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Topic: Fatigue (material)

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Metal Fatigue

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	Fatigue Failures
		Metal fatigue is caused by repeated cycling of of the load.
		It is a progressive localized damage due to fluctuating stresses and strains on the material.
		Metal fatigue cracks initiate and propagate in regions where the strain is most severe.
	www.materialsengineer.com /CA-fatigue.htm (337 words)

	Fatigue (material) Summary
		While the concept of metal fatigue was not completely unknown in the 1800s by the scientific and engineering communities, it was a concept that was neither thoroughly observed nor investigated until the twentieth century.
		In materials science, fatigue is the progressive, localized, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material.
		Fatigue life is influenced by a variety of factors, such as temperature and surface finish, in complicated ways.
	www.bookrags.com /Fatigue_(material) (2281 words)

	Material Testing Services - Fatigue Testing - DDL
		DDL offers a wide range of material testing services that draw upon industry standards and use best practices testing techniques.
		DDL material testing capabilities include strength testing and fatigue testing.
		The information that DDL engineers compile from these tests help you to select the optimal material for your specific application.
	www.testedandproven.com /material_testing.html (138 words)

	Fatigue Fracture Testing,Fatigue Material Crack Test,High and Low Cycle Fatigue Test,Fatigue Crack Growth Rate Test ...
		The name “fatigue” is based on the concept that a material becomes “tired” and fails at a stress level below the nominal strength of the material.
		The Stress-Life (S-N) or Total Life method is widely used for high-cycle fatigue applications—here the applied stress is within the elastic range of the material and the number of cycles to failure is large.
		While low-cycle fatigue is typically associated with fatigue life between 10 to 100,000 cycles, high-cycle fatigue is associated with life greater than 100,000 cycles.
	www.metallurgicallab.com /fatigue_testing.html (711 words)

	Fatigue
		The fatigue behavior of a specific material, heat-treated to a specific strength level, is determined by a series of laboratory tests on a large number of apparently identical samples of that specific material.
		Now suppose the fatigue test is halted after 20 to 25% of the expected life of the specimen and a small thickness of material is machined off the outer surface of the specimen, and the surface condition is restored to its original state.
		An accepted contemporary practice (ref-2:3:328) to estimate the maximum fatigue loading which a specific design can survive is the Marin method, in which the laboratory test-determined EL of the particular material (tested on optimized samples) is adjusted to estimate the maximum cyclic stress a particular part can survive.
	www.epi-eng.com /BAS-Fatigue.htm (2176 words)

	Properties of Materials
		Fatigue is a dynamic phenomenon that initiates small (micro) cracks in the material or component and causes them to grow into large (macro) cracks.
		Fatigue crack initiation is normally associated with the endurance limit of a material and the stress concentration.
		Fatigue crack propagation is associated with the fracture toughness and crack growth characteristics of a material.
	www.ae.msstate.edu /vlsm/materials/fatigue/fatigue.htm (672 words)

	The Posture Theory
		They may in fact report that the fatigue accrues in an obscure way until they reach a state of extreme exhaustion again, and the process of recurring severe exhaustion may happen three or four times over a period of a decade before they decide to restrict their lifestyle as a means of preventing the relapses.
		In the extreme case the fatigue involves restlessness, wakefulness, the inability to sleep for days or weeks at a time, but later waking up several times at night and not being able to get back to sleep again, and waking up tired, and tiredness occurring several times throughout the day are features.
		The fatigue seems particularly linked to the faintness which occurs when leaning forward, either toward a desk, a bench, a washing machine, or the kitchen sink etc. As another example, in order to clean low windows on a house it is necessary to squat down and lean forward.
	users.chariot.net.au /~posture (7924 words)

	SwRI Fall 1998 Technology Today Article
		Understanding metal fatigue, a mysterious and potentially catastrophic phenomenon that can destroy an aircraft engine or shatter an industrial turbine, is made all the more difficult by the lengthy study periods and complex equipment needed to duplicate, observe, and measure it in a laboratory.
		Fatigue cracks growing at these rates have never been fully characterized before and it is expected that knowledge of how these cracks develop and interact with the microstructure of the material will provide useful information for the manufacture, use, and inspection of a variety of advanced engine materials.
		In addition, it has been found that fatigue cracks that were thought to be open at minimum load under conditions of high static stress are, in fact, usually closed at the minimum cyclic load, and don't open until about half the maximum load is applied.
	www.swri.org /3pubs/ttoday/fall98/fatigue.htm (1409 words)

	SwRI Fall 1998 Technology Today Article
		Understanding metal fatigue, a mysterious and potentially catastrophic phenomenon that can destroy an aircraft engine or shatter an industrial turbine, is made all the more difficult by the lengthy study periods and complex equipment needed to duplicate, observe, and measure it in a laboratory.
		Fatigue cracks growing at these rates have never been fully characterized before and it is expected that knowledge of how these cracks develop and interact with the microstructure of the material will provide useful information for the manufacture, use, and inspection of a variety of advanced engine materials.
		In addition, it has been found that fatigue cracks that were thought to be open at minimum load under conditions of high static stress are, in fact, usually closed at the minimum cyclic load, and don't open until about half the maximum load is applied.
	www.swri.edu /3pubs/ttoday/fall98/fatigue.htm (1409 words)

	Fatigue
		Fatigue occurs when a material is subject to alternating stresses, over a long period of time.
		A fatigue fracture will have two distinct regions; One being smooth or burnished as a result of the rubbing of the bottom and top of the crack(steps 1 and 2); The second is granular, due to the rapid failure of the material.
		Beachmarks, or clamshell marks, may be seen in fatigue failures of materials that are used for a period of time, allowed to rest for an equivalent time period and the loaded again as in factory usage.
	www.sv.vt.edu /classes/MSE2094_NoteBook/97ClassProj/anal/kelly/fatigue.html (1478 words)

	Principal Metals
		Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress.
		This is the usual and accepted method of dressing the edges of annealed spring steel strip after slitting in cases where edgewise slitting cracks are objectionable or slitting burr is to be removed.
		A third material that is melted concurrently with the parent metal during fusion or braze welding.
	www.principalmetals.com /glossary/fdoc.htm (1784 words)

	Untitled
		Fatigue failures are often the result of geometrical or strain discontinuities, poor workmanship or improper manufacture techniques, material defects, and the introduction of residual stresses that may add to existing service stresses.
		In a fatigue crack growth experiment, the progress of a crack growing under a cyclic load is measured, and the results are plotted as a fatigue crack growth rate curve, da/dN versus K (that is, change in crack length divided by change in number of cycles to failure versus change in fracture toughness).
		Fatigue failure results under repeated cycling and the life is measured by the number of strain cycles to failure.
	www.sv.vt.edu /classes/MSE2094_NoteBook/97ClassProj/exper/meyer/www/meyer.html (2157 words)

	Designfax - Automotive Forgings and Fatigue
		Material mechanical properties and manufacturing parameters play decisive roles, and the weaknesses and strengths of each manufacturing process need to be available to designers in these respects, to enable them to choose the optimum choice for the specific component and application.
		Fatigue behavior is, therefore, a key consideration in design and performance evaluation of automotive components, and to address the issue effectively and economically, engineers need to model and design for mechanical fatigue early in the product design stage.
		This research was motivated by a practical need to assess and compare fatigue performance of components produced by competing manufacturing processes, to develop a general durability assessment methodology for automotive chassis (and similar) components, and to implement an optimization methodology that incorporates structural durability performance, material properties, manufacturing and cost considerations for such components.
	www.manufacturingcenter.com /dfx/archives/0805/0805automotive_forgings.asp (1887 words)

	Material and fatigue properties of old metal bridges
		This thesis aims to answer questions regarding material and fatigue properties of bridges built between the end of the 19th century to 1940’s.
		The aim of the investigation was to determine the material properties of bridges in the specified interval and compare these with properties in evaluation codes.
		The objective was to investigate the fatigue resistance of riveted structures.
	epubl.luth.se /1402-1757/2006/26 (254 words)

	[No title] (Site not responding. Last check: 2007-10-26)
		Although fatigue loading due to traffic movement on bridges is well known, the resulting damage to the concrete deck slabs in the form of fatigue crack growth is not often recognized.
		The total fatigue life of concrete structures is the sum of the cycles required for the dominant crack initiation and the cycles required for the fatigue crack propagation.
		The fatigue life of the macrocrack propagation depends strongly on the bridging behaviour within the fracture zone, which is controlled by the bond degradation laws of aggregate/matrix and fiber/matrix interfaces during cyclic loading.
	www-personal.engin.umich.edu /~nowak/projects/fatigue_durability_decks.htm (7482 words)

	CTL-Technical Brief on Fatigue Failure
		Fatigue failure is the phenomenon leading to fracture under repeated or fluctuating stresses that are less than the tensile strength of the material.
		Although striations are the most characteristic microscopic evidence of fatigue fracture, they are not always present on fatigue fracture surfaces.
		Whenever there is an interruption in the propagation of a fatigue fracture a unique feature of macroscopically visible marks or ridges may be found.
	www.corrosionlab.com /papers/techincal-brief-fatigue-failure.htm (417 words)

	IGTI: Understanding Fatigue, page 3
		LCF is the mode of material degradation when plastic strains are induced in an engine component due to the service environment.
		Fatigue test results in the aggressive environment (left curve) were an order of magnitude lower than the baseline fatigue life tested in air (right curve).
		In engine components where HCF is a concern, turbomachinery designers observe what is referred to as a material's fatigue strength.
	igti.asme.org /resources/articles/fatigue3.html (588 words)

	Multiaxial Fatigue Research
		Experimental fatigue analysis tends to be costly and often impractical for today's complex machines.
		Fatigue crack growth models also come in several flavors; they will not be discussed here.
		The strain-life curve is the standard uniaxial model that relates the fatigue life to the applied strain range.
	www.me.umn.edu /~langlais/research/methods.html (691 words)

	ESDEP LECTURE NOTE [WG12]
		Fatigue is commonly referred to as a process in which damage is accumulated in a material undergoing fluctuating loading, eventually resulting in failure even if the maximum load is well below the elastic limit of the material.
		Fatigue is a process of local strength reduction that occurs in engineering materials such as metallic alloys, polymers and composites, eg.
		Secondly, the material in the small region at the bottom of the notch experiences a support effect caused by the constraint from the surrounding material so that the average strain in the critical region is less than that indicated by the elastic stress concentration factor.
	www.kuleuven.ac.be /bwk/materials/Teaching/master/wg12/l0200.htm (9556 words)

	Engineering Materials – NOTES – Chapter 8 – Failure
		Fracture occurs, typically at a 45 degree angle to the tension as this is the angle of maximum shear stress.
		Material failure may depend on the loading conditions as well as the type of material.
		Materials with no fatigue limit (such as aluminum) – The material is continually weakened by the application of a cyclic load.
	www.uwplatt.edu /~mirth/me3040ch8.htm (1556 words)

	Fatigue - Definitions from Dictionary.com
		She brought fatigue shorts to wear on the hike.
		fatigue "weariness," from fatiguer "to tire," from L. fatigare, originally "to cause to break down," later, "to tire out," from reconstructed adj.
		Fatigues appeared 1836, from sense of a soldier's non-military duties (1776).
	dictionary.reference.com /browse/Fatigue (675 words)

	Fatigue Material
		The fatigue material uses a modified rainflow cycle counting algorithm to accumulate damage in a material using Miner's Rule.
		This material "wraps" around another material and does not influence the stress-strain (or force-deformation) relationship of the parent material.
		The Fatigue material assumes that each point is the last point of the history, and tracks damage with this assumption.
	opensees.berkeley.edu /OpenSees/manuals/usermanual/3203.htm (366 words)

	Fatigue Life
		Evaluating the fatigue strength to be used for component design should be carried out using validated material information and with careful consideration of all factors relevant to the stress locations.
		If the component is stressed to a constant stress level for its operating life then fatigue loading design is not appropriate and for ductile materials the stress concentration factors are not important...If the component is brittle e.g.
		The fatigue modifying factors must be considered and the stress concentration factors should also be considered.
	www.roymech.co.uk /Useful_Tables/Fatigue/Fatigue_life.html (510 words)

	Material Fatigue Anodize Coating at Anodizeprocess.Com
		Material Fatigue Anodize Coating is on Anodizeprocess.Com Chemical salts trapped below a particular paint film will eventually consequence within blistering or else corrosion questions.
		Please get a particular instant in addition to let us understand who you are in addition to how we can be of service.
		Many of those engines developed deformed in addition to overheated exhaust valves...a little were swallowed up within the seat bore.
	www.anodizeprocess.com /Material-Fatigue-Anodize-Coating.php (567 words)

	ETBX Strain-Life Fatigue Analysis Module
		This module calculates the fatigue life of a part under constant amplitude oscillatory loading assuming the strain range controls fatigue life.
		Due to the constraint imposed by the elastically-stressed material surrounding the plastic zone, deformation at the notch root is considered strain-controlled.
		The Strain-Life method is not valid for a material that exhibits a different response in tension and compression (e.g., gray cast iron).
	www.engrasp.com /doc/etb/mod/fm1/strainlife/strainlife_help.html (2917 words)

	Pultrusion Research Abstracts - University of Mississippi CMRG (Site not responding. Last check: 2007-10-26)
		Graphite-epoxy is a potential candidate composite material for fatigue applications that can be produced by one of the more cost-effective processing methods called pultrusion.
		The type and amount of fatigue damage in pultruded composite materials of identical specimen geometry is influenced by processing variables used to produce these materials.
		Also, the extremes of fatigue test variables were determined and recorded at regular intervals during the fatigue test to explain any unusual developments in the damage measurements.
	www.olemiss.edu /depts/compmatl/abstract/abst025.html (442 words)

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