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An angle beam is a beam of concentrated, directional sound waves used to test welds and metal industrial components for faults or small cracks perpendicular to the surface of the piece being tested. Tiny cracks in welds or in metal may be invisible to the naked eye, but an angle beam assembly can detect such faults. Angle beams are important tools for testing many important industrial components including machinery, pipes, welds of all types, and machined or forged metal components.
Testing equipment for using angle beams consists of a hand-held apparatus made up of two parts, a wedge and a transducer. The wedge is designed to hold the transducer at an angle relative to the surface of the piece being tested. The transducer is a powered device that generates and projects the sound waves into the piece. Most angle beam assemblies are constructed so as to allow different wedges to be attached to the transducer. Each different wedge aims the beam at different angles for a variety of different testing conditions.
Angle beam assemblies rely on Snell's Law. This law allows for the calculation of the angle at which a sound wave will bounce when striking a boundary between two materials of differing density. The angle beam fires the beam into the piece being tested and detects any return beams, which indicate cracks or faults perpendicular to the surface of the test piece.
Transducers are specialized; they must be set at a specific frequency depending on the material to be tested. The most common types are for steel testing. Other transducers are manufactured for the testing of materials such as aluminum and titanium. A transducer designed for testing one type of material is not suitable for testing another material, as each is calibrated for the specific sound conductivity of only one substance.
Wedges for angle beam transducer assemblies are sometimes manufactured with a curve in order to give more accurate readings while testing materials with curved surfaces. They can be either convex or concave, with the axis of the curve running either perpendicular or parallel to the line of the transducer beam. Different designs allow testing the inside or outside curves of pipes or other equipment.
Angle beam transducer assemblies also exist for testing other materials, like plastics, high-density ceramics, and metals like copper and lead. Dual-beam transducers are sometimes used for higher accuracy testing results while testing certain materials like stainless steel. High-temperature angle beam wedges are available for specialized testing under high-temperature conditions.