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The application of thermoelastic stress analysis in composite materials is particularly complicated because of the anisotropy of the material, which determines the thermoelastic effect to be depended on the material property and mechanical performance. This paper describes a theoretical and experimental analysis on full-filed stress distribution from thermoelastic measurements and its application to determination of stress concentration. The sum of the principal stress can be measured by Thermal Stress Analysis (TSA). Lock-in Thermography has been applied to measure the sum of principal stress distribution of component structure by its high thermal resolving. In this study, Experiments were carried out with GFRP composite ply and foam materials under cyclic load. The thermoelastic constant is obtained for GFRP and foam composite materials. The stress concentration is analyzed for a specimen with a hole. The experimental results show the stress distribution can be measured and analyzed using Lock-in thermography. It is found that the composite material structure stress can be evaluated with good accuracies by lock in thermography.

Abstract:In the process of heating for materials, ordinary PID control methods cause the high temperature overshoot, which damages the structure and properties of the sample. In views of the large thermal inertia under the vacuum system, A PID control based on dynamic temperature assignment (PID-DTA) was proposed. According to temperature differences between the current temperature and target temperature, the assignment temperature of PID controller is changed until the heating temperature reaches the set value. The PID-DTA heating method is validated by experiments using the high vacuum heating system. It is proved by experiment that the PID-DTA heating method effectively reduces the temperature overshoot of heating, and shortens the stability time of temperature control.

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This article analyzed the temperature control system of the dyeing machine in the textile industry, adopted the technology of PLC to automatically control the temperature and realized the automatic temperature adjustment in the work process of the dyeing machine. The spot adjustment proved that this method could fulfill the basic requirement of the dyeing machine to the temperature.Keywords: PLC, Dyeing machine, Temperature 1. The temperature control principle of the dyeing machine The application of automatization technology in the textile industryThe textile machinery manufacturing of China has been quickly developed for almost twenty years and has acquired great achievements, and the technical level and product stability of textile machinery have been fully enhanced. The automatic control of the textile machinery takes the sports control as its core, and is assisted by the textile technical parameters. In recent ten years, the electric power electronic technology, computer control technology and network communication technology have been applied and extended in the control and production management of the textile machinery quickly, which make the mechanical and electronic integration level of China fully enhanced. The intention of the controlThe parameters of the textile technology are numerous, which generally includes temperature, pressure, flux, liquid position, length, speed and displacement. The dyeing technology of the textile has strict requirement of the temperature, and the temperature ascending process, temperature keeping process, temperature descending process of the dyeing trough must accord with the technical requirements, and the manual control is very difficult. If the used machine is the small sample machine, it may bring trouble for the bulk samples. And the production equipments will make the color replay difficultly and induce serious kettle difference, and finally bring unnecessary losses for the production. Therefore, the automatic temperature control of the dyeing machine is very important. The control system is required to freely set up the temperature ascending curve, temperature keeping curve, temperature descending curve, and the operation time, actual temperature and process temperature in the work process can be displayed to ensure the right implementation of the technology. The Structure of the temperature systemThe control objective is the dyeing sample machine, and the structure of its temperature system is seen in Figure 1. The temperature control range of the system is from 20 to 150 centigrade degree, and because the water can not achieve 150 centigrade degree, so the glycerin is adopted. The glycerin can achieve 150 centigrade degree under normal pressure.When the dyeing machine is working, the temperature of the glycerin in the dyeing trough must be changed according to the technical requirements. If the temperature is lower than the set value, the temperature control system should close the heat switch 7, heat glycerin through the heating wire and stop heating unt...