Device for determining changes in dimension due to temperature fluctuation

• US 7,052,174 B2
• Filed: 09/16/2004
• Issued: 05/30/2006
• Est. Priority Date: 09/16/2004
• Status: Expired due to Fees

• Current Assignee: US Army Corps of Engineers (U.S. Department Of Defense)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Korhonen, Charles J.
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): Vaughn, Megann E.
• Application Number:
  US10/941,958
• Publication Number:
  US 20060056483A1
• Time in Patent Office: 621 Days
• Field of Search: 374/7, 374 55- 57, 374/45, 374/142, 374/5, 73766-803, 738/656
• US Class Current: 374/55
• CPC Class Codes: G01N 33/383 Concrete, cement

Abstract

An apparatus for non-destructively testing the response of a specimen to temperature change. An embodiment temperature cycles a specimen, such as a wet mortar beam, dynamically measuring change in dimension and the temperature of the specimen during the cycle. Among other elements, the apparatus employs an accelerometer, a thermistor, a thermocouple, a temperature controller, linear variable differential transducers (LVDTs), an FFT device, a data logger and a heat tape controller. A typical cycle involves using liquid nitrogen to reduce the temperature in an insulated test chamber from ambient to less than −60° C. and returning to ambient by dispersing the nitrogen with a source of ambient air. Further, in select embodiments, the apparatus measures fundamental frequencies induced by a micro-hammer as measured transversely along a dimension of a specimen during the cooling-warming cycle. Also provided is a method for testing specimens using devices representative of embodiments of the present invention.

Claims

1. An apparatus for dynamically quantifying changes in dimension of a specimen caused by temperature variation, comprising:

means for simultaneously subjecting at least three like specimens to at least one cycle of cooling and warming;

means for sensing and reporting temperature to enable control thereof, said means for sensing temperature in operable communication with at least a first one of said three like specimens;

means for detecting and reporting change in at least one dimension of at least said first like specimen during said at least one cycle;

means for detecting and reporting the instantaneous temperature of at least said second like specimen during said at least one cycle;

means for impacting at least said third like specimen in order to cause vibration in said third like specimen; and

means for detecting and reporting at least the frequency of said vibration.

2. The apparatus of claim 1 in which said means for simultaneously subjecting comprises:

at least one base plate;

enclosures to include an innermost enclosure and at least one outer enclosure;

means for support in operable communication with said at least one base plate, said means for support holding said enclosures on said at least one base plate;

means for retaining said specimens, said means for retaining in operable communication with at least one of said enclosures means for insulating said at least one outer enclosure;

coolant;

at least one programmable proportional temperature controller,

wherein said controller controls the amount of air and said coolant provided to change the temperature of said innermost enclosure;

at least one thermistor in operable communication with said controller and said first one of said like specimens;

at least one needle valve in operable communication with at least said temperature controller,

wherein operation of said needle valve may be facilitated by a source of air; and

at least one insulated line in operable communication with at least said needle valve,

wherein said insulated line provides said coolant from an external source.

3. The apparatus of claim 2 in which said means for support comprises at least blocks at the corners of said at least one outer enclosure.

4. The apparatus of claim 2 in which said means for retaining comprises:

at least one biased rod disposed at each of two opposing ends of said first like specimens;

at least one roller disposed beneath each of said first and second like specimens; and

at least one fixed support disposed beneath said third like specimen.

5. The apparatus of claim 4 in which said means for retaining further comprises at least one tube in which said at least one biased rod is enclosed, each said tube in operable communication with at least one of said enclosures.

6. The apparatus of claim 5 in which said means for detecting and reporting change in dimension comprises

at least one linear variable differential transducer in operable communication with at least one said biased rod.

7. The apparatus of claim 6 further comprising at least one data logger in operable communication with at least each said transducer.

8. The apparatus of claim 7 in which said means for measuring the frequency further comprises means for measuring at least one fundamental frequency of vibration of said third like specimen.

9. The apparatus of claim 8 in which said means for measuring said at least one fundamental frequency comprises:

at least one micro-hammer disposed to contact said third like specimen at pre-specified times;

at least one FFT device in operable communication with said data logger; and

at least one accelerometer in operable communication with said FFT device and said third like specimen.

10. The apparatus of claim 7 in which said means for measuring temperature comprises at least one thermocouple, wherein said thermocouple is in operable communication with said data logger and said second like specimen.

11. The apparatus of claim 6 further comprising:

at least one heat tape power supply; and

heat tape,

wherein said heat tape is wound around said tube to maintain the temperature of each said rod near that of ambient temperature during said at least one cycle.

12. The apparatus of claim 2 in which said means for insulating comprises:

at least one said outer enclosure disposed to maintain at least one air gap between said innermost enclosure and said at least one outer enclosure; and

insulation material disposed adjacent both said air gap and at least one inner surface of said at least one outer enclosure.

13. The apparatus of claim 2 in which said coolant is liquid nitrogen.

14. A method for measuring changes in dimension of a first specimen due to temperature fluctuation, said first specimen like each of a second and third specimen, comprising:

providing an apparatus comprising;

a first detector mechanism for detecting and reporting change data correlated to change in length of said first like specimen;

a second detector mechanism for detecting and reporting data correlated to the instantaneous temperature of said second like specimen, said second detector mechanism in operable communication with said second like specimen;

a third detector mechanism for generating and detecting data correlated to instantaneous frequency of vibration of said third like specimen, said third detector mechanism in operable communication with said third like specimen;

a first control sensor for providing data to control temperature, said first control sensor in operable communication with said first like specimen;

a first support mechanism for containing said first like specimen, said first support mechanism incorporating at least one biased rod in operable communication with said first like specimen;

a second support mechanism for containing said second like specimen;

a third support mechanism for containing said third like specimen;

an innermost enclosure for enclosing said specimens and at least part of said support mechanisms;

at least one outer enclosure for enclosing said innermost enclosure, said at least one outer enclosure providing at least airspace and at least some insulation material disposed so as to create an air gap between said outer enclosure and said innermost enclosure;

at least one controller in operable communication with at least said first control sensor;

an impact mechanism in operable communication with at least said controller, said impact mechanism suitable for providing impacts to said third like specimen;

at least one mechanism for varying temperature within said innermost enclosure, said temperature varying mechanism in operable communication with at least said controller, at least said first control sensor and at least said air gap;

support blocks in operable communication with at least one said outer enclosure; and

at least one base support plate in operable communication with at least said support blocks, said controller and said mechanism for varying temperature;

at least one data logger in operable communication with at least said detector mechanisms and said controller; and

at least one FFT device in operable communication with at least said third detector mechanism and said data logger;

inserting first, second and third like specimens in said apparatus,

wherein said first like specimen is the test specimen, said second like specimen is provided for taking temperature measurements and said third like specimen is provided for taking frequency measurements;

instrumenting each of said first specimens with at least one said first detector mechanism and at least one said first control sensor;

instrumenting each of said second specimens with at least one said second detector mechanism;

instrumenting each of said third specimens with at least one said third detector mechanism;

varying the temperature of all said specimens over a pre-specified range for a pre-specified time;

striking said third specimen via said impact mechanism at pre-specified times; and

at pre-specified intervals providing data from at least said detector mechanisms and said FFT device to said data logger.

15. The method of claim 14 in which said first control sensor comprises at least one thermistor, said first detector mechanism comprises at least one linear variable differential transducer in operable communication with at least one said biased rod, said second detector mechanism comprises at least one thermocouple, and said third detector mechanism comprises at least one accelerometer for outputting data correlated to instantaneous frequency to said FFT device.

16. The method of claim 14 striking at least said third like specimen via at least one micro-hammer, said micro-hammer striking said third like specimen at pre-specified times to establish instantaneous fundamental frequencies of response in said third like specimen.

17. The method of claim 14 varying said temperature through at least one freeze-thaw cycle.

18. The method of claim 17 varying said temperature from ambient temperature to approximately −

60°

C. and returning to ambient temperature over a pre-specified period via introducing a coolant to lower temperature and ambient air to raise temperature.

19. The method of claim 14 providing said specimens as mortar beams.

20. The method of claim 19 providing said mortar beams as wet mortar beams.

21. An instrument that simultaneously subjects at least three like specimens to at least one cycle of cooling and warming to enable quantification of changes in dimension that are caused by temperature variation, said instrument comprising:

at least one base plate;

enclosures to include an innermost enclosure and at least one outer enclosure;

support structure in operable communication with said at least one base plate, said support structure restraining said enclosures on said at least one base plate;

retaining structure for said specimens, said retaining structure in operable communication with at least one of said enclosures;

insulation applied to the inside of said at least one outer enclosure, disposed to form an air gap between said insulation and said innermost enclosure;

coolant;

at least one programmable proportional temperature controller,

wherein said controller controls the amount of air and said coolant provided to said innermost enclosure;

at least one thermistor in operable communication with said controller and a first one of said like specimens;

at least one needle valve in operable communication with at least said controller,

wherein operation of said needle valve may be facilitated by a source of air; and

at least one insulated line in operable communication with at least said needle valve,

wherein said insulated line provides said coolant from an external source;

at least one temperature control sensor to enable control of temperature within said innermost enclosure, said sensor in operable communication with at least said first like specimen;

at least one first detection mechanism for detecting and reporting change in at least one dimension of at least said first like specimen;

at least one second detection mechanism for detecting and reporting the temperature of at least said second like specimen;

at least one impact device for striking at least said third like specimen in order to cause vibration in said third like specimen;

at least one third detection mechanism for detecting and reporting at least the frequency of said vibration, and

at least one data logging device in operable communication with at least said detection mechanisms.

22. The instrument of claim 21 in which said support structure comprises at least blocks at the corners of said at least one outer enclosure.

23. The instrument of claim 21 in which said retaining structure comprises:

biased rods, at least one each disposed at each of two opposing ends of said first like specimen;

at least one roller disposed beneath each of said first and second like specimens; and

at least one fixed support disposed beneath said third like specimen.

24. The instrument of claim 23 in which said retaining structure further comprises at least one tube, each said tube at least partially enclosing at least one said biased rod and in contact with at least one of said enclosures.

25. The instrument of claim 21 in which said coolant is liquid nitrogen.

26. The instrument of claim 24 in which said first detection mechanism comprises at least in part at least one liner variable differential transducer in operable communication with at least one said biased rod.

27. The instrument of claim 24 further comprising:

at least one heat tape power supply; and

heat tape,

wherein said heat tape is wound round said tube to maintain the temperature of each said rod near that of ambient temperature during each said cycle.

28. The instrument of claim 21 in which said second detection mechanism comprises at least one thermocouple, wherein said thermocouple is in operable communication with at least said data logger and said second like specimen.

29. The instrument of claim 21 in which said third detection mechanism comprises at least one detector for measuring the instantaneous fundamental frequency of vibration of said third like specimen.

30. The instrument of claim 29 in which said mechanism for measuring said fundamental frequency comprises:

at least one micro-hammer disposed to strike said third like specimen at pre-specified times;

at least one FFT device in operable communication with at least said data logger; and

at least one accelerometer in operable communication with at least said FFT device and said third like specimen.

31. The instrument of claim 21 in which said specimens are beams composed of mortar.

32. The instrument of claim 31 in which said mortar is wet mortar.