The advantages and disadvantages of ultrasonic waves in detecting industrial defects
The ultrasonic waves are used to detect the presence of flaws in the form of cracks , blowholes , porosity in metallic pipes as those used in conveying the natural gas or parts of nuclear reactors .
The cracks , holes , air bubbles and welding defects can be detected by passing ultrasonic waves through the material to be examined , and measuring the time internal of the reflected beam , so, flaws in the metal block can be determined .
The defects in manufactures can be detected through the variation in the intensity ( amplitude of vibration ) of the reflected waves .
The ultrasonic waves can be used in detecting the industrial defects as the waves reflected from the areas which contain air bubbles ( the defects in welding ) have a different intensity than those reflected from well welded areas .
Ultrasonic Testing (UT) uses high frequency ultrasonic waves to detect the surface breaking and internal imperfections , It measures the material thickness and it determines acceptance or rejection of a test object based on a reference code or standard .
The sound waves travel through a given medium at a specific speed or velocity , and in a predictable direction , When they encounter a boundary with a different medium , they will be reflected or transmitted according to simple rules , This is the principle of physics that underlies ultrasonic flaw detection.
The velocity of sound wave varies depending on the medium through which it is traveling , It is affected by the medium’s density and elastic properties , And different types of sound waves will travel at different velocities .
When an ultrasonic wave is passed from one medium to another, some energy is reflected and the remaining energy is transmitted , so , it is very important to understand how effectively ultrasonic waves pass from one medium to another .
The advantages of ultrasonic waves in detecting industrial defects
Ultrasonic testing has high sensitivity , high penetrating power that allows the detection of flaws deep in the part , it permits the detection of extremely small flaws .
It has greater accuracy than other nondestructive methods in determining the depth of internal flaws and the thickness of parts with parallel surfaces .
Ultrasonic testing can estimate the size , the orientation , the shape and the nature of defects , it is not dangerous on the operations or on the nearby personnel and it has no effect on the equipment and the materials in the vicinity .
The disadvantages of ultrasonic waves in detecting industrial defects
It is very important to know that ultrasonic testing is manual operation which requires careful attention by experienced technicians .
Extensive technical knowledge is required for the development of inspection procedures , and the parts that are rough , irregular in shape , very small or thin , or not homogeneous are difficult to inspect .
Inspected items must be water resistant , when using water based couplants that do not contain rust inhibitors , and couplants are needed to provide effective transfer of ultrasonic wave energy between the transducers and parts being inspected unless a non-contact technique is used .