Stress and fracture surface analysis of uncoated and coated 7075-T6 specimens under the rotating bending fatigue loading

Safety designs and fracture designs are the two important fields of crack theory. The fracture problems of middle carbon steel under extra-low cycle rotating bending fatigue loading are studied in this paper. The experiments have been made in special rotating bending fatigue fracture machine designed by us. Several problems, the relations of the cycle times of fracture and the strain amplitude near notch tip to the deflection, the effects of depth and tip radius of notch to the cycle times of fracture, are discussed through the experiments. The mathematical expression of fracture toughness to the cycle times of fracture is obtained. The suitable parameters of rotating bending fatigue fracture model for middle-carbon steel in extra-low cycle times has been proposed.

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The Application of Fracture for Middle Carbon Steel in Extralow Cycle Inverse Rotating Bending Fatigue Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.261-263.1147 ◽

2004 ◽

Vol 261-263 ◽

pp. 1147-1152 ◽

Cited By ~ 11

Author(s):

You Tang Li ◽

Chang Feng Yan ◽

Yao Bing Wei

Keyword(s):

Carbon Steel ◽

Fatigue Fracture ◽

Fatigue Loading ◽

Special Equipment ◽

Bending Fatigue ◽

Cycle Times ◽

Rotating Bending Fatigue ◽

Rotating Bending ◽

Tip Radius ◽

Made In

The rotating bending and the inverse rotating bending are the two different forms of fatigue fracture. Some fracture problems for middle carbon steel in extra-low rotating bending fatigue loading are studied in this paper. The experiments of inverse rotating bending fatigue have been made in special equipment designed by us. Several problems, the relations of the cycle times of fracture and the strain amplitude near notch tip to the deflection, the relations of the depth of crack propagation to the cycle times of fracture, are discussed through the experiments. The effects of depth and tip radius of notch to the cycle times of fracture are studied also in this paper. The suitable parameters of inverse rotating bending fatigue fracture model for middle-carbon steel in extra-low cycle times has been proposed.

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Stress concentration on artificial pitting holes and fatigue life for aluminum alloy 6061-T6, undergoing rotating bending fatigue tests

MRS Proceedings ◽

10.1557/proc-1276-26 ◽

2010 ◽

Vol 1276 ◽

Author(s):

Víctor H. M. Lemus ◽

Gonzalo M. D. Almaraz ◽

J. Jesús V. Lopez

Keyword(s):

Aluminum Alloy ◽

Stress Concentration ◽

Fatigue Loading ◽

Fatigue Tests ◽

Stress Concentrations ◽

Bending Fatigue ◽

Aluminum Alloy 6061 ◽

Rotating Bending Fatigue ◽

Rotating Bending ◽

Alloy 6061

AbstractThis work deals with rotating bending fatigue tests on aluminum alloy 6061-T6, under loading condition close to the elastic limit of the material. Results have been obtained for three types of specimens: without artificial pitting, specimens with one artificial pitting hole and specimens with two neighboring artificial pitting holes. Results show that fatigue endurance is reduced in the case of one pitting hole and considerably for two neighboring pitting holes. In order to explain this behavior, numerical analysis by FE are carried out to determine the stress concentrations for the three types of specimens. It is found that the stress concentration for two neighboring pitting holes is an exponential function of the separation between the two holes, under uniaxial loading. The probability to find two or more neighboring pitting holes in real industrial materials, such as cast iron, corroded or pitting metallic alloys is high; then, the stress concentration for two or more neighboring pitting holes needs to be considered for the fatigue prediction life under fatigue loading and corrosion attack applications.

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Ultrasonic Fatigue of Radical Nitrided Ni-Base Superalloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.417-418.209 ◽

2009 ◽

Vol 417-418 ◽

pp. 209-212

Author(s):

K. Yamane ◽

Norio Kawagoishi ◽

Kazuhiro Morino ◽

K. Fukada

Keyword(s):

Fatigue Strength ◽

Fracture Surface ◽

Fatigue Tests ◽

Loading Frequency ◽

Bending Fatigue ◽

Fatigue Process ◽

Rotating Bending Fatigue ◽

Ultrasonic Fatigue ◽

Rotating Bending ◽

Base Superalloy

Ultrasonic and rotating bending fatigue tests were carried out for aged and nitrided Ni-base super alloys to investigate the effects of loading frequency and nitriding on fatigue strength. Loading frequencies were 19.5 kHz under ultrasonic and 50 Hz under rotating bending, respectively. Fatigue strength under ultrasonic was higher than that under rotating bending in both alloys. Moreover, in both tests, fatigue strength was improved by nitriding. The increase in fatigue strength by nitriding was large in ultrasonic fatigue. These results were discussed through the successive observation of fatigue process at specimen surface and fracture surface observation.

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