Material variables

Materials to be inspected are, for example Concrete with lest frequencies of about 50 kHz, sandwich components with 500 kHz, metallic materials up to 10 MHz and thin components up to 35 MHz. Apart from the difference of materials, variable thicknesses and attenuations require different amplifications and signal processings. 

Among the key variables in strategic alkylphenol planning are feedstock quaHty and availabiHty, equipment capabiHty, environmental needs, and product quahty. In the past decade, environmental needs have grown enormously in their effect on economic decisions. The manufacturing cost of alkylphenols includes raw-material cost, nonraw-material variable cost, fixed cost, and depreciation. 

Nonraw-material variable costs consist largely of utiHty costs, but other costs can be significant in this area. Eor example, operating costs for additional waste treatment are in this category. Nonraw-material variable costs account for 5—20% of the total manufacturing cost of an alkylphenol operation. 

There are material and processing limitations that can influence the fabrication and performances of products. These subjects are reviewed in Chapter 6, MATERIAL VARIABLE and Chapter 8, EQUIPMENT/ PROCESSING VARIABLE. 

As reviewed throughout this book, designing acceptable products requires knowledge of the behavior of the different plastics and their processing characteristics (Chapter 6, MATERIAL VARIABLE and Chapter 8 EQUIPMENT/PROCESSING VARIABLE). 

In addition to material variables, as reviewed in Chapter 6, there are a number of factors in equipment hardware and controls that cause processing variabilities. They include factors such as accuracy of machining component products, method and degree of accuracy during the assembly of component products, temperature and pressure control capability particularly when interrelated with time and heat transfer uniformity in metal components such as those used in molds and dies. 

The effect of raw material variability on tablet production [2,30,31] and suggestions for improving tableting quality of starting materials [21] has been the subject of several publications. Table 3, which lists the characteristics of different sources of magnesium stearate, clearly illustrates the variability of this material [32]. Phadke and Eichorst have also confirmed that significant differences can exist between different sources, and even different lots, of magnesium stearate... 

Given the fact that the effectiveness of magnesium stearate is due, in large part, to its large surface area, these variations should not be overlooked. In addition, studies assessing raw material variability emphasize the need for physical as well as chemical testing of raw materials to ensure uniformity of the final product. 

Lee S.M. (1984). Correlation between resin material variables and transverse cracking in composites.. /. 

To test the agreement of the experimental and theoretically predicted slopes, the index of refraction inferred from equation (1) and the experimental data of Figure 3, n = 1.4, is compared with the optically determined index, n = 1.6 (. This is reasonably good agreement in view of the material variability and simplifying assumptions involved. 

A power-law expression of the form of Eq. (5.115) adequately describes the creep properties of SMC composites. The creep response of the SMC-R50 composite at various temperatures shown in Figure 5.105 is representative of this behavior. Among the material variables, fiber content once again has the greatest influence on the creep strain. At a given temperature and stress level, creep strain is higher if the fiber content is reduced. 

An important consideration in all failure studies is the influence of material variability. Statistical distributions of failure incidence must be known and properly accounted for if reliability limits are to be set. Wiegand and co-workers (14, 113) have discussed propellant sample and batch variability, and its effect on failure behavior, in numerous reports. These studies point out the statistical nature of failure and the fact that knowledge of the distributions is required to set conservative design values for motor stress and strain capability. Statistical distributions permit the prediction of the probability of failure, but mission considerations dictate the allowable failure frequencies. 

Representative samples of each lot will be collected for testing in accordance with the established procedure. The number of containers to sample and the sample size should be based upon appropriate criteria as required by 211.84 (3) (e.g., raw material variability, confidence levels, degree of precision desired, past quality history of the supplier, and the quantity needed for analysis). Sample containers should be properly labeled. The label should include, at minimum, information about the sample name, manufacturer name, sample size, and date and hour of sampling. Raw material containers selected for sampling should be opened, sampled, and resealed in a manner that prevents contamination of their contents and of other raw materials. 

Given the existence of interphases and the multiplicity of components and reactions that interact to form it, a predictive model for a priori prediction of composition, size, structure or behavior is not possible at this time except for the simplest of systems. An in-situ probe that can interogate the interphase and provide spatial chemical and morphological information does not exist. Interfacial static mechanical properties, fracture properties and environmental resistance have been shown to be grealy affected by the interphase. Careful analytical interfacial investigations will be required to quantify the interphase structure. With the proper amount of information, progress may be made to advance the ability to design composite materials in which the interphase can be considered as a material variable so that the proper relationship between composite components will be modified to include the interphase as well as the fiber and matrix (Fig. 26). 

When technology allows it, there is a natural tendency to specify lower and lower tolerances on equipment parameters but this does not necessarily bring significant advantage because, for many properties, the contribution to uncertainty from material variability far outweighs that from machine accuracy. When reduced tolerances cannot be fully justified there is an unreasonable cost burden to be borne by the laboratory. 

A further step back from application to powder production is the processes that create the desired powder properties. Thus, another major area of research involves the study of these processes, and investigating how raw material variables and process input variables affect the engineering of the desired powder properties. Finally, as mentioned above, a very important aspect of research for food powders is component stability, all the way from powder production,... 

Li and Manas-Zloczower (31) used the CFM commercial FIDAP FEM package to simulate the three-dimensional isothermal flow patterns and distributive mixing in three consecutive filled, closed C-shaped chambers of fully intermeshing, counterrotating extruders, having the dimensions of Leistritz 30.34 (30 denotes the centerline distance and 34 the barrel diameter in mm units). An equal pressure drop per C-shaped chamber was applied for the calculations. The melt was assumed to be Power Law above y() and Newtonian below it. The design, process, and material variables are given by the authors. 

In addition to material variables, there are a number of factors in... 

Problems and facts that in the author s personal experience arise in the industrial application of tannin-based adhesives for timber sometimes indicate lack of correspondence with laboratory practice and results. These are often problems related to unusual characteristics of the adhesive itself, or of its application technique, which could not be noticed during research under laboratory conditions, but the existence of which could easily jeopardize successful implementation of laboratory technology into industrial practice. Correcting the credibility gap between research focus and industrial usage is seen as a critical step toward market expansion for these new products. Important considerations are consistency of tannins, extracts and adhesives properties due to the natural raw material variability formulation in cold-setting adhesives and application conditions (such as wood moisture and adhesive-content or pressing time) in particleboard adhesives. These problems have been overcome in use of wattle tannin-based adhesives as shown by a visual comparison of tannin-, phenolic-, and melamine-bonded particleboards exposed to the weather for 15 years and the growing use of tannin-based adhesives in other countries. 

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