工艺参数对高强拼焊B柱内板成形性能的影响

高强度拼焊板具有减轻车身重量、节能环保、改善车身安全性能等优点.针对差厚拼焊板冲压成形时,制件局部容易出现破裂、起皱和回弹过大等问题,利用有限元分析软件Dynaform对B340LA高强拼焊板B柱内板成形过程进行模拟,研究了压边力、模具间隙对B柱拼焊板成形的影响规律,并通过实验进行验证.研究结果表明,随着压边力增大,制件减薄率增大,增厚率减小,焊缝移动增大,制件回弹量减小;随着模具间隙增大,减薄率和增厚率都减小,焊缝移动增大,回弹量增大.合理工艺参数为压边力1200 kN,即该压边力为理论计算值的1.03倍,模具单边间隙为板厚的1.1倍.     

基于应变路径的拼焊板盒形件成形性能研究

利用Dyanform对拼焊板盒形件进行冲压成形数值模拟,研究不同压边力对拼焊板盒形件拉深过程中破裂危险点应变路径和成形性能的影响规律;同时,提出台阶式变压边力控制方法.结果表明:通过调整压边力的大小和变化方式,可以实现对拼焊板盒形件破裂危险点处应变路径的控制以及减小焊缝移动,从而提高拼焊板盒形件的冲压成形性能.     

拼焊板方盒件冲压成形压边力数值模拟分析

用有限元分析软件Dynaform对拼焊板方盒件成形进行数值模拟,研究不同压边力对拉深过程中破裂危险点应变路径和焊缝移动的影响规律。通过调整压边力的大小和变化方式,可以实现对拼焊板方盒件薄板破裂危险点处应变路径的控制以及减小焊缝移动,从而提高拼焊板方盒件冲压成形性能。     

压边力分布对差厚拼焊板盒形件焊缝移动的影响

采用有限元数值模拟技术,对不同的压边力分布对拼焊板盒形件拉深成形中焊缝移动的影响规律进行了研究。通过调整压边力的大小和随位置的分布,实现对拼焊板盒形件成形过程中焊缝移动的控制。研究表明:不同的压边力大小和分布对拼焊板盒形件焊缝移动有很大影响,增大薄侧板料的压边力以及减小厚侧板料的压边力能有效控制焊缝移动量。利用随位置变化的多点控制的分块压边力更能有效控制拼焊板盒形件的焊缝移动,有利于控制板料在凹模中的流动,有效提高拼焊板盒形件的冲压成形性能。     

拼焊板盒形件冲压成形失效及应变路径分析

采用自制液压机和分瓣压边圈模具,通过模拟仿真和实冲试验,变化各工艺参数,研究分析拼焊板方盒件冲压成形的应变路径、焊缝移动和成形极限,以提高其成形性能。研究表明,厚/薄侧压边力的大小和分布对破裂危险点的应变路径和成形裕度有很大的影响,合理的压边力分布可调节失效破裂的位置,减少焊缝移动和提高成形极限深度;凹模圆角半径的增大,对薄侧侧壁圆角处破裂危险点应变路径影响较大,拼焊板盒形件成形极限深度逐渐增大;厚度比较小时,破裂出现在薄侧圆角处,而厚度比较大时,焊缝移动量大,破裂易出现在薄侧焊缝处;板料毛坯形状和尺寸对失效破裂的位置和成形性能影响显著。因此,以薄侧侧壁圆角处和薄侧焊缝位置附近为破裂危险点,通过优化压边力、凹模圆角半径、板料厚度比、板料毛坯形状和尺寸等工艺参数,改变危险点的应变路径,调节失效破裂的位置,减小其焊缝移动量,可有效地提高拼焊板方盒件的冲压成形性能。     

镁合金拼焊板冲压成形过程数值模拟

借助MSC-Marc模拟软件,采用大变形弹塑性有限元法,建立了镁合金拼焊板筒形件冲压成形有限元模型,对相同厚度、不同成分的镁合金拼焊板冲压成形过程进行了数值模拟。得到了筒形件底部及侧壁法兰处焊缝移动规律;分析了压边力及板料初始温度对焊缝移动情况的影响。对于拼焊板冲压成形的研究具有一定意义。     

压边力对双焊缝差厚拼焊板拉延成形焊缝移动的影响

拼焊板在拉延成形时焊缝移动受多方面因素的影响,本文模拟分析了不同压边力值和分段压边力对具有两道焊缝的差厚激光拼焊板汽车后纵梁在拉延成形过程中焊缝移动的影响。通过分析在不同压边力下两条焊缝的移动量得出了焊缝最大移动量随压边力的增大而增大的规律。为了减小两条焊缝的移动量,成形过程中在保证总压边力不变的情况下对差厚拼焊板的不同板厚部分设置不同的压边力。通过模拟分析得出了焊缝最大移动量随着薄侧压边力的增大和厚侧压边力的减小而减小。合理的增大薄侧板料压边力,减小厚侧板料压边力可以减小焊缝移动量,提高成形质量。     

应用变压边力控制技术改善拼焊板的成形性能

基于简化的拼焊板2D截面模型分析了控制焊缝移动的拼焊板薄厚两侧所需的压边力关系式,提出了分段压边圈作用下的拼焊板冲压成形方案。应用数值模拟技术进行了矩形盒冲压仿真,验证了分析结果的有效性,分析了变压边力对拼焊板成形性能的影响。研究结果表明:拼焊板薄侧加载比厚侧较大的压边力,有效减少了焊缝移动,减小了薄侧材料的应变集中,改善了薄厚两侧材料变形均匀性,从而提高了拼焊板的成形性能,为提高拼焊板成形质量提供了新思路。     

拼焊板柱面扁壳成形焊缝移动与回弹研究

建立柱面(X向)和曲面方向(Y向)焊缝的柱面扁壳有限元模型,改变压边力、板厚比,研究拼焊板拉深切边成形时的焊缝移动、曲面方向回弹及其相互关系,并与光板对比。结果表明:压边力大小影响焊缝移动,曲面方向回弹随压边力增加而减小;Y向焊缝拼焊板回弹最大,光板及X向焊缝拼焊板厚侧次之,薄侧最小;板厚比不低于0.5时,板料成形性能平稳且焊缝偏移量、回弹随板厚比减小而增加,在实际应用中得到验证。     

差厚激光拼焊板焊缝移动与回弹控制

研究具有纵向焊缝的拼焊板在不同压边力作用下的回弹与焊缝移动及其相互关系,为拼焊板的回弹控制找到切入点.基于厚/薄侧变形均匀的思想,采用拼焊板两侧的截面应力相等的方法,理论推导了控制焊缝移动的公式,以此计算控制焊缝移动和拼焊板回弹所需要的拼焊板两侧压边力分布值.研究表明,总压边力的增大,带来双重效应:一方面随总压边力的增大拼焊板回弹降低;另一方面随总压边力的增大拼焊板焊缝移动增加,焊缝移动增加回弹增加.维持总压边力不变,通过调整压边力分布,消除焊缝移动,同时回弹也达到最小值.采用足够高的压边力的同时,对拼焊板厚/薄侧施加不均匀压边力,降低焊缝移动,这为拼焊板回弹控制提出了新的理论和方法.     

变压边力优化设计提高仪表板支架冲压成形精度

提出了一种变压边力优化设计方法 ,以抑制冲压件回弹变形、提高成形精度。基于数值模拟确定变压边力曲线中各设计变量 ,如不同区段压边力的大小、压边力变化时刻等的取值范围 ,并将正交试验设计方法引入到优化解的搜索过程中以提高优化过程的效率。将这种方法应用到一个实际轿车冲压件———仪表板支架的成形过程中 ,通过与数值模拟相结合 ,得到能够提高其成形精度的变压边力曲线     

随行程变化变压边力拼焊板盒形件成形性能研究

焊缝两侧材料变形不均匀引起的焊缝移动和成形性能下降是拼焊板成形过程中需要解决的难题,变压边力技术可以增大成形工艺调整范围、提高冲压件成形质量。本文在拼焊板成形过程中加载随行程线性渐增变化的变压边力,并应用动力显式数值模拟软件模拟差厚拼焊板盒形件的成形过程,研究变压边力控制对拼焊板成形性能的影响。结果表明,在相同的焊缝移动量下,线性渐增变压边力与定常压边力相比增大了引起焊缝移动的薄侧变形区域材料的长度,缓解了薄侧材料的应变集中,提高了拼焊板成形性能。     

Variable blankholder force in U-shaped part forming for eliminating springback error

Springback is the main defect in U-shaped part forming, which can badly affect the shape of a part. Applying reasonable variable blankholder force in the forming process is one of the useful methods to solve this problem, but determination of the curve of blankholder force vs. punch displacement is still difficult. A method is advanced in this paper to control the forming process of a U-shaped part, by which a reasonable blankholder force curve can be easily gained. Comparing with constant blankholder force, higher forming quality can be obtained in both avoiding cracking and improving dimension accuracy. The benchmarks of the 2D draw bending problem in NUMISHEET’93 has been utilized to validate the method by FEM, and good results of springback elimination have been obtained.     

Formability Enhancement of Galvanized IF-Steel TWB by Modification of Forming Parameters

Tailor-welded blanks (TWBs) have numerous advantages over traditional blanks used in manufacturing, such as energy conservation and environment protection. Low formability and weld line movement during forming operation are main limitations of these blanks. In this research, the effects of forming parameters including thickness ratio (TR), rolling direction with respect to the weld line and direction of major stress with respect to the weld line, on formability and weld line movement of TWBs made of galvanized Interstitial-Free (IF) steel were investigated experimentally. Also the effect of application of non-uniform blankholder force on weld line movement was studied by FEM simulation. By utilization of ABAQUS software, blankholders with different geometries, namely one-piece and two-pieces were modeled and forming process was simulated. The results revealed that formability maximized when the major stress and rolling direction were along the weld line. The results showed applying different blankholder forces, by application of the two-pieces blankholder, leads to more uniform strain distribution and correspondingly less weld line movement in TWBs with TR greater than 1. It was also concluded that the effect of geometric discontinuities on reducing formability was greater than the effect of the weld region.     

Eliminating springback error in U-shaped part forming by variable blankholder force

Springback is the main concern in U-shaped part forming, which would adversely affect desired part geometries. The use of variable blankholder force in the forming process is one effective method to reduce springback. However, there has not been a systematic way to determine the blankholder force trajectory. In this article, a methodology of obtaining this blankholder force trajectory in forming a U-shaped part that considers the wrinkling limit and fracture limit in the forming process was proposed. The method was validated numerically by using the Finite Element Method to simulate the benchmark of a 2-D draw bending problem in NUMISHEET’93. With the calculated blankholder force trajectory, higher forming quality was obtained and compared with constant blankholder force cases. Springback was kept at a minimum while avoiding cracking.     

The effect of ultra-low frequency pulsations on tearing during deep drawing of cylindrical cups

In sheet metal forming there is an increasing demand for deep drawing of light weight components with complex shapes. However, thinner and more ductile materials are more susceptible to tearing during the process. It is known that greater draw depths can be achieved without tearing if the blankholder is subjected to a pulsating force. The present paper describes experimental investigations in which cylindrical-shaped cups are drawn with a pulsed blankholder force (PBHF) at ultra-low (<1 Hz) and low (1–10 Hz) frequencies. The tests were performed with blanks of steel (DC04) and of aluminium (5754-H111) over a range of draw ratios.The tests showed that tearing occurred within a well-defined part of the punch stroke. Of the two parameters, amplitude and frequency of the pulsed force, the latter had a more pronounced effect. For draw ratios resulting in a narrow working range of the static blankholder force, the process can be made more robust if the PBHF is applied at ultra-low frequencies. In addition to this, the PBHF must be synchronised in such a way that, during the identified critical tearing part of the stroke, the instantaneous PBHF is kept below the static tearing limit by synchronising the punch force and PBHF. Feasible values of the frequency depend on the length of the critical tearing part of the stroke and the upper and lower BHF limits of the process.     

Stamping and stamping simulation with a blankholder gap

Applying a blankholder gap is the main method of control of the blankholder in stamping or its simulation. In this paper, the nature of stamping with a blankholder gap is provided as well as two advantages of stamping simulation with a blankholder gap. Finally, a reasonable blankholder gap for cup deep drawing and the reverse drawing process is proposed.     

基于板料冲压的压边力拉深成形数值模拟分析

压边力是板料拉延成形过程的重要工艺参数之一,合理控制压边力的大小,可避免成形件起皱或破裂等缺陷.建立了三角冲压件的有限元模型,利用DYNAFORM软件,采用数值模拟的方法研究了三角形冲压件拉深时,压边力随时间及位置变化对成形性能的影响.分析结果表明,通过控制拉深过程压边力值的大小和分布,能有效地控制金属的流动,提高板材的成形性能.