11th week unanswered terms - Gani Can Öz

Double cantilever beam tests (DCB)

This popular test (ASTM 3433) is used to obtain the mode I fracture energy of the adhesive bonds, which is a measure of the fracture toughness of the adhesive in the presence of flaws. Similar to a wedge test, a crack is initiated first by inserting a wedge. The specimen is then loaded by pulling apart the two beams at a certain rate, this increasing load resulting in increased deflection of two beams. At a certain critical load, the crack begins to propagate resulting in a slight drop in the load (due to the increased compliance). At this point, the beams are stopped from moving apart, thus keeping the deflection constant. The drop in load (due to increasing crack length) and the crack length are carefully followed. Following the equilibration of the crack, the specimen is consecutively unloaded and then loaded. Ideally, the compliance of the fixture should remain the same during these two cycles if there is no further propagation of the crack. This overall procedure is repeated several times leading to total cleavage of the specimen. The data finally collected at various times consists of load, deflection, crack length and the compliance.

Crystallization, Morphology, Thermal Stability and Adhesive Properties of Novel High Performance Semicrystalline Polyimides Chapter 7: Wedge and Double Cantilever Beam Tests on a High Temperature Melt Processable Polyimide Adhesive, RATTA, VARUN

Bugra cengiz 11th week

Duplex Stainless Steel

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

Transverse Cracking 


Transverse cracks in weld metal formed when predominanr contraction are in directionof the weld axis They can be hot cracks which seperates intergranularly as the result of hot shortness or localized planar shrinkage, or thet can be transgranular separations produced by stresses exceeding the strength of the material. Tranverse cracks lie in a plane normal to the axis of the weld. and are usually open to the surface. They usually extend across the entire face of weld and usually open the surface. They usually extend the across the entire face of weld and  sometimes porpagete into the base metal.
  Tranverse cracks in base metal occur on surface in or near the HAZ. They are result of the high residual stresses induced by thermal cycling during welding. high hardness excessive restraint and the precense of hydrogen promote theri formation. Such crack propoganete  ino the weld or beyond the HAZ into the base metal. as far as needed to relive the residual stresses.

Steve Lampman,ASM International, Weld integrity and performance: a source book adapted from ASM international


Poke Yoke (Poka Yoke)

Althought the concept of poka yoke has existed for a long time in various forms, iı was japanese manufacturing engineering Shigeo Shingo who developed idea into the formiable tool for achieving zero defects and evantually eliminating quality control inspection.The method he avocates were formerly called "fool-proofing" reconizing that this is label could often many workers, Shingo came up with the term poka-yoke generally translated as " mistake proofing" or " fail safing". The idea behind the poka-yoke is to respect the intelligence of workers. By taking over respetitive tasks or actions that depend on vigilance or memory, poka-yoke can free a worker's time and mind to pursue more creative and value-adding activities
    Many thing can go wrong in complex enviroment of workplace; every day there are opportunities  to make mistake that will result in defective products. Defects are wastefull and if they are not discovered they disappointed the costumer expectations of quality. Behind poka- yoke is the conviction that is not accepteable to produce small number of defective goods.. To become world class competitor. a company mus adopt not only philosophy but a producing zero defects. Poka-yoke methods are simple concepts for achieving this goal.


Poka-yoka, Improving Product Quality by Preventing Defects, P. XI 

Flux Cored Arc Welding

http://www.robot-welding.com/arc_weld_processes.htm

Flux Cored Arc Welding  is a fusion welding process in which weld heating is produced from an arc between the work and a continiously fed filter metak electrode. Atmosferic shielding is provided in complately or in part by the flux sealed within the tubular electrode.Extra shielding may or may not supplied through a nozzle in the same way in GASW.

     Although the process was introduced in 1950's it represented less than % 5 of the total amount of welding done in 1965. In 2005  it passed the %50 of mark and still is rising

Advantages.
High Deposition Rate
Minimum Electrode aste
Ecellent controll.

Larry Jeffus,Lawrence Bower,Welding Skills, Processes and Practices for Entry-Level Welders, P.114

Gökhan Güngör (11th week)

1- Production part approval process
2- Machine frame & frame types
3- Goal programming
4- Metallizing
5- Mechanical key torque limiter
6- Holonomic motion ( in robotics)
7- Peening
8- Lead screw drive
9- Fettling
10- Perforating

Gani Can Öz - 11th Week

1- Contact adhesives
2- Hot adhesives
3- Multi-part adhesives
4- One-part adhesives
5- Natural adhesives
6- Synthetic adhesives
7- Peel tests
8- Wedge tests
9- Double cantilever beam tests (DCB)
10- End notch flexure tests

503101305
Gani Can Öz

A. Selim PARLAKYİĞİT - 11th Week

1. Vulcanization
2. Vacuum Thermoforming
3. Pressure Thermoforming
4. Mechanical Thermoforming
5. Hubbing
6. Doctor-Blade Process(New Ceramics Shaping Method)
7. Cutoff(Sheet-Metal-Cutting Operations)
8. Parting(Sheet-Metal-Cutting Operations)
9. Polyvinylchloride(PVC)
10.Phenolformaldehyde(Bakelite)

ÖMER TAYLAN BOYA 030070099 11th WEEK

Styrofoam (10:27am 23.04.2011)

--Polystyrene another named styrofoam is a high volume world-wide consumed plastic. It is used in many different formulations. Styrofoam is noted for its sparkling clarity, hardness, low water absorption, extreme ease of processing general purpose PS, excelent colorability, dimensional stability, and relatively low cost. This amorphous TP often competes favorably with higher priced plastics.
--In its basic crystal PS form it is brittle, with low heat and chemical resistance, poor weather resistance. High impact polystyrene is made with butadiene modifiers that provides significant improvement in impact strength and elongation over crystal polystyrene accomponied by a loss of transparency and little other property improvement.

(Dominick V. Rosato,Donald V. Rosato,Matthew V. Rosato, Plastic product material and process selection handbook, page 63)

Polypropylene (11:15 am 23.04.2011)

--Polypropylene is a thermoplastic material that is produced by polymerizing propylene moleculesi which are the monomer units, into very long polymer molecule or chains. There are number of different ways to link the monomers together but PP asa commercially used material in its most widely used form is made with catalyst that is a semi-crystalline solid with good pysical, mechanical and thermal properties. Another form of PP, produced in much lower volumes as a byproduct of semicrystalline PP production and having very poor mechanical and thermal properties, is a soft, tacky material used in adhesives, sealants, and caulk products. The above two products are often referred to "isostatic" (crystallizable) PP (i-PP) and "static" (non-crystallizable) PP (a-PP), respectively.

(By Karian, Marcel Dekker, Handbook of Polypropylene and Polypropylene Composites, page 10)

Hot Adhesives (14:52 pm 24.04.2011)

--A hot melt adhesive is defined as an adhesive applied from the melt and it gains strength upon solidification and crystallization. Hot melt adhesives are applied without solvents. The increase in solvent emission regulations has increased the demand for hot melt adhesives. Certain types of hot melt adhesives cure over time after application. However, with the general purpose hot melt adhesive, the material is applied as a thermoplastic melt and the resulting adhesive is also a thermoplastic. Attention has to be paid to the type of polimers forming the adhesive, since the resultant material has be low viscosity in the melt (for easy application) but must solidify into a cohesively strong material.
--Hot melt adhesives are divided into two classes; the first class depend upon formulation design. That is, the properties of hot melt come from the combination of components that give the desired balance of properties. This situation should now be familiar, as it was encountered for elastomer based as well as structural adhesives. In the second class of hot melt adhesives, adhesive performance is molecularly designed. That is, the hot melt performance does not come from formulation, but rather from the choice of monomers used to make the base polymer.

(Alphonsus V. Pocius, Adhesion and adhesives technology: an introduction, page 271)

Natural Adhesives (15:14 pm 24.04.2011)

This term is used to include vegetable and animal based adhesives and natural gums. These include organic materials such as casein, blood, albumin, hide, bone, fish, starch, resin, shellac, asphalt, chitosan, and inorganic adhesives like sodium silicate. Their use, except for the inorganic adhesives, is mostly limited to paper , paperboard, foil, and light wood. They are inexpensive, easy yo apply, and have a long shelf life. These adhesives develop tack quickly, but have low strength properties. Most are water soluble and use water as a solvent. They are supplied as liquids or dry powders to be mixed with water. Some are dispersions in organic solvents.

( Sina Ebnesajjad, Adhesives Technology Handbook, page 49)

Kayra Ermutlu-030060081 (11th Week)

Duplex Mills (in Roll Forming)

Two cantilevered mills facing each other are called a duplex mill. Duplex mills have one common base and drive. They can form both edges of narrow or wide products leaving the center flat. The minimum strip widths depend on how close the opposing rolls can be pushed together, and the maximum widths usually depend on how far the two mills can be moved from each other. The width of the formed duplex mill with one or two adjustable row products can be changed quickly by adjusting of stands. Duplex mills have the same advantages and disadvantages as the cantilevered mills, except that the shaft end connecting pieces cannot be used. Some duplex mills have shafts extended at the other side of the mill, which can be used to form narrow sections. Duplex mills either have one side fixed and the other one adjustable, or both sides adjustable. Adjustment of a side is usually accomplished by placing all stands on one plate, which, with proper guides, can be moved in and out, thus changing the gap between the two cantilever mills. For duplex mills with one adjustable row of stands, the centerline of the product changes with width change. In the case of duplex mills with two adjustable rows of stands, the centerline of the products remains in the same position. This arrangement is used when holes are prepunched at or around the centerline, either when the cutoff die has to be kept symmetrical or for other reasons when it is advantageous to keep the centerline in the same position. The width adjustment can be manual or motorized.

(Halmos G.T., Roll Forming Handbook, pg. 2-7, Kayra Ermutlu)

Conventional Injection Molding (in PMC)

In PMC shape processing, injection molding is used for both TP- and TS-type FRPs. In the TP category, virtually all thermoplastic polymers can be reinforced with fibers. Chopped fibers must be used; if continuous fibers were used, they would be reduced anyway by the action of the rotating screw in the barrel. During injection from the chamber into the mold cavity, the fibers tend to become aligned during their journey through the noozle. Designers can sometimes exploit this feature to optimize directional properties through part design, location of gates, and cavity orientation relative to the gate.

Whereas TP molding compounds are heated and then injected into a cold mold, TS polymers are injected in to a heated mold for curing. Controll of the process with thermosets is trickier because of the risk of premature cross-linking in the injection chamber. Subject to the same risk, injection molding can be applied to fiber-reinforced TS plastics in the form of pelletized molding compound and dough molding compound.

(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, pg. 337, Kayra Ermutlu)

Polysulfone

Polysulfone is a family of sulfur-containing thermoplastics. It was first introduces as Bakelite Polysulfone (Udel-TM) by Union Carbide in 2965. The family of polysulfones also includepolyarylsulfones, polyethersulfones, polyphenylsulfones, and polyarylether sulfones. Polysulfones are prepered via two different methods of condensation polymerization. The first is polysulfonylation; the second is polyetherification. The principle characteristics of polysulfones include their outstanding heat resistance, exceptional resistance to creep, rigidity, transparency, and their resistance to greases, solvents and chemicals. Additionally, they are self-extinguishing. They are among the higher priced engineering thermoplastics and so are only used in situations where polycarbonates or other cheaper materials are not suitable. Polysulfones have the highest service temperature (170C) of all melt-processible thermoplastics.

(DIANE Publishing Company, New Materials Society, Challenges and Opportunities, Vol-2, pg.8-50, Kayra Ermutlu)

Surface Processing Operations

The major categories of surface processign operations are cleaning, surface treatments, and coating and thin film deposition. Cleaning refers to industrial cleaning processes that remove soils and contaminants that result from previous processing or the factory environment. They include both chemical and mechanical cleaning methods. Surface treatments are mechanical and physical operations that alter the part surface in some way, such as improving its finish or impregnating it with atoms of a foreign material to change its chemistry and physical properties.

Coating and thin film deposition include variousprocesses that apply a layer of material to a surface. Products made of metal are almost always coated by electroplating (e.g. chrome plating), painting or other processes. Principal reasons for coating a metal are to provide corrosion protection; enhance product appearance (e.g. providing a specified color or texture); increase wear resistance and/or reduce friction of the surface; increase electrical conductivity; increase electrical resistance; prepare a metallic surface for subsequent processing; and rebuild surfaces worn or eroded during service. Nonmetallic materials are also sometimes coated. Examples include plastic parts coated to give them metallic appearance; antireflection coatings on optical glass lenses; and certain coating and deposition processes used in the fabrication of semi-conductor chips and printed circuit boards. In all cases, good adhesion must be achieved between coating and substrate, and for this to occur the substrate surface must be very clean.

(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, pg.668, Kayra Ermutlu)

Burcu Atay, 140060029, 11th week

Truck-Mounted Mills

Installers of construction products occasionally find it necessary and often more economical to form the products at the job site.

For example, to reroof an existing building, the architect may specify over 100-ft (33-m) long sheets. Because transporting and handling these sheets from the plant to the job site is not practical, it is easier to move the complete line to the job site.

Most special, trailer-mounted lines have their own diesel generator, hydraulic or other drive, cutoff press, and an uncoiler that can be loaded from ground level (Figure 2.29).

Figure 2-29 Trailer-mounted roll forming line

These self-contained units are also used in less developed countries or at any place where, owing to the lack of proper infrastructure, it is easier to transport the equipment in one truck and the coils in another one than to ship many truckloads of finished products.Several types of truck-mounted units are used by contractors for job site manufacturing of eavestrough, sidings, soffits, and similar products. These units usually have a “plug-in” electrical motor drive. Small items such as eavestrough are often manufactured in a “stop-and-go” operation, and the products are cut by a manual shear mounted at the end of the mill.

(Halmos,G.T, Roll Forming Handbook,Taylor & Francis,2-17,18)

Vulcanization

Vulcanization is a process generally applied to rubbery or elastomeric materials. These materials forcibly retract to their approximately original shape after a rather large mechanically imposed deformation. Vulcanization can be defined as a process which increases the retractile forces and reduces the amount of permanent deformation remaining after removal of the deforming force. Thus vulcanization increases elasticity while it decreases plasticity. It is generally accomplished by the formation of a crosslinked molecular network ( fig.1.)

According to the theory of rubber elasticity, the retractile force to resist a deformation is proportional to the number of network supporting polymer chains per unit volume of elastomer. A supporting polymer chain is a linear polymer molecular segment between network junctures. An increase in the number of junctures or crosslinks gives an increase in the number of supporting chains. In an unvulcanized linear high polymer (above its melting point), only molecular chain entanglements constitute junctures.

Vulcanization, thus, is a process of chemically producing network junctures by the insertion of crosslinks between polymer chains. A crosslink may be a group sulfur atoms in a short chain, a single sulfur atom, a carbon to carbon bond, a polyvalent organic radical, an ionic cluster, or a polyvalent metal ion. The process is usually carried out by heating the rubber, mixed with vulcanizing agents, in a mold under pressure.

(Mark, J., Erman, B., Eirich, F.R., Science and technology of rubber, 3^rd Edition, pg.322)

Hubbing

Hubbing is a deformation process in which a hardened steel form is pressed into a soft steel (or other soft metal) block. The process is often used to make mold cavities for plastic molding and die casting. The hardened steel form, called the hub, is machined to the geometry of the part to be molded. Substantial pressures are required to force the hub into the soft block, and this is usually accomplished by a hydraulic press. Complete formation of the die cavity in the block often requires several steps- hubbing followed by annealing to recover the work metal from strain hardening. When significant amounts of material are deformed in the block, as shown in our figure, the excess must be machined away. The advantage of hubbing in this application is that it is generally easier to machine the positive form than the mating negative cavity. This advantage is multiplied in cases where more than one cavity are made in the die block.

(Groover, M.P, Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, pg.419)

Flowability

It is that property of the metal powder by virtue if which it flows readily, uniformly and rapidly into the die or mould cavity. It governs the time required to fill a die or mould and the rate of production. The shapes of the particle, size and its distribution, coefficient of inter-particle friction and the absorbed moisture are the factors affecting flowability. Coarse and spherical particle possess good and maximum flowability whereas fine and irregular particles have poor as well as reduced flowability respectively.