| 摘要 |
A tubular metal blank to be formed into a vehicle steering column or other stress-subjectable corrugated tubular product is first deformed by radially inwardly moving dies or other forming devices to produce a plurality of substantially equally spaced shallow annular depressions separated by slightly raised crowns. The blank is then axially compressed to form and close a plurality of convolutions under a selected load within predetermined limits and to a selected closed length within predetermined limits, the variations being dependent on the strength of the material. Finally, the blank is stretched using a selected stretch pressure within predetermined limits and to a selected expanded length within predetermined limits, expanding the convolutions to a plurality of generally similar spaced corrugations. When the end product is used as an energy absorbing tube, the above method minimizes the variations from a selected compressive axial load which would be required to collapse the finished column.
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