The Physical Parameters Of Grain

At present,the government and social all circles attach great importance to food work,especially food quality and food hygiene safety.The physical parameters of grain are important reference indicators for evaluating food quality.Grain is as an important biological agriculture as agriculture and producers in China.Grain storage and the problem of grain damage had already existed for a long time.There are many studies on the physical properties and mechanical properties of cereals at home and abroad,many of which focus on wheat.However,at present,the experimental studies on the factors affecting the physical and mechanical properties of wheat are not systematic and in-depth.Most of the studies focus on the external friction and mechanical damage,which need further in-depth study.In this paper,wheat is mainly selected as the research object.The basic physical properties of grain and the mechanical strength,constitutive relationship and deformation characteristics of grain under triaxial compression are discussed and analyzed through the basic physical experiments and triaxial experiments.The main research tasks of this paper are as follows: 1.According to relevant grain national criterions,the basic physical properties of wheat samples are determined by experiments.For instance,wheat initial moisture content,bulk density,1000-grain weight,porosity,hardnesss and so on.The influence of moisture content on density,bulk density and porosity is analyzed in this paper.2.The angle of repose of wheat at different moisture content is measured by self-made experimental instrument,and the external friction coefficients of wheat stack with different materials(wood,concrete,steel and acrylic)are measured at different moisture content.3.The undrained tests of conventional triaxial compression on Zhengzhou wheat are conducted by the triaxial apparatus to investigate the effect of confining pressure,moisture content,loading rate and porosity on the stress-strain curves.The Mohr circle of wheat is obtained by using the stress-strain relationship and Mohr-Coulomb theory.Strength coefficient is obtained by strength analysis of Mohr circle envelope Wheat(internal friction angle ? and cohesion c).4.According to Mohr-Coulomb criterion of strength,the internal friction angle and occlusion force parameter of wheat stack under different porosity,shear rate and confining pressure are analyzed,and the macro and micro factors that may lead to these changes are analyzed in this paper.5.The stress-strain curves of grain stack under triaxial test are divided into four stages,and the characteristics of the four stages are analyzed.In the stress strengthening stage,secant modulus of wheat and its influencing factors are studied.The parameters of secant modulus are determined by triaxial test,which provides theoretical basis for PFC3 D numerical simulation of grain flow.The characteristics of dilatancy of different grain were analyzed under the condition of triaxial test.