  
F. J. Bradshaw
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Aluminium Alloy ◽  
Fatigue Crack Propagation ◽  
Stress Level ◽  
Stress Conditions ◽  
Specimen Geometry ◽  
Aircraft Industry ◽  
Test Results ◽  
Obvious Advantage

In recent years there has been an increasing need for data on the rates of fatigue crack propagation in alloys of interest to the aircraft industry. In general alloys in which cracks grow slowly, under given stress conditions, have an obvious advantage over those in which cracks grow faster; there is more time to detect a crack before failure. It is possible that, in the future, quantitative crack propagation data may be used to give better estimates of the safe life of a structure. There is, however, a need to rationalise the presentation of such data and to study the effect of such parameters as specimen geometry and stress level. Some experiments to investigate the effect of varying some of these parameters in one clad aluminium alloy, DTD 5070A are described. It is a summary of work contained in two RAE Technical Reports.

Research on the Fatigue Assessment Method for Steel Pressure Vessels Containing Surface Defects

2014 ◽  
Vol 628 ◽  
pp. 137-141
Author(s):  
Xian Lei Meng
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Life Prediction ◽  
Safety Assessment ◽  
Surface Defects ◽  
Great Influence ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Test Results ◽  
Fatigue Assessment

Defects have great influence on the safe running of pressure vessels, and the safty assessment for in-service pressure vessels containing defects can realize safe and economical operation of presure vessles.Aiming at the fatigue assement of defect in steel pressure vessels,the fatigue assement method is studied and a primary program can be uesd to calculate fatigue crack propagation and life prediction is programed based on GB19624.The comparison between test and calculated results indicates that the method provided is suitable for fatigue assessment of defects.Combining the test results and cricical conditonds, the presient approach can provide a basis for the fatigue safety assessment and the reasonable overhaul cycle of in-service pressure vessels.

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