AERO2359: Aerospace Structures
Stiffened Structures Assignment
This is an individual assignment. The assignment requires the use of Individual Parameters. These are obtained by attempting the “Stiffened Structures Assignment: Individual Parameters” Quiz (Ungraded Survey), which is found on Canvas. See Canvas for more details and the link to the Quiz.
You must submit your solutions as a single spreadsheet, which strictly follows the spreadsheet template available on Canvas. Instructions for completing the spreadsheet can be found in this document, and the spreadsheet template.
Your spreadsheet must be submitted on Canvas. The late submission penalty is 10% per calendar day late.
Spreadsheet solutions are marked based on accuracy of final solutions. No marks for working are available. This is in line with professional practice expectations, and encourages developing error checking and critical review techniques.
Consequential marking: The questions and marking scheme are developed with some provision for consequential marks (whereby an incorrect value obtained in an intermediate solution step is used in any subsequent steps and only one mark penalty is applied per error), where this is possible. A basic rubric for spreadsheet solutions is provided below.
Between 0 and full marks |
Full marks |
Errors or omissions in the solutions and/or graphs not prepared according to provided instructions. |
Final solutions are all correct, including graphs prepared according to provided instructions |
This assignment also requires the submission of a video assessment component. This submission is made by attempting the “Stiffened Structures Assignment: Discussion video” Quiz (Ungraded Survey), which is found on Canvas. See Canvas for more details and the link to the Quiz. The marks for the video submission are included in the marking for Assignment assessment task. The rubric for the video submission is provided below. Note that professionalism and quality of audio and visual content is not assessed. However, your face must be clear and identifiable, and the audio and video must be sufficient for assessment purposes.
|
Full marks |
Between 0 and full marks |
0 marks |
Length of recording |
Recording is less than 1 minute |
(intermediate marks not awarded) |
Recording is more than 1 minute |
Quality of response |
Video response has sufficient clarity, depth and accuracy |
Video response has insufficient clarity or depth, and/or contains errors |
Video response has insufficient clarity, depth and accuracy |
Attempt ALL questions.
The following is allowed:
. You are allowed to work individually.
. You are allowed to use software-based numerical aids like Microsoft Excel, Mathworks MATLAB, Wolfram Alpha.
. You are allowed to use any calculator.
. You are only allowed to use your Individual Parameters. The following is NOT allowed:
. You are not allowed to communicate or discuss with anyone regarding the problems or the solutions to the problems contained within this assignment.
. You are not allowed to disclose your Individual Parameters to others.
. You are not allowed to post the problems or the solutions on any online forum.
. You are not allowed to pay or get another person to prepare your assignment.
. You are not allowed to submit work prepared by another person.
. You are not allowed to copy any other person’s work.
. You are not allowed to use parameters other than the Individual Parameters allocated to you.
. Any other activity categorised as academic misconduct according to the definitions below.
According to the Student Conduct Policy, a student commits academic misconduct if the student:
a) cheats or attempts to gain an unfair academic advantage in any assessment task,
b) impersonates, or allows impersonation by, another for any assessment task,
c) plagiarises or submits the work of another person as the student’s own work,
d) knowingly enables or encourages another student to plagiarise their work,
e) takes into or uses in connection with any assessment session, any information or device other than information or devices specifically permitted by RMIT,
f) obtains from or gives to a student during any assessment session, information relating to the assessment task without prior approval from the staff member in charge of the assessment task, and which undermines the integrity of the assessment task,
g) commits a breach of the research code and RMIT’s published standards for conduct of ethical and responsible research, or
h) behaves in any manner that may provide a misleading basis for an assessment task.
A breach of any of the above may result in disciplinary action in accordance with the University policies relating to assessment and academic integrity. Please refer to RMIT’s Academic integrity webpage for further information.
Question 1 (40%)
Consider a stiffened beam using the “Q1 Rib” as provided in the Individual Parameters. The beam is assumed to consist of stiffeners carrying only direct stress and shear panels carrying only shear stress. The material used has E = 12000 ksi, G = 4500 ksi, σty = 55 ksi, σcy = 42 ksi, σsy = 36 ksi.
(a) Calculate the stiffener axial loads (lbf) at the end of each beam segment and the shear flows (lbf/in) along each panel edge. (30%)
(b) Size the beam by determining stiffener areas (in2) and shear panel thicknesses (in). (10%)
For stiffeners, size to yield stress (in tension or compression), considering the maximum load in each segment (i.e. each segment can have a different area).
For the shear panels, size to yield stress (in shear, maximum in each panel) or shear buckling, whichever is critical. For the buckling calculation, assume that the shear panels are simply supported on all edges, and for the tapered panels use the smaller edge dimensions (i.e. assume a rectangular panel with the smaller of the width and height edge dimensions), as per the diagram example below (only applicable for buckling K factor determination).
When sizing, use a minimum possible stiffener area of 0.35 in2 and a minimum possible panel thickness of 0.0065 in.
Question 2 (60%)
Consider a beam with cross-section given by the “Q2 Wing” as provided in the Individual Parameters. The beam uses stiffeners connected with shear panels. Assume the shear panels do not carry any direct stress. The material properties are: E = 69 GPa, G = 25 GPa, σty = 265 MPa, σcy = 235 MPa, τy = 165 MPa.
(a) Calculate the shear flow (N/mm) in each panel and determine the critical margin of safety in shear (ignore buckling or any other mode). (50%)
(b) Conduct a sizing exercise to determine a suitable set of panel thicknesses. You should achieve the following design requirements:
1. all margins of safety greater than or equal to 0.0
2. no panel thickness less than 0.2004 mm
In re-sizing the panels, you should consider that the beam cross-section dimensions and stiffener areas are fixed, and that only the panel thicknesses can be varied. You should only consider material failure (no buckling failure).
Your design exercise should also aim to achieve the lowest weight design possible for your configuration (which could be an increase or decrease compared to the panel thicknesses in Q2a).
Provide the shear flow (N/mm) and the thickness (mm) for each panel after the sizing exercise has been conducted. (5%)
(c) Provide a video submission as a reflection on the sizing exercise conducted in Q2(b) (5%). You should address the following question:
“ What was the method you used to conduct your sizing exercise and how did you achieve a low weight design?”
Your video response should:
. be less than 1 minute (video content after 1 minute will not be reviewed)
. address the question provided
. be clear (i.e. be coherent and follow a logical sequence in discussion)
. be of sufficient depth (i.e. no major omissions and not just a superficial response)
. be accurate (i.e. not contain errors)
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