FATIGUE LIFE ESTIMATION OF CIRCULAR KNITTING NEEDLE

Needles are the most important stitch formation elements of the knitting process and they are exposed to variable and repetitive loads and forces during fabric production. Stresses that are obtained due to these forces are smaller than the material yield and tensile strength. However, after a while the material cannot carry these dynamic loading they are exposed and finally broken. This is regarded as the fatigue of the needles. Any abraded or fracture of these needles cause unwanted and irrecoverable faults on fabric like uneven loop structure, holes and dropped stitches, which cause huge cost loss. Considering that the number of needles on circular knitting machines (varying from 1000 to 2800 averages depending on machine type) and the average price of 6 Euro/per needle, it is very important to estimate the needle deformation to avoid fabric production faults and reduce the operating costs by extending needle life. From this point, the study was designed to predict the fatigue lives of needles under certain production conditions. To do so, a model using finite element method was developed to determine the forces acting on the needles during knitting production process. The stress values obtained were imported to nCode Designlife program in order to estimate the fatigue damage of circular knitting needle. The model showed that by changing production data, the fatigue lives of the needles, can be determined very quickly at low cost.