Question 1
A sectional impression of a stainless steel pressure vessel used in a nuclear material processing plant is shown in Figure Q1. The pressure vessel needs to be installed in a rigid concrete (assume Grade 40, density 2400 kg/m3) cover as shown and closed with a hemispherical cover dome. A flexible leak protection seal will be placed around the concrete dome. Assume there is no clearance between the vertical walls of the vessel and the concrete enclosure walls. The vessel is resting on the bottom concrete slab as shown.
The initial conditions of the vessel estimated as ambient pressure, 1 bar and ambient temperature, 25 0C. Major design dimensions are shown and the thickness T needs to be determined by a FE Analysis. The vessel needs to withstand 0.5 MPa internal pressure and temperature increased up to 900C (at steady operational state). The vessel needs to be designed for 25% pressure surges and maximum stress in the vessel walls needs to be minimized as possible. You need to check your answers with appropriate manual calculations. (Assume the concrete cover adjacent to vessel's outer vertical walls, the interface at concrete dome and the vessels top dome reach 500C at the steady state. Determine a suitable trial value for thickness "T " Use the trial value for FEA and refine it until you meet the optimal design criteria. You need to (list all your assumptions):
1. Assume a trial thickness and perform simple manual calculations for a pressure vessel i.e. hoop and axial stresses at ambient conditions. Compare your manual calculations with an axi-symmetric FEA (2D Static FEA) carried out using Creo 4.0 Simulate. Then perform an axi-symmetric FEA for combined static & steady state thermal. You need to continue trial values of thickness "T" until you find an optimized condition according to your judgment. A data sheet for boiler steel is provided in the study desk.
2. Provide appropriate contour plots as necessary to show stress, strain and the temperature distributions of the final design.
3. Perform an appropriate 3D FEA analysis for the final design of the vessel (Combined static & steady state thermal). Provide stress/strain /temperature contour plots as necessary to show stress, strain and the temperature distributions of the final design and compare your 2D FEA results with 3D FEA results by using a table.
4. Provide your comments on the 2D & 3D FEA analysis. Also include your suggestions for an improved design (geometry, materials of the vessel and the concrete dome) if the operational conditions cause higher stresses than allowable stresses.
Question 2
Figure Q2 shows an engineer's sketch of a proposed vertical stainless steel shaft which will drive a mixer of a chemical plant. The larger end of the shaft will be coupled to a 5kW, 4000 rpm electrical motor through a flexible coupling and the smaller end will be coupled to the shaft of the mixer. The length of bearing surfaces can be assumed as indicated in the drawing. Bearing A and the connection at mixer do not allow axial movements. The estimated thrust created on the shaft by the mixer P = 2kN. A 30 mm thick steel pulley is attached at the middle of the shaft as indicated in the figure. The surface of the smaller diameter shaft is fully insulated by safety covers (to cover hot surface and not shown here) The portion of bigger diameter of the shaft and pulley surfaces will be exposed to ambient air (convection coefficient can be taken as 50 W/m2/0C) .
Your task is to find the stresses/strain/temperature distribution of the shaft under the operational condition :
1. Create an appropriate FEA model on Creo Simulate 4.0. Assume and justify any missing details you required. You need to list assumptions with your justification in the report.
2. Perform (i) static, (ii) thermal and (iii) static +thermal analyses. Provide appropriate stress/strain (Von Mises, principal etc) temperature and heat flux distribution. If the yield strength of stainless steel is 220MPa, determine the overall safety factor of the shaft. (Note: Since the shaft is rotating at 4000rpm, you need to add centrifugal force in to your FEA model). If the stress levels under operational conditions are beyond yield strength of stainless steel, list your recommendations to reduce the stresses below yield strength.
3. Perform a vibration analysis. Show results of first 3 natural frequencies and mode shapes of the shaft.
4. Determine the highest safe rotational speed of the motor considering the vibration characteristic of the shaft and the possible yielding of the pulley.
Question 3
Figure Q3 shows a conceptual model of a connecting rod which was prepared for an initial stress/strain analysis. The maximum normal operational pressure acting on the Gudgeon pin at the power stroke was estimated as 20MPa. The material of the connecting rod is steel alloy 42CrMo4 (E=198 GPa, Poisson ratio =0.3, Ult. Strength 800 MPa - 1000 MPa, Coef. of Expansion=17.3 x 10E-6 /0C)
(a) Create a suitable 3D model in Creo4. Simulate to analyse the structural performances of the connecting rod at the maximum load application. You need to show, force applications, constraints and the refined model with the mesh using appropriate graphical representations.
(b) Perform a 3D static analysis and show appropriate surface stress/strain contour plots (Von Mises, Principal) including through the thickness stress/strain contour plots at the sections planes indicated by the dotted lines.
Note: You need to create a coarse mesh first and a then refine the mesh appropriately. You can use symmetry for FEA modelling. Assume missing dimensions and list your assumptions.
Attachment:- Assignment.rar