Çift katlı ipliklerin mekanik özelliklerinin tek katlı ipliklerle karşılaştırmalı olarak incelenmesi
Küçük Resim Yok
Tarih
1990
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Ege Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
Tekstil endüstrisinde iplikler ince ve basit örgülü kumaşlar dışında çoğu kez çift katlı olarak kullanılırlar. Katlama-bükme işlemi sonunda sadece üretim işlemleri sırasındaki gerilimleri daha iyi taşıyabilen, numara, büküm ve mukavemet gibi özellikleri açısından daha az değişim gösteren iplikler elde edilmekle kalmayıp, ipliklerin esneklik, yumuşaklık veya sertlik, parlaklık, düzgünlük, sürtünme dayanımı gibi özelliklerinde de gelişme sağlanması mümkün olmaktadır. Çift katlı ipliklerin oldukça yaygın kullanımına rağmen iplik yapı ve özelliklerine ilişkin araştırma ve incelemelerde model olarak genellikle tek katlı iplik ele alınmaktadır. Oysa çift katlı iplik gerek geometrik yapı, gerekse fiziksel özellikleri açısından tek katlı iplikten çok farklıdır. Tek ve çift katlı ipliklerin kopma mukavemeti, kopma uzaması ve eğilme rijidliği gibi mekanik özelliklerinin karşılaştırmalı olarak incelendiği bu çalışmada ilk aşama olarak önemli bir boyutsal parametre olan iplik çapının ölçümü için optik bir deney düzeneği kurulmuş, çift katlı ipliğin birbirine benzer iki silindirik helisin bir eksen etrafına sarılmasından oluştuğunu ve çift katlı iplik yapısı içerisindeki tek katlı iplik enine kesitlerinin elips şeklinde olduğunu varsayan bir teorik model oluşturularak tek katlı ipliğin optik çapından hareketle çift katlı iplik optik çapının hesaplanmasını sağlayan bir hesap yöntemi geliştirilmiştir. Deney materyali olarak seçilen çeşitli numara ve büküm seviyesindeki çift katlı pamuk, polyester /pamuk ve yün ipliklerinde yapılan ölçüm değerleri ile teorik olarak hesaplanan değerler karşılaş tırılmış ve yeterli yaklaşımın sağlandığı görülmüştür. Çalışmanın bundan sonraki aşamasında "Z" bükümlü tek katlı ipliklerin "S" yönünde katlanmasıyla elde edilen değişik numara ve büküm seviyelerindeki çift katlı ipliklerin kopma yükü, kopma uzaması ve eğilme rijidlikleri deneysel olarak incelenmiş ve çift katlı iplikler bu özellikleri açısından yapılarında bulunan tek katlı iplikler ile karşılaştırılmıştır. Elde edilen sonuçlar çift katlı kesikli- 169 - lif ipliklerinin kopma mukavemetinin genel beklentinin aksine her zaman kendisini oluşturan tek katlı ipliğin mukavemetinin iki katından fazla olmadığını, katlama-bükme işlemi sonucu tek katlı ipliğe göre sağlanan mukavemet artışını yükseltmek için ya düşük bükümlü tek katlı iplikleri yüksek katlama bükümü ile katlamak veya yüksek bükümlü tek katlı iplikleri düşük katlama bükümü ile katlamak gerektiğini ortaya koymaktadır. Daha sonra çift katlı kesikli lif ipliğinin sabit uzama artışı ile çekilmesi durumunda, belirli bir uzama oranı için çift katlı ipliğe etkiyen eksenel gerilmenin hesaplanabilmesini sağlayacak bir teorik yaklaşım geliştirilmeye çalışılmıştır. Bu amaçla çift katlı ipliğin ve çift katlı iplik yapısı içerisindeki tek katlı ipliklerin deformasyonunun sabit hacimde gerçekleştiği varsayımı yapılarak önce tek katlı iplik ekseni doğrultusunda etkiyen yük saptanmış, daha sonra çift katlı iplik ekseni doğrultusundaki kuvvet bileşenleri bulunup toplanarak çift katlı ipliğe etkiyen toplam yük belirlenmiş tir. Tabii ki sabit hacim varsayımı nedeniyle bu yaklaşımın tüm uzama oranları için, özellikle kopma uzaması için, geçerli olması beklene mez. Ancak elde edilen bulgular geliştirilen teorik yaklaşımın lineer bölge sınırları içerisinde yeterli olabileceğini göstermektedir. Tek ve çift katlı ipliklerin eğilme rijidlikleri incelenirken, tek ve çift katlı ipliklerin eğilme davranışının katı yapıların eğilme davranışına benzediği, eğilme rijidliğinin iplik enine kesitinin atalet momenti ile orantılı olacağı ve çift katlı iplik yapısı içeri sindeki tek katlı ipliğin enine kesitinin elips şeklinde olduğu varsa yılmıştır. Bu temelden hareketle tek ve çift katlı ipliklerin atalet momenti oranları hesaplanmış ve bu oranlar deneysel bulgulardan hesaplanan eğilme rijidliği oranları ile karşılaştırılmıştır. Elde edilen sonuçlar incelendiğinde pamuk ipliği gibi nispeten yoğun bir yapıya sahip ipliklerde ve yüksek büküm seviyelerinde çift katlı ipliğin tek bir katı cisim gibi davrandığını varsaymanın pek yanlış bir yaklaşım sayılamayacağı, ancak düşük büküm seviyelerinde ve yün iplik-lerinde çift katlı ipliğin tek bir katı cisim gibi davranamadığı ve çift katlı iplik eğilme rijidliğini tek katlı iplik eğilme rijidliklerinin toplamı olarak düşünmenin daha gerçekçi bir yaklaşım olacağı anlaşılmaktadır
The yarns in the textile industry are very often used as twofold except in fine and simple weave fabrics. As a result of the process of doubling and twisting, not only the yarns which can support better the tensions during production processes and which show less variation from the point of view of properties like count, twist and strength are produced, but it can also be made possible to promote the yarn properties like flexibility, softness or hardness, brightness, regularity. and frictional wear resistance. In spite of quite extensive use of twofold yarns a single yarn is usually taken as model in the research and investigations related to the yarn structure and properties. In contradiction to this, the twofold yarn is very different from the single yarn from the point of view of both its geometrical structure and of its physical proper ties. In this work in which mechanical properties such as breaking strength, breaking elongation and bending rigidity of single and double yarns are examined comparatively, an optical arrangement has been set up to measure the yarn diameter which is an important dimen sional parameter, as a first step, and a method of calculation has been developed, which enables the calculation of the optical diameter of the twofold yarn based on the optical diameter of the single yarn by developing a theoretical model which assumes that a twofold yarn is formed by two similar cylindirical helices being wrapped together along the same axis and that the transversal yarn sections of single yarns within the body of the twofold yarn are elliptical. The values of the measurements made on twofold cotton, polyester/ cotton and wool yarns of varying count and twist levels chosen as experimental material are compared with calculated theoretical values and it is seen that sufficient agreement has been obtained. In the next stage of the work the breaking load, breaking elonga tion and bending rigidities of twofold yarns obtained by twisting single yarns of "Z" twist in the "S" direction at different count- 172 - and twist levels are investigated experimentally and the twofold yarns are compared with the single yarns existing in their own structure from the point of view of these properties. Results obtained show that the breaking strength of twofold staple fibre yarns are not always higher than two times the strength of the single yarns by which it is formed and that to promote the strength increase relative to the single yarn, provided by as a result of doubling and twisting process, it is necessary either to twist low twist single yarns with a high doubling twist or to twist high twist single yarns with a low doubling twist. Later on it is tried to bring a theoretical approach which would enable the calculation of the axial stress acting on the twofold yarn at a given strain when the twofold staple yarn is subjected to an extension at constant rate. For this purpose the load acting along the axis of the single yarn is determined first, making the assumption that the single yarns within the body of the twofold yarn suffer constant volume deformations, and then the total load acting on the twofold yarn is determined by finding and summing the force components along the axis of the twofold yarn. Naturally it cannot be expected that this approach is valid for all strain ratios and for the breaking elongation in particular because of the the assumption of constant volume. Nevertheless the findings obtained have shown that the theoretical approach developed can be adequate within the limits of the linear area. In examining the bending rigidities of single and twofold yarns it has been assumed that the bending behaviour of single and double yarns resemble the bending behaviour of solid structures; the bending rigidity will be proportional to the moment of inertia of the yarn cross section and that the transversal section of the single yarn within the body of the twofold yarn is elliptical. Moving from this premises the ratios moments of inertia of single and double yarns have been calculated and these ratios have been compared with those calculated from the experimental findings. When the results obtained are examined it is seen that it will not be considered as such a- 173 - wrong approach to assume that in yarns such as cotton yarn, which is a dense structure, and at high twist levels the twofold yarn behaves like a single solid body, but that at low twist levels and in wool yarns the twofold yarn does not behave like a single solid body and that it will be a more realistic approach to consider the bending rigidities of the twofold yarn as the sum of the bending rigidities of the single yarns.
The yarns in the textile industry are very often used as twofold except in fine and simple weave fabrics. As a result of the process of doubling and twisting, not only the yarns which can support better the tensions during production processes and which show less variation from the point of view of properties like count, twist and strength are produced, but it can also be made possible to promote the yarn properties like flexibility, softness or hardness, brightness, regularity. and frictional wear resistance. In spite of quite extensive use of twofold yarns a single yarn is usually taken as model in the research and investigations related to the yarn structure and properties. In contradiction to this, the twofold yarn is very different from the single yarn from the point of view of both its geometrical structure and of its physical proper ties. In this work in which mechanical properties such as breaking strength, breaking elongation and bending rigidity of single and double yarns are examined comparatively, an optical arrangement has been set up to measure the yarn diameter which is an important dimen sional parameter, as a first step, and a method of calculation has been developed, which enables the calculation of the optical diameter of the twofold yarn based on the optical diameter of the single yarn by developing a theoretical model which assumes that a twofold yarn is formed by two similar cylindirical helices being wrapped together along the same axis and that the transversal yarn sections of single yarns within the body of the twofold yarn are elliptical. The values of the measurements made on twofold cotton, polyester/ cotton and wool yarns of varying count and twist levels chosen as experimental material are compared with calculated theoretical values and it is seen that sufficient agreement has been obtained. In the next stage of the work the breaking load, breaking elonga tion and bending rigidities of twofold yarns obtained by twisting single yarns of "Z" twist in the "S" direction at different count- 172 - and twist levels are investigated experimentally and the twofold yarns are compared with the single yarns existing in their own structure from the point of view of these properties. Results obtained show that the breaking strength of twofold staple fibre yarns are not always higher than two times the strength of the single yarns by which it is formed and that to promote the strength increase relative to the single yarn, provided by as a result of doubling and twisting process, it is necessary either to twist low twist single yarns with a high doubling twist or to twist high twist single yarns with a low doubling twist. Later on it is tried to bring a theoretical approach which would enable the calculation of the axial stress acting on the twofold yarn at a given strain when the twofold staple yarn is subjected to an extension at constant rate. For this purpose the load acting along the axis of the single yarn is determined first, making the assumption that the single yarns within the body of the twofold yarn suffer constant volume deformations, and then the total load acting on the twofold yarn is determined by finding and summing the force components along the axis of the twofold yarn. Naturally it cannot be expected that this approach is valid for all strain ratios and for the breaking elongation in particular because of the the assumption of constant volume. Nevertheless the findings obtained have shown that the theoretical approach developed can be adequate within the limits of the linear area. In examining the bending rigidities of single and twofold yarns it has been assumed that the bending behaviour of single and double yarns resemble the bending behaviour of solid structures; the bending rigidity will be proportional to the moment of inertia of the yarn cross section and that the transversal section of the single yarn within the body of the twofold yarn is elliptical. Moving from this premises the ratios moments of inertia of single and double yarns have been calculated and these ratios have been compared with those calculated from the experimental findings. When the results obtained are examined it is seen that it will not be considered as such a- 173 - wrong approach to assume that in yarns such as cotton yarn, which is a dense structure, and at high twist levels the twofold yarn behaves like a single solid body, but that at low twist levels and in wool yarns the twofold yarn does not behave like a single solid body and that it will be a more realistic approach to consider the bending rigidities of the twofold yarn as the sum of the bending rigidities of the single yarns.
Açıklama
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Anahtar Kelimeler
Tekstil ve Tekstil Mühendisliği, Textile and Textile Engineering, Mekanik özellikler, Mechanical properties, Çift katlı iplik, Double layer yarn, İplik, Yarn
