Modelling the mechanical behaviour of pharmaceutical powders during compaction
Modelling the mechanical behaviour of pharmaceutical powders during compaction
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DOI：
10.1016/j.powtec.2005.01.010
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发表时间：
2005-04
影响因子：
5.2
通讯作者：
Chuan-Yu Wu;O. M. Ruddy;A. Bentham;Bruno C. Hancock;S. Best;J. Elliott
中科院分区：
文献类型：
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作者：
Chuan-Yu Wu;O. M. Ruddy;A. Bentham;Bruno C. Hancock;S. Best;J. Elliott
使用有限元方法 (FEM) 分析药粉在压实过程中的机械行为，其中将粉末建模为弹塑性连续体材料。选择 Drucker–Prager Cap (DPC) 模型作为介质的屈服面，它代表了失效和屈服行为。还使用带有仪表模具的压实模拟器进行了单轴压实实验。这些实验的目的有两个：（1）研究压实过程中药物粉末的行为，分析粉末床相对密度随施加压力的变化； (2) 通过实验测量来校准 DPC 模型，从中生成真实的粉末特性并将其输入有限元分析 (FEA)。还从有限元分析中获得了粉末床的相对密度和施加压力之间的关系，并与实验数据进行了比较。实验结果与 FEA 结果之间观察到良好的一致性，这表明 FEA 可以捕获压实过程中粉末行为的主要特征。此外，对卸载过程中应力分布演变的仔细检查表明，从片剂的顶部边缘到底部中心存在一条狭窄的带，其中存在局部的、强烈的剪切应力。正是在此范围内，可能会引发潜在的失效区域，例如裂纹。 X 射线显微断层扫描图像和破裂片剂摄影的实验证据已经证明了这一点。因此，事实证明，有限元分析可以预测压实过程中可能的失效机制，例如封盖。
The mechanical behaviour of pharmaceutical powders during compaction is analysed using Finite Element Methods (FEM), in which the powder is modelled as an elastic–plastic continuum material. The Drucker–Prager Cap (DPC) model was chosen as the yield surface of the medium, which represents the failure and yield behaviours. Uniaxial compaction experiments were also carried out using a compaction simulator with an instrumented die. The objectives of these experiments were two-fold: (1) to investigate the pharmaceutical powder behaviour during compaction, for which the variation of relative density of the powder bed with applied pressure is analysed; and (2) to calibrate the DPC model with the experimental measurements, from which realistic powder properties are generated and fed into finite element analysis (FEA). The relationship between relative density of powder bed and applied pressure is also obtained from FEA and compared with the experimental data. Good agreement between the experimental and FEA results is observed, which demonstrates that FEA can capture the major features of the powder behaviour during compaction. Furthermore, close examination of the evolution of the stress distribution during unloading reveals that there is a narrow band existing from the top edge towards the bottom centre of the tablet, in which there are localised, intensive shear stresses. It is in this band that potential failure regions, such as cracks, can initiate. This has been demonstrated with experimental evidence from X-ray microtomographical images and photography of fractured tablets. It is therefore demonstrated that FEA can predict the possible mechanism of failure, such as capping, during compaction.