湖北清江高坝洲水利枢纽升船机主提升机系统完成厂内机电联调并通过出厂验收

高坝洲电站是清江干流三个梯级电站中最下游的一个梯级电站,设置有垂直式升船机一座。该机由杭州大力机械技术工程有限公司设计,由夹江水工机械厂制造。它是我国目前在用和在建的第4座大型垂直升船机,采用钢丝绳卷扬全平衡垂直提升式,其主要技术参数为;船厢总重量1560t(平衡重总重1560t),运行速度为0.125m/s,额定提升力1600kN,最大提升高度40.3m。2003年12月25日,在四川夹江水工机械厂,由工程业主单位主持,通过了对该机进行的“厂内机电联调暨专业验收”。2004年元月7日,在业主单位主持下,又进行了高坝洲升船机主提升机系统整体出厂验收。…     

船坞围堰拆除爆破数值模拟及优化分析磁

利用DDA方法对船坞围堰的拆除爆破进行数值模拟,分析倾斜孔低水位、倾斜孔高水位、垂直孔和倾斜孔结合低水位以及垂直孔和倾斜孔结合高水位4种不同方案下的爆破特性和规律。研究结果表明：在某公司1#、2#船坞围堰的拆除爆破过程中,水位高低对倾斜孔装药影响不大,对垂直孔和倾斜孔结合装药有明显影响;垂直孔和倾斜孔结合装药高水位工况下形成的边坡较缓,低水位工况下形成的爆堆较低,容易产生水突然涌入坞门的现象;综合分析,选择倾斜孔装药爆破会得到更好的爆破效果。     

渡槽结构考虑流固耦合的横向地震响应研究

渡槽结构是一种薄壁杆件结构,有其自身特点,依据符拉索夫(Volasov)及豪斯纳尔(Housner)理论建立考虑槽内水体流固耦合的渡槽薄壁结构空间地震响应分析模型,该模型综合考虑了渡槽横向、竖向、纵向、自由扭转、约束扭转变形以及槽内水体对槽身的流-固相互作用等。由能量原理推导给出了渡槽薄壁梁段单元刚度矩阵及质量矩阵,建立了渡槽结构无水空载及槽内有水时横向地震响应计算方程。利用该模型对某单墩渡槽进行了多工况地震时程响应计算,经与解析解比较,证明模型的正确性,同时说明在地震荷载作用下,渡槽在无水空载及设计水位时的横向位移有所变化。模型计算简单易行,是考虑槽内水体流固耦合作用的渡槽薄壁结构实用的地震响应分析模型。     

一种新的制备有机-无机杂化膜的方法——前驱体水解聚合法制备聚偏氟乙烯-硅杂化膜

首次提出一种制备有机-无机杂化膜的新方法,即将正硅酸乙酯(TEOS)直接添加到聚偏氟乙烯(PVDF)铸膜液中,在入水凝胶时,PVDF逐渐固化成膜,而TEOS同时也与水发生水解聚合反应,生成硅氧聚合物,这就为形成无机高分子与PVDF互穿网络结构或分子链相互缠绕创造了机遇,为制备力学性能优良的聚偏氟乙烯-硅杂化膜提供了可能.实验初步考察了正硅酸乙酯的添加量对聚偏氟乙烯-硅杂化膜的超滤性能和力学性能的影响,对杂化膜进行了能谱分析.结果表明:1)能谱实验证明杂化膜表面有Si元素存在,表明TEOS在凝胶过程中发生水解聚合反应,生成硅氧聚合物留在杂化膜中;2)在无致孔添加剂存在时,随TEOS添加量的增加,杂化膜的纯水通量增大,而对牛血清蛋白的截留率呈现持续下降的趋势;当TEOS含量为8%时,与无TEOS的PVDF膜相比,杂化膜的拉伸强度σt和弹性模量E几乎增加一倍;3)在有致孔添加荆PVP K30和无水LiCl存在时,杂化膜的纯水通量随TEOS添加量的增加呈先升后降然后再上升的趋势,对牛血清蛋白的截留率呈现持续下降的趋势.当TEOS添加量为12%时,与无TEOS的PVDF膜相比,超滤性能相近,但杂化膜的拉伸强度σt和弹性模量E增加近一倍.     

螺栓连接对结构模态及传递特性影响研究

针对螺栓刚度及预紧力对装配体模态、传递函数影响较大而在设备装配中因处理困难常被忽略问题,利用有限元计算、试验结合对比方法分析、研究。用ANSYS软件预应力模态分析及谐响应分析对装配体进行仿真计算;对三种刚度螺栓分别施加相同预紧力,对钢制螺栓施加六组不同预紧力进行试验;分析对比计算值与试验值误差。结果表明,忽略接触阻尼的计算值与试验值存在最大误差约15%;同一预紧力时,随螺栓刚度的提高固有频率呈增大趋势,各阶频率的最大变形量随之增大;随预紧力的增大,结构传递函数趋于明朗化。     

剪叉式升降平台设计与有限元分析

目的针对市场上现有单级剪叉式升降平台的不足,提出一种可变幅面、可设定升降高度的剪叉式升降平台,设计其机械结构,并进行力学性能分析。方法利用三维建模软件SolidWorks对升降平台进行三维实体建模;利用有限元分析软件Ansys Workbench建立有限元模型,对其静态承载性能进行仿真分析。结果得到了该平台在特定载荷下,在升起且伸缩台板合上,升起且伸缩台板拉开,降下且伸缩台板合上,降下且伸缩台板拉开4种工作状态下的总体变形和等效应力情况。其中最大总体变形主要位于伸缩台板左边缘,上述4种工作状态下的最大总体变形分别为1.97,1.07,0.73,0.33 mm,都在允许范围内;最大等效应力出现在剪刀撑铰点附近,上述4种工作状态下的最大等效应力分别为47.51,40.10,185.34,170.02 MPa,均小于结构钢材料的屈服极限(235 MPa),强度满足要求。结论所提出的可变幅面、可设定升降高度的剪叉式升降平台,拓展了传统升降平台的功能。     

Analysis of Slide Gate Mounting Bolt Failure in Steel Ladle Due to Fatigue

The mounting bolt failed during slide gate operation of a steel ladle was investigated. Metallurgical analysis confirms the bolt as IS 1367 10.9 grade high-tensile 42CrMo₄ steel. On comparative study with a good un-fractured sample, a striation of fine banded ferrite in pearlite matrix was revealed in failed bolt under optical microscopy. The bolts failed due to fatigue and crack initiated from the surface of machined bolt threads. Comparatively lower hardness, low UTS associated with lower %Cr and %Mo content found to aggravate premature failure of bolts during ladle operation. Microstructure of un-fractured sample found with tempered bainite phase. The fatigue failure of bolts occurred due to repetitive nature of shear force development during steel pouring through slide gate system. Preventive measures to reduce fatigue failure of the mounting bolts are proposed.     

Failure analysis of connecting bolts and location pins assembled on the plate of main-shaft used in a locomotive turbochanger

Three connecting bolts, three location pins and navel of turbo-disk fractured, which were assembled on the plate of the main-shaft used in a locomotive turbochanger. Detailed fractographic study and metallurgical analysis were focused on the trouble bolts. The fatigue fracture is the main failure mechanism of the bolts. Appearance of the surface decarburization layer in the thread tip and root regions of the three failed bolts make the hardness at the thread regions decrease intensely so that the fatigue cracks initiated form the root at the first engaged thread. Surface damage morphology with cutting, wear and plastic deformation features was found on the working flanks of the engaged threads. Other components fractured in succession after the trouble bolt fractured.     

Experimental characterization of hybrid composite-to-metal bolted joints under flexural loading

Presented is an investigation of the structural performance of hybrid composite-to-metal bolted joints loaded in flexure. The main goal was to develop a watertight, hybrid connection to resist bending loads. The effect of bolt type, doubler plate geometry and foam inserts was studied. Fourteen different joint configurations were tested including standard bolted joints and bolted joints with doubler plates. The performance of connections loaded cyclically in flexure was assessed by comparing: (1) the initial damage and failure loads; (2) the types of failure modes; and (3) the joint initial rotational stiffness. Instability in the hysteresis loops, where the load drops in subsequent cycles, is used as an indication of damage. A joint using a short doubler plate, a foam insert, and a single row of bolts, was found to be at least 33% stronger and 29% stiffer when compared to a standard bolted joint with two rows of the same diameter bolts. Use of doubler plates and foam inserts in a bolted joint resulted in higher strength and stiffness and can effectively mitigate joint opening, which improves the ability to seal the joint and maintain watertight integrity.     

Determination of forces in bolted joints

We propose a new approach to the determination of forces applied to a bolt in a tightened joint taking into account the variations of its stiffness and present the results of experimental investigations of the stress-strain diagrams of bolts for different values of tightening forces applied to the joints. The proposed procedure for the determination of forces acting on the bolt in the joint subjected to the action of variable loads takes into account the behavior of the stiffness of the joint regarded as a function of the load and tightening forces. We analyze different methods aimed at the determination of forces applied to the bolt according to the results of fatigue tests of bolts in tightened simple joints and present preliminary initial data required for the analysis of variable forces acting on the bolts in tightened joints. By using a new approach, we propose basic principles of design of economically efficient joints.     

Quasi-static behaviour of composite joints with protruding-head bolts

An experimental study of the quasi-static behaviour of composite bolted joints under tensile and compressive loading has been performed. The joint plates made of quasi-isotropic and 0°-dominated lay-ups were fastened by two, four, or six titanium bolts. Two specimen configurations were tested: single lap and double lap. Strain gauges were applied in order to measure strain between the bolt rows and to calculate the load transfer of the bolt rows. Bolt-movement measurements were performed using extensometers to examine bolt behaviour under static loading. The obtained experimental results showed that bolted joints with four and six bolts perform better resistance to quasi-static loading than joints with two bolts. Strain distribution between two bolts is significantly affected by the bolt presence and their behaviour under loading. The load-transfer calculations showed that different bolt rows transfer slightly different amounts of load.     

Strength of bolted moment connections in ferrocement construction

In continuation of an experimental investigation reported earlier by the authors on bolted moment joints in ferrocement construction, this study regards (1) further testing of ten such joints to broaden the range of the principal parameters – thickness of the connected ribs and location of bolts and (2) simple analytical modeling for design. Test results, as presented and discussed in this paper, indicate that the mode of failure of a joint depends on whether the applied moment is in the opening or closing mode. Under the closing mode, failure always occurs by shear punching of the bearing plates through the connected ribs. In contrast, failure in the opening mode occurs by bending failure of either the connected or the longitudinal rib. Based on observed failure modes, expressions have been derived for predicting the strength of such a joint. A comparison of theoretical predictions with present test results and those reported earlier shows good agreement.     

Determination of forces in bolted joints

We propose a new approach to the determination of forces applied to a bolt in a tightened joint taking into account the variations of its stiffness and present the results of experimental investigations of the stress-strain diagrams of bolts for different values of tightening forces applied to the joints. The proposed procedure for the determination of forces acting on the bolt in the joint subjected to the action of variable loads takes into account the behavior of the stiffness of the joint regarded as a function of the load and tightening forces. We analyze different methods aimed at the determination of forces applied to the bolt according to the results of fatigue tests of bolts in tightened simple joints and present preliminary initial data required for the analysis of variable forces acting on the bolts in tightened joints. By using a new approach, we propose basic principles of design of economically efficient joints. Translated from Problemy Prochnosti, No. 5, pp. 126–134, September–October, 1997.     

考虑紧固螺栓的三排滚柱式转盘轴承载荷分布计算

螺栓是转盘轴承的关键紧固件。为考察紧固螺栓工作参数对转盘轴承载荷分布的影响,提出了一种针对三排滚柱式转盘轴承的有限元等效建模方法。首先,基于三排滚柱式转盘轴承的结构特点和受力情况,建立考虑紧固螺栓的转盘轴承有限元模型,并从减少计算量和保证计算效率等方面考虑,采用非线性弹簧单元模拟滚子,通过有限元仿真快速获取了该转盘轴承的载荷分布。然后,设计并开展三排滚柱式转盘轴承静态加载试验,通过有限元仿真结果和试验结果的对比验证了所构建有限元模型的准确性。最后,基于构建的有限元模型,分析了螺栓预紧力和螺栓结合面处摩擦系数对三排滚柱式转盘轴承载荷分布的影响。仿真结果表明：螺栓预紧力对三排滚柱式转盘轴承载荷分布的影响显著,而螺栓结合面处摩擦系数的影响微弱,其中上排滚子承受的最大载荷随螺栓预紧力的增大而增大,下排滚子承受的最大载荷随预紧力的增大而减小;在轴向力和倾覆力矩的联合作用下,三排滚柱式转盘轴承下排滚子承受的载荷总体上高于上排滚子,充足的螺栓预紧力可以提高转盘轴承的承载能力,而螺栓预紧力不足则会使下排滚子承受更大的载荷,导致转盘轴承提前失效。研究结果可为转盘轴承的安装和后期维护提供参考。