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The purpose of this paper is to theoretically compute and predict the needle penetration force (NPF) in woven denim fabrics with twill 3/1 weave pattern on the basis of geometrical, physical, and mechanical properties of yarns and fabric, and characteristics of sewing needle.

To predict the NPF by mathematical relations, the proposed models by Stylios and Xu (1995) and Lomov (1998) are extended for a twill woven structure. The NPF is calculated based on resistance forces due to yarn tensile elongation, yarn resistance to bending in the near of the sewing needle while the needle penetrates into the fabric, friction between weft and warp yarns, needle profile shape, and friction between sewing needle and yarns. In order to evaluate the obtained results, nine different denim fabric samples are produced, and five sewing needles with different sizes are used. The NPF is measured on the Instron tensile tester to simulate sewing process.

The results show that there is a good relationship between the predicted and experimental values of the NPF (R2=0.831, MSE=0.079, and MAPE=9.51 percent). Moreover, it is found that the performance of developed model to predict the NPF for needle sizes of 80, 90, 100, and 110 (Nm) is better than that of needle size of 120 (Nm). Generally, the developed theoretical model can predict the NPF in fabrics with twill 3/1 weave pattern.

The fabrics with twill weave pattern have a complicated structure than plain pattern. So, in this research work, the NPF of denim fabric with twill 3/1 weave pattern was theoretically predicted on the basis of yarn elongation, changing of yarn bent shape in the near of the sewing needle, and friction between warp and weft yarns. The NPF was measured in the successive cycle loading conditions similar to sewing machine process by using a designed and constructed instrument, which is mounted on the Instron tensile tester.

The purpose of this paper is to theoretically calculate and predict the needle penetration force (NPF) in woven denim fabrics with twill 3/1 weave pattern, based on the geometrical, physical, and mechanical properties of fabric and constituent weft and warp yarns.

In order to calculate the NPF by mathematical relations, the suggested model by Stylios and Xu (1995) is extended. While the needle penetrates into the fabric, the NPF is calculated on the basis of yarn tensile elongation, needle profile shape, and friction between needle and yarns. To accurately evaluate the developed model, nine different commercial denim fabric samples with various weft densities and linear density of weft yarns are produced, also five needles with different sizes are utilized. The NPF is measured in the successive cycle loading conditions similar to sewing machine process by using a designed and constructed instrument, which mounted on the Instron tensile tester.

Comparing the predicted and experimental values indicated that the accuracy of model to predict the NPF is partly acceptable (R2=0.734). To improve the developed model, in addition to the forces which applied on needle due to yarn elongation, the other forces such as friction between weft and warp yarns, and yarn resistance to bending in the near of the sewing needle, which resist against needle penetration, can be considered.

The fabrics with twill weave pattern have a complicated structure than plain pattern, therefore, in this paper the NPF of denim fabrics with twill 3/1 weave pattern were theoretically calculated based on yarn elongation. The spacing between centers of yarns in these fabrics is obtained by deriving a new formula. The NPF is measured on the Instron tensile tester to simulate sewing process.

This paper aims to predict the needle penetration force (NPF) in denim fabrics using the artificial neural network (ANN) and multiple linear regression (MLR) models based on the effects of various sewing parameters.

In order to design the ANN and MLR models, four parameters including fabric weight, number of fabric layers, weave pattern, and sewing needle size are taken into account as the input parameters and NPF as the output parameter. According to these parameters, 140 samples of data were resulted. Each sample was tested five times. From these 140 data (input-output data pairs), 112 were used for training the ANN and MLR models and 28 samples were used to test the performance of ANN and MLR. Also, the NPF was measured on the Instron tensile tester to simulate sewing process.

The results indicated that the NPF in denim fabrics can be well predicted in terms of sewing parameters by using ANN and MLR models, in which the ANN model exhibits greater performance than MLR (RANN=0.989> RMLR=0.901).

The NPF measurement method is limited at low speed.

Using the ANN model for forecasting NPF in denim fabrics can help the garment manufactures to produce high-quality denim products and improve the sewing process through reducing seam damage. The NPF could be also measured in the cycle loading conditions similar to sewing machine process by using a special designed tools mounted on the Instron tensile tester.