Evrim Berk 030060161 6th Week - Part #2

3-) Film Deposition

Previous One

Thin-film deposition is about phase transition from the vapor phase to solid phase. Atoms condense on a substrate. These adsorbed atoms are subject to desorption and surface diffusion. Some adsorbed atoms bond to each other, reducing the desorption probability. More atoms aggregate and some of the bigger clusters avoid desorption. (Franssila, S., Introduction to Microfabrication, p. 78)

New One

Films are typically the most desirable medium for use in semiconducting devices. The hybrid perovskites are often soluble in common polar solvents and both components generally volatilize at relatively low tepmperatures. In addition, the range of interactions both within and between the organic and inorganic components structure typically strongly favors the formation of the hybrid perovskite crystals or thin films using a number of simple processes, including vacuum thermal evaporation, solution-based techniques such as spin-coating and stamping, and even melt processing. Each of these options provide advantages for selected applications, thereby enabling convenient deposition on a range of substrates, including those envisioned for flexible plastic displays and low-cost electronic devices.

(Gomez-Romero P. Sanchez C., Functional Hybrid Materials, p. 362)

4-) Photochemical Machining

Previous One

The specific steps that are involved when photochemical machining (PCM) is performed with the use of photoresists. These are as follows: 1. Clean the workpiece. 2. Coat the workpiece with a photoresist, usually by hot-roller lamination of dry-film photoresists, on both sides, although liquid photoresists may also be applied by dipping, flowing. rolling, or electrophoresis (i.e., migration of charged molecules in the presence of an electric field). For liquid photoresists, the coating is heated in an oven to remove solvents. 3. Prepare the artwork. A drawing of the workpiece is made on a computer-aided design (CAD) system. 4. Develop the phototool. The CAD file is used to derive a photographic negative workpiece. Several methods may be used. Typically, the CAD drawing is downloaded to a laser-imaging system that exposes the desired Image directly onto photograph (e.g., silver halide) film. In the past, oversized artwork was used to Increase the curacy of the phototool through photographic reduction of the artwork. 5. Expose the photoresist. Bring the phototool in contact with the workpiece, a vacuum frame to ensure good contact, and expose the workpiece to Intense violet (UV) light 6. Develop the photoresist. Exposure of the photoresist to intense UV light alters the chemistry of the photoresist, making it more resistant to dissolution in certain solvents. By placing the exposed maskant in the proper solvent, the unexposed areas of the resist are removed, exposing the underlying material for etching. All residue is rinsed away 7. Spray the workpiece with (or immerse it in) the reagent 8. Remove the remaining maskant. PCM has been widely used for the production of small, complex parts, such as printed circuit boards, and very thin parts that are too small or too thin to be blanked or milled by ordinary sheet metal forming or machining operations, respectively Refinements to the PCM process are used in the microeletronics fabrication.

(MATERIALS AND PROCESSES IN MANUFACTURING 10th edition, J. Temple Black, Ernest Paul DeGarmo, Ronald A. Kohser, p.489)

New One

Photochemical machining, as also known chemical blanking, involves producing parts by chemical action. It is accomplished by placing an exact image of the part to be produced on a sheet of metal and immersing them both in a chemical. The chemical action dissolves all of the metal except the desired part. Most photochemically machined parts are thin and flat.

Photochemical machining has a number of applications where in it provides unique advantages. Some of these include: working on extremely thin materials when handling difficulties and die accuracies preclude the use of normal mechanical methods; working on hardened or brittle materials when mechanical action would cause breakage or stress concentration points. Production of extremely complex parts for which die costs would be prohibitive. And producing short-run parts for which the relatively low setup costs and short time from print to production offer advantages. This is especially important in research and development projects and in model shops.

(Goetsch L.D., Technical Drawing, p. 774)

5-) Proximity Sensors

Previous One

Proximity sensing using optical or acoustic techniques is useful when a robot tool is brought into contact with a workpiece. Since the robot is designed to be very stiff and the workpiece is usually quite rigid, the contact force between them builds very rapidly when the robot contacts the workpiece with finite velocity. Even if force sensing is used, the contact force may build to damaging levels before the system can respond. Proximity sensors are short-range, noncontact sensors which allow fine control of tool velocity shortly before contact to avoid severe impacts. Optical systems based on triangulation or simply the intensity of light reflected off the workpiece have been tested. Ultrasonic rangefinders using a sonar-type principle offer an alternative technology.

(Standard Handbook of Machine Design, Robots and Smart Machines, Kenneth J. Waldron, Ph.D.,p47.20)

New One

Proximity Sensing is the technique of detecting the presence or absence of an object with an electronic noncontact sensor.

Mechanical limit swtiches were the first devices to detect objects in industrial applications. A mechanical arm touching the target object moves a plunger or rotates a shaft which causes an electrical contact to close or open. Subsequent signals will produce other control functions through the connecting system. The stich may be activating a simple control relay or a sophisticated programmable logic control device, or a direct interface to a computer network. This simple activity, once done successfully, will enable variaties of manufacturing operations to direct a combination of production plans according to the computer-integrated-manufacturing strategy.

Inductive proximity sensors are used in place of limit switches for noncontact sensing of metallic objects. Capacitive proximity switches are used on the same basis as inductive proximity sensors; however capacitive sensors can also detect non-metallic objects. Both inductive and capacitive sensors are limit switches with ranges up to 100 mm.

The distinct advantage of photoelectric sensors over inductive or capacitive sensors is their increased range. However dirt, oil mist, and other environmental factors will hinder operation of photoelectric sensors during the vital operation of reporting the status of a manufacturing process. This may lead to significant waste and buildup of false data.

(Soloman S., Sensors Handbook, p1.21)

Week 6 Missed Terms Gani Can Öz

Semi-crystalline Polymers

Long polymer chains consisting of identical monomeric units are, in principle, capable of being organized into crystalline arrays. Usually the chains are parallel bundles and the unit cell is based in some elementary way on the monomeric repeat unit. However, because of their great chain lengths it is kinetically difficult for polymers to form large crystals or to crystallize completely. In the case of quiescent crystallization from the melt the common morphology involves very thin lamellar crystals in which the crystallizing chains fold back and forth across the growth face. A given chain may be incorporated into several lamellae where the latter are organized in ribbon-like sheaves. It is inevitable that a considerable fraction of chain units will be constrained from being laid down on the growth faces. An appreciable fraction of uncrystallized material results. The local organization is that of stacked lamellae separated by amorphous layers. Thus crystallizable polymers are typically semi-crystalline two-phase systems. The degree of crystallinity, i.e., the volume of the crystal phase relative to the specimen volume can vary according to the crystallization conditions. Slow cooling versus rapid quenching, annealing etc. are typical variables. Higher degrees of crystallinity tend to be accommodated by thicker crystal lamellae with a relatively minor role for the amorphous interlayer thickness.

(Polymer Dynamics and Relaxation, By Richard Boyd University of Utah, By Grant Smith University of Utah)

Kelvin Model

The classical Kelvin-Voigt viscoelastic solid (see Kelvin [6], Voigt [8]) can be viewed as a mixture

of a linearized elastic solid and a linearly viscous °uid that co-exist. The one-dimensional model

is represented as a linear spring in parallel with a linearly viscous dashpot. A generalization of the

mechanical analog is to consider a non-linear spring in parallel with a non-linearly viscous dashpot.

Such a one-dimensional model can be appropriately generalized to obtain a three dimensional

model.

(On Kelvin-Voigt model and its generalizations, M. Bulicek, J. Malek, K. R. Rajagopal)

Kayra Ermutlu-030060081 (6th Week)

Double-action Drawing

The blankholding requirements for large panels, which comprimise the majority of exterior body panels, necessitates the use of double-action drawing to achieve proper control of metal movement. Many smaller, irregular shaped parts that present difficult problems in metal control are drawn by this method. In double-action drawing, punch is mounted on the inner slide of the press and the blankholder is mounted on anouter slide. The part is usually drawn open side up.

(Lascoe O.D., Handbook of Fabrication Processes, pg.193, Kayra Ermutlu)

Tooling for Drop-Hammers

Sheet metal is readily formed by the stamping action of heavy drop hammers. Most drop-hammer tooling today is cast metal (usually Kirksite or steel). Cast epoxy ceramic drop-hammers however, have shown that they can successfully form aluminum, titanium and steel with little or no tool wear. The tool-contruction cost for the epoxy-ceramic hammer die, exclusive of materials, is about onefourth that Kirksite. Data on tool life and repair costs for this tooling is currently incomplete.

(Lascoe O.D., Handbook of Fabrication Processes, pg.315, Kayra Ermutlu)

Evrim Berk 030060161 6th Week

Expert Systems: Designers and production engineers must be capable of assessing the impact of design modifications on process selection and on assembly, inspection, tools and dies, and product cost. Establishing quantative relationships is essential in order to optimize the design for ease of manufacturing and assembly at minimum product cost. Expert Systems, which have optimization capabilities and thus can expedite the traditional iterative process in design optimization, are powerful tools in such analysis. These systems are basically complex computer programs, they have the capacity to perform various tasks and solve difficult real life problems much as human experts would.

(Manufacturing Engineering and Technology 5th Edition, Kalpakjian S, Schmid S.R., Pages:15,35)

Process Selection Charts: This charts help you to find the processes which can forma a given material to a given shape, size and precision. Progress can be made by using the hard copy charts. Greater resolution is possible with computer aided process selection software. The axes of a process selection chartare mesaures of two of the attributes. These are roughness & tolerance, melting temperature & hardness, slenderness & volume and size & complexity level charts

(Materials Selection in Mechanical Design, 2nd Edition, Ashby M.F., Pages: 264 - 270)

Design For Recycling: Design for Recylcing is a list of principles to save and reuse raw materials in order to move towards more sustainable development, the following possibilities can be considered;

• reducing material use through better utilisation and by reducing waste during production

• substituting materials for those becoming rare and expensive

• recycling materials by reusing or reprocessing production waste, products and parts of products.

In what follows, possible types of recycling and recycling processes are explained based on VDI Guideline 2243. Production waste recycling involves reusing production waste in a new production process, for example offcuts (after they have been preprocessed).

Product recycling involves reusing a product or part of it, for example reusing a vehicle’s engine (after it has been reconditioned).

Used material recycling is the reuse of old products and materials in a new production process, for example the reprocessing of materials from scrapped vehicles (after they have been preprocessed). These secondary materials or parts do not necessarily have a lower quality than new materials or parts, in which case they can be reused. When the quality is significantly reduced, they can only be used for other purposes.

Preprocessing and reconditioning make significant contributions to effective recycling.

(Engineering Design - A Sytematic Approach, 3rd Edition, Pahl G., Weitz B., Felhuldsen J, 2007, Pages: 388 - 389)

EWMA Charting: An exponentially weighted moving average chart is a control chart for variables data. ıt plots weighted moving -average values. A weighting factor is chosen by the user to determine the relative impact of older data to more recent data on the calculated moving average value. Because the EMWA chart uses information from all samples, it detects much smaller process shifts than a normal control chart.

(Six Sigma Demystified, Keller P, Page: 247)

ÖMER TAYLAN BOYA 030070099 6TH WEEK

Hole Drilling Method ( 13:12 18.03.2011)

The hole drilling method is a mechanical method for measuring residual stresses and it is standardized in the ASTM E837. The basic hole drilling procedure involves drilling of a small hole diameter d0 into the surface of a stressed material. The stress equilibrium is locally disturbed due to this intervention whereby a new aquilibrium is reached. This change is measured usually radial to the hole with special stain-gage rosets in the form of relieved strains.

(Enrique Garcia Sobolevski, Residual stress analysis of components with real geometries using the incremental hole-drilling technique and a differential evaluation method, page 18)

Ring Core method (time 13:21 18.03.2011)

The ring core method is also based on the strain caused by disturbing the stress field, but in this case a relatively stress-free island of material is isolated by making a shallow ring around a strain-gage. This method is one of the least destructive mechanical stress-relief techniques and are relatively simple and economical.

(George E. Tottem, Handbook of residual stress and deformation of steel, page 110)

ESPI Electronic Speckle Pattern Interferometry (14:36 18.03.2011)

An extended laser beam is used to provide coherent illumination of a test sample which is viewed with a CCD camera or other electronic image sensor. Coherent light scattered from an optically rough test surface impresser a laser speckle pattern on the image of the test object, and the spatial characteristics of the speckle pattern are determined primarily by the finite resolution of the imaging lens. The interferometer optics, might be one of many configurations depending on the measurement objectives. The basic function of interferometer is to deliver two dinstint coherent wavefronts to the imaging system.

(Donald O. Thompson,Dale E. Chimenti, Review of progress in quantitative nondestructive evaluation, page 373)

Contour Method (15:02 18.03.2011)

In the approach of Contour method, the analysed specimen is carefully cut in two along a plane using a wire EDM machine. Residual stresses relax as free surface is created by the cut. After cutting , the contours of the two opposing surfaces created by the cut are measured using a CMM machine or by laser scanning. Assuming that the contours are caused by elastic relaxation of the residual stresses, a straightforward finite element calculation, in which the opposite averaged contour is applied as boundary conditions to the FE model, permits to reveal the original residual stresses component (sigma x) normal to the cut surface.

(E. E. Gdoutos, Experimental Analysis of Nano and Engineering Materials and Structures, page 635)

Burcu Atay, 140060029, 6th week

Amorphous Polymers
Amorphous polymers are generally useful only if ther Tg is above ambient temperature; otherwise they creep in service. This means that strains imposed during thermoforming need not be plastic since quenching from the forming temperature, which is above Tg, can freeze the viscoelastic deformation. so amorphous thermoplastics are thermoformed just above Tg and cooled in the die to 'fix' the shape. this enables relatively low temperatures and low cycle times to be used.
(Edwards, L., Endean M., MAterials in Action Series: Manufacturing With Materials,1995,pg.194)

Neutron Diffraction
Neutron Diffraction (ND) is capable of measuring the elastic strains induced by residual stresses throughout the colume of relatively thick stess components with a spatial resolution as small as 1 mm^3. Such capabilities provide for residuals-tress measurement inside components without sectioning or layer removal. Principal ND methos, as with XRD methods, measure the spacing between crystallographic planes in a component, and this spacing is affected by residual and applied stress. The spacing between a selected set of a crystallographic planes is related to the angle of incidence and diffraction of where teh neutron radiation, which are equal, and the wavelength of the monochromaric radiation by Bragg's Law:

λ= 2 d sin θ

The elastic strain induced bt the residual stress perpendicular to teh diffracting crystallographic plane then is related to d by:

ε= (d-d0)/do= sinθ0(sinθ-sinθ0)

(Totten, G., Howes, M., Inoue, T., Handbook of Resifual Stress and Deformation, 1st Printing, March 2002, pg.113)

Springback

The stress state is extremely complex in bending. The complete tensile and compressive stress-strain curves of the material are traversed on rthe tensile and compressive sides of the bend, respectively. This means that around the neutral plane the stresses must be elastic. When the forming tool is retracted, the elastic components, of the stress cause springback, and a residual stress pattern. Springback increases both the angle and radius of the bent part. The elastic zone is more extensive for a relatively gentle bend(large R_b/h ratio) and for a material with high ratio of yield strength σ_0.2 to elastic modulus E; therefore springback also increases according to the approximate formula

Rb/Rf=1-3(Rb*σ_0.2)/(h*E)+4((Rb*σ_0.2)/(h*E))^3

where Rb is the radius of the bending die and Rf is the radius obtained after the forming spressure is released.

Springback established a new force equilibrium with a residual stress distribution typified by a compressive stress on the outer and tensile stress on the inner surface

Several techniques are used to combat springback:

1. If springback for a given material is known and if the material is of uniform quality and thickness, compensation for springback is possible for overbending.

2. Alternatively, the elastic zone can be eliminated at the end of the stroke by one of two means. First, the two ends of the sheet may be clamped before the punch bottoms out, so that the end of the stroke involves stretching of the part, causing tensile yielding in the entire sheet thickness. In the second method the punch nose is shaped to indent the sheet, so that plastic compression takes place throughout the thickness

3. If a counterpunch is used with a controlled pressure, compressive stress are maintained in the bend zone during the entire process. Since this also has the effect of imposing a hydrostatic pressure on the bend zone, bending beyond the limits given by

Rb=h(1/2q-1) for q<0.2

Rb=h((1-q)^2)/(2q-q^2) for q>0.2

4. Less ductile materials may have to be bent at some elevated temperature; because the yield strength is lower, springback is also less.

(Schey, J.A., Introduction to Manufacturing Process, 2nd Edition,pg.299,300,301)

ISO 14000

ISO 14000 is a family of standards first published in September of 1996 and pertaining to international Environmental Management Systems (EMS). It concerns the way an organization's activities affect the environment throughout the life of its products. These activities (a) may be internal or external to the organization (b) range from production to ultimate disposal of the product after its useful life, and (c) include effects on the environment, such as pollution , waste generation and disposal, noise, depletion of natural resources, and energy use.

A rapidly increasing number of companies in many countries ( with Japan leading) have been obtaining certification for this standard. The ISO 14000 family of standards has several sections: Guidelines for Environmental Auditing, Environmental Assessment, Environmental Labels and Declarations, and Environmental Management.

(Kalpakjian S., Schmid S.R.,Manufacturing Engineering and Technology, 5th Edition, pg.1119)

Ozlem Salman (6th week)

1 XRD X ray diffraction
2Neutron diffraction
3 ESPI Electronic speckle pattern interferometry
4Layer removal method
5Contour method
6Hole drilling method
7Ring core method
8Slotting method
9Tube splitting method
10Sectioning method

Clue: Residual strees measuring methods

Gani Can Öz (6th Week)

1 Amorphous Polymers
2 Semi-crystalline Poymers
3 Crystalline Polymers
4 Cross-linked Polymers
5 Glass Transition Temperature
6 Viscoelastic Behaviour
7 Maxwell Model
8 Kelvin Model
9 Burger Model
10 Plasticizer

Gani Can Öz

503101305

A. Selim PARLAKYİĞİT - 6th Week

1. Spaghetti Diagram
2. EWMA Charting
3. Ultrasonic Sensors
4. Fault Tree Analysis
5. Sand Blasting
6. Electrostatic Coating
7. Laser Beam Welding
8. Lancing
9. Buckling
10.Hardcoating