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Natural gas pipelines are an essential part of the economy. Natural gas pipelines may leak after aging, strong vibration signals may be generated in the pipeline when leakage occurs, and vibration signals may be noisy. Traditional variational mode decomposition (VMD) noise reduction methods need to set parameters in advance, and so may not achieve the best decomposition effect. To solve this problem, this paper proposes a method for pipeline leakage location based on the sparrow search algorithm (SSA) optimization of VMD combined with generalized quadratic cross-correlation. The method first calculates the original signal-to-noise ratio (SNR), and if the SNR is low, wavelet threshold denoising is used to process the signal. Then, SSA optimization is used to refine the two key parameters of VMD (penalty parameter α and mode decomposition number K) based on sample entropy. Subsequently, the signal undergoes decomposition into K intrinsic mode function (IMF) components through VMD according to the obtained analysis parameter combination. Then, the IMF components are screened to obtain the reconstructed signal. Finally, the noise reduction signal is obtained. The signal delay after noise reduction is obtained through a generalized quadratic cross-correlation and the accurate leakage position is obtained using the delay. Experiments showed that the minimum relative error of this method could reach 0.6%, which was more accurate than the traditional VMD method, and effectively improved the accuracy of noisy signals in pipeline leakage locations. [ABSTRACT FROM AUTHOR]

The identification of the yarn roll's margin represents a critical phase in the automated production of textiles. At present, conventional visual detection techniques are inadequate for accurately measuring, filtering out background noise, and generalizing the margin of the yarn roll. To address this issue, this study constructed a semantic segmentation dataset for the yarn roll and proposed a new method for detecting the margin of the yarn roll based on deep learning. By replacing the encoder component of the U-Net with the initial 13 convolutional layers of VGG16 and incorporating pre-trained weights, we constructed a VGG-UNet model that is well suited for yarn roll segmentation. A comparison of the results obtained on the test set revealed that the model achieved an average Intersection over Union (IoU) of 98.70%. Subsequently, the contour edge point set was obtained through the application of traditional image processing techniques, and contour fitting was performed. Finally, the actual yarn roll margin was calculated based on the relationship between pixel dimensions and actual dimensions. The experiments demonstrate that the margin of the yarn roll can be accurately measured with an error of less than 3 mm. This is particularly important in situations where the margin is narrow, as the detection accuracy remains high. This study provides significant technical support and a theoretical foundation for the automation of the textile industry. [ABSTRACT FROM AUTHOR]

Weft-knitted fabric is formed by interlocking loops, which results in an unstable and easily deformable structure. In particular, fancy weft-knitted fabric exhibits diverse structural variations and uneven distribution, leading to more prominent characteristics of instability and deformation. Achieving the desired pattern effect and dimensions often requires drawing multiple designs. In this work, to obtain the geometric model of fancy fabric, mesh-loop models with movement vectors are established based on the basic structure of four stitch types: plain stitch, tuck, float, and loop transfer. The cubic Catmull–Rom spline curves are used to fit the geometric centerline of the yarn. The movement vectors are used to represent the changes in the position of the key points of the standard loops in the fancy fabric, which are derived from the analysis of the pattern grid. A physical model is established based on the force analysis of the yarn, and the positions of yarn control points are determined by solving the Euler–Lagrange dynamic equations. Through iterative calculations, the deformation effects of the fabric are obtained, enabling the simulation of fancy weft-knitted fabric. The proposed algorithms were implemented using Visual C++. The reliability and accuracy of the simulation method are demonstrated by comparing the contours of the simulation results with the actual samples. [ABSTRACT FROM AUTHOR]

This article focuses on the nonlinear dynamics of transverse vibration of the axially moving yarn system. In this article, the motion of yarn in actual production is analyzed, and the transverse nonlinear vibration equation of the viscoelastic axially moving yarn system with Kelvin model is established by using Newton's second law. In the modeling process, the viscoelasticity of yarn material and the periodic fluctuation of tension in the process of movement are considered. The partial differential control equations of the system are transformed into ordinary differential equations by the Galerkin method. In the first three modes, when the speed is low, the related trial functions occupy the main part, and with the increase of speed, the trial functions of other orders occupy more proportion in the modal functions. Through numerical analysis, it is found that when the moving yarn is subjected to external excitation, the lateral vibration displacement has an increasing trend, and it is found that the nonlinear dynamic phenomenon alternates with the change of system parameters, such as single periodic motion, double periodic motion, and multiple periodic motion. Finally, an experimental platform for lateral vibration of yarn transmission was built and its working principle introduced. The lateral vibration of axially moving yarn was studied from the experimental point of view. It was proved that there are abundant phenomena of periodic motion, period doubling motion, and chaotic motion in the axially moving yarn system, which provides an experimental reference for theoretical research of lateral nonlinear vibration of axially moving yarn. [ABSTRACT FROM AUTHOR]

In order to solve the problem of low response frequency and poor consistency of conventional yarn grippers in weft accumulators, in this study, a piezoelectric yarn gripper is used instead of conventional yarn grippers and the motion characteristics of its actuator are studied. This gripper uses a bimorph piezoelectric bending actuator with a low-cost, well integrated self-sensing method based on charge measurement. The modeling of the piezoelectric micromanipulator is based on the piezoelectric and Euler–Bernoulli beam equations. The static and dynamic characteristics of the piezoelectric actuator as well as the self-sensing capability were experimentally tested. The experimental results show that the maximum output displacement at the end of the piezoelectric actuator is 834 μm, and the maximum output force is 388 μN at 150 V driving voltage. The stability and consistency of its response are also very good, with a response speed of 24 ms. The self-sensing test of the output force also proved the feasibility of the self-sensing method used, with an error of 0.74%. The piezoelectric yarn gripper studied in this paper is promising for practical clamping applications. [ABSTRACT FROM AUTHOR]

This study proposes a method for 3D modeling of weft knitted fabric and simulating its deformation behavior. A geometric model of the fabric was established using a loop-mesh unit, and the surface of the yarn was calculated using a reference frame. The patterns of the fabrics were represented by bitmap images. To simulate the deformation behavior of the fabric, a physical model was built based on a dynamic spline that included stretching and bending of the yarn. To simplify the collisions between continuous yarns, collisions were detected using a discrete sphere-spring model. The Euler-Lagrange theorem was introduced to achieve the energy balance of the system, and a stable shape was obtained by solving the Euler-Lagrange equation explicitly according to the convergence conditions. Rendering and deformation of the model were implemented using a simulator program via C++ and OpenGL. The simulation displayed the 3D appearance of the weft knitted fabric. The deformed shapes of fabrics were accurately predicted by the proposed method. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the malfunction of knitting machines caused by the unstable operation of the piezoelectric needle selector during the jacquard process, a state detection scheme for the piezoelectric needle selector that integrates the sensor and drive function co-located is proposed. The motion state of bimorph piezoelectric cantilever beam and its bi-directional piezoelectric effect in the jacquard process of piezoelectric needle selector are analyzed. Electrical and dynamic models were established for the electrical characteristics inside the bimorph piezoelectric cantilever beam and the dynamic characteristics of the cutter head and baffle of the needle selector. The signal detection circuit is designed to realize the real-time detection of the piezoelectric needle selector state by analyzing the time domain and frequency domain characteristics of the electrical signal. The results show that in the normal working state of the piezoelectric needle selector, the internal electric signal of the piezoelectric driver has two characteristic frequencies, which are between 155 and 180 and between 1630 and 1670 Hz, and the time for the piece to swing to the limit position is relatively long under abnormal working conditions. [ABSTRACT FROM AUTHOR]

In the process of textile production, the detection of yarn tension is very important to ensure product quality. In order to detect yarn tension efficiently and conveniently, a non-contact detection method based on transverse frequency was established. Firstly, the governing equation of yarn motion was derived by using the Hamilton principle and solved by the Galerkin truncation method. Then, the natural frequencies of yarns with different linear density were calculated according to the yarn characteristic equation. Finally, the fitting formulas of tension, speed, and frequency of yarn axial motion were derived. By measuring the natural frequency of yarn, the yarn tension could be calculated conveniently and quickly. A high-speed camera was used to measure the transverse vibration displacement of yarn and detect the free vibration frequency of yarn. Through experiments, the results of tension sensor and yarn tension detection based on vibration frequency were compared, and the results show that the error was within 5%, which verifies the effectiveness and accuracy of this method. [ABSTRACT FROM AUTHOR]

Custom socks, such as medical compression socks and hiking socks, are precisely designed and knitted according to the user's foot shape. However, developing styles of custom socks with commercial computer-aided design software requires workers to manually calculate the knitting parameters, and repeatedly adjust the knitting parameters through sample-making to meet the design requirements. We present a method to optimize the manual calculation and adjustment process of knitting parameters by using graphics technology. Our method converts a sock mesh model created by conventional modeling software into knitting parameters. Hosiery machines are able to knit socks with the same dimensions as the mesh based on the output parameters. Specifically, given user-defined top and toe markers on an input mesh, our system runs a sampling procedure over this mesh to gradually generate a knitting path that contains shape and dimension features of the mesh, and transforms the knitting path into knitting parameters for machine knitting. We demonstrated the feasibility of our method by knitting on a computerized hosiery machine. Filling the knitted socks with a soft foam model, we found that the knitted socks fit roughly well with the mesh surface, and the dimensional gap between the input mesh and the knitted socks (relaxed state) in several positions was below 4.90%. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical properties of a blended yarn and its correlation with the characteristics of constituent yarns of different materials. Each yarn's creep and stress relaxation tests are curves fitted to a six-element constitutive model. The results show that the higher the chemical fiber content in the yarn, the better the plastic properties. The experimental data fit the six-element model with 99% confidence. Compared with the commonly used viscoelastic Burgers and Ering models, the six-element model has a much more precise forecasting ability. Within the scope of this study, the ratio of yield stress to initial stress under different stress conditions calculated from the same yarn test is similar, and the ratio is only related to the blending ratio of polyester-cotton blended yarn. In yarns with strong plasticity, this ratio can reflect the proportional relationship between plastic deformation and elastic deformation in relaxation experiments. [ABSTRACT FROM AUTHOR]

Aiming at the disadvantages of complex structure and high cost of multi-dimensional displacement measurement system, a single solid integrated sensor was proposed. In order to accurately describe the mechanical characteristics of the elastic element of the sensor, the quasi-static uniaxial compression test of the elastic element of the sensor was carried out under different strain rates. The hyperelastic constitutive model was sorted and simplified by using Taylor expansion to obtain the stress-strain relationship, and the stress-strain curve was fiited by using Origin. Four hyperelastic constitutive models, Mooney-Rivilin, Yeoh, Biderman and Ogden, were selected to describe the experimental curve. The results show that the Biderman model has the best fiiting effect on the curve, the Mooney-Rivilin model has the worst fiiting effect, and other models have small strain fiiting diiferences and moderate or higher deviations. The final obtained stress-strain relationship provides an important reference for the further research on the sensor. [ABSTRACT FROM AUTHOR]

To reveal the relationship between the strain at the fixed end of the polyurethane elastomer displacement sensor and the position and torsion of the moving end, based on the stress-strain relationship obtained from the uniaxial tensile experiment of rubber materials, the most suitable Ogden constitutive model and material parameters were determined by data fitting. The non-linear finite element model of the polyurethane elastomer displacement sensor was established with ABAQUS software, and the stress, strain and displacement change laws of the sensor under the displacement and torsion of the moving end were analyzed. The study shows that the strain at the fixed end increases with the loading of displacement and torsion of the moving end. When the displacement reaches 30 mm, the maximum strain appears at a distance of 4 mm from the fixed end; when the torsion reaches 15°, the maximum shear strain area is in the entire elastic body deformation part. This distribution law guides the placement of the strain gauges in the sensor design. Comparing the sensor simulation with the experimental data, the error is within 10%, which meets the requirements of the sensor. [ABSTRACT FROM AUTHOR]

In this study, the performance of braided composite tubes under low-velocity transverse impact loading at mid-span was investigated using both numerical and experimental methods. Three types of braided composite tubes with different braiding angles (30°, 45°, and 60°) were manufactured. The transverse punch behavior of the tubes was examined on a low-velocity imspact test bench. A meso-level finite element model of the composite tube was also established for identifying the damage initiation and development. The numerical results showed a good correlation with the experimental data. The mechanical response including force–time histories, force–displacement histories, and fracture morphologies was compared between three types of composite tubes for analyzing the influence of braiding angle on the impact response and failure mode. Although suffering from the low bending stiffness depends on fiber volume fraction at initial impact stage, the braided tube with 30° angle engaged more portion to resist impact loading in subsequent process and thus presented higher peak loading than the one with large angle. In addition, there are distinct different failure modes between composite tubes with various braiding angles. Shear yarn breakage underneath the punch was prone to occur in 30° sample because the braiding yarn was closer to the axial direction of tube. In contrast, the resin was deboned severely from the braiding yarn and then the braiding yarn exhibits plastic deformation in 60° sample due to the stress concentration caused by the large braiding angle. [ABSTRACT FROM AUTHOR]

In order to solve the problem of loose hosiery products that caused by the poor stability and low real-time performance of the domestic cotton socks machine control system, a control system based on STM32F207 main control chip was proposed. Based on the research of the structure and technology of the cotton socks machine, through the analysis of the key process of the socks machine, especially the trajectory of each step, the overall hierarchical control structure was proposed, and the hardware system of main control chip based on STM32F207 was designed. The control system of the needle selector, air valve and motor board based on Freescale KE06 chip was designed. The data transmission form between the main control and the drive board was designed based on CAN bus protocol. According to the external encoder pulse count, the current needle number and needle position signal were obtained and the zero-detection circuit was designed. The function test was carried out in combination with RUMI WELLKNIT's AOTU RSD model cotton socks machine. The research results show that the designed control system can precisely control the actuator with good coordination, and the accurate needle position capture and the high real-time performance is achieved. The pattern of woven socks is well connected and socks has no detachment or loose. [ABSTRACT FROM AUTHOR]