Mahmut Özel

Model-based control of an elastic aircraft engine rotor with piezo stack actuators

Due to the fact that natural bending frequencies of elastic jet engine shafts lie in the speed range, passive or active damping is necessary to reduce radial rotor vibrations. In this study, a test rig with a high-speed turning rotor investigating active damping with piezo stack actuators was constructed. Additionally, a software-based model including nonlinear behaviors as the gyroscopic effect of the rotor and hysteresis of the piezo stack actuators was designed. The notable result of this study is that the rotor vibration and bearing force magnitudes could be reduced considerably by the implemented closed-loop control. This makes it possible to have a secure run-up passing the natural bending frequencies of the excited unbalanced rotor.

Accelerating the FE‐Simulation of Roll Forming Processes with the Aid of specific Process’s Properties

Roll forming is an effective and economical sheet forming process that is well‐established in industry for the manufacturing of large quantities of profile‐shaped products. In cold‐roll forming, a metal sheet is fed through successive pairs of forming rolls until it is formed into the desired cross‐sectional profile. The deformation of the sheet is complex. For this reason, the theoretical analysis is very difficult, especially, if the strain distribution and the occurring forces are to be determined [1]. The design of roll forming processes depends upon a large number of variables, which mainly relies upon experience based knowledge [2]. In order to overcome the challenges and to optimize these processes, FE‐simulations are used. The simulation of these processes is time‐consuming. The main objective of this work is to accelerate the simulation of roll forming processes by taking advantage of their steady state properties. These properties allow the transformation of points on the sheet metal according t...

The Result: A New Design Paradigm

One of the key challenges faced by engineers is finding, concretizing, and optimizing solutions for a specific technical problem in the context of requirements and constraints (Pahl et al. 2007). Depending on the technical problem’s nature, specifically designed products and processes can be its solution with product and processes depending on each other. Although products are usually modeled within the context of their function, consideration of the product’s life cycle processes is also essential for design. Processes of the product’s life cycle concern realization of the product (e.g., manufacturing processes), processes that are realized with the help of the product itself (e.g., use processes) and processes at the end of the product’s life cycle (recycling or disposal). Yet, not just product requirements have to be considered during product development, as requirements regarding product life cycle processes need to be taken into account, too. Provision for manufacturing process requirements plays an important role in realizing the product’s manufacturability, quality, costs, and availability (Chap. 3). Further life cycle demands, such as reliability, durability, robustness, and safety, result in additional product and life cycle process requirements. Consequently, the engineer’s task of finding optimal product and process solutions to solve a technical problem or to fulfill a customer need is characterized by high complexity, which has to be handled appropriately (Chaps. 5 and 6).

Computer-Integrated Engineering and Design

Virtual product development aims at the use of information modeling techniques and computer-aided (CAx-) tools during the product development process, to represent the real product digitally as an integrated product model (Anderl and Trippner 2000). Thereby, data related to the product as well as product properties are generated and stored as result of the product development process (e.g., product planning, conceptual design) (Pahl et al. 2007; VDI 2221 1993). Within virtual product development CAx process chains have been established. They comprise the concatenating of the applied tools and technologies within the steps of the virtual product development process enabling the consistent use of product data (Anderl and Trippner 2000). The computer-aided design (CAD) technology aims at the integration of computer systems to support engineers during the design process such as design conceptualization, design, and documentation. It provides the geometry of the design and its properties (e.g., mass properties, tolerances) which is abstracted to be used in computer-aided engineering (CAE) systems (e.g., finite element method (FEM)) for design analysis, evaluation, and optimization. The computer-aided process planning (CAPP) technology provides tools to support process planning, Numerical Control (NC) programming, and quality control (Hehenberger 2011; Lee 1998; Vajna 2009). The advantages are continuous processing and refinement of the product model, minimizing the modeling efforts regarding time as well as costs and avoiding error sources. In addition, all relevant data and information related to the product can be provided for subsequent processing (Anderl and Trippner 2000). CAx technologies have been widely established within the product development processes in industry. They have been further developed in the last years; however efforts to integrate and to automate them are still a topic of research. Especially, with the introduction of innovative manufacturing technologies such as linear flow and bend splitting require new methods and tools for the virtual product development process. These technologies enable the production of a new range of sheet metal products with characteristic properties (e.g., Y-profile geometry, material properties) that are not addressed in state-of-the-art methods and tools.

New Challenges: Technology Integrated Market-Pull

Newly developed products usually do not only face the market requirements. With the manufacturing induced properties it is possible to satisfy the constantly rising market requirements, e.g., in the mechanical engineering market or the building industry. Besides the original functions, the new products often have to meet other requirements such as lightweight construction, multifunctionality, reliable joints, or aesthetical demands.