Scenario

You are a Design Engineer at ProsOrtho Corp. (POC) a technology-led company specialising in the design of orthopaedic prostheses.

Your main rival Femoral Hardware Inc. (FHI) has a new product ready to be launched and you have been asked by the CEO to prepare a suitable response in the form of a new hip prosthesis which will out-perform their product. Luckily an insider at FHI has been able to deliver to you the design of your competitor’s product and even a suggestion of how to model it in SolidWorks (see separate handout).

 

Your brief is to put together a project plan which will establish the characteristics of your competitor’s product and a number or recommendations on improvements which could be made in order to maintain an advantage over the competition. This all has to be done quickly in order for POC to make a Stock Exchange announcement about its upcoming product.

The CEO has summarised the tasks to be done as follows:

 Model Femoral Hardware Inc.’s product: conducting a finite element analysis of it to evaluate its peak von Mises stresses under static load (as benchmark).

 Propose a new design which reduces the benchmark peak von Mises stresses by at least 10% with minimal (if any) increase in mass.

 Identify the best material for your new design. This needs to bear in mind at least two main factors: (i) the need to have a high value of specific tensile strength; (ii) the need to have excellent corrosion resistance in the body (for our initial selection we can assume that this is an acidic, salty environment). The Food and Drug Administration (FDA) website might yield interesting information about the required surface properties in their ‘master files’.

 Search out other potential competitors to ensure you have the best concept and are able to identify possible patents which your design might infringe (don’t do a full infringement check – leave this to the Patent Attorney). Estimate the size of the market for such a product.

 Write a proposal for the CEO in the form of a report summarising your research findings, explicitly justifying your material choices (including the materials you have discounted) and outlining the advantages of your product and its envisaged position in a new market.

 

What you must do for the coursework assignment

Task 1

Use the Web and any other tools to establish the market and the position of your new product within it. Information on, for example, numbers of appropriate operations per year, or sales per year may be useful here. You may need to combine figures from different geographical regions or extrapolate from selected regions if you aim for the global market. You’ll need to find how many potential users there are for your product, what is already on the market and what patents you might infringe with your new product – don’t go through the patents you find claim by claim – leave this to the patent attorney, though the Patent Attorney will need your help in identifying similar products as a starting position. You may find the Derwent Innovations Index and Esp@ceNet useful for this.

Task 2

Use SolidWorks to CAD model the stem of Femoral Hardware Inc.’s (FHI) hip prosthesis (details of its shape and size are attached). A quickly scribbled note from Doug (the mole) indicates that the FHI prosthesis is manufactured from stainless steel – but no grade is mentioned. Once you’ve modelled the part you’ll then need to conduct a Finite Element

 

Analysis (FEA) using SolidWorks Simulation to extract the stress patterns, maximal stress and its location.

Task 3

Use your research findings, to select a sensible material for the component. As this is a detailed design. You are looking for a material which satisfies the established design criteria. Consider your material options and identify your optimum material. Describe in detail the method that you used to select your material of choice (for instance, use of Property limits etc,etc). Specify clearly if you have used any other additional constraints that you have employed in your selection, and justify the use of those constraints (including numerical values where appropriate).

You will also need to think about biocompatibility of materials and provide a brief list of traceable references (journal and archived conference articles only) concerning biocompatibility of the material type that you are concerned with. You may feel in-vivo or clinical evidence of biocompatibility is more compelling than in-vitro evidence.

As part of your final recommendation, include the material record for your chosen material. Comment on undesirable aspects of the material choice.

Also, comment on possible methods of manufacture of the product in your chosen material and identify the processing steps envisaged. Setting up tooling and supply chains for new and perhaps exotic materials, new and possibly complicated shape is expensive, so you must convince ProsOrtho Corp.’s manufacturing team and justify why your proposed selections are best.

ProsOrtho Corp.’s board of investors are known to have strong links with Surgeons Speciality Groups and are very keen to make their products attractive to surgeons by easing their task. So you should be thinking about how this might be accommodated during your redesign.

In all cases, be sure to support your arguments with logical reasoning, data and well-referenced evidence.

Task 4

Undertake a design study in order to propose and justify a redesigned prosthesis, for ProsOrtho to penetrate the market you’ve selected.

Using SolidWorks CAD and FEA tool, remodel your prosthesis to create ProsOrtho’s first prototype; detail your geometry and use your selected material to analyse and show that for no increase in mass you have been able to effect a 10% reduction in von Mises stresses with respect to the FHI benchmark.

(note: in reality these prostheses primarily fail because of loosening of the stem/bone/adhesive interface and fatigue failure rather than due to static loading).

 

Task 5

Prepare a 15 page (approximately) succinct, logical, justified and easy to follow report (excluding appendices) for your CEO. This needs to be a professional report which gives some engineering detail (as and where appropriate) and which includes, amongst other things:

 An analysis of FHI’s prosthesis (benchmark)

 A discussion of the market size for your proposed hip prostheses and the key competitors

 A discussion of existing patents (include a list of patents in the appendix of the report for the Patent Attorney)

 Discussion of the key benefits of your new prototype including justification and description of materials and geometry selected.

 

Rules of Engagement

 This is an individual exercise – you must submit your own (unique) report. Cite authors of all work which is not your own using numeric citation/referencing.

 

 The project is somewhat contrived – play along with it wherever possible. It is not unusual at all to get an incomplete brief from one’s boss and you will have to interpret what is being asked for and make decisions on how best to deliver what you believe is needed. You are the expert Engineer that the CEO has tasked with this requirement.

 

 For assessment you will need to supply an electronic copy of the report supported with all model files – DO NOT change any of the names of the files. Use the Pack-and-Go function within SolidWorks to archive your model files ready for submission. Electronic submission of the report (complete with embedded images as necessary) and the CAD/FEA model files should be made through BlackBoard.

Assessment

The coursework assignment is worth 70% of the module assessment and will be marked out of 100.

Remember that the scenario is wider in scope than your assessed work. You only gain credit for the stated tasks even though you may wish, for realism, to spend a little time researching and working on other aspects of the scenario.

Marks are given below for each task and important aspects (the things the markers will be looking for) are highlighted:

Task 1 – Data gathering and research (15 marks): quality and relevance of data, quantity and diversity of sources of information, critical appraisal and processing of gathered data and information.

Task 2 – Material selection (25 marks): Care in the selection of material and justification of its use, evidence for ruling out other material choices, including consideration of biocompatibility, specific tensile strength, use of CES, and clarity of reporting within task 5.

Task 3 – Modelling and FEA (25 marks): accuracy with which the FHI prosthesis is CAD modelled (size, shape, etc.), accuracy of the results (values in the additional handout are not representative – I’ve used an unknown material), and evidence of mesh independence and result convergence. Accuracy of the CAD redesign and its FEA analysis, justification and clarity of reporting within task 5.

Task 4 – Redesign (15 marks): suggested modifications to enable reduction in stresses yet maintain or better the functionality.

Task 5 – Reporting (20 marks): quality of layout (usual engineering report including summary, background, methods, results, discussion, recommendation, references/bibliography, appendices, etc.), but this does not give excuse to make it dry and uninteresting. The CEO is going to need the technical information to present to the board of investors but they are not all Engineers, so you are going to have to make it understandable to the layperson, visually appealing, succinct, logical, justified and easy to follow.

Hints and Support

You can get assistance with this work during your regular tutorial sessions. Additional support on the CAD and FEA aspects of the project is available from the CAD clinic (keep an eye out on the notice boards).

There are also online tutorials for SolidWorks and Simulation available at the SolidWorks website: www.solidworks.com. Further supporting information will be published through BlackBoard as it becomes available, so checking regularly is recommended.

Remember that this coursework must be your own work. You are encouraged to discuss the problem and possible solutions with others. What you hand in must, however, not have been done by anyone else unless their contribution is included in the References and Acknowledgements.