基于ABAQUS串列立管碰撞的有限元分析

以两串列立管碰撞为研究对象,运用有限元分析软件ABAQUS,考虑水耦合作用研究串列立管的局部碰撞行为。通过模拟立管碰撞前的静态弯曲和动态碰撞过程,将静态分析的结果导入动态分析步中,从单一因素方面分析碰撞速度、立管夹角、内压对立管碰撞应力的影响,并将考虑水耦合作用和不考虑水耦合作用的应力变化情况进行了对比分析。结果表明:在给定工况下,两立管发生多次碰撞,考虑水耦合作用时,立管碰撞产生的应力较小。在分别考虑和不考虑水耦合时,碰撞速度、夹角、内压对立管应力变化的影响是不同的,初始碰撞产生的应力随碰撞速度的增大而增大,存在某一适当的夹角和内压值,使立管较为安全,可以避免立管遭受撞击而发生破坏,为立管群的排列布置提供参考。     

海底管道受坠物撞击的三维仿真研究(稿号5913修改稿)

采用三维非线性有限元法模拟海底管道受到船锚或其他坠落物体的冲击碰撞过程,并采用Newmark法和N-R迭代法相结合求解了海底管道的动力响应过程,分析了物体形状、碰撞角度、物体与管道间摩擦、混凝土厚度及管道内压对管道碰撞的影响。结果表明相同撞击条件下,立方体和球体对管道的撞击产生的最大Mises应力要比圆锥体大的多,随着圆锥角角度的增加管道的最大Mises应力是增加的;碰撞角度为90°时对管道的影响最大;摩擦对管道撞击影响较小;管道最大Mises应力随着混凝土层厚度的增加而减小,但随混凝土厚度的增加,减小的幅度越来越小;内压的存在使管道等效应力增加,但能减小管壁上的局部变形,使得冲击能量更多被用来产生整体变形。     

海底管道受坠物撞击的三维仿真研究

采用三维非线性有限元法模拟海底管道受到船锚或其他坠落物体的冲击碰撞过程,并采用Newmark法和N-R迭代法相结合求解了撞击动力学方程,分析了物体形状、碰撞角度、物体与管道间摩擦、混凝土厚度及管道内压对管道碰撞的影响.结果表明相同撞击条件下,立方体和球体对管道的撞击产生的最大Mises应力要比圆锥体大的多,随着圆锥角角度的增加管道的最大Mises应力是增加的;碰撞角度为90°时对管道的影响最大;摩擦对管道撞击影响较小;管道最大Mises应力随着混凝土层厚度的增加而减小,但随混凝土厚度的增加,减小的幅度越来越小;内压的存在使管道等效应力增加,但能减小管壁上的局部变形,使得冲击能量更多被用来产生整体变形.     

基于ANSYS的气液两相流海洋立管流固耦合特性分析

运用ANSYS软件对气液两相流海洋立管进行了流固耦合特性分析,包括模态分析和动力学分析。模态分析研究了有无流固耦合存在时立管振动模态的变化以及流体边界条件对立管固有频率和阵型的影响;同时,将仿真分析同DNV公式求解的固有频率进行了对比验证。动力学分析研究了单、双向流固耦合振动分析,并将单、双向流固耦合进行了对比分析,同时考虑了立管支承方式、流体边界条件对立管振动的影响,提出了立管减振措施。分析结果对海洋立管的优化设计和运行的可靠性提供了重要的理论意义。     

斜交简支梁桥纵向地震碰撞反应精细化研究

为精细化分析简支斜交桥地震碰撞反应,首先基于Hertzdamp碰撞理论,采用开放式地震模拟软件OpenSees建立能够考虑碰撞过程中摩擦作用的简支斜交桥精细化计算模型;然后从动力特性、动力反应层面验证模型的可靠性;最后采用三维精细化计算模型分析斜度、摩擦对斜交简支梁桥纵向地震碰撞反应的影响。结果表明：梁体与桥台间最大碰撞力的产生位置随着斜度的变化而改变;最大碰撞力的大小不仅与斜度有关,而且与斜交桥梁端与桥台间摩擦系数也存在一定关系;摩擦作用削弱了斜度对梁端锐角处纵向最大位移的影响,大幅度减少上部结构峰值转角,使峰值转角最大值滞后在较大斜度时出现;不考虑摩擦作用会高估锐角处梁端纵向最大位移反应。     

隧道开挖和爆破扰动耦合作用下埋地管道安全性研究

随着我国交通系统的快速发展,临近埋地管道施工的工程案例越来越多,隧道开挖不可避免地会影响管道的安全。为研究隧道开挖变形及爆破扰动耦合作用下临近埋地管道的安全性,以深圳市大山陂1号隧道施工为背景,建立管-土-隧动静耦合作用模型以分析不同管道内压、围岩弹模、管隧间距、单段最大装药量条件下埋地管道的应力和振速变化规律,进一步引入Morris筛选法对各因素的影响程度进行评价分析。结果表明:管道应力和管道振速受管道内压和单段最大装药量的影响最大;管道应力峰值随着管道内压的增大、围岩弹模的增大、管隧间距的减小和单段装药量的增大而增大;管道远离拉应力峰值的区域,在各种参数的综合影响下,可能出现压应力。     

基于整体分析的钢悬链线立管触地点动力响应分析

在立管动力平衡系统的力学模型中考虑浮式平台的惯性作用和管-土相互作用,研究在不同参数激励下钢悬链线立管触地点动力响应。基于大挠度柔性索理论,分别采用具有弯曲刚度的大挠度细长梁、弹性地基梁模拟立管的悬垂段和流线段,考虑触地点处的大曲率,建立了立管的三维有限元模型,利用Galerkin方法对运动方程离散为一组非线性二阶常微分方程,运用Newmark-β法求解离散方程。通过在立管的动力方程中引入δ函数来体现浮式平台对立管的惯性和水动力影响,将悬链线立管与浮式平台作为一个整体进行动力分析,以工程中实际使用的1800m水深的钢悬链线立管为例,通过对立管顶部进行谐波激励,分别就水动力系数、管内流体密度和海床土体刚度对立管特征点动力分析的影响进行分析,研究表明:水动力系数的改变对立管触地点的动力响应的影响较为显著,主要体现在弯矩和张力幅值的增加;管内流体密度不同,触地点位置不同,表明立管在输送不同液体或气体可能发生疲劳破坏的位置也不同;而海床土刚度对立管触地点区域的弯曲应力影响较大,对轴向应力则影响不大,其结果对SCR设计具有重要的指导意义。     

喷丸处理对2219铝合金搅拌摩擦焊焊接残余应力的影响

对2219铝合金板进行了搅拌摩擦焊(FSW)和喷丸处理，采用X射线衍射仪(XRD)测量了搅拌摩擦焊和喷丸产生的残余应力，分析了残余应力的分布特征，研究了弹丸直径、弹丸材料、喷射距离等参数对搅拌摩擦焊接残余应力分布的影响。结果表明：焊接后，焊缝附近存在较大的残余拉应力，焊缝中心线±20 mm范围内的平均应力高达100.9 MPa,而远离焊缝的母材区域接近零应力状态；喷丸后，试样残余应力分布发生显著变化，表层残余应力表现为压应力，并且该压应力数值随着深度的增加先增大后减小，最后保持为拉应力；增大弹丸直径可提高最大残余压应力值和残余压应力层深度，但当弹丸直径继续增大至1.2 mm时，最大残余压应力值不再继续增大；选用合适的弹丸材料可获得理想的残余压应力分布情况；随着喷射距离的增大，最大残余压应力值和残余压应力层深度先增大后减小。     

地震作用下曲线梁桥非均匀碰撞效应研究

曲线梁桥在地震作用下产生的不规则平面旋转位移使得应用碰撞单元法计算曲线梁体碰撞效应存在一定的局限性,为了探讨曲线梁桥地震碰撞效应的非均匀分布规律,提出了采用显式动力接触算法计算曲线梁桥地震碰撞效应的数值模拟方法,并分析曲线连续梁桥碰撞效应引起的主梁、挡块和桥墩的冲击地震反应特点。结果表明,主梁与桥台胸墙的碰撞作用限制了主梁的切向位移,使得固定墩墩底弯矩小于不考虑碰撞时的墩底弯矩。碰撞后梁端截面顶板正应力和曲线内外侧挡块径向应力的分布严重不均匀,梁端截面悬臂翼缘的正应力明显小于腹板间顶板的正应力,曲线外侧挡块的径向应力显著大于内侧挡块的径向应力。地震碰撞作用使得主梁的最大拉应力和压应力通常会发生在梁体曲线的内外侧。这为合理解释曲线连续梁桥在强震下的碰撞破坏震害现象提供了理论指导。     

圆钢管加工方法诱导的残余应力分布检测与分析

为了研究圆钢管加工方法诱导的纵向残余应力分布规律,该文采用盲孔法对截面规格为 φ325×8的5组15个不同强度、不同加工方法的圆钢管试件进行了测量。基于测量数据,得到了试件截面残余应力分布和拉、压残余应力的数值大小,研究了埋弧焊、高频焊和热轧三种不同加工方法对残余应力分布的影响。试验结果表明,埋弧焊对圆钢管截面纵向残余应力的影响强于高频焊,高强度焊接圆钢管的残余应力分布比较均匀,且焊缝区最大残余拉应力分布在焊缝两侧各40 mm区域内;普通强度钢管截面的最大纵向残余压应力为0.35σ_y,而Q690高强钢焊接圆钢管截面的最大纵向残余压应力为0.21σ_y,同中点截面的纵向残余应力峰值相比,起焊点和落焊点截面处的纵向残余应力峰值偏小。不同于焊接圆钢管,热轧无缝圆钢管同一截面内外表面的最大纵向残余应力数值大小相同,符号相反,其最大值为0.15σ_y。     

基于简化Jones-Harris方法的球轴承接触角研究

作为球轴承重要的结构参数之一,接触角对轴承组件的载荷分布、运动关系、润滑、摩擦等都有重要的影响。将求解惯性力所涉及的变量耦合关系进行简化,提出了用于研究球轴承接触角特性的简化Jones-Harris方法(SJHM),通过预先给定内圈偏转角,克服了直接迭代法难以考虑内圈偏转角对接触角影响规律的不足。以b218轴承为对象,验证了SJHM方法的有效性;在此基础上,分析了多种因素对接触角的影响规律。研究结果表明：相比陀螺力矩的影响,离心力对内、外接触角的影响更加显著;接触角对轴承内圈偏转角的变化非常敏感,内圈偏转角会使同一个滚动体的内、外接触角同时增大或减小。     

轮轨横向碰撞引起的脱轨研究

建立了车轮和钢轨的三维摩擦碰撞方程,根据刚体碰撞力学理论推导出碰撞后车轮的瞬时速度,讨论了摩擦碰撞过程中切向状态的变化。根据运动学关系和能量守恒定律推导出车轮横向碰撞钢轨的跳轨脱轨判别准则,包括车轮的横向碰撞临界速度和以车轮横向力峰值、轮重和碰撞时间确定的判别公式。参数分析表明：增大轮缘角、摩擦系数和轮缘有效高度均能够提高跳轨脱轨限值;轮缘角越大出现粘滞状态的临界摩擦系数越小;车轮接触点纵向相对速度减弱了阻碍车轮跳轨的切向摩擦阻力,加大了脱轨的危险性。     

Transformation of sliding motion to rolling during spheres collision

In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and dimensionless analysis is used for investigating normal interaction force; furthermore, Coulomb friction is considered during sliding. Experimental data for collisions show when sliding exists through the impact, tangential impulses can be taken as frictional impulses using the Coulomb law if the dynamic regime is not stick regime. To identify transformation of sliding motion to rolling or sticking during the impact process, linear and trigonometric functions are considered as an approximation for the normal interaction force. Afterwards, we have obtained the condition for the possibility of this transformation; moreover, we can estimate the duration of sliding and rolling or sticking. We have obtained an analytical solution for maximum force and deformation, collision time, impulses and post-collision linear and angular velocities in three dimensions.     

Oblique Low-Velocity Impact on Fiber-Metal Laminates

In the present study, oblique low-velocity impact (OLVI) on GLARE fiber-metal laminates (FMLs) has been modeled using finite element analysis (FEA) for the first time. Two types of boundary conditions (BCs) can be considered for impactor in the low-velocity impact: constrained (if the impact angle between the impactor and target remains constant during and after the contact) and free (if rotation of the impactor and change in angle with respect to the target is likely) BCs. The more details of these BCs are described in the paper. The OLVI is numerically modeled for four different impact angles. Effect of BC types and impact angle on energy absorption, as well as maximum contact force, is investigated. Due to lack of experimental results for the OLVI on FMLs in the open literature, the authors had to validate the present modelling via the experimental data of the perpendicular low-velocity impact. An excellent agreement was obtained between the numerical results and the experimental data. The results of present study reveal that at the same impact angle, the maximum contact force and energy absorption are greater for the constraint oblique impact (Constrained OLVI). In addition, in the Constrained OLVI, the maximum energy absorption occurs at larger impact angles, while this occurs at smaller impact angles for free oblique impact (Free OLVI). The conclusion to be drawn from all of the cases studied in this paper is that the maximum contact force occurs in the Constrained OLVI with smaller impact angles. Moreover, the maximum energy absorption takes place in the Constrained OLVI at higher impact angles.     

极端工况下的高压柱塞马达密封环摩擦特性

为减少极端工况下因密封环摩擦磨损导致的疲劳断裂,保证马达的容积效率和可靠性。以法向正压力和剪切应力线性表示密封环摩擦力,并通过模态分析法和有限体积法分别研究系统多体动力学与缸孔内流体动力学,计算不同主轴转角、不同宽径比和弧面锥角下密封环的法向正压力和壁面剪切应力。研究结果表明:改变主轴转角引起的排量变化对摩擦力的影响较小;而密封环结构参数的变化影响明显,当宽径比小于0.3和弧面锥角小于1.8°时,摩擦力随宽径比和锥角增大而减小,在宽径比为0.3,弧面锥角为1.8°时摩擦力达到最小,最大缩减率分别为28%和25%;但当宽径比大于0.3和弧面锥角大于1.8°时,摩擦力随宽径比和锥角增大而增大;另剪切应力随着宽径比增大而增大;而受弧面锥角影响较小。研究结果为柱塞马达密封环减摩设计提供理论基础和依据。     

Oblique impact of inflated balls at large deflections

A planar theory for oblique impact of thin-walled spherical balls against a rough rigid surface has been developed on the basis of an assumed deformation field—an initially spherical ball is assumed to flatten against the constraint surface while the remainder of the ball remains undeformed. For inflated thin-walled balls, which are represented by these assumptions (basketballs, soccer balls, volleyballs, etc) the normal reaction force acting on the flattened contact patch is predominately due to the internal gas pressure—the reaction due to shell bending is insignificant in comparison with this gas force. During impact of a thin-walled ball there also is a non-conservative momentum flux reaction that is caused by the flow of momentum into and out-of the flattened contact patch. If the ball is translating as well as rotating about an axis perpendicular to the plane of motion, the distribution of the normal component of velocity for material entering and exiting the flattened contact patch results in a distribution of momentum flux force intensity around the periphery of the contact patch and consequently, a momentum flux torque acting on the flattened sphere. The effect of these reaction forces and torque on oblique impact of thin-walled spherical balls is calculated as a function of the ball deflection (or normal component of impact velocity). In comparison with rigid body calculations for oblique impact of a spinning ball against a rough surface at angles<45° from normal, the effect of maximum deflections as large as half the initial radius is to slightly accentuate the effect of friction on angle of rebound and moderately decrease the angular velocity of the ball. However, for angles >45° from normal, the final angular velocity can be as small as 40% of that predicted by rigid body theory. The most significant changes in rebound angle are for cases with initial backspin—a technique commonly used in many ball sports.     

Effect of crack face contact and friction on Brazilian disk specimens—A finite difference solution

A full curvilinear transformation is employed to study the effect of contact and friction on Brazilian disk specimens containing a crack and subjected to concentrated loads at angles 0° <  < 90°. Homogeneous and bimaterial disks made of glass and epoxy are considered. The effect of loading angle and friction coefficient on the stress intensity factors, as well as the contact length is studied. The results are compared to available semi-analytical and finite elements results. It is found that when the crack faces are in contact without stick zones, an increase in friction causes a decrease of the normal gap, tangential shift and stress intensity factors. When stick conditions appear in the contact zone, an increase in the coefficient of friction also results in increasing the stick zone within the contact zone.     

包装生产线输送碰撞仿真及分析

以ADAMS 的碰撞仿真理论为基础,在综合分析了碰撞参数物理意义的基础上,研究了块状刚性物体与柔性接触面的运动机构碰撞过程中的动力学特性,并采用柔性碰撞动力学进行了求解,运用拉格朗日碰撞动力学方法求出了碰撞时的运动状态,再用IMPACT 碰撞理论求解其碰撞力,然后运用ADAMS 软件对其运动进行了仿真分析,并根据仿真结果对包装输送线线上离线机构进行了参数优化选择。     

刚体碰撞约束柔性体局部撞击载荷特征分析

目的 掌握碰撞局部撞击载荷及其特征,为产品安全防护设计、碰撞响应分析与评估提供理论基础。方法 抽象刚体碰撞柔性体的共性特征,分别将被撞击柔性体的碰撞局部刚度特性和整体结构效应表征为弹簧力-位移关系,建立系统的二自由度刚-柔碰撞动力学模型,应用数值方法系统分析刚柔碰撞局部撞击载荷的特征及不同因素的影响。结果 获得了刚体初始碰撞速度、柔性体碰撞局部刚度特性与整体结构效应等主要因素对局部撞击载荷时程、冲量、峰值和脉宽等撞击载荷特征的影响规律。结论 深化了刚-柔碰撞局部撞击载荷的认知,为防护结构设计提供了理论基础。