Reference no: EM132859363
MP4702 Advanced Materials And Materials Selection - University of Central Lancashire
Maintenance Engineering
Learning Outcome 1: Able to communicate effectively on material selection with material scientists
Learning Outcome 2: Able to understand the implications of different modes of material failure
Learning Outcome 3: To understand the effects of composition and heat treatment on the properties of different types of material
Learning Outcome 4: To select materials to minimise the likelihood of component failure
SECTION A
ASSIGNMENT BRIEF FOR SECTION A:
You have been asked to design the structure of a solar panel and a pole (mounting for the solar panel) for power transmission. The designed material needs to be light, strong, stiff and as cheap as possible. The cross section of the PANEL is specified as rectangular cross-section with b as breadth and h as height of the panel. The cross section of the POLE is specified as a COLUMN of circular cross-section, d. The designed panel and column have a length, L. Write down an equation for the material cost of the panel and column in terms of its dimensions, the price per kg of the material, Cm, and the material density, ρ.
Provide a detailed, professional report that contains the following items mentioned below:
1. Definition and translation of the problem.
Hint 1: You have to document the whole selection process.
Hint 2: The dimensions of the panel and column are not given. You can decide your own realistic dimensions and the constraints for both the panel and column.
Hint 3: You will need to decide extra constraints and find out the equations for a panel and a column.
Hint 4: You will need to decide your objective and to compare the results with real world materials.
Hint 5: You will need to provide a clear definition of the problem and write down the necessary equations used in the problem.
Hint 6: You will need to translate the problem based of the definition and equation provided in the previous steps.
2. Derive the performance index or indexes.
3. Use GRANTA EduPack to select some screening constraint and select the actual material graphically.
SECTION B
Jet engines are combustion engines and it is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. While this broad definition can include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an airbreathing jet engine such as a turbojet, turbofan, ramjet, or pulse jet. Airbreathing jet engines typically feature a rotating air compressor powered by a turbine, with the leftover power providing thrust through the propelling nozzle - this process is known as the Brayton thermodynamic cycle. Jet aircraft use such engines for long-distance travel. Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines. They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high speed applications (ramjets and scramjets) use the ram effect of the vehicle's speed instead of a mechanical compressor. The thrust of a typical jet liner engine went from 22,000 N (de Havilland Ghost turbojet) in the 1950s to 510,000 N (General Electric GE90 turbofan) in the 1990s, and their reliability went from 40 in-flight shutdowns per 100,000 engine flight hours to less than 1 per 100,000 in the late 1990s. This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin-engine airliners by the turn of the century, where previously a similar journey would have required multiple fuel stops.
QUESTION B1
(a) Draw the Time Temperature Transformation T-T-T diagram for nickel-based superalloy (Inconel 718) used in jet engines and show on the diagram the critical cooling curve, the transformation lines, the phases, the axis.
(b) Explain the change of structure with martensitic transformation in steels used in jet engines.
(c) With help of a phase diagram illustrate the various phase transformation occurring in the commercial titanium alloys (Ti - 6Al - 4V) used in the jet engines.
(d) With help of a phase diagram discuss the following phase transformation reaction occurring in the commercial Titanium alloys (Ti - 6Al - 4V) used in the jet engines
(i) Peritectic reaction and Peritectic point
(ii) Peritectoid reaction and Peritectoid point
QUESTION B2
Using suitable industrial examples, explain creep and oxidation of nickel based super alloys used in jet engines at high temperatures. Discuss three strategies to reduce creep and three strategies to reduce oxidation in jet engines at high temperatures.
QUESTION B3
An aluminium alloy for an airframe component used in jet planes were tested in the laboratory under an applied stress which varied sinusoidally with time about a mean stress of zero. The alloy failed under a stress range Δσ of 300 MPa after 105 cycles. Under a stress range of 220 MPa, the alloy failed after 108 cycles. Assume that the fatigue behaviour of the alloy can be represented by
ΔσNfb = C
where b and C are material constants.
(a) Find the number of cycles to failure for a component subject to a stress range of 200 MPa.
(b) A jet plane using the airframe components has encountered an estimated 3.2 ×108 cycles at a stress range of 200 MPa. It is desired to extend the life of the airframe by another 4.5 ×108 cycles by reducing the performance of the aircraft. Use Miner's rule to find the decrease/increase in the stress range needed to achieve this additional life.
QUESTION B4
A jet engine spline coupling made up of high strength steel, is subjected to axial load, bending moment and torque during the flight take-off and landing. The spline coupling is tested under the laboratory using the scaled spline testing simulating the real operating conditions. The initial axial load applied was 55 kN, alternating bending moment was ± 650 Nm and a torque of 15 kNm. The specimen is subjected to fatigue loading until failure. The test is performed under a tension - tension cycle with a stress ratio of 0.1. The yield strength of the material is 1350 MPa.
(a) Calculate the initial stresses applied on the sample.
(Hint: Use the equation of the maximum principal stresses and shear stresses for a bi-axial loading condition).
(b) After 90,000 cycles the crack propagation is faster and leads to final fracture. Explain with help of a simple sketch, the various regions of fatigue crack growth and microstructural variation seen in the jet engine spline coupling during the fatigue crack growth testing.
Attachment:- Course Work_Semester.rar