Method Article
The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.
The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.
Finite Element (FE) simulations have become a powerful tool for optimizing process parameters in the metal forming industry. The reliability of FE simulation results is dependent on the accuracy of the material definition, input in the form of flow stress data or constitutive equations, and the assignment of the boundary conditions, such as the friction coefficient and the heat transfer coefficient. In the past few years, advanced FE simulations have been developed via the implementation of user-defined subroutines, which have significantly broadened the capability of FE software.
The use of such advanced FE simulations in the design of forming processes for structural components has been investigated by both the aviation and automotive industries, with the intention of producing lightweight structures that reduces operating costs and CO2 emissions. Particular focus has been placed on the replacement of steel components with lower density materials, such as aluminum alloys and magnesium alloys. However, these alloys, especially the stronger variants, offer limited formability at room temperature and thus complex-shaped components cannot be manufactured using the conventional cold stamping process. Therefore, advanced high temperature forming technologies, such as warm aluminum forming 1-4, hot stamping of aluminum alloys 5-9 and hot stamping of high strength steels 10, have been developed over the past decades to enable complex-shaped components to be formed. In general, high temperature forming processes involve significant temperature variations, strain rate and loading path changes 11, which would, for instance, cause inevitable viscoplastic and loading history dependent responses from the work piece materials. These are intrinsic features of high temperature forming processes and may be difficult to represent using conventional FE simulation techniques. Another desirable feature would be the ability to predict the tool life over multiple forming cycles in such processes, since they require low friction characteristics achieved through coatings that degrade with each forming operation. To represent all these features via the implementation of user-defined subroutines would be computationally very expensive. Moreover, the development and implementation of multiple subroutines would require excessive multi-disciplinary knowledge from an engineer conducting the simulations.
In the present work, a novel Knowledge Based Cloud FE (KBC-FE) simulation technique is proposed, based on the application of modules on a cloud computing environment, that enables an efficient and effective method of modeling advanced forming features in conjunction with conventional FE simulations. In this technique, data from the FE software is processed at each cloud module, and then imported back into the FE software in the relevant consistent format, for further processing and analysis. The development of these modules and their implementation in the KBC-FE is detailed.
1.高温成形极限预测模型的建立
2.交互式摩擦/磨损模型的建立
3. KBC-FE模拟案例
KBC-FE仿真缩口预测
在烫印过程中,使用的形状优化的空白,不仅节约材料成本,还有助于减少缺陷,如缩,龟裂,起皱和存在。初始坯料形状在成形过程中影响了材料流动显著,因此,坯件的形状的一个合理的设计是在热冲压工艺的成功和质量的最终产品的关键。为了减少试错误实验努力确定最佳坯料几何形状,KBC-FE模拟被证明是用于与缩颈最小化区域高效且有效的方法。使用这种技术,各模拟约需2小时,而对于缩颈预测并行云模块计算是在4小时内完成。
图4示出了在热冲压,汽车车门内组件的一个例子中使用的毛坯形状的演变。最初的坯料形状,从传统的冷冲压工艺采用,在KBC-FE模拟首次使用。在图4中的实验结果(一)表明,在大故障(破裂或缩颈)地区烫印后可见。坯料形状优化的一个迭代,它在图4中可以看出(b)之后,一个几乎完全成功的面板用少得多的缩颈形成相比,使用初始毛坯形状。可以看出,仍然存在着在右上方的口袋和面板的左边拐角缩颈的指示。在图4(c)还优化后,与面板上没有可见的缩颈最终得到优化的毛坯形状。由KBC-FE模拟确定的优化坯料形状是通过热冲压实验验证试验由生产系统制造商提供了一个全自动化的生产线进行。
KBC-FE仿真刀具寿命预测
金属成形过程的常规有限元模拟为单个周期进行。但是,在生产环境中,多个成形周期在给定的工具,它被发现,增加成形的循环次数导致形成部件之间的增加的变化进行的。多周期工具装载期间的这种变化是改变的表面形貌的结果。例如,形成具有功能性涂层的工具的多周期加载会导致因磨损的涂层厚度减少。此外,该涂层的击穿也将通过形成参数,如负载/压力,成形速度等 。KBC-FE技术使得影响仿真金属板材成形多循环载荷条件下的过程,这对于形成具有先进功能涂料工具的在职寿命预测至关重要。
以调查对工具寿命毛坯压持力,5,20,和50千牛毛坯压持力值的影响进行了检查为250毫米/秒的恒定形成速度。 图5示出了具有不同的压边力300形成循环后的剩余的刀具涂层厚度分布。它清楚地表明,剩余的涂层厚度的增加的坯料夹持力降低。
图6示出300形成循环后具有5,20和50千牛顿,分别的坯料夹持力的压力和剩余的涂层厚度分布,沿管芯的曲线的距离。由于区域AB表示冲模耳鼻喉科在U形弯曲加工朗斯区域,压力和在该区域的相对磨损距离比管芯的其他区域的高得多。因此,涂层的磨损主要发生在这个区域。有在20千牛和涂层厚度减少的两个峰值50千牛对应于压力下的两个峰。同时,剩余的涂层厚度与坯料夹持力的增加而降低。为5,20和50千牛顿压边力最低剩余涂层的厚度,分别为0.905,0.570,和0.403微米,分别,其中的初始涂层厚度为2.1微米。
图1: 在不同温度下的实验,并预测成形极限应变的比较。成形极限菌株随着温度升高,在250毫米的恒定速度/秒,或等同地,6.26 -1的应变速率。 请点击此处查看该图的放大版本。
图 2: 一个金属板材成形工艺的基础知识云的有限元模拟原理图。商用有限元模拟软件,是用来运行模拟和导出各个模块所要求的结果。这些模块, 例如 ,成形性,热传导,形成后强度(微观),刀具寿命预测,模具设计等 ,在云中同时独立工作,从而使前沿知识从多个来源成有限元模拟的融合。 请CLICK这里查看该图的放大版本。
图3: 工件和工具的U形弯曲模拟的几何。该工具, 即冲,压边和模具,使用刚性单元模拟。壳单元被用于对工件(空白)的元件。 请点击此处查看该图的放大版本。
图 4: 门内板(在有限元模拟显示)的烫金坯料形状的演变。剩下: 绿色帧中的数字代表每个优化阶段空白的形状,并以红色的那些帧对应于它的优化前的毛坯形状。右:在每一个优化缩颈的预测结果。 (a)用大故障的初步结果(裂化/缩颈所示红色),(B)减少未与优化的第一级,(c)与不可见的颈缩最终优化毛坯形状后一些缩颈。 请点击此处查看该图的放大版本。
图5:剩余涂层厚度分布(在有限元模拟显示)与压边力:(1)5千牛顿,(B)20千牛,和(c)50千牛,在250一个恒定的冲压速度300形成循环后毫米/秒。 请点击此处查看该图的放大版本。
图6:接触压力的预测和剩余涂层厚度与压边力:(1)5千牛,(B)20千牛,以及(c)50千牛,沿着模具的曲线距离在250恒定的烫印速度毫米/秒。 请点击此处查看该图的放大版本。
该KBC-FE模拟技术实现先进的模拟,以使用专用的模块进行场外。它可以运行于云环境的功能模块,即从不同的特化连接起来的节点,以确保过程仿真尽可能准确地进行。在KBC-FE模拟关键方面可能涉及有限码的独立性,计算的效率和功能模块的准确度。每个高级功能的一个模块中实现将依赖于一个新的模型和/或一个新的实验技术的发展。例如,成形极限模块是基于新的统一的成形极限预测模型11开发的,摩擦刀具寿命预测模块目前已经被互动式摩擦模型20实施开发。该KBC-FE模拟技术也提供了选择性的计算履行选择功能, 也就是说 ,只有元素标准选择用于各个模块进一步的评估。例如,工具寿命预测模块自动选择其中硬涂层倾向于破裂,由排名第1的所有元素的磨损率成形周期的元素,该元素的因而通常小于1%将被选择用于进一步多周期载荷条件下的刀具寿命评估。在本研究中,300形成循环后的工具寿命预测可在5分钟内完成。
通过进行相关试验,并相应地校准,成形极限模型可以适用于形成处理模拟,以从而确定用于成功地产生由这种合金的组分的最佳参数,并且没有缩颈的发生率。成形极限预测模型被开发为,这是独立的有限元软件的被利用云模块,并且可以被应用到任何有限元软件评估过程中的材料的成形性成形,无需复杂的子程序17。通过导入相关数据到模型,计算可以被进行,以确定故障是否发生,在该用户可以指定该组件的区域,从而节省了计算资源。然而,应该指出的是,作为应力 - 应变曲线是输入到通过简单的查表的有限元软件,可能难以在模拟过程中,以充分代表在不同温度和应变率的材料特性。
在刀具寿命预测模块,成型过程中的摩擦行为可以通过导入所需的变形历史数据到验证摩擦模块20,然后再导入为每个元素放回有限元软件的云模块计算出的离散数据点进行预测。这保证了高级摩擦模块可以被所有的FE码被使用,无论其掺入用户子程序能力。此外,国防部ULE可以并行运行,以进一步减少计算时间。交互式摩擦/磨损模型假定没有磨损颗粒的过程中的初始滑动,并作为一个结果,这将是合理的预期摩擦系数0.17 20的恒定初始值。尽管该模型揭示摩擦分布的演变,在成形过程中的摩擦行为是非常复杂的,并且难以从云模块的复合摩擦行为完全融入有限元模拟。
作为未来的技术,KBC-FE模拟将依靠专用基础和强大的互联网有限元模拟软件包开发,这需要一个高利润,但完全不同的商业模式,由软件开发商建立。此外,专用的内部网络需要在合作各方内部建立确保数据安全和工业系统的控制可靠性。
The authors have nothing to disclose.
The financial support from Innovate UK, Ultra-light Car Bodies (UlCab, reference 101568) and Make it lighter, with less (LightBlank, reference 131818) are gratefully acknowledged. The research leading to these results has received funding from the European Union's Seventh Framework Program (FP7/2007-2013) under grant agreement No. 604240, project title 'An industrial system enabling the use of a patented, lab-proven materials processing technology for Low Cost forming of Lightweight structures for transportation industries (LoCoLite)'. Significant support was also received from the AVIC Centre for Structural Design and Manufacture at Imperial College London, which is funded by Aviation Industry Corporation of China (AVIC).
Name | Company | Catalog Number | Comments |
AA6082-T6 | AMAG | Material | |
AA5754-H111 | AMAG | Material | |
1,000 kN high-speed press | ESH | Forming press | |
ARGUS | GOM | Optical forming analysis | |
PAM-STAMP 2015 | ESI | FE simulation software | |
Matlab | MathWorks | Numerical calculation software | |
Gleeble 3800 | DSI | Uniaxial tensile test | |
High Temperature Tribometer (THT) | Anton Paar | Friction property test | |
NewViewTM 7100 | ZYGO | Surface profilometer | |
Magnetron sputtering equipment | Coating deposition | ||
Microhardness tester | Wolpert Wilson Instruments | ||
Nano-hardness indenter | MTS |
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