偏心卸料筒仓与粮食散体材料相互作用研究

发布时间：2018-12-19 11:59

【摘要】：钢筒仓是粮食储藏的主要仓型,目前工程中已有直径超过30m的大型钢筒仓应用,筒仓的安全问题一直是专家学者研究的重要课题。筒仓通常采用中心卸料的方法,但由于造价、空间或其他因素的限制,有时需要采用偏心卸料的方法。偏心卸料薄壁钢筒仓易引起仓体应力的剧烈变化,不同偏心率下筒仓与散体材料的相互作用差别较大,故有必要对其进行深入研究,然而偏心卸料筒仓试验过程较为复杂,试验代价大,因此有必要进行数值模拟。本文在国家自然科学基金项目(51408197)的支持下,对偏心卸料时仓壁与储料的相互作用问题进行研究。通过对郑州小麦进行直接剪切试验与三轴剪切试验,分析其剪切特性,并根据试验结果获得本构模型所需参数,使用有限元软件ABAQUS建立有限元模型,对偏心卸料筒仓与储料相互作用进行研究,并与规范进行对比分析。本文主要研究工作如下:(1)通过直接剪切试验得出剪切速率对小麦强度参数的影响,随剪切速率增大内摩擦角逐渐减小,咬合力逐渐增大。(2)通过三轴压缩试验研究初始密度以及应力路径对小麦剪切特性的影响,结果表明,随初始密度的增大,小麦试样的内摩擦角以及咬合力随之增大,破坏比fR呈增大趋势;常规三轴压缩试验下应力应变关系呈应变硬化型且无明显应变软化现象,应变较小时有明显剪缩现象;等p三轴压缩试验下有轻微应变软化现象,剪缩现象不明显;减p三轴压缩试验表现出明显的应变软化现象,基本无剪缩现象。(3)通过筒仓与储料相互作用有限元模型研究高径比对筒仓侧压力的影响,结果表明,高径比对静态平衡阶段筒仓侧压力影响较小,对筒仓动态卸料时侧压力有一定影响,在相同卸料口直径情况下高径比对小直径筒仓影响较大。(4)通过筒仓与储料相互作用有限元模型研究偏心率对筒仓侧压力的影响,结果表明,三种直径筒仓在偏心率由0增大至0.6的过程中,靠近卸料口一侧所受侧压力先增大后减小,直径为24m在偏心率为0.4左右达到最大,直径为16m和8m筒仓在偏心率为0.2时最大;筒仓其它两侧的侧压力随偏心率的增大逐渐增大。(5)将高径比为1.5的深筒仓动态数值计算结果与规范对比,发现其能较好的符合欧洲规范计算结果,我国规范以及美国规范动态侧压力系数较大,计算结果较为保守,可以对不同高径比的筒仓分别定义侧压力系数。
[Abstract]:Steel silo is the main type of grain storage. At present, large steel silo with diameter more than 30m has been used in the project. The safety of silo has been an important subject studied by experts and scholars. Silos usually use the central unloading method, but due to cost, space or other factors, it is sometimes necessary to use the eccentric unloading method. Eccentric unloading thin-walled steel silo can easily cause severe changes in the stress of silo body, and the interaction between silo and bulk material is quite different under different eccentricity ratio, so it is necessary to deeply study it, but the test process of eccentric unloading silo is more complicated. The cost of the test is high, so it is necessary to carry out numerical simulation. Supported by the National Natural Science Foundation of China (51408197), the interaction between silo wall and storage material during eccentric discharge is studied in this paper. The shear characteristics of Zhengzhou wheat were analyzed by direct shear test and triaxial shear test. According to the test results, the parameters needed for constitutive model were obtained, and the finite element model was established by using finite element software ABAQUS. The interaction between eccentric unloading silo and storage material is studied and compared with the specification. The main work of this paper is as follows: (1) the effect of shear rate on wheat strength parameters is obtained by direct shear test, and the internal friction angle decreases with the increase of shear rate. (2) the effects of initial density and stress path on the shear properties of wheat were studied by triaxial compression test. The results showed that the internal friction angle and bite force of wheat samples increased with the increase of initial density. The damage ratio of fR increased; Under the conventional triaxial compression test, the stress-strain relationship is of strain hardening type and has no obvious strain softening phenomenon, and the strain is obviously shear-shrinkage phenomenon when the strain is small, and the slight strain softening phenomenon is not obvious in the iso-p triaxial compression test, but the shear shrinkage phenomenon is not obvious. The triaxial compression test shows obvious strain softening phenomenon and no shear-shrinkage phenomenon. (3) the influence of height to diameter ratio on the lateral pressure of silo is studied by the finite element model of silo and storage material interaction. The ratio of height to diameter has little influence on silo lateral pressure in static equilibrium stage, which has certain influence on silo dynamic discharge pressure. In the case of the same discharge diameter, the ratio of height to diameter has a great influence on the silo. (4) the influence of eccentricity on the lateral pressure of silo is studied by the finite element model of silo and storage interaction. In the process of increasing the eccentricity ratio from 0 to 0.6, the lateral pressure near the discharge port first increases and then decreases, and the diameter of 24m reaches the maximum at the eccentricity rate of 0.4. The eccentricity ratio of the silo with diameter of 16m and 8m is the highest at 0.2; The lateral pressure on other two sides of silo increases with the increase of eccentricity. (5) comparing the dynamic numerical results of deep silo with the specification when the ratio of height to diameter is 1.5, it is found that the calculated results are in good agreement with the European Code. The dynamic lateral pressure coefficient of Chinese code and American code is large and the calculation result is conservative. The lateral pressure coefficient can be defined for silo with different aspect ratio.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU375

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