The aim of this experiment is to obtain and graph deflections and bending stresses for a cantilever beam under a point load and observe the affect that changing the mass of the point load has on the deflection and bending stress graphs. Hypothesis As the loading on the bar Increases, the magnitude of deflection and bending stresses will become greater. Procedure 1 . Clamp the strain gauge instrumented steel beam to the rig. Place the dial gauge at ammo and zero it. 2. First acquire a reading with a zero load then load the beam tit different weights (4 different weights is recommended) at ammo. Enter the mass into the corresponding box and ‘Acquire’ the data point. 3. Enter the parameters of the beam Including the conversion factor to plot the theoretical deflection and stress curves. Note: to delete an Individual data point, click on that row on that table and then click ‘delete row’. Remember to label your plot including units. Diagram Results Discussion The experiment has shown that as the loading mass is increased, the magnitude of the deflection and bending stress became greater, thus confirming the hypothesis.
However there was a clear amount of error between the
Repeating the experiment multiple times for each mass and taking the average of the measurements could have improved the consistency of the results. Doing this would decrease the amount of human error associated with the investigation. Also calibrating the computer to take into account the mass of the bar would greatly improve the accurateness of the measurements. Calculations and Uncertainty Analysis An uncertainty value was put on measurements taken from the investigation that have a direct correlation to the equipment used to take each measurement. ‘ (keg) h’ (meter’s) ‘ (meter’s) 0. 0005 0. 00001 Using the formula: From this formula the second moment of area about the Z-axis, with an uncertainty, can be obtained. Where: h = 2. Mom b=19. Mm Hence uncertainty would have an affect on the theoretical calculations of bending stress and deflection as shown in the calculation below. Bending stress plus uncertainty: where P=mass * g L = 0. Mm X = 0. Mom (distance from fixed point to stress gauge).