【正文】 e economy of the aircraft. And the reliability of the landing gear is by its original design program of the science and engineering analysis. So it is a great significance to research the modeling of the landing gear. This report start at civil aviation maintenance engineering professional characteristics, and bining with 3D technology through to the landing gear of the modeling and finite element analysis, simulation the stress of the landing gear in the real situation, estimated the failure, loading of the important parts such as hydraulic ponents. It plays a vital significance to fault prediction of aircraft structure. The history of CATIACATIA started as an inhouse development in 1977 by French aircraft manufacturer Avions Marcel Dassault, at that time customer of the CAD/CAM CAD software to develop Dassault39。e Tridimensionnelle Interactive — French for Interactive Aided Threedimensional Design ) — it was renamed CATIA in 1981, when Dassault created a subsidiary to develop and sell the software, and signed a nonexclusive distribution agreement with IBM. In 1984, the Boeing Company chose CATIA V3 as its main 3D CAD tool, being its largest customer. In 1988, CATIA V3 was ported from mainframe puters to UNIX. In 1990, General Dynamics Electric Boat Corp chose CATIA as its main 3D CAD tool, to design the . Navy39。 shape design, mechanical engineering, equipment and systems engineering. CATIA provides a suite of surfacing, reverse engineering, and visualization solutions to create, modify, and validate plex innovative shapes. From subdivision, styling, and Class A surfaces to mechanical functional surfaces. CATIA enables the creation of 3D parts, from 3D sketches, sheet metal, posites, and molded, forged or tooling parts up to the definition of mechanical assemblies. It provides tools to plete product definition, including functional tolerances, as well as kinematics definition. CATIA facilitates the design of electronic, electrical as well as distributed systems such as fluid and HVAC systems, all the way to the production of documentation for manufacturing.CATIA can be applied to a wide variety of industries, from aerospace and defense, automotive, and industrial equipment, to high tech, shipbuilding, consumer goods, plant design, consumer packaged goods, life sciences, architecture and construction, process power and petroleum, and services. CATIA V4, CATIA V5, Pro/ENGINEER, NX (formerly Unigraphics), and SolidWorks are the dominant systems.Chapter2 Overview the landing gear Definition of landing gearThe undercarriage or landing gear in aviation is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land. Typically wheels are used, but skids, skis, floats or a bination of these and other elements can be deployed, depending on the surface.Aircraft designers of the 1920s knew that reducing drag on an airplane in flight was important to improving speed and fuel efficiency, as well as maneuverability and controllability. But they still had relatively little understanding of what actually caused drag on airplanes. Various structures obviously caused drag, but they had first to identify the most important sources before they could address them.In 1927, the National Advisory Committee for Aeronautics (NACA) opened its new Propeller Research Tunnel (PRT) at Langley Memorial Aeronautical Laboratory in Virginia. The PRT was a very large wind tunnel for the time, with a diameter of 20 feet ( meters). It was designed to allow the testing of an entire airplane fuselage with engine and propeller, as opposed to simply a part of an airplane or a scale model. NACA aeronautical engineers suspected that the aircraft landing gear contributed to much of the drag of an airplane, and the PRT was the first wind tunnel that would allow them to test this.Landing gear consists of the wheels that stick out below the fuselage so that an airplane can roll down the runway during landing and takeoff. In early aircraft, they were fixed in an open position so that they protruded at all times, even while the plane was flying and nowhere near the ground. Tests in the PRT immediately demonstrated that landing gear contributed up to 40 percent of fuselage drag, which shocked the researchers. They realized that reducing the drag produced by the landing gear would significantly improve the performance of the airplane in flight. There were several ways to reduce the drag of the landing gear. The two most obvious methods were to either retract the landing gear inside the aircraft or redesign a fixed landing gear so that it produced less drag while still protruding below an aircraft. Retracting landing gear were not a pletely new idea in the 1920s. . Wartin39。s speed increases. As aircraft speeds continued to increase during the 1930s, particularly as aircraft began to reach speeds of 200 miles per hour, the increased weight of retractable gear became less important than reducing drag, and retractable landing gear became monplace to most aircraft. Today, many lowspeed private aircraft still have fixed landing gear because of cost and maintenance concerns. Some even have the streamlined pants coverings over their wheels. But virtually all larger and faster aircraft have pletely retractable landing gear. Designing such gear presents engineers with a number of problems, particularly how to mount them on the airplane without affecting other parts of the aircraft design. Large mercial airliners like the 747 and Airbus A340 have enough internal volume so that the landing gear can fit inside the fuselage diameter. But some smaller mercial aircraft have to promise. Their fuselages are so small that fitting the landing gear inside the primary fuselage would result in a large bump inside the cabin that passengers would have to walk over. So their landing gear are often fitted inside bulges that stick outside of the fuselage.