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Advanced Mechanical Engineering
AUTOMOTIVE CHASSIS ENGINEERING

Assignment 1

“To investigate the design features of a modern car specifically aimed at improving occupant safety and to overview the test procedures incorporated within the homologation procedure that validates their effectiveness”
Submission Deadline: 12 Noon Thursday 29 October 2015
Aims:

• To provide each student with the opportunity to demonstrate independent thought and lateral thinking.
• To develop the student’s information search skills using a systematic logical approach to finding information.
• To provide the opportunity for the student to investigate the safety features being developed and incorporated into modern cars and develop an understanding of the subject of automotive crash design, test and analysis.
• To overview the scenarios where a vehicle occupant may be at risk and identify the current design procedures in-place to minimise the effects.
• To investigate the inevitable reliance on software and the potential of software failure or incorrect application.
• To review and comment on the test procedures adopted to validate the safety criteria and to consider the potential, and probabilities, of failure under impact/crash/incident conditions.
• To consider the practical and ethical issues that may be present with the safety features being incorporated – automatic door unlocking & seatbelt tensioning?

Introduction:

Definition: http://en.wikipedia.org/wiki/Crashworthiness

Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different criteria are used to determine the crashworthiness of the structure. Crashworthiness may be assessed either prospectively, using computer models (e.g., LS-DYNA, MSC Dytran, MADYMO) or experiments, or retrospectively by analyzing crash outcomes. Several criteria are used to assess crashworthiness prospectively, including the deformation patterns of the vehicle structure, the acceleration experienced by the vehicle during an impact, and the probability of injury predicted by human body models. Injury probability is defined using criteria, which are mechanical parameters (e.g., force, acceleration, or deformation) that correlate with injury risk. A common injury criterion is the Head impact criterion (HIC). Crashworthiness is assessed retrospectively by analyzing injury risk in real-world crashes, often using regression or other statistical techniques to control for the myriad of confounders that are present in crashes.

It is some years ago that the “Law Lords” announced that engineers would be personally liable for the failure of their designs. The consequences of that ruling meant that the public could take legal action against the company and the individual if they were injured using that product. Fortunately companies maintain corporate and personal liability insurance cover to mitigate the effects of such action – protecting themselves and their employees. Regardless, it is every engineer’s ethical duty to ensure their designs are safe and effective. The key to any effective safety design feature is in anticipating the scenarios of incidents that a road user may experience.
Example – In the USA a 4-wheeler rolled over and the rear door window opened during the event. Regrettably a small child was thrown through the small window with fatal consequences. It was established that the catch lock was at fault and as a result the family were awarded damages of over 100 million dollars. Clearly such a design flaw would be difficult to anticipate but effective testing would have possibly revealed such a flaw. It is therefore necessary to ensure effective testing is in-place.

Task:

You are the future of automotive engineering and as such the safety of the general public lies in your hands. It will be down to your innovative approach, and thorough understanding of crash worthiness. Such a complete understanding will lead to effective and economic designs that will fulfil that faith of meeting customer expectations. To embark on this task, you need to thoroughly understand the implications of current technology and trends. Seek to see if there are any “gaps” in the existing systems – if so what are the solutions to fill that gap? As such you are required to undertake a study of the implementation of modern technology with an emphasis on safety. You will consider the current legislation and make comment on its effects on vehicle development. This development may sometimes take control of the vehicle from the driver (ABS, ESP?) – is that good? You may consider driver and occupant positioning? Will passengers need to still face forward or is rear facing safer – using cameras to observe traffic? Regardless of any design feature there is a need to consider the human form – the “non-standard” in any design consideration (see definition)? You may wish to study the skeletal response to any unusual incident and how the body needs to be constrained? Crashworthiness needs to look at the vehicle construction – will that be influenced, for example, by “active crash absorbers” – are there cost implications in replacing the “sacrificial” parts? Cost verses safety will always feature in any design – should it?

It is expected that you will endeavour to determine the broad basis of safety features being currently employed and what they focus on. You may find this to be an opportunity for you to consider a variety of scenarios – for example, in addition to fore, aft and lateral impacts there is a need to consider roll-over and the vehicle trying to “lozenge” as it rolls – at speed. There are dynamic and static criteria so, if the vehicle rolls onto its roof, can the frame support the chassis? This leads onto frame/structure designs and the differing materials used to give strength and rigidity. Look at myriad vehicles and observe the barriers fitted to commercial vehicles to stop cars entering under the vehicle. Do they effectively protect the driver if it is a corner impact?
Note: With regard to such “barriers”, you be expected to undertake a simple “first order” calculation to demonstrate your understanding of the mechanisms and forces involved.

Looking many years ahead, autonomous vehicles may be the norm and as such they will need to be “safe” in many more ways than now – the situations where system protocols fail.

Finally you need to consider pedestrian safety in the event of them being struck by a vehicle. What are the design features in-place to minimise their injuries and maximise their survival.

You may report on the general history of vehicle safety but concentrate on the progression to “modern safety technology, design techniques and testing”. Your review is not intended to be superficial or focussed on one vehicle – on the contrary it is intended to encourage you to understand very thoroughly what is happening now and formulate your ideas of how you may contribute towards safety development in the future.

Reporting:

The main report will be a unique individual report, typically of length 6-10 pages including figures. References and bibliography need to be at the end of the report. You may make use of appendices to hold additional information such as extended tabulation of data, FE analysis results, additional images, testing images and testing protocol – the homologation process. The “Turnitin” system on the VLE will be used to check for plagiarism

It is essential you acknowledge the source of information through correct referencing. If information is downloaded from the internet then give due credit. Regardless, you MUST provide YOUR opinion of the information whether it be supportive or controversial. It is your interpretation of the systems that are in place and any trends that is important.

Do make maximum use of images and technical information currently available AND do make reference to up-to-date research data through news releases, journals and the internet.

NOTE:
Remember that this piece of work may serve you well at interview for a professional position so a professional approach is necessary.

You will gather lots of information so consider at the outset how you will store it effectively so that it may be readily retrieved in 5 years – sectionalise the data and give meaningful titles to each entry. Much of the information may appear to be irrelevant now but you will soon realise that everything you read and store is categorised as experience, so don’t discard it unnecessarily. The appendix or dedicated file for this project is as good a place as any.
AUTOMOTIVE CHASSIS ENGINEERING

Assignment 1
“To investigate the design features of a modern car specifically aimed at improving occupant safety and to overview the test procedures incorporated within the homologation procedure that validates their effectiveness”
Submission Deadline: 12 Noon Thursday 29 October 2015

Marking Scheme

General Overview:

A general overview of the historical impact of the approach to safety in vehicle design and a review of “poor” design decisions – typically the “ripple effect”. It is expected that the research will reveal the most common type of injury and investigate unusual impact scenarios. Typically, the passenger side impacting the rear corner of a commercial vehicle – would the passenger survive such an incident – if not why not. This section should look at the range of collision scenarios that may occur – can this information be tabulated? What if only one vehicle is involved – sleeping driver and “lane drift”? Seek to explore the full range of incidents – only then can the issues be effectively addressed.
Mark 25%

Technical Background:

The overview will lead to research considering the most up-to-date technology used in designing and validating “safe” vehicles and where/how it is currently being applied. Do current testing programmes readily replicate the “real” situation? Because of the memory involved many packages may only allow “idealised” impacts to be analysed – e.g. in-line impacts – how many of this type occur? Ethically, is it correct to issue legislation that considers only idealised situations? In essence it is necessary to undertake an in-depth review of design techniques, validation and testing – both static and dynamic. It is expected that you will identify appropriate software being used – list this for your future reference and seek to understand their application and limitations.

Look at the designs currently in-place. Do they include sacrificial components (replaceable at a cost) or absorbers that may be reset (folding crash rails/skirts on a commercial vehicle)? Look at materials being used and the shape of members – side doors are a good example of structural integrity using a variety of component shapes and materials.

Give an example of how you would analyse an impact structure. Only a simple vehicle member need be considered for you to demonstrate your understanding of the mechanisms and forces involved – typically the rear and side frame on a commercial vehicle – the frames that protect the fuel tanks or stop a car running under the chassis.

Is there an identifiable barrier that is reached where “absolute” safety cannot be achieved because of cost implications? If so possibly provide answers.
Marks 45%

Discussion and Conclusions:

A personal opinion of where vehicle designers should focus their efforts when considering passenger/owner enjoyment, safety and vehicle maintainability. The author will concentrate on how they would like to influence any trend and will express their thoughts as to where they consider the future lies.
Mark 20%
Presentation:

A good concise report devoid of repetition and irrelevances. Full use made of visual material. Full and complete referencing.
Mark 10%

To achieve an overall pass mark of 50%, the project report should contain at least the discussion of the overall current applications and possible future trends.

To achieve a first class or distinction mark of 70% or above, the overall project must consider significant features in some depth. The report will reflect advanced investigative skills and will produce information not readily available. It will also provide thoughtful, innovative discussion and comment on the findings. The overall submission will be of a standard expected of a professional engineer.

MECH 5185M: AUTOMOTIVE CHASSIS ENGINEERING

Assignment 1

Feedback Form

Student Name:

Report Section Possible Mark Actual Mark
General Overview:
General overview of the historical impact of the approach to safety.
Identification of poor designs and bad practice.
Crash research to identify range of crashes, scenarios and the effects on passengers and pedestrians. Tabulation of data and how the incident is mitigated in the vehicle design. 25
Comment:

Technical Background:
Identification of the most up-to-date technology used in design. Compare design scenarios to reality.
Knowledge of test procedures to validate designs. Comment on reality.
Identify and comment on significant points within current legislation.
An in-depth review of design techniques, validation and testing – both static and dynamic.
It is expected that you will identify appropriate software being used – list this for your future reference and seek to understand their application and limitations.
Comment on design philosophies – sacrificial or recoverable.
Sample calculation.
Consideration of materials and protection against degradation.
The implications of cost v safety.
45
Comment:
Discussion and Conclusions:
A personal opinion of where the designers’ should focus their efforts when considering passenger/owner/pedestrian safety. The author will concentrate on how they would like to influence any trend and will express their thoughts as to where they consider the future lies regarding the approach to crash worthiness.
Discussion on the reliance on the uses of software and their limitations and your concerns.
Comment on the test procedures and their relevance to real situations.
Discussion on where it is considered there are “gaps” in current designs and how these may be overcome.
20
Comment:
Presentation:
A good concise report devoid of repetition and irrelevances. Full use made of visual material. Full and complete referencing. Good record of research within appendices.
10
Comment:

Final Mark

100