scholarly journals Strength and Fatigue Properties of Sandstone under Dynamic Cyclic Loading

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Mingming He ◽  
Ning Li ◽  
Yunsheng Chen ◽  
Caihui Zhu
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Mechanical Characteristics ◽  
Stress Amplitude ◽  
Dynamic Strength ◽  
Fatigue Properties ◽  
Loading Frequency ◽  
Strength And Deformation ◽  
Metal Materials ◽  
The Relationship

This paper presents an experimental investigation of strength and fatigue properties of intact sandstone samples subjected to dynamic cyclic loading in the laboratory. Tests were conducted on sandstone samples with loading frequencies ranging in 0.5, 1, 2, and 4 Hz, loading amplitudes of 1, 15, 30, 60, 90, and 120 kN, and loading speeds of 0.5, 1, 2, 4, and 8 kN/s. In this study it was shown that the loading frequency, as well as the amplitude and loading speed, was of great significance and affected the mechanical characteristics of sandstone under dynamic cyclic loading. The fatigue life of sandstone was found to decrease with loading speeds and amplitudes but increase with loading frequencies. It was found that the minimum of the dynamic strength and deformation factor of sandstone was obtained at loading speeds of 2 kN/s but the maximum at loading frequencies of 1 Hz. Finally, it was concluded that the relationship between the fatigue life and loading speed, frequency, and stress amplitude under dynamic cyclic loading would be expressed as theS-Ncurve, which showed that the fatigue characteristic of sandstone was similar to that of metal materials.

Low Cycle Fatigue Properties of FGH720Li Superalloy

2021 ◽  
Vol 1035 ◽  
pp. 292-296
Author(s):  
Zi Chao Peng ◽  
Jun Ying Sheng ◽  
Xu Qing Wang ◽  
Yue Tang
Keyword(s):  
Fatigue Life ◽  
Powder Metallurgy ◽  
Applied Stress ◽  
Low Cycle Fatigue ◽  
Influencing Factor ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Nickel Base Superalloy ◽  
Loading Frequency ◽  
Cycle Fatigue

Low cycle fatigue (LCF) properties of a powder metallurgy(PM) nickel base superalloy FGH720Li were systematically studied in this work, including smooth LCF and notched LCF tested at various temperatures and different stress. The relationship between the fatigue life and applied stress was analyzed both for smooth fatigue and notch fatigue tests. The effects of loading frequency and stress ratio on LCF behavior were also studied. As an important influencing factor of the fatigue life in powder metallurgy superalloy, the effect of inclusions on LCF life was also investigated. The results showed that the fatigue properties of FGH720Li alloy was excellent, when tested at the temperature of 450°C and applied stress of 1230MPa, the fatigue life could exceed 5×104 cycles. When tested at 650°C and 1150MPa, the average fatigue life was still beyond 2×105 cycles.

Relationship Between Fatigue Life Distribution, Notch Configuration, and S-N Curve of a 2024-T4 Aluminum Alloy

1985 ◽  
Vol 107 (3) ◽  
pp. 214-220 ◽  
Author(s):  
T. Shimokawa ◽  
Y. Hamaguchi
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Amplitude ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Wide Range ◽  
Life Distributions ◽  
The Relationship ◽  
Test Stress

The objective of this study is to identify the most closely related variable to the distribution of fatigue life in unnotched and three kinds of notched 2024-T4 aluminum alloy specimens. Carefully designed fatigue tests under a constant temperature and humidity condition provided fatigue life distributions over a wide range of stress amplitude. This study used about 1000 specimens. On the basis of the test results, the dependence of the scatter in fatigue life on notch configuration, the period to crack initiation, the level of stress amplitude, the median fatigue life, and the slope of the median S-N curve is investigated, and the relationship between the distributional form of fatigue life and the shape of the median S-N curve is discussed. It is concluded that the slope and shape of the median S-N curve in the vicinity of the test stress level are closely related to the scatter and distributional form of fatigue life respectively. This is common to the unnotched and three kinds of notched specimens. A variability hypothesis to correlate the median S-N curve with fatigue life distributions is examined.

scholarly journals Experimental Study on Acoustic Emission and Resistivity Response of Sandstone under Constant Amplitude Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kui Wang ◽  
Xue Li ◽  
Zheng Huang ◽  
Mingjie Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Stress Amplitude ◽  
Rate Of Change ◽  
Rapid Decline ◽  
Engineering Practice ◽  
Loading Frequency ◽  
Constant Amplitude ◽  
Ae Signal

A lot of engineering practice shows that, during the construction and operation of rock mass projects, in addition to the static load, the rock is more subjected to cyclic load. Constant amplitude cyclic load is one of the simpler cyclic loading methods. The damage of rocks gradually accumulates under the action of periodic cyclic load, and finally, fatigue damage occurs, which affects the stability of the project. Therefore, it is necessary to study the mechanical properties of the rock under the action of constant amplitude cyclic load. Acoustic emission (AE) parameters and resistivity are both sensitive to the damage process of the rock and can well describe the damage evolution law of the rock. Under the action of constant amplitude cyclic loading, different loading conditions, different state specimens, and so on, factors will make a big difference to the AE signal and resistivity, such as the difference in stress amplitude, loading rate, and saturation. Therefore, in this paper, the typical sandstone in the Chongqing area is taken as the research object, the AE characteristics and resistivity characteristics of sandstone under different test conditions such as different stress amplitude, different loading frequency, and different saturation are tested, and the evolution of AE is found. It also has a three-stage rule: in the initial stage, the deformation is faster and the AE signal is strong; in the constant velocity stage, the deformation develops slowly and the AE signal is also stable; in the acceleration stage, the deformation develops sharply and the AE signal also becomes more intense. With the increase of cyclic loading stress amplitude, or the decrease of cyclic loading frequency, or the decrease of rock sample saturation, the acoustic emission signal generated in each cycle will be stronger. The resistivity as a whole shows a rapid decline in the loading phase and a rapid rebound in the unloading phase. The changes in resistivity at different stress amplitudes show differences in the first few cycles; the overall change trend of resistivity at different frequencies is consistent, but the rate of change increases with decreasing frequency, and the variation trend of resistivity is very different under different saturation.

scholarly journals Effect of Carburizing and Nitriding on Fatigue Properties of 18Cr2Ni4WA Steel in Very High Cycle Fatigue Regime

2021 ◽  
Vol 45 (3) ◽  
pp. 207-215
Author(s):  
Zhenduo Sun ◽  
Dongbo Hou ◽  
Wei Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Internal Defect ◽  
Surface Fatigue ◽  
Very High Cycle Fatigue ◽  
The Relationship ◽  
Very High

The work aims to study the influence of carburizing and nitriding on fatigue properties of 18Cr2Ni4WA high strength steel in very high cycle fatigue regime. Very high cycle fatigue tests were carried out on 18Cr2Ni4WA Steel after carburizing and nitriding respectively. The micro morphology of fatigue fracture was observed by scanning electron microscope, the failure mode and failure mechanism were discussed. The relationship between fatigue life and defect size, FGA size, fish eye size of fracture was analyzed. The characteristic size of defects is evaluated by Gumbel, Weibull and GEV distribution functions, and a modified Akiniwa fatigue life prediction model considering the relationship between FGA size and inclusion size was established. The results showed that, nitriding and carburizing treatment improve the surface fatigue limit of the steel. The fatigue life decreases with the increase of internal defect size and FGA size. After carburizing and nitriding treatment, the internal fatigue strength of the specimen decreases slightly. When the failure probability is 99%, the internal defect sizes of nitrided specimens calculated by Weibull, Gumbel and GEV distributions are 141.5 μm, 148.4 μm and 211.7 μm respectively. The calculated internal defect sizes of carburized specimens are 47 μm, 67.8 μm and 40 μm respectively. Compared with the experimental data, the fatigue strength predicted by GEV is the most appropriate. carburizing and nitriding treatment can improve the surface fatigue strength of 18Cr2Ni4WA steel, but slightly reduce the internal fatigue strength. The prediction result of the new model is conservative when the failure probability is 99%, which is suitable for engineering application.

scholarly journals Half-threaded holes markedly increase the fatigue life of locking plates without compromising screw stability

2020 ◽  
Vol 9 (10) ◽  
pp. 645-652
Author(s):  
Ching-Kong Chao ◽  
You-Lin Chen ◽  
Jinn Lin
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Bending Strength ◽  
Locking Plates ◽  
Titanium Plate ◽  
Plate Design ◽  
American Society ◽  
Future Work ◽  
Mechanical Strengths ◽  
The Relationship

Aims To determine whether half-threaded screw holes in a new titanium locking plate design can substantially decrease the notch effects of the threads and increase the plate fatigue life. Methods Three types (I to III) of titanium locking plates were fabricated to simulate plates used in the femur, tibia, and forearm. Two copies of each were fabricated using full- and half-threaded screw holes (called A and B, respectively). The mechanical strengths of the plates were evaluated according to the American Society for Testing and Materials (ASTM) F382-14, and the screw stability was assessed by measuring the screw removal torque and bending strength. Results The B plates had fatigue lives 11- to 16-times higher than those of the A plates. Before cyclic loading, the screw removal torques were all higher than the insertion torques. However, after cyclic loading, the removal torques were similar to or slightly lower than the insertion torques (0% to 17.3%), although those of the B plates were higher than those of the A plates for all except the type III plates (101%, 109.8%, and 93.8% for types I, II, and III, respectively). The bending strengths of the screws were not significantly different between the A and B plates for any of the types. Conclusion Removing half of the threads from the screw holes markedly increased the fatigue life of the locking plates while preserving the tightness of the screw heads and the bending strength of the locking screws. However, future work is necessary to determine the relationship between the notch sensitivity properties and titanium plate design. Cite this article: Bone Joint Res 2020;9(10):645–652.

scholarly journals Experimental investigation of pretensioned bolts under cyclic loading: Damage assessment using acoustic emission

2019 ◽  
Vol 15 (5) ◽  
pp. 155014771984935 ◽  
Author(s):  
Tieliang An ◽  
Xigui Zheng ◽  
Dengxing Zhu ◽  
Deyu Qian ◽  
Yu Guo ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Loading Path ◽  
Loading Frequency ◽  
Damage Factor ◽  
Acoustic Emission Energy ◽  
Pull Out ◽  
Anchorage System ◽  
The Relationship

Understanding the acoustic emission effects on bolts under cyclic loading is of great significance for the support of roadways. The presented research focuses on the acoustic emission characteristics of bolts under cyclic loading. The following main conclusions were drawn: (1) With a higher loading frequency, the acoustic emission counts rate increases, while the total energy released in a given cyclic loading path decreases. (2) A fitting formula is established according to the relationship between the tension amplitude and cumulative acoustic emission counts, which can analyze the tension magnitude level of the cyclic load. (3) A damage factor for a cyclic load is proposed based on the acoustic emission counts generated during the cyclic and monotonic loading process that can analyze the degree of damage to the anchorage system caused by the cyclic load. (4) Based on the spatial distribution of the acoustic emission orientation points and the acoustic emission energy generated during the pull-out process, the acoustic emission damage evolution process of the anchorage specimens is deduced, and the mechanism of the high stability of the pretension anchorage system after cyclic loading is analyzed. The above conclusions may provide some experimental references for the application of acoustic emission technology in bolts supporting roadways.

Fatigue Life Prediction of CFRP Laminates under Variable Stress Amplitude and Frequency

2007 ◽  
Vol 334-335 ◽  
pp. 445-448 ◽  
Author(s):  
Masayuki Nakada ◽  
Junji Noda ◽  
Yasushi Miyano
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Life Prediction ◽  
Statistical Approach ◽  
Stress Amplitude ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Bending Fatigue ◽  
Cfrp Laminates ◽  
Three Point Bending

This paper is concerned with the fatigue life prediction of CFRP laminates under variable cyclic loading using the linear cumulative damage (LCD) rule with statistical approach. Three-point bending fatigue tests for plain-woven CFRP laminates were carried out undervarious cyclic loading with constant and variable stress amplitude and frequency. As results, the applicability of LCD rule to the flexural fatigue life was confirmed for this CFRP laminates.

Fatigue properties of parts printed by PolyJet material jetting

2015 ◽  
Vol 21 (6) ◽  
pp. 675-685 ◽  
Author(s):  
Jacob P. Moore ◽  
Christopher B. Williams
Keyword(s):  
Fatigue Life ◽  
Optical Microscope ◽  
Design Guidelines ◽  
Test Method ◽  
Fatigue Properties ◽  
Repeated Loading ◽  
Material Interface ◽  
Content Type ◽  
End Use ◽  
The Relationship

Purpose – This paper aims to seek to fill a gap in the literature by characterizing the fatigue life and microstructure of a printed elastomer material, the TangoBlackPlus material. Design/methodology/approach – Because the TangoBlackPlus material is marketed as “rubber-like”, the printed elastomer specimens were tested according to the ASTM D4482-11 “Test Method for Rubber Property Extension Cycling Fatigue”. The microstructure of the printed material and multi-material interface was examined by slicing specimens and examining them under an optical microscope. Findings – Findings are developed to show the relationship between elongation and expected fatigue life. Findings also indicate that the smoother, non-support encased “glossy” surface finish option for PolyJet parts improve the fatigue life of components and that there are a number of microscopic voids in the TangoBlackPlus material that seem to be concentrated at layer and print head boundaries. Research limitations/implications – This paper provides a glimpse into the fatigue properties and microstructure of printed elastomeric parts, a previously unstudied area. This work is limited in that it only looks at specimens created in a single orientation, on a single machine, with a single material. More work is needed to understand the general fatigue properties of printed elastomers and the factors that influence fatigue life in these materials. Practical implications – The authors provide several design guidelines based on the findings and previous work that can be used to increase the fatigue life of printed elastomer components. Originality/value – As additive manufacturing (AM) technology moves from a prototyping tool to a tool used to create end use products, it is important to examine the expected lifespan of AM components. This work adds to the understanding of the expected product lifecycle of printed elastomer components that will likely be expected to withstand large repeated loading conditions.

scholarly journals Mechanical Behavior Evolution and Damage Characterization of Coal under Different Cyclic Engineering Loading

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-19 ◽  
Author(s):  
Huajun Wang ◽  
Jian Li
Keyword(s):  
Cyclic Loading ◽  
Stress Amplitude ◽  
Early Stage ◽  
Peak Stress ◽  
Cyclic Stress ◽  
Loading Frequency ◽  
Porous Rocks ◽  
Strength Change ◽  
Drastic Increase

The cyclic loading causes the strength change of porous rocks, which can be frequently encountered in underground coal mining. In order to quantify the cumulative damage of porous coal, multilevel uniaxial cyclic compressive tests were carried out considering different loading frequencies. The results show that under cyclic loading, Young’s modulus of coal shows a first drastic increase and then decrease trend in terms of the number of loading-unloading cycles, while the Poisson’s ratio gradually increased at lower peak stress amplitudes and then increased sharply with peak cyclic stress amplitude until losing load bearing capacity, following a stepwise rising trend. At a higher loading frequency, volumetric compressibility-dilatancy transition is shifted to an earlier time. The loading/unloading response ratio (LURR) was used to evaluate the damage of coal under cyclic loading. It is found that LURR is an effective parameter to evaluate the damage of coaly rock under cyclic loading and is also useful in distinguishing different deformation mechanism at different loading stages. The results also show that the damage of coal can initiate at the early stage of cyclic loading at a low loading frequency; however, the increase in frequency of cyclic loading can delay the damage time, requiring a relatively higher level of peak cyclic stress amplitude.

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