Pendulum technique

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

The automation of the torsion pendulum utilizing a desktop computer eliminates the tedious data analysis previously associated with that technique. Any one of four data reduction methods can be used the experimental conditions will determine which is the optimum one to employ. The torsion pendulum technique provides quantitative values of shear modulus and logarithmic decrement and in the torsion braid mode provides a qualitative analysis of materia i, especially in the liquid-to-solid transition region. 

Sai] Inverted torsion pendulum technique, infinred analysis of C using a high frequency combustion technique Internal friction cold rolled C-Fe-Si samples with small amount of Si (0.050 to 0.832 mass%) and C (0.45 to 0.47 mass%) and decaburization annealing at 700°C... 

Characterization and evaluation of performance by means of the torsional pendulum technique has been discussed by Hussain Wierenga et al. have used ultramicro indentation measurements for the determination of the viscoelastic properties of coated optical fibers... 

To verify this supposition, the FIR spectra of MMA and oc-methyl styrene oligomers and also of cross-linked PS and PMMA have been considernL In addition, the FIR spectra of cross-linked PMMA (MMA-DMEG copolymers) were compared with the mechanical loss spectra measured by torrional pendulum technique at 1 Hz in the range 100-450 K. 

Many different experimental techniques exist today to study the effects of elevated temperature on dynamic mechanical properties of plastics. Perhaps, the most meaningful and simplest technique is the torsion pendulum technique. Using this technique, one can derive a plot of short-time modulus versus temperature up to the beginning of melting and degradation. 

Zayas VA, Low SS, Mahin SA (1990) A simple pendulum technique for achieving seismic isolation. Earthquake Spectra 6 317-333... 

As discussed in section 15. 4.1, the shear modulus of fibers is important, and it determines the fiber torsional rigidity. The shear modulus of a fiber can be measmed by using the torsion pendulum technique. Figure 15.32 shows the schematic of a... 

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 ... 

The Snoek pendulum, which in the most general sense is a device to measure relaxations, has also been used to measure relaxation caused by tangential displacements at grain boundaries. This application has been the central concern of a distinguished Chinese physicist, Tingsui Ke, for all of the past 55 years. He was stimulated to this study by Clarence Zener, in 1945, and pursued the approach, first in Chicago and then in China. This exceptional fidelity to a powerful quantitative technique was recognised by a medal and an invitation to deliver an overview lecture in America, recently published shortly before his death (Ke 1999). 

There are several other comparable rheological experimental methods involving linear viscoelastic behavior. Among them are creep tests (constant stress), dynamic mechanical fatigue tests (forced periodic oscillation), and torsion pendulum tests (free oscillation). Viscoelastic data obtained from any of these techniques must be consistent data from the others. 

Torsion property As noted, the shear modulus is usually obtained by using pendulum and oscillatory rheometer techniques. The torsional pendulum (ASTM D 2236 Dynamic Mechanical Properties of Plastics by Means of a Torsional Pendulum Test Procedure) is a popular test, since it is applicable to virtually all plastics and uses a simple specimen readily fabricated by all commercial processes or easily cut from fabricated products. 

Methods employed to determine the impact resistance of plastics include pendulum methods (Izod, Charpy, tensile impact, falling dart, Gardner, Dynatup, etc.) and instrumented techniques. In the case of the Izod test, what is measured is the energy required to break a test specimen transversely struck (the test can be done either with the specimen notched or unnotched). The tensile impact test has a bar loaded in tension and the striking force tends to elongate the bar (Chapter 5, Impact Strength). 

One of most popular techniques for dynamic mechanical analysis is the torsion pendulum method. In a modification of this method designed to follow curing processes, a torsion bar is manufactured from a braid of fibers impregnated with the composition to be studied this is the so-called torsional braid analysis (TBA) method.61 62,148 The forced harmonic oscillation method has been also used and has proven to be valuable. This method employs various types of rheogoniometers and vibroreometers,1 9,150 which measure the absolute values of the viscoelastic properties of the system under study these properties can be measured at any stage of the process. The use of computers further contributes to improvements in dynamic mechanical analysis methods for rheokinetic measurements. As will be seen below, new possibilities are opened up by applying computer methods to results of dynamic measurements. 

WCo2 = r = h4Pco00 corresponding to the E-R mechanism is not satisfied. At present the pendulum has swung to the opposite side and most research workers [98] are sure that, over a wide range of the reaction parameters (T = 450-950 K, P = 10-7 to 10 5 Torr), only the adsorption mechanism (L-H) is valid. This belief is based on the data obtained in unsteady-state experiments and using modern physical methods, in particular the molecular beam technique [98, 52, 107]. But a fairly good qualitative description on the basis of the L-H mechanism has been obtained in only a few cases [56, 57] and this description concerns rather limited experimental... 

Various types of vibration experiments can be carried out to measure E and E2 at a certain frequency. An example is the torsion pendulum, in which the sample, connected to an auxiliary mass, is brought into a free torsional oscillation. From the frequency of the pendulum (around 1 to 10 sec) E is calculated, from the rate of damping tan 8 and E2. Other types of dynamic mechanical measurements can be carried out at higher frequencies, such as bending vibrations with or without extra mass, wave propagation, etc. By combining a number of these different techniques, a time scale ranging from 10 to 10"8 sec can be covered. 

The last decade saw the pendulum swing the other way, It was appreciated that there is no conflict between computer and graphical techniques, and that the two can coexist. It was realized that tbe graphical techniques themselves can be programmed and used side fay side with computer simulation. This hybrid approach combined the speed and accuracy of the computer with the analytical and visual value of tbe graphical techniques. 

Other techniques that have been introduced recently in association with adsorption manometry include the use of a magnetic suspension balance (Dreisbach et al., 1996) and a rotational pendulum (Keller, 1995). 

Some experimental techniques yield a modulus rather than a sound speed, but the underlying physical properties are the same. In a torsional pendulum, for example, the shear modulus, G, is measured while in a Rheovibron, Young s modulus, E, is measured. When there... 

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