亚共析20CrMnTiA钢的超塑性研究

超塑成形技术已被广泛应用于兵工及民用产品中 ,其中对工业上大量应用的亚共析钢超塑性行为的研究却鲜有报道 ,该文对常用的亚共析 2 0CrMnTiA钢的超塑性行为进行了探讨 ,找出了超塑拉伸时应变速率和温度的最佳匹配 ,对制定其超塑成形工艺具有一定的参考价值 ,并由实验结果得出了超塑性变形时的应变速率敏感指数m值。同时初步探讨了亚共析钢获得超塑性的显微组织特点     

大葱93-H301品系的选育

笔经多年研究，杂交组合斤-507X29—110—9优势明显，其后代经多代系统选育，培育出基因型稳定的93-H301大葱品系。     

含椭圆孔的压电材料反平面应变问题的基本解

用复变函数研究了含椭圆孔的压电材料反平面问题的基本解和裂纹尖端的场强度因子．结果表明：应力强度因子与普通材料的应力强度因子相同，而电位移强度因子与前者有相同的表达形式．     

Partial Characteristics of Hydrogen Production by Fermentative Hydrogen-producing Bacterial Strain B49

0　IntroductionHydrogenproducedbymicroorganismsisrecog nizedasaclean ,efficient ,sustainableandabundantenergyinthefuture .ManystudiesonbiohydrogenproductionhavebeenreviewedbyNandietal[1] .andbyBenemann[2 ] .EnterobactercloacaeIIT BT0 8iso latedfromleafextractbyKumar[3] hadanexcellentabilityto producehydrogenat 2 9.6 3mmolH2 / gdrycell·h .EnterobacteraerogensstrainE .82 0 0 5iso latedfromleavesofMilabilisjalapabyTanisho[4 ] ,evolvedhydrogenat 17mmolH2 / gdrycell·h .Enter obacteraerogens…     

Study of Stress and Strain Distributions of First Pass Conventional Spinning Under Different Roller-trace

Based on simplified axisymmetrical forming model, a elasto-plastic FEM simulation system of multi-pass conventional spinning is developed. Taking the typical draw-spinning as the study object, and establishing reasonable mechanics model, research on the first pass of spinning process is carried out with FEM system developed. The distributions of the stress and strain are obtained by three types of roller-trace curves: straight line, involute curves and quadratic curves. The results are as follows: (1) The v...     

基于积分法的轴对称拉深成形凸缘区应力、应变数值解

在平面应力、平面应变和等效应变与位置半径反比假设条件下,对轴对称拉深成形凸缘区的应力、应变的解析解进行比较.在平面应力假设条件下,给出了基于直接积分法的凸缘区应力、应变计算流程,简化了参数方程的求解过程,得到了考虑厚度变化的应力应变数值解.理论分析和有限元模拟结果表明,3 种假设条件下的径向应力数值解与有限元模拟结果都相差较小,平面应力假设条件下的应力、应变数值解与有限元仿真结果更接近.采用0.87mm 厚的ST16钢板进行了圆筒形件拉深成形实验,测量了凸缘区的应变,分析表明,平面应力假设条件下得到的应变数值解与实验结果更相符, 有限元仿真结果与实验结果接近且趋势-致.     

Experimental and numerical analyses of pure copper during ECFE process as a novel severe plastic deformation method

In this paper,a new severe plastic deformation method called equal channel forward extrusion(ECFE) process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength,ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa,204 MPa and68 HV as the annealed condition to 269 MPa,285 MPa and 126 HV after the fourth pass of ECFE process,respectively. In addition,scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1,the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet.     

稳定温度场下层状路面体系的解析层元解

从热弹性力学平面应变问题的控制方程出发,利用Fourier变换及Laplace变换推导其解析解,进而得出稳定温度场下平面应变问题的精确刚度矩阵,即解析层元;根据边界条件和层间连续条件对各层元进行组装,得到总刚度矩阵;求解总刚度矩阵方程,得到积分变换域内的解;应用Laplace-Fourier逆变换技术,得到物理域内的解.编制相应的计算程序进行验证及分析,结果表明,该解答与有限元软件模拟结果吻合,分层特性对层状路面体系温度应力和竖向位移量影响显著.     

BH-IF钢超快速加热退火工艺

研究了不同退火条件对BH-IF钢组织和织构演变及性能的影响.结果表明:随着加热速率的增加,BH-IF钢晶粒得到细化,但并不明显,强度和延伸率提高,再结晶织构仍为典型的管状γ织构;在超快速加热速率条件下,XRD织构分析显示BH-IF钢γ取向纤维织构组分及强度差异缩小,各组分更趋均匀.随保温时间增加,γ取向纤维织构强度增加,因而由其决定的r值(塑性应变比)增加.在超快速加热速率条件下,试样平行于轧向的r0降低,而垂直于轧向的r90增加,其均值rm无明显变化.     

低Ni，Cr，Cu和Mo高性能桥梁钢的动态再结晶行为

采用单道次压缩实验研究了一种低Ni,Cr,Cu和Mo高性能桥梁钢的动态再结晶行为.同时,采用9次多项式对实测真应力-真应变曲线进行了拟合,消除了实测曲线上的波动,进而确定了不同条件下的加工硬化率-真应力曲线.加工硬化率-真应力曲线特征表明,在所研究的不同热压缩变形工艺条件下,均发生了动态再结晶.通过计算将常数α修正为0009MPa-1,得到了实验钢的动态再结晶激活能,确定了εc=063εp关系式,建立了动态再结晶临界应变模型.而且降低Ni,Cr,Cu和Mo含量将显著降低动态再结晶激活能.