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312   Chapter Nine


             ■ Conversely, restore consumable parts of an object directly during
               operation.
             Principle 35: Parameter changes
             ■ Change an object’s physical state (e.g., to a gas, liquid, or solid).
             ■ Change the concentration or consistency.
             ■ Change the degree of flexibility.
             ■ Change the temperature.

             Principle 36: Phase transitions.  Use phenomena occurring during
             phase transitions (e.g. volume changes, loss or absorption of heat).
             Principle 37: Thermal expansion
             ■ Use thermal expansion (or contraction) of materials.
             ■ If thermal expansion is being used, use multiple materials with
               different coefficients of thermal expansion.
             Principle 38: Strong oxidants
             ■ Replace common air with oxygen-enriched air.
             ■ Replace enriched air with pure oxygen.
             ■ Expose air or oxygen to ionizing radiation.
             ■ Use ozonized oxygen.
             ■ Replace ozonized (or ionized) oxygen with ozone.
             Principle 39: Inert atmosphere
             ■ Replace a normal environment with an inert one.
             ■ Add neutral parts, or inert additives to an object.
             Principle 40: Composite materials. Change from uniform to com-
             posite (multiple) materials.

             Example 9.12  Using 40 Principles and Contradiction Table to Improve
             Wrench Design  When we use a conventional wrench to take off an over-
             tightened or corroded nut (as shown in the picture), one of the problems is
             that the corners of the nut are getting concentrated load so they may wear
             out quickly. We can reduce the clearance between wrench and nut, but it
             will be difficult to fit in. Is there anything we can do to solve this problem
             (Darrel Mann 2002)?
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