Simplified Measurements Research Articles

Adaptation of the Rheovibron to the Measurement of Dynamic Properties of Vulcanizates at Elongations up to Sample Rupture

Abstract The Rheovibron dynamic tester can be adapted to the measurement of dynamic properties of elastomers at high deformations, up to sample rupture. The method used is superimposing small sinusoidal oscillations on statically extended specimen. In order to obtain significant dynamic data it is necessary to determine the value of Kc exactly, the correction factor for instrumental displacements, as well Kv, to correct for the deformation of the part of the specimen held within the clamps. It appears that Kv is dependent on amplitude, frequency, temperature, and sample characteristics and must be determined for each sample at each imposed condition separately. At higher extensions Kv corrections assume a major ro^le in the measurements, greatly complicating the procedures. The method for calculation of the correction factors advanced by Massa for glassy polymers does not hold for elastomers. A novel specimen arrangement has been developed, resulting in a zero Kv correction, independent of amplitude, frequency or temperature. With elastomers the Kc correction is generally also zero, leading to greatly simplified measurements as well as to more accurate results. The temperature control system of the Rheovibron was modified to permit specimen temperatures in the range of − 70° to +120° C, either at programmed increases or decreases or at any constant temperature in the range. The movement of the extension clamp was motorized, to ensure a regular, reproducible motion.

Average Mechanical Impedance for Random Vibration

The response of a system to a random stationary process applied at selected points of a mechanical structure is readily formulated in terms of the mechanical impedance matrix of these points. However, in practice the results suffer from many uncertainties: uncertainties in the measurements of the mechanical impedances; uncertainties in the boundary conditions of the subsystems; uncertainties in the power spectral densities of the excitation itself. These uncertainties are reviewed. The propagation of the uncertainties in the calculations lead to errors which grow rapidly with the complexity of the calculations. At the other extreme, simplified but approximate calculations using average (over frequency bands) impedances lead to errors which do not grow as rapidly because the dynamic range of average impedances is much smaller than the dynamic range of true impedances, and because the calculation format is simpler. The simplified measurements of, and calculations with, average impedances may be used either as a practical criterion for determining where the classical calculations break down, or as a practical compromise in the estimates of the response.

Determination of the Pressure Drop Optimum Pipe Size for a Two-Phase Slug Flow in an Inclined Pipe

A simple model of two-phase slug flow in inclined pipes is proposed. The model parameters are determined experimentally using five different size copper pipes at 5, 10, 15 deg inclinations on an air-water mixture at one atmosphere with up flow. The model predicts the total pressure gradient due to the sum of gravity and wall shear stresses. An investigation of the relationship between pressure gradient and pipe size results in an optimum pipe size at which the pressure gradient is minimum. A comparison between the simplified model predictions and experimental measurements shows a good agreement in the total pressure drop.

Simplified Direct Speed Measurements of Nonrepetitive Signals

A method is described for measuring speed directly without the necessity of any subsequent calculations. Using basically the method of discharging a capacitor through a resistor the advantage consists in matching the voltage to the hyperbolic velocity vs time relation. Thus, by giving a direct speed readout, this inexpensive design is preferable in many cases to the generally used counters and oscilloscopes. Speeds in practically all ranges can be measured and accuracies within fractions of a percent can be achieved. This opens wide fields of application in ballistics, gas dynamics, and primarily in shock tube techniques.

Paper 5: The Correlation between Subjective Assessments and Physical Measurements of the Vibratory Motion in a Saloon Car

Panels of observers travelled short distances in three vehicles, which were identical except for suspension components. The motion experienced by the observers was varied by alterations to tyre pressures, spring rates, dampers, and types of road surface, and was measured by accelerometers and a gyro feeding a magnetictape recorder or a galvo-recorder. Good correlation was found between subjective assessments and simplified data obtained from detailed frequency analyses of the recorded motions of the vehicles. It is shown that the average vertical acceleration passed by a 0·75-6-c/s filter as measured by an accelerometer placed between a passenger and his seat is a good measurement of how subjects react to the low-frequency ride of a vehicle. Higher frequency floor motions, measured as the average acceleration passed by a 7-50-c/s filter, also showed good correlation with subjective assessments. The average angular displacement in pitch passed by a 0·75-6-c/s filter showed some relationship with subjective assessments of pitching of the vehicles, but roll was seldom commented on by the subjects. The simplified measurements of linear and angular motions in two relatively wide frequency bands yield useful ride quality data; the information can be obtained by the use of relatively simple and inexpensive equipment.

Calcium studies in malignant tumors.II. Application of simplified measurements to clinical problems

Calcium studies in malignant tumors.II. Application of simplified measurements to clinical problems

Integrating instruments for simplified quality-control measurements

In quality control work, it is often necessary to determine the mean and the standard deviation of an important variable. To accomplish this, a measurement system has been developed for applications in which the material is tested while moving continuously, most of the necessary calculating functions being performed by two new integrating instruments. This paper describes the application of such a system to the measurement of yarn thickness.

Simplified Measurements of Phase and Frequency Modulation Caused by Flutter in Sound Recording

Laboratories and small manufacfacturers are frequently faced with the problem of accurately measuring the flutter content of sound recording equipment, but are not able to do so because of the cost and/or measuring limits of commercial flutter meters. Although flutter is basically undesirable speed variations of the recording medium due to imperfections of the mechanical drive system, the principal annoyance value that flutter causes is frequency modulation of the intelligence signal. This paper describes flexible and comparatively simple methods of measuring phase and frequency modulation effects caused by flutter and how these measurements can be used to determine quantitative and qualitative values of flutter.

On the Radiation of Sound into a Circular Tube, with an Application to Resonators

The radiation from a plane piston into a rigid circular tube is treated. Consideration is given to the propagation of higher order sound waves. Curves of radiation impedance and pressure distribution are given together with an analysis of the elements of the equivalent impedance circuits. In addition to the closer study for special values of the tube's end impedance, some outline of the general case is given. Simplified measurements verify the calculations in the case of a tube closed by a rigid wall. Finally, the resonance frequency of cylindrical resonators is discussed.

Simplified Porosity Measurements

With the increasing importance of acoustical impedance and its relation to flow resistance and porosity in homogeneous porous materials, a simplification in the technique of porosity measurement seems in order. It is the purpose of this paper to describe a dynamic method of measuring porosity. The essential feature of the dynamic method is the use of the compliance of the air in the pores of the material to control the period of the free damped oscillation of a mechanical system. The dynamic method has the advantage of small temperature dependence and minimal time for a single measurement.

Simplified Flow Resistance Measurements

A simplified apparatus for the measurement of the flow resistance of porous acoustical materials is described. The method used is absolute, not comparative. An improved technique for the preparation of the samples is discussed.

Simplified measurements of sound absorption

Discussion and authors' closure of a paper by Arthur L. Albert and Tom B. Wagner published in the August 1934 issue, page 1160–2, and presented for oral discussion at the selected subjects session of the Pacific Coast convention, Salt Lake City, Utah, September 7, 1934.

Simplified measurements of sound absorption

A modification of the tube or reflected wave method for measuring the sound absorption coefficients of acoustic and building materials over a wide frequency range is described in this paper. Modern communication equipment is used, and a high degree of reliability is obtained. The method is especially well adapted to rapid routine tests of acoustic materials in commercial production, and in other instances where measurements by the more elaborate and expensive reverberation-chamber method are not justified.

Simplified Measurements of Sound Absorption

A modification of the tube or reflected wave method for measuring the sound absorption coefficients of acoustic and building materials over a wide frequency range is described in this paper. Modern communication equipment is used, and a high degree of reliability is obtained. The method is especially well adapted to rapid routine tests of acoustic materials in commercial production, and in other instances where measurements by the more elaborate and expensive reverberation-chamber method are not justified.