In the present paper, finite element simulations are used to gain a better understanding of the setting process of a blind rivet nut. A blind rivet nut is a mechanical fastener capable of clinching materials whilst providing a threaded solution without the need for thread forming. The technique relies on plastic deformation introduced by axial compression of the rivet nut in such a way that a counter head is formed on the opposite side of the work piece. For certain applications, stresses in the plate material induced by the setting process are detrimental for the fastener’s integrity. Hence an improved design of the fastener is desired. To embark on such a redesign, an appropriate numerical model to reveal the influence of several parameters is indispensable. In this work, a strategy is presented to simulate the setting process involving large plastic strains and contact pressures. An FE based inverse method was used to identify the local plastic material properties of the blind rivet nut. The forming simulation was validated in terms of predicted shape of the rivet nut and the evolution of the setting force. A quasi-static FE model using the shape and solution variables of the deformed rivet nut was used to reproduce the torque-to-turn resistance as a function of the setting force. The strategy was successfully applied on two blind rivet nuts, different in geometry and base material. Finally, three industrial case studies confirmed the viability of the model.

中文翻译：

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盲铆螺母扭矩转数值的数值预测

在本文中，使用有限元模拟来更好地了解铆钉螺母的安装过程。铆钉螺母是一种机械紧固件，能够铆接材料，同时提供螺纹解决方案，而无需进行螺纹成型。该技术依赖于通过铆钉螺母的轴向压缩而引入的塑性变形，使得在工件的相对侧上形成对端头。对于某些应用，由凝固过程引起的板材中的应力对于紧固件的完整性是有害的。因此，需要紧固件的改进设计。为了进行这样的重新设计，必须要有一个合适的数值模型来揭示几个参数的影响。在这项工作中 提出了一种策略来模拟涉及大塑性应变和接触压力的凝固过程。基于有限元的反演方法用于识别铆钉螺母的局部塑性材料特性。根据铆钉螺母的预测形状和坐封力的变化验证了成形模拟。使用变形铆钉螺母的形状和固溶变量的准静态有限元模型，用于重现转弯阻力与设定力的关系。该策略已成功应用于两个几何形状和基础材料不同的盲铆螺母。最后，三个工业案例研究证实了该模型的可行性。根据铆钉螺母的预测形状和坐封力的变化验证了成形模拟。使用变形铆钉螺母的形状和固溶变量的准静态有限元模型，用于重现转弯阻力与设定力的关系。该策略已成功应用于两个几何形状和基础材料不同的盲铆螺母。最后，三个工业案例研究证实了该模型的可行性。根据铆钉螺母的预测形状和坐封力的变化验证了成形模拟。使用变形铆钉螺母的形状和固溶变量的准静态有限元模型，用于重现转弯阻力与设定力的关系。该策略已成功应用于两个几何形状和基础材料不同的盲铆螺母。最后，三个工业案例研究证实了该模型的可行性。几何形状和基础材料不同。最后，三个工业案例研究证实了该模型的可行性。几何形状和基础材料不同。最后，三个工业案例研究证实了该模型的可行性。