Development of a Virtual Instrument for Immersion Type Ultrasonic Inspection with a Computer Controlled Multi-Axis Motion Controller
The Pulse Echo (PE) technique is a widely used ultrasonic non destructive testing technique to test materials by analyzing ultrasound echoes reflected from flaws and discontinuities. In conventional PE technique, called contact type PE, an ultrasonic transducer is in constant contact with a test piece, transmitting and receiving ultrasonic signals from the test specimen. The inherent shortcomings of PE are the need for; uniform couplant conditions, the ultrasonic transducer to remain in contact with the test object throughout the scan and a limitation to scan regular surfaced objects only. This paper provides for extending a system initially developed for contact type PE, to perform Immersion Testing (IT) which is a contactless pulse-echo inspection method with the probe and test piece separated by a predetermined volume of water of certain thickness. A computer controlled 3-axis transducer position manipulator (motion frame) is constructed for assistance in conducting automated tests. The efficacy of immersion testing relies on the precise control of the motion of transducer. The existing immersion type motion controllers along with dedicated data acquisition and analysis system are quite expensive and are beyond the affordability of smaller ultrasonic labs. Hence the proposed system including the motion frame and Data Acquisition Unit (DAQ) can serve as a competent, low-cost and reliable IT system benefitting several small scale industries and labs.
Ultrasonic Testing Machines with Robot Mechanics – A New Approach to CFRP Component Testing
For a long time, Ultrasonic Testing Machines for aircraft components have been built with almost 100% custom made mechanics (gantry or bridge design) to match customer needs. This design comes with several disadvantages like price, delivery time or lack of flexibility. This article illustrates an alternative approach to Testing Machine design for the Aerospace industry and describes in detail the advantages of robot based mechanics together with different types of coupling mechanics and shows the abilities of today’s state of the art machine design to face CFRP component testing challenges. Non destructive testing of large aircraft parts or engine components made of CFRP or sandwich materials by using the ultrasonic method is a challenge for every manufacturer of testing machines. These aircraft components, which can easily have a length of 20 meters and more, require leading edge technology to answer the requirements of the inspection task in terms of part handling, mechanics’ accuracy, ultrasonic capabilities and data processing. 1 General Layout of an Ultrasonic Testing Machine Basically, an ultrasonic testing machine consists of the mechanical part, ultrasonic hardware and computer peripherals. Mechanics can be divided into the part handling components to position and fix the part under test, coupling mechanics to provide proper and stable ultrasonic signals and scan mechanics like a bridge, robots or linear manipulators. The electronics comprise one or more ultrasonic transducers appropriate to the actual application and ultrasonic hardware for pulse generation, phased array beam forming, receiving and signal processing. Last but not least, powerful computer hardware is needed for scan path generation, data evaluation and storage. 2nd International Symposium on NDT in Aerospace 2010 Mo.4.A.3 Licence: http://creativecommons.org/licenses/by-nd/3.0 1 [1] Exemplary basic layout of an ultrasonic testing machine 2 Coupling Mechanics State of the art UT testing machines for the inspection of large CFRPand Sandwich components are mainly based in two types of coupling methods: "Squirter" and "Bubbler". Immersion Technique is of course also being used and provides most stable coupling conditions, but due to restrictions in water basin size, immersion technique is not applicable in many cases. Therefore, only first two mentioned systems will be described in detail in this article. 2.1 Squirter Systems A squirter system uses a water jet to guide the ultrasonic pulse into the part under test. The Squirter technique is always used together with through transmission. [2] Squirter nozzles for through transmission testing
Description of roughness profiles by separating the random and periodic components
Abstract The probability that it is not possible to obtain a significant description of roughness profiles composed of random and periodic components by using statistical methods is discussed. It is shown that the random and periodic components can be separated by using the frequency spectrum and the autocorrelation function of the profile. The physical significance of the separate components is discussed and it is shown that it is possible to describe a long crested surface by a single profile using these components The method of separating the random and periodic components allows a parametrical description of the roughness profile to be given. It is then possible to use these parameters to calculate a synthetic signal sign with the same basic properties as the measured profile.