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Institute of Materials Research

Zuschnitt Hzg Ben Khalifa Noomane 0030

Photo: HZG/Rolf Otzipka

Prof. Dr.-Ing. Noomane Ben Khalifa
After completing his mechanical engineering studies at the TU Dortmund in 2005, Noomane Ben Khalifa worked as a researcher at the the Institut für Umformtechnik und Leichtbau at TU Dortmund. There he finished his doctorate in 2012. Since 2018 he has been professor at Leuphana University in Lüneburg and is head of a working group at the Helmholtz-Zentrum Geesthacht.

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Becoming More Climate Friendly, Step by Step

Light metal components made in Geesthacht

A new group in HZG’s Institute of Materials Research is involved in the manufacturing of light metal components. Their leader is Prof Noomane Ben Khalifa, mechanical engineer and professor of manufacturing technology at Leuphana University in Lüneburg. One of his group's main research areas is to find customised manufacturing methods and process routes for the materials developed at the institute, which should also conserve resources.

Multi-material components

Photo: HZG/Rolf Otzipka

The modern metal industry consumes a great deal of resources and roduces large quantities of CO2. For producing just one ton of crude steel, 1.7 tons of CO2 emissions are generated. This contrasts with the fact that by 2030, industry must reduce its greenhouse gas emissions by approximately half compared to 1990. This, at least, is what the German government's climate protection plan stipulates for the industrial sector. This sector is therefore searching for ways in which to become more sustainable and climate friendly. This can, on the one hand, be done using skilful alloy development, but on the other, by adapting the processing steps, whereby the manufacturing technology is tailored to the materials.

From Antiquity into the Future

Noomane Ben Khalifa (second from the left) in conversation with scientist Merle Braatz (left) and  doctoral students Jonas Isakovic and Danai-Glykeria Giannopoulou (right).

Noomane Ben Khalifa (second from the left) in conversation with scientist Merle Braatz (left) and
doctoral students Jonas Isakovic and Danai-Glykeria Giannopoulou (right). Photo: HZG/Rolf Otzipka

Metallurgy in itself is nothing new. Humanity began to utilise metals some ten thousand years ago, working the material through forging, hammering and rolling. Even as early as the Copper, Bronze and Iron Ages, humans had figured out that the properties of their sword or plough could be altered through the respective fabrication process. The tools became harder by heating them several times, or sharper if they used additives such as ash.

Multi-material components

Using various methods, the research group develops and tests multi-material components for combining different material properties. Photo: HZG/Rolf Otzipka

The experiential knowledge from forging ultimately led to material innovations. Even today such innovations often arise through new or improved materials and from the associated processes and machining work. Noomane Ben Khalifa explains, “One example of innovative materials are lithium-ion batteries used in electric cars and smartphones. Today’s batteries can be charged more quickly and have a longer lifespan than those of a few years ago. The speed of innovation has increased enormously. Products wind up on the shelves much faster than thirty years ago. Modern industries must keep up with this tempo.” Ben Khalifa also sees potential for production engineers in small and mediumsized metal industry businesses, where the trend is turning away from mass production towards flexibility and individualisation. The components or products manufactured in small quantities should be affordable and also be produced in a manner that conserves resources.

New Technologies for New Materials

Two multi-material components

Photo: HZG/Rolf Otzipka

Due to climate change, lightweight materials are in demand in automotive engineering. For example, reducing the weight of a car by just three hundred kilograms will lower its fuel consumption by approximately one litre per one hundred kilometres and the CO2 emissions by two kilograms. Lightweight engineering, however, has its challenges. Structural components of a car body, for example, can be made lighter by using new materials, but they must also be strong enough to protect occupants in an accident. Noomane Ben Khalifa says, “Our colleagues in the institute develop new, lightweight materials, and we analyse the further process chains, asking ourselves which screws we can adjust.” This is because the new materials, due to their formability and mechanical strength, are often more difficult to process. This sometimes requires entirely new forming technologies so that the sheet metal for the car bodies can actually be produced from the light metal alloy.

Scientists working at the extrusion.

One processing technique used at the HZG for research is extrusion. Photo: HZG/Rolf Otzipka

The researchers combine the varying manufacturing technologies together to produce components with the best properties. “In principle, the blacksmiths from earlier times would have done the same thing,” explains the scientist. “Nevertheless, we use the most modern analysis methods and model simulations, such as finite element simulations, machine learning or artificial intelligence.” Thanks to these digital tools, materials science is even more innovative, whether it is incremental forming, deep drawing or even extrusion. The scientists closely examine the different methods to find the optimal process for the specific application. In doing so, they check which technology consumes the least energy and how materials can be optimally recycled.

Scientists working

In this method, the metal is heated and then pressed through a die using the extrusion press. Photo: HZG/Rolf Otzipka

Ben Khalifa names one application: “We are thinking about new concepts for wind turbines made of light metals, such as aluminium and magnesium. These materials are, in comparison to reinforced plastic components, considerably more climate friendly, both in terms of production and in recycling after use.“

In order to develop such customized materials, the scientists must acquire basic knowledge on composition, synthesis, and modelling as well as on manufacturing and processing technologies. Through targeted temperature control or by changing different parameters in the process, for example, the material properties can be improved.

From Computer Modelling to the Finished Component

The extrusion

Each material has its individual properties and requirements in terms of the manufacturing process. What these are exactly, the HZG wants to find out. Photo: HZG/Rolf Otzipka

Complex simulations provide the scientists with initial insights into which materials are suitable. Only after this step are experiments carried out and the material is processed further. The advantage at the HZG is that the entire chain - that is, from the simulation to the production to the processing and detailed description - is covered at the institute.

What challenges does manufacturing technology face today? “One challenge is certainly the short innovation cycles that characterise the economy today. From an economic point of view, however, the greatest challenge is the low CO2 production of lightweight components,” adds Ben Khalifa

Author: Heidrun Hillen (HZG)
Published in in2science #9 (April 2020)