Nip Width Research Articles

A COMPARISON OF THE THEORY WITH THE EXPERIMENT OF THE VISCOELASTIC BEHAVIOR OF ROTATING RUBBER-COVERED ROLLES

The nip width and the driving torque were measured during rotation of metal and rubber-covered rollers under dead weight and with constant peripheral speed. The characteristic values of mechanical model of the cover were also decided from the measurement of the dynamic modulus and tan δ of the rubbers, and a comparison of the dynamic mechanical characteristic of model with them was made.Comparing the experimental results with the calculated ones using the method explained in the previous paper, the following conclusions were obtained:(1) In our test apparatus the center distance between the rollers changes with peripheral speed, particularly when soft rubber is used. Thus our theory is compared with the experiments of hard rubber-covered rollers.(2) The nip width during rotation is smaller than that of standing still, and it decreases with an increase in peripheral speed.(3) For soft rubber-covered rollers the rolling friction increases with an increase in peripheral speed, and for rollers covered by hard rubber it is constant or decreases in the high range of speed.(4) The experimental results do not coincide with the calculated ones. The disagreement is considered to arise from the fact that the characteristic values of mechanical model are decided on the basis of the measurement of the dynamic modulus of the cylindrical test pieces, where the free deformation of the test piece is allowed.

Mill Processing Behavior of Ethylene-Propylene-Hexadiene Terpolymers

The mill processing behavior of ethylene/propylene/hexadiene terpolymers, one type of EPDM, has been described. In agreement with the general observations of Tokita and White, the milling characteristics of the polymers change from an elastic band (region 2) to a crumbling bag (region 3) and then to a viscoelastic fluid (region 4) as the temperature is increased from 5°C to 175°C. The 2–3 transition can be treated as a failure process which is time and temperature dependent. Hence, a continuous curve relating the transition nip setting; and the temperature exists for each polymer sample. The transition nip setting at a given temperature (or the transition temperature at a given nip width) was found to be wider (or higher) for samples of broader molecular weight distribution.

ANALYSIS OF BEHAVIOR OF ROTATING RUBBER-COVERED ROLLER BY A VISCOELASTIC MODEL

In this paper the mechanical behavior of a rubber-covered roller which is pressed against a metal roller under constant load and rotates with constant peripheral speed is analyzed on the basis of a viscoelastic model.The results are as follows:(1) Assuming that the behavior of rubber is represented by a model constructed of a Voigt model combined in series with a spring of modulus G0, the nip width is given by the following equation when rollers stand still.where W: load 1: rubber thickness L: roller width R: 1/R1+1/R2=1/R R1: radius of a rubber-covered roller R2: radius of a metal roller D: (G0+G)/G G: modulus of spring in Voigt model(2) When rollers rotate, the nip width decreases with its peripheral speed.(3) When rollers rotate, the pressure distribution becomes asymmetric to incline to the opposite direction of rolling.(4) The rolling friction increases with increasing peripheral speed, and the larger the instantaneous modulus, the value on the basis of the nip width at rest becomes larger.

A theoretical study of liquid‐film spread heights in the calendering of newtonian and power law fluids

AbstractThe relationship between spread height and upstream reservoir thickness, with power low coefficient as parameter, was obtained analytically. At all values of n studied, the value of r (ratio of spread height to nip width) increases with increasing values of H/ho where H is upstream reservoir thickness and ho is nip width. At higher values of H/ho, the curves of r, versus H/ho tend to “flatten” out, and r approaches an asymptotic value. For example, the asymptotic value of r for Newtonian fluids (power law constant of 1) is 1.226. Asymptotic values of r increase with decreasing values of the power law constant.

DYNAMICAL PRESSURE DISTRIBUTIONS OF MANGLIHG ROLLERS

The pressure distribution along the arc between contacting rollers is one of the essential factors of mangling action. In this experiment, a rubber-covered driven roller 14cm in diameter and metal driving roller 16cm in diameter were used as a test apparatus. With a pressure transducer mounted radially in the metal roller, the pressure distribution was measured in a range of the surface speed of the roller between 4.38m/min and 24.31m/min.The results obtained were as follows:1. The pressure distribution along the arc of contact of the test mangle can be expressed by the formula: where f(x) is an normalized pressure distribution along the arc of contact and the coefficients a, b, c and d are the parameters of cubic expression calculated from the ratio between the measured and the Hertzian pressure distribution using the method of least squares.2. As the surface speed of the metal driving roller is increased, the nip width is decreased and the maximum pressure is increased. Further, the pressure distribution is deformed as if the maximum point of pressure distribution moves to the opposite direction of rotation of mangling rollers.3. The statical theory seems to be applicable to the mangling actions of the test apparatus within the range of nip width over 0.7cm, third order moment less than -0.3, and the maximum value of pressure distribution over 5kg/cm2.As a result, the dynamical theory should be applied to mangling actions in the region out of the above mentioned.

Calculation of the Behavior of Rubber-Covered Pressure Rollers

Abstract Data are given which enable the properties of nips between metal and rubber-covered pressure rollers to be calculated from the parameters of the system. The properties with which the calculation is primarily concerned are the nip width and the mean pressure in the nip, but the principle can be extended to include the peak pressure and the distribution of pressure through the nip. The calculation is based on the well-known Hertzian formula and on empirical relations, which express the important effects of the rubber-cover thickness. The data refer not only to roller systems in which the loading is uniform, but also to non-uniform nips, in particular to those which show what is probably the commonest cause of non-uniformity, roller deflection. Although the calculations refer primarily to nips between one hard roller and one relatively soft, covered, roller, they are directly applicable to nips between two identical covered rollers and may be applied, within limits, to systems in which the rollers are dissimilar in properties.

Calculation of the behaviour of rubber-covered pressure rollers

Data are given which enable the properties of nips between metal and rubber-covered pressure rollers to be calculated from the parameters of the system. The properties with which the calculation is primarily concerned are the nip width and the mean pressure in the nip, but the principle can be extended to include the peak pressure and the distribution of pressure through the nip. The calculation is based on the well-known Hertzian formula and on empirical relations, which express the important effects of the rubber-cover thickness.