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Solidification Process (Newer) (Manufacturing) (better)

Casting is a solidification process where the molten material is poured into a mold and then allowed to freeze into the desired final shape. Many of the structural features  that ultimately control product properties are set during solidification. Furthermore, many casting defects, such as gas porosity and solidification shrinkage, are also solidification phenomena and they can be reduced or eliminated by controlling the soldification process.

Solidification is a 2 stages, nucleation and growth process and ıt's important to control both of these stages. Nucleation occurs when stable particles of solid form from within the molten liquid. When a material is at temperature below its melting point, the solid state has a lower energy than the liquid. As solidification occurs internal energy is released. At the same time, however, interface surfaces must be created between the new solid and the parent liquid. Formation of these surfaces requires energy. In order for nucleation to occur, there must be a net reduction or release of energy. As a result, nucleation generally begins at a temperature somewhat below the equlibrium melting point. The difference between the melting point and the actual temperature of nucleation is known as the amount of undercooling.  (J.T. Black, R. Kohser, DeGarmo's Materials and Process in Manufacturing, pg.271)

Solidification processes (older) (better)

 With reference to figure 10.1, the solidification processes can be classified according to the engineering material that is processed: 1- metals, 2- ceramics, specifically glasses, and 3- polymers and polymer matrix composites (PMCs). (Fundamentals of modern manufacturing: materials, processes, systems - Mikell P. Groover - page 205 )  ------------------------------------------------------------------------------------------------------------

Material removal processes:(older)

The material removal processes are a family of shaping operations in which excess material is removed from starting workpart so that what remains is the desired final geometry. The family tree is shown in figure 21.1. The most important branch of the family is conventional machining, in which a sharp cutting tool is used to mechanically cut the material to achieve the desired geometry. The tree principal machinig processes are turning, drilling and milling. The other machining operations in figure 21.1 include shaping, planing, broaching and sawing. ( Fundamentals of modern manufacturing: materials, precesses and systems - Mikell P. Groover - page 483 )

Material Removal Process (Newer) (Manufacture) (better)

Material removal process are very common in modern manufacturing. Most of the common material removal processes are conducted where the amount and location of the material to be removed is known beforehand. An example of this is CNC machining. The stock size, the orientation and the position of the stock and the part and the CAD  model of the part are all known and therefore a fixture can be used to maintain the correct position. In this case, path planning can be made in advance and simulations can be done to check the final result. If the simulation result is accepted, corresponding machining codes will be generated and sent to the machine and the part can be created automatically and precisely.

However, there are a number of material removal processes whereby not all the information given above is known. An example is the post shakeout material removal operations for metalcastings. The locations, size and shape of the excess material to be removed are different for each casting even though they're made from the same pattern. In this type removal process, a normal automatic system is often not feasible and the material removal is done via tedious manual processes such as hand grinding. Manual operations can take advantage of an intelligent operator with experience and be very flexible. However, humans can also be incosistent and less efficent. In addition, there are significant ergonomic issues associated with having a human operator remove large amounts of metal via hand grinding. (Danni Wang, A General Material Removal Strategy Based on Surface Sampling and reconstruction on unknown object, pg.1)

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Electro jet drilling(older)

 Electro jet drilling process is gaining prominence in the machining of micro and macro holes in difficult to machine materials used in space, aviation, electronics and computers, medical, and automobile industries. As the trend towards miniaturization continues, this process is gaining increasing importance as it has shown its superiority over other contemporary non-conventional micro and macro hole drilling processes.( Advance design and manufacturing in global competition-C. Deng- page 435)

Electro Jet Drilling (Advanced Machining) (Newer)

Electro jet drilling (EJD) is one such non-conventional process. Which possesses all the requisite capabilities in the meeting the modern day demands of drilling small and micro holes.

EJD is a non-conventional machining process in which a negatively charged stream of acid electrolyte is impinged on the workpiece to form a hole. The acid electrolyte (10-25% concentration) is passed under pressure ( 0.3-1.0 N/mm^2) through a finely drawn glass tube nozzle. The electrolyte jrt gets charged when a platinium wire, inserted into the glass tube is connected to the negative terminal of DC power supply. The workpiece acts as anode. (M. Sen, Optimization of Machining Conditions in Electro Jet Drilling UUsing Genetic Algorithm )

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Wöhler Curve (older)

To generate data useful for fatigue designs using the stress-life approach stress-loife fatiqu tests are usally carried out on several specimens at different fell reversed stress amplitudes ovar a range of fatigue lives for identically prepared specimens. The fatigue test data are often plotted on either semilog or log-log coordinates. The single curve that represents the data is called the S-N curve or Wöhler curve. When plotted on log-log scales, the curve becomes linear. The portion of the curve or the line with a negative slope is called the finite life region , and horizontal line is the infinite life region.

When generation log-log graphs of applied stress versus fatigue life from S-N fatigue tests , the y-coordinate is expressed in terms of the stress amplitude or the stress range , and the x-coordinate is expressed in terms of the number of reversals to failure or the number of cycles to failure.(Fatigue testing and analysis: theory and practice ; Yung-Li Lee , pg , 105 ; 2005)
Wohler Curve (better) (newer)(dynamic material stregth)
Data from reversed bending experiments are plotted as the fatigue strength versus the logarithm of the total number of cycles to failure T(t)' each specimen. These plots are colled S-N diagrams or Wöhler Curve after August Wohler, a German Engineer who published his fatigue research in 1870. They're a standard method of presenting fatigue data and are extremely common and informative. Two general patterns for 2 classes of material, thoe with and those without endurance limits, emerge when plotting the fatigue stregth versus the logarith of the number of cycles to failure.
For some materials with endurance limits, such as ferrous (iron based) and titanium alloys, a horizontal straight line occurs at low stress levels, implying that an endurance limit S(e)' is reached below which failure won't occur. This endurance S(e)' represents the largest fluctuating stress that won't cause failure for an infinite number of cycles. For many steels the endurance limit ranges between 35 and 60% of the material's ultimate strength. (B. Hamrock, S. Schmid, Fundamentals of Machine Elements, pg.265)   

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Laminar flow (older)

Laminar flow may occur in many situations.,ıts distinguishing features, however, are always the same: individual particles of fluid follow paths that do not cross those of neighbouring particles. There is nevertheless a velocity gradient across the flow, and so laminar flow, and so laminar flow is not normally found except in the neighbourhood of a solid boundary, the retarding effect of which causes the transverse velocity gradient.Laminar flow occurs at velocities low enough for forces due to viscosity to predominate over inertia forces, and thus, if any individual particle attempts to stray from its prescribed path, viscosity firmly restrains it, and the orderly procession of particles continues.(Bernard Stanford Massey,John Ward-Smith,Mechanics of fluids, 1. cilt,p.204)
Laminar Flow (Fluid mechanics) (Newer)
A viscous flow can be clasified as either a laminar flow or a turbulent flow . In a laminar flow the fluid flows with no significant mixing of neighboring fluid particles. If dye were injected into the flow, it wouldn't mix with the neighboring fluid except by molecular activity; it wouldn't retain its density for a relatively long period of time. Viscous shear stresses always influence a laminar flow. The flow may be highly time dependent, due to the erratic motion of a piston (M.C. Potter, H. Ramadan Menchanics of Fluids, pg.102)