Materials Evaluation and Selection

Materials evaluation and selection are fundamental considerations in engineering design. If done properly, and in a systematic manner, considerable time and cost can be saved in design work, and design errors can be avoided. 

The design of any apparatus must be unified and result in a safe functional system. Materials used for each apparatus should form a well coordinated and integrated entity, which should not only meet the requirements of the apparatus functional utility, but also those of safety and product purity. 

Materials evaluation should be based only on actual data obtained at conditions as close as possible to intended operating environments. Prediction of a material s performance is most accurate when standard corrosion testing is done in the actual service environment. Often it is extremely difficult in laboratory testing to expose a material to all of the impurities that the apparatus actually will contact. In addition, not all operating characteristics are readily simulated in laboratory testing. Nevertheless, there are standard laboratory practices that enable engineering estimates of the corrosion resistance of materials to be evaluated. 

Environmental composition is one of the most critical factors to consider. It is necessary to simulate as closely as possible all constituents of the service environment in their proper concentrations. Sufficient amounts of corrosive media, as well as contact time, must be provided for test samples to obtain information representative of material properties degradation. If an insufficient volume of corrosive media is exposed to the construction material, corrosion will subside prematurely. 

The American Society for Testing Materials (ASTM) recommends 250 ml of solution for every square inch of area of test metal. Exposure time is also critical. Often it is desirable to extrapolate results from short time tests to long service periods. Typically, corrosion is more intense in its early stages (before protective coatings of corrosion products build up). Results obtained from short-term tests tend to overestimate corrosion rates which often results in an overly conservative design. 

Materials evaluation should be based only on actual data obtained at conditions as close as possible to intended operating environments. 

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The testing time has to be sufficiently short for the material evaluation and selection to be made before a deadline set by the practical application. 

Notwithstanding the guidance given below under Evaluation and selection of subcontractors, this requirement does not relieve you of the responsibility for ensuring the quality of subcontracted parts, materials, and services. Therefore, it would be unwise to place orders on a customer-specified subcontractor without first going through your evaluation and selection process. You can obviously take some short cuts but don t make assumptions. The customer will not be sympathetic when you are late on delivery or your price escalates. If you find a subcontractor that can meet all your product/service requirements at a lower price you can submit details to your customer for approval. 

The compressive data are of limited design value. They can be used for comparative material evaluation and design purposes if the conditions of the test approximate those of the application. The data are of definite value for materials that fail in the compressive test by a shattering fracture. On the other hand, for those that do not fail in this manner, the compressive information is arbitrary and is determined by selecting a point of compressive deformation at which it is considered that a complete failure of the material has taken place. About 10% of deformation are viewed in most cases as maximum. 

The targets of electrocatalysis are at the basis of recent developments in the field of water electrolysis. First, it is necessary to distinguish between materials evaluation and materials selection. The former is the search for materials with better and better properties for the wanted electrode process. The latter implies global considerations of applicability. This is probably what makes academic research differ from R D. The former is favored by scientifically exciting performance, in the latter it is necessary to find a compromise between, for instance, activity and stability or between efficiency and economic convenience. 

Recommendation 3-5. The Chemical Materials Agency should evaluate and select appropriate methods for the treatment and disposal of mercury-contaminated carbon. Mercury-contaminated carbon should not be intermingled with other contaminated carbons during storage. 

Recommendation 3-9. The Chemical Materials Agency should evaluate and select an appropriate method to dispose of the VX hydrolysate currently being stored at the Newport, Indiana, site, with preference for offsite disposal. 

The main purposes of corrosion testing are (i) evaluation and selection of materials for a given application (ii) evaluation of new or old materials to determine the environments which are suitable (iii) control of corrosion resistance of the material or corrosivity of the environment and (iv) study of the corrosion mechanism. 

Material component evaluation and selection are critical steps in the development of a MDI formulation [140,141], The materials must be chemically resistant and compatible with all components of the formulation. Gaskets must have appropriate mechanical properties and work effectively as a seal, preventing leakage of the formulation and moisture ingress. While the basic components themselves have... 

For optimization purposes, it is convenient to use analytical 0.46 x 25-cm columns filled with the stationary phase available in bulk quantities for PHPLC. Primary evaluation and selection of the stationary and mobile phases, based on the selectivity of separation, column efficiency, and product retention, should be done initially on an analytical scale, including experiments under overload conditions on an analytical column. A particular set of chromatographic conditions includes the column, programmed mobile phase, flow rate, sample solution composition and amount injected, temperature, and collection points. These conditions are evaluated to obtain optimization of the maximum recovery of the desired material with required purity, or the maximum available purity for the required yield based on the HPLC analysis of collected fractions. 

To illustrate the ARS form selection process, two pharmaceutical examples of ARS form selection are provided. Indinavir sulfate is the API for Crixivan , a specific and potent inhibitor of the HIV-1 protease used in the treatment of AIDS. Indinavir sulfate is produced as a crystalline ethanolate sulfate salt. If the material is stored in double polyethylene liners within fiber containers or repeatedly exposed to ambient conditions changes occur in both crystallinity and solvation. Using XRPD, KF, and RP-HPLC, conversion of the crystalline ethanolate to amorphous material or to a hydrate crystal form has been detected and degradation is observed. However, the material is stable if stored in a tightly sealed container impermeable to ethanol/moisture transport under an inert nitrogen atmosphere at a controlled room temperature.82,83 These storage conditions are not practical for a routinely used ARS. Therefore, the free base monohydrate form of indinavir sulfate was evaluated and selected as the ARS. This form of the API was demonstrated to be extremely stable under ambient conditions needed for routine analysis. 

So far, no definitive decision mechanisms covering the choice of salt formers have been developed, so the final evaluation and selection process remains essentially empirical to a large extent. In addition to the reasons mentioned earlier that in the major pharmaceutical companies the search for crystalline salts occurs very early along the development timeline, there is further reason. Preclinical investigations are necessarily initiated at a time when the candidate drug substance is usually impure (often around 95% pure) and material is at a premium. Here the formation... 

Researching, developing, evaluating, and selecting disposal methods for all nonstockpile chemical material ... 

In recent years a variety of novel antifriction polymer-based materials have been developed and the known improved at different research centers and laboratories of the world. However, even a very learned expert in the field of friction is in a difficulty to evaluate truly the publicity and literary data when maJcing comparative analysis or selecting proper materials for particular friction applications. The reasons lie in the unavailability of common methods for friction testing of materials as well as evaluating criteria on the friction characteristics of materials. Explanation and selection of evaluating criteria largely depend upon the factors that influence the friction characteristics of polymers, and capabilities of the testing equipment. 

Evaluation and selection of material or protection method for a specific environment and a certain application. Testing for this objective is initiated by the user, often by engagement of consultants, testing laboratories or research institutions. People determining test conditions are often faced with the following dilemma ... 

Such artifacts affect the laboratory response of the core materials to surfactants and can complicate the evaluation and selection of surfactants for use in the reservoir. 

The most common experiments for the evaluation and selection of corrosion-resistant materials focus on the variation of the mass according to the length of exposure to the aggressive atmosphere, which is determined through the equation ... 

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