Direction Of Seam Research Articles

Weakly confined slotted cartridge blasting in jointed rock mass

Directional fracture blasting can improve the smooth blasting effect of layered jointed rock masses. However, few studies have comprehensively considered the interaction between joints and slit blasting, and there is a lack of quantitative research and analysis on slit blasting. Therefore, this study combined slit blasting, pouring model test blocks for explosion testing, and numerical simulations for auxiliary research. Finally, practical engineering applications were conducted. The results showed that the weakly constrained PVC material has a high instantaneous strength under impact and can achieve a good energy accumulation guidance effect. The joint angle has a significant impact on the isolation effect of explosion stress and crack propagation. The isolation effect of the explosion stress gradually weakened with an increase in joint angle. The smaller the angle, the more vulnerable the crack propagation direction is to the “traction” of the joint and tends to the trend of the joint, and the more serious the phenomenon of crack turning, deviation and bifurcation. The results show that the explosion energy propagates preferentially from the cutting seam direction, and the stress in the cutting seam direction reaches the peak value first. The energy in the cutting seam direction has a strong transmission ability and a directional fracture effect on the joints, and the application of weakly restrained slotted pipes in layered rock tunnel blasting construction has a good effect.

Unveiling the dynamics of seam performance: a regression analysis approach for predictive modeling

The performance of seams is crucial for the garment manufacturing industry's sustainability. This study delves into the factors impacting seam slippage, strength, and efficiency. By analyzing fabric specifications (weight and weave), machine settings (presser foot pressure and speed), and seam direction, the study uncovers their influence on seam properties. Samples of 100% cotton plain and twill fabrics, both of low (120 g/m2 to140 g/m2 ) and high (275 g/m2 to320 g/m2) weights, were chosen. Lock stitch type (301) and superimposed seam class were employed, with samples stitched in both weft and warp directions using the same stitch type, seam class, and substantial core spun sewing thread. An experimental design was created using variable parameters (fabric weight, weave, machine speed, and presser foot pressure), resulting in a 23 × 32 regression analysis. This design facilitated the development of 72 stitched samples. The regression analysis yielded an optimized solution, with square regressions indicating significant seam strength (85%) and efficiency (93%). In summary, this research provides insights into optimizing seam performance by understanding the interplay of fabric, machine, and stitching parameters, crucial for enhancing the quality and durability of garment seams.

Laser Weld Seam Curved Path Effect on 6063 Aluminum Alloy Strength and Temperature Distributions: COMSOL Numerical Simulation

To improve the welding performance of aluminum alloys, a thermal source model of an irregular weld seam was established. COMSOL software was used for numerical simulation of the weld seam geometry effect on the temperature and stress fields in laser welding, which results were experimentally validated. The results show that the ellipsoidal laser welding melted micropool exhibited quasi-steady-state temperature field characteristics. The temperature gradient and thermal stress showed an increase followed by a decline. The temperature fluctuation amplitude of the square-tooth-shaped weld seam exceeded that of the arc-toothshaped one. The temperature evolution of the broken line tooth-shaped weld seam showed a slightly increasing trend, except for the inflection point. The experimental average tensile strength of the weld seam was the highest, reaching about 210 MPa, i.e., roughly 85% of the base material (245 MPa), which coincided with the COMSOL-based temperature field simulation results. With increasing deformation amplitude and transition radius, the maximum tensile force, tensile strength, and elongation at fracture showed an increasing trend. However, the deformation amplitude should be below a certain limit because its increase elongates the welding path and reduces the distance between weld seams, resulting in serious heat accumulation. The tensile fracture morphology of the 6063-T6 base material was curved shear, with shallow toughness pits, small tearing edges at the edges, and small granular objects, indicating small plastic deformation during the fracture process. The tensile fracture of the welded part spanned the weld seam and the base material, and the fracture occurred along the tangent direction of the weld seam. The fracture surface was smooth, the tearing edges at the edge of the toughness pit shifted along the weld seam direction, forming many co-directional slip bands, with highly pronounced plastic deformation.

Research on reasonable layout parameters of working faces based on the concept of harmonic extraction to reduce the damage of coal seam waiting for upward mining

Based on the idea of harmonic extraction, the problem of reducing the damage of the coal seam waiting for upward mining. Using the theoretical analysis method, a schematic diagram of coordinated mining along the dip direction of coal seam is established, and the calculation method of reasonable layout parameters of coal seam working face early mining is given. Based on the upward mining problem of the No.1 coal seam in the fifth panel of Zaoquan Coal Mine, the influence parameters of the No.2 coal seam, No.6 coal seam and No.7 coal seam mining on the No.1 coal seam were determined by similar simulation test. Then, the layout parameters of working face were determined. The research method of numerical calculation was used to evaluate the degree and uniformity of movement and deformation of the No.1 coal seam, combining five indicators: subsidence, horizontal movement, inclined deformation, curvature deformation, and horizontal deformation. The results indicate that when the working face is arranged using the layout parameters provided in this article, it can promote the further subsidence of the No.1 coal seam at the position of the remaining coal pillar. The movement and deformation indicators of the No.1 coal seam all reach the most uniform degree of the geological mining conditions, which can effectively offset the uneven deformation problem of the No.1 coal seam caused by the influence of the remaining coal pillars, making multiple mining operations a favorable condition for upward mining and achieving the goal of reducing the damage of the No.1 coal seam.

Numerical simulation of pressure relief stress distribution of diamond beaded rope saw cutting in low permeability coal seam

The diamond bead slit is a practical method for changing the stress distribution of low permeability coal seam and achieving pressure relief and reflection improvement. The stress distribution of coal seam in large scale is not clear due to the influence of diamond bead slit parameters and geological parameters, making it difficult to identify. In this paper, the finite element model with built-in Coulomb friction contact surface is used to simulate the stress distribution in coal with different angles, seam length, working face length, seam friction coefficient and different in-situ stress difference. This investigation is conducted to examine the stress distribution of parallel working face, vertical coal seam, and advance working face. The simulation results show that the mechanism of stress transfer in large scale diamond beaded rope saw cutting coal seam is mainly due to the tangential slip of coal body on both sides of seam surface, forming concentrative zone and pressure relief zone with axial distribution, center symmetry and phase. The pressure relief range and maximum pressure relief range of all three direction present a "single peak" distribution with the change of angel α between slit and maximum in-situ stress, i.e. when α = 45°, both of them are maximum. The slit length mainly affects the stress distribution in the advancing direction of the working face, and the length of working face mainly affects the stress distribution in the direction of parallel working face and vertical coal seam, both of which are positively correlated with the pressure relief range and the maximum pressure relief amplitude. The friction coefficient of seam surface and the difference of in-situ stress affect the relative dislocation of coal body on both sides of seam surface, and they inhibit and promote the pressure relief range and the maximum pressure relief amplitude respectively, and are greatly affected by α. The simulation results above suggest that it is reasonable to select fracture and geological parameters in practical engineering.

A new category of "Aha!" driven by touch: A grip sensation into the directional seam on a baseball.

We report an "Aha!" experience which differs from conventional Aha's studied over a century in psychological science. The Aha we introduce is driven by touch instead of the visual and verbal modalities widely studied to date. It can occur when gripping a baseball, with a simple input that the red seam on the ball has a direction. Aided by a symmetry analysis and subsequent survey over literature, we show how our mental and physical representation of a baseball can change suddenly by the seam direction and unravel the factors that make the tactile sense into a joyful-and-insightful sensation. Our study sets a new category of Aha driven by touch, opens a new path to investigate the role of touch in our cognition process, reveals the seam direction as a new degree of freedom in baseball aerodynamics and pitching mechanics, and deepens the insights into throwing a baseball from our fingertips.

Permeability of micro-scale structure in coal: Insights from μ-CT image and pore network modelling

For developing coalbed methane resources, it is necessary to quantify the heterogeneity embodied in pore size and spatial distribution, and on the basis of which the correlation between the gas transportability and pore structure could then be clarified in coal. In this study the μ-CT imaging technique was used to examine the micro-scale 3D pore structure in two Qinshui basin coals, and the permeability was estimated based on the reconstructed real pore structure. With CT image processing and 3D pore structure, the pore size, connectivity and the pore spatial distribution were displayed, and the connected pores and isolated pores were distinguished, and the proportion of connected pores of the two studied coals was estimated to be 54.22%–68.52% and 79.48%–91.86%, respectively. The surface porosity of 2D structure slice interprets the local pore connectivity, the minimum surface porosity in certain direction of 3D structure was close to 0 for the studied coals, which means that the pore structure is not connected and it has poor permeability in the direction of coal seam. The gas flow path and flow fluxe in 3D structure was visualized and quantified by gas transport simulation based on real coal pore structure, and the permeability and its anisotropy was evaluated. It indicates that the gas pressure appears to be distributed in a “cluster” shape, and the heterogeneity could be major reason for the low gas transport capacity in coal. The permeability of the two studied coals in the horizontal direction is significantly higher than that in the vertical direction, because the transport channels with low surface porosity in the vertical direction have the tendency to hinder the gas transport.

Characteristics of Modern Geostress and Removability of No. 15 Coal Reservoir, Yangquan Mining Area, China

Based on injection pressure drop test data and acoustic emission test data of 13 records for samples from the Wenjiazhuang and Sijiazhuang mines in the Yangquan mining area, the vertical distribution characteristics of modern in situ stress and its influence on permeability in the Yangquan mining area were analyzed, and the exploitation of the No. 15 coal reservoir was studied. The results show that the Yangquan mining area is a low-stress area within burial depths of 400–760 m, moderate-stress area within 760–950 m, and high-stress area within 950–1300 m. The Yangquan mining area hosts a strike–slip fault stress field within burial depths of 400–900 m and a normal fault stress field within burial depths of 900–1300 m, and the permeability showed a “decrease–increase–decrease” trend with an increase in burial depth. The pressure coefficient K of the modern in situ stress field in the Yangquan mining area decreased with increasing burial depth, and its relationship formula with burial depth was 68.25/H + 0.2846 ≤ K ≤ 397.63/H + 0.6061. The permeability of No. 15 coal seam had a strong logarithmic relationship with horizontal principal stress, a strong exponential relationship with horizontal principal stress difference, and a strong power function relationship with effective stress. With an increase in stress and in stress difference, permeability decreased rapidly. The results of the acoustic emission tests of the No. 15 coal were analyzed. The in situ stress type of the Sijiazhuang mine and Wenjiazhuang mine is the normal fault stress field type, which is consistent with the well test analysis results. The high ring counts in the horizontal direction of coal seam 15 lasted for a long time, which was conducive to the generation of several network-forming fractures in the process of fracturing. The No. 15 coal reservoir is located in strike–slip fault stress field and normal fault stress field areas, and the fractures generated by hydraulic fracturing expanded along the vertical direction and the maximum horizontal principal stress direction, which was favorable for the fracturing transformation of coal reservoirs and the production and development of coalbed methane.

Effect of yarn count and loop length on needle penetration force and needle cut index in single jersey fabrics

The present study embodies the sewability of single jersey knitted fabric based on needle penetration force and needle cut index. Four types of single jersey fabric, viz. 100% cotton, polyester/cotton, polyester/lycra, and cotton/lycra, are taken for investigation. The materials are prepared on circular knitting machine by varying the yarn count and loop length. The influence of various parameters, viz. type of fibre, yarn count and loop length, on needle penetration force and needle cut index have been analyzed. In addition, the influence of seam direction on the needle cut index is also studied. A 3 _ level factorial design is employed to analyse the influence of there parameters. The statistical analysis shows that yarn count and loop length has a significant effect on needle penetration force and needle cut index. It has been observed that in all single jersey knitted fabrics, cotton-lycra and polyester-lycra half plated fabrics have higher value of needle penetration force than cotton and polyester/cotton. The test results also show that for both coarser yarn and finer yarn count, longer loop length gives a lower value of needle penetration force. The needle cut index decreases with increase in the yarn count and loop length. Also it is observed that, the needle cut index is more in wale direction as compared to that in course direction. It is also concluded that cotton fabric samples are more susceptible to needle damages as compared to their counterparts.

Study on Eccentric Uncoupled Blasting Effect of Cutting Seam Pipe

In order to study the blasting effect and the damage to the rock mass when the cutting seam cartridge is eccentrically and uncoupled. The ANSYS/LS-DYNA® nonlinear dynamic platform was used to simulate the blasting effect of five eccentric uncoupled coefficients on the cutting seam cartridge, and the crack growth process under the condition of complete eccentricity was simulated. By comparing and analyzing the stress of measuring points in the direction of cutting seam, vertical cutting seam direction, and circumferential cutting seam pipe under different working conditions. It is concluded that the effect of detonation products is affected by the wrapping property of the cutting seam pipe and the eccentric uncoupled coefficient. With the increase of the eccentric uncoupled coefficient, the load distribution presents obvious non-uniformity. The pressure on the uncoupled side of the blasthole is smaller than that on the coupled side, and the peak time of the uncoupled side also lags behind that on the coupled side. When the eccentric uncoupled coefficient is 1, the peak pressure on the coupled side is 5.78 times that of the uncoupled side, and the explosive stress field is biased toward the coupled side. The existence of the cutting seam pipe causes stress concentration at the opening, which enhances the guiding effect of the initial crack, and the stress in the non-cutting seam direction is buffered. Therefore, the eccentric arrangement of the cutting seam pipe determines the formation of the initial crack and the subsequent blasting effect. When the cutting seam cartridge is arranged eccentrically and uncoupled, it will cause under-excavation at the connection direction of blasthole, which will cause less disturbance to the rock mass on the uncoupled side. If the retaining side rock mass is on the coupled side in actual blasting, the eccentric uncoupled arrangement will cause greater over-excavation and damage. Therefore, it is necessary to avoid this situation as far as possible and provide better guidance for the actual construction.

Effect of Different Sewing Parameters on Lockstitch Seam Strength for Denim Fabric

Seam strength plays a very important role in acquiring the desired quality seam which ultimately defines the quality of any clothing. The paper is aimed to study the strength of seam produced from denim fabric, how different sewing parameters like sewing thread type, type of seam, seam direction as well as the density of stitches influence the strength of seam, and it is observed that they have direct effect on lockstitch seam strength of denim fabric with various degree. For research denim fabric with 3/1 weaves structure and three different sewing threads namely 100% cotton spun with 14tex linear density, 100% polyester spun with 24tex and 60tex linear density were used. Seam class used for the research was superimposed seam prepared with two layers, SSa and three layers, SSb. The samples were made by stitching with lockstitch sewing machine both in warp and weft way. Three different stitch densities were used to sew the samples and they were-7, 9 and 11 stitches per inch. The strength of the produced seams was tested on a universal strength tester machine-the titan tensile strength tester. Test was performed according to ASTM D5034 test method. The outcome of the research shows that seam type, seam direction, thread types, and stitch density have direct effect on lockstitch seam strength of denim fabric with various degrees. Higher seam strength was obtained for the SSb type seam produced in warp direction with coarser sewing thread (60tex) and 11 stitches per inch (SPI). The influence of independent variables on the seam strength was assessed statistically using a multivariate variance analysis (ANOVA) with the help of SPSS software and it was found that they effect significantly. Regression analysis was done to develop the regression equation to predict lockstitch seam strength before production process.

A Study on the Distribution and Evolution of Mining Induced Stress under the Condition of Multiple Mining

Mining of multiple coal seams and sections is the main method adopted by the vast majority of coal mines in China at present. However, because of multiple mining, the damage and deformation of surrounding rock increases a lot when comparing with single coal seam mining. Moreover, the normal production and safety of coal mine may also get affected. In multiple coal seam mining, the distribution and alteration of mining induced stress are the main reasons of the above problems. In this study, based on the geological conditions and mining design of Weijiagou Coal Mine, the mining induced stress under multiple mining conditions were studied. According to the failure state, the surrounding rock was divided into the damaged zone, plastic zone and elastic zone. The distribution and range of mining stress in different areas were calculated by utilizing Strain Softening Model. Based on FLAC3D numerical simulation, the distribution and change of mining induced stress along the strike and dip direction of coal seam were obtained. By using the Logarithmic function and the Fourier function, the empirical formula of the relationship between the maximum mining stress in front of the working face and the advancing distance of the working face is obtained. This study provides a reference for the design of roadway support and mining face under multiple mining conditions.

Comparison of sewn fabric bending rigidities obtained by heart loop method: effects of different stitch types and seam directions

Sewing quality is an important factor that contributes to the overall quality of an end-product. Sewing quality compro - mises different components such as bending, seam strength, seam slippage, elasticity etc. Among these components, bending has a special importance because of causing changes in appearance, sensorial comfort and drape of a garment. Therefore, in this study, effects of stitch type and seam direction on the bending rigidities of sewn fabrics were evaluated and compared. A polyester woven fabric which is suitable for sportswear was sewn with three basic stitch types (lock stitch, chain stitch and overlock stitch), in 5 different directions (warp, weft, 30°, 45° and 60° angles). As reference, samples without stitches were tested, too. Bending properties of samples were determined via heart loop method. According to the results, sewing increased the fabric bending rigidity. The degree of bending rigidity increment was dependent on the stitch type. Highest bending rigidity values were obtained for overlock stitched samples those were approximately 4 times higher when compared to non-sewn reference samples. Thickness of sewn parts was in accordance with the bending rigidity results. For oriented seams, bias sewing especially for 45˚ oriented samples, showed the most advantageous bending results. This study showed the usability of heart loop method for sewn samples via consistent results for different stitch types and seam directions.

Seam Strength of the Plain and Medium Weight Selected Apparel Wear Fabrics Stitched with Lockstitch-301 Seam

A study on lockstitch - 301 seam mechanics by stitching on medium weight selected apparel wear fabrics have been carried out. The effect of fabric types and numbers of fabric layers, on to on to the seam strength, seam efficiency and seam elongation is studied. It has been found that the seam strength is depends on to the stitch density for both warp and weft direction while seam efficiency is only depends on the fabric type irrespective of the seam direction. The seam elongation is only affected by the number of layers in war direction.

Roof Deformation Associated with Mining of Two Panels in Steeply Dipping Coal Seam Using Subsurface Subsidence Prediction Model and Physical Simulation Experiment

This research investigates roof deformation and failure characteristics, as well as mechanical interaction between the panels of the roof strata above two adjacent working faces in a steeply inclined coal seam. Physical modeling with photogrammetry measurement method has been employed in this investigation. The movement of roof strata and section pillar, as well as the stratum morphological characteristics, was quantitatively analyzed. Results show that the roof movement direction above the two panels has zoning characteristics, especially in the lower panel. Roof migration in the lower panel of the working face is larger than that in the upper panel. The roof to floor closure perpendicular to the seam direction is larger than the sliding along the seam. The maximum roof concave and convex bending occurred at the middle and upper parts of both panels; the roof bending in the upper panel mining area indicates a larger mining disturbance induced by lower panel mining. The void ratio contour of the lower panel is an asymmetrically arched shape, which is different from that of the upper panel area. The higher roof strata above the upper panel exhibit separation and breaking, whereas the lower roof exhibits compression due to mining in lower panel. The section pillar is compressed and slides slightly, which aggravates the mechanical interaction between the panels and increases the caving height of the roof over the lower panel and the periodic weighting intensity.

Stress Distribution and Failure Characteristics for Workface Floor of a Tilted Coal Seam

A mechanical model for the tilted workface floor along the tilted direction of coal seam was proposed. Stress expressions of an arbitrary point inside the tilted workface floor were deduced. Calculation formula for the maximum failure depth of the lateral floor strata of the tilted workface was also deduced. Based on the Mohr-Coulomb yield criterion, the tilted workface floor’s stress distribution, and failure depth and shape were simulated by using FLAC3D software for different coal seam’s dip angles, buried depths, and workface widths. Results show that the concentration coefficient, the peak value and the distance between the peak position of the lateral abutment pressure and the roadway on both sides of the tilted workface decreases with the increases in coal seam’s dip angle. The vertical stress isoclines present a “spoon-shaped” distribution along the tilted direction of workface. Both sides of the workface form “bubble-shaped” distribution shear stress and its peak value increases first and then decreases with the increases in coal seam’s dip angle and reaches maximum at 30°–35°. The tilted workface floor’s plastic failure zone presents a “spoon-shaped” distribution along the tilted direction of workface, which is large on the lower side and small on the upper side. The plastic zone’s failure depth increases first and then decreases with the increases in the dip angle of coal seam and reaches maximum at 30°.

Experimental Study on Directional Fracture Blasting of Cutting Seam Cartridge

Since the cutting seam cartridge has sound directional breaking effect, in order to explore its blasting wave mechanism, an experimental study was conducted on the blast wave of a cutting seam cartridge using a high‐speed laser schlieren system and air overpressure test system. The research results show that during cartridge explosion, the cutting seam pipe can effectively control the energy release and detonation gas dynamic behaviors. Additionally, the cartridge blast wave and the detonation gas remain highly symmetrical in expansion form. The blast wave first propagates along the cutting seam direction, and the detonation gas initially expands from the seam in the direction of the cutting seam. The pressure in the cutting seam direction is higher than that in the noncutting seam direction. The blast wave change of the whole flow field of the cutting seam cartridge was numerically simulated and was basically consistent with the results of the schlieren test in distribution form. The presence of a cutting seam prolongs the blast wave effect. During expansion of the cutting seam pipe under the influence of a blast wave, the inner wall of the cutting seam pipe is mainly subject to tensile stress. When the tensile force applied to the inner wall reaches the local yield limit, the cutting seam pipe fails.

Experimental investigation of mechanical properties, formability and forming limit diagrams for tailor-welded blanks produced by friction stir welding

In this study, the mechanical properties, formability and forming limit diagrams (FLDs) of the tailor-welded blanks (TWBs) produced by friction stir welding (FSW) were analyzed experimentally. At first, the suitable FSW parameters were achieved. The formability and FLDs of TWBs were evaluated for sheets with the same or different thicknesses and compared to the base metal sheet. This study was performed on low carbon steel (St14) sheets with a lot of applications in automobile industries. The welded zone properties were evaluated by some experiments. The tensile test, micro hardness testing, and metallographic studies were done. The effect of welding seam directions on formability and FLD were investigated concerning two aspects. The welding process was carried out in rolling and transverse directions with no effect on formability, and then the welding process was performed in the principal stress direction and perpendicular to it; these directions had a significant effect on formability. Also, it was revealed that welding caused formability decrease, and in TWBs with different thicknesses, this negative effect was higher. In addition, the initial orientation of sheets had none effect on FSW process.

Determination of a sewing quality index of denim fabrics

This paper reports a determination of a sewing quality index in order to assist the industry in providing quality clothing before production. The particularity of this work lies in the fact that it encompasses various sewing quality parameters (efficiency, slippage, and puckering) into a single overall quality index. Moreover, a program was investigated, to determine the quality index, so that the manufacturer has only to enter the available data. In fact, by entering the input parameters which are blend composition, seam direction, fabric mass, stitch density, and seam thread linear density, an overall quality index will be given and the seam quality as well as the defect sources will be displayed. To reach this aim, regression models were determined to predict seam quality. In this work, 18 denim fabrics were sewn with two commercial sewing threads. Their influences, ranked according to the seam quality, were also determined. The seam efficiency was calculated by determining both the seam and the fabric's tensile strength. The seam slippage was determined by calculating the difference between the elongation at the break of the seam and the elongation at the break of the fabric. Seam puckering was determined by measuring both the fabric and seam’s thickness.

Effects of Knit Fabric Layering and Flat Seam Direction on Stretchability and Clothing Pressure

This study analyzes the stretchability and clothing pressure of fabrics made from stretchy knit materials, and uses the baseline data to develop various functional clothing made from stretchy knit fabrics. To observe the changes in the stretchability and clothing pressure, we observed the compatibility of the two materials (tricot and power-net), presence of flat seam, fabric layering, and flat seam direction as key variables. A standard test method for stretch properties (ASTM D2594) was used for measuring the stretchability of the material. Clothing pressure measurements were analyzed in terms of the mean and standard deviation values, and the correlation of the stretchability. In the case of tricot, the presence of flat seam increased the stretchability of the fabric regardless of the fabric layering. However, when tricot and the less stretchable power-net were combined, the presence of flat seam did not increase the stretchability. Flat seam did not interfere with or limit the stretchability of the fabric, but they did increase the clothing pressure at the seam. The stretchability had a negative correlation with the clothing pressure except along the flat seam.