Effects of Grain Size on Fatigue Strength of Notched Specimen : Part 1, Rotary Bending Fatigue Test of Deep Hyperbolic Notched Specimens

This paper deals with the evaluation of influence of the manufacturing methods precision forging and conventional hobbing on the bending fatigue strength of carburized gears. The forging has advantages in productivity and strength. The forged gear has a continuous directed fiber flow which runs along the gear profile. To clarify the effect of strength enhancement, a bending fatigue test is performed for the forged and the hobbed gears. The material of test gears is SCr420H in the JIS and all gears are carburized. The electrohydraulic servo-controlled fatigue tester is used in the constant stress-amplitude fatigue test. The strength is expressed by the fillet stress level, which is calculated by FEM. The obtained strengths of forged and hobbed gear are 1613 MPa and 1490 MPa, respectively. The strength of forged gear is increased 8% in comparison with that of the hobbed gear. The surface hardness is higher and the surface roughness is smaller in the forged gear, however, the residual stress is approximately same. The effect of improvement of the roughness by forging on the strength is small in 1%, and the main reason of the improvement of fatigue strength is considered as the continuous fiber flow.

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Effects of Heating Time, Electric Power and Frequency on Bending Fatigue Strength of Induction Hardened Gears

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.118.527 ◽

2006 ◽

Vol 118 ◽

pp. 527-532 ◽

Cited By ~ 1

Author(s):

Kouitsu Miyachika ◽

Kazuteru Oda ◽

Hideaki Katanuma ◽

Jun Iwanaga ◽

Satoshi Oda

Keyword(s):

Fatigue Strength ◽

Electric Power ◽

Fatigue Test ◽

Hardened Layer ◽

Heating Time ◽

Bending Fatigue ◽

Bending Fatigue Test ◽

Optimum Heating ◽

Bending Fatigue Strength ◽

Micro Structures

The measurement of hardened layer and the bending fatigue test of S35C and S45C steel gears induction-hardened under various heating conditions were carried out, and then profiles of hardened layer and S-N curves (bending fatigue strength) were obtained. Effects of the heating time, the electric power and the frequency on profiles and micro-structures of hardened layers of gears were examined. Relationship between the bending fatigue strength and the profile of hardened layer was determined. Optimum heating conditions for the bending fatigue strength of induction-hardened S35C and S45C steel gears were indicated.

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Effects of Overload on Fatigue Strength of SUS316 Having a Crack-Like Surface Defect

ASME 2010 Pressure Vessels and Piping Conference: Volume 5 ◽

10.1115/pvp2010-25570 ◽

2010 ◽

Author(s):

Hiroko Oosedo ◽

Koji Takahashi ◽

Kotoji Ando

Keyword(s):

Fatigue Strength ◽

Fatigue Test ◽

Surface Defect ◽

Compact Tension ◽

Crack Size ◽

Fatigue Tests ◽

Stress Intensity Factor Range ◽

Bending Fatigue ◽

Bending Fatigue Test ◽

Key Factor

The effects of overload on the fatigue strength and threshold stress intensity factor range (ΔKth) in SUS316 were studied. Tensile overload was applied to compact tension (CT) specimens with a large crack and fatigue tests were carried out to determine the ΔKth. Tensile or compressive overload was applied to bending fatigue test specimens with a small crack-like surface defect and fatigue tests were carried out to determine the fatigue limit and ΔKth. It was found that the ΔKth increased by tensile overloading. The increasing rate of ΔKth in the CT specimen is larger than that in the bending fatigue test specimen. Thus, the crack size effects on the improvement of ΔKth after overloading were observed. The results are discussed from the viewpoint of fracture mechanics. The size of compressive residual stress is the key factor of the increasing rate.

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Properties of Grain Boundary and Fatigue Strength on Bending Fatigue Test of Carburized Steel

Journal of the Japan Institute of Metals and Materials ◽

10.2320/jinstmet.75.645 ◽

2011 ◽

Vol 75 (11) ◽

pp. 645-650

Author(s):

Tatsuro Ochi ◽

Manabu Kubota

Keyword(s):

Fatigue Strength ◽

Grain Boundary ◽

Fatigue Test ◽

Bending Fatigue ◽

Carburized Steel ◽

Bending Fatigue Test

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20 kHz 3-point bending fatigue of automotive steels

MATEC Web of Conferences ◽

10.1051/matecconf/201816522020 ◽

2018 ◽

Vol 165 ◽

pp. 22020

Author(s):

Mohamed Sadek ◽

Jens Bergström ◽

Nils Hallbäck ◽

Christer Burman

Keyword(s):

Fatigue Strength ◽

Fatigue Test ◽

Pearlitic Steel ◽

Fatigue Tests ◽

Test Rig ◽

Staircase Method ◽

Bending Fatigue ◽

Load Frequency ◽

Bending Fatigue Test ◽

Short Time

The 20 kHz load frequency enables fatigue tests for very high cycle fatigue life, 109-1013 cycles, within conveniently short time. In automotive applications, many components are subjected to flexural loading and hence bending fatigue is an important test mode. Ultrasound fatigue test instruments have been used successfully in several assessments of fatigue strength and more commonly in uniaxial loading. Here, a 3-point bending fatigue test rig operating in resonance at 20 kHz load frequency has been designed to test plane specimens at R=0.1 loading. The test rig design and stress calculations are presented. Testing for fatigue strength was conducted using the staircase method with 15 specimens of each steel grade, specimens reaching 108 cycles were considered run-outs giving fatigue strength at 108 cycles. Additional 15 specimens of each grade were tested for S-N curves with the upper limit above 109 cycles. Two different common automotive steels, 38MnSiV5, a micro-alloyed ferritic-pearlitic steel, and 16MnCr5, a carburizing martensitic steel, were tested. The fatigue strengths achieved from the staircase testing are 340 and 419 MPa stress amplitudes for the 38MnSiV5 and 16MnCr5 steels, respectively. The S-N curves of the steels appear to be quite flat in the tested life range 107 – 109.

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