One of the main objectives of production engineering is to reproducibly manufacture (complex) defect-free parts. To achieve this, it is necessary to employ an appropriate process or tool design. While this will generally prove successful, it cannot, however, offset stochastic defects with local variations in material properties. Closed-loop process control represents a promising approach for a solution in this context. The state of the art involves using this approach to control geometric parameters such as a length. So far, no research or applications have been conducted with closed-loop control for microstructure and product properties. In the project on which this paper is based, the local martensite content of parts is to be adjusted in a highly precise and reproducible manner. The forming process employed is a special, property-controlled flow-forming process. A model-based controller is thus to generate corresponding correction values for the tool-path geometry and tool-path velocity on the basis of online martensite content measurements. For the controller model, it is planned to use a special process or microstructure (correlation) model. The planned paper not only describes the experimental setup but also presents results of initial experimental investigations for subsequent use in the closed-loop control of α’-martensite content during flow-forming.
Oxygen is the second-most abundant
element in the earth’s
atmosphere and plays an important role in various engineering applications.
The precise knowledge of its thermophysical properties is thus important.
As a fully fledged thermodynamic property, the speed of sound substantially
contributes to the development and parametrization of equations of
state. This work presents experimental speed of sound data for oxygen
measured with an apparatus that is based on the pulse-echo technique
with a double path-length. When working with pure oxygen at high temperatures
and pressures, tight safety requirements have to be met, limiting
the present measurements to 500 K and 100 MPa.
For developing an active workpiece holder, piezo actuators are used to apply compensation forces and displacements. These actuators suffer from hysteresis effects which impair accuracy and performance. The focus of this work is the modelling of the actuator's hysteresis and establishing a corresponding inverse model to compensate the effect in an open-loop approach. The model, on the basis of easy to calculate sigmoid functions, is shown to yield good linearization of the actuator's behavior.
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