Abstract: An inertia friction welding process comprises: a) providing first and second work pieces to be welded together; b) imparting motion to the first work piece relative to the second work piece thereby imparting kinetic energy to the first work piece relative to the second work piece; c) applying a predetermined force to move one or both of the first and second work pieces towards the other to create an upset length in the work pieces; characterized by; d) measuring the rate of motion of the first work piece relative to the second work piece; e) determining a predicted final upset length from the said measured rate of relative motion and said forth; f) comparing the predicted final upset length with a desired final upset length; g) adjusting the aforesaid kinetic energy to achieve substantially the desired final upset length.

Abstract: A boss 10 is welded onto a thin casing 12. The casing 12 is held in a fixture (not shown) with a backing plate 20 adjacent surface 18. The backing plate 20 is located on the opposite side from the surface 14 onto which the boss 10 is to be welded. By using a backing plate 20 the depth of the weld zone, h, can exceed the casing thickness, t. The backing plate 20 is sacrificial and is released by removing the central part of the boss 10 where it has been bonded to the plate 20. Provided that the diameter D1 of the central part of the boss 10 exceeds the diameter of the bonded region D2 the plate 20 is released from the casing 12.

Abstract: An inertia friction welding process comprises: a) providing first and second work pieces to be welded together; b) imparting motion to the first work piece relative to the second work piece thereby imparting kinetic energy to the first work piece relative to the second work piece; c) applying a predetermined force to move one or both of the first and second work pieces towards the other to create an upset length in the work pieces; characterised by; d) measuring the rate of motion of the first work piece relative to the second work piece; e) determining a predicted final upset length from the said measured rate of relative motion and said forth; f) comparing the predicted final upset length with a desired final upset length; g) adjusting the aforesaid kinetic energy to achieve substantially the desired final upset length.

Abstract: A boss 10 is welded onto a thin casing 12. The casing 12 is held in a fixture (not shown) with a backing plate 20 adjacent surface 18. The backing plate 20 is located on the opposite side from the surface 14 onto which the boss 10 is to be welded. By using a backing plate 20 the depth of the weld zone, h, can exceed the casing thickness, t. The backing plate 20 is sacrificial and is released by removing the central part of the boss 10 where it has been bonded to the plate 20. Provided that the diameter D1 of the central part of the boss 10 exceeds the diameter of the bonded region D2 the plate 20 is released from the casing 12.