Final answer:
The flattening of a bend refers to the deformation caused by external pressure on a pipe or tube. There are industry standards that specify the maximum allowed difference in diameters at any cross section. The percentage limit is determined by engineering standards or codes.
Step-by-step explanation:
In engineering, the term 'flattening of a bend' refers to the deformation or flattening that occurs when a pipe or tube is subjected to external pressure. The difference between the maximum and minimum diameters at any cross section of the bend is called the 'ovality' or 'out-of-roundness.'
To ensure the structural integrity of the pipe or tube, there are industry standards that limit the amount of flattening or ovality allowed. In the case of external pressure, the difference between the maximum and minimum diameters should not exceed a certain percentage of the nominal outside diameter. This percentage is specified by the relevant engineering standards or codes.
For example, let's say the nominal outside diameter of a pipe is 10 inches. If the maximum difference in diameter at any cross section is limited to 5% of the nominal outside diameter, then the maximum difference in diameters should not exceed 0.5 inches (10 inches x 5%).