Analysis of melt flow in thick-walled heated element butt welded thermoplastic joints by FE simulation.

通过有限元模拟分析厚壁加热元件对接焊接热塑性接头的熔体流动。

• 批准号: 529312191
• 负责人: Professorin Dr.-Ing. Birgit Awiszus
• 金额: --
• 依托单位: Professur Kunststoffe
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/529312191?language=en
• 关键词: Analysis; melt; flow; thick; walled

Due to the further development of pipe winding technology and extrusion technology in pipeline construction, pipe dimensions of more than 3,000 mm diameter and wall thicknesses of more than 100 mm can be produced. The joining of semi-finished products of these wall thicknesses has led to a need to re-evaluate current strength theories. As investigations and cases of damage have shown, the effective relationships of thin-walled components cannot be transferred to thick-walled components by means of the law of similarity. The significantly longer flow channel of thick-walled components leads to higher rheological flow velocities and melt contact times. This, in conjunction with the long shear of the melt as a result of the joining process, possibly leads to the formation of a high state of order and thus to anisotropic material behavior in the edge regions. It is therefore conceivable that, in addition to the criterion of the minimum flow rate of the melts, there must also be a criterion of the maximum flow rate in conjunction with a maximum time-dependent shear or melt movement. The technical/scientific reason for the research application is the increased occurrence of weld fractures on weld seams in components with large wall thicknesses, in some cases with short-term loading in installation situations. The scientific necessity is based on the fact that the structurally relevant shear and strain flow velocities in the joining of large wall thicknesses encompass much larger scale ranges than have been investigated in scientific work to date. In conjunction with the more inhomogeneous cooling conditions, this leads to weld morphologies and residual stress states that were not previously understood. Preliminary investigations show that the melt in thick-walled components is in the plastic state for longer than previously assumed. Currently, this is not taken into account in German DVS 2207-1, English WIS 4-32-08 or American PPI-TR33. In the project, the gaps in the understanding of the process are to be closed by setting up numerical models for the heating behavior and the melt flow in the joining phase, as well as linking the influences to the short- and long-term strengths. This requires the experimental elaboration of the complex dependencies, e.g. on melt layer thickness and flow velocity. The simulation serves to improve the understanding of the process and to minimize the exp. effort. In the cooperation of the two applicants, this research idea has high prospects of success and makes a significant contribution to the in-depth understanding of the solidification and crystallization processes in thick-walled components and extends the understanding of the strength mechanisms. Furthermore, the simulative description of the thermal/rheological processes in the weld seam enables the optimal process design with regard to strength, service life and residual stress-free weld seam formation.

由于管道施工中管道缠绕技术和挤压技术的进一步发展，可以生产直径3000毫米以上、壁厚100毫米以上的管道尺寸。这些壁厚的半成品的连接导致需要重新评估当前的强度理论。调查和损坏案例表明，薄壁部件的有效关系不能通过相似定律转移到厚壁部件。厚壁部件的显着更长的流道导致更高的流变流速和熔体接触时间。这与连接过程导致的熔体的长剪切相结合，可能导致形成高有序状态，从而导致边缘区域的材料行为各向异性。因此可以想象，除了熔体的最小流速标准之外，还必须有最大流速连同最大时间相关剪切或熔体运动的标准。这项研究应用的技术/科学原因是，大壁厚部件的焊缝上焊接断裂的发生率增加，在某些情况下，在安装情况下会出现短期载荷。科学必要性基于以下事实：大壁厚连接中结构相关的剪切和应变流速所涵盖的尺度范围比迄今为止科学工作中研究的范围大得多。再加上更不均匀的冷却条件，这会导致以前无法理解的焊接形态和残余应力状态。初步研究表明，厚壁部件中的熔体处于塑性状态的时间比之前假设的要长。目前，德国 DVS 2207-1、英国 WIS 4-32-08 或美国 PPI-TR33 中未考虑这一点。在该项目中，通过建立连接阶段的加热行为和熔体流动的数值模型，以及将影响与短期和长期强度联系起来，来弥补对工艺理解的差距。这需要对复杂的依赖关系进行实验性的阐述，例如熔层厚度和流速的关系。模拟有助于提高对过程的理解并最大限度地减少exp。努力。在两位申请人的合作中，这一研究思路具有很高的成功前景，对深入理解厚壁构件的凝固和结晶过程以及扩展对强度机制的理解做出了重大贡献。此外，焊缝中热/流变过程的模拟描述可以实现强度、使用寿命和无残余应力焊缝形成方面的最佳工艺设计。