This article analyzes the mechanical non-linear property of spun yarn in initial tensile deformation which has an important bearing on the handle of fabrics.
The article describes observations and a statistical analysis of spun yarn structures in different stages of tensile deformation.
This statistical analysis mathematically expresses spun yarn structure and makes it possible to present an idealized mechanical structure model.

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A model of the mechanical structure of spun yarn is assumed on the basis of the analysis reported on in a previous part I. On this assumption, a mathematical formula is derived to express the non-linear tensile property of spun yarn as a function of the tensile property of fibers and variables of yarn structure, such as the distribution of fiber segments, diameter shrinkage function, yarn twist and the number of fibers in yarn. Experimental data are presented to verify this theory.

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Presented here are the basic conditions needed to obtain-as a first step to investigate the resin distribution in resin-finished fabrics by using a carbon-14 tracer-a good microautoradiograph in the cross section of resin-finished fabrics and monofilaments with the aid of three kinds of commercially sold photo-sentitive materials.
1. The proper RI concentration in the resin solution is from 150 to 375μCi/10cc
2. With the contact method used, the exposure time needed is 35-14 days for a process hard dry plate, and 3-1.5 days for X-ray film. With an autoradiographic dry plate used by the stripping method, the exposure time needed is longer than if a process hard dry plate is used by the contact method.
3. Adequate conditions for developing are 15 minutes at 20°C if a Fuji Microfine developer for process hard plates is used; 4 minutes at 20°C if a Rendol developer for X-ray film is used and 7 minutes where an autoradiographic dry plate is used.

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An apparatus to determine the bending modulus of fibers and strips has been devised based on the reed-vibrating method. Specimens are driven to resonance by electrostatic force and their vibrations detected accurately by a photo-transistor, instead of microscopically.
This electrcnic device is the features of Automatic Vibroscope which has already been developed by the authors to determine the denier of fibers. The new apparatus is Automatic Vibroscope slightly remodelled to suit the instrument for the reed-vibrating method. It makes possible detection under smaller amplitudes of vibration than those readable through a microscope in the conventional instrument. Therefore, the new apparatus reduces errors caused by departure from the ideal conditions of the theory, lessens distortions in frequency response curves and cuts down personal errors in measurement.
The new apparatus can also be used for measurement of mass per unit length (denier) in samples of filamentous form. Therefore, even where the density of test pieces is unknown, its bending modulus is determinable easily by this apparatus alone.
Some interesting and useful results have been obtained as to the characteristics of photoelectric detection and an interpretation of these behaviors is made. Measurements with our instrument have revealed anisotropy on the bending modulus of polyethylene film which was variously heat-treated, processed and cut in various angle for drawing direction into strips for use as specimens. The results obtained agree well with those of the other studies.

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