A Computer for the Automatic Processing of Fiber,Yarn,and Fabric Stress-Strain Data

Abstract

During single-fiber tensile tests, major transitions in rheological behavior occur at the Young's modulus and yield-point regions. In the former region there is a transition from uncrimping (nonlinear spring) to approximate spring-like or Hookean behavior, and then to viscoelastic or plastic flow. In the latter region the transition is from Hookean extension to maximum plastic flow. The center of each transition region provides the basis of a new and better definition of the Young's modulus and yield points since these points are directly determined by the molecular-flow properties of the fiber. The uncrimping point is also defined on the basis that it is at or near the center of a transition from pure lielical spring to nonlinear spring and then to approximate Hookean behavior. An advantage of defining the parameters in this way is that they may be located through the use of the second and third stress derivatives as obtained by electronic analog computer techniques. Such techniques involve the use of inexpensive standard laboratory-type computer components. Thirty percent stretch and the ultimate tensile points may also be obtained. Voltage analogs of stress, strain, slope, and energy are stored in the computer's memory section at any of these points, or at any other selected stress or strain points. Twenty-one or more parameters may be computed and stored. Adaptations to yarn and fabric tensile tests and a modification to automatically dial in initial fiber length and reverse elongation are also descrihed. Through the use of analog-to-digital converters, these data may be automatically punched on cards or tape for storage or further analysis on a digital computer.