Experimental Study On Mechanical Characteristic Of Cotton Stalk

Biomass straw pretreatment is the premise and key of comprehensive utilization of the feed, fuel and fertilizer. The research of shear, bending mechanical properties and compression stress relaxation characteristics of cotton straw is good for the development processing technology and machinery.Due to the diversity of cotton stalk,This paper take different varieties of cotton stalk as test materials in different regions in Hubei province, and make mechanical properties test of cotton straw by universal material testing machine and self-made clamp. The research analysis the stress relaxation characteristics respectively from the moisture content, wood fiber content,initial density and deformation and shear, bending mechanical properties from the loading speed, moisture content. Also this research analysis relevance of Wood fiber content of cotton stalk and compression stress relaxation characteristics.For the study of the shear mechanical properties of cotton stalk, The article take "emian23" and "Xiangzamian8" cotton stalk as the research object, and make single shear test on cotton stalk by universal material testing machine to discuss the factors that the loading speed, moisture content, shear angle and shear cutter location of cotton stalk affecting on shear strength and shear power. The results show that Loading rate has significant effect on shear strength and no significant influence on the shear power of cotton stalk, The part of cotton stalk has no significant effect on shear strength and significant influence on the shear power, The moisture content has significant effect on shear strength and the shear power, The shear angle has no significant effect on shear strength and the shear power, but the shear power of15degrees angle of the cutter is significantly smaller than the shear power30degrees.(1)For the study of the bending mechanical properties of cotton stalk, The article take "emian23" and "Xiangzamian8" cotton stalk as the research object, and make bending test on cotton stalk by universal material testing machine to discuss the factors that the loading speed, moisture content, the gauge and bending location of cotton stalk affecting on flexural strength and modulus of elasticity. The results show that Loading rate has no significant influence on flexural strength and modulus of elasticity of cotton stalk, The part of cotton stalk has no significant effect on flexural strength and modulus of elasticity, The moisture content has significant effect on flexural strength and modulus of elasticity.(2)This article collect47different varieties of cotton stalk particles from different growing areas and environment and implemented stress relaxation test on it by RGM-6010universal material testing machine.The stress relaxation curve of cotton stalk particles is fitted by the three-element of generalized Maxwell model, the five-element of generalized Maxwell model and the peleg model. And this article using the grey relation theory analysis association of the stress relaxation characteristics and lignocellulose of cotton straw powder. Results show that the five-element of generalized Maxwell model is best to depict stress relaxation characteristics of cotton stalk particles and the fitting coefficient of determination, balance elastic modulus, the first stress time, and the second stress time are0.999,4.477MPa,4.30s and48.48s respectively. The lignocellulose of cotton stalk particles has an obvious effect on the compress stress relaxation time. The influence degree of the maximum is cellulose and the minimum degree is hemicellulose. And the correlation between the equilibrium modulus and lignocellulose are at about0.70, and the numerical has little difference. Therefore cellulose, hemicellulose and lignin, neutral detergent fiber and acid detergent fiber effect on the equilibrium modulus is close.(3)Taking the equilibrium modulus and stress relaxation time ratio combined as test index, this article make compression stress relaxation test on cotton stalk particles by universal material testing machine to investigate the effect of the initial density, deformation and moisture content on the equilibrium modulus and stress relaxation time and the ratio combined. The results show that the deformation, initial density and moisture content has significant effect on the equilibrium modulus and stress relaxation time and the ratio combined under certain conditions.