Dr.-Ing. Malte Stonis

Function:
Managing director
Phone:
+49 (0)511 279 76-119
E-Mail:
stonis@iph-hannover.de
vCard:
vCard
Xing:
https://www.xing.com/profile/Malte_Stonis
ResearchGate:
http://www.researchgate.net/profile/Malte_Stonis

Doctoral thesis

Defects like folds can arise using forging for the production of long flat pieces made of aluminium. A special defect is the formation of inner folds. These can be seen in the grain flow. Inner folds have a negative effect on the dynamic properties of the forged part. As a production process, forging can be divided into single-directional and multi-directional forging. The formation of inner folds was observed at the single-directional forging. By using the multi-directional forging, a forming operation working from different directions, the forming can be set variably. Thus the development of folds can be prevented. A newly developed method can help in the selection of the forming process and in determining an appropriate tool geometry. Here especially the area is adapted, where the development of inner folds occur. Therefore a calculation model was developed. It integrates a computer-aided identification of the inner folds. Using this model, a correction of the parametrically constructed forging tool is possible.

multidirectional-forging, long flat pieces, aluminium, fibre orientation

Publications

The Collaborative Research Centre 1153 (CRC 1153) “Process chain for the production of hybrid high-performance components through tailored forming” aims to develop new process chains for the production of hybrid bulk components using joined semi-finished workpieces. The subproject B1 investigates the formability of hybrid parts using cross-wedge rolling. This study investigates the reduction of the coating thickness of coaxially arranged semi-finished hybrid parts through cross-wedge rolling. The investigated parts are made of two steels (1.0460 and 1.4718) via laser cladding with hot-wire. The rolling process is designed by finite element (FE)-simulations and later experimentally investigated. Research priorities include investigations of the difference in the coating thickness of the laser cladded 1.4718 before and after cross-wedge rolling depending on the wedge angle, cross-section reduction, and the forming speed. Also, the simulations and the experimental trials are compared to verify the possibility of predicting the thickness via finite element analysis (FEA). The main finding was the ability to describe the forming behavior of coaxially arranged hybrid parts at a cross-section reduction of 20% using FEA. For a cross-section reduction of 70% the results showed a larger deviation between simulation and experimental trials. The deviations were between 0.8% and 26.2%.

cross-wedge rolling, hybrid forming, FEA, coating thickness

Within the Collaborative Research Centre (CRC) 1153 “Tailored Forming “the manufacturing of hybrid bulk components is investigated. Therefore, a process chain consisting of joining, forming, milling and quality control has been established by multiple subprojects.Within subproject B1 of the CRC forming of hybrid parts by the incrementally forming cross-wedge rolling (CWR) process is investigated. The superior aim is to determine process limits and capabilities, when forming parts consisting of different materials joined by varying technologies.

In this paper, the investigation of cross-wedge rolling of serially arranged hybrid parts made of steel and aluminum is described. The focus of the research presented in this publication is the displacement of the joining zone of hybrid parts due to the cross-wedge rolling process. Therefore, finite element simulations have been developed, that allow the investigations of hybrid solid components. After simulation of various variations of the cross-wedge rolling process, i.e.  differently shaped tools and forming velocities, experimental trials were carried out with identical parameter sets. A comparison of simulation and experiment, showed that the simulation model is capable of describing the cross-wedge rolling process of hybrid parts. The standard deviation of the displacement of the joining zone between simulation and experimental trials is 8.8% with regard to all investigated cases.

tailored forming, cross-wedge rolling, material forming, aluminum, steel

Within the Collaborative Research Centre (CRC) 1153 Tailored Forming a process chain for the manufacturing of hybrid high performance components is developed. Exemplary process steps consist of deposit welding of high-performance steel onto low cost steel and pre-shaping the component by cross-wedge rolling (CWR), supported by an optical quality control system. A combination of a fringe projection profilometry setup with a thermal imaging camera is used to monitor the components before and after the CWR process. Both geometry and thermal imaging data are combined, assigning temperature values to 3D data points.
In this paper, the acquisition of combined temperature-geometry data is described. The data before and after the CWR is compared to the input and the result data of the forming simulation that was used to design the CWR process. The comparison shows the quality and sustainability of the heating process as well as the influence of the transportation of the hot component prior to forming. Additionally, the accuracy of the used simulation model and software are evaluated by data examination. The examination shows the limits of idealised and simplified assumptions for the simulation, e.g., a homogeneous temperature distribution before forming or the modelling of the heat transfer on contact surfaces.

tailored forming, cross-wedge rolling, material forming, aluminum, steel, optical measurement

Within the Collaborative Research Centre 1153 “Tailored Forming“ a process chain for the manufacturing of hybrid high performance components is developed. Exemplary process steps consist of deposit welding of high performance steel on low-cost steel, pre-shaping by cross-wedge rolling and finishing by milling.
Hard material coatings such as Stellite 6 or Delcrome 253 are used as wear or corrosion protection coatings in industrial applications. Scientists of the Institute of Material Science welded these hard material alloys onto a base material, in this case C22.8, to create a hybrid workpiece. Scientists of the Institut für Integrierte Produktion Hannover have shown that these hybrid workpieces can be formed without defects (e.g. detachment of the coating) by cross-wedge rolling. After forming, the properties of the coatings are retained or in some cases even improved (e.g. the transition zone between base material and coating). By adjustments in the welding process, it was possible to apply the 100Cr6 rolling bearing steel, as of now declared as non-weldable, on the low-cost steel C22.8. 100Cr6 was formed afterwards in its hybrid bonding state with C22.8 by cross-wedge rolling, thus a component-integrated bearing seat was produced. Even after welding and forming, the rolling bearing steel coating could still be quench-hardened to a hardness of over 60 HRC. This paper shows the potential of forming hybrid billets to tailored parts. Since industrially available standard materials can be used for hard material coatings by this approach, even though they are not weldable by conventional methods, it is not necessary to use expensive, for welding designed materials to implement a hybrid component concept.

tailored forming, cross-wedge rolling, hard material coatings, PTA

By using digital tools in the factory planning process, the planning quality can be improved and the duration of the project can be shortened. In order to exploit these potentials, data consistency must be guaranteed throughout the planning process. In this article, digital factory planning tools, used at the Institut für Integrierte Produktion Hannover (IPH), will be presented and their applications and requirements will be discussed.

digital factory planning, factory planning process, data consistency, digital tools

To this day, the design of preforms for hot forging processes is still a manual trial and error process and therefore time consuming. Furthermore, its quality vastly depends on the engineer’s experience. At the same time, the preform is the most influencing stage for the final forging result. To overcome the dependency on the engineer’s experience and time-consuming optimization processes this paper presents and evaluates a preform optimization by an algorithm for cross wedge rolled preforms. This algorithm takes the mass distribution of the final part, the preform volume, the shape complexity, the appearance of folds in the final part and the occurring amount of flash into account. This forms a multi-criteria optimization problem resulting in large search spaces. Therefore, an evolutionary algorithm is introduced. The developed algorithm is tested with the help of a connecting rod to estimate the influence of the algorithm parameters. It is found that the developed algorithm is capable of creating a suitable preform for the given criteria in less than a minute. Furthermore, two of the five given algorithm parameters, the selection pressure und the population size, have significant influence on the optimization duration and quality.

preform optimization, genetic algorithm, cross wedge rolled, adaptive flash

Bulk-formed components are used in many applications in automotive and plant engineering. The conditions under which the components are manufactured, often at more than 800°C and thousands of tons of forming force, lead to high die wear. One way to reduce wear is to use suitable protective coatings. Initial basic investigations showed that the use of hard Diamond-like Carbon (DLC) wear-resistant coatings can significantly reduce the tribological effects on the die surface. With new methods such as the use of multilayer layer coatings and temperature measurement on the die surface by use of thin layer sensors, the potential of wear protection for semi-hot massive forming is to be investigated and expanded.

DLC, hot forging, wear

The melt level and oxide layer quantity in an aluminum melting furnace cannot be monitored by contact sensors, since the melting bath is not accessible due to the high holding temperature (above 600°C). Therefore, the method of monitoring the melting bath by means of optical sensors is investigated for the first time. For this purpose, suitable optical measuring systems can be applied which will be able to record the melting bath. The height change of the melt is to be elaborated by means of image analysis and any oxide layer on the bath surface is to be detected.

aluminum melting furnace, metling bath monitoring, oxide layer

Abstract: For factory planning projects the layout capturing and layout processing process need a huge amount of effort, because they are typically done by hand. These processes could be accelerated and optimized by using a drone and automated analysis algorithms. Furthermore, this article shows a way to raise the digitization level for industrial processes. The key aspect lies on the usage of a drone in indoor environment and the processing of three-dimensional point cloud models for factory planning processes.

drone, factory planning, 3D-factory layout, object recognition

Material efficiency and the development time of a forging sequence are decisive criteria for increasing the economic efficiency in the production of complex forgings. SMEs can often only interpret forging sequences in a shortened form due to insufficient capacities and high competitive pressure. Therefore, a generally valid method is to be developed that automatically generates multi-stage, efficient forging sequences based on the mass distribution of any forged part.

automated process design, die forging, resource efficiency

In this paper, the validation of an inductive sensor for an energy self-sufficient sensor for condition monitoring of wet-running steel disc clutches in marine gearboxes is presented. For a reliable operation of these a permanent monitoring of their state is advisable. As part of condition-based maintenance, more and more sensors are being installed in machines. Reliability becomes even more important when people are endangered by possible failure of the machines. In shipping, it is essential that, for example, the powertrain and thus the transmission are in perfect condition. In case of long distance traveling, wear or even damage of important components has to be known so that maintenance can be carried out proactively. To address this need an energy self-sufficient and wireless sensor network is developed. Miniaturized sensor nodes monitor torque, rotational speeds, temperatures as well as the wear condition of the torque transmitting components. The energy needed to operate these sensors is obtained from the surrounding environment. Thus, the system operates wirelessly and without an external energy supply, whereby the installation and maintenance costs decrease significantly. In addition to the concept of sensor integration in the transmission, the energy harvesting concept is also described in more detail. Finally, measurements are taken in a gear-like environment and the behavior of a magnetoinductive sensor in a not constantly supplied situation has been examined.

ship, gearbox, wear, sensor, torque

The joint is the weak point at a hybrid metal semifinished product in tube hydroforming. In real forming processes, a deformation at the joint would be prevented in order to avoid failure. A better knowledge of the forming behavior enables to reduce the effort in process design. Thus, this study investigates in hybrid material combinations and the forming behavior of the joint area regarding their suitability for tube hydroforming.

hydroforming, tube, steel-aluminum, FEA

This paper describes the development and prototypical implementation of an energy self-sufficient sensor for condition monitoring of wet-running steel disc clutches in marine gearboxes. For the precise control of an automated system and the monitoring of its performance, the knowledge about the possible wear is an essential prerequisite. In addition, the storage of sensor data over the life of the system offers the possibility of long-term condition monitoring. The combination with various other technological components creates a solution that enables cost-effective condition monitoring of marine gearboxes. Compared to existing systems, for example, the costs for installation and maintenance are significantly reduced. Both the methodology from the morphological box to the fine concept as well as the first measurements of the sensors are presented.

automated system, condition monitoring, metrology, clutch, gearbox

Lightweight automotive construction increasingly relies on hybrid structures made of steel and aluminium. These materials are currently joined mainly by form locking, for example by riveting. Welding and bonding are also used for joining the two materials. Hybrid composite forging allows to join the two components during the forming process. This shortens the process chain. With the help of zinc as a brazing material, the components are joined to form a material bond. This publication explains the results of the simulative parameter study. It shows how temperature, geometry and speed influence the joining result. Furthermore, first results of practical joining tests are presented.

lightweight construction, aluminum, simulative parameter study

Resource depletion and climate change are the main drivers for the rapid change of power generation structures. The energy transformation is causing an increase in energy prices for manufacturing small and medium-sized enterprises (SMEs). Within the last decade energy prices in Germany have doubled and are expected to grow even further . Metal processing SMEs are already attributing 4.5 percent of their gross production value to electricity costs. The paper shows the possible savings potential of the use of inventory levels as energy storage and provides approaches to an efficient solution of the associated optimization problems.

production program planning, energy costs, inventory level, energy storage

In average, more than 1,275 wind turbines were installed annually since 1997 in Germany and more than 27,000 wind turbines are in operation today. The technical and economic life time of wind turbines is around 20 to 25 years. Consequently, dismantling of aging wind turbines will increase significantly in upcoming years due to repowering or decommissioning of wind farms and lead to millions of costs for operators. An option to supersede the costly and time-consuming dismantling of wind turbines entirely on-site is to establish a dismantling network in which partly dismantled wind turbines are transported to specialized dismantling sites for further handling. This network requires an optimization model to determine optimal locations and an appropriate distribution of disassembly steps to dismantling sites. The challenge is to consider the networks dependency on the trade-off between transportation and dismantling costs which, in turn, depends on the selection of dismantling depths and sites. Building on the Koopmans-Beckmann problem, we present a mathematical optimization model to address the described location planning and allocation problem. To permit a proof-of-concept, we apply our model to a case-study of an exemplary wind farm in Northern Germany. Our results show that the model can assist dismantling companies to arrange efficient dismantling networks for wind turbines and to benefit from emerging economic advantages.

dismantling, wind turbine, optimization model

Structured factory planning is a key to ensure the competitiveness concerning to the increasing pressure from globalization and the high market dynamic. Companies though avoid to do factory planning projects, because of the high effort. For this reason, the processes of factory layout capture and factory layout assessment are in need of improvement in order to increase the efficiency, which will be achieved through new technologies and a semi automation of the processes.

factory planning, drone, photgrammetry, laserscan, image data processing

Constantly increasing quality requirements and ever-stricter conditions pose difficult challenges for the foundry industry. They must produce the high-quality components demanded by the market at a reasonable cost. Modern technologies and innovative methods help to master this challenge. Until recently, production, from the design of the aluminum melting furnace to daily process, relied largely on traditional methods and experience. However, important data and information about the melting process—for example, the temperatures and the shape of the aluminum block in the furnace—can hardly be obtained with conventional experimental methods, as the temperatures exceed 700 °C. Therefore, this research project investigates the method of monitoring a melting process by means of optical sensors for the first time. The purpose of this paper is to predict the surface shape of the block during the melting process, as it is not possible to maintain a constant monitoring due to the heat and energy loss during measurement (Einsatz einer Lichtfeldkamera im Hochtemperaturbereich beim Schmelzvorgang von Aluminium. To generate the necessary data, a 3D light-field camera is installed on top of an aluminum melting furnace in order to monitor the process. The basic idea is to find a general method for curve modeling from scattered range data on the aluminum surface in 3D space. By means of the (x, y, z) data from the 3D camera, the aluminum surface is modeled as a polynomial function with coefficient derived using various interpolation and approximation methods. This study presents an attempt to find the optimal polynomial function model that describes the aluminum surface during the melting process by interpolation or approximation methods. The best method for curve fitting will be extended and implemented for surface modeling. 

melting process light-field, polynomial function, interpolation, approximation, aluminum surface

The development of an ecological logistical impact model for the holistic consideration of the logistics performance should allow companies and especially SMEs to be able to record the CO2 emissions of the logistics transparently. For the development of such a model, the basic influencing factors must be defined and furthermore established as quantitatively assessable criteria. This paper discusses the basic relationships between logistics and ecology. Moreover, the boundaries for an ecological and logistical impact model are discussed and procedures for the definition of the required evaluation criteria are described.

Ecology, Logistics, CO2 calculation, Impact Modell, sustainabilty

A hot forging process allows to produce parts of excellent quality and technical properties. Nevertheless, it is not possible to forge undercut geometries like piston pin bores, it is usually necessary to manufacture them in subsequent processes. Thus, an undercut-forging process was newly developed. Such a process requires a multidirectional forming tool, which is challenging due to a high clamping force of the tool during the process. With the research results, the requirements to the crucial tool components of heavy springs diminish, allowing using standard spring devices instead of large and expensive custom designed devices. The aim of this study is to analyze the clamping force, its origin, and influencing factors in order to facilitate the tool design. Therefore, in forming simulations the input parameters press velocity, initial temperature, and punch shape were investigated, and their effect on the clamping force was statistically evaluated. The press velocity has the major impact on the resulting clamping force. The initial part temperature and the shape of the punch tool showed minor but still significant effects. This combination of input parameters reduces the load and the stress on the tool, enabling to perform the process on smaller forging presses. Eventually, forging trials validated the results.

forging, undercut, FEA, multidirectional, clamping force, tool design