粉末爆炸烧结材料参数效应数值研究

用二维流体弹塑性体模型和Ｅｕｌｅｒ算法完成了粉末爆炸烧结的数值模拟；给出了爆炸烧结过程中密度分布和压力分布；研究了炸药和粉末参数对爆炸烧结的影响；讨论了几种实验装置设计方案的效果。数值模拟和实验结果作了比较，结果是令人满意的。     

PBX-01炸药水中爆轰产物状态方程研究

提出通过水中实验确定炸药的水中爆轰产物JWL状态方程参数的方法;选择PBX-01高能炸药进行水中实验,利用ANSYS/LS-DYNA程序建立炸药的水中实验模型,将实验结果与数值计算结果进行对比,确定PBX-01炸药水中爆轰产物的JWL状态方程参数。研究结果显示,圆筒实验确定的JWL参数在反映炸药水中爆轰产物的膨胀状态时有所不足,水中实验确定的JWL状态方程参数能够更准确地描述PBX-01炸药水中爆轰产物的膨胀过程,因此对水中爆炸的研究需要通过水中爆炸实验建一套状态方程参数。     

水及盛水容器对近距离爆炸载荷影响的实验研究

为研究用水包围炸药的方式对爆炸载荷的作用机理,在两端开口的钢筒内进行了水直接包覆炸药的爆炸实验,利用光纤位移干涉仪获取了钢筒外壁的径向速度和动态变形。结果表明:不同于无水爆炸,爆轰产物通过水的“裂缝”在空气中形成冲击波,造成该冲击波出现时间更晚、强度更低、持续时间更长,并要求相应的数值模拟采用二维以上的计算模型;盛水结构的材料密度越低、厚度越小对爆炸载荷的影响越小。     

铝纤维炸药土中扩腔现场实验与数值模拟

为检验铝纤维炸药的做功能力,对铝纤维炸药土中爆炸扩腔现象进行实验,并采用ANSYS/LS-DYNA软件进行数值模拟,得出铝纤维炸药爆腔半径随药量变化的关系。结果表明,现场实验与数值模拟均能较好地表征铝纤维炸药土中爆炸扩腔的规律,铝纤维炸药相对于工业乳化炸药做功能力强,且由于其成型效果好等特点,应用于一些复杂的环境能够取得理想效果,可为类似工程提供参考。     

高能炸药摩擦感度的数值模拟

为了研究炸药摩擦安全性,利用熔化摩擦模型对几种高能炸药的摩擦感度进行了数值模拟,结果符合实验,并根据热分解反应速率分析了感度规律。由于炸药熔点一般低于点火温度,所以基于一个考虑熔化现象的炸药摩擦模型,在炸药感度实验条件下进行了一维数值模拟,给出了炸药熔化结果和摩擦点火的时间:4种摩擦感度较弱的炸药包括DATB、NQ、TATB和TNT的点火时间的顺序即感度顺序符合实验结果,说明摩擦点火模型适应性。进一步结合炸药热分解反应速率的大小顺序,数值模拟证明,在一定摩擦强度下,点火顺序会发生交换,说明摩擦感度实验不能完全说明炸药摩擦感度强弱顺序。     

爆炸载荷作用下铀气溶胶形成机理研究

针对铀材料在爆炸载荷作用下形成放射性气溶胶的过程,采用光滑粒子流体动力学方法开展了数值模拟和实验研究。通过将颗粒动力学和SPH方法结合,建立了炸药爆轰作用于铀金属壳的数值模拟模型,以铀材料比内能为气溶胶转化判据,获得了铀材料转化为气溶胶的物理过程,得到了在相同爆炸当量下,不同质量铀材料的气溶胶转化效率,并与实验结果进行了对比分析。结果显示,铀材料在爆炸载荷作用下,当其比内能达到1.9 MJ/kg时,即可认为完全转变为气溶胶,对于本文中的爆炸装置结构形式,当炸药质量为铀材料质量的6倍时,转化率超过90%。实验验证了数值模拟结果,表明该方法能够对铀材料的气溶胶转化过程进行准确描述。     

爆炸烟云扩散的时空分布模型及特性

针对爆炸烟云扩散的时空分布问题，在严格限定实验条件的前提下，设计并开展了不同当量、不同地面条件、不同炸药装置壳体厚度的3组TNT爆炸烟云扩散外场实验，获得了不同实验条件下烟云扩散时空分布数据，运用计算流体力学(computational fluid dynamics, CFD)对爆炸烟云的扩散过程进行了数值模拟。通过分析实验和数值模拟获取的烟云时空分布数据，得到了烟云扩散形态演变过程及浮力流场信息，确定了厚水泥地面条件和硬质地面条件下不同的爆炸烟云扩散高度分布模型。研究结果表明:采用实验与数值模拟相结合的方法来表征烟云时空分布模型是科学可行的，爆炸烟云高度随时间呈1/2次幂函数增长，烟云宽度短时间内几乎呈线性扩展，烟云温度随时间呈反比例函数衰减，爆轰地面条件和炸药装置壳体厚度对烟云扩散高度均有不同程度的影响。     

爆炸产物发生化学反应对药室压力影响的研究

研究了爆炸产物发生化学反应对约束爆炸准静态压力的影响,推导了考虑爆炸产物发生化学反应时,约束空间内准静态压力的计算公式.以TNT炸药发生约束爆炸为例,分析了不同药量体积比下爆炸产物的化学反应动力学过程.编写了计算TNT炸药约束爆炸后准静态压力的程序,将程序计算结果与实验测量结果和ConWep程序计算结果进行对比,验证了计算方法的准确性,证明了爆炸产物发生化学反应对约束爆炸准静态压力有重要的影响.考虑爆炸产物发生化学反应对压力的影响,利用LS-DYNA对TNT炸药在一长方体药室内的爆炸进行了数值模拟,模拟结果表明,考虑爆炸产物发生化学反应时,药室会出现局部塑性应变与应力集中现象,最大塑性应变达到0.8‰.     

壳装炸药殉爆实验和数值模拟

进行了壳装固黑铝炸药殉爆实验,通过观察残留炸药、壳体和见证板变形,判断被发炸药的爆炸情况,得到了炸药临界殉爆距离。建立了壳装炸药殉爆实验计算模型,采用非线性有限元计算方法,对壳装固黑铝炸药殉爆实验进行了数值模拟。计算中采用预设壳体单元破片方法描述主发炸药壳体破片的形成和破片对被发炸药的撞击起爆,炸药临界殉爆距离的计算结果与实验结果基本一致。主要是主发炸药中部的壳体破片撞击到被发炸药,被发炸药起爆位置也在装药中部。炸药壳体厚度主要影响破片速度和质量、被发炸药的防护性能,从而影响炸药临界殉爆距离。 更多还原     

合金工具钢的水下爆炸焊接

针对水下爆炸焊接法对超薄、高硬度脆性材料的独特应用特点,开展合金工具钢与铜箔的焊接复合实验。采用高爆速炸药倾斜装药方式,开展实验研究。利用有限元软件ANASYS/LS-DYNA对水下爆炸冲击波驱动飞板的飞行过程进行数值模拟,验证焊接参数合理性。模拟结果显示,飞板与基本碰撞速度沿焊接方向逐渐减小。微观组织观察显示,界面整体表现为爆炸焊接波状形态,呈沿焊接方向逐渐减弱的趋势,与模拟预计结果一致。对焊接实验样品界面处进行显微硬度测试,显示近界面处硬度稍有增加。     

On the Correlation of FEM and Experiments for Hyperelastic Elastomers

Correlation of modern finite element methods (FEM) with advanced experimental techniques for elastomers, biomedical materials, and living organs requires study and modification of the behavior of these materials. In this study, the mechanical behavior of a commonly-used elastomer, silicone rubber, which provides excellent biocompatibility, was examined under different applied loading configurations, and large deformations were investigated through both experiment and simulation. The stress-strain behaviors of silicone rubber were tested, using multiple homogeneous experiments, including uniaxial extension and equibiaxial tension, the load-apex displacement response, and digitized deformed shapes of two of the most-used structures for nonlinear hyperelasticity—the inflation of a clamped circular membrane, and indentation of the membrane by a spherical indenter. Uniaxial and equibiaxial data were evaluated simultaneously, characterized by various constitutive models for implementation in the FE simulation. These constitutive models examined the prediction of the FE simulations for the inflation and indentation tests in comparison to the results of experiments at various load-apex displacement levels. The results showed that the constitutive models calibrated with the uniaxial and equibiaxial tests, predicted nearly the same results as the actual experimental results, particularly for the applied loads that generated moderate strain. However, when the FE simulations based on the constitutive models were adjusted, employing only uniaxial or equibiaxial tests, they predicted different results, where the degree of their correlations with experimental results was incomplete or in some states simply poor. The simulations suggested that the inverse FE procedure should not be restricted to the choice of material models, while more attention should be given to the choice of ranges of deformation.     

Simulation of jet disintegration in a supercritical reactor

This work deals with the simulation of jet disintegration in supercritical conditions. In this validation case, nitrogen at 140 K is injected into a reactor at 298 K in conditions of turbulent flow. The simulation results are confronted with experimental data from literature. The simulation also compares the use of incompressible and compressible models in order to justify the compressibility assumption frequently used in literature. Both models fit well the experimental results indicating that in the investigated conditions, compressibility effects can be neglected.     

各向同性超弹性本构模型数值计算及验证

现有多种形式的橡胶本构模型试图预测橡胶力学性质,其中部分模型已写入有限元软件中用于仿真计算,还存在较多拟合性较好的模型无法在有限元材料库中直接获得。本文详述了由不变量和主伸长率描写的各向同性超弹性本构模型的数值实现方法,并结合最新的本构模型开发了UHYPER和UMAT子程序。将UHYPER用于有限元实现对多孔橡胶板的拉伸仿真,对比仿真和试验结果,验证子程序的正确性以及评估本构模型预测复杂应变场的准确性;将UMAT用于单轴、等双轴和剪切拉伸的有限元仿真,对比仿真和本构模型理论结果,验证子程序的可靠性。结果表明,有限元仿真结果与理论结果拟合较好,子程序能够契合本构模型的力学描述,所述方法可以用于超弹性材料的数值计算。     

刚架桁架模型有效性的试验与数值研究

为了比较桁架模型和刚架模型的差异, 结合了一种简单试验结构,实测了试验刚架和桁架的特定截面的内力和中节点位移; 同时应用ANSYS软件对两种模型进行了有限单元模拟. 验证了刚架和桁架两种力学模型的有效性, 通过试验和数值计算的结果, 得到了两种结构的受力特点, 分析了实际桁架和理想桁架的差别, 对结构设计和教学具有一定的参考意义.     

Comparisons and applications of numerical simulation methods for predicting aerodynamic heating around complex configurations

Numerical simulation methods of aerodynamic heating were compared by considering the inuence of numerical schemes and turbulence models,and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data,four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing and comparing,some inuencing regularities of numerical schemes and turbulence models on calculating heat flux had been acquired. It is clear that AUSM+-up scheme with rapid compressibilitymodified high Reynolds number k-ω model should be appropriate for calculating heat flux. The numerical methods selected as preference above were applied to calculate the heat flux of a 3-D complex geometry in high speed turbulent flows. The results indicated that numerical simulation can capture the complex flow phenomena and reveal the mechanism of aerodynamic heating. Especially,the numerical result of the heat flux at the stagnation point of the wedge was well in agreement with the prediction of Kemp-Riddel formula,and the surface heat flux distribution was consistent with experiment results,which implied that numerical simulation can be introduced to predict heat flux in engineering applications.     

炸药多点起爆超高速光电分幅摄影技术研究

为获得炸药多点起爆的爆轰波传播过程精细细节,研究相适应的超高速光电分幅摄影技术,采用自主研制的超高速光电分幅相机,结合有机玻璃光快门,拍摄到以HMX和以TATB为基的塑料粘结炸药在三点同步起爆条件下纳秒时间分辨爆轰波发展高清晰序列图像,成功观察到爆轰波的整个传播及相互作用过程,捕获到内聚相互作用、马赫杆等波形细节结构。实验结果表明:超高速光电分幅摄影技术基于独立曝光模式,且具有曝光时间短、幅间隔连续可调、空间分辨高等优势,可精细观察到爆轰波传播、相互作用细节信息,该实验方法及其结果对于爆轰波相互作用及爆轰波马赫反射等问题研究具有一定的参考价值。     

爆炸荷载下钢筋混凝土梁的变形和破坏

利用爆炸压力模拟器进行钢筋混凝土简支梁爆炸冲击实验,详细介绍了实验设计,通过实验系统分析了钢筋混凝土(RC)梁变形破坏特征以及钢筋作用机理和对变形破坏的影响,并建立了RC梁的分离式有限元模型,利用LS-DYNA分析了实验过程,对计算结果与实验结果进行了比较,分析了误差产生的原因,得到了爆炸冲击荷载作用下RC梁的损伤破坏特征和机理,可为毁伤评估和结构抗爆设计提供参考。     

Experimental study of filmwise condensation considering wave initiation

The problem of wavy filmwise condensation was recently investigated using both analytical and numerical concepts. The analytical solution assumed the film profile as a simple sinwave moving with a constant phase velocity and the problem was reduced to a closed integral form. While the numerical solution considers variations in the wave length and amplitude of the proposed sin wavy free surface. In order to find out the validity of the suggested theoretical models, an experimental test rig was installed, where the experimental parameters were controlled to generate data in the range of 40 <Re < 200. The results of this work demonstrate the possibility of accurate simulation of long vertical condenser using laboratory set of a reasonable dimensions. This simulation yields better results when the thermal and hydrodynamical average quantities at the entrance are properly corrected. Good agreement was found by comparing the generated experimental data, together with others data, with the analytical and numerical models. Imperical formulas for heat transfer were considered and differences between the correlation coefficients was found to be mainly due to unproper definition of the validity ranges of the used dimensionless groups. More realistic definition for the range of validity was introduced with these imperical formulas.     

Computational Fluid Dynamics (CFD) modelling of transfer chutes: Assessment of viscosity,drag and turbulence models

Computational Fluid Dynamics (CFD) has been successfully applied to evaluate potential dust emissions from bulk material transfer chutes. The implementation of appropriate models and modelling parameters is shown to be critical to the overall accuracy of the simulation results. This paper presents the influence of different models on the CFD simulation of transfer chutes and follows from an earlier study that details the influence of model parameters. The aim of this paper is to offer guidance to select models, and provide a better understanding of their influence in order to evaluate the most appropriate viscosity model, drag model and turbulence model for this application. A two-phase three-dimensional Euler–Euler model in commercial CFD software ANSYS FLUENT has been selected to model the granular and air flow in the transfer chute. The simulated air velocity profiles are discussed by comparing with each other and against experimental data obtained from Particle Image Velocimetry (PIV) results. The simulated particle velocity distributions were compared with results obtained using a well-established continuum method which was developed by Roberts. Furthermore, the air mass flow rates were analysed to evaluate the influence of different models. The results show that the granular viscosity model had a strong influence on the predictions of both air and particle flow. It was observed that both the drag model and turbulence model had limited influence on the outlet air velocities. The results also indicate that the Di-Felice drag model and SST k–ω turbulence model provide solutions closer to the experimental values than the other models investigated.     

几种实体桥梁的光弹实验分析与结构评价

为探询桥梁整体结构特点,按照实验力学的相似理论,采用数控加工方法将六种典型实体结构的桥梁制成光弹性模拟试件。通过光弹性实验分析获取它们承载状况下的等色线和等倾线图,经计算机数据采集和处理后,得到模型结构的二维应力分布趋势以及应力沿桥面的变化规律。根据系统工程理论,对它们整体结构进行评价并提出局部改进建议。实验证明光弹法对桥梁结构及复杂弹性几何体承载规律的研究非常有效,是研究这一类问题的一种很好的实验仿真方法。结合理论计算和专家分析系统可以综合的进行桥梁结构方案的优选设计,为理论计算的准确合理性提供实验依据。该实验研究结果可以作为桥梁结构教学素材,为实际建桥方案的拟定提供参照。