应变速率对V-Nb微合金化钢筋抗震性能的影响

研究了V-Nb微合金高强度钢筋在应变速率范围为:1×10-5~1×10-3s-1的室温拉伸试验过程中的力学性能以及断口形貌的变化。结果显示:随着应变速率的加快,试验钢屈服强度和抗拉强度都增大,屈服强度增幅较抗拉强度小;随着应变速率的增加,断后伸长率逐渐减小,最大力下伸长率先增大后减小且变化范围不是很大;采用SEM对韧窝进行了分析显示,随着变形速率的提高,韧窝尺寸逐渐减小。     

温度对Zr-45Ti-5Al-3V合金准静态力学性能的影响

在-100~200℃范围内不同应变速率(10-4,10-3和10-2s-1)下利用准静态拉伸和压缩实验研究了温度对Zr-45Ti-5Al-3V合金力学性能的影响.结果表明,在拉伸条件下,Zr-45Ti-5Al-3V合金具有较高的屈服强度和抗拉强度,室温时其屈服强度超过1355 MPa,但延伸率较小.随着温度的升高,合金的屈服强度和抗拉强度均下降,而塑性变形量则上升.在压缩条件下,温度对屈服强度的影响与拉伸时一致,而塑性变形量和断裂强度均在室温时最高,其他温度下变化规律与拉伸时一致.应变速率对合金的力学性能影响不大.     

不同应变速率对10MnNiCrMOV船体钢力学性能的影响

利用不同应变速率下的拉伸试验及光学显微镜、透射电镜(TEM)、扫描电镜(SEM)观察,研究了应变速率对10MnNiCrMoV钢室温拉伸力学性能的影响.结果表明,在2.0×10-3-1.2×103s-1应变速率范围内,10MnNiCrMoV钢的抗拉强度由低应变速率(2.0×10-3s-1)时的620 Mpa增加到高应变速率(1.2×103s-1)时的648 Mpa;伸长率则南低应变速率(2.0×10-3s-1)时的23%增加到高应变速率(1.2×103s-1)时的31.2%;其断裂机制为穿晶型塑性断裂;10MnNiCrMoV钢高应变速率下有增塑效应,主要与位错充分扩展和滑移有关.     

镁合金AZ31轧制板材的单向拉伸行为

通过单向拉伸试验研究了AZ31镁合金轧制板在不同温度和应变速率下的力学性能。根据镁合金在50℃~400℃范围内的单向拉伸曲线分析结果,找出AZ31镁合金的抗拉强度、伸长率随变形温度、变形速度的变化规律。结果表明:AZ31镁合金轧制板的塑性随着应变速率的降低有明显提高;温度的升高可明显改善轧制板的塑性;当应变速率为1.5×10-2s-1、温度为400℃时,伸长率达到123.9%。     

温度及应变速率对Q235B钢连铸坯高温力学性能的影响

采用Gleeble-1500D热/力模拟试验机对Q235B连铸坯高温力学性能进行了测试。测试了试验温度为950℃,应变速率分别为1×10-3、5×10-3、1×10-2、5×10-2s-1时Q235B钢连铸坯的高温力学性能,以及应变速率为5×10-3s-1的条件下,测试温度在700~1000℃时Q235B钢连铸坯的高温力学性能。结果表明:Q235B钢连铸坯的高温抗拉强度和屈服强度随应变速率的升高而增大,而断面收缩率随着应变速率的升高则降低;应变速率对Q235B钢连铸坯高温强度的影响分为敏感区和不敏感区,温度为950℃时,临界应变速率ε觶c为1×10-2s-1;随温度升高,Q235B钢连铸坯的高温抗拉强度和屈服强度均降低,Q235B钢连铸坯的断面收缩率Z随温度的升高总呈上升趋势;在850~950℃内出现了脆化区,在900℃左右时,Z值为58%;温度对硬化指数n的影响较为复杂,硬化指数n随应变速率的增大而降低。     

汽车用6005A-T6铝合金动态力学性能研究

通过对6005A-T6铝合金进行准静态拉伸试验和动态拉伸试验,研究了应变速率对6005A-T6铝合金准静态和动态力学性能及断裂行为的影响。结果表明:6005A-T6铝合金的强度随着应变速率提高而增大,当拉伸应变速率达到200s-1时,抗拉强度、屈服强度分别较准静态拉伸提高30MPa、25MPa,其中以准静态到应变速率10 s-1的过程中,材料的抗拉强度、屈服强度上升最为明显;试样应变速率与流变应力的关系符合Johnson-Cook本构模型,其拟合得到的本构方程为σ=(220.56+298.85ε~(0.506))(1+0.0209ln■)。6005A-T6铝合金塑性随着应变速率的增大而逐渐增大,当应变速率达到200s-1时塑性反而下降。在高速拉伸变形状态下,位错密度的增加和滑移带的增多是导致高速状态下强度及延伸率提高的主要原因;当应变速率达到200s-1时由于拉伸速率过快,晶粒来不及进行大量变形是断后延伸率反而降低的主要原因。     

应变速率对含稀土TRIP/TWIP钢变形行为的影响

分析了含RE的TRIP/TWIP钢的变形行为。结果表明:在动态条件下,屈服强度随应变速率的增加呈缓慢上升的态势,但当应变速率达到1×10~3s~(-1)时,屈服强度显著增加;抗拉强度随应变速率的增加而下降,应变速率达到1×10~3s~(-1)时,抗拉强度增加;应变速率愈快,屈服强度与抗拉强度的差值愈小;伸长率则随应变速率的增加在低应变速率下变化不明显,当达到1×10~3s~(-1)时,下降较明显。在1×10~3s~(-1)下的应变速率,屈服强度和n值高于静态下的屈服强度和n值,这说明高速应变下的抗载能力和拉延性更强。     

动态应变时效对35CrMo钢力学性能的影响

采用慢应变速率拉伸、电子显微镜等现代分析方法,研究了35CrMo钢动态应变时效现象对力学性能的影响.结果表明:在应变量为5％、应变速率为5×10-4s-1的不同温度(293、323、373和473 K)下动态应变时效后的35CrMo钢的伸长率变化不大,但动态应变时效后的抗拉强度均明显增加;35 CrMo钢动态应变时效的最佳温度为373K.35CrMo钢试样在室温下经过动态应变时效处理之后的室温屈服强度明显增加.     

高温拉伸对2524铝合金显微组织与力学性能的影响

在应变速率为10~(-4)~10~(-1 )s~(-1)和温度为250~450℃范围内对2524铝合金板材进行单向热拉伸试验,研究了热变形参数对其显微组织及力学性能的影响。结果表明,当温度为400℃,应变速率为10~(-3 )s~(-1)时,2524铝合金开始表现出动态再结晶特征,升高温度以及降低应变速率,均有利于动态再结晶发生。在温度为250℃,应变速率为10~(-1 )s~(-1)时,抗拉强度最高为312 MPa,伸长率最低为13%。当温度恒定为250℃时,随应变速率的减小,抗拉强度降低42.9%,伸长率提高15.4%;当应变速率恒定为10~(-1 )s~(-1)时,随温度的升高,抗拉强度降低77.2%,伸长率提高285%,断口呈韧性断裂。     

应变率对高强度TRIP力学性能的影响

研究了不同应变率(10-4～10-2 s-1)时高强度TRIP钢的力学性能。结果表明,随应变率的增加,抗拉强度与屈服强度总体呈上升趋势,而断裂伸长率及强塑积单调下降。在变形初始阶段(ε0.01),应变率高的实验钢n值较大。随变形量的增加,n值不断下降,且应变率高实验钢的n值下降较快。另得出,应变率越高,初期残余奥氏体向马氏体转变越快。     

GdF_3:Ce~(3+),Ln~(3+)(Ln~(3+)=Eu~(3+),Tb~(3+),Dy~(3+),Sm~(3+))纳米晶体的制备与发光性能研究

应用共沉淀法,制备共掺同一敏化剂(Ce3+)和不同激活剂(Tb3+,Eu3+,Sm3+,Dy3+)的GdF3纳米晶体。在单一波长(254nm)紫外光的激发下,掺杂不同镧系激活离子的样品能够发射出不同颜色的明亮可见发光,因而适用于多色生物标记。     

三自由度并联机构（3SPS 3SRR）的位置分析

针对一种3SPS-3SRR并联机构,运用符号法对该机构进行位置分析建模及求解。构建动、静坐标系,通过矩阵转换对机构建立约束方程,运用Sylvester消元方法进行消元得到机构单变元输入输出方程,求得机构位姿的封闭解。最后进行实例求解,得到该机构处于一般姿态的32组实数解,并使机构处于特殊位姿,将所得封闭解与预估解对比,从而验证该位置求解模型的正确性。基于符号法的3SPS-3SRR并联机构位置分析模型具有准确、高效的特点,规避了基于数值法的诸多缺点,对该机构的深入分析具有重要理论意义及实用价值。     

Thermodynamic analysis of the CsNO3-KNO3-NaNo3 system

The thermodynamic properties of the CsNO₃-KNO₃-NaNO₃ system have been derived from an optimization procedure using experimental and published information concerning phase diagram and thermodynamic data for the constituent binary systems and ternary liquid phase. The results are in very close agreement with the experimental data.     

Phase diagrams of binary systems: AgNO3KNO3 and AgNO3 -@#@ NaNO3

AgNO₃-KNO₃ and AgNO₃-NaNO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The apparatus is described briefly. Figure 1 shows a continuous solid solution in equilibrium with the liquid phase. It exhibits a eutectoid mixture (20 mol% NaNO₃) at 380.7 K. Figure 2 shows a eutectic mixture (45 mol % KNO₃) at 413 K, a eutectoid mixture (20 mol % KNO₃) at 409 K, and a continuous invariant at 404 K.     

3-D or not 3-D

When developing mathematical models of physical phenomena, physical scientists have been limited to two-dimensional solutions. In some cases, those solutions may be qualitatively correct, but in many others, the solutions are far from reality. This paper presents three examples of the limitations of two-dimensional modeling :diffusion-limited electrolytic reduction of a liquidproduct from a liquid electrolyte, morphological development of a solid dendrite, and behavior of a two-phase fluid under shear.     

3

In this paper, a planning algorithm for multi-path/multi-layer circular locus is poposed. The algorithm is applied to weld the nipples on the header of boiler. Multi-path/multi-layer circular locus is planned according to three teaching points, which is lapped head-on-end to satisfy the requirement of technology. For the nipples wherever they are arranged radially or axially, even if there are errors caused by positioning and thermal deformations, providing that nipple's position and orientation relative to the teaching one can be measured, the multi-path/multi-layer circular locus can be planned without teaching any more. The algorithm has been applied in welding robot for manufacturing power station' boiler.     

BiFeO3-BaTiO3-LaFeO3三元多铁性陶瓷材料的制备及性能

采用固相法制备了1-x(0.71BiFeO3-0.29B aTiO3)-xLaFeO3 (x=0.0,0.1,0 2,0 3,0 4,0.5)三元多铁性陶瓷材料,并研究了LaFeO3含量对陶瓷物相结构、微观组织、电学性能和磁电耦合性能的影响。结果显示,所有陶瓷均为单一钙钛矿结构,但随LaFeO3含量的增加,伴随着结构相变。所得陶瓷晶粒尺寸均匀,表现出良好的微观形貌,陶瓷晶粒随LaFeO3含量的增加而明显变小。虽然LaFeO3的加入在一定程度上降低了陶瓷的介电常数,但分析发现,x=0.1时能降低陶瓷的漏导,其漏电流达到了最小值,在10-7~10-8 A/cm2数量级,并且该陶瓷的剩余极化强度Pr和磁电耦合系数αME均达到最大值,分别为0.45μC/cm2和132.21 mV/cm·Oe (120 kHz)。因此,与0.71BiFeO3-0.29BaTiO3陶瓷相比,添加少量LaFeO3可以在一定程度上增加陶瓷的铁电性和磁电耦合性能。     

Electronic structures of semiconducting FeGa3, RuGa3, OsGa3, and RuIn3 with the CoGa3- or the FeGa3-type structure

Electronic structure of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the crystal structures belonging to the space group of P4n2 (No. 118), which is usually referred to as the CoGa₃-type structure, and P4₂/mnm (No. 136), which is usually referred to as the FeGa₃-type structure, have been calculated using a first-principle pseudopotential method based on the density-functional theory within the local density approximation (LDA) with the generalized gradient correction. All of them have the similar band structure in that the valence band maximum occurs at or near A and the conduction band minimum occurs at a point between Z and Γ. From the total energies calculated, compounds with the FeGa₃-type structures are more stable than those with the CoGa₃-type structures. The band gaps of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the FeGa₃-type structure are about 0.50, 0.26, 0.68, and 0.30 eV, respectively, which are wider than those with the CoGa₃-type structure. Calculated band gaps are wider than the observed gaps, which is unusual in the LDA calculation.     

Features of feathery γ structure in a near-γ TiAl alloy

This work characterizes the feathery-like structures produced in a Ti–46.8Al–1.7Cr–1.8Nb (at.%) alloy during rapid continuous cooling from the α domain. Their morphology and crystallography are described using different microscopy and orientation mapping techniques. These feathery-like structures are divided into many small domains, characterized by low-angle misorientations (rotated less than 15°) between the domains. The domains comprise multiple parallel γ lamellae and rare traces of α₂. These lamellae follow the Blackburn orientation relationship and have a {1 1 1}_γ habit plane. Two types of γ-feathery structures were identified according to their location and crystallography. The grain-boundary γ-feathery structures originate from lamellar structures that grow into a neighboring grain. Alternatively, the internal γ-feathery structures are located in the interior of prior α grains and show an average misorientation of 36° around one $〈100{〉}_{{\mathrm{\gamma }}_{\text{L}}}$ axis of the lamellar structure in which it is embedded. This paper describes these two γ-feathery structures in detail and discusses their development in light of the mechanisms available in the literature, particularly sympathetic nucleation.     

PMN-PNN-PT单晶的固相法生长研究

采用两步法和埋入PMN-PT单晶为模板的等离子放电烧结（SPS）技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷，随后在1200℃下退火100h来诱导晶体的生长。实验结果表明，PMN-PNN-PT单晶〈111〉方向的生长速度明显快于〈001〉方向，而〈111〉方向生长的晶体形状为V字形，这是由钙钛矿结构的生长机理决定的，钙钛矿结构晶体的生长是通过〈001〉方向的层状生长来实现的。