准脆性SiC_p/Al复合材料SHPB实验中入射波整形技术

针对陶瓷体积分数为50%的准脆性SiCp/Al复合材料恒应变率动态压缩实验,研究了入射波整形原则和理想入射波设计方法.结果表明:采用原始透射波和修正后反射波叠加设计的新入射波,通过控制整形器尺寸和子弹初速获得了理想的入射波,实现对准脆性复合材料的恒应变率加载;以测试材料力学特性为基础设计的整形器,可调整入射波形使之与透射波具有相同形状.针对准脆性SiCp/Al复合材料,SHPB实验中应变率只取决于入射波的幅值,而与整形后的入射波加载率关系不大,入射波中平台段实现试样的恒应变率变形;入射波形设计成梯形波,使之与SiCp/Al复合材料的透射波波形相似,实现了对复合材料的恒应变率加载.     

基于不同材料模型的混凝土SHPB试验数值模拟

为了分析不同材料模型对混凝土分离式霍普金森压杆(SHPB)试验数值模拟结果的影响,在LS-DYNA软件中分别运用KC,HJC,CSC三种材料模型对混凝土的SHPB试验进行模拟.利用脉冲整形器对入射波进行整形以减小弥散效应,实现恒应变率加载,并从SHPB试验的基本假定出发验证了有限元模型的准确性.通过数值模拟得到了不同撞击速度下基于3种材料模型的混凝土破坏过程及其应力-应变曲线.结果表明:KC,HJC,CSC三种模型基本上能够反映混凝土的动态力学特性,且KC模型和CSC模型的失效模式为核心塌陷,而HJC模型则表现出留核现象;在相同的平均应变率下,HJC模型和KC模型的动力放大系数大于CSC模型;随着平均应变率的增加,峰值应变增大,CSC模型和HJC模型的割线刚度减小,而KC模型的割线刚度变化不明显.     

脆性材料SHPB试验中实现近似恒应变率加载必要性的研究

基于分离式霍普金森压杆(SHPB)试验的数值模拟,对脆性材料SHPB试验中是否需要实现近似恒应变率加载的必要性进行了研究。结果表明在脆性材料的SHPB试验中,即使整形入射应力波在反射应力波中产生了一个近似平台,脆性材料试样中仍旧存在显著的由惯性产生的径向围压,说明在SHPB试验中实现了由反射应力波中的近似平台所表征的近似恒应变率加载也不能表示SHPB试样中的应变率为近似恒定。因此,在脆性材料SHPB试验中应用波形整形技术并不能改变转折应变率表征SHPB试样中应力状态转变的特性。无论是否采用了波形整形技术,应用脆性材料SHPB试验结果时都应考虑惯性引起的径向围压的影响。     

Zr50.5Cu36.5Ni4Al9块体非晶合金低温动态压缩特性

通过铜模铸造法制备Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金. 利用分离式霍普金森杆（SHPB）,S-4800型扫描电镜等测试分析手段,研究Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金在室温（25℃）和低温下（-40℃）动态压缩特性和断口形貌特征. 结果表明:在动态压缩载荷作用下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金抗压强度随载荷增加而降低. 在-40℃低温条件下,动态抗压强度具有低温敏感性. 在室温条件下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金断口微观形貌特征主要是脉状花样,伴随裂纹和非晶合金熔化现象;在-40℃ 低温条件下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金微观形貌特征主要是鱼骨状花样.      

混凝土材料SHPB主动围压实验的数值模拟

文章利用LS-DYNA软件,采用混凝土HJC动态本构模型,对Φ74mm分离式变截面霍普金森压杆主动围压实验做了数值模拟;通过在试件径向施加恒定压力的方法模拟主动围压的作用,试件单元的压力时间历程曲线显示该方法可以获得恒定、均匀的围压值,即该方法可以对SHPB主动围压实验进行合理的模拟;利用上述主动围压模拟方法对混凝土材料主动围压下的力学性能进行了研究,模拟时采用弥散较小的三角形速度波加载,并利用波形良好的入射波、透射波重构了混凝土的应力应变曲线,重构结果显示混凝土材料在围压作用下力学性能发生变化,混凝土峰值应力、峰值应力对应的应变、韧性都随围压的增大而增加,与理论结果相符。     

高强混凝土巴西圆盘动态劈裂试验

以圆形紫铜片作为波形整形器,利用直径100 mm的霍普金森压杆装置,研究了不同弹速冲击下高强混凝土平台巴西圆盘试件的动态拉伸强度,得到了高强混凝土在冲击作用下的劈裂强度、破坏模式和应力时程曲线。试验结果表明:随着冲击应变率的提高,高强混凝土试件的动态劈裂强度和破坏程度不断增大,具有显著的应变率敏感性。高速冲击荷载下的混凝土断面区较为光滑,裂缝直接穿过石子导致试样断裂。     

节理倾角对类岩石冲击能量传递影响的试验研究

用砂浆材料模拟不同倾角的节理岩石试件,并借助霍普金森压杆试验系统(SHPB)装置对其进行相似速度下的冲击试验,研究节理倾角对应力波穿越节理面时的波动特性和能量传递及耗散的影响,并给出能量耗散比随节理倾角变化的表达式。研究结果表明:在相似入射能量条件下,随着节理角度增大,反射能量比ER/EI(即反射波能量ER与入射波能量EI之比)先增大后减小,透射能量比ET/EI(即透射波能量ET与入射波能量EI之比)先减小后增大,且在节理倾角等于破坏角时,反射能量比和透射能量比到达极值;能量耗散比ED/EI(即节理试件耗散能量ED与入射波能量EI之比)随节理倾角的变化有所波动,分别在倾角为30°和90°时取得2个极大值。     

基于混凝土试件SHPB实验的波形特征分析

为了研究混凝土分离式霍普金森压杆(SHPB)实验中的波形特征,结合Shaper技术进行了混凝土试件的大尺寸(Φ120mm×100mm)SHPB实验。分别分析了不同应变率下波形曲线上的一些典型特征点,揭示并解释了混凝土类脆性材料反射波"双峰"现象和反射波尾出现"压缩波段"的现象,同时分析了混凝土试件的塑性承载能力。研究结果表明,反射波尾的"压缩波段"现象及混凝土试件的"可持续"塑性承载能力均会随着加载速度的增加而消失,而反射波"双峰"现象是混凝土类脆性材料特有的性质,随着加载速度的增加反而逐渐明显。     

加载速率对岩石动态断裂韧度影响的试验

摘要：
采用CCCD SHPB(Central Cracked Circular Disk Split Hopkinson Pressure Bar)试验系统对花岗岩试件实施不同加载速率下的纯Ι型加载试验,测得平均载荷P(t)随时间的变化关系.将实测的载荷代入到推广的中心裂纹圆盘试件应力强度因子计算公式,获得花岗岩在不同加载速率下的动态断裂韧度,揭示加载速率与动态断裂韧度的相关性.试验结果表明,加载速率为50~350 GPa·m1/2/s时,随加载速率的增加,断裂韧度呈现出线性上升趋势.
关键词：
动态断裂韧度; 加载速率; 霍普金森压杆; 中心裂纹圆盘
中图分类号： TU 45
文献标志码： A     

薄壁圆管膨胀变形行为的量纲分析及理论研究

通过有限元数值方法及已有圆管膨胀试验对金属圆管膨胀的变形行为进行研究，研究发现圆管膨胀后的几何尺寸h和D₁主要受圆管和压模初始几何结构参数影响，而受圆管材料和摩擦因数的影响较小；基于量纲分析，得到膨胀后圆管的几何尺寸h和D₁与主要影响因素之间的量纲一关系式.结合量纲一关系式与能量守恒定律，提出圆管稳态膨胀过程中稳态下压力的预测模型，模型中考虑了材料的应变强化效应和压模外径对膨胀管弯曲区域曲率的影响，结果表明该模型的预测值与试验结果、仿真结果能较好地吻合.      

Composition operators with linear fractional symbols on vector-valued Bergman spaces

0　IntroductionLetDdenotetheopenunitdiskinthecomplexplaneC , DitsboundaryanddAtheLebesguemeasureonD ,normal izedsothatA(D) =1.ForaBanachspace (X ,‖·‖X) ,wewriteH(D ,X)fortheclassofallX valuedanalyticfunctionsonD .Let1≤ p<∞ ,theX valuedBergmanspaceBp(X)istheclassofallf∈H(D ,X) forwhich‖f‖Bp(X) =∫D‖f(z)‖pXdA(z) 1 /p <∞ (1)IfX =C,thenwewriteBp =Bp(C) fortheclassicalBergmanspaces.Letφ∶D→Dbeananalyticself mapofD .Thenthee quation Cφf=f φdefinesacompositionoperator…     

The nonwandering set of some Hénon map

For the Hénon mapT _{a, b}(x, y) = (1 −ax ² +y, bx), Benedicks and Carleson proved that for (a,b) near (2, 0) andb > 0, there exists a setE with positive Lebesgue measure, whose corresponding mapT _{a, b} possesses a strange attractor. Viana conjectured that if (a, b) ∈E, then the nonwandering set of the mapT _a, b Ω(T_{a, b}) = ∧_{a, b},Uq _a, b, where ∧_{a, b}, is the strange attractor, q_a,b is a hyperbolic fixed point in the third quadrant. It is proved that this conjecture holds true for a positive measure set E₁ ⊂E.     

On the boundary value problem for harmonic maps of the Poincaré disc

The boundary value problem for harmonic maps of the Poincare disc is discussed. The emphasis is on the non-smoothness of the given boundary values in the problem. Let T . be a subspace of the universal Teichmüller space, defined as a set of normalized quasisymmetric homeomorphisms h of the unit circle S onto itself where h admits a quasiconformal extension to the unit disc D with a complex dilatation μ satisfying where ρ(z)|dz|2 is the Poincare metric of D. Let B . be a Banach space consisting of holomorphic quadratic differentials φ in D with norms It is shown that for any given quasisymmetric homeomorphism h : S1→S1∈ T . , there is a unique quasiconformal harmonic map of D with respect to the Poincare metric whose boundary corresponding is h and the Hopf differential of such a harmonic map belongs to B .     

QSPR between Physical-Chemical Properties and Molecule Parameters of Alkanes

A set of molecule parameters, namely, N, N′, p, q, n, were used to express the structures of alkanes. A correlative model was established between certain physical-chemical properties and molecular parameters of alkanes by regression method. Eight physical-chemical properties, such as evaporation heat （△vHm^20）, density（D^20 ）, capacity （C^20）, surface tension （δ^20）, boiling point （Tb）, critical temperature（Tc）, critical pressure（Pc） and critical volume（Vc）, of fifty-six C3-C16 alkanes were calculated directly from the model in this paper. The calculated values are in good accordance with the literature ones reported for alkanes, and the correlation coefficients （R） equal or exceed 0.99 . The research results indicate that the principle of the method is simple and clear, the method is practical, the correlativity is excellent, and the predicted data are credible.     

Roles of Phe58 residue in stabilizing structure of cytochrome b<Subscript>5</Subscript>

To understand effect of π-stacking interactions between the side chain of aromatic amino acids and the porphyrin ring on structures and properties in cytochrome b₅ (cyt b₅), the Phe58 residue was mutated to tyrosine and tryptophan, respectively by site-directed mutagenesis. The denaturation of cyt b₅ F58W and F58Y toward guanidine hydrochloride was examined by UV-visible and fluorescence spectroscopy. The kinetics of heme transfer reactions between apo-myoglobin and the mutants were studied. The results indicated that the mutation of F58 residue for Y58 or W58 reduced the interaction between of peptide and the heme group, resulting in decrease of the T _m and C _m values of the proteins, increase of the heme transfer reaction rate, and shifts of the redox potential.     

The formation depth of coesitebearing eclogite, Dabie UHPM zone, China, modified by tectonooriginal additional hydrostatic pressure

The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field T in the crust is a combination or superposition of total hydrostatic pressure P with differential stress σ , and the total hydrostatic pressure P at any point in the crust comprises two parts: one is spherical stress tensor PG caused by the gravity, and the other is spherical stress tensor Ps caused by tectonic stress; therefore P could not be attributed to the gravity of overlying rocks only. The results obtained by a finite-element simulation indicate that the tectono-original additional hydrostatic pressures Ps decrease gradually from the compressive zone (Pcs) to the shear zone (PSHs) and to the tensile zone (PTs), i. e. PCS>PSHs> PTs in the same depth. On the basis of the above-mentioned research, the method of measurement and calculation of metal logenetic depth corrected by Ps is established, i.e. first tectonic additional hydrostatic pressure Ps is removed from general hydrostatic pressure P to get PG, gravity additional pressure, then accordingly the depth data are measured and calculated. The plastic deformation of garnet in coesite-bearing eclogite, quartz eclogite and garnet amphibo-lite of the ultrahigh-pressure metamorphic (UHPM) complex in the Yingshan County in Dabie Mt. is studied by the transmission electron microscope (TEM). It is shown that the garnets have ductile deformation in the metamorphic condition of eclogite and amphibolite facies. Microstructures of the garnet vary greatly among coesite-bearing eclogite, quartz eclogite and garnet amphibolite. The tectonic principal stress in three-dimensional space and the tectonic additional hydrostatic pressure are reconstructed by differential stress and strain ratio (α) of garnet in minor coesite-bearing eclogite, then the gravity and thickness of overlying rocks are determined. The formation depth of ≥ 32.09-32.106 km of the coesite-bearing eclogite in Yingshan County in the Dabie UHPM zone is obtained from difference PG which comes from P minus Ps, Ps = (σ1 + σ2 + σ3) /3. The value of P is 2.8 GPa resulting from Qz-coes geobarmeter. This result is at all different from other researchers' conclusion that the formation depth of eclogite in Dabie UHPM zone is ≥100 km by the method of weight/ special weight (W/SW). The strong tectionic action makes a great contribution to the formation of e-clogite in the Dabie UHPM zone at so shallow depth of about 32 km, therefore it is thought that attention should be paid to the tectonc-original additional hydrostatic pressure in the study on UHPM zone.     

错列距离对被动控制双柱体流致振动特性的影响

针对双柱体这种极具代表性的多柱体结构,采用数值方法研究错列距离改变引起的双柱体流致振动特性的变化,分析间隙流与振动响应之间的相互影响关系。结果显示:错列双柱体的振动模态存在周期振动、双周期振动、多周期振动和拟周期振动等多种模态。上游柱体振幅受间距比的影响很小,间距比变化时,最大振动幅值均在约化速度U~*=6时取得。对于下游柱体,振动幅值随间距比大幅变化,尤其是当T=0.6D(D为柱体直径)时。随着来流速度的变化,上下游柱体振幅曲线发生交叉,存在一个临界约化速度U~*_c=7,当U~*U~*_c时,上游柱体振幅低于下游柱体振幅。当T/D0.6、U~*8时,为间隙流主导区。在该区域内,上游柱体脱落的漩涡形成间隙流,附着在下游柱体的表面,使下游柱体的边界层分离提前,柱体振动增强。     

Zircon SHRIMP U-Pb dating of meta-diorite from the basement of the Songliao Basin and its geological significance

Located in the east portion of the North Orogenic Belt, the Songliao Basin is bounded by the Da Hinggan Mountains in the west, the Xiao Hinggan Mountains in the north, the Zhangguangcai Range in the east, and the North China Craton (NCC) in the south (Fig…