It asks to get the strain depth graph for the 100, 200 and 300 load using the av

Question

It asks to get the strain depth graph for the 100, 200 and 300 load using the average gauge values can you do an example because I don't understand

EXPERIMENT NO 1 BENDING STRESS INASIMPLY SUPPORTED BEAM BACKGROUND The bending stress distribution in a linear elastic beam varies linearly from the top of the beam to the bottom, with a value of zero at the neutral axis. In this experiment, the strain is measured at a number of different locations through the depth of a simply supported beam. The stress is determined by multiplying the strain by Young's modulus. The theoretical stress may be calculated using the Bending Stress Fomula: My PROCEDURE The beam set-up is shown in the figure W 350mm 350mm 835mm 23 31.7 Beam section showing Strain gauge locations Dims mm 6.4 38.1 Take initial strain readings at zero load by choosing the number with the selector switch. Repeat this process for loads of 10 200N and 300N- Enter you data in Table 1 Correct the strain readings for the zero reading and convert the load to bending moment in Table 2. Einally average the readings at the same level in the beam in Table 3. For the three load levels, plot a graph of Etrain v depth. Calculate the maximum theoretical stress at 300N load level and compare with that calculated using the experimental strain value. Assume E for aluminium is 69 GNm Take 26.25mm and I 58010 mm

Explanation / Answer

As the instruction says ....the strain is measured at number of difference locations through the depth of the ... The term depth means position of strain gauges with some refernce line which can either the top of web of the inverted-TEE section or the bottom of flange of the section. Since, stress and hence strain is zero at neutral axis, it is recommended to calculate the location of neutral axis and then calculate depth of the strain gauges from this axis.

At different depth [alternatively different height or y-valye], the strain value would be different as stress is linearly proportional to the location of strain measurement point with respect to the neutral axis.

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