Effect of retained austenite on the impact-fatigue strength of steel

Abstract Almost all gears used for power transmission of automobiles have been case-hardened by carburizing. Recently, strict demand for reducing running noise and vibration from the power transmission gears requires, in most cases, an additional finishing operation such as grinding and/or honing after carburizing. Nitriding is conducted at a temperature of about 820 K which is lower than the transformation temperature, and thus quenching is not required, resulting in smaller heat treatment deterioration. However, nitrided gears hardly used in practice as for power transmission gears. In the present investigation, experiments were conducted, using test gears case-hardened by two different methods, carburizing and plasma-nitriding. Test results showed that the fatigue strength of carburized gears was higher than that of nitrided gears in most cases when the test gears were made from the same steel. However, the impact fatigue strengths of nitrided gears made from a high tension steel with additional alloy elements Mo and V were higher than those of carburized gears made from the carbon and alloy steels which have been, used as for gear material. The other high tension steel containing neither Mo nor V could not bring about a sufficiently high fatigue strength in comparison with the conventional carburized gears. It should be noted that the impact fatigue strength of carburized gears made from the high tension steel was higher than the ones made of conventional carburizing steel.

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Increasing the impact fatigue strength of ring valve plates

Chemical and Petroleum Engineering ◽

10.1007/bf01137837 ◽

1976 ◽

Vol 12 (12) ◽

pp. 1114-1115 ◽

Cited By ~ 1

Author(s):

V. A. Pyshkin ◽

V. A. Yakovlev ◽

V. Yu. Kuznetsov ◽

S. A. Abramenko

Keyword(s):

Fatigue Strength ◽

Impact Fatigue ◽

Ring Valve ◽

The Impact

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Effect of distance between impact point and hole position on the impact fatigue strength of composite laminates

Composite Structures ◽

10.1016/j.compstruct.2017.02.045 ◽

2017 ◽

Vol 168 ◽

pp. 33-39 ◽

Cited By ~ 3

Author(s):

R.A.M. Santos ◽

P.N.B. Reis ◽

M.J. Santos ◽

C.A.C.P. Coelho

Keyword(s):

Fatigue Strength ◽

Composite Laminates ◽

Impact Point ◽

Impact Fatigue ◽

Hole Position ◽

The Impact

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M. W. Tofique, A. Löf, C. Millward, Z. Günther. Testing and calculation of impact fatigue strength of Flap-X and SS 716 flapper valve steel grades / trans from Engl. M. A. Fedorova

Omsk Scientific Bulletin Series Aviation-Rocket and Power Engineering ◽

10.25206/2588-0373-2021-5-3-63-74 ◽

2021 ◽

Vol 5 (3) ◽

pp. 63-74

Author(s):

M. A. Fedorova ◽

Keyword(s):

Fatigue Strength ◽

Service Life ◽

Fluid Pressure ◽

Test Method ◽

Impact Fatigue ◽

Staircase Test ◽

Reliable Service ◽

Steel Grades ◽

Valve Steel ◽

The Impact

During the operation of reciprocating compressors, the flapper valve opens and closes under fluid pressure and flow. As it closes, it strikes against the valve seat, generating stresses and noise. This cycle of loading produces bending and impact fatigue stresses in the reed. This load pattern is repeated billions of times during the service life of a compressor and it defines the service life and reliability. The goal of this study was to calculate the impact fatigue strength of the Flap-X and the SS 716 grades and, to provide the compressor manufacturers with the information they can use to specify a steel grade to be used in their compressors, for reliable service. Impact fatigue tests were conducted on a custom-built impact fatigue test rig that used air pulses to produce movement of the reed valves manufactured by a major European compressor manufacturer Nidec Global appliance GmbH, at a frequency of 315 Hz and pulse width of 2,2 milliseconds. The testing was conducted according to the staircase test method detailed in the International Standard SS-ISO 12107:2012. The impact fatigue strength of the Flap-X and SS 716 steel valves was calculated in terms of the impact velocity according to the modified staircase test method in the standard. The test results and their statistical analysis showed that the impact fatigue strength of the Flap-X grade was higher compared to the SS 716 grade. The calculation and testing of the impact fatigue strength of the flapper valve steel grades could help the compressor designers to select the optimum material for their compressor designs, to provide reliable service. The higher impact fatigue strength of the Flap-X grade, lower failure rate and longer impact fatigue life will allow the compressor manufacturers to design thinner valves, as Flap-X can sustain higher impact fatigue stresses reliably for longer time and, at the same time help reduce noise, as thinner valves produce less noise for a given pressure and frequency.

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