Laser generated ultrasound by material ablation using fiber optic delivery

Hopko, Sandra Nowland; Ume, I. Charles

doi:10.1016/s0041-624x(98)00046-8

Cited by 26 publications

(8 citation statements)

References 16 publications

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“…Ultrasonic sensors [11][12][13][14][15][16][17] are widely used to determine the boundaries of the liquid and metal in the weld pool.…”

Section: Ultrasonic Sensing Methodsmentioning

confidence: 99%

“…At Georgia Institute of Technology, Ume leaded the development of non-contact ultrasonic penetration sensors based on laser-phased array techniques [13,14]. Recently, in order to overcome the contact requirement of the ultrasonic sensing method, various non-contact ultrasonic sensing methods have been developed, such as laser ultrasonic sensing [11,17], electromagnetic acoustic transducer (EMAT) ultrasonic sensing [12], and laser-EMAT ultrasonic sensing [16], etc.…”

Section: Ultrasonic Sensing Methodsmentioning

confidence: 99%

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Real-Time Measurement of Three Dimensional Weld Pool Surface in GTAW

Zhang¹,

Liu²,

Zhang³

2012

Welding Processes

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“…Ultrasonic sensors [11][12][13][14][15][16][17] are widely used to determine the boundaries of the liquid and metal in the weld pool.…”

Section: Ultrasonic Sensing Methodsmentioning

confidence: 99%

Section: Ultrasonic Sensing Methodsmentioning

confidence: 99%

Real-Time Measurement of Three Dimensional Weld Pool Surface in GTAW

Zhang¹,

Liu²,

Zhang³

2012

Welding Processes

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“…A fiber phased array contained in a copper ring is used to direct the laser onto the welding sample. 21 The fiber phased array is composed of three line sources. Each of the three sources consists of seven silica-silica fibers with a 400 m core.…”

Section: A Experimental Methods and Proceduresmentioning

confidence: 99%

Three-dimensional ray tracing of laser ultrasound for weld penetration sensing

Ume

2004

The Journal of the Acoustical Society of America

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The time-of-flight ͑TOF͒ method is an ultrasonic nondestructive testing ͑NDT͒ technique. The TOF of an ultrasonic wave can be correlated to weld penetration depth, and hence weld quality. Changes in material properties due to temperature gradients will cause ultrasonic speed to vary during welding, which causes a curved propagation path. A ray tracing algorithm is required in order to study how ultrasound propagates within a weld sample. In this paper, a three-dimensional ͑3-D͒ ray tracing algorithm based on Fermat's principle is presented. First, ray equations are derived using the calculus of variation. Then, a numerical algorithm is developed to solve the derived ray equations and obtain the curved propagation path. This algorithm includes finite element analysis ͑FEA͒ to obtain the transient temperature distribution during the welding and shooting method to solve the boundary value problem. After the curved ray path is obtained, the TOF can be found by integrating the time variable along the ray path. An analytical relationship between the TOF and penetration depth can be established by repeating the ray tracing algorithm for different penetration depths. Experimental measurements of TOF have been performed, and this data is to be used to validate the numerical results.

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“…A theoretical model for ablative and thermoelastic laser generation of ultrasound has been developed by various researchers. [6][7][8][9][10] The strength of generated ultrasound versus propagation angles away from the generation point is called a directivity pattern. The directivity pattern for ultrasound generated from one laser point source is different for ablatively generated shear waves, ablatively generated longitudinal waves, thermoelastically generated shear waves, and thermoelastically generated longitudinal waves.…”

Section: Introductionmentioning

confidence: 99%

Effects of Broadband Laser Generated Ultrasound on Array Gain

Kita

Ume

2006

AIP Conference Proceedings

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The array gain model for laser phased arrays was derived using an assumption that ultrasound from each array source interferes with each other. However, laser generated ultrasound is broad band and ultrasound from each array source may not interfere with each other. A theoretical model called the frequency modulation of phased arrays (FMLPA) was developed and experimentally verified for use when ultrasound from each array member does not interfere with each other. It was experimentally verified that current array gain equations still apply when ultrasound from array members interfere with each other. The FMLPA can be used to create new techniques for measuring weld penetration depth, crack location, and dimensions of objects.

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Laser generated ultrasound by material ablation using fiber optic delivery

Cited by 26 publications

References 16 publications

Real-Time Measurement of Three Dimensional Weld Pool Surface in GTAW

Real-Time Measurement of Three Dimensional Weld Pool Surface in GTAW

Three-dimensional ray tracing of laser ultrasound for weld penetration sensing

Effects of Broadband Laser Generated Ultrasound on Array Gain

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