Testing of Fatigue

Fatigue is determined under cyclic loading, when a crack is initiated and then grows to a critical size, with failure occuring at stresses below the value obtained for normal static tests. 

Strain measurement Strain gage Extenso meter - Strain gage 

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Nil-ductility transition temperature Fracture toughness Dynamic Tndt Blunt changes to sharp Sharp crack Drop-weight specimen test e.g., ASTM E 208. Uses brittle weld crack starter on test specimen. Propagation test Fracture toughness test of fatigue pre-cracked... 

In tests of fatigue crack propagation in a high-strength, eutectoid, cold-drawn steel with 0.82% C, 0.6% Mn, 0.18% Si, 0.01% P and 0.024% S, used to make tension wire in prestressed concrete, it was observed that in seawater low frequencies and cathodic polarisation due to contact with zinc accelerate crack propagation 80). 

Carroll, R. J. (2005). Pilot test of fatigue management technologies. FMCSA Report FMCSA-RT-04-009. U.S. Department of Transportation, Washington DC. 

At contact fatigue tests of different steel and cast iron types was used the acoustic emission technique. Processed records from the AE analyser show importance of acoustic response of tested surface continuous sensing. In graphs are obvious characteristic types of summation curves, or may be from significant changes of AE signal course identified even phases of the wear process. 

There are no classification requirements for routine NDE beyond thickness testing and visual inspection except for repairs, modifications or where service history has identified a specific problem in which case the Surveyors will request NDE at the same locations in similar ships. Under circumstances where visual inspection has found evidence of fatigue cracking the Surveyor can also call for NDE to assess the full extent... 

Corrosion-fatigue cracks can be detected by nondestructive testing techniques such as magnetic particle inspection, radiography, ultrasonics, and dye penetrant. Corrosion-fatigue cracks may occur in numerous tubes simultaneously. Nondestructive testing of tubes at locations similar to those in which cracks are observed can be useftil. 

A series of fatigue crack growth tests on a moulding grade of polymethyl methacrylate gave the following results... 

In Tube Turns tests of eUl types of flanged assemblies, fatigue failure invariably occurred in the pipe or In an unusually weak weld, never In the flange proper. 

Rust, T, E. and Swaminathan, V. P, Corrosion fatigue testing of steam turbine blading alloys , EPRI Workshop on Corrosion Fatigue of Steam Turbine Blade Materials, Palo Alto, California, September 1981, Pergamon Press, (1983)... 

Special requirements for fatigue testing in aqueous environments are addressed in the Annexe to ASTM E647 1986a Standard Test Method for Measurement of Fatigue Crack Growth Rates . 

Horger undertook rotating-beam fatigue tests of press-fitted assemblies using specimens as large as 305 mm diameter shafts. 

Warlow-Davies used a technique in which specimens were subjected to fretting corrosion and then tested in fatigue to show the effect of fretting damage in lowering resistance to fatigue. 

Test method for measurement of fatigue crack growth rates... 

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