School of Civil Engineering Instruction for CIVL2110/CIVL9110: Take-Home Final Exam 2021 This take-home final exam is to be submitted before Sunday 6 June 12pm using the CANVAS site for this UoS. This is an INDIVIDUAL assessment task. As explained previously, the solutions to each problem need to be handwritten (you can either scan the solutions or use a tablet to write your solutions by hand). You will need to submit a single pdf file with your solutions – the file should not be longer than 10 pages A4. The file should be named: SID-Exam.pdf There is a total of five problems and the number of marks attributed for each problem is stated at the start of the problem. The total number of marks for this exam is 100. Problem 1: (20 marks) You are a part of civil engineering team, that was asked to select a material for a spherical pressure vessel to be built in refinery. The stress in the vessel wall is t pr 2 = , where p is the internal pressure, r the outer radius of the sphere, and t the wall thickness. The mass of the vessel is  trm 2 4= , where ρ is the material density. The operating stress of the vessel will always be S y   , Where S is the safety factor. 1.1) Show that the minimum mass of the pressure vessel will be y rpSm    3 2= . 1.2) Given the following table, select the alloy that will produce the lightest vessel. Explain your reasoning and calculations. 1.3) Using the same table, select the alloy that will produce the minimum cost vessel. Explain your reasoning and calculations. Alloy σy (MPa) ρ (g/cm3) Cost ($/kg) 1040 carbon steel 600 7.8 0.63 304 stainless steel 205 7.8 3.70 3003-H14 aluminium 145 2.73 3.00 Ti-5 Al- 2.5 Sn (titanium alloy) 827 4.46 15.00 Problem 2: (15 marks) A single crystal of a metal that has the FCC crystal structure is oriented such that a tensile stress is applied parallel to the [110] direction. The critical resolved shear stress for this material is 1.75 MPa. 1) Calculate the magnitude of applied stress necessary to cause slip to occur on the (111) plane in the direction. 2) Calculate the magnitude of applied stress necessary to cause slip to occur on the (111) plane in the direction. 3) Which of these two slip systems is the most favorably oriented (which system will see first plastic deformation)? And why? Problem 3: (25 marks) The mechanical properties of a 4030-carbon steel have been measured in the lab and are as follows: E = 205 GPa; σy = 860 MPa; UTS = 1280 MPa; ν = 0.29. A 22 mm diameter bar of this alloy is used as a structural member in an engineering design. The length of the bar is 2 m. 3.1) The structural load on the bar is the last five digits of your SID in newtons. For example, if your SID is 123456789, the load applied is 56,789N. If the 5th digit of your SID is 0 (eg. 123406789) then replace this 0 by a 1 so the load applied becomes 16,789N. 3.1.1) What will be the length of the bar under this structural load? Justify the use of any equation. 3.1.2) What will be the diameter of the bar under this structural load? Justify the use of any equation. 3.2) The design engineer is considering a structural change that will increase the tensile load on this member. What is the maximum tensile load that can be permitted without inducing plastic deformation of the bar? Problem 4: (15 marks) Pure iron goes through a polymorphic change from BCC to FCC upon heating at 912°C. 4.1) Calculate the volume change associated with the change in crystal structure from BCC to FCC if at 912°C the BCC unit cell had a lattice constant a = 0.293 nm and the FCC unit cell a lattice constant a’ = 0.363 nm. Make sure to explain clearly the different steps you have undertaken to come up with the solution. 4.2) What consequences this change of volume could have? Give an example where this change of volume is important to consider. Problem 5: (25 marks) You played Lotto and you have won large amount of money that you decided to spend on your dream house. You are having a big vision to build the “house of the future”. Please choose 2 main civil construction materials that you will use to execute your dream house (excluding conventional steels) 1) Why did you choose those materials? 2) What are their crystal structure, microstructure and mechanical properties? 3) What are the formability and joining properties of yours materials? 4) Describe durability and maintenance strategy for your chosen materials? 5) Describe 2 destructive and 2 non-destructive methods of testing the materials properties of your choice.




























































































































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