Scale-up of a high shear wet granulation process using a nucleation regime map approach

Scale-up of the high shear wet granulation (HSWG) process is considered a challenge because HSWG is complex and influenced by numerous factors, including equipment, formulation, and process variables. For a system of microcrystalline cellulose and water, HSWG experiments at three scales (1, 2, and 4 L working vessel) were conducted with a granulator. Scale-up was implemented on the basis of a nucleation regime map approach. To keep dimensionless spray flux and drop penetration time constant, water addition time at three processing scales were 300, 442, and 700 s, respectively. The other process parameters were kept unchanged. Granule size distributions were plotted and compared, and scanning electron microscopy was used to analyze granule surface morphology. Physical characterization was undertaken using a modified SeDeM method. At nearly all scales, granule yield was greater than 85% and all the cosine values were larger than 0.89. At the same experiment points, granules at all scales had similar surface morphology and similar physical characteristics. The results demonstrate that a rational scaling-up of the HSWG process is feasible using a regime map approach.     

Numerical simulation for the simple shear test in amorphous glassy polymers

In this paper, a driving stress finite element method of elastic-plastic large deformation based on implicit time integrating algorithm and an eight-chain molecular network model is used for the numerical simulation of the simple shear test of polycarbonate (PC) materials. The simulated results are compared with experimental ones. The strain localization propagation for the shear band deformation for simple shear deformation is investigated numerically. The effects of microstructure parameters in the model on strain softening and orientation hardening of the PC are discussed in detail. Supported by the National Natural Science Foundation of China.     

轮胎胎体层的剪切模量研究

本文用胎体层的组分材料基本材料性能参量和内胎的充分气压力，预报了含有内胎的胎体层的宏观切向刚度和当量剪切模量。其预报值与实验值吻合很好。     

包括各向异性效应在内的地球介质中井孔的稳定性

为了研究地球介质深的斜井（这种井既受到内压又受到非静水应力场的作用）有必要发展一种分析表述方式，这种表述方式包括井孔周围应力的三维分析，并把它和井孔内压组合后，求出总应力分布的近似解。在实际现场条件睛，井孔的取向、原地应力和岩层层面倾斜都可能是任意的。对井孔的拉伸破坏和剪切破坏都进行了研究，当井孔最小主应力超过拉伸强度时，出现拉伸破坏，这就是拉伸破坏准则，对剪切破坏而言，采用了向向异性材料的修正的     

Expansion of cylindrical shells subjected to internal explosive detonations

Two explosively loaded cylindrical shell experiments were conducted to provide experimental data for benchmarking numerical codes. Each shell was subjected to internal high-explosive detonations, which caused it to expand outwardly at strain rates on the order of 10⁴ s^–1. At approximately 150 percent strain, multiple plastic instabilities appeared on the surface of these shells in a quasi-periodic pattem. These instabilities continued to develop into bands of localized shear and eventually formed cracks before causing the shell to fragment. Diagnostic equipment on these experiments included a Fabry-Perot interferometer and a fast-framing camera. The experiments and the data obtained from the diagnostic equipment are discussed and illustrated.     

塑料多轴冲击标准与试验技术探讨

分析比较了ISO 6603-2和ASTM D3763中关于塑料多轴冲击试验方法的异同,着重讨论了这些标准在测试技术上的不同要求,探讨了试验机性能对试验结果的影响,并提出了对试验机测控系统软硬件设计的技术要求。     

纳米流控能量吸收耗散系统

基于纳米流控行为设计的新一代能量吸收耗散系统(nanofluidic en-ergy absorption system,NEAS)将会比传统吸能材料具有更高的能量吸收密度,而且还可以重复使用,特别是在小体积应用环境下具有显著的优势.本文从实验和计算模拟两方面综述了目前关于NEAS能量吸收耗散行为的最新研究进展,其中实验研究主要包括准静态压缩和动态压缩测试,计算模拟研究主要是采用基于经验势的分于动力学模拟方法.通过准静态压缩实验,可以测量NEAS模型的载荷–位移关系曲线,从而获得NEAS模型的临界渗透压强,了解卸载后系统是否能够恢复到加载前的状态(即是否可以重复使用),井通过载荷–位移关系曲线下面积估算NEAS模型的吸能密度;通过动态压缩实验可以测量NEAS模型对脉冲载荷的缓冲保护作用,主要体现为降低脉冲载荷幅值和扩展脉冲宽度.计算模型研究可以明确给出NEAS对外载荷的微观响应,从而可以准确了解NEAS的能量吸收耗散机制以及吸能密度的主要影响因素.本研究可以帮助我们全面了解NEAS的研究进展,为NEAS的设计与优化提供重要指导.     

High order numerical simulation of the thermal load on a lobed strut injector for scramjet applications

In this paper, the thermal load on an actively cooled lobed strut injector for scramjet (supersonic combustion ramjet) applications is investigated numerically. This requires coupled simulations of the strut internal and external flow fields together with the heat conduction in the solid injector body. In order to achieve a fast mixing, the lobed strut is positioned at the channel axis to inject hydrogen into the core of a Mach 3 air stream. There it is exposed to the extremely high temperatures of the high speed flow. While the external air and hydrogen flows are supersonic, the strut internal hydrogen flow is mainly subsonic, in some regions at very low Mach numbers. To enable a simulation of the internal flow field which ranges from very low to very high Mach numbers (approximately Mach 2.25 at the nozzle exit), a preconditioning technique is employed. The compressible finite‐volume scheme uses a spatially fourth order multi‐dimensional limiting process discretization, which is used here for a first time to simulate a geometrically and fluid mechanically highly complex problem. It will be demonstrated that besides its high accuracy the multi‐dimensional limiting process scheme is numerically stable even in case of demanding practical applications. The coupled simulation of the lobed strut injector delivers unique insight into the flow phenomena inside and outside the strut, the heat fluxes, the temperature distribution in the solid material, the required hydrogen mass flux with respect to cooling requirements and details concerning the conditions at the exit of the injector. Copyright © 2016 John Wiley & Sons, Ltd.     

EXPERIMENTAL INVESTIGATION AND COMPUTER SIMULATION ON DYNAMIC BUCKLING BEHAVIOR OF LIQUID-FILLED CYLINDRICAL SHELLS UNDER AXIAL IMPACT

This article reports an experimental investigation on the axial impact buckling of thin metallic cylindrical shells fully filled with water. Low velocity impact tests are carried out by DHR-9401 drop hammer rig. The whole process of dynamic buckling is simulated using LS-DYNA computer code. The consistency between experimental observation and numerical simulation is quite satisfactory. The investigation indicates that quite high internal hydrodynamic pressure occurs inside the shell during the impact process. Under the combined action of the high internal pressure and axial compression plastic buckling occurs easily in the thin-walled shells and buckling modes take on regular and axisymmetric wrinkles. This project is supported by the National Natural Science Foundation of China(19672039) and the Shanxi Foundation for Returned Scholars from Abroad.     

The mechanism for fracture resistance in β‐nucleated isotactic polypropylene

The effects of molecular weight (MW) of isotactic polypropylene (iPP), the content of β‐PP, the size of its spherulites and the morphology of its α‐phase and β‐phase (α‐ and β‐PP) on the impact strength, with different contents of β‐nucleating agent, were investigated by two ways. The results show that the impact strength of iPPs increased initially, and then decreased with the content of β‐nucleating agent (maximum at 0.1 wt%). The impact strength was related to the size of β‐spherulites and had no apparent correlation with the content of β‐PP. The morphology of the bundle shape and intercrossing boundaries of β‐spherulites were dominant in improving impact strength with low content of β‐nucleating agent, while the MW of iPP was dominant with high content of β‐nucleating agent. Copyright © 2009 John Wiley & Sons, Ltd.