بررسي و مدلسازي رفتار پارچه هاي اسپيسر در برابر ضربه

چكيده انگليسي :

Abstract The three dimensional fabrics have drawn much attention in the recent years and are used in different industries So study of the physical properties and mechanical behavior of these fabrics are important One of the most important properties of spacer fabrics is their reactionary properties So one of the most important application of these type of fabrics is using as a protector from impulsive forces Nowadays modeling of the relationship between structural parameters and textile properties as well as prediction of their properties by using these models has received considerable attention by researchers In this research with due attention to the magnitude to the behavior of three dimensional fabrics to applied impulsive forces in application at various industries a model have been provided for prediction the behavior of these fabrics to damp the resulting force of impact Because of the reactionary property of spacer fabrics a mechanical model containing lumped mass and spring has been used for studying the vibrating behavior of spacer layers due to impulse Viscous damping occurs in a mechanical system because of friction which is usually due to drag or internal forces So a mechanical device called a dashpot has been added to the system for producing the damping force The study of vibrations begins with the mathematical modeling of vibrating systems Mathematical modeling of vibrations problems leads to differential equations with constant coefficients At the model that has been used for spacer layers there are the mass stiffness and damping constants By solving the resulting equations the displacement of the system has been obtained as a dependent variable that is function of the time independent variable and shows the mechanical behavior of the system Eventually by application of the second low of Newton the resulting force of impulse has been calculated as function of time The mathematical model is only an approximation to the true physical system and the actual system behavior may be somewhat different than that predicted using the mathematical model So for investigating the actual behavior of the system and comparing with modeling results the experimental tests have been done For this purpose by falling a shot freely on the spacer layers the time history of the force resulting of the impact have been recorded by means of a load cell as the force time curves By extension of the model used for single layer a method has been provided for prediction the behavior of composite samples that contain several layers to applied impulsive loads too Also in order to investigate the effect of parameters of middle monofilaments on the response of spacer fabrics to applied impulsive forces four different types of samples that simulated with actual spacer fabrics were prepared These samples were different in length fineness and packing density of middle monofilaments The results of impact tests on these simulated samples showed that with decreasing the fineness and length of monofilaments and increasing their density the force transmitted in to the shot during collision with the spacer fabric is decreased The resulting values of modeling showed a good agreement with the force time curves obtained from the impact tests for single layer and multi layers samples The results of statistical tests showed that there is not significant difference between theoretical and experimental results Key words Spacer Fabric Impact Stiffness Constant Damping pdfMachine Is a pdf writer that produces quality PDF files with ease Produce quality PDF files in seconds and preserve the integrity of your original documents Compatible across nearly all Windows platforms if you can print from a windows application you can use pdfMachine Get yours now

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بررسي و مدلسازي رفتار پارچه هاي اسپيسر در برابر ضربه

ثابت سختي , ميرايي , مونوفيلامنت هاي مياني