基于AutoForm的Z向拉延筋截面参数理论求解

为解决AutoForm拉延筋截面参数在3D软件设计中无法直接使用的问题,推算了在3D软件中可以直接使用的Z向拉延筋截面参数求解公式,主要有流入、流出侧Z向立面与拉延筋中心线的距离、凸筋圆角、凹筋圆角。使用CATIA软件设计的拉延筋与AutoForm自动生成的拉延筋进行模拟对比,得到了理想的验证结果,其中筋宽误差和筋高误差均控制在小于0.05 mm,拉延流入量误差控制在小于1 mm。

The development of real time data driving multi-axis linkage and synergic movement control system of 3D variable cross-section roll forming machine

The three dimensional variable cross-section roll forming is a kind of new metal forming technology which combines large forming force,multi-axis linkage movement and space synergic movement,and the sequential synergic movement of the ganged roller group is used to complete the metal sheet forming according to the shape of the complicated and variable forming part data.The control system should meet the demands of quick response to the test requirements of the product part.A new kind of real time data driving multi-axis linkage and synergic movement control strategy of 3D roll forming is put forward in the paper.In the new control strategy,the forming data are automatically generated according to the shape of the parts,and the multi-axis linkage movement together with cooperative motion among the six stands of the 3D roll forming machine is driven by the real-time information,and the control nodes are also driven by the forming data.The new control strategy is applied to a 48axis 3D roll forming machine developed by our research center,and the control servo period is less than 10ms.A forming experiment of variable cross section part is carried out,and the forming precision is better than±0.5mm by the control strategy.The result of the experiment proves that the control strategy has significant potentiality for the development of 3D roll forming production line with large scale,multi-axis ganged and synergic movement.

Influence of Axial Feeding on Hydroforming of Aluminum Alloy Tubular Part with Rectangular Section

The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distribution and relation between corner radius and internal pressure were analyzed.The influence of lubricant was discussed.Microstructure and hardness of different region were observed.It is shown that thickness reduction in the transition region between the corner and center region is the biggest.Friction condition has influence both on the thickness distribution and calibration pressure of the corner.As the increase of the axial feeding,the calibration pressure is decreased.There is only little change for the microstructure,but the hardness is increased by 23.3% for the transition region.

Second premolar agenesis is associated with mandibular form： a geometric morphometric analysis of mandibular cross-sections

The aim of this study was to compare mandibular form （i.e., size and shape） between patients with agenesis of the lower second premolar （P2） and a control group with no agenesis. Three hypotheses were tested： （H1） agenesis causes a change in mandibular morphology because of inadequate alveolar ridge development in the area of the missing tooth （mandibular plasticity）; （H2） agenesis is caused by spatial limitations within the mandible （dental plasticity）; and （H3） common genetic/ epigenetic factors cause agenesis and affect mandibular form （pleiotropy）. A geometric morphometric analysis was applied to cross-sectional images of computed tomography （CT） scans of three matched groups （n= 50 each）： （1） regularly erupted P2; （2） agenesis of P2 and the primary second molar in situ; and （3） agenesis of P2 and the primary second molar missing for 〉3 months. Cross-sections of the three areas of interest （first premolar, P2, first molar） were digitized with 23 landmarks and superimposed by a generalized Procrustes analysis. On average, the mandibular cross-sections were narrower and shorter in patients with P2 agenesis compared with that in the control group. Both agenesis groups featured a pronounced submandibular fossa. These differences extended at least one tooth beyond the agenesis-affected region. Taken together with the large interindividual variation that resulted in massively overlapping group distributions, these findings support genetic and/or epigenetic pleiotropy （H3） as the most likely origin of the observed covariation between mandibular form and odontogenesis. Clinically, reduced dimensions and greater variability of mandibular form, as well as a pronounced submandibular fossa, should be expected during the treatment planning of patients with P2 agenesis.

NUMERICAL SIMULATION OF ROLL FORMING FORCHANNEL SECTION WITH OUTER EDGE

The finite strip method in structural analysis has been extended, and elastic-plastic large deformation spline finite strip method based on the Updated-Lagrange method (U. L. method) was established to simulate roll forming process of channel section with outer edge. The deformation characteristics of strip was analyzed, and the three-dimensional displacement field, strain field and stress field of deformed strip were got. The calculation example proves that the peak transverse pressing membrane strain is on the corner part of the deformed strip, and the peak longitudinal stretching strain is on the outer edge part of the deformed strip in front of rolls. In addition, the transverse deformation of the deformed strip is principal, and the longitudinal deformation is small.

Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections

A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.

嵌套加强的LQ550高强冷弯薄壁C型钢连续檩条受力性能研究

为提高LQ550级高强冷弯薄壁C型钢连续檩条的承载能力,采用在支座处嵌套的方法来加强连续檩条。对未加强和采用两种嵌套方式加强的檩条共7组试件进行三点受弯试验,得到了试件的承载性能和破坏形态,试验结果表明加强后的试件出现跨中局部屈曲和嵌套端部局部屈曲两种破坏形态。采用ABAQUS软件建立了非线性有限元模型对嵌套加强的檩条进行数值模拟,有限元分析得到的承载力和破坏形态与试验结果吻合良好,验证了有限元模型的准确性。基于验证的有限元模型,分析了两种嵌套方式和不同嵌套长度对檩条承载力的提升,且表明嵌套檩条的长度宜取为连续檩条跨度的1/5~1/4。

冀西北地区高速公路防雪网板数值模拟研究

公路是现代文明的重要标志,也是经济和社会发展的根本需求。确保公路的正常运行是社会发展的基础。冀西北地区特殊的地形特征和气候条件,使得该地区公路极易形成风积雪灾害,造成交通瘫痪,道路封闭,影响居民正常出行,给该地区人民的生活带来了极大的不便。针对冀西北寒冷地区的地形地貌和气候特点,借助Fluent软件,对不同形状、不同孔隙率的防雪网板前后风速流场变化进行数值模拟,得出防雪网板设计的最佳参数,并运用到实际工程中,对改善冀西北地区高速公路风积雪灾害,保障公路正常通行具有重要实际意义。为冀西北地区高速公路风积雪的防治措施提供一个切实可行的方案。通过分析研究得出以下结论:孔隙率为20%和30%的网板防雪效果优于其他孔隙率网板;有折角的蝶形网板在相同孔隙率情况下比平面网板防雪效果好。

大截面变化率对称结构管整体液力成形工艺研究

为解决某汽车排气尾管一体化成形中成形道次多的制造问题,提出了与传统压扁特征处对称结构(A型)设计思路不同的圆截面处对称结构(B型),并采用液力成形工艺对其进行成形,通过对比成形道次和零件质量,分析了两种对称结构工件成形的优缺点。研究发现,由于A型结构工件一道次成形时圆角处会出现裂纹,需采用多工步成形才能实现;而B型结构工件一道次成形效果良好;经多工步成形的A型结构工件和一道次成形的B型结构工件最大壁厚减薄率均小于25%。但是,与A型对称结构工件相比,B型对称结构工件圆角处壁厚减薄率更低,成形效果更好,并且模具数量由3套减少为1套。通过合理的零件结构设计,该结构打破了传统圆形截面端部密封的设计束缚,不仅有效降低了模具成本,还提高了生产效率,大幅提高了零件成形效果。

3003Al-H14薄壁微小通道扁管波形冲压成形尺寸对截面变形的作用规律

薄壁微小通道波形扁管是建设新能源汽车锂电池组恒温系统的绝佳材料,成形尺寸是影响其冲压成形截面变形的关键因素。建立了实验验证的3003Al-H14微小通道薄壁扁管的波形冲压-回弹有限元模型。基于所建模型,研究了截面高度、管坯壁厚、内外面相对弯曲半径缩放系数等成形尺寸,对截面变形率和平均截面变形率的作用规律。研究发现:①横截面上边缘孔的截面变形率通常较大,其余孔的截面变形率相对较小且大小一致;纵截面上孔的截面变形率呈现波峰波谷高、中间段低的分布特点。②扁管的截面变形率随着截面高度增大而增大,当截面高度超过4 mm时,扁管内的筋显著弯折,横截面塌陷严重。③扁管的平均截面变形率随着壁厚增大呈指数函数下降;当壁厚等于0.1 mm时,所有截面都畸变严重,而当壁厚超过0.3 mm时,最大截面畸变率下降至24.71%。④内外面相对弯曲半径的缩放系数越大,则内外面的实际弯曲程度越小,平均截面变形率也越小。研究成果对薄壁微小通道波形扁管的精确成形具有科学意义和工程价值。

装配式轻钢结构乡村住宅模块化设计研究——以重庆为例

针对我国乡村住宅建设技术与施工水平滞后的现状,本文在调研基础上归纳了重庆乡村住宅的空间模式与问题。研究了国内装配式轻钢结构在乡村的相关实践,通过对比装配式与传统建造流程提出了模块的层级划分方式,并运用冷弯薄壁型钢体系进行单体设计示范,从模块功能体系的标准化设计与多样化组合、结构体系标准化构件库建立、模块重要节点构造做法3个层面探究了装配式乡村住宅设计方法,以期为轻钢体系乡村住宅的模块化设计及推广提供思路。

冻结条件下井筒支护结构稳定性研究

内蒙古自治区的查干淖尔煤矿一号井的主斜井上段采用冻结法施工时,围岩遇到解冻水后形成高膨胀性围岩压力,导致直墙半圆拱形支护结构变形和严重破坏.为解决原支护方案支护力不足的问题,采用FLAC 3D对原支护方案建模,分析原支护方案的变形机理,基于此提出似马蹄形断面的双层井壁支护方案,并对新方案井筒的极限承载力进行计算,对比分析原方案与新方案的顶底板位移量、两帮移近量以及应力值.结果表明:似马蹄形断面的双层井壁支护形式能达到抵抗高膨胀性围岩压力和抑制底鼓的效果.

悬挂式单轨大跨连续梁关键构造研究

悬挂式单轨作为一种新型轨道交通制式,具有建设周期短、适应性强、造价低、占地少、美观舒适度高等特点。本文针对悬挂式单轨大跨连续梁的轨道梁截面形式及线间横向连接等关键构造展开研究,分析不同轨道梁截面形式对车桥耦合动力特性的影响及对结构刚度、应力状态的影响,研究线间横梁截面形式及横梁分布数目对整体刚度和应力水平的影响。结果表明,轨道梁采用顶箱+侧箱组合截面时,结构能体现出更好的抗弯、抗扭性能;横梁采用闭口箱型截面时,结构的横向整体刚度更优;跨中横梁数目以及空间分布方案应综合考虑经济性与安全性。研究成果可为相关设计提供借鉴。

3车道瓦斯隧道通风流场及瓦斯运移规律研究

为有效进行大断面公路瓦斯隧道施工期通风降气,以古金高速公路大梁子隧道工程为依托,采用SCDM软件建立2台阶带仰拱的计算模型,使用Fluent软件进行数值模拟,揭示在不同台阶长度、风筒出风口距掌子面距离、双风筒布设形式下,隧道掌子面及附近区域的通风流场特征和瓦斯运移规律,并结合现场监测数据进行验证。研究结果表明:1)流场在通风20 min后基本稳定,上台阶和仰拱段会形成涡流阻碍瓦斯的运移、扩散和稀释,在风筒非对称布设情况下,掌子面风筒对侧的墙角处出现瓦斯积聚现象;2)隧道内通风降气效果的敏感性影响因素排序为双风筒及布设形式>风筒出风口距掌子面距离>台阶长度,建议优先采用双风筒同侧布设送风,其次调整风筒出风口距掌子面距离为20~25 m和台阶长度为15~20 m;3)采用双风筒同侧布设通风时,掌子面及附近区域风速提高、瓦斯体积分数大幅降低,且施工现场开展的送风试验与数值计算结果吻合度高,验证了双风筒同侧送风的可靠性。

冷弯薄壁型钢纯弯构件截面分类

为研究冷弯薄壁卷边槽钢纯弯构件截面分类,基于试验数据验证后的有限元模型,对不同板件宽厚比下冷弯薄壁卷边槽钢纯弯构件进行了大量的参数分析。结果表明:抗弯承载力随翼缘与腹板宽厚比的减小而增大。在考虑翼缘与腹板相关作用的前提下,基于截面承载力得出板件截面宽厚比限值,提出了冷弯薄壁卷边槽钢纯弯构件截面分类方法。

瓶罐玻璃行列机成型与操作

基于玻璃成型与玻璃性质的关系,通过研究制瓶机的气动机构,阐述了行列机成型的操作与调整的要领,行列机热端成型主要是成型的稳定,为正确检查和识别玻璃瓶缺陷,行列机成型要设立专门的工艺管理人员,负责全部成型工艺的规范操作以及设备的正常运转等工作,以保障生产安全,提高产品质量。

T型截面铝合金型材零件成组加工技术研究与应用

针对目前飞机T型材零件单件弯曲成形效率低成形精确差的问题,提出了T型材弯曲件成组拉弯成形的成组加工方法。基于截面尺寸、引导线的曲率半径等信息建立了成组分析算法,对T型材进行分组,使用长型材拉弯成形后切割分段得到符合精确外形要求的T型材零件。通过理论计算、模拟分析和拉弯试验,验证了T型材拉弯成形成组加工技术的可行性,该方法提高了零件的制造效率和成形精度,可以大幅度降低人工矫正的工作量和加工成本。

144型高性能转向节预锻件优化设计与精锻工艺研究

144型转向节是中重型高端商用车转向部件中的核心零件,其对延伸率和断面收缩率均有严格要求,根据传统锻造工艺理论设计的预锻方案不能满足断面收缩率要求,研究其预锻件的优化设计与精锻终成形工艺对于获得合格锻件具有重要意义。首先采用经典塑性成形理论分析了基于传统方法设计的预锻件存在的问题,然后基于损伤理论提出了其预锻件结构的优化设计方法,同时提出了基于平面薄飞边的精锻终成形工艺。应用结果表明,生产的144型转向节精密锻件阶梯杆部的关键技术指标延伸率A≥12.5%,断面收缩率Z≥50%,超过了国外客户所提技术指标的要求。

路基支挡结构之锚固桩的“方”与“圆”

从截面抵抗能力、桩土相互作用机理、经济效益和施工角度等多方面,充分论证方形桩与圆形桩的优缺点,改进方形桩成桩工艺并应用于3个施工项目。结果表明:用于边坡支挡的锚固桩,无论从受力性能还是经济性上,方形桩均具有优势,仅是施工工法和施工机具落后于圆形桩;目前方形桩的成孔技术和机械机具已在研发与应用中,并有较成功的经验;相较于圆桩,方桩依然是边坡支护的首选。

基于DYNAFORM的内高压成形中预成形工艺改进

对复杂形状空心构件内高压成形工艺进行了数字模拟研究。采用有限元模拟,对矩形截面空心零件弯曲部位在内高压成形过程中产生起皱、破裂等缺陷进行了分析;针对矩形截面空心件弯曲部位,提出采用椭圆截面充液预成形的方法,控制起皱、破裂缺陷的产生,成形质量较理想。并通过试验进行了验证,采用较低压力可以改善内高压成形过程中材料的分布、提高材料的成形极限、控制缺陷产生并提高产品质量。