Planetary gearboxes are used to transmit power and motion between rotating shafts using high reduction ratio. Design optimization of such gears requires information about the stress level on contacting surfaces of meshing gears, as it may influence durability and efficiency of the gearbox.
Stress distribution in gears and pinions was estimated using following methods:
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a)
Image correlation – photogrammetry – technique
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b)
Holographic interferometry – holometry – technique
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c)
Finite element analysis of contact problems.
Image correlation is the white light technology. For the image correlation methodology digital pictures of the measured object taken simultaneously by two cameras are automatically correlated in ARAMIS 3D system. By means of triangulation calculation of coordinates of all the points in the images can be performed. Accuracy of the method depends on the field of view so very limited view area was considered for measurements.
Holographic interferometry – holometry – utilizes laser light to create fringe pattern of the interference between reflected image of the object in the real time and restored original image of the same object from the hologram.
Both photogrammetry and holometry measurements require gear prototypes and loading fixtures to be made. This may be not very practical in the early design stage of the gearbox, when a lot of design changes are made. Therefore contact stress data from the experiment should be transferred to finite element code database to fine tune results of analysis.
In a described experiment the fully machined gears were loaded until failure. Contact stresses and meshing teeth ratio were calculated using image correlation, holographic interferometry and finite elements methods. A good correlation in terms of contact position and stress distribution has been found.