Mechanical Behaviour of Materials in Service

Bachelor in Mechanical Engineering or in related areas.

In theoretical lessons the content is presented through the use of both the board and PowerPoint slides. In theoretical-practical classes typical exercises are solved. 

The main objective of this unit is to understand the concepts and acquire the procedures about the fundamental tools in design and control of mechanical components failure, taking into account their service conditions. The application of these concepts and tools covers a wide area of application, namely, in aerospace, aeronautic and naval industries, in the design of transport vehicles and pressure vessels, and also in several other components and structures subjected to static or dynamic loadings.

1. Main rupture and failure modes in mechanical components.

Excessive elastic deformation, plastic deformation, ductile rupture, wear, stress corrosion, brittle fracture, creep, fatigue.

2. Materials fatigue

High-cycle fatigue. Low-cycle fatigue. Behaviour of metals to cyclic plastic deformation. Deformation-life curves. Life prediction of notched components.

3. Linear elastic fracture mechanics

Griffith’s theory. Rupture modes. Definition of the stress intensity factor. Plastic zone at the crack tip. Experimental determination of KIc. Applications of Linear Elastic Fracture Mechanics.

4. Stress corrosion

Introduction. Stress corrosion tests. da/dt-K curves. Application of the da/dt-K curves.

5. Application of fracture mechanics to fatigue

Introduction. da/dN-DK curves. Mean stress effect. The crack closure phenomenon. Main crack propagation laws. Variable amplitude loading crack growth  .

6. Creep and stress relaxation

Long duration creep tests. Stress relaxation and recovery. Elementary problems in creep design.

NAO

• FERREIRA, J. A. M., BORREGO, L. P. (2023). Fadiga de Materiais, Textos Pedagógicos, ISEC.
• BORREGO, L. P. (2008). Complementos da Fadiga de Materiais, Textos Pedagógicos, ISEC.
• BORREGO, L. P. (2008). Aplicação da Mecânica da Fractura à Fadiga, Textos Pedagógicos, ISEC.
• BORREGO, L.P ., BRANCO, R. S. (2008). Colectânea de Problemas Teórico-Práticos, ISEC.
• BRANCO, C. M., FERNANDES, A. A. CASTRO P. T. (1986). Fadiga de Estruturas Soldadas, Fundação Calouste Gulbenkian.
• HERTZBERG, R. W. (1987). Deformation and Fracture Mechanics of Engineering Materials, Ed. John Wiley Sons.            ISBN O-471-61722-9.
• DOWLING, N. (1999). Mechanical behavior of Materials: Engineering Methods for Deformation, Fracture and Fatigue, Prentice-Hall. ISBN 0-13-905-720-X.
• ELLYN F. (1997) Fatigue Damage, Crack Growth and Life Prediction, Chapman & Hall. ISBN 0-412-59600-8.