| Blade’s structure design is essential of helicopter design, and its performance greatly influencesthe helicopter. Blade structure design implemented in the prototype design system centered on sectiondescription, which has played an important role in the past few years and made great contribution tothe development of helicopter technology. But with the development of science and technology, someproblems of this design method gradually emerges, such as low efficiency, poor precision, difficulty inexpressing the real structure of blade, neglecting the internal relationship between the design andmanufacture of blade. These inherent defects indicate that the prototype design system focusing onsection description can not meet the need of helicopter digitized development system with technicalcharacteristics of the digitized prototype and MBD (model based definition). Therefore, the moduleparametric definition for composite rotor blade centered in full three-dimensional (3D) description isproposed in this paper. Based on this, several key technologies are further studied systematicly,including3D geometric automatic modeling, sectional and global characteristics calculation,optimization design for blade structure and design process integration. Besides, a new blade structuredesign model based on iinteger-oriented parametric definition has formed, and some approaches basedon this model, such as geometric modeling, structure characteristic computation, structure parameteroptimization and design process integration, are proposed in this paper. The main contents andinnovative points are summarized as follows:1. According to the geometric characteristics and compositions of helicopter composite blade, theinteger-oriented parametric definition which precisely reflects the real shape of blade structure is firstprovided after a comprehensive considering of the need of product digitized development system withtechnical characteristics of the digitized prototype and MBD. As regards the most complicatedcomposite skin structure in the blade, the paper concludes four main types and twelve subtypes ofblade skin ply, and the parametric definition of blade skin is implemented by combining the globaldefinition with the hierarchical definition of ply; Based on its structure geometric characteristics, theirglobal parametric definitions are made for other components. This method not only realizes the globalparametric description of blade structure, but also introduces blade analysis and manufacturesinformation, such as ply sequence, material types and ply orientation angle based on parametricdefinition. And it puts forward a comparatively complete expression mechanism of data structure forcomposite blade component, which not only provides the required data for blade geometric modeling and structure analysis but also for blade manufacture. The blade component definition module withintelligent guiding is developed to guide engineering designers to realize the component definition inconvenient interactive mode. Therefore, the global parametric definition of blade component is thefoundation of this paper’s research work.2. A geometric automatic modeling algorithm is put forward for composite blade structure. Basedon the proposed global parametric definition, the algorithm summarizes the structure characteristics ofblade components and comprehensively applies the geometric modeling theory and method includingB-Rep solid data structure, NURBS surface system, surface offset, surface trimming and so on. Andthen the3D shape of composite blade structure is constructed in parametric driving modeautomatically and effectively. According to the composite skin components, the slicing successiveconstruction method of blade skin shape is proposed, and the shape of the current skin ply isautomatically constructed by the last laminated inner surface; as for other blade components, twodifferent geometric modeling algorithms such as segmental combining and integral forming are putforward by the different parametric definition. The proposed blade automatic modeling algorithm isthe first systematic study of helicopter composite blade modeling. The blade modeling is significantlyimproved and the digital design for blade structure is effectively enhanced, which establish the basisfor digital manufacture based on3D model definition.3. A blade structural characteristics analysis method based on global parametric componentdefinition and modeling is proposed. It can be suitable for the change brought out the globalparametric definition of blade components. The calculations of blade sectional property and bladestructural characteristics are taken as the core, and their calculation formulas are respectively derivedfrom the corresponding definition and physical meaning. According to the emphasis and difficulty inblade structure characteristic analysis such as the sectional torsional stiffness calculation, the conceptsof ply block hypothesis and length to thickness are proposed, and the effective calculation ofcomposite blade sectional torsional stiffness is given by the theory of closed cross section thin-walledbeams; For the whole blade structural characteristic, its calculation formula is derived by assumingthe sectional quality linear density and sectional barycenter distribution are in accordance withpiecewise-linear continuity. The software module of blade structure characteristic analysis with globalparametric definition and seamless integration of blade automatic modeling is developed to realize theautomatic calculation of blade structure characteristic parameters. Experiments demonstrate that theproposed method is available and effective.4. The optimum design method based on global parametric component definition is put forward for composite blade structure. Based on the global parametric definition of blade components, theautomatic geometric modeling of blade structure and the analysis of blade structural characteristics,the blade structure design problem is decomposed to the sectional and global optimization designproblems. The former is the acquisition process of the initial values of blade structure globaloptimization by optimizing the sectional parameters extracted from global structure parameters. Thelatter is the design process of blade structure optimization by adjusting the blade global structureparameters. Different from the previous research on blade optimization design based on the abstractsimplified model, the optimization design parameters are directly from the global definitionparameters of blade structure, and the corresponding optimization results can be reflected on the realstructure of3D blade component. Therefore, it can effectively improve the efficiency and accuracy ofthe practical blade structure design process. The effectiveness and advantages of the proposed methodare confirmed by means of the practical optimization experiments of blade structure.5. The overall scheme of digital integrated system of blade structure design is presented, and thecorresponding platform based on Web is established. Different from the existing structure design flowof original-quasi design, check, interactive design and modification, recheck and re-amendment, theproposed design process is first taking digital design as a guide, and then the input and output of theprocesses are effectively integrated by the digital transformation for blade structure design to providethe process modeling method, which can be selected, reconstructed and WYSIWYG (what you see iswhat you get). This method establishes not only the conventional subsequent design process similar tothe origin blade structure design, but also the automatic iterative design process according to theconcrete design task. By integrating the design related software, the driven workflow engine is used torealize the automatic running of the design process. With the improvement of blade structure designmethod, the corresponding design process is rapidly and efficiently established. And it can improvethe design efficiency of global blade structure by establishing the automatic iterative design process. |
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