PCM-Based Energy Storage System with High Power Output Using Open Porous Aluminum Foams

Thermal comfort (heating, ventilation and air conditioning, HVAC) and the energy consumption involved with it can put a strain on the driving range of fully electric vehicles (FEV), especially in certain times of the year as midsummer or winter. In order to reduce the energy consumption of HVAC, improved thermal management and adapted means of energy storage are needed. One part of the solution can be the use of phase change materials (PCM) for storing waste heat. For the specific application, however, a high loading/unloading power rate is required, which is challenging as the PCMs exhibit low heat conductivities. In the presented work, a storage demonstrator system was investigated which is part of an HVAC system of a specific fully electric vehicle. The profile of requirements of the system (power, stored capacity and allowed volume) make a new design of the storage necessary. Two demonstrator units, in which the PCM was combined with aluminum foam, were manufactured and their power output in dependency on the fluid flow of the coolant system was compared. An adapted squeeze casting process with polymer placeholders was used for the production of the aluminium foam. This process results in foams with a specific pore structure and allows the in-situ integration of the heat transfer fluid (HTF) pipes. Both newly developed PCM storage systems satisfy the HVAC system requirements

Under water glued stud bonding fasteners for offshore structures

International audienceThe installation of offshore wind turbines has achieved rapid and substantial progress worldwide and further increase is predicted by enhanced technologies that will reduce costs and increase service time. Secondary structures applied to the primary structure, as the transition piece of a monopole, can be e.g. cable support, boat landing or anode systems. These structures are often welded, which leads to problematic notch effects and hydrogen embrittlement, especially for underwater applications. Also the handling of technical equipment as power current or artificial housings for scuba divers for underwater welding is challenging. Adhesive bonding will lead to cost reduction as the mentioned negative aspects can be avoided. The corrosion protection coating and the primary structure will no longer be damaged and therefore do not need a subsequent coating. This article focuses on the area which is permanently exposed to water. A critical point is how the capability to form adhesion and cohesion, will be influenced by the application process under water. Therefore, stud bonding fasteners are designed that enable the injection of adhesive to the bonding area under water. The load capacities for different adhesives, surface pre-treatments and the degradation by exposure to artificial sea water were investigated. Adhesion was achieved with two different adhesives, which were able to cure and realize reasonable strength under water. Furthermore, two selected coating systems were able to improve the performance of the adhesive bond

Low Cycle Fatigue Behaviour of DP Steels: Micromechanical Modelling vs. Validation

This study aims to simulate the stabilised stress-strain hysteresis loop of dual phase (DP) steel using micromechanical modelling. For this purpose, the investigation was conducted both experimentally and numerically. In the experimental part, the microstructure characterisation, monotonic tensile tests and low cycle fatigue tests were performed. In the numerical part, the representative volume element (RVE) was employed to study the effect of the DP steel microstructure of the low cycle fatigue behavior of DP steel. A dislocation-density based model was utilised to identify the tensile behavior of ferrite and martensite. Then, by establishing a correlation between the monotonic and cyclic behavior of ferrite and martensite phases, the cyclic deformation properties of single phases were estimated. Accordingly, Chaboche kinematic hardening parameters were identified from the predicted cyclic curve of individual phases in DP steel. Finally, the predicted hysteresis loop from low cycle fatigue modelling was in very good agreement with the experimental one. The stabilised hysteresis loop of DP steel can be successfully predicted using the developed approach

Low cycle fatigue behaviour of DP steels

This study aims to simulate the stabilised stress-strain hysteresis loop of dual phase (DP) steel using micromechanical modelling. For this purpose, the investigation was conducted both experimentally and numerically. In the experimental part, the microstructure characterisation, monotonic tensile tests and low cycle fatigue tests were performed. In the numerical part, the representative volume element (RVE) was employed to study the effect of the DP steel microstructure of the low cycle fatigue behavior of DP steel. A dislocation-density based model was utilised to identify the tensile behavior of ferrite and martensite. Then, by establishing a correlation between the monotonic and cyclic behavior of ferrite and martensite phases, the cyclic deformation properties of single phases were estimated. Accordingly, Chaboche kinematic hardening parameters were identified from the predicted cyclic curve of individual phases in DP steel. Finally, the predicted hysteresis loop from low cycle fatigue modelling was in very good agreement with the experimental one. The stabilised hysteresis loop of DP steel can be successfully predicted using the developed approach

In Laubholz eingeklebte Stäbe - experimentelle und numerische Bewertung der Tragfähigkeit

Glued‐in Rods (GiR) represent an adhesively bonded structural connection widely used in timber engineering. This article presents an overview over extensive research carried with nine adhesives, three EWP and four types of rods. Investigations started at component level, by fully characterizing all adhesives, EWP, and rods. Investigations at full scale followed, involving five different adhesives, three EWP and four rod types. A total of 180 individual samples were tested. The results allowed to draw conclusions about the relationship between performance of GiR connections, and mechanical properties of their components. In addition to the experimental part, the modelling and strength prediction of Glued‐in Rods was developed and validated. Combining the material characterization with FEA, and reformulating strength in probabilistic terms, then allowed to perform predictions of joint capacities for all 60 experimentally investigated GiR‐configurations. The comparison between predicted and experimental values showed a good agreement with relative difference amounting to –1 ± 9 % (averaged over all GiR‐configurations). Results clearly showed that transverse tensile strength of the wood is at least as important as shear strength for joint capacity of GiR, and that longitudinal strength plays a minor role

TACITUS - Bewertung und Modellierung der Leistungsfähigkeit von Verbindungselementen aus Laubhölzern mit eingeklebten Stäben aus Stahl und Verbundwerkstoffen: Vortrag gehalten auf dem 17. Kolloquium Gemeinsame Forschung in der Klebtechnik, 14. - 15. Februar 2017, Maternushaus Köln

Laubhölzer sind Hochleistungsprodukte mit herausragenden Materialeigenschaften, die im Bauwesen einen noch vergleichsweise geringen Marktanteil besitzen. Innerhalb der nächsten Dekaden wird sich infolge der Klimaerwärmung der europaweit vorherrschende Baumbestand ändern. Zusätzlich liegen seit Kurzem qualitativ hochwertige und hochleistungsfähige Baumaterialien aus Laubholz vor, die die ohnehin schon guten Eigenschaften der Laubhölzer zusätzlich verbessern, z.B. Buchen- und Eichenbrettschichtholz sowie Buchenfurnierschichtholz. Mit Hilfe in Holz eingeklebter Stäbe lassen sich standardisierte, stoffschlüssige, starre, duktile und ästhetische Anschlüsse realisieren, die letztlich zu wirtschaftlichen Konstruktionen führen. Der Verbindungsansatz eingeklebter Stahlstäbe in Nadelholz ist normativ geregelt und anerkannt, allerdings nur für ruhende Lasten. Weitestgehend unbekannt ist dagegen das Einkleben von Stäben in Laubholz. Dies betrifft sowohl Stäbe aus Stahl als auch glasfaserverstärkte Kunststoffe (GFK). An dieser Stelle setzt das Forschungsprojekt „Tacitus“ an

Eingeklebte Stäbe in Laubholzkonstruktionen

Forschung. Eingeklebte Stahlstäbe ( Gewidestäbe oder Betonrippenstähle) werden seit vielen Jahren erfolgreich als Verbindungsmittel für Nadelholzprodukte genutzt. Sie eignen sich zur Kraftübertragung und Verstärkung in Anschlüssen und Stößen. Eingeklebte Stahlstäbe besitzen zahlreiche Vorteile gegenüber mechanischen Verbindungsmitteln; insbesondere können standardisierte, stoffschlüssige, starre, duktile und ästhetische Anschlüsse realisiert werden. Die Verbindungstechnologie zeigt für Nadelhölzer ihr großes Potenzial, ist jedoch für Laubhölzer kaum erforscht. Dies ändert sich gerade unter anderem mit dem Forschungsprojekt TACITUS

Ermüdungsverhalten von eingeklebten Stäben

Verbindungstechnik, Teill*l DIN EN 1995-1-1/NA:2013-08 sowie DIN 1052-10:2015-05 in Verbindung mit den jeweiligen allgemeinen bauaufsichtlichen Zulassungen regeln in Deutschland die Bemessungs- und Konstruktionsansätze für eingeklebte Stahlstäbe bei vorwiegend ruhenden Beanspruchungen. Für nicht vorwiegend ruhende Beanspruchungen, also Ermüdungsbeanspruchungen, wie sie etwa bei Straßenverkehrsbrücken aus Holz auftreten, fehlen dagegen größtenteils umfassende Versuchsdaten für eine normative Regelung. Der folgende Beitrag gibt hierzu einen Überblick und liefert auf der Grundlage einer durchgeführten Versuchsreihe in dem Forschungsprojekt Tacitus neue Erkenntnisse im Hinblick auf den Ermüdungsnachweis