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Ultrasonic Sensors
Ultrasonic sensors radiate a short ultrasonic pulse in the 20kHz-500kHz range. The pulse bounces off a local object and the echo is detected, often by the transducer which lkaunched the pulse. Operation depends on the transmission of air and the sonic reflectivity of the target, which is a function of the orientation and material of its surfaces. Ultrasonic s is quite useful in sea water, which attenuates E and H fields but transmits sound well. Soft materials such as cloth and foam do not reflect well. (Capacitive Sensors, Baxter, p.68)

Swift Cup Test
In the sweep cup test, a deep-drawn cup is used to determine the limiting draw ratio of blank size to cup diameter. It is obtained with a 50mm diameter flat bottom punch and a draw die appropriate for the thickness of the specimen. A circular blank is cut to a diameter smaller than the expexted draw limit. Lubrication is provided by two oiled polyethylene disks, one on each side of the blank. The blank is drawn to maximum punch load, which occurs before the cup is fully formed. Successively larger blanks are drawn until one fractures before being drawn completely through the die. The diameter of the largest blank that can be drawn without fracturing, divided by cup diameter, determines the limiting draw ratio. (Aluminum and Aluminum Alloys, ASM Specialty Handbook, p.232)

Stretcher Bending
This process for sheet metal forming uses a machine known as a stretcher bender, wherein a sheet metal formed section such as an angle, channel, or Z section is pulled against a radiused die block to accurately form structural frame sections to a specified radius of curvature. The frame structures of rockets and aeorospace vehicles which have a single radius of curvature are formed on the stretcher bending machine. This is the only cost effective method known for producing such sheet metal frame parts quickly and accurately on a relatively simple machine. (Electromechanical Design Handbook, 3rd Edition, Walsh, p.11.12)

Turret Punch
Turret punch contains a turret with variety of punches that can execute various sized holes nonstop. The tool change is very rapid since same size cuts are made on a sheet that is moved back and forth below the punch.
Most sheet metal punching is done on CNC sheet metal machining center with limited contouring and forming abilities. These machines are extremely accurate and very fast, and perform rapid tool changes. (Industrial Design, 2nd Edition, Lesko, p.63)