Impact breakage of particulate solids
Impact breakage of particulate solids
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发表时间：
1998
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通讯作者：
D. Papadopoulos
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作者：
D. Papadopoulos
不受控制的颗粒破碎可导致产品质量劣化和工艺性能降低，并带来严重的经济后果。因此，识别和理解负责颗粒破碎的过程和机制是至关重要的。本工作的目的是提供一个系统的方法来分析颗粒固体的冲击破碎。这种方法涉及观察，分析和建模的组成机制的颗粒破碎的压痕断裂力学。在各种载荷条件下的颗粒破碎的研究文献是丰富的。然而，建模主要集中在量化而不是预测颗粒破碎。造成这一不足的主要原因有两个。首先，结果往往是从多粒子试验中获得的，其中加载模式，即加载条件和接触几何形状，是不明确的。其次，几乎没有采取任何措施来确定颗粒破碎对杨氏模量、硬度和断裂韧性等机械性能的依赖性。本文采用单颗粒冲击试验研究了冲击速度、冲击次数、颗粒尺寸和冲击角度等因素对具有多种性能和结构的材料破碎的影响。测试材料包括聚甲基丙烯酸甲酯（PMMA）挤出物、硝酸铵颗粒、分子筛珠粒和用作催化剂载体的三种类型的高度多孔的二氧化硅颗粒（表示为PS1、PS2和PS3）。测试材料的选择将其科学价值与当前的工业利益相结合。PMMA的硬度是用压痕法测量的，而断裂韧性是从文献中获得的。应变速率和测试配置的断裂韧性值的影响，适当的冲击试验条件下，仔细考虑。使用压痕断裂测量PS3珠的硬度和断裂韧性。然而，由于颗粒的表面粗糙度和/或不规则形状，硝酸铵小球、PS1和PS2颗粒的机械表征非常困难。使用高速记录技术观察撞击事件，并使用光和扫描电子显微镜检查撞击产物的形态，以确定作为撞击速度函数的试验材料的断裂模式。结果的解释，然后进行压痕断裂和颗粒破碎的裂纹形态的基础上，如文献中所述。1只适用于定性工作。
Uncontrolled particle breakage can result in deterioration of product quality and reduction of process performance with severe economical consequences. Therefore, identification and understanding of the processes and mechanisms responsible for particle breakage are of paramount importance. The objective of this work is to provide a systematic approach to the analysis of the impact breakage of particulate solids. Such an approach involves observation, analysis and modelling of the constituent mechanisms of particle breakage by means of indentation fracture mechanics. The literature is rich of studies of particle breakage under various loading conditions. However, modelling has mainly focused on quantifying rather than predicting particle breakage. Two main reasons are responsible for this inadequacy. First, results have often been obtained from multi-particle tests where the mode of loading, i.e. loading conditions and contact geometry, is ill-defined. Second, little has been done to establish the dependence of particle breakage on mechanical properties such as Young's modulus, hardness and fracture toughness. Single particle impact testing is used in this work to investigate the effect of impact velocity, number of impacts, particle size and impact angle on the breakage of materials with a wide range of properties and structures. The test materials involve polymethylmethacrylate (PMMA) extrudates, ammonium nitrate prills, molecular sieve beadsl and three types of highly porous silica particles used as catalyst carriers (denoted as PS1, PS2 and PS3). The selection of the test materials combines their scientific merit with the current industrial interest. The hardness of PMMA is measured using indentation, while the fracture toughness is obtained from the literature. The effect of strain rate and test configuration on the value of fracture toughness, appropriate for the impact test conditions, is carefully considered. The hardness and fracture toughness of the PS3 beads are measured using indentation fracture. However, the mechanical characterisation of the ammonium nitrate prills, PS1 and PS2 particles is very difficult due to the roughness of the surface and/or the irregular shape of the particles. Observation of the impact event using high-speed recording techniques and examination of the morphology of the impact product using light and scanning electron microscopies are employed to identify the breakage pattern of the test materials as a function of impact velocity. Interpretation of the results is then carried out based on crack morphologies of indentation fracture and particle breakage, as described in the literature. The breakage 1 Only for qualitative work.