THE UNIVERSITY OF MELBOURNE DEPARTMENT OF INFRASTRUCTURE ENGINEERING Semester 2 Assessment, 2016 ENGR20003 Engineering Materials Pass and Honours Exam Duration: Two (2) hours Reading Time: 15 minutes This paper has 22 pages Authorised materials:  Only approved electronic calculators may be used.  Protractor and compass may be used. Instructions to invigilators:  Closed book examination  All the answers need to be written on this exam paper  Students can use scrip books as a draft Instructions to students:  All questions should be attempted  Sections A, B and C are to be answered on this exam paper.  You are allowed to use a scrip book as a draft  Marks allocated to each question are as indicated.  Total marks for the examination equal 100. Paper to be lodged with Baillieu Library ENGR20003 Engineering Materials Page 2 of 22 Section A Construction Materials A1. Steel Construction A 1.1. Indicate which section is more suitable to be used as a column member and which section is more suitable to be used as a beam member. Justify your answer. Figure 1. Figure 2 (8 mark) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 3 of 22 A 1.2. a) Draw a beam to column connection that has no eccentricity. b) Does the connection need any stiffener? If Yes explain why we need a stiffener. (8 mark) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (Total marks for QA1 = 16) ENGR20003 Engineering Materials Page 4 of 22 A2. Timber Constructions A2.1. Briefly describe using sketches the difference between plain sawn and quarter sawn timber. Discuss with the aid of sketches the issues associated with using plain sawn timber in construction. (5 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ A2.2. Briefly discuss two advantages of using laminated veneer lumber over sawn timber in construction. (5 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 5 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (Total marks for QA2 = 10) A3. Concrete formulation: You have to provide a concrete formulation to your concrete supplier at the mixing plant. The concrete you need to make has the following requirements: - Average compressive strength of 25 MPa after 28 days of curing (CS28), safety precautions included. - Slump at 100 mm At the mixing plant they only have the 3 types of aggregate represented in Figure 4 on the page 7. Data: - The sand has a true density of 2.50 t/m3 and is of good quality - The small coarse aggregates have true density of 2.53 t/m3 , and of pass quality - The larger coarse aggregates have an absolute density of 2.67 t/m3, and of pass quality - The cement available is a general purpose cement (GP) with a density ρ(C)=3.1 t/m3 and a true class (Tc) equal to 45 MPa. Equations:  = ′ ( − .) Bolomey, where CS28 =targeted strength, A’ = Aggregate Coefficient, Tc = True class of cement, C=cement amount for 1 m3 and W= water amount for 1m3  V = (C0 - Vc), where V= absolute volume aggregates, Vc =Volume of cement, C0 = compactness Your colleague started to use the Dreux-Gorisse’s method in order to determine the amount of cement and water you need for the formulation and he found 400 kg/m3 of General purpose cement (GP) and a W/C of equal to 0.53. ENGR20003 Engineering Materials Page 6 of 22 A3.1. Redo the calculations again, in order to confirm the amount of cement and the W/C that your colleague found using Table 1, Figure 3 and 4 and the data provided. Show on figure 3 the construction marks you used to obtain the amount of cement. (4 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Table 1: Aggregate coefficient A’ = Aggregate Coefficient (given by the following table) depending on the quality of the maximum aggregates size. Quality of the aggregates Dimension Dmax of the Aggregates Fines Dmax ≤ 12.5 mm Medium 12.5mm < Dmax ≤ 35mm Big Dmax > 35 mm Excellent 0.55 0.60 0.65 Good 0.45 0.50 0.55 Pass 0.35 0.40 0.45 Figure 3: Chart to determine the cement content ENGR20003 Engineering Materials Page 7 of 22 Your colleague has also drawn the Dreux broken line, which is represented on Figure 4 below. Using your partner’s Dreux broken line and assuming that the compactness coefficient of the concrete equals to 0.840, provide the complete formulation by answering questions A3.2., A3.3. and A3.4. Figure 4. A3.2. Determine the proportion of each aggregate (%) using Figure 4. (4 marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ A3.3. Calculate the total volume of aggregates and deduce the volume of each aggregate. (3 marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 8 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ A3.4. Provide the complete formulation to your concreter for 1 cubic meter of concrete by completing the following table and showing your calculations. (3 marks) __________________________________________________________________________ 1m3 Cement (kg) Water (kg) Sand (kg) Small coarse agg. (kg) Large coarse agg. (kg) Formulation ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (Total marks for QA4 = 14) ENGR20003 Engineering Materials Page 9 of 22 A5. Masonry A5. Briefly discuss: a. The effects of mortar on the compressive strength of masonry walls ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (3 marks) b. The effects of increasing mortar thickness on the compressive strength of masonry walls ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (2 marks) (Total marks for Question A5 = 5) End of Section A (Total Marks for Section A =45) Section B starts on the next page ENGR20003 Engineering Materials Page 10 of 22 Section B Mechanics of Materials B1. B 1. The state of stress in a body is represented by a stress block shown in Figure 5. Figure 5 B1.1. Draw the Mohr’s Circle of the stress element (6 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 11 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ B1.2. Determine the principle stresses and the planes on which they act. Sketch the planes with the principle stresses acting on them. (7 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 12 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ B1.3. What are the maximum shear stresses and the planes on which they act? Show using the sketch. (7 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 13 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (Total marks for QB1 =20) B2. Describe using sketches the concept of shear dislocation of crystal lattice and its effect on the stress-strain relationship of a mild steel material. (9 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 14 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ B3. Explain using sketches three (3) advantages of using ductile material over brittle in construction (6 Marks) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 15 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ End of Section B (Total Marks for Section B =35) Section C starts on the next page ENGR20003 Engineering Materials Page 16 of 22 Section C Materials Chemistry QUESTION 1 (3 marks) Circle the correct answer. 1. What is/are the closest packing crystal structures? a) FCC and HCP b) FCC and BCC c) HCP [0.5 marks] 2. What types of interstitial sites are found in closed pack structures? a) hexahedral and octahedral b) tetrahedral and octahedral c) tetrahedral and hexahedral [0.5 marks] 3. If a very small-size atom impurity (C) is to be diffused through a host metal lattice structure (Fe), the most likely mechanism for its diffusion will be: a) Vacancy diffusion b) Self-diffusion. c) Interstitial diffusion [0.5 marks] 4. What is the main feature in a potential energy versus interatomic separation discatance graph that relates to the melting point of a material? a) The depth of the potential well b) The width of the potential well c) The curvature of the potential well [0.5 marks] 5. Strength in metals is increased by making dislocation motion…. a) easy b) difficult c) faster [0.5 marks] 6. Martensite is a… a) Equilibrium phase b) Metastable phase c) Intermetallic compound. [0.5 marks] (Total for Q1 = 3 marks) ENGR20003 Engineering Materials Page 17 of 22 QUESTION 2 (4 marks) Using the periodic table below containing the electro-negativity values for each element, what type of bond would form for each type of atom pair? Write the answer on the line provided. I) Na-Na _________________ II) O-O ___________________ III) Na-S __________________ IV) Na-K _________________ V) S-O ___________________ VI) Na-O __________________ VII) Ca-Zr _________________ VIII) K-Br __________________ (Total for Q2 = 4 marks) QUESTION 3 (6 marks) Calculate the density of Martensite. Martensite is the metastable Body Centred Tetragonal phase in the Fe-C system that results from rapid quenching. The structure is shown in the figure. Assume the Fe atoms touch along the base edges and that the carbon atom touches the Fe atoms above and below it. The molar ratio of C to Fe is such that one C atom is shared between 4 unit cells as shown in the Figure. Atomic Radius Atomic Mass Fe 1.22 Angstroms 55.8 g/mole C 0.80 Angstroms 12.0 g/mole Avogadro’s number is 6.02 x 1023 atoms per mole. (Total for Q3 = 6 marks) ENGR20003 Engineering Materials Page 18 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 19 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 20 of 22 QUESTION 4 (7 marks) Using the phase diagram below for brass (copper-zinc system), determine: i. the phases present [ 2 marks] ii. the composition (wt % Zn) of those phases and [ 2 marks] iii. the amount (wt %) of each phase [ 2 marks] a) for a copper-zinc alloy (30 wt % Zn) at 500 oC. b) for a copper-zinc alloy (40 wt % Zn) at 600 oC. c) for a copper-zinc alloy (90 wt % Zn) at 500 oC. d) A particular brass alloy has 20 % Zn. What temperature will it start to melt at upon heating. [1 mark] (Total for Q4 = 7 marks) h Wt% Wt% ENGR20003 Engineering Materials Page 21 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ENGR20003 Engineering Materials Page 22 of 22 ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ (Total Marks for Section C = 20) End of Examination (Total Marks for Examination = 100)