Mec-B8 — Engineering Materials
Working properties and applications of metallic, non-metallic, polymer, and composite materials. High temperature materials, microscale and nanoscale mechanisms responsible for their unique properties (e.g., molecular mobility and phase transitions). Selection and testing of materials. Testing of engineering materials. Emphasis on those used in aircraft, highspeed ground transportation vehicles, underwater, and space applications.
Subject outline
Mec-B8 Engineering Materials is a Mechanical Engineering technical exam (PEO National Examination 16-Mec-B8). Its official syllabus covers the working properties of steel and of aluminium, magnesium and titanium light alloys, superalloys and metal-matrix composites; high-temperature materials, metallic foams and other cellular materials, precursor-derived ceramics, corrosion, intermetallics, multicomponent alloys, biomedical materials, polymeric composites as structural materials, and ultrafine and nanostructured materials, with the micro- and nanoscale mechanisms behind their properties; polymers, shape-memory alloys, piezoelectric materials, electrorheological fluids, magnetostrictive materials and fibre-reinforced composites; and the selection and testing of engineering materials, with emphasis on aircraft, high-speed ground transport, underwater and space applications. The two 2019 papers solved here examined the fundamentals beneath that list, and that is what this course teaches: atomic bonding and why it sets every property; crystal structure and counting atoms; diffusion through Fick's two laws and the Arrhenius relation; stress, strain and the tensile test; strain hardening, the Hollomon law and Considère's criterion for necking; cold work, recovery and recrystallization; phase diagrams and the lever rule; iron–carbon, isothermal transformation diagrams and heat treatment; corrosion, the galvanic series and Faraday's law; and composites and polymer selection. It does not teach superalloys, metal-matrix composites, cellular materials, precursor-derived ceramics, intermetallics, multicomponent alloys, biomedical or nanostructured materials, smart materials (shape-memory alloys, piezoelectrics, electrorheological fluids, magnetostrictive materials), high-temperature materials, or materials testing beyond the tensile test (fatigue, creep, fracture toughness, hardness, impact and non-destructive testing).
The paper is 3 hours and open book; any non-communicating calculator is permitted. Answer any five questions — the May 2019 paper sets eight and the December 2019 paper seven: any five constitute a complete paper, only the first five as they appear in the answer book are marked, and all problems are of equal value. If doubt exists as to the interpretation of a question, state your assumptions clearly in the answer book. Because the paper is open book, the formula sheet in this course is built to be checked against your own text and taken in — together with the property charts printed on page 4 of the December paper, which the cold-work, heat-treatment and phase-diagram questions read their values off.
The same examination is also listed as 08-Mfg-B5 — the Manufacturing Engineering listing of the same paper; the question papers themselves are headed 16-Mec-B8. Same paper, same syllabus, two faculty codes.
What this course gives you
Worked solutions — all fifteen questions from May 2019 (eight) and December 2019 (seven), fully retypeset as live maths with the final answers pulled out ahead of the working, and every published answer checked — with nine corrections flagged at the exact step that goes wrong. Four of them are answers that do not follow from their own working: the December Q2 cold-working schedule stops at 19.09 mm (17.3 %CW) with no anneal, which is neither the 13.5 mm diameter nor the 350 MPa the question asks for — copper at 17.3 %CW is only about 290 MPa, and because the strength floor (about 38 %CW) sits above the ductility ceiling (about 20 %CW) no single pass can meet both; the December Q6(c) eutectic constituents are computed as products instead of the lever-rule difference, giving 0.0816 and 0.00438 where the answers are 0.035 and 0.050; the December Q4 titanium–304 stainless couple is settled correctly in one sentence and then contradicted by the solution's own summary; and the May Q4 anode current is divided by a garbled denominator (14 years, and 24 seconds to the hour) that would evaluate to 1.08 A where the answer is 12.6 mA. The other three flag a carbon flux quoted in at%·m/s rather than atoms/m²·s and convert it, an ABS selection for a box bolted to an engine that the solution's own property list rules out on service temperature, and a porosity explanation of why engineering ceramics are light that is wrong for alumina and silicon carbide. Two more correct a chart reading and a definition: the December Q6(d) θ boundary at 350 °C is read at 56.8 wt% Cu, beyond the θ field of CuAl₂ (about 52.5 %), so the fractions are 0.864 α and 0.136 θ, not 0.878 and 0.122; and the May Q8 ultimate tensile strength is quoted as the true stress at necking, 212.5 MPa, where the UTS — the engineering stress at maximum load — is 147 MPa. Where a published figure stands it is used; where it does not, the published value is quoted and a flagged correction of its own — headed, and set into the working at the exact step that fails — explains what went wrong and gives the corrected value. Nothing has been silently overwritten. Selection and process questions — five of the fifteen are materials-selection and process cases, and each is argued in full: FRP consolidation routes for aircraft structure, ABS against phenolic for an under-bonnet box, aluminium–lithium alloy substitution for transport-aircraft floor beams, choosing material classes from their bonding, and galvanic couples in sea water. Study notes — ten condensed topics: bonding and why it sets every property; crystal structure and counting atoms; diffusion; stress, strain and the tensile test; strain hardening and the onset of necking; cold work, recovery and recrystallization; phase diagrams and the lever rule; iron–carbon, IT diagrams and heat treatment; corrosion and electrochemistry; and composites and polymer selection — with the exam questions each one answers called out along the way. Formula sheet — two pages in eight groups: structure and counting, diffusion, mechanical behaviour, strain hardening and necking, cold work and grain size, phase diagrams, corrosion, and composites — every relation these two papers use. This exam is open book, so print it, check it against your own text and take it in. Reference links — eleven, each with a note on what it is good for: six to reading (NPTEL's worked corrosion problems, FRP processes compared, ABS resins and the PEO syllabus page, plus web searches for Callister & Rethwisch and for the sea-water galvanic series) and five to YouTube, each opening a search for the topic it names — isothermal transformation diagrams, the lever rule, cold work and recrystallization, Considère's criterion, and the rule of mixtures. Printable resources — four blank exam stationery templates: a ruled answer sheet matching the answer-book layout, dot-grid rough-work paper, graph paper and isometric paper — plus the formula sheet, all printing straight from the page. Practice papers — the two question papers on their own, unmarked, for a timed run: May 2019 (3 pages, questions 1 to 8) and December 2019 (4 pages, questions 1 to 7, with the property charts on page 4) — the same two sittings that are solved above.
Throughout, 90 figures were drawn for this pack — 42 in the solutions and 48 in the notes — alongside 7 images kept from the source material (the five property charts the December paper supplies and two moulding schematics), so the unit cells, diffusion profiles, stress–strain curves, cold-work windows, phase diagrams, IT diagrams, corrosion cells and rule-of-mixtures plots are shown rather than described.