2 -Kingery - Introduction to bestthing.info - Ebook download as PDF File .pdf), Text File .txt) or view presentation slides online. Ceramics consist of a host of different materials with special properties. Silicon . Optimization of cost is possible with the introduction of machining, which could. A Concise Introduction to Ceramics. Authors. George C. Phillips. Book The Nature of Ceramic Materials. Front Matter. Pages PDF · Atomic Structure.
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INTRODUCTION. INTRODUCTION TO CERAMICS. A ceramic is an inorganic non-metallic solid, made up of either metal or non-metal compounds that have. Introduction to ceramic materials. Classification of ceramics and general properties. 2. Week Traditional ceramics. Classification and applications of traditional. for Ceramic Processing and Biomaterials she has been working mainly in the field For an optimum presentation of the PDF-file please use the current Adobe .
Photo: A ceramic Percy Pig piggy bank. It started life as a soft piece of clay molded to shape, fired hard in a pottery kiln, then painted with bright colors. What are ceramics? Photo: Porcelain plates are very familiar examples of ceramics, but there are other, much more surprising uses of ceramics too.
Glass, tiles, pottery, porcelain, bricks, cement, diamond, and graphite—you can probably see from this little list that "ceramics" is a very broad term, and one we're going to have difficulty defining. What do all these very different materials have in common? From a chemical viewpoint, we define ceramics in terms of what they're not. So you'll find most science textbooks and dictionaries telling you ceramics are nonmetallic and inorganic solids ones that aren't metal or based on carbon compounds ; in other words, ceramics are what we're left with when we take away metals and organic materials including wood , plastics , rubber , and anything that was once alive.
Some books also try to define ceramics as "refractory" materials, which is a technical, materials science term that means capable of putting up with everyday abuses like extremes of temperature, attacks from acids and alkalis, and general wear-and-tear.
It often seems easier to define materials in terms of their properties how they behave when we heat them, pass electricity through them, or soak them in water, for example.
But once we start doing that, things can get confusing. For example, graphite a form, or allotrope, of carbon is considered a ceramic because it's nonmetallic and inorganic, yet unlike most ceramics it's soft, wears easily, and is a good conductor of electricity. So if you looked only at the properties of graphite, you wouldn't consider it a ceramic at all. Diamond another form of carbon is also a ceramic for the same reason; its properties couldn't be more different from those of graphite, but they're similar to those of other ceramics.
Like modern ceramics such as tungsten carbide, diamond has long been used in cutting and drilling tools. Types of ceramics People first started making ceramics thousands of years ago pottery, glass, and brick are among the oldest human-invented materials , and we're still designing brand new ceramic materials today—things like catalytic converters for today's cars and high-temperature superconductors for tomorrow's computers.
There's quite a big difference between age-old, general-purpose ceramics like brick and glass and modern, engineered ceramics that are sometimes designed for a single, specific purpose, such as filtering soot from a truck's dirty diesel engine or making a drill bit that lasts five times longer.
That's partly why materials scientists like to divide ceramics into two kinds: traditional, and advanced or engineering ceramics.
Traditional ceramics Photo: Traditional ceramics: Toilets are a good example, though the lid and seat are typically made of plastic or wood. Bricks, pottery, glass, porcelain, tiles, cement, and concrete are our classic, time-tested ceramics. Although they all have different uses, we can still think of them as general-purpose materials.
Take tiles, for example. We can put them inside our homes or outside; on the walls, the floors, or the roof; and we can stick glass in our windows or poke away at it on our smartphone screens—we can even drink champagne out of it. Ceramics like this are ancient materials—ones our ancestors would recognize—that have gradually found more and more uses as the centuries have worn on.
Advanced engineering ceramics By contrast, advanced ceramics are ones that have been engineered mostly since the early 20th century for highly specific applications. For example, silicon nitrides and tungsten carbides are designed for making exceptionally hard, high-performance cutting tools—though they do have other uses as well.
Most modern engineered ceramics are metal oxides, carbides, and nitrides, which means they're compounds made by combining atoms of a metal with oxygen, carbon, or nitrogen atoms. So, for example, we have tungsten carbide, silicon carbide, and boron nitride, which are hard, cutting-tool ceramics; aluminum oxide alumina and silicon dioxide are used in making integrated circuits "microchips" ; and lithium-silicon oxide is used to make the heat-protective nose cones on space rockets.
High-temperature superconductors are made from crystals of yttrium, barium, copper , and oxygen. Not all high-tech ceramic materials are simple compounds. Some are composite materials , in which the ceramic forms a kind of background material called the matrix, which is reinforced with fibers of another material often carbon fibers, or sometimes fibers of a totally different ceramic. A material like this is known as a ceramic matrix composite CMC.
Photo: Advanced ceramics: Silicon and carbon fuse to form silicon carbide powder left , which can be made into a hard and hard-wearing ceramic called silicon carbide that can survive high temperatures. It has many applications, from drills and cutting tools to components middle, right that can withstand high temperatures in gas-turbine engines that would melt ordinary metal parts. Ceramic components are also used in ordinary car engines for the same reason.
What properties do ceramics have? As we've already seen, the most important general property of ceramics is that they're refractory: they're rough-and-tumble materials that will put up with fair amounts of abuse in the most ordinary and extraordinary situations. Just consider, most of us tile our kitchens and bathrooms because ceramic tiles are hard, waterproof, largely resistant to scratches, and keep on looking good for year upon year; but engineers also put very different!
If we're summarizing their properties, we can say that ceramics have: High melting points so they're heat resistant. Great hardness and strength. Considerable durability they're long-lasting and hard-wearing. Low electrical and thermal conductivity they're good insulators. Chemical inertness they're unreactive with other chemicals.
Most ceramics are also nonmagnetic materials, although ferrites iron-based ceramics happen to make great magnets because of their iron content. Those are the useful points, but, thinking about traditional ceramics like glass or porcelain, you'll also have noticed one major drawback: they can be fragile and brittle, and they'll smash or shatter if you drop them subject them to "mechanical shock" or suddenly change their temperature "thermal shock".
Why are ceramics like this? The interesting question is why ceramics behave like this—and the no-less-interesting answer boils down to materials science : it's all to do with how the atoms inside are bonded together. That explains how most materials work In metals, for example, atoms are relatively weakly bonded which is why most metals are fairly soft ; their electrons are shared between them in a kind of sea that can "wash" right through them, which is simplistically speaking why they conduct electricity and heat.
A material like rubber , on the other hand, is made of long-chain molecules polymers that are very weakly attached to one another; that's why raw, white, latex rubber is so stretchy and why black, vulcanized rubber like that used in car tires is harder and stronger, because heat-and-sulfur treatment makes strong cross-links form between the polymer chains, holding them tightly together.
All the electrons are locked up in bonds of various kinds none are free to carry an electric current , and that's why rubber is generally a good insulator. Ceramics are different again. Their atoms are ionically bonded like sodium and chlorine in sodium chloride, common salt , which holds them firmly in place making ceramics hard and strong and locks up all their electrons so, unlike in metals, there are no free electrons to carry heat or electricity.
Metals can bend, stretch, and be drawn into wires because their rows of regularly packed atoms will slide past one another. But in a ceramic, there are no rows of atoms; the atoms are either locked in a regularly repeating three-dimensional crystal or randomly arranged to make what's called an amorphous solid a solid without a neat and tidy, internal crystalline structure. If you whack a lump of metal with a hammer, the mechanical energy you supply is dissipated as layers of atoms jump past one another; in other words, the metal bends out of shape.
However, for complicated ethical decisions, the answer is not always easy to see, even after all the data has been analyzed. In this particular example, there is no clear decision, which is often the case. The decision that you make will be dependent on your morals and your particular life situation at the time.
Just as this step is critical in the design of any new material, testing and evaluation is just as important in deciding a particular ethical course of action. For ethical decisions, the most useful form of testing and evaluation is to talk to other people and get their perspectives concerning not only the situation in general, but especially the chosen solution. While this may seem like a simple step, for many, it can be the most difficult. Often many people will make decisions in isolation for fear of appearing weak or not in control of a particular situation.
Though sometimes difficult, it is crucial to discuss an ethical dilemma with someone who is not close to a situation to gain their insights, and possibly show you some options that you previously did not consider.
In our example, there are many people who could help in evaluating the best course of action. A patent or intellectual property lawyer would be an excellent source of information, especially for any potential legal issues. Your professional society is another resource for information see the next section for a more in-depth discussion. Objective peers not related to either company would be helpful, or you can always contact a former college professor or some other industry expert for additional guidance.
Important professional decisions such as detailed in our example should never be made without input fiom qualified, objective sources. The major professional engineering societies go a step further in the field of ethics and provide their members with ethical guidance in the form of formal codes, discussion forums, Ethical Issues in Design case studies including real world examples , and general guidance for possible ethical dilemmas that an engineer may encounter.
For every engineer who graduates from an accredited engineering institution, the Accreditation Board for Engineering and Technology ABET provides the initial Codes of Ethics of Engineers based on the following principles: Engineers uphold and advance the integrity, honor and dignity of the engineering profession by: From these principles, engineering ethical fbndamental canons were developed that should apply to all practicing engineers, regardless of field or licensing see inset.
Hold paramount the safety, health and welfare of the public in the performance of their professional duties. Perform services only in areas of their competence. Tssue public statements only in an objective and truthful manner. Act for each employer or client as faithful agents or trustees, and shall avoid conflicts of interest. Build their professional reputation on the merit of their services and shall not compete unfairly with others.
Act in such a manner as to uphold and enhance the honor, integrity and dignity of the profession. Continue their professional development throughout their careers and shall provide opportunities for the professional development of those engineers under their supervision. An Introduction to Ceramic Engineering Design paramount the safety, health and welfare of the public sounds very much like the utilitarian ethical h e w o r k.
Because of the very nature of engineering as a costbenefit-analysis profession, the greatest good for the greatest number theory often is a guiding principle for engineers. Engineers are expected to uphold the highest standards of both personal and professional integrity. The Code of Ethics for the National Society for Professional Engineers NSPE , an umbrella professional organization for licensed professional engineers, is almost identical to the ABET code, as are the specific ethical codes for all other major engineering societies.
However, it is important to remember that a code of ethics is simply a framework for ethical decision-making. The codes are not comprehensive and are not the final moral authorization for a particular act. As previously discussed, the role of the professional society cannot be over-emphasized for the engineer who faces a difficult ethical decision.
Codes of ethics provide basic guidelines but because of their limited nature, they cannot be expected to cover every possibility. This is why it is so important to remember that engineering professional societies have a large number of objective experienced engineers on hand who have either faced similar situations or know someone who has.
Before making an ethical decision that could result in either professional censure or a lawsuit, it is critical to remember the testing and evaluation stage of an ethical decision and talk to someone. I f it cause the death of the son of the owner of the house, they shall put to death a son of that builder.
I f it cause the death of a slave of the owner of the house, he shall give to the owner of the house a slave of equal value. If it destroy property, he shall restore whatever it destroyed, and because he did not make the house which he built firm and it collapsed, he shall rebuild the house which collapsedfrom his own property.
Engineers must make safety paramount in their designs. As you will recall, this is the first fundamental canon of engineering ethics. As technology and the resulting applications grow more complex, the more risk and safety become crucial issues in engineering.
As previously discussed, the engineering design process typically follows a basic utilitarian cost benefit approach, and this is especially true when considering acceptable levels of risk in a design.
Types of ceramics
When considering risk, safety, and design, an engineer may look to prescribed government codes concerned with safety or industry standards for acceptable levels of risk. Unfortunately though, when an engineer or a group of engineers embarks on previously untried technology, there are no accepted practices or even previous experience fiom which to draw. Sometimes with cutting edge technologies and designs, which are usually highrisk endeavors to begin with, mistakes are made and failure occurs.
When an engineering failure occurs, whether it is a bridge that collapses or a power plant that shuts down due to a s o h a r e glitch, some kind of human error occurred in the design or manufacturing engineering processes that allowed the accident to happen. What is critical to remember in such cases is that humans will err and it is unrealistic to think that in any human endeavor, especially one as complex as engineering, that no mistakes will be made. Success may be grand, but disappointment can often teach us more.
While no engineer strives to build something that will catastrophically fail, it is just such failures that elevate an entire field of engineering to a higher level of competence. The Tacoma Narrows Bridge example is just such a case. Often used as an engineering ethics case study, the Tacoma Narrows Bridge is actually a much better example of engineering culture and failure.
In , a narrow twolane suspension bridge, the first of its kind, was built between Washington State and the Olympic Peninsula. Instead of the typical deep stiffening truss design used up to that point in history, shallow plate girders were used instead. Just a few months after its opening, the bridge catastrophically failed in high wind conditions, twisting and undulating with such force that the bridge seemed to be made of rubber instead of concrete and steel.
While the final failure seemed quite extreme, the bridge had communicated its instability long before its collapse, and even did so during the construction phase. Even up to the moment of final collapse, the Tacoma Narrows Bridge engineers were hard at work trying to solve the motion problems. After the failure, they were able to determine that bridge essentially was subjected to tremendous aerodynamic forces that were previously not accounted for in earlier designs.
Did the engineers make mistakes? Yes, but they did not act in an unethical manner. In , suspension bridge design was still in its infancy, and the lessons learned fiom the Tacoma Narrows Bridge collapse will not be repeated in the future. Bridges today are now tested in wind tunnels to prevent such mistakes fiom reoccurring. Ethical Issues in Design Unethical decisions in design engineering often result when an engineer or manager is faced with a decision concerning a bad design.
While many engineering decisions concerning risk and safety certainly straddle ethical gray areas, history shows us that some were made without appropriate ethical considerations. During production, engineers discovered that the rear-mounted gas tank of the Pinto, which was built to industry standards, could possibly explode in a rear-end collision.
When management of Ford was notified of the gas tank problem, they applied a cost-benefit approach and determined the cost to fix the problem as opposed to the cost that could be paid out in lawsuits.
When faced with a questionable design and a decision concerning money, Ford chose to save money and not recall the Pintos. Consumer action groups maintain that almost people died in Pinto crashes, and Ford endured more than 50 subsequent lawsuits.
A Concise Introduction to Ceramics
Ford was eventually forced to recall and fix the Pintos. Did Ford make an unethical decision by making a choice based upon a cost-benefit analysis? Was this decision process utilitarian? Can you put a price on a human life, and do you think this situation could happen today? The tread belts of these tires had a tendency to separated fkom the walls of the tires at high speeds, often causing the vehicle to roll over as a result.
The vehicle affected most by this tire problem was the Ford Explorer. While the Firestone recall was voluntary, news stories reported six months earlier An Introduction t o Ceramic Engineering Design prompted the recall when it was discovered that approximately 50 people had died in rollover accidents caused by tread separation.
The number of deaths in the United States associated with this catastrophic tire failure would eventually rise to , with over injuries. In the resulting legal furor over responsibility for the tires, Firestone charged that Ford shouldered a large part of the responsibility as well because the design of the Ford Explorer was flawed. While this issue will undoubtedly be debated in the court for years to come, one critical issue was raised. When did Firestone know about the problem?
In legal documents, Firestone was forced to admit that they were first made aware of the tread separation problem in from a dealership in Saudi Arabia who noticed an unusual number of these failures.
Do we have to have a fatality before any action is taken on this subject? Similar problems surfaced in Thailand, Malaysia, and Venezuela, and the common denominator for these regions was the hot climate.
A internal Firestone memo showed that management was aware of the overseas tread separation problem but resisted consumer notification of overseas customers for fear that North American markets would become aware of the problem and demand action.
Firestone hired an independent expert to determine the cause of the tread separation, Dr. A Firestone October report proved that they knew the tires from Decatur plant experienced significantly higher failures than at other plants. In addition, a subsequent Ford investigation revealed that failure rates for the AT and ATX tires manufactured at the Decatur, Illinois plant exceeded tires per million in , per million in , and per million in These same tires manufactured at other plants failed at the rate of tires per million.
When questioned, Tom Baughman, engineering director at Ford North America Truck said the industry standard for tire failure is 5 per million. Ethical Issues in Design 1. Who should bear the ultimate responsibility for the deaths resulting fiom the tread separation: Firestone management, the engineer who designed the tire, or the Decatur plant engineer responsible for the production process?
Are design engineers absolved of responsibility when their product enters the manufacturing stage? Are they responsible for what happens in the management and marketing sequence?
When do you think would have been an appropriate time to institute a recall? If the industry standard for tire failure is 5 per million, why do you think such gross failure rates were accepted and who was responsible? Is a tire failure rate of 5 per million ethically acceptable and how do you think this number is determined? Environmental issues, intellectual property concerns, conflicts of interest are just some of the areas engineers may encounter ethical questions. This section will provide a brief overview of these issues, and if you have -er questions, consult the recommended reading list at the end of the chapter for additional sources of information.
The word green implies environmentally conscious, and unfortunately in the past, engineering in general has not been seen as a profession that promotes the environment. Chemical plants, dams that flood vast farmlands, and noise and air pollution from automotive engines are just some of the engineering projects that often receive negative publicity.
However, even though many engineering designs promote human progress over nature, there has been increasing emphasis on engineering design that minimizes the impact on the environment.
To this end, many branches of engineering have taken an active role in promoting the role of the environment in the life cycle of an engineering process or product. As noted in the earlier professional societies section, the American Society for Civil Engineers is committed to sustainable development, which means that engineering projects should not negatively impact the environment to An Introduction t o Ceramic Engineering Design the extent that it is permanently altered for future use.
In addition, many universities offer undergraduate green engineering programs that incorporate sustainable development practices in engineering design.
Intellectual Property Chapter Seventeen focused on definitions and discussions of intellectual property issues, and this is one area that most material engineers will find themselves faced with in their futures. It is critical that all engineers gain a basic understanding of intellectual property issues, especially in regards to employment.
Many engineering graduates are surprised and unprepared for the lengthy contracts they are presented in their first jobs.
Of particular concern, the contracts will state that the company owns any design created by an employee, and should a new engineer wish to quit, the company can stipulate that the employee cannot work for any competitor for a stated period of time. One intellectual property area that cannot be clearly defined either legally or ethically is that of tacit knowledge, or that know-how and experience that a person gains simply by working in a particular industry or culture.
Engineers cannot leave behind this tacit knowledge once they decide to change jobs, and it is often diflicult to clearly define what knowledge is proprietary and what is experience, and what if any can be translated to a position with another company.
Legally, employers are within their rights to insist on contractual and legal safeguards of both their investments and proprietary information. Ethically, potential employees may disagree and feel that their individual rights are violated by such contractual demands. If an engineer disagrees with such employment practices, he can simply find another employer.
However, should a dispute arise concerning copyright, patent, or trade secret issues while employed for a company, the engineer should seek advice from an intellectual property attorney, a professional society, or both.
Conflicts of Interest. As seen in the intellectual property section, employers can legally demand a certain level of loyalty from their employees through intellectual Ethical Issues in Design property laws, but ethically engineers should be committed to avoiding situations that might result in a conflict of interest.
A professional conflict of interest occurs when an engineer is faced with a situation in which she may have an interest, which may compromise their ability to act as a faithful agent for either a client or employer.
For example, suppose Contractor A offers to take an engineer responsible for hiring contractors to dinner? Does a conflict of interest exist? If Contractor A is attempting to circumvent proper bidding channels, then a conflict of interest may exist. Certainly that could be seen as an outright bribe. However, what if Contractor A is a relative and they often have dinner?
What if during this dinner, they are seen by Contractor By who does not know of the familial relationship. Then an apparent conflict of interest exists, and while no improper behavior took place, the perception exists that Contractor A is given preferential treatment. Conflicts of interest can be very complicated and often require delicate handling.
They can occur in every aspect of engineering from employee relations to intellectual property issues. Unfortunately, even the most well-intentioned ethical engineers can frnd themselves in either a potential or apparent conflict of interest through no overt fault of their own.
To avoid finding yourself in this position, it is always best to notify a superior of any personal relationship that could be seen as a professional conflict of interest. In addition, seek advice in situations where you are unsure and remember that your professional society can offer guidance in such confusing situations. One other area concerning conflicts of interest and company loyalty is whistleblowing.
What should engineers do if they find themselves in situations where loyalty to their companies might mean taking unethical actions? This situation is where the concept of whistleblowing comes into play. There is some confusion as to what exactly whistleblowing is. Many people think whistleblowing takes place when an employee goes to the media to essentially tattle tale on unsavory andor unethical business practices of her employer. While this is one form of whistleblowing, it is the most extreme.
WhistIeblowing occurs when any employee goes outside normal company channels to air a grievance or dispute. Whistleblowing can essentially take two forms, internal and external.
If you feel your superior is asking you to take an action that could result in harm to the public, you should always attempt to resolve this conflict at the lowest level possible before going outside the company. You can always approach another manager within your area of the company or outside your area but still within the company.
All of the aforementioned solutions are considered internal forms of whistleblowing. When you have exhausted all of these avenues, then it is ethical to violate An Introduction to Ceramic Engineering Design company loyalty and use an external form of whistleblowing. One option would be to notify a regulatory or governmental body, but the media should be your last resort and this should always be qualified with immediate safety concerns. Your first ethical responsibility is to the public, but loyalty to your company is an important consideration.
Any decision to blow the whistle should be weighed carefully, and following the previously mentioned design steps in making this decision will be critical for resolving a potential conflict and protecting both your career and your company.
Shiley, Inc. The valve consisted of a convexo-concave disc inside a Teflon coated metal ring with two wire holders mounted on each side of the disk. One of the wires, the inflow strut, was an integral part of the ring while the second wire, the outflow strut, was welded on after the manufacture of the ring. Failures of the valves were first noted during clinical trials, however, despite these problems, the FDA approved the C-C valves. Soon after the valves were released on the open market, they began to experience more failures, which were sometimes fatal.
In subsequent investigations, it was discovered that all of the C-C valve failures were ftactures of the outflow strut. Between , Shiley recalled the valves three times and in each instance, replaced the defective valves with purportedly improved versions. The FDA asked Shiley twice between to remove the valves from the market on a voluntary basis, but Shiley refused. A total of 86, valves were implanted worldwide.
Of these, fractured resulting in approximately deaths. Independent investigations revealed discrepancies in both the manufacture of the parts and the quality control process. The Shiley supervisor for the drilling and welding procedures on the C-C valves from January - September , George Sherry, came forward with disturbing information concerning the engineering and the manufacturing of the valves. Sherry, who left Shiley in protest over the poor manufacturing procedures, stated that it was impossible to Ethical Issues in Design manufacture the valves according to the drawings.
The welders, who were not certified he said, used amperage levels that were times greater than recommended, causing welded joint temperatures to rise too quickly, which would weaken the joint.
In addition, if cracks were discovered in the valves, which sometimes occurred in the manufacturing process, the valve was to be either rewelded or discarded.
Unfortunately, many valve records were falsified, indicating that some of the valve cracks had not been rewelded, and instead merely polished over. Sherry testified that management knew of the problems, and in one internal Shiley memo, management indicated concern over the rapid rate of valve inspections and the fatigue of the quality control inspectors.
Due to mounting lawsuits, Pfizer and Shiley removed the Bjork-Shiley CC artificial heart valves from the market in How would a utilitarian view this case? How would this position compare to the Respect-for-Persons viewpoint? What were the ethical and professional responsibilities of the engineers who designed the valves?
Were they absolved of any responsibilities because the FDA approved the devices? Do you think the engineers adequately tested their design of the artificial heart valve? Should materials and designs of biomedical devices be held to a more rigorous testing protocol that those used in other engineering applications?
Of the 86, valves implanted, 0. Is this an acceptable failure rate and if not, what would be? How do you determine an acceptable failure rate, especially in biomedical engineering?
Should engineers anticipate the use of incorrect manufacturing techniques and what can be done to prevent this in the design process? How much responsibility for the valve failures and resulting deaths should 6. Should George Sherry have come forward with his information sooner? What other options did he have? There are many more ethical topics that every engineer should consider; employment concerns, global issues, weapons design,just to name a few. For the future engineer, probably the first source for information relating to professional ethics should be your professional society.
If your society does not provide detailed ethical guidance, the National Society of Professional Engineers or the National Institute for Engineering Ethics are also excellent starting points see website list below. Just as in technical aspects of engineering, ethical issues are constantly emerging and changing, especially in areas such as intellectual property. Professional societies can help you stay on top of these critical ethical and legal issues.
The Recommended Reading section below also contains several engineering ethics books that could prove useful. Just as preventive maintenance is crucial for efficient and safe operation of machinery, preventative ethics is critical for recognizing and preventing future ethical conundrums.
The ability to recognize an existing or potential ethical dilemma is not always straightforward and often requires analytic skills that engineers do not typically hone. The study of ethics in engineering, while relatively new in some universities is only going to become more emphasized as technology advances and profoundly impacts the world in which we live.
The professional engineer should consider the ethical issues of his or her design to be just as important as the technical aspects because their impact could conceivably be much more far-reaching.
Harris, C. Pritchard, and M. Rabins, Engineering Ethics: Concepts and Cases. Second ed. China's Three Gorges Dam: Is the "Progress"worth the ecological risk? Nof, D. Bulletin of the American Meteorological Society, April Petroski, H. Vintage Books. Firestone Tires. Thefirestorm continues, in Consumer Reports.
Govindjee, D. January 30, Ethical Issues in Design 8. Ethical Issues in Biomedical Engineering: The Bjork-Shiley Heart Valve. Burkholz, H. Schinzinger, R. The National Institute for Engineering Ethics: Virginia Tech Green Engineering: Answer the questions for Case Study 2.
In addition, safety standards are generally not as stringent in Middle Eastern and Asian markets. Is it ethical for a U. Why or why not? Answer the questions for Case Study 3. How far into the future should engineers track the successes and failures of their designs? Explain your answer. Go to the ethics Internet page on the website for the National Society of Professional Engineers http: Discuss your missed questions. If you work for a ceramic design company and you invent a ceramic device completely on your own time at home with no company materials, do you think you should own the patent?
Does the law support you? Research and discuss your answer. Apply the five steps of ethical decision making to Case Study 1 and formulate a decision as to whether or not the dam should be built. Jack Lackey George W. The initial step typically utilizes knowledge of mechanics or heat transport to permit derivation of a Material Index, i. As an example, the best material for making a light, strong tie has the largest value for the ratio of strength divided by density.
Existing plots of material property data or s o h a r e are used to identify materials having large values for the Material Index. Methods for considering cost, cross sectional shape, and process are also described. The person needs to be intimately familiar with the function and requirements for the component as well as being equally familiar with the properties and performance of numerous materials.
Unfortunately, not many such people exist. Another approach is necessary, particularly in the case where a new product is being designed and thus the experience base is limited.
Such computer programs do not exist today. Fortunately, there are other alternatives. The one that the author likes best is a graphical approach developed by Professor Michael F. Much of this chapter is based on his book. It is here, during conceptual design, that one must consider essentially all materials in order to minimize the chance that promising materials are not overlooked. To facilitate this difficult task, graphs Materials Selection that display material properties are available.
Note that the units on density are millions of grams per cubic meter. This gives the same numerical value as the more customary units of grams per cubic centimeter. For example, the bubble for alumina shows that the elastic modulus and density vary over a range, accounting for different grades sources of alumina. A quick scan of the graph shows that most technical ceramics have higher moduli than most metals. Porous ceramics, such as structural clay products bricks and pottery have lower moduli than the technical ceramics.
The graph also confirms what the reader likely already knows about polymers. They have low values for Figure 1. Strength versus density.
Figure 2 is a graph of strength versus density and is described later. Briefly, the selection procedure consists of five steps which are presented in detail through case studies described later.
Step 1: Identify the design goals and constraints. Derive an expression, depending on the specific design, that permits identification of the property s to be optimized. Step 3: Use existing property graphs to select a short list of candidate materials. Step 4: Step 5: Select preferred materials s based on process and cost analyses. Materials Selection As implied above, the methodology to be described permits quantitative analysis of the influence of component shape and bulk material cost.
A graphical approach for selecting the best fabrication process will also be explained. Process selection is based on consideration of component attributes such as size, aspect ratio, minimum section thickness, desired tolerance and surface finish, maximum use temperature, etc. Suppose we wish to select a material for a light, strong tie.
Green David J. An Introduction to the Mechanical Properties of Ceramics
As shown in Figure 3, the tie of known length, L, must hold a heavy object of known weight without failing. The weight exerts a given force, F, on the tie and places it in tension.
Further, we wish to select a material for making the tie so that the tie will be light. We would wish the tie to be light if it were to be a component in an aerospace application. This is a simple problem and the reader may guess the correct answer. It is perhaps obvious that the best mateiral for a light, strong tie is one that has a low density and large tensile strength. That is, the best material for the tie has the maximum value for the ratio of tensile strength, uf , to density, p , i.
We call this ratio a Tie Material Index, M. Even though we have obtained the Material Index for this problem by an educated guess, let us derive it. The general method we use here will work for more complex problems where the I Material Index cannot be obtained by guessing. The method for deriving the Force Material Index consists of first identifjmg the goal.
For a light, Figure 3. Schematic of tie. However, we have a constraint that the tie must not fail. Many material selection problems, at least the easier ones, have one objective and one constraint.
For the tie, this equation describes its mass. The mass of the tie is obtained by multiplying its density by its volume as shown in Equation 1. The constraint is that the tie must not fail.
In other words, the stress, 0,in the tie must be less than the tensile strength, O f , of the tie material as expressed in Equation 2. Since the stress in the tie is equal to the force exerted by the heavy weight divided by the cross sectional area of the tie, we can rewrite Equation 2 as follows: F Next solve Equation 3 for the free variable, A, obtaining: Think of it this way: If we selected a high strength-high density material, the cross sectional area of the tie would be less than that for a tie made of a lower strength-lower density material.
The mass of the two ties might be equal. Materials Selection Let us get back to deriving the Material Index. The next step is to substitute the expression for the flee variable, i.
Equation 4, into Equation 1. This yields: The first two terms, F and L, are fixed and are known for a specific problem. This is the Material Index we defined previously. Obviously, we need to select materials which have maximum values for the Material Index in order to minimize the mass of the tie. It seems simple. The material that has the largest value for M is the best choice for the tie. Or is it this simple? We can only perform some limited number of calculations and we might overlook a superior material, i.
We need a more thorough method that examines all, or at least many, materials. The appropriate graph for the light, strong tie problem was previously presented as Figure 2. Note that both strength and density are plotted on logarithmic scales, the numbers shown are actual rather than logarithmic values.
Tensile strengths are plotted for metals, polymers, and composites, while compressive strengths are plotted for ceramics. Thus, for ceramics, the values on the graph should be adjusted by dividing by to reflect the fact that ceramics are weaker in tension than compression.
The better materials for the light, strong tie appear at the upper left corner of the graph. How do we pick the best two or three materials? If we take the logarithm of both sides of Equation 7, we obtain: For a plot of log Gf on the y-axis and log p on the x-axis, this equation plots as a straight line for a fixed value of the Material Index, M. Materials of equal merit have the same value for the Material Index.
Thus, materials of equal merit fall on the same line. This is an important fact. It tells us that on a graph such as Figure 2, or the simplified version shown in Figure 4, we can draw lines that identifL materials that are equally good for our light, strong tie. A series of such lines having a slope of unity are shown in Figure 4. For each line, there is a fixed value for M, the Material Index. The next step is to realize that the line that is closest to the upper left corner of the graph has the largest value of the Material Index.
That is, materials located near the upper left corner of the graph are best for use in making a light, strong tie. Materials A and B are on the same line and thus are equally good choices for the tie. They are better choices than material C. The tie made from material C would be inferior in that its mass would be larger than the mass of a tie made from either materials A or B.
This is reiterated by Equation 9. The cross sectional area of the tie made from material A would be larger than that made with material Materials Selection B because A has a lower density, but the masses of the two ties would be the same. If other aspects of the design restrict the space available for the tie, then the large cross sectional area of the tie made from material A might be a disadvantage compared to the use of mateiral B. Since the tie has the same mass regardless of whether material A or B are used, the final decision would be made by considering other factors including availability and cost.
Based on what we have learned so far, we can pick several promising materials fkom the upper-left portion of Figure 2 using a design guideline having a slope of unity.
Wood and the stronger of the titanium and steel alloys are only slightly less satisfactory. The solution sample of YSZ is cooled from the bottom to the top in a unidirectional fashion. This forces ice crystals to grow in compliance to the unidirectional cooling. Inside the solution, as it is cooling, these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary.
At this stage of the process we have pure ice crystals lined up in a unidirectional fashion alongside concentrated pockets of the YSZ colloidal particles. The next step of the process is the sublimation step. The sample is simultaneously heated and the pressure is reduced enough to force to ice crystals to subliminate, since the sample is also heated the YSZ pockets begin to anneal together too form the first macroscopically aligned ceramic microstuctures.
The sample is then further sintered to confirm the evaporation of the residual water and the final consolidation of the ceramic microstructure. During the execution of this technique a few variables can be controlled to influence the pore size and morphology of the microstructure.
These important variables of the ice-templating technique are namely the initial solids loading of the colloid, the cooling rate, the sintering temperature and time length, and also it has been shown that certain additives can influence the micro-structural morphology during this process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.
Most of these are transition metal oxides that are II-VI semiconductors, such as zinc oxide. While there are prospects of mass-producing blue LEDs from zinc oxide, ceramicists are most interested in the electrical properties that show grain boundary effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain threshold voltage.
Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to a few hundred ohms. The major advantage of these is that they can dissipate a lot of energy, and they self-reset — after the voltage across the device drops below the threshold, its resistance returns to being high.
This makes them ideal for surge-protection applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in electrical substations , where they are employed to protect the infrastructure from lightning strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application.
Semiconducting ceramics are also employed as gas sensors. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced. Superconductivity[ edit ] The Meissner effect demonstrated by levitating a magnet above a cuprate superconductor, which is cooled by liquid nitrogen Under some conditions, such as extremely low temperature, some ceramics exhibit high-temperature superconductivity.
The reason for this is not understood, but there are two major families of superconducting ceramics. Ferroelectricity and supersets[ edit ] Piezoelectricity , a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to measure time in watches and other electronics.
Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion powering the device and then using this mechanical motion to produce electricity generating a signal.
The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again. The piezoelectric effect is generally stronger in materials that also exhibit pyroelectricity , and all pyroelectric materials are also piezoelectric.
These materials can be used to inter convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in motion sensors , where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal.
In turn, pyroelectricity is seen most strongly in materials which also display the ferroelectric effect , in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in ferroelectric capacitors , elements of ferroelectric RAM. The most common such materials are lead zirconate titanate and barium titanate. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency loudspeakers , transducers for sonar , and actuators for atomic force and scanning tunneling microscopes.
Positive thermal coefficient[ edit ] Silicon nitride rocket thruster.
Handbook of Advanced Ceramics
Left: Mounted in test stand. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until joule heating brings it to the transition temperature, at which point the circuit will be broken and current flow will cease.Are design engineers absolved of responsibility when their product enters the manufacturing stage?
Either Equation 25 or 27 can be used to calculate values of the Material Index for specific porous ceramics. The MSE and CSE communities would be better served by a series of design textbooks available for teaching as well as for reference. We would just identify multiple sets of materials and again look for a material that appeared in each set. Then an apparent conflict of interest exists, and while no improper behavior took place, the perception exists that Contractor A is given preferential treatment.
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