Sami Chatti

Development of a tele-operative testing cell as a remote lab for material characterization

Laboratory experiments play a significant role in engineering education. The experience gathered during the labs is one of the most important experiences during studying engineering because there is a strong connection between theory and practical relevance. A tele-operative testing cell for material characterization for forming processes is presented. This testing cell is used as a remote lab so that students can gain their experiences location and time-independent via the internet. In addition, the tele-operative testing cell is also used within the scope of lectures to combine the theory with live experiments in interaction with the students. The main aspects are, on the one hand, the developments in the field of engineering and the implementation of the IT components like iLab and, on the other hand, the integration of the tele-operative testing cell into engineering education.

Numerical Investigation of the Incremental Tube Forming Process

As a response to the recent years’ growing demand for innovation in manufacturing processes towards lightweight design in several industrial sectors, a new process, called Incremental Tube Forming (ITF), and a corresponding machine layout have been developed. ITF is a process to manufacture bent tubes with varying cross-sections. During ITF a tube is clamped in a feeding device, which transports the tube through a spinning tool, where the diameter reduction takes place. This stage is followed by a superposed bending process without suppressing continuous feeding. This combination leads to various advantages such as improved tool life with reduced tool forces and improved product accuracy (e.g. springback behavior), as it is shown in various experimental works. This paper presents a complementary numerical treatment of the process using FEA. For this purpose, a 3D model is constructed using ABAQUS/Explicit, where the tube is modeled with conventional shell elements with uniformly reduced integration to avoid shear and membrane locking (S4R), whereas the spinning rolls are modeled as discrete rigid. With this model, the influences of process parameters, such as diameter reduction ratio and tool geometry, are investigated. This helps not only to gain a deeper understanding of the process but also to interpret already gathered experimental data with better precision and, thus establishing a basis for further improvement and optimization of this fairly new process.

Development of a tele-operative control for the incremental tube forming process and its integration into a learning environment

A deficient access to experimental equipment leads to the usage of remote labs to improve engineering education and open experiments for every student location - and time - independent. The usage of a tele-operative controlled industrial bending process in lecture combines theoretical learning contents with practical experiences. Lecturers can make experiments in interaction with the students, who are able to assist in choosing the process values. The chosen and presented bending process is the incremental tube forming process that uses in contrast to many ordinary bending processes targeted the superposition of stresses. By superposing of stresses, in this process for example a tube bending and a tube spinning process, several fundamental process characteristics can be observed and integrated into lectures to visualize the theoretical fundamentals behind. Incremental tube forming combines the tube spinning process, which affects the diameter of the tube all along the tube and creates a compressive stress, and a bending process. The understanding of superposition of stresses and the process phenomena are ambitious, so that experimental experience is very useful. By using a tele-operative control, the experiment is location- and time-independent available for lecturers and students all over the world. They can interact with the process like stopping it, influencing it during the process or laying it up. The possibilities for a usage in learning environments are described and pointed out.

Closed-loop control concept for kinematic 3D-profile bending

Kinematic tube and profile bending processes produce bending contours by the relative movement of single process axes. Tools only need to be adapted to fit the cross-section of the tubular material. While offering a great flexibility in production, kinematic bending processes cause a high part springback and as a result, compensatory methods are needed to achieve target contours. These compensatory methods are generally embedded in bending tables or analytical calculations that in turn are embedded into the process control software. This procedure can cope with known material behavior, as for instance gained through a tensile test of the material batch prior to the bending process. Material variations inside a batch cannot be detected however and cause contour deviations. To counter this error, a closed-loop control system can be used, which can quickly adapt axes’ movements to produce target shapes and thus reduce scrap. In this paper, two methods to apply closed-loop control to 3D profile bending will b...

Forming Limit Extension of High-Strength Steels in Bending Processes

Bending is a commonly used forming technology in metal forming. The occurring springback and low forming limits of high-strength steels especially during air bending are the main disadvantages. In this paper, the conventional air bending process is applied with a hydrostatic pressure in the bending zone. This was done using an elastomer tool. The advantage of this method is that the flexibility of air bending is maintained by reducing the springback while the forming limits are extended. Furthermore, different geometries for the elastomer tool were investigated by means of a FEM simulation. The investigation leads to a reduction of the process forces by minimizing the springback and to an extension of the forming limits.

miniLABs – Focused Lab Sessions in Manufacturing Technology Related to Forming Processes

Laboratory experiments play a significant role in engineering education. The main concern of the described hands-on miniLABs initiative (as a work in progress) is lowering the hurdles in order to provide engineering students with an informal and straightforward access to experiments carried out in labs of the IUL at TU Dortmund University. miniLABs will offer students different, short and voluntary hands-on lab sessions, consisting of two different modes and different aspects related to manufacturing technology in the field of forming processes. In small teams, students can get in touch with practical engineering activities in the fields of present scientific research, either to study a certain phenomenon or to look at a wider engineering context. Based on the framework of experiential learning, miniLABs tries to foster the shift from teaching to deep learning. Finally, this initiative aims to inspire young students for real and hands-on engineering experiments and to contribute to the science education of these young and future engineers.

Lightweight Construction by Means of Profiles

This paper shows some product and process developments at the Institute of Forming Technology and Lightweight Construction of the TU Dortmund University supporting the lightweight construction. It presents the manufacturing of lightweight profiles by hot extrusion and their benefits as well as their design, material, and manufacturing potential for lightweight construction. Examples of process extensions in hot extrusion like curved profile extrusion, twisted profile extrusion and manufacturing of functional graded profiles and profiles with variable cross-sections during extrusion are shown. These procedures allow a flexible change of the profile geometry or contour in longitudinal axis and, therefore, support the shape lightweight construction. Other extensions like composite profile extrusion and energy efficient extrusion of profiles from scrap materials like chips support the material lightweight construction. The manufacturing and use of these profiles allow the realisation of diverse lightweight construction principles and promise to become a pillar of lightweight construction in future.

Manufacturing of Profiles for Lightweight Structures

The paper shows some investigation results about the production of straight and curved lightweight profiles for lightweight structures and presents their benefits as well as their manufacturing potential for present and future lightweight construction. A strong emphasis is placed on the manufacturing of straight and bent profiles by means of sheet metal bending of innovative products, such as tailor rolled blanks and tailored tubes, and the manufacturing of straight and curved profiles by the innovative procedures curved profile extrusion and composite extrusion, developed at the Institute of Forming Technology and Lightweight Construction (IUL) of the University of Dortmund.

System for Design and Computation of Lightweight Structures Made of Bent Profiles

The process chain for the production of lightweight profile structures consists of the design and computation phases, the manufacturing of straight profiles, the manufacturing and further processing of bent profiles, and the joining of single profiles to lightweight structures. A sophisticated lightweight construction design of profile structures is characterised by the use of the correct material at the correct place with the correct dimensions. To design in this way means to purposefully find the technically and economically best solution. This requires a holistic technological approach covering the whole system “design-material-manufacturing”. Furthermore, appropriate experiences in design and the use of calculation software for the determination of several mechanical component properties as well as the simulation of manufacturing processes are necessary. A satisfactory component optimisation and a manufacturing specific design of the components presupposes, however, the integration of design, computation, and manufacturing knowledge into a single system using modern CA technologies to realise simultaneous engineering.

Live demo of two experiments using a remote lab for forming technology

In engineering courses, it is more and more important to combine theory with practice. Therefore, at the Institute of Forming Technology and Lightweight Construction of TU Dortmund University a tele-operative testing cell for material characterization was developed. This remote lab was successfully integrated to different scenarios. On the one hand, the remote lab was integrated to forming technology lectures. Thereby the lecturer configures the experiment in interaction with the students in the lecture hall. After the experiment is finished the results can be discussed face to face. On the other hand, the tele-operative testing cell becomes a part of different online learning scenarios like online courses. With this remote lab lectures and students are able to do experiments of forming technology via internet. In the following the design of the remote lab and two experiments for a live demo are described.