Test techniques

Nondestructive testing techniques for welded joints usually include visual, radiographic, magnetic particle, liquid penetrant, and ultrasonic testing methods. Of interest in this paper is the radiographic testing (RT) technique. 

There is some uncertainty connected with testing techniques, errors of characteristic measurements, and influence of fectors that carmot be taken into account for building up a model. As these factors cannot be evaluated a priori and their combination can bring unpredictable influence on the testing results it is possible to represent them as additional noise action [4], Such an approach allows to describe the material and testing as a united model — dynamic mathematical model. 

Particles magnetic is one of the most useful testing techniques in industry. It allows the detection of surfacic and sub-surfacic defects. The main difficulty of this technique is to optimize the control conditions allowing an easiest interpretation of the results which necessite a great experience of the operator. 

Magnetic particles is one of the most used nondestructive testing techniques in industry. It allows detection and localization of surfacic and subsurfacic defects of ferromagnetic pieces by making conspicuous leakage fields by a magnetic developer. 

Our method consists in the use of all magnetic particles testing techniques and to bear in mind the physical approach and the different processes combinations. 

As reported before [Ref. 1], there are some essential parameters that influence the results of the testing, such as the thickness of the expired specimen, the quality and coarse grain of the built-in concrete, and the properties of the specimen-surface for the transducer s coupling. At the onset of testings none of tlrese parameters were available. As a result, we had to carry out preliminary investigations in order to prove the applicability of our testing-technique "in situ". 

Today the coin-tap test is a widely used technique on wind turbine rotor blades for inspection of thin GFRP laminates for disbonded and delaminated areas. However, since the sensitivity of this technique depends not only on the operator but also on the thickness of the inspected component, the coin-tap testing technique is most sensitive to defects positioned near the surface of the laminate. Therefore, there has been an increasing demand for alternative non-destmctive testing techniques which is less operator dependent and also more sensitive to delaminations and disbonded areas situated beyond thicker GFRP-laminates. 

The common civil engineering seismic testing techniques work on the principles of ultrasonic through transmission (UPV), transient stress wave propagation and reflection (Impact Echo), Ultrasonic Pulse Echo (UPE) and Spectral Analysis of Surface Waves (SASW). 

The type of food and its processing affect flavoring efficiency therefore, flavor materials must be taste-tested in the food itself. Because there has been a lack of standardization of testing techniques, a committee on sensory evaluation of the Institute of Food Technologists has offered a guide (112) which is designed to help in developing standard procedures. 

Many special appHcations of iadentation hardness testing techniques to unusual materials or conditions have been developed, some of which are hsted ia Table 4. 

Destructive Testing. Destmctive testing is used to determine the strength of the weld and the effect of the explosion-welding process on the parent metals. Standard testing techniques can be utilized on many composites however, nonstandard or specially designed tests often are required to provide meaningful data for specific appHcations. 

Plastics testing encompasses the entire range of polymeric material characterizations, from chemical stmcture to material response to environmental effects. Whether the analysis or property testing is for quaUty control of a specific lot of plastic or for the determination of the material s response to long-term stress, a variety of test techniques is available for the researcher. 

Bottom-Feed Procedure The procedure for coUecting data using bottom-feed leaf test techniques is as follows ... 

Emissions must be quantifiable, and trades among them must be even. Each emission point must have a specific emission hmit, and that limit must be tied to enforceable testing techniques. 

Modtilus Measurements Another SCC test technique is the use of changes of modulus as a measure of the damping capacity of a metal. It is known that a sample of a given test material containing cracks will have a lower effec tive modulus than does a sample of identical material free of cracks. The technique provides a rapid and reliable evaluation of the susceptibility of a sample material to SCC in a specific environment. The so-called internal friction test concept can also be used to detect and probe nucleation and progress of cracking and the mechanisms controlling it. 

Electrochemical Impedance Spectroscopy (EIS) and AC Impedance Many direct-current test techniques assess the overall corrosion process occurring at a metal surface, but treat the metal/ solution interface as if it were a pure resistor. Problems of accuracy and reproducibility frequently encountered in the application of direct-current methods have led to increasing use of electrochemical impedance spectroscopy (EIS). 

Use and Uimitations of Electrochemical Techniques A major caution must be noted as to the general, indiscriminate use of all electrochemical tests, especially the use of AC and EIS test techniques, for the study of corrosion systems. AC and EIS techniques are apphcable for the evaluation of very thin films or deposits that are uniform, constant, and stable—for example, thin-film protective coatings. Sometimes, researchers do not recognize the dynamic nature of some passive films, corrosion produc ts, or deposits from other sources nor do they even consider the possibility of a change in the surface conditions during the course of their experiment. As an example, it is note-... 

Warnings are noted in the literature to be careful in the interpretation of data from electrochemical techniques applied to systems in which complex and often poorly understood effects are derived from surfaces which contain active or viable organisms, and so forth. Rather, it is even more important to not use such test protocol unless the investigator fuhy understands both the corrosion mechanism and the test technique being considered—and their interrelationship. 

Recently test-methods of the analysis are widely used they differ by rapidity, cheapness, simplicity of detenuination and don t demand availability of the expensive equipment. These methods are used at the control of manufacture, in diagnostic labs, in field and domestic conditions etc. Test -technique have received special distribution in the analysis of objects of environment natural and sewages, soils, air. The improvement both existing and developing of new methods and techniques of test-determination of elements is an actual problem of modern analytical chemistry. 

The test-techniques of hydrargyrum (II) and zincum (II) ions determination in aqueous solutions with the use of congo red and brilliant green adsorbed on polyurethane foam accordingly are desighed on the basis of received data for organic reagents adsorption on it s. 

The research of congo red and stilbazo adsoi ption on aerosil is carried out. The test - techniques of hydrargymm and cupmm determination with the use of obtained solid phase reagents are designed. 

Flumequine is a representative of fluoroquinolones which are high-effective antimicrobial medicines used as fodder supplements in cattle-breeding. This causes the necessity in effective testing techniques to detenuine the content of flumequine in meat products. Fluorimetric determination based on sensitized luminescence of fluoroquinolone chelates with lanthanides is a promising one. The literature lacks information of flumequine detemiination with the aid of sensitized fluorescence. 

It is known that Selenium catalyzes reaction of some dye reduction by Sulphide. On this basis spectrophotometric and test-techniques for Selenium determination are developed. Inefficient reproducibility and low sensitivity are their deficiencies. In the present work, solid-phase reagent on silica gel modified first with quaternary ammonium salt and then by Indigocarmine was proposed for Selenium(IV) test-determination. Optimal conditions for the Selenium determination by method of fixed concentration were found. The detection limit of Se(IV) is 10 ftg/L = 2 ng/sample). Calibration curve is linear in the range 50-400 ftg/L of Se(IV). The proposed method is successfully applied to the Selenium determination in multivitamins and bioadditions. 

Corrosion-fatigue cracks can be detected by nondestructive testing techniques such as magnetic particle inspection, radiography, ultrasonics, and dye penetrant. Corrosion-fatigue cracks may occur in numerous tubes simultaneously. Nondestructive testing of tubes at locations similar to those in which cracks are observed can be useftil. 

Most defects can be detected using one or more appropriate nondestructive testing techniques. However, in the absence of routine nondestructive testing inspections, identification of defects in installed equipment is generally limited to those that can be observed visually. Defects such as high residual stresses, microstructural defects such as sensitized welds in stainless steel, and laminations will normally remain undetected. Defects that can be detected visually have the following features ... 

Among the available nondestructive testing techniques are ultrasonic tests, eddy-current tests, air-underwater and hydrostatic tests, and visual examinations. All of these techniques must be executed by technically qualified personnel. 

Identification. If accessible, defects from burnthrough may be visually identified as fused holes in the tube wall. Various nondestructive testing techniques, such as radiography and ultrasonics, may also detect this defect. The defect generally causes leakage soon after affected equipment is placed in service. 

Occasionally, corrosion of this type produces large cavities covered by a thin outer skin of weld metal (Fig. 15.5). Even close examinations of such sites under a low-power microscope may fail to reveal the cavities. Compare Figs. 15.6 and 15.7. Generally, such sites are detected either by fluid leakage or by nondestructive testing techniques such as radiography and ultrasonics. 

Identification. Slag inclusions will not be visually identifiable unless slag particles emerge at the weldment surfaces. Radiography, eddy-current testing, and ultrasonics are nondestructive testing techniques that can disclose slag inclusions. 

Cautions. Sensitization is a metallurgical condition. It can be identified by certain specialized nondestructive testing techniques or by destructive metallurgical examinations, but it cannot be identified by simple visual examination. It becomes visually apparent only after exposure of the sensitized metal to a sufficiently aggressive environment produces corrosion that is, weld decay. 

Identification. Weld-root cracks originate at the root of the weld and run longitudinally along the weld, perpendicularly to the base-metal surface and parallel to the axis of the weld. In general, they may be identified visually or by various nondestructive testing techniques such as radiography or ultrasonics. Failures from weld-root cracking may occur soon after start-up or after extended periods of successful service. 

Although not commonly listed as a weld defect, high-welding stress nevertheless provides an essential ingredient to stress-corrosion cracking and other failures. It differs in an important respect from other types of weld defects in that stresses cannot be visually identified or revealed by conventional nondestructive testing techniques. 

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