6. To Perform Bending Test on Wooden Beam (26-11-2008) Apparatus 10 ton Buckton UTM, Deflection Gauges, Wooden Beam, Measuring Tape
Objective •
To study the bending or flexural behavior of the beam
•
To determine the Modulus of Elasticity and Modulus of Rupture of the wood.
Related Theory Shear Force The sum of all the forces acting perpendicular to the section or forces which tend to slides two part of the section on each other.
Elastic Curve A line representing the deformed form of the center line of the beam is known as Elastic Curve.
Flexural Stress Stresses produced by the bending moment is known as Flexural Stress.
Stresses Internal resistance of the material against loading is known as Stress.
Flexural Equation It is the fundamental relationship between the Bending moment and geometry of deformation.
Flexural Formula It gives a relationship in bending moment and flexural stresses.
Modulus of Rupture • •
It is the energy absorbed per unit volume when the specimen is loaded from zero to failure. It is the maximum tensile stress which can be developed in the beam before failure. 1 Bending Test on wooden Beam Javed 07Civil73
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Difference between Modulus of Rupture & Modulus of Toughness •
Modulus of Toughness can be determined by tension or compression test (axial tests) and it is for any type of member.
•
But Modulus of Rupture is only for a member having flexural or bending.
Loading Arrangement for Experiment Loading arrangement for this certain experiment is “Two point Arrangement”. This is to produce only bending, it will not cause any shear force in the beam.
Two point Arrangement Two equal loads acting at the equal distance from the supports is known as two point loading system. In such a system the shear force acting between the loads
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is zero and bending moment between the loads is constant
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Load is being applied on wooden bean in 10ton Buckton UTM
Wooden Beam after the Fracture
Procedure 1. First of all measure the breath and height of the wooden sample 2. 3. 4. 5.
through the measuring tape. Fix the wooden beam sample in 10 ton Buckton UTM. Fix the dial gauges under the beam as shown figure the figure above, according to the distances shown. Now apply the load gradually on the beam and note down the amount of deflection against each loading. Note down all the deflection up to failure of specimen and finally find the Modulus of Elasticity, Modulus of Rupture from their respective formulae.
Precautions 1. Apply the loads gradually so that we can read the deflection against
each reading easily. 2. Remove the gauges before the failure load, otherwise they may get damages. 4 Bending Test on wooden Beam Javed 07Civil73
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3. Stay away from the machine or otherwise the particles may hurt
you.
Observations and Calculations Sr. No
Load (Tons)
Deflection Gauges Gx
1 2 3 4 5 6 7 8 9 10 11 12
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
100 136 150 190 215 244 269 304 326 355 385 412
Gy 100 135 146 186 210 240 263 296 320 347 375 400
(Gx+Gy)/2 100 135.5 148 188 212.5 242 266 300 323 351 380 406
Gc 100 152 173 229 266 308 342 391 426 466 508 545
Net Deflection (mm) Δ=(Gc-Mean)X
L.C.X25.4 0 16.5 25 41 53.5 66 76 91 103 115 128 139
0 0.4191 0.635 1.0414 1.3589 1.6764 1.9304 2.3114 2.6162 2.921 3.2512 3.5306
Load (N) tonsX9810 0 490.5 981 1471.5 1962 2452.5 2943 3433.5 3924 4414.5 4905 5395.5
6000 y =1534.x- 76.62 5000
4000
) (N d a o L
3000
2000
1000
0 0 -1000
0.5
1
1.5
2
2.5
3
3.5
4
net deflectione (mm)
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Calculations of Modulus of Rupture and Modulus of Elasticity b= 50 mm, h= 50mm,
l=1000mm
Breaking Load (Pmax):
1.15 tons = 11281.5 N
Modulus of Rupture =
=
Modulus of Elasticity = Slope of Straight line in graph i.e.
= 1534.4
Comments Wooden beam should be fracture symmetrically from the both sides because we have applied symmetrical load by Two Point Load System, but we can see from the sketch of wooden beam after fracture, it did not fracture in that manner. This can be due to some weakest plane in the way of fracture. On the right side of the beam it fractured perfectly.
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