Two-dimensional optical measurement techniques based on optic birefringence effects

A new, non-perturbing optical measurement technique was developed to characterize medical ultrasound fields generated by High Intensity Focused Ultrasound (HIFU) transducers using a phenomenon called ‘acoustic streaming’. The acoustic streaming velocity generated by HIFU transducers was measured experimentally using Digital Particle Image Velocimetry (DPIV). The streaming velocity was then calculated numerically using the finite-element method. An optimization algorithm was developed to back-calculate acoustic power and intensity field by minimizing the difference between experimental and numerical streaming velocities. The intensity field and acoustic power calculated using this approach was validated with standard measurement techniques. Results showed that the inverse method was able to predict acoustic power and intensity fields within 10% of the actual value measured using standard techniques, at the low powers where standard methods can be safely applied. This technique is also potentially useful for evaluating medical ultrasound transducers at the higher power levels used in clinical practice.

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A Comparative Study on Hydraulic Bulge Testing and Analysis Methods

ASME 2008 International Manufacturing Science and Engineering Conference, Volume 1 ◽

10.1115/msec_icmp2008-72238 ◽

2008 ◽

Cited By ~ 4

Author(s):

Eren Billur ◽

Muammer Koc¸

Keyword(s):

Flow Stress ◽

Optical Measurement ◽

Measurement Techniques ◽

Material Behavior ◽

Biaxial Stress ◽

Dome Height ◽

Bulge Test ◽

Analysis Methods ◽

Bulge Testing ◽

Hydraulic Bulge

Hydraulic bulge testing is a material characterization method used as an alternative to tensile testing with the premise of accurately representing the material behavior to higher strain levels (∼70% as appeared to ∼30% in tensile test) in a biaxial stress mode. However, there are some major assumptions (such as continuous hemispherical bulge shape, thinnest point at apex) in hydraulic bulge analyses that lead to uncertainties in the resulting flow stress curves. In this paper, the effect of these assumptions on the accuracy and reliability of flow stress curves is investigated. The goal of this study is to determine the most accurate method for analyzing the data obtained from the bulge testing when continuous and in-line thickness measurement techniques are not available. Specifically, in this study the stress-strain relationships of two different materials (SS201 and Al5754) are obtained based on hydraulic bulge test data using various analysis methods for bulge radius and thickness predictions (e.g., Hill’s, Chakrabarty’s, Panknin’s theories, etc.). The flow stress curves are calculated using pressure and dome height measurements and compared to the actual 3-D strain measurement from a stereo optical and non-contact measurement system ARAMIS. In addition, the flow stress curves obtained from stepwise experiments are compared with the ones from above methods. Our findings indicate that Enikeev’s approach for thickness prediction and Panknin’s approach for bulge radius calculation result in the best agreement with both stepwise experiment results and 3D optical measurement results.

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A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

Metrology and Measurement Systems ◽

10.1515/mms-2016-0028 ◽

2016 ◽

Vol 23 (3) ◽

pp. 461-480 ◽

Cited By ~ 36

Author(s):

Sze-Wei Khoo ◽

Saravanan Karuppanan ◽

Ching-Seong Tan

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Strain Measurement ◽

Surface Deformation ◽

Optical Measurement ◽

Image Correlation ◽

Two Dimensional ◽

Full Field ◽

Computation Efficiency ◽

Dimensional Measurements

Abstract Among the full-field optical measurement methods, the Digital Image Correlation (DIC) is one of the techniques which has been given particular attention. Technically, the DIC technique refers to a non-contact strain measurement method that mathematically compares the grey intensity changes of the images captured at two different states: before and after deformation. The measurement can be performed by numerically calculating the displacement of speckles which are deposited on the top of object’s surface. In this paper, the Two-Dimensional Digital Image Correlation (2D-DIC) is presented and its fundamental concepts are discussed. Next, the development of the 2D-DIC algorithms in the past 33 years is reviewed systematically. The improvement of 2DDIC algorithms is presented with respect to two distinct aspects: their computation efficiency and measurement accuracy. Furthermore, analysis of the 2D-DIC accuracy is included, followed by a review of the DIC applications for two-dimensional measurements.

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