【作者】 白雪卫；

【导师】 李旭英；

【作者基本信息】 内蒙古农业大学 ， 机械设计及理论， 2006， 硕士

【摘要】 为进一步探索草物料的压缩理论,在压捆试验台上对含水率为17%的紫花苜蓿进行整株压缩。在压捆室不同截面下,分别进行应力松弛试验及移动过程压缩试验。采用虚拟仪器数据采集系统,记录试验过程中的压缩力、草片在压捆室内的移动及草片厚度变化量。采用逐次余数法对应力松弛试验数据进行处理,获得不同截面下草片的粘弹性力学模型,其模型均为3个麦克斯威尔单元(Maxwell Element)构成的广义麦克斯威尔模型。基于该模型,应用粘弹性力学理论,获得松弛函数及蠕变函数,建立苜蓿草片的微分型和积分型本构方程。在此基础上,以Matlab及Simulink仿真软件为平台,建立本构方程的仿真模型。在对直接压缩后的应力松弛试验进行仿真时,仿真曲线与试验数据吻合较好,说明采用粘弹性力学模型描述草片的力学行为是合理的。为比较不同截面草片的应力松弛规律,取各模型松弛应力起始值相同,仿真发现:0～3s内,截面为360㎜×460㎜的草片模型应力松弛的最快;在3～6s内,截面为385㎜×460㎜的草片应力下降为最小;在松弛了约10s后,截面为510㎜×460㎜的草片应力下降最为迅速。说明截面变化对应力松弛规律有影响,在压捆机的设计过程中,压捆室截面的确定要考虑压缩频率的影响,反之亦然。通过仿真移动过程中第一片草片应变随时间的变化,及移动全过程应力随时间的变化,可得到与草片实际变形过程相近的变形规律。更多还原

【Abstract】 To treat the compression theory for herbage material, alfalfa with moisture content 17% is compressed on baling test board. Stress relation and engineering compression experiments are conducted in different cross-area of baling room, compress force, displacement and variety of alfalfa wafer’s depth are recorded with virtual instruments data logging system. Viscoelastic model in different cross-area of baling room are obtained, through stress relation experiment data processed with method of successive residuals. The model is generalized Maxwell model constituted of 3 parallel Maxwell elements. Relation modulus and creep compliance are gained on base of the model and the viscoelastic theory, establish the constitutive equation. In Matlab and Simulink platform, simulation model of constitutive equation is found. Simulation on stress relation experiment verifies generalized Maxwell model is appropriate to describe the mechanical behaviors of wafer. To compare the stress relation between wafer of different cross-area, on the same starting point of stress, simulation on stress relation of wafers in different cross-area shows that: stress declines at lowest for model of cross-area 360㎜×460㎜ in time interval 0~3s, in time interval 3~6s, model of cross-area 385㎜×460㎜ declines more faster than other cross-area, after 10 seconds relation of stress, the model of cross-area 510㎜×460㎜ becomes the lowest. That is, determination of compress frequency should take the influence of cross-area into account while designing baler, and vice versa. Simulation of strain-time relation of first wafer in translation process as well as stress-time relation of the entire compress process finds the similar deformation characteristics with realistic deformation of wafer.更多还原