CAPE1720 – Materials Science and Engineering

ASSESSED COURSEWORK: MATERIALS SELECTION ASSIGNMENT

INTRODUCTION

The end of Semester 1 introduced the concept of materials selection in product design. Materials selection is an essential technique for engineers developing components for products in addition to choices about materials processing routes. Materials processing will also be introduced more fully this semester but does not form. a central focus of this assignment. This assignment will focus specifically on the method of systematically refining a set of candidate materials for a component of particular product.

Historically, intricate and long-studied expert knowledge of many materials was used to arrive at a choice of the materials for making things. Here, we will shift our attention to a systematic method termed the Ashby method. This method is based on first identifying,  in general terms, performance  requirements  and  priorities. These requirements are then translated into equations which can be used to identify a particular figure of merit or performance index to screen (filter) and rank materials in a database. Fortunately, while products are highly varied, the equations and indices  used can be boiled down to a finite set. This assignment will ask you to identify appropriate indices and apply these within a software database (Ansys EduPack.,

OVERVIEW OF THE ASSIGNMENT

You will be assigned to a group of 4 or 5 students. You will work in this team to submit a written report considering the materials selection for components of a specific product (number of components = number of students in the group). The report will include a group element as well as an individual component as outlined below. The report should be completed using the template on Minerva which also outlines the sections required (see also  key elements below as well as definitions in Appendix 1 and marking criteria in Appendix 2).

As a group, choose one of the 5 product options:

1.   Photo-bioreactor for growing algae, cyanobacteria, and other phototrophic organisms in a stirred tank reactor

2.  Boiler and steam turbine

3.  Incinerator

4.  Horizontal axis wind turbine

5.  Advanced Gas-Cooled Nuclear Reactor

The individual components for each product are listed on the next page. The group assignment must be submitted on a single product.  Each individual component must be on one of the listed components. The individual component must be on a different component to any other member of the assigned group (one component per group member). Reports from groups of 4 students should report on 4 of the 5 components.

DEADLINE AND SUBMISSION

The report is due by 2:00 PM on 17 March 2025. Marks and feedback will be shared on return from Easter.

As a group, make one eIectronic submission in the (MateriaIs SeIection Assignment, submission within the Assessment area on Minerva. Note: Each team member must complete and digitally sign (by form. completion) the Academic Integrity Declaration (a Microsoft form. linked from the assignment folder on Minerva). Failure to submit the Academic Integrity Declaration ahead of the submission deadline will be mean the individual component is not considered submitted. A late submission of the Academic Integrity Declaration will considered a late submission of the individual component.

All submissions will be checked via Turnitin and charts as well as text will be reviewed during marking to check for collusion or plagiarism. Do not work together with other groups. Carry out individual components independently.

THE PRODUCTS

As a group, choose one from the following list of“products”(or“technical systems”). Multiple designs are possible for each product. It is recommend that you agree on a single overall design at an early stage of the group work so as to narrow the scope and ensure coordination between the individual assignment tasks (tasks for each component of the product).

There are 5 components identified for each product. By agreement within the group, assign one component to each member of the group. Only 4 out of the 5 components will be assigned in groups of 4 students. All 5 components should be assigned in groups of 5 students. Label in your group report which team member has been assigned to each component. If you find that the description below is broad and contains multiple parts, you are welcome to specify a single part you have worked on in the individual section of the assignment.

If you are unsure of what the product is, take some time to search (online or in the library) and read more about the product. Bear in mind, this assignment is not a research project but instead is aimed at applying the Ashby method for materials selection.

1.    Photo-bioreactor for growing algae, cyanobacteria and other phototrophic organisms in a stirred tank reactor:

a.   Tank lid

b.    Tank lid seal

c.    Tank walls

d.   Rotary impeller shaft

e.    Rotary impeller mixing blades

2.    Boiler and steam turbine:

a.    Pressure vessel

b.    Steam/water recirculation pipe

c.    Turbine blades

d.    Turbine shaft

e.    Turbine bearings

3.    Incinerator:

a.    Firebox

b.   Heat exchanger

c.    Exchanger water inlet pipe

d.    Exchanger water outlet pipe

e.   Chimney

4.    Horizontal axis wind turbine:

a.    Turbine blades

b.    Turbine shaft

c.    Brake

d.   Nacelle

e.    Tower

5.    Advanced Gas-Cooled Nuclear Reactor:

a.    Pressure vessel lining

b.   Pressure vessel outer

c.    Gas recirculator

d.   Heat exchanger

e.    Exchanger water recirculator

KEY ELEMENTS OF THE ASSIGNMENT

Stage 1 - Group

Report sections: (1) Description & design requirements, (2) Identification of components and their loading geometry

•     Write a concise description of your product - what does it do?

•     Specify performance requirements of the product as a whole

•     Sketch a representation of your product with text/numerical annotations

•     Write a brief accompanying paragraph describing the components in the sketch

Stage 2 - Individual

Report sections: (3) Specification of performance requirements at component level, (4) Design translation at the component level, (5) Materials indices based on the design  translation, (6) Screening materials  using primary constraints in Ansys EduPack, (7) Selection of the optimal material using materials indices in Ansys EduPack

•     Specify performance requirements for each of your individual components

•     Analyse the objective, function, constraints, and free variables in the design for your individual component

•     Choose appropriate materials indices

•     Carry out screening and ranking processes in EduPack software

•     Show graphs and write accompanying paragraph text to describe the process you have used (and thereby provide evidence of your approach to analyse the selection problem and carry out materials selection using Ansys EduPack).

•     Select the optimal material using EduPack software and write a justification of the choice

Stage 3 - Group

Report components and marking criteria: (8) Discussion of the limitations of the materials selection process,

(9) Discussion of the  validity of the materials selection and comparison with materials currently used for the components, (10) Presentation, (11) References

•     Write a conclusion with a final recommendation on materials for the product selected by the group

•     Write a discussion of the reliability of these selections

•     Write a comparison of these to materials used commercially for similar products

•      Include appropriate and consistent referencing throughout 一 all sources must be referenced and cited in the text

•     Check  the report  for  high quality  presentation of plots, drawings,  figure  captions, sectioning, and referencing

As a guideline, it should not be necessary for your team’s report to exceed 2,500-4,500 words in length. Inclusion of material not relevant to the materials selection process will be penalized, and conciseness will be rewarded.

SUPPORT

A.  Lecture sessions: At the start of Semester 2, we will work through the Ashby method and the use of Ansys EduPack across three lecture sessions delivered by Dr Sean Collins.

B.  Three online self-learning (Units 1-3) are available to go into further detail on using EduPack software.

C.  A worked example is available on Minerva. Note, the worked example includes only 4 components and is presented (section-by-section.’The individuaI sections shouId be (component-by-component’in the report.

D.  Computing cluster drop-in sessions have been set aside to ensure access to computers and software. Dr Sean Collins will be available to answer questions during these drop-ins, but they will not be structured otherwise.

E.  The textbook Materials Selection in Mechanical Design by Mike Ashby (available electronically via the library website) presents further useful information and examples.

Please get in touch by email ([email protected]), raise a question during or immediately after a lecture or drop-in session on the materials selection assignment, or post questions to the Discussion Board on Minerva. In- person meetings (individually or as a group) can also be arranged by appointment.

APPENDIX 1: RECAP OF THE MATERIALS SELECTION METHOD

Description & design requirements: Describe the overall functional system and its design requirements, i.e. the things that this assembly has to do effectively.

Identification of components and their loading geometry: Present a diagram or annotated image to clearly indicate the overall design, the individual components (dimensioned where relevant) and their position in the assembly. Describe the geometry of the loading that will act upon each component in service.

Specification of performance requirements at the component level: Estimate performance requirements, i.e. some reasonable values of each component’s loads (where these can be estimated) or service environment, (e.g.  operating temperature, pressure, speeds).  What materials properties are therefore  required?  What dimensions (length, diameter, etc.) of the components are constrained by the design? What failure modes may apply? You may spend some time reading about the product, but please note that researching the product is not the aim of this assignment. A reasonable estimate that can be referenced or justified otherwise is sufficient. Often,  identifying which  performance requirements are most  important is  the most useful rather than identifying a single numerical value. Keep requirements loose initially to ensure plenty of candidate materials can be identified and tighten the requirements as you screen and rank to identify an optimal material.

Design translation at the component level: Translate the performance requirements into function, objective, constraints, and free variables for each component by defining what objectives (e.g.  minimised cost) and constraints (e.g. design-prescribed length, the temperature it needs to tolerate as a minimum) apply to each component. These will be used to look up appropriate materials indices and to define primary constraints. Review the tables of materials indices (appendix of Unit 3 and on Minerva) to help in identifying appropriate objectives, constraints and free variables.

Materials indices based on the design translation: Using the defined function, objective, and free variables for each component, you can now identify a list of primary constraints (where there is a defined limit arising from the design translation) and ideally one (or perhaps two at most) appropriate materials index/indices, which will be  used  in  screening  and  ranking  the  material(s), respectively. In many  applications,  toughness is  a key consideration; applying a minimum“rule of thumb”fracture toughness (see also self-learning module Unit 3) as a primary constraint can rule out materials with unacceptably low toughness.

Screening materials using primary constraints in Ansys EduPack: The primary constraints defined above will then allow you to use Ansys EduPack to screen-out materials which cannot do the job, e.g. materials that cannot operate at a sufficiently high temperature. You need to choose which selection method (tree, limit, or graph) is best suited to each of these stages for each of the components. For the maximum operating temperature, consider whether the component can be cooled. Be sure to include evidence or justification for selecting limit stages with mechanical property values.

Selection of the optimal material using materials indices in Ansys  EduPack: Appropriate materials indices, defined above, will enable you to use Ansys EduPack to rank those materials which survive screening in order of how well they meet one/perhaps two materials index/indices to determine which material can best do the job. This will leave you with a shortlist of materials for that component and you can then complete your analysis by using your judgement to say which material on your shortlist might be the most appropriate; other constraints (where no limit is specified) may also now be considered during this final selection stage, e.g. by using a bar chart to rank them against another constraining property such as fracture toughness, corrosion resistance, fatigue limit or price.

Discussion of the limitations of the materials selection process: Say whether there are other factors that Ansys Edupack doesn't take into account (e.g. fatigue, creep, corrosion ?) and thus what are the limitations of the approach used. Some key limitations are that high temperature performance is not covered in detail, durability is general and not condition specific (including friction and wear) and fatigue is not component specific.

Discussion of the validity of the materials selection and comparison with materials currently used for the components: Comment on how different (or similar) your selection is to materials that are currently used for that component and how valid your selection is based upon material sources from the lectures, from literature and/or from web sites.

APPENDIX 2 : MARKING CRITERIA

The table below shows the weightings for each section of the report and what would be required to gain maximum marks under each of these headings. Each section will receive a mark out of the maximum number available in the section. You will be assessed individually for your component in the sections highlighted in bold (70%) and as a team on the other sections (30%). Note: An individual student will not be eligible for credit from the team sections of the assignment if the individual student has not made a serious attempt on the individual section (<40% on the individual sections taken together).