Joining Case Study

Length: 7 weeks (Introductory lecture, interim presentation, poster presentation)

Level: Year 2 Materials Science and Engineering Course

Key Skills: Group working, communication, poster presentation, independent study.

Assessment: Group report and poster and peer assessment


The basic processes for joining materials were covered in year one and this year these will be extended to consider design, defects and production of joints with reference to specific requirements. This is carried out using a team case study approach and so this part of the module is completely continuously assessed with no examination question. This case study will involve a number of activities and will overlap with aspects of Selection and Design, Fatigue and Fracture, Corrosion, Ferrous Metals, Non-ferrous Metals, Polymers and other Materials Processing courses.

Joining engineers usually work within teams in specifying joining processes for components/materials, quality control (welds are a major source of defects and failure initiation) and in failure analysis. This case study will address the first of these activities, but will be broadened as the material and process choice is open, whereas, frequently, these are limited by other aspects of the component or processes available to the company.

The case study activity will extend over the weeks allocated for the joining part of the MSE M2B module. 1 credit module represents 10 student effort hours and, as joining is one third of the 8 credits assigned to the M2B2 module then each student should put in 27 hours work. The teams have 5-6 members and so each case study represents 135-162 hours work.

Your case study specifications could be any one of the following.   These specifications are similar to those that might be given to joining engineers at the beginning of a job.  The material and joining method you use is entirely up to you as long as it is appropriate to the given specifications.

1. Pipeline 1000 kms in total length.

1m outside diameter and 12.5 mm maximum wall thickness.

Minimum yield stress 450 MPa..

Prepared in lengths up to 14m and joined on site.

Construction and service temperatures between –40 and +40 ºC.

Cl¯ ion corrosion resistance needed.

27 J minimum impact energy at -40ºC.

Pipeline lifetime 30 years.

Cost should be kept as low as possible commensurate with non failure in service.

2.  Lightweight radiator system for high performance automobile

Rectangular with maximum frontal area 40 x 60 cm and maximum depth 7.5 cm.

Fixing to vehicle only along vertical edges.

Temperature range -40 to +100°C.

Intermittent salt exposure to external surfaces; internal surface should have controlled composition (distilled water), but anti-freeze will be added in winter.

Fatigue resistance required.

Lifetime at least 15 years.

Production rate will be a few 1000s a year.

3.  Aeroengine compressor drum

Safety critical

Lightweight

Maximum operating temperature 500°C.

High and low cycle fatigue resistance.

Minimum yield stress 650 MPa.

Minimum distortion.

Five discs joined together in each drum.20 year lifetime in service.

Maximum annual production of 600 units.

4. Power station heat exchanger bundles.

50 tubes fitted into a 1m diameter, 20 mm thick plate at each end.

Maximum tube wall thickness 5 mm.

Tube outside diameter 100mm.

Gas temperature (outside tube) 650?C.

Water inside tube has to be controlled composition therefore wet corrosion risk is low.

Fatigue risk is low.

Lifetime at least 15 years.

Operating stress 120Mpa maximum.

No more than 100 produced per year.

High cost of failure in cost down time.

5. Lightweight tube structure (linked at both ends).

Maximum tube length 1m.

Tube outside diameter 25 mm.

‘T’ joints with a variety of angles between 70 and 110.

Must be capable of being coloured by paint or polymer coating.

10 yr lifetime under service conditions of intermittent chloride spray exposure and temperatures between –40 and +40C.

Total structure size 1 x 0.2 x 0.2 m.

Production 100, 000s per annum.

No fatigue failure during vehicle lifetime.

Maximum load experienced 100 kgf in bending or corrosion.

Range of costs acceptable.

6. External tram body.

Length 20 m, diameter 2.5 m.

Closed at both ends, but containing door and window cut outs.

Maximum stress 150 Mpa.

100s produced each year.

External appearance must be smooth.

Capable of being coloured by paint.

Low cost and low maintenance costs.

20 year lifetime under service conditions of intermittent chloride spray exposure and temperatures between –40 and +40C.

Lightweight, stiff structure with high fatigue life.

Low distortion.

7. Box girders for bridge section.

Hollow pre-fab. unit assembled on site.

Box units 10 x 5 x 2 m.

Total span 4 km over sea water.

100 yr lifetime in ambient temperature range between –40 and +40C.

Minimum yield stress 600 MPa.

Low cycle fatigue loading (traffic).

Corrosion protection to be provided.

Minimum Charpy impact of 27 J at -40C.

Initial Activities

All groups should arrange a meeting to cover their ideas with the lecturer before the end of the second week. After that groups should contact the lecturer as needed during the rest of the case study. In the last week of term groups must give a 10 minute progress presentation.

Assessment

The assessment for this activity will be made up of three components:

(i) A final group report outlining the activities undertaken and the recommendations for the materials, design and joining process to be adopted for the specifications given. Reasons need to be given for any decisions made and references should be provided. Quantification of any decisions by e.g. stress calculation is strongly encouraged.

(ii) A poster to be presented in this study room.

(iii) A peer assessment rating, which will be used as a weighting factor for the group marks.

Resources

Easterling, K. E., Introduction to Physical Metallurgy of Welding, Butterworths, London.

Endean, M.  and Edwards L., Manufacturing with Materials, Butterworths, London.

Lancaster, J. F. Metallurgy of Welding, Allen and Unwin, London.

www.twi.co.uk

www.bath.ac.uk/Centres/AWJU/home.html

www.matweb.com

www.amweld.org

ASM Materials handbook

Joining books, slides and notes (Dr Strangwood)

Staff researching on joining and associated areas (see School web pages)