The idealized geometrical elements of a tube bend as opposed to the physical regions of the tube bend. Related geometrical and physical terms are often used synonymously, but should be distinguished because each define fundamentally important but different aspects of the tube bend. For example:
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Line of tangency (geometry) vs. point of bend (region)
Centerline radius (geometry) vs. neutral axis (region)
Inside radius (geometry) vs. intrados (region)
Outside radius (geometry) vs. extrados (region)
