Q345 中厚板 V 形折弯应力 应变分析

目的研究Q345中厚板在V形折弯时的应力应变中性层内移规律。方法通过对中厚板135°折弯过程进行数值模拟,分析了板料在成形过程中的等效应力应变及其中性层内移现象,测得了应变中性层与几何中间层之间的距离变化。在此基础上,采用厚度为16 mm的Q345板料进行物理实验,并与模拟结果进行了对比分析。结果在成形过程中,等效应力应变中性层均产生了内移现象,且应力中性层的内移量明显大于应变中性层的内移量;成形结束之后,应变中性层与几何中间层的距离为3.3 mm;实验结果显示,应变中性层的内移量为3.1 mm左右,与模拟值较为一致。结论数值模拟方法可以为应力应变中性层计算提供指导。对于中厚板折弯,采用几何中间层展开求得的坯料尺寸并不准确。     

多点复合渐进成形与单点渐进成形的对比分析

为提高金属板材渐进成形的成形质量、成形精度、成形效率和成形极限,了解不同渐进成形工艺对制件成形性能的影响,本文以典型方锥台制件为研究对象,利用有限元软件MSC.Marc对2种渐进成形工艺进行了三维建模,对比分析了单点渐进成形和多点复合渐进成形对制件等效塑性应变、厚度分布和成形精度的影响.数值模拟结果表明:单点渐进成形的等效塑性应变和厚度减薄主要集中在制件相邻侧壁间的拐角处,而多点复合渐进成形的等效塑性应变和厚度减薄均匀地分布在制件成形区;相同成形工艺参数下,相比单点渐进成形,多点复合渐进成形更有利于制件的成形效率、成形质量、成形精度和成形极限的提高,更有利于抑制破裂等失稳现象的产生.2种渐进成形工艺的成形试验表明,数值模拟结果与试验相符.     

平面应变板料拉弯成形回弹理论分析

基于平面应变假设,采用服从Hill平方屈服准则和指数强化材料模型,建立了板料拉弯成形回弹量预测的理论模型。应用该模型计算了一个拉弯成形回弹实例,分析了单位宽度切向拉力、凸模圆角半径、摩擦因数及各向异性参数对板料回弹量的影响。分析结果表明,只有当中性层偏移距离超过板厚的四分之一时,增大切向拉力才能有效地控制板料回弹量,而且弯曲半径越大,增大切向拉力控制板料的回弹量越为有效,然而拉力不能无限制的增大,它的计算准则为板料最外层的等效应变应不大于极限应变。同时还表明,摩擦因数对板料回弹量的影响随切向拉力的增大变得更为显著,而各向异性参数对板料拉弯成形回弹量的影响也较为明显。与有限元数值模拟预测结果的对比表明,理论模型预测板料拉弯成形回弹量与有限元数值模拟结果很接近。     

LY12超塑性成形有限元分析

基于LY12铝合金超塑性材料属性建立了弹-粘塑性本构模型.利用该本构模型并结合最大等效应变速率控制压力变化算法对LY12铝合金板超塑性圆杯成形进行数值模拟,得到圆杯变形过程中的应力应变分布、板料厚度变化及所需成形时间.根据模拟获得的优化压力时间曲线对圆杯进行超塑性气压胀形加载实验,制件厚度分布与模拟结果非常接近.     

3D打印双点渐进成形支撑模具的可行性

目的为了更快速、简单、有效地完成双点渐进成形加工中支撑模具的加工。方法采用3D打印设备完成支撑模具加工,用加工完成的模具作为支撑,通过板料渐进成形技术对1 mm厚的铝板进行成形,选取8个标本点测量工件的壁厚,并与普通模具完成的零件进行比较,再对3D模具成形的工件进行成形精度分析。结果通过实验数据分析,板料壁厚变化完全符合正弦定律,计算出的理论轮廓与实际轮廓的成形精度偏差绝对值算术平均值基本符合生产要求。结论这种与3D打印技术相结合的双点渐进成形加工工艺完全可行,与普通模具相比节省了模具加工经费,降低了渐进成形加工的时间。     

板料渐进成形数值模拟与实验研究

为提高渐进成形的成形效率和成形质量,了解板料渐进成形的变形规律及工艺参数对成形的影响,采用有限元方法对板料渐进成形过程进行了数值模拟研究,分析了斜壁盒形件渐进成形过程应力分布和厚度变化趋势,通过对不同进给量和不同成形路径进行数值模拟,分析了工艺参数对成形的影响.结果表明,斜壁盒形件最大应力和最大厚度减薄发生在底面拐角处;成形过程中工具头运动轨迹应尽量采用走螺旋线的方式,可以提高成形件的成形能力和成形质量.渐进成形实验表明,数值模拟结果与实验结果基本吻合.     

波长对板料锤击式渐进成形性能的影响

目的研究不同波长对板料锤击式渐进成形性能的影响规律。方法以波长为单一因素,将波长值从0.5~5 mm进行多次重复性实验,分别与普通渐进成形实验结果进行对比。结果波长对材料的成形性有显著影响,锤击式渐进成形波长值在0.5~5 mm时,板料的成形性能均高于普通渐进成形,随着波长的增加,板料的成形性能降低,成形时间减少。结论锤击式渐进成形相对于普通渐进成形在成形性能方面具有优越性,综合考虑成形性能、加工时间和表面质量等因素,板料锤击式渐进成形波长为0.5 mm时,成形性能最好。     

Al6063管件外增量成形工艺研究

目的 研究6063铝合金管件外增量成形过程,分析管件的成形效果,改进管件成形质量。方法 设置3组目标成形管件,使用Abaqus软件进行成形过程的数值模拟,通过考察成形管件的几何精度、壁厚分布、表面质量、成形力,分析成形质量和可能出现的问题。通过使用长120 mm、直径50 mm、壁厚1.5 mm的Al6063铝管进行管件外增量成形实验,验证数值模拟结果的可靠性。结果 成形管件会发生管端变形现象,具体表现为管端不圆与轴向伸长,成形件管端椭圆度为10.11%,管端变形程度与成形道次成正比,且在距离管端越近的成形区域,管端变形越明显。管壁成形区厚度增大并呈现不均匀分布。成形件管壁直线度偏差为0.34,且表面质量与径向进给量和轴向进给速度成反比,管件的圆角尺寸难以严格控制。径向力是成形过程中主要的成形力,其大小与工具头直径成正比。结论 管件外增量成形原理可靠,基于此能够实现多种目标管件的成形。由于成形原理的限制,成形件的成形质量还有很大的提升空间,合理制定工艺参数对提高成形质量十分重要。     

基于渐进弯曲成形双曲马鞍形金属板工艺研究

目的 解决马鞍形板成形困难、成形效率低和成形精度低的问题。方法 通过理论分析和仿真方法对马鞍形板成形过程中的加载路径和回弹情况进行研究,分析马鞍形板成形所需最小能量加载轨迹和回弹补偿数值。在此基础上,采用渐进弯曲成形方法对3 mm厚的Q235钢板进行马鞍形板成形实验,并与仿真研究结果进行对比分析。结果 马鞍形板在不同冲压点的回弹高度基本相同,为12 mm左右,没有辅助支撑成形马鞍形板的实验结果和设计目标的平均误差为6.2 mm,增加辅助支撑成形马鞍形板的实验结果和设计目标的平均误差为4.1 mm。结论 渐进弯曲成形方法能提高马鞍形板的成形效率和成形精度,节约成形加工成本。增加辅助支撑能明显改善马鞍形板的成形质量。     

拼焊板U形件弯曲成形回弹补偿和焊缝移动规律研究

为了提高预测回弹的准确性,选用了拼焊板U形件作为研究对象,运用Dynaform软件,进行冲压成形和回弹的有限元数值模拟研究,得出了压边力、板料强度以及板料厚度对焊缝移动的影响规律,并探讨了焊缝、压边力、材料性能参数和板料厚度对回弹的影响,最终进行回弹补偿与实验验证.研究结果表明随着压边力的增大,焊缝向厚侧移动;板料强度不同时,焊缝向强度高的一侧移动;厚度不同时,焊缝向板料厚的一侧移动;焊缝会令板料的回弹量增大;随着压边力的增大,回弹量减小;弹性模量相同的条件下,材料屈服极限σs越高,回弹角越大;材料硬化指数n越小,回弹角越大;保持厚侧板料不变的情况下,另一侧板料越薄,回弹量越大.     

Finite element modelling and experimental investigation of single point incremental forming process of aluminum sheets: influence of process parameters on punch force monitoring and on mechanical and geometrical quality of parts

New trends in sheet metal forming are rapidly developing and several new forming processes have been proposed to accomplish the goals of flexibility and cost reduction. Among them, Incremental CNC sheet forming operations (ISF) are a relatively new sheet metal forming processes for small batch production and prototyping. In single point incremental forming (SPIF), the final shape of the component is obtained by the CNC relative movements of a simple and small punch which deform a clamped blank into the desired shape and which appear quite promising. No other dies are required than the ones used in any conventional sheet metal forming processes. As it is well known, the design of a mechanical component requires some decisions about the mechanical resistance and geometrical quality of the parts and the product has to be manufactured with a careful definition of the process set up. The use of computers in manufacturing has enabled the development of several new sheet metal forming processes, which are based upon older technologies. Although standard sheet metal forming processes are strongly controlled, new processes like single point incremental sheet forming can be improved. The SPIF concept allows to increase flexibility and to reduce set up costs. Such a process has a negative effect on the shape accuracy by initiating undesired rigid movement and sheet thinning. In the paper, the applicability of the numerical technique and the experimental test program to incremental forming of sheet metal is examined. Concerning the numerical simulation, a static implicit finite element code ABAQUS/Standard is used. These two techniques emphasize the necessity to control some process parameters to improve the final product quality. The reported approaches were mainly focused on the influence of four process parameters on the punch force trends generated in this forming process, the thickness and the equivalent plastic deformation distribution within the whole volume of the workpiece: the initial sheet thickness, the wall angle, the workpiece geometry and the nature of tool path contours controlled through CNC programming. The tool forces required to deform plastically the sheet around the contact area are discussed. The effect of the blank thickness and the tool path on the punch load and the deformation behaviour is also examined with respect to several tool paths. Furthermore, the force acting on the traveling tool is also evaluated. Similar to the sheet thickness, the effect of wall angle and part geometry on the load evolution, the distribution of calculated equivalent plastic strain and the variation of sheet thickness strain are also discussed. Experimental and numerical results obtained allow having a better knowledge of mechanical and geometrical responses from different parts manufactured by SPIF with the aim to improve their accuracy. It is also concluded that the numerical simulation might be exploited for optimization of the incremental forming process of sheet metal.     

板厚对08Al薄板单点渐进成形中成形极限的影响

目的 针对渐进成形中成形极限测量难的问题,提出一种新的评定成形极限方法.方法 选用08Al为实验材料,通过模拟和实验相结合的方法,研究不同板厚下成形极限角和减薄率的关系,提出利用成形极限角和最大减薄率2个参数组合的方法判断薄板的成形极限,并通过数控实验验证提出方法的准确性,分析板厚对单点渐进成形工艺成形极限的影响.结果...     

Shape accuracy analysis of multi-point forming process for sheet metal under normal full constrained conditions

In order to study the shape accuracy of multi-point forming (MPF) process for sheet metal under normal full constrained conditions, the in-depth analysis of shape accuracy of workpieces in multi-point forming with individually controlled force-displacement (MPF-ICFD) process is conducted in this paper by combining experiment, theoretical analysis and numerical simulation. The influences of normal force, material thickness and material properties on the shape accuracy of the feature surface are studied, and the shape accuracy characteristics of the sheet under different parameters are obtained. Afterwards, the stress and strain characteristics of sheets are obtained by numerical simulation. Finally, the effect of normal force on shape accuracy was revealed by establishing a mechanical model of the sheet metal under normal full constrained conditions. Moreover, the amount of springback reduction in MPF-ICFD is defined quantitatively. Compared with the normal unconstrained conditions, the shape accuracy of sheet metal is improved significantly under normal full constrained conditions. The stress and plastic deformation are more uniform and the amount of springback is smaller. For Q 295 steel plate with thickness of 2.0 mm, the difference between the maximum value and the minimum value of the reaction force of punch decreases from 4515.9 N to 1475 N when the forming force is 2500 N. Besides, the bending moment of the sheet on the unit width decreases from 357.9 N???mm to 328.1 N???mm. The average shape error E _rr and the amount of springback Δk decreases by 60.05% and 16.03%, respectively.     

单点渐进成形工艺参数对正五边锥形件壁厚的影响

目的 利用数值模拟方法研究单点渐进成形工艺参数对制件成形区最小壁厚的影响规律,得出最优工艺参数组合,提高制件的成形质量。方法 在对2024铝合金正五边锥形件建立有模单点渐进成形数值仿真模型的基础上,对进给率、层间距、成形工具头直径和摩擦因数对制件成形区最小壁厚的影响进行单因素和正交试验分析,并通过物理试验对仿真优化后的工艺参数组合进行验证。结果 正五边锥形件单点渐进成形加工过程中,最小壁厚与进给率、层间距成反比,与成形工具头直径成正比,而摩擦因数对最小壁厚的影响较小;各工艺参数对最小壁厚的影响程度为进给率＞层间距＞成形工具头直径＞摩擦因数;最佳工艺参数为成形头直径9 mm、进给率200 mm/min、加工层间距0.2 mm和摩擦因数0.1。结论 通过有限元仿真得出了单点渐进有模成形工艺对制件最小壁厚的影响规律,通过正交试验分析得出了正五边锥形件单点渐进有模成形最佳工艺参数组合,利用该参数组合可以得到壁厚较为均匀的正五边锥形件。     

增量成形内凸螺旋波纹管研究

目的 研究增量成形螺旋波纹管过程中,工具头的单次压下量与摩擦因数对成形质量和极限的影响规律,优化成形工艺参数。方法 通过ABAQUS有限元模拟和实验相结合,对各个成形工艺参数进行有限元模拟;使用前端直径为8 mm的成形工具头对外径40 mm、壁厚0.8 mm的304不锈钢进行增量成形螺旋波纹管实验研究。结果 不同摩擦因数对成形极限影响较小,对成形质量有较大影响。单次进给量为0.1 mm,摩擦因数为0.02时,螺纹深度极限可以提高10.5%。模拟和实验都验证了工艺参数的合理性。结论 摩擦因数一定的情况下,单次压下量越小,成形力越小,螺纹深度极限越大。     

Experimental investigations and optimization of forming force in incremental sheet forming

Incremental sheet forming process has been proved to be quiet suitable and economical for job and batch type production, which exempts expensive and complex tooling for sheet forming. Investigation of forming forces becomes important for selecting the appropriate hardware and optimal process parameters in order to assure perfection and precision of process. Moreover, lack of available knowledge regarding the process parameters makes the process limited for industrial applications. This research paper aims at finding out effects of different input factors on forming forces in single-point incremental forming (SPIF) process. For operation sustainability and hardware safety, it becomes critical to optimize forming forces for a given set of factors to form a particular shape. In this study, optimization of input factors has been performed to produce conical frustums with helical tool path using Taguchi analysis as design of experiment (DOE) and analysis of variance (ANOVA). The optimal experimental conditions for forming forces have been calculated as sheet thickness (0.8 mm), step size (0.2 mm), tool diameter (7.52 mm), tool shape (hemispherical), spindle speed (1000 rpm), feed rate (1000 mm/min) and wall angle (50^o). Effects of tool shape and viscosity of lubricants have also been investigated. An intensive understanding of the mechanism of forming forces has been presented, which shows that force trend after peak values depends upon instant input factors that can be categorized as a safe, severe and crucial set of parameters.     

高冲击载荷作用下平面式电涡流阻尼器特性数值模拟研究

为探究平面式电涡流阻尼器在冲击环境中的应用特点,开展了高冲击载荷作用下平面式电涡流阻尼器响应特性数值模拟研究.基于ANSYS Maxwell电磁学有限元软件建立平面式电涡流阻尼器二维数值仿真模型,分析了永磁体和磁靴结构尺寸、导电层和导磁层厚度以及气隙间距对电磁阻尼力的影响.研究结果表明:平面式电涡流阻尼器能够满足安全制...     

The effect of pressing direction on the 5-axis CNC incremental forming quality

The effect of pressing direction on forming quality in the 5-axis CNC incremental forming was studied by using the digital simulation technology based on the finite element analysis method. Four kinds of finite element analysis models were created according to the different pressing directions, and were simulated by using ANSYS/LS-DYNA software. Through comparing with the simulation results of the four kinds of finite element analysis models, the relationships between the pressing direction and sheet thickness distribution, sheet thickness thinning rate, outline of the middle surface and the equivalent strain of middle surface were presented.