Fatigue Analysis of Preloaded Threaded Fasteners

2011 ◽  
Author(s):  
Sayed A. Nassar ◽  
Rania A. Ali
Keyword(s):  
Fatigue Strength ◽  
Fatigue Test ◽  
Tensile Load ◽  
Fatigue Performance ◽  
Mean Stress ◽  
Damage Analysis ◽  
Data Set ◽  
Threaded Fasteners ◽  
The Mean ◽  
Set Up

This study investigates the fatigue performance of a preloaded threaded fastener under two scenarios of axial cyclic in-service loading. Since the fastener mean stress level would naturally affect the fatigue performance, various methods are investigated for their suitability for use to generate mean-stress adjusted S´-N´ fatigue curves. The maximum in-service cyclic tensile load that may externally be applied to the joint for a desired fatigue performance is also investigated. Limited fatigue test data set-up is generated for comparison with various methodologies for generating the mean stress-adjusted fatigue strength curves of A286 fasteners. Cumulative damage analysis is also performed in accordance with commonly used damage theories.

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.

FATIGUE PROPERTIES OF AUTOMOBILE HIGH-STRENGTH BOLTS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5539-5544 ◽  
Author(s):  
CONGLING ZHOU ◽  
SHIN-ICHI NISHIDA ◽  
NOBUSUKE HATTORI
Keyword(s):  
Tensile Strength ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Stress Level ◽  
High Strength ◽  
Fatigue Properties ◽  
Screw Thread ◽  
Mean Stress ◽  
Stress Levels ◽  
The Mean

This study is focused on the fatigue properties of automobile high-strength bolts, including the effect of mean stress level, pre-processing schedule and the residual stresses. And the mean stress levels are 0.3, 0.5 and 0.7 times to the tensile strength (σ B ) of the material respectively. The main results obtained are as follows: 1) the fatigue strength increases under the mean stress loading, but the differences between the loading levels are not so evident; 2) most of the cases in this study are broken from the bottom of the screw thread, and the crack initiated from the impurities.

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.

Effect of Non-Conforming Thread Root Radius on the Fatigue Performance of Preloaded Threaded Fasteners

2008 ◽  
Author(s):  
Sayed A. Nassar ◽  
Brian S. Munn ◽  
X. Yang
Keyword(s):  
Test Data ◽  
Stress Test ◽  
Sem Analysis ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Optical Methods ◽  
Root Radius ◽  
Threaded Fasteners ◽  
The Mean ◽  
Thread Root

This paper presents an experimental investigation of the effect of thread root non-conformance on the fatigue performance of preloaded M12×1.5 Class 10.9 fasteners. Thread roots were dimensionally inspected using optical methods in accordance with the DIN 933 specification. Axial load fatigue tests were performed in accordance with ISO 3800. Each bolt specimen was subjected to a fixed stress amplitude of 42 MPa above and below various levels of the mean tensile stress. Test data was analyzed and fracture surfaces were examined using a Scanning Electron Microscope (SEM). Analysis of the test data showed that a non-conforming thread root radius had an adverse effect on the fatigue performance of preloaded threaded fasteners.

A Study of Induction Hardening Hole Surfaces in Clearance Fit Joints to Improve Fatigue Strength

1980 ◽  
Vol 102 (1) ◽  
pp. 19-24
Author(s):  
D. L. Carlson ◽  
V. Pavelic
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Stress Distribution ◽  
Induction Hardening ◽  
Material Strength ◽  
Mean Stress ◽  
Strain Gages ◽  
The Mean ◽  
Improve Fatigue Strength ◽  
Improve Fatigue

The feasibility of using induction hardening to improve the fatigue strength of clearance fit clevis-type joints was investigated. Clearance fit joints are desired to facilitate machine assembly and disassembly in applications where accessibility and safety are a problem. The purpose of induction hardening the hole surface was to induce compressive residual stress near the hole to reduce the mean stress and to increase material strength. According to the Goodman criterion for steel, a greater stress range is possible with a reduced mean stress. The residual stress distribution produced near the hole was estimated by induction hardening rings and using a modification of the Sachs boring out method. The hole surfaces of a typical link were induction hardened and tension-tension fatigue tested. The load stress distribution was estimated using strain gages. It was determined that the fatigue strength of a clearance fit joint can be increased by at least 100 percent by induction dardening the hole surfaces.

scholarly journals Fatigue Performance of Welded Joints Under Variable Amplitude Loading Spectra

2019 ◽  
Author(s):  
Xu Liu ◽  
Yan-Hui Zhang ◽  
Bin Wang
Keyword(s):  
Welded Joints ◽  
Plate Thickness ◽  
Fatigue Cracking ◽  
Damage Parameter ◽  
Fatigue Performance ◽  
Mean Stress ◽  
Variable Amplitude ◽  
The Mean ◽  
The Impact ◽  
Loading Spectrum

Abstract Offshore pipelines are generally subjected to variable amplitude (VA) loading in service due to waves or ocean currents. Welded joints often represent the most critical locations for fatigue cracking. Use of the current fatigue design guidance, for example, BS 7608, to assess fatigue performance of the welded joints in such structure may lead to inaccurate estimates depending on the nature of the VA loading spectrum. Further studies on the effect of VA loading spectra on fatigue performance of welded joints are needed. In this research, both uniaxial and 3-point bending fatigue tests were performed on non-load carrying fillet welded plates under VA loading spectra to investigate the effects of mean stress and the type of VA loading spectra. The influence of plate thickness was also investigated. Test results suggest that the spectrum with a high constant maximum tensile stress (cycling-down) could significantly degrade fatigue performance of welded joints, with the damage parameter D only at around 0.5. The severity of this type of loading spectrum depends on the mean stress level and the plate thickness. An analytical model has been developed to predict fatigue crack propagation (FCP) by considering the interaction of stresses in the loading spectrum. The model considers the impact of the mean stress generated by the preceding load on FCP in the subsequent cycles. FCP predicted by the model shows a good agreement with the experimental data.

scholarly journals Effect of the Mean Stress on the Fatigue Strength of 18% Ni Maraging Steel

1977 ◽  
Vol 43 (369) ◽  
pp. 1557-1566
Author(s):  
Keizo FUJITANI ◽  
Keizo NAKAGAWA ◽  
Tsuneshichi TANAKA
Keyword(s):  
Fatigue Strength ◽  
Maraging Steel ◽  
Mean Stress ◽  
The Mean

Surface Optimisation by Engineering the Stress and Roughness

1996 ◽  
Author(s):  
Peter O’Hara
Keyword(s):  
Fatigue Strength ◽  
Surface Finish ◽  
Shot Peening ◽  
Surface Condition ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Mean Stress ◽  
Corrosion Pitting ◽  
The Mean ◽  
Damage Tolerant

Performance of turbine components can significantly be affected by surface/subsurface characteristics. Techniques applied today and being developed further entail introducing into a components surface a residual compressive stress of predictable magnitude and depth followed by superfinishing to improve the surface finish. The effect will be to lower the mean stress which will increase component life and fatigue strength or enable higher loads through present designs; develop a damage tolerant layer capable of withstanding corrosion pitting or strike damage while in service and produce a final roughness capable of improving flow characteristics on turbine blades/buckets. The processes to achieve the above include Controlled Shot Peening and Superfinishing. In combination, an optimised surface condition will result.

scholarly journals Application of the S-N Curve Mean Stress Correction Model in Terms of Fatigue Life Estimation for Random Torsional Loading for Selected Aluminum Alloys

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2985
Author(s):  
Michał Böhm ◽  
Krzysztof Kluger ◽  
Sławomir Pochwała ◽  
Mariusz Kupina
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Effect ◽  
Mean Stress ◽  
Torsional Loading ◽  
Correction Model ◽  
Life Estimation ◽  
Mean Stress Effect ◽  
Fatigue Life Estimation ◽  
The Mean

The paper presents the experimental fatigue test results for cyclic constant amplitude loading conditions for the case of the torsion of the PA4 (AW-6082-T6), PA6 (AW-2017A-T4) and PA7 (AW-2024-T3) aluminum alloy for a drilled diabolo type test specimen. The tests have been performed for the stress asymmetry ratios R = −1, R = −0.7, R = −0.5 and R = −0.3. The experimental results have been used in the process of a fatigue life estimation performed for a random generated narrowband stress signal with a zero and a non-zero global mean stress value. The calculations have been performed within the time domain with the use of the rainflow cycle counting method and the Palmgren−Miner damage hypothesis. The mean stress compensation has been performed with the S-N curve mean stress model proposed by Niesłony and Böhm. The model has been modified in terms of torsional loading conditions. In order to obtain an appropriate R = 0 ratio S-N curve fatigue strength amplitude, the Smith−Watson−Topper model was used and compared with literature fatigue strength amplitudes. The presented solution extends the use of the correction model in terms of the torsional loading condition in order to obtain new S-N curves for other R values on the basis of the R = −1 results. The work includes the computational results for new fatigue curves with and without the mean stress effect correction. The results of the computations show that the mean stress effect plays a major role in the fatigue life assessment of the tested aluminum alloys and that the method can be used to assess the fatigue life under random conditions.

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