During the production of the tubular knitted fabric with loops formed vertically and horizontally, defects sometimes appear on fabrics due to malfunctions of the Circular Knitting Machine. Previously, we had proposed the simple analyzing method to detect the vertical line defects, which occurs sometimes, using an average brightness and its moving average in the fabric image. In this method, the quality of the captured image of fabric is important for detection of the defects. It is necessary to analyze the defects by using lower quality fabric images in this industry because the production rate and volume is fast and heavy. Therefore, the effect of the image quality on the detection sensitiveness of vertical line defects was investigated in terms of the lighting direction during capturing, the grayscaled captured image and the resolution of the captured image. As a result, it was concluded that the vertical line defect even with around one loop width could be detected with a back light, resolution of 2 pixels per loop and monochrome image.
In processing synthetic fiber yarn, a lot of rollers are rotated at high-speed. Power loss for rotating such rollers has become larger and larger according to increasing yarn processing speed. Former studies proposed that power consumption for rotating yarn package might be reduced by 30% by locating the cover around it in order to limit the air flow. It is important to limit the air flow for saving power consumption. Now it becomes possible to calculate much more complex flow because of development of both the hard-ware of the personal computer and the software for computational fluid dynamics (CFD) analysis. The present study focused on air flows around a single drawing roller as the first step of a series of studies in which we are going to numerically analyze air flows around drawing rollers to clarify the effect of structures of their covers on the reduction of power consumption to rotate them. The comparison of experimentally measured power consumption with corresponding computational results has identified the validity of the present CFD analysis. The CFD analysis also confirmed that the energy-saving effect of the cover exists even if there is a slit on the cover in order to thread air stream caused by high-speed yarn running.
In this study, we proposed a method based on forming simulation to estimate wrinkles under CFRP molding in the preform process. In order to generate winkles criteria, a mold of S-rail shape was used, and forming simulation using lamina with orientation of 0˚, 45˚, 90˚, -45˚ respect to longitude direction was carried out. By considering the strain energy balance of fiber direction and transverse direction, wrinkle generation criteria in this study was treated as a linear function of strain εL and εT. The wrinkle generation criteria of each orientation was proposed based on the corresponding strain states of the element where the wrinkle occurs. The proposed wrinkle generation criterion was applied to laminate model with a lay-up of [45/90/-45/0]s. The predicted location of wrinkle using proposed wrinkle generation criterion showed a good agreement with experiment about wrinkle location and relative relationship of size. Based on the method of evaluating wrinkle occurrence limits proposed in this research, it leads to reduction of the number of prototypes and shortening of lead time such as feedback to design.