盘形件两工步对称增厚旋压工艺

对称增厚旋压是一种针对薄辐板厚轮缘类盘形件的特种旋压技术，利用有限元模拟研究了两工步对称增厚旋压过程中坯料的变形规律、成形特点和缺陷的产生，以及各工艺参数对成形的影响。结果表明：摩擦因数μ、旋轮进给速度v以及坯料旋转速度ω对成形过程影响较小。在第1工步中，旋轮槽底宽度h、旋轮凹槽倾角α以及坯料长厚比γ对成形影响显著，随着旋轮槽底宽度h和旋轮凹槽倾角α的增大以及坯料长厚比γ越大，坯料越容易失稳形成缺陷；在第2工步中，旋轮槽底宽度h以及坯料的初始形状对成形影响显著，旋轮槽底圆角半径R能够改善坯料外边缘的应力状态，且R越大改善效果越明显。     

热旋压轮缘对称增厚成形数值模拟及实验研究

在加热条件下通过旋压成形的方法对圆形板料轮缘进行对称增厚,最终得到一种辐板较薄而轮缘较厚的盘形类零件,并借助ABAQUS仿真软件建立有限元模型来研究对称增厚成形过程。结果表明,在热旋压对称增厚成形过程中,径向旋压分力逐渐增大,而轴向和切向方向的旋压分力相对较小。对工艺参数的研究表明,摩擦系数μ和型槽倾角α取相对较小值时有利于成形,而进给比f取相对较大值时会更合适。随着坯料长厚比γ和成形增厚比η的不断增大,旋压对称增厚成形呈现出不同的变形特征。当γ过大时,成形易出现屈曲失稳;当η过大时,成形易出现鼓起失稳。最后,选取了一组合适的工艺参数进行增厚实验,实验得到的成形件与模拟结果吻合,验证了工艺的可靠性。     

两旋轮旋压首道次压下率对轮毂旋压成形的影响

针对低压铸造A356铝合金轮毂的两旋轮旋压成形特点,通过旋压成形数值模拟及实验分析了在两旋轮旋压工艺下首道次压下率对轮辋壁厚均匀性、 坯料隆起高度、 旋轮所受压力以及轮辋微观组织与力学性能的影响.结果表明,当首道次压下率为40％时,轮辋壁厚较均匀,成形质量较好,坯料隆起高度较小,材料贴模性较好,两个旋轮所受压力较稳定,...     

管坯料内壁多槽劈挤成形折叠成因及规律分析

劈挤成形容易出现折叠缺陷。为了研究管坯料内侧劈挤成形时出现的折叠规律,以内径50.2 mm和外径为57 mm的管坯料为研究对象,劈挤成形出高度为20 mm,槽数为40的内齿槽。在劈分角和劈刃倾角不变的情况下,运用Deform-3D数值模拟软件对成形过程进行了模拟分析,研究了相邻凸模夹角β不变的情况下,劈挤凸模工作面间夹角α和劈入深度h0对劈挤产生折叠的影响。结果显示,在夹角β一定的情况下,α值越大,折叠越严重,且折叠变化越急剧,当α≤30°时,没有折叠;劈入深度h0越小,折叠越严重,当h0≥1.3 mm时,折叠消失。从应用的角度考虑,α宜取较小值,h0应取较大值。     

变截面零件辊锻过程数值模拟优化

采用美国MARC公司的MSC／superform软件对叶片辊轧工艺进行了数值模拟。模拟建立两种有限元模型——对称模型和非对称模型，在两种模型下分别分析了坯料与轧辊之间的摩擦系数对中性角的影响，得出中性角随摩擦系数增大而增大，前滑区变形金属随之增多。反之，摩擦系数过小影响坯料的正常咬入，出现打滑现象。模拟结果显示摩擦系数取0．3为最佳选择。在不同模拟模型下不同型槽内变形区金属的流动情况不同。非对称型槽成形的工件由于上下表面金属流动速度不同，出现弯曲现象；对称型槽成形的工件较平直。因此，为保证叶片的成形质量，设计选用对称型槽形式。通过数值模拟优化设计工艺参数，为叶片辊轧工艺的制定提供依据。     

旋轮参数对铝合金分形旋压的影响规律

铝合金分形旋压是一个复杂的多因素耦合影响的塑性成形过程,研究其旋轮参数对成形过程的影响可为相关成形参数的确定和优化设计提供理论依据。基于建立的可靠的铝合金分形旋压三维有限元模型,文章研究揭示了旋轮分形角、旋轮圆角半径、旋轮轴向进给比等旋轮参数对成形过程中的切向拉应力、周向压应力以及成形凸缘的不均匀变形程度和最终壁厚偏差的影响规律。结果表明,增大旋轮分形角,可以消除旋轮前方的金属堆积和降低成形过程中坯料开裂失效的可能性,可以使得成形凸缘的不均匀变形程度减小和成形精度降低;旋轮圆角半径的改变,对消除旋轮前方的金属堆积和降低成形过程中坯料开裂失效的可能性影响并不明显,但增大旋轮圆角半径,可以使得成形凸缘的不均匀变形程度增大和成形精度升高;旋轮轴向进给比的改变,对消除旋轮前方的金属堆积和成形凸缘的成形精度的影响并不明显,但增大旋轮轴向进给比,可以降低成形过程中坯料开裂失效的可能性,可以使得成形凸缘的不均匀变形程度减小。     

弹壳拉深成形工艺分析及模具设计北大核心CSCD

以某型号弹壳盂子为研究对象,针对初始设计方案拉深成形后盂子中心底厚超差的问题,通过数值模拟分析其原因:第1次拉深过程中,坯料的弯曲变形量过大,使得坯料无约束底部的弯曲半径变小、径向拉应力过大,从而导致坯料底部减薄超差。在此基础上,提出控制坯料第1次拉深成形的弯曲变形量、减少坯料底部径向拉应力的优化方案,数值模拟结果显示,盂子中心底厚达到3.43 mm,中心底厚得到有效提升。采用优化方案进行工艺试制,其结果表明,盂子中心底厚平均值达到3.452 mm,盂子外径、高度和中心底厚均达到了设计要求。数值模拟结果与实验结果的吻合度高,其对实际生产具有指导性作用。     

基于灰色系统理论的汽车横梁充液成形用坯料优化

类似汽车横梁这些复杂管类结构件的充液成形,是一个不均匀的变形过程,坯料的相对形状及尺寸,是影响金属流动的关键因素,从而对充液成形零件的最小壁厚、最大壁厚等评价对象有重要影响。以坯料的弯曲角度、弯曲半径、轴线高度差为因子,建立正交试验设计方案,进行有限元模拟,获得不同坯料尺寸下的最小壁厚、最大壁厚参考序列。利用灰色系统理论,计算各个参考序列与比较序列之间的关联系数,将多目标转化为以关联度为目标的单目标。进一步计算各坯料结构尺寸的平均关联度,获得优化的坯料尺寸组合参数,以此进行有限元模拟和生产实验。验证结果表明,该优化方法能够获得满足质量要求的充液成形的汽车横梁。     

厚轮缘盘形件多工步旋压增厚成形工艺

针对厚轮缘盘形件设计了多工步旋压工艺及每一步的旋轮尺寸。通过有限元模拟,分析了旋压增厚工艺的成形过程,试验验证了模拟结果。分析了旋轮圆角半径R和上倾角α对成形的影响规律,设计了5工步旋压增厚成形方案。研究结果表明,直径Φ326 mm,厚度3 mm的圆形板坯,经过5个工步,可以成形为轮缘厚度为9.1 mm,宽度为7.8 mm的盘形件。成形过程中,第1、2、3步可以分为3个阶段,第4、5步可分为2个阶段。每一工步最大的旋压力为80~120 kN,与试验值之间的误差小于7%。最后,研究了成形件横截面的硬度分布规律,探讨了硬度分布的原因。     

基于Forge的皮带轮旋压成形仿真分析

分析了某型皮带轮的旋压成形原理,运用有限元软件Forge建立了皮带轮旋压成形仿真分析模型,对其在不同旋压时间下的成形形状、等效应力、等效塑性应变及材料分布特性进行了仿真。结果表明:随着旋压不断进行,高速旋轮不断对皮带轮毛坯进行挤压,皮带轮槽逐渐成形;等效应力及等效塑性应变逐渐增加,最大值基本分布在轮槽上,工艺参数对皮带轮旋压成形材料分布均匀性影响较大。     

Numerical and experimental study on expansion forming of inner grooved tube

Inner grooved copper tubes have attracted more and more attention in recent years. In mass production of tube–fin heat exchanger plates in ACR (air conditioning and refrigeration) industry, mechanical expansion is a key forming process which joins the fins to the tubes. During the process, the spiral grooves inside the tube with thermally efficient geometries are deformed and the tube–fin joints are influenced by the groove layer. In this paper, tube expansion forming process is studied and effect of the groove shape on forming quality is analyzed. Experiments are performed with tubes of different groove types. FE (finite element) model of the forming process is developed. Influences of the key geometry parameters, such as groove height ratio, apex and helix angle, on strength of the grooves as well as tube wall thinning are investigated. Sections of the tube–fin joints are observed and the die geometry on the joining status is examined. The results indicate that helix angle has significant effect on groove height reduction while groove height ratio is the main factor influencing the deformation resistant force; outer diameter and radius of the front part of the expanding die influence the tube–fin joining status.     

劈楔立棱面倾角对燕尾槽槽口张开的影响研究

介绍了燕尾槽的劈挤成形及劈楔,并针对燕尾槽成形过程中出现的槽口张开现象,在楔头主要几何参数中,固定劈分角为60°,从+30°～-30°范围内取4种劈刃倾角,进行数值模拟试验。结果表明:劈楔立棱面倾角决定了槽断面成形顺序,正值立棱面倾角是造成槽口张开的主要因素,该结果也得到了物理模拟试验验证;为保障劈楔强度,建议立棱面倾角取0°,制造误差应向负方向偏离。     

悬空特征结构件电弧增材制造成形及算法优化

将增材制造技术与弧焊机器人相结合,针对具有悬空特征预制件增材制造焊接工艺进行研究. 首先针对预制件成形尺寸预测进行算法优化,实现对成形高度及宽度预测;针对悬空焊缝下淌现象,研究焊枪倾斜角度对焊缝成形影响,确定最优焊枪倾斜角度范围,并设计试验对成形方法进行验证,有效改善悬空焊缝表面成形质量,然后在此基础上提出焊枪倾斜角度预测算法,实现对悬空焊过程中焊枪倾斜角度的预测. 最后焊制具有悬空特征预制件验证预测算法及成形方法的准确性. 结果表明,预制件表面成形质量较好,成形尺寸误差小于1 mm.     

斜齿圆柱齿轮一步精密成形数值模拟

探索一种集成了分流成形与推过整形优点的一步法斜齿圆柱齿轮精密成形新工艺,以模数为4 mm、齿数为12、螺旋角为14°、齿宽为29 mm的斜齿圆柱齿轮为研究对象,设计了成形模具,采用Deform-3D软件对成形过程进行模拟研究。首先进行了新工艺的成形力分析,之后,采用控制变量法探索了齿宽方向扩腔范围b、扩腔斜角α和齿高方向扩腔范围h这3个扩腔空间结构参数对齿轮下角隅充满效果及成形力的影响。分析结果表明,新工艺能明显降低成形力。即金属分流量的多少决定着成形效果,金属分流量由b、α和h三个参数组合决定,三者影响规律类似。即当其他条件一定时,若b(或α亦或h)过小,则成形力很大,分流量不足,导致下角隅填充不饱满;反之,虽然成形力较小,能得到完整齿形,但分流量过多,容易产生废料;当b、α和h取合理组合值:b为16 mm,α为10°和h为3 mm时,成形力适中且分流量合理,可以得到无废料的完整齿形。     

TA2钛环形管热推成形的三维有限元数值模拟

应用商业有限元软件ANSYS对TA2钛环形管热推弯曲成形过程进行了有限元数值模拟。并对成形过程中环形管内侧凹边、外侧凸边及侧面的应力、应变分布数据以及弯曲成形过程中壁厚的变化进行了分析。结果表明：管件峦变形过程中等效应力值总的变化随着弯曲角度的的增大而增大，而且弯曲管件的内侧凹边管壁的应力值比外侧凸边管壁要大，内壁受到压应力而外壁受到的拉应力；等效应力变数值内侧管壁的应变值比外侧管理壁要大，在弯曲过程中由于弯曲半径小，弯曲变形大，在弯制过程中，弯管内侧凹边受压缩使壁厚墙厚，而外侧凸边因受拉伸而壁厚减薄。数值模拟与实验所得结果一致。     

Plate forging of tailored blanks having local thickening for deep drawing of square cups

A plate forging process of tailored blanks having local thickening for the deep drawing of square cups was developed to improve the drawability. A sheet having uniform thickness was bent into a hat shape of two inclined portions, and then was compressed with a flat die under restraint of both edges to thicken the two inclined portions. The bending and compression were repeated after a right-angled rotation of the sheet for thickening in the perpendicular direction. The thickness of the rectangular ring portion equivalent to the bottom corner of the square cup was increased, particularly the thickening at the four corners of the rectangular ring undergoing large decrease in wall thickness in the deep drawing of square cups became double. The degree of thickening can be adjusted by controlling the punch stroke in the bending. By using the tailor blanks having local thickening, not only the decrease in wall thickness at the bottom corner of the square cup was prevented, but also the limiting drawing height of the cup without fracture was increased to 28.3 mm, whereas that for the uniform blank was 21.3 mm.     

Investigation of a new incremental counter forming in flexible roll forming to manufacture accurate profiles with variable cross-sections

A roll-formed profile with variable cross-sections fabricated by flexible roll forming has a shape error, such as warping, because of geometrical deviations in transitional zones of the profile between the initial metal strip and the roll-formed profile. To reduce the shape error, a new process called incremental counter forming (ICF) is proposed. Our investigation of the ICF process shows that the longitudinal strain distribution at the flange of the roll-formed profile can be controlled by combinations of forming parameters of the ICF process. As the forming parameters increase the longitudinal strain distribution in the concave zone, the shape error decreases. However, when the longitudinal strain distribution in the straight zone reaches a critical limit, the additional longitudinal strain works as an excessive longitudinal strain to worsen the shape error. An analytical model, which describes the longitudinal strain at the flange during roll forming, is adopted to reveal that the increase of the longitudinal strain is induced by increasing derivatives of a bending angle, which is controlled by the forming parameters of the ICF process. Finally, the FE simulation has been carried out to compare with the experimental results, which show that the ICF process is effective for reducing the shape error of the profile with variable cross-sections in flexible roll forming.     

A novel spindle inclination error identification and compensation method in ultra-precision raster milling

In the ultra-precision raster milling (UPRM) process, the existence of spindle inclination error can directly affect the dimensional accuracy of machined components. This study developed a novel spindle inclination error identification and compensation method based on the groove cutting in UPRM. In this method, the tilt angle of the intersection curve of two toruses (ICTT) generated from two neighboring rotary cuts in UPRM was measured to identify the spindle inclination error. A mathematical model was developed to simulate the ICTT profile and present the relationship between the tilt angle of ICTTs and the spindle inclination error by solving the differential of the ICTT function, by which the spindle inclination error can be solved under the given cutting parameters and the tilt angle of ICTTs. The effects of cutting parameters on the tilt angle of ICTTs were explored. An error compensation procedure was designed and a group of groove cutting experiments was conducted to identify and compensate the spindle inclination error. The theoretical and experimental results show that the proposed method can compensate for the spindle inclination error effectively and accurately.     

V型弯曲件回弹规律的有限元分析

以V型件弯曲和回弹过程为分析研究对象，通过对V型件弯曲及回弹过程的有限元数值模拟，分析获得了成形参数对V型件弯曲回弹的影响规律。结果表明：回弹角随弯曲角及材料的硬化系数的增大而增大，随材料的变形程度及硬化指数的增大而减小。     

直齿圆柱齿轮冷挤压可控运动凹模成形工艺

为降低直齿圆柱齿轮冷挤压成形载荷和改善齿形角隅部分充填性,在分析直齿圆柱齿轮成形过程中金属流动特性基础上,提出了采用可控运动凹模的成形工艺。利用Deform-3D软件对此成形工艺过程中的金属流动规律、成形载荷、成形缺陷进行了数值模拟分析,并对该工艺进行了优化。分析结果表明,当凹模速度为冲头速度的1/2时,成形过程中齿形充填均匀、齿形角隅部分充填饱满,成形载荷最小,较传统单向挤压成形载荷降低了约20%。对优化后的成形工艺进行了成形试验研究,试验成形齿轮齿形饱满,无塌角缺陷,试验结果与模拟结果基本吻合。