Mechanical Engineering Question

Assignment Task Brief Mechanics of Materials (Group 30)

You are required to complete a full engineering analysis and design report based on the provided assignment brief. The work must be carried out individually and presented professionally, as it will be assessed through a 30-minute presentation and viva session.

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Overall Objective

Deliver a complete, well-structured engineering solution that demonstrates strong understanding of stress analysis, fatigue, and mechanical design principles. The work must include clear methodology, justified assumptions, accurate calculations, and critical discussion.

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Question 1 Shaft Analysis (60 Marks)

You are required to analyse a hollow steel shaft subjected to combined cyclic loading.

### Given (Group 30 Data)

– Hole diameter (a) = 6 mm

– Outer diameter (D) = 36 mm

– Material = AISI 1030 CD

– Torque = 120 Nm (completely reversed)

– Bending moment = 150 Nm (completely reversed)

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## Task 1(a): Factor of Safety Analysis

Perform a complete fatigue and static failure analysis using:

– Gerber fatigue criterion

– Langer static yield criterion

### Requirements:

– Determine stresses due to bending and torsion

– Include stress concentration effects (due to hole)

– Calculate alternating and mean stresses

– Determine factor of safety for:

– Fatigue failure

– Static failure

– Present S-N curve clearly

– Use spreadsheet or MATLAB where appropriate (with explanation)

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## Task 1(b): Literature Review

Provide a critical discussion on:

– The role of Factor of Safety in fatigue design

– How it influences fatigue life prediction

– Trade-offs between safety, weight, and cost

Support your discussion with academic references.

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## Task 1(c): Hollow Shaft Design Process

Conduct a literature-based discussion covering:

– Material selection criteria

– Geometric optimization (diameter, thickness, fillets)

– Methods to reduce stress concentration

– Failure modes (fatigue crack initiation & propagation)

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# Question 2 Aircraft Door Handle Design (40 Marks)

You are required to design a structural component (door handle) under load.

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## Task 2(a): Material Selection

Select a suitable aircraft-grade aluminum alloy.

### Requirements:

– Justify selection based on:

– Strength-to-weight ratio

– Fatigue resistance

– Corrosion resistance

– Support with material data and references

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## Task 2(b): Stress Analysis & Design

Design the component to safely withstand the applied force.

### Requirements:

– Calculate stresses at the critical location

– Determine:

– Principal stresses

– Maximum shear stress

– von Mises stress

– Identify critical planes

– Apply an appropriate failure criterion

– Ensure a reasonable Factor of Safety

– Provide clear diagrams and stress representation

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## Task 2(c): Experimental Validation

Explain how you would independently verify material properties:

– Describe testing methods (e.g., tensile, fatigue tests)

– Identify relevant engineering standards

– Explain specimen preparation and data extraction

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# Deliverables

## 1. Engineering Report

– Structured, clear, and detailed

– Includes all calculations, diagrams, and references

– Logical flow and justified decisions

## 2. Spreadsheet / Numerical Work

– All calculations clearly shown

– Proper use of formulas

– Well-organized and labeled

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# Presentation & Viva (IMPORTANT)

The assessment will be conducted as follows:

### First 15 minutes Presentation

You must:

– Clearly explain your methodology

– Present key results and findings

– Use visuals (graphs, diagrams, stress plots)

### Next 15 minutes Viva (Q&A)

You must be able to:

– Justify your assumptions

– Explain every step of your calculations

– Discuss design decisions confidently

– Demonstrate full understanding (not memorization)

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# Key Expectations

– All work must be original

– No plagiarism or collaboration

– Clear reasoning is more important than final answers

– Engineering judgement is essential

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# Final Note

– Stress Analysis

– Fatigue Behaviour

– Mechanical Design Principles

Ensure the work is professional, defensible, and presentation-read