Student research projects and final theses

Topic

Power ultrasound is an established technology that is used in many areas to improve products and processes. However, correctly adjusting the ultrasound system to the different processes is a challenge. In particular, identifying the impedance at the interface to the process is the decisive factor for optimal adjustment of the ultrasound system.

The identification of impedance at the process interface using artificial intelligence is to be investigated as part of a master's thesis. For this purpose, a test bench is to be set up in which an ultrasonic transducer can be guided and pressed onto a sample by its own weight. Artificial intelligence is to be developed and trained on suitable hardware so that, after a short period of operation, the artificial intelligence can identify the sample based on the operating data. The ultrasonic transducer is operated in resonance. A dSpace system is used for control and data acquisition. The hardware for the artificial intelligence must communicate with the dSpace system in order to perform the task.

Requirements

• Studies in mechatronics or a comparable field
• Enjoyment of experimentation
• Experience with Matlab Simulink desirable
• Independent and responsible approach to work

Start & Duration

Immediately, 6 months

Topic

Passive vibration isolators, which usually consist of very weakly damped, soft springs, are generally used to install sensitive machines. The springs are matched to the mass to be isolated in such a way that these complete systems have very low natural frequencies (typically < 2 Hz).

As part of this work, an existing spring element for an active vibration isolator is to be structurally expanded to include a damper element that has a weak damping effect in the low frequency range but damps relatively strongly in the higher frequency range (> 200 Hz). In particular, the natural vibrations of the spring are also to be damped. The work includes the design solution, a vibration/damper design using FE or analytical consideration, and experimental verification of the damping effect (with support).

Requirements

• Interest in constructive solutions and TM4
• Motivation to test your own solution directly in practice
• Independent working style

Start 

Starting immediately

Motivation

Ultrasonic assisted silver sintering is a promising die bonding technology that can reduce sintering time while maintaining high joint strength and reducing silver consumption. However, during practical ultrasonic thermocompression bonding, it has been observed that when the ultrasonic tool comes into contact with the sample, a significant amount of heat is absorbed by the tool, resulting in a sudden drop in temperature at the bonding interface. This transient cooling may influence the sintering behavior, affect the bonding quality, and lead to deviations between experimental results and the expected process performance. At present, the magnitude and time scale of this temperature drop are not yet quantified. The objective of this project is to investigate this temperature transient and its impact on the ultrasonic assisted silver sintering process.

Tasks

• Numerical simulation of temperature transients.
• Quantification of temperature drop magnitude and duration.
• Experimental temperature measurement under realistic conditions.
• Development of strategies to anticipate and compensate temperature drop
• Results discussion and academic writing.

Prerequisites

• Major in mechanical engineering or a comparable field
• Enjoy simulative and experimental work
• Independent and responsible approach to work

Experience with experiments/ANSYS desirable

Motivation

To improve the optical homogeneity and electrical efficiency of solar cells, triangular busbars formed from round aluminum wires have been proposed as an alternative to conventional flat busbars. By concentrating reflected light and reducing shading losses, this concept offers clear advantages for next-generation photovoltaic manufacturing. In previous work, a novel ultrasonic welding approach was developed, in which round wire simultaneously formed into triangular shape and bonded to the cell surface using a specially designed ultrasonic sonotrode. A simplified prototype sonotrode was designed, manufactured, and experimentally tested, successfully demonstrating the feasibility of simultaneous forming and bonding of a single wire at a fixed local working position. Building upon this initial success, the present project represents the next stage of research, focusing on further experimental validation and parameters study of the ultrasonic welding system.

Tasks

• Investigation of key process parameters and establishment of the process window
• Improvement and evaluation of wire guidance accuracy
• Enhancement of control performance and process stability
• Welding quality assessment
• Results discussion and academic writing.

Prerequisites

• Major in mechanical engineering or a comparable field
• Enjoy simulative and experimental work
• Independent and responsible approach to work
• Experimental experience preferred

Motivation

Ultrasonic assisted silver sintering is a promising die bonding technology that can reduce sintering time while maintaining high joint strength and reducing silver consumption. The focus of this project is to investigate, by means of molecular dynamics simulations, the effect of ultrasonic excitation on atomic diffusion in metallic systems relevant to silver sintering. In particular, the interactions and diffusion behavior between silver–silver, silver–copper, copper–copper, and copper–oxide interfaces will be studied. The simulations will be performed using the LAMMPS software package in order to capture the atomistic mechanisms activated by ultrasonic vibration.

Tasks

• Development of atomistic molecular dynamics models.
• Analysis of ultrasonic effects on atomic diffusion.
• Comparison of diffusion behavior at Ag–Ag, Ag–Cu, and Cu–Cu interfaces.
• Quantification of ultrasonic-enhanced diffusion rates.
• Results discussion and academic writing.

Prerequisites

• Major in mechanical engineering or a comparable field
• Enjoy simulative and experimental work
• Independent and responsible approach to work
• Experience with LAMMPS desirable

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