轻载装载机变速箱振动特性分析与试验

为了给装载机变速箱减振降噪提供依据,通过集中参数和有限元法相结合的方式对变速箱进行振动分析。综合考虑液力变矩器激励、齿轮系统内部激励等因素,建立装载机变速箱传动系统的弯-扭耦合动力学模型,求解得到各轴承的动态支反力;建立箱体有限元模型,进行模态分析,以轴承动态支反力为激励,在模态的基础上进行箱体谐响应分析,得到箱体在激励下的振动响应,选择箱体表面的振动测点,分析测点的振动加速度,找到并分析振动峰值及对应振型;最后进行变速箱振动试验,验证仿真的正确性。结果表明：传动系统的激励主要集中在输入和输出平行轴齿轮处,传动系统和箱体振动的峰值频率均和齿轮啮合频率相近,变速箱箱体振动较大的位置位于箱体的底部。试验与仿真对比,试验中存在和仿真相近的峰值频率,仿真和试验所得的振动加速度均方根误差值小于20%,验证了仿真的正确性。     

基于灵敏度分析的车门尺寸和拓扑优化

为了改善微型车X30的车门在使用过程中振动过大这一问题,利用Hypermesh建立该车车门的有限元模型,并对其进行模态分析。分析结果发现车门的一阶频率偏低,容易与白车身一阶弯曲频率发生共振。因此,基于灵敏度分析方法结合尺寸优化和拓扑优化方法对车门进行以提升车门一阶模态频率为目标的优化设计。首先,对车门各零部件进行质量灵敏度和一阶模态频率灵敏度分析,并定义相对灵敏度值;然后,根据相对灵敏度值结果选择合适的设计变量进行部件厚度的尺寸优化设计;最后,基于变密度法对相对灵敏值最大的部件进行拓扑优化,根据优化结果对该部件有限元模型进行修改。结果表明,在车门质量减少4.5%的情况下,车门一阶模态频率提高8.9%,有效地改善了车门的振动情况。     

基于ANSYS有限元法的某型车床主轴振动频率响应分析（英文）

以机械加工中常用车床CA6140为研究对象,分别采用基于ANSYS的有限元法和实验法对其主轴进行了振动模态与频率响应分析,并对两者的计算结果进行了对比分析,验证了ANSYS数值仿真的准确性。数值仿真和实验结果表明:主轴在一阶频率和五阶频率处容易发生共振,但未达到共振,且低阶频率要比高阶频率对主轴的振动影响大;通过实验得出,主轴在工作状态下的最大振动主要集中在其两端轴承附近区域,因此改进轴承是减小主轴振动、保证主轴加工精度的重要途径,其研究结果可对车床的结构优化设计提供理论指导。     

基于正交试验的双圆弧齿轮约束模态模型研究北大核心

齿轮模态分析主要依靠数值模态分析和试验模态分析法,存在求解过程繁琐且无法直接获取齿轮参数与模态频率振型之间耦合关系的问题。为进一步掌握齿轮主要参数对约束模态频率的影响,根据模态有限元计算理论,对双圆弧齿轮约束模态模型进行研究;分析前6阶模态振型图,采用正交试验方法,运用方差分析,计算各因素对模态频率的影响因子;定量分析双圆弧齿轮的齿数、模数、螺旋角、齿宽因素对约束模态的影响。结果表明:齿数是影响固有频率的主要因素,其次是模数、螺旋角和齿宽;对试验结果进行中心化一次非线性回归模型计算,建立双圆弧齿轮约束模态频率计算模型,实现双圆弧齿轮约束模态的快速计算,对比验证1阶频率计算值的准确性。研究结果为全面研究双圆弧齿轮的振动和噪声特性提供参考。     

生物质环模成型机致密成型过程振动分析

环模成型机作为生物质致密成型的主要设备,成型过程中的剧烈振动问题会影响其工作的稳定性,降低生物质的成型质量。针对环模成型机成型过程中的振动问题,根据实际工况在RecurDyn和EDEM中分别建立环模成型机的动力学仿真模型和离散元模型,通过联合仿真来模拟环模成型机的攫取过程。根据联合仿真结果,得到不同主轴转速下环模所受的挤压力情况,在有限元软件中得到环模的等效应力云图,结果表明：环模所受的最大等效应力为95.930 MPa,发生在环模模孔入口处。以环模所受最大挤压力作为载荷进行环模成型机预应力模态分析及谐响应分析。根据预应力模态分析得知,环模成型机变形主要表现为摆动及扭转。根据谐响应分析得到环模成型机在X、Y和Z方向的振幅-频率曲线,结果表明,在第1阶、第3阶和第5阶固有频率处环模成型机容易产生共振,应避免其在该激励频率附近工作。     

Y7125型磨齿机砂轮主轴的模态分析

基于有限元方法,对Y7125型磨齿机的砂轮主轴进行模态分析,得出了四阶主振动频率,并对数据进行了处理.     

S形焊接金属波纹管振动特性分析

针对S形焊接金属波纹管密封的振动问题,选用面体代替波片实体单元进行数值建模和模态分析;研究了单元尺寸对波纹管振动频率的影响,提出了波片选用面体单元时的单元尺寸应小于0.5 mm,并验证了其有效性。利用电动振动试验平台进行振动试验测试,得到了波纹管的振动特性曲线。通过对比分析仿真结果和试验测试结果,确定了波纹管的前6阶振动固有频率和振型,揭示了波纹管的振动机制和影响因素,阐明了波纹管的数值建模方法和试验测试技术。研究结果对焊接金属波纹管密封的设计、制造和应用提供了参考。     

多工况下发动机振动噪声研究

针对某公司生产的内燃机在780 r/min转速下振动噪声过大的问题,对内燃机做振动噪声试验并得出振动噪声过大的原因,得到该内燃机噪声与振动的分布规律,为后续内燃机的悬置设计提供一定的实验依据.测试内燃机转速分别为780、820、2200 r/min且负载不同工况下的振动信号,和内燃机在750～3390 r/min加速工况下的瞬态噪声信号.对所测稳态信号进行频谱分析,计算振动烈度,得出该内燃机转速与负载对噪声的影响,并对瞬态信号进行阶次分析,得到各阶次信号随转速的变化和主要的贡献阶次.最后根据以上对内燃机振动噪声的分析结果对内燃机悬置系统的模态进行设计.结果表明:稳态工况下,随着转速的提升基频也随之增加,Z轴的振动烈度比同转速的X、Y轴大;内燃机在780 r/min的振动烈度大于在820 r/min的振动烈度,说明内燃机在780 r/min时产生了共振;噪声主要由1阶、2阶、4阶、6阶、8阶机械噪声合成,机械噪声是由轴承或静偏心导致的机械噪声阶次及其谐波阶次,为内燃机的悬置模态设计提供了参考.     

多工况下发动机振动噪声研究

针对某公司生产的内燃机在780 r/min转速下振动噪声过大的问题,对内燃机做振动噪声试验并得出振动噪声过大的原因,得到该内燃机噪声与振动的分布规律,为后续内燃机的悬置设计提供一定的实验依据.测试内燃机转速分别为780、820、2200 r/min且负载不同工况下的振动信号,和内燃机在750～3390 r/min加速工况下的瞬态噪声信号.对所测稳态信号进行频谱分析,计算振动烈度,得出该内燃机转速与负载对噪声的影响,并对瞬态信号进行阶次分析,得到各阶次信号随转速的变化和主要的贡献阶次.最后根据以上对内燃机振动噪声的分析结果对内燃机悬置系统的模态进行设计.结果表明:稳态工况下,随着转速的提升基频也随之增加,Z轴的振动烈度比同转速的X、Y轴大;内燃机在780 r/min的振动烈度大于在820 r/min的振动烈度,说明内燃机在780 r/min时产生了共振;噪声主要由1阶、2阶、4阶、6阶、8阶机械噪声合成,机械噪声是由轴承或静偏心导致的机械噪声阶次及其谐波阶次,为内燃机的悬置模态设计提供了参考.     

车体振动模态对疲劳强度的影响分析

铁路运输车辆不断朝着高速以及轻量化方向发展,车体承受着复杂的交变载荷,极大地增加了车体结构疲劳断裂的风险。为探究车体结构振动对车辆结构安全性的影响,利用ANSYS Workbench进行车体模态仿真计算。结合服役环境下动车组车体运行模态测试数据,提取出车体1阶菱形(8~9 Hz)、1阶垂弯(12~13 Hz)、1阶横弯(15~16 Hz)及1阶扭转(17~18 Hz)模态频率,对车体有限元模型进行对比修正。利用雨流计数法对部分实测载荷谱数据谱进行处理,得到载荷谱雨流计数矩阵。在模态分析的基础上进行谐响应分析,得到上述不同模态频段范围内的频率响应函数,结合nCode疲劳仿真软件对车体疲劳强度进行仿真计算,得到不同频段范围内车体的疲劳损伤;采用Miner线性累积疲劳损伤理论对仿真计算结果进行疲劳损伤评估,结果表明:车体1阶菱形模态(8~9 Hz)附近频段对车体造成的损伤最大,其损伤位置在车钩与枕梁交接处附近。     

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.     

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.     

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.