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 Non relevant Ultrasonic Indications can usually be identified as one of the following: Electrical Interference Interference form the transducer (search unit) Interference form the surface of the specimen Interference caused by mode conversion of the sound beam Interference caused by the shape of the specimen Interference caused by material structure Electrical interference can be caused by improper electrical connections of sound energy from the interface between the wedge and test specimen surface. In Immersion Testing, Air bubbles either on the transducer or specimen can cause reduced signal amplitude form the back surface and at times also from the front surface. Surface Interface A small amount of surface wave energy is usually transmitted in all directions around a transducer as shown below. If the transducer is near the edge of a plate, a signal may appear on the CRT.   When inspecting with shear waves, it is possible to detect a surface discontinuity with the small amo...

  Ultrasonic Testing In Ultrasonic Testing we use something called “Ultrasonic Vibrations” we must know two facts about a vibration: A vibration is a back and forth movement. A vibration is energy in motion A depression of a surface from its normal position is called a displacement. Vibrations pass through a solid material as a succession of particle displacements; this can be visualized as shown below: The structure of a material is actually many small particles or groups of atoms. These particles have normal or rest positions and can be displaced from these positions by some force, when the force is removed, the particles will tend to return to their original positions. Energy is transmitted through a solid material by a serious of small material displacements within the material. The transmission of Ultrasonic vibrations through a material is related to the elastic properties of the material. In Ultrasonic Testing a transducer made of Piezo-electric crystals is ...

 This blog will discuss types of discontinuities that can be evaluated with the ultrasonic testing in NDT method. Discontinuities can be divided into three general categories inherent, processing and service Inherent discontinuities are usually formed when the metal is molten. Inherent wrought discontinuities relate to the melting and solidification of the original ingot before it is formed into slabs, blooms and billets. Inherent cast discontinuities relates to the melting, casting and solidification of a cast article. Usually caused by inherent variables such as inadequate feeding, gating, excessive pouring temperature or entrapped gases. Processing discontinuities are usually related to the various manufacturing process such as machining, forming, extruding, rolling, welding, heat treating and plating. Service discontinuities are related to the various service conditions such as stress, corrosion, fatigue and erosion. During the manufacturing process, many d...