Abstract
This paper reports on an extensive two-dimensional photoelastic study of the basic deformation behavior of gear teeth under load. Limitations of existing bending-strength design procedures are used to formulate a test program which considers the magnitude of the critical root-fillet stresses, the effects of varying the load position on the flank, the effects of friction forces at contact and the relationship between bending and shearing deformations. Particular interest is devoted to a study of the observed movement of the maximum-stress position around the fillet as load moves up the tooth flank and to the associated variation in stress-concentration factors (around the fillets) due to radial, bending and shear loads. Note is also made of the problems associated with observed ‘proximity effects’ and of the procedures carried out in an attempt to qualify the nature of the effect.
The results of the program have been used to, explain certain anomalies observed in earlier three-dimensional photoelastic model tests1.7 and reference is made to the development of a new design procedure for the bending strength of helical gears.
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Abbreviations
- W :
-
tooth load
- x,y :
-
coordinate position of load application point on gear flank
- θ:
-
inclination of tooth loadW
- t :
-
thickness of model and gear
- b :
-
width of nominal section AB (Fig. 6)
- K s :
-
shear stress-concentration factor
- K b :
-
bending stress-concentration factor
- K v :
-
direct stress-concentration factor
- σ t :
-
tensile fillet stress
- σ c :
-
compressive fillet stress
- e :
-
eccentricity of load about datum=np cos θ=y cos θ-x sin θ
- np :
-
station on gear center line specifying line of action of loadW for load positionn
- α:
-
general position around fillet boundary
- α t :
-
angle defining positionT of stress concentration in the tensile fillet
- α c :
-
angle defining positionC of stress concentration in the compressive fillet
- α s :
-
angle defining positionS of the maximum fillet stress due to shear alone
- α b :
-
angle defining positionR of the maximum fillet stress due to bending or radial load
- y o :
-
distance of base of tooth from some arbitrary datum
References
Hearn, E.J., “A Photoelastic Investigation of the Stress Distribution in Epicyclic Gears,” PhD Thesis, Surrey University (1974).
Kelley, B.W. and Pederson, R., 1957 SAE Annual Earth Moving Conference, Proceedings SAE,66 (1958).
Heywood, R.B., “Tensile Fillet Stresses on Loaded Projections,” 1948 Proceedings, I. Mech. E., London,159,384; also,158,235.
Dolan, T.J. and Broghamer, E.L., “A Photoelastic Study of the Stresses in Gear Tooth Fillets,” University of Illinois Bull. 335 (March 1942).
Lewis, W., “Investigation of the Strength of Gear Teeth,” Proc. Eng. Club Phil., 1893, 16–23.
Allison, I.M. and Hearn, E.J., “A New Design Procedure for the Bending Strength of Helical Gears,” Engineering, 1055–1057 (Oct. 1978).
Allison, I.M. and Hearn, E.J., “A Three-Dimensional Photoelastic Investigation of the Stress Distributions in Helical Gears,” Strain (July 1979).
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Allison, I.M., Hearn, E.J. A new look at the bending strength of gear teeth. Experimental Mechanics 20, 217–225 (1980). https://doi.org/10.1007/BF02327704
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DOI: https://doi.org/10.1007/BF02327704