Student research projects and final theses

Topic

The targeted influencing of the oscillation form in ultrasonic systems can be realized through the use of wired passive piezoceramics. Passive electrical components such as capacitors, inductors and resistors are used for the circuitry. In previous studies, the use of capacitors in particular has proven to be effective. A digitally switchable capacitance decade is now to be developed for automated influencing of the oscillation form in ultrasonic systems.

The decade makes it possible to provide different capacitance values so that the oscillation shape in the ultrasonic system can be dynamically adapted to external boundary conditions. It is controlled entirely via the dSpace platform and Matlab Simulink. The aim is to provide a flexible and adaptive solution that allows precise control of the vibration modes and thus enables the efficiency and effectiveness of ultrasonic excitation in processes.

• Familiarization with ultrasonic technology and the operation of ultrasonic transducers
• Design of a capacitance decade with interference-free switching processes
• Also possible: design of a control system for optimum wiring of the ultrasonic system with capacitors

Requirements

• Responsible and independent way of working
• Previous knowledge of Matlab or the use of measuring devices desirable
• The scope of the tasks will be adapted to the respective type of work (Bachelor's, student research project, Master's thesis)

Please send your inquiries, including a list of grades, to the e-mail address provided.

Topic

The properties of a weld seam can be specifically influenced by exciting the weld pool using ultrasound. A typical ultrasonic transducer is used for this purpose (see illustration). This transducer actively influences the welding process, but is also stressed by the process conditions. This interaction is reflected in the electrical signals of the transducer - in particular in the current and voltage curves. The signals measured on the ultrasonic transducer therefore offer the possibility of drawing conclusions about the welding process. The aim of the student's work is to investigate the extent to which there is a correlation between these electrical signals and the course of the welding process. In particular, it is to be analyzed which characteristics of the resulting weld seam can be associated with certain signal curves.

Both classic signal processing methods and modern machine learning approaches are suitable for evaluation. This raises key questions such as: Is there a correlation between weld penetration depth and electrical impedance? Can potential defects in the weld seam be identified on the basis of conspicuous signal characteristics?

• Familiarization with ultrasound technology and the operation of ultrasonic transducers
• Design of algorithms for data evaluation in Matlab
• Planning and conducting experiments to validate the correlations found

Requirements

• Responsible and independent way of working
• Previous knowledge of Matlab or the use of measuring devices desirable
• The scope of the tasks will be adapted to the respective type of work (bachelor's thesis, student research project, master's thesis)

Please send your inquiries, including a list of grades, to the e-mail address provided.

Topic

The Institute of Dynamics and Vibrations is researching the laser beam welding process with supporting excitation by ultrasound. Previous studies have shown that exciting the weld pool with ultrasound has many advantages in welding, such as better mixing of the molten components.

An important parameter in laser beam welding is the welding depth. It provides information about the quality of the connection between the joining partners. This parameter is measured directly during the process using an OCT sensor. Based on this sensor, a welding depth control was developed for the process. This control system is now to be extended as part of the student project. This results in the following scientific questions, among others:

• How must the control be adapted depending on the material of the joining partners?
• How must the OCT measurement signal be processed so that the control remains stable?
• What must a welding depth profile look like in order to prevent heat build-up in round bars?
• Are the signals from the ultrasonic transducer suitable as a feedback variable?

Requirements and remarks

• Responsible and independent way of working
• Enjoy simulative and experimental work
• Previous knowledge of Matlab and the simulation environment Simulink required
• The scope of the student research project will be adapted to the type of work (Bachelor's thesis, student research project, Master's thesis)

Please send your inquiries, including a list of grades, to the e-mail address provided.

Motivation

The interest in power ultrasonic oscillators that use torsional vibrations has increased continuously in recent years. In this work, the various possibilities for generating torsional ultrasonic vibrations (here approx. 20 - 50 kHz) are to be investigated.

The procedure

Internship

• Research on the currently known systems and the mechanisms used to generate vibrations (e.g. use of special piezoelectric elements, conversion of longitudinal vibrations into torsional vibrations via geometric measures, ...) in patent literature and scientific databases
• Development/derivation of new concepts
• Preliminary investigations with the FEM

Master's thesis

• Analysis of the advantages and disadvantages and evaluation of the concepts identified, including an opportunity and risk assessment.
• Design of functional models of the two best concepts with the FEM, taking into account the piezoelectric effect → Update of the evaluation
• Creation of production documents for the best concept
• Construction and experimental characterization of the prototype and evaluation of results

Desired requirements

• Knowledge of vibration technology (preferably continuous systems)
• Knowledge in the application of FEM, e.g. with Ansys
• High level of independence and motivation
• Good communication skills in German or English

Start immediately or by arrangement

Topic

The Piezo and Ultrasound Technology working group conducts research into power ultrasound systems for various applications. Sensors such as current clamps and voltage probes are required for the operation and analysis of ultrasonic systems. Uncalibrated sensors lead to uncertainties and possibly measurement errors that interfere with both operation and analysis. In addition, depending on the investigation, different measuring systems are used whose measuring channels have different input impedances.

As part of a student project, a procedure is to be developed with which the sensors can be calibrated for the measurement of any power ultrasound systems within the frequency range of interest. The procedure is to be designed in such a way that the calibration can be carried out before the start of each measurement.

Requirements

• Study in the field of mechatronics or comparable
• Analytical way of thinking
• Experience with Matlab Simulink desirable
• Independent and responsible way of working

Start as of now