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 ForceThe 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 CurveA line representing the deformed form of the center line of the beam is known as Elastic Curve.

Flexural StressStresses produced by the bending moment is known as Flexural Stress.

StressesInternal resistance of the material against loading is known as Stress.

Flexural EquationIt is the fundamental relationship between the Bending moment and geometry of deformation.

Flexural FormulaIt 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.

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.

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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 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

Procedure1. First of all measure the breath and height of the wooden sample through the

measuring tape.2. Fix the wooden beam sample in 10 ton Buckton UTM.3. Fix the dial gauges under the beam as shown figure the figure above, according to

the distances shown.4. Now apply the load gradually on the beam and note down the amount of deflection

against each loading.5. Note down all the deflection up to failure of specimen and finally find the Modulus

of Elasticity, Modulus of Rupture from their respective formulae.

Precautions1. 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.3. Stay away from the machine or otherwise the particles may hurt you.

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Observations and Calculations

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Calculations of Modulus of Rupture and Modulus of Elasticityb= 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

CommentsWooden 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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