Study On The Compression Performance And Rheological Properties Of Straw Bales

Agricultural fiber material has the properties of light,osteoporosis,large volume,low density,which is difficult to collection,transport and storage.Straw compression molding technology becomes an effective way for agricultural fiber material cyclic utilization.People have made extensive research on the rheological properties on the compression process of agricultural fiber material.The rheological properties of straw-bales in the process of low density compressed were detailed studied in the present paper.The purpose was to provide a certain theoretical guidance for low density compressed of straw,and to improve the theory of straw processing forming,which was significantly important to the straw-bales in the area of straw-bale building and straw-bales wall solar greenhouse.The research was stuied based on the the compression performance and rheological properties in the process with the density from natural to the maximum density(300kg/m).The materials was rice,wheat and corn straw with moisture content of 15%and length of 20 mm,as well as rice straw with moisture content of 10%and length of 10 mm,20 mm,30 mm,respectively.The initial feed quantity was 17 g,19 g and 21 g.The stress-strain rule and rheological properties was analyzed in the compression process.And the cftool toolbox of MATLAB software was used to complete the data analysis and numerical simulation.The stress relaxation and creep law after compression with different test conditions.Finally,the creep deformation of straw-bales wall in solar greenhouse was monitored for more than one year,which was explained according to the creep rule of straw-bales in the laboratory.The present study was also used to optimize the design of low density straw-bales compression equipment,to provide theoretical basis for energy consumption,to guide new direction for the rational utilization of straw resource in the future.This main research contents and conclusions are showed as follows:(1)Under the experimental condition,the relationship between stress and strain in the process of straw compression,the stress relaxation and creep law after straw compression was discussed by the data collected from the changes of stress and displacemen,also including stress and strain values along with the change of time.The relationship of stress-strain under different feed quantity of rice,wheat and corn straw,as well as rice straw along with different chopped length is discussed.The results showed that the stress relaxation behavior could be described by two parallel four components of the generalized Maxwell model[M]model;the compression creep properties could be represented by the four components of burgers model([B]model).(2)The the relaxation time of rice,wheat and corn straw with moisture content 15%was 40 s under low density compression through the analysis of related parameters on the stress relaxation model.While it was 45 s for rice straw with moisture content 10%and length of 30 mm.(3)It suggested that the appropriate kinds of straw should be choosen to produce straw-bales in order to reduce energy consumption according to the different final requirements and the results of stress strain rule of compression under different test conditions.Also,the chopped straw would be easily compressed,which was beneficial for nergy consumption.(4)The results obtained from the analysis about compression rule and rheological properties of the rice,wheat and corn straw,showed that the wheat straw required the largest energy in compression process requires the largest energy consumption,the highest intensity of twine for straw-bales,and a better ability keeping deformation after compression.The results of compression rule and rheological properties with different length of straw showed that the shorter straw can be compressed easily with smaller pressure stress,and the stress relaxation time and strapping time wwere also shorter.The intensity of twine was lower.Above all,,the wheat straw is better selection for straw-bales wall raw material than that of rice and corn straw.The length of straw was also better than that of shorter ones.(5)The results from the creep deformation of straw-bales wall in the solar greenhouse showed that the deformation has important relationship with the density of straw-bales.The higher density of straw-bales wall has smaller deformation for the straw-bales wall.So it should be larger density for building straw-bales wall from the aspect of wall stability.