Transactions of Japan Society of Spring Engineers

Effects of Inclusions on Fatigue Strength of a Suspension Spring Steel

Yukitaka MURAKAMI, Katsumi KAWAKAMI, Makoto SAITO

1990 Volume 1990 Issue 35 Pages 1-7
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.1

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The fatigue limit of high strength steels does not increase linearly with hardness, and moreover the scatter of the fatigue limit is very large. Spring steels are a typical material which shows such kinds of fatigue characteristics. The fatigue fracture origin of high strength steels is not slip band cracks or grain boundary cracks but usually nonmetallic inclusions contained in the materials.
In this paper, the combined effects of nonmetallic inclusions with the hardness of a matrix on fatigue strength is considered by the fracture mechanics and an equation to predict quantitatively the fatigue strength of high strength steels is proposed. The crucial geometrical parameter of inclusions which controls fatigue strength is the square root of the area (_??_area) of the inclusion projected onto a plane perpendicular to the direction of the maximum tensile stress and the crucial material parameter is the Vickers hardness (Hv). The prediction method is applied to evaluate the fatigue limit of an automobile suspension steel (SUP12) and it is shown that the predictions of the fatigue strength reduction caused by inclusions are in good agreement with the experimental results.

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The Warm Sagging of Ti-Ni Shape Memory Alloy Spring

Hitoshi AOYAMA, Koei GENBA, Yoshihisa OKAZAKI, Yoshihiro HANAI

1990 Volume 1990 Issue 35 Pages 8-12
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.8

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Recently Ti-Ni shape memory alloy springs are used in automobile devices. As the automobile use, it is very important to know the degradation of shape memory effect under somewhat higher temperature.
The authors carried out warm clamping test to examine the effects of chemical compositions and treatment temperature on warm sagging.
The results are as follows;
(1) The recovery force decreases by the test. the higher the treatment temperature gets and the lower the Ni content gets, the recovery force decrease becomes greater.
(2) The recovery temperature changes by the test. It shows the different behavior according to Ni content.
(3) These phenomena seems to be associated with the precipitation of excess Ni content.

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Development of a High-Strength Oil-Tempered Wire for Carbo-Nitriding Process

Yoshitoshi HAGIWARA, Yukio ITOH, Toshio OZONE, Katsuhiko YAMADA, Hiroa ...

1990 Volume 1990 Issue 35 Pages 13-20
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.13

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The effect of carbo-nitriding process on the fatigue of valve springs is well known. To make use of the process more successfully at a higher temperature, a heat resistant oil tempered wire for valve springs was developed, to which the process was applied at higher temperatures than that for Si-Cr oil-temperd wire springs.
As expected, the developed valve springs processed at the optimum temperature were found to exhibit fatigue lives about five times as long as that of Si-Cr valve springs carbo-nitrided at a conventional temperature around 420°C.

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Mechanical Properties of a Titanium Alloy Ti-22V-4Al for Springs

Yuzo OHTAKARA, Akihiro SUZUKI

1990 Volume 1990 Issue 35 Pages 21-24
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.21

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Tensile and torsion test are examined to evaluate mechanical and elastic properties of a beta titanium alloy, Ti-22%V-4%Al, for application of spring material. We confirm this alloy has good properties for spring material.
Tensile strength is 76kgf/mm² in solution treated condition and it increases over 150kgf/mm² by combination of aging with cold working. This alloy has good cold workability. Reduction in area keeps the level as large as the one in solution treated condition. Age hardening is accelerated by cold working. 0.2% proof stress in torsion is indicated by about 0.7 times of 0.2% proof stress in tension. Elastic modulus changes from 8000kgf/mm² in solution treated and cold worked condition to 10300kgf/mm² in aged condition. Microstructure in aged condition shows existence of precipitated alpha phase in beta matrix. Change of the above properties during aging is due to precipitated alpha phase.

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An Isoparametric Element for Curved and Twisted Beam

Masayoshi SHIMOSEKI, Heiichi FUJINUMA

1990 Volume 1990 Issue 35 Pages 25-34
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.25

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Several reports have been published on the FEM analysis for coil springs. All of them, however, based on the beam theory, so that it is difficult to get the stress distribution in the cross section. So, we have been obliged to use, for example, the Wahl's stress correction factor.
To get over this difficulty, we developed the isoparametric element analysis for curved and twisted beams.
In this report, we introduce such method and some examples. We think that it is usefull to analize not only coil springs, but also wiresprings and stabilizer bars.

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Working Characteristics of Continuous Coil Cut with Synchronous Cutter

Kazunori TSUSHIMA, Takahiko KUNOH, Shinichiro NISHIOKA, Masanari HASHI ...

1990 Volume 1990 Issue 35 Pages 35-40
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.35

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In this paper, we describe an experimental study on the cutting off characteristics of continuous coils with the especially designed synchronous cutter during coiling. The summary of experimental results is shown as follows:
(1) Abrasive wear amount of cut-off wheel increases exponentially to the infeed rate.
(2) Mean cut-off force and abrasive wear anount are in proportion to the power of abrasive infeed rate.
(3) The less abrasive infeed rate is, the better working accuracy of coil ends is. And so taking a view of cost and coil working accuracy, optimum abrasive infeed rate is≅5.0mm/min.

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Development of Leaf-Spring Profile Non-Touching Automatic Measuring System

Masanobu ITO, Toshio HAMANO

1990 Volume 1990 Issue 35 Pages 41-46
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.41

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For analyzing the creak or beat proper to the profile of leaf spring, we usually mesure the profile of leaf spring before processing the measurement data using a computer.
In this respect, unfortunately, we have to admit that the operational efficiency provided by the conventional system still remains insufficient. This is because two stages of the operation, profile measurement and data processing, are done separately from each other, and in particular the measurement method is not automatic.
This new system allows an not touching automatic measurment of the profile of leaf spring by linking optical detectors with a personal-computer, and will provide an integrated analysis system with superior operational efficiency.

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Effects of Modified Ausforming on Mechanical Properties and Anti-Setting of Spring Steel

Nobuhide ITOH, Miyajiro OHMORI, Takanori ADACHI

1990 Volume 1990 Issue 35 Pages 47-53
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.47

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Effects of modified ausforming on the softening resistance to tempering, yield strength and antisetting of Mn-Cr spring steel (SUP9A) have been investigated.
The modified-ausformed steel was rolled at a temperature range from 860 to 750°C and oil quenched immediately after rolling. Rolling reduction was varied from 30 to 50%. The modified-ausformed steel showed surpassing softening resistance to tempering and yield strength in comparison with the conventionally heat treated steel at the whole tempering temperature range from 400 to 700°C, however the percentage elongation of the modifiedausformed specimen was slightly lower than that of the conventionally heat treated one. The antisetting of modified-ausformed steel was superior to that of the conventionally heat treated steel under condition of the same tempering temperature (500°C) or of the same tempered hardness (Hv390). These results have shown that modified ausforming is useful for improvement in properties of spring steel.

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Evaluation on Dynamic Properties of Leaf Springs

Committee for Characteristics and Designing of

1990 Volume 1990 Issue 35 Pages 54-62
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.54

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Relations between the inter-leaf frictional force of laminated springs and the sum of vertical forces acting on the extreme points of the leaves are investigated statistically.
As the frictional force seems to be in proportion to the vertical force, the regression lines with the 95% confidence limit lines are determined for the laminated springs and the stacked single leaf springs respectively.
Using those rerations, a method of estimating the frictional force from the vertical one is proposed, which may be useful in the dynamic designing of leaf springs.

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Trends of Spring Technology Material

S. ABEYAMA, E. SUZUKI

1990 Volume 1990 Issue 35 Pages 63-64
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.63

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Trends of Spring Technology Design & Performance

M. SHIMOSEKI, K. KATO

1990 Volume 1990 Issue 35 Pages 65
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.65

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Trends of Spring Technology Design Manufacturing, Testing, Inspection

K. SAITO, H. TOSHINO

1990 Volume 1990 Issue 35 Pages 66-67
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.66

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Trends of Spring Technology Material Standards

N. MIYAGAWA, T. OZONE

1990 Volume 1990 Issue 35 Pages 68
Published: March 31, 1990
Released on J-STAGE: February 26, 2010

DOIhttps://doi.org/10.5346/trbane.1990.68

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