Mechanical Torque Measurements

Reliable torque measurement is indispensable for protecting the extruder. Here, two speed ranges are particularly important. One of them is zero speed, when large torques can stress the screw shafts during start-up if the screw shafts are jammed by solidified product or product residue. The other is the operating situation when nominal extruder torque has been reached and the mechanical safety clutch should be kept from triggering. Case one is... 

Rake torque measurement is usually provided by the thickener manufacturer as part of the rake drive mechanism. Typical methods involve load cells, motor power measurement, hydraulic pressure, or mechanical displacement against a spring. Torque-measuring devices are designed to produce a signal that may be utilized for alarming or control. 

PA-6 (85) / PP (7.5-15) / PP-g-AA (6% AA) (0-7.5) internal mixer or TSE at 235-255°C / selective solvent extraction / morphology /mechanical and viscosity properties / reaction kinetics from torque measurements Dagli etal., 1994... 

Mechanical for measurement of position, velocity, acceleration, force, pressure, stress, strain, torque, flow velocity, viscosity, etc. 

MBBA SiO, oblique evaporation Direct measurement of the mechanical torques in a deformed nematic 10 (in the vicinity of Tni) [73]... 

Here, the sample is subjected to a sinusoidal oscillating mechanical deformation, in the rheometer s preheated test chamber, which is opposed by a mechanical resistance, measured as torque. The time for 90% or 95% increase in torque for a rheograph is regarded as the optimum cure time. The rise in torque is considered to be proportional to increase in crosslink density and the crosslink density determines the physical properties of the compounded rubber. 

Mechanical Properties of Native and Chemically-Modified Zein Mechanical strength measurement was performed to evaluate the bulk properties of the tensile bars from both native and chemically-modified zeins. Triediylene glycol (TEG) is an excellent plasticizer (12) for zein. Native and chemically modified zeins were each blended with either 10 or 1S% TEG in a Haake Rheocord 90 torque rheometer equipped with high shear roller blades to yield a taffy like matrix. The rheometer was stopped when the torque dropped and became constant. 

Finally, there are some unique measurements of the mechanical torque connected with an elastic deformation of the nematic. Faetti et al. [63] determined the splay and bend elastic constants by means of such torsion measurements, and Grupp [ 139] made measurements of the twist elastic constant 22-... 

In order to determine the viscoelastic properties of silicone gel materials, vibrational measurement techniques are used. The principle of vibrational measurement techniques involves determining die viscoelastic quantities by observing the responding mechanical behavior when cyclic deformation is applied repeatedly. Dynamic viscoelastic property measurements are performed with a dynamic mechanical spectrometer such as the RDA-II from Rheometrics. This instrument measures the complex modulus G and loss factor tan S from the torque measured by the transducer equipped at the upper portion of the sample chamber when shear deformation is applied to the sample at a specified shear strain and frequency from the actuator at the bottom of the sample chamber. 

The cone and plate viscometer is ideal for determining the absolute viscosity of fluids in a small sample volume. The commercially available cone and plate viscometer (e.g., Wells-Brookfield), a precise torque-measuring system, which consists of a calibrated beryllium-copper spring connecting the drive mechanism to a rotating cone, senses the resistance to rotation caused by the presence of sample fluid between the cone and a stationary flat plate. The resistance to the rotation of the cone produces a torque that is proportional to the shear stress in the fluid. The amount of torque is displayed digitally. A commercially available viscometer is illustrated in Figure 7-3fi. 

ILs have been recently evaluated as non-volatile plasticizers and as external or internal lubricants in several polymers including PVC [3], PMMA [4] and polyamides [5]. In this article, an amorphous PL A (polylactide) polymer is blended with two phosphonium-based ILs at various ratios by melt-blending, solution casting and a microencapsulation technique in order to investigate polymer/IL miscibility and its role in the development of a modified polymer with novel rheological, mechanical and thermal characteristics. Results of thermogravimetric analysis, differential scanning calorimetry, capillary rheometry, batch mixer torque measurements and optical microscopy are discussed. 

Belt Presses Belt presses were fiiUy described in the section on filtration. The description here is intended to cover only the parts and designs that apply expression pressure by a mechanism in adchtion to the normal compression obtained from tensioning the belts and pulling them over rollers of smaller and smaller diameters. The tension on the belt produces a squeezing pressure on the filter cake proportional to the diameter of the rollers. Normally, that static pressure is calculated as P = 2T/D, where P is the pressure (psi), T is the tension on the belts (Ib/hnear in), and D is the roller diameter. This calculation results in values about one-half as great as the measured values because it ignores pressure created by drive torque and some other forces [Laros, Advances in Filtration and Separation Technology, 7 (System Approach to Separation and Filtration Process Equipment), pp. 505-510 (1993)]. 

Where stray currents are involved, several measurements have to be taken that are continually changing with time, simultaneously with each other. A double recorder is most suitable for this. Linear recorders with direct indication of the measurements cannot be used for potential measurements because the torque of the mechanism is too small to overcome the friction of the pen on the paper. Amplified recorders or potentiometer recorders are used to record potentials. In amplified recorders, as in amplified voltmeters, the measured signal is converted into a load-independent impressed current and transmitted to the measuring mechanism, which consists of a torque motor with a preamplifier. The amplifier results in an... 

The mechanical power can be calculated with the formula when the RPM and torque are known. Both are measured downhole in Anadrill geosteering system ... 

Mechanical rheometry requires a measurement of both stress and strain (or strain rate) and is thus usually performed in a simple rotating geometry configuration. Typical examples are the cone-and-plate and cylindrical Couette devices [1,14]. In stress-controlled rheometric measurements one applies a known stress and measures the deformational response of the material. In strain-controlled rheometry one applies a deformation flow and measures the stress. Stress-controlled rheometry requires the use of specialized torque transducers in conjunction with low friction air-bearing drive in which the control of torque and the measurement of strain is integrated. By contrast, strain-controlled rheometry is generally performed with a motor drive to rotate one surface of the cell and a separate torque transducer to measure the resultant torque on the other surface. 

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