MECH3362: Materials II
Laboratory Report
Brittle Rupture of Glass Plates
Guirguis Rezk SID 199991603 Objectives:
To understand mechanisms of the fracture of brittle materials (in this case, glass) To recognize the variations in deformation and failure mechanisms which occur with a difference in flaw size, (i.e. between scratched and unscratched samples) Defining flaw sizes in glass plates by employing linear elastic fracture mechanics (LEFM) Utilizing the Weibull statistics approach in predicting probable failure in brittle materials.
Testing Procedure:
1. The thickness (t) and width (w) of the rectangular glass sample is measured. The first glass slide is placed in the Instron 3-point bending apparatus with the
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This tension is produced by the bending moment of the load. For this reason the plates were placed with scratches facing downwards so that the procedure could test the effect of flaw size on fracture stress. Otherwise the experiment would have probably shown little difference between scratched and unscratched samples. The scratched samples also showed consistent directions in that they were nearly always perpendicular, this was due to linkage of cracks. Whereas for unscratched glass, the crack will propagate according to the local shape and direction of the defect. The three point bending test is used for brittle materials only for two reasons. The first is because brittle materials cannot be tested with conventional uniaxial tension tests because of early failure at the grips. The second reason is that LEFM can only be applied in bending tests to brittle materials because yielding occurs around the same point as failure, so failure stresses can be used to calculate normal tensions in the beam using σ = Mc/I. That is the stress versus strain diagrams remain nearly linear up until failure. Fracture toughness is the ability of a material to withstand brittle fracture in the presence of a crack or flaw. The equation as mentioned earlier is derived from linear elastic fracture mechanics and stipulates that crack length is inversely proportional to fracture stress. The
The specimen ends were not thick or had moving wedge grips to keep it secure in the holders of the servo-hydraulic load frame. The movement of the specimen in the machine causes some of the data to be an inaccuracy. Also, the transverse strain causes issues with the strain gages that are called transverse sensitivity. The transverse sensitivity affects the accuracy of the data that is being collected for the transverse strain more than the longitudinal strain. This is greatly seen in the percent difference in the strain values such as in one case the Longitudinal strain was .4% while the transverse strain was 30%. Another issue with the strain gages was that if the strain gages weren’t properly placed on the specimen the data accuracy would
cpy. As seen in the time domain as well, the distribution of fracture in time is essentially random.
15. Which parameter of glass is measured with bromoform and bromobenzene mixtures in a column?
The mole is a convenient unit for analyzing chemical reactions. Avogadro’s number is equal to the mole. The mass of a mole of any compound or element is the mass in grams that corresponds to the molecular formula, also known as the atomic mass. In this experiment, you will observe the reaction of iron nails with a solution of copper (II) chloride and determine the number of moles involved in the reaction. You will determine the number of moles of copper produced in the reaction of iron and copper (II) chloride, determine the number of moles of iron used up in the reaction of iron and copper (II) chloride, determine the ratio of moles of iron to moles of copper, and determine the number of atoms and formula units involved in
Due to the assumptions that it demonstrates a linear distribution for plane strains throughout the laminate thickness and that out of plane strains can therefore be ignored.
In a test tube, 0.5mL of the sample will be added with 0.5 mL of water and shaken vigorously. Take note for its solubility by parts (0.5mL is one part). Keep adding parts of the solvent until the sample is soluble. If not, add until ten parts of the solvent and determine its solubility. To separate test tubes, water will be replaced with ethanol, chloroform, ether, and acetone as solvents. Same procedures were
For instance, a car becomes overheated from sitting in the sun for too long, and then the air conditioner is turned on high or the car is washed with cold water, or that a very cold cold car sudenly is exposed to heat. This is reason why, in the winter, ice should be scraped or melted off the windshield with cold water, but never with warm or hot water. The cracks almost always start at the edge of the windshield. Stress cracks will normally be a straight line(or slightly bent), and will not have any sign of impact. A perfect way to test if a crack is not a stressed crack is by using a “pen test” in which a ballpoint pen is run along the crack, and if it dips anywhere, it is not a stress crack. This is because with a stress crack, no glass would comes off the
The purpose of this lab is to use chemical and physical properties to identify a material. We are working on observing, inferring and predicting. We are learning if the properties of materials that appear similar can be used to tell them apart.
Scrunch up a small piece of aluminum foil and put it in a second test tube. Set it in the test-tube rack. With the graduated cylinder, quantify 2 mL of Solution D and add it to the test tube.
Examine a piece of nichrome wire. On the data sheet, record the color and the luster of the metal. Use a forceps to hold the wire in the flame of your burner for about two minutes (recall where the hottest part of the flame is located). Describe the appearance of the wire while held in the hottest part of the flame. Allow the wire to cool and reexamine it. From your observations, determine if there was a physical or a chemical change. Give specific reasons for your conclusions. Save the nichrome wire for step #2.
Pore sizes,. Shapes, and aggregate sums were measured. On crack surfaces, Also X-beam films;. These estimations were identified with. Mechanical properties in the transverse.
Alum is a chemical compound that can be created by oxidation and a precipitate. Oxidation is a process in which electrons are lost and oxygen combines with another element, resulting in a change of appearance. All types of alum are double salts but not all are used in a crystal form. Certain types of alum are used in baking, medicine, or pickling. The alum created in this lab became a crystal in an octahedral form. The purpose of this lab was to create alum crystals from aluminum foil and various solutions. Aluminum is a common metal and by adding an aqueous solution to small pieces of aluminum, a crystal structure can be formed. Aluminum is being reduced in the reaction contributing to the formation of the octahedral alum crystal. Hydrogen was being oxidized in the reaction as well. The purpose of the experiment was to take aluminum foil and transform it into an alum crystal through oxidation, in order to calculate the amount of alum created.
We also became aware of how to perform mass measurements using three different balances. Upon weighing the penny we found that the results from all the scales where within 0.08g of each other. The results from weighing 2 pennies was not much different with a deviation of 0.04g between all three scales. For the glass beaker we obtained two results as the maximum on the analytical balance is 200g, the object we weight was well over this weight. We did however get to compare the top loader and the triple beam balances. The difference in these two scales was 0.16g. Because we do not have a true mass value for the penny we cannot prove that the mass measurements are accurate although they are precise as we received the same value each time we put the object on the balance. When we performed the volume measurement we dispensed 10-ml in to all three measuring devices using the pipet. We found that on the 10-ml graduated cylinder the colored solution passed the 10-ml line. Similarly, on the 50-ml beaker the solution was over 0-ml yet under 20-ml which left us inconclusive results. Lastly the 50-ml graduated cylinder measured 10.1ml which was the most accurate of the three measuring devices. Ultimately the 50-ml beaker and the 10-ml graduated cylinder proved not to be accurate which is supported by the data. The only measurement that proved to be more
In 1869, the Russian chemist Dmitry Mendeleyev organized the elements in a table according to their atomic weights. Dmitry Mendeleyev organized the elements based off their physical and chemical properties. In the experiment, the similarities and differences in the properties of the representative elements in Group I, II, III, AND IV is observed. The trend in the acidity or the basicity of the elements in the third period of the periodic table are observed using H2O and HCl. The purpose of the lab is to explore the reactivity trends of metals, halogens and third party elements in groups and periods of the periodic table.
According to the Griffith theory of failure, the critical point ought to be the centre where the ratio of compression to tension (in terms of magnitude) is 3. With a principal stress ratio of 3, failure ought to result from the application of the tensile stress alone, without any complication from the simultaneous compression parallel to the eventual rupture plane.