Heat treatment evaluation

With the reference block method the distance law of a model reflector is established experimentally prior to each ultrasonic test. The reference reflectors, mostly bore holes, are drilled into the reference block at different distances, e.g. ASME block. Prior to the test, the reference reflectors are scanned, and their maximised echo amplitudes are marked on the screen of the flaw detector. Finally all amplitude points are connected by a curve. This Distance Amplitude Curve (DAC) serves as the registration level and exactly shows the amplitude-over-distance behaviour" of the reference reflector for the probe in use. Also the individual characteristics of the material are automatically considered. However, this curve may only be applied for defect evaluation, in case the reference block and the test object are made of the same material and have undergone the same heat treatment. As with the DGS-Method, the value of any defect evaluation does not consider the shape and orientation of the defect. The reference block method is safe and easy to apply, and the operator need not to have a deep understanding about the theory of distance laws. 

Practical considerations enter into the experimental plan in various other ways. In many programs, variables are introduced at different operational levels. For example, in evaluating the effect of alloy composition, oven temperature, and varnish coat on tensile strength, it may be convenient to make a number of master alloys with each composition, spHt the alloys into separate parts to be subjected to different heat treatments, and then cut the treated samples into subsamples to which different coatings are appHed. Tensile strength measurements are then obtained on all coated subsamples. 

Most other rotor parts in gas turbines are individually forged. This includes compressor wheels, spacers, distance pieces, and stub shafts. All are made from quenched and tempered low-alloy steels (Cr-Mo-V or Ni-Cr-Mo-V) with the material and heat treatment optimized for the specific part. The intent is to achieve the best balance of strength, toughness with ductility, processing and nondestructive evaluation capability, particularly when it is recognized that some... 

The evaluation of heat treatments or the effectiveness of stabilisation by limiting carbon content of these stainless steels can be determined by subjecting specimens to the ASTM standardised acid copper sulphate test or boiling nitric acid test (ASTM A262 1986 see also Sections 9.5 and 1.3). 

Brown has pointed out that Du Pont use evaluation tests for (a-) as-received unstabilised alloys containing more than 0-03% C to check the effectiveness of the final heat treatment and (b) stabilised or special low-carbon grades after a sensitising treatment (1 h at 677°C) to determine whether susceptibility might develop during a subsequent welding operation. 

Thus, under the circumstances already outlined, the test can be misleadingly severe, but it is particularly valuable for evaluating alloys for use in HNO3 or in other strongly oxidising acid solutions to ensure that they have received the correct heat treatment and have an appropriate composition, i.e. a low carbon content or the correct ratio of (Ti or Nb)/C. 

Yoo, J.J. and Rhee S.H. (2004) Evaluations of bioactivity and mechanical properties of poly (e-caprolactone) silica nanocomposite following heat treatment. Journal of... 

Spiced Layer Cake. Investigation was undertaken to evaluate navy bean hulls as an alternative source of dietary fiber in spice-flavored layer cakes and to compare hull flour from beans with no heat treatment to hull flour from beans roasted for 2 min at 240°C. Results of the objective analyses performed on both the batter and the cakes indicated that the addition of 15% navy bean hulls resulted in a thicker batter, due to the high water absorbancy of the hulls however, only the batter containing the unroasted hulls was significantly more viscous than the control batter. Cakes prepared with the roasted navy bean hulls tended to be slightly more... 

Characteristics and implementation of the treatments depend on the expected results and on the properties of the material considered a variety of processes are employed. In ferrous alloys, in steels, a eutectoid transformation plays a prominent role, and aspects described by time-temperature-transformation diagrams and martensite formation are of relevant interest. See a short presentation of these points in 5.10.4.5. Titanium alloys are an example of the formation of structures in which two phases may be present in comparable quantities. A few remarks about a and (3 Ti alloys and the relevant heat treatments have been made in 5.6.4.1.1. More generally, for the various metals, the existence of different crystal forms, their transformation temperatures, and the extension of solid-solution ranges with other metals are preliminary points in the definition of convenient heat treatments and of their effects. In the evaluation and planning of the treatments, due consideration must be given to the heating and/or cooling rate and to the diffusion processes (in pure metals and in alloys). 

The transport properties studies were made in the framework of the evaluation of the effect of radiation crosslinking and heat treatment on the PVA, and the possibility to Improve the RO performance of these membranes using these methods. The water... 

While gelation temperature Is usually considered a characteristic property of a given protein system, the heating conditions required for gel formation may be Interrelated to all of the previously mentioned factors. It has been observed that WPG dispersions In 0.2 M NaCl will gel at 75 C while a temperature of 90 C Is required to gel WPG dispersions In distilled water (1). Heating time, at a specific temperature, required to form a protein gel structure Is generally considered to decrease with Increased protein concentration. Alteration of heat treatment conditions affects the gel s macroscopic and microscopic structural attributes. This has been dramatically shown by Tombs (A) with electromlcroscoplc evaluation of bovine serum albumin gels. 

Mustakas et al. (46) evaluated the effects of extruder-processing on nutritional quality, flavor, and stability of the product in an attempt to describe extruder conditions which would be acceptable in all three respects. Urease activity was used as an estimation of trypsin inhibitor activity thus the area between the two urease curves in Figure 2 indicates processing conditions which strike a balance between too much and too little heat treatment, showing optimal nutritional quality. Using the flavor and peroxide value isograms, processing conditions may be chosen such that acceptable flavor and stability may also be achieved. 

Detectable concentrations of various antibacterials in milk attained by different microbiological tests are presented in Table 27.2. Milk constitutes a matrix that, apart from heating to destroy natural inhibitory substances, does not generally necessitate further sample treatment. Some antibiotics, however, exhibit some instability to heat treatment (54-56) and, therefore, if further confirmation is required reference frozen samples should always be available. When raw milk is directly analyzed, critical evaluation is generally required because natural inhibitors such as somatic cells, immunoglobulins, and metabolites may cause zones of inhibition (56, 57). Furthermore, several factors including marked pH-devia-tions, use of paper disks that contain inhibitory substances, and work with forceps that are too hot or have not been cleaned properly can readily lead to falsepositive readings (56, 58). 

Harland, H. A., Coulter, S. T., Townley, U. Y. and Jenness, R. 1955. A quantitative evaluation of changes occurring during heat treatment of skimmilk at temperatures ranging from 170 to 300°F. J. Dairy Sci. 38, 1199-1207. 

Fig. 30.3. Evaluation of the efficiency of the dsDNA denaturing treatment. (A) Heating treatment of the dsDNA before immobilization. (B) Heating treatment of the dsDNA before immobilization plus denaturing alkaline treatment after immobilization. 153.8 ng of poly(dA)poly(dT) as DNA target 9.97 pmol dT(50)-biotin and 9.00 /ig of enzyme conjugate. The nonspecific adsorption signal is shown in black (more details in Ref. [2]).

In contrast to this, the technique reported herein uses the weight loss of pitch during heat treatment to evaluate a set of apparent kinetic data (reaction order, frequency factor, and activation energy), taking into account that the composition and nature of the reactants are varying. 

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