Apparatus and method for determining the stress and strain in pipes, pressure vessels, structural members and other deformable bodies

• US 5,065,331 A
• Filed: 05/27/1986
• Issued: 11/12/1991
• Est. Priority Date: 05/18/1981
• Status: Expired due to Term

• Current Assignee: Reginald I. Vachon, William F. Ranson
• Original Assignee: Reginald I. Vachon, William F. Ranson
• Inventors: Ranson, William F., Vachon, Reginald I.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/886,747
• Time in Patent Office: 1,995 Days
• Field of Search: 364/506-508, 364/550, 364/552, 364/525, 364/551.01, 358/106, 358/107, 73/800, 356/32, 356/35.5, 356/345, 356/354, 356/355, 356/359, 356/360
• US Class Current: 356/35.5
• CPC Class Codes: G01B 11/164 by holographic interferometry
• CPC Class Codes: G01L 1/24 by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet

Abstract

An apparatus and method of measuring and analyzing the deformation of deformable bodies which includes a source of an electromagnetic or accoustical signal emitted from a deformable body which can be received and analyzed so that the signal can be analyzed when the body is in a reference state with the signal being subsequently analyzed when the body is undergoing or has undergone deformation with the reference state signal and deformation state signal being compared and analyzed to provide significant information with respect to various characteristics of the body.

Claims

1. An apparatus for determining stress and strain associated with a body, said apparatus comprising:

means associated with said body to cause said body to produce a speckle pattern;

data receiving means for sensing a reference speckle pattern and a succeeding speckle pattern produced by the body when undergoing deformation, said data receiving means further serving to digitize signals provided by said reference and succeeding speckle patterns; and

computation means for mathematically analyzing the amplitude of said digitized signals to determine displacement between the speckle pattern produced by the body in a reference state and the speckle pattern produced by the body when deformed and thereby to determine stress and strain associated with said body.

2. The apparatus for determining stress and strain associated with the body as defined in claim 1, wherein said means to produce a speckle pattern includes means emitting a receivable signal from the body.

3. An apparatus for determining stress and strain associated with a body, said apparatus comprising means associated with said body to cause said body to produce a speckle pattern, data receiving means for sensing a reference speckle pattern and a succeeding speckle pattern produced by the body when undergoing deformation, said data receiving means further serving to digitize signals provided by said reference and succeeding speckle patterns;

and computation means for mathematically analyzing the amplitude of said digitized signals to determine displacement between the speckle pattern produced by the body in a reference state and the speckle pattern produced by the body when deformed and thereby to determine stress and strain associated with said body, said means to produce a speckle pattern including means emitting a receivable signal from the body, said data receiving means including a video camera and digitizer to form a digitized speckle pattern, said computation means including a computer for producing a light intensity surface by grayscale interpolation from said digitized signals.

4. The apparatus as defined in claim 3 wherein the means associated with the body to cause the body to produce a speckle pattern includes means producing a signal in a measurable spectrum from the body.

5. An apparatus as defined in claim 4 wherein the body is an artery subject to deformation in response to blood pressure during diastole and systole portions of blood flow through the artery with the reference speckle pattern and succeeding speckle patterns, respectively, indicating soft and hard plaque areas in the artery and providing a change in the quantitative value of the dimension of an artery as a ratio to an original quantitative value of the dimension of the artery over a given time interval, said computation means indicating elasticity of the artery by determining displacement between the reference speckle pattern of the artery during the diastole portion of blood flow and the succeeding speckle pattern of the artery during the systole portion of blood flow.

6. The method of correlating speckle pattern displacement produced by a body undergoing deformation, said method including the steps of utilizing means associated with said body to produce a reference speckle pattern and a succeeding speckle pattern when the body has been deformed, obtaining said reference and succeeding speckle patterns from a transducer means and a data digitizer by respectively digitizing a speckle pattern produced by said body when in a reference state to form a signal in said data digitizer in response to said speckle pattern when the body is in said reference state and said succeeding speckle pattern produced by said body when undergoing deformation to form a signal in said data digitizer in response to said speckle pattern when the body is in a deformed state, receiving said signals in computation means for correlating displacement of said speckle patterns.