复合螺旋管弹性联轴器强度寿命分析与结构改进
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摘要
弹性联轴器应用十分广泛。无论是在航空还是在其它领域,弹性联轴器都有十分重要的应用价值。本文研究的多层结构的复合螺旋管弹性联轴器具有尺寸小、传递功率大、寿命长等特点。本文针对其结构特点,首先采用理论和有限元方法针对单层螺旋管的扭转刚度和强度进行了分析,然后采用接触非线性有限元方法,对复合螺旋管弹性联轴器不同受载条件下的扭转变形、刚度、强度等进行了详细分析。得到以下研究结果:
1.建立了接触非线性有限元计算模型,详细分析研究了联轴器扭转刚度的非线性特性。研究结果表明:联轴器的扭转刚度与受载密切相关,初始阶段为线性特性,随着载荷增加,其刚度表现为阶段性线性增加,其原因与联轴器结构形式相关;同时刚度也受到转速变化的影响,其原因是离心力影响联轴器的接触应力。
2.动载荷作用下,当频率比小于1时,联轴器等效刚度随频率比的增大而减小,当频率比大于1时,随着频率比的增加,等效刚度逐渐增大。在某一轴系中,为使联轴器起减振作用,要求动力放大系数Km小于1,对应最小激励频率随着刚度的增加而增加,增加趋势逐渐放缓。在阶跃载荷作用下,联轴器传递的总扭矩的最大值不变。脉冲载荷作用下,为使联轴器起减振作用,激励扭矩的最大脉冲时间随刚度的增大而减小,减小趋势逐渐放缓。
3.由于非线性接触的影响,随着扭矩的增加,联轴器最大应力增加速度逐渐变缓;一定转速范围内,随着转速的增加,联轴器的最大应力逐渐变小;扭矩较小时径向偏转对联轴器的最大应力影响不大,当扭矩足够大时,联轴器径向补偿能力减弱。
4.通过基于应力确定寿命的方法,使用多种非对称应力循环等效方法,根据不同疲劳损伤理论,对联轴器的疲劳寿命进行计算分析,并对得到的结果进行对比分析。为联轴器的使用和改进提供了依据。
5.对联轴器进行结构上的改进,得到一种新式复合螺旋管弹性联轴器,使其相同扭矩下的最大应力相对于改进之前降低27%左右,并且结构重量也降低了14.82%。
本文的研究对于弹性联轴器发展具有重要的促进意义。
Flexible coupling is widely applied. Whether in aviation or other fields, flexible couplings play a very important role in industry. The flexible coupling with multi-layer structure compound spiral tube which was studied in this paper has characteristics of small size, high transmission power and long lifespan. In this paper, the torsional stiffness and strength of the single spiral tube is firstly analyzed with theory and method of the finite element according to the structural characteristics, then emphasis is put on studying the stiffness, strength, as well as lifespan issues under different loadings of the flexible coupling with compound spiral tube making use of nonlinear finite element method. The results are obtained as following:
1. Nonlinear finite element model of contact is set up, non-linear characteristic of the torsional stiffness of the coupling is detailedly analyzed and studied. The results show that the torsional stiffness of the coupling is closely related to the loading and linearity in the initial stage, the stiffness performs staggered linear increase as the load increasing, and that is associated with the coupling’s structure. The stiffness is also influenced by changes of speed, because the centrifugal force is associated with the contact stress of the coupling.
2. Under dynamic loading, when the ratio of frequency is smaller than 1, the equivalent stiffness of the coupling decreases as the ratio of frequency increasing; when the ratio of frequency is bigger than 1, the equivalent stiffness increases as the ratio increasing. In a certain shafting, in order to have a damping effect of the coupling, it means Km<1, according to the minimum frequency of the torque increases as the stiffness increasing; and the rate of increase gradually slow down. The maximum total torque transferred by coupling does not change under step load. In order to have a damping effect of the coupling under pulse load, the maximum pulse time of the torque decreases as the stiffness increasing, and the rate of decrease gradually slow down.
3. The maximum stress of the coupling increases as the torque increasing for influence of nonlinear contact, and the rate of increase gradually slow down. In a certain speed range, the maximum stress of the coupling decreases as the speed increasing. When the torque is relatively small, the radial deflection of the coupling doesn’t have much influence on the maximum stress; when the torque is big enough, the radial compensation function of the coupling is weakened.
4. By the method of determining life based on stress, several equivalent methods of asymmetrical stress cycling are used to calculate and analyze the fatigue life of the coupling on the basis of different fatigue damage theory. Then the results is compared, which provides the basis for the applications and improvement of the coupling.
5. The structures of the coupling are correspondingly improved, a new flexible coupling with compound spiral tube is obtained. Its maximum stress decreases by 27% than before under the same torque, and structural weight also decreases by 14.82%.
The research has an important active significance to the development of the flexible coupling.
1.建立了接触非线性有限元计算模型,详细分析研究了联轴器扭转刚度的非线性特性。研究结果表明:联轴器的扭转刚度与受载密切相关,初始阶段为线性特性,随着载荷增加,其刚度表现为阶段性线性增加,其原因与联轴器结构形式相关;同时刚度也受到转速变化的影响,其原因是离心力影响联轴器的接触应力。
2.动载荷作用下,当频率比小于1时,联轴器等效刚度随频率比的增大而减小,当频率比大于1时,随着频率比的增加,等效刚度逐渐增大。在某一轴系中,为使联轴器起减振作用,要求动力放大系数Km小于1,对应最小激励频率随着刚度的增加而增加,增加趋势逐渐放缓。在阶跃载荷作用下,联轴器传递的总扭矩的最大值不变。脉冲载荷作用下,为使联轴器起减振作用,激励扭矩的最大脉冲时间随刚度的增大而减小,减小趋势逐渐放缓。
3.由于非线性接触的影响,随着扭矩的增加,联轴器最大应力增加速度逐渐变缓;一定转速范围内,随着转速的增加,联轴器的最大应力逐渐变小;扭矩较小时径向偏转对联轴器的最大应力影响不大,当扭矩足够大时,联轴器径向补偿能力减弱。
4.通过基于应力确定寿命的方法,使用多种非对称应力循环等效方法,根据不同疲劳损伤理论,对联轴器的疲劳寿命进行计算分析,并对得到的结果进行对比分析。为联轴器的使用和改进提供了依据。
5.对联轴器进行结构上的改进,得到一种新式复合螺旋管弹性联轴器,使其相同扭矩下的最大应力相对于改进之前降低27%左右,并且结构重量也降低了14.82%。
本文的研究对于弹性联轴器发展具有重要的促进意义。
Flexible coupling is widely applied. Whether in aviation or other fields, flexible couplings play a very important role in industry. The flexible coupling with multi-layer structure compound spiral tube which was studied in this paper has characteristics of small size, high transmission power and long lifespan. In this paper, the torsional stiffness and strength of the single spiral tube is firstly analyzed with theory and method of the finite element according to the structural characteristics, then emphasis is put on studying the stiffness, strength, as well as lifespan issues under different loadings of the flexible coupling with compound spiral tube making use of nonlinear finite element method. The results are obtained as following:
1. Nonlinear finite element model of contact is set up, non-linear characteristic of the torsional stiffness of the coupling is detailedly analyzed and studied. The results show that the torsional stiffness of the coupling is closely related to the loading and linearity in the initial stage, the stiffness performs staggered linear increase as the load increasing, and that is associated with the coupling’s structure. The stiffness is also influenced by changes of speed, because the centrifugal force is associated with the contact stress of the coupling.
2. Under dynamic loading, when the ratio of frequency is smaller than 1, the equivalent stiffness of the coupling decreases as the ratio of frequency increasing; when the ratio of frequency is bigger than 1, the equivalent stiffness increases as the ratio increasing. In a certain shafting, in order to have a damping effect of the coupling, it means Km<1, according to the minimum frequency of the torque increases as the stiffness increasing; and the rate of increase gradually slow down. The maximum total torque transferred by coupling does not change under step load. In order to have a damping effect of the coupling under pulse load, the maximum pulse time of the torque decreases as the stiffness increasing, and the rate of decrease gradually slow down.
3. The maximum stress of the coupling increases as the torque increasing for influence of nonlinear contact, and the rate of increase gradually slow down. In a certain speed range, the maximum stress of the coupling decreases as the speed increasing. When the torque is relatively small, the radial deflection of the coupling doesn’t have much influence on the maximum stress; when the torque is big enough, the radial compensation function of the coupling is weakened.
4. By the method of determining life based on stress, several equivalent methods of asymmetrical stress cycling are used to calculate and analyze the fatigue life of the coupling on the basis of different fatigue damage theory. Then the results is compared, which provides the basis for the applications and improvement of the coupling.
5. The structures of the coupling are correspondingly improved, a new flexible coupling with compound spiral tube is obtained. Its maximum stress decreases by 27% than before under the same torque, and structural weight also decreases by 14.82%.
The research has an important active significance to the development of the flexible coupling.
引文
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[29]赵华莱,姜放,李珣,等. C型环试验的加载应力计算[J].天然气与石油, 2007(2):21-24.
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[2] Liu J.Y., Hong J.Z. Geometric stiffening effect on rigid-flexible coupling dynamics of an elastic beam [J]. Journal of Sound and Vibration, 2004,278(4-5):1147-1162.
[3] Xu M, R D Marangoni. Vibration Analysis Of A Motor-Flexible Coupling-Rotor System Subject To Misalignment And Unbalance, Part I: Theoretical Model And Analysis [J]. Journal of Sound and Vibration, 1994,176(5):663-679.
[4]唐云冰.航空发动机高速滚动轴承力学特性分析[D].南京航空航天大学能源与动力学院, 2005.
[5] Jiang W.G, J L Henshall. A novel finite element model for helical springs [J]. Finite Elements in Analysis and Design, 2000,35(4):363-377.
[6] Johnson C. An introduction to flexible couplings[J]. World Pumps, 1996,363:38-43.
[7] B. Gottlicher, K Schweizerhof. Analysis of flexible structures with occasionally rigid parts under transient loading [J]. Computers & Structures, 2005,83(25-26):2035-2051.
[8] Vebil Y?ld?r?m, Erol Sancaktar. Linear free vibration analysis of cross-ply laminated cylindrical helical springs [J]. International Journal of Mechanical Sciences, 2000,42(6):1153-1169.
[9] G. G. Chassie, L E Becker W. On the buckling of helical springs under combined compression and torsion [J]. International Journal of Mechanical Sciences, 1997,39(6):697-704.
[10] E.L.Starostin, G H M Van. Cascade unlooping of a low-pitch helical spring under tension [J]. Journal of the Mechanics and Physics of Solids, 2009,57(6):959-969.
[11] Dammak Fakhreddine, Taktak Mohamed, Abid Said, Dhieb Abderrazek, Haddar Mohamed. Finite element method for the stress analysis of isotropic cylindrical helical springs [J]. European Journal of Mechanics - A/Solids, 2005,24(6):1068-1078.
[12]刘占生,赵广,龙鑫.转子系统联轴器不对中研究综述[J].汽轮机技术, 2007(5):321-325.
[13]梅庆,力宁.弹性联轴器动力特性分析与实验研究[J].振动与冲击, 2008(6):128-131.
[14]傅洪军,金晓刚. PG6551B燃气轮机辅助联轴器故障的分析和处理[J].浙江电力, 2002(5):21-22.
[15]吴玉进. PG9351FA型燃气轮机安装过程中的关键技术[J].电力设备, 2005(11):62-64.
[16]方力,孟广太. PG9351FA型燃气轮机加热与通风系统[J].发电设备, 2008(3):228-230.
[17] Al-Hussain K M. Dynamic stability of two rigid rotors connected by a flexible coupling withangular misalignment [J]. Journal of Sound and Vibration, 2003,266(2):217-234.
[18] Chaika V. Steady State Response Of A System Of Rotors With Various Types Of Flexible Couplings [J]. Journal of Sound and Vibration, 1994,177(4):521-537.
[19] Dean A. Taming vibration demons with flexible couplings [J]. World Pumps, 2005,465:44-47.
[20] J.J.Madge, S B Leen I. Contact-evolution based prediction of fretting fatigue life: Effect of slip amplitude [J]. Wear, 2007,262(9-10):1159-1170.
[21] Jeroen Van Wittenberghe, Jan De Pauw. Experimental determination of the fatigue life of modified threaded pipe couplings [J]. Procedia Engineering, 2010,2(1):1849-1858.
[22] Wei Siang Sum, Edward J Williams Sean. Finite element, critical-plane, fatigue life prediction of simple and complex contact configurations[J]. International Journal of Fatigue, 2005,27(4):403-416.
[23] Forsthoffer, W E Bill. Flexible coupling design, installation and operation[M]. 179-196, 2005.
[24]张芸.简介高弹性联轴器在船舶动力装置中的使用[J].船舶, 2006(1):34-38.
[25]桑楠,杨新明,徐达.矩形截面弹簧应力及变形分析[J].国外建材科技, 2003(3):49-51.
[26]李蕾.整枝机传动机构中矩形截面弹簧的研究[D].北京林业大学机械设计及理论, 2008.
[27]王修春,王新力,洪贵来,等.矩形截面扭转弹簧的研制[J].山东科学, 2000(2):41-43.
[28]胡荣恒.圆形截面与矩形截面扭簧的优化换算设计[J].机械工程师, 1999(12):28-29.
[29]赵华莱,姜放,李珣,等. C型环试验的加载应力计算[J].天然气与石油, 2007(2):21-24.
[30]芮宏斌,黄玉美.弹性基础梁弯曲问题有限元解析与直接边界元法解析的研究[J].机电产品开发与创新, 2008(5):126-128.
[31]孙林松,王德信,谢能刚.接触问题有限元分析方法综述[J].水利水电科技进展, 2001(3):18-20.
[32]卫冬生,徐筱欣,钟凯.大功率膜片联轴器扭转刚度计算研究[J].机械传动, 2006(6):7-8.
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