Pendulum effect

Pendulum effect Refers to the pull of gravity on a body tendency of a pendulum to return to a vertical position. 

Figure 5.2. (a) Arrangement of a Snoek pendulum, (b) Internal friction as a function of temperature, at different pendulum frequencies, for a solution of carbon in iron, (c) Diffusion of carbon in iron over 14 decades, using the Snoek effect (-30-200°C) and conventional radioisotope... 

It is worthwhile to present this episode in eonsiderable detail, beeause it eneapsulates very elearly what was new in physieal metallurgy in the middle of the eentury. The elements are an aecurate theory of the effects in question, preferably without disposable parameters and, to check the theory, the use of a technique of measurement (the Snoek pendulum) which is simple in the extreme in construction and use but subtle in its quantitative interpretation, so that theory ineluctably comes into the measurement itself. It is impossible that any handwaver could ever have conceived the use of a pendulum to measure dissolved carbon concentrations ... 

Stokes, G.G., 1851. On the effect of the internal friction of fluids on the motion of pendulums. Transactions of the Cambridge Philosophical Society, 9, 8. 

Pendulum technique The basic principle involved is gravity or the plumb-bob effect. ... 

Pendulum hookup A bit and drill collar with a stabilizer to attain the maximum effect of the pendulum. 

Assume that we have a pendulum (Fig. 6-14) provided with a piece of soft iron P placed coaxially with a coil C carrying an alternating current that is, the axis of the coil coincides with the longitudinal axis OP of the pendulum at rest. If the coil is excited, one finds that the pendulum in due course begins to oscillate, and th oscillations finally reach a stationary amplitude. It is important to note that between the period of oscillation of the pendulum and the period of the alternating current there exists no rational ratio, so that the question of the subharmonic effect is ruled out. 

Explosive D is approx 80% as brisant as TNT, as indicated by sand tests, but fragmentation tests in shell have shown it to be about 95% as brisant. Both expls have about the same rate of detonation at a d of 1.56g/cc hence, approx equality of brisance would be expected. The rate of detonation of Explosive D has been found to be somewhat affected, particularly at lower loading densities, by the granulation of the material, but this effect is not pronounced. Its expl strength is 98% that of TNT, as evidenced by the ballistic pendulum test (see below)... 

A mechanical system, typified by a pendulum, can oscillate around a position of final equilibrium. Chemical systems cannot do so, because of the fundamental law of thermodynamics that at all times AG > 0 when the system is not at equilibrium. There is nonetheless the occasional chemical system in which intermediates oscillate in concentration during the course of the reaction. Products, too, are formed at oscillating rates. This striking phenomenon of oscillatory behavior can be shown to occur when there are dual sets of solutions to the steady-state equations. The full mathematical treatment of this phenomenon and of instability will not be given, but a simplified version will be presented. With two sets of steady-state concentrations for the intermediates, no sooner is one set established than the consequent other changes cause the system to pass quickly to the other set, and vice versa. In effect, this establishes a chemical feedback loop. 

In the case when the pendulum path is an ellipse the effect of the earth s rotation is to cause the ellipse to rotate with an angular velocity equal to (—co sin X). As we know, at the poles it is approximately 7.3 x 10 s. In accordance with Equation (3.94), for an observer located at the z-axis above the earth the rotation is clockwise in the northern hemisphere, (A>0), and counterclockwise in the southern hemisphere, (A<0). For example, at the North Pole the direction of the pendulum rotation and the earth are opposite to each other. During swinging the pendulum moves from the point a to the opposite point of the path b, which is shifted at some small distance because of the earth s rotation. Fig. 3.5c. Suppose that the radius of the circle is sq, then the displacement bd during a half period of swinging, Tjl, is... 

A very similar application of the modified Bloch equations was based in the work of Adams and Connelly.4 ESR spectra (Figure 5.8) of [Mo P(0 Me)3 2(MeC = CMc)Cp] show the expected triplet (two equivalent 31P nuclei) at 280 K, but only a doublet at 160 K. At intermediate temperatures, the lines broaden. The interpretation is that the alkyne undergoes a pendulum oscillation, which in the extrema diverts spin density from one or the other phosphite. Interestingly, the diamagnetic cation undergoes a similar motion on the NMR time scale, but then the alkyne undergoes a complete rotation. Thus, analysis of the effect leads to a measure of the rate of the oscillation. The... 

The networks studied were prepared from reactions carried out at different initial dilutions. Aliquots of reaction mixtures were transferred to moulds, which were maintained at the reaction temperature under anhydrous conditions, and were allowed to proceed to complete reaction(32). Sol fractions were removed and shear moduli were determined in the dry and equilibrium-swollen states at known temperatures using uniaxial compression or a torsion pendulum at 1Hz. The procedures used have been described in detail elsewhere(26,32). The shear moduli(G) obtained were interpreted according to Gaussian theory(33 34 35) to give values of Mc, the effective molar mass between junction points, consistent with the affine behaviour expected at the small strains used(34,35). 

An apparatus which demonstrates the Gough-Joule effect. It comprises a pendulum adjusted so that a rubber sample is under stretch. Heat from a lamp causes the rubber to contract and swing the pendulum. This pulls the rubber into a shaded section where it extends and moves the pendulum back to the original position, whereupon the cycle is repeated. 

The Griffin mill is similar to the pendulum mill, other than it employs only one grinding head and the separation of the product is effected using a screen mesh fitted around the grinding chamber. A product fineness from 8 to 240 mesh at an output from 0.15 to 1.5 kg/s may be obtained. These mills are widely used for dry fine grinding in many industries and are noted for their simplicity and reliability. 

The tests most used are Ballistic Mortar and Trauzl Block Tests. See also Ballistic Pendulum, Coefficient d utilisation pratique, Cratering Effect, Kraftzahl, Mortar Test and Quinan Test. Cook (1958), pp 36-7 claims... 

Ballistic pendulum) 5-23 5-24 (Trauzl test) and 5-28 5-29 (Cratering effect) 27) C.G. Dunkle private communication, Jan 1968... 

It is to be Qoted that the total effective work capacity of an explosive usually has two resultants — (1) fragmentation and (2) blast effect or the movement of matter. These can be measured separately. As there is no shattering effect in the ballistic pendulum test, this test may be considered to measure total effective work capacity Ref W.H. Rinkenbach, Private communication, Allentown, Pa, Feb 20, 1964 Detonation, ZND (ZeTdavicb- von Neumann-Doering) Model. See Detonation NDZ (Neumann-Doring-Zel dovich) Theory, pD454... 

KL) Anon, "Military Explosives", TM 9-1300-214/TO 11A-1-34 (1967). Chapter 5. Properties and Tests of High Explosives Sensitivity to Frictional Impact (pp 5 1 to 5-3) Sensitivity to Friction (5 3 to 5-6) Sensitivity to Frictional Impact (5-6) Sensitivity to Heat and Spark, which includes Explosion Temperature Test (5-6 to 5-9) Sensitivity to Initiation (5-9) Stability Tests, which include 75° International Test, 100° Heat Test, Vacuum Stability Test and Potassium Iodide—Starch Test (5 9 to 5-15) Brisance Tests which include Sand Test, Plate Dent Test and Fragmentation Test (5 15 to 5-18 and Fig 5 13 on p 5-19) Initiating Value (5-18 5-20) Sympathetic Detonation (5-20 to 5-21) Power which includes Heat of Explosion Test, Ballistic Pendulum Test and Trauzl Lead Block Test (5-21. to 5-24) Blast Effect (5-24 to 5-27) Cratering Effect (5-28 5 29) and Munroe-Neumann Effect (5-29 to 5 35)... 

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