Material selection influencing factors

The choice of a turboexpander load may be influenced by the desire to optimize refrigeration. In other words, a dynamometer load may be chosen over a generator load due to speed considerations. Additionally, there are other constraints imposed on optimal design. Factors such as impeller peripheral velocity (tip speed), bearing design, axial load balance, material selection, and manufacturing methods (which have greatly improved in the recent decades) all have an influence. 

Early workers viewed carriers or catalyst supports as inert substances that provided a means of spreading out an expensive material like platinum or else improved the mechanical strength of an inherently weak material. The primary factors in the early selection of catalyst supports were their physical properties and their cheapness hence pumice, ground brick, charcoal, coke, and similar substances were used. No attention was paid to the possible influence of the support on catalyst behavior differences in behavior were attributed to variations in the distribution of the catalyst itself. 

Separation depends on the selection of a process in which the behaviour of the material is influenced to a very marked degree by some physical property. Thus, if a material is to be separated into various size fractions, a sieving method may be used because this process depends primarily on the size of the particles, though other physical properties such as the shape of the particles and their tendency to agglomerate may also be involved. Other methods of separation depend on the differences in the behaviour of the particles in a moving fluid, and in this case the size and the density of the particles are the most important factors and shape is of secondary importance. Other processes make use of differences in electrical or magnetic properties of the materials or in their surface properties. 

In the last mentioned case, where a time factor may introduce bias, or in cases where inhomogeneities of the sampled material may influence the responses, block designs can be chosen. To eliminate several block effects one can select a latin square design. With regard to the arrangement of experiments we refer to appropriate text books, e.g. [BANDEMER et al., 1973 MORGAN, 1991]. There the reader may find special types of design which fit his requirements. 

The cathodic conversion of a functional group into another one is a very useful synthetic procedure, applicable to a great variety of functional groups. Also here the majority of syntheses performed prior to 1955 have been run under constant current conditions, thus making the composition of the SSE (especially with regard to pH) and the electrode material the decisive factors in the control of product selectivity. Excellent discussions of these factors and their influence can be found elsewhere 6>7>9 and need not be repeated here. 

Raw material selection for shortenings has been influenced by availability and economics. These factors were the main reasons for the development of lard substitutes, introduction of pure vegetable shortenings, major processing improvements, the development of additives to fortify specific performance characteristics, and most of the other changes. Table 1 give U.S. information on fats and oils used... 

Environmental consciousness. It is a modem material that emphasizes sustainability, its low energy demand during manufaeture and its carbon storage capacity and eventually it can be recycled. While aesthetic and economic considerations are major factors influencing material selection, these environmental advantages increasingly influence material selection. 

In pervaporatlon, reverse osmosis, ultrafiltration and to a lesser extent microfiltration, both steric and chemical factors Influence permeation and separation. Thus, proper membrane material selection la Important. While the physical structure of the membrane is in large part a function of membrane preparation procedures, the chemical nature and, to some degree, the physical properties of the membrane are dependent upon the chemical nature of the membrane material. Thus, membrane material selection based on the chemical nature of the polymer and the solution components to be separated is feasible. 

MATERIALS. Selection of a base polymer thermoplastic resin from which a molded substrate is produced is influenced by factors of price and performance. Secondary considerations include supplier preference. Given the uniqueness of each product application, standardization of generic polymers is unlikely. In fact, the selection possibilities are likely to grow with continued diversification of application requirements/specifications. 

In practice economic factors, in addition to physical properties, will influence the material selected and a compromise between ideal and locally available materials might be necessary. In this way a cover system can represent an effective treatment procedure at reasonable cost. 

The selection as to which process should apply to a particular material is influenced by a number of factors, which affect cost, production rate, flexibility, and part quality. Probably the two most important factors are (Chryssolouris 2006) 1. The lot size of the parts to be made. Small lot sizes require flexible processes, such as material removal processes, capable of accommodating different geometric features. Large lot sizes allow the use of primary forming or... 

There are many factors in design from which defects may result. One factor is selection of materials. For a particular product, cost, durability, function, maintenance, appearance, and strength influence material selection. 

The influence of coolant chemistry on radiation buildup can be expected to differ from plant to plant, due to plant specific parameters such as chemical composition and morphology of the surface oxide layers in the system, operating parameters (e. g. temperature), and the structural materials employed. In order to take into account these parameters in the selection of an optimum primary coolant chemistry, the empirical code Optimi was developed which uses a so-called Chemistry Influence Factor which is calculated from the differences in the concentrations of dissolved iron in the coolant at the primary system hot-leg and cold-leg side (Marchl and Greger, 1989). By comparing the results of the calculated chemis-... 

Materials selection depends on a wide variety and range of factors, including cost, technical suitability, safety, energy requirements in production and service, quality, the ability to be manufactured in the required quantities and to be satisfactorily assembled and finished, the influence of the service environment, recycling and waste recoverability, its estimated lifetime, and many other factors, which are often interrelated. All these elements must be considered before deciding that the use of a particular material makes good sense. 

Even for the correct selection of materials and correct processing, corrosive attack cannot be excluded in a corrosion system as it may be caused by previously unknown critical conditions and influencing factors or subsequently modified operating conditions. 

Material Selection. Information regarding material selection and properties is contained in ANSI/AGMA 2004-B89, Gear Materials and Heat Treatment Manual. Many factors influence the selection of gear materials, and their relative importance will vary. These factors include, but may not be limited to, the following ... 

The solidification process of the extruded material also influences the filament diameter. Materials that solidify quickly would not lead the molten material to spread over i.e. the dimension of the deposited filament remains same as the diameter of the filament as extruded. The appropriate selection or setting of process parameters is crucial for successful extrusion of polymer scaffolds. Many different factors contribute to successful deposition. The extruded material must flow consistently through the nozzle when pressure is applied to avoid inadequate dispensing. However, it is also essential that the pressure should not set too... 

Some particular requirements and typical selection considerations are presented in Table 8.2. The materials selection process is also influenced by the fact that the materials are either considered for the construction of a new system or for the modification or repairs in an existing facility. For the construction of new equipment, the selection procedure should begin as soon as possible and before the design is finalized. The optimum design for corrosion resistance will often vary with the material used. In a repair application, there is usually less opportunity for redesign, and the principal decision factors will be centered on delivery time and ease of fabrication in the field. It is also advisable to estimate the remaining life of the equipment so that the repair is not overdesigned in terms of the corrosion allowance. 

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