CE/ME 312
Experiment 7
TRANSVERSE TEST OF TIMBER, CAST IRON, AND PLAIN CONCRETE
References:
Experimental Mechanics and Properties of Materials, by Muhlenbruch,
Experiment 8.
The Testing and Inspection of Engineering Materials, by Davis, Troxell,
and Wiskocil, pages 165-183, 356-360, and 408-426.
Equipment:
Tinius-Olsen, 200 kip, Universal Testing Machine (UTM); Riehle, 30 kip,
UTM; reaction blocks, loading block, dial gage, outside calipers, steel
scale, steel bearing plates, cord, chalk.
Specimens:
One piece of wood (Douglas fir, coast region, 1500 psi flexure
strength), approximately 2 inches square by 16 inches long. One castiron bar, 14 inches long and approximately 5/8 inches in diameter. One
concrete beam 2 inches wide, 6 inches deep, and 14 inches long.
Procedure:
Students must have a clear understanding of how to operate
the Tinius-Olsen UTM and Riehle UTM before starting an
experiment with these machines.
Timber: Measure and record the width and depth of the wooden beam to the nearest 0.01 inch.
Draw pencil tines on all sides of the specimen at the center, and at points 6 inches from the center.
Place the reaction blocks on the loading table of the Tinius-Olsen UTM. Make sure that they are 12
inches apart, and that they are placed symmetrically with respect to the movable head. Place narrow
steel plates over the reaction blocks and then place the specimen on the blocks, and check position
by means of the pencil lines. Place the third steel plate on the top of the test beam at the center
under the loading block, and apply an initial load. Place the deflectometer under the specimen so
that it will give deflections of the center of the beam.
SECURE THE INSTRUCTOR'S APPROVAL OF THE SET-UP BEFORE STARTING TEST.
Increase the load in 10 to12 equal increments, and take simultaneous load and deflection readings.
A field curve should be plotted at the same time, so that the recorder will know when the proportional
limit has been passed. Take at least 5 readings after the proportional limit has been passed, then
take further load and deflection readings by means of larger increments of deflections, until fracture
occurs. Record the ultimate and the rupture loads. Note carefully the nature of the failure, and make
a simple sketch of it.
Cast Iron: Measure and record the diameter of the cross-section at the center of the bar to the
nearest 0.01 inch. The bar is to be tested as a beam with a span length of 12 inches, subjected to a
central concentrated load. Mark the center section, and the points of support, 6 inches to each side
of the center with chalk. Connect the ends of the specimen with a slack cord, tying each end tightly
in order to prevent the pieces from flying when the bar breaks, and use protecting shield.
Place the bar on the reaction blocks and center the assembly under the loading block on the crosshead of the Tinius-Olsen UTM. Place the dial on the specimen so that it will give deflections of the
center of the beam. Apply a minimum initial load, and adjust the deflection dial reading to zero.
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CE/ME 312
Experiment 7
SECURE THE APPROVAL OF THE INSTRUCTOR BEFORE PROCEEDING FURTHER.
Now apply the load and record deflections in 10 to 12 equal increments, until the proportional limit is
reached, taking simultaneous readings of load and deflection. Readings should be taken as rapidly
as is consistent with accuracy, because specifications require that a central deflection of 0.10 inch be
produced in 15 to 40 seconds. It is more important, however, to secure fairly reliable readings than
to attempt to adhere to this rapid rate of loading at the expense of accuracy. Hence student groups
may require as much as 40 minutes to attain 0.10 inch deflection.
Record the rupture load and examine the surfaces of the break in the test specimen.
Repeat a similar procedure for the concrete beam except use the Riehle UTM and the load
increments should be such that approximately 20 readings are taken before ultimate load is reached.
DATA SHEET
1. List the experiment number, title, and date at the top of data sheet.
2. Record the cross-sectional dimensions, span length, and position of load.
3. Use the following column headings for tabulated data:
Load
Lbs.
Deflection
Inches
4. Sketch the bars showing location of the break, and shape of break.
REPORT
Graph
Plot a curve for the wood showing the relation between load and deflection up to the yield region,
and, on the same paper, show the complete loading cycle using the same load scale but a different
scale for deflection.
Calculations
1. For timber, calculate the extreme fiber bending stress, and maximum shearing stress at
proportional limit from the formula:
m 
Mc
I
and
 max 
3V
.
2bd
2. For all specimens, calculate the modulus of rupture or ultimate shearing strength, depending on
the type of failure.
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CE/ME 312
Experiment 7
3. Using any rational increment of load, and the corresponding increment of deflection from the
straight-line portion of the curve, calculate the modulus of elasticity of timber specimen from the
formula:
y 
( P ) L3
48EI
Questions
1. Compare the results of the test with accepted standards. Give typical values of working stresses
(for flexure and longitudinal shear) for the type of wood tested. Use the Uniform Building Code as
standard reference.
2. Discuss the type of failure of the wood. Compare it with that of the cast-iron beam.
3. Using the modulus of elasticity as determined from the graph, calculate the center deflections of
the wood for a load of 400 Ibs., and for the load at the last reading taken before rupture occurred.
How do these compare with the observed deflections?
4. Discuss the type of failure of the cast iron and concrete test bars. Can you draw any conclusions
relative to the ductility of the material? What is the most common characteristic for cast iron and
concrete?
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