Papers by Keyword: Fatigue

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Authors: Christina Radlbeck, Mathias Rengstl, Senta Pessel, Martin Mensinger
Abstract: DIN EN 1999-1-3 presents a comprehensive framework for fatigue design of aluminum structures. Various structural details and joints are included. For safety checks against High-Cycle Fatigue, three design concepts are available: Safe-Life-Design, Damage-Tolerant-Design and Design assisted by Testing. Respective safe-life-design lines are based on a databank including results from stress controlled Wöhler fatigue tests. The phenomenon of Low-Cycle-Fatigue (<105 cycles) is treated in Annex F, giving design regulations for selected structural details. Thereby, the influence of different alloys and thus different yield strength values is not considered. In addition, plasticizing effects under high stress ranges are neglected. In general, engineers face the following questions: Which cycle numbers require (Low-Cycle-) fatigue design and thus where is the limit for static design? Furthermore, how to define the maximum allowable stress range? Respective answers are investigated in a current research project carried out by the Chair of Metal Structures, TU Munich.In this contribution, the state of the art of fatigue design according to DIN EN 1999-1-3 is presented. European design concepts are discussed in view of available data and new developments in research, quality control, fabrication of specimen as well as testing techniques. The focus is then laid on Low-Cycle Fatigue. A new concept, including the influence of alloy type and the effects of plasticizing, is worked on. To this purpose an extensive testing program has started, including a large number of strain-controlled-tests.
Authors: Xue Song Huang, Ning Peng
Abstract: 6-Gingerol was extracted and isolated from fresh ginger (Zingiber officinale Roscoe) to determine its effect on anti-fatigue. The loading forced swimming time, glycogen content in liver and muscle, lactic acid in blood and the content of urea nitrogen in serum were determined from the mice treated orally with 0.30 mg/kg of 6-gingerol for 6 weeks. The results show that the mice swimming time treated orally with 6-gingerol was prolonged two-fold longer than that treated with distill water and the glycogen content in liver and muscle and the recovery rate of lactic acid in bloodare increased (P<0.05). And 6-gingerol also significantly decreased the urea nitrogen in serum after swimming (P<0.05). It concludes that 6-gingerol exhibits fatigue resistance. The anti-fatigue mechanism of 6-gingerol is the results from increasing the glycogen storage in muscle and liver, which enhance the aerobic metabolic ability in strenuous muscle activities, accelerate the elimination of fatigue and enhance the adaptation to load exercise.
Authors: Xiao Ling Zhao, Masoud Motavalli
Abstract: There is a great potential in using fibre reinforced polymer (FRP) to strengthen aging metallic structures. This paper briefly describes the benefit of using FRP to strengthen metallic structures. It then addresses how fatigue load affects the bond between FRP and steel. FRP fatigue strengthening of cracked steel plates and connections are discussed. Furthermore, effects of using prestressed FRP on flexural and fatigue behaviours of a FRP-steel composite system are addressed. Bonded and un-bonded FRP-to-steel applications, as two different approaches for steel strengthening, are discussed. Finally fatigue strengthening of metallic riveted bridges using un-bonded pre-stressed FRP plates is presented. A comprehensive list of references is provided.
Authors: Il Ho Kim, Tae Sang Park, Se Young Yang, Soon Bok Lee
Abstract: Fatigue behaviors of 63Sn37Pb and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling to solder joints than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluate the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder joint in BGA packages. The results revealed that lead free solder joints have a good fatigue property in the low temperature condition, where a small strain was induced. In the high temperature condition where a large strain was induced, however, lead contained solder joints have a longer fatigue life.
Authors: Er Nian Zhao, Wei Lian Qu
Abstract: The fatigue strength of weldments is remarkably different form smooth specimens due to the welding. To deal with the fatigue assessment of the various types of the weldments, the weld detailing catalog is widely adopted in the fatigue recommendations. This paper focuses on the comparison of fatigue design recommendations for welded details. Meanwhile the resent development method in the fatigue assessment is also discussed.
Authors: A.J. Morris, R.F. Robey, P.D. Couch, E. De los Rios
Authors: Sergio Baragetti, Stefano Cavalleri, Federico Tordini
Abstract: In this work a preliminary data set including experimental results from fatigue tests on smooth and foreign object damaged (FOD) aluminium samples coated with WC/C deposited with PVD (physical vapour deposition) technique was considered before testing WC/C-coated spur gears for racing motorcycles under rolling contact fatigue (RCF). The fatigue behaviour of the samples was correlated with the results obtained with the RCF tests on the coated gears. A special device mounted on a universal testing machine was used to carry out the RCF tests.
Authors: Hynek Lauschmann, Ondřej Kovářík
Abstract: The reference texture is a subset of the image texture in SEM fractographs of fatigue fractures. It is common to all fractures caused by loadings in which significant events occur sufficiently regularly and frequently. The reference crack growth rate is unambiguously related to the reference texture. A particular loading is characterized by the ratio of the reference and conventional crack growth rates called reference factor. Its value may be related to the sequence of successive sizes of cyclic plastic zone, while the mechanism of the effect of overloads follows the models of Wheeler and Willenborg. Application to a set of three test specimens from stainless steel AISI 304L loaded by various loading regimes is shown.
Authors: Phani C.R. Sree, Daniel Kujawski
Abstract: The Smith-Watson-Topper (SWT) parameter was originally suggested and is still widely used to account for mean stress effects in fatigue life analysis. It is well recognized however, that the SWT parameter might be non-conservative for cyclic loads that involve relatively large compressive mean stresses. Such large compressive mean stresses can develop in notches after overloads. An energy interpretation of the SWT parameter is presented first. Based on analogy with the Neuber’s rule a new deviatoric formulation of the SWTD parameter is proposed. It is found that for positive mean stresses and moderate negative mean stresses the original SWT parameter and the proposed deviatoric SWTD parameter yield similar results. At large compressive mean stresses and non-proportional biaxial fatigue, the deviatoric SWTD parameter demonstrates a fairly good correlation to test data while the original SWT parameter results in wide scatter.
Authors: Len Davidson
Abstract: From 1998 until 2001 a series of engine failures occurred in a fleet of large marine diesel engines due to the failure of precombustion nozzles. The nozzles are screwed into the head of the engines and are held in place by a tightening torque and a high temperature ceramic adhesive. The preliminary findings of an engineering investigation after one such failure concluded that cracking occurred in the nozzle at the time of the installation, due to poor installation technique, and that this cracking resulted in the loss of tightening torque causing the nozzle to become loose. However, the investigation also recommended that fractography be undertaken to verify the cause of failure since this would influence the engineering solution. The current paper focuses on the fractography that was conducted on the failed nozzle to determine its mode of failure and provides a reminder of the importance of fractography in failure analysis.
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