A Probabilistic Fatigue Damage Model for Aluminum 6061-T6 10-Gauge Sheet-Type Material

2021 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Cyclic Load ◽  
Damage Model ◽  
Fatigue Tests ◽  
Load Level ◽  
Cyclic Loads ◽  
Test Machine ◽  
Axial Loads ◽  
Fatigue Specimen

Abstract The 6061-T6 10-gauge sheet-type flat fatigue specimen was designed, manufactured, and tested on an Instron 8081 fatigue test machine. The fatigue tests were performed under five different cyclic axial loads with 195 tests. This paper will display how to use these 195 test data under different cyclic axial loads to build a probabilistic fatigue damage model. The model is validated by the results obtained from the traditional P-S-N curve approach. One advantage of this probabilistic fatigue damage model is that it can calculate the reliability of a component under any type of cyclic loads at any cyclic load level.

A Probabilistic Fatigue Damage Model for Describing the Entire Set of Fatigue Test Data of the Same Material

2019 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Test Data ◽  
Stress Level ◽  
Damage Model ◽  
Fatigue Tests ◽  
Small Sample ◽  
Test Machine ◽  
Stress Levels ◽  
D Model

Abstract One typical widely-accepted approach for describing the fatigue test data is the P-S-N curve approach. However, the P-S-N curve approach has some issues such as: (1) If there are only a few fatigue test data at a fatigue test stress level, the P-S-N curve approach is not valid due to the small sample size; (2) When the total number of fatigue tests under different stress levels might be larger such as more than 30 even though the number of fatigue tests at the same stress level is small, the P-S-N curve cannot be used to analyze such set of fatigue data; (3) It is difficult to calculate the reliability of a component under a cyclic stress level when the probabilistic distribution function under this stress level is not available in the P-S-N curves. The author has proposed the K-D probabilistic fatigue damage model (K-D model) to overcome those issues. The 6061-T6 10-gauge sheet-type flat fatigue specimen was designed, manufactured, and tested on the Instron 8081 fatigue test machine to verify this K-D model. The fatigue tests were under five different cyclic axial loadings with a total of 195 tests. In this paper, the fatigue test data will be analyzed by the P-S-N curve approach and the K-D model. The systematic comparisons between the P-S-N curve approach and the K-D model have approved and verified that the K-D model can be used to analyze and to describe the fatigue test data under all different fatigue stress levels and can be used to calculate the reliability of a component under any type of cyclic fatigue loading.

scholarly journals An Ultra-High Frequency Vibration-Based Fatigue Test and Its Comparative Study of a Titanium Alloy in the VHCF Regime

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1415
Author(s):  
Wei Xu ◽  
Yanguang Zhao ◽  
Xin Chen ◽  
Bin Zhong ◽  
Huichen Yu ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Test ◽  
High Frequency ◽  
High Efficiency ◽  
Fatigue Tests ◽  
Loading Frequency ◽  
Fatigue Specimen ◽  
Ultra High Frequency ◽  
High Frequency Vibration ◽  
Testing Data

This paper proposes an ultra-high frequency (UHF) fatigue test of a titanium alloy TA11 based on electrodynamic shaker in order to develop a feasible testing method in the VHCF regime. Firstly, a type of UHF fatigue specimen is designed to make its actual testing frequency reach as high as 1756 Hz. Then the influences of the loading frequency and loading types on the testing results are considered separately, and a series of comparative fatigue tests are hence conducted. The results show the testing data from the present UHF fatigue specimen agree well with those from the conventional vibration fatigue specimen with the loading frequency of 240 Hz. Furthermore, the present UHF testing data show good consistency with those from the axial-loading fatigue and rotating bending fatigue tests. But the obtained fatigue life from ultrasonic fatigue test with the loading frequency of 20 kHz is significantly higher than all other fatigue test results. Thus the proposed ultra-high frequency vibration-based fatigue test shows a balance of high efficiency and similarity with the conventional testing results.

Fatigue Performance of Grade R4 and R5 Mooring Chains in Seawater

2014 ◽  
Author(s):  
Jonathan Fernández ◽  
Walther Storesund ◽  
Jesús Navas
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Fatigue Tests ◽  
Design Methods ◽  
Full Scale ◽  
Fatigue Performance ◽  
Test Program ◽  
Gas Industry ◽  
Fatigue Design ◽  
Cumulative Fatigue Damage

With more than 50.000 tons in service to date, the Oil&Gas Industry has the need to understand the tension fatigue performance of grade R5 chains in straight tension, and corroborate the validity of the existing design methods. The chain fatigue design curves in API and DNV are based on fatigue tests obtained in the nineties and early two thousands. However the tests were performed on lower grades such as ORQ, R3 and R4, and small chains, 76 mm diameter being the largest studless chain tested. The industry has moved towards the use of large studless chains, especially in permanent units, where chain diameters above 150 mm are not unusual. This paper gathers information from a full scale fatigue test program on grade R4 and R5 studless chains, performed in seawater and with diameters between 70 mm and 171 mm. The chains being tested are actual production chains supplied for different drilling units and large permanently moored production floating units. The paper analyses the data and determines tension-tension fatigue curves based on API and DNV methods for computation of cumulative fatigue damage, regardless of other damaging mechanisms. Improved fatigue capacity is obtained with respect to the above recommended design methods.

Analysis on High Cycle Fatigue Properties and Fatigue Damage Evolution of TC25 Titanium Alloy

2016 ◽  
Vol 697 ◽  
pp. 658-663
Author(s):  
Rong Guo Zhao ◽  
Ya Feng Liu ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Qi Bang Li ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Strain Hardening ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
High Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Properties ◽  
Test Machine ◽  
Cycle Fatigue

The high cycle fatigue tests for smooth specimens of TC25 titanium alloy under different stress ratios are carried out on a MTS 809 Material Test Machine at a given maximum stress level of 917MPa at ambient temperature, the high cycle fatigue lifetimes for such alloy are measured, and the effects of stress amplitude and mean stress on high cycle fatigue life are analyzed. The initial resistance is measured at the two ends of smooth specimen of TC25 titanium alloy, every a certain cycles, the fatigue test is interrupted, and the current resistance values at various fatigue cycles are measured. The ratio of resistance change is adopted to characterize the fatigue damage evolution in TC25 titanium alloy, and a modified Chaboche damage model is applied to derive the fatigue damage evolution equation. The results show that the theoretical calculated values agree well with the test data, which indicates that the modified Chaboche damage model can precisely describe the accumulated damage in TC25 titanium alloy at high cycle fatigue under unaxial loading. Finally, the high cycle fatigue lifetimes for TC25 titanium alloy specimens at different strain hardening rates are tested at a given stress ratio of 0.1, the effect of strain hardening on fatigue life is investigated based on a microstructure analysis on TC25 titanium alloy, and an expression between fatigue life and strain hardening rate is derived

An Influence of Cyclic Loading on Behaviour of a Hysteretic Interface Damage Model

2019 ◽  
Vol 827 ◽  
pp. 275-281
Author(s):  
Roman Vodička
Keyword(s):  
Cyclic Loading ◽  
Cyclic Load ◽  
Endurance Limit ◽  
Damage Model ◽  
Interface Layer ◽  
Actual State ◽  
Cyclic Loads ◽  
Inertial Effects ◽  
Damage Propagation ◽  
Interface Damage

A computational interface damage model which takes into account crack initiation andgrowth along connections between parts of a multi-domain structure is proposed and is exposed tosituations where cyclic loading and its effects on the structure are noticeable, though the inertial effects are not considered. Modelling of damage takes into account various aspects of damage propagation and invoking of an interface crack. First, the degradation function of the interface layer controls the stressseparation relation on damage evolution. Second, the instant of triggering and cessation of damage propagation may in situations of cyclic loads depend on the actual state of the structure, influencing thus its endurance limit. Finally, the hysteretic character of damage provides together with loadingunloading conditions a fatigue-like character, where the crack appears for smaller magnitude of the cyclic load than for pure uploading. The numerical solution and a short parametric study is provided for a simplified situation of single damageable interface spring.

Observations of Fatigue Damage in the Press-Fitted Shaft under Bending Loads

2006 ◽  
Vol 326-328 ◽  
pp. 1071-1074 ◽  
Author(s):  
Dong Hyung Lee ◽  
Seok Jin Kwon ◽  
Jae Boong Choi ◽  
Young Jin Kim
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Surface Profile ◽  
Fretting Fatigue ◽  
Fatigue Tests ◽  
Fretting Wear ◽  
Multiple Cracks ◽  
Test Machine ◽  
Edge Region ◽  
Fretting Damage

In this paper, the characterization of fretting damage on press-fitted specimens is proposed by experimental methods. A series of fatigue tests and interrupted fatigue tests on pressfitted specimens were carried out by using a rotate bending fatigue test machine. Macroscopic and microscopic characteristics were observed to identify fretting damage mechanism with a scanning electron microscope (SEM) and profilometer. The mechanism of fretting fatigue damage on pressfitted structure is discussed from experimental results. It is found that small cracks of 30~40m in depth are initiated when the specimen reached about 10% of the total life, and thus almost 90% of the fretting fatigue life of press fits can be considered to be in the crack propagation phase. Most of fatigue cracks are initiated at 1050m inner side of contact edge, and multiple cracks are nucleated and interconnected in the fretted surface. The crack nucleation angle in the near contact edge region is larger than that in the inside of the contact edge region. The fretting wear increased with increasing fatigue cycle. Since the fretting wear is relevant to the evolution of surface profile, the fretting fatigue is observed to be closely related with the fretting wear.

Fatigue Test on a Full Scale Panel

2006 ◽  
Vol 324-325 ◽  
pp. 719-722 ◽  
Author(s):  
A. Apicella ◽  
Enrico Armentani ◽  
Renato Esposito
Keyword(s):  
Fatigue Test ◽  
Complex Loading ◽  
Constant Load ◽  
Load Level ◽  
Full Scale ◽  
Test Machine ◽  
Element Analysis ◽  
Deformation State ◽  
Longitudinal Joint ◽  
Load Tests

Fatigue test on a full scale panel with complex loading and geometry has been carried out by using a tri-axial test machine located in the laboratory of the University of Naples. The aeronautical test panel was designed and manufactured by Alenia. The demonstrator is made up of two parts which are linked by a transversal joint that is parallel to the stringer direction. A fatigue load was applied in the normal direction to the longitudinal joint, while a constant load was applied in the joint direction. The full scale panel was equipped with strain gauges for deformation state measurements. Preliminary static load tests were performed in order to provide deformation measurements for numerical correlation. The outcomes confirmed that the applied load level is consistent with a linear elastic material behaviour. Three intermediate failures occurred before the final one: the first two under a clip, while in the third case a panel frame failed. Finally after about 177,000 cycles the demonstrator broke down. A non linear finite element analysis was also carried out in order to correlate failure events that occurred during the demonstrator testing.

Damage Mechanics-Finite Element Full-Couple Method to Predict the Fatigue Life of Metallic Material

2014 ◽  
Vol 707 ◽  
pp. 390-396
Author(s):  
Xian Min Chen ◽  
Di Guan ◽  
Feng Ping Yang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Test ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Fatigue Tests ◽  
Damage Initiation ◽  
Strain Threshold ◽  
Couple Method

A damage accumulation model is presented for fatigue life prediction of metallic structures. Based on the energy theory and material fatigue test data, the plastic strain threshold for damage initiation was modified for HCF and LCF respectively. The damage evolution parameters were determined according to the fatigue test results of standard specimens. A damage mechanics-finite element full-couple method was adopted to simulate the process of fatigue damage evolution, incorporating elastic modulus reduction due to fatigue damage. Comparisons are made with the fatigue tests of 2A12-T4 open-hole plates and good agreement was obtained.

A crack growth–based individual aircraft monitoring method utilising a damage metric

2017 ◽  
Vol 17 (5) ◽  
pp. 1178-1191 ◽  
Author(s):  
Paul White ◽  
David Mongru ◽  
Lorrie Molent
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Fatigue Test ◽  
Fatigue Damage ◽  
Damage Model ◽  
Monitoring Method ◽  
Tracking Method ◽  
Fatigue Monitoring ◽  
Aluminium Alloy 7050 ◽  
Growth Methods

The need and benefits of individual aircraft fatigue monitoring are now well established. There are broadly two fatigue damage methods employed for this purpose, namely, crack growth and stress (or strain)-life. The crack growth methods tend to provide a relative comparison between an aircraft’s usage and a baseline usage, while the strain-life methods provide a measure of the amount of fatigue life consumed against that (generally) demonstrated through a fatigue test. In this article, a new crack growth–based tracking method is described that also includes a measure of the certified fatigue life consumed. The damage model is compared against the results of an extensive coupon fatigue test programme for aluminium alloy 7050-T7451.

Mean Load Impact on Mooring Chain Fatigue Capacity: Lessons Learned From Full Scale Fatigue Testing of Used Chains

2019 ◽  
Author(s):  
Øystein Gabrielsen ◽  
Kjell Larsen ◽  
Oddgeir Dalane ◽  
Hans B. Lie ◽  
Svein-Arne Reinholdtsen
Keyword(s):  
Fatigue Test ◽  
Limit State ◽  
Fatigue Tests ◽  
Load Level ◽  
Full Scale ◽  
General Corrosion ◽  
Test Results ◽  
Original Design ◽  
The Mean ◽  
Mooring Chain

Abstract Fatigue of mooring chain is for many floating offshore installations a limiting factor in design. With aging installations and the need for field life extension beyond the original design life, questions on mooring chain endurance are raised. Current SN curves utilized in fatigue limit state (FLS) calculation are based on full scale testing of new chain, performed at a high mean load level (20% of the chains minimum breaking load (MBL)). The high mean load level in the tests do not correspond to the conditions for many chains in operation, as mean load in fatigue relevant seastates are often significantly less than mean load used in the new chain fatigue tests. Mooring chains in operation also experience different degree of corrosion, both general corrosion and pitting. Surface roughness and corrosion pits contribute to crack initiations, and thus reduce fatigue capacity. Fatigue tests with new chain condition cannot be assumed representative for corroded chains. As part of mooring integrity programs, Equinor has been replacing mooring chains since year 2000. To assess actual fatigue capacity, many chain segments have been full scale fatigue tested. First tests started in 2011, and the tests cover different degrees of corrosion. The tests have been performed at typical mean load levels relevant for operation of the installations, which for most cases are less than 20%MBL. From these tests it is observed that fatigue capacity in some cases are better than expected for new chain, even for chain segments with significant corrosion. Fatigue test results show a large effect of the mean load. For test cases with significant corrosion and high mean load (20%MBL), a significant reduction in fatigue capacity compared to new chains is found. This paper presents some of the fatigue test results on used chain, highlighting the effect of the mean load for the given chain conditions. Effect of corrosion at mean load of 20%MBL is also included. The paper discusses some of the underlaying causes for the mean load dependency.

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