20CrMnSiNi2MoA凿岩用钢等温自由锻模拟及试验研究

针对凿岩钻头用钢20CrMnSiNi2MoA,基于JMatPro软件模拟计算材料的应力应变曲线,并线性回归出材料的流变应力方程;基于DEFORM-3D有限元软件对材料进行了不对称V型砧锻造法等温自由锻造压缩,并预测了微观组织变化趋势。研究结果表明：原始奥氏体晶粒随着压缩量的变大,发生了动态再结晶,晶粒尺寸得到细化;温度一定时,随着变形速率的提高,晶粒平均尺寸变小。将通过不对称V型砧锻造法等温自由锻及热处理得到的钻头成品的机械性能与国外同类产品的机械性能进行了对比。     

A multiscale mechanics approach for modeling textured polycrystalline thin films with nanothickness

A multiscale method is proposed for calculating elastic constants of textured polycrystalline thin films of nanothicknesses. In this method the molecular simulation and finite element method are hierarchically employed. The elastic constants for each single crystal are first calculated through the simulations of on- and off-axis tension tests of the single crystal using molecular statics. Subsequently, the constitutive relations for the single crystal are used in conjunction with a finite element code to study the macro-mechanical deformation and stresses in textured polycrystalline nanofilms. The result indicates that both film thickness and grain size influence the macro-Young's modulus and Poisson's ratio of the nanofilm. Specifically, for nickel, the value of the macro-Young's modulus decreases as film thickness decreases and increases as grain size decreases. The value of the macro-in-plane Poisson's ratio increases as the thickness decreases or grain size increases.     

胶囊机器人磁驱动力建模与测量

可吞式无线磁驱胶囊机器人在胃肠道内的诊疗效果与机器人受到的外部磁驱动力密切相关。本文建立了外部磁驱动力的理论模型,基于等效磁荷模型推导了两径向充磁环形永磁体相互作用的数学表达式,采用自适应递归式计算方法开展了数值计算。此外,发展了环形永磁体间磁力实时测量方法,并开发了磁力-间距同步测量仪器开展实验研究,且建立了3D环形永磁体有限元仿真模型。实验测量磁力-间距关系曲线与理论计算和有限元仿真结果吻合较好,误差小于4%,验证了理论模型和有限元仿真模型的准确性和可靠性。通过参数分析,揭示了胶囊机器人内置永磁体长度、厚度和体积对磁力的影响规律。研究结果为精准驱动胶囊机器人在胃肠道内运动奠定了理论基础。     

大型饼类锻件预镦粗工序的数值模拟研究

为了解决镦粗变形缺陷,将饼类锻件的预镦粗工序分为锥台砧镦粗和平砧端面整平两个阶段,利用DEFORM-3D计算平台建立锻造过程的有限元模型并进行仿真分析;分别从锻件内部的应力场和应变场等方面研究了锥台砧锥角和压下率对镦粗过程的影响,平砧旋转锻造方式和下砧砧形对端面整平过程的影响,以获得合理的预镦粗锻造工艺参数,指导实际生产过程.     

Inverse calculation of the friction coefficient during the warm upsetting of molybdenum

This study focused on the variation of the friction coefficient during the upsetting process and the concept of treating the solution of unknown parameters as an inverse problem. Based on the experimental measurement data, the Levenberg–Marquardt method, a numerical optimization approach was used in conjunction with the constrained function, convergence criterion and the axial symmetry thermo-elastic-plastic finite element method to solve, inversely, the variation of friction coefficient during the upsetting process.The inverse calculation steps of the warm upsetting of the molybdenum proposed in this paper was based on the load values measured in the upsetting experiment. The inverse calculation procedures were taken to solve the variation of the friction coefficient during the warm upsetting process. The results related to stress distribution, strain distribution, temperature distribution and shape variation were then compared with those reported in other studies. The comparison further confirmed the justification of using the load to solve the friction coefficient inversely. By means of the inverse algorithm presented in this paper, physical phenomena that better approximated the reality could be obtained, and the entire upsetting forming simulation could be more complete.     

Sensor elements made of conductive silicone rubber for passively compliant gripper

Grinding is regarded as a special multiple edge cutting process, in which the abrasive grains remove the workpiece material at the microlevel. The grain–workpiece interaction, which resembles the microcutting process, directly modifies the workpiece surface and dominates all the output measures of grinding process. Recently, a virtual single-layer cubic boron nitride (CBN) grinding wheel model is developed by simulating each wheel fabrication step, which makes the estimation of the single grain material removal mode possible in grinding. Therefore, the study of the grain–workpiece interaction through microcutting behavior on the abrasive grains becomes necessary for the quantitative investigation of grinding processes. In this paper, the influence of the grain orientation on the microcutting performance of CBN grains is studied through finite element method (FEM) simulation based on response surface methodology (RSM). The FEM simulation helps in both qualitative and quantitative understanding of microcutting process. And the RSM analysis is proved to be an effective tool for factorial analysis in this paper. The results indicate that the single grain microcutting force is sensitive to the grain wear condition and orientation status, and there exists preferable orientation condition for microcutting with abrasive grains to achieve minimum cutting force.     

Mooring alignment for marine SINS using the digital filter

Strapdown inertial navigation system (SINS) is presently used in several applications related to aerospace system and marine navigation. The accurate initial attitude is essential to ensure the precise determination of the position and attitude of the moving platform, which is usually calculated using initial alignment. When the vehicle is moored, the SINS inevitably experience disturbing motion. The method of ground coarse alignment, which is based on the assumption that SINS is on a stationary carrier with limited vibration, therefore cannot be used to perform the SINS mooring alignment. In this paper, a novel method processing the gyro and accelerometer measurements with infinite impulse response (IIR) digital low-pass filter to remove the high frequency noise is investigated for marine mooring alignment. Its algorithmic principle is described in details. The results obtained from both simulation and mooring experiment show that the attitude determined by this novel method can meet the accurate alignment.     

肠道胶囊式微机器人轴向磁拉力特性

提出一种以径向磁化的瓦状多磁极组成的圆筒式永磁体为外驱动器，以嵌入机器人本体内与外驱动器同磁极结构的永磁体为内驱动器的非接触式驱动控制方案。通过外驱动器的旋转产生旋转磁场，借助于磁机耦合作用，驱动机器人旋转并在其外螺纹表面形成的流体动压力作用下产生轴向推力，进而实现胶囊式机器人在肠道内旋进。基于等效磁荷理论，采用磁荷积分法建立了驱动器的轴向磁拉力模型，对驱动器磁极结构参数与磁拉力的关系特性以及磁拉力与机器人游动关系特性进行了理论与试验研究。     

Matrix-presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting

The main purpose of this paper is to develop the matrix presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting to obtain the friction coefficients during the upsetting process. This inverse model assumed the linear material and based on the modified experimental loading increments using the linear modified experimental upsetting loading standard proposed in this paper. Then the friction coefficients of contact boundary between the workpiece and the die at specific finite element analysis stages can be derived. Finally, using the cubic spline fitting, the history of friction coefficient during the upsetting process can be obtained. It is demonstrated that the workpiece profile of upsetting experiment is quite identical to the workpiece profile of simulation using the result obtained in this paper as the history of friction coefficient of contact boundary, and furthermore the distribution of stress and strain of the workpiece during upsetting process can be understood.     

陶瓷CBN砂轮地貌建模与磨削仿真

针对砂轮表面上磨粒形状的不规则性、尺寸的不确定性以及分布的随机性特点,采用随机空间平面切分实体的方法生成了具有实际磨粒几何特征的不规则多面体磨粒;提出了虚拟格子法,实现了磨粒空间位置的随机分布,构建了陶瓷CBN砂轮地貌仿真模型;采用有限元法和光滑粒子流体动力学法的耦合方法进行了砂轮地貌模型磨削仿真,通过切削层SPH粒子的运动情况,分析了磨粒的切削机理及工件表面的创成机理。     

Position and orientation detection of capsule endoscopes in spiral motion

In this paper, a position and orientation detection method for the capsule endoscopes devised to move through the human digestive organs in spiral motion, is introduced. The capsule is equipped with internal magnets and flexible threads on their outer shell. It is forced to rotate by an external rotating magnetic field that produces a spiral motion. As the external magnetic field is generated by rotating a permanent magnet, the 3-axes Cartesian coordinate position and 3-axes orientation of the capsule endoscopes can be measured by using only 3 hall-effect sensors orthogonally installed inside the capsule. However, in this study, an additional hall-effect sensor is employed along the rotating axis at a symmetrical position inside the capsule body to enhance measurement accuracy. In this way, the largest position detection error appearing along the rotating axis of the permanent magnet could be reduced to less than 15mm, when the relative position of the capsule endoscope to the permanent magnet is changed from 0mm to 50mm in the X-direction, from −50mm to +50mm in the Y-direction and from 200mm to 300mm in the Z-direction. The maximum error of the orientation detection appearing in the pitching direction ranged between −4° and +15°.     

电弧增材成形单道两层熔积过程中的晶粒生长模拟

晶粒生长的数值模拟是研究复杂微观组织演变的重要手段,现有的研究较少涉及电弧增材成形中晶粒生长的数值模拟。采用有限元和元胞自动机方法建立了碳钢电弧增材成形过程的宏观传热和微观组织演变的耦合模型,模拟单道第两层熔积的熔池凝固过程中晶粒动态演变过程。模拟结果显示,单道第一层熔积熔池凝固过程中晶粒从熔合线位置形核后向熔池中心生长,在温度梯度方向与枝晶臂优先生长方向的共同作用下,枝晶呈现竞争生长,晶粒优先生长方向与温度梯度方向一致的晶粒生长更快,部分晶粒生长被抑制,最终形成交错、完全粗大的柱状晶组织,枝晶之间出现溶质富集的现象;单道第二层熔积的晶粒在上一层粗大柱状晶基础上形核并生长,随后的生长过程与第一层类似,第二层熔积时熔池温度梯度方向的改变导致晶粒的主要生长方向与第一层之间有一定夹角。与模拟相同成形工艺的成形试样金相照片验证了模拟结果。研究结果可为电弧增材成形微观组织控制以及后续工艺规划提供依据和参考。     

Understanding the residual stress distribution in brazed polycrystalline CBN abrasive grains

This article investigates the brazing-induced residual stresses in the polycrystalline cubic boron nitride (PCBN) abrasive grains based on finite element simulation. The effects of embedding depth and gap thickness on the residual stress distribution in brazed PCBN grains are discussed. Results obtained show that, compared with the Ag-Cu-Ti alloy joining CBN grains and AISI 1045 steel substrate, the AlN binder materials in the polycrystalline CBN grains always have a greater effect on the brazing-induced residual stresses; meanwhile, large residual tensile stresses usually exist at the interface between the microcrystalline CBN particles and AlN binders. In comparison to the embedding depth, the gap thickness has little influence on the brazing-induced residual stresses. Furthermore, compared with the other embedding depth, in the case of the embedding depth of 40 %, the residual stresses in the brazed PCBN grain are generally the lowest in the grain bottom and the largest in the grain top surface. Finally, the finite element model applied in the current simulation work is validated through measurement experiments of the brazing-induced residual stresses in the monocrystalline CBN grain.     

减小电镦下沉深度与混晶改善的增材调控研究

在电镦成型时,尤其是大型件的成型时,为了获得所要求的“蒜头”直径,往往会造成坯料前端的下沉缺陷。下沉缺陷的存在,一方面,大的下沉深度会使坯料端面晶粒分布极其不均匀,出现混晶;另一方面使坯料在后续的模锻成型时出现闭气问题。通过增材调控的方法,不仅能使下沉深度减小,而且可以使电镦端面的混晶区域的晶粒趋于均匀化,大大提升了电镦件的质量。     

永磁涡流耦合传动特性研究

永磁涡流耦合传动技术采用非接触传动方式,能实现较软的传动特性,应用在一些特殊场合有非常好的效果。永磁涡流耦合器采用永磁涡流耦合传动技术,具有节能、过载保护、允许较大的对中误差、结构简单、使用寿命长等优点。为实现永磁涡流耦合传动特性研究,针对油田应用设计永磁涡流耦合器。对耦合驱动原理进行理论分析,建立永磁涡流耦合的数学模型;利用Ansoft仿真软件建立三维有限元模型,对耦合器的传动特性进行仿真研究,得到传递转矩与间隙、转速差之间的对应关系,随着间隙的减小,转速差的增大,耦合器传递转矩增加;建立耦合器传动试验平台,对样机进行试验研究,验证有限元仿真可以作为耦合器传动特性的研究方法,同时从试验结果曲线上确定耦合器合理的工作区间,在此工作区间内,耦合器具有高效率和较高的启动转矩,能够缓冲负载波动,传动性能良好。     

电磁搅拌对HK40钢离心铸管显微组织及蠕变性能的影响

电磁离心铸造HK40钢管的凝固组织由外层的倾斜柱状晶和内部等轴晶组成，随着励磁电流的增大，柱状晶偏斜角增加，等轴晶晶粒变细，晶界共晶碳化物数量增加，时效析出二次碳化物减少。在3A的励磁电流搅拌作用下，共晶碳化物引起的晶界强度和二次碳化物引起的晶内强度获得最佳配合，使HK40离心铸管蠕变抗力最大，增加或减少励磁电流都会使蠕变抗力降低。     

热锻成形过程温度场的热力耦合数值模拟

介绍了采用刚粘塑性有限元法热力耦合数值模拟热锻成形过程的基本原理,导出了以节点速度和节点温度对时间的导数为基本未知量的热力耦合方程式。采用新开发的程序系统对20钢热镦粗成形全过程温度场进行了模拟研究,得出了反映热镦粗成形流动规律的网格变化图和反映温度场变化情况的温度分布图,并将热力耦合分析得到的热镦粗载荷与行程关系曲线与试验测得的曲线作了比较,两者基本相符。     

基于磁热耦合仿真的筒式永磁调速器散热研究

针对筒式永磁调速器长时间运转发热严重的问题,利用磁热耦合分析方法,建立磁场、温度场分析的数学模型和有限元模型,通过Maxwell 3D和Steady-State Thermal模块联合仿真,得到铜环、永磁体温度场分布情况。通过对散热片进行优化仿真,显著降低了铜环和永磁体的最高温度。     

管道攀爬机器人非接触变磁隙式永磁吸附机构的设计与吸附性能优化

设计了一种能自适应吸附不同直径管道的非接触变磁隙式攀爬机器人。采用矢量磁位法和有限元法建立了吸附机构的磁场分布模型和磁吸附力模型。基于空间力系统的平衡方程建立了机器人的力学模型,得出爬壁机器人需要的最小磁吸附力。基于磁场和磁吸附力的理论模型与Maxwell仿真,通过离散组合法得到了最优磁铁宽度和磁吸附力。通过不同磁场和磁吸附力的对比计算,在最优磁铁宽度为80 mm时,得出近似圆弧机构单位体积的磁吸附力为0.0078 N/mm3,大于矩形磁铁单位体积的磁吸附力0.0047 N/mm3,它产生的磁吸附力满足单个机构所需的最小磁吸附力2100 N的负载要求。最后,通过实验获得了磁吸附机构的磁吸附力特性,证明了磁吸附机构优化设计的可行性。     

圆平动化学机械研抛过程的流体动力性能分析

根据圆平动化学机械研抛(C ircular-translational-moving Chem icalMechan ical Polishing,CTM-CMP)的运动关系,建立了极坐标下非稳态流体膜厚方程和非稳态下牛顿流体在CTM-CMP过程中的润滑方程。利用有限差分法数值求解获得了瞬时工件与研抛盘间的压力分布和膜厚分布,分析了压力积分载荷、倾覆力矩与研抛速率及姿态角的变化关系。结果表明CTM-CMP过程易于形成负压,有利于提高研磨效率。随着研抛速率的增加,承载能力和倾覆力矩线性增加;随着倾角的增加,承载能力和倾覆力矩非线性增大。分析结果有助于指导CTM-CMP的应用。