Failure of Materials and Components

Learning Outcomes

Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

• Analyse complex service failure problems and apply the correct fracture mechanics approach
• Propose appropriate lifing methodologies for service applications
• Identify appropriate testing approaches to evaluate materials' service performance
• Relate these failure micromechanisms to optimised materials microstructures
• Assess likely service failures for a range of service conditions
• Describe failure micromechanisms occurring for a range of service conditions
• Critically analyse the factors affecting component/structure performance

Full CEng Programme Level Learning Outcomes

Having successfully completed this module you will be able to:

• Course content and final exam directly address aspects of materials selection, manufacturing choices, inspection methods, service environment and risk, in relation to different failure processes. Engineering judgement and reaching conclusions is specifically covered and assessed via the coursework, requiring the students to make engineering recommendations for novel manufacture of engineering components in the light of academic and industrial literature.
• The coursework is a manufacturing case study, requiring consideration of potential use of additive manufacturing for specific engineering applications: candidates are given information to assess failure performance for AM (and non-AM) processing, and they are asked to provide a critical analysis of AM use (identifying favourable and unfavourable failure characteristics).
• Throughout the module the multi-disciplinary nature of failure processes requires various mathematical representations, physical science and engineering reality to be discussed, and then tested in the exam. Knowledge of the forefront is introduced via analysis methods (including specialised FE approaches, novel 3D assessment of structure/fractography) and application areas (e.g. failure analysis in the context of additive manufacturing).
• Students are taught a range of fracture mechanics principles and analysis methods (inc linear elastic fracture mechanics (LEFM), long and short fatigue crack lifing, Weibull statistics), with clear indications of limitation (e.g. detailed validity criteria linked to LEFM, LEFM accommodation in short fatigue crack analysis). These points are tested within exam questions.
• Implications of uncertainty are addressed, and quantification methods discussed, for: fatigue lifing of parts/structures, and statistical treatment of failure in intrinsically brittle systems (particularly engineering ceramics), which are tested by exam questions.
• The coursework is a manufacturing case study, where the students are provided with contemporary literature (Journal review article and ATI/InnovateUK technical report), from which they must identify information that falls within their understanding (from the module and their prior engineering understanding) and perform cross-referencing to open literature (the service condition of certain parts), to then address three specific manufacturing problems.
• Risk of loss of life in failure events is discussed via an in-room class exercise, to highlight societal perceptions of risk for engineering and non-engineering activities (e.g. air travel, sports activities, pregnancy).

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

• Why components/structures can give unsatisfactory service
• In-service performance of commercial materials and be able to extend this to the performance of composite systems
• What can be done to improve the in-service performance of components/structures, and thus promoting sustainable development through extending service lifetimes
• Issues involved in predicting the fatigue strength of a component, bolted structure and welded Structure

Subject Specific Practical Skills

Having successfully completed this module you will be able to:

• Assess fractographic images in some detail
• Predict how a component/structure would behave under given service conditions
• Predict the fatigue strength of a component with a complex geometry, a bolted structure and a welded structure.

Transferable and Generic Skills

Having successfully completed this module you will be able to:

• Analyse key factors influencing materials failure: evaluate complex materials/structural failure situations and propose appropriate engineering solutions
• Work as materials specialist within a design context

• Introduction to the course: excessive deformation, introduction to composite classes (3 lectures).
• Micromechanisms of failure in materials (3 lectures).
• Fracture and fracture mechanics, toughening mechanisms in ceramics and composites, probabilistic failure assessment (6 lectures).
• Fatigue: total life and damage tolerant approaches, persistent slip band formation, stage I and II crack growth, closure mechanisms, long and short crack behaviour, fatigue in ceramics, composites and hybrid laminates (5 lectures).
• Performance of components and structures subjected to mechanical stresses.The influence of design and manufacturing processes on service performance will be examined and the importance of defects and residual stresses associated with manufacturing processes emphasised. A detailed case study on the performance of joints will be undertaken to demonstrate how the fatigue performance of welded and mechanically fastened joints is related to the quality and design of the joint (6 lectures).
• Performance of components and structures subjected to environmental effects. Corrosion, stress corrosion cracking and hydrogen induced failures will be analysed and the methods of preventing these failure modes by correct alloy selection, stainless steels, design and the use of surface coatings, e.g. paints, metallic coatings discussed. (4 lectures).
• The performance of materials at elevated temperatures will be considered: high temperature fatigue, creep, oxidation, high temperature corrosion and liquid metal embrittlement will be discussed. (3 lectures).
• Industrial guest lecture (1 lecture).
• Mid-course classroom quiz (‘pub quiz) (1 lecture).
• Revision lectures (2 lectures).

Teaching methods include:

• Lectures which develop the themes described in this module. Skeleton notes are given out at the start of the course, which means you only have to note down the key points during the lecture, but still have a full set of notes to work from.
• Additional research review papers are provided to give an overview of the themes of the course.
• Case study forms part of the lectures.
• Industrial guest lecture addresses industrial context and applications.

Learning activities include

• Access to past paper exam question bank
• Small group self-marked classroom quiz (‘pub quiz’)
• Individual work on question sheets supported by surgery sessions & revision lectures
• Revision questions set by both lecturers which are intended for small group self-study teams

Formative

This is how we’ll give you feedback as you are learning. It is not a formal test or exam.

Quiz

• Assessment Type: Formative
• Feedback: Classroom quiz feedback is via group discussion of model answers.
• Final Assessment: No
• Group Work: No

Summative

This is how we’ll formally assess what you have learned in this module.

Referral

This is how we’ll assess you if you don’t meet the criteria to pass this module.

Repeat

An internal repeat is where you take all of your modules again, including any you passed. An external repeat is where you only re-take the modules you failed.