Viscoelastic branching and merging flows in a Y-shaped channel is observed by means of flow visualization technique and numerically simulated by the finite difference method. Influences of parameters, such as rheological constants, flow rate and branching angle, on flow patterns are discussed.
(1) In a branching flow of viscoelastic liquid, streamlines swell near the wall just upstream of the acute angle turn.
(2) Deviation of viscoelastic flow from Newtonian flow becomes more pronounced as viscosity decreases due to shear thinning.
(3) In a merging flow the secondary flow just upstream of the acute angle turn grows larger as the flow rate ratio

View full abstract

The effects of some factors on the defect in plain-weft knitting due to knots are investigated in detail, using a cotton yam and a worsted yarn. The results obtained are as follows:
(1) The knitting defect due to the knot is almost the knitting hole caused by the end breakage in plain-weft knitting zone. The end breakage occurs near the knot on the take-down side.
(2) The end breakage rate increases together with the increase of the depth of stitch draw, the input tension, the take-down weight, the machine gauge, the coefficient of yarn friction, the step length of cam, and the machine speed. But the increase of the cam angle decreases the end breakage rate.

View full abstract

Twisting effect is an important factor determining the mechanical properties and structure of fabrics. An investigation was made of the relation between yarn and fabrics properties in terms of their tensile and bending properties when the resultant count of the plied yarn was varied.
1) A high correlation was found between yarn and fabric properties such as tensile, bending, and physical properties (thickness, and weight).
2) Surface roughness increases with increasing resultant count of piled yarn. Superficial crepe effect was obtained in coarse yarn fabrics when the constituent single yarns differed greatly in count.
3) The bending rigidity of gray and finished fabrics of coarse yarns were greater than those of fine yarn fabrics. The constant (R) indicating the degree of correlation between yarn and fabric in their bending rigidities is expressed as: R=X_f; /N•X_y; where, X_f; : bending rigidity of fabrics, X_y; : bending rigidity of yarns, and bending rigidity of fabrics, N: number of yarns per unit width of fabric.
The value of R for cotton/cotton plied yarn fabrics is larger than those for cotton/polyester multi-filament plied yarn fabrics irrespective of the resultant yarn count.

View full abstract