Improved Design of a Hydraulically Expanded Overhead Cylinder for an Automotive Torsion Beam

The design of hydro-bulge molds,able to provide hollow parts with special-shaped cross-sections,is still a pretty complicated task(especially for what concerns the design of the related hydraulic system and its“synchronization”).In the present work,this task is addressed through the introduction of a new type of overhead cylinder hydraulic synchronization system,able to correct automatically any deviation from the optimal process.Using the AMESim software,the displacement synchronization curve of the piston rods of the two cylinders is obtained and it is verified that the system is able to implement an automatic deviation correction function by adjusting the bidirectional servo valve.A mathematical model for the synchronization system is presented,and the transfer function of the closed-loop control system is determined accordingly.The results show that the system response is generated at about 0.1∼0.2 s with the system reaching an equilibrium state at about 0.2 s.

Simulation Analysis of Torsion Beam Hydroforming Based on the Fluid-Solid Coupling Method

Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts.This paper reports a hydraulicforming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings.A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis.The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results.On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method,a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics.The effects of fluid characteristics,shaping pressure,axial feed rate,and friction coefficient on the wall thicknesses of torsions beams during formation were investigated.Fluid movement speed was related to tube deformation.Shaping pressure had a significant effect on rounded corners and straight edges.The axial feed speed was increased,and the uneven distribution of wall thicknesses was effectively improved.Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region,it had a significant influence on a large deformation of wall thickness in the V-shaped area.In this paper,a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.

The Effects of the Longitudinal Axis of Loading upon Bending, Shear and Torsion of a Thin-Walled Cantilever Channel Beam

Three aluminium channel sections of US standard extruded dimension are mounted as cantilevers with x-axis symmetry. The flexural bending and shear that arise with applied axial torsion are each considered theoretically and numerically in terms of two longitudinal axes of loading not coincident with the shear centre. In particular, the warping displacements, stiffness and stress distributions are calculated for torsion applied to longitudinal axes passing through the section’s centroid and its web centre. The stress conversions derived from each action are superimposed to reveal a net sectional stress distribution. Therein, the influence of the axis position upon the net axial and shear stress distributions is established compared to previous results for each beam when loading is referred to a flexural axis through the shear centre. Within the net stress analysis is, it is shown how the constraint to free warping presented by the end fixing modifies the axial stress. The latter can be identified with the action of a ‘bimoment’ upon each thin-walled section.

Theory of Flexural Shear, Bending and Torsion for a Thin-Walled Beam of Open Section

Aspects of the general Vlasov theory are examined separately as applied to a thin-walled channel section cantilever beam under free-end end loading. In particular, the flexural bending and shear that arise under transverse shear and axial torsional loading are each considered theoretically. These analyses involve the location of the shear centre at which transverse shear forces when applied do not produce torsion. This centre, when taken to be coincident with the centre of twist implies an equivalent reciprocal behaviour. That is, an axial torsion applied concentric with the shear centre will twist but not bend the beam. The respective bending and shear stress conversions are derived for each action applied to three aluminium alloy extruded channel sections mounted as cantilevers with a horizontal principal axis of symmetry. Bending and shear are considered more generally for other thin-walled sections when the transverse loading axes at the shear centre are not parallel to the section = s centroidal axes of principal second moments of area. The fixing at one end of the cantilever modifies the St Venant free angular twist and the free warping displacement. It is shown from the Wagner-Kappus torsion theory how the end constrained warping generates an axial stress distribution that varies with the length and across the cross-section for an axial torsion applied to the shear centre. It should be mentioned here for wider applications and validation of the Vlasov theory that attendant papers are to consider in detail bending and torsional loadings applied to other axes through each of the centroid and the web centre. Therein, both bending and twisting arise from transverse shear and axial torsion applied to each position being displaced from the shear centre. Here, the influence of the axis position upon the net axial and shear stress distributions is to be established. That is, the net axial stress from axial torsional loading is identified with the sum of axial stress due to bending and axial stress arising from constrained warping displacements at the fixing. The net shear stress distribution overlays the distributions from axial torsion and that from flexural shear under transverse loading. Both arise when transverse forces are displaced from the shear centre.

Symmetric Equations for Evaluating Maximum Torsion Stress of Rectangular Beams in Compliant Mechanisms

There are several design equations available for calculating the torsional compliance and the maximum torsion stress of a rectangular cross-section beam, but most depend on the relative magnitude of the two dimensions of the crosssection(i.e., the thickness and the width). After reviewing the available equations, two thickness-to-width ratio Independent equations that are symmetric with respect to the two dimensions are obtained for evaluating the maximum torsion stress of rectangular cross-section beams. Based on the resulting equations, outside lamina emergent torsional joints are analyzed and some useful design Insights are obtained. These equations, together with the previous work on symmetric equations for calculating torsional compliance, provide a convenient and effective way for designing and optimizing torsional beams in compliant mechanisms.

Coupled flapwise-chordwise-axial-torsional dynamic responses of rotating pre-twisted and inclined cantilever beams subject to the base excitation

A rotating pre-twisted and inclined cantilever beam model (RPICBM) with the flapwise-chordwise-axial-torsional coupling is established with the Hamilton principle and the finite element (FE) method. The effectiveness of the model is verified via comparisons with the literatures and the FE models in ANSYS. The effects of the setting and pre-twisted angles on the dynamic responses of the RPICBM are analyzed. The results show that:(i) the increase in the setting or pre-twisted angle results in the increases in the first-order flapwise and torsional frequencies while the decrease in the first-order chordwise frequency under rotating conditions;(ii) a positive/negative setting angle leads to a positive/negative constant component, while a positive/negative pre-twisted angle leads to a negative/positive constant component;(iii) when the rotation speed is non-zero, the pre-twisted angle or non-zero setting angle will result in the coupled flapwise-chordwiseaxial- torsional vibration of the RPICBM under axial base excitation.

Coupled flexural-torsional vibration band gap in periodic beam including warping effect

The propagation of coupled flexural-torsional vibration in the periodic beam including warping effect is investigated with the transfer matrix theory. The band structures of the periodic beam, both including warping effect and ignoring warping effect, are obtained. The frequency response function of the finite periodic beams is simulated with finite element method, which shows large vibration attenuation in the frequency range of the gap as expected. The effect of warping stiffness on the band structure is studied and it is concluded that substantial error can be produced in high frequency range if the effect is ignored. The result including warping effect agrees quite well with the simulated result.

Restrained Torsion of Thin-walled Box Beam with Honeycomb Core

Restrained torsion of thin-walled box beam with honeycomb core is analyzed on the basis of rigid profile assumption. The method of variable separation is applied and two ordinary differential governing equations are established and solved. The boundary conditions are satisfied rigorously and the solutions are expressed by means of eigen function expansions. The diagram of torque is formulated by trigonometric series and used to determine the coefficients in above expansions. The results of computation provide the chord-wise and span-wise distributions of normal and shear stress in the face plate along with shear stress in the honeycomb core.

型钢混凝土T形梁纯扭及弯扭性能试验研究

为研究型钢混凝土T形梁在纯扭和弯扭作用下的受力性能,以翼缘宽度、型钢含钢率、配箍率、翼缘纵筋直径及弯扭比为变化参数,设计并完成12根型钢混凝土T形梁的纯扭、弯扭静载试验。观察了试件的破坏过程,获取了试件的扭矩-扭率全过程曲线、开裂扭矩和极限扭矩等特征参数,深入分析了纯扭、弯扭作用下不同变化参数对型钢混凝土T形梁抗扭性能的影响规律,揭示了其抗扭破坏机理。结果表明:T形截面梁和矩形截面梁的破坏形态基本一致,其中钢筋混凝土梁呈现为脆性破坏,型钢混凝土梁呈现为延性破坏;T形试件翼缘、型钢和混凝土之间存在相互约束作用,翼缘和型钢大幅增强了试件的抗扭强度和延性;试件翼缘的最优高宽比为2.33;随着型钢含钢率的增大,试件的抗扭强度和延性呈增大趋势,平均提升幅度分别为30.99%、101.14%;试件的极限扭矩随着弯扭比的增大而增大,平均提高了7.86%。最后,提出了型钢混凝土T形梁的开裂扭矩和极限扭矩计算方法,所得计算结果与试验结果吻合良好。

扭力梁式后悬架扭转工况下横梁疲劳特性研究

基于有限元仿真,对扭力梁式后悬架扭转工况下横梁的疲劳特性进行了分析,提出了一种利用等效试样预测复杂结构零件疲劳寿命的新方法;建立了扭力梁式后悬架仿真模型,分析了横梁的应力分布规律;基于静力学分析结果,结合FB590高强钢疲劳寿命曲线、成形后横梁表面粗糙度以及表面残余应力,根据名义应力法和Gerber平均应力修正计算了横梁的疲劳寿命,并根据危险区弯曲变形程度设计了不同弯曲半径的等效试样(AR、R20和R10)进行疲劳试验和疲劳断口分析,实现了对横梁疲劳台架试验结果的有效预测。结果表明,在扭转工况下横梁疲劳危险区与应力集中区位于过渡段转角处,横梁的工况幅值-寿命曲线有效覆盖了服役情况下的所有负载情况,并得到了实际载荷谱的应力幅值参考范围;在台架试验中,R10与AR、R20等效试样交点寿命在横梁实际断裂寿命区域内,表明设计的等效试样疲劳试验可以有效表征横梁危险区的疲劳性能。

复合纤维的三角形截面梁组合扭转理论研究

基于板梁理论,首先通过各板件的位移、应变、应力及FRP(增强复合纤维)材料的本构关系推导出悬臂梁在端部受集中扭矩情况下组合扭转的总应变能及总势能,接着基于能量变分法构建了FRP三角形梁组合扭转问题的能量变分模型与微分方程模型,最后通过边界条件求得最大扭转角的近似解析解,并与Ansys有限元软件模拟结果进行验证,验证结果表明理论计算得到的近似解与有限元模拟解基本吻合,证明了理论模型的正确性,可为工程设计提供参考。

基于数值仿真的扭力梁变形对前束外倾影响的分析

为研究扭力梁悬架车辆在整车下线状态下由于扭力梁变形对前束外倾角产生的影响,以某电动出租车扭力梁前束外倾角为研究对象,利用数值仿真技术和台架验证相结合的方式,在扭力梁零/部件开发阶段就完成前束外倾角的机加工补偿和台架验证。相比传统利用小批量整车前束外倾角的统计分析结果对扭力梁前束外倾角进行机加工补偿的方法,该方法大幅缩短了开发周期,为主机厂对扭力梁悬架前束外倾角的机加工补偿提供了新的设计和验证方法。主要结果如下:1)利用扭力梁变形数值仿真方法,计算求得弹簧对扭力梁施加下线载荷后的扭力梁前束角变化为2.7′、外倾角变化为-31.5′;2)扭力梁结构对前束角变化影响较小,对外倾角变化影响较大;3)基于扭力梁前束外倾角数值仿真变形结果,给与扭力梁前束外倾角等值、反向的机加工角度补偿,利用扭力梁悬架系统台架进行实物验证;4)对比扭力梁前束外倾角变化的数值仿真数据和台架验证数据,误差均在10%以内,扭力梁变形数值仿真结果与台架验证结果的一致性较好。最后,通过整车批量验证,较好地满足了主机厂的生产要求。

圆孔工字型蜂窝梁扭转模态自由振动研究

从能量等效角度,提出了一种圆孔工字型截面蜂窝梁连续型模型,应用新的薄壁构件扭转理论:板-梁理论,建立了构件扭转模态自由振动能量泛函模型,明确了圆孔工字型截面蜂窝梁名义约束扭转惯性矩(翘曲常数)、自由扭转常数、转动惯量。通过变分运算,获得了平衡微分方程模型。基于扭转模态试函数,推导了圆孔工字型截面蜂窝梁自由振动扭转模态振动圆频率,并与有限元结果对比校验理论模型预测精度。开展了悬臂圆孔工字型蜂窝梁受集中扭矩作用的端部截面转角理论分析与有限元计算,进一步检验了基于板-梁理论建立的蜂窝梁连续模型的适用性。应用板-梁理论对圆孔工字型截面蜂窝梁自由振动扭转的分析过程及推导步骤,为其他开孔类型工字型蜂窝梁扭转模态自由振动研究提供了直接参考。

基于板-梁理论的FGM矩形截面杆扭转振动的理论研究

基于板-梁理论和Saint-Venant扭转理论的研究成果,将纵向位移假设为含有待定系数的表达式,通过几何方程推导了功能梯度材料矩形截面杆的总应变能方程,并利用最小应变能原理确定待定系数,得到自由扭转刚度的理论公式。在此基础上对矩形截面杆的自由振动出现纯扭转模态时的动能进行研究,求出在夹支条件下的扭转振动时的动能表达式、总势能的表达式及频率表达式。利用有限元软件ANSYS建立具有功能梯度材料特性的矩形截面杆的扭转振动的有限元模型,通过后处理命令查看对应边界条件的振动频率。通过有限元软件验证表明:基于板-梁理论推导得出的理论解与有限元解吻合较好,最大误差在4%以内。

弯扭柱-螺旋梁观光塔结构设计与静力分析

对重庆长江艺术湾区中岛艺路项目的观光塔结构设计要点进行阐述和分析。观光塔分为塔身和飘带,塔身高38.1m,飘带高25.66m。塔身是由三根逆时针旋转的弯扭箱形柱和顺时针旋转的螺旋箱形梁正交组成的螺旋结构,飘带是由两根弯扭箱形梁和中间连系梁组成的弯扭结构。该结构体型复杂,依据风洞试验确定了结构的风荷载体型系数。对结构的关键构件和关键节点进行了设计,并采用有限元软件MIDAS Gen和ABAQUS对结构的变形、构件内力、应力、结构整体稳定性和节点极限承载力进行了详细分析。结果表明,结构具备较高的安全可靠度。

基于数值仿真的扭力梁正向开发关键技术研究

针对扭力梁正向开发的常见问题和关键技术,利用数值仿真手段,以封闭管梁和开口板梁这2种结构的扭力梁为例进行了对比研究,包括扭力梁方案设计、DMU校核、产品和工艺CAE校核、扭力梁变形数值仿真以及变形补偿等关键技术,为主机厂正向开发扭力梁提供一定的参考。主要研究如下:1)依据设计输入,首先需进行横梁位置和截面设计,重点是确定横梁剪切中心,由数值仿真结果可知不同的横梁截面设计对剪切中心的Z向距离影响较大;2)在扭力梁式悬架运动间隙校核中,相比平行轮跳工况,反向轮跳工况严苛,易导致轮胎和轮罩产生干涉磨损风险;3)利用数值仿真技术研究了2种扭力梁结构的扭转刚度,相比开口板梁,封闭管梁具有较好的轻量化效果,利用数值仿真技术研究了2种扭力梁结构在扭转工况下的外应力、2种横梁成形过程中的内应力,如果横梁同位置处的内、外应力叠加,必然会产生较大的疲劳开裂风险,应从材料、结构和工艺角度给出解决方案;4)在整车下线弹簧载荷作用下,扭力梁的变形对前束和外倾会产生较大的影响,应给予扭力梁前束和外倾等值、反向机加角度补偿。

中温回火温度对22MnB5钢扭力梁疲劳性能的影响

对冷成形22MnB5钢管状扭力梁进行960℃感应淬火和中温回火,研究了回火温度(220,350,400,450,500℃)对扭力梁拉伸性能、冲击性能和疲劳寿命的影响。结果表明:随着回火温度从350℃升至500℃,22MnB5钢扭力梁的抗拉强度降低,断后伸长率增加,强塑积先增大后减小,450℃回火后最大,达到12.3 GPa·%;随着回火温度从220℃升至450℃,22MnB5钢扭力梁显微硬度减小,冲击吸收力增加;回火后扭力梁表面残余应力下降,且回火温度越高,下降程度越大;随回火温度升高,扭力梁疲劳寿命呈先下降后增再降的变化趋势,450℃回火疲劳寿命最长,达(15.8±2.4)万次;22MnB5钢扭力梁的最佳回火温度为450℃。

某大跨度现浇楼盖结构中框架边梁裂缝原因分析

通过对某大跨度现浇楼盖结构中框架边梁破坏现象的观察和计算结果的分析,得出以下结论:框架边梁与楼盖次梁整体现浇时,端部存在嵌固约束作用,特别是支承多根大跨度次梁的框架边梁始终处于弯剪扭复合受力状态。框架边梁两端1/3跨度内协调扭转嵌固约束作用显著,应高度重视,不可折减或忽略,设计时应考虑抗扭作用;框架边梁中部约1/3跨度内次梁的嵌固约束作用不显著,可不计边梁的约束影响,边梁的最大扭矩变化较小,中部约1/3跨度内次梁可按照两端简支梁设计。

汽车多连杆与扭转梁后悬架结构的共线生产应用

现有汽车制造过程中,多车型、多平台共线生产逐渐成为应用趋势。为提高汽车底盘系统装配线的柔性,结合产品结构特点及生产现场实际情况,从装配工艺、设备形式、质量保证3个方面出发,阐述了汽车多连杆与扭转梁式后悬架结构的共线生产的特点和要求,总结了2种后悬架结构共线生产的原则及措施,以便更好地适应汽车柔性化生产需求。

轴向补料量对扭力梁内高压成形质量的影响

研究了轴向补料量对CP800材料扭力梁内高压成形质量(成形壁厚分布和成形精度)的影响,结果表明:轴向补料能改善扭力梁的壁厚分布和成形精度,但补料过多会导致连接区起皱,影响其成形质量;当轴向补料量为12 mm时,最大减薄率为8.3%,整个扭力梁的尺寸精度都在0.5%以内,满足零件的设计要求。