Tec memo project

EGEN 208 Axial / Torsional stress analysis Fall 2020 Project Due: October 9th 2020 Submit via: Gradescope (Tech Memo 2) You are providing the max stress analysis of a propeller shaft in a Panamax freighter to determine the overall design factor of safety. The New Panamax container ships are massive engineering marvels that are designed to carry over 120,000 tons including cargo, fuel, and crew. A giant engine produces 64,000 kW of power at the propeller shaft to turn a single 10m diameter propeller. As the ship accelerates, the engine will turn the shaft at 74 rpm and produce up to 5,000 kN of thrust (normal force on the shaft). Other components of the shaft design indicate that an additional longitudinal normal stress of up to 25 MPa should be accounted for in the determination of the max stress resulting from potential bending of the shaft. The solid 800 mm diameter propeller shaft is made of a steel alloy with a max yield strength of 621 MPa, and a max shear stress of 255 MPa. Using the provided information you are tasked with determining the factor of safety within the propeller shaft design.

Technical Memo Core Components:

1) Memo Body: a. Provide a brief statement of purpose for the analysis / problem statement and

written communication of a results summary. (This section typed in the memo body covering the problem statement in the introduction, description of your solution the solution section, and summary of results in Results.)

b. Provide a Free Body Diagram (FBD) of the shaft to determine external forces and illustrate orientation of your stress element. (Competed on engineering paper or graphical software, labeled and inserted within Memo body.)

c. Communicate results of the stress analysis by illustrating a stress element with the base oriented along the longitudinal axis of the propeller shaft and communicate rotation angle to principal stresses, the principal stress, max shear and average normal stress using a 45-45-90 degree triangle. (May be hand illustrated)

d. Communicate the results of your factor of safety analysis.

Technical Memo Extension Components: A thrust block toward the rear end of the ship transfers all normal stresses from the propeller shaft to the hull of the ship. After the thrust blocks, intermediate sections of the propeller shaft which are made of the same shaft material transmit only a torque. The length of the propeller shafts from the trust block to the engines which are located closer to the middle of the ship is approximately 45 m and that material has a modulus of elasticity E = 200 MPa and a Poisson’s Ratio 𝜈 = 0.25.

1) (Extension) If a factor of safety of 2.0 is required in the propeller shaft what is the minimum required shaft diameter in units of mm?

2) (Extension) At full power, what is the angular deflection of the shaft along the 45m’ length of the intermediate shafts assuming you apply the minimum calculated diameter?

3) (Extension) The intermediate shafts are built in 50’ sections connected by coupling flanges. The flanges are bolted together using 35mm diameter bolts arranged in a circular pattern around the shaft; each bolt center is a distance of 500mm from the shaft center. If the bolts are made of the same material as the shaft and there is a required factor of safety equal to 2.5, how many bolts are required in the flange?

Technical Memo Rubric:

• Memo was submitted prior to the due date. • Written descriptions are typed and the document organized into sections that reflect the

assignment deliverables noted in the Core and/or Extension components. • Written language is clear and contains only minor spelling and grammatical errors. • Requested images are incorporated into the document and hand written sheets for FBDs

and/or calculations are labeled and attached. • Calculations are clear, well presented, units are carried through and results are technically

correct. • All Core memo components are labeled and completed. • If Desired: All extension memo components are labeled and completed.