1. Lecture 26 – Causes of failure
Prescribed Text:
Ref 1: Higgins RA & Bolton, Materials for Engineers and Technicians, 5th edition, Butterworth Heinemann. ISBN:
Readings:
Callister: Callister, W. Jr. and Rethwisch, D., 2610, Materials Science and Engineering: An Introduction, 8th Edition, Wiley, New York. ISBN
Ashby 1: Ashby, M. & Jones, D., 2611, Engineering Materials 1: An Introduction to Properties, Applications and Design, 4th edition, Butterworth-Heinemann, Oxford UK. IBSN:
Ashby 2: Ashby, M. & Jones, D., 2611, Engineering Materials 2: An Introduction to Microstructures and Processing, 4th edition, Butterworth-Heinemann, Oxford UK. IBSN:
Lecture (2 hrs):
Ref 1, Ch 1: Engineering materials;
Ref 1 Ch 2: Properties of materials.
Laboratory 1 (2 hrs): Hardness test
Callister: Ch 1, 2, 26-26
Ashby 1: Ch 1, 2
Ashby 2: Ch 1 1

2. Causes of failure Reference Text Section
Higgins RA & Bolton, Materials for Engineers and Technicians, 5th ed, Butterworth Heinemann
Ch 26
Reference Text
Section
Engineering Materials and Processes

3. 26.2 Causes of failure (Higgins 26.2)
Overstressing (abuse)
Fatigue (Alternating loads)
Creep (High temp)
Sudden loads (earthquake, storm, accident)
Expansion (or contraction)
Thermal cycling (hot/cold stresses)
Degradation (Environmental)
Engineering Materials and Processes

4. 26.2 Causes of failure (Higgins 26.2)
Types of fracture surfaces
Ductile failure with metals
Brittle failure with metals
Fatigue failure with metals
Failure with polymers
Failure with ceramics
Failure with composites
Engineering Materials and Processes

5. 26.3 Non-destructive testing (Higgins 26.3)
The detection of surface cracks and flaws
Penetrant methods
Engineering Materials and Processes

6. 26.3 Non-destructive testing (Higgins 26.3)
Magnetic particle methods
Engineering Materials and Processes

7. 26.3 Non-destructive testing (Higgins 26.3)
Acid pickling methods
Engineering Materials and Processes

8. 26.3 Non-destructive testing (Higgins 26.3)
The detection of internal defects
X-ray methods
Gamma-ray methods
Engineering Materials and Processes

9. 26.3 Non-destructive testing (Higgins 26.3)
Ultrasonic testing:
Principle of ultrasonic testing. LEFT: A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo.
RIGHT: A defect creates a third indication and simultaneously reduces the amplitude of the back wall indication. The depth of the defect is determined by the ratio D/Ep
Engineering Materials and Processes

10. 26.4 Degradation of metals by oxidation (Higgins 26.4)
Attack by sulphur
Engineering Materials and Processes

11. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
Electrolytic corrosion is like a
Battery.
Engineering Materials and Processes

12. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
The Electrochemical (or Galvanic) Series
Engineering Materials and Processes

13. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
Cladding of metal sheets
Engineering Materials and Processes

14. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
Cladding of metal sheets
Engineering Materials and Processes

15. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
Rusting of iron and steel
Engineering Materials and Processes

16. 26.6 The protection of metal surfaces
(Higgins 26.6)
Painting
Stove-enamelling
Coating the surface with another metal
Hot dipping
Spraying
Sherardising
Electroplating
Cladding
Protection by oxide coatings
Engineering Materials and Processes

17. 26.6 The protection of metal surfaces
(Higgins 26.6)
Metals and alloys which are inherently corrosion-resistant
Galvanic protection
Engineering Materials and Processes

18. 26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
Stress corrosion
Engineering Materials and Processes

19. 26.7 Stability of plastics (Higgins 26.7)
Weathering of plastics materials
Perishing of rubbers
Stress cracking and crazing of polymers
Stability to solvents
Engineering Materials and Processes

20. 26.8 Preservation of timber (Higgins 26.8)
Insect pests
Fungus attack
Engineering Materials and Processes

21. 26.9 Service life (Higgins 26.9)
• External loading levels, rate of loading (impact loading), frequency
of loading (fatigue), duration of loading (creep).
• Material property degradation (corrosion).
• Defects in the form of cracks, porosity (in castings), cavities (in
welds) introduced during manufacturing.
• Conditions under which used, e.g. temperature, temperature cycling,
humidity, chemicals, contact with other materials.
• Bad design features such as the presence of notches, sharp corners,
small holes, surface roughness.
• Lack of, or inappropriate, maintenance.
Engineering Materials and Processes

22. Videos
Joining Metals
Sheppard, Phil. Bendigo, Vic. : Classroom Video, c2006. DVD (29 min.).
An introduction to the methods of joining metals, including riveting and fusion and non-fusion methods of welding.
Mt Druitt College Library: DVD 671.5/JOIN
Joining Metals Notes (pdf)
Recommended Viewing: All sections.
h ttp://
S how this website on screen. Will be using this later.
Engineering Materials and Processes 22

23. Resources. Wikipedia: Welding Ashby diagrams
h ttp://
S how this website on screen. Will be using this later.
Engineering Materials and Processes 23

24. Glossary Sacrificial anode Galvanising Electro-negativity
Stress corrosion
Electrolysis
Oxidation
Ductile/brittle failure
Fatigue failure
Engineering Materials and Processes

25. QUESTIONS: Joining of Materials
Higgins Ch26, Newell, Timmings, Sheedy, Callister, Ashby
Define all glossary terms
(a) Explain what is meant by the term corrosion. (b) List three essential conditions for corrosion to occur. (c) Describe how an anode and cathode can be formed. (d) Describe how corrosion can be controlled or prevented.
Briefly describe the different types of corrosion listed below:
(a) uniform (general) corrosion
(b) galvanic corrosion
(c) crevice corrosion
(d) stress corrosion
(e) corrosion fatigue
(f) de-alloying (selective leaching), for example de-zincification
(g) high temperature (dry) oxidation corrosion
Briefly outline the processes by which plastics suffer degradation
Explain the differences between corrosion resistance of platinium and titanium. What other metals would fall into each of these two groups?
Describe ways to counter galvanic corrosion in PhotoVoltaic systems.
Engineering Materials and Processes 25