Damage Rate is a Predictor of Fatigue Life and Creep Strain Rate in Tensile Fatigue of Human Cortical Bone Samples

2004 ◽  
Vol 127 (2) ◽  
pp. 213-219 ◽  
Author(s):  
John R. Cotton ◽  
Keith Winwood ◽  
Peter Zioupos ◽  
Mark Taylor
Keyword(s):  
Fatigue Life ◽  
Cortical Bone ◽  
Creep Strain ◽  
Stress Level ◽  
Fatigue Tests ◽  
Human Cortical Bone ◽  
Damage Rate ◽  
Tensile Fatigue ◽  
Stress Cycles ◽  
Cycles To Failure

We present results on the growth of damage in 29 fatigue tests of human femoral cortical bone from four individuals, aged 53–79. In these tests we examine the interdependency of stress, cycles to failure, rate of creep strain, and rate of modulus loss. The behavior of creep rates has been reported recently for the same donors as an effect of stress and cycles (Cotton, J. R., Zioupos, P., Winwood, K., and Taylor, M., 2003, “Analysis of Creep Strain During Tensile Fatigue of Cortical Bone,” J. Biomech. 36, pp. 943–949). In the present paper we first examine how the evolution of damage (drop in modulus per cycle) is associated with the stress level or the “normalized stress” level (stress divided by specimen modulus), and results show the rate of modulus loss fits better as a function of normalized stress. However, we find here that even better correlations can be established between either the cycles to failure or creep rates versus rates of damage than any of these three measures versus normalized stress. The data indicate that damage rates can be excellent predictors of fatigue life and creep strain rates in tensile fatigue of human cortical bone for use in practical problems and computer simulations.

scholarly journals Fatigue Performance of Natural and Synthetic Rattan Strips Subjected to Cyclic Tensile Loading

Forests ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 76
Author(s):  
Yanting Gu ◽  
Jilei Zhang
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Ultimate Tensile Strength ◽  
Applied Stress ◽  
Stress Level ◽  
Tensile Loading ◽  
Constant Amplitude ◽  
Tensile Fatigue ◽  
Number Of Cycles ◽  
Cycles To Failure

Tensile fatigue performances of selected natural rattan strips (NRSs) and synthetic rattan strips (SRSs) were evaluated by subjecting them to zero-to-maximum constant amplitude cyclic tensile loading. Experimental results indicated that a fatigue life of 25,000 cycles began at the stress level of 50% of rattan material ultimate tensile strength (UTS) value for NRSs evaluated. Rattan core strips’ fatigue life of 100,000 cycles started at the stress level of 30% of its UTS value. Rattan bast strips could start a fatigue life of 100,000 cycles at a stress level below 30% of material UTS value. SRSs didn’t reach the fatigue life of 25,000 cycles until the applied stress level reduced to 40% of material UTS value and reached the fatigue life of 100,000 cycles at the stress level of 40% of material UTS value. It was found that NRSs’ S-N curves (applied nominal stress versus log number of cycles to failure) could be approximated by S=σou(1−H×log10⋅Nf). The constant H values in the equation were 0.10 and 0.08 for bast and core materials, respectively.

Combination of Cyclic Fatigue Testing and Materials Characterisation to Investigate Ageing of Elastomers

2017 ◽  
Vol 44 (4) ◽  
pp. 1-8 ◽  
Author(s):  
T. Kroth ◽  
D. Lellinger ◽  
I. Alig ◽  
M. Wallmichrath
Keyword(s):  
Fatigue Life ◽  
Molecular Mass ◽  
Fatigue Testing ◽  
Cyclic Fatigue ◽  
Chain Scission ◽  
Thermal Ageing ◽  
Fatigue Tests ◽  
Additive Package ◽  
Number Of Cycles ◽  
Cycles To Failure

Cyclic fatigue testing and elastomer characterisation were combined to study changes in material properties and network structure of elastomers during thermal ageing. Natural rubber containing a typical additive package with carbon black was studied as a model material. The samples were aged at different temperatures in air or under a nitrogen atmosphere. The fatigue life in number of cycles to failure (S-N curves) was determined from force- and displacement-controlled fatigue tests on tensile bar specimens after different thermal ageing times. Changes in mechanical properties and crosslink density were studied by tensile tests, dynamic mechanical analysis, stress relaxation experiments, compression set measurements, swelling measurements and solid-state NMR. Changes in network density during thermal ageing are related to the interplay between the formation of new crosslinks and chain scission. The average molecular mass of the network chains was found to be a suitable parameter for comparing different characterisation methods. An initial decrease in the molecular mass between two crosslinking points due to post-curing is followed by an increase due to chain scission. A similar trend was found for fatigue life in number of cycles to failure (N) in force-controlled fatigue tests: an increase in N for short ageing times is followed by a decrease after longer ageing times.

The effect of seismic-like induced cyclic loading on damage response of sandstone and granite

2020 ◽  
Author(s):  
Rashid Geranmayeh Vaneghi ◽  
Arcady V. Dyskin ◽  
Klaus Thoeni ◽  
Mostafa Sharifzadeh ◽  
Mohammad Sarmadivaleh
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Stress Level ◽  
Maximum Stress ◽  
Low Frequency ◽  
Life Time ◽  
Rock Types ◽  
Axial Tensile ◽  
Stress Cycles ◽  
Level Loading

<p>The detailed study of rock response to cyclic loading induced by natural phenomena, such as seismic and volcanic activities, and man-made explosions and excavation is necessary for failure prediction and hazard mitigation. The effect of the maximum stress level, loading amplitude, and frequency of stress cycles on the fatigue life and failure mechanisms of two microstructurally different rocks of granite/granodiorite and sandstone is investigated. Test data obtained from comprehensive experiments conducted on these rock types incorporated with the results of previous studies show that the fatigue life time of both rock types increases with a decrease in either maximum stress level or stress amplitude. Nevertheless, the fatigue strength threshold of hard rocks like granite is generally lower than that of soft rocks like sandstone. The study also shows that the low-frequency cyclic loading has more damaging effect on both rock types than the high frequency loading. This investigation demonstrates that the failure mechanism of rocks under cyclic loading is characterized by the development of more tensile microcracks compared to the monotonic loading and the opening and extension of the axial tensile microfractures are more evident at higher maximum stresses or loading amplitudes or at lower loading frequencies. The results presented in this study will contribute to a deeper understanding of the fatigue responses of sandstone and granite to seismic-generated loading–unloading processes under different conditions of stress cycles.</p>

Fatigue Tests on Aluminum Specimens Subjected to Constant and Random Amplitude Loadings

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Morteza Rahimi Abkenar ◽  
David P. Kihl ◽  
Majid T. Manzari
Keyword(s):  
Fatigue Life ◽  
Aluminum Alloys ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Test Results ◽  
Number Of Cycles ◽  
Mechanical Devices ◽  
Cycles To Failure ◽  
Amplitude Versus ◽  
Weight Structures

Increasing interest in using aluminum as the structural component of light-weight structures, mechanical devices, and ships necessitates further investigations on fatigue life of aluminum alloys. The investigation reported here focuses on characterizing the performance of cruciform-shaped weldments made of 5083 aluminum alloys in thickness of 9.53 mm (3/8 in.) under constant, random, and bilevel amplitude loadings. The results are presented as S/N curves that show cyclic stress amplitude versus the number of cycles to failure. Statistical procedures show good agreements between test results and predicted fatigue life of aluminum weldments. Moreover, the results are compared to the results obtained from previous experiments on aluminum specimens with thicknesses of 12.7 mm (1/2 in.) and 6.35 mm (1/4 in.).

Analysis on Fatigue of Natural Corrosion Steel Bars

2010 ◽  
Vol 163-167 ◽  
pp. 3237-3241 ◽  
Author(s):  
Shi Bin Li ◽  
Wei Ping Zhang ◽  
Xiang Lin Gu ◽  
Ci Mian Zhu
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
Fatigue Tests ◽  
Power Exponent ◽  
Accelerated Corrosion ◽  
Negative Power ◽  
Axial Tensile ◽  
Attenuation Rate ◽  
Steel Bars ◽  
Natural Corrosion

To reasonablely assess the residual fatigue life of aged existing reinforced concrete(RC) bridges, axial tensile fatigue tests were conducted on fifteen naturally carbonation-induced corrosion steel bars. The fatigue test results indicate that the existence of corrosion pits reduces the fatigue life of steel bars significantly under the same fagitue stress; with the development of corrosion, the fatigue life of steel bars decays according to negative power exponent law approximately and the attenuation rate increases with stress level augment. The fatigue deterioration law of natural corrosion steel bars is similar to that of accelerated corrosion steel bars, but the attenuation rate is different from that of accelerated corrosion steel bars, and also the influence of stress level on the attenuation rate is just cross to that of accelerated corrosion steel bars. For the complexity of fatigue and corrosion, further pertinent conclusions remain to be confirmed.

scholarly journals The study of the relationship between life limiting factor and stress level for FGH96

2018 ◽  
Vol 165 ◽  
pp. 22031 ◽  
Author(s):  
Didi. Yang ◽  
Yi. Shi ◽  
Guolei. Miao ◽  
Xiaoguang. Yang ◽  
Duoqi. Shi
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
Fatigue Tests ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Lower Stress ◽  
Surface Residual Stress ◽  
Nickel Based Superalloy ◽  
Loading Ratio ◽  
Lower Stress Level

FGH96 is a Chinese made powder metallurgy nickel based superalloy. This reserach aims to investigate the effect of stress on the microstructure of the worst fatigue life at 600°C. The specimens were first polished by abrasive paper and then electropolished to elimate the effect of surface residual stress. The fatigue tests were conducted at 600°C, and the loading ratio was 0.05 at the frequency of 5Hz. Tests were conducted at 900, 1000, 1100, 1200MPa respectively. The fatigue life under the same condition were compared and the fractography of specimens were examined under SEM to further identify the life-limiting factors of the material. The initiation mode transferred from facet initiated to inclusion initiated from lower stress level to higher stress level. Meanwhile, the initiation position transferred from internal to surface with the increase of stress level. This means at higher stress level, fatigue life is mainly limited by inclusion at surface while at lower stress level the limit is controlled by internal facet.

Effect of Prior Creep Strain on High Cycle Fatigue Life of Ti 834

2018 ◽  
Author(s):  
Xijia Wu ◽  
Dongyi Seo ◽  
Marc Head ◽  
Stephen Chan
Keyword(s):  
Fatigue Life ◽  
Creep Strain ◽  
Room Temperature ◽  
High Cycle Fatigue ◽  
Crack Nucleation ◽  
Failure Process ◽  
Creep Damage ◽  
Constant Load ◽  
Fatigue Tests ◽  
Creep Fatigue

Room-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550°C and 600°C, respectively. Microstructural and fractographic examinations on specimens with prior creep strain > 3% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep, followed by fatigue crack propagation in coalescence with the internally distributed damage, leading to the final fracture. The amount of prior creep damage increased with creep strain. The fatigue life of Ti 834 was significantly reduced by prior creep straining. The behavior is rationalized with the integrated creep-fatigue theory.

Fatigue Life of CrMoV Steel after Long Term Service

2014 ◽  
Vol 224 ◽  
pp. 57-62
Author(s):  
Stanisław Mroziński ◽  
Grzegorz Golański ◽  
Jacek Słania
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Hysteresis Loop ◽  
Steam Pressure ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Constant Amplitude ◽  
Bainitic Microstructure ◽  
Stress Cycles

The paper presents the results of research on the microstructure and mechanical properties of 12HMF steel after long-term service. The investigated material was taken from a pipe after service at the temperature of 490°C, steam pressure of 8 MPa and service time of 419 988 hours. Performed research has shown that the 12HMF steel after service was characterized by ferritic-bainitic microstructure without any visible advanced processes of its degradation, a typical microstructure for this grade of steel. The tests of mechanical properties have proved that the examined steel after service was characterized by very low impact strength KV, and yield strength lower than the required minimum. Performed fatigue tests of constant amplitude, as well as the programmed ones, have shown that the investigated steel after service is characterized by cyclic softening without a clear period of stabilization of the parameters of hysteresis loop. Moreover, it has been proved that slight changes in the hysteresis loop parameters, as a function of the number of stress cycles, have a significant influence on the obtained material data used when calculating the life.

scholarly journals The effects of testing methods on the flexural fatigue life of human cortical bone

1999 ◽  
Vol 32 (1) ◽  
pp. 105-109 ◽  
Author(s):  
L.V. Griffin ◽  
J.C. Gibeling ◽  
R.B. Martin ◽  
V.A. Gibson ◽  
S.M. Stover
Keyword(s):  
Fatigue Life ◽  
Cortical Bone ◽  
Testing Methods ◽  
Flexural Fatigue ◽  
Human Cortical Bone
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