| The thin-walled structure has the characteristics of lighter weight, greater strength, material used more efficiently than other structures. Therefore, it is widely applied in engineering practices. At present, the thin-walled structure mechanics has became an important branch of elastic mechanics. In this paper, study on a special kind of thin-walled structure——thin-walled bar and its restrained torsion theoretical, its engineering applications. Mainly acquire research results as following several aspects:1. Study on the restrained torsion problem of a similar-oval section closed thin-walled bar with the method of Wumansji theory and MSC.PATRAN/NASTRAN. Through a lot of examples, analyse the geometry dimensions(such as cross section length-width ration, thickness, length) how influent the calculation accuracy of restrained torsion angle, based on the definition of thin-walled rob structure,acquire that if the length-width ration is not bigger than4/3,the maximal relative error between theoretical and experimental values is about3%. This meets engineering actual requirements, thus determine the applicable scope of the theory calculation.2. Comprehensively analyse the mechanics performance of the large tonnage jib with oval section and large rounded rectangle section, propose a similar-oval section jib form. Through the Wumansji theory, calculate the warping coefficient, acquire that similar-oval section jib owns better restrained torsion characteristic than rectangle section jib under the same conditions. And then, choose a similar-oval section jib as research object, calculate its restrained torsion warping displacement, warping normal stress and critical torsional moment, which could provide theoretical references for this jib.3. Respectively deduce the restrained torsion calculation formulas of common pentagon, hexagon, and octagon jibs, and verify their correctness based on MSC.PATRAN/NASTRAN. Then, through examples learned that the key points which influence on restrained torsion characteristic,and the critical torsional moment. Which can be taken as the references for engineering design and structure improvement. At the last, acquire that the pentagon jib owns the best restrained torsion characteristic, and similar-oval jib is better than the others.4. Consult the achievements in bridge engineering, propose a "Y model" rigid frame gantry cranes structure.The results based on ANSYS show that, the new structure has better mechanics characteristic;Through the project example of a BIW vibration modal, study on the influence of thin-wall bar for the bend and torsion modal. They show that the thin-wall bar structure has widely engineering prospect,and reflect that the thin-wall structure mechanical propertiesis are important for mechanical structure statical design and dynamic analysis. |
