Materials and Manufacture | My Assignment Tutor

ME413_P1_SEM2_2018/2019 Page 1 of 12sSCHOOL OF COMPUTING, ENGINEERING AND MATHEMATICSSEMESTER 2 EXAMINATIONS 2018/2019ME413Materials and Manufacture – Part I Student ID:Date:Place Number:Venue:Course Title:Extra pages used: Time allowed: THREE hoursABCAnswers:QuestionsAttemptedExaminer’sMarksVerifier’sMarksYou should write your answers to eachquestion in the space provided within thispaper. If you run out of space use thereverse of the paper and extra paper ifneeded.Attempt TWO questions in Part I and TWOquestions in Part II.Items permitted:Any non-programmable calculator.Total%DNo. ofQuestionsAnsweredItems supplied:Formula sheet ME413_P1_SEM2_2018/2019 Page 2 of 12 Marks for whole and part questions are indicated in brackets ( ) Attempt TWO questions in Part IQuestion 1Stress Analysis(a) Write the type of stress on the labels of all THREE elements.This is ………………………………………………………..This is ………………………………………………………..This is ………………………………………………………..(3 marks)(b) State the SI units of , and .is given in ………………………………………………………..is given in ………………………………………………………..is given in …………………………………………………………(3 marks)Question 1 is continued on the next pageME413_P1_SEM2_2018/2019 Page 3 of 12(c) Calculate the tensile stress in a 1 mm diameter wire that is supporting a 2 kg massfrom the ceiling. Assume g = 9.81 ms-2. Write your answer in the box provided.(4 marks)(d) Calculate the strain in a steel bar with Young’s Modulus is 200 GPa, if the tensilestress is 80 MPa. Write your answer in the box provided.(3 marks)Question 1 is continued on the next pageME413_P1_SEM2_2018/2019 Page 4 of 12(e) Calculate the shear stress in a 3 mm metal plate if a force of 25 kN is applied topunch a 20 mm diameter hole. A diagram of the punched plate is shown below. Writeyour answer in the box provided.(5 marks)Question 1 is continued on the next pageME413_P1_SEM2_2018/2019 Page 5 of 12(f) Consider the following stress-strain curve for mild steel and fill-in the SEVEN gaps inthe statements below.Point ‘a’ is the………………………………………………………………………………..Point ‘b’ is the………………………………………………………………………………..The gradient at ‘c’ is the……………………………………………………………………The portion of the graph to the left of point ‘b’ is called the ……………………………region.The portion of the graph to the right of point ‘b’ is called the……………….……..……region.The graph slopes down after point ‘a’ because ………………………………….……..occurs.For a component that is to be re-used, ductile failure occurs at point ………………..…(7 marks)ME413_P1_SEM2_2018/2019 Page 6 of 12Question 2Thermal properties, creep and impact. (a)The specific heat capacity of copper is 385 J/kg∙K, the melting temperature is 1356 K,and the latent heat of fusion is 2×105 J/kg. Calculate the heat necessary to raise the temperature of 1 kg of copper from 356 K to1356 K.(3 marks)Answer: _____________(b) Calculate the heat required to melt the copper at 1356 K.(2 marks)Answer: _____________(c) The ends of a metal bar are secured to prevent thermal contraction. Calculate thenormal stress in the bar if the temperature dropped from 55°C to 15°C. E=200 GPa.Coefficient of linear expansion = 12×10-6/°C.(5 marks)Answer: _____________Question 2 is continued on the next pageME413_P1_SEM2_2018/2019 Page 7 of 12(d) A steel pan that is 1 mm thick is placed on a 500°C stove and contains boiling water at100°C.Calculate the heat flux into the water if the thermal conductivity of the steel is 50W/m∙K.(5 marks)Answer: _____________(e) The energy required to fracture an aluminium alloy specimen is studied with a Charpyimpact test. The pendulum is lifted to the height of 1.85 m above floor level. Afterbreaking the specimen, the pendulum swings to a final measured height of 0.85 mabove the ground level. What is the energy absorbed by the specimen if the mass ofthe pendulum is 12 kg?Acceleration due to gravity is 9.81 m/s2.(5 marks)Answer: _____________Question 2 is continued on the next pageME413_P1_SEM2_2018/2019 Page 8 of 12(f) A material is subject to an applied stress of 60 MPa at a temperature of 800 K. Thecreep rupture data for the material is shown in Figure Q2. What is the expected time tofailure for this material?(5 marks)Figure Q2Answer: _____________304050607080901001101201.00E+04 1.00E+05 1.00E+06Stress (MPa)Rupture life (hours) 800K750K700 K ME413_P1_SEM2_2018/2019 Page 9 of 12Question 3Fracture Mechanics and Fatigue (a)Compare the following stress-strain curves for two different materials. Fill-in the FIVEgaps in the statements below with either ‘a’ or ‘b’. Material……………………………………….. is stronger.Material……………………………………….. is ductile.Material……………………………………….. is stiffer.Material……………………………………….. is brittle.Material……………………………………….. is tougher.(5 marks)Question 3 is continued on the next pageME413_P1_SEM2_2018/2019 Page 10 of 12(b) State the fatigue fracture characteristics in the TWO gaps below:…………………………can be seen with the naked eye or a low powered microscope.…………………………can be seen with an electron microscope.(2 marks)(c) Consider the following S-N curve and fill-in the TWO gaps in the statements below.The fatigue limit for 10,000,000 cycles is approximately ………………………The fatigue lifetime for 57 MPa is approximately …………………………..(4 marks)Question 3 is continued on the next pageME413_P1_SEM2_2018/2019 Page 11 of 12(d) Explain the differences between (i) stable crack propagation in a ductile material and(ii) unstable crack propagation in a brittle material. Write your answer in the boxprovided.(6 marks)Question 3 is continued on the next pageME413_P1_SEM2_2018/2019 Page 12 of 12(e) A cracked polymer tensile test specimen is shown below. It has a breadth (b) of 40mm and a thickness (t) of 5 mm. Fast fracture occurs when the load (F) is 2.75 kN.The geometric factor is 1.15 and the crack length is 3 mm.Calculate the specimen’s fracture toughness. Write your answer in the box provided.(8 marks)

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