Experimental studies on the energy dissipation of bolted structures with frictional interfaces:A review

Bolted joints play a more and more important role in the structure with lighter weight and heavier load.This paper aims to provide an overview of different experimental approaches for the dynamic behavior of structures in the presence of bolted joints,especially the energy dissipation or damping at frictional interfaces.The comprehension of energy dissipation mechanisms due to friction is provided first,while the key parameters and the measurement techniques,such as the excitation force,the preload of the bolt,or the pressure at the interfaces,are briefly introduced.Secondly,the round-robin systems aim to measure the hysteresis parameters of the frictional joints under tangential loads are reviewed,summarizing the basic theory and the strategies to apply the excitation force or acquire the response in different testing systems.Followed by parameter identification strategies for bolted structures,the test rigs with one or more simplified bolted joints are summarized to give an insight into the understanding of typical characteristics of bolted structures,which are affected by the presence of friction.More complex test rigs hosting real-like or actual engineering structures with bolted lap or flange joints are also introduced to show the identification process of the dynamic characteristics of bolted connections employed in specific applications.Based on the review paper,researchers can get the basic knowledge about the experimental systems of the bolted structures,especially several classical round robin systems,such as the Gaul resonator and widely used Brake-Reußbeam system.Readers can take advantage of this background for more creative and effective future studies,make more progress on the study of assembled structures and understand the influence of bolting frictional connections on the dynamic response better.

Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

Analysis of the influence of joint characteristic parameters on roadway deformations

By means of numerical simulation, the roadway deformation affected by joints was analyzed and the pre-tensioned bolts for reinforcing roadway roof in jointed rock mass was studied. The results show that the roadway roof deformation increases gradually with the accretion of joint length, the increase of joint number, the de- crease of intervals, angles and friction angles of joints. The increase is obvious at beginning and then tends slowly. After pre-tensioned bolts are used, roadway roof deformations reduce obviously, and the supporting action of pre-tensioned bolts is more remarkable with accretion of joint length, increasing of joint number, reducing of joint interval, decreasing of joints angle and joint friction angle, and increasing of joint number that bolts drilling through. With comparison of different cases, the joints supporting effect is more remarkable at a small angel. It indicates that the supporting mechanism of pre-tensioned bolts is to reinforce weak faces, such as joints. The more joints the roof includes, the more visible the pre-tensioned bolts strengthening effect is.

Ⅱ型截面双层组合梁摩擦型螺栓连接节点弯矩分配系数

为探究Ⅱ型截面双层组合梁摩擦型螺栓连接节点翼缘和腹板的弯矩比,通过对3种腹板螺栓布置形式的Ⅱ型截面双层组合梁连接节点接触面滑移特征和力学传递机理的分析,进行Ⅱ型截面组合梁螺栓连接节点弯矩分配系数研究。结果表明:组合梁摩擦型螺栓连接节点滑移和力学传力过程可分为翼缘外接触面未完全滑移和完全滑移以及翼缘内接触面完全滑移3个阶段;组合梁摩擦型螺栓连接节点接触面承担弯矩与无连接板截面弯矩之和等于该梁截面处的理论弯矩,腹板接触面承担的弯矩主要由其上的水平摩擦力承担;摩擦型螺栓连接节点接触面上的摩擦力随节点滑移而重新分配,腹板螺栓布置形式对连接节点弯矩分配系数影响明显;根据推出的组合梁摩擦型螺栓连接节点的弯矩分配系数计算式所得结果与数值模拟结果吻合良好,最大误差为7.13%,该计算可用于优化螺栓连接设计。

Analysis of friction‐related acoustic emission in bolted joint structures

A bolted joint may be in a state of continuous fretting friction and wear under random oscillatory loading,which makes the bolted joint prone to loosening.Therefore,it is essential to find a way to monitor the contact state of a bolted joint on time and handle it adeptly.Acoustic emission(AE)signals will be generated during the reciprocating friction of the bolted joint interface.Exploring the relationship between the frictional slip features and the acoustic emission characteristics under different bolt preloads can lay the foundation for using the acoustic emission techniques to monitor the pretightening state of bolted joints.This paper experimentally investigates the acoustic emission signals of a bolted joint structure during friction under different preloads,three repeated tests are implemented.The relationship between friction behavior and acoustic emission characteristics under different preloads is studied.The evolution of classical acoustic emission parameters and kinematic parameters with bolt preload levels is also analyzed.The 3‐D topography of the specimens after parametric tests is analyzed.The results show that the characteristics of both burst‐type and continuous‐type acoustic emission can reflect different friction behavior under different bolt preloads.The evolution curves of acoustic emission parameters changed under the interaction of both frictional kinematic parameters and bolt preload levels.For the 3‐D surface topography,the reciprocating friction shears the peaks and fills the surface valleys,and the topography of the scratched surface areas is redistributed.

振动工况下螺栓连接自松弛机理研究

为研究振动工况下螺栓连接自松弛机理,利用ANSYS参数化语言建立考虑螺纹的三维螺栓连接有限元模型,用降温法加载预紧力,进行螺栓连接横向振动瞬态分析;研究横向激励幅值、初始预紧力、螺纹啮合面、螺栓头及螺母承压面以及连接物之间结合面的摩擦因数等对螺栓连接自松弛影响。结果表明,横向振动时完全滑移先发生于螺纹啮合面处;横向激励幅值越小、初始预紧力越大、螺纹啮合面及螺栓头、螺母承压面摩擦因数越大,螺栓连接自松弛越不易发生;激励幅值一定时连接物间结合面摩擦因数对自松弛无影响,但摩擦因数越大,发生横向振动所需剪切载荷越大。研究结果对理解螺栓连接自松弛、指导防松设计具有重要意义。

复合材料层合板连接件力学性能影响因素分析

在位移载荷作用下,基于二维有限元模型,通过编写材料失效准则和刚度退化规则的ABAQUS用户子程序USFLD,并考虑剪切非线性效应,分析了一般铺层下配合间隙、挤压面切向摩擦系数和开孔形状对复合材料层合板单钉螺栓连接力学性能的影响。结果表明:小的配合间隙、大的挤压面切向摩擦系数和开孔形状采用圆孔时均有利于提高连接强度。

螺栓联结预应力施加方法改进研究

要在各种瞬态行为(碰撞、冲击等)中真实计算出含预紧螺栓结构系统的动态响应,就必须真实模拟出螺栓联结的真实内部应力分布。在以往研究的基础上,改进了只适合简化模型和轴向受力螺栓模型的轴向预紧力施加方法,并提出了使用局部降温法和等效摩擦法联合加载螺栓联结结构预应力的方法。将M24预紧螺栓结构的仿真结果与理论分析进行了比较,结果表明:该方法能够正确地模拟出应力在预紧螺栓结构中的分布,应力计算值误差也在工程允许误差范围之内。

螺纹联接件的微动损伤研究

从试验和数值分析两个方面研究了螺栓预紧力矩对LY12CZ铝合金双盖板对接螺纹联接件微动损伤的影响。在高频疲劳试验机上进行了微动试验 ,对接触表面间的微动损伤状况进行了观察分析。此外 ,在考虑摩擦力的情况下 ,用边界元法对联接板接触面间的位移场和应力场进行了计算 ,并用微动摩擦功来衡量接触面上微动损伤的严重程度 ,所得的结果表明 ,螺栓预紧力矩值的大小对螺纹联接件的微动损伤有较大的影响 ,在某一力矩下其微动损伤程度较轻。

构件强度控制的高强螺栓承压型连接研究

高强螺栓承压型连接是否考虑构件间的摩擦力会直接影响构件强度控制情况下的承载力.根据高强螺栓承压型连接的作用机理对这种过程进行了分析,并采用数值实验方法模拟了这种情况的受力过程,用降温法模拟施加在高强螺栓上的预应力.结果表明:当连接的承载力由构件强度控制时,若不考虑构件间的摩擦力,则高强螺栓承压型连接的承载力会被低估.在分析基础上提出了合理的计算方法.

高强螺栓承压型连接抗剪承载力计算

针对现行规范在计算高强度螺栓承压型连接的抗剪承载力时不考虑连接板之间的摩擦力,与承压型高强螺栓的受力机理不相符的问题,采用虚功原理推导了预拉力模拟方法,并采用有限元方法对这一连接的受力过程进行分析.分析结果表明,当连接的承载力由螺栓强度控制时,若不考虑构件间的摩擦力,则高强螺栓承压型连接的承载力会被低估.在数值分析的基础上对这种连接方式的抗剪承载力提出了考虑连接板间摩擦力的计算方法.与有限元结果比较,该计算方法的误差在10%以内.

拼接板厚度对框架中钢梁高强螺栓拼接性能的影响

拼接板厚度是高强螺栓摩擦型连接中的一个重要参数.采用有限元分析方法,同时考虑材料、几何和接触状态3个非线性,对框架结构中钢梁高强螺栓拼接采用不同拼接板厚度时的性能,进行单调和循环荷载作用下的模拟研究.结果表明:采用较薄的拼接板时,试件的拼接区滑移出现得早,拼接板的塑性屈曲变形也变大;在设计中加大拼接板的厚度则不会对拼接区的性能造成明显影响.

切向加载、卸载和振荡强耦合下机床螺栓结合部之摩擦能量耗散机制

在保持微凸体受法向力恒定的状态下,侧重导出切向力和变形量的切向加载、切向卸载和切向振荡接触方程。当2个球形微凸体接触时,构建每循环中切向接触摩擦能量耗散力学模型。按照赫兹静力弹性法向接触理论,得到微凸体顶端曲率半径。根据微凸体分担法向力的光滑性与连续性法则,校正临界弹性变形微接触面积与临界变形量的数学表达式。面向有条件等式,在弹性和纯塑性变形基础上,建立整个结合部法向力与切向接触摩擦能量耗散的理论模型。以北京机电院高技术股份有限公司直线电机驱动Linear MC6000普莱诺五面体加工中心上的龙门横梁-导轨螺栓结合部为研究对象,分析法向预紧力、表面粗糙轮廓分形维数、切向力、分形粗糙度、相关因子、单轴向屈服应变及静摩擦因数等7个相对独立参数对切向接触摩擦能量耗散的影响规律。可视化的数值分析结果表明:切向接触摩擦能量耗散随着法向预紧力的增大先增大后减小;表面粗糙轮廓分形维数在较小范围内,切向接触摩擦能量耗散随着表面粗糙轮廓分形维数或分形粗糙度的增大而增大;表面粗糙轮廓分形维数在较大范围内,切向接触摩擦能量耗散随着表面粗糙轮廓分形维数或分形粗糙度的增加而减小;切向接触摩擦能量耗散随着切向力、相关因子、单轴向屈服应变的增加而加大;切向接触摩擦能量耗散随着静摩擦因数的增加而降低与经典结论完全相反,这是因为当静摩擦因数较大时,根据近代分形几何理论可知法向预紧力越大,微滑趋势将更小,导致较小切向接触摩擦能量耗散。

栓焊钢桥3种典型细节的疲劳损伤试验

为了研究搭接节点、不承载角焊缝节点、摩擦型高强螺栓连接节点这3种典型栓焊钢桥细节的疲劳损伤演化规律,采用MTS疲劳试验机和正弦波加载的方法研究了这3种细节的损伤程度与循环比之间的关系,共进行了4个单面盖板搭接节点、2个不承载角焊缝节点和2个摩擦型高强螺栓连接节点的疲劳试验,建立了这3种典型细节基于Chaboche疲劳损伤模型的损伤演化方程:单面盖板搭接节点细节:D=1-[1-(n/Nf)0.1970]0.1779;不承载角焊缝节点细节:D=1-[1-(n/Nf)0.01606]0.01858;摩擦型高强螺栓连接节点细节:D=1-[1-(n/Nf)0.01147]0.02153,可用于栓焊钢桥的疲劳寿命预测.

腹板摩擦式钢框架节点震后可更换性能的试验研究

主要针对梁腹板带有摩擦耗能螺栓的自复位钢框架节点结构进行抗震性能和可更换性能的试验研究,探讨该类节点在往复荷载作用下的滞回性能以及节点域的变形特征。在参数选型的基础上,对5组钢框架节点试件进行了低周反复荷载作用下的拟静力试验,其中:4组试件具有自复位能力,分析了各试件的承载力、刚度、耗能性能和滞回特性等性能。综合研究结果表明:所提出的拼接节点能够利用摩擦螺栓的滑移提高节点的耗能能力,有效减少梁和柱主体构件的损伤,同时预应力筋提供了结构的自复位能力。试验结果表明:在地震作用之后,通过更换腹板及摩擦螺栓可以使结构的承载能力和耗能性能与震前基本一致,从而实现结构功能的快速恢复。

连接界面黏滑摩擦模型参数辨识研究

连接界面的非线性黏滑摩擦行为对结构的动力学响应有重要影响。基于描述界面多尺度黏滑摩擦行为的Iwan模型建模连接刚度和阻尼的非线性特性,利用连接结构的幅变非线性动力响应时程信息,提取响应包络作为特征参量,构造用于模型参数辨识的多层前馈神经网络,并分别以含非线性连接的集总参数系统和螺栓搭接梁结构为对象,进行数值和实验验证。结果表明,该方法所提取的特征量和构造的神经网络能够有效地应用于连接界面非线性黏滑摩擦模型参数的辨识,且具有简单、精度高和对噪声有一定鲁棒性的优点。

胀塞式过盈普通螺栓联接

介绍了胀塞式普通螺栓联接,它具有结构紧凑,装拆方便,并可按不同过盈量及胀拉长度,来调整齿面正压力的大小和部位.胀塞式普通螺栓联接与普通螺栓联接进行对比分析后得出:胀塞式普通螺栓联接具有双面接触,压力大、摩擦力大的特点,它的摩擦力矩比普通螺栓联接大得多,因此,胀塞式普通螺栓联接,在变载荷作用下,具有更好的防松能力,是一种新型的防松装置.

复合材料螺栓干涉连接结构压钉过程轴向力建模

复合材料干涉连接结构在螺栓压入过程中,由于螺栓杆与连接孔孔壁间存在显著的轴向相互作用,有可能在复材孔周引起分层损伤,更准确的控制轴向力对于提升复材干涉连接结构强度具有重要的意义。根据干涉配合螺栓压入过程中接触关系的变化,对压钉过程进行了阶段划分,并在经典层合板理论假设基础上,结合弹性力学复变函数方法,以干涉量为变量建立了螺接过程轴向力解析模型。基于ABAQUS软件,建立了干涉压入压钉过程的仿真模型,验证了解析模型的正确性。

摩擦型高强度螺栓连接可靠度的研究

为使摩擦型高强度螺栓连接设计计算更趋合理,结合大量有关摩擦型高强度螺栓的试验资料,通过对影响高强度螺栓连接承载能力的多种主要随机因素的分析,利用一次二阶矩实用概率理论,给出了一种当高强度螺栓连接达到最大设计容许承载力时的可靠度的评估方法,并结合具体算例验证了该方法的可行性.

复杂钢管结构电视塔塔柱拼接形式研究

河南省广播电视发射塔为高388m的综合性钢结构电视塔,其外塔柱节点间直线段长度达48m,为了满足热浸锌防腐、运输、吊装等工艺要求,必须对其进行分段,在施工现场进行外塔柱拼接,且拼接节点要求抗弯刚度连续。目前钢柱拼接对H形截面柱可采用高强螺栓抗剪连接和全熔透坡口对接焊,但对于箱形截面柱和管形截面柱采用的都是全熔透坡口对接焊拼接方法。为了不破坏热浸锌防腐蚀层,提高施工质量和施工速度,希望能够采用工厂焊接,现场螺栓法兰连接的施工方法。在以往钢塔设计中,法兰连接作为部分刚性连接,不要求其抗弯刚度的连续性,而只要求其受力性能满足设计荷载要求。采用高强螺栓摩擦型连接的法兰来保证河南省广播电视发射塔外塔柱承载力和抗弯刚度的连续性,并通过构件的缩尺加载试验进行验证,说明了该拼接节点的合理性和施工的可行性。