In this report we look at the physical properties of beams
of different sizes and materials as well as
how different materials respond to tensile testing. For this we used the
tensile tester kit and the Deflection of beams and cantilevers from the
TecQiupment apparatus. The results showed us that thicker beams made of harder
materials are more stable under load. The tensile test showed us that the beams
made of alloys (especially steel) are stronger under tension.
Beams are used in all aspects of construction. From supports
in tables, to bridges. They are key aspects of any design and lots of work and
calculations go into deciding what material they should be made from and what
shape they need to be. They are made
from varying materials and varying layouts, from solid beams to hollow
cylindrical beams and I beams.
Beams are commonly used in bridges. The best example of this
is a beam bridge (figure 1) This uses a beams with pillars to support a load,
such as a road, trainline or walkway. The design of bridges has developed
overtime, where solid beams used to be prevalent I (or H) beams are more common
as they offer similar strength but far less weight, making the more useful in
structures as these structures require less support due to the reduced weight.
In this experiment we
aimed to test how different forces act on the beams and how the forces affect
the beam. We tested point loads on beams with different materials of beams and
different dimensions of beams. We also tested the tensile strength of 3
different materials. For the two separate experiments we will be using 2
different main equations. For ES4 we will be using the equation for maximum
deflection for a simple cantilever beam with a single point load: ?=-WL3/48EI.
We have rearranged the formula to give us 48?I/L3
which will allow us to calculate the young’s modulus of the material when
plotted against weight(W) in newtons. In ES6 for the tensile test, we will be
using Force(N)/Cross sectional area (m2) to calculate stress
In our experiments we hoped to find out how different loads
and different types of load affect the beams. We also tested how changing the
material and shape of the beams can affect this reaction to the loads.
The aim of these experiments to determine how beams made of
different materials are affected by varying amounts of weight. Another aim was
to assess how different sizes of beam can also change how the beams are
affected by weight.
I have inserted the methods used for both experiments we
undertook. Please refer to appendices for more information on the methods.
Set up apparatus as shown below. You will use the same setup
for the whole of ES4
Set up apparatus as shown below.
Results for adding weight to an Aluminium beam are shown below in table 1.
Results for adding weights to beams made of different materials is shown in
Measured deflection from beams of different dimensions but
the same material
For this data set I have only added the graphs as there is a large amount of
data. The red point at the end of eaceh graph
indicates a break.
We tested how different
materials are affected by different loads. Comparing the data from the beam
material comparion experiment (tables x.y.z) we can see Aluminium is the weakest metal as it
deflects a load of 0.269 mm (table x) at 500g. This is due to aluminium being a
pure metal. This means all of its atoms are similalry sized and can easily pass
over each other (see figure x). Brass and steel are both alloys so have a much
lower deflection than aluminium. Brass has a deflection at 500g of 0.179mm (table y) Steel has a
lower delfection at 0.095mm (table
z) than brass as brass has a crystalline struscutre (see figure x)
whereas Steel has a lattice structure (see figure x)which makes it stronger
The dimensions of the beam also greatly affect
its defelection. For example, the thicker the material is in the direction of
load the stronger it is and the less it delfects when weight is added.
As the material gets wider the deflection will decrease but only slightly,
thickness is more of a factor. The dimensions of the cross sectional area don’t
particularly matter as a beams that have the same cross sectional area will
have different deflections due to having different thicknesses.
We performed a tensile test
to gather more data on materials used in beams. During a tensile test there are
3 key features an elastic region, a plastic region and a break. However the
shape of the graphs are all different. (Looking at graph 1) Aluminium for
example slowly elongates then slowly breaks, with no majour break or snap. (looking
at graph 2) PVC elongates during the elastic region (the straight line of the
graph) but then shortens again with no majour elongation before it eventaully
snaps. (graph 3) Steel has a very clear elastic region before dropping a bit at
the yeild point. The strain does drastically increase before it snaps, unlike
the previous two. Looking at the combined graph, it makes it much easier to
compare the 3 tensile tests. Using this data we can clearly see that aluminium
takes far less strain (elongates less) before it snaps compared to the PVC and
steel samples. We can also see it takes far less force to break the aluminium sample
compared to steel and PVC. PVC also takes the most stress before starting to deform
but has a much steeper elastic region (also means a higher youngs modulus) than
We were asked why we thought a
constant temperature and pressure were important for the pvc, more than the
metals, and this is due to pvc being a polymer which has a much lower melting
point than either metals and a constant force needs to be applied as due PVC
being a polymer it has a youngs modulus around 100 times smaller than that of
either metal (es4 and http://www.dielectriccorp.com/materials/thermoplastics/pvc.htm)
so it would return to the original shape
if we did not apply a constant pressure it would go back to its original shope,
making our results incorrect.
In conclusion, we can say
that having a thicker beam made of an alloy would be the best for making a
strong beam. A thicker beam is stronger but will however add more weight. Using
an alloy of multiple elements (such as steel) will be stronger than a pure
material as well as having the benfit of being able to alter its chemical
properties by using different elements in its compostion.
We can assume that some of
the results may be slightly incorrect due to human error however these errors
should not affect the overall results or conclusion of the experiment.