钢纤维混凝土的层裂特征

利用大直径Hopkinson压杆作为实验设备,通过试件后面的吸收杆应变波形分析了钢纤维增强混凝土的层裂特征。实验结果表明,钢纤维混凝土的层裂强度与钢纤维含量、混凝土压缩强度以及加载速率有关,并给出了经验公式。和素混凝土相比,钢纤维混凝土具有更高的层裂强度和更好的阻止损伤演化和裂纹扩展的能力。高速摄影结果表明,钢纤维混凝土层裂时,层裂段的飞离是由于陷在层裂段中应力波的动量效应,而且在层裂段中不易出现再次层裂的现象。这些现象和相同加载条件下素混凝土的层裂破坏有明显差别,说明钢纤维可以很好地提高混凝土抗层裂能力,其结论对相关的数值模拟和防护工程设计有重要意义。     

Neutron spallation source and the Dubna Cascade Code

Neutron multiplicity per incident proton,n/p, in collision of high energy proton beam with voluminous Pb and W targets has been estimated from the Dubna Cascade Code and compared with the available experimental data for the purpose of benchmarking of the code. Contributions of various atomic and nuclear processes for heat production and isotopic yield of secondary nuclei are also estimated to assess the heat and radioactivity conditions of the targets. Results obtained from the code show excellent agreement with the experimental data at beam energy,E < 12 GeV and differ maximum up to 25% at higher energy     

利用MSDM分析p+208Pb散裂反应产物

多步动力学模型(MSDM)研究中、高能质子引起的散裂反应分为3个过程:核内级联、粒子预平衡发射以及通过蒸发粒子和裂变方式的剩余激发核退激发过程.利用Ignatyuk能级密度公式代替MSDM模型中的费米气体能级密度公式,改进其研究质子入射引起散裂产物的形成截面.采用Ignatyuk能级密度公式MSDM研究p+208Pb散裂产物的电荷、质量分布以及产物核形成截面,结果很好地再现了实验数据,且比利用费米气体能级密度的MSDM结果好得多. The level density of Ignatyuk formula is introduced into the Many stages dynamics model ( (MSDM)) instead of Fermi-gas formula to improve the simulation of spallation fragments. The results of (MSDM) with Ignatyuk formula reproduced the experimental data well for the mass and charge distributions, the formation cross sections of isotopic product of proton-induced spallation on~(208)Pb. The calculations are in agreement with the experimental data and better than some simulations by MSDM with Fermi-gas ...     

Quantum molecular dynamics approach to estimate spallation yield from<Emphasis Type="Italic">p</Emphasis> +<Superscript>208</Superscript>Pb reaction at 800 MeV

The spallation yield of neutrons and other mass fragments produced in 800 MeV proton induced reaction on²⁰⁸Pb have been calculated in the framework of quantum molecular dynamics (QMD) model. The energy spectra and angular distribution have been calculated. Also, multiplicity distributions of the emitted neutrons and kinetic energy carried away by them have been estimated and compared with the available experimental data. The agreement is satisfactory. A major contribution to the neutron emission comes from statistical decay of the fragments. For mass and charge distributions of spallation products the QMD process gives rise to target-like and projectile-like fragments only.     

中能质子在重核上的散裂反应的产物分布

利用量子分子动力学和裂变理论,统一计算了入射能量为322,660和800MeV的p+²⁰⁸Pb散裂产物的质量和电荷分布.计算结果能较好地再现实验测量数据.     

Die Entwicklung der Kernphysik

Die Gröβe des bei LSC-Messungen zu erwartenden Zufallsfehlers wurde ermittelt und die einzelnen Beitrāge zumGesamtfehler diskutiert. Es wird gezeigt, daβ sich Relativmessungen unter exakt vergleichbaren Meβbedingungen mit einer Genauigkeit von ≦ ± l% (3σ) durchfūhren lassen. Anhand von Beispielen wird nachgewiesen, daβ der Effektivitätsbestimmung mit āuβerem Standard gewisse Anwendungsgrenzen gesetzt sind. Im Zweifelsfall sollte immer eine Kontrolle mit einem inneren Standard durchgeführt werden.     

混凝土板在接触爆炸作用下的震塌和贯穿临界厚度计算方法

采用刚塑性模型描述介质的动力学行为，结合不可压缩条件和质量守恒条件及边界条件，构造塑性区的动力学许可速度场；利用极限平衡原理推导动力学许可速度场所对应的介质抗力的量纲一表达式；根据初始条件和边界条件，求解运动方程，分别得到爆炸震塌的临界厚度和爆炸贯穿的临界厚度，并推得能够反映爆炸源参数和材料参数综合性质的量纲一冲击因子。将推得的计算公式与经验公式对比分析，证明本文计算结果合理，推导的计算公式揭示了经验公式的物理本质，且具有较为广泛的适用范围。     

延性材料动态损伤演化模型研究

从微损伤系统的统计描述出发，应用Ｍｏｒｉ－Ｔａｎａｋａ理论的物理思想，考虑了微孔洞间的相互作用，建立了延性材料动态损伤的统计演化模型。结果能够描述材料在外载作用下的损伤弱化效应。还分析了材料变形中的两种不同的耗散机制，考虑了含损伤的本构关系。将上述模型用于几种材料的层裂过程数值模拟，并与实验结果作了初步比较。     

滑移爆轰作用下内爆柱形钢壳层裂的数值模拟

 Иванов等发表了滑移爆轰作用下内爆柱形钢壳层裂实验的回收试件测量结果，也给出了相应的数值模拟结果，但两者的差别较大。本文利用损伤度函数方法，对上述实验做了数值研究，所得到的回收试件尺寸数值结果与Иванов实验结果十分相符。这说明，损伤度函数方法对研究动态断裂问题有一定的普适性。本文还对Иванов实验的柱形钢壳内爆运动过程进行了数值模拟，讨论了临界损伤度α_c取值对断裂面位置、钢层运动轨迹及钢壳运动速度历史的影响，指出了在分析界面不稳定性问题时要注意α_c取值的影响。     

Interaction of 12.7 GeV He ions with U, Pb, Au and Ag targets

The processes of production of fragments Z 8 in the interactions of 12.7 GeV ⁴He with U, Pb, Au and Ag have been analyzed using the polycarbonate track detector Makrofol. A sandwich technique was used which enables direct evidence for multiple fragment emission by a single nucleus. The decay channels ending with one, two or more (three, four) fragments were detected. A classification scheme based on the multiplicity of heavy fragments M_H (Z> 20) was used in order to identify events belonging to the different reaction channels. Cross sections, excitation energies and multiplicities of intermediate mass fragments (8 Z 20) have been evaluated for various reaction mechanisms. The experimental features of the fragmentation process have been analyzed as a function of the target mass.