Seam strenght prediction using residual swing thread strength

Abstract

During high speed sewing, needle thread is subjected to repeated tensile stresses, heat, newlinebending, pressure, torsion and wearing. These stresses act on the thread repeatedly and the newlinethread passes 50-80 times through the fabric, the needle eye and the bobbin case newlinemechanism, before getting incorporated in to the seam. As a result both the sewing thread newlineand the yarns in the fabric get abraded/ severed during the seaming process. A number of newlineresearchers observed that there could be 30% to 40% strength loss in the needle thread after newlinesewing. Thread becomes weaker while being incorporated in the seam thus affecting the newlineseam strength. In this work impact of thread strength loss on seam strength is discussed in newlinedetail. newlineLoop strength is widely used in the calculation of seam strength but there was no newlinestandard gauge length for the loop strength testing .In order to standardize the gauge length newlinefor loop strength testing effect of gauge length on tensile and loop strength has been newlinediscussed in this work. Tensile testing and loop strength testing of cotton and polyester newlinethreads is done at different gauge lengths. It is observed that tensile strength of threads newlinedecreases with the increase in gauge length. Stress is distributed over the whole test length newlineof the thread with more concentration over the weakest link resulting in failure of thread. newlineThe probability of such a weak point increases with the increase in test length. But the test newlinelength does not have any significant effect on the loop strength of a thread as the stress newlineconcentration is always at the intersection point resulting in failure from the outer part of the newline U shaped bent, which is extended more than the inner part. However, elongation % in both newlinetensile and loop strength tests is found to decrease with increase in gauge length for all the newlinethreads. Therefore, it is concluded that loop strength tests can be carried out at any gauge newlinelength unlike tensile testing of threads. newlineiv newlinev newlineA detailed study has been carried out by using different asymmetrical needle/bo