writing objective for a Lab report
writing objective for a Lab report. The subject Mechanical Engineering
1
OAKLAND UNIVERSITY
School of Engineering and Computer Science
ME 361 Mechanics of Materials
Laboratory 4
STUDY OF BEAM DEFLECTION
1. Objective
To compare theoretical and experimental deflections of a simply supported prismatic beam under transverse
loading.
2. Reference
2.1 Class Notes
2.2 Mechanics of Materials, 4th Ed., by Beer and Johnson, Mc Graw-Hill, Inc., 2005.
2
3. Apparatus/Materials
3.1 One prismatic beam, with two adjustable simply supports.
3.2 Dial gauges
3.3 Weights and hangers.
4. Procedure
The prismatic beam provided for the experiment is to be centrally located on the two provided simple
supports. Along the length of the bar are several pre-set weight hanger locations for the applied loads. In this
experiment, three offset loading conditions must be considered. Figure 1 shows a typical offset loading, on a
simply supported beam. L is the overall length of the beam; Lp is the distance to the applied load from A, L1
and L2 are the distances to the dial gauges from A respectively. L2 should be set at L/2. The position of the
dial gauge may remain constant throughout the experiment.
4.1 Set the beam upon the supports and adjust support heights so that the beam is level. Measure and record
the distance between the knife-edges of the supports, this will be the overall length L.
4.2 Set up the dial gauges with one centered between the knife-edges (L/2) and one at the arbitrary location
L1, so long as there are at least 6 inches separating L1 & L2. Carefully measure and record these distances.
Adjust the dial gauge to read zero. Be sure to check the setting of the dial gauges during the course of the
experiment.
4.3 Choose an arbitrary location for an offset loading condition. Carefully measure and record this distance as
Lp.
4.4 Apply a load at this location (start with 4 lb)
4.5 Record the deflections of the dial gauges. Note the readings of the dial gauges are in 1/1000 in.
4.6 Remove the weight from the beam and check the dial gauges for zero.
4.7 Repeat steps 4.3 4.5 for another two additional weights (6lb and 8 lb).
5. Calculation
5.1 Compare deflections at L1 when weight is at A1 with the deflection at A1 when weight is at L1.
Comment on your findings.
5.2 Determine the theoretical deflections at L1 and L2 by using the procedures from Mechanics of Materials.
Youngs modulus of the bar: psiE 61016.10
Width of bar (b): 1.0 inch
Height of bar (h): 0.375 inches
3
5.3 Compare the theoretical and experimental values of deflection at L1 & L2. Provide error analysis and
explain any differences observed.
5.4 Calculate the position and value for the maximum deflection of the beam for each load in each case.
6. Questions
6.1 In this experiment we consider a case where the width of the beam is greater than the thickness. If the
width is smaller than the thickness, would you expect larger or smaller deflections than what you
observed in your experiments? Explain.
6.2 Why is there discrepancy between the theoretical and experimental results observed? List and explain the
reasons.
6.3 Does the maximum deflection of the beam occur at the position of the applied load? Explain.
6.4 Explain why an engineer may be interested in knowing the deflection of a beam. Explain with an
example.
_______________________________________________________________________________
SAMPLE OF EXPERIMENTAL DATA
L1=7.75 in, L2=17.5 in, LP=23.5 in, L=35 in
Load
Conditions
Dial Gauge 1*
(*0.001 in.)
Dial Gauge 2
(*0.001 in.)
P=0 V0=5.8 V-V0 V0=1.1 V-V0
P=4 lbs 47.1 41.3 75.8 74.7
P=6 lbs 67.8 62 110.5 109.4
P=8 lbs 89.8 84 146.0 144.9
V: is deflection of beam at position L1 and L2.
Theoretical values of deflection of beam at L1 & L2 position:
))((103.39
,4
)75.1092(1022565.1
])[(
6
3
1
36
322
in
LxlbsPwhile
xxP
xxbL
EIL
bP
v Sheet1
Load Dial gauge 1 Dial gauge 2
0 LB 0 V-V0 0 V-V0
4 LB 79 79 147 147
6 LB 117 117 216 216
8 LB 164 164 302 302
Highlighted parts will be used in calculation
