共查询到20条相似文献,搜索用时 31 毫秒
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Experimental study of oil-filled high-speed spin forming micro-groove fin-inside tubes 总被引:2,自引:1,他引:2
Y. Tang Y. Chi J.Ch. Chen X.X. Deng L. Liu X.K. Liu Zh.P. Wan 《International Journal of Machine Tools and Manufacture》2007,47(7-8):1059-1068
This paper presents an oil-filled high-speed spinning process of manufacturing micro-groove fin-inside tubes. In spinning, a high-pressure oil-film, which squeezes the tube outer-wall, is formed as the spinning speed increases. A floating mandrel extrudes the tube inside wall to form the micro-grooves/fins continuously. By experiments of spinning micro-groove fin-inside tubes, this paper analyzes the influences of each process parameter on the formation quality, and optimizes each parameter. The experimental results show that the dynamic pressure can significantly improve the stability of spinning and the quality of finished surface; the minimum thickness of oil-film is decided by the spinning speed and the oil viscosity directly. In the case of full oil dynamic lubrication, there is no obvious scrape on tube surfaces. The main factors affecting the groove depth and the surface roughness are the ratio (α) of the wall thickness of the tube before drawing to the finished one, the material plasticity, the ratio (β) of drawing to spinning, the spinning speed (n), and lubricating state, etc. The axial drawing force mainly depends on the friction between the floating mandrel and the tube internal wall, the friction between the reducing mold and the outer surface, and plastic deformation resistance in the reducing mold area and spinning area as well. 相似文献
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基于有限元模拟的内螺纹铜管旋压成型参数确定 总被引:1,自引:0,他引:1
内螺纹铜管传热面积大,可以造成紊流效果,提高换热效率,是空调、冰箱的主要换热介质。旋压成型是制造内螺纹铜管的高效成型工序。为研究内螺纹铜管旋压成型过程中的材料流动规律,运用非线性有限元分析软件,对内螺纹旋压成型过程进行了仿真。结果表明,在旋压过程中,铜管经历了类似于行星辊轧的,从圆形到多边形,最后恢复圆形的过程;此外铜管除了发生横截面方向弯曲外,还发生轴向运动,两者叠加产生了羽片扭转;当铜管材料填满螺纹槽后,多余的材料沿旋压方向流动,将耗费过多的能量。减少管坯的直径和壁厚,可以减少截面方向弯曲,并可以减少壁厚过大导致多余材料周向流动的能量损失。文章讨论了旋压速度的选取,认为尽可能选用低的旋压速度,可以减少羽片扭转。 相似文献
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针对管端成形过程中金属塑性流动引起的轴向伸缩及卸载回弹导致的成形精度问题,研究金属的塑性流动和回弹对管端成形的影响。以不锈钢卡压式直通管件为研究对象,运用LS-DYNA的有限元显式算法和隐式算法对薄壁管管端成形进行数值模拟,得到管材的金属流动分布和卸载后的回弹结果,并进行了实验验证。研究表明,管端扩孔和缩孔中,在变形急剧处,金属出现一定程度的累积,壁厚有较明显地增加。金属的流动对管端的径向尺寸影响可以忽略,但是对管端的轴向尺寸影响较大,需对坯料进行补偿;管端卸载后的回弹尺寸影响成形的精度,需通过模具进行补偿。对金属塑性流动和回弹进行有限元分析,能有效地指导管端成形的模具设计及优化加工工艺,极大缩短产品开发和模具设计周期。 相似文献
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采用MPX-2000盘-销式摩擦试验机研究了边界润滑条件下滑动速度与界面载荷对304不锈钢与SKD11模具钢之间摩擦系数的影响。运用Matlab软件对实验数据进行处理分析,得出摩擦系数随滑动速度与界面载荷变化的规律,建立了基于滑动速度与界面载荷的变摩擦系数模型。并对典型U形件进行了实际冲压实验与有限元仿真,比较了定摩擦系数模型和变摩擦系数模型的回弹预测结果与测量值之间的误差。分析结果表明:滑动速度为30.615~44.22 mm·s~(-1)时,304不锈钢与SKD11模具钢之间的摩擦系数随滑动速度的增加而逐渐减小;界面载荷为2.038~4.076 MPa时,摩擦系数随界面载荷的递增而递减,且随着载荷的增加,摩擦系数减小的趋势逐渐变缓。采用修正后摩擦模型的回弹预测结果与测量值之间误差较小,预测精度较高。 相似文献
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Pierre Stéphan Florestan Mathurin Jean Guillot 《Journal of Materials Processing Technology》2012,212(4):766-775
Thread forming screws are being increasingly used, particularly in the automobile industry. They are designed to directly assemble two parts by displacing material to form their own thread. This specificity implies knowledge of the screwing torque needed for the thread to be formed in the lower plate of the assembly and of the tightening torque necessary so as to establish the preload in the assembly. The experimental study presented in this paper is divided into two parts.The first concerns the thread forming process and shows the influence of the geometrical parameters of the thread forming screw and of the work-piece, and the influence of the process parameters on the maximum forming torque. A compromise can be proposed for the choice of the lead hole diameter, which is the most important parameter to be considered in order to keep a reasonable forming torque while obtaining threads deep enough to avoid stripping problems.The second part concerns the tightening process. An original experimental device is used to enable an empirical formula to be proposed, based on the ISO standard screw formula giving the tightening torque according to the preload applied inside the assembly. 相似文献
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管材激光弯曲是一种柔性金属塑性加工方法,特别适合薄壁管材弯曲。文章对大径厚比薄壁管材的激光弯曲过程进行热力耦合有限元分析,建立了管材激光弯曲热力耦合有限元分析模型,并进行实验验证。对于薄壁管材激光弯曲,弯曲内侧局部凸起现象较为严重,激光光斑尺寸对凸起程度有一定影响,但不显著。 相似文献
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本文根据C型多点成形压机机架结构、受力状况,以三维实体为单元,建立了压力机机身有限元模型和机身结构优化的数学模型。有限元分析表明,本模型行之有效,优化结果理想。 相似文献
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管材流体压力成形三维成形极限图 总被引:1,自引:0,他引:1
成形极限图是一种评估单向拉伸到双向等拉应力范围内板料成形性能的有效手段。传统板料成形中,法向受到的应力远小于面内应力,所以,传统成形极限图是基于忽略法向应力而简化为平面应力状态的理论计算。该文论述了传统成形极限图以及现有的考虑法向应力影响的二维成形极限图在研究液压成形中流体压力影响时存在的缺陷与不足;同时,在二维成形极限图以及固体现实应力空间的基础上,建立了以法向流体压力p的函数f(p)为第三轴的三维成形极限图。该三维成形极限图不仅可以考虑液压成形中流体压力的影响,而且能够形象直观呈现出成形极限随流体压力的变化速率。 相似文献
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《Journal of Materials Processing Technology》2014,214(5):1120-1130
Digital image correlation (DIC) analysis methods can provide very accurate strain measurement that is useful for identifying the onset of localized necking and thus determining the forming limit strains of sheet metals. Several different DIC procedures to establish a forming limit diagram (FLD) are compared including both position dependent and time dependent measurement methods where the latter is found to be more accurate for an Al–Mg–Si alloy. Since FLD standards are still being developed to include DIC methods, a new DIC-based time dependent measurement method for the forming limit strains is proposed in this research: (1) Surface topography is extracted from the DIC data and changes in surface height difference are obtained, of the test specimen; (2) The onset of localized necking is identified by the limit of stable flow of the surface height difference or the first derivative of the surface height difference near the development of a local neck when using the Marciniak test procedure. Compared to existing methods, this new procedure more accurately defines the onset of necking and the boundary of safe deformation of an FLD. 相似文献