Vibrations and Fatigue in Mechanical Structures

Aim

Many failures in mechanical structures are caused by material fatigue. Fatigue may appear when a structure is loaded by a cyclic load, and in many cases this load may come from resonance vibrations of the structure. Thus, knowledge of the vibrational behaviour of mechanical systems is a prerequisite in understanding the fatigue phenomenon. The course Vibrations and Fatigue in Mechanical Structures will provide understanding and knowledge about these phenomena. After the course, the student should be familiar with the following items that are dealt with in the course:

the physical behaviour of vibrating mechanical systems,

theories used when analysing practical vibrational problems,

influence of different structural parameters on the vibrational behaviour of structures, material fatigue phenomena, and

theories used when analysing fatigue problems. Course content On vibrations: Fundamental relationships describing the behaviour of vibrating mechanical systems. Equations of motion for vibrating systems. Influence of mass, stiffness, and damping. Resonances and its consequences for the mechanical system. Vibrations of discrete systems and continuous systems. On fatigue: Fundamental relationships describing the fatigue phenomenon. High-cycle fatigue and low-cycle fatigue. The Wöhler diagram and the Haigh diagram. Safety factors. Damage accumulation, the Palmgren-Miner rule. Load spectra. The Ramberg-Osgood material model. Fatigue life models according to Manson-Coffin. Influence of stress concentration. Fracture Mechanics. Teaching and working methods Lectures, tutorials, laboratory work, and problem solving. Examination UPG1Laboratory work and home assignments1.5 creditsU, GTEN1A Written Examination4.5 creditsU, 3, 4, 5Grades for examination modules are decided in accordance with the assessment criteria presented at the start of the course. Grades Four-grade scale, LiU, U, 3, 4, 5 Other information About teaching and examination languageThe teaching language is presented in the Overview tab for each course. The examination language relates to the teaching language as follows: If teaching language is “Swedish”, the course as a whole could be given in Swedish, or partly in English. Examination language is Swedish, but parts of the examination can be in English.If teaching language is “English”, the course as a whole is taught in English. Examination language is English.If teaching language is “Swedish/English”, the course as a whole will be taught in English if students without prior knowledge of the Swedish language participate. Examination language is Swedish or English depending on teaching language.OtherThe course is conducted in such a way that there are equal opportunities with regard to sex, transgender identity or expression, ethnicity, religion or other belief, disability, sexual orientation and age.The planning and implementation of a course should correspond to the course syllabus. The course evaluation should therefore be conducted with the course syllabus as a starting point. The course is campus-based at the location specified for the course, unless otherwise stated under “Teaching and working methods”. Please note, in a campus-based course occasional remote sessions could be included. Department Institutionen för ekonomisk och industriell utveckling Course literature Additional literatureCompendiaDahlberg, T, Material fatigue, Kompendium

Content

On vibrations: Fundamental relationships describing the behaviour of vibrating mechanical systems. Equations of motion for vibrating systems. Influence of mass, stiffness, and damping. Resonances and its consequences for the mechanical system. Vibrations of discrete systems and continuous systems. On fatigue: Fundamental relationships describing the fatigue phenomenon. High-cycle fatigue and low-cycle fatigue. The Wöhler diagram and the Haigh diagram. Safety factors. Damage accumulation, the Palmgren-Miner rule. Load spectra. The Ramberg-Osgood material model. Fatigue life models according to Manson-Coffin. Influence of stress concentration. Fracture Mechanics.