030070010 Celal Selçuk Tiftik 9th week

Thermosetting Polymers


Thermosetting Polymers  are network polymers.They become permanently hard during their formation and do not soften upon heating. Network polymers have covalent crosslink between adjacent molecular chains .During heat treatments, these bonds anchor the chains together to resist the vibrational and rotational chain motion at high temperature .Thus , the materials do not soften when heated . Crosslinks is usually extensive , in that 10% to 50% of the chain repeat units are crosslinked.Only heating to excessive temperatures will cause  severance of these  crosslink bonds and polymer degration. Thermoset polymers are generally harder and stronger than thermoplastics and have better dimensional stability.

(Fundamentals of Materials Science and Engineering: An Integrated Approach

 Yazar: William D. Callister,David G. Rethwisch p.120)

***There is no old definition




-----------------------------------------------------
Duplex Stainless Steel (new)


Duplex stainless steels contain both ferrite and austenite in significant quantities at roomtemperature. The first commercial duplex stainless steel was produced in 1929 by AvestaJernverk. The steel, designated as 453E, had 25% Cr and 5% Ni. The shortage of nickelduring the Korean War (1950–1951) stimulated the development of duplex stainless steels,which contained less nickel than the austenitic grades. However, while the duplex gradeswere known to have advantages such as higher strength and resistance to stress corrosioncracking relative to the fully austenitic grades, they were inferior in toughness, ductility,and ease of fabrication. In this first generation of duplex stainless steels, the problemwas due to the continuous network of ferrite, particularly in the heat-affected zones of welded joints. As such, the world production of duplex stainless steels was much less thanthe austenitic grades and they tended to be used in very specific circumstances (Table 6).The development of duplex stainless steels was given another boost in the 1970swhen there was another nickel shortage. Moreover, the boom in the offshore oil industryled to a demand for steels with good resistance to the aggressive marine environments. Theadvent of vacuum and argon-oxygen decarburization processes in steel making allowedtighter control of residual elements, in particular carbon, nitrogen, sulfur, and oxygen,resulting in better formability and less likelihood of cracking during hot working. Theaddition of nitrogen marked the development of the so-called second generation duplexstainless steels. The nitrogen helps promote austenite stability and break up the ferritenetwork. This has enabled these steels to be used in the as-welded condition withoutpost-weld heat treatment.

(Lee's Loss Prevention in the Process Industries ,Yazar: Sam Mannan,Frank P. Lees sayfa 12-15)

Duplex Stainless Steel (old)

In early 1980's, various steel companies developed a steel with both ferritic and austenitiv microstructure called duplex stainless steel. It contains the characteristics of ferritic steel such as high yield strength and good weldability with resistance to generak corrosion, pitting and stress corrsion cracking Duplex steels from different mills each have slightly have diffrent chemical copmpositions.,
C(max)= %0,03
Si (max)=%1
Mn(max)= %2
P(max)= %0,03
S(max)= %0,02
Cr=%22
Ni=%5.5
Mo= % 3

Pitting and crave corrosion protection depends on chromium and molydenum present in the steel. Because its ferritic properties duplex steel has high resistance to erosion corosion. The relatively low nickel content may make duplex steel more economical than austenitic steels. That of course, depend on pricing policies of the steel mills: Duplex stainless steels resist the cavitation and caviation corrosion.


Uno Wahren,Practical introduction to pumping technology P.98
--------------------------------------------------------------------


Poka-Yoke (new)



Human beings will invariably make mistakes. It is not possible to remembereverything that has to be done at every step of producing every product withevery job. People will make errors; it happens; however, errors are the notsame as defects. A defect is what takes place after an error occurs. By sortinggood product from defective product at the end of the process, a company cannot hope to achieve a defect-free environment. If, however, errors arecaught before they lead to defects, then a defect-free environment becomespossible. This is where the power of Poka-yoke comes into play.Poka-yoke, another aspect developed by Shingo after World War II, inconjunction with source inspection, was designed to focus on the pursuit of quality at the source and capturing feedback on defects as close as possibleto the root cause. In
 Zero Quality Control: Sources Inspection and the Poka-Yoke System, he states:
“A Poka-yoke system possesses two functions: it cancarry out 100 percent inspections and, if abnormalities occur, it can carry out immediate feedback and action.
Poka-yoke, or mistake proofing, is accomplished through the deploymentof simple, inexpensive devises designed to catch errors so they do not becomedefects. These devices are placed in the process to ensure that it is very easy for the operator to do the job correctly or very dif ficult for the operator todo the job incorrectly. The tools could be physical, mechanical, or electrical
A Poka-yoke could be as simple as a checklist for the operator or techni-cian to ensure that all steps in the process are covered, much in the samemanner as pilots going through a pre-flight checklist before taking off. Theintent of the Poka-yoke is to stop defects at the source, to provide immediatefeedback as to the cause, and to prevent the passing on of defective productsto the next customer in the process.


(Lean Manufacturing Tools,Techniques,andHow ToUse Them , WILLIAM M. FELD, p.84)

Poka-Yoke (old)

      Poka-Yoke method has been implemented in one of the companies of automotive industry. This organization shall have two main production sectors: manufacture and assembly gearboxes and manufacture of engines for factories belonging to its own group. The organization currently employs around 700 employees.

     The main purpose is the manufacture of these elements of high quality, which meet quality standards in accordance with the principles processes continuous improvement (Kaizen). One of the ways of realization the improve strategy is to use Poka-Yoketechniques. Taking into account that the engine shall consist of approximately 310-350 part, they are very useful in just such as companies concerned with putting together of elements and manufacturing of parts. The produced elements must have a large precision therefore should be to minimize in the processes possibility of appearance a large risk omissions "something" or errors.

      By introducing techniques Poka-Yoke company guided by the following principles:

following principles:

 Defects arise most as a result of human errors. The following types of errors committed by people have been distinguished:

 1) Although the worker is aware of the mistake he makes, he continuous to do the same,

 2) The errors due to the misunderstanding,

 3) Incorrect identification,

 4) Forgetting,

 5) Lack of training,

 6) Good intentions but improperly implemented. All errors arising in the company are recorded and then analysed. Most of them can be prevented by using techniques Poka-Yoke.

7) Poka-Yoke techniques are a kind of response to errors in the short term. The reaction to obtain the information of the formation error must be immediate. Poka-Yoke must be exactly in the place where the error occurred or which may occur. It is also important that seek to provide, where error may arise.

 8) Use of Poka-Yoke causes, that the frequency of errors is less.

 9) Techniques used are simple, does not require the intervention of engineers, are cheap and effective.

(M. Dudek-Burlikowska, D. Szewieczek, The Poka-Yoke method as an improving quality tool of operations in the process, vol.36, 2009)

----------------------------------------------------

Die Bonding

The bonding of die to the package is primarily required to allow for electrical connections (signal I/O and power)  between the package pins and the die circuitry. Once the die has been secured to the package (allowing for thermal bonding for heat removal (using materials with similar Thermal Coefficient of Expansion(TCE)) and sometimes electrical

connection from the back of the die to the package), the die bonding is required. If the materials have different  Thermal Coefficients of Expansion, during device heating and cooling under normal and extremes of operation, thermal stresses may be introduced which can lead to problems in the interconnection such as broken joints.

      Wire bonding (using fine gold or aluminum wires), Tape Automated Bonding (TAB) or flip-chip solder bonding allow for  the electrical connections to be made.

(Integrated Circuit Test Engineering: Modern Techniques ,Ian Grout page: 31-32)

***There is no old definition

-----------------------------------------------------------------

Transfer Film (new better)

Transfer films, which play a dominant role in the coating response and failure [13], [24], [26] and [27], were represented by including a free third body in the contact. The friction coefficient of this material was set at 0.05 for both the interface with the coating, and the interface with the indentor. This value was assumed from both the properties of the coating and the observation that the transfer film is composed almost entirely of the friction reducing constituents of the coating. The transfer film (Fig. 1(a) and (d)) was assumed to have uniform homogenized material properties based on an equal weighted average using properties of Au, MoS2 and DLC which were identified by microscopy to be the primary constituents of the transfer film [13]. The transfer film is assumed not to contain oxidation products as the components of the transfer film, with the exception of MoS2, do not readily form oxides. The lower and upper surfaces of the transfer film were assumed to be smooth. Contact elements were placed along the upper and lower surfaces. The upper surface of the transfer film had the same curvature of the indenter, while the lower surface was flat. Therefore, the transfer film increased in thickness with increased distance from the center of contact. The thickness underneath the center of contact is approximately 200 nm, and the width of the transfer films was 1.5 mm. This results in an aspect ratio greater than unity and an increasing thickness away from the center of contact consistent with that typically observed experimentally [28]. Based on a convergence analysis, transfer films were meshed with 10,000 quadrilateral elements.

(Microstructural Modeling and Design Optimization of Adaptive Thin-film Nanocomposite Coatings for Durability and Wear, James Deon Pearso page. 15)

Trasfer Film : (15:11 21/04/2011) (old)
Many plastics sliding against hard mating surfaces result in formation of transfer films of plastic onto the mating surface. The formation and behavior of the transfer films are important factors in the friction and wear of these plastics. Once a transfer film has formed, subsequent interaction occurs between the plastic and a layer of similar material, irrespective of the substrate. On further sliding the plastic may continue to wear by adding material to the transfer film, since the interfacial bond to the counterface is often stronger that that within the bulk of the polymer itself. The trasfer film also wears through generation of wear particles and reaches a steady thickness in an interface with low friction and wear. The coefficien of friction for initial sliding on a clean hard substrate is not particlarly low and the trasfer film is on the order of micrometers thick. As sliding progresses the coefficient of friction drops to a much lower value; the trasfer film becomes much thinner and contains molecular chains strongly oriented parallel to the sliding direction.(Bharat Bhushan, Introduction to Tribology, p.262)