可调螺距螺旋桨叶根螺栓应力分析
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摘 要:针对可调螺距螺旋桨叶根螺栓头部与杆身圆角过渡区域应力集中的问题,根据弹性和弹塑性理论,利用MSC Marc分析叶根螺栓在预紧工况以及螺旋桨处于工作状态的应力分布情况. 采用截面法和渗透接触法分别计算预紧力的加载. 结果表明,螺旋桨处于工作状态下叶根螺栓头部与杆身圆角过渡区域产生较小的塑性变形,对叶根螺栓强度的影响较小;采用截面法和渗透接触法均能有效地模拟螺栓预紧过程.
关键词:可调螺距螺旋桨; 螺栓; 预紧; 应力集中; MSC Marc
中图分类号:U664.33; TB115
文献标志码:A
Stress analysis on blade-base-bolt of controllable pitch propeller
YANG Wenkai1, ZHENG Bailin1, YI Xiaodong2, XIE Qingcheng2
(1. Institute of Applied Mechanics, Tongji Univ., Shanghai 200092, China;
2. 704th Research Institute, China Shipbuilding Industry Co., Shanghai 200031, China)
Abstract: As to the issue that there exists stress concentration in the rounding transition field between the top and the screw of the blade-base-bolt of a controllable pitch propeller, based on elastic and elastic-plastic theory, MSC Marc is used to analyze the stress distribution of the blade-base-bolt which is under the pre-load status and the status that the propeller is in work. For the analysis, the section method and the penetration contact method are used to calculate the load of pre-load force. The results indicate that, during the period of the propeller is in work, small plastic deformation occurs in the rounding transition field between the top and the screw of the blade-base-bolt and has a little effect on the strength of the bolt; both the section method and the penetration contact method can simulate the pre-load process of the bolt effectively.
Key words: controllable pitch propeller; bolt; pre-load; stress concentration; MSC Marc
な崭迦掌:2009-06-17 修回日期:2009-08-02
作者简介: 杨文凯(1985―),男,山东兖州人,硕士研究生,研究方向为工程数值模拟,(E-mail);
郑百林(1966―),男,陕西岐山人,教授,博士,研究方向为复合材料力学与数值,(E-mail)0 引 言
可调螺距螺旋桨(简称调距桨)由桨叶、桨毂机构、配油器、液压系统及电子遥控系统等组成,桨叶不固定在桨毂上,可围绕垂直于桨轴的轴线转动.利用桨毂内的操纵机构驱动桨叶旋转,改变螺旋桨螺距,从而改变桨叶所受推力的大小和方向,以适应船舶前进、后退、制动和变速等要求.[1]
调距桨桨叶由叶片、叶根法兰、曲柄盘和叶根螺栓组成.叶根法兰与曲柄盘通过叶根螺栓连接,叶根螺栓在装配时被拧紧,使连接在进入工作状态之前承受预紧力的作用.预紧的目的在于增强连接的可靠性与紧密性,防止受工作载荷后被连接件(叶根法兰与曲柄盘)之间出现缝隙或相对滑移.在调距桨工作状态下,由于螺距角的存在,桨叶绕桨毂锥体轴线匀速旋转时承受海水推力和扭力以及自身离心力的共同作用,推力、扭力在叶根法兰处会产生较大弯曲和扭转应力,离心力致使叶根螺栓承受更大的拉伸应力.同时,叶根螺栓承受非工作状态下的预紧力,螺栓头部与杆身连接部分由于截面形状突变产生比较明显的应力集中,容易发生断裂现象.[2]因此,在设计时须合理分析螺栓,在保证安全的前提下充分发挥螺栓的性能.
1 螺栓预紧应力
20世纪30年代开始,国外以美国为中心开展高强度螺栓的研究,并相继形成较为成熟的高强度螺栓设计规范.日本和德国的高强度螺栓设计拉力以材料的屈服强度为准则,美国和英国以抗拉强度为基准.[3]国内机械设计规范要求对一般机械的螺栓连接,预紧应力σp=(0.5~0.7)σy,特殊连接如高强度螺栓连接时,预紧应力σp=0.75σy,其中σy为螺栓材料的屈服应力.[4]
本文所研究的调距桨叶根螺栓以扭矩拧紧法拧紧,通过扭矩扳手显示的扭矩值控制螺栓的预紧力.拧紧螺栓时,拧紧力矩等于螺纹副的螺纹阻力矩及螺栓头部与法兰螺孔支撑面间的端