Ultrasonic method

These methods are based on the response of the bonded joint to loading by low-power ultrasonic energy. Ultrasonic methods are especially useful in detecting unbonds of the following types  

Unbonds between the facing sheet to adhesive interfaces in honeycomb structures 

Unbonds between the adhesive-to-core interfaces in honeycomb structures 

Unbonds between adherends in adhesive-bonded laminate 

1 Ultrasonic Pulse Echo Contact Impedance Testing 

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Therefore, it is important for judging the performance and the safety of the product to understand the size of the defect and the position by the ultrasonic method quantitatively. And, the reliability of the product improves further by feeding back this ultrasonic wave information to the manufacturing process. 

H.Toda Quantiative evaluation of fretting fatigue cracks on the surface of the railroad axles by grazing SH Wave ultrasonic method. Journal of JSNDI, Vol. 40, March, pl58-164, (1991)... 

Ultrasonic Microhardness. A new microhardness test using ultrasonic vibrations has been developed and offers some advantages over conventional microhardness tests that rely on physical measurement of the remaining indentation size (6). The ultrasonic method uses the DPH diamond indenter under a constant load of 7.8 N (800 gf) or less. The hardness number is derived from a comparison of the natural frequency of the diamond indenter when free or loaded. Knowledge of the modulus of elasticity of the material under test and a smooth surface finish is required. The technique is fast and direct-reading, making it useful for production testing of similarly shaped parts. 

Density. Density of LLDPE is measured by flotation in density gradient columns according to ASTM D1505-85. The most often used Hquid system is 2-propanol—water, which provides a density range of 0.79—1.00 g/cm. This technique is simple but requires over 50 hours for a precise measurement. The correlation between density (d) and crystallinity (CR) is given hy Ijd = CRj + (1 — Ci ) / d, where the density of the crystalline phase, ify, is 1.00 g/cm and the density of the amorphous phase, is 0.852—0.862 g/cm. Ultrasonic methods (Tecrad Company) and soHd-state nmr methods (Auburn International, Rheometrics) have been developed for crystallinity and density measurements of LLDPE resins both in pelletized and granular forms. 

A component is made of a steel for which K. = 54 MN m. Non-destructive testing by ultrasonic methods shows that the component contains cracks of up to 2a = 0.2 mm in length. Laboratory tests show that the crack-growth rate under cyclic loading is given by... 

Various methods including the repulsion between two electrode wires immersed in a solution, further friction and ultrasonic methods etc., which have not gained practical importance, have been reviewed elsewhere [67Arg]. Some methods, which have been employed to some extent and cannot be fitted easily into one of the groups reviewed above, are briefly treated in the following. 

Ultrasonic methods can also be applied to velocity measurements based on measurement of the Doppler shift in the frequency of an ultrasonic wave scattered from a moving particle. The angle between the velocity vector and the direction of ultrasound propagation must be known, which practically limits the appHcation of the technique to the measurement of unidirectional flows. However, this Hmitation may be overcome again by the use of an array of transducers [11]. 

Suhtnicion nickel powders luive been synthesized successfully from aqueous NiCh at various tempmatuTKi and times with ethanol-water solvent by using the conventional and ultrasonic chemical reduction method. The reductive condition was prepared by flie dissolution of hydrazine hydrate into basic solution. The samples synthesized in various conditions weae claractsiz by the m ins of an X-ray diffractometry (XRD), a scanning electron microscopy (SEM), a thermo-gravimetry (TG) and an X-ray photoelectron spectroscopy (XPS). It was found that the samples obtained by the ultrasonic method were more smoothly spherical in shape, smaller in size and narrower in particle size distribution, compared to the conventional one. 

To find the effect of reaction temperature and ultrasoimd for the preparation of nickel powders, hydrothermal reductions were performed at 60 °C, 70 °C and 80 °C for various times by using the conventional and ultrasonic hydrothermal reduction method. Table 1 shows that the induction time, when starts turning the solution s color to black, decreases with increasing the reaction temperature in both the method. The induction time in the ultrasonic method was relatively shorter, compared to the conventional one. It assumes that hydrothermal reduction is faster in the ultrasonic method than the conventional one due to the cavitation effect of ultrasound. 

As the previously shown in Table 1, the tap density of the mple obtained by using the ultrasonic method was relatively higher than that obtained by the conventional one. The reason is that the surface morphology and particle size of fee sample obtain by the ultrasonic method are much smooth and small as fee shown in SEM results, respectively. 

Alig et al. [194] have reviewed new ultrasonic methods for characterisation of polymeric materials. 

Unusual nanostructures with different shapes of mercury oxide have been synthesised by the direct ultrasonic method [29]. Influence of different factors on the size, morphology and crystallinity of HgO nanocrystallites has been reported. The effect of ultrasound on the size and morphology of the nanoparticles has been confirmed... 

Askarinejad A, Morsali A (2009) Synthesis and characterization of mercury oxide unusual nanostructures by ultrasonic method. Chem Eng J 153 183-186... 

There are several approaches to measuring electrolyte sensors [13], ultrasonic methods (acoustical), photo-acoustic cells [14] (Siemens C02 Controller), optical IR-detection and liquid-state electrochemical... 

A very reactive form of a finely divided metal is a so-called Rieke powder [79]. These materials are produced as fine powders by chemical precipitation during the reduction of various metal halides ivith potassium metal in refluxing tetrahydrofuran. Obviously this is a potentially hazardous laboratory procedure and ultrasound has provided an alternative method of preparation of these extremely valuable reagents [80]. The sonochemical technique involves the reduction of metal halides with lithium in TH F at room temperature in a cleaning bath and gives rise to metal powders that have reactivities comparable to those of Rieke powders. Thus powders of Zn, Mg, Cr, Cu, Ni, Pd, Co and Pb were obtained in less than 40 min by this ultrasonic method compared with reaction times of 8 h using the experimentally more difScult Rieke method (Tab. 3.1). 

Hydrogenated isoxazole derivatives were obtained by single electron transfer (SET) cyclization of /9,y-unsaturated oximes , by thermal [4- -2] cycloaddition of aldox-imes or ketoximes to conventional dienophiles or isomerization/cyclization of an ortho halogeno or nitro-substituted amidoximes. Preparation of 1,4-disubstituted 3-hydroximino-2-nitro-l-butenes and their oxidative cyclization to 4-nitroisoxazoles are reported " . Synthesis of fluorine-containing substituted isoxazolidines as well as isoxazoles by ultrasonic methods has been also described. 

Culea et al. reported a quantitative GC-MS analysis of procaine and some neurotransmitters in rat brain tissue [94], Procaine was extracted fi om brain homogenates by the ultrasonication method of Sundlof et al. [95], and was determined in its underivatized form on a 24 m glass capillary column coated with Silar IOC (temperature programmed from 120°C to 225°C at 12°C/min with pyrene as the internal standard). It was found necessary to wash the injector liner and the GC-MS interface stainless steel tubing with 1 1 0.1 M KOH-methanol so that the interface tubing could be coated with a film of OV-17 (from acetone solution), and to condition the apparatus by injecting bis-(trimethylsilyl)-acetamide and triethylamine. 

Our choice of methods is not exhaustive. We have not, for example, covered shock or ultrasonic methods, electrolytic methods, or the preparation of heterogeneous catalysts. Our aim here, therefore, is not to provide a way of choosing the method for a particular product. (Indeed, several of the examples given in this chapter demonstrate that several methods can be suitable for one substance.) Instead, we hope to give a few pointers to deciding whether a particular method is suitable for a particular material. 

As decribed in Chapter 4.3.2, it is increasingly common to design and manufacture such apparatus as monobloc reactors. Furthermore with modem testing facilities with, for example, ultrasonic methods it is possible to check the finished apparatus up to wall-thicknesses of 350 mm. These developments are an excellent contribution for the safe operation of high-pressure vessels. 

Perturbation of a chemical equilibrium by ultrasound results in absorption of the sound. Ultrasonic methods determine the absorption coefficient, a (neper cm-1), as a function of frequency. In the absence of chemical relaxation the background absorption, B, increases with the square of the frequency f (hertz) that is, a/f2 is constant. For a single relaxation process the absorption increases with decreasing frequency, passing through an inflection point at the frequency at (radians sec-1 = 2nf) which is the inverse of the relaxation time, t (seconds), of the chemical equilibrium [Eq. (6) and Fig. 3]. 

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