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Interface dynamics in bolted joint connections

螺栓连接中的界面动力学

基本信息

批准号：
282970347
负责人：
Professor Dr. Norbert Hoffmann
金额：
--
依托单位：
Institut für Laser- und Anlagensystemtechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/282970347?language=en
关键词：
Interface dynamics bolted joint connections

项目摘要

Bolted joints are the most used and most important joints in mechanical engineering and steel construction. But engineers still have to deal with failures during the tightening process and in operation. During the tightening process, failures often manifest themselves in the form of or are related to stick-slip phenomena. During operation, bolted joints may turn loose when they are subjected to dynamic loads in form of shock, vibration, or cyclic thermal loadings. In both cases, failures are initiated by microslip motion and hence by a transition from sticking to sliding. Recent findings, especially from physics and the geosciences, have shown that wave processes and fracture-like dynamics may play a decisive role in the transitions between sticking and sliding of the contact partners. Against this background, static friction can be no longer considered as a pure material constant. In fact, first modeling approaches treat static friction as a dynamical process. Especially the beginning (microslip) of the sticking to sliding transition of the interface as well as the whole process (complete failure) is determined by the stress distribution in the interface. In this project, these findings should be transferred to the dimensioning, the tightening, and the operational behavior of bolted joint connections. By the development of appropriate models, taking the friction dynamics in the interface into account, we will gain knowledge on the mechanics of microslip and complete failure of bolted joint connections. For the validation of these models, four experimental parts are included in the program. In the first part, we will study asymmetries affecting the stress distribution in the interface and thus the static friction coefficient on a disc-on-disc setup. In the second part, we will investigate how the shape of the bolt head is affecting the stress distribution in the interface and thus stick-slip motion during the tightening process of bolted joints. In the third part, we will combine the most promising principles from the first two parts by designing new types of stick-slip reducing bolts. In the fourth and last part, we will study the effect of vibrations on the self-loosening of bolted joints during operation. As a consequence of the theoretical and experimental work, we will derive a first set of guidelines for designing bolted joints which are robust to stick-slip during tightening and will not suffer from failure in operation due to vibrational motion.

螺栓连接是机械工程和钢结构中使用最多、最重要的连接形式。但工程师们仍然必须处理紧固过程和操作中的故障。在紧固过程中，故障往往表现为粘滑现象或与粘滑现象有关。在运行过程中，当螺栓接头受到冲击、振动或循环热载荷形式的动态载荷时，螺栓接头可能会松动。在这两种情况下，故障启动的微滑运动，因此从粘附到滑动的过渡。最近的研究结果，特别是物理学和地球科学的研究结果表明，波动过程和类似岩石的动力学可能在接触伙伴的粘附和滑动之间的过渡中起决定性作用。在这种背景下，静摩擦力不再被认为是一个纯粹的材料常数。事实上，第一建模方法将静摩擦视为动态过程。特别是界面粘结-滑动转变的开始（微滑移）以及整个过程（完全破坏）取决于界面应力分布。在本项目中，这些发现应转移到螺栓接头连接的尺寸确定、拧紧和操作行为中。通过发展适当的模型，考虑到界面的摩擦动力学，我们将获得关于螺栓连接的微滑移和完全失效的力学知识。为了验证这些模型，在程序中包括四个实验部分。在第一部分中，我们将研究非对称性对界面应力分布的影响，从而影响盘对盘装置上的静摩擦系数。在第二部分中，我们将研究螺栓头的形状如何影响界面中的应力分布，从而影响螺栓连接拧紧过程中的粘滑运动。在第三部分中，我们将联合收割机的最有前途的原则，从前两个部分，通过设计新型的粘滑减少螺栓。在第四部分，也是最后一部分，我们将研究振动对螺栓连接在运行过程中的自松的影响。作为理论和实验工作的结果，我们将推导出第一套设计螺栓连接的准则，这些螺栓连接在拧紧过程中对粘滑是鲁棒的，并且不会由于振动运动而在操作中发生故障。