We investigate experimentally the orientation of the fibers in the flow of both Newtonian and viscoelastic fluids through a parallel plate channel and a channel with an abrupt contraction. We obtain quantitatively the development of the fiber orientation from initial orientation to stable equilibrium orientation along the channel and the variation of orientation in the direction of the channel width. We also study, in the flow through a channel with an abrupt contraction, the fiber orientation along the stream lines which can be found as the path lines of small tracer particles suspended in the fluid. The relation between the fiber orientation and the velocity field is examined. The effects of shear thinning and elasticity on the fiber orientation are also discussed by comparing the results in the viscoelastic flow with those in the Newtonian flow. The conclusions are summarized as follows :
(1) The fibers orient well along the stream lines with an increase in viscoelasticity in both a parallel plate channel and a channel with an abrupt contraction. This phenomenon is essentially equivalent to the phe nomenon that a slender body, namely a straight circular cylinder with a large length to diameter ratio, rotates towards a vertical orientation when falling through quiescent polymer solutions. Both shear thinning and elas ticity, thus, strongly contribute to the orientation process of fibers ; however, elasticity plays a dominant role.
(2) The drastic change of the velocity field is due to viscoelasticity and flow rate in a channel with an abrupt contraction. The fiber orientation state, thus, is strongly influenced by these factors ; the fibers align in a manner of wine-glass shape as the contraction is approached, and the fiber orientation abruptly expands in the immediate downstream region of the contraction in a highly elastic fluid flow.

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The yarn posture in an interlacer is investigated by using a still camera to take photographs of yarns on interlacing process and then by analyzing statistically yarn positions by a micro-computer as a fundamental experiment to clarify the yarn motion in the interlacer. The relations between the yarn positions in the interlacer and the number of tangles are also discussed. Results are as follows.
(1) The cross section of yarn path is divided into 6 areas and the yarn positions within each area are examined in the yarn axial direction in order to analyze the yarn posture in the interlacer. As a result, the yarn posture has no distinctive feature in this experiment.
(2) Yarns are located evenly on both sides of the air jet axis and traverse frequently the air jet at the air pressure ranging from 2 to 4 kg/cm². However, many opening and tangling parts are not produced because of the low air pressure. Yarns are located on one side of the air jet axis and the frequency of yarn traverses is small at the high air pressure of 5 ∼ 7 kg/cm². The reason of a small number of tangles at low air pressure is different from that at high air pressure. Hence, taking the change of not only the air pressure but also the yarn motion into account makes it easy to understand the variation of the number of tangles which takes the maximum value at the air pressure of 4.5 kg/cm².
(3) The yarn positions become one-sided and the frequency of traversing the air jet decreases as the yarn speed increases. It is considered that this decrease causes the number of tangles not to be simply in inverse proportion to the yarn speed.
(4) As the feed ratio increases and the resultant yarn tension decreases, the number of tangles decreases since the yarn does not frequently traverse the air jet. In the case of the small feed ratio, the yarn is restricted in its movements near the center of the yarn path and consequently traverses the air jet very often. However, many tangling parts are not produced owing to the large yarn tension. Hence, the number of tangles is maximum when the feed ratio is about 1%.

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The construction of pattern recognition system for detecting fabric defects requires to solve the following problems : 1) How can we obtain the suitable parameters of the defect itself? 2) What is the analytical metohd for evaluating these parameters? 3) To what extent can we explain the relation between the recognition sytem and ordinary visual sensory property? A streakiness defect was discussed to answer the above questions. Fourier analysis predicted that streakiness defect was influenced by the statistical deviations of the irregularities of a yarn coarseness (σ_d) and of a yarn arrangement (σ_p).Experimentally, the combination of the above two deviations, √σ²_dR²/2+2σ²_p= 0.11 and the ratio of a yarn coarseness to a yarn spacing R = 0.71, were obtained by using a commercial fabric in the recog nition system.

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