Ultrasonic drilling

Also used for hardness determination are impact abrasion and rattle methods. In impact abrasion methods (impact abrasion hardness), three abrasive techniques are used a freely falling abrasive grain flow—the Scott tower method (Fig. 4.4.3a and b), pressure abrasion—the Macken-sen-Zeiss blower method (Fig. 4.4.7), and ultrasonic drilling—the Sonic Mill method (Fig. 4.4.18). 

Drilling by a diamond-tipped drill bit (15 s per hole) is much faster than ultrasonic drilling (15 min per hole). On the other hand, ultrasonic drilling allows all holes to be drilled simultaneously with a multi-tipped ultrasonic drill bit [ 108]. 

The appearances of the holes formed by ultrasonic drilling, laser machining, and sand-blasting are compared in Figure 2.9 [104]. 

FIGURE 2.9 SEM micrographs of micromachined holes in borosilicate glass using three different methods, (a) Ultrasonically drilled hole hole diameter, 500 pm. (b) Laser machined hole hole diameter, 300 pm. (c) Sand-blasted hole hole diameter 1000 pm [104], Reprinted with permission from the Institute of Physics Publishing. 

In order to provide access holes on fused quartz cover chips, laser drilling [151,152,828,1006] or ultrasonic drilling [349,1041] have been used. In order to remove particulates caused by drilling, the drilled quartz plate was rinsed in 0.5% HF for 5-10 min in an ultrasonic bath [153,658]. However, in some cases no drilling was performed, with the end of the channel protruding out of the coverslip [148],... 

Diepold, T., Obermeier, E., Smoothing of ultrasonically drilled holes in borosifi-cate glass by wet chemical etching.. /. Micromech. Microeng. 1996, 6, 29-32. 

The material can be tooled with diamond saws and ultrasonic drilling machines... 

The 45° transducer was used to inspect side drilled holes, with their centres located 40 mm below the surface. Due to the coarse material structure the echoes from the holes were totally masked by clutter. An example of an ultrasonic response signal, emanating from a hole with a diameter of 8 mm, is shown in the left part of Figure 3. Scanning the surface above the 8 mm and 10 mm holes resulted in the B-scan image shown in the upper part of Figure 4. 

Mephisto is devoted to predict the ultrasonic scans (A,B or C-scans) for a priori knowledge of the piece and the defects within. In the present version Mephisto only deals with homogeneous isotropic materials. The piece under test can be planar, cylindrical or have a more complex geometry. The defects can be either planar (one or several facets), or volumetric (spherical voids, side drilled holes, flat or round bottom holes). 

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. 

Besides large-diameter pipes, ultrasonic testing is used for checking the welded joints of drill bits, components of wind-driven electric plants, welded joints of light alloys and non-metallic materials, for an integrated inspection of various objects. A range of training aids developed at the Institute allows the operators to be trained effectively. 

Drilhng. Glass is dtiUed with carbide or bonded-diamond dtiUs under a suitable coolant such as water or kerosene. Other drilling processes include a metal tube rotating about its axis (core drilling), an ultrasonic tool in combination with an abrasive slurry, or an electron beam. Tolerances less than 0.1 mm are readily obtained with diamond-core drilling and, if required, holes smaller than 25 )J.m-dia can be made with the electron-beam method. 

In most ultrasonic tests, the significant echo signal often is the one having the maximum ampHtude. This ampHtude is affected by the selection of the beam angle, and the position and direction from which it interrogates the flaw. The depth of flaws is often deterrnined to considerable precision by the transit time of the pulses within the test material. The relative reflecting power of discontinuities is deterrnined by comparison of the test signal with echoes from artificial discontinuities such as flat-bottomed holes, side-drilled holes, and notches in reference test blocks. This technique provides some standardized tests for sound beam attenuation and ultrasonic equipment beam spread. 

We need the porosity. R is given by R in the lower sand. We also need R. Ultrasonic Caliper and Sonic Log while Drilling... 

The connection between the use of ultrasound for the machining and drilling of hard materials (see below) and dentistry is clear since tooth enamel is a very hard material. In the dentist s surgery a new instrument has been introduced which is essentially a small ultrasonic probe operating at 25 kHz with a variety of attachments. Although... 

Archaeological bone samples were treated for diagenesis before sample analysis. The bone samples were first mechanically cleaned with the Patterson NC-350 dental drill equipped with a carbide burr to remove any organic matter or contaminants. The mechanical cleaning also removed the layers of cortical bone most susceptible to diagenetic contamination, as well as all traces of trabecular bone. The bone samples were then chemically cleaned in an ultrasonic bath. The samples were first sonicated in water for 30 minutes, then rinsed and sonicated in 5% acetic acid for 30 minutes, and finally rinsed and sonicated with 5% acetic acid for 5 minutes (30, 53, 55, J9).The bone samples were dried for 1 hour at approximately 80°C. Finally, the bone samples were placed in a crucible and ashed at approximately 800°C for 10 hours. 

Drill a hole (3mm i.d.) through a PYC rod (8mm o.d., 4cm long) and insert the GC rod (diameter = 3 mm, length = 5 cm) so that it fits tightly in the PVC rod, resulting in a GC disk electrode (Fig. 4.1). Polish the GC disk electrode surface with successively finer grades of sandpaper and diamond pastes, and finally with 0.3 pm alumina. Clean ultrasonically for at least 15 min. 

HF etching (4 min, 1 mm dia., 145 um deep) C02 laser drilling Ultrasonic abrasion Electrochemical discharge machining Powder blasting... 

The fluid oscillations can be detected by shuttle balls, ultrasonic and piezoelectric detectors. In noisy installations, dual piezoelectric elements provide noise compensation. The various detectors can measure one of the following (1) the oscillating flow across the face of the bluff body, (2) the oscillating pressure difference across the sides of the bluff body, (3) the flow through a passage drilled through the bluff body, (4) the oscillating flow or pressure at the rear of the bluff body, or (5) the presence of free vortices downstream to the bluff body. 

Ultrasonic machining (USM) is also of particular importance when very hard type materials are to be cut. As an assist to drilling, HDM energy can extend the drill life when producing holes in reinforced plastics. If the plastic is conductive, electrical discharge machining (EDM) or electrochemical machining (ECM) may be useful. 

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