Breaking load and breaking elongation. Book: Materials Science of Garment Production How to measure the breaking load of a fabric

The ability to stretch, bend, change under the influence of friction are the main mechanical properties fabrics. Each of these properties is described by a number of characteristics:

tension - tensile strength, elongation at break, endurance, etc.

bending - rigidity, drapeability, creasing, etc.; change under the action of friction - thread separation, shedding, etc.

The tensile strength of a fabric is determined by the load at which the fabric sample breaks. This load is called breaking load and is a standard measure of fabric quality. Distinguish between warp breaking load and weft breaking load. The breaking load of the fabric is determined on a tensile testing machine. We fix the tested sample of fabric with a width of 50 in two clamps of the tensile testing machine. The distance between the clamps when testing woolen fabrics is 100 mm, and when testing all other fabrics, 200 mm. The fixed sample is stretched to break. Fixed at the moment of rupture load; ka is the breaking load. The test is subjected to three rectangular strips of fabric, cut along the warp, and four, cut out along the weft. Samples are cut out in such a way that one; would not be a continuation of another. The extreme equity threads in diarrhea 1 must be intact. It is necessary that the length of the strips be "100 - 150 mm more than the clamping length. The strength of the fabric is at times;" warp tear is considered the arithmetic average of three tests: samples cut on the warp, rounded to the third significant figure. The weft tensile strength is considered to be the arithmetic average of four tests of samples cut on the weft.

In order to save fabrics, a method has been developed for testing small strips, in which strips 25 mm wide are torn at a clamping length of 50 mm.

Expressed breaking load in newtons 1N) or decanewtons (daN):

1O N = 1 daN.

When assessing the quality of fabric in laboratories, the breaking load is determined and its value is compared with the standards of the standard.

The strength of fabrics depends on the fibrous composition, structure and linear density of the yarns that form it, structure and finish. Other things being equal, fabrics made from synthetic threads have the greatest strength. An increase in the linear density of threads 1 yarn), an increase in the actual density of the fabric, the use of weaves with short overlaps and multilayer weaves, rolling, decating, mercerizing, finishing, applying film coatings lead to an increase in

tissue strength. Boiling, bleaching, cutting, napping somewhat reduce the strength of fabrics.

Simultaneously with the strength on the tensile machine, it determines the elongation of the fabric, which is called the elongation at break, or the absolute elongation at break. It shows the increment in the length of the tested tissue sample at the moment of rupture, i.e.

1p \u003d U.k-ye

where 1p - absolute elongation at break, mm, hh - length of the sample to the moment

gap, mm, L~ - initial 1 clamped) sample length, mm

The relative breaking elongation k is the ratio of the absolute breaking elongation of the sample to its initial clamping length, expressed in %, i.e.

vr: 1r / t b "100.

Breaking elongation (absolute and relative), as well as breaking load, is a standard indicator of quality.

Full elongation is considered to be an elongation that occurs under the action of a load close to breaking. In the syutava of full elongation, the shares of elastic, elastic and plastic are distinguished. elongation. The total elongation and the ratio of the shares of elastic, elastic and plastic elongation depend on the fibrous composition and structure of the threads (spinning), weaving, fabric structure phases and fabric finishing.

The largest proportion of elastic elongation is possessed by fabrics made from spandex threads, from textured high-tensile threads, dense pure wool fabrics made from twisted yarn, dense fabrics made from wool with lavsan. Fabrics made from fibers with a large proportion of elastic elongation are less wrinkled; well keep the shape of products in the process of wearing; jams that occur in products quickly disappear without wet-heat treatment. Fabrics made from fibers of animal origin (wool, silk) have a significant proportion of elastic elongation, so they gradually restore their original shape after removing the deforming load. The creases that occur on products during wear disappear over time, as clothing has the ability to sag. The proportion of plastic elongation prevails in the composition of total elongation in fabrics made from plant fibers (cotton, flax), which are strongly wrinkled and require wet-heat treatment to restore shape. Flax has the largest proportion of plastic elongation.

During the operation of clothing, as well as during the processing of fabrics, they are subjected to various mechanical stresses. Under these influences, tissues stretch, bend, and experience friction.

The ability to stretch, bend, change under the influence of friction are the main mechanical properties of tissues. Each of these properties is described by a number of characteristics:

Tension - tensile strength, elongation at break, endurance, etc.;

Bending - rigidity, drape, creasing, etc.;

Change under the action of friction - thread separation, shedding, etc.

Tensile strength tissue tension is determined by the load at which the tissue sample breaks. This load is called breaking load , it is a standard indicator of fabric quality. Distinguish between warp breaking load and weft breaking load. The breaking load of the fabric is determined on a tensile testing machine. A 50 mm wide fabric sample to be tested is fixed in two clamps of the tensile testing machine. The distance between the clamps when testing woolen fabrics is 100 mm, and when testing all other fabrics, 200 mm. The fixed sample is stretched to break. The load fixed at the moment of breaking is the breaking load. Three rectangular strips of fabric cut along the warp and four strips cut along the weft are subjected to the test. Samples are cut out in such a way that one is not a continuation of the other. The extreme equity threads in the strips must be intact. It is necessary that the length of the strips be 100-150 mm longer than the clamping length. The tensile strength of the fabric by warp is the arithmetic mean of three tests of samples cut by warp, rounded to the third significant figure. The weft tensile strength of the fabric is the arithmetic average of four tests of samples cut by the weft.

In order to save fabrics, a method for testing small strips has been developed, in which strips 25 mm wide are torn at a clamping length of 50 mm.

The breaking load is expressed in Newtons (N) or decaNewtons (daN):

10 N = 1 daN.

When assessing the quality of fabric in laboratories, the breaking load is determined and its value is compared with the standards of the standard.

The strength of fabrics depends on the fibrous composition, structure and linear density of the threads (yarn) that form it, structure and finish. Other things being equal, fabrics made from synthetic threads have the greatest strength. An increase in the linear density of threads (yarn), an increase in the actual density of the fabric, the use of weaves with short overlaps and multilayer weaves, rolling, decating, mercerizing, finishing, applying film coatings lead to an increase in the strength of fabrics. Boiling, bleaching, dyeing, napping somewhat reduce the strength of fabrics.

Simultaneously with the strength on a tensile machine, the elongation of the fabric is determined, which is called the elongation at break, or absolute breaking elongation . It shows the increment in the length of the tested tissue sample at the moment of rupture, i.e.

Where Lр - absolute breaking elongation, mm; Lk is the length of the sample at the moment of rupture, mm; Lo - initial (clamping) length of the sample, mm.

Elongation at break is the ratio of the absolute elongation at break of the specimen to its initial clamping length, expressed in %, i.e.

Breaking elongation (absolute and relative), as well as breaking load, is a standard indicator of quality.

Full elongation is considered to be an elongation that occurs under the action of a load close to breaking. In the composition of the full elongation, the shares are distinguished elastic, elastic and plastic elongation . The total elongation and the ratio of the shares of elastic, elastic and plastic elongation depend on the fibrous composition and structure of the threads (yarn), weaving, fabric structure phases and fabric finishing.

The largest proportion of elastic elongation is possessed by fabrics made from spandex threads, from textured high-tensile threads, dense pure wool fabrics made from twisted yarn, dense fabrics made from wool with lavsan. Fabrics made of fibers with a large proportion of elastic elongation are less wrinkled; well keep the shape of products in the process of wearing; jams that occur in products quickly disappear without wet-heat treatment. Fabrics made from fibers of animal origin (wool, silk) have a significant proportion of elastic elongation, so they gradually restore their original shape after removing the deforming load. The creases that occur on products during wear disappear over time, as clothing has the ability to sag. the proportion of plastic elongation prevails in the composition of total elongation in fabrics made of plant fibers (cotton, flax), which are strongly wrinkled and require wet-heat treatment to restore their shape. Linen has the highest proportion of plastic elongation.

In fabrics from a mixture of fibers, the ratio of elastic, elastic and plastic elongations depends on the ratio of fibers of different origin in the mixture. The addition of staple viscose fibers to wool reduces the elasticity of the fabric, the addition of staple lavsan increases it. In order to increase elasticity, up to 67% of lavsan is introduced into the composition of linen fabrics in the form of threads or staple fibers. The introduction of elastic or spandex threads into the structure of the fabric ensures its high elasticity and elasticity, which makes it possible to use such a fabric for sports and corsetry products.

With the same fibrous composition, the proportion of elastic deformation of the fabric depends on its properties: the linear density and twist of the yarn, the degree of warp and weft curvature, and the absolute density of the fabric. An increase in the thickness and twist of the yarn, an increase in the density of the warp and weft contribute to an increase in the share of elastic deformation in the total elongation of fabrics.

The magnitude and duration of the tensile load affect the ratio of disappearing (reversible part) and remaining (irreversible part) elongations in the composition of the full elongation of tissues.

The proportion of remaining elongations grows in proportion to the magnitude and duration of the tensile force.

Multiple loads that occur during prolonged wear lead to the accumulation of irreversible deformation and loss of the product shape.

To reduce the extensibility of parts, give them a shape and maintain it, cushioning materials (hair fabrics, woven and non-woven adhesive pads) are placed in garments, which are connected to the top materials by a thread or adhesive method.

The extensibility of fabrics in different directions and the increased extensibility of elastic fabrics must be taken into account in the manufacture of garments. To protect the seams from destruction during the operation of products, it is necessary that the extensibility of the line and the extensibility of the material be commensurate. This is achieved in the following ways: using an edge along the seam to reduce the stretch of the line; the use of stitches of easily deformable weaves (chain, overcast instead of shuttle); the use of sewing threads of increased extensibility (lavsan, kapron instead of cotton).

The extensibility of the seams is greatly influenced by technological parameters sewing: sewing frequency and thread tension on the sewing machine. Increasing the thread tension on the sewing machine reduces the stretch of the seam.

With an increase in the frequency of stitches in a line, the extensibility of the seams increases. By changing the stitch length and thread tension on the sewing machine, you can achieve the necessary stretch and strength of the seams.

Products made of fabrics in the process of wearing are subjected to the action of small in size, but repeatedly repeated tensile strains. This leads to a gradual loosening of the tissue structure, deterioration of its properties and, ultimately, destruction. The ability of a fabric to withstand, without collapsing, the action of multiple tensile strains characterizes it. endurance - the number of cycles of multiple deformations that a tissue sample can withstand before destruction. By endurance, one can judge how the fabric will behave during the production process and during the operation of clothing.

Endurance, or durability, of a fabric is due to the relationship between the elements of the fabric structure, as well as its fibrous composition.

An increase in density and linear filling leads to an increase in the strength of the bonds of the fabric structure and increases the resistance to repeated stretching. Fabrics containing elastic fibers have greater endurance: synthetic, wool, natural silk. Fabrics made from fibers with low elasticity have less endurance: cotton, viscose.

In the same fabric, the lowest endurance is observed if repeated loads are applied at an angle of 45 ° to the direction of the warp and weft threads. This property of fabrics must be taken into account when designing and constructing clothing.

characteristic feature fabrics is their easy bendability. Fabrics bend, forming wrinkles and folds, under the influence of a small load or even their own weight. The main characteristics of the bend are stiffness, drape and creasing.

Rigidity- the ability of a fabric to resist shape change. Fabrics that easily change shape are considered flexible. Flexibility is the opposite of rigidity.

The stiffness and flexibility of the fabric depends on the fibrous composition, the structure of the fibers, the structure and degree of twist of the yarn (threads), the type of weave, density and finish of the fabric. The stiffness of the fabric increases with an increase in the twist of the threads, its thickness and density. Linen fabrics are more rigid than cotton and wool. Fabrics made of thin threads of weak twist have little stiffness. Weaves with long overlaps give the fabric less rigidity than short ones. An increase in tissue density leads to an increase in its rigidity. Sizing and calendering also increase stiffness.

Lining fabrics should have increased rigidity. For them, stiffness is a standard indicator of quality. Top fabrics for children's and sportswear, on the contrary, should have low stiffness.

The stiffness of fabrics during their processing in the clothing industry and V operation of finished products is a negative property. Clothes made of rigid fabrics create discomfort and make it difficult to move.

At the same time, in the manufacture of garments, to give them the required shape, a certain rigidity is necessary (to maintain the given shapes - large, to create an easily draped product - small). The rigidity of textile materials affects not only the dimensional stability of products, but also technological process their manufacture. The increased rigidity of materials makes it difficult to cut them due to the intense heating of the cutting elements of cutting machines. When grinding materials of increased rigidity, a significant increase in the temperature of the needle of the sewing machine is observed, which leads to a decrease in strength and breakage of sewing threads; the number of damages to the ground materials increases.

The ability of a material to form a spatial shape of clothing details by changing the geometric dimensions of the material in separate areas and to stably maintain it is called the molding ability of the material. The molding ability of the material is characterized by two stages: shaping and fixing the shape. shaping serves to create folds in clothes, the volumetric shape of shelves, sleeves, to form a collar and other details. sustainable form pinning and its preservation is an indispensable condition for a good appearance products during operation.

The shaping of textile materials is possible due to the fact that they contain a significant volume of air (the density of most types of fabrics does not exceed 0.5 mg / mm 3, the porosity is about 50-80%) and there are mobile and stable bonds in the structure of the material. Therefore, textile materials are easily amenable to various types of deformations (bending, stretching, compression), which determine its ability to form.

The shaping of fabrics in clothing is a consequence of a forced change in the angle between the warp and weft threads. The ability of fabrics to form is evaluated by elongation in tension under the action of a load of 1-2 daN applied to a sample cut at an angle of 45°.

Woolen fabrics are more prone to shaping, less semi-woolen, containing synthetic threads and yarn; there is practically no formability in non-woven interlining fabrics of the glued production method.

When shaping occurs as a result of deformations (bending, stretching, compression, thinning, changing the angle between the threads), the equilibrium state of the material structure is disturbed. It is possible to fix the deformation of the textile material during wet-heat treatment of parts and products. For stable fixing of the shape of clothing parts, hot-melt adhesive padding materials (polyethylene mesh), fabrics and non-woven fabrics with an adhesive coating, hot-melt adhesive chemical compositions applied to the upper fabrics are used.

To obtain a stable shape, cotton and viscose fabrics are subjected to a pre-treatment called fornis - molding of indelible products. The crease resistance of fabrics with fornis treatment increases by 30-50%, the stability of the folds increases. Sewing products from fabrics processed by the fornis method, they are subjected to wet-heat treatment with moistening at a temperature not exceeding 140 ° C and a pressing time of 30-40 s.

Stable fastening of the shape of products can be ensured through the use of thermoplastic fibers in the structure of the material. During wet-heat treatment, the fibers straighten out, fixing the created shape.

drape called the ability of the fabric to form soft rounded folds. Drapability is related to the weight and stiffness of the fabric. The use of monofilaments, metal threads, highly twisted yarns and threads, increasing the density of the fabric, sizing, varnishing, film coating increase the stiffness of the fabric and, consequently, reduce its drape. Brocade, taffeta, dense fabrics made of twisted yarn, hard fabrics made of wool with lavsan, raincoat and jacket fabrics with water-repellent impregnations, fabrics made of complex nylon threads, artificial leather and suede do not drape well. Massive fabrics of pile weaves, soft flexible massive curtain fabrics, low-density fabrics made of flexible thin threads and slightly twisted yarn, flexible fabrics with a pile, woolen fabrics of crepe weaves and soft coat woolen fabrics are well draped. The shape of the product depends not only on its design, but also on the drape, rigidity, flexibility of the materials used for the upper and lining.

Drapeability is determined various methods. The simplest method is to test a 200x400 mm sample to determine drapeability in the warp and weft directions. Four points are marked on the smaller side of the sample, through which the sample is pierced with a needle, forming three identical folds. The tissue on the needle is compressed with stoppers, the sample is hung on the needle and the distance A is measured between the lower corners of the tissue sample (Fig. 36). Drapery D,%, calculated by the formula

D \u003d (200-A) 100/200.

To determine drape, regardless of the direction of the warp and weft threads, use the disk method (Fig. 37). A sample of the tissue to be tested in the form of a circle is thrown over a disk of smaller diameter raised on a leg. The edges of the material, hanging from the disk, take one form or another, depending on the stiffness of the fabric. The disc is illuminated from above. On paper placed under the disc, a tissue projection is obtained and its area is measured. Drapery coefficient K%, calculated by the formula

Kd \u003d (So-Sp). 100/So

where So - sample area, mm Sp - sample projection area, mm

Drapability is considered good if the following drape coefficients are obtained: for all cotton, wool suit and coat fabrics - more than 65%, for woolen more than 80%, for dresses - more than 80%, for silk dresses - more than 85%.

Fig.1. Definition of drape Fig.2. Definition of drape

needle method disk method

Wrinkle- the ability of fabrics under the action of bending and compression to form wrinkles and folds, which are eliminated only by wet heat treatment.

The cause of creasing is the occurrence of plastic deformation of the fibers under the action of bending and compression. Crinkling spoils the appearance of products and reduces their strength due to frequent wet-heat treatments. Collapse depends on the ratio of elastic, elastic and plastic deformations. The fibrous composition, structure and finish of fabrics also determine its wrinkling. Fabrics made from plant fibers with a high degree of plastic deformation have the highest creasing ability: cotton, viscose, polynosic, and especially pure linen.

Fabrics made from fibers of animal origin and some synthetic fibers (polyamide, polyester, polyurethane), which have a greater proportion of elastic and elastic deformation, wrinkle weakly and restore their original shape without wet heat treatment.

An increase in the twist of yarn, an increase in the density of fabrics prevent the displacement and deformation of the fibers during torsion and compression, and therefore reduce the wrinkling of fabrics.

The sheen, coloring, and pattern of the fabric can emphasize or visually reduce wrinkling. The most noticeable wrinkles and folds on shiny smooth light fabrics.

Wet fabrics wrinkle more than dry fabrics because wet elongation increases. When squeezing and twisting fabrics containing acetate fibers, hard-to-remove jams occur, so it is not recommended to wring out products from them after washing and soaking. Products that are highly wrinkled when wet are recommended to be straightened and dried on a coat hanger. In order to reduce creasing, components are rationally selected in the manufacture of fabrics from a mixture of fibers; in the production of silk fabrics, elastic acetate, triacetate and textured threads are widely used; cotton, linen and viscose fabrics undergo a wrinkle-resistant finish. In the sewing industry, to obtain crease-resistant products that retain their shape well, the fornis is finished.

Collapse is determined by a manual collapse test or with the help of special devices. There are devices for determining oriented and non-oriented collapse.

When determining the crease resistance, a manual test, depending on the nature of the formed folds and their disappearance from smoothing the fabric by hand, gives the following assessment: strongly crumpled, wrinkled, slightly wrinkled, non-wrinkled.

The creases that form during crumpling should be distinguished from creases, i.e., unremovable folds that occur as a defect in the process of rolling cloth fabrics or during dyeing and wet-heat treatment of fabrics containing thermoplastic fibers.

In the manufacture of clothing, as well as during its operation, the fabric is subjected to friction. This occurs when the fabric comes into contact with the surface of surrounding objects or other layers of fabric and simultaneously moves along them.

The force that prevents the relative movement of two touching tissues is called the force of tangential resistance. The force of tangential resistance keeps the fibers in the yarn, the threads in the fabrics in the position that they took in the process of spinning and weaving.

If the force of tangential resistance is insufficient and cannot withstand the mechanical forces that the fabric experiences during production or operation, the threads move apart and the sections fall off as a result of the threads of one system, for example, the warp, sliding along the threads of another.

The characteristic of the tangential resistance force is tangential resistance coefficient.

This coefficient depends on the fibrous composition, the surface structure of the fabric and the type of finish. Fabrics with a fleecy surface made of threads of weak (flat) twist, having weaves with long overlaps, have a large tangential resistance. If the coefficient is too low, the structure of the fabric is disturbed, as a result of which the threads move apart and the fabric sections fall off. The threads of one system are displaced along the threads of another system. A lot of friction between the contact surfaces of clothing makes it difficult to move, which is unacceptable for linen and lining fabrics.

In textile materials, the forces of friction and adhesion appear simultaneously. Their characteristic is the coefficient of tangential resistance, which affects such properties of textile materials as abrasion resistance, advancing, sliding of the material, resistance to shedding of fabric sections, knitwear looseness, etc.

When cutting and grinding parts from materials with a small coefficient of tangential resistance, parts are easily displaced, which leads to distortion, deformation and contraction of parts and seams.

Great importance friction and grip have during the operation of clothing. For example, lining fabrics should have a reduced coefficient of tangential resistance in order to reduce the friction and adhesion forces that occur when clothing surfaces come into contact (a coat with a suit or dress, a suit with a shirt, etc.). A lot of friction and adhesion between the contact surfaces of clothing makes it difficult to put on and take off.

Increased friction makes it difficult to move the material under the sewing machine foot when sewing. An increase in friction is observed when processing film-coated materials; glued non-woven fabrics; materials duplicated with foam rubber; rubberized materials, etc.

The coefficient of tangential resistance for different materials varies widely and depends on the fibrous composition, type of weave, density, finishing method, type of coating, etc. To facilitate the movement of materials with an increased coefficient of friction (artificial leather, non-woven adhesive cushioning materials, rubberized fabrics, etc.), their grinding is performed on sewing machines using a Teflon foot and a roller press or on sewing machines with a differential mechanism for moving materials.

Character extensions depends on the type of fiber, the structure of the threads and fabric, the ratio of the thickness of the warp and weft threads and their density, as well as on the finish of the fabric. More often the warp threads are displaced along the weft threads. The greater the difference in the thickness of the warp and weft threads, the greater the separation. Singeing and shearing increase the separation of the threads, while sizing and rolling reduce it. The spreading worsens the appearance of the fabric and shortens the period of wear of products from it.

The spreading of threads in a fabric is characterized by the displacement of the threads of one system relative to the threads of another system (the warp relative to the weft or the weft relative to the warp). The spreading occurs due to insufficient tangential resistance to the mutual movement of the threads in the fabric. It can be a consequence of the structural features of the fabric - the presence of extreme phases of the structure (in individual fabrics, for example, poplin), the use of rapport with large overlaps (in satin fabrics), the use of threads of reduced twist, a decrease in the density of the fabric, as well as violations of the structure and finishing of the fabric during its production.

IN finished goods thread separation is manifested mainly in the area of ​​​​the seams (seams for grinding tucks, the middle seam of the back, the seams for sewing in sleeves, side seams). The resistance to thread separation in seams is determined by testing on tensile machines stitched fabric samples with a width of 50 mm under the influence of a tensile force perpendicular to the seam line. The resistance of the thread connection to separation is evaluated by the load at which the displacement of the fabric threads from the stitching is 2 mm on each side.

It is possible to reduce the spreading of threads in the seams of finished clothes by appropriate selection of the design and model of the product. In the manufacture of products from fabrics of increased extensibility, it is recommended to provide models of a free silhouette, in fitted products - to avoid the use of the middle seam of the back.

shattering- the phenomenon of displacement and loss of threads from open tissue sections. The crumbling depends on the same factors as the sliding. Flaking is higher in fabrics with long overlaps in the weave. The twist of the threads has an effect on the shedding, although it does not affect the spreading. Threads with more twist fray more easily.

Large separation and flaking of tissues worsens the processes garment production, complicate the processing of the material, increase the consumption of fabric for the product.

The shedding of the fabric is characterized by the displacement of the threads near the cut edge of the fabric until the threads of one system fall off from the threads of another (warp from weft or weft from warp).

The shedding of the fabric is a consequence of insufficient fixing of the threads in the structure of the fabric; it is mainly due to the small forces of friction and mutual adhesion that occur between the warp and weft threads. The shedding of the fabric is determined by the type of fiber and the weave of the fabric, the structure of the yarn, the density of the fabric, the phase of its structure, the linear density of the warp and weft, the direction of the cut of the fabric, and other factors.

Fabrics made of chemical threads have the greatest shedding, woolen and cotton fabrics have the smallest. The reason for this is the differences in the coefficients of friction, the cohesion of the fibers and the nature of the threads.

The shedding of fabrics largely depends on their fibrous composition. In ascending order of the degree of shedding, the fabrics are arranged in the following sequence: woolen cloth; cotton; wool worsted; from mixed yarn; semi-woolen worsted with chemical threads; from natural silk; from viscose yarn; from acetate, triacetate, lavsan, kapron threads.

The type of weave of the fabric has a great influence on the shedding (the shedding of satin weave fabrics is 3 times greater than that of plain weave). Satin weave fabrics with large overlaps of threads are characterized by the greatest shedding, and linen fabrics are characterized by the least. A decrease in the density of fabrics in one of the systems of threads causes an increase in the shedding of the threads of the opposite system.

The shedding of tissue sections located at different angles to the warp or weft threads is not the same. Sections of fabrics along the warp and weft threads or at an angle of no more than 15 ° to the warp and weft threads have the greatest shedding. When the cut is located at an angle of 45 ° to a particular system of threads, shedding is minimal.

Increased shedding of sections of parts increases the consumption of materials and labor costs for the manufacture of products, degrades their quality. The shedding of the fabric significantly affects the wear resistance of clothing, since significant shedding leads to the rapid destruction of the seams during the operation of the clothing. To prevent the destruction of the seams as a result of shedding of the fabric, cuts are overcast, the edges of the parts are glued, the width of the seams is increased, and seams of special designs are used.

Resistance to shedding of cuts of seams processed at the hem is 25-30% higher, and with a closed cut three times more than overcast cuts. The most resistant to shedding sections are in double stitching and edging seams.

The reliability of fastening the sections increases with an increase in both the width of the overcasting line and the number of stitches by 1 cm. With an increase in the width of the line when overcasting from 3 to 6 mm, the resistance of sections to shedding increases by 3-5 times. With an increase in the number of stitches from three to six per 1 cm line, the resistance of cuts to shedding increases by 2.5-7 times.

Penetration when grinding a textile material is characterized by partial or complete destruction of individual threads of the material by a needle during the sewing process.

The destruction of the threads, which manifests itself after washing products, is commonly called hidden cutting. Cutting through the textile material leads to a deterioration in the appearance of the product, a decrease in the strength of the seam, and ultimately to the unsuitability of the product for use.

The degree of penetration of the material depends on a number of factors: structure, density, stiffness, type of finish of the original yarn and the material itself, as well as the type and size of the needle, tension sewing thread and etc.

Damage during the grinding process occurs in the manufacture of products from any dense materials: fabrics, artificial leather, knitwear. Cutting through is especially dangerous for knitwear, as it causes the loops to unravel.

The finish used in the manufacture of the material has a significant effect on cutting through. Certain types of material finishing lead to a decrease in its coefficient of friction on the needle, reduce cutting through during grinding.

The cutting through of the material, due to the sewing process, is significantly affected by the thickness (number) of the machine needle. With a change in the machine needle number from 90 to 100, the cutting through of knitted fabrics can increase by 1.5-3 times.

Sewing thread has less of an impact on injury rates than a needle. But still, the softer the sewing thread, the less cutting through the material being processed. For example, seams made using yarn (cotton and staple polyester) as sewing threads are cut less, more - using reinforced, complex synthetic or transparent nylon sewing threads (monofilaments). With frequent breaks in the sewing thread, the number of needle damage to the materials being sewn increases significantly, since the cutting is affected by the temperature of the needle, which rises sharply as a result of a thread break.

The needle plate must be carefully selected to prevent cutting through materials. The diameter of the hole in the needle plate should not exceed the diameter of the needle by more than 1.7-1.8 times.

GOST 29104.4-91

Group M09

INTERSTATE STANDARD

TECHNICAL FABRICS

Method for determining breaking load and elongation at break

industrial fabrics.
Method for determination of breaking stress and extension

MCC 59.080.30
OKSTU 8209, 8309

Introduction date 1993-01-01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the USSR State Committee for Light Industry

DEVELOPERS

V.V. Stulov, Ph.D. tech. sciences; I.S.Davydova, Ph.D. tech. sciences; G.K.Schenikova

2. APPROVED AND INTRODUCED BY Decree of the Committee for Standardization and Metrology of the USSR dated September 27, 1991 N 1541

3. INSTEAD OF GOST 3813-72 regarding technical fabrics

4. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS

	Section number, paragraph
TU 25-1894.003-9

5. REPUBLICATION. September 2004

This International Standard applies to technical fabrics and specifies a method for determining breaking load, elongation at break and standard load.

1. SAMPLING METHOD

1. SAMPLING METHOD

Sampling of point samples - according to GOST 29104.0 with the following addition: the length of a point sample must be at least 500 mm.

2. EQUIPMENT AND MATERIALS

2.1. For testing use:

breaking machines, providing a constant rate of lowering the lower clamp (pendulum type), or a constant rate of deformation, or a constant rate of increase in load with a relative error of indications of a breaking load of ±1.0%, an absolute error of indications of an elongation of ±1.0 mm, with an average duration of a gap , adjustable from (30±15) to (60±15) s.

In case of disagreement, the tests are carried out on pendulum-type tensile testing machines;

metal measuring ruler according to GOST 427;

stopwatch according to TU 25-1894.003.

2.2. Explosive machines must be equipped with clamps of the VNIITT system (Fig. 1).

1 - clamp body; 2 - fixed sponge; 3 - intermediate movable sponge;
4 - extreme movable sponge; 5 - clamping screws; 6 - clamping screw; 7- clamping bar

2.3. Gaskets may be used in the clamps of tensile testing machines to avoid slipping or biting of the elementary sample. In this case, the ends of the spacers should be at the level of the clamp planes that limit the clamping length of the sample.

3. PREPARATION FOR THE TEST

3.1. Before testing, incremental samples are kept in climatic conditions according to GOST 10681 for at least 24 hours.

The fabric test is carried out under the same conditions.

3.2. From each point sample, seven elementary samples are taken in the form of strips: three for the warp and four for the weft.

Elementary samples are pre-marked so that one sample is not a continuation of another. The longitudinal threads of the elementary sample shall be parallel to the corresponding warp or weft threads of the incremental sample. The first elementary sample in the direction of the base is marked at a distance of at least 50 mm from the edge of the incremental sample. Elementary samples in the weft direction are marked at a distance of at least 50 mm from the edge of the incremental sample, distributing them sequentially along the length.

The scheme of cutting elementary samples is shown in Figure 2.

Weft elementary samples; , , - basic elemental samples;
- a strip of fabric with an edge; - fabric width; - length of the spot sample,
dependent on the clamping length of the elemental sample

3.3. The dimensions of elementary samples are taken equal to 50x500 mm or 80x500 mm. Permissible deviations in the size of elementary samples are set mm.

It is allowed, depending on the design of the clamping devices, to use elementary samples with a length of more than 500 mm.

3.4. The working width of elementary samples should be 25 or 50 mm. The permissible deviation should not be more than 0.5 mm.

3.5. To obtain the working width of the elementary sample, the threads of the longitudinal directions are removed from both sides until the load-bearing width becomes 25 or 50 mm.

3.6. When preparing elementary samples from tissues with crumbling marginal threads, one of the following methods is used:

a) on an elementary sample with easily crumbling edge threads, the working width is marked and the elementary sample is loaded into the clamps of the tensile testing machine. On both sides of the sample perpendicular to the direction of stretching in the middle, cuts are made along the longitudinal threads to the lines indicating the working width. The threads cut on both sides of the sample are removed, except for 2-4 threads bordering the marked lines;

b) on an elementary sample with low shedding marginal threads, the threads are removed from both sides along the length of the elementary sample, leaving 2-4 threads on each side of the marked lines. In the part of the elementary sample that will be loaded into the upper clamp, these threads are withdrawn and cut to 25-30 mm more than the length of the jaw of the clamp. The end of the prepared sample with the remaining threads is loaded into the lower clamp, the other end is inserted into the upper clamp.

3.7. On the tensile machine, the distance between the clamps is set equal to (200 ± 1) mm.

3.8. The load scale of the tensile testing machine should be selected so that the average breaking load of the test sample is between 20% and 80% of the maximum scale value.

3.9. The lowering speed of the lower jaw of the tensile testing machine is set so that average duration the process of stretching an elementary sample to rupture corresponded to (40 ± 25) s.

4. CONDUCTING THE TEST

4.1. One end of the elementary sample is inserted into the upper clamp of the tensile testing machine without distortion and clamped lightly. The other end of the sample is loaded into the lower clamp and the preload weight is hung. When the top clamp is released under preload, the elemental sample drops slightly. Then firmly clamp first the upper and then the lower clamps. After that, the lower clamp is activated.

4.2. The preload value is selected depending on surface density technical fabrics according to the table.

Surface density, g/m	Preload, N (kgf), with dimensions of elementary samples, mm
St. 75 to 500 incl.
" 500 " 800 "
" 800 " 1000 "
" 1000 " 1500 "
" 1500 " 2000 "

4.3. When an elementary sample breaks in the clamp or at a distance of 5 mm or less from the clamp, the test result is taken into account only if its value is not less than the minimum breaking load provided for in the normative and technical documentation for technical fabrics. Otherwise, additional elementary samples are subjected to rupture.

4.4. The values ​​of breaking load and elongation at break are taken from the corresponding scales of the tensile testing machine after the break of the elemental sample.

4.5. When testing technical fabrics from combined threads, the readings of the scales of the machine are taken at the moment of the first stop of the arrows of the force meter.

4.6. The elongation of the fabric under a standard load is fixed at the moment the pointer of the force meter indicates the load set in accordance with the normative and technical documentation for a particular fabric, or according to the "load-elongation" diagram, which is obtained on a self-recording device of a tensile machine. The chart processing technique is given in Appendix 1.

In case of disagreement, the elongation at standard load is determined from the load-elongation diagram.

5. PROCESSING THE RESULTS

5.1. For the breaking load of the fabric, the arithmetic mean of the results of all measurements on the warp or weft is taken.

The calculation is carried out to the first decimal place, followed by rounding to an integer.

5.2. The elongation () of an elementary sample at break in warp or weft as a percentage is calculated by the formula

where - elongation at break, mm;

200 - distance between clamps of the tensile testing machine, mm.

The final result is taken as the arithmetic mean of all warp or weft measurements.

For the elongation of the fabric under standard load, the arithmetic mean of all measurements on the warp or on the weft is taken.

Calculations are carried out with an error up to the second decimal place, followed by rounding to the first decimal place.

5.3. The test report is given in Appendix 2.

APPENDIX 1 (mandatory). PROCESSING OF THE "LOAD-EXTENSION" DIAGRAM

ANNEX 1
Mandatory

The "load-elongation" diagram is taken on a scale of at least M 1: 1 and processed as follows:

1. From a point on the curve, a perpendicular is lowered onto the axis. The length of the perpendicular corresponds to the value of the actual breaking load of the elementary sample. Using a measuring metal ruler, measure the length of the perpendicular in millimeters.

2. On the perpendicular, a segment is marked corresponding to the value of the load established in the regulatory and technical documentation for a particular fabric or from the actual breaking load of an elementary sample. The length of the segment () in millimeters is calculated by the formula

where is the load rate at which it is necessary to determine the intermediate value of elongation, daN (kgf);

- perpendicular length, mm;

- actual breaking load of an elementary tissue sample, daN (kgf).

3. A straight line is drawn from a point parallel to the axis until it intersects with the curve (point).

4. A perpendicular is lowered from a point onto the axis.

5. The segments and are measured on the axis.

6. The intermediate value of elongation () in percent is calculated by the formula

where - elongation at break, %

- segment length, mm;

- segment length, mm.

APPENDIX 2 (mandatory). TEST REPORT

APPENDIX 2
Mandatory

The test report must contain:

fabric name;

lot number;

type of breaking machine;

preload value, N (kgf);

breaking load of the elementary test on warp and weft, daN (kgf);

arithmetic mean value of breaking load on warp and weft, daN (kgf);



arithmetic mean value of elongation at break in warp and weft, %;

elongation at standard load on warp and weft, %;

arithmetic mean value of elongation at standard load on warp and weft, %;

the date of the test;

the signature of the person responsible for the test.

Electronic text of the document
prepared by Kodeks JSC and verified against:
official publication
M.: IPK Standards Publishing House, 2004

LECTURE #11

1. Purpose and essence of the method.

2. Determination of coefficients that take into account the proportion of warp and weft threads in the fabric.

3. Determination of the conditional length of the fabric.

4. determination of the number of warp and weft threads in the fabric.

5. Improvement of the design method prof.O.S. Kutepov.

6. The procedure for designing a fabric for a given tensile strength using the corrections of prof. O.S. Kutepova.

The method was named "Method of engineer A. A. Sinitsyn" by the name of the author who proposed it in 1932. Later this method was supplemented by prof. O.S. Kutepov. It is used in cases where it is necessary to design a fabric with a given breaking load of a fabric strip along the warp and weft.

The purpose of this method is to determine the number of warp and weft threads per 10 cm of fabric while maintaining the surface density of the fabric and the thickness of the threads for a given breaking load of a strip of fabric.

To solve this problem, A. A. Sinitsyn uses the concept the breaking length of the fabric on the warp and on the weft (;). The physical meaning of the breaking length of a strip of fabric expresses the length of the fabric strip (in km), at which the fabric will break under the action of its own mass.

For designing, a standard fabric is accepted that has the following data:

Surface density of the fabric (Mm 2);

) and duck();

The number of warp threads () and the number of weft threads () per 10 cm of gray fabric;

The linear density of the warp () and weft ().

The breaking load of a strip of fabric is determined taking into account the percentage of use of warp and weft threads according to the following formulas.

The percentage of use of warp threads in the fabric is:

The percentage of use of weft threads in the fabric is:

where is the breaking load of the yarn on the warp and weft, cN/tex.

Knowing the breaking load of a strip of fabric over the warp and weft and the surface density of the fabric, A.A. Sinitsyn determines the breaking length of a strip of fabric using the following formulas.

Breaking length of a strip of fabric along the warp:

where 20 is the conversion factor for a strip of fabric measuring 50,200 cm.

When a strip of fabric is torn along the warp, the weft plays a passive role and therefore it slightly changes the strength of the strip of fabric along the warp. Exactly the same phenomenon is observed with the warp threads when a strip of fabric is torn along the weft. Therefore, A.A. Sinitsin introduced the concept conditional breaking length of the fabric in warp and weft, the threads of which bear the main influence of the breaking load.

Conditional breaking length of the fabric on the warp:

Conditional breaking length of the fabric in the weft:

Subsequent calculations are reduced to determining the coefficients α and β, which determine the proportion of warp and weft threads in the surface density of the fabric.

Provided that α + β \u003d 1, it can be written that the mass of warp threads in 1m 2 of fabric will be equal to

Mm 2 \u003d α Mm 2 + β Mm 2,

where the mass of the warp threads is - α ;

the mass of weft threads is - β .·

Let us determine the coefficients α and β for the reference fabric. To do this, we determine the ratio of the masses of the warp and weft threads - M o / M y, equal to:

(16.4)

where is the shrinkage of the fabric in the finish, %.

Equating the left and right parts of the resulting expression, previously replacing the mass values ​​of the warp threads with the expression M o =α and masses of weft threads expression M y \u003d β , and adding the equation α + β = 1 we obtain a system of equations of the form:

Having determined the coefficients α and β, determine the conditional breaking length for the warp and weft.

Knowing the conditional breaking length for the warp and weft of the reference fabric, Sinitsyn makes the transition to the calculation of the fabric being designed. In this case, the following assumption is introduced: the conditional breaking length for the reference fabric and the designed fabric remains constant, i.e. And .

In this case, it can be written that the conditional breaking length of the reference fabric along the warp is equal to:

where , is the breaking load of the strip of the fabric being designed, cN;

α′, β′ are the share of warp and weft yarns in the surface density of the designed fabric.

Sinitsyn transforms the above equations into the form

from which determines the proportion of warp threads in the designed fabric.

The proportion of warp threads in the designed fabric is:

from which it finds the values ​​β¢ and α¢.

The proportion of weft threads in the designed fabric is equal to:

Having determined the expressions for α "and β", by analogy with the equation (), they compose an equation of the form

The basis density in the designed fabric is equal to

where is the warp and weft density in the fabric being designed.

In this equation, there are two unknowns Ro and Ru. To solve this equation, A.A. Sinitsyn used the empirical method proposed by Brierley. However, the Brierley method is applicable to a very narrow range of fabrics. Basically, these are fabrics of the following weaves: plain, satin weave and matting. For fabrics of other weaves, the method of Eng. A. A. Sinitsyn cannot be used. Because of these limitations and the complexity of the calculations, the Sinitsin method in this presentation has not found wide application.

However, it can be used for other weaves of single-layer fabrics by applying the thread density factors in the fabric introduced by Prof. O.S. Kutepov. In this case, the fabric being designed is conditionally equated to a fabric with a square structure, after which the proportion of warp and weft threads is recalculated in accordance with the given value of the coefficients α and β. In this case, the design order is as follows.

Depending on the destination, certain requirements will be imposed on the rope.

Typically, the selection of a rope is carried out according to 3-4 of the above properties. And now in more detail:

Price

Depends on many factors. The most obvious is the cost of raw materials. Additional operations in the form of preparation of threads, the complex structure of the rope (the presence of cores), final processing - complicates production and affects the price. Production in a streaming mode (i.e. in large volumes) allows you to reduce cost by reducing waste and no time wasted on setting up equipment.

Breaking load

It is measured in kgf - kilogram-force (equal to the weight of a body weighing 1kg) or newtons; 1 kgf = 9.8N. Indicate the load at which failure occurs. Its value allows you to determine the suitability of the rope for certain purposes. It must be understood that the tests are carried out by the manufacturer under ideal conditions - new rope, smooth application of the load, normal conditions(temperature, pressure, humidity), etc. The recommended operating load is up to 40% of the breaking load.

Diameter

Important in a number of cases:
-For example, 400m of rope with a diameter of 8mm takes up the same volume as 256m of d10mm. (In practice, when wound on a coil, the ratio is somewhat different, but the meaning is the same).
-The rope works in roller systems. Roller diameter and groove size must match the rope diameter. Otherwise it won't work.
- Work by hand. For comfortable work (moving loads), the diameter of the rope must be at least 14mm.
- The rope passes through holes of a certain diameter.

Line Density

The mass of a unit length of the rope. Measured in g/m. Sometimes the concept of tex, denier is used. Although it is more for fibers and threads. Tex - the weight of 1 km of thread in grams. (g/km). Den - the weight of 9 km of thread in grams.
Line density determines how light your rope is. Relevant if there is a weight limit - travel, especially on foot, space flights, etc.
Depends on the material, type of rope. As you get heavier: polypropylene. In general, ropes with a core are heavier than those without.

Tensile under load

When a load is applied, materials stretch and ropes are no exception. As a rule, it is indicated how much the rope has lengthened under loads close to breaking. Measured in percentage. It is possible to measure extensibility under a certain load (for example, this is true for safety ropes). The load/extensibility curve is not linear. New ropes stretch better than used ones.
Depends on the material and type of rope. Tensile downwards polyamide>polypropylene>polyethylene>polyester>high molecular weight polyethylene>aramid.
High extensibility allows you to "extinguish" sudden loads (jerk) - good for towing, mooring, etc.
Low extensibility - when using ropes for winches, lifting mechanisms. For steering (traction) systems in some vehicles, usually waterborne. Control lines in paragliders and the like.

UV resistance

All synthetic ropes "age" (degrade) under the influence of ultraviolet radiation, but at different rates. This time is determined by the material, the diameter of the rope. UV absorption leads to the destruction of bonds in polymer molecules. As a result - loss of elasticity, strength. Resilience descending: polyester>high molecular weight polyethylene>polyamide>polypropylene>aramid.
Protection: minimization of UV exposure, special additives in the original polymer, protective impregnations for finished ropes.
The globe can be divided into zones of ultraviolet radiation intensity (see map of the intensity of solar radiation in the world). If the rope is to be used outdoors, its service life can be determined. Many imported manufacturers indicate the presence of light stabilizers. For example, a polypropylene rope with a stabilization of 120kLy (kilolangly) - when exposed to solar radiation with an intensity of 120kLy for a year, should lose no more than 50% in strength.

Resistance to mechanical stress

External friction - at the points of contact of the rope with the working surfaces. Methods of protection - extremely smooth surfaces, round shape.
Measurement method: a reference abrasive surface on which the ropes move under a certain load. Measured in number of cycles, relative value. The stability depends on the material. In order of decreasing abrasion resistance: polyester>high molecular weight polyethylene>polyamide>aramid>polypropylene.
Structurally: the resistance to abrasion is affected by the preliminary twist of the threads, the spunness of the rope. The higher the spice (finer weave) - the better.
Internal friction - occurs in the rope, between the fibers. The smoother the threads, the less friction between them. The situation is improved by special anti-friction additives and impregnations. Resistance to internal friction deteriorates in the series: high molecular weight polyethylene, polyester>polyamide>aramids, polypropylene

Chemical resistance

Everything is simple here. Ropes are used in real conditions. These can be the effects of acids, alkalis, solvents, etc. Knowing where the rope will be used, you can choose a material that will last longer.

Permissible temperature range

It is determined by the permissible operating temperatures and depends on the rope material. In normal situations, heating can occur due to the following reasons (one of, or all at once):
-External heat sources (high ambient temperature, various thermal radiation).
- Warming up as a result of frictional forces. The greater the load, the greater the friction force, the greater the heating. If there is no normal cooling, then up to reflow.
By heat resistance in the direction of decreasing: aramid>polyester>polyamide>high molecular weight polyethylene>polypropylene
It should be remembered that the temperature environment, in which the rope is used, must be less than the maximum allowable values ​​for this material, because during operation, additional heating will occur (friction forces).

Possibility of termination

Ogony (splash) is a loop made in a special way at the end of the rope. Most often, for work, the rope needs to be attached to various devices. Knots are suitable for domestic purposes - tie something, hang it, manually lift loads. For special applications, eg thimbles are required at the end(s) of the rope. This ensures the convenience of working with the rope - easy fastening in carabiners, without the need to tie / untie knots. In addition, the correct termination of the ends provides greater strength. Fires weaken the rope by 10%, and knots by 40-90%, depending on the material, type of rope, type of knot.
The most common ways to get fires:
- Braiding. Twisted and some types of braided ropes (both with and without a core) are suitable for this. The most easily braided are twisted three-strand ropes and braided without a core. There are several braiding methods for braided ropes. All of them require special accessories and a certain skill of work. It is better to ask the manufacturer about the possibility of braiding.
- Crimp. Metal bushings are used, the process is similar to pressing metal ropes.
-Firmware. Fires are obtained by stitching on special machines, reminiscent of sewing machines.

Buoyancy

Rarely critical. This parameter can be important when working on water. For example, when lowering an anchor to the bottom of a reservoir, you can not be afraid to "miss" the other end of the rope, because. in this case, it will float on the surface of the water. It is clear that instead of an anchor, some equipment (for example, video / sound recording or other measuring devices) can appear. Often, it makes sense to think about this point and use a floating rope.

Intensity of exploitation

Color

Weaving type

Winches (capstans)
The key is winding density. drum surface.

Pulleys, rollers
Kinks in the rope under load cause uneven loading of the fibers. Only a part of the fibers work - therefore, the real loads that the rope can withstand will always be less than laboratory tests. In addition, operation in such conditions causes increased internal friction, which reduces the service life. For most applications, the pulley (roller) diameter should be 8-10 rope diameters (at least 6 diameters). For some materials (e.g. aramids), the roller diameter must be at least 20 times the rope diameter.
The rollers must rotate freely. The profile of the groove should be in the form of a half ring, with a diameter 10% larger than the diameter of the rope. The V-groove will compress the rope, causing more friction. This shortens the life of the rope.