| The gear mainly regards the machine type of transmission as principle. Because it has the tightly packed structure, the high efficiency, the long life span, and the work credibility with maintain convenient etc. It has got the widespread application in the aspects of exercising and dynamically delivering, and the designing method has already equal norm and standard. But as along with the people's exaltation to the automobile economical and the weight reducing, hope the gear under the circumstance that the size and the weight is as small as possible, still can deliver the high speed and heavy load. This puts forward the higher request to the calculation of the gear strength.However, the traditional design of the gear project adopted handicraft design method, not only the long period of the design, but also the low efficiency. Because of the design theory is too"safe", the gear is so"robust", can't satisfy the request of the weight reducing. In the 80's, the local business enterprise began to make use of the BASIC computer language to design the gear, but as along with the technical development of the computer hardware and software, the language of the earlier period has not been supported, so the program compute design can't be carried out in fact.In the end of 90's, some business enterprises begin to apply the CAD/CAE technique to design the gear, and some abroad large business software companies start gradually entering the Chinese market. While the engineering software after all differs from the generally commercial software, it has the higher request to users. Although some software such as ANSYS and NASTRAN have already made the design process as simple as possible, and the interface is friendly and commutation, but the finite element principle is abstruse, the step tedious, any operational error or the error in judgment would produce a mistake, or even get the quite contrary conclusion, impossibly letting the business enterprise or the engineer study it. So the applied circumstance of the abroad finite element software is not very well, greatly parts of business enterprises still all staying around to draw the 3-D part design, making it much visual. The few have the ability to apply the finite element method in the gear design.The thesis is aiming at the actual circumstance, developing the finite element software analysis for bending stresses of transmission gears, making the difficultly of the CAD model design and the abstruse principle of the CAE analysis get out of the gear design, letting the engineer face just as the gear mold, the gear count, and the gear coefficient becoming etc, these gear basic parameters that they are acquainted with. So the engineer could design the transmission gears with the abundant experience of traditional design and the high technique of the CAD/CAE that is forerunner, convenience, and accuracy.The main content and conclusion of the thesis are as following:(1)Five types of gear transition curve modeling and emulatingBecause the gear transition curve have played an important part in the gear bending stresses, by exact analyzing of the gear bending stresses could extent the gear life span. This part takes five types of transition curve as foundation, summarizes five parameter equations of transition curve, and carries on deduce the fifth parameter equation of transition curve. Taking one type of the gear as an example, and applies MATLAB to emulate the five types of gear transition curve, draw the transition curve and the corresponding diagram of gear contour. Using the parameter equation to set up the transition curve mode and emulation, but doesn't adopt the former method seeing it as the arc to act or the curve approaching method, in order to get the exact computing transition curve and the homologous node coordinate, thus by the exact analyzing of the gear bending stresses to lay the foundation.(2)The preprocessor of the finite element analysis for bending stresses of transmission gearsThe main work of this part builds up the model of the gear, meshes, and accords to the concrete structure choice the gear material and bound, makes sure the load that carries on the size, direction and the point. Among them, meshing the gear automatically and the calculation of the load are the point and the difficulty in this chapter. This part adopts the control line method to mesh, so the quality of the gear control line directly relates to calculate right or wrong. This part adopts the level and perpendicularity control line mixing method, avoids the single level control line violating the element demarcation principle, or the single perpendicular control line creating the element abnormal. The load that carries on the gear is the point to raise the finite element method accuracy, the former finite element analysis for bending stresses couldn't calculate the dangerous point on the gear, just could carry the load on the top of the gear. Although this method is simple, it takes sacrificing the calculation accuracy as the price. This stanza doesn't adopt the 30 tangent method to calculate the dangerous interface of the gear, but makes use of the gear thick and the arm of the load to get the precision position, indirectly looking for to the gear dangerous point in the matching area, and then establishes this point as the node.(3)Development software on finite element analysis for bending stresses of transmission gearsAiming at the questions of establishing element stiffness, solving the movement and stresses on the node in the triangle element and the quad equal parameter element, carries on the concrete analysis and discussion. For the sake of improving the visual of calculation result, developing the postprocessor program on finite element analysis, converting the abstract database into the intuition graph. Developing the graphical user interface for the engineer, gets out of the CAD model design and the abstruse principle of the finite element analysis, faces the basic parameter that they are acquainted with, and carries on the abundant experience and the high technique finite element method perfect combine.(4)Using and proving the software on finite element analysis for bending stresses of transmission gearsThis part commences to analyze the variety of the basic parameter of the transmission gears influencing the gear bending stress in response, such as the gear transition curve, the gear mold, the gear counts, the gear becoming coefficient etc, and gives some suggestions basing on the result of the software analysis. While through changing the type of the analysis gear parameters, such as the element type, the bound and the load sort, according to the analysis result of the gear software, found their influence to the gear bending stress in response creatively. Finally through the data of the result and the picture contrasting between the software that is developed according to the thesis and the ANSYS, proving the software on finite element analysis for bending stresses of transmission gears is reliable, and have the higher calculation accuracy, really being a set of the finite element software that can be applied in the actual transmission gears design. |
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