Source: http://www.google.com/patents/US5841019?dq=7222078
Timestamp: 2017-11-20 22:35:51
Document Index: 483513080

Matched Legal Cases: ['art 1', 'art 2', 'art 2', 'art 2', 'art 2', 'art 2', 'art 1', 'art 2', 'art 2', 'art 2']

Patent US5841019 - Method for non-destructive measuring compressive and tensile strengths of ... - Google Patents
This invention provides a method for direct non-destructive measuring compressive and tensile strengths of materials with negligible viscous properties and more particularly, but not exclusively, concrete, by separately measuring the duration of the compressive phase t0 t1 of an impact of a body by an...http://www.google.com/patents/US5841019?utm_source=gb-gplus-sharePatent US5841019 - Method for non-destructive measuring compressive and tensile strengths of concrete in the structure
Publication number US5841019 A
Application number US 08/892,018
Publication number 08892018, 892018, US 5841019 A, US 5841019A, US-A-5841019, US5841019 A, US5841019A
Inventors Sergey Drabrin, Yuriy Boguslavskiy
Original Assignee Drabrin; Sergey, Boguslavskiy; Yuriy
Patent Citations (11), Non-Patent Citations (2), Referenced by (16), Classifications (5), Legal Events (5)
Method for non-destructive measuring compressive and tensile strengths of concrete in the structure
US 5841019 A
This invention provides a method for direct non-destructive measuring compressive and tensile strengths of materials with negligible viscous properties and more particularly, but not exclusively, concrete, by separately measuring the duration of the compressive phase t0 t1 of an impact of a body by an impacter and the duration of the rebounding phase t1 t2 of the impact Where t0 is the time when the impacter initially contacts the body, t1 is the time when the impacter first stops moving and t2 is the time when the impacter loses contact with the body. An important feature of the test is that in the compressive phase of the impact, the body experiences small compressive damage in the contacting areas, thus providing for direct characterization of compressive and tensile strengths similar to conventional destructive testing methods.
1. A non-destructive method for measuring the compressive strength of a body constituting the resistance of the body to finite compressive deformations exceeding an elastic recoverable compressive deformation and comprising:
(a) impacting the body with an impacter having a kinetic energy immediately prior to the impacting, the kinetic energy being sufficiently large that the body undergoes compressive damage at areas where the impacter strikes the body but not be so large that the damage prevents the body from such rebounding that the impacter loses contact with the body; wherein said impacting provides pressure to said body resulting in finite compressive deformation in the impact area exceeding elastic recoverable deformation;
(b) measuring the resistance of said body to said impacting compressive deformation constituting a compressive strength of said body by measuring the duration of the compressive phase of the impact; said duration of compressive phase being the time interval that begins when the impacter touches the surface of the body and ends when the compression of the body by the impacter stops.
2. A non-destructive method for measuring the tensile strength of a body constituting the resistance of the body to finite tensile deformations exceeding an elastic recoverable tensile deformation and comprising: p1 (a) impacting the body with an impacter having a kinetic energy immediately prior to the impacting, the kinetic energy being sufficiently large that the body undergoes compressive damage at areas where the impacter strikes the body but not be so large that the damage prevents the body from such rebounding that the impacter loses contact with the body; wherein said rebounding provides tension to said body resulting in finite tensile deformation in the impact area exceeding elastic recoverable deformation;
(b) measuring the resistance of said body to said rebounding tensile deformation constituting the tensile strength of said body by measuring the duration of the rebounding phase of the impact; said duration of rebounding phase being the interval that begins when the compression of the body by the impacter stops and ends when the rebounded impacter loses contact with the body.
3. A non-destructive method for measuring the compressive and tensile strengths of a body in one act of the impact as recited in claims 1 or 2 and comprising:
(a) impacting the body with an impacter having a kinetic energy immediately prior to the impacting, the kinetic energy being sufficiently large that the body undergoes compressive damage at areas where the impacter strikes the body but not be so large that the damage prevents the body from such rebounding that the impacter loses contact with the body; wherein said impacting provides pressure to said body resulting in finite compressive deformation in the impact area exceeding elastic recoverable deformation in the compressive phase of the impact and said rebounding provides tension to said body resulting in finite tensile deformation in the impact area exceeding elastic recoverable deformation;
(b) measuring the resistance of said body to this impacting compressive deformations constituting the compressive strength of said body by measuring the duration of the compressive phase of the impact; said duration of compressive phase being the time interval that begins when the impacter touches the surface of the body and ends when the compression of the body by the impacter stops;
(c) measuring the resistance of said body to said rebounding tensile deformation constituting the tensile strength of the body by measuring the duration of the rebounding phase of the impact; said duration of rebounding phase being the time interval that begins when the compression of the body by the impacter stops and ends when the rebounded impacter loses contact with the body.
4. The steps recited in claim 1 followed by the step of calculation of the compressive strength, Sc, for a sphere-shaped impacter as: ##EQU25## where m is the mass and R is the radius of the impacter, and tc is the duration of the compressive phase.
(c)! measuring said duration of said compressive phase by measuring the amplitude of the electrical signal caused by changing of resistance between the impacter and the body, wherein said duration being the time interval that begins when the signal's amplitude just becomes different from zero and ends when this amplitude becomes approximately constant.
measuring the duration of said rebounding phase by measuring the amplitude of said electrical signal caused by changing of resistance between the impacter and the body due to rebounding of the impacter by the body, wherein said duration being the time interval that begins when said amplitude just becomes approximately constant due to end of compressive phase of the impact and ends when the amplitude becomes equal to zero.
This invention relates to the testing of compressive and tensile strengths of materials and more particularly, but not exclusively, concrete by impacting the material with an impacter that rebounds from the material as a result of the impact.
The strength of concrete is usually determined by destructive tests in which standard control specimens, such as cubes, prisms, or cylinders, are compressed until the specimens' failure which is characterized by the deformation of the specimen until cracks are developed in it. The pressure required to achieve this state of stress is used to characterize the compressive or tensile strength of the material, depending on the mode of loading. The specimens are taken off the batch when the concrete is mixed. These methods, however, indicate only the potential strength of the concrete in question since the curing conditions and the degree of compaction are major factors affecting the strength of concrete and these may be different for the tested specimen and the structure in which the batch of concrete is used.
One embodiment of the invention involves a non-destructive measuring compressive and tensile strengths of materials with negligible viscous properties in structures that does not require correlations with other materials for scaling purposes. In order to achieve this objective, an impacter with specific kinetic energy at the time of impact strikes the body. This kinetic energy should be sufficiently large that the body undergoes compressive damage at areas where the impacter strikes the body but not be so large that the damage prevents body from rebounding until the impacter loses contact with the body.
FIG. 1 is a schematic diagram of the invention's embodiment utilizing gravity for supplying the kinetic energy to the impacter.
This invention provides a method for non-destructive measuring compressive and tensile strengths of materials with negligible viscous properties and more particularly, but not exclusively concrete, by separately measuring the duration of the compressive phase of an impact of a body by an impacter and the duration of the rebounding phase of the impact.
Two methods for measuring the duration of the compressive phase of an impact are disclosed here. Both methods can be used simultaneously for verification purposes or separately. The first method measures the duration of the compressive phase by measuring the amplitude change of electrical signal developed between the impacter and the body. For this part 1 of the guiding system is made of electrically non-conducting material; part 2 of the guiding system and the impacter is made of electrically conducting material. The guiding system touches a body with its conducting part 2. The impacter is operably connected to a pole of an input terminal of an amplifier 9 by an electrically conductive cord 5. Cord 5 is fastened to the impacting body at a point close to the axis of the guiding system 1 so as to provide at most a minimum amount of disturbance to the impacter's fall. Also for that reason, the cord is made of coiled cord which expands easily without significant pull on the impacter. The conducting part 2 is connected via an electrical wire 7 to one terminal of a battery 8; the other terminal of battery 8 is connected via an electrical wire to the second pole of the input terminal of amplifier 9. The output terminal of amplifier 9 is connected via electrical cable 10 to terminal I of device 6. When the impacter is at its initial position 3 and during its fall through the guiding system but prior to the contact with the material inside part 2, electrical resistance between the impacter and part 2 is very large because air and part 1 is electrically non-conducting, thus electrical current does not go through the electrical circuit that includes terminal I of device 6, electrical cable 10, output terminal of the amplifier 9, an input pole of the terminal of the amplifier 9, cord 5, the impacter, the body inside part 2, part 2, wire 7, battery 8, the second pole of the input terminal of the amplifier 9, the electrical cable 10, and the terminal I of device 6. Therefore, the electrical signal on terminal I of 6 is equal to zero. When the impacter touches the body, the compressive phase begins (time t0). The electrical resistance between the impacter and part 2 decreases proportional to increasing contacting surface between the impacter and the body, thus the electrical current through the electrical circuit increases the electrical signal on terminal I of 6. When the impacter first stops moving, the electrical signal becomes approximately constant thus constituting the end of the compressive phase (time t1). This increase of electrical signal is shown in FIG. 2 as a time-amplitude graph produced by an impact of the aluminum sphere with the diameter of 0.0254 m and mass of 0.024 kg. The duration of compressive phase, tc. is equal to 0.10±0.005 millisecond. The concrete's compressive strength computed with formula (1) is approximately 37.8×106 N/m2 (5500 psi) which matched concrete's compressive strength measured with the conventional destructive compression method.
The second method measures the duration of the compressive phase by measuring an acoustic compressive wave caused by the impact of the impacter on the body, and by measuring a duration as the time intervals between two first two consecutive zero levels on a time-amplitude diagram of the compressive wave as shown in FIG. 3. For measuring the acoustic wave, an acoustic transducer (e.g., microphone) 11 in FIG. 1 is placed close to the place of impact at a distance less than twice the distance to any boundary of the tested structure to avoid the influence of acoustic signals reflected from the body's boundaries. At the beginning of the compressive phase, (time t1) the particles of the body start moving away from the impacter, which is accompanied by an increase of the amplitude of the compressive wave which is transformed by the transducer 11 in the increasing electric signal on the terminal IV of device 6. The compressive phase (time t0) ends when the compressing movement of the impacter and corresponding movement of body's particles ceases. This causes the decrease of amplitude of the compressive wave to zero level (time t1). For the same conditions as were discussed in the previous example, the duration of the compressive phase, tc, is equal to 0.10±0.005 msec which is approximately equal to the duration of the compressive phase measured with the first method. In this example, both methods were used simultaneously.
The time-amplitude graph of the rebounding phase of the impact of the aluminum sphere with the diameter of 0.0254 m and mass of 0.024 kg upon concrete is shown in FIG. 2. The duration of the rebounding phase, tr, is equal to 0.80±0.005 msec. Concrete's tensile strength computed with formula (2) is approximately 4.7×106 N/m2 (690 psi) which matched the concrete's tensile strength measured with conventional destructive split-cylinder test.
Derivation of Formula for Calculating the Compressive Strength
P.sub.m =0.4mR.sup.-1 t.sub.c -2                           (A.10)
U.sub.1 +U.sub.2 +U.sub.3 =U4                              (A.11)
where U1 is the kinetic energy of the rebounding sphere; U2 is the potential energy of the body in the state of finite tensile deformations; (U3 is the energy loss in the rebounding phase; and U4 is the potential energy of the body immediately prior to the rebounding. The energy U1 can be expressed as ##EQU21## The energy U2 is equal to 1/2Eeff R3-n°hn as follows from the dimensional analysis, Eeff is the secant modulus of the body in the state of finite tensile deformations exceeding elastic deformations. The energy U4 is equal to 1/2Eeff R3-n hm n. Therefore, formula (A.11) becomes: ##EQU22## By integrating formula (A.12), the pressure, Pm, can be derived as: ##EQU23## where tr is the duration of the rebounding; L=mv2 -2U3 ; and L=Eeff R3-n hm n -2U3.
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U.S. Classification 73/12.11, 73/12.09