Fatigue limit

About: Fatigue limit is a research topic. Over the lifetime, 20489 publications have been published within this topic receiving 305744 citations. The topic is also known as: endurance limit & fatigue strength.

Mechanisms of fatigue in short glass fiber reinforced polyamide 6

Abstract: An adaptation to existing failure models for fatigue fracture of short fiber reinforced thermoplastics is presented, based on results using some new experimental methods. These results lead to the following conclusion: Cracks in polyamide remain bridged (by plastically drawn matrix material and/or fibers) until just before final fracture. Important is the conditioning of the polyamide: conditioned to equilibrium water content, this mechanism occurs, but not when it is dry as molded. Fatigue damage measurements were done on thin foils cut from the fatigued specimen. When tensile tested, these foils show a change in both strength and fracture strain after fatigue. Further observations during the experiments and SEM fractography strengthen the conviction that fatigue damage initiates and grows in the form of bridged cracks. A correlation between tensile strength and fatigue strength was found; the degree of fiber alignment has a similar effect on both tensile and fatigue properties.

Fatigue Strength of Shear Connectors

Abstract: An experimental investigation was undertaken at Lehigh University to determine the fatigue strength of shear connectors for steel and concrete composite beams . Factorial experiments were designed to provide information regarding the effect of stress range and minimum stress level on the cycle life. Included are f.atigue tests of 35 push-out specimens having the concrete slab connected to the steel beam section by t-i-in. stud connectors, 9 fatigue tests of push-out specimens using 1/o-in . stud connectors and 12 fatigue tests of push-out specimens using 4-in., 5. 4lb channel connectors. The test data are described by mathematical equations which express the fatigue life as a function of the stress range. Based on the reported fatigue tests and previous static and fatigue studies , a design criteria is proposed for the shear connectors of composite beams.

DEVELOPMENT OF A FABRICABLE GAMMA-PRIME (γ') STRENGTHENED SUPERALLOY

Abstract: A recently developed wrought γ'-strengthened superalloy, HAYNES® 282® alloy, is introduced. The new alloy is a candidate for several high-temperature applications in both aero and land-based gas turbine engines. It is also being considered for aerospace structural components, as well as automotive and steam turbine applications. The metallurgical features of the new alloy are reported, and the relationship between these features and certain key properties of the alloy is discussed. It was found that carefully balancing the equilibrium amount of the γ' phase was crucial for producing an alloy which could be readily formed and welded, and yet still maintain exceptional creep strength. Too high levels of the γ' phase can lead to difficulties in fabrication, particularly the phenomenon of strain-age cracking. However, a certain amount of γ' is necessary for adequate creep, tensile, and fatigue strength. The γ' level in 282 alloy was optimized to achieve the best balance of strength and fabricability. Alloy properties such as creep, tensile, low-cycle fatigue, and thermal stability were presented for 282 alloy along with those of comparative alloys, R-41 alloy, Waspaloy alloy, and 263 alloy. The fact that 282 alloy was found to have equivalent or better mechanical properties compared to alloys with higher γ' content can be attributed in large part to the alloy's outstanding thermal stability.