Master's thesis: Mission Synthesis for vibration testing

Background
Quality assurance of vibration-sensitive equipment is important and relies on durability testing on a vibrator. A typical vibration test specification has a simplified vibration description in the form of stationary random vibration or swept sinusoidal vibration. Such a vibration description can be taken from testing standards or it can be a unique formulation that is developed from analysis of a measured vibration environment (or several environments from successive missions like transport, normal operation, etc. along the life profile of the equipment). The vibration testing is often performed on electrodynamic shakers, using sequential testing in one direction at the time. 

The vibration analysis that derives the optimal simplified test profile, tailored after measured 
vibration environment where the equipment is mounted, is sometimes called mission synthesis or test tailoring analysis. 

The benefit from excellence in mission synthesis is often present as transparency and efficiency in the relation between e.g. a car manufacturer and its equipment supplier, in form of equipment specification clarity. 

Description
The vibration environment that a certain equipment, component or structure is subjected to is 
usually difficult to describe in a compact form, because the vibration character is changing when operating conditions or missions are changing. One analysis method has been identified as superior, for efficient description of shock and vibration environments. This method is based on the response spectrum concept and uses results called Max Response Spectrum (MRS) and Fatigue Damage Spectrum (FDS). It is considered superior because it avoids the use of Fourier analysis and by that makes relevant analysis of complex, nonstationary vibration data possible. 

The compact form of a vibration description in the test specification is a Power Spectral Density 
(PSD), which describes a stationary random vibration test completely (together with the test 
duration). The alternative swept sinusoidal vibration test is described with an amplitude spectrum. Both types will be considered in this project and in both cases the test descriptions are determined from the mission synthesis analysis, through comparison of damage equality with measured field vibration through comparison of MRS and FDS. Comparison of MRS gives the relation in “max vibration level” for different frequencies at any short instance during the field data or vibration test. Comparison of FDS also includes the vibration “dose” as FDS increases with vibration duration even if the maximum level is not increasing

Thesis work can be subdivided into 3 main activities:

1. Literature survey and exercises to understand the theory behind mission synthesis.
2. Construct a flowchart for the mission synthesis methodology.

Build a user-friendly graphical interface (GUI) in e.g. MATLAB for mission synthesis analysis flow, 
resulting in an optimal test specification and analysis traceability.

Qualifications
We are looking for two students with interest in both structural dynamics and vibration analysis that are challenged by a clever design of an intuitive GUI. The students should be comfortable with
MATLAB. High programming skill is a prerequisite. Knowledge in random processes is a merit.

Terms
The thesis work covers 30 ECTS (academic credits) and starts in January 2025. It is possible to reduce the scope and find a way to most achievements as a single thesis worker. However, the benefit of teamwork makes a single-student project less favourable.

Contact persons at RISE
Albin Bäckstrand, +46 730772816, albin.backstrand@ri.se
Martin Olofsson, +46 706215310, martin.olofsson@ri.se

Suggested examinator at Chalmers University of Technology
Professor Håkan Johansson, hakan.johansson@chalmers.s

Welcome with your application!
Candidates are encouraged to send in their application as soon as possible but at the latest by November 10, 2024. Suitable applicants may be interviewed as soon as applications are received.