The Bionic Hole Structure Optimization Design Of Piston Skirt And Finite Element Analysis

With the rising of automobile quantity, the research of engine'performance has become an important subject for economics and society. Piston is an most important accessory, and it can compose reciprocal motion friction pair with cylinder liner, and the piston skirt'wear is one of the main factors causing engine failure, as a result, increasing the piston skirts'abrasion resistant is important to improve the engine'life.Currently, the engine pistons design and improvement mainly concentrated on the piston skirt material and piston structure. The piston skirts'materials research mainly includes traditional aluminum or iron material optimization's design and the application of new materials; the piston skirt structure research mainly has two aspects including piston skirt surface's optimization and improvement of the piston skirts'whole structure. However, the traditional design method's ability is limited in improving the piston performance, and the new material cost is higher, so the methods have not been in application generally. While using bionic non-smooth theory, it can improve the wear resistant of piston skirt friction pair to processing bionic hole structure in the piston skirts, and the costs is lower, so it has a better research worth.The holes structure can effectively improve the pistons wear resistance for piston skirts, but at present, the study still focused on design ideas, and the holes'dimensions, distribution and types'influence law to the pistons character have not been researched. Because the method of bionic pistons'structural parameters optimization design also need effective analysis and research, and it can effectively promote bionic pistons'application and dissemination, thus bionic piston design optimization methods'research has high value and practical significance.The cost of engine test bench test is higher, and it has a long longer cycle, but the engine improvement design cycle is becoming shorter, so it need simulation test to reduce the model number by optimizing the pistons'structure, and it also can reduce the cost. Along with the progress of computer technology and precision increasing of numerical calculation method, simulation analysis technology also got applications in the piston design, especially the application of finite element simulation. Finite element structure analysis, thermal analysis and thermal-structure coupling analysis have good ability achieving accurate structure characteristic parameters in the pistons design, and it can provide basis for pistons'optimization. Because structure parameters of piston design involve many parameters in the paper, and it has a higher cost if using test methods only. So it can choose finite element simulation technology, and depending on the pistons'structure analysis and thermal-structure coupling analysis, it researched the piston structure characteristic and thermal-structure coupling characteristics influence by holes'dimensions, distribution and types. Then it optimized the structural parameters of bionic pistons, as a result it can determine the comprehensive optimization pistons with structure characteristics and thermal-structural coupling characteristics.In order to improve the universality of bionic pistons'application, the paper chooses popularity car engine of Jetta, and improved the standard pistons of RSH1.6 L Jetta engine. By researching engine start up conditions and normal working conditions, it calculated the stress load and temperature load, and supplied boundary conditions for finite element structure analysis and thermal-structure coupling analysis. Under the biggest load conditions of the piston, calculating the structure characteristic and thermal-structure coupling characteristics can accurately reflect the actual structure and thermal-structure coupling characteristics of piston.For researching the pistons comprehensive influence of holes dimensions, distribution and type, this paper designed bionic piston of different holes dimensions, distribution and type and researched the structure characteristics and thermal-structure coupling characteristics by finite element structure analysis and thermal-structure coupling analysis, thus it designed the bionic piston with comprehensive optimal structure and thermal-structure coupling characteristics. Therefore this paper's main job is bionic pistons'structure design and analysis of the structural and thermal- structure characteristics of bionic piston, and main research works and features include following aspects:(1) Engine condition analysis and the load calculationThe paper researched the engine start-up condition and normal working conditions, calculated the stress load and temperature load, and established the piston skirts'pressure loads space distribution formula and temperature load of standard piston providing accurate boundary conditions for finite element analysis.(2) The standard pistons'finite element analysisAfter catching the piston's three-dimensional data by reverse engineering, the paper established standard piston entity model using CATIA, and builded ANSYS finite element model. According to the working condition analysis and engine piston skirt pressure load and temperature load, it made the structural analysis and thermal-structure coupling analysis of standard piston, and provided the basis for the design of bionic piston.(3) Structure design of bionic piston and finite element analysisAccording to standard piston finite element analysis results and the pistons'second motion, it designed the bionic piston by the different hole dimensions, distribution and type, its aim is to ensure the stress distribution of the bionic piston skirt and oil film on the skirt surface. Then it calculated load distribution formulas of bionic pistons according to the different bionic piston model, and made structural analysis and thermal-structure coupling analysis of bionic piston.(4) Multi-objective optimization of bionic piston structural parametersFor analyzing comprehensive influence law of the bionic pistons structural parameters to the structure characteristic and thermal-structure coupling characteristics, this paper choose the structure characteristic and thermal-structure coupling characteristic variables as research targets, and determined comprehensive optimal characteristics using multi-objective synthesis balance anslysis method.Through the above works, this paper established the Jetta RSH1.6 L engine standard piston skirts'maximum load distribution function and the standard piston's temperature load; and established bionic piston skirts'maximum load distribution function with different holes dimensions, distribution and type; then it made the structure analysis and thermal-structure coupling analysis, and extracted structural characteristics parameters and thermal-structure coupling characteristic parameters of the various bionic piston model.Through the above analysis, this paper established the relation model between the target variables and holes dimensions, distribution and type; and it adopted multi-objective synthesis balance analysis method, the paper analyzed the 9 kinds of bionic pistons model with structural and thermal-structure coupling characteristics to determine the optimal structure and thermal-structure coupling characteristic bionic piston.