Seam Opening Research Articles

Load extension behavior of spun sewing threads on seam slippage

The present research is focused to develop the relationship between the seam slippage and mechanical properties of sewn fabric by considering the spun thread and fabric configuration in the stitched assembly. Plain and twill weave fabric was used for the sample development stitch with the spun thread while the sewing machine setting was kept constant to produce a balanced seam. Different stitched samples are prepared in warp and weft direction for investigation by considering superimposed, flat, and bound seam classes with multi-thread chain, lock, and cover stitches. Experiment findings highlight the optimum load of seam slippage in N at 6 mm seam opening at stitched assembly by employing mentioned seam classes and stitch types. The results showed that 189.97 N maximum load was found at 6 mm seam opening for plain weave fabric in warp direction at flat seam sample with a lock stitched while in weft direction 80.65 N minimum load at the bound seam with multi-thread chain stitch. For twill weave fabric 94.72 N minimum slippage load at a 6 mm seam opening was observed in the weft direction at the bound seam with multi-thread chain stitch while in the warp direction maximum slippage load of 200 N was reported at the superimposed, flat and bound seam with multi-thread chain, lock and cover stitches. Established findings have a significant coefficient of determination (R2 0.90) between sewing thread extension and seam slippage load at 6 mm seam opening in both directions. The present research provides the guidelines to select the spun sewing thread which was possessed the minimum extension (%) against the respective load (N) to overcome the seam slippage in the stitched garment.

Study on the working performance of Wudongde Arch Dam during the first impounding period

The first impounding process in the foundation pit of an arch dam will lead to stress redistribution, and the working state of the dam needs to be reanalyzed. Taking the Wudongde Arch Dam under construction in China as the engineering background, ABAQUS finite element analysis software simulates the dam stress distribution and transverse seam opening of Wudongde Dam under four different impounding elevations. According to stress distribution and the opening degree of transverse seams, the optimal impounding elevation with the most negligible influence on the joint grouting process is determined. The simulation results indicate that the pressure generated by impounding will increase the dam deformation to the downstream river and banks. The maximum compressive stress of the upstream dam heel and the maximum tensile stress of the left and right arch abutments would decrease to some extent after impounding. The transverse seams have a tight compression tendency after impounding, and this tendency increases as the water level rises. According to the simulation results, the working performance of the dam is the best when the elevation difference between the impounding elevation and the joint grouting elevation is 36 m. Timely impounding is beneficial to the stress state of the dam and joint grouting process during the construction period.

Hydrogen-Assisted Cracking in GMA Welding of High-Strength Structural Steel—A New Look into This Issue at Narrow Groove

Modern arc processes, such as the modified spray arc (Mod. SA), have been developed for gas metal arc welding of high-strength structural steels with which even narrow weld seams can be welded. High-strength joints are subjected to increasingly stringent requirements in terms of welding processing and the resulting component performance. In the present work, this challenge is to be met by clarifying the influences on hydrogen-assisted cracking (HAC) in a high-strength structural steel S960QL. Adapted samples analogous to the self-restraint TEKKEN test are used and analyzed with respect to crack formation, microstructure, diffusible hydrogen concentration and residual stresses. The variation of the seam opening angle of the test seams is between 30° and 60°. To prevent HAC, the effectiveness of a dehydrogenation heat treatment (DHT) from the welding heat is investigated. As a result, the weld metals produced at reduced weld opening angle show slightly higher hydrogen concentrations on average. In addition, increased micro- as well as macro-crack formation can be observed on these weld metal samples. On all samples without DHT, cracks in the root notch occur due to HAC, which can be prevented by DHT immediately after welding.

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.

Structural Monitoring and Performance Assessment of Shield Tunnels during the Operation Period, Based on Distributed Optical-Fiber Sensors

The weak parts of shield tunnels are not obvious, so it is urgently necessary to implement distributed monitoring based on an advanced sensing method. As the horizontal loads at both sides of the shield tunnel present a type of symmetric distribution, the deformation parameters under the vertical loads are often selected as the key monitored parameters, such as convergence, settlement, and seam opening. In this paper, the monitoring of the proposed deformation parameters is innovatively implemented with only one sensing technology, namely distributed optical-fiber strain sensing technology. First, the improved distributed optical-fiber sensors are introduced with the sensing performance. Second, a structural health monitoring (SHM) system for operational shield tunnels is proposed, including optical-fiber sensor installation, data logging and saving, key parameter analysis, and structural health assessment. The key monitoring theory and technology are also proposed. The proposed system has been verified by experiments at the Nanjing Yangtze River tunnel. In the experiments, the proposed optical-fiber sensors were installed on the surface of a selected tunnel ring, with a longitudinal span of approximately 90 m long. The experiments were conducted over 55 days to measure the distributed strain and temperature. Then the key parameters were obtained from the measurements, with which the structural health was assessed. The possibility that the shield tunnel SHM system can be constructed with the improved distributed optical-fiber sensors, monitoring theory, and technology is proven.

Influence of heat control on hydrogen distribution in high-strength multi-layer welds with narrow groove

High-strength low-alloyed (HSLA) steels with yield strength ≥ 690 MPa are gaining popularity in civil engineering and construction of heavy vehicles. With increasing yield strength, the susceptibility for degradation of the mechanical properties in the presence of diffusible hydrogen, i.e., hydrogen-assisted cracking (HAC), generally increases. HAC is a result of the critical interaction between local microstructure, mechanical load, and hydrogen concentration. In existing standards for welding of HSLA-steels, recommendations including working temperatures and dehydrogenation heat treatment (DHT) are given to Limit the amount of introduced hydrogen during welding. These recommendations are based on investigations into conventional arc welding processes. In the past decade, modern weld technologies were developed to enable welding of narrower weld seams with V-grooves of 30°, e.g., the modified spray arc process. In that connection, a reduced number of weld runs and weld volume are important technical and, economic benefits. In the present study, the hydrogen distribution in S960QL multi-layer welds with thickness of 20 mm was analyzed. The influence of different weld seam opening angles, heat input, working temperature and DHT were investigated. The results show that weldments with narrow grooves contained an increased amount of diffusible hydrogen. Hydrogen concentration has been reduced by decreasing both the heat input and working temperature. Hydrogen-free weldments were only achieved via subsequent DHT after welding. Furthermore, hydrogen distribution was experimentally determined across the weld seam thickness in HSLA gas metal arc welded multi-layer welds for the first time.

煤矿斜井隧道管片力学性能及防水性能仿真分析

在盾构法施工煤矿斜井隧道的过程中，管片作为衬砌体系的受力主体，需要承受隧道周围的水、土压力和其他各种荷载，对其力学性能和防水性能有较高的要求。本文采用数值模拟方法，进行了盾构拆解区域管片力学性能和防水性能的仿真分析。通过分析，我们得到了管片的内力、变形、接缝张开量和错位量等参数，为工程的顺利实施提供了理论支撑。 As the main body of coal mine slant in the shield construction, segment need to bear the sur-rounding water pressure, soil pressure and various other loads. It has high requirements for me-chanical property and waterproof performance of segment. In this paper, the simulation analysis was studied on mechanical property and waterproof performance of segment in the shield con-struction tunnel. Through analysis, internal force, deformation, seam opening and dislocation of the segment are obtained. It provides theoretical support for the implementation of the project.

Study on Deformation Law of Longitudinal Seam between Shield Tunnel Segments under Staggered Seam Assembling

This study focus on the deformation law of longitudinal seam between shield tunnel segments, under the load of the overburden layer after assembling. Finite element method is used to calculate the seam opening angle between two adjacent segments under different circumstances, including different joint stiffness, different cap segment locations and different load of cross-section. The result shows that the stiffness of the joints will affect the seam opening amount within a certain range, the cap segment position leaves limited impact on the inner and outer seams opening amount, while different cross-section will have a significant different effect on them.

The Evaluation of Yarn Slippage at the Sewn Seam in Woven Fabrics Using the New Methods

In the present study, the new methods for the investigation of the yarn slippage at the sewn seams in woven fabrics and for the determination of the parameters of yarn pulling out from woven fabrics were suggested. The original test methods capable to imitate similar to the real clothing wearing conditions, to evaluate the influence of external friction, of deformation method and of the position of seam allowances in respect to stitching line on the yarn slippage parameters were designed. Applying the new method based on the yarn pulling out from woven fabric with sewn seam, the analysis of the friction that occurs between warps and wefts during their sliding was done. Consequently, the behavior of the sewn seams in woven fabrics was analyzed applying the linear regression model which describes the dependence between the parameters such as: yarn pull out force Fpull-out, yarn pull out displacement epull-out, the woven fabrics’ mechanical characteristics such as: bending rigidity in warp direction B1, fabric elongation in warp direction E100-1 and yarn slippage at sewn seam parameter (seam opening d). The created three-cluster model enabled to split the investigated woven fabrics into three statistically different groups.DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2423

Influence of Laundering on the Quality of Sewn Cotton and Bamboo Woven Fabrics

In the presented study the effect of laundering on the quality of sewn cotton and bamboo plain woven fabrics was investigated considering both the textile parameters and the type of chemical treatment. Quality parameters of sewn cotton and bamboo woven fabrics such as: fabric strength, seam strength and seam slippage at the moment of 4 mm seam opening were evaluated before and after washing with “Tide” washing powder without softeners or with softeners: “Surcare” and “Pflege Weicspuler”. There was also determined surface density, warp and weft densities as well as thicknesses under the pressures 0.625 kPa and 3.125 kPa, and calculated the comparative thickness that was considered as softness or porosity of fabrics. Notwithstanding that both the investigated fabrics were cellulosic their behavior after laundering was different. Under the tested conditions, unwashed and laundered with or without chemical softeners cotton fabric didn’t demonstrate seam slippage. The seam slippage resistance of laundered without or with softener specimens of bamboo fabric was increased in respect to control fabric. The larger changes in seam efficiency and seam strength because of laundering were determined for bamboo woven fabric then for cotton fabric. They could be influenced by the higher changes in bamboo fabric’s structure. The highest difference between the structure parameters of both fabrics was determined for comparative thickness. It was significantly increased for cotton fabric and decreased for bamboo fabric after chemical softening comparing to untreated fabrics.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3831

Field Monitoring of Segments Deformation during Metro-Station Construction Based on Shield Tunneling

To ensure the influence degree on the environment during constructing metro-station based on shield tunneling is very important in the subway construction. After the shield machine passed the metro-station, the field monitoring of these segments is carried on during getting rid of the segments. The connecting seam opening length of segments, the tunnel convergence and the internal force of the segments’ bolt are estimated. The results show that the opening length of segments of circular connecting seam is larger than that of longitudinal connecting seam, and all the changes of the opening length value is within 1.5 mm. Tunnel convergence change generally contains a gradually becoming smaller and a gradual recovery process, and the tunnel convergence is primarily vertical. Bolt internal force change generally involves stress increasing rapidly, and then decreasing slowly. The field monitoring study will potentially provide the knowledge and reference for similar projects

Relationship between the Stitch Size and the Seam Opening Evaluation of Function and Appearance of Seams of Sewn Fabrics for Japanese Style Clothes (Part 2)

Relationship between the Stitch Size and the Seam Opening Evaluation of Function and Appearance of Seams of Sewn Fabrics for Japanese Style Clothes (Part 2)

Predicting Seam Opening Behavior of Woven Seat Fabrics

The slippage-based opening at the seam line occurs on the woven fabrics due to movement in the fabric of the weft yarns over warp yarns (or warp yarns over weft yarns) at a sewn seam during utilization. Recurrent sitting down and standing up or continuously sitting down produces a load at the seam line and causes transverse strain at stitch rows. Owing to this strain, displacement (seam slippage) of the stitch could occur, leading to opening in the fabric at the seam line. This study is focused on constructing a system which is based on a non-linear regression mathematical model to predict the seam opening properties of woven fabric within two different seam opening standard test methods. The first is the fixed load test method; the other is dynamic seam fatigue. The physical properties of the fabric and stitch density play important roles in the seam opening of the seat fabric. The number of weft yarns per unit length, yarn linear density and stitch density were selected as influential factors. The prediction equation is based on completely randomized variance analyses model. The coefficients of the curves fitted were computed by means of non-linear regression analysis. Regression coefficient ( R2) values for these curves were observed to be highly reliable at more than 0.9. Also the correlation coefficients ( r) between actual and predicted values were very high at more than 0.96.

Sewing Needle Penetration Forces and Elastane Fiber Damage during the Sewing of Cotton/Elastane Woven Fabrics

This paper presents an experimental study of the effects of elastane draw ratio, pre-setting temperature and finishing process on the penetration forces of a sewing needle and damage to the elastane fibre during the sewing of cotton/elastane woven fabrics. Seam strength and seam opening strength of the fabrics were also determined for assessment of seam performance. In this study three fabric types with three different elastane weft yarn draw ratios were taken as samples for the experiments. As the first step a pre-setting process was applied to all three types of fabric at two different temperatures and at the finishing process half of the samples were treated with silicone and the other half were washed only. In total, 12 samples having different specifications were obtained. For these fabrics, nylon/elastane air-covered yarn was used as the weft yarn and cotton yarn as the warp yarn. Seam strength, seam opening strength, needle penetration forces and “needle damage index” were determined for these fabric samples. The needle penetration forces were between 100 and 140 cN and the “needle damage index” values were between 20 and 42%. Photographs were taken with an optical microscope and a scanning electron microscope to show the elastane fiber damage during the sewing.

Opening Behavior of Lockstitch Seams in Woven Fabrics Under Cyclic Loading Conditions

The opening behavior of lockstitch seams (seam type 1.01.01, SSa-1, stitch type 301 ) under cyclic loading conditions has been analyzed, using models of the slippage of yarns in the fabric and the deformation of the stitch itself. The extension properties of the sewing thread under constant cyclic loading conditions were included by using an empirical formula to predict the maximum strain in terms of the applied load and its number of repetitions. Similarly, an empirical formula was used to predict the amount of yarn slippage in woven fabric, in terms of the applied load and its number of repetitions. This formula was obtained from experiments in which the sewing threads in a lockstitch seam were replaced by pins. These results were combined to provide a method for predicting the deformation of a stitch under cyclic loading conditions. The amount of seam opening actually occurring was measured experimentally under different conditions and compared with the calculated values. Reasonable agreement was obtained, with the model explaining the influence of thread properties, stitch density, thread consumption, applied load, and the number of loading cycles. The model was therefore effective in predicting seam opening behavior under cyclic loading conditions.

Surface Transfer Impedance of Cable Shields Having a Longitudinal Seam

The magnitude of noise induced into communication cable from electromagnetic influences is reduced by the shielding properties of the metallic shield. One of these properties is the surface transfer impedance. The surface transfer impedance relates the current induced on one side of a shield to the longitudinal voltage appearing on the other side due to that current. At low frequencies the surface transfer impedance for nonpermeable materials is equal to the dc resistance of the shield. At high frequencies it decreases rapidly. The frequency at which the decrease begins is a function of the thickness and conductivity of the metal. For cylindrical shields having longitudinal seams, the transfer impedance increases at somewhat higher frequencies. The size of the seam opening determines the frequency at which the increase begins. Although the size of the seam opening is difficult to control, experimental results are in relatively good agreement with theoretical calculations.

Surface Transfer Impedance of Cable Shields Having a Longitudinal Seam

The magnitude of noise induced into communication cable from electromagnetic influences is reduced by the shielding properties of the metallic shield. One of these properties is the surface transfer impedance. The surface transfer impedance relates the current induced on one side of a shield to the longitudinal voltage appearing on the other side due to that current. At low frequencies the surface transfer impedance for nonpermeable materials is equal to the dc resistance of the shield. At high frequencies it decreases rapidly. The frequency at which the decrease begins is a function of the thickness and conductivity of the metal. For cylindrical shields having longitudinal seams, the transfer impedance increases at somewhat higher frequencies. The size of the seam opening determines the frequency at which the increase begins. Although the size of the seam opening is difficult to control, experimental results are in relatively good agreement with theoretical calculations.