Productivity, and stress

Traffic congestion leads to vehicular pollution, loss of precious time (hampering productivity), and stress to citizens and thus has a serious negative effect on the penetration of automobiles. 

Fiedler, N., Laumbach, R., Kelly-McNeil, K., Lioy, P., Fan, Z.H., Zhang, J.F., Ottenweller, J., Oilman-Sttickland, P. and Kipen, H. (2005) Health effects of a mixture of indoor air volatile organics, their ozone oxidation products, and stress. Environmental Health Perspectives, 113 (11), 1542-8. 

A final operation is needed to obtain the target product by determining its formulation, so that its properties correspond to its intended uses. These products include plastics, synthetic fibers, fertilizers, solvents, elastomers, insecticides, detergents etc. Figure 1 illustrates the links existing between petroleum raw materials and mass-consumption finished products, and stresses the main processes employed. 

Increasing production and therefore inspection rates may increase the stress to the inspector and result in a decreasing reproducability and flaw detection rate. In addition by replacing the human inspector by a fully automatic image processing tremendeous cost savings are achieved. 

The observation that a system at equilibrium responds to a stress by reequilibrating in a manner that diminishes the stress, is formalized as Le Chatelier s principle. One of the most common stresses that we can apply to a reaction at equilibrium is to change the concentration of a reactant or product. We already have seen, in the case of sodium acetate and acetic acid, that adding a product to a reaction mixture at equilibrium converts a portion of the products to reactants. In this instance, we disturb the equilibrium by adding a product, and the stress is diminished by partially reacting the excess product. Adding acetic acid has the opposite effect, partially converting the excess acetic acid to acetate. 

At the same time, a decrease in orientation- and stress-birefringence for the modified BPA-PC could be achieved by optimizing the processing conditions (184,187,189,190,193) this lowers birefringence below 20 nm/mm (single path) for injection-printed injection molded CDs and substrate disks (Fig. 24) (191). The typical characteristics of a modified BPA-PC especially developed for CD production are Hsted in Table 6 (187,193). 

Stress corrosion cracking, prevalent where boiling occurs, concentrates corrosion products and impurity chemicals, namely in the deep tubesheet crevices on the hot side of the steam generator and under deposits above the tubesheet. The cracking growth rates increase rapidly at both high and low pH. Either of these environments can exist depending on the type of chemical species present. 

Decorative chromium plating, 0.2—0.5 ]lni deposit thickness, is widely used for automobile body parts, appHances, plumbing fixtures, and many other products. It is customarily appHed over a nonferrous base in the plating of steel plates. To obtain the necessary corrosion resistance, the nature of the undercoat and the porosity and stresses of the chromium are all carefliUy controlled. Thus microcracked, microporous, crack-free, or conventional chromium may be plated over duplex and triplex nickel undercoats. 

Operating experience (Wuestner et al., loc. cit.) has shown that roll diameters about 1 m are preferred, as a compromise between production rate and stress on the equipment. The press must be operated choke fed, with a substantial depth of feed in the hopper otherwise it will act like an ordinary roll crusher. 

A proposed product development process that facilitates designing capable and reliable products has been outlined above. It must be stressed that the product development process itself will not produce quality products, and consideration of many issues are crucial to success, such as company strategy, management structure, commitment, sufficient resources, communication, and most importantly proficient engineering practices, such as the following. 

Not all product components are subjected to a load in fact most are not subjected to loads requiring an engineering analysis via engineering equations, etc. Experience in the material behavior on similar products and/or similar performance requirements are all that is needed. In these products designers become involved in their processing features that will prevent or reduce internal stresses, with elements that will lead to consistent and economical production, with appearance and dimensional control, etc. 

Creep rupture. Creep-rupture data are obtained in the same way as creep data except that higher stresses are used and the time is measured to failure (Figs. 2-28 and 29). The strains are sometimes recorded, but this is not necessary for creep rupture. The results are generally plotted as the log stress versus log time to failure (110). In creep-rupture tests it is the material s behavior just prior to the rupture that is of primary interest. In these tests a number of samples are subjected to different levels of constant stress, with the time to failure being determined for each stress level. General technical literature and product data sheets seldom provide a complete description of a material s behavior prior to rupture. It should include the development of any crazing and stress whitening, its strain-time... 

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Stress analysis involves using the descriptions of the product s geometry, the applied loads and displacements, and the material s properties to obtain closed-form or numerical expressions for internal stresses as a function of the stress s position within the product and perhaps as a function of time as well. Tlie term engineering formulas refers primarily to those equations reviewed previously and given in engineering handbooks by which the stress analysis can be accomplished. 

A common use is with a plastic hub or boss accepting either a plastic or metal insert. The press fit operation tends to expand the hub creating a tensile or hoop stress. If the interference is too great, a very high strain and stress will develop. The plastic product will (1) fail immediately by developing a crack parallel to the axis of the hub to relieve the stress, a typical hoop stress failure, (2) survive assembly but fail prematurely when the product is in use for a variety of... 

The process of design for static loads involves a great deal more than the mechanical operation of the stress-strain data to determine the performance of a section. The results obtained from the stress analysis are used to determine the functionality of the product and then, combined with the other factors involved to decide on a suitable design. 

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