MEng Aerospace Engineering

Predicting the rate of in-service deterioration of materials in engineering infrastructure and industrial plant is of significant benefit to the economy and the society. This assists designers in selecting appropriate materials and exploitation engineers in planning maintenance outages.  Further, any justified decision for life extension of existing structures could yield substantial savings.  The knowledge and skills for making life assessment therefore become of ever increasing importance to the major industries – power, aerospace, automotive and manufacturing.

This unit on Structural Integrity covers a set of methodologies used to assess the life of engineering structures or their components at design and exploitation stage. The first aim of this unit is to equip the students with the necessary skill set for life assessment: the current industrial practice for calculating sub-critical crack growth (fatigue) and fitness-for-service (failure assessment diagram). The second aim is to develop further their engineering judgement competence by firm understanding of the uncertainties in such assessments and practicing individual analyses and recommendations.

This unit provides an advanced foundation for analysis of structures containing defects (measured or postulated) that reflects the current engineering practice in this area.  It builds upon prior knowledge of engineering materials to further the students’ understanding on how materials’ constitutions control their mechanical properties, focusing on in-service deterioration and failure. This is used to introduce the theory of linear elastic fracture mechanics (LEFM) and the new, for the students, property of fracture toughness. Plasticity in metals is introduced to explain the elastic-plastic conditions ahead of a defect and to formulate the plastic collapse failure mechanism.  This theoretical background is then put together to equip the students with a contemporary tool for integrity assessment – the Failure Assessment Diagram, as defined in R6 procedure “Assessment of the Integrity of Structures Containing Defects”.  Details of applying the procedure are provided, including how to account for residual stress effects in assessments.  The growth of small defects via mechanical fatigue, i.e. repetitive loading, is covered in a second part of the course. This provides the students with several approaches to fatigue life assessment, specifically stress-life (S-N) approach, strain-life (e-N) approach, and LEFM approach for fatigue crack propagation.

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