Criteria for the closure and pressure welding of pores in open die forging

开式模锻气孔封闭和压焊标准

• 批准号: 283878720
• 负责人: Professor Dr.-Ing. Gerhard Hirt
• 金额: --
• 依托单位: Institut für Bildsame Formgebung (IBF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/283878720?language=en
• 关键词: Criteria; closure; pressure; welding; pores

Ingots produced from ingot casting for open-die forging have pores and shrinkage cavities due to volume shrinkage during solidification, which can cause cracks to form in the later component under load and thus lead to critical failure. The aim of open-die forging is therefore to close these pores so that the pore surfaces come into contact and then weld them together to form a material bond. There are already a large number of criteria for describing pore closure, but for most criteria significant deviations in the prediction remain compared to numerical and experimental investigations. Welding and especially the possible re-opening of pores due to the prevailing forming conditions is not considered in any known criterion.Therefore, it was the aim of the first funding period to select a criterion which can describe the pore closure as a function of different pore geometries and orientations with respect to the load direction. The "Cicaporo" criterion fulfils these conditions for a constant load direction, so this was first selected and parameterised. Furthermore, it has been extended in such a way that it can describe pore closure even under changing load directions, as is usually the case in open die forging due to the rotation of the component. The criterion was implemented in the finite element (FE) simulation and validated experimentally by simulations with representative volume elements and forging tests. Furthermore, model experiments for the description of the bond formation were carried out, in which for different temperatures, deformations and surface conditions the derivation of a criterion for the description of the welding of pores after closing was made possible.Based on these findings, the aim of the second funding period is to minimise further inaccuracies in the prediction of the criterion developed in the first funding period. Therefore, the criterion has to be extended to take into account the influence of occurring shear during pore closure, since shear is generated in the material, among other things, at the die edges of each stroke. Furthermore, a criterion based on the model experiments of the first funding period has to be derived, which can assess the welding of the pores after closure. This can be a lower-bound statement, such as "safely or not safely welded" or a more complex description of the connection, e.g. by specifying a bond strength between the contacting pore surfaces. The criteria for pore closure and welding should then be implemented in combination in the FE simulation and validated experimentally. Once this has been done, the application possibilities are to be extended to other material classes typical for open-die forging.

用于开放式锻造的铸入式铸造产生的铸币是由于固化过程中的体积收缩而导致的毛孔和收缩腔，这可能会导致载荷下的裂纹在后期的组件中形成，从而导致严重失败。因此，开放锻炼的目的是关闭这些孔，以便接触孔表面，然后将它们焊接在一起形成材料键。与数值和实验研究相比，预测中的大多数标准已经存在大量的标准，但是对于大多数标准，该预测的显着偏差仍然存在。在任何已知标准中都不考虑焊接，尤其是由于主要形成条件而可能重新开放毛孔。因此，首个融资期的目的是选择一个可以将孔封闭的标准描述为不同孔隙几何的函数和与负载方向相关的方向的函数。 “ cicaporo”标准可满足这些条件的恒定载荷方向，因此首先选择并参数化。此外，它的扩展方式已被扩展，即使在变化的载荷方向下，它也可以描述孔闭合，就像由于组件的旋转而开放的死锻造情况，通常情况下也是如此。该标准是在有限元（FE）模拟中实现的，并通过具有代表性量元素和锻造测试的模拟对实验验证。此外，还进行了对键形成描述的模型实验，其中在不同的温度，变形和表面条件下，在关闭后的孔隙焊接中的描述是可能的。基于这些发现，这些发现是可能的。第二个资金的目的是在首次获得筹款活动中的第二个资金时期的目标，以最大程度地减少筹款活动。因此，必须扩展标准以考虑到孔闭合期间发生的剪切的影响，因为材料在每个中风的模具边缘中都会产生剪切。此外，必须得出基于第一个融资期的模型实验的标准，该标准必须得出，该标准可以在关闭后评估孔的焊接。这可能是一个较低的说明，例如“安全或不安全焊接”或对连接的更复杂描述，例如通过指定接触孔表面之间的键强度。然后，应在FE模拟中结合实现孔隙闭合和焊接的标准，并通过实验验证。完成此操作后，应用程序的可能性将扩展到开放式锻造的其他材料类。