Prof. Dr.-Ing. Bernd-Arno Behrens

Function:
Managing partner
Phone:
+49 (0)511 279 76-119
E-Mail:
info@iph-hannover.de
vCard:
vCard
ResearchGate:
http://www.researchgate.net/profile/Bernd-Arno_Behrens

Publications

In order to achieve higher energy yields of wind turbine generator, the most expedient approach is to enlarge the tower height. By increasing the height the usable wind energy increases exponentially, but also does the tower weight. Therefore in a research study several constructional designs for lightweight tower design have been investigated. The design considered several design solutions which proved successfully in bionic, aerospace and automotive applications. FEA simulations were used to compare different structures and to estimate their feasibility. The best-fit identified constructional design is based on trapezoidal sheet. The developed design enables a weight reduction up to 20 % in comparison to standard towers.

xxl-product, large-scale, xxl, wind turbine, wind power, lightweight construction, tower constructio

A smart option to increase the energy yield of wind turbine generators is to increase its height. There is an exponential increase of the usable wind energy at enlarging the tower’s height, but also an exponential increase of the tower’s weight. The application of lightweight design concepts in the production of wind turbine tower sections may lead to weight reduction while keeping the tower’s stiffness at an equal level. Here the results of a study for lightweight concepts and their implementation on towers and a guiding systematic approach are being presented. The investigated design solutions proved successfully in bionic, aerospace and automotive applications. FEA simulations were used to compare the different structures and to estimate their feasibility. The investigation’s main result is a lightweight structure which provides weight reductions up to 20 %, by using lower wall thicknesses.

xxl-product, large-scale, xxl, wind turbine, wind power, lightweight construction, tower constructio

For a systematic complaint handling the 8D method has been established. However, so far there are no adequate measurement and evaluation techniques to assess the quality of an 8D report. As a consequence it can not be guaranteed at any time that the complaint processing is carried out correctly and efficiently. In a research project of the FQS, the Institute of Metal Forming (IFUM) and the IPH - Institute of Integrated Production gGmbH an automated metric system for measuring and evaluating the quality of 8D reports was developed. To determine the metrics algorithms are used for text mining. Also manual reviews are used to realize the required range of reviews efficiently and reliably.

8d-report, claims management, complaint, quality management

This paper describes the development of a warm cross wedge rolling process with one area reduction. The paper also includes results of finite element analysis (FEA), experimental trials with a downsized work piece and the adaption to the industrial work piece in original size. In the FEA simulations tools with serrations on the side have been used. The downsizing method is explained and the difference between FEA, downsized and originally sized work piece with the focus on forming forces, temperature distribution and defects are presented.

warm forging, cross wedge rolliing

A suitable technology for pre-forming of highly loaded forgings is the cross-wedge rolling. With little effort, investigations are now carried out using a new module for cross-wedge-rolling with flat dies. To expand the existing geometric limitation of warm forged steel components, the cross-wedge-rolling at temperatures between 650 °C and 950 °C was investigated. In addition, first studies with aluminum using the new module are described.

warm forging, cross-wedge-rolling

The early detection of defects in forged parts offers economical advantages due to the possibility of sorting them out of the process chain. The aim of the presented research project is the development of a forging process monitoring without sensors. In the process electric current is flowing through the forged part. The quality of the forged parts is measured by the electrical signal. Typical defects of forgings like underfilling and wrong temperature of the billet show characteristic signals and therefore can be detected. These parts are sorted out of the process chain. The user of the forging machine is able to adjust the forging process immediately.

forging, process monitoring

The implementation of process monitoring technologies in manufacturing processes allows significant cost and time savings. An online process monitoring of die cavity filling in warm forging processes could not be realized until now. Important process parameters for example billet volume, billet temperature or lubrication could only be observed after forging. This paper describes the implementation of an online process monitoring system based on electricity.

forging, process monitoring

To produce preforms for complex long flat parts with an unsteady mass distribution along the longitudinal axis rolling processes, like cross wedge rolling, can be used. Tools for cross wedge rolling processes can be constructed as roller or flat, both with wedges. In the collaborative research project "SFB 489 - Process chain for the production of precision forged high performance parts" the subproject "Innovative machine and tool technology for precision forging" deals with the development of a flashless forging process for a two cylinder crankshaft with pin and flange. This process is developed by IPH - Institut für Integrierte Produktion Hannover. The first preform of the developed forging sequence is produced by a cross wedge rolling process on the basis of flat with wedges. To consider the mass distribution of the two cylinder crankshaft in the preform for a rolling process four mass concentrations for the crank arms and mass concentrations for pin and flange are needed.

crankshaft, cross wedge rolling (CWR), forging sequence, preform, rolling process

Lightweight design of cars is one way to reduce fuel consumption and increase the range of cars. This is an important factor to attain the EU limit values for CO2 emissions for vehicles and thus to avoid penalties for exceeding these limits as of the year 2012. The growing number of uses for high-strength steels or lightweight structures are adequate means to reduce weight. At IPH - Institut für Integrierte Produktion Hannover gGmbH a method to produce hollow profiles made of aluminum was developed. This method, called hydroforging, combines flashless forging and tube hydroforming. It allows the production of thick-walled hollow aluminum profiles with undercuts without the need for complex tool kinematics. The forging is supported by an active medium. A tool concept has been developed using the drives of a hydraulic press with die cushion. With this tool, various part geometries shall be produced and analyzed. To produce the tools' interior pressure and the forming pressure, liquid tin as an incompressible active medium is used. The forming is initiated by upsetting the aluminum profiles and supported by the active medium, so that the profile is pushed against the cavity of the dies. The process was designed based on simulations and will be verified by practical experiments. This paper describes the development of the forging process with an active medium.

hydroforming, forging, tubes, aluminium, FEA

Sheet metal parts often have to be connected by fasteners. Fasteners like bolts are mostly welded individually after the forming process and outside the working tool. This spatial separation of production steps requires complex handling operations and has negative impact upon the positioning accuracy of the fasteners. Every executable manufacturing step inside the sheet metal working tool shortens the process chain significantly. Furthermore, using a combined process the precision of position and orientation of fasteners improves. The challenges of integrating the welding process into the sheet metal working tool are handling the emissions and associated pollutions of the tool as well as creating a reliable monitoring-system for the welding-process. Within the scope of a research project, a reliable technology for the integration of condenser discharge stud welding with tip ignition was developed and tested. It complements existing solutions for integrated resistance welding processes.

sheet metal, capacitor discharge arc stud welding, cd arc stud welding, tip ignition, follow-on tool

Many forged parts include piercings e.g. as bearings. The web of the forged pieces has to be pierced in an additional manufacturing step. By integrating this so far separately performed operation into the final forging step the process chain can be shortened. However, up to date there is no information available on how the process parameters influence quality relevant factors. Therefore, a combined forging-/piercing process is designed and performed. The results of previous research projects showed that the variation of the inserted mass and the forging temperature have a distinct effect on the dimensional and form accuracy of the work pieces. In this project different punch and work piece geometries and the influence of a different forming sequence on tool stress and the material flow was investigated. The punch and work piece geometry show no effect on form accuracy of the piercing while an inappropriate forming sequence leads to failure of the tool.

forging, flashless, precision, piercing

In the past, scientific analysis of development and production of large-scale products has not been conducted very often. In the joint project „Innovations for the production of large-scale products“, sponsered by two German ministries in the state of lower saxony, IPH – Institut für Integrierte Produktion Hannover gemeinnützige GmbH will make a contribution to reply scientific questions in consideration of development, production and recycling of large-scale products.

xxl-products, development, manufacturing, recycling

Cross wedge rolling is a method for reshaping cylindrical billets for getting a better mass distribution. Against the backdrop of rising material costs, this method is increasingly becoming the focus of many forging companies - but the high investment costs for tools and equipment prevents the economical benefit of the process. With flat cross wedge tools and corresponding rolling machines tooling costs can be reduced and the process is therefore interesting for small batches. Moreover, studies show that CWR is also applicable in warm temperature range.

warm forging, process chain, cross wedge rolling

Closer tolerances, reduced surface roughness, no scale and reduced decarburization can be realized by warm forging. However, the geometrical spectrum of warm forged parts is limited by flow stress. To overcome this geometrical limitation, innovative warm cross wedge rolling and forging processes are developed in the project presented in this paper. To investigate the effect of lower temperatures on process parameters, e. g. force, die wear and material properties in comparison to hot forming processes, Finite Element Analysis (FEA) and experimental tests using downsized model geometry were performed. In this paper the new warm cross wedge rolling process is explained and results of warm cross wedge rolling trials (e. g. work piece characteristics), FEA simulations of forming forces and material analysis are shown. The results of these analyses allow industrial application of warm cross wedge rolling for the first time.

warm forging, process chain, cross wedge rolling

Many forged parts include piercings e.g. as bearings. The web of the forged pieces has to be pierced in an additional manufacturing step. By integrating this so far separately performed operation into the final forging step the process chain can be shortened. However, up to date there is no information available on how the process parameters influence quality relevant factors. Therefore, a combined forging-/piercing process is designed and performed. The results of previous research projects showed that the variation of the inserted mass and the forging temperature have a distinct effect on the dimensional and form accuracy of the work pieces. In this project different punch and work piece geometries and the influence of a different forming sequence on tool stress and the material flow was investigated. The punch and work piece geometry show no effect on form accuracy of the piercing while an inappropriate forming sequence leads to failure of the tool.

forging, flashless, precision, piercing

A new tool design and die assembly developed at IPH has the ability to form flashless, near-net-shape forgings and pierce the workpiece all in one stroke. The tooling concept for the combined flashless forming and punching process was developed for rotationally symmetric parts. The die assembly is designed to fit into a standard forging press. The tool consists of an upper die, an upper punch (combined forming and punching die), gas-filled springs, a lower die, a lower punch and a release mechanism. The design of this forging sequence was facilitated by material-flow simulation programs using finite element analysis (FEA) techniques.To determine the influencing parameters forging trials have been made on Muller Weingarten PSH 265 screw press. The feasibility of a combined forming and punching process to produce near-net-shaped parts has been successfully demonstrated.

forging, flashless, precision, piercing

Saving resources becomes more and more important. Therefore the forging industry tries to develop processes with less flash than the conventional techniques or to avoid flash completely. Currently only simple parts like gears can be forged without flash. In a research project flashless forging processes for crankshafts were developed. In this paper the evolution of the flashless forging process and the process steps will be described. The collaboration research project "process chain for the production of precision forged high performance parts" has been conducted in the last few years at IPH and was funded by the German Research Foundation (DFG).

precision forging, flashless, crankshaft

Flashless precision forging is a special process of drop forging performed in closed dies. This process is distinguished by high quality and the ability to achieve a near net-shape part. Latest research results have shown that it is possible to forge a two-cylinder crankshaft without flash. This was realized using a multi-directional forging tool and a flashless precision forging operation. In this paper a new method for a three dimensional shrinking compensation is presented that facilitates the construction process

forging flashless precision near-netshape

Large-scale products (XXL-products), such as bearing rings for wind turbines, pose special challenges to the production technology. For example, the continuous growth of product dimensions puts challenges on forming technologies as they reach their technical limits. Scaling effects, that occur when scaling up, can include physical limits for a further upscaling. These effects have only been studied for small scale production processes so far. The consideration of such effects in the large scale production offers the opportunity to exploit the potential of metal forming processes and improve the calculation forecasts.

xxl-products, forging, flowproperties, scaling factor, scaling effect, ring compression test

As a result of increasing globalization in procurement an increased competition exists for production companies. In the field of sheet metal forming companies will therefore be required to produce proper quality products with short delivery times at high punctuality at lowest possible production costs.

sheet metal forming, experience recovery, equipment effectiveness