基于弹性基体磨具的3D打印高温合金叶片磨抛试验

目的 验证弹性基体磨具自适应磨削抛光加工增材制造镍基高温合金叶片的工艺可行性。方法 以硅橡胶基体磨具弹性磨抛技术为基础,建立弹性磨具与叶片接触的有限元模型,分析磨具与工件接触区域内应力和材料去除分布。以有限元分析结果为指导,研究磨具接触变形和材料去除对轨迹规划的影响,确定合理的轨迹步长和间距,并通过控制工件位姿角的变化,保证在磨抛过程中磨具与工件的接触状态不变。以GH4169镍基合金叶片为加工对象,采用硅橡胶弹性固结磨料磨具在小型四轴加工平台上进行磨抛试验。结果 仿真结果表明,弹性磨具与曲面工件之间的接触区域为椭圆形,应力和材料去除分布都由椭圆心到周围逐渐减小;当弹性磨具的压缩量为3 mm时,基于弹性接触有限元分析结果确定的最优轨迹间距为9 mm。试验结果表明,采用自适应磨抛轨迹抛光后,叶片表面无明显划痕和抛光纹理,表面粗糙度Ra由开始的1.846μm降至0.182μm,标准差由0.108μm降至0.026μm,材料去除率为3.432×10⁹μm³/min。结论 硅橡胶弹性固结磨料磨具可用于GH4169镍基合金叶片的超精密磨抛,基于弹性磨具接...     

超声复合磨料振动抛光方法有限元分析与实验

为研究超声复合磨料振动抛光方法对工件表面材料去除量与工件表面粗糙度的影响,分析了超声复合磨料振动抛光方法;并利用ANSYS Workbench软件分别分析了超声振动条件下和超声复合磨料振动条件下工件表面结构与应力变化情况,同时在超声复合磨料振动条件下通过实验验证超声复合磨料振动抛光技术对工件表面材料去除量与工件表面粗糙度的影响程度。结果表明:超声复合磨料振动条件下工件表面位移小于超声振动条件下的工件表面位移,超声复合磨料振动条件下工件表面应力大于超声振动条件下的工件表面应力;在超声复合磨料振动条件下,影响工件表面粗糙度最显著的因素是磨料质量分数,影响工件表面材料去除量最显著的因素是抛光时间,且磨料质量分数为30%、抛光时间为4 h时,抛光效果最佳。     

焊头几何尺寸对铜/铝超声波焊接接头塑性变形的影响

进行了1mm厚铜/铝异种金属超声波焊接实验研究,分析了焊头几何尺寸对工件表面接触区域变形、焊接区塑性变形的影响.结果表明:工件在高频振动作用下,焊头会在工件表面接触区域留下压痕,并使焊接区发生塑性变形,形成局部机械自锁.焊头面积相同时,圆形焊头更容易造成工件表面材料流动,从而形成更深的压痕,而矩形焊头能够产生更强烈的焊接区塑性变形.焊头形状相同时,面积小的焊头能够形成更深的压痕,而面积大的焊头使焊接区塑性变形程度更强烈.     

数值模拟外转角半径及背压对纯钛ECAP变形的影响

使用DEFORM-3D软件模拟等通道转角挤压过程中外转角半径及背压对纯钛应力和应变分布的影响,探讨不同R值对材料流动的影响规律。结果显示:当R=6mm时,工件上下表面应力状况较为平衡,从而得到均匀的等效应变分布;当R<6mm时,在外转角形成的死区使材料之间相互搓动,导致工件底部区域出现剧烈畸变,工件不同区域之间的等效应变量差别较大;当R>6mm时,工件上表面与模具内转角之间的相互作用力增加,使工件顶部变形加剧并导致工件等效应变量不均匀;施加背压(pb)后,能有效提高等效应变量;适当的R值与pb匹配可使工件得到均匀的应变分布。     

铝合金点焊预压接触分析

利用有限元模拟分析,研究了铝合金点焊在采用固定的预应力和变化预应力时,工件与工件间的应力分布状态。结果表明,工件间接触区域的半径比电极端面半经大;随着预应力的增大,工件间出现应力峰值的位置向对称轴方向移动。     

干式切削20Cr表面粗糙度和残余应力研究

针对低渗碳钢20Cr材料制作齿轮轴等零件表面质量要求,如表面粗糙度低于1.6μm,零件表面耐疲劳性能良好。试验采用干式切削20Cr钢材方式,在背吃刀量固定的工序中,研究切削速度和进给量对20Cr材料表面粗糙度的影响,同时结合有限元技术,分析切削速度和进给量对20Cr表面残余应力的影响。干式切削试验采用单因素方法,进行多组干式切削20Cr工件,对比分析各组工件表面粗糙度,结果表明当进给量较小时,切削速度对工件表面粗糙度有显著影响,表现为表面粗糙度随切削速度增加而变大;当切削速度一定时,进给量增加导致表面粗糙度变大,并且进给量对表面粗糙度的影响大于切削速度;对于工件表面残余应力,增加切削速度和进给量均导致残余应力变大,因而较小的切削速度和进给量可以降低工件表面残余应力,改善应力分布状态。     

大型工件间推挤式等通道转角大应变技术模具受力分析

运用有限元软件DEFORM-3D研究了大型工件间推挤式等通道转角大应变技术模具受力。结果表明,它的载荷变化和应变规律与小型ECAP(equal channel angular pressing)极为类似。压头的最大应力位于压头与工件接触部分外侧,其值为原始工件材料变形应力的10.7倍。凹模的最大应力位于压头与工件接触部分周围,其值为原始工件材料变形应力的6.43倍。     

GH4169镍基高温合金薄壁钻削过程中的应力及变形研究

利用ABAQUS有限元仿真软件建立了镍基高温合金GH4169薄壁件钻削模型,分析钻削GH4169薄壁件过程中的薄壁变形和应力变化。根据钻削过程中钻头下方工件材料的应力及变形特点将其钻削过程分为5个阶段:第1阶段,工件变形以整体弹性下凹变形为主,并在钻头横刃旋转接触圆形区域下方发生了局部塑性形变;第2阶段,在制孔区以塑性变形为主,在非制孔区弹性变形量大于塑性变形量;第3、第4、第5阶段工件变形相差不大,在孔口边缘形成了较大的材料外翻,其余部分形成了一定的塑性变形。在钻头横刃刚与薄壁件接触时,钻头横刃与薄壁件接触部分表现为应力集中;随着钻头的向下进给,钻头后刀面与薄壁件呈面接触,应力波开始以大致为圆形的波形扩散在薄壁件上,随后以近似方形传递到薄壁件四边。     

加工间隙对CBN磁性磨料研磨904L不锈钢表面完整性的影响

目的 针对904L高性能不锈钢工件进行磁力光整加工试验研究,分析加工间隙对不锈钢表面完整性的影响.方法 对不同加工间隙的磁感应强度进行了仿真与测试的对比分析,在不同加工间隙下,采用雾化法制备的新型CBN/铁基球形磁性磨料对904L高性能不锈钢进行磁力研磨加工.利用手持粗糙度仪和精密电子天平对不同间隙下工件表面粗糙度和材料去除量进行测量与分析,利用金相显微镜观察不同加工间隙下工件表面形貌不同变化情况,利用应力测试仪检测不同间隙下工件表面残余应力变化情况,利用润湿角测量仪对不同间隙下工件表面的亲疏水性效果进行观察与分析.结果 当加工间隙为2.5 mm时,CBN/铁基球形磁性磨料磁力光整加工904L不锈钢效果最好.工件表面粗糙度由研磨前的0.5μm下降至0.05μm,5 min内材料去除量可达36 mg,工件表面均匀,划痕被完全去除,同时没有凹坑的产生.工件表面的残余压应力由127.8 MPa增加到318 MPa,工件表面与液滴的润湿角由20°增加至83°,疏水效果达到最好.结论 加工间隙对CBN磁性磨料磁力光整加工904L不锈钢表面完整性有很大影响,当加工间隙为2.5 mm时,工件表面粗糙度最低,表面形貌光整均匀,残余压应力变大,工件的疲劳强度增强,工件表面疏水性变好,达到最佳研磨效果.     

复杂曲面研抛加工材料去除廓形建模研究

为了研究复杂曲面工件研抛加工时的去除量,建立了复杂曲面工件移动研抛表面材料去除廓形的预测模型。利用圆形赫兹接触理论对球形磨头和复杂曲面工件的接触压强分布进行分析建模,同时对球形磨头研抛区域的相对线速度分布进行理论推导,利用微元积分原理和移动材料去除指数建立了移动研抛表面材料去除廓形的理论方程并用MATLAB软件对材料去除廓形的理论方程进行了仿真。结果表明材料去除深度与法向正压力、磨头转速、研抛倾角成正比,与进给速度成反比;廓形宽度与法向正压力成正比,磨头转速、研抛倾角、进给速度不影响廓形宽度;研抛偏角对去除深度和廓形宽度的影响可以忽略不计。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.