| Because harmonic gear drive have many merits such as big ratio of transmission, smallvolume and light weight, high drive accuracy, little return difference and so on, it has beenapplied successfully to many fields including aerospace, atomic reactor and high-energyaccelerator, radar system, robot, military field, optical instrument and general machine. Theflexspline is the important part of the harmonic drive. And the invalidation of the harmonicdrive mostly is the fatigue rupture of the flexspline. The flexspline bear the role of alternatingstress in the work. As to improve the life-span of the harmonic drive, the improving of theflexspline intensity is required. This article mainly studys the fatigue strength anddisplacement of flexspline by using of finite element method.（1）The theory and characteristic of harmonic gear is described in this article. Based onthe experimental result, the stress and displacement of flexspline are analyzed. The expressionof the fatigue strength of flexspline is obtained. This is the basic theory in studying of theflexspline.（2）Taking B3-160type universal harmonic gear reducer cylindrical cup-shaped flexiblewheel for example. In the three-dimensional modeling software Pro/ENGINEER to create thegeometric model of the flexspline and to simplify the actual situation, and then imported intofinite element analysis software ANSYS, the finite element model generation. Under themodule in ANSYS Multiphysics analyses the flexspline for static stress. The results showedthat: the maximum stress occurred at the flexspline round ring gear and the four force-typewave generator with the contact area, approximately within±20°; the maximum valueappeared at the roots of flexspline, simplified and tooth top force is relatively small; the ringgear stress gradient around the smaller; smooth tube body part in the direction of stress alongthe flexible wheel bus decreases; The flexspline bus along the circumferential and axial hasoffset, causing the phenomenon of stress concentration in the flexspline round ring gear.（3）The mode analysis of the structure has been done. Based on modal analysis theory,mode shapes and natural frequencies of the flexspline are obtained. The results showed that:two forms of the first10rounds of soft modal ideal, consistent with the theory, of which thefirst four vibration mode of the frequency distribution is reasonable. The frequency of variable load excitation is50Hz to90Hz, far less than the torsional vibration naturalfrequency. So the resonance will not occur.（4）To establish the three-dimensional model of the flexible wheel, the flexspline roundring gear is simplified as constant thickness of the cylinder. On the basis of the model inabove paragraphs, some important geometrical parameters of flexsPline are analyzed and therecommendatory values of these parameters are given based on the changes of flexspline’sstress and displacement. This can help the designers to design the flexspline. |
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