Study of residual stresses in tailor rolled blanked Al5J32-T4 sheets

Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.

差厚板U形件工艺孔成形性能仿真

以冷冲压差厚板U形件作为研究对象,通过有限元仿真分析了工艺孔的位置、数量、尺寸以及形状对成形性能的影响.结果表明,差厚板在薄区侧壁处开孔时有利于减少侧壁的残余应力;差厚板的回弹与工艺孔在板件中的位置分布关系不大,与工艺孔的数量、半径及形状有关.从成形性能和回弹影响角度考虑,工艺孔优先选差厚板U形件端部的厚区与过渡区区域,如果必须在侧壁开孔,优选侧壁薄区区域.在相邻区域,工艺孔的数量尽量不超过2个,工艺孔尺寸小一些更合适,工艺孔形状沿轧制方向距离越小越合适.

TRB及其轧制应用关键技术

讨论了车身用连续变截面辊轧板(TRB)在轧制和应用过程中的关键技术。TRB技术的实质是传统纵轧与辊间距实时调整变化相协调的过程,TRB轧制的关键是建立板厚综合系统控制模型,TRB在车身上的应用需要解决相应的冲压模具设计及冲压成型性评价等技术。该研究为实现车身轻量化拓宽了思路。

影响TRB单向拉伸的几何参数研究

将连续变截面辊轧板(Tailor Rolled Blanks,TRB)厚度过渡区离散为有限数量的等厚度区域,采用线性插值的方法描述TRB材料的非均匀性,建立TRB材料的应力应变场。参照等厚度板的单向拉伸试验国家标准,提出TRB单向拉伸试验的概念,在有限元软件ABAQUS中建立TRB单向拉伸的数学模型。以影响TRB单向拉伸的板料过渡区长度、板料厚度比等为参数,以厚度过渡区伸长率和厚度过渡区移动量等为评价标准,通过数值模拟和回归分析对不同方案下的厚度过渡区伸长率和厚度过渡区移动量进行比较。最后得到板厚比和伸长率之间关系的三次拟合曲线,分析厚度过渡区长度、板厚比对厚度过渡区移动量的影响。其结果为TRB拉伸性能标准的制定以及推动TRB在车身轻量化上的应用提供了重要的技术参考。

TRB轧制集成建模及成型关键技术

给出了实现连续变截面辊轧板(TRB)厚度控制的框架模型,研究了TRB轧制液压伺服系统建模控制方法,并进行了仿真分析。为进一步提高板厚形状控制精度,提出了将数学模型、人工智能和虚拟制造集成起来建模的策略,并给出了相应厚度集成控制模型。分析了基于虚拟技术的覆盖件产品开发平台和反映TRB制造过程的多层次信息模型,为TRB轧制控制提供了一种有效方法。

利用ABAQUS与正交试验理论的TRB成形参数优化

在有限元软件ABAQUS中建立连续变截面板的数值模型,以影响变截面板矩形件成形的板料过渡区长度、板料过渡区位置和板料厚度比等为参数,以最大料厚减薄率和板料节约率等为考核目标,通过数值模拟和正交优化方法,对比分析不同方案下最大料厚减薄率和板料节约率,确定最优方案,以提高变截面板的成形性能。结果表明,厚度过渡区的长度对矩形件成形的影响最大,过渡区的位置次之,厚度比的影响最小。

高强钢TRB高温下热流变特性

为了准确仿真高强钢板热冲压成形过程,获得高强钢高温下的材料本构关系模型,利用Gleeble3500热模拟试验机在不同温度和应变速率下对不同厚度的高强钢B1500HS钢板进行了单向拉伸试验,获得各种工艺条件下的应力-应变曲线,并基于变形抗力数学模型,引入板材厚度参数,通过最小二乘法进行数据拟合获得高强钢TRB高温下的材料本构关系.利用试验结果对本构关系模型进行的拟合验证表明,拟合程度较好,说明建立的材料本构关系能很好地描述高强钢TRB在高温下的应力-应变关系.

CR340轧制差厚板纵梁成形性能研究

目的研究复杂应力状态下轧制差厚板塑性变形行为和韧性损伤机理,获得轧制差厚板成形性能规律,促进轧制差厚板在汽车工业轻量化中的应用。方法应用细观损伤理论,采用有限元逆向法构建轧制差厚板GTN细观损伤模型,进一步结合有限元数值模拟技术研究轧制差厚板塑性变形行为和韧性损伤机理,对比分析差厚板与等厚板塑性变形特点,研究CR340轧制差厚板纵梁成形性能规律。结果将有限元逆向法和实验相结合,获得了损伤参数值,建立了描述轧制差厚板韧性损伤行为的GTN细观损伤模型,结合有限元分析可知,孔洞体积分数在过渡区变形最大的区域增加最为明显,孔洞最先在此处聚集发展;相比于等厚板,轧制差厚板成形纵梁时,在和厚区交界处的过渡区产生了显著的应力集中,引起过渡区应变急剧增大,使应力和应变整体分布的不均匀性增加。结论应用细观损伤理论和有限元数值模拟分析了轧制差厚板成形纵梁时韧性损伤最先产生的区域,结合应力和应变分布特点可知,与薄区相邻的过渡区在最大应变处最易出现成形缺陷。

退火工艺下轧制差厚板非均匀温度场研究

轧制差厚钢板具有连续变化的厚度特性,因此在退火工艺下不同厚度区域的温度变化路径存在显著差异。这种差异改变了轧制差厚钢板的微观组织及力学性能,进而直接影响其后续成形及服役性能。为掌握退火工艺下轧制差厚钢板具有的性能差异化特性及产生内因,需要对轧制差厚钢板热处理过程中的温度分布及规律进行系统研究。研究所用轧制差厚钢板的几何特征为:薄区、过渡区及厚区纵向长度均为50 mm;薄区厚度1 mm,厚区为1.5 mm,差厚比1.5,过渡区厚度连续变化且无突变。建立了同步考虑轧制差厚钢板厚度连续变化特性及综合传热形式的温度场非稳态理论模型,并通过实验方法验证理论模型准确性。结果表明,在预设退火温度780℃的升温历程中,以薄区达到临界温度的时间(75 s)为测温终点,各厚区最高温度为779.3℃;最高温差135.1℃,整体呈现先增后减的趋势;最大升温速率为21.9℃/s,之后各区域升温速率逐步递减且在到达37 s时各厚区升温速率的高低顺序发生转变。研究通过分析轧制差厚钢板随时间变化的温度分布态势与其内在规律,以期为轧制差厚钢板热处理后的性能差异化预测提供理论基础及有效方法。

CR340 TRB的晶体塑性有限元模拟及参数标定

基于Voronoi图形方法生成了随机晶粒形状的二维多晶体几何模型。同时将轧制差厚板的晶体塑性本构模型通过用户子程序嵌入到分析软件Abaqus中,进行单向拉伸模拟。结合晶体塑性理论和有限元数值模拟,采用控制变量法研究了参考剪切应变率、应变率敏感指数、初始硬化模量、饱和流动应力、初始临界分剪切应力对模拟结果的影响,通过拉伸试验和模拟得到应力应变曲线,确定了轧制差厚板晶体本构方程的各项参数。

TRB板轧制-弯曲-回弹的多工步分析

轧制差厚板的变厚度轧制过程中,由于厚区和薄区的变形程度不同,使得厚区和薄区的残余应力分布不均匀,对后续弯曲成形制件的回弹产生较大影响。将轧制和成形的有限元分析相结合,研究轧制差厚板的弯曲制件的残余应力对回弹的影响。推导了变厚度轧制过程中轧辊竖直方向运动的速度公式,用于实现变厚度轧制的有限元分析。把轧制差厚板的弯曲成形作为多工步塑性成形的后续工序,将轧制引起的残余应力继承到弯曲回弹的分析中,分析了轧制对回弹的影响。所得结果与物理试验进行对比,验证了该方法的有效性。

TRB结构的某车型仪表板横梁轻量化设计

为了实现某车型的仪表板横梁轻量化设计,利用CAE和连续变截面板(TRB)结构的特点对目标横梁进行优化设计。首先在有限元软件ANSYS中通过APDL的参数迭代,在满足仪表板横梁刚度的前提下将厚度截面的横梁管优化为连续变截面管。其次通过各支架部件的模态因子来定量分析各部件减重对仪表板横梁模态的影响,以明确支架零件的减重方向。最终仪表板横梁整体减少质量9.65%。

基于TRB结构的汽车前纵梁轻量化设计

以某汽车的前纵梁为例,参照我国C-NCAP中车辆正面碰撞测试要求,建立汽车前纵梁碰撞简化模型作为有限元仿真模型,并通过正交试验采样和多项式回归法构建响应面近似模型,将连续变截面板技术应用于前纵梁轻量化设计。结果表明:基于连续变截面板结构的汽车前纵梁相对于等厚板前纵梁具有更好的耐撞性,并且具有明显的减重效果,前纵梁质量减少了3.85kg,减重17.7%。

不同类型铝硅镀层热成型钢的耐蚀性研究

[目的]铝硅镀层热成型钢的镀层厚度对其防腐性能影响较大,有必要对汽车上使用的铝硅镀层热成型常规镀层板(镀层厚度20~33μm)、薄镀层板(镀层厚度6~14μm)及变厚度板的耐蚀性进行比较。[方法]采用中性盐雾(NSS)试验对热成型前后试样的耐蚀性进行考察。[结果]热成型前,常规镀层板在NSS试验1109 h时才出现红锈,薄镀层板在283 h后便出现红锈,变厚度板薄区618 h后出现红锈;热成型及电泳后,常规镀层板和薄厚度板的单边扩蚀宽度分别为0 mm和4.0 mm,变厚度板上基板厚度为2.3、2.0和1.8 mm的区域的单边扩蚀宽度分别为0.5、2.0和2.0 mm。[结论]热成型前,铝硅镀层板的耐蚀性与镀层的表面层隔离作用有关;热成型及电泳后,镀层的扩散层厚度对腐蚀的影响较大,变厚度板的防腐性能较薄镀层板好,但比常规镀层板差。

基于TRB技术的车身减量化设计与优化分析

连续变截面薄板(Tailor Rolled Blank,TRB)是新型的厚度连续变化的板材,它是实现轻量化的有效途径之一。基于TRB技术,结合车身碰撞力的传递路径及载荷流的合理分布的设计方法,以某款SUV车侧面碰撞中的主要关重件为例,对其结构进行优化设计。研究表明:应用新型TRB板材,在侧面碰撞过程中降低了整车的变形和胸部以及骨盆处侵入速度峰值,保证在耐撞性不减的前提下,整车质量减轻了5.5 kg,零件数量减少了5个。相应地也减少焊接工艺、生产工序,同时实现耐撞性和减量化的双重目标。

Study on Nonuniform Deformation of Tailor Rolled Blank During Uniaxial Tension

The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension was set up, and the deformation formulae for the thinner side and for the thicker side were derived to quantify the deformation of TRB. On this basis, uniaxial tension tests on TRB and ordinary blanks （the thinner side and the thicker side of TRB） were conducted. Lagrange polynomial interpolation method was adopted to construct the stress-strain fields of unannealed and annealed TRBs for solving TRB material parameters, and then, uniaxial tension simulation on TRB was completed. Deformations and properties of unannealed TRB were compared with those of annealed TRB, and the thinner side and the thicker side were also compared. Finally, the research results were explained by metallurgical structure. The results show that nonuniform deformation happens in TRB during uniaxial tension, and the necking occurs on the thinner side. The agreement of analysis, test and simulation confirms the correctness of the analytical model and the deformation formulae. The findings of this paper can lay the foundation for the future study on TRB stamping formability and provide a way for TRB modeling.

Forming Limit and Thickness Transition Zone Movement for Tailor Rolled Blank during Drawing Process

The process of automobile lightweight can be promoted by the application of tailor rolled blank（TRB）in the automobile industry.Therefore,research on the formability of TRB is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight.Aiming at the present condition of lack of researches on the influence of characteristic parameters on TRB drawing process,the drawing formability of TRB was studied with a combination method of simulation and experiment by taking square box as the research object.Firstly,drawing simulation and experiment of TRB were carried out.Then,effects of thickness transition zone（TTZ）position and blank size on the drawing formability of TRB were analyzed.Forming limit and TTZ movement for TRB square box during the drawing process were respectively discussed,when transition zones of TRB were located at different positions and blanks were of different sizes.The results indicate that lubrication condition exerts greater influence on TRB forming limit in comparison with TTZ movement,and the smaller blank size and TTZ being located at the blank center or slightly offset to the thinner side are preferable for acquiring greater forming limit and smaller TTZ movement.

Crack defect of tailor rolled blank in deep drawing process

The deformation process of tailor rolled blank (TRB)is different from that of a monolithic blank as a result of the variable thickness in the rolling direction,and thus,the mechanism of the crack phenomenon needs to be further studied.The crack defect of TRB square box was studied by numerical simulation and stamping experiment.The stress state of TRB square box was elaborated.On this basis,the forming characteristics of TRB square box were summarized.The effects of blank size and blank holder force (BHF)on the thickness thinning of TRB were discussed.Finally,the mechanism.of the crack defect for TRB square box was revealed.Results indicate that non-uniformity is the most prominent characteristic during forming of TRB square box.The larger the blank size and BHF on the thinner side are,the more inclined TRB is to crack. Excessive BHF or insufficient BHF on the thicker side can also lead to the occurrence of the crack defect.BHF on the thinner side slightly greater than that on the thicker side (40 kN on the thinner side and 20 kN on the thicker side)is advantageous to restrict the excessive thickness thinning of TRB and acquire a better formability.The location inclined to crack for TRB square box is the round comer of the wall on the thinner side.

Transverse Bending Characteristics in U-channel Forming of Tailor Rolled Blank

Research on the formability of tailor rolled blank （TRB） is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight. However, the forming of TRB is problematic because of the varying properties; especially, springback is a main challenge. The transverse bending （bending axis is perpendicular to the rolling direction） of TRB U channel was studied through simulation and experiment. The forming characteristics of TRB U channel during transverse bending were analyzed. The mechanisms of forming defects, including bending springback and thickness transition zone （TTZ） movement, were revealed. On this basis, effects of blank geometric parameters on springbaek and TTZ movement were discussed. The results indicate that springback and TTZ movement happen during transverse bending of TRB U-channel. Nonuni form stress distribution is the most fundamental reason for the occurrence of springback of TRB during transverse bending. Annealing can eliminate nonuniform stress distribution, and thus diminish springbaek of TRB, especially springback on the thinner side. Therefore, springback of the whole TRB becomes more uniform. However, annealing can increase the TTZ movement. Blank thickness and TTZ position are the main factors affecting the formability of TRB U-channel during transverse bending.

Numerical Simulation and Experimental Investigation of Springback in U-Channel Forming of Tailor Rolled Blank

In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation and stamping experiments.Fundamental theories of springback were analyzed.The stamping and springback processes of annealed 1.2 / 2.0mm TRB , 1.2mm and 2.0mm plates for U-channel were simulated , and the simulation results were compared with the experiments.The results indicate that the springback of TRB falls in between those of the 1.2mm and 2.0mm plates.It is desirable for the TRB U-channel to have die clearance of 1.1times maximum blank thickness and friction coefficient of about 0.12 , and longer thickness transition zone is preferable.The simulation data demonstrate reasonably good agreement with the experiments.