PBX炸药二维冲击起爆机理的数值模拟

建立了基于KIM模型的一个化学反应速率方程模型,用于分析PBX起爆和爆轰行为的损伤作用.运用遗传算法确定了反应速率方程的相关参数,通过与Forest-Fire反应速率模型数值模拟结果对比,验证了所建模型的合理性.将所建反应速率方程模型嵌入有限元程序对PBX炸药二维冲击起爆过程进行数值模拟,数值模拟结果与试验结果吻合较好,可以描述分析受冲击加载造成孔隙率、颗粒尺寸等变化的损伤炸药的冲击起爆过程.     

平纹织物混杂纤维复合材料低速冲击性能试验研究

使用玻璃纤维、碳纤维和芳纶纤维3种平纹纤维织物和乙烯基酯树脂,通过真空导入工艺制备了4种不同混杂组合的平纹织物纤维增强层合板,并对其进行了摆锤冲击试验;通过有限元模拟软件Abaqus对试验过程进行仿真建模,并与试验结果相比较。结果表明:低速冲击荷载下,纯玻璃纤维试样所受冲击力最大,吸能效果最差;碳纤维/芳纶纤维加入混杂后,冲击力、吸能效果均得到提升。其中:G2/A4/G2试样缓冲效果最好,冲击力减少54. 4%; C2/G4/C2试样吸能效果最好,吸能提高了34. 1%。Abaqus模拟结果与试验结果较为接近,可较好地反映复合材料的损伤过程。     

管线钢管理化性能试样截取与加工质量分析

理化性能试验对于保证管线钢管的性能至关重要。试样截取或是尺寸上的微小差异都会给试验结果带来影响。本文首先介绍了试样截取过程中的注意点,之后分析了几种常用的理化性能试样,例如拉伸试样、夏比冲击式样、落锤撕裂试样、弯曲试样等,针对其加工质量控制进行详细分析。     

韧脆转变区夏比冲击试验的数值模拟研究

对16MnR钢在韧脆转变区进行了夏比冲击试验,利用有限元分析软件ABAQUS考虑了冲击过程中高应变率对基体材料的强化效应,并耦合延性损伤GTN模型对转变区的夏比冲击试验进行了数值模拟研究。对比试样断面上的延性裂纹扩展长度发现,GTN模型的预测结果是可接受的。通过有限元模拟获得了试样在冲击过程中各时刻的力学场,研究了在延性裂纹扩展过程中裂纹尖端应力应变场的变化规律和应变率分布规律。模拟分离得到夏比冲击功AKV包含的各部分能量,发现在冲击过程中塑性功消耗占绝大部分。     

美式落锤冲击试验在PVC-U异型材冲击性能评价中的应用

介绍了采用美式落锤法对PVC-U异型材的冲击性能进行量化评价的试验方法。结果表明,美式落锤冲击试验受很多因素(如温度、试样尺寸和试样的成型工艺)影响。     

浅析用摆锤式冲击试验法测试塑料冲击性能的影响因素

塑料冲击性能是指聚合物材料在高速冲击下表现出来的韧性或抵抗断裂的能力。目前常用的有模拟实际冲击过程的三种冲击试验方法。其中被广泛用于对产品质量进行控制与监督的是摆锤式冲击试验方法 ,包括悬臂梁 (Ｉｚｏｄ)、简支梁 (Ｃｈａｒｐｙ)冲击试验。使用的试样是截面为长方形或正方形的板条 ,但更为常见的是在试样中间部位人为地用模塑或机械加工的方法制造一个缺口 ,其形状和大小有严格规定。摆锤式冲击试验中试样有无缺口以及缺口的锐利程度对测试结果的影响是很大的 ,同时 ,由于该试验是一种高速破坏试验 ,对试验的温度有很强的敏感…     

PVC／环氧树脂E51合金性能的研究

采用模压法制备了PVC/环氧树脂E51合金,研究了环氧树脂E51用量对合金力学性能及维卡软化温度的影响.结果表明:当环氧树脂E51用量为1～5份时,随着环氧树脂E51用量的增加,试样的缺口冲击强度、拉伸强度、断裂伸长率、维卡软化温度先增加后减小.当环氧树脂E51用量为3份时,试样的缺口冲击强度、拉伸强度、维卡软化温度出现最大值;当环氧树脂E51用量为4份时,试样的断裂伸长率出现最大值;当环氧树脂E51用量为5份时,试样的缺口冲击强度、拉伸强度、维卡软化温度虽有所降低,但仍比原始PVC试样(指未添加环氧树脂E51的试样)高,而试样的断裂伸长率则骤降,比原始PVC试样还低.在试验条件下,环氧树脂E51的最佳用量为3份.试样冲击断面SEM照片的分析结果与缺口冲击强度的测试结果相符.     

复合射孔器推进剂装药的损伤特性

以复合射孔器装填的AP-丁羟(HTPB/AP)复合推进剂为主要研究对象,通过不同载荷作用下的模拟试验,对装药试样进行模拟损伤.采用药柱密度测量技术和密闭爆发器试验,分析了试样的损伤程度,并对损伤装药的燃烧性能进行了研究.结果表明,HTPB/AP复合推进剂在不同载荷作用下,内部结构发生了微观变化及损伤,其损伤度由高到低依次为高速冲击、低速撞击、准静态压缩和高温冲击.试样的损伤程度越大,其燃烧性能的变化越大,其中经高速冲击和低速撞击的HTPB/AP复合推进剂的燃烧特性已转变为对流燃烧或压缩燃烧,在一定的外界约束条件下,很有可能产生燃烧转爆轰现象.     

浅析简支梁冲击强度的影响因素

简述了简支梁冲击破坏的原理,分析了试样尺寸、温度、冲击改性剂、缺口以及缺口加工方式对试样冲击强度的影响。结果表明:①试样的厚度越大,试验跨度越大,冲击强度就越大;②简支梁冲击强度随温度的降低而降低;③ACR的加入能提高简支梁冲击强度;④缺口敏感性材料受缺口尖端半径影响较大;⑤一次注塑的缺口试样冲击强度较高,而经二次机械加工成型的缺口试样冲击强度较低,其中又以经铣床加工的缺口试样冲击强度最低。     

ASTM A 370-17a与GB/T229-2007标准关于冲击试验方法的区别和联系

在石油天然气行业制造企业中,取得API(美国石油协会)产品会标规范的装备必须符合API产品标准,API产品标准中对冲击试验方法的标准引用一般为ASTM A 370。本文通过对ASTM A 370-17a《钢制品力学试验的标准试验方法和定义》与GBT229-2007《金属材料夏比摆锤冲击试验方法》标准的对比和分析,介绍了两者的区别和联系,从试样要求、试验设备、试验程序以及试验结果等方面进行了阐述,对试样尺寸、摆锤刀刃、试验温度等有较大差异的因素进行了详细的说明,明确了两者的差异,确定了试验过程中的关注点。     

基于ANSYS/LS-DYNA对薄壁壳屈曲分析

利用有限元分析软件ANSYS/LS-DYNA,通过实体建模对薄壁壳进行仿真计算.借助ANSYS/LSDYNA程序从网格密度、材料属性、单元类型、接触类型、沙漏控制等五个方面,讨论了薄壁壳在轴向冲击力作用下的屈曲变化情况,并得到了钢管不同时刻的变形情况、应力分布情况、应变分布情况.结果表明,采用该软件模拟薄壁壳屈曲分析是...     

湿筛混凝土动态受压力学性能及破坏形态细观数值模拟

湿筛混凝土通常用来代替由于骨料粒径较大而不便开展物理试验的水工全级配混凝土。为了研究加载速率对湿筛混凝土力学性能及破坏形态的影响,从细观角度出发,运用颗粒流离散元软件PFC^2D建立湿筛二级配混凝土细观数值试件,根据拟静态单轴压缩(应变速率10^-5 s^-1)试验数据标定出数值试件中砂浆颗粒之间、粗骨料颗粒之间及砂浆颗粒与粗骨料颗粒接触面之间的细观参数,进而开展应变速率为10^-4 s^-1、10^-3 s^-1、10^-2s^-1的动态加载并进行动态力学性能及破坏形态的数值模拟和机理分析。结果表明,不同应变速率下试件的应力-应变曲线形状相近,峰值应力随着应变速率的增加而增大,增长率为7.3%～37.9%,峰值应力处应变增大幅度不大。试件破坏形态与物理试验现象吻合较好,随着应变速率的增加,裂缝数量不断增加,裂缝分布趋于均匀,裂缝数量增长率平均为峰值应力增长率的4.2倍。此外,随着应变速率的增加,数值试件内部...     

Review: An investigation of single particle breakage tests for coal handling system of the gladstone port

Aspects of the literature on single particle breakage test have been reviewed in this article. The test procedures that are commonly used by the researchers in examining and measuring the breakage characteristics of the ore and coal particles are also discussed. It appears that most of the common size distribution function fitting techniques were not suitable for accurate representation of the size distributions obtained from a pendulum breaking process. The single impact test, double impact test (drop weight test, pendulum test) and slow compression test can be used to study the behaviour of the single particle breakage events. The single impact test, slow compression test and drop weight test cannot measure the energy utilization pattern in single particle breakage events, but this can be determined from the pendulum test.The energy utilized for breakage was predominantly dependent upon the size and shape of the specimen, level of input energy and the breakage properties of the specimen. This review highlights that the size distribution curves were linear in the fine particle region and have varying curvature in the coarser region, the gradient of the linear fine particle region of the size distribution curves increases with an increase in the specific comminution energy. The comminution energy increases with input energy at lower levels of input energy but at the higher levels of input energy the comminution energy did not show the same proportional increase. At a given level of input energy, the size distribution resulting from the breakage of the particles by the pendulum apparatus can be represented by a one-parameter family of curves.     

弹丸转速对PELE侵彻钢筋混凝土靶横向效应的影响

为了研究弹丸转速对横向效应增强型侵彻体(PELE)侵彻钢筋混凝土靶横向效应的影响,运用ANSYS/LS-DYNA软件在着靶速度600、700和800m/s条件下,对具有不同转速的PELE侵彻钢筋混凝土靶进行数值模拟,并通过试验方法对不同着靶条件下的仿真模型进行验证。结果表明,开孔尺寸的数值模拟结果与实验结果之间的误差小于5%,仿真模型能够准确模拟PELE侵彻钢筋混凝土靶的过程;随着转速的不断提高,损失更多的转速动能转化为钢筋混凝土靶开孔破坏所需的能量,使钢筋混凝土靶的开孔尺寸增大;在同一着靶速度下,转速从10 000r/min提高至25 000r/min,开孔尺寸提高了约(8±2)%。因此,在同一着靶速度下,增加弹丸转速有利于提高PELE对钢筋混凝土靶的开孔尺寸。     

The impact endurance of polycrystalline graphite

Repeated impact tests have been carried out on a wide range of polycrystalline graphites. Two modes of test were employed using centrally impacted rods and discs with the rods supported horizontally at their ends and the discs supported around the circumference. The resulting impact endurance curves for all the different graphites under repeated impacts of constant energy were found to have a substantially common shape in both the disc and the rod tests. The absolute levels of the endurance curves differ considerably and correlate well with other mechanical properties of graphites, in particular the strain energy density at failure in bend. Measurement of impact forces on the single impact failure of graphite rods supports this correlation by showing that the dynamic stresses generated at failure in a single impact are the same as the corresponding static 3-point bend strengths in the same test mode. Measurement of impact forces at energies less than those required to cause failure in a single impact show that the fraction of energy absorbed as specimen strain energy is dependent on specimen size and shape but is not very sensitive to impact energy. A fracture mechanics model based on incremental crack growth and previously used to interpret stress-cycling fatigue data for graphite is proposed to describe also the endurance of polycrystalline graphite under repeated impacts. The model describes available experimental data obtained under both impact and fatigue conditions. On this model, the difference between the two cyclic stressing modes is the rate of crack growth per stress cycle, this being greater under repeated impacts than under fatigue cycles of the same stress amplitude.     

Influence of the micro- and nanoscale local mechanical properties of the interfacial transition zone on impact behavior of concrete made with different aggregates

The influence of the microscale local mechanical properties of the interfacial transition zone (ITZ) on macro-level mechanical response and impact behavior is studied for concretes made with copper slag and gravel aggregates. 3D nanotech vertical scanning interferometry, scanning electron microscopy coupled with energy dispersive X-ray micro-analysis, digital image analysis, and 3D X-ray computed tomography were used to characterize the microstructures and the ITZs. It was deduced that a stronger and denser ITZ in the copper slag specimen would reduce its vulnerability to stiffness loss and contribute to its elastic and more ductile response under impact loading. The analysis also indicated that a significant degeneration in the pore structure of the gravel specimen associated with a relatively weaker and non-homogeneous ITZ occurred under impact. Finally, it was also concluded that increased roughness of ITZ may contribute to the load-carrying capacity of concrete under impact by improving contact point interactions and energy dissipation.     

Impact testing of polypropylene blends and comosites

Polypropylene (PP) composites containing 0.30 vol% of talc filler, in addtion to blends modified with an ethylene-propylene copolymer (EPR) elastomer were prepared and their fracture resistance was determined by the standard Ixod impact test and by a fracture mechanics technique. Effects of composition, type of modification, specimen size, and temperature were studied. The validity of linear elastic freacture mechanics (LEFM) conditions were checked: It was shown that under the conditions applied they can be satisfied even twith specimens of reasonable size (4 × 10 × 80 mm) prepared by conventional processing techniques. Calculations of minimum specimen thickness must be carried out, with material properties obtained under the conditions of impact. For heterogeneous blends and composites yield stress should be corrected for the effect of decreasing load-bearing cross section. Linearity of the fracture energy (U) vs. BD? or U vs. B(D - a) plots is not a proof for either elastic of plastic fracture. The composition dependence of fracture properties proved to be practicaly independent of specimen size, temperature, or measurement technique.     

结合均匀化理论对钢纤维混凝土梁的疲劳性能分析

钢纤维混凝土(SFRC)在工程中应用日益广泛,为了探究其疲劳破坏现象内在机理,本文结合Mori-Tanaka均匀化理论预测了不同体积掺量下钢纤维混凝土的弹性模量,并以此为基础建立钢纤维混凝土梁四点弯曲有限元模型,采用Miner疲劳损伤准则,分别进行了静力抗弯试验和疲劳试验的数值模拟。模拟结果与相关试验结果拟合较好,验证了模型的可靠性。利用疲劳分析软件,预测了钢纤维混凝土梁的疲劳寿命和疲劳强度,分析了纤维掺量、尺寸效应和纤维长度对疲劳寿命的影响。结果表明:钢纤维可以大幅提高混凝土梁的疲劳寿命,应力水平越低、纤维掺量越大,增幅越大;尺寸效应对疲劳强度和疲劳寿命有一定影响,但随着构件尺寸增加对疲劳性能影响减小;纤维长度越长,梁的抗疲劳性能越好。     

天然气处理工艺流程改造及优化研究

为提高轻烃回收率,实现节能降耗和经济效益最大化的目标,利用HYSYS工艺流程模拟软件,建立天然气处理工艺模型,对天然气处理工艺流程进行了改造可行性研究和优化分析。研究表明:利用HYSYS软件进行模拟优化研究具有一定的准确性和可靠性;通过工艺流程的改造,丙烷收率提高了25.07%,C3+收率亦有所增加,改造方案是可行的;通过建立数学优化模型,对主要工艺参数进行了优化,膨胀机压缩端出口温度由原来66.99℃下调为64℃,此时C3回收率增大且Opt取得最小值,取得了最大化经济效益。另外,此研究对国内旧天然气处理厂的改造优化具有一定的指导意义。     

Effect of specimen size on fracture energy and softening curve of concrete: Part II. Inverse analysis and softening curve

The size effect of fracture energy was observed in experiments presented in the preceding paper. In this paper, the softening curve representing the relationship between the crack opening and the gradual stress drop after tensile strength was found for each specimen of the experiments by an inverse analysis. The effect of the size-dependent fracture energy on the softening curve was then investigated. It was found that the first steep branch of the softening curve is very similar for different size specimens whereas the tail of the curve becomes longer with increased specimen size. The observed size-dependent fracture energy can be explained by the features identified on the softening curve, and a possible mechanism of the fracture process zone with respect to the size effect is discussed herein.