Bending Test on Wooden Beam

6. To Perform Perform Bending Test 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 Bendi Bending ng Test Test on wood wooden en Beam Beam  Javed 07Civil73

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Difference between Modulus of Rupture & Modulus of Toughness •

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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 l oads

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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 Bendi Bending ng Test Test on wood wooden en Beam 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 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 26 269 304 32 326 355 385 412

Gy 100 135 146 186 210 240 26 263 296 320 347 375 400

(Gx+Gy)/ 2 100 135.5 148 188 212.5 242 266 300 323 351 380 406

Gc 100 152 173 229 266 308 34 342 391 42 426 466 508 545

Net Deflection eflection Load (N) (mm) Δ=(Gc-Mean an)X tonsX9810 L.C.X25.4 0 0 0 16.5 0.4191 490.5 25 0.635 981 41 1.0414 1471.5 53.5 1.3589 1962 66 1.6764 2452.5 76 1.9304 2943 91 2.3114 3433.5 103 2.6162 3924 115 2.921 4414.5 128 3.2512 4905 139 3.5306 5395.5

6000 y =1534.x =1534.x -76.62 - 76.62 5000

4000

3000    L    d    (    N    )   o   a

2000

1000

0 0 -1000

0.5

1

1.5

2

2.5

3

3.5

4

net deflecti deflectione one (mm)

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Calculations of Modulus of Rupture and Modulus of Elasticity b= 50 mm, mm, h= 50 50mm mm,,

l=10 l=1000 00mm mm

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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