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Dikim işlemi sırasında sürtünme ısısına etki eden malzeme değişkenlerinin incelenmesi

The Investigation of the effects of material characteristics on frictional heat during sewing

  1. Tez No: 21976
  2. Yazar: FATMA KALAOĞLU
  3. Danışmanlar: PROF. MUSTAFA KÖSEOĞLU
  4. Tez Türü: Doktora
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1992
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 143

Özet

ÖZET Hu çalışmada, dikiş işlemi sırasında ortaya çıkan sürtünme ısı sı ve ısınmayı etkileyen malzeme değişkenleri incelenmiştir. Dikiş iğnesi, kumaşa batarken kumaşın sürtünme mukavemetini yenmek zorundadır. Yüksek hızlı dikim işlemleri sırasında iğne ile kumaş arasındaki sürtünme sonucunda iğne ısınma problemi ortaya çıkmak tadır. 50Q0-6D0Q dev/dak hızda çalışan bir dikiş makinasında 2-5 mm ilmek uzunluğunda çalışıldığı takdirde dikiş ipliği üzerindeki her hangi bir nokta iğne gözünden 20-60 defa ileri-geri geçmekte ve ipliğin akış hızı da 150 km/saat seviyesine ulaşmaktadır. Bu sırada dikiş iğnesi, dikiş oluşumu için kumaşa dakikada 5000-6000 kez bat makta ve geri çıkmaktadır. İğne, kumaş ve dikiş ipliği arasındaki sürtünme sonucunda sürtünme ısısı açığa çıkarak iğne sıcaklığında artışa neden olmaktadır. Bu şekilde, iğne sıcaklıkları termoplastik liflerin erime sıcaklığına ulaşabilmekte ve bazı durumlarda 350- 400 C sıcaklığa kadar çıkabilmektedir. Bugüne kadar yapılan çalışmalar incelendiğinde sürtünme ısınmasına etki eden makina değişkenlerinin incelendiği görülmüştür. Bu çalışmada kumaş ve dikiş ipliği gibi malzeme özelliklerinin etkisi incelenmiştir. Çalışma yedi ana bölüm halinde düşünülmüş, bunlardan 1. Bölüm konuya giriş ve çalışmanın amacına ayrılmıştır. 2. Bölüm 'de konuyla ilgili esas kavramlar, 3. Bölümde bu konuda yapılan önceki çalışmaların özeti verilmiştir. 4.Bölüm'de kullanılan malzeme özellikleri ve deney metodları tanıtılmış, 5. Bölüm* de ise deney sonuçları verilmiş ve sonuçlar istatiksel açıdan değerlendirilmiştir. 6. Bölüm1 de elektron mikroskopla yapılan çalışmalar açıklanmıştır. Son olarak 7. Bölüm nihaî değerlendirmelere ayrılmıştır.

Özet (Çeviri)

SUMMARY The Investigation Of The Effects Of Material Characteristics On Frictional Heat During Sewing In stitching or sewing, the sewing needle has to penetrate through one or more fabric layers. During this operation the needle has to overcome some opposing farces produced by the fabric, which in turn generate heat causing an increase in needle temperature. This heat can affect the fabric, the needle, and the thread and has been the subject of much concern to garment manufacturers. In addition to the apparel industry, needle heating problems are common to many other industries such as; carpet tufting, needle punching, stitch banding. The heat often causes burn marks on natural fibers such as cotton or wool and it causes synthetic fibers to soften or melt, leaving a weakened seam or a melted residue on the fabric surface. Also, the thread may melt and break. Rethreading is time--..onsuming and in some cases is not passible because melted thread fibers may fuse and fill the eye of the needle. The heat may draw the temper of the needle and weaken it, so that it bends or fails by breaking. The amount of heat generated at the surface between the fabric and the needle depends upon the type of fabric, the needle size and shape, the needle surface finish, the sewing speed and the interrelationships of all these factors. The effect of the heat. is governed by the way in which it is dissipated. It may be transferred to the needle, the cloth or to the surrounding atmosphere. The rate of heat transfer depends on the bulk and surface thermal properties of the needle and the cloth, an the motion of the air around the needle, and on the temperatures of these three heat sinks. As the needle is continously exposed to the heat, its temperature increases very quickly. Steadystate condition is reached in which the amount of heat generated by friction exactly equals the amount of heat lost by the needle when it is not in contact with the -VI-cloth. The temperature of a point an the needle will eye le-it increases immediately after passing through the cloth and decreases while exposed to the air. The symptom of cloth burning or melting is the field definition of a sewing heat problem. This is only a qualitative measurement. Synthetic fibers soften or melt when the needle temperature reaches their melting point temperature, so the fabric or thread will be damaged. For this reason,; the needle temperature was chosen as the best measurement to use in this investigation of the factors which affect sewing heat problems. To obtain quantitative measurements of needle temperatures several methods have been used. Temperature-sensitive waxes and lacquers have been used to determine needle temperatures by placing them in the needle groove. These materials melt or change color when they reach a specific temperature. Most results reported about needle temperature in the literature have been obtained by using an attached thermocouple. Usually, this is done by soldering or welding a wire other than steel to the needle to form a thermocouple, with the needle itself serving as one of the junction metals. The disadvantages of this technique are the mechanical problems associated with the wire leads to the needle and relatively slow response to temperature changes, when compared with an infrared detector. Measurements have also been made by touching a thermocouple tot the hot needle after the sewing machine is stopped. The last technique is to measure the needle temperature by infrared radiation microscope. Any body at a temperature above absolute zero, emits energy in the form of thermal radiation. The amount and spectral distribution of the thermal radiation emitted by a body depends on its absolute temperature and surface characteristics. A real body wiil emit only a fraction of the energy which is emitted by a black body. A black body also absorbs all the radiation falling upon it. The ratio of the absorption of a real body to a black body is called the absorptivity. At thermal equilibrum, the absorptivity and emissivity of a body are equal. These quantities very with the wavelength of the radiation and so. are functions of temperature. The quantity which can be measured is the amount of emitted energy which is absorbed by a detecting device. An experimental system has been developed which permits the accurate measurement of complete needle temperature by infrared method. The instrument Hatra sew, was used in conjunction with a sewing machine and measured the sewing needle temperature by means of an infrared detector. -vii-Hatra Sew consists of detector head, preamplifier and main amplifier. Detector responds to heat radiation, emitted by the sewing mechine needle. The signal from the preamplifier is fed into the main amplifier after which it is processed to give a meter output, which is directly related to the temperature of the sewing needle. Since the apparatus is designed to provide information about the frictional condition of fabric, the scale marking has been simplified. The meter registers the F- index on a scale between 0-10. Calibration of the meter in (°C) has not been carried out, because the calibration varies according to the particular sewing machine and test conditions. The relationship plotted in Appendix A is the calibration curve applicable to a lockstitch machine sewing at 4500 stitches per minute. In this work, the effects of fabric and sewing thread characteristics on needle temperature were investigated. The Hatra Sew was mounted on a Singer 591 D 300 A lockstitch sewing machine and a size 14 sharp point sewing needle was used throughout. 54 different fabrics and 29 different sewing threads were used. The physical tests were carried out on the threads and fabrics using standard equipment, test methods and atmosplaeric conditions. The count, twist, tenacity, paraffine ratio of the sewing threads were measured for each of the thread. The mass, air permaability, weft and warp yarn count, utett and warp thread;' per centimeteö* were measured for each of the fabric. The fabrics were tested with different sewing threads on two plies of fabric, as well as without sewing thread with four of the fabrics. The other sewing conditions was kept constant. The sewing machine was run at 4500 stitches per minute and stitch density was 6 stitches per centimeter. A one-meter length of fabric was sewn in the warp direction in each case. Tnis length of fabric was required for the F-index value to reach a maximum.. In each case the maximum reading on the F-index scale was taken and the experiment was repeated three times. The average value of a fabric was taken and converted to temperature by means of calibration curve. -Vlll-From the results it can be seen that fabric structure has a significant effect on needle temperature. Air permeability is an important factor in the performance of fabrics. üJeaye, yarn crimp and yarn twist influence the shape and the area of the spacing between yarns in fabric, as more spacing is covered by yarn permeability is reduced. A very high correlation (r=0,91) was obtained between needle temperature and fabric air permeability. As the fabrics air permeability decreased, the needle temperature increased. There were also good correlations between needle temperature and fabric cover factor and fabric density (kg/m2). As the fabric became tighter and heavier, the needle temperature increased.. The number of layers of cloth being sewn influences the maximum needle temperature. The thread is able to cool the needle by conducting heat away, the transfer occurring between the hot needle and the cold thread. However, heat is also generated by the thread passing through the eye of the needle at very high speeds. The use af thread lubricants had significant effect on needle temperature. Needle temperature varied between the different types of thread with those produced from synthetic fibers generally having the lowest needle temperature, probably because they had been properly lubricated. It was found that sewing thread count and twist have slight effects on needle temperature. The scanning Elektron Microscope was to probe into the surface structure of the sewing threads ebserved after sewing and to find out the nature and extent of dama ge due to high needle temperatures. An attempt was made to support the visual evidence with physical data. From the figures in the last chapter it can be easily- seen that synthetic sewing threads influenced from the -ix-frictional heat and they melt. Cotton threads withstand high. te..jerature but it is seen that a large number of bracken ends of the fibers come out of the thread. The threads which are finer and more compactly twis ted showed less damage. Also, the threads which are well lubricated show less danaqe to the fiber surface. -x-

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