Vu-Con® System
Impact
Echo System for measuring the thickness and quality of concrete.
ApplicationsRoads and
Runways
Retaining
Walls
Bridge
Decks
Accurately determines concrete
thickness without drilling cores
or using similar destructive
techniques.
Quickly locates delaminations and
voids in concrete slabs & structures where access is limited to a
single side.
Rugged design for
field use.
Rapid results within
seconds at the jobsite.
Large easy to view
display for data analysis on site and in daylight.
Data can be stored
and uploaded to a PC for later analysis and inclusion in reports.
Conforms to ASTM
C-1383.
The Vu-Con® System provides the engineer with the sturdiest, most
reliable system for impact echo analysis. No moving parts and
implementation of the latest microcomputer technology has created a
system that is both sophisticated and reliable. The unit comes with a 90
mm (3.5) by 115 mm (4.5¯) graphic display screen that is easily viewed
in daylight. This allows rapid analysis of results in situ. It may
store more than 200 individual tests with time and date indication.
The
data is easily uploaded to a PC for inclusion in reports and data
analysis. Data communication takes place via the RS-232 port and Windows
compatible PC software. The unit allows the user to select sensitivity
levels to adapt to varying conditions in the field.
The James Vu-Con®System uses the impact echo method to
evaluate concrete and masonry structures. The impact echo method is
based on the use of impact generated stress waves that propagate through
the material and are reflected by both the materials external surfaces
and internal flaws.
This method can be used to make accurate
non-destructive measurements of thickness in concrete slabs and plates, and to locate internal flaws such as
honey combing,debonding and delaminations. It can measure thickness, locate cracks, voids and other
defects in masonry structures where mortar bonds the masonry together.
Finally, the impact echo method is not affected by the presence of steel
reinforcing bars.
The method works by creating a short
duration mechanical impact on the surface of the material under
examination. This is typically performed by small steel balls that
produce low frequency stress waves that propagate through the material
and reflect off of other surfaces and internal flaws back to the surface
used for testing (See diagram below) By recording and analyzing the vibration from the mechanical
impact at the surface, thickness and other physical features (referred
to in the preceding paragraph) can be determined. The advantage of using
an impact rather than other more classic ultrasonic techniques is the
low frequency and the long wave length of the stress waves that are
produced. Low frequency stress waves treat concrete and masonry as a
single elastic homogeneous material as they propagate through.
Diagram
of Vu-Con™ System Test.
The Vu-Con®
Analyzer provides the engineer with the sturdiest, most reliable system
for impact echo analysis. No moving parts and implementation of the
latest microcomputer technology has created a system that is both
sophisticated and reliable. The unit comes with a 90 mm (3.5¯) by 115 mm
(4.5¯) graphic display screen that is easily viewed in daylight. This
allows rapid analysis of results in situ. It may store more than 200
individual tests with time and date indication.
The data is easily
uploaded to a PC for inclusion in reports and data analysis. Data
communication takes place via the RS-232 port and Windows compatible PC
software. The unit allows the user to select sensitivity levels to adapt
to varying conditions in the field.
The
built-in menu system has provisions for determining all the parameters
for the material under test. The thickness menu allows rapid display of
the frequency spectra of an impact. Peaks are automatically found and
highlighted for a given test. The velocity menu, for use with the dual
transducer set, facilitates determination of the stress wave speed in a
given material. This allows the operator to gather and analyze data
quickly and easily in the field. Finally, the user can select from
multiple gain settings for various material dimensions. There is also a
selection of multiple data sampling rates and an adjustment for
different trigger levels which help the user produce accurate and
reliable results
The resulting
amplitude waveform from the transducer can be displayed for analysis
both with respect to time and frequency. This is illustrated by graphs.
The time domain waveform can be described as a sum of a series of
different frequency waveforms.
This allows the user to:
Analyze the
dominant frequencies of vibration found from the impact and determine
thickness as well as distance to features within the material.
Compare
the frequency spectra to obtain indications of homogeneity of the
concrete.
Calculate the rate of decay of the vibrations to glean
information regarding the sub-grade.
The Vu-Con™ System represents the latest technology in concrete ultrasonic
analysis, allowing the engineer to see¯ into the concrete surface.
Display of Frequency Spectra for a single test.
Display of time domain waveform.
Instr. Weight: | 6 lbs. (2.75Kg) |
Ship Weight: | 17 lbs.
(7.7 Kg) |
Dimensions:
| 4.5 x 8.5¯ x 10.5¯ (114.3mm x
223.5mm x 267mm)
|
Freq. Range: | 50khz |
Impactor Sizes: | 6, 8, 10, 12, 14, & 16mm |
Gain Selection: | .5, 1,
1.5, 25, 50 |
Battery: | 12 Volt. 4-10 hours continuous use |
Display: | 320 by 240; backlit for
daylight use |
Storage: | 200 plus readings |
Software: | Windows compatible 9x/me
32MB Ram, 100MB Ram |
Temperature: | 0Ā° - 50Ā°C |
Q. What
Types of Stress Waves are Introduced
into a Structure by Impact?
A. If transient stress waves
are introduced into a concrete structure by mechanical impact at a point
on the surface, as shown in Fig. 1, the stress waves include a
dilatational (P-) wave and a distortional (S-) wave, which propagate
into the structure along hemispherical wave
fronts, and a Rayleigh (R-) wave, which propagates along the
surface of the structure. Among the stress waves, the P-wave propagates
fastest and the R-wave propagates slowest. The S-wave propagates
slightly faster than the R-wave. In an infinite isotropic elastic solid,
the P-wave speed, Cp, and the S-wave speed, Cs, are related to the
Young's™ modulus of elasticity, E, Poisson™ ratio, v, and the density,
p. For a Poisson™ ratio of 0.2, the R-wave speed is 92% of the S-wave
speed and 56% of the P-wave speed. The motion of a particle disturbed by
the P-wave is parallel to the direction of wave propagation while the
particle motion disturbed by the S-wave is
perpendicular
to the wave propagation direction as schematically illustrated in Fig.
1.
The particle
motion disturbed by the R-wave is elliptical. The vertical disturbance
of a particle on the impact surface caused by the R-wave arrival is much
larger than that caused by the S-wave and P-wave arrivals.
