BE 210
BIOENGINEERING LABORATORY II
FINAL PROJECT PROPOSAL
Further Tensile Testing to Fully Understand
Fracture Properties of the Chicken Leg
BY KARAN SHAH
DUE DATE: 4/25/07
A. BACKGROUND
The mechanical behavior of the chicken leg is determined mainly by the mechanical behaviors of its three major components: the skin, the bone, and the muscle surrounding the bone. In the lab so far, the structural and material properties of the chicken skin and bone have been measured. The fracture properties of both have been analyzed through the lab this year, but the structural and mechanical properties of the muscle are still unknown. Outside of the lab, the environmental conditions act upon the chicken leg as a whole, a system of the three major components. Because it is difficult to measure the properties of all of the components in a single lab, the lab has divided it into separate components. Now it is time to combine the information learned from Experiment 3 and 4 with an expansion on experiment 3 which measures the structural and material properties of the muscle around the bone. The properties of the chicken leg system can be better understood after analysis of the data gathered in this experiment.
In using in the Instron 4444 as it was used in the chicken skin experiment (Appendix 1), we will determine the structural and mechanical properties of the chicken muscle. However, this experiment is different than that of the chicken skin in that each chicken leg has a different amount of muscle. While the thickness of the chicken skin was basically uniform across all of the chicken legs, the quantity of muscle on each leg will be different. This leads us to ask what affect the quantity of muscle has on the chicken leg. What affects does the thickness of the muscle have? What affects does the length of the muscle have on the chicken bone? These are all issues that must be addressed in this lab.
Defining the structural and material properties of muscle is important in understanding the mathematical models to predict the reaction of the chicken leg when it is places under various stresses. This experiment wraps up the analysis of the chicken leg, and thus the understanding of the system as a whole.
B. HYPOTHESIS/OBJECTIVE AND AIMS
As stated in the background, the different affects of muscle on the structural and mechanical properties of the chicken leg system as a whole must be considered in this experiment. Therefore, the properties of the chicken muscle must be analyzed under different conditions. All of the muscle that the lab groups take off of the chicken legs can be assumed as having uniform properties. But how does thickness and length affect the muscle and its properties? The following objectives must be completed in this experiment:
· How does the thickness of the muscle affect the structural properties of the muscle as well? Does the thickness provide more resistance to loads? Also, does the way you measure structural properties using the Instron 4444 provide a realistic simulation of real-life situations?
· How does the amount of muscle on the chicken leg change the structural properties as a whole? Each chicken leg that you receive is bound to have a different quantity of muscle and so it imperative that you understand the effects of this.
· Finally, how does length of the muscle on the chicken leg affect the structural properties of the leg as whole?
The purpose of this lab is to create an understanding of the chicken leg system as a whole, through developing an understanding of its parts.
C. EQUIPMENT
Major Equipment:
Instron 4444- The Instron 4444 will be used to measure the structural and fracture properties of the chicken muscle. It will be used in the same manner as it was in the chicken skin lab, pulling apart the muscle, rather than applying a downward force as was done in the chicken bone experiment.
Labview software- The Labview software will once again be used to create force/displacement graphs for the material in question. The data, including the graphs, is obviously very important and the experience gained doing other experiments using Labview will help in doing this experiment.
Lab Equipment:
Scalpel/Scissors/Cutting Board - Used to cut the chicken muscle.
Rulers/Caliper- Used to measure the size of the chicken muscle. Make sure to use the caliper to get precise measurements of the chicken muscle thickness.
Weight Set- The weight set will be used in the same manner as experiment three. The Instron 4444 needs to be calibrated before carrying out the experiment and using the weight set as the standard, the Instron can be calibrated, and any error can be seen and recorded before carrying out the experiment.
Tweezers- The tweezers can be extremely helpful in placing the muscle into the Instron 4444. The clamps of the Instron can exert a lot of pressure so the use of tweezers provides a level of safety.
Safety Glasses- When the muscle fails; small muscle pieces and germs could fly in to your eyes, so they must be protected.
Supplies:
Chicken Legs- The muscle must be taken off of the chicken legs. Since there are two aspects of the muscle that need to be analyzed, thickness and length, each group will need more than the 5 chicken legs that they were given for experiments 3 and 4. In order to efficiently do t-tests, we must assume that each size of chicken muscle they used must be run 3 times. Each group will need about 9 chicken legs for their experiments.
Foam- Used to run practice trials for the group to get reacquainted with the Instron 4444.
Budget Items:
Valor - Fillet Knife Tarpon Bay 10.75" OA w/Nylon Sheath- $4.19 x 10 = $41.90+tax.
Since this is the only budget expense, the $2000 threshold will not be crossed. The knives will be necessary for the groups to thinly slice the chicken muscle to the appropriate thickness.
However in the case of a shortage of chicken legs, the remaining ~$1950 can be used to purchase the additional chicken legs for this experiment.
D. PROPOSED METHODS & ANALYSIS
Proposed Protocol:
1. The calibration of the Instron 4444 must be carried out in the same manner as it was in experiment three. Once again, calibration is very important as any discrepancies in the Instron measurements can make this experiment useless and inconclusive. They should also make sure at this time that the units that the Instron is measuring in are correct. This should take the lab group no more than 30 minutes.
2. The next key component to the protocol is specimen harvesting. The skin must be removed from the chicken leg, and then the muscle must be taken off the bone. The muscle must also be taken off the bone in a manner such that it is not in a bunch of smaller pieces, but rather larger pieces that can be then cut up into smaller pieces. The muscle should be stored in wet paper towels to avoid dryness. This should not take more than 30 minutes.
3. The lab group should then use the foam to run surrogate trials to get reacquainted with the Instron 44. The lab group should determine the amount of specimen need to be in the clamp to avoid slippage. This should take the lab group about 45 minutes.
4. The lab group should then cut the muscle into the appropriate sizes. There will be three different groups for this experiment. One of the size groups will be used as a standard. The other two groups will be as follows: 1. The same thickness and width as the standard group, but will be twice as long, 2. The same length and width as the standard group, but twice as thick. This will allow the lab group to compare each of the 2 additional groups to the standard during their data analysis. This should take the lab group anywhere from 45 minutes to an hour.
5. The group will then be ready to test their samples. The samples will be tested in the same manner that the chicken skin samples were tested in experiment 3, and the same way the surrogates were earlier in this experiment. This should take the group no more than 3 hours.
6. The final clean-up of the lab can be done in the remaining 15-30 minutes.
Analysis:
The analysis of this experiment will be the key component in making this experiment useful for the students in the lab. Since the experiment is designed in such a manner that the structural properties come to the forefront ahead of the material properties, the lab groups should put an emphasis on conducting the appropriate analysis of their data. The yield point, the ultimate strength, and the rupture strength are all possibilities for analysis.
While the lab groups will be responsible to reach conclusions for the goals highlighted in the hypothesis section, the lab groups will also be responsible for calculations of the basic properties of the specimens: the initial geometry, loading rate, failure displacement, failure force, failure strength, failure strength, stiffness, Young’s modulus, and tensile failure strength. (Experiment 3 Handout page 8)
The lab groups will also be responsible for any additional research in relation to the interpretation of their data. Studies are being conducted to measure the affects of loading forces on human bones, and their surrounding components. Research by the students on studies being done, and how those studies related to this experiment should be done to develop a further understanding of how loading forces affect a system as a whole.
All of the information spoken of above should be included in the group’s lab reports for this experiment. This lab requires the students to do additional research on their own to get the full value out of this experiment. As an experiment that brings the other experiments done in the BE 210 lab full circle, this experiment requires the additional research in order to apply all of the data that was gathered in this experiment to real-life situations.
Statistical Analysis:
The statistical analysis in this experiment will be done with two separate paired t-tests. Showing that length and thickness do provide stronger/weaker structural properties that are significantly different (p<.05). The statistical tests can be done in MS Excel. However, the actual calculations of various values using the graphs and data collected in Labview should be done in MATLAB.
E. POTENTIAL PITFALLS & ALTERNATIVE METHODS/ANALYSIS
Potential Pitfalls:
There are many potential pitfalls for groups who are carrying out this experiment that they could fall into if they are not careful in carrying out the experiment. The first major problem that could arise in this experiment is that the lab group does not correctly remove the muscle from the chicken bone. If the group takes the muscle off the chicken bone too quickly, without paying attention to keep the pieces of muscle intact, then the experiment will not be able to be done. Also, if the group does not efficiently cut the muscle, then they may have not have enough muscle to run the minimum of 9 trials that are required for this experiment.
Another potential pitfall of this experiment is the Instron not being calibrated properly. If the lab group does not calibrate the Instron, the data and the graphs from the trails that they run will lead to faulty data. Also, if the Instron does not return to the same non-zero point, the data won’t be consistently off, which will make the data even less useless.
The final major pitfall of this experiment involves the lab group being unable to correctly research the background material for this experiment. Without the additional research, this lab is essentially a repeat of experiment 3, which in turn would add little to the lab group’s knowledge. Therefore it is imperative that the lab groups find the link between this experiment (along with experiment 3 and 4) and current trauma studies that are being carried out right now.
Alternative Methods/Analysis:
Considering this lab is pretty straight-forward in terms of methods, there is little room for deviation. However, in the unforeseen circumstance that the lab group is unable to get enough muscle off of its chicken legs to run the experiment, (the group must realize this by the 6th chicken leg) then the group may be able to use the Instron in the 3-point bending manner. Since the lab group has already done experiment 4, they can place the whole chicken leg on the Instron and see the affects of the loading force on the leg as a whole. They skin and muscle will have some effect on the loading reaction of the bone/leg and then the data taken in this lab could be compared to that of the data gathered in experiment 4. This however, may be not be a very efficient experiment in terms of the equipment, because the Instron may just break through the muscle and then act on the bone, which would be the same as experiment 4. Therefore this is should be used as a worst-case scenario alternative.
F.BUDGET
There should be little problems in terms of staying within the budget here as only additional expense for the lab groups is the fillet knives. However, if the use of 9 chicken legs per group is excessive in terms of supplies in the lab, then there is ~$1950 left for the purchase of additional chicken legs.
Filler Knives:
Valor - Fillet Knife Tarpon Bay 10.75" OA w/Nylon Sheath- $4.19 each (Appendix 2)
10 knives (One for Each Group)
10 x $4.19=$41.90 + Shipping + Tax
Supplier: All in General Outdoors- http://allingeneral.com
G. REFERENCES
Experiment 3 and 4 Lab Manuals
Appendix One Picture Taken from: http://www.plasticsmag.com/article_images/Tensile%20Test.JPG