Choice of test method

The choice of test method for examining pitting resistance depends on the objective. For evaluation of surface condition, the methods in the first group are preferable, while the methods in the second group give the best characterization of the alloy. 

The results of dynamic tests are dependent on the test conditions test piece shape, mode of deformation, strain amplitude, strain history, frequency and temperature. ISO 4664 gives a good summary of basic factors affecting the choice of test method. Forced vibration, non-resonant tests in simple shear using a sinusoidal waveform are generally preferred for design data as... 

There are many methods of hardness testing, fairly widely used, depending on tradition and laboratory equipment. Moreover, the materials to be tested vary in nature owing to their particular structure, chemical properties and texture. A proper choice of test method for a given type of materials is therefore a fundamental problem in petrotechnical estimation of materials, rocks and products of their technological processing, chiefly ceramic materials (Katz and Lenoe, 1976). 

Characteristics of PMCs influencing the design and choice of test methods include the following. 

Depending upon the partitioning and persistence of an active substance in the sediment phase of natural water sediment study, data may be required on its toxicity to sediment dwelling invertebrates. Details of when this study is required and choice of test method are given in the Aquatic Guidance Document. Information is also given in Section 8.2.7 of Directive 96/12/EC. 

The method of measmement of Tg is often a matter of personal choice or of available equipment. The use to which values are to be used may also influence the choice of test method. If the Tg is to be used to determine the upper operating temperature of an adhesive, then a mechanical method of measurement would be most appropriate. However, to be of most use to other workers, the exact experimental details used in determining the Tg must be quoted. 

The choice of test methods and their required nominal values and tolerances are normally agreed upon between user and supplier. 

It is clear to those who regularly perform knee wear testing, and especially those who try hard to do testing well, that the devil is in the detail . With the exception of some specialist workshops (e.g., by ASTM) even scientific conferences appear lately to be more focused on results they leave little room for detailed discussion, especially on methodological detail where most of the variability in results emanate, in the author s view. Nevertheless, this chapter is still not a detailed how-to manual. International standards (where available) are cited instead. Published international standards typically describe such methods in sufficient detail. Nor is this text a review of the results of TKR tests from the literature, as useful as that may be. The results are too many and varied only some are cited here to illustrate specific points. The main emphasis here is on matters of rationale and know-how to avoid pitfalls in the choice of test methods, in their implementation, and in the interpretation of results. This emphasis should help engineers in the orthopedic industry and in the research community who hunger for the type of detail they cannot usually find in published research papers, usually for lack of space in such result-oriented research articles. 

The LLNA is the preferred method when compared to the GPMT because (a) it can equivalently predict human contact dermatitis, (b) a dose-response can be obtained, and (c) it is in line with current animal welfare efforts. Nevertheless, several situations exist where the GPMT is advantageous, depending predominantly on the choice of test substances. The LLNA is known for less powerful detection of the sensitization potential of metallic compounds, high molecular weight proteins, strong irritants, and for substances with low adhesion to the skin surface (skin wettability is a prerequisite for the successful application of LLNA) [136-140],... 

The critical pitting temperature (CPT) is widely used as a measure of the resistance of stainless steel against pitting attack. Various methods for determination of the CPT are described here, special attention being given to the choice of test potential for the control of stainless steel quality. 

Because these different viability tests all reflect different aspects of cell viability, the choice of test depends on the aim of the study. For toxicity studies where biotransformation is an important bioactivation or detoxification step, metabolic function tests should be included to judge the validity of the method, whereas viability tests are needed to assess toxic effects. Both positive and negative controls should be included in such studies. When human liver is used, the characterization of metabolic activity is especially important because of the large inter-individual variability associated with this property [75]. 

The choice of test equipment and methods has become extremely wide and, apart from large, integrated, electronic colorimetric and spectrophotometric instrumentation, field personnel can choose from miniburettes, direct-reading titrators (modified syringes), digital titrators, drop tests, tablet tests, permanent color standard comparators, indicator papers, portable colorimeters, immunoassays, etc. Today, field-test methods tend to be tailored by equipment manufacturers to their own analytical systems, and consequently the specified use of particular standard methods for the examination of water, from any one technology or official body, is probably not realistic. Rather it is the fitness-for-purpose rule that is more relevant. 

Clearness and transparency with respect to the choice of models, methods, assumptions, distributions and parameters are two prerequisites for trust and confidence openness about uncertainties is another. Exposure assessment as an applied science should follow the main scientific desiderata empirical testing, documentation and reproducibility of results, explicit reporting of uncertainty, peer review and an open debate about underlying theories and models. This way, the main attributes for characterizing uncertainty discussed in the last chapter, the appraisal of the knowledge base and the subjectivity of choices, are clarified. 

Waksman and Reilly have summarized the factors which have a bearing upon the choice of the method to be employed in measuring quantitatively the activity or potency of an antibiotic substance. They have cited literature references to the more commonly used methods. Loo and coworkers have described a suitable method for the quantitative determination of streptomycin by the filter paper disc, agar plate diffusion technique using Bacillus subtilis as the test organism. The procedure proved satisfactory in the assay of surface and submerged culture beers and of preparations obtained in isolation and purification... 

According to the above, most tested carbons may be used as filter beds in water treatment plants. The choice of carbon should be carried out on the basis of indicators, analysis of costs, possibiUty and rate of regeneration. Adsorption capacity and parameters of work should be determined by pilot scale studies. Studies of testing methods and model adsorption should give standard carbons for removal of characteristic groups of water pollutants. Both powdered and granular carbons should be used, the former to pre—treatment or periodically at the time of peak load, and the latter, to final water treatment in compensated conditions. 

Selection and validation of testing methods are key issues in paternity testing. Specific requirements for paternity testing may be mandated by local laws and agreements. Thus the choice of methods and genetic systems should be based on an agreement between the client(s) and the laboratory. 

The choice of which method to use may be decided by the type of polymer/plastic material and the metal required for analysis. With the analysis of a completely unknown sample it may be necessary to carry out trial and error tests of different methods with and without spiking before accepting the final sample preparation method. Once confidence is achieved in the method of analysis, the procedure is noted for future reference. 

The analysis of real samples, such as the soil and rock samples brought back to the earth from the moon by the Apollo astronauts, is usually quite complex compared with the analysis of materials studied in laboratory courses. As discussed in this chapter, the choice of analytical method for real materials is not simple, often requiring consultation of the literature, modification of existing methods, and extensive testing to determine method validity. 

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