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ENMAT101A Engineering Materials and ProcessesAssociate Degree of Applied Engineering (Renewable Energy Technologies)Lecture 26 – Causes of failure
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Causes of failure
EMMAT101A Engineering Materials and Processes
Reference Text Section
Higgins RA & Bolton, 2610. Materials for Engineers and Technicians, 5th ed, Butterworth Heinemann
Ch 26
Reference Text Section
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26.2 Causes of failure (Higgins 26.2)
EMMAT101A Engineering Materials and Processes
Overstressing (abuse)Fatigue (Alternating loads)Creep (High temp)Sudden loads (earthquake, storm, accident)Expansion (or contraction)Thermal cycling (hot/cold stresses)Degradation (Environmental)
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26.2 Causes of failure (Higgins 26.2)
EMMAT101A Engineering Materials and Processes
26.2.1 Types of fracture surfacesDuctile failure with metalsBrittle failure with metalsFatigue failure with metalsFailure with polymersFailure with ceramicsFailure with composites
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26.3 Non-destructive testing (Higgins 26.3)
EMMAT101A Engineering Materials and Processes
26.3.1 The detection of surface cracks and flawsPenetrant methods
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26.3 Non-destructive testing (Higgins 26.3)
EMMAT101A Engineering Materials and Processes
Magnetic particle methods
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26.3 Non-destructive testing (Higgins 26.3)
EMMAT101A Engineering Materials and Processes
Acid pickling methods
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26.3 Non-destructive testing (Higgins 26.3)
EMMAT101A Engineering Materials and Processes
26.3.2 The detection of internal defectsX-ray methodsGamma-ray methods
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26.3 Non-destructive testing (Higgins 26.3)
EMMAT101A Engineering Materials and Processes
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
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26.4 Degradation of metals by oxidation (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
Oxidation26.4.1 Attack by sulphur
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
Electrolytic corrosion is like aBattery.
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
26.5.1 The Electrochemical (or Galvanic) Series
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
26.5.2 Cladding of metal sheets
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
26.5.2 Cladding of metal sheets
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
26.5.3 Rusting of iron and steel
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26.6 The protection of metal surfaces (Higgins 26.6)
EMMAT101A Engineering Materials and Processes
26.6.1 Painting26.6.2 Stove-enamelling26.6.3 Coating the surface with another metalHot dippingSprayingSherardisingElectroplatingCladding26.6.4 Protection by oxide coatings
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26.6 The protection of metal surfaces (Higgins 26.6)
EMMAT101A Engineering Materials and Processes
26.6.5 Metals and alloys which are inherently corrosion-resistant26.6.6 Galvanic protection
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26.4 Degradation of metals by electrolytic corrosion (Higgins 26.4)
EMMAT101A Engineering Materials and Processes
26.5.4 Stress corrosion
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26.7 Stability of plastics (Higgins 26.7)
EMMAT101A Engineering Materials and Processes
26.7.1 Weathering of plastics materials26.7.2 Perishing of rubbers26.7.3 Stress cracking and crazing of polymers26.7.4 Stability to solvents
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26.8 Preservation of timber (Higgins 26.8)
EMMAT101A Engineering Materials and Processes
26.8.1 Insect pests26.8.2 Fungus attack
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26.9 Service life (Higgins 26.9)
EMMAT101A Engineering Materials and Processes
• External loading levels, rate of loading (impact loading), frequencyof loading (fatigue), duration of loading (creep).• Material property degradation (corrosion).• Defects in the form of cracks, porosity (in castings), cavities (inwelds) 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.
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EMMAT101A Engineering Materials and Processes
Videos
Joining MetalsSheppard, 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/JOINJoining Metals Notes (pdf)Recommended Viewing: All sections.
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EMMAT101A Engineering Materials and Processes
Wikipedia: Welding
Resources.
Ashby diagrams
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Glossary
EMMAT101A Engineering Materials and Processes
Sacrificial anodeGalvanisingElectro-negativityStress corrosionElectrolysisOxidationDuctile/brittle failureFatigue failure
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QUESTIONS: Joining of MaterialsHiggins Ch26, Newell, Timmings, Sheedy, Callister, Ashby
1. Define all glossary terms 2. (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.
3. 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
4. Briefly outline the processes by which plastics suffer degradation5. Explain the differences between corrosion resistance of platinium and titanium.
What other metals would fall into each of these two groups?6. Describe ways to counter galvanic corrosion in PhotoVoltaic systems. http://
www.civicsolar.com/node/10621
EMMAT101A Engineering Materials and Processes