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MECH 4175
Project 2
Keith Benedix
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Introduction
Solid Works was used to examine the residual Von Mises stresses in a 2006 Burton Freestyle
snowboard binding (shown on the cover). In order to model the assembly in the program,
some minor adjustments needed to be made to the material being tested. The actual binding is
made of a composite called Nylon 6/6 30% glass-‐fiber reinforced (Nylon 6/6 GF30) to improve
mechanical performance in toughness and abrasion resistance. This nylon variant has been
known to exhibit increased structural and impact strength, and rigidity. The addition of
glass fibers to nylon 6/6 in various amounts (10%, 20%, 30% and 40%) increases tensile
strength, stiffness, compressive strength, and a lower thermal expansion coefficient over
conventional unfilled grades. Glass filled nylons offer better strength than general
purpose nylon but it is highly abrasive and will abrade or gall mating surfaces. (Emco
Industrial Plastics, Inc.). Since Solid Works does not include this material in its material
calendar, Nylon 6/10 was used instead to obtain the most accurate results. Figure 1 is a table
comparing the mechanical properties of the three materials.
Mechanical Property
Nylon 6/6 Nylon 6/6 GF30 Nylon 6/10
Tensile Strength [psi]
12,400 27,000 8,700
Elongation [%] 90 3 90 Flexural Strength
[psi] 17,000 39,100 11,000
Flexural Modulus [psi]
4.1e5 12e5 2.9e5
Rockwell Hardness [ft-‐lb/in]
1.2 2.1 -‐-‐
Figure 1: Mechanical Properties of Nylon 6/6, Nylon 6/6 30GF, and Nylon 6/10 (taken from Plastic Products, Inc.)
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As can be seen in the table, Nylon 6/10 is weaker than Nylon 6/6 and significantly weaker than
Nylon 6/6 GF30. This just means that the results in the FEA will be extremely conservative
compared to the real world model.
The assembled model only consists of three parts. This was done in Solid Works with the
intention of doing an analysis on the assembly, but unfortunately when attempted, the analysis
either failed or gave inaccurate results. This probably had a lot to do with the way the assembly
was constrained and the flexural modulus of the material. Instead, each pertinent part in the
assembly (namely the base plate and the high back) was tested individually to get accurate
results. Figure 2 is an exploded view of the assembly for the purpose of showing the name of
each part.
Figure 2: Exploded View of the Binding
High Back
Lock Disk Base Plate
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It should be noted that the heel and toe straps were not included in this model due to the fact
that the motivation in this simulation was to only analyze the parts of the binding that would
break after experiencing high impact (i.e. landing flat from a high drop). In such cases, it would
be unusual for the binding straps to experience any significant forces at all.
Methods
Previously, we learned that the mesh and run method was a decent way to get a numerical
value as a starting point, but was inaccurate in practice. So, this method was dropped and the
h-‐adaptive and p-‐adaptive methods were used to run the FEA on the base plate and high back
of the binding. The base plate was loaded at the crux of what is known as the heel cuff with an
external vertical force of 1000 lbs. and fixed on the bottom surface. The p-‐adaptive method was
run first, but proved to be inconclusive as its associated convergence graph in Figure 3 showed
no plateau.
19000
20000
21000
22000
23000
24000
25000
26000
27000
28000
29000
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Von Mises Stress [psi]
Loop Number
Figure 3: Maximum Von Mises on Base plate Using the P-‐AdapXve Method
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There’s nothing particularly interesting about this plot, only the fact that the method used
proved to give inconclusive results. The h-‐adaptive method did, however, yield accurate
results. Figure 4 shows the convergence graph when the h-‐adaptive method was used.
As can be seen by the plot above, the method converges and we have an accurate readout in
the simulation of the maximum Von Mises stress being around 32,000 psi after only the third of
the five loops that the simulator runs. Moreover, a screen shot of the results in the Solid Works
Simulator (depicted in Figure 5) shows where the base plate might fail. We can see in Figure 5
that there doesn’t seem to be any significant area that experiences any stress above the yield
stress. Given the loading conditions, it is apparent that the base plate of this binding is safe in
the most extreme case, given that the average American male has a mass of 75 kg. and would
not likely load the binding in such a way.
15000
17000
19000
21000
23000
25000
27000
29000
31000
33000
0 0.5 1 1.5 2 2.5 3
Von Mises Stress [psi]
Loop Number
Figure 4: Maximum Von Mises on Base plate Using the H-‐AdapXve Method
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Figure 5: Results of H-‐Adaptive Method Analysis in Solid Works Simulator
The high back was loaded a little differently than the base plate because of numerous large
displacement failures. A load of 100 lbs. was applied to the front face (where the back of a
rider’s boot would make contact) and fixed where it makes its assembly connection and where
it rests on the heel cuff of the base plate. Figure 6 is the convergence graph for the analysis in
which the p-‐adaptive method was utilized.
400
450
500
550
600
650
700
750
1 1.5 2 2.5 3 3.5 4
Von Mises Stress [psi]
Loop Number
Figure 6: Maximum Von Mises on High Back Using the P-‐AdapXve Method
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Figure 6 shows that the p-‐adaptive method was able to show convergence, and so it is likely
that the results are accurate. Figure 7 is a screen shot of the results in the Solid Works
Simulator.
Figure 7: Results of P-‐Adaptive Method in Solid Works Simulator
According to the readout the part does not yield with the given loading conditions. This time,
the h-‐adaptive method was the one that did not converge. Figure 8 is the diverging plot of the
results from the h-‐adaptive method for this part. Again, there is nothing interesting about
Figure 8, only that the h-‐adaptive method has proven to have an inconclusive result. It should
be noted, however, that it is quite curious that for both parts only one of either of the two
methods gave good results. In the past, either both were divergent or convergent when the
plots were looked at. Also, upon comparison with the mesh and run case for this part (shown
in Figure 9), we can see that the results are really not that far apart from each other.
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Figure 8: Results of Mesh and Run Method in Solid Works Simulator
0
500
1000
1500
2000
2500
3000
0 0.5 1 1.5 2 2.5 3 3.5 4
Von Mises Stress [psi]
Loop Number
Figure 8: Maximum Von Mises on High Back Using the H-‐AdapXve Method
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Discussion
In summary, this part is safe to use on a snowboard (which it should be). The main parts that
would take all of the applied loads in a real world situation don’t seem to meet the fail criteria.
FEA was used and backed up by three different methods: the mesh and run (as an estimate),
the p-‐adaptive, and the h-‐adaptive. In the past, it has been seen that the h-‐adaptive method
was the most accurate way to obtain desired results. In light of this most recent study, it seems
that the convergence graphs on either method used are a good way to prove that the results
that the simulator gives are accurate. Figure 9 is a summary of all the results found in this
analysis.
Method VM Stress on Base Plate [psi] VM Stress on High Back [psi]
Mesh and Run 17,975 564.4
P-‐Adaptive -‐-‐ 726.9
H-‐Adaptive 32,171.6 -‐-‐
Figure 9: Summary of All Results for Project 2
