Reference no: EM132278174 , Length: 8 pages
Introduction
In this assignment you are asked to provide a short report (maximum 10 A4 pages) on the design and analyse of traffic signpost, shown in Figure 1. The signboard and the signpost, are made of carbon steel and are subjected to a wind gust of 110 kms/hr.
1. You are required through a literature survey to choose the type of carbon steel for the material to be used in the design and list all required properties.
2. Calculate the total force exerted on the structure due to the wind.
The relation should include the density of air, the wind speed, and the frontal area of the sign.
3. Find the deflection of the end of the traffic signpost due to applied load, calculated in part 2, using method of energy.
Note: Analyse the traffic signpost as a simple cantilever beam. The deflection has to be then calculated in z-direction.
4. The design is expected to withstand a drag force without yielding.
a. Size your design to provide a reasonable Factor of Safety for static yielding.
You should find the stresses at the most critical location with respect to the coordinate system shown. Then find the Principle 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 suitable static failure criteria.
b. Optimize the design on the signpost such that the static deflection should not exceed 25 mm.
5. The service load consists of the locking and unlocking force applied to the signpost. Hence, for fatigue life calculations, the signpost can be considered to be subjected to a sinusoidal force with Fmax= Fdrag and Fmax=- Fdrag. Resize your design so that you can provide a reasonable factor of safety for infinite life in fatigue. (By doing a literature survey, try to find the actual S-N diagram of the Carbon steel you have chosen.)
6. 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.
7. Write a report including above parts 1-6. The report should contain the formulas used, calculations, all relevant graphs and charts. Include a summary table in a specified format for geometric dimensions, loads, stresses, stress concentration factors, stress intensity factors, and safety factors. Please ensure that you satisfy the required factors of safety by iterating your design.
