Youngs Modulus of Nylon Essay Example for Free

Youngs Modulus of Nylon Essay Introduction This investigation aims to find the value of Youngs Modulus for a specific material, in this case nylon fishing line. Youngs Modulus (E) is a measure of a materials stiffness, determined by the formula: The standard unit of measure for Youngs Modulus is the pascal (Pa). 1 pascal is the same measure as 1 Nm-2 (Nm being Newton Metre). A material always retains the same Youngs Modulus value regardless of how much it is stretched or strained, and this should be revealed in this investigation by gathering a definite value of the modulus for nylon. Hypothesis Through research that I conducted before starting the investigation, I have determined that the correct Youngs Modulus value of Nylon lies in the range 1-7GPa (the large range being due to different make-ups of Nylon with it being a compound). I should therefore be looking at achieving a final result within or very close to this range. Since stress is proportionate to strain in the Youngs Modulus formula, and the modulus value remains the same, I would expect the value of stress and strain to proportionally increase with each other. Experiment Plan In order to carry out this investigation into the value of Youngs Modulus of nylon, I will conduct an experiment to gather the values of stress and strain when increasing force is added to the material, and will take readings as weight increases until the breaking point of the nylon is reached. In order to calculate stress and strain, I will need to record each of the following variables throughout the experiment: Force applied to the material [F] (Newtons/N) Area of a cross-section of the material [A] (Metres-squared/m2) Original length of the material [Lo] (Metres/m) Amount of extension when the force is applied [L] (Metres/m) These variables will then allow the values of stress and strain to be calculated using the following formulas: This leads to a final Youngs Modulus calculation formula of: The set-up I will be using to carry out this experiment consists of the nylon fishing line suspended from a stand using a clamp, and another clamp to ensure there is no movement in the stand itself. I will create a suitable loop at the bottom of the hanging material so that weights can be added but will need to ensure this loop does not weaken any area of the material and cause a drop in the breaking point value, as this would compromise the reliability of my experiment and result in premature breakage of the length of nylon. At each stage of the experiment I will take readings of length using a standard 1m ruler, and will measure the area of a cross section by gathering the diameter value using a micrometer, halving this value to gather radius and then use the formula Before any weights are added, I will need to take a control measurement of the length and area of the nylon before any stress or strain is applied. Once this is done I will proceed to apply weight in intervals of 100g (0.981 N) and record the values of each variable stated at bottom of the previous page after each 100g weight is added, with the exception of original length which is a constant value and only needs to be recorded at the beginning of the experiment. I will continue to add weights until the material reaches its elastic limit and snaps, at which point I will record the force applied to break the object. In order to achieve an adequate number of results from each experiment to make a fair analysis and conclusion to the investigation, I will need to take a minimum of eight readings (i.e the nylon should withstand at least 800g/7.849N). If this fails in the actual experiment then I will need to re-evaluate my plan and decide on a new method of conducting the experiment to me et this criteria. To increase reliability, accuracy and to eliminate possible anomalous results, I will aim to repeat the entire experiment three times to gather average readings. If all three of these experiments were to be perfect then the final Youngs Modulus value would be the same in each, so this will be a good test of how much my investigation has suffered from error when I examine the range in the three values. N.B In my actual practical experiments, I have decided to measure Engineering Stress, as opposed to True Stress. As Engineering Stress does not take into account cross-sectional area changes, this will prevent me from damaging the nylon with repeated micrometer readings, and hence my values for area will always remain the same. Technical List of Apparatus * Nylon Fishing Line * Manual Micrometer (accurate to 0.01mm with a range of 25mm) * Standard Wooden 1m Ruler (accurate to 1mm) * Clamp stand with clamp * Set of Weights with hanging hook (in 100g/0.981N intervals) * G-Clamp Variables In this investigation the variable I intend to be changed is the amount of extension of the piece of nylon, required to calculate the value for strain. Other unintentional variables will also be present in the experiment, notably the cross-sectional area of the nylon wire, which will decrease as more strain is applied and the material stretched. By calculating engineering stress, the effect of this variable can be negated. Safety Whilst the practical side of this investigation does not include any particularly dangerous apparatus or methods, there are still some safety considerations to be taken. Eye protection will have to be worn whilst the nylon has stress and strain applied to it, as the material will be taken to breaking point, which could result in the material whipping back very quickly at this point, posing an eye damage hazard. It is also worth noting that at this point a substantial amount of weight will be dropping so arms and feet should be kept back from below the experiment and all persons in the vicinity should be on their feet to allow them to move back quickly if required. Error Reduction The practical side of this investigation is prone to errors through a number of factors. In order to attempt to reduce the number of errors that will affect the results of the investigation during the implementation of the practical, the following steps will be taken, in addition to the experiment being repeated three times as already mentioned above: * Micrometer should be checked before each use to make sure it lies on the zero value when fully closed. * Double-check all readings to be taken from the micrometer and ruler, and double-check the calculations for area on calculator. * Nylon should not be interfered with once set-up on the clamp, in order to reduce added stress or weakening through factors not related to the intentional weights being added.