Shape Memory Workpiece Expansion With Staged Thermal Shaping

The patent divides the single-step expansion process into multiple sequential expansion steps with intermediate cooling phases. The workpiece is expanded in stages (e.g., first expansion to an intermediate diameter, then cooling, then second expansion to final diameter), which segments the total deformation into manageable portions that prevent locally excessive elongations while achieving the desired final geometry.

The patent implements a periodic cycle of heating, expanding, cooling, and reheating steps. Each cycle consists of heating the workpiece to shaping temperature, performing an expansion step, then cooling to an intermediate temperature before the next expansion. This periodic action allows precise control over deformation and environmental conditions at each stage while completing the overall shaping process efficiently.

The patent utilizes the workpiece's own thermal energy and shape memory properties to facilitate the process. During intermediate cooling phases, the workpiece naturally retains heat and can partially maintain its expanded state without active heating, reducing the energy required for subsequent heating steps. The workpiece essentially serves itself by utilizing its inherent thermal mass and shape memory characteristics.

The patent segments the cooling process into multiple stages rather than applying rapid single-step cooling. After each expansion step, the workpiece is cooled to an intermediate temperature (not immediately to room temperature), allowing gradual thermal adjustment. This segmented cooling approach prevents thermal shock damage while maintaining process efficiency through the structured multi-step protocol.