Fatigue Performance of Concrete with Pre-Cracks in Tension-Compression Cycles

2014 ◽  
Vol 584-586 ◽  
pp. 1054-1061
Author(s):  
Jian Shen ◽  
Xiao Yun Liu ◽  
Lang Wu
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Cyclic Loading ◽  
Fatigue Test ◽  
Stress Ratio ◽  
Fatigue Property ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Fatigue Load ◽  
Compression Cycle

A tension-compression cycle fatigue test was performed in order to study the fatigue property of C50 concrete with pre-cracks in cyclic loading. The stress ratio was-1 and the amplitude was 0.2 MPa ~1.30 MPa. The results show that the modified coefficient of fatigue strength is 0.198~0.265 and the infinite life fatigue strength is below 0.45MPa. While the log value of fatigue life is approximately linear with the amplitude of fatigue load stress, the discreteness of fatigue life, the particularity of concrete, has little to do with the amplitude. The S-N, P-N fatigue life curves and the constant fatigue life diagram of pre-crack concrete are obtained.

scholarly journals The effect of decarburization on the fatigue life of overhead line hardware

2021 ◽  
Vol 121 (10) ◽  
pp. 1-6
Author(s):  
J. Calitz ◽  
S. Kok ◽  
D. Delport
Keyword(s):  
Fatigue Life ◽  
Tensile Properties ◽  
High Cycle Fatigue ◽  
Fatigue Performance ◽  
Span Length ◽  
Cycle Fatigue ◽  
Overhead Line ◽  
Fatigue Load ◽  
Homogeneous Microstructure ◽  
Overhead Power Line

Altering the microstructure in order to improve the tensile properties of bow shackles resulted in inconsistency in the fatigue performance. This raises the question whether the inconsistency in fatigue life can be attributed to microstructural changes along the profile of the shackle or to decarburization at the surface. Bow shackles forged from 080M40 (EN8) material were subjected to different heat treatments in order to alter the microstructure. The shackles were subjected to five different fatigue load cases, which represented typical loads experienced at termination points for an overhead power line with a span length of 400 m, with changes in conductor type, configuration, wind, and ice loading. Although the change in microstructure does improve both the tensile and fatigue performance, we found that the depth of the decarburization layer has a greater effect on the high cycle fatigue life of bow shackles than the non-homogeneous microstructure.

Statistical Analysis of Fatigue Test Data

2017 ◽  
Author(s):  
Carol Johnston
Keyword(s):  
Statistical Analysis ◽  
Fatigue Strength ◽  
Cyclic Loading ◽  
Fatigue Test ◽  
Test Data ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Test Results ◽  
Girth Welds ◽  
New Procedures

The offshore environment contains many sources of cyclic loading. Standard design S-N curves, such as those in DNVGL-RP-C203, are usually assigned to ensure a particular design life can be achieved for a particular set of anticipated loading conditions. Girth welds are often the ‘weak link’ in terms of fatigue strength and so it is important to show that girth welds made using new procedures for new projects that are intended to be used in fatigue sensitive risers or flowlines do indeed have the required fatigue performance. Alternatively, designers of new subsea connectors, used for example in tendons for tension leg platforms, mooring applications or well-heads which will experience cyclic loading in service, also wish to verify the fatigue performance of their new designs. Often operators require contractors to carry out resonance fatigue tests on representative girth welds in order to show that girth welds made using new procedures qualify to the required design S-N curve. Operators and contractors must then interpret the results, which is not necessarily straightforward if the fatigue lives are lower than expected. Many factors influence a component’s fatigue strength so there is usually scatter in results obtained when a number of fatigue tests are carried out on real, production standard components. This scatter means that it is important first to carry out the right number of tests in order to obtain a reasonable understanding of the component’s fatigue strength, and then to interpret the fatigue test results properly. A working knowledge of statistics is necessary for both specifying the test programme and interpreting the test results and there is often confusion over various aspects of test specification and interpretation. This paper describes relevant statistical concepts in a way that is accessible to non-experts and that can be used, practically, by designers. The paper illustrates the statistical analysis of test data with examples of the ‘target life’ approach (that is now included in BS7608:2014 + A1) and the equivalent approach in DNVGL-RP-C203, which uses the stress modification factor. It gives practical examples to designers of a pragmatic method that can be used when specifying test programmes and interpreting the results obtained from tests carried out during qualification programmes, which for example, aim to determine whether girth welds made using a new procedure qualify to a particular design curve. It will help designers who are tasked with specifying test programmes to choose a reasonable number of test specimens and stress ranges, and to understand the outcome when results have been obtained.

Improve the Fatigue Performance of Welded Joints with Undercuts by TIG Dressing Treatment

2012 ◽  
Vol 472-475 ◽  
pp. 1300-1304 ◽  
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Adverse Effects ◽  
Dynamic Loading ◽  
Weld Joint ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Fatigue Performance ◽  
Weld Toe

Undercuts often exists in the surface at weld toe. Undercuts affects the capability of weld subjected to dynamic loading greatly and fatigue cracks usually initiate from these zones with undercuts. Combining with low-alloy middle strength steel 16Mn，study of increasing the fatigue strength and the fatigue life was carried out. Compared with specimen without defects, the fatigue strength of specimen with undercuts has been increased by 10~20%. Study also shows that comparing with as-welded specimen with defects, with TIG dressing treatment, fatigue strength of cruciform weld joint of steel 16Mn has been increased by 70%, fatigue life by 5~8 times. Compared with as-welded specimen without defects, fatigue strength has been increased by 34%, fatigue life by 3~4 times. Undercuts have no adverse effects on fatigue property of welded joints under TIG dressing.

scholarly journals Stress Ratio and Notch Effects on the Very High Cycle Fatigue Properties of a Near-Alpha Titanium Alloy

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1778 ◽  
Author(s):  
Kun Yang ◽  
Bin Zhong ◽  
Qi Huang ◽  
Chao He ◽  
Zhi-Yong Huang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Ratio ◽  
High Cycle Fatigue ◽  
Stress Sensitivity ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

Ultrasonic fatigue tests up to 1010 cycles were performed on a turbine engine titanium alloy (Ti-8Al-1Mo-1V) at the stress ratio (R) of −1 with smooth specimens and at R = −1, 0.1 and 0.5 with notched specimens. As a result, with increase of fatigue life, the source of reduced fatigue life caused by multi-point surface crack initiation changes from crack propagation stage to crack initiation stage in the high cycle fatigue regime. Notch effect further promotes the degeneration of high cycle and very high cycle fatigue strength at R > −1. The bilinear model, extended from the Goodman method, can better estimate the mean stress sensitivity of this titanium alloy. The fatigue mean stress sensitivity and fatigue-creep mean stress sensitivity of this material increased with the increase of fatigue life. The new model, based on the Murakami model, can provide more appropriate predictions for notch fatigue strength.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

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

Experimental Study on the Effect of Surface Integrity on Fatigue Performance of Aero-Engine Blades

2021 ◽  
Author(s):  
Yun Huang ◽  
Shaochuan Li ◽  
Guijian Xiao ◽  
Benqiang Chen ◽  
Yi He ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Surface Texture ◽  
Surface Characteristics ◽  
Service Performance ◽  
Aero Engine ◽  
Vibration Fatigue

Abstract As the core component of aero-engine, the service performance of aero-engine blade has an important influence on the engine’s reliability and safety performance. Existing studies have shown that machined surface characteristics affect the fatigue strength of components. However, current studies are all based on regular fatigue samples. The structure of blades different from fatigue samples, and the influence mechanism of structural differences on the service performance of blades is still unclear. In addition, the conventional fatigue test conditions are not representative for the blades’ actual service conditions, so it is difficult to realize the processing process for the service performance optimization. In this study, the aero-engine blades processed by abrasive belt grinding and the vibration fatigue test bench were used to explore the influence of surface roughness, surface texture, and surface residual stress on the fatigue performance of aero-engine blades under actual working conditions. The aero-engine blades were ground with different process parameters to obtain different single-factor surface characteristics. By comparing the vibration fatigue life of blades with different surface features, the influence degree of each surface feature on the fatigue life was explored. Results showed that surface roughness has the greatest influence on fatigue strength, followed by residual stress, and surface texture has the least influence on fatigue strength.

The Effects of Specimen Size on the Very High Cycle Fatigue Properties of FV520B-I

2015 ◽  
Author(s):  
Ming Zhang ◽  
Weiqiang Wang ◽  
Aiju Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Specimen Size ◽  
Fatigue Properties ◽  
Test Results ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Heat Effects ◽  
Very High

The authors researched the effects of specimen size on the very high cycle fatigue properties of FV520B-I through ultrasonic fatigue testing. The test results showed that the very high cycle fatigue mechanism was not changed and the fatigue properties declined as the specimen size increased. The S-N curve moved downward and the fatigue life decreased under the same stress level maybe due to the heat effects of large specimens in tests. The fatigue strength and the fatigue life were predicted by relevant models. The prediction of fatigue strength was close to test result, and the prediction of fatigue life was less effective compared with the previous prediction of small size specimen test results.

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