基于箭形累积损伤的裂纹尖端力学:奇异性分级和多尺度分段

在适度的空间和时间尺度组合下,裂纹既可在几个月中蠕变几个纳米,也能在几秒钟内扩展10km.虽然裂纹的尖端没有实际的质量,但是它能通过激活周围的物质而处于高能量状态.依赖于材料的损伤方向,激活质量的减少和增加可发生在尺度转变之前或之后.每个尺度区的分段阈值被假定为与裂纹尖端速度的平方a~2和激活质量密度M的乘积有关:W=M_(↓↑)a_(↑↓)~2和D=M~(↓↑)a_(↑↓)~2.W和D分别被称为直接吸收和自耗散能量密度.正如下标/上标符号所示,激活的质量密度M_(↓↑)和M~(↓↑)与裂纹尖端速度a变化趋势相反,既可增加也可减少.a~2和M的互补效应隐含着常用于宇宙物理学建模的膨胀和/或收缩的物理过程.在用于尺度敏感的裂纹尖端的行为时,激活的质量密度有相同的解释.分段时的多尺度可以由…皮观、纳观、微观和宏观…组成.因此,形象地说,材料损伤过程可以通过裂纹扩展过程中非均匀的总体和局部能量的传递来模拟.疲劳裂纹扩展引起的材料损伤被用来阐释由大到小和由慢到快的尺度/时间序,热力学中的冷→热和有序→无序转换.这一过程正巧与宇宙演化的箭形方向相反,宇宙演化遵循小→大和快→慢,而热力学相反,遵循热→冷和无序→有序.为了表示由损伤萌生所造成的类裂缝型缺陷的不均匀性,提出了一个被称为裂纹尖端力学(crack tip mechanics,CTM)的新模式.涉及的范围是模拟原子列之间的界面裂纹或连续体中分叉的切口.假如需要的话,尺寸和时间的范围可以复盖从皮观到宏观甚至更大.虽然采用疲劳裂纹来说明CTM的基本原理,在宇宙物理学背景中与直接吸收和自耗散相关的膨胀和收缩的情况可以描述裂纹周围激活质量的行为,它们可看为能量的汇或源.奇异性被用来捕获能量的源或汇的特性,物理上,两者作为界面的一部分,从数学上看则是不连续的线的一部分.能量从一种形式变为另一种形式取决于能量吸收或耗散的箭形损伤时间,这之中牵涉到尺度分段和奇异性强度的联合应用.材料组分随时间的劣化是根据指定的设计寿命导出的,从而使材料的响应与加载率的时间历史匹配.2024-T3铝板的皮观/纳观/微观/宏观开裂模型用来说明什么地方可以增加结构的寿命部分.皮观/纳观/微观/宏观/结构系统的性能随时间劣化可以用9个尺度转变物理参数来描述:纳观/微观区有3个(μ_(na/mi)~*,σ_(na/mi)~*,d_(na/mi)~*),微观/宏观区有3个(μ_(mi/ma)~*,σ_(mi/ma)~*,d_(mi/ma)~*),皮观/纳观区有3个(μ_(pi/na)~*,σ_(pi/na)~*,d_(pi/na)~*).下标pi,na,mi,ma和struc分别表示皮观、纳观、微观、宏观和结构.只要知道两个相连的尺度敏感参数,在较低尺度的时间相关的局部物理参数就完成了分析连续体的形式论,虽然它们并不需要用实验来知道.更具体地说,根据皮观→纳观→微观→宏观分别有1.25/1.00/0.75/0.50的λ奇异性强度,皮观裂纹、纳观裂纹、微观裂纹和宏观裂纹的转变特征是从时间箭形的指定的寿命预期来确定的.附加的0.25强度的奇异性可用于结构元件.回想起来,λ=0.5相应于断裂力学中的应力分量与r~(0.5)成反比,r是与宏观裂纹尖端的距离.微观裂纹、纳观裂纹和皮观裂纹分别赋予r~(-0.75),r~(-1.0),r~(-1.25)的奇异性.箭形时间(以年为单位)取决于问题的定义.设备的关键部件可用1.5~±/2.5~±/3.5~±/5.5~±寿命分布和总寿命为13~±年(a)的皮观/纳观/微观/宏观尺度来设计运行.上标±表示多于或少于实际运行的时间.累进损伤被假定为发生在皮观→纳观→微观→宏观方向.同样的方案用于20年总寿命的2024-T3铝板的疲劳损伤,按照1.5~±/2.5~±/3.5~±/5.5~±/7.0~±的方式将它的寿命分布在皮观、纳观、微观、宏观和结构的尺度上,这样的指定只是满足在每个尺度范围内损伤内部材料结构所用的能量匹配,因此可以强制执行在总寿命的跨度内精确的时间相关的材料性能劣化过程.     

旋流阻塞与旋流扩散复合内消能泄洪洞的壁面压强特性

结合雅砻江两河口水电站3#导流洞改建的水工模型试验,研究了新型旋流阻塞和旋流扩散复合内消能泄洪洞的壁面压强特性。研究结果表明:在淹没堰流流态时,壁面压强在进口的堰面、竖井段和旋流洞段因阻塞的顶托作用整体增大;在起旋器出口下游侧的旋流洞的顶部仍然存在局部范围的低压区或负压区;在旋流阻塞段,流速增大,壁面压强减小,水流空化数降低;在旋流扩散段,壁面压强略大于或小于大气压。     

泡沫铝夹芯双方管结构准静态轴压性能的实验研究

对几种泡沫铝夹芯方管结构的准静态轴压性能进行了实验研究。结果表明,较空管及泡沫铝夹芯单管结构,泡沫铝夹芯双管结构的承载能力及能量吸收效率明显得到增强。双管夹芯结构中外管撕裂模式的结构行程利用率和能量吸收效率高于相应的外管周期折叠模式。而泡沫铝四角填充方式提高了双管夹芯结构相同变形模式下的能量吸收效率和结构变形的稳定性。同时研究了内管管壁及材料强度对泡沫铝夹芯双管结构的影响。随着内管壁厚增大,双管夹芯结构的能量吸收效率提高,而内管材料强度影响不明显。     

湍流能量耗散率标度律实验研究

应用粒子图像测速(PIV)系统对平板湍流边界层内流向和法向的瞬时速度进行了测量。湍流的能量耗散率由轴对称假设得到,同时在研究湍流动能耗散率标度律的过程中采用传统的统计学方法。实验结果显示,对于不同尺度上和不同法向位置湍流耗散率标度律来说,湍流耗散主要发生在小尺度上,也就是说湍动能耗散率标度律在小尺度上具有普适性。另外,根据层次结构理论假设,通过PIV实验数据对最高激发态的标度指数进行了研究,结果发现,最高激发态存在绝对标度指数,并且绝对标度律是由信号中最强耗散涨落的局部结构产生的。     

乳酸配合物(NH4)2[Sr(C3H5O3)4]的晶体结构、Hirshfeld表面分析和溶液化学性质

合成了无水乳酸配合物(NH₄)₂[Sr(C₃H₅O₃)₄]。用X射线单晶衍射仪对该配合物的晶体结构进行了表征,确定了其组成、空间结构和配位方式。绘制了配合物的Hirshfeld表面和2D指纹图,揭示了分子间的相互作用以及该配合物具有多个配位位点和较强的配位活性。根据相关的晶体数据计算出了该配合物的晶格能及其对应阴离子的摩尔体积,计算得到该配合物的晶格能为2742.9 kJ·mol^-1。用等温环境反应-溶解量热计测量了该配合物在298 K超纯水溶剂中的溶解焓。根据Pitzer电解质溶液理论,在298 K下获得了该配合物的无限稀释摩尔溶解焓△_sH_m^∞和Pitzer参数,确定该配合物的△_sH_m^∞为(114.01±0.04) kJ·mol^-1。计算了该配合物的表观相对摩尔焓(^ΦL)以及不同浓度下溶质和溶剂的相对偏摩尔焓(L₁和L₂)。最后,根据晶格能和△_sH_m^∞设计了热化学循环,并计算出了阴离子的水合焓值。热重和微商热重曲线进一步揭示了该配合物的结构。     

Ab initio Study of Mechanism of Forming Germanic Bis-Heterocyclic Compound Between Dichloro-Germylene Carbene (Cl2Ge=C:) and Formaldehyde

The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet dichloro-germylene carbene and formaldehyde has been investigated with CCSD(T)//MP2/6-31G^* method, from the potential energy profile, we predict that the re-action has two competitive dominant reaction pathways. The presented rule of this reaction: the 2p unoccupied orbital of the C atom in dichloro-germylene carbene insert the π orbital of formaldehyde from oxygen side, resulting in the formation of intermediate. In the interme-diate and between two reactants, because of the two bonding π orbital in dichloro-germylene carbene and formaldehyde have occurred [2+2] cycloaddition reaction, forming two four-membered ring compounds in which Ge and O are in the opposite orientation and in the syn-position, respectively. Because of the unsaturated property of C atom from carbene in the two four-membered ring compounds, they further reacts with formaldehyde, resulting in the generation of two germanic bis-heterocyclic compounds.     

氘核破裂效应对质子出射能谱的贡献(英文)

基于连续离散化耦合道理论（CDCC）, 并在假设剩余核不仅可处于束缚态而且可处于一系列的激发态的基础上, 本工作论述了氘核破裂效应对质子出射能谱的贡献。计算结果可以基本解释质子出射能谱在大约氘核入射能量一半处出现峰值结构的实验现象。本工作的计算结果与C.Kalbach的经验公式基本保持一致。Based on the continuum discretized coupled channels(CDCC) theory, and the hypothesis that the residual nucleus locates not only in bound state but also in a series of excited states, the contribution of deuteron breakup effect in outgoing proton energy spectra are studied in the present work. And the results can basically explain the experimental results that a peak structure is appeared in the outgoing proton energy spectra at about half of the incident energy. The results of present calculation generally agree with those obtained from C. Kalbach’s empirical formulaum.     

高能核-核碰撞中直接光子各向异性的数值模拟研(英文)

通过计算给出了在LHC能区非对心核 核碰撞中由椭圆流ν₂ 表示的高横动量直接光子的方位角不对称性。该高横动量光子是由喷注与热密介质相互作用而辐射出来的。光子椭圆流与强子椭圆流ν₂ 相差π/2的相位, 是直接光子椭圆流中负值的来源。同时, 计算表明LHC能区直接光子ν₂随粒子横动量p_T的变化趋势与RHIC上的实验结果一致, 但LHC能区较RHIC能区有更低的直接光子流ν₂ 值, 且ν₂ 值由负到正对应的转换p_T值更高。这表明在LHC能区喷注淬火效应更为明显, 表面发射的直接光子对光子椭圆流的贡献份额增强。The azimuthal anisotropy of high p_T direct photons is investigated by using the coefficient of elliptic flow ν₂ in non-central nucleus-nucleus collision at LHC energies. These photons come from radiation induced by the interaction between jet and hot/dense medium. The azimuthal anisotropy of high p_T direct photons is investigated by using the coefficient of elliptic flow ν₂ in non-central nucleus-nucleus collision at LHC energies. These photons come There is π/2 difference between direct photons and hadrons for the azimuthal elliptic flow ν₂. Such photons are the main source of the negative part of ν₂ for direct photons. The dependence of the direct photon ν₂ on the transverse momentum p_T at LHC energy is found to be consistent with the experimental results at RHIC energy. Furthermore, we find that the value of the direct photon ν₂ at LHC energy is smaller than that at RHIC energy. The value of the transverse momentum at which the direct photon ν₂ changes from negative value to positive at LHC is higher than that at RHIC. It’sfound the enhanced jet quenching effect and enhanced contribution for the elliptic flow ν₂ of the direct photons emitted from surface at LHC energy.     

A new method for high-energy pulsed Gamma measurement within intense background x-rays

The accelerator-generating 6.13~MeV pulsed Gamma by ¹⁹F(p, αγ )¹⁶⁰ reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1~MeV. This paper proposes a new method, named the scattering and absorbing method, to diagnose the 6.13~MeV Gamma. This method includes two parts: the detector and a scatterer placed in front of the detector. The detector converts the Gamma to electrons and then collects the electrons by a scintillator. In order to restrain the interference of the low-energy background, the scintillator collects the electrons at a small angle. The scintillator is wrapped with electro-absorbing material to absorb the low-energy electrons generated by background x-rays. The theoretical sensitivity ratio of 6.13~MeV Gamma to 1~MeV x-rays is greater than 150. The scatterer is a pretreatment tool to scatter some background x-rays away from the radial beam before they enter the detector. By varying the length, the scatterer can reduce the background x-rays to an acceptable level for the detector.     

用于高能轻粒子探测的延迟线PPAC(英文)

气体探测器有成本低廉、制备简单、性能可靠和方便使用等特点。研制了一种5层板结构的延迟线平行板雪崩电离室（PPAC）,用于兰州放射性束流线（RIBLL）上开展的实验。在57.6 MeV/u的6He束流条件下测试了这种探测器对高能轻粒子的适用性,得到了位置分辨为1.8 mm (FWHM), 时间分辨为2.6 ns, 以及可靠的探测效率。The gas detectors have the characteristics of low cost, easy preparation, reliable capability and convenient for use etc. A delay line parallel plate avalanche counter(PPAC) with five plates has been developed for the experiments at Radioactive Ion Beam Line in Lanzhou(RIBLL). The applicability of counter for high energy light ion has been tested with 57.6 MeV/u 6He beam. A position resolution of ~1.8 mm(FWHM) and a timing resolution of ~2.6 ns are achieved. The detection efficiency is reasonable.