36 Phase Transitions
Use phenomena occurring during phase transitions. (e.g. volume changes, loss of absorption of heat etc.)
■ Latent heat effects in melting/boiling
■ Soak rocks in water, then freezing causes water to expand –thus opening fissures in rock, making it easier to break
■ Heat pumps use the heat of vaporization and heat of condensation of a closed thermodynamic cycle to do useful work
■ Volume expansion during water-to-steam transition
■ Superconductivity
37 Thermal Expansion
A. Use thermal expansion (or contraction) of materials
■ Fit a tight joint together by cooling the inner part to contract, heating the outer part to expand, putting the joint together, and returning to equilibrium
■ Metal tie-bars used to straighten buckling walls on old buildings
■ Thermal switch/cut-out
■ Shape memory alloys/polymers
■ Shrink-wrapping
B. Use multiple materials with different coefficients of thermal expansion
■ Bi-metallic strips used for thermostats, etc
■ Two-way shape memory alloys
■ Passive blade tip clearance control in gas turbine engines
■ Combine materials with positive and negative thermal expansion coefficients to obtain alloys with zero (or specifically tailored) expansion properties –e.g. cerro - trualloy used in the mounting and location of fragile turbine blade components during manufacture operations
38 Accelerated Oxidation
A. Replace common air with oxygen-enriched air
■ Scuba diving with Nitrox or other non-air mixtures for extended endurance
■ Place asthmatic patients in oxygen tent
■ Nitrous oxide injection to provide power boost in high performance engines
B. Replace enriched air with pure oxygen
■ Cut at a higher temperature using an oxy-acetylene torch
■ Treat wounds in a high pressure oxygen environment to kill anaerobic bacteria and aid healing
■ Control oxidation reactions more effectively by reacting in pure oxygen
C. Expose air or oxygen to ionising radiation
■ Irradiation of food to extend shelf life
■ Use ionised air to destroy bacteria and sterilise food
D. Use ionised oxygen
■ Speed up chemical reactions by ionising the gas before use
■ Separate oxygen from a mixed gas by ionising the oxygen
E. Replace ozonised (or ionised) oxygen with ozone
■ Oxidisation of metals in bleaching solutions to reduce cost relative to hydrogen peroxide ■ Use ozone to destroy micro-organisms and toxins in corn
■ Ozone dissolved in water removes organic contaminants from ship hulls
39 Inert Atmosphere
A. Replace a normal environment with an inert one
■ Prevent degradation of a hot metal filament by using an argon atmosphere
■ MIG/TIG welding
■ Electron beam welding conducted in a vacuum
■ Vacuum packaging
■ Foam to separate a fire from oxygen in air
B. Add neutral parts, or inert additives to an object
■ Naval aviation fuel contains additives to alter flash point
■ Add fire retardant elements to titanium to reduce possibility of titanium fire
■ Add foam to absorb sound vibrations – e.g. hi-fi speakers
40 Composite Materials
Change from uniform to layered/composite (multiple) structures
■ Aircraft structures where low weight and high strength are required
■ Composites in golf club shaft
■ Concrete aggregate
■ Glass-reinforced plastic
■ Fibre-reinforced ceramics
■ Hard/soft/hard multi-layer coatings to improve erosion properties
TRIZ for Engineers: Enabling Inventive Problem Solving, First Edition. Karen Gadd.
© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd. ISBN: 978-0-470-74188-7
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