Fatigue Characteristics of Vulcanized Natural Rubber for Automotive Engine Mounting

2007 ◽  
Vol 353-358 ◽  
pp. 178-181 ◽  
Author(s):  
S. Shibata ◽  
K. Ochi ◽  
Y. Aono ◽  
Hiroshi Noguchi ◽  
Hideki Oshima
Keyword(s):  
Fatigue Crack ◽  
Natural Rubber ◽  
Crack Length ◽  
Early Stage ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Miner’S Rule ◽  
Fatigue Characteristics ◽  
Stress Ratios ◽  
Miner's Rule

In order to investigate fatigue characteristics of vulcanized natural rubber (NR), fatigue tests are carried out under various stress ratios R (R = minimum stress / maximum stress). It was considered that the fatigue cracks were initiated from flaws in very early stage of total life. The fatigue damage process was almost the fatigue crack propagation process and it is independent of R. The crack growth rate was proportional to the crack length to about the first power, when the crack length was defined as the length of the direction perpendicular to the loading direction. Miner’s rule was examined to observe the fatigue crack behavior and checked by using two-step loading fatigue tests experimentally. It seems Miner’s rule has a possibility to predict fatigue lives.

Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

2014 ◽  
Vol 891-892 ◽  
pp. 1711-1716 ◽  
Author(s):  
Loic Signor ◽  
Emmanuel Lacoste ◽  
Patrick Villechaise ◽  
Thomas Ghidossi ◽  
Stephan Courtin
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Crystal Plasticity ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

Fatigue

2020 ◽  
pp. 529-546
Author(s):  
Lallit Anand ◽  
Sanjay Govindjee
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Failure Analysis ◽  
Crack Growth ◽  
Fatigue Failure ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Repeated Loads

This chapter introduces methods for analysing fatigue failure of materials under repeated loads. The notions of defect-free and defect-tolerant failure analysis are discussed. For defect free analysis the notion of S-N curves is introduced and Coffin-Mason low cycle as well as Basquin high cycle relations are discussed. Miner’s rule is also introduced. For a defect-tolerant approach Paris’s law for fatigue crack growth is presented.

scholarly journals Detection of Micro-Cracks in Metals Using Modulation of PZT-Induced Lamb Waves

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3823
Author(s):  
Sang Eon Lee ◽  
Jung-Wuk Hong
Keyword(s):  
Quantitative Analysis ◽  
Crack Length ◽  
Crack Detection ◽  
Lamb Waves ◽  
Early Stage ◽  
Fatigue Cracks ◽  
Excitation Frequency ◽  
High Sensitivity ◽  
Detection Algorithm ◽  
Modulated Waves

The ultrasonic modulation technique, developed by inspecting the nonlinearity from the interactions of crack surfaces, has been considered very effective in detecting fatigue cracks in the early stage of the crack development due to its high sensitivity. The wave modulation is the frequency shift of a wave passing through a crack and does not occur in intact specimens. Various parameters affect the modulation of the wave, but quantitative analysis for each variable has not been comprehensively conducted due to the complicated interaction of irregular crack surfaces. In this study, specimens with a constant crack width are manufactured, and the effects of various excitation parameters on modulated wave generation are analyzed. Based on the analysis, an effective crack detection algorithm is proposed and verified by applying the algorithm to fatigue cracks. For the quantitative analysis, tests are repeatedly conducted by varying parameters. As a result, the excitation intensity shows a strong linear relationship with the amount of modulated waves, and the increase of modulated wave is expected as crack length increases. However, the change in the dynamic characteristics of the specimen with the crack length is more dominant in the results. The excitation frequency is the most dominant variable to generate the modulated waves, but a direct correlation is not observed as it is difficult to measure the interaction of crack surfaces. A numerical analysis technique is developed to accurately simulate the movement and interaction of the crack surface. The crack detection algorithm, improved by using the observations from the quantitative analyses, can distinguish the occurrence of modulated waves from the ambient noises, and the state of the specimens is determined by using two nonlinear indexes.

Effect of Pre-Strain on Fatigue Properties of NHH Rail

2004 ◽  
Vol 261-263 ◽  
pp. 1239-1244
Author(s):  
Wen Xian Sun ◽  
S. Nishida ◽  
Nobusuke Hattori ◽  
X.L. Yue
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Slip Lines ◽  
Propagation Behavior ◽  
Strain Process ◽  
Initiation And Propagation

In the present study, fatigue tests have been performed to study the effect of pre-strain on fatigue properties of NHH (New Head-Hardened) rail. The objectives of this study were: (1) to observe the microscopic behavior of specimens during pre-strain process, (2) to research the influence of pre-strain on fatigue strength of NHH rail and (3) to investigate initiation and propagation behavior of the fatigue crack. The results showed that plastic pre-strain decreased the fatigue strength of NHH rail; fatigue limits had no obvious variation among the different pre-strain ratios. Fatigue cracks initiated in the microscopic cracking or slip lines that were originated in the pre-strain process and propagated from these sites in the later fatigue test.

scholarly journals Fatigue behaviour of an industrial synthetic rubber

2018 ◽  
Vol 165 ◽  
pp. 22004 ◽  
Author(s):  
Thomas Balutch ◽  
Bertrand Huneau ◽  
Yann Marco ◽  
Pierre Charrier ◽  
Clément Champy
Keyword(s):  
Natural Rubber ◽  
Fatigue Cracks ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Damage Scenario ◽  
Root Cause ◽  
Synthetic Rubber ◽  
Initiation And Propagation ◽  
Cause Of Failure ◽  
The One

For some automotive anti-vibration applications, for instance exhaust hangers, center bearing bushes or torsional vibration dampers, temperature constraints make the use of synthetic rubbers, such as EPDM, necessary because of their better heat aging resistance compared to natural rubber. The aim of this paper is to understand the features of the fatigue behaviour of an industrial EPDM compared to the wellknown natural rubber. To do so, fatigue tests are conducted on hourglass-shaped specimens, and fracture surfaces are analysed using optical microscopy and scanning electron microscopy (SEM). It appears that every samples exhibit only one root cause of failure. Thus, two types of precursors are identified as responsible of the final fracture of samples: material’s inclusions and mold flaws. Interrupted fatigue tests are then performed and fatigued samples are observed with SEM. The built procedure allows us to follow fatigue cracks initiation and propagation along cycles, and to propose local damage mechanisms for each type of precursors. A global damage scenario is finally considered and compared to the one of natural rubber described in the literature.

A First Investigation on Cumulative Fatigue Life for a Type 304-L Stainless Steel Used for Pressure Water Reactor

2009 ◽  
Author(s):  
A. Fissolo ◽  
J. M. Stelmaszyk
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Damage Effect ◽  
Final Conclusion ◽  
Variable Loading ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Type 304

In order to estimate the crack initiation damage, and also the water leakage conditions on PWR pipes, uniaxial fatigue curves are often used. They were deduced from strain or stress load control tests using normalised cylindrical specimens. However, severe thermo-mechanical loading fluctuations are observed in operating conditions. Components may also be submitted to transient loadings. The purpose of the present work is to start investigation on the fatigue life with a variable loading, in order to examine cumulative damage effect in fatigue. In this frame, multilevel strain controlled fatigue tests have been performed on a Type 304-L stainless steel (elaborated in accordance with the RCC-M specifications). The experimental results show that linear Miner’s rule is not verified in our conditions. When the strains are applied in a decreasing order (High-Low strain sequence), the summation of cycle ratios is smaller than unity, whatever the number of applied levels, whereas this summation is higher than one for an increasing order (Low-High strain sequence). A loading sequence effect is clearly evidenced. Different cumulative fatigue damage theories, proposed in literature, have been also tested. Some of them have been given better estimation than the Miner’s rule. That is the case of the so-called “Hybrid Theory” proposed and tested before by Bui Quoc on a Type 304-L steel. Extension of a model proposed by S. Taheri would seem also promising. At this stage, final conclusion cannot be yet deduced, additional investigations are needed.

An Analysis of the Behavior of Small Fatigue Cracks Emanating from Stress Concentrators

2008 ◽  
Vol 385-387 ◽  
pp. 641-644
Author(s):  
Satoshi Ikeda ◽  
Daisuke Koyanagi ◽  
Masahiro Endo ◽  
Yuki Sakamoto
Keyword(s):  
Fatigue Crack ◽  
Stress Concentration ◽  
Fatigue Cracks ◽  
Plastic Zone Size ◽  
Fatigue Tests ◽  
Zone Size ◽  
Dugdale Model ◽  
Stress Concentrators ◽  
Uniform Tension ◽  
Small Fatigue Crack

The plastic zone size (PZS) at the tip of a crack emanating from stress concentrators subjected to uniform tension was calculated based upon the Dugdale model. A method was proposed for the prediction of fatigue notch effects in terms of the McEvily method that has widely been used for the analysis of small fatigue crack growth. In modifying this method, the elastic-plastic effects due to stress concentration were taken into account using the values of PZS calculated in this study. The results predicted by this method accounted successfully for the behavior of small fatigue cracks near the threshold levels observed in the fatigue tests conducted using notched steel specimens.

The Fatigue Behavior of Steel Structures under Random Loading

2008 ◽  
Vol 378-379 ◽  
pp. 3-16
Author(s):  
Henning Agerskov
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Test ◽  
Steel Structures ◽  
Fatigue Tests ◽  
Test Series ◽  
Test Results ◽  
Random Loading ◽  
Mechanics Analysis ◽  
Miner’S Rule ◽  
Miner's Rule

Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series with a total of 540 fatigue tests have been carried through on various types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel or high-strength steel. The fatigue tests and the fracture mechanics analyses have been carried out using load histories, which are realistic in relation to the types of structures studied, i.e. primarily bridges, offshore structures and chimneys. In general, the test series carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner’s rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from Miner’s rule will depend on the distribution of the load history in tension and compression.

Development of a “stick-and-detect” wireless sensor node for fatigue crack detection

2016 ◽  
Vol 16 (2) ◽  
pp. 153-163 ◽  
Author(s):  
Peipei Liu ◽  
Hyung Jin Lim ◽  
Suyoung Yang ◽  
Hoon Sohn ◽  
Cheul Hee Lee ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Sensor Node ◽  
Crack Detection ◽  
Early Stage ◽  
Fatigue Cracks ◽  
Ultrasonic Waves ◽  
Wireless Sensor ◽  
Wireless Sensor Node ◽  
Target Structure ◽  
Fatigue Crack Detection

A fatigue crack and its precursor often serves as a source of nonlinear mechanism for ultrasonic waves, and nonlinear ultrasonic techniques have been widely studied to detect fatigue crack at its very early stage. In this study, a wireless sensor node based on nonlinear ultrasonics is developed specifically for fatigue crack detection: (1) through packaged piezoelectric transducers, ultrasonic waves at two distinctive frequencies are generated, and their modulation due to a microcrack (less than 0.1 mm in width) is detected; (2) an autonomous reference-free crack detection algorithm is developed and embedded into the sensor node, so that users can simply “stick” the sensor to a target structure and automatically “detect” a fatigue crack without relying on any history data of the target structure; and (3) the whole design of the sensor node is fulfilled in a low-power working strategy. The performance of the sensor node is experimentally validated using aluminum plates with real fatigue cracks and compared with that of a conventional wired system. Furthermore, a field test in Yeongjong Grand Bridge in South Korea has been conducted with the developed sensor nodes.

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