Product Design and Concurrent Engineering 8. Design for Selection of Manufacturing Processes Manufacturing Properties of Materials are especially those properties, which are important in manufacturing processes. Classification of Engineering Materials. A. Metals and Alloys: Inorganic. Manufacturing Processes for Engineering Materials, 5th Edition. Serope Kalpakjian, Illinois Institute of Technology. Steven Schmid, Illinois Institute of.
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Author: Serope Kalpakjian Pages: Publication Date Release Date: ISBN: Product Group:Book Ebook download any. Manufacturing Processes for Engineering Materials, 5th ed Method Strength Design Variability Small Parts Large Parts Tolerances Relibility Ease of. manufacturing processes for engineering materials - Download as PDF File .pdf) , Text File .txt) or read online. contents.
Materials Metals And Alloys Iron-base alloys, particularly the carbon and low-alloy steels, are among the most widely used structural materials in industry.
Structure change can be achieved easily in iron-carbon alloys using straightforward thermal treatments that rely on the change in solubility for carbon and alloying elements that accompany iron's allotropic transformations.
As expected, mechanical properties vary with the structure. Furnace-cooled i. Volume change accompanying the austenite-martensite transformation can lead to high residual stresses and substantial distortion, along with a risk of part cracking, due to differential cooling in parts with large changes in cross section.
Hence, hardened parts are usually tempered to relieve the stresses and to stabilize the part dimensions. Structure-change processes in nonferrous i. These materials depend on change in solubility of alloying elements with temperature. However, in the absence of allotropic transformation in the base material, changes in mechanical properties depend on solution treatment followed by precipitation aging. The final structure and properties in these dispersion-hardened materials depend on the times and temperatures used for the precipitation treatment.
The upper temperature limit for the use of these alloys is determined by the propensity of the precipitates to coalesce and coarsen. Such a microstructure retains its strength even at relatively high temperatures, hence the name ''superalloy. However, the thermal treatment practice is handicapped by the low thermal diffusivity inherent to ceramics.
Also, slow heating and cooling rates are used to minimize risk of cracking by thermal stresses. This problem is aggravated by the higher thermal treatment temperatures necessary for structure change in ceramics.
Structure change in nominally amorphous ceramic materials uses thermal and thermomechanical treatments comparable to those for metals and alloys Weidmann et al. Glass-ceramic oven tops, for example, are mechanically processed and thermally treated to create a final microstructure with a very low thermal coefficient of expansion.
Exceptional thermal shock resistance is obtained through control of microstructure. Ceramics pose problems in structure change because of the directionality of their molecular bonding, high inherent hardness, slow achievement of 1 Page 69 Share Cite Suggested Citation:"5 Structure-Change Processes. Despite these limitations, thermally treatable, tough ceramics such as partially stabilized zirconia have been developed and are finding increasing use as structural ceramics. Polymers Nominally amorphous polymeric materials are normally processed by melt-to-solid transformations.
However, extraordinary strength gains can be obtained in some polymers e. Precise strain, strain rates, and thermal treatments are necessary. Structure-change processing to obtain high strengths in common polymers is not widely used.
Injection-molded tubular polyethylene terephthalate preforms are stretched and blow molded when the material is elastomeric. Processing conditions are selected and used to prevent any structure change between injection molding and heating for blow molding.
Process temperature and time are adjusted to suppress spherulite formation and to promote partial crystallization.
Final strengths obtained in the part e. Surface Treatment Many coating processes have been developed to deposit microthin films that allow close control of coating thickness and composition not possible with traditional surface treatment processes e.
These processes also allow well-bonded thin films to be deposited at relatively low temperatures. Examples of these thin-film deposition technologies currently in commercial use include halide metallurgy i. In CVD processes, halide compounds such as TiCl4 with hydrogen are used to deposit thin films on hot substrates.
Process streams and operating conditions are chosen to obtain viable coating rates and to maximize deposition efficiency. Specially developed CVD phase diagrams and computation packages are used.
Kinetic variables such as the total flow rate, coating system geometry, substrate chemistry, and surface finish play a role in determining the nature and quality of films deposited Bhat, High temperatures used in CVD make post-coat thermal treatments necessary.
Coating internal stresses and thermal stress-induced cracking of the deposited films are common. CVD for hard coating of steel products is therefore not common.
Light alloy parts are not coated with CVD processes. Since hard coating of ferrous components and most mechanical parts requires lower deposition temperatures, PVD processes are used. To date, a variety of film-deposition techniques have been developed to produce the needed coatings: activated reactive evaporation Bunshah and Raghuram, ; ion plating; direct current, radio frequency and magnetron sputtering Bunshah, ; hollow cathode discharge Komiya and Tsuruika, ; and are coating Ramalingam et al.
The structure, properties, and adhesion of the films deposited with PVD processes depend on coating-source characteristics, the substrate temperature, bias applied, and the ambient pressure Thornton, By admitting reactive gases during film deposition, coatings of compounds are obtained.
Control of compound stoichiometry requires coupling of the gas admission rate with the coating-flux generation rate. All the thin-film deposition technologies mentioned above, as well as the more recently developed microwave-assisted plasma deposition processes, are in commercial use to support integrated circuit fabrication.
In these applications, deposition occurs on very flat surfaces in relatively thin films less than 1 millimeter in thickness. Laser Processing Lasers can be used to alter the microstructure and properties of metals, polymers, ceramics, and glasses.
Lasers can change the surface properties of finished parts without affecting the parts' inherent bulk properties. This capability can be used to clad material onto a worn surface, thereby greatly extending a part's useful life, or to repair high-value components without causing extraneous damage.
Although lasers do not require any special processing environment, such as a vacuum, environmental control can be utilized when the material being processed requires it.
Through rapid heating by the laser beam and subsequent quenching, the microstructure of a layer of material near the surface can be modified without affecting the bulk of the workpiece. Laser heat treatment of alloy steels can significantly increase their strength, toughness, sliding wear resistance, and abrasive wear resistance.
The microstructure formed near the surface is essentially dislocated packets of martensite surrounded by retained austenitic films. Laser heat treatment can also be used to relieve residual stresses caused by mechanical processes through annealing.
One example is selective stress relieving of glass components using a carbondioxide laser. Laser heat treatment is currently limited to specialized operations, mainly due to its low processing speeds for continuous production. However, as the energy densities of new lasers increase, laser heat treatment may become economically viable for the large-scale continuous processing of metals, since much higher scan rates and beam velocities could be attained.
Another development may be the use of an array of diode lasers as a direct heat source. This approach has a number of advantages. First, the diode array would allow area coverage of the workpiece, resulting in a uniform heat treatment.
Second, the diode array is stationary, providing better reliability than a moving laser head. Finally, diode arrays can be placed next to both the top and bottom surfaces of the workpiece, allowing simultaneous heat treatment of both sides Warner and Sheng, Lasers can be used for surface modification processes i.
This melting and solidification is often accompanied by the introduction of powder elements or a predeposited layer of new material to combine with the base material. These processes are influenced by factors such as the laser power and power density, size and shape of the beam profile, scan velocity, and chemistry and metallurgy of the substrate.
Laser melting involves rapid heating and phase change of a small surface layer of a substrate through beam impingement and subsequent rapid quenching. The melting and solidification rates are so rapid that most elements go into solution with little opportunity to precipitate back to the grain boundaries. By controlling parameters e. Laser surface alloying is a process in which the surface of an alloy is melted to a desired depth using a continuous-wave or pulsed laser beam with the simultaneous addition of powdered alloying elements.
The combination of convection and diffusion redistributes the alloying elements uniformly throughout the molten pool. Skip to main content. Log In Sign Up. Tribhuvan Sharma. Manufacturing Processes for Engineering Materials, 5th ed.
Note the formation of a flash at the joint, which can later be trimmed off. About one-half of all large-scale industrial welding operations use this process.
Unfused flux is recovered and reused. This operation is similar to gas metal arc welding. Deep and narrow welds are made by this process at high welding speeds. American Welding Society, Welding Handbook, 8th ed. IIT Research Institute.
ISBN No. The weld line is at the center of the photograph. Courtesy of Allegheny Ludlum Corp. Incomplete fusion from oxide Incomplete fusion in a or dross at the center of a joint, groove weld Incomplete fusion in fillet welds.
Courtesy of Packer Engineering.
Warping can be reduced Angular distortion Longitudinal or eliminated by proper weld shrinkage design and fixturing prior to a b c d welding. Courtesy of the American Welding Society.
Weld a b Manufacturing Processes for Engineering Materials, 5th ed. After J. See also Fig. Raised nugget b 2. Hole left in part Button diameter indicates quality 3. Force is brought into contact under an axial force. The upset length is the distance the two pieces move inward during Force 4. If necessary, the flash gth Upset len can be removed by secondary operations, such Time as machining or grinding.
Aluminum-alloy plates up to 75 mm 3 in. Pressure 2. Current 3.