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Precision Measurement Method of Misalignment, Cracks, Contours, and Gaps in Aerospace Industry

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2012 ASEE Annual Conference & Exposition


San Antonio, Texas

Publication Date

June 10, 2012

Start Date

June 10, 2012

End Date

June 13, 2012



Conference Session

ETD Design II

Tagged Division

Engineering Technology

Page Count


Page Numbers

25.1053.1 - 25.1053.24



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Paper Authors


Devdas Shetty University of Hartford

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Professor of Mechanical Engineering and Dean of Research at the University of Hartford. Has published more than 200 papers and conference presentations and three text books.

The field of expertise of Dr. Shetty involves (1) Mechatronics System Desgn, (2) Innovative Product Design, (3) Laser Instrumentation, (4) Laser material processing, (5) Unmanned Aerial Systems, (6) Guided Projectiles, (7) Rehab System for Gait and Walking without fall, (8) Engineering education and (9) ABET accreditation.

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Claudio Campana University of Hartford

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Claudio Campana is a Research Engineer at the Engineering Applications Center and Adjunct Professor of mechanical engineering in the College of Engineering Technology and Architecture at the University of Hartford, West Hartford, Conn. He holds a master's of engineering degree in mechanical engineering from the University of Hartford and a bachelor's of science degree in mechanical engineering from Boston University. His areas of research include computer-aided design and manufacturing, online inspection/supervision of manufacturing process, and mechatronics design and instrumentation.

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Precision Measurement Method of Scratches, Cracks, Contours and Gaps in Aerospace IndustryPrecise measurement of surface defects is of critical importance in parts manufactured for theaerospace industry. The measurement of different characteristics of the testing samples arepresented in this paper. They are measurement of micro scratches, cracks, contours and gaps. Theinstrumentation setup for them measurement of the above parameters included laser source,collimators, imaging and vision acquisition system, three axis (xyz) stage, graphicalprogramming and computerized image analyzer.For measurement of the major geometrical dimensions of scratches and cracks such as theirdepths and widths a laser optical system is proposed. Here a low power (2mW) Helium-Neon(HeNe) laser source, which is well coherent and monochromatic, has been used in all of thedifferent types of measurements. Due to relatively high wavelength of the red photons irradiatedfrom the HeNe laser source, the incident laser beam will posses very high level of reflectivityand negligible penetration. These two circumstances will significantly increase the measurementaccuracy. It is well known that such characteristics of the laser ray as its reflectivity and itspenetration depend on also the testing materials’ chemical composition as well as its surfaceconditions. The detecting sample may be either pure metal or its alloys. Here the sample’ssurface is considered as a finished one possessing with some scratches and cracks.A methodology for non-contact measurement of radius of curvature on the finished surface ofmanufactured parts is presented in this paper. Unique optical methods including a line laser and abacklight are explored. In each case, a light source illuminates the features to be measured andseveral sets of high-contrast images are produced. The advantage for using this type of laser isthat it generates low energy red photons having about two to three electron-volt energy andpossessing perfect reflectivity. The low energy photons have negligible low penetration.In addition, a hybrid approach consisting of laser based triangulation, photogrammetry and edgedetection techniques has been investigated to measure inner surfaces of parts that have limitedaccess, especially where human presence is impossible. The system is capable of detecting andmeasuring misalignments, gaps, inclinations as well as surface variations such as cracks anddents. The system employs the accuracy and speed of measurement of triangulation systems andcombines these with the mobility and cost effectiveness of photogrammetry and edge detectiontechniques. In addition to gap and alignment offset inspections, the methodology and theinstrument enables angle measurements, detailed surface texture examinations and otherinspections needed to be done inside assemblies with narrow openings, with its compact body.Graduate and undergraduate students from the Electrical and Mechanical EngineeringDepartment at the College of Engineering were involved in research, development and practicaltesting of the measurement system used for detection of the finishing surface defects such asscratches, cracks, contours and gaps.

Shetty, D., & Campana, C. (2012, June), Precision Measurement Method of Misalignment, Cracks, Contours, and Gaps in Aerospace Industry Paper presented at 2012 ASEE Annual Conference & Exposition, San Antonio, Texas. 10.18260/1-2--21810

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