beam profile for structural steel, for fabrication of beams and other used in structural steel
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O=l c ssaF'l n e ,\ Fqo~ I~q UQ 0:) a~ ,1<:lJSUP ·"w, T 50 1.. IN •• ". SurfaclI A 1.3 22 5.16 . Institute of Weldins (I.O.W.) Beam Profile Blook ~----------------------------------------------- This block (Figure 5.16) is designed primarily for beam profile measurement and offers eight different direct scan approaches to the target holes for 45° , 60° and 10° probes, as shown in Figure' 5. i. 7 .- There are eight more approaches by indirect (one bounce) scan for 45° probes and'six for 60° probes but none for 70° probes. The total number of useable probe positions in any case is determined by the size of the probe and the probe angle. • Figure
Transcript
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Institute of Weldins (I.O.W.) Beam Profile Blook~-----------------------------------------------This block (Figure 5.16) is designed primarily for beamprofile measurement and offers eight different direct scanapproaches to the target holes for 45° , 60° and 10° probes,as shown in Figure' 5. i. 7 .- There are eight more approachesby indirect (one bounce) scan for 45° probes and'six for60° probes but none for 70° probes. The total number ofuseable probe positions in any case is determined by thesize of the probe and the probe angle.
•
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Figure 5.18 b.
Vertioal Plane
Figure 5.18 a.
( a)
With the probe in its forward position at position b thp.bottom edge of the beam strikes the target hole while in thebackward position C the top edge of the beam strikes thp.target hole. The beam profile is then plotted as follows:Draw the probe angle with the probe index as its startingpoint. At the appropriate hole depth plot the reading ab(forward position) behind the beam axis while the reading ae(backward position) IS plotted in front of the beam axis.Repeat the procedure for holp;; at other depths and join thepoints.
The 1.5 rom target holes are sighted in succession fromsurfaces A and B of the 10 W block. For each case, theposition of the probe index corresponding to the maximumecho amplitude is marked on the block. The probe is thenmoved to and fro so that the target is swept by the beam,the extremes of displacement being reached when the positionof the probe index corresponds to a decrease of 20,dB, or10 % of the original height of the echo, from the maximumecho amplitude., These positions are marked as b tindc inFigure 5.18 with mark a representing the position of theprobe for maximum a~mplitude.
5.2.3.1 Plotting ot Beam Protile
(b) Horizontal Plane
The probe is placed on surface A or B and the maximumamplitude is obtained from the selected target ~igure5.19a). The range is'noted and a reference line is drawnacross the block marking the position of the rear edge ofthe probe. The probe is then moved away from the edge ofthe block and at right angles to it until the echo drops by20 dB. The half beam spread at this particular range(X -22 in Figure 5.19 a) is fOlmd by subtracting the 22 romdrilled depth of the hole from the distance between the edgeof the block and the beam axis (X in Figure 5.19 b). The
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5.19 c .
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probe is then placed on the opposite side of the hole and thesequence is repeated to determine the other half beam spreadwhich is equal to ( X - 22) mm in Figure 5.19 c Theprocedure is repeated for other holes and the beam spreadagainst the range is plotted as shown in Figure 5.20.
5.2.4
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5.2.5
ASHE Referenoe B100k
This block is made from the same material as that of thespecimen and contains a side drilled hole whose diameterdepends on the thickness of the specimen. A typical ASMEreference block used for the inspection of welds is shown inFigure 5.21.The block is used to construct a distance - amplitudecorrection (DAC) curve on the CRT screen by noting thechanges in echo amplitude from the hole with change inscanning distance (multiple skip), ,
Area - amplitude blocks providedifferent sizes at the same depth.the same 2" diameter round stock,
artificial flaws ofEight blocks made from
each 3 3/4'" in height
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PRACTICAL IX BEAM PROFILE IN VERTICAL AND HORIZONTAL PLANE-------------------~------------------------A. Beam Profile in Vertical Plane
1. Calibrate the time base of your flaw detector for arange of 100mm (or 200mm).
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beam profile graphequal to the depthcontact surface.
, on thedistancefre,mthe
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the echo height from t.his dri lIed hole bythe probe forwards and bac,kwardfJ. Mark theof the exit point on the block and identify it
horizontal linebelow the X-axisselected drilled
t.he probe forwards unti 1 t.he eoho heieht dropsMark the new position of the exit point on
and identify it.as "B"
,\Note that AB corrl':.spondsto the distance betweenbeam axis and thl':.trailing beam 'edge, and AC.between tbe beam axis and the leading bl':.amedge .Hence. on the basis of (12), mark out two(.on O'X' at di::,tance[; of AB andint.erf.'ectionof tbe bealliaxi.s. OZ. andline, .\l X ' .
Draw apaperof the
B. Now move the probe hackwards until the echo height againdropfJ by 20 dB. Nark the 3rd pOf;il~ionof the exit pc.;inton the block and identify it as "C" .
5. Maximiseslidingpositionas "A"
7. Move20dB.block
9. Measure the distances AB and AC 1n mm using u ruler.
3. Put. the probe on the lOW Block and direct the beamtowards any convenient dri lled hole.
4. You will most likely see a number of echoes on the CRTscreen but identify the particular one coming from yourselected hole. This identification can be easilyachieved by comparing the position of the echo with theactual beam path (i.e the distance between the exitpoint and the selected drilled hole) measured by using aruler.
6. Adjust the sensitivity (gain/attenuutor) oontrol and setthe echo height to, say. BO% of the full CRT screenheight.
2. Determine the angle and exit point. of your angle beamprobe.
13.
12.
10.
11. Draw a line. OZ. from thE< origin of the &x'is at MJ angle(as measljred anticlockwise from ~he Y·-axis) equal tothe proue anglE< det.eno1in<~dl':.urli,,"rin 2. Use theangular scale at the graph bottom for this purpose.This line will now reprE<sent the beam axis.
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270
1. Maximize th~ echo obtained from a selected hole.
B. Beam Profile in Horizontal Plane
B'C' is now the beam width in the vertical plane OXZY atthe depth 00'
271
samet.he
other holes using thebeam spread against
7. Find the beam spread forprocedure and plot thecorresponding value of Y.
4. Record the distance of the probe centre from the edge ofthe block, say-Xl
5. Find half the beam spread for thi,.;particular value of Yby subtracting 22 mm from Xl, where 22 mm is the holedepth in the lOWmm block. If a different referenceblock is used, check the hole depth using a wire, forexample a straightened paper clip.
3. Move the probe away from the edge of the block at rightangle to it.until the echo.drops by 20dB.
6. Place the probe on the other side of the hole and findthe oth~r half using steps 1 to 5
2. Record the surface distance, y, between the probe indexI and surface position of the hole, and draw a reference
line across the block marking the.rear edge of theprobe.
14. Repeat steps 3 to 13 for at least six pairs of points atdifferent depths.
15. Draw the best-fit straight line for the points on eachside of the beam.
