基于有限元分析的飞刀优化设计及安全校核

汽车同步器齿套的滑块槽属难加工内表面。介绍了滑块槽加工工艺的国内外现状和加工原理,建立了切削滑块槽飞刀的数学模型,设计了加工齿套滑块槽部位的刀具。经过强度和刚度分析,证明刚度问题为首要校核目标。通过优化设计得到基于等刚度原理的飞刀结构,实践检验证明该刀具是适用的。     

The determination of initial blank shape by using the one-step finite element method and experimental verification

Many process parameters have an effect on the sheet metal forming process. A well-designed blank shape causes the material to flow smoothly, reduces the punch force, and yields a product with a uniform thickness distribution. Therefore, the determination of an initial blank shape plays the important role of saving time and cost in the sheet metal forming process. For these reasons, some approaches to estimate the initial blank shape have been implemented. In this paper, the one-step approach using a finite element inverse method will be introduced to predict the initial blank shape. The developed program is applied to several sheet metal forming examples for the demonstration of its validity. Moreover, the usefulness of the developed one-step approach program is investigated as compared with the FAST-3D program, which is a commercial package that is commonly used. Finally, the verification will be performed by comparing the predicted and experimental results.     

Expert system to automate the finite element analysis for non-destructive testing

This work describes an expert system that provides an intelligent interface between the non-destructive testing engineer and the finite element analysis (SDRC/I-DEAS) software. The system helps in efficiently evaluating the stress concentration resulting from the presence of volumetric discontinuities inside the body of the material.This expert system has a wide knowledge base and decision-making skills that are taken from the published documentation and the experience of human experts. In addition, it contains a large number of rules that determine the appropriate type of elements, meshing and solving techniques that should be used for different welded joints.The expert system asks the user questions about the shape and dimensions of the basic part that contains the discontinuities and the shape and dimensions of the embedded discontinuities. Then, it operates I-DEAS, creates the geometry of the basic part and the discontinuities, prepares surfaces for meshing, meshes according the appropriate set of rules, applies loads and boundary conditions and solves the model using the appropriate solving techniques. Finally, it produces a report describing the stress concentration around each discontinuity and checks whether it is harmful to the structure or not.The expert system has a modular structure that can be easily updated and applied for more sophisticated jobs.     

Edge-chipping reduction in rotary ultrasonic machining of ceramics: Finite element analysis and experimental verification

Rotary ultrasonic machining (RUM) is one of the machining processes for advanced ceramics. Edge chipping (or chamfer), commonly observed in RUM of ceramic materials, not only compromises geometric accuracy but also possibly causes an increase in machining cost. In this paper, a three-dimensional finite element analysis (FEA) model is developed to study the effects of three parameters (cutting depth, support length, and pretightening load) on the maximum normal stress and von Mises stress in the region where the edge chipping initiates. Two failure criteria (the maximum normal stress criterion and von Mises stress criterion) were used to predict the relation between the edge chipping thickness and the support length. Furthermore, a solution to reduce the edge chipping is proposed based upon the FEA simulations and verified by experiments.     

膨胀套管铜制悬挂系统有限元分析及试验研究

以膨胀套管铜制悬挂系统为研究对象,对影响施工作业安全性和可靠性的膨胀力和悬挂力进行非线性有限元分析和实物试验研究。结果表明:有限元模拟结果和试验结果在趋势上吻合性较好,所需膨胀力相对误差为9.8%,悬挂力相对误差为11.3%,有限元模型能够满足工程预测需求;铜制悬挂系统会导致膨胀力在膨胀锥通过铜环时发生激增,所需最大膨胀力随铜环过盈量、长度和厚度的增大而增大,在施工过程中应防止由于膨胀力发生突变而导致系统失稳。铜制悬挂系统单个铜环悬挂力随着铜环过盈量、长度和厚度增大而逐渐增大。铜环周向不均匀压缩会导致铜制悬挂系统实际悬挂力小于理论计算值。     

Multi-pass deformation design for incremental sheet forming: Analytical modeling,finite element analysis and experimental validation

Incremental sheet forming (ISF) is a promising rapid prototyping technology with high potential to shape complex three-dimensional parts. However, a common technical problem encountered in ISF is the non-uniform thickness distribution of formed parts; particularly excessive thinning on severely sloped regions. This may lead to fracture and limit the process formability. Design of multi-stage deformation passes (intermediate shapes or preforms) before the final part, is a desirable and practical way to control the material flow in order to obtain a more uniform thickness distribution and avoid forming failure. In the present paper, a systematic methodology for designing multi-stage deformation passes considering the predicted thickness strains given the design shape is proposed based on the shear deformation and the strain compensation mechanism. In this methodology, two analytical models (M1 and M2) are developed by taking into account; the global average thickness strain and only the material in the final part region used in the forming (M1), and the local weighted average thickness strain and the additional material around the final part region used in the forming (M2), respectively. The feasibility of the proposed design methodology is validated by finite element analysis (FEA) and experimental tests using an Amino ISF machine. The results show that a more uniform thickness strain distribution can be derived using M2. The incurrence of the highest strains can be delayed in the intermediate stages and the flow of material is allowed into the deformed region, thereby allowing a compressive stress state to develop and enabling steeper shapes to be formed. Therefore, the process formability can be enhanced via the optimized design of deformation passes.     

Development of single-action,two-step clinching system using finite element analysis

Traditional manufacturing processes for bending and combining the upper and lower heat insulation plates for a car catalytic converter need two kinds of bending dies. This study was carried out to develop a single-action, two-step clinching system for clinching heat insulation plates. To design the operating mechanism for this clinching system, finite element analysis was used to estimate the bending load needed and to predict the bent shape of the heat insulation plate. Then a recovery and cushioning system was designed for the bending die. It is expected that this new process will improve the manufacturing quality of heat insulation plates and will reduce manufacturing cost. And a higher value-added technique for mold and pressing systems was introduced.     

Development and finite element analysis of the finishing system using rotating magnetic field

A polishing system using rotating magnetic field has been developed for the internal finishing of tubes, especially curved tubes which are very difficult to finish by typical finishing methods. The mechanism and characteristics of the developed system are summarized. Finite element method was used to analyze the magnetic flux distribution and flux density in the working zone for two driving modes, from which the desirable mode for efficient polishing was determined.     

翼子板拉延成形的一步法有限元分析

研究了一步法数学模型及其中的一些关键问题,建立了一步法分析软件系统。提出了投影均值法得到较优的毛料初步解;提出了一种适用的压边力施加方法。通过计算NumiSheet2002标准考题,证明系统能较快、较准确地计算出翼子板拉延成形的下料较优毛坯形状尺寸和基本变形情况。     

带缺口的焊丝拉拔试验及有限元分析

对带缺口的活性无镀铜焊丝的变形趋势进行试验和有限元分析,解决金属在拉拔过程中自接触的算法问题。得出带有纵向U型缺口焊丝添加活性剂的效果最好,纵向V型缺口次之,横向U型缺口添加活性剂的效果最差。并对带缺口的焊丝进行拉拔试验,验证有限元分析的正确性,同时对焊丝截面进行扫描电镜能谱分析,得出闭合后的凹槽内部确实含有拉拔前涂覆的活性剂中的Se元素。     

Finite element analysis and verification of laser marking on eggshell

The first aim of the study was to establish the temperature model of the eggshell by the finite element analysis software ANSYS and realize the eggshell temperature field based on the laser marking processing. The eggshell surface which created the meshing model, set the parameters with the ANSYS Parameter Design Language and simulated that the Gaussian distributed laser beam acted on the surface were established. In addition, marking characters made use of the CO₂ laser processing system on the brittle eggshell to analyze whether laser beams caused damage to the inner of the eggshell. According to the results of the comparison between the simulation by ANSYS and the experiment of laser marking, it is revealed that the heat-affected area by laser marking is similar to that of the simulation.     

汽车变速销模锻成形有限元分析及实验验证

针对汽车变速销的形状、尺寸以及材料性能等特点,选定了单工步开式模锻的成形方法。使用CAE有限元分析软件Deform-3D对初始工艺方案进行仿真研究,分析了材料成形过程中的热、力情况,否定了初始工艺方案的可行性。从坯料尺寸、坯料温度以及模具结构3个方面出发,对成形工艺进行改进,制定了3套改进方案,并通过模拟方法得到较优工艺,即:坯料尺寸为Φ17 mm×47.5 mm,坯料温度为700℃,在凹模上增加Φ60 mm×0.2 mm的飞边槽以及在凸模前端设置1个Φ12 mm×0.5 mm的凸起。采用改进后的模具及优化工艺进行实验验证,证明了该工艺的可行性。     

TRT机壳热弹塑性有限元模拟与试验研究

采用大型通用有限元软件对TRT焊接机壳进行焊接过程的模拟。利用有限元软件中的单元生死技术和热-结构耦合技术,成功的预测了TRT机壳焊后残余应力及变形,并通过焊后残余应力测试试验验证对比。结果表明,有限元模拟机壳在焊接过程中,焊缝附近残余应力较大,局部达到其屈服强度;远离焊缝处的壳体上应力较小,均处于弹性变形。进行"盲孔法"测量残余应力,试验测量的残余应力跟模拟所得残余应力分布趋势相同,峰值应力出现的点基本重合。由于机壳实际焊接中施加的约束较多,应力得不到释放,导致试验数值略高于模拟数据。     

钢管压力矫直过程有限元分析

通过分析不同直径、不同壁厚、不同支点间距的钢管在矫直时的矫直力、矫直行程,总结得出矫直修正量的精确计算公式,为自动矫直机的控制提供了可靠依据.首先应用DEFORM 3D软件计算出载荷力,即工件实际屈服的加载力,然后在Marc中用求得的加载力实际加载和卸载,从而求得载荷撤销后压头处回弹剩余挠度和实际行程最大挠度值,利用其...     

板料冲压成形一步正向有限元分析

提出基于理想成形理论的板料冲压成形一步正向有限元分析方法。给出迭代初始解获取、线性化处理、收敛条件判定等具体算法,以及所使用的材料应力应变关系和屈服准则。运用该方法进行带凸缘盒形件和无凸缘筒形件的冲压成形模拟,将减薄率与增量有限元方法计算结果进行比较,并就无凸缘筒形件进行实验验证。结果表明,该方法计算结果可靠,使用简便,计算效率高。     

TRB板轧制-弯曲-回弹的多工步分析

轧制差厚板的变厚度轧制过程中,由于厚区和薄区的变形程度不同,使得厚区和薄区的残余应力分布不均匀,对后续弯曲成形制件的回弹产生较大影响。将轧制和成形的有限元分析相结合,研究轧制差厚板的弯曲制件的残余应力对回弹的影响。推导了变厚度轧制过程中轧辊竖直方向运动的速度公式,用于实现变厚度轧制的有限元分析。把轧制差厚板的弯曲成形作为多工步塑性成形的后续工序,将轧制引起的残余应力继承到弯曲回弹的分析中,分析了轧制对回弹的影响。所得结果与物理试验进行对比,验证了该方法的有效性。     

径向摩擦焊夹持模型三维有限元分析

应用ANSYS有限元分析软件,对弹带径向摩擦焊的夹持模型进行了三维非线性接触摩擦有限元分析,着重研究了传统和改进后的夹持模型中不同受力状态下保持弹体与夹持机构间相对静止所允许的最大摩擦扭矩的变化规律,为径向摩擦焊夹持防扭提供了理论依据。     

基于有限元分析的压机用螺纹的比较

通过有限元软件对压机用锯齿形螺纹和潘克螺纹的齿面应力和齿根应力进行分析比较,阐明了潘克螺纹较锯齿形螺纹具有明显的优势,表现为应力在每一牙上分布的均匀程度高,齿根应力高应力分布范围窄。锯齿形螺纹已经阻碍了现代压机的技术进步,急需一种新型螺纹来代替。期望本文对压机用螺纹技术进步起到积极的推进作用。     

多工位冲压自动送料系统运动规划仿真及实验验证北大核心CSCD

基于销合链链板多工位冲压自动化加工平台,对其自动送料系统的运动可靠性展开研究。首先,依据实际工况,对自动送料系统的动作需求进行分析,并完成各运动部件的运动规划及动作时序的划分。然后,基于ADAMS软件建立自动送料系统的仿真模型,设置好仿真参数和各运动的驱动约束函数,通过运动仿真获得各构件的位移、受力和力矩的变化曲线;对自动送料系统的末端执行机构的水平、竖直方向的速度与加速度进行分析。最后,在完成控制系统设计的基础上,搭建了销合链链板多工位冲压自动化加工平台样机,并进行实验验证。实验结果表明:销合链链板多工位自动冲压的生产效率可以达到6~7件·min^(-1),满足销合链链板生产节拍≤10 s/件的要求。     

高强度涂层结合性能的试验研究及有限元分析

采用线切割沿涂层/基体界面切成对称切口,两边粘结后直接拉伸的试验方法对高强涂层抗拉结合强度进行评价.并借助有限单元法对涂层/基体交界面上的应力分布及切口附近的应力集中进行了分析,为正确评价涂层/基体的结合强度提供了理论依据.按此方法对不同工艺参数的热喷涂烧结涂层结合强度进行了评价.结果表明,此方法可对高强涂层与基体的结合强度进行评价.