Experimental Study on Fatigue Life of Steel Beams Strengthened with a CFRP Plate

2008 ◽  
Vol 33-37 ◽  
pp. 163-168 ◽  
Author(s):  
Jun Deng ◽  
Marcus M.K. Lee ◽  
Pei Yan Huang
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Test ◽  
Interfacial Stress ◽  
Steel Beams ◽  
Test Results ◽  
Load Range ◽  
Cfrp Plate ◽  
Crack Initiation Life

The adhesive bonding between the steel beam and carbon fibre reinforced polymer (CFRP) plate is the weakest link and fatigue performance is a major consideration. This paper gives details of a fatigue test programme of a series of small-scale steel beams bonded with a CFRP plate. Two phases of the fatigue life, including crack initiation life and crack propagation life, are considered. Backface-strain technique was applied to monitor crack initiation. An S-N curve was developed from the test results. The curve correlates the maximum principal interfacial stress at the plate end to the crack initiation life. The fatigue limit of the S-N curve was found to be about 30% of the ultimate static failure stress. In accordance with Paris Law, moreover, an equation was developed to predict the number of cycles during the crack propagation. The empirical coefficients of the equation were obtained from the fatigue test results. This equation can correctly predict the crack propagation life. The fatigue load range affects the fatigue life, but its significance is much less than the magnitude of the maximum load in the load range.

Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads

2010 ◽  
Author(s):  
Masao Itatani ◽  
Keisuke Tanaka ◽  
Isao Ohkawa ◽  
Takehisa Yamada ◽  
Toshiyuki Saito
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Static Tension ◽  
Cyclic Torsion ◽  
Cyclic Tension ◽  
Crack Initiation Life

Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.

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.

A Calculation Method of Vibration Fatigue Life with Coupling Effect

2011 ◽  
Vol 338 ◽  
pp. 411-414
Author(s):  
Wen Guang Liu ◽  
Hong Lin He
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Calculation Method ◽  
Coupling Effect ◽  
Element Model ◽  
Test Results ◽  
Engineering Structures ◽  
Vibration Fatigue ◽  
Crack Initiation Life ◽  
Total Life

There are different modes of damage in any engineering structures, and most of them are cracks. In order to study the influence of coupling effect on the fatigue life, a calculation method of structure vibration fatigue life with crack propagation is proposed. In analysis, a series of finite element model with crack of different length is built to simulate the crack propagation, and Paris equation is employed to calculate the vibration fatigue life by stepwise method. The crack initiation life is got based on the change law of natural frequency from test results, and the total life is calculated in the end. Results indicate that the simulation results identical with the experimental results well.

Fatigue Life Prediction for Short Dents in Petroleum Pipelines

2002 ◽  
Author(s):  
Adam J. Rinehart ◽  
Peter B. Keating
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Propagation ◽  
External Force ◽  
Life Prediction ◽  
Fatigue Behavior ◽  
Contact Region ◽  
Fatigue Cracking ◽  
Fatigue Life Prediction ◽  
Crack Initiation Life

Pipeline dent fatigue behavior has been shown to be strongly dependent upon dent length and external force dent restraint characteristics. Full-scale laboratory tests have shown that short dents that are unrestrained by an external force typically experience fatigue cracking in the dent periphery outside of the dent contact region. A fatigue life prediction method for short dents is presented here. In order to assess method accuracy, predictions are made for cases in which fatigue life has been measured experimentally. The predictions account for both crack initiation life and crack propagation life. Stress concentration values used in the predictions are determined using finite element modelling on a case-by-case basis for comparison purposes. Appropriate crack initiation life estimates, stress intensity factor predictions, and crack propagation models are taken from existing literature. Predicted and measured fatigue lives are compared for the cases studied.

Fatigue Performance Study of E36 Steel Welding Joint

2011 ◽  
Vol 80-81 ◽  
pp. 173-177
Author(s):  
Z.X. Song ◽  
Dong Po Wang ◽  
G.A. Wei ◽  
C.H. Yang
Keyword(s):  
Fatigue Life ◽  
Fracture Surface ◽  
Crack Initiation ◽  
Fatigue Test ◽  
Test Results ◽  
Constant Amplitude ◽  
Performance Study ◽  
Welding Seam ◽  
Cycle Times ◽  
Welding Joint

Fatigue test was carried out on E36 steel no reinforcement welding joint under the same constant amplitude load with ultrasound fatigue tester independent designed by Tianjin University. Test results showed that the specimen would enter infinite life area after 1 x 109 cycle times; All broken specimens fractured in the welding seam. We observed fracture surface using SEM and found all the crack initiation from defects. This paper further analysed the influence of nature, size, position, and distribution of defects on fatigue life.

scholarly journals Analysis of the Correlation between the Static and Fatigue Test Results of the Interlayer Bondings of Asphalt Layers

2016 ◽  
Vol 62 (1) ◽  
pp. 83-98 ◽  
Author(s):  
A. Szydło ◽  
K. Malicki
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Asphalt Mixture ◽  
Fatigue Tests ◽  
Test Results ◽  
Static Tests ◽  
Bonding State ◽  
Road Pavement ◽  
The Future ◽  
Pavement Structure

Abstract The bonding state of the asphalt layers in a road pavement structure significantly affects its fatigue life. These bondings, therefore, require detailed tests and optimization. In this paper, the analyses of the correlation between the results of laboratory static tests and the results of fatigue tests of asphalt mixture interlayer bondings were performed. The existence of the relationships between selected parameters was confirmed. In the future, the results of these analyses may allow for assessment of interlayer bondings’ fatigue life based on the results of quick and relatively easy static tests.

scholarly journals Study of Fatigue and Bending Properties For Epoxy / Kevlar - Glass Fibers and Hybrid Composite

2014 ◽  
Vol 11 (2) ◽  
pp. 540-546
Author(s):  
Baghdad Science Journal
Keyword(s):  
Fatigue Life ◽  
Glass Fiber ◽  
Fatigue Test ◽  
Hybrid Composite ◽  
Glass Fibers ◽  
Fatigue Property ◽  
Test Results ◽  
Kevlar Fiber ◽  
Prepared Material ◽  
Better Than

In this research a study of the effect of quality, sequential and directional layers for three types of fibers are:(Kevlar fibers-49 woven roving and E- glass fiber woven roving and random) on the fatigue property using epoxy as matrix. The test specimens were prepared by hand lay-up method the epoxy resin used as a matrix type (Quick mast 105) in prepared material composit . Sinusoidal wave which is formed of variable stress amplitudes at 15 Hz cycles was employed in the fatigue test ( 10 mm )and (15mm) value 0f deflection arrival to numbers of cycle failure limit, by rotary bending method by ( S-N) curves this curves has been determined ( life , limit and fatigue strength) of composite . The results show us the reinforcement has important act to increased resistance to the fatigue compared with specimens have non reinforcement this side the specimens reinforcement of glass fiber have resistance to fatigue and fatigue life better than the specimens reinforcement of Kevlar fiber . According to hybrid composite sample fatigue test results showed that the sample which reinforced (Kevlar - regular glass – Kevlar) has a best results which showed stress carrying the most powerful and longer fatigue life with more than (1.3 ×10 6) cycle from other hybrids , while the sample with the sample with three Kevlar reinforced layers have less resistant to fatigue

A Standardised Method of Representing Fatigue Test Results

1958 ◽  
Vol 62 (570) ◽  
pp. 456-457 ◽  
Author(s):  
M. Fine
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Test Results ◽  
Flat Part

Figure 1 is a set of S-N curves for DTD. 150, taken from Rotol Structures Department Report No. 337. It is difficult to estimate N accurately on the flat part of the curve, and estimates of fatigue life by different people can be very different. Fig. 1, although based on scanty test results, is typical of S-N curves.

Crack Initiation Process for Semi-Circular Notched Plate in Fatigue Test at Elevated Temperature

2008 ◽  
Author(s):  
Bopit Bubphachot ◽  
Osamu Watanabe ◽  
Nobuchika Kawasaki ◽  
Naoto Kasahara
Keyword(s):  
Elevated Temperature ◽  
Crack Initiation ◽  
Fatigue Test ◽  
Video Camera ◽  
Test Results ◽  
Structural Components ◽  
Crack Initiation And Propagation ◽  
Propagation Process ◽  
Initiation Process ◽  
Initiation And Propagation

Crack initiation and propagation process of fatigue test in semi-circular notched plates at elevated temperature were observed by the CCD video camera. Test specimens are made of SUS304 stainless steel, and temperature is kept to be 550°C, and geometry of semi-circular notched plate specimens are changed by diameter size of the circular hole. Photographs in all cycles were recorded to investigate crack initiation process in structural components having stress concentration and obtain number of cycle of crack initiation (Nc). The test results were compared with predictions by Stress Redistribution Locus (SRL) method and Neuber’s rule’s method.

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