For the control of dynamic systems such as an Electro-Hydraulic Actuator (EHA), there is a need to optimize the control based on simulations, since a prototype or a physical system is usually not available during system design. In consequence, no system identification can be performed. Therefore, it is unclear how well a simulation model of an EHA can be used for multicriteria optimization of the position control due to the uncertain model quality. To evaluate the suitability for control optimization, the EHA is modeled and parameterized as a grey-box model using existing parameters independent of test bench experiments. A method for multi-objective optimization of a controller is used to optimize the position control of the EHA. Finally, the step responses are compared with the test bench. The evaluation of the step responses for different loads and control parameters shows similar behavior between the simulation model and the physical system on the test bench, although the essential phenomena could not be reproduced. This means that the model quality achieved by modeling is suitable as an indication for the optimization of the control by simulation without a physical system.

Testing and reliability assessment are crucial aspects when considering the thermal domain’s influence on the overall system. Thermal interactions occur between all subsystems, and their separation can disrupt internal thermal interactions, altering temperature profiles. Evaluating functional system reliability requires accounting for the thermal domain’s impact on temperature-dependent performance and thermal damage limits. However, testing faces challenges due to the lack of a suitable thermal coupling system capable of transferring thermal interactions by heat conduction between spatially separated subsystems. To address this issue, this paper introduces a thermal coupling system that focuses on the control system and its validation through experimental studies. Two scenarios were investigated: (I) the original assembly situation with direct heat transfer between two subsystems, and (II) a spatially separated scenario utilizing the thermal coupling system to establish heat transfer between the subsystems. The evaluation variables are the temperature curves and the deviations between the two scenarios. Two different tests with a different amount of heat flows are carried out. The thermal coupling system utilizes thermal actuators, specifically Peltier devices, to ensure a zero temperature difference between the original contact points. The control system employs both closed-loop and open-loop control to regulate the heat flow and achieve energy conservation between the spatially separated subsystems. The results demonstrate that the described thermal coupling system yields only slight deviations in temperature curves, indicating its applicability for early evaluation of functional system reliability. This research contributes to a better understanding of thermal interactions in complex systems and provides a valuable tool for enhancing overall system reliability through thermal testing and validation.

Impact tightening is widely used in industrial assembly of bolted joints. Friction plays a decisive role in the impact tightening process of bolted joints, yet the dynamic frictional behavior during this process remains insufficiently understood. While previous studies have focused on single bolt sizes, this work expands the experimental investigation to M10, M16, and M20 bolted joints, revealing scale-dependent frictional mechanisms. The influences of bolt diameter, impact wrench power, socket length and preload level on the distribution of coefficients of thread and bearing friction are analyzed. Results show that both bolt diameter and impact wrench power significantly influence the dynamic coefficients of friction, with smaller bolted joints exhibiting higher coefficients and greater scatter. These transitions indicate changes in real contact conditions and stick–slip behavior under impulsive torque input. These insights advance the understanding of frictional dynamics in impact tightening and provide quantitative input for improving predictive models of impact tightening and preload estimation, supporting the development of more reliable industrial assembly processes.

Zusammenfassung: Tangential-schlagende Anziehprozesse erlauben eine schnelle und einhändige Montage von Schraubenverbindungen bei großen Drehmomenten. Ein zentrales Problem ist jedoch die große Streuung der Vorspannkraft, die auf den hohen Einfluss der Reibung zurückzuführen ist. Die Reibung ist dabei von verschiedenen Faktoren abhängig, sodass eine Betrachtung der Effekte auf mehreren Skalen notwendig ist. In diesem Beitrag wird daher eine skalenübergreifende Methode zur Simulation von tangential-schlagend angezogenen Schraubenverbindungen vorgestellt. Ein besonderer Fokus liegt auf der numerischen Bestimmung von Kontaktdrücken und Reibungszahlen, welche Eingangsgrößen für eine Mehrkörpersimulation darstellen. Die unter dem Schraubenkopf und am Gewinde herrschenden Kontaktdrücke werden in Abhängigkeit der aktuellen Vorspannkraft und des Radius mithilfe eines FE-Modells auf Makroebene bestimmt. Mithilfe von Weißlichtinterferometrie werden Oberflächentopografien gemessen und für die Anwendung in einer Reibsimulation digitalisiert. Aus einem FE-Modell auf der Mikroebene werden Reibungszahlkennfelder in Abhängigkeit des Anpressdrucks, der Gleitgeschwindigkeit und der Oberflächentopografie bestimmt. Ein höherer Kontaktdruck führt dabei zu einer geringeren Reibungszahl. Für die Gleitgeschwindigkeit kann der Zusammenhang nicht quantifiziert werden. Die abgeleiteten Kennfelder können durch die dargestellten Methoden effizient durch weitere Stützstellen erweitert werden und ermöglichen die Berücksichtigung von sich während des Anziehprozesses variierenden Kontaktdrücken sowie Reibungszahlen in der Mehrkörpersimulation.