单轴压缩下断续节理岩体动态损伤本构模型

断续节理将对工程岩体的强度及变形等力学特性产生显著影响,损伤力学中视节理为岩体的一种宏观损伤,因而采用损伤张量来刻画其对岩体的影响。目前学术界提出了用节理的几何、强度及变形等3类参数来描述节理的物理力学性质,而目前的岩体损伤张量计算方法都只涉及前2类参数,均没有涉及其变形参数即法向及切向刚度。为此,在前人研究的基础上,基于断裂及损伤理论提出了考虑节理法向及切向刚度的单轴压缩下单条断续节理引起的损伤张量计算公式,进而通过考虑节理间相互作用给出了单组单排或多排节理岩体损伤张量计算公式。其次,以岩石细观动态损伤模型为基础,结合宏细观损伤耦合观点提出了一个能够同时考虑节理几何、强度及变形参数的断续节理岩体动态损伤本构模型。最后,利用该模型讨论了节理参数及载荷应变率等对岩体动态力学特性的影响,认为节理长度减小及摩擦角增大将导致岩体动态峰值强度及弹性模量增大;岩体动态峰值强度及弹性模量则随着节理法向及切向刚度的增大分别减小或增大;而当节理法向及切向刚度按照同一比例增大时,岩体动态峰值强度及弹性模量则是增大的。岩体动态峰值强度与载荷应变率呈正相关。     

高锁螺栓连接件动态拉伸响应与失效机理

飞机坠撞过程中结构的变形模式和吸能对乘员保护具有重要意义，而连接结构的载荷传递和失效形式是影响飞机结构变形的重要因素之一。为了获取航空高锁螺栓连接件在坠撞载荷下的动态响应和失效机理，基于抗剪型平头高锁螺栓设计了2种材料（2024-T3和7050-T7451）的单钉单搭接连接件，利用高速液压伺服材料试验机进行4种速度（0.01、0.10、1.00和3.00 m/s）下的拉伸测试，得到连接件的动态响应、极限载荷、能量吸收和失效模式随速度的变化规律，并分析了连接件的失效机理。结果表明，连接件的失效模式受母材和高锁螺栓/螺母材料强度影响较大，而受加载速度影响较小；当速度从0.01 m/s增加到3.00 m/s时，2024-T3连接件的极限载荷和能量吸收分别增加了2.17%和34.43%，7050-T7451连接件的极限载荷和能量吸收分别增加了5.53%和6.58%。     

Limiting deformability and strength of basalt–plastic shells under internal explosive loading

The dynamic strength and deformability of basalt–plastic specimens under single pulsed (explosive) loading are studied experimentally. The results obtained show that the basalt–plastic specimens possess high specific strength and their strength characteristics are close to those of similar tubular specimens from glassreinforced plastic based on a highmodulus glass fiber. It is found that a twofold increase in all geometrical dimensions of the specimens does not affect their specific carrying capacity.     

基于正交设计的冲击荷载下型钢混凝土梁动力性能有限元分析

为研究冲击荷载下型钢混凝土梁的动力性能,取试验结果验证模型有效性后,使用有限元软件ABAQUS建立了型钢混凝土梁落锤冲击模型．在对比了型钢混凝土梁与钢筋混凝土梁的动力性能后,分析了落锤速度对型钢混凝土梁的冲击位移、冲击力、冲击力位移曲线、惯性效应、塑性耗能等性能的影响,然后基于正交设计,研究了落锤质量、落锤速度、混凝土强度等参数对型钢混凝土梁动力性能的影响．研究结果表明：型钢混凝土梁的抗冲击性能较好;落锤速度是影响构件动力性能的主要参数,落锤质量对动力性能的影响较大,提高混凝土强度有助于增强构件的抗冲击性能．     

Development of a technology for laser welding of the 1424 aluminum alloy with a high strength of the welded joint

Results of an experimental study of properties of joints obtained by using different regimes of laser welding of the 1424 alloy (Al–Mg–Li) are reported. The strength and structure of the welded joints are determined. The influence of various types of welded joint straining on its strength is studied. It is demonstrated that the joint strength increases in the case of plastic straining.     

钢筋混凝土平面框架节点单元BCJ⁃5N

本文基于四根刚臂梁结合12个外接一维单元建立了钢筋混凝土框架节点单元，单元具有5个节点15个 自由度，称之为“BCJ-5N”单元．每个节点具有3个自由度，与普通梁单元一致，从而确保本单元适合于同普 通一维梁柱单元一起进行钢筋混凝土结构平面非线性分析．单元考虑了梁受力钢筋在框架节点内的黏结滑移作 用，并通过钢筋混凝土梁正截面强度设计建立了梁端弯矩与截面转角关系的骨架曲线，结合Lowes加载卸载模 型，组成了完整的静力、动力分析的框架节点单元，并将其移植到 ABAQUS通用分析平台上，通过对两跨三 层钢筋混凝土框架结构的滞回分析和三跨三层钢筋混凝土框架结构的动力分析两个算例，验证了本模型适合于 进行循环荷载和动力荷载作用下平面框架结构非线性响应分析．     

单向增强玻璃钢复合材料静/动态拉伸实验研究

本文针对单向增强玻璃钢复合材料，进行了一系列静/动态拉伸试验，利用高速摄影与DIC相结合的方法，获得了材料不同方向、不同应变率的应力-应变曲线以及材料在不同方向上的动态失效应变，精确地描述了材料的静/动态拉伸及失效行为。实验结果表明，纤维增强方向在不同应变率（10?3、10、102 s?1）拉伸应力-应变曲线均存在一个刚度减小的刚度变化点N，变化后的E_changed分别为初始弹性模量E_initial的67.5%、39.0%、21.4%。此材料在不同应变率（10?3、10、102 s?1）拉伸情况下，纤维增强的方向1上强度最高（分别为608、967、1 123 MPa），方向2强度最低（分别为75、67、58 MPa），方向3强度较低（分别为90、151、221 MPa）。利用高速摄影与DIC相结合的方法，获得了100 s?1应变率下，不同铺层方向破坏时刻的动态失效参数（方向1～3的动态失效应变分别为0.267、0.078、0.099），可以更加精确地描述此单向增强玻璃钢复合材料的动态失效行为。     

GFRP加固RC双向板抗爆性能试验研究

为探讨化爆条件下玻璃纤维对钢筋混凝土结构的加固效果,对粘贴玻璃纤维条带钢筋混凝土复合板以及普通钢筋混凝土板同时进行了抗爆性能试验,并将两者的结果进行了对比分析。结果表明,玻璃纤维能够有效阻止混凝土裂缝的发展,提高钢筋混凝土板的抗爆能力,研究结果可为玻璃纤维加固机理研究及复合结构的抗爆设计提供依据和参考。     

An approach for calculating the dynamic load of deep groove ball bearing joints in planar multibody systems

This study is focused on dynamic modeling of planar multibody systems with multiple deep groove ball bearing joints, in which the radial clearance, contact deformation, and bearing kinematics are included. By using the approach presented, the variation of the joint reaction force and the dynamic load on each ball element in bearings can be simulated. The deep groove ball bearing joints are modeled by introducing a nonlinear force system, which takes into account the contact elastic deformations between the ball elements and the raceways. The contact force is calculated by the Hertzian contact deformation theory that accounts for the geometrical and material properties of the contacting bodies. A planar slider-crank mechanism with two deep groove ball bearing joints is chosen as an example to demonstrate the application of the methodologies presented in this paper. In this model, one bearing locates at the joint between the ground and crank, while the other one locates at the joint between the crank and connecting rod. By numerical calculation, the dynamic load distribution characteristics of bearings under real mechanism movement conditions are simulated. From the results, it can be concluded that the dynamic load on each rolling element varies differently and belongs to a variable load with the change of mechanism configuration. Load characteristic analysis is the foundation of developing research on the fatigue life and reliability of bearings. This study will provide a key mechanical support for the performance evaluation, dynamic design, and geometrical parameter optimization of the joint rolling element bearings.     

高温后玄武岩纤维增强混凝土的动态力学特性

为研究温度、加载速率、纤维掺量对玄武岩纤维增强混凝土(BFRC)动态压缩强度和冲击韧度的影响,利用?100 mm分离式霍普金森压杆(SHPB)装置,对经历不同温度作用后的BFRC进行冲击加载实验。结果表明:高温后BFRC的动压强度及冲击韧度在同一温度下随平均应变率的上升近似线性增大;温度的升高总体上导致BFRC在同一加载速率下的动压强度及冲击韧度减小、应变率敏感性减弱;同一工况下,BFRC的动压强度和冲击韧度较素混凝土普遍提高,且当纤维体积掺量为0.2%时强韧化效果相对最佳。由此可见,高温后BFRC的冲击压缩特性受温度、加载速率、纤维掺量的综合作用影响,掺入玄武岩纤维可以有效降低高温后BFRC的损伤劣化程度。     

Experimental study and analysis of RC beams strengthened with CFRP laminates under sustaining load

Six reinforced concrete beams strengthened in flexure using carbon fiber reinforced polymer (CFRP) laminates subjected to different sustaining loads were tested. The main goal of the test is to examine the effects of initial load and load history on the ultimate strength of strengthened reinforced concrete beams by externally bonded CFRP laminates. The main experimental parameters include different levels of sustaining load at the time of strengthening and load history. To explain the experimental results in quantitative terms, a theoretical model for flexural behavior of the strengthened reinforced concrete beam is also developed. Test results in the current study show that sustaining load levels at the time of strengthening have important influence on the ultimate strength of strengthened reinforced concrete beams. If the initial load is basically same, the ultimate strength of reinforced concrete beams strengthened with CFRP laminates is almost same regardless of load history at the time of strengthening.     

新型外包加强型混合节点非线性数值模拟及参数分析

采用Abaqus有限元软件建立新型外包加强型混合节点模型,在验证模型正确性的基础上对其进行拟静力作用下的非线性分析,深入研究各个加载阶段的受力性能及破坏机制,并进行了相关参数对节点抗震性能的影响分析。结果表明,新型节点的最终破坏形态为梁端塑性铰破坏,外包混凝土及扩大包脚的嵌固作用使塑性铰远离节点核心区域,可以有效保护节点核心区和传力路径的连续性;滞回曲线较为饱满,具有较好的耗能能力和塑性变形能力;适当增大扩大包脚立面高度和水平长度,可以提高节点的初始刚度与承载力等性能,并根据相关参数研究给出了合理的设计建议范围,以便为工程设计提供参考。     

The effects of micro-defects and crack on the mechanical properties of metal fiber sintered sheets

The effects of three types of defect (i.e., two micro defects—broken fibers and separation of fiber joints and one macro defect—crack) on the mechanical properties of porous metal fiber sintered sheets (MFSSs) are investigated by a combination of numerical simulation, analytical modeling, and experimental test. All simulations are based upon the previously developed micromechanics random beam model (Jin et al., 2013). Broken fibers are realized by removing cell edges (i.e., fibers between two joints) in an otherwise perfect model. Their induced decreases in the elastic moduli and strengths are found to be much lower than those of two dimensional (2D) foams and Kagome grids. For the defect in the form of separation of fiber joints, both analytical and numerical models are developed. The predicted linear decreases in the moduli and strengths (except for the compressive strength) with increasing number of separated fiber joints indicate that MFSSs be insensitive to the defect of joint separation. To explore the effect of crack, fracture toughness of MFSSs is measured and is found to be significantly higher than that of metal foams of the same relative density (i.e., volume fraction of the constituent solid material). The underlying ductile mechanism of MFSSs is further investigated by numerical simulations, showing that plastic deformation spreads all over the fibers in ligament rather than concentrates around crack tip. This study shows that MFSSs are superior in view of their resistance to the considered micro-defects and crack.     

钢筋混凝土对边简支板的爆炸试验

爆炸载荷作用下钢筋混凝土板是建筑结构破坏的薄弱环节,其破坏还导致结构整体刚度 退化和动力响应升级. 以对边简支钢筋混凝土板为试验对象,在两个相同的试样上进行独立 的爆炸试验,观测钢筋混凝土板在弹性区动力响应和塑性区破坏特征,为碳纤维加固钢筋混 凝土板抗爆炸试验研究提供有效的数据和参照,实验现象和数据可供同类研究参考.     

平面编织复合材料胶螺混合连接接头拉伸性能分析

对平面编织复合材料胶螺（单排螺钉）混合连接结构拉伸性能进行了试验研究,分析了螺钉直径为4mm和6mm两种情况下连接结构的破坏形式。基于ANSYS平台建立了胶螺混合连接三维损伤扩展模型,其中融入了非线性接触问题,数值计算的结果与试验结果吻合良好。研究发现,机械连接可以通过分担部分载荷而起着加强胶接连接的作用;如果机械连接工艺稳定的话,应该有螺钉直径越大,其加强效果越明显的规律;对于胶接与多钉混合连接复合材料结构的拉伸性能分析和计算确实存在很大困难,应该谨慎使用。研究结果与分析方法可以为今后的复合材料胶螺混合连接接头的设计提供一定的依据与技术支撑。     

考虑节点损伤的钢框架结构分析模型

钢框架结构在强震作用下将进入非线性状态,结构的刚度和强度等力学性能随之降低,从而影响到结构以后的抗震性能.本文利用断裂力学的基本原理,通过对栓焊节点存在焊缝裂纹的钢框架刚性连接节点的分析,推导了裂纹的有效长度和有效深度,获得了有损伤刚性连接节点的M-θ关系;并推导了节点有损伤的梁单元刚度矩阵.在数值计算的基础上分析了节点刚度变化对框架结构内力的影响,结果表明节点损伤对结构内力分析影响显著,对有损伤钢框架结构进行承载力评估时必须考虑节点损伤的影响.     

梁柱不同混凝土强度的高层框架节点试验和有限元分析

高层框架结构设计时，梁板与柱常常会采用不同的混凝土强度等级，柱的混凝土强度等级往往高于梁板。对于梁柱的节点，一般多采用与柱相同的强度等级，这给施工带来很大麻烦，如果采用与梁板相同强度等级混凝土时。虽然方便了施工，但降低了节点的抗震性能。本文的研究是通过对此类节点采取加强措施，以弥补混凝土强度等级降低的不利影响。通过节点模型试验，研究其受力性能及破坏机理，验证加强措施的有效性。并在试验研究的基础上，用有限元方法对受力复杂的节点进行分析，结果表明节点区混凝土存在应力集中和应力扩散现象以及存在混凝土侧向受拉的现象．证实了梁加腋和增设X型钢筋后节点受力性能得到了改善和加强。这些研究成果对目前高层建筑梁柱节点采用不同混凝土强度等级的设计、施工提供了有益的参考。     

固-液结合面法向动态接触刚度及阻尼的理论模型与实验分析

固-液接触状态广泛存在于机床核心单元关键零部件的接触运动副中,精确获得固-液结合面法向接触刚度及阻尼参数是高档数控机床产品在研发阶段就存在的一个关键理论与技术问题,并且仍然尚未根本解决。固-液结合面在介观层面上表现为两个粗糙表面的接触,在微观层面上表现为微凸体之间的接触,并在中/重载荷作用下微凸体可能会发生弹性/弹塑性/塑性变形。为了揭示静动态外载荷对固-液结合面接触刚度及阻尼的影响,分别基于GW模型、KKE模型和AF模型对接触微凸体弹性/弹塑性/塑性变形展开研究,并结合流体动力润滑REYNOLDS方程,建立了考虑接触微凸体弹性/弹塑性/塑性变形的固-液结合面接触刚度及阻尼模型。并对其进行实验验证,结果表明：随着预载荷的增大固-液结合面法向动态接触刚度表现出先减小后增大的规律,当接触载荷小于某阈值时动态接触刚度较大,反之静态接触刚度较大;法向动态接触刚度随着法向相对位移幅值的增大而增大,在低载荷时呈线性规律,而高载荷呈非线性规律;法向动态接触刚度随激振频率增大呈线性增大,且载荷越大线性斜率越小。对于法向接触阻尼,随着法向相对位移幅值和接触载荷增大呈非线性增大,随着激振频率增大几乎不变。精确获得固-液结合面法向接触刚度和阻尼及其关键因素的影响规律,对机械系统的分析、设计、优化以及静、动态性能控制都具有重要的理论意义。     

Upper bound of the limit load for a tensile cylinder with a soft welded (soldered) joint containing a crack

The limit load is one of the main characteristics in estimating the performance of different structures, in particular, structures with soft welded (soldered) joints. In some cases, the difference between the yield strengths of the main material and the joint material is so great that plastic strain is localized in a thin joint. With some features of such strain distribution taken into account, an upper bound of the limit load of a tensile axisymmetric sample with a crack in a welded (soldered) joint is obtained.