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Mechanics of Materials Coursework: You are asked to design a door handle in an aircraft, as shown in Figure 1. The loads and major dimensions are provided in Table 1. You, as a designer, are free to choose the other geometric parameters freely considering that design requirements for safety factors are satisfied. The bracket is mounted on the locking mechanism by the help of a flange. There is a fillet of radius r at the transition from the hollow shaft to the flange. I do d₁ Figure 1 Door handle geometry Parameterised geometric data choices are given in Table 1. Table 1. Parametric data for design problem. F a b (N) (mm) (mm) 1600 100 165 F h 1) By doing a literature survey and/or consulting materials databases, choose a type of aircraft grade aluminium alloy for the material to be used in the design. [10 marks] 2) The bracket is expected to withstand a force of F without yielding. Size your design to provide a reasonable Factor of Safety for static yielding. [15 marks] Please refer to the techniques taught in the year 2 modules: "Stress Analysis". You should find the stresses at the most critical location with respect to the coordinate system shown. Then find the Principal Stresses, Maximum Shear Stress, von Mises Stress and the planes on which Principle Stresses and Maximum Shear Stress are acting. Show these planes by drawing a schematic at the critical location. Use a suitable static failure criterion!
3) Find the vertical and horizontal deflection of the end of the handle under the applied load using an energy method of your choice. Size your handle so that the static deflection in y- direction should not exceed 1.5 mm. [15 marks] 4) The service load consists of the locking and unlocking force applied to the end of the handle. So for fatigue life calculations, the bracket can be considered to be subjected to a sinusoidal force with F=F and F =-F. Resize your design so that you can provide a reasonable factor of safety for infinite life in fatigue. (By doing a literature survey and/or consulting materials databases, try to find the actual S-N diagram of the aluminium alloy you have chosen.) [15 marks] 5) If the bracket is subjected to a sinusoidal force function with F2F and F=0 what will be the safety factor for infinite life in fatigue? [15 marks] 6) Given the fact that the alloy used is a ductile material, find the orientation of the plane at which crack initiates and progresses with respect to the coordinate system shown. Find the dimensions of the crack that will lead to a catastrophic failure. [15 marks] 7) Considering that the data retrieved from literature or provided by the manufacturer may not be reliable, you decided to test the specimen in the laboratory yourself. Find the relevant standards for obtaining the relevant material data for your design, provide a brief description of the specimens and procedures in your report. [15 marks]