Battery thermal management systems (BTMSs) ensure that lithium-ion batteries (LIBs) in electric vehicles (EVs) are operated in an optimal temperature range to achieve high performance and reduce risks. A conventional BTMS operates either as an active system that uses forced air, water or immersion cooling, or as a complete passive system without any temperature control. Passive systems function without any active energy supply and are therefore economically and environmentally advantageous. However, today’s passive BTMSs have limited cooling performance, which additionally cannot be controlled. To overcome this issue, an innovative BTMS approach based on heat pipes with an integrated thermal switch, developed by the Fraunhofer Cluster of Excellence Programmable Materials (CPM), is presented in this paper. The suggested BTMS consists of switchable heat pipes which couple a passive fin-based cold plate with the battery cells. In cold state, the battery is insulated. If the switching temperature is reached, the heat pipes start working and conduct the battery heat to the cold plate where it is dissipated. The environmental benefits of this novel BTMS approach were then analysed with a Life Cycle Assessment (LCA). Here, a comparison is made between the suggested passive and an active BTMS. For the passive system, significantly lower environmental impacts were observed in nearly all impact categories assessed. It was identified as a technically promising and environmentally friendly approach for battery cooling in EVs of the compact class. Furthermore, the results show that passive BTMS in general are superior from an environmental point of view, due their energy self-sufficient nature.

In this paper a novel approach to manipulate the force distribution in deep drawing tools using high load SMA actuators is presented. Nowadays, deep drawing is one of the most used processes for metal forming. It is used to form flat sheet metal efficient and precisely into complex, three-dimensional shapes and is widely used in many industries. However, on one hand ever-increasing demands on the process by increasingly complex geometries, smaller tolerances, and novel materials pushing the processes to the limits of their stability. On the other hand, the issue of the complex installation of a new or used tool becomes increasingly important. Here, the lack of automation makes this complex installation process labor-intensive and costly. Today, well-trained specialists with extensive experience are indispensable for the fine adjustment of the force distribution in deep drawing tools. However, growing scarcity of specialist, e. g. due to demographic change, not only increases the cost pressure, but also the risk of this technology. For these reasons, it is necessary to automate the fine adjustment of deep drawing tools, or more precisely, their force distribution. For this automation, an actuator-array which introduces different micro-deformations into the tool and changes the stiffness distribution is required. High load actuators based on thermal shape memory alloys (SMAs) are ideal for this task. Unlike competing technologies, they offer a small installation space, sufficient forces, low costs, and a simple control. SMA high load actuators can, not only, statically optimize the press force distribution during fine adjustment processes, minimizing costs and time, but also enable dynamically compensation for fluctuating process parameters from stroke to stroke, effectively preventing the production of reject parts. The approach presented in this paper is the integration of high load SMA actuators into the blank holder to create an adaptive pressure pad. In this study, an array of sixteen high load SMA actuators was integrated into the blank holder of a benchmark deep drawing tool to reduce the influence of process variations and speed up fine adjustment processes. The shape memory components (SMCs) of the actuators were additively manufactured from a Ni45.0Ti50.0Cu5.0 alloy using laser powder bed fusion (PBF-LB/M). The better degradation properties, smaller thermal hysteresis, and more stable phase transformation temperatures (PTTs) of these SMCs compared to conventionally manufactured SMCs are exploited for high-load SMA actuators. Each actuator is capable of exerting forces up to 5 kN and deformations up to 180 mu m. Within the scope of this study, the successful integration of high-load SMA actuators into a deep drawing tool for a sample application is achieved with minimal installation space, utilization of forces in the kN range, and without the need for additional supply media such as hydraulic aggregates or complex amplifier technology. Finally, a simple control system for the actuator array is presented.

A major limiting factor in the charging time of fast-charging electrical vehicles is the maximum electrical power that can be transmitted through the contact points between the charging plug and the vehicle inlet. The electrical contact resistance (ECR) thereby plays a decisive role. By increasing the contact surface between these contact points, it is possible to decrease the ECR, leading to higher transmission power and reduced charging times. Due to the limited construction space, high contact forces between the charging plug and the vehicle inlet are required to reduce the ECR. However, high contact forces complicate the insertion of the plug by hand. In consequence, lower contact forces and significant heating of the connection have to be accepted. For this reason, today’s systems (e.g., Combined Charging Systems (CCS)) include active cooling of the contacts. This paper presents an alternate system that temporarily increases the contact force of connectors during charging with shape memory alloy (SMA) actuators. To ensure industrial applicability, the research is conducted on the example of a CCS Type 2 charging plug. Initially, the correlations between extraction force, contact normal force and resulting ECR are investigated experimentally. Subsequently, basic mechanisms for increasing the contact normal force with SMA wires are presented and experimentally validated. As a result, a reduction in ECR of up to 60% has been experimentally demonstrated.

This paper advances the knowledge of the cyclic thermomechanical behavior and fatigue of high load SMA-Actuators. Due to their small volume and weight, these actuators provide an attractive alternative to conventional actuators. Especially in production plants and machines, where the requirements for installation space and weight are becoming increasingly crucial for a successful manufacturing process, they find a wide field of application. Quite in contrast to small force applications, more massive geometries and new integration concepts of the shape-memory-components (SMC) are substantial. However, well developed semi-finished products are not yet available. Furthermore, this changes mechanical and functional cycle fatigue, an issue well known from wire based small force SMA-Actuators. Comprehending how these changes significantly alter the SMA behavior will eventually enable novel designing and optimizing. Therefore, the cyclic behavior of the SMC is investigated, using a high load SMA-Actuator, that has been designed for integration in machines tools. The SMCs, cycled in the SMA-Actuator have been manufactured with different methods. Here, a classical manufacturing process is compared to an additive process (PBF-LB/M). The additive processed SMCs show microcracks and pores. Nevertheless, the cyclic properties exceed those of the classical processed specimen in all measured properties. Especially the tiny hysteresis, low shortening of the SMC can be highlighted.

The lack of suitable connectors for thin‐walled carbon concrete elements with their known resource and material saving properties still represents a major obstacle for practical application. On top, the on‐site installation remains a labor‐intensive task. To overcome this limitation, we report the development of an active assembly connector that enables simple and safe installation of carbon concrete façade elements and increases assembly efficiency. Moreover, the active assembly features permit an assembly without physical access to the connector, called blind assembly. Its concept is based on the recovery expansion of iron‐based shape memory alloys (Fe‐SMA). This paper presents material characteristics such as recovery stress and strain of the Fe‐SMA in compression. The connector concept uses an anchor rail that blocks the recovery extraction of a Fe‐SMA‐fastener to produce a stable, frictional and linear connection. Tensile tests show the impact of design parameters and high pull‐out forces with sufficient design. Also, ongoing long term tensile tests show small creep, so far. The anchor channels integrate well with carbon concrete façade panels. The heating concept with heating cartridges works well, even under cold winter conditions. Wind test results exceed requirements. Finally, a field test shows excellent installation results and proves the ease of assembly as well as the ability for blind assembly.

BautechnikVolume 99, Issue 1 JahresinhaltsverzeichnisFree Access Jahresinhaltsverzeichnis Bautechnik 2021 First published: 07 January 2022 https://doi.org/10.1002/bate.202270106AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume99, Issue1January 2022 RelatedInformation

Thermal switches contribute to efficient and safe thermal management of components and overall systems in various technical applications by actively controlling heat transfer in response to varying thermal loads and ambient conditions. Heat pipes are passive heat transfer devices constituting an integral part of various thermal management systems such as in spacecraft or consumer electronics thermal control. Heat pipes also form a promising approach for thermal switches due to their high effective thermal conductivity. In this paper, a wickless copper-water heat pipe based thermal switch with an electromagnetic linear actuator is presented. The magnetically actuated motion of a plunger integrated into the heat pipe affects the latent heat transport cycle leading to a switchable heat transfer. Thermal measurements conducted to determine the total thermal resistance of the heat pipe demonstrate the efficacy of the thermal switch. It was found that the thermal resistance of the heat pipe was increased by up to 53% in off state while the heat pipe performance in on state was not significantly affected by the integrated mechanism.

Die Umsetzung einer modularen, vorgefertigten Bauweise sowie der weitreichende Einsatz von Leichtbauelementen aus Carbon‐ oder Textilbeton verlangen neue Verbindungselemente. Bauteile aus Carbonbeton werden wesentlich schlanker als vergleichbare Stahlbetonelemente ausgeführt. Neben den geometrischen Bedingungen für die Verbindung stellt insbesondere die Kraftübertragung in entsprechend dünnen Elementen eine Herausforderung für Planer und Bauausführung dar. Eine nachhaltige, modulare Bauweise benötigt darüber hinaus Verbindungselemente, die eine einfache und sichere Montage einzelner Elemente ermöglichen und die Ästhetik des Bauwerks nicht beeinflussen. In diesem Aufsatz werden für genau diesen Anwendungsfall innovative Verbindungselemente vorgestellt, die auf Basis von Formgedächtnislegierungen (FGL) funktionieren. Die neuen Verbindungskonzepte streben eine deutliche Vereinfachung der Montage auf der Baustelle an. Durch den Einsatz von Memory‐Stahl als aktives Verbindungselement kann auf eine mechanische Zugänglichkeit zur Verbindung verzichtet werden. In diesem Beitrag werden das primäre Anwendungsfeld der FGL‐Verbinder sowie die ersten Konzepte und Entwicklungen aufgezeigt.

The implementation of a modular, prefabricated construction method as well as the extensive use of lightweight elements made of carbon or textile reinforced concrete requires new types of connection elements. Component parts made of carbon reinforced concrete can be made much slimmer than comparable reinforced concrete elements. In addition to the geometric conditions for the connection of such thin-walled carbon reinforced concrete components, the force transmission in such thin elements creates great challenges for the planner and the executing staff. In connection with the simplest possible assembly on the construction site, these seem to be insurmountable hurdles. As part of a research project, new and innovative connections that work on the basis of shape memory alloys (SMA) were developed for this specific application. The newly developed connection concepts aim to significantly simplify assembly on the construction site. By using memory steel as an active connection element, mechanical accessibility for connection can be dispensed with. In this article the primary field of application of the SMA connectors as well as the first concepts and developments are shown.

After reporting on the ability of micro-EDM to significantly alter the transformation behaviour of Nitinol whereby increasing discharge energy reduces thermal hysteresis and results in a three-peak reverse phase transformation on heating, this study helps to further characterize the Nitinol micro-EDM process. This is by closely varying discharge energy so as to establish the boundary conditions for the three peak transformation behaviour as well as establish the influence of arcing on the mechanical properties of Nitinol. Samples machined using micro-EDM and jet-ECM are analysed using differential scanning calorimetry as well as tensile testing with five loading and unloading cycles after which the samples are loaded fill failure. Moreover, discharge pulses are used to analyse arcing. From the results, it is not only possible to conclusively identify and establish arcing as the main phenomenon behind the three peak transformation behaviour, but also that the thermal damage caused by arcing results in a high residual strain, reduced elongation to failure, loss of machining accuracy and a reduction in upper and lower plateau stresses. It is also evident that if the discharge energy is carefully controlled to avoid arcing, it can be increased over a significant range (from approximate to 3.4 mu J to approximate to 130.2 mu J in this study) without significantly altering the phase transformation behaviour of Nitinol, which is very closely linked with its shape memory and superelasticity.