Gas forming a V-shape aluminum sheet into a trough of saddle-contour

A sheet metal trough of aluminum alloys is manufactured by gas-forming process at 500 °C. The product with slope walls is of ∼1.2 m long and ∼260 mm opening width, comprising two conical sinks at two ends. The depth of one sink apex is ∼350 mm, which results in the depth/width ratio reaching 1.4. To form such a complex shape with high aspect ratio, a pre-form of V-shape groove is prepared prior to the gas-forming work. When this double concave trough is turned upside down, the convex contour resembles the back of a twin hump camel. The formability of this configuration depends on the gas pressurization rate profile, the working temperature, material's micro-structure, as well as pre-form design. The latter point is demonstrated by comparing two aluminum alloys, AA5182 and SP5083, with nearly same compositions but very different grain sizes.