Finite element modeling and simulation of cotton fiber assembly carding process based on 3-D braided and fractal theory
Objective Carding is the core step of cotton carding process.Its principle is to separate the fiber bundles in cotton roll into a single fiber by means of needle surface movement.In order to achieve the carding effect and prevent cotton fiber from being damaged due to excessive force at the same time,it is essential to control the carding force of cotton fiber within a reasonable range.To study the stress of cotton fiber assembly in carding process and improve the quality of cotton sliver,a new model of cotton fiber assembly was built.Method The cotton fiber units were established based on the fractal theory,combined with the modeling idea of three-dimensional braided composite materials.The fractal cotton fiber units were arranged according to the fiber distribution in the internal single unicellular structure of three-dimensional four-way braided composite.The model was applied to simulate the carding process of cotton fiber assembly.The stress and strain variation of cotton fiber was studied by finite element method,the change of carding force over time was analyzed.Results The carding process of cotton fiber under the fixed moisture regain was simulated by using finite element software.The cotton fiber was in the working area between cylinder and plate of the carding machine.In this process,cotton fiber was held by the needle teeth of cylinder and sorted by the needle of plate.The carding force of cotton fiber assembly,the stress and strain variation of cotton fiber over time were studied.Stress relaxation parameters shows that the stress and strain of cotton fiber first increases and then decreases as time goes on.It can be seen from assembly diagram that the stress of cotton fiber mostly occurs in the part directly in contact with the needle of plate and the part held by the needle teeth of cylinder.The effect of cotton fiber moisture regain on carding process was analyzed.The simulation parameters of cotton fiber under different moisture regain conditions were determined.The change of moisture regain will cause the change of friction coefficient of cotton fiber surface,and then affect the carding force.On the basis of the existing friction coefficient values of cotton fiber surface,the interpolation polynomial of friction coefficient and moisture regain was determined by method of undetermined coefficients.The friction coefficient values of cotton fiber under different moisture regain conditions were obtained.With the rise of moisture regain,static friction coefficient between cotton fiber and metal decreases,while dynamic friction coefficient increases.Both static friction coefficient and dynamic friction coefficient between cotton fibers increase.The stress of cotton fiber and the carding force on cotton fiber assembly increase first and then decrease with the rise of moisture regain.Conclusion The simulation results of carding force are in agreement with the experimental results,indicating that the model of cotton fiber assembly is reasonable.As moisture regain increases,both the stress of cotton fiber and the carding force of cotton fiber assembly generally increases first and then decreases.According to the stress cotton fiber assembly under different moisture regain conditions,when the moisture regain is 6.5%and 8.5%,the stresses in both conditions are not very different and are relatively large.But the carding force is greater when the moisture regain is 6.5%,in this condition the carding effect is the best.The finite element method can better analyze the process of cotton carding,provide reference for the parameter setting of each part of the carding machine,and improve the carding efficiency and quality.
cotton fiber assemblycarding processfinite element modelsliver qualitycarding forcemoisture regain
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