The Role of Stress Concentration in the Fatigue of Delrin

Wolf, Lawrence J.; Diboll, W. B.

doi:10.1115/1.3670832

Cited by 6 publications

(2 citation statements)

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“…The material often selected to replace steel worm is acetal as it is considered to be the most popular of structural plastics [5,6]. Hooke et al [7] examined several materials, including acetal and nylon, and they concluded that acetal gears were superior in performance and would last longer, provided the contact stress and maximum temperature do not exceed 50 MPa and 80 C, respectively.…”

Section: Introductionmentioning

confidence: 99%

Finite Element Analysis of Composite Worm Gears

Maheedhara

Pourboghrat

2007

Journal of Thermoplastic Composite Materials

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Worm gears are commonly used in windshield wipers and power windows of automobiles. The goal of this work is to study several material problems, such as production bottlenecks and excessive scrap, resulting from the production of steel worm shafts. A possible solution is explored in this work by characterizing material properties of a promising candidate (glass reinforced acetal copolymer) that can replace steel in worm gears. Finite element analysis of the worm thread under static loading and constant temperature is performed in order to calculate the size of the new composite part. The results obtained in this work support the possibility of manufacturing composite worm shafts that could operate at elevated temperatures without sacrificing part performance, while reducing part weight leading to improved fuel economy, noise reduction, and manufacturing problems associated with the steel part. The finite element analysis shows that compared to a steel gear, the axial pitch of a composite worm gear must be increased by 250% in order for it to operate without failure for 10 years at a constant temperature of 23%C. This increase in the axial pitch would ramp up to 400%, if the composite worm gear is expected to operate for 10 years at a constant temperature of 100 C.

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Section: Introductionmentioning

confidence: 99%

Finite Element Analysis of Composite Worm Gears

Maheedhara

Pourboghrat

2007

Journal of Thermoplastic Composite Materials

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“…As expected, the general effect of the presence of stress concentration is to reduce the fatigue life. For example, Wolf and Diboll [9] observed that the fatigue strength of polyoxymethylene was a direct function of the theoretical stress concentration factor. Crawford and Benham [10] also observed a large reduction in fatigue performance of polyoxymethylene, polypropylene, and polycarbonate when a notch was introduced in these materials.…”

Section: Introductionmentioning

confidence: 99%

Fatigue performance of an injection molded talc-filled polypropylene

Zhou

Mallick

2005

Polym. Eng. Sci.

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This paper reports the fatigue behavior of an injection molded 40wt% talc-filled polypropylene. The effects of specimen orientation relative to the flow direction, weld line, hole stress concentration and test frequency on the fatigue performance of this material have been considered. The fatigue strength in the flow direction was higher than that normal to the flow direction. However the orientation effect decreased at lower fatigue stress level. The presence of weld line reduced the fatigue strength. On the other hand, the fatigue strength showed very little sensitivity to the presence of hole stress concentration. The failure mode in fatigue was influenced by the test frequency. When the test frequency was less than or equal to 2 Hz, the failure mode of the talc-filled polypropylene was due to fatigue and the fatigue life increased with frequency. However, when the test frequency was greater than or equal to 5 Hz, the failure of the talc-filled polypropylene was due to thermal softening and the fatigue life did not appear to be influenced much by the frequency.

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