Wyniki wyszukiwania - BazTech

1

Numerical investigations for cutting of wires and threads

Ulbricht V., Franeck J., Schirmacher F., Offermann P.

Autex Research Journal

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2003

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Vol. 3, no. 1

9--15

EN

Strengthening threads or strings are incorporated in technical textiles for example to protect against vandalism. Among other things, the resistance to mechanical destruction (e.g. cut) depends on the material, the cross-section of the strengthening threads and the support points in the base fabric. An essential criterion for durability is the maximum size of the cutting force, which increases with the decrease in the span. In preceding investigations with spring steel wire, it was shown that an optimum apparently exists for this span. The purpose of the investigations was the development of methods for ascertaining the maximum cutter strengths on the basis of standardised experiments (tensile test) and the proof of the existence of a span optimum. The investigations will be focused on monofilament wire.

2

Barrier effect of woven fabrics used for surgical gowns

Aibibu D., Lehmann B., Offermann P.

Autex Research Journal

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2003

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Vol. 3, no. 4

186--193

EN

Surgical gowns must have a barrier effect between the sources of infection and the user (i.e. a healthy person), as well as good wearing comfort. They are often made of woven polyester fabrics. Different fabric constructions are available for this purpose; these are evaluated with reference to their barrier properties. We present an optical method of obtaining cross-section figures of woven fabrics. The fabric is cut in warp and weft directions, and embedded perpendicularly in a cylindrical sample carrier using an epoxy resin. After the manufactured samples have hardened, they are smoothened and polished. Subsequently, images of the cross-sections of the fabrics are obtained by using an optical microscope linked to a digital camera and a computer. The images show the microstructure of the woven fabrics, i.e. the size and distribution of the pores in the filament yarn, and between the filament yarns with respect to the fabric weave and yarn density. The porosity is determined by image analysis methods using ImageC ® by Aquinto. The distributions of the width of the pores and of the pore areas are calculated. Pore channels are shown. The results of structural barrier effect are compared with the results of penetration tests. Synthetic blood or particle-loaded liquids containing microspheres comparable with the sizes of bacteria are used. The time necessary to soak the fabric with liquids or the contamination on the back of the fabric is determined.

3

Fuzzy-stochastic evaluation of uncertainties in material parameters of textiles

Abdkader A., Graf W., Möller B., Offermann P., Sickert J. U.

Autex Research Journal

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2002

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Vol. 2, no. 3

115--125

EN

Open textile structures made of AR glass filament yarns are finding increasing application in civil engineering, e.g. as reinforcement in thin concrete strengthening layers. A knowledge of material parameters is a precondition for the application of such materials. In this paper, experimental and numerical investigations aimed at collecting information on the uncertain material parameters of AR glass filament yarns are presented. This information serves as a basis for mathematical modelling. Uncertainty is here interpreted as fuzzy randomness, and quantified using fuzzy probability distribution functions.

4

Fully fashioned biaxial weft knitted fabrics

Cebulla H., Diestel O., Offermann P.

Autex Research Journal

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2002

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Vol. 2, no. 1

8--13

EN

Advanced composite manufacturing processes demand the use of fully fashioned near-net shape preforms. Flat knitting technology is especially suited for the production of such products. Research work which has been carried out at the ITB proved the possibility to obtain biaxial reinforced multi-layer weft knitted fabrics with fixed fabric edges, by varying the number of stitches in wale direction. The capability of this method is shown for an open cuboid and a spherical shell.

5

Dynamics of yarn tension on knitting machines

Pusch T., Wünsch I., Offermann P.

Autex Research Journal

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1999/2000

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Vol. 1, no. 2

54--63

EN

The submitted paper reports a study of investigation of the dynamics of yarn tension, i.e. to the time dependence of the yarn tension on large-diameter circular knitting machines (LCKM). The special feature of this study is the fact that predictions are made for the course of the yarn tension during a single stitch-forming process. Only the yarn tension in the area of the yarn feeder and the yarn guide eye can be measured. Some results of such experimental investigations have already been published [1,2]. In this paper, additional results of theoretical model calculations are presented. In particular, by these calculations it will be possible to determine the structure of the yarn tensile force at the knitting point, i.e. in the region between knitting needles. The calculation of the yarn tension required a numerical solution of a system of non-linear differential equations. The special difficulty lies in the formulation of the non-equilibrium state of the running yarn, especially in the formulation of the robbing-back effect.