Gökhan Malakçı-030070802-8th Week

Feedback Control 02.04.2011 21:26

A feedback control system is a control system that tends to maintain a prescribed relationship of one system variable to anohter by comparing functions of these variables and usig the difference as a means of control.With an accurate sensor, the measured output is a good approximation of the actual output of the system.

A feedback control system often uses a function of a prescribed relationship between the output ans reference input to control the process.

(Richard C.dorf and robert H.Bishop,Modern Control Systems, 11th edition page 3)

Epoxy 02-04-2011 23:35

Epoxy resins are based on a chemical group called the epoxides. The sim­plest formulation of epoxide is ethylene oxide (C₂H₃0). Epichlorohydrin (C3H5OCI) is a much more widely used epoxide for producing epoxy resins. Uncured, epoxides have a low degree of polymerization. Toincrease molecular weight and to cross-link the epoxide, a curing agent must be used. Possible curing agents include polyamines and acid anhydrides. Cured epoxies are noted for strength, adhesion, and heat and chemical re­sistance. Applications include surface coatings, industrial flooring, glass fiber-reinforced composites, and adhesives. Insulating properties of epoxy thermosets make them use­ful in various electronic applications, such as encapsulation of integrated circuits and lamination of printed circuit boards.

(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 164-165)

Elastomers 02.04.2011 23:42

Elastomers are polymers capable of large elastic deformation when subjected to relatively low stresses. Some elastomers can withstand extensions of 500% or more and still return to their original shape. The more popular term for elastomer is, of course, rubber. We can divide rubbers into two categories: (1) natural rubber, derived from certain biological plants; and (2) synthetic elastomers, produced by polymerization processes similar to those used for thermoplastic and thermosetting polymers.

(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 167)

Composite 02.04.2011 23:47

Composites do not really constitute a separate category of materials; they are mixtures of the other three types. A composite is a material consisting of two or more phases that are processed separately and then bonded together to achieve properties superior to those of its constituents. The term phase refers to a homogeneous mass of material, such as an aggregation of grains of identical unit cell structure in a solid metal. The usual structure of a composite consists of particles or fibers of one phase mixed in a second phase, called thematrix.

Composites are found innature (e.g., wood), and they can be produced synthetically. The synthesized type is of greater interest here, and it includes glass fibers in a polymer matrix, such as fiber-reinforced plastic; polymer fibers of one type in a matrix of a second polymer, such as an epoxy-Kevlar composite; and ceramic in a metal matrix, such as a tungsten carbide in a cobalt binder to form a cemented carbide cutting tool.

Properties of a composite depend on its components, the physical shapes of the components, and the way they are combined to form the final material. Some composites combine high strength with light weight and are suited to applications such as aircraft components, car bodies, boat hulls, tennis rackets, and fishing rods. Other composites are strong, hard, and capable of maintaining these properties at elevated temperatures, for example, cemented carbide cutting tools.

(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 10)

Gökçe Dil 8.week

1. Composite
2. Matrix material
3. Epoxy
4. Resin
5. reinforced plastic
6. Elastomers
7. Non structural adhesives
8. Structural adhesives
9. Mechanical fasteners
10. Deoxidizing

Barış ERDEM (030060085) 8th Week

Air Carbon Arc Cutting

In the air carbon-arc cutting (AAC), the arc is normally obtained between a copper- coated graphite or carbon electrode and the workpiece with the molten metal being forced out by means of compressed air at apressure of 550 to 690 kPa. It may be possible to use a very low pressure of order of 280 kPa in some manuan torches for field application but is not generally recommended. The air consumption is in the range of 85 to 1400 L/min depending on the thickness of the metal being cut. The copper coating is used to reduce the oxidation of the electrodes and to help cool the electrode. 

(Rao P. N., Manufacturing Tehcnology Vol. I, 2009, p. 394-395)

 Hot Dipping 

Zinc is the metal most widely applied by this method, and for heavy steel sections is the only one. Tin and lead are commonly applied by hot-dipping but not for structural steelwork. Aluminum is also applied by this method, particularly to sheet steel, which is marketed as a pre-coated product, often as Zn-Al-coated steel. Although aluminium can be applied to havier sections of steel by hot-dipping, it is a more difficult and expensive process then for zinc and is rarely, if ever, used. However, if an economic form of this process could be developed it might well prove to be a suitable method of coating with alıminium, which, in many situations, provides a higher degree of corrosion resistance than does zinc.

Zinc is particılarly suited to hot-dipping because of its low melting point (420 ⁰C) and the nature of the alloy layer formed during the process. For many years hot-dipped galvanising has been specified by BS 729:1971 (1986). A new International and European Standard BS EN ISO 1461:1999 has now been published. Aluminium is by no means as easy to apply by dipping techniques. It has a higher melting point than zinc (660⁰C) and this means that the bath usually has to be operated at a temperature over 700⁰C. At this temperature the reaction between aluminium and steel is rapid, resulting in high dross formation. Futhermore, at this temperature, because of the reaction with steel, it is necessary to use ceramic-lined tanks, which are more expensive than the standart steel type used for Zinc. Aliminium oxides readily to produce an oxide (Al₂O₃) and this makes fluxing more difficult than with zinc. Oxide particles may also become entrapped in the coating.


(Bayliss D. A., Deacon D. H., Steelwork Corrosion Control, 2002 p.169)

Buffing

The purpose of buffing is to improve the surface appearance of the metal and to produce a smooth, tihht surface. Buffing is used as a fina finishing opperation and is particularly adaptable to finishing a localized area of a part. Items such as body prostheses, pacemakers, and heart valves reauire a highly buffed, tight surface to prevent entrapment of particles. Close fitting parts for euipment, such as the modern guidance systems and electronics appilications, require highly polished surfaces obtained by buffing. In addition, sheet sizes too large to be proccesed by other abrasive finishing methods, such as mass finishing or wet blasting, can be economically processed by buffing.

(Donachie M.J., Titanium: A Technical Guide, 2000, p.90)

Superfinishing

Superfinishing is an abrading process, efficient in surface refining of cylindrical, flat, spherical and cone shaped parts. It is not primarily a dimension changing process but mainly used for production fnished surface of fine quality on metals. Only a slight amount of stock is removed (avarage 0.002 to 0.02 mm on a disc). The smoother finishes do not have scratch exhibit any directional effect. The honing process involves two motions whereas superfinishing requires three to five even more. As a result of this motions the abrasive particle path is random and never repeat itself.

The operation is mainly concerned with external work. Superfinishing is generally used for:

(i)                 Correcting inequalities of geometry

(ii)               Removing surface fragmention.

(iii)             Reducing surface stresses and burns and thus restoring surface integrity

(Rajput R. K., A Textbook of Manufacturing Technology: Manufacturing Processes, p. 552)

Osman Süzen 030060804 8th week

Harmonic motion:Oscillaratory motion may repeat itself regularly, as in the balance wheel of a watch, or display considerable irregularity, as in earthquakes . When the motion is repeated in equal intervals of time (T), it is called periodic motion. The repetition time T is called the period of oscillation, and its reciprocal, f=1/T, it is called the frequency. If the motion is designed by the time function x(t), then any periodic motion must satisfy the relationship x(t) = x(t +T). The simplest form of periodic motion is harmonic motion. It can be demonstrated by a mass suspended from a light spring. If the mass is displaced from its rest position and released, it will oscillate up and down. By placing a light source on the oscillating mass, its motion can be recorded on a light-sensitive filmstrip, which is mado to move past it at a constant speed.The motion recorded on the film strip can be expressed by the equation x = A.sin2(pi).t/T where A is the amplitude of oscillation, measured from the equilibrium position of the mass, and T is the perion. The motion is repeated when t=THarmonic motion is often represented as the projection on a straight line of a point that is moving on a circle at constant speed as shown in Fig 1.1-2. ( Theory of vibration with applications- Willia Thomson- page 6)

WIPER BENDING: Bending is the operation of deforming a flat

sheet around a straight axis where the neutral plane lies. it is a very common forming process for changing sheet and plate in to channel, drums, tanks, etc. Wiper bending is used for 90 degree bends only. Here the work is held firmly to the die, and the punch bends the extended portion of the blank. ( Manufacturing Processes - R.K. Rajput - page 178 )

Corrosion ( as a mechanical failure mode) : corrosion may be defined as the undesired deterioration of material through chemical or electrochemical interaction with the environment, or destruction of materials by means other than purely mechanical action.

Failure by corrosion occurs when the corrosive action renders the corroded device incapable of performing its design function.Corrosion often interacts synergistically with another failure mode, such as wear or fatique, to produce the even more serious combined failure modes, such as corrosion-wear or corrosion- fatique. ( Mechanical design of machine elements and machines - Jack A. Collins, Henry R Busby, Geoerge H. Stabb- page 64 )

Electro-magnetic Clutches: The rear axle differential, center differential, and transfer case ( Figure 10-42) on some vehichles are equipped with electromagnetic clutches for lockup of the differential. The clutch may be controlled by a switch ar by a traction control computer. When one wheel or axle loses traction and speeds up, the computer energizes the clutch, which locks up the differential and provides equal power to both wheels or axles. The electromagnetic clutch consist of an actuator coil, an armature, an a stack of steel clutch plates. When the clutch is energized, a magnetic field is produced to compress the clutches, thereby locking the differential. ( Manual transmission and transaxles - Jack Erjavec - page 470)

Ezgi UĞUR - 030060195 8th Week

Boronizing

Boronizing is one of the recent methods of surface hardening, which may applied to any ferrous material but is generally adopted for carbon steels and tool steels. Both pack and gaseous techniques can be applied for surface hardening. In the case of pack process, the components are packed in heat-resistant boxes with mixtures of granules or paste of boron carbide or other boron compounds with additions of activators and diluents at 900-1000 centigrade degree. Boron diffuses inwards and iron borides (FeB and Fe2B) layers are formed. On the surface, FeB phase forms, while in the interior, Fe2B phase is formed. FeB phase is more brittle and is not desirable. Higher temperatures, longer treatment times and higly alloy steels favour teh formation of FeB phase. The boride layers are very hard. They have hardness which is even greater than 1500VPN.

The heat threatment time required for a case depth of 0.15mm is 6 hours at about 900 centigrade degree. This layer has high wear resistance, and such components are used in tractor parts, drop forging dies and jig bushes.

In this process, threatment temperature is very high, and hence hardening of components before boronizing is not required. Only in the case of tool steels after boronizing, hardening and tempering are required to have the desired mechanical properties.

(T. V. Rajan, C. P. Sharma, A. Sharma, Heat Treatment: Principles and Techniques, pp.163-164)

Chromizing

Like boronizing process, chromizing is also used for surface hardening of both carbon and tool steels.

There are two types of chromizing: pack chromizing and gaseous chromizing. The components to be chromized

are packed with fine chromium powder and additives. A typical chromizing mixture consist of 60 percent chromium

or ferro chrome (with carbon content not exceeding 0.1%), 0.2 percent ammonium iodide, and 39 percent kaoin

powder. Diffusion of chromium carbide is formed on the surface of steel. The threatment time needed for achieving

a case depth of 0.02-0.04 mm is 12 hours at 900-1020 centigrade degree. Hardness of chromium carbide layer

is about 1500 VHN.

(T. V. Rajan, C. P. Sharma, A. Sharma, Heat Treatment: Principles and Techniques, pp.164)

Carbonitriding

Carbonitriding is one of the case hardening process in which carbon and nitrogen are diffused into

the surface of the component simultaneously at a predetermined temperature followed by

quenching.

The process is carried out in a controlled atmosphere so that both carbon and nitrogen are absorbed

simultaneously by teh heated component. The concentration of hardening elements is more at

the outer surface of the steel and decreases progressively towards the core. The carbonitrided

components may be subsequently heat treated so as to form a hard wear-resistant case of the

type normally obtained by treatment in a cyanide salt bath.

The process is used in the production of shallow cases on carbon and alloy steels. The treatment is

usually done at 850-900 centigrade degree using a carburizing gas with low additions of ammonia.

Ammonia dissociates into hydrogen and nitrogen, the latter reacting with the surface of the steel

to form nitrides. In addition, however, a small amount of nitrogen goes into solution increasing the

hardenability to some extent. The subsequent quenching ensures the final full skin hardness.

Carbonitriding results in a higher hardenability of the surface layer as compared to carburizing

and allows steel with lower content of alloying elements to be used.

The primary object of carbonitriding is to impart a hard case to the steel in order to provide

resistance to metallic and abrassive wear. The process competes with liquid cyaniding, carburizing

and to a lesser extent with nitriding.

( K. H. Prabhudev, Handbook of Heat Treatment of steels, p.386)

Chemical Blanking

Chemical blanking uses chemical erosion to cut very thin sheet -metal parts- down to 0.025 mm thick and/or for intricate cutting patterns. In both instances, conventional punch-and-die

methods do not work because the stamping forces damage the sheet material, or the tooling cost would

be prohibitive, or both. Chemical blanking produces parts that are burr free, an advantage over

conventional shearing operations.

Methods used for applying the maskant in chemical blanking are either the photoresist mothod or

the screen resist method. For small and /or intricate cutting patterns and close tolerances, the

protoresist method is used; otherwise, the screen resist method is used. The small size of the work

in chemical blanking exludes teh cut and peel maskant method.

Application of chemical blanking is generally limited to thin materials and/or intricate patterns.

Maximum stock thickness is around 0.75 mm. Also, hardened and brittle materials can be processed

by chemical blanking where mechanical methods would surely fracture the work.

Tolerances as close as +- 0.0025 mm can be held on 0.025 mm thick stock when the photoresist

method of masking is used. As stock thickness increases, more generous tolerances must be allowed.

Screen resist masking methods are not nearly so accurate as photoresist. Accordingly, whwn close

tolerabces on the part are required, the photoresist method should be used to perform the masking

step.

(M. P. Groover, Fundamentals of Modern Manufacturing: Materials, Processes, and

Systems, pp.638-640)

Ali Utku Gökçe-030060060-8th week

Crank Mechanism

The cranck mechanism converts the reciprocating motion to a rotary motion, and vice-versa. A simple crank mechanism for a single-cyclinder engine is shownn in figure1.2. It consists of a piston which moves inside a cylinder, a crank of length r which rotates about a point O and a connecting rod of length L which is attached to the piston at point P and to the crank shaft at point C. The crank pin C follows a circular path while the wrist pin P oscillates along a linear path. Points on the connecting rod between C and P follow an elliptical path.

(P. Srinivasculu, C.V. Vaidyanathan, Handbook of Machine Foundations, p.4)

Photolithography (Optical Lithography)

Optical Lithography(also called photolithography) uses light as the writing material. The drawn(greased) and undrawn(moistened) areas on the limestone in lithography become bright and dark regions on a reticle or phptmask, the template of optical lithography. Just as greased ink discriminately deposits on the limestone, light passes only through the clear opening the mask. The transmitted energy is recorded on a light-sensitive medium called the photoresist.

(Alfred Kwok- Kit Wong, Resolution Enhancement Techniques In Optical Lithograpy,p.2)

Sputtering

When a solid surface is bombarded with energetic particles such as accelerated ions, surface atoms of the solid are scattered backward due to collisions between the surface atoms and the energetic particles. This phenımenon is called back-sputtering, or simply sputtering.When a thin foil is bombarded with energetic particles, some of the scattered atoms transmit through the foil. The phenomenon is called transmission sputtering. The word “spluttering” is synonymous with “sputtering”. Cathode sputtering, cathode disintegration, and impact evaporation are also used in the same sense.

(Kiyota Wasa, Thin Film Materials Technology: Sputterşng Of Compound Materials, P.39)


Bead Weld

If you weld at a rapid pace, the penetration depth and bead with decreases, and the bead is dome shaped. If the speed is increased even faster, undercutting-producing a weld surface level lower than base metal- can ocur. Welding at too low a speed can cause burn- through holes. Ordinarily, welding speed is determined by base metal thickness and/or voltage of the welding machine.

(James E. Duffy, Robert Scharff, Auto Body Repair Technology, p. 192 )

A. Selim PARLAKYİĞİT - 8th Week

1. Hot Dipping
2. Sputtering
3. Chromizing
4. Boronizing
5. Carbonitriding
6. Superfinishing
7. Buffing
8. Chemical Blanking
9. Air Carbon Arc Cutting
10.Photolithography (Optical Lithography)

Taha Selman Cakir
030070023
8th week

Forced vibrations:

Vibrations are usually classified as free or forced. In the case of forced vibration, the body is subjected to external force functions that make it vibrate with the frequency of the exciting force. An alternating external force system may arise as a consequence of many natural phenomena such as waves, sound, blast, earthquake, and heavy vehicular traffic on highway pavements and bridges, as well as from any mechanically produced causes. In each case the wave motion of the disturbance will vibrate a structure at the frequency of the oscillating force. A condition of resonance will occur if the frequency of the applied force system coincides with one of the natural free frequencies of the body. At the resonant condition the amplitude of vibration will approach infinity with time. In practical situations, however, the amplitude of vibration may exceed allowable values in a short period of time, with the subsequent loss of structural integrity.

(Fertis D. G., Mechanical and structural vibrations, 1995, p. 9,10)

Piezoelectric materials:

Piezo derives from the Greek verb piezin- "to press"- and piezoelectricity is a seperation of charge that occurs when pressure is applied to a piezoelectric material. The piezoelectric effect occurs only in certain crystalline electrical insulators, and the charge seperation is manifested by an electrical potential difference between opposite faces of a crystal. A converse effect to piezoelectricity also exists; when an electrical field is applied to a piezoelectric crystal, the crystal becomes distorted as long as the field is present.

Most piezoelectric materials are ionic salts, which consists of positively charged cations and negatively charged anions. In the solid state, these ions form a regular lattice that is described by a unit cell-the smallest group of ions that represent the whole structure of the cell- and a crystal can be thought of as a three-dimensional array of unit cells. A few piezoelectric materials are highly polar crystalline polymers, such as polyvinylidene chloride.

(Marshall Cavendish Corporation, How it works: science and technology, 2002, p. 1744)

Free vibrations:

This type of motion is characterized by an oscillation that occurs with a linear spring and mass system without any external force or excitation. The system is initially streched beyond a static equilibrium position and then released. Typical free-vibration problems provide the value of the initial displacement (deformation), denoted by x0, and require solutions for the amplitude, velocity, period, and/or natural frequency at a given time or position.

(Olia M., Casparian A. S., How to prepare for the fundamentals of engineering, FE/EIT exam, 1999, p. 91)

Semi-active actuators:

The power at the output port of the actuator can be expressed as a function of the conjugate variables as:

PTrans =F. v

for translational output mechanical energy, and:

PRot = T . w

for rotational mechanical energy.

Semiactive actuators are those whose output mechanical power is not positive: PTrans <0 or Prot <0. This means that the energy level in the plant is reduced. Semiactive actuators dissipate the energy of the plant they are coupled to.

Semiactive actuators can actively modulate power dissipation, but the effort they supply (whether a force or a torque) can only oppose the flow in the plant (whether a velocity or an angular rate)

(Pons J. L., Emerging actuator technologies: a micromechatronic approach, Ed. 1st, p. 33, 34)

Ertan Toparlak 8th Week

1-Harmonic motion

2-Amplitude

3-Free vibrations

4-Forced vibrations

5-Frequency

6-Piezoelectric material

7-Piezoelectric stack actuators

8-Semi-active actuators

9-Feedback Control

10-Feedforward control

Ertan TOPARLAK

503091329

Bugra Cengiz 030060178 8th week

Stiffness
Stiffness is a measure of  a systems's resistance to deformation. A rubber band is easily deformed by hand but a steel wire or rod of the same cross-sectional area is not. The stiffness of steel is greater than that of rubber.

Frederick A. Leckie,Dominic J. Dal Bello, The strength and the stiffness of The Engineering Systems, P.48 

Implsion (Implosion Hazard)


The pressure differance (0,1MPA) between inside of the vacuum enclosure and outside initiate an accidental implosion of an evacuated birttle containeer, resulting in flying fragments. Glass and perspex viewports represen an implosion hazard. 

R. Hellborg, Electrostatic accelerators: fundamentals and applications, P.366

Flexible Systems (Flexible Productio Systems)
Mass production is predicated largely on the principles of Frederick W. Taylor. one of the leaders of the scientific management movement in the early 1901s.  According to Taylor, workers had to be told every detail of their work methods and were incapable of planning their own tasks. By comparison.Lean production makes use of worker teams to organize the tasks to be accomplished and worker involvement to solve technical problems. One of the findings reported in The Machine thai Changed the World was that workers in Japanese "lean production" plants received many more hOUTSof training than their U.S, counterparts (380 hours of training vs.46 hours).Another finding was the lower number of job classifications in Japanese lean plants. The study showed an average of 11.9 job classifications in Japanese plants versus an average of 67.1 in L:.S. plants. Fewer job classifications mean more cross-training among workers and greater nexttunty ill the work force.                                  
     In mass production, the goal is to maximize efficiency. This is achieved using long
production runs of identical parts. Loeg production runs tolerate long setup changeovers, In lean production. procedures are designed to speed the changeover. Reduced setup times allow for smaller batch sizes. thus providing the production system with greater flexibility. Flexible production systems were needed in Toyota's comeback period because of the much smaller car market in Japan and the need to be as efficient as possible.


Groveer, Automation, Production Systems and CIM, P. 835

Eray Çavuş 030060022 8th week

Casting Defects(02,04)

Casting often contain various imperfections which often contribute to normal quality variations. These defects not only give a bad appearance to the castings but also decrease their strength and practical utility. Casting defects generally occur due to improper control of the manufacturing cycle.

Defects in castings occur due to different causes. Practically it is quite difficult to establish a relationship between defects and causes. Roughly, casting defects can be classified into the following groups:

-Defects caused by patterns and moulding boxes.

-Defects due to improper moulding or core making materials

-Defects due to improper sand mixing

-Defects due to moulds, cores, runners and risers

-Defects due to improper metal temperature

-Defects due to improper pouring.

(Manufacturing Process, Yazar: H.S. Bawa,P.76)

Guillotines Shears (02,04)

Guillotine shears are used to cut sheet materials such as metal, plastic, paper, card and composite material and may be treadle operated or power driven. Before using any machine, the operator should be fully conversant with the controls, ensure that all the guards are in position and know the the emergency stop procedure. On some power driven machines a photo-electric cell is positioned in front of the blade to prevent operation if any object breaks the beam. For efficient use, the blades should be kept sharp and the clearence between the blades should be adjusted to suit the type and thickness of the material being cut.

(Basic Manufacturing, Yazar: Roger Timings, P.157)

Matrix Material (03,04 - 00.25)

The matrix phase can be any of three basic material types; polymers, metals, or ceramics. The secondary phase may also be one of the three basic materials, or it may be an element such as carbon or boron. Possible combinations in a two-component composite material can be organized as a 3 * 4 chart. We see that certain combinations are not feasible, such as a polymer in a ceramic matrix. We also see that the possibilities include two-phase structures consisting of the same material type, such as fibers of Kevlar (polymer) matrix. In other composites the imbedded material is an element such as carbon or boron.

(Mikell P.Groover, Fundamentals of Modern Manufacturing , page 188-189)

Mechanical Fasteners (03,04- 00.38)

The mechanical fastening generally requires that the components to be joined have holes through which fasteners such as bolts, screws, rivets, pins, etc. may be inserted and the jointing or clamping results either by screwing the nut on the threaded bolt or by riveting the head of the pin. Mechanical fasteners are preferred over other methods of jointing for the following reasons.

-Ease in manufacturing (drilling or tapping)
-Joint is not permanent and has ease of assembly and disassembling for repairing or maintenance
-Easy to create designs of joints requiring moveable joints such as hinges
-Lower overall cost
-Joints are easy to design to resist tensile and shear loads.

(Manufacturing Processes, Yazar: Kaushish, p.535)

Cemre Ablay, 030060150, 8th Week

Pickling: (01.04.2011, 18:47)

Another chemical cleaning process is pickling, which is an acid-cleaning treatment that removes oxide scale and flux residues. Pickling involves cleaning of metal parts in dilute acids by spraying or immersion. Common acids used in pickling are 10% H2SO4 at 150-185°F or HCl acid in room temperature. The part is first cleaned with an alkali to allow acid to reach all surfaces. Pickling solution does not attack certain types of oils and grease, and alternative cleaning treatments may be needed.

(Asthana R. et al., Materials Processing an Manufacturing Science, p.316)

...............................................................................................

Amplitude: (02.04.2011, 22:49)

Amplitude is the maximum value of displacement. While describing simple harmonic motion (SHM), we mentioned that energy of a system executing SHM alternates between kinetic and potential forms. At the extremities of the oscillation, which are also called the turning points, the kinetic energy is zero and the potential energy is maximum.

(Garg S., Ghosh C.K., Gupta S., Oscillations and Waves, page 42)

...............................................................................................

Frequency: (02.04.2011, 22:49)

Frequency is the number of complete oscillations executed per second. It is expressed in cycles per seconds or simply [1/s] or Hertz (Hz). If the frequency is v, the system executes v oscillations per second.

(Garg S., Ghosh C.K., Gupta S., Oscillations and Waves, page 42)

...............................................................................................


Resin: (03.04.2011, 00:02)

A resin is a high-molecular-weight organic material with no sharp melting point. Resins usually exhibit a tendency to flow when subjected to stress, and they fracture in a ductile mode. Most resins are polymers. In reinforced plastics, the resin is the material used to bind together the reinforcement material (i.e., the matrix).

(Harper C.A., Petrie E.M., Plastics Materials and Processes: A Concise Encyclopedia, p.482)

Ahmet Gökay Öztürk 030050143 (8th week)

AC motors

Electric motors designed to operate with alternating current (AC)
supplies are themselves broadly categorized into two classes: induction
and synchronous. There are many variations of synchronous machines.
AC motors work by setting up a magnetic field pattern that rotates
with respect to the stator and then employing electromagnetic forces to
entrain the rotor in the rotating magnetic field pattern. Synchronous
machines typically have a magnetic field which is stationary with respect
to the rotor and which therefore rotate at the same speed as the stator
magnetic field. In induction motors, the magnetic field is, as the name
implies, induced by motion of the rotor through the stator magnetic
field.
(J.Kirtley, Electric Motor Handbook, pg.3)


DC motors

DC motors, as the name implies, operate with terminal voltage and
current that is “direct”, or substantially constant. While it is possible to
produce a “true DC” machine in a form usually called “acyclic”, with
homopolar geometry, such machines have very low terminal voltage
and consequently high terminal current relative to their power rating.
Thus all application of DC motors have employed a mechanical switch
or commutator to turn the terminal current, which is constant or DC,
into alternating current in the armature of the machine.DC motors have usually been applied in two broad types of application.
One of these categories is when the power source is itself DC. This is
why motors in automobiles are all DC, from the motors that drive fans
for engine cooling and passenger compartment ventilation to the engine
starter motor.
A second reason for using DC motors is that their torque-speed
characteristic has, historically, been easier to tailor than that of all AC
motor categories. This is why most traction and servo motors have been
DC machines. For example, motors for driving rail vehicles were, until
recently, exclusively DC machines.
(J.Kirtley, Electric Motor Handbook, pg.2-3)


Pneumatics

Pneumatics is the discipline that deals with mechanical properties of gases
such as pressure and density, and applies the principles to use compressed
gas as a source of power to solve engineering problems. The most widely
used compressed gas is air, and thus its use has become synonymous with
the term pneumatics. Hydraulics is the discipline that deals with the mechanical
properties of liquids, and applies the principles to solve engineering
problems. Gases and liquids are both fluids as opposed to solids.
Pneumatics and hydraulics are similar in many respects and often described
by the generic term fluid power.
(Peter Beater, Pneumatic Drives System Design, Modelling and Control, pg.1)



Lever Mechanism

Levers are the simplest of mechanisms; there is evidence that
Stone Age humans used levers to extend their reach or power;
they made them from logs or branches to move heavy loads such
as rocks. It has also been reported that primates and certain birds
use twigs or sticks to extend their reach and act as tools to assist
them in obtaining food.
A lever is a rigid beam that can rotate about a fixed point
along its length called the fulcrum. Physical effort applied to one
end of the beam will move a load at the other end. The act of
moving the fulcrum of a long beam nearer to the load permits a
large load to be lifted with minimal effort. This is another way to
obtain mechanical advantage.
(N. SCLATER, N. P. CHIRONIS, MECHANISMS AND MECHANICAL DEVICES SOURCEBOOK 4th ed., pg 4)

Bahadır Coşkun 030070008 (8th Week)

Hardness Alterations (01.04.2011 17:43)

In general, hardness measurement are carried out with Vickers or Knoop diamond indenters using the average indented diagonal in the former or the longer diagonal in the latter. Due to the fact that hardness may vary considerably within a short distance, loads below 1 N (microhardness test) are often employed. However, in contrast to the high loads typically employed for hardness testing, microhardness value depends on the applied load. Tönshoff and Brinksmeier [30] compared Knoop and Vickers indenters and noticed that the former presents the following advantages: the longer diagonal reduces the risk of misreading, the influence of lack of homogeneity normal to the surface is reduced due to the smaller indentation depth, the small diagonal allows measurement near the machined surface and it can be used to measure anisotropy. On the other hand, the Vickers indenter is less affected by form errors on the surface and the indenter is cheaper. Additionally, the above-mentioned authors state that owing to the steep variation in microhardness values, especially near the machined surface, measuring should be performed using the slope method, in which the indentations are produced on an tapered surface, thus allowing the measurement of hardness close to the machined surface (not possible when the sample is cross-sectioned due to the fact that a distance of not less than 2.5 times the diagonal indentation must be kept from a disturbed area). Finally, the polishing method employed prior to microhardness testing may affect the results: higher hardness values and wider scatter are obtained when grinding the samples in comparison with electrolytic polishing, probably due to microstructure non-homogeneity and work hardening induced by the former procedure.
(Davim. J. P., Machining of Hard Materials, 2011, p. 127-128)

Fatigue Strength (01.04.2011 17:43)

The fatigue process consists of three stages: initial fatigue damage leading to crack nucleation and crack initiation in regions where the strain is most severe, progressive growth of the crack (crack propagation) and finally sudden fracture of the remaining cross-section [44]. Czyryca [45] states that many testing devices and specimen designs are available for fatigue testing according to the mode of loading: direct (axial) stress, plane bending, rotating beam, alternating torsion or combined stress. The selected loading mode should replicate, as accurately as possible, the actual service condition of the sample being tested.
(Davim. J. P., Machining of Hard Materials, 2011, p. 136-137)

Evolutionary Algorithms (01.04.2011 17:43)

Evolutionary algorithms are a set of heuristics simulating the process of natural evolution (Figure 6.10). Although the underlying mechanisms are simple, these algorithms have proven them as a general, robust and powerful search tool. In particular, they are especially convenient for problems involving multiple conflicting objectives and large and complex search spaces.
In spite of the wide diversity in the proposed approaches, an evolutionary algorithm can be characterized by three features:
• A set of candidate solutions is maintained.
• A competitive selection process is performed on this set.
• Several solutions may be combined in terms of recombination to generate new
solutions.
There are two main evolutionary heuristics: the German school of evolution strategies (ES), and the American school of GAs. The main differences between these two approaches are summarized in Table 6.1. Some papers have shown the application of evolutionary techniques in hardmachining optimization [26, 33].
(Davim. J. P., Machining of Hard Materials, 2011, p. 191)

Piezoelectric stack actuators (02.04.2011 16:45 )

In current work, piezoelectric stack actuators (PSA) have been studied as an alternatice solution to allow for satisfying all desirable characteristics without compromising between them. The main motivation for such study is actuator not only demonstrates all properties (advantages) of a single piezoceramic actuator, but it also provides a high actuation force partially by accumulating the produced force of each single piezoceramic in one unit. Other contributing factor of producing large actuation force in a piezoelectric stack lies in the large actuation force in a piezoelectric stack lies in the utilization of direct direction of polarization.

(Mehrdad R. Kermani,Mehrdad Moallem,Rajni V. Patel, Applied vibration suppression using piezoelectric materials, 2008, p. 90)

Ufuk Güneş Civelek 030050161 8th week

Tee Joint

Joints where the pieces come together at right angles to each other are called tee joints.A tee joints has welding surfaces areas (fusion faces) in close proximity to each other and more area for heat to dissipate to than any other basic joint.That is why tee joints require more heat for proper fusion and good welding than the other joints.Turn up your heat when appliying a fillet weld to a tee joint.
There are joints that needs as much heat as a tee joint, such as theroot pass of a V-groove weld with a 1/4-inch root opening and backing plate.Welding this first pass requires more heat for the same reason a tee joint does- the close proximity of multiple fusion faces on the joint.
( Todd Bridigum, How To Weld, p.47)

Bayonet-type clamping

In this system, a bayonet disk is used.The disk is provided with holes, sligthly bigger than the heads of the fixing screws. The clear holes are connected with slots, slightly (0,5) bigger than the threaded diameter. The bayonet disk acts like a special washer. Rotating the disk to align the bigger holes with screw centers, allow allows removal (or insertion) of the plate without removing entire screws (or Nuts). Rotation of the disk in the opposite direction brings the smaller slots to the screw centers. Tightening the screws in this position, secures the workholder to spindle nose. Thus, we only have to losen screws/nuts by a quarter turn, to remove the
bayonet disk and the workholder. Similary, securing workholder requires the rotation of the bayonet disk through small angle (15 degree), and turning the clamping screws/nuts through a small angle, to tighten them.
(P. H. Joshi, Machine tools handbook: design and operation, p.374)

Kudinov’s expression

Shows the polar curves for combined (tool face and flank) force, for 3 different values of flank wear. At zero frequency (w), the polar curves intercept the real axis R at x=Ks, the static characteristic. It has been observed that the flank wear land dampens the vibrations. Also, as the flank wear increases, there is a reduction ,n the frequency range, in which the dynamic cutting force lags behind the displacement. For flank wear land of 1 mm, frequency (w)=1,000. For all vibrations with frequency (w)>150hz, the cutting process provides a damping effect. There are more vibrations during actual metal cutting.
(P. H. Joshi,Machine tools handbook: design and operation, p.512)

Hydro-dynamic bearings

Hydro-dynamic bearings or fluid film bearings provide for high precision anf a long
life span due to their inherent good damping and heat dissipation properties, and the
absence of any metal to metal contact. The journal (spindle) acts like a pump, delivering
oil into the clearence between the shaft and the bearing. However, the narrowing clearance
in the direction of rotation, causes pressure rise till the hydro-dynamic force counter-balances
the load on the bearing
(P. H. Joshi,Machine tools handbook: design and operation, p.388)

Selim Şen, 030060185, 8th week

Preload

Whether a threaded fastener serves its intended purpose depends to a large degree on the amount of torque applied to tighten it. Once the bolt or screw has been rotated it is seated against the part surface, additional tightening will increase the tension in the fastener (and simultaneously the compression in the parts being held together); and the tightening will be resisted by an increasing torque. Thus, there is a correlation between torque required to tighten the fastener and the tensile stress experienced by it. To achieve the desired function in the assembled joint (e.g., to improve fatigue resistance) and to lock the threaded fasteners, the product designer will often specify the tension force that should be applied. This force is called preload. (Mikell P. Groover; Fundamentals of Modern Manufacturing Materials, Processes, and Systems 3rd Edition; pg.769, 770)

Retaining Ring

A retaining ring, also known as a snap ring, is a fastener that snaps into a circumferential groove on a shaft or tube to form a shoulder. The assembly can be used to locate or restrict the movement of parts mounted on the shaft. Remaining rings are available for both external (shaft) and internal (bore) applications. They are made from either sheet metal or wire stock, heat treated for hardness and stiffness. To assemble a retaining ring, a special plier’s tool is used to elastically deform the ring so that it fits over the shaft (or into the bore) and then is release into the groove. (Mikell P. Groover; Fundamentals of Modern Manufacturing Materials, Processes, and Systems 3rd Edition; pg.775)



Hot Rolling

Most rolling processes are very capital intensive, requiring massive pieces of equipment, called mills, to perform them. The high investment cost requires the mills to be used for production in large quantities of standard items such as sheets and planets. Most rolling is carried out by hot working, called hot rolling, owing to the large amount of deformation required. Hot-rolled metal is generally free of residual stresses, and its properties are isotropic. Disadvantages of hot rolling are that the product cannot be held to close tolerances, and the surface has a characteristic oxide scale. (Mikell P. Groover; Fundamentals of Modern Manufacturing Materials, Processes, and Systems 3rd Edition; pg.391)


Cold Rolling

Further flattening of hot-rolled plates and sheets is often accomplished by cold rolling, in order to prepare them for subsequent sheet metal operations. Cold rolling strengthens the metal and permits a tighter tolerance on thickness. In addition, the surface of the cold-rolled sheet is absent of scale and generally superior to the corresponding hot-rolled product. These characteristics make cold-rolled sheets, strips, and coils ideal for stamping, exterior panels, and other parts of products ranging from automobiles to appliances and office furniture. (Mikell P. Groover; Fundamentals of Modern Manufacturing Materials, Processes, and Systems 3rd Edition; pg.392)

ÖMER TAYLAN BOYA 030070099 8th WEEK

Planer (machining) (9:50 am 01.04.2011)

Planer and shaper are popular single point precision machining methods. A shaper operates by moving a cutting tool backwards and forwards across the workpiece. The workpiece mounts on a rigid square table that can traverse sideways underneath the reciprocating tool, which is mounted on a ram. The table motion is controlled by a precise feed mechanism. The ram slides back and forth about the workpiece and the tool can be positioned to cut the flat surface on the top of the workpiece. A Planer is a type of machining tool analogous to a shaper, but larger and with the entire workpiece moving beneath the cutter instead of the cutter moving above a stationary workpiece. Planers and shapers are generally used for two types of work: generating large accurate flat surfaces and cutting straight microgrooves. Modern planers are used for producing precision stamping dies and plastic injection molds for light-guiding plates of liquid crystal displays, large scale linear fresnel lenses.

( J. Paulo Davim, Mark J. Jackson, Nano and micromachining, page 178)

Carriage ( about lathe) ( 10:04 am 01.04.2011)

Carriageis mounted on the outer guideways of lathe bed and it can move in a direction parallel to the spindle axis. It comprises of important parts such as apron, cross slide, saddle, compound rest and tool post. The lower part of the carriage is termed the apron in which there are gears to constitute apron mechanism for adjusting the direction of the feed using clutch mechanisms and the split half of nut for automatic feed. The cross slide is basically mounted on the carriage, which generally travels at right angles to the spindle axis. on the cross slide , a saddle is mounted in which the compound rest is adjusted which can rotate and fix to any desired angle. The compund rest slide is actuated by s screw, which rotates in a nut fixed to the saddle.

(Rajender Singh, Introduction to basic manufacturing processes and workshop technology, page 410)

Abrasive Wear (16:04 03.04.2011)

Abrasive wear is defined as wear due to hard particles or hard protuberances forced against and moving along a solid surface. This form of wear in metals is most frequently caused by non-metallic materials but metallic particles can also cause abrasion. Generally a material is seriously abraded or scratched only by a particle harder than itself.

(Joseph R. Davis Surface Engineering for Corrosion and Wear Resistance, page 56)

Addition Polymerization (16:34 03.04.2011)

Addition polymerization is the polymerization of the monomers by a chain mechanism involving active sites on the growing chain. Addition polymerization is frequently accomplished with unsaturated monomers, it is also called vinl polymerization when the unsaturated monomer contains the group -CH2=CH2-

(Charles A. Harper, Edward M. Petrie, Plastics materials and processes: a concise encyclopedia page 13)

Anıl UZAL, 030070012, 8th Week

Cam Mechanisms: (01.04.2011 ; 01:10)

A simple cam mechanism consists of three basic parts, a cam, a follower, and a frame. A cam is an irregularly shaped machine member which serves as a driving link by rotating with a constant velocity and imparting motion through direct contact to a driven link, the follower, which in turn moves in a desired motion. A cam (K_A) is adjacent to a follower (K_Af) and a frame (K_F) with a cam joint (J_A) and a revolute joint (J_R), respectively. A follower, which is adjacent to the frame with a revolute joint or a prismatic joint (J_P), is usually driven to move with varying speeds in a noncontinuous and irregular motion.

(Hong-Sen Yan, Reconstruction Designs of Lost Ancient Chinese Machinery, page 65)

Brittleness: (01.04.2011 ; 01:37)

Brittleness is the property which renders substances easily broken, or separated into irregular fragments. This property belongs chiefly to hard bodies.

It does not appear that brittleness is entirely opposed to elasticity, since in many substances, both these properties are united. Glass is the standard, or type of brittleness, and yet a ball, or fine threads of this substance are highly elastic, as may be seen by the bounding of the one, and the springing of the other. Brittleness often results from the treatment to which substances are submitted. Iron, steel, brass, and copper, become brittle when heated and suddenly cooled, but if cooled slowly, they are not easily broken.

(Comstock J.L., A System of natural Philosophy: in Which The Principles of Mechanics, Hydrostatics, Hydraulics, Pneumatics, Acoustics, Optics, Astronomy, Electricity and Magnetism, page 22-23)

Wire Drawing: (01.04.2011 ; 02:30)

Drawing wire is a method similar to extrusion. Copper wire often starts as coils of thick wires produced by hot rolling, with successive coils welded together to maintain continuous production. Copper wire is then fed through an insulate line. Each insulate line performs several different functions, such as additional wire drawing, annealing (softening), and applying insulation.

The first step in the pulling process is to reduce the size of the copper wire by drawing it again, which uses diamond dies and reduces the wire to another size based on American Wire Gauge (AWG) codes (discussed in section 5.3, “Labeling and Certifying Cable”).

After being drawn, wire is very brittle and can be easily fractured if flexed. Finished copper wire has to be flexible to be useable, so the wire is annealed by passing a large electrical current through the wire for a fraction of a second. This raises the wire’s temperature briefly to 1000F. Wire is annealed in water to prevent oxidation, and also to cool and clean the wire before applying insulation. Wire that is not properly annealed tends to be brittle and break easily.

The wire is then passed through an extruder, where a thin coating of plastic containing high-density pellets of the insulating material is applied. As the wires are pushed through the extruder, the insulation pellets heat until they melt onto the wire.

(R. Shimonski, R.T. Steiner, S.M. Sheedy, Network Cabling Illuminated, page 124-125)

Alligatoring: (01.04.2011 ; 03:18)

Term describing the appearance of a film that is cracked into large segments resembling the hide of the alligator. When alligatoring is fine and incomplete, it is usually called checking.

Alligatoring may be caused by one coat being applied over another before the bottom coat is thoroughly hard and dry and/or having the material skinning over so that the lower portion of the film is still soft and elastic, or by less elastic material being applied over a more elastic undercoating. When these conditions are present and the finished article is exposed to actinic rays or changes in temperature and moisture content, expansion or contraction of the film cracks the hard outer crust while the softer core gives without breaking.

With excessively heavy coats of rather dilute materials, this cracking of the outer crust can take place without temperature change by the shrinking action of the bottom portion – much like clay mud is cracked under the summer sun.

Other causes of alligatoring include the too rapid evaporation of solvents or thinners and excessive air being forced into the film during spraying.

(National Research Council (U.S.). Building Research Institute. Conferences, New Joint Sealants: Criteria, Design, and Material, page 175)

FARUK SOYDAN (8TH WEEK TERMS)

1. BRITTLENESS

2. STIFFNESS

3. WIRE DRAWING

4. WIPER BENDING

5. GUILLOTINE SHEAR

6. CUPOLA

7. CASTING DEFECTS

8. ALLIGATORING

9. CARRIAGE (ABOUT LATHE)

10. PLANER (MACHINING)

FARUK SOYDAN

503091332