Flexible Ultrasound Patch Ultrasonic sensors Makes damage detection in complex structures easier

- Jun 04, 2019-



Recently, the research team at the University of California, USA, developed a flexible flexible patch that makes it easier to perform ultrasound imaging in a variety of profiled structures, such as engine parts, turbines, reactor elbows, and railroads. Traditional ultrasonic devices are often difficult to detect.


background

Around us, sound waves are everywhere. However, the range of acoustic frequencies that can be heard by the human ear is (20 Hz to 20 KHz). "Ultrasonic" means a sound wave with a frequency higher than 20K Hz, which cannot be heard by the human ear.


what is ultrasound


The ultrasonic direction is good, the penetration is strong, the energy is concentrated, and the transmission distance in the water is long. It can be used in ranging, speed measurement, cleaning, welding, crushing stone, sterilization, etc. It has many applications in medicine, military, industry, agriculture and other fields.

Ultrasonic technology is a hot technology area that deserves attention, and there are also a variety of innovations in the field. I have previously introduced some classic cases about ultrasonic technology, let us review:


1) The research results of the University of Bristol in the United Kingdom show that in the future, wearable devices such as smart watches can use ultrasonic imaging to sense hand movements.


wearable devices such as smart watches can use ultrasonic imaging to sense


2) The University of Sussex in the United Kingdom turns the palm into a human-computer interactive display device by transmitting ultrasonic waves on the back of the hand and detecting tactile signals on the palm of the hand.


ultrasonic waves on the back of the hand and detecting tactile signals


3) The University of California, Riverside (UCR) has developed a skull implant made of ceramic material to help doctors send ultrasound into the brain and use ultrasound to treat brain diseases.


send ultrasound into the brain and use ultrasound to treat brain diseases


4) The University of Missouri has developed a safer laser device that combines ultrasound technology with laser light to deliver laser light into the skin tissue through direct contact.


combines ultrasound technology with laser light to deliver laser light into the skin tissue


In addition to the above cases, ultrasonic testing is also a non-essential use of the technology. Ultrasonic testing is a conventional non-destructive testing method using ultrasonic technology. It uses the difference in acoustic properties of the material and its defects to examine the internal defects of the material by the ultrasonic wave propagation reflection and the energy variation of the penetration time.


In the picture below: On a construction site, technicians are using ultrasonic phased array equipment to test for defects in pipe welds. The detection device consists of a frame with a magnetic wheel that is brought into contact with the pipe by a spring. The wet area is an ultrasonic couplant that allows sound waves to penetrate the pipe wall.


Ultrasonic testing is a conventional non-destructive testing method using ultrasonic technology


The general principle of ultrasonic testing is shown in the figure below. Left: The probe sends ultrasonic waves to the inside of the test material. There are two logos: the first one from the probe and the second from the interface. Right: The defect creates a third marker and at the same time reduces the amplitude of the reflected wave. The depth of the defect is determined by D/Ep.


principle of ultrasonic sensor testing


However, the base of a conventional ultrasonic probe is flat and rigid, so that it does not maintain good contact when scanning curved, wavy, angled, and other irregular surfaces. According to Sheng Xu, a professor of nanoengineering at the Jacobs School of Engineering at the University of California, San Diego (the author of the paper on innovative research to be introduced below), this is very limited because non-planar surfaces are very common in everyday life. .


Francesco Lanza di Scalea, a professor of structural engineering at the University of California, San Diego, and co-author of the paper, said: "The bends, corners and other structural details happen to be the most critical areas of failure. These are high-stress areas. Traditional rigidity Planar probes are not ideal for imaging internal defects in these areas."


In order to make the probe and the surface of the object better in contact with the test, gel, oil, water and the like are usually used. But too many of these substances will filter out some signals. In addition, conventional ultrasonic probes are also very bulky and cannot detect these hard-to-reach parts.


If a car has a crack in a hard-to-reach area, the inspector needs to disassemble the entire engine and immerse the part into the water to obtain a complete three-dimensional image.


Innovation


However, a new device overcomes the shortcomings of current ultrasonic devices and can be applied to objects that are not completely flat surfaces. Relevant research results were published in the journal Science Advances on March 23.


Recently, a research team led by engineers at the University of California, USA, developed a flexible, flexible patch that enables ultrasound imaging in a variety of profiled structures such as engine parts, turbines, reactor elbows, and railroad tracks. It's easier, and traditional ultrasound equipment is often difficult to detect. This ultrasonic patch is a more convenient and versatile tool for inspecting deep defects and damage to machine parts and building components.


ultrasonic devices and can be applied to objects that are not completely flat surfaces


technology


The flexible ultrasound probe developed by the University of California team works on shaped surfaces without the need for water, gel or oil. It is a thin patch with a silicone elastomer pattern with an "island bridge" structure. Fundamentally, this is an array of small electronic components (islands), each connected to each other by a spring-like structure (bridge). The island contains electrodes and piezoelectric transducer devices. When the current passes, it produces ultrasonic waves. The bridge is a spring-like elastically curved copper wire that allows the patch to adapt to non-planar surfaces without affecting its electronic function.


Flexible ultrasonic transducer array design schematic


Flexible ultrasonic transducer array design schematic


Flexible ultrasonic patches do not affect their electronic function when stretched and twisted.


Flexible ultrasonic patches do not affect their electronic function when stretched and twisted


The researchers tested the device on an aluminum block with a wavy surface. There is a defect of 2 to 6 cm below the surface of the aluminum block. The researchers placed the probe at different points on the surface of the waveform, collected the data, and reconstructed the image using a custom data processing algorithm. The probe can image holes and cracks that are two millimeters wide inside the aluminum block.


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