Erdem Özdemir - 030070307 - 7th Week Definitions

Abrasive Jet Machining

Manufacturing

A high-speed stream of abrasive particles earned by a high pressure gas or air is impinged on the surface of workpieee. I he metal is removed due to erosion caused by the impact of high-speed abrasive particles as a jet. The yas stream flows through a no/zle at pressures upto 0.7 MPa and a velocity of 300 ms. The chipping action produced is very effective on hard and brittle mntcrials.
examples: glass, silicon, tungsten, ceramics, etc


(Fundamentals Of Machining And Machine Tools, 2008, Singal R.K. Et.Al, R. K. Singal, Mridual Singal, P 160)

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High-speed (HS) Machining 

Manufacturing
New- Better Definition

High-speed (HS) machining involves cutting metal at speeds 5 to 10 times higher than conventional machining However, the rotational speed of the cutting tool and the rate at which the tool is forced against the workpiece ultimately depend upon the type of material being worked. The rotational speed of spindles that hold the cutting tools on HS machining centers typically exceed 20,000 rpm. and some companies report it approaches 40.000 rpm.
The benefits of HS machining are increased rates of removal of material from the workpiece; reduced costs due to shorter production cycles; higher output in a gpven time and. therefore, increased productivity: lower investment costs as the result of reduced machine requirements; improved manufacturing flexibility as production times are improved and output raised; and accuracy in terms of dimension, shape, and surface due to the reduced cutting forces.






(Tools, Dies, and Industrial Molds, U.S. International Trade Commission, P 2-7)

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HSM means using cutting speeds that are significantly higher than those used in conventional machinig operation.


Other definitions of HSM have been developed to deal with the wide variety of work materials and tool materials used in machining. One popular HSM definition is by the DN ratio—the bearing bore diameter (mm) multiplied by the maximum spindle speed (rev/min). For high-speed machining, the typical DN ratio is between 500,000 and 1,000,000. This definition allows larger diameter bearings to fall within the HSM range, even though they operate at lower rotational speeds than smaller bearings. Typical HSM spindle velocities range between 8000 and 35,000 rpm, although some spindles today are designed to rotate at 100,000 rpm.


Another HSM definition is based on the ratio of horsepower to maximum spindle speed, or hp/rpm ratio. Conventional machine tools usually have a higher hp/rpm ra­tio than machines equipped for high-speed machining. By this metric, the dividing line between conventional machining and HSM is around 0.005 hp/rpm. Thus, high-speed ma­chining includes 50 hp spindles capable of 10,000 rpm (0.005 hp/rpm) and 15 hp spindles that can rotate at 30,000 rpm (0.0005 hp/rpm).


(Mikell P. Groover, Fundamentals of Modern Manufacturing, Materials, Processes and Systems ,page 536)

Corrosion (as a mechanical failure mode)

Mechanical Failure Mode

Corrosion can be defined in many ways. Some definitions are very narrow and deal with a specific form of corrosion, while others are quite broad and cover many forms of deterioration. The word corrode is de-rived from the Latin COrrodere, which means "to gnaw to pieces." The general definition oí corrode is to eat into or wear away gradually, as if by gnawing. Tor purposes here, corrosion can be defined as a chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its proper-lies.
The environment consists of the entire surrounding in contact with the material. The primary factors to describe the environment are the follow¬ing: (a) physical state—gas. liquid, or solid: (b) chemical composition— constituents and concentrations; and (c) temperature. Other factors can be important in specific cases. Examples of these factors are the relative velocity of a solution (because of flow or agitation) and mechanical loads on the material, including residual stress within the material. The emphasis in this chapter, as well as in other chapters in this book, is on aqueous corrosion, or corrosion in environments where water is pres¬ent. The deterioration of materials because of a reaction with hot gases, however, is included in the definition of corrosion given here.
To summarize, corrosion is the deterioration of a metal and is caused by the reaction of the melal with the environment. Reference to marine corrosion of a pier piling means lhat the steel piling corrodes because of its reaction with the marine environment. The environment is air-saturated seawater. The environment can be further described by speci¬fying the chemical analysis of the seawaler and the temperature and ve¬locity of the seawater at the piling surface. When corrosion is discussed, ii is importun! to think of a combination of a material and an environment. The corrosion behavior of a material cannot be described unless the environment in which the material is lo be exposed is identified. Similarly, the corrosivity or aggressiveness of an environment cannot be described unless the material that is to be ex-posed to that environment is identified. In summary, the corrosion be-havior of the material depends on the environment to which it is sub-jected, and the corrosivity of an environment depends on the material exposed to (hat environment.
It is useful to identify both natural combinations and unnatural combi-nations in corrosion. Examples of natural or desirable combinations of material and environment include nickel in caustic environments, lead in water, and aluminum in atmospheric exposures. In these environ-ments, the interaction between the metal and the environment does not usually result in detrimental or costly corrosion problems. The combi-nation is a natural combination lo provide good corrosion service.
Innatural combinations, on the other hand, are those thai result in se-vere corrosion damage to the metal because of exposure to an undesir-able environment. Examples of unnatural combinations include copper in ammonia solutions, stainless steel in chloride-containing environ-ments (e.g.. seawater), and lead with wine (acetic acid in wine attacks lead). It has been postulated that the downfall of the Roman Empire can be attributed in part to a corrosion problem, specifically the storage of wine in lead-lined vessels. Lead dissolved in die wine and consumed by the Roman hierarchy resulted in insanity (lead poisoning) and contrib-uted to the subsequent eventual downfall. Another anecdote regarding lead and alcoholic beverages dales back to the era of Benjamin Frank-lin. One manifestation was the "dry bellyache" with accompanying pa-ralysis, which was mentioned by Franklin in a letter to a friend. This malady was actually caused by the ingestion of lead from corroded lead coil condensers used in making brandy. The problem became so wide-spread that the Massachusetts legislature passed a law in the late 1700s that outlawed the use of lead in producing alcoholic beverages.

(Corrosion: understanding the basics, 563, Joseph R. Davis, P 3)

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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 )

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