《材料成形过程数值模拟》课程的案例型教学实践与持续改进

结合工程教育专业认证的持续改进要求,针对《材料成形过程数值模拟》课程理论性强、内容范围广、实践操作要求高的特点,推行案例型教学改革,通过导入企业工程案例、学校科研项目不断优化教学内容,通过引入企业工程师参与课程评价、反馈,不断完善评价方法。同时,与企业联合推进校企协同育人,将螺钉紧固件的热镦、热处理工艺等工程实际需求融入课程建设,促使教学内容更贴近材料成形“高精尖”制造业发展前沿,提高了工科专业仿真类课程培养学生解决复杂工程问题的能力。

变压器用翅片式散热结构数值模拟研究

为了提高变压器片式散热器散热能力,本文将传统的片式散热结构和翅片相结合,构建翅片式散热片模型,利用有限元分析软件Fluent,分别对翅片式散热片和普通式散热片模型进行自然油循环下自冷和风冷散热数值模拟研究。在自然油循环自冷情况下,随油速增大,翅片式散热片换热量较普通式提高了约58%~62%。在自然油循环风冷情况下,随着风速增大,翅片式散热片换热量较普通式提高了28%~48%;随油速增大,翅片式散热片换热量较普通式提高了22%~33%。翅片式散热片散热性能有明显提高。研究结果为片式散热结构的优化设计提供了指导作用。

项目教学法在“材料成形过程的数值模拟”课程中的应用

为提高教学效果,培养学生自主学习兴趣和能力,可以采用项目教学法对"材料成形过程的数值模拟"课程进行全新的课程设计和教学实践。本文介绍了项目教学法的实践经验和实施过程中应注意的几个关键问题。总之,项目教学法能够有效提高材料类专业的"材料成形过程的数值模拟"课程的教学效果,值得进一步推广。

均匀设计和遗传算法在板料成形数值模拟中的应用

介绍了均匀设计和遗传算法各自的特点,分析它们在板料成形数值模拟中的应用,并以方盒件成形为例,以凸模的运动速度凸模和压边圈与板料的摩擦系数凹模与板料的摩擦系数为决策变量,进行均匀实验设计,以成形后的最大减薄率为目标,优化成形工艺参数,提高成形质量,取得了令人满意的效果。

板料成形数值模拟的冲压模具结构分析方法探析

模具对金属塑性加工而言有着重要意义,有较大刚度与强度的模具为可忽略变形的刚性体,但模具在冷锻及冷挤压等受力恶劣的精密成形中的变形,大大影响着成形件尺寸精度。本文就是基于复杂结构的冲压件成形模具,对板料成形数值模拟的冲压模具的结构分析方法进行分析与探讨。

Forming defects in aluminum alloy hot stamping of side-door impact beam

The forming defects, including thinning, rupture, wrinkling and springback, usually arising in producing a side-door impact beam, were investigated by trial and numerical simulation. A temperature-related constitutive model specific to the temperature range from 350 °C to 500 °C was established and used for the numerical simulation. The trial and numerical simulation were conducted to clarify the quantitative characteristics of forming defects and to analyze the effects of process parameters on the forming defects. Results show that the rupture situation is ameliorated and the springback is eliminated in the aluminum alloy hot stamping. The wrinkling severity decreases with increasing blank holder force (BHF), but the BHF greater than 15 kN causes the rupture at the deepest drawing position of workpiece. The forming defects are avoided with lubricant in the feasible ranges of process parameters: the BHF of 3 to 5 kN and the stamping speed of 50 to 200 mm/s.

FINITE ELEMENT MODELING OF MODERATELY THICK COMPOSITE PLATE WITH PIEZOELECTRIC SENSORS AND ACTUATORS

A rectangular finite element for laminated plate with bonded and/or embedded piezoelectric sensors and actuators is developed based on the variational principle and the first order shear deformation theory. The element has four-node, 20-degrees-of-freedom with one potential degree of freedom for each piezoelectric layer to represent the piezoelectric behavior. The higher order derivation of deflection is obtained by using the normal rotation expressions to take the effects of transverse shear deformation into considerations. The finite element can accurately simulate the deformation of both thin and moderately thick plates. A Fortran program is written and a number of benchmark tests are exercised to verify its effectiveness. Results are compared well with the existing data. The unbalanced composite with piezoelectric layers is then analyzed by using the model. Results show that the changes of the ratio between the thickness of positive angle layers and the negative angle layers have an effect on the deformation of the structure under the same electric loading.

Numerical simulation of dynamic surface deformation based on DInSAR monitoring

Differential interferometric synthetic aperture radar （DInSAR） technology is a new method to monitor the dynamic surface subsidence. It can monitor the large scope of dynamic deformation process of surface subsidence basin and better reflect the surface subsidence form in different stages. But under the influence of factors such as noise and other factors, the tilt and horizontal deformation curves regularity calculated by DInSAR data are poorer and the actual deviation is larger. The tilt and horizontal deformations are the important indices for the safety of surface objects protection. Numerical simulation method was used to study the dynamic deformation of LW32 of West Cliff colliery in Australia based on the DInSAR monitoring data. The result indicates that the subsidence curves of two methods fit well and the correlation coefficient is more than 95%. The other deformations calculated by numerical simulation results are close to the theory form. Therefore, considering the influence, the surface and its subsidiary structures and buildings due to mining, the numerical simulation method based on the DInSAR data can reveal the distribution rules of the surface dynamic deformation values and supply the shortcomings of DInSAR technology. The research shows that the method has good applicability and can provide reference for similar situation.

CAE技术在汽车覆盖件模具设计中的研究与应用

简要介绍板料成形CAE技术的发展概况,阐述有限元模拟分析软件AUTOFORM的特点和功能。以某汽车覆盖件为例,利用AUTOFORM软件实现汽车覆盖件的模具设计,包括模具压料面、工艺补充面以及拉延筋设计,对覆盖件的成形过程进行模拟和分析,为完善模面设计方案提供依据。数值模拟技术的应用改变了传统的在有限元模拟后依靠CAD软件频繁进行模具修改的方法,在有限元软件内部实现了模具的参数化设计,既缩短了模具设计时间,又提高了模具设计的可靠性。

A Numerical Study on the Effects of Orography During the Landfall Process of Typhoon Haitang

The landfall process of typhoon Haitang which affected East China seriously was simulated by using the MM5 model and the track, intensity, precipitation and structure of typhoon were successfully reproduced. Then through the sensitive test, the effects of terrain were analyzed Results show that the irregular track during the period of typhoon passing through Taiwan and later landfalling at Fujian was in relation to the occurring and developing of orthographic impressed depression. The amount of rainfall was enhanced more than one time and the strength of typhoon was weakened 4 to 5 hPa. It is found that the effect of terrain on the structure of typhoon is limited at low level and is backward in space compared with the one at high level. In addition, the phenomenon that the equivalent temperature in the typhoon＇s moving direction inclines to the west on the eye of landfall may be concerned with the terrain.

Freak wave simulation based on nonlinear model and the research on the time-frequency energy spectrum of simulation results

VOF （volume of fluid） method has been used to make the numerical simulation of freak wave come true. The comparisons between the numerical results and linear theoretical results corresponding to Eq.（5） have been carried out to show that the numerical results have a better exhibition of nonlinear characteristics. Wavelet analysis method has been adopted to investigate the time-frequency energy spectrum of simulation freak waves and the results reveal strong nonlinear interaction enables energy to be transferred to high harmonics during the progress of its formation. Varying water depth can enhance the nonlinear interaction, making much more energy be transferred to high harmonics and freak waves with higher asymmetry be generated.

Analysis of granular assembly deformation using discrete element method

The discrete element method is used to simulate specimens under three different loading conditions（conventional triaxial compression,plane strain,and direct shear）with different initial conditions to explore the underlying mechanics of the specimen deformation from a microscale perspective.Deformations of specimens with different initial void ratios at different confining stresses under different loading conditions are studied.Results show that the discrete element models successfully capture the specimen deformation and the strain localization.Particle behaviors including particle rotation and displacement and the mesoscale void ratio distributions are used to explain the strain localization and specimen deformation.It is found that the loading condition is one of the most important factors controlling the specimen deformation mode.Microscale behavior of the granular soil is the driving mechanics of the macroscale deformation of the granular assembly.

Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Numerical simulation of solidification morphologies of Cu-0.6Cr casting alloy using modified cellular automaton model

The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental results.In numerical simulation aspect, finite difference(FD)method and modified cellular automaton(MCA)model were used to simulate the macro-temperature field, micro-concentration field,nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting operations.From the observed casting experiment,the preliminary grain morphologies are the directional columnar grains by the VCC process.The solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.

Numerical Simulation of NO_x Formation in Coal Combustion with Inlet Natural Gas Burning

A full two-fluid model of reacting gas-particle flows and coal combustion is used to simulate coal combustion with and without inlet natural gas added in the inlet. The simulation results for the case without natural gas burning is in fair agreement with the experimental results reported in references. The simulation results of different natural gas adding positions indicate that the natural gas burning can form lean oxygen combustion enviroment at the combustor inlet region and the NOx concentration is reduced. The same result can be obtained from chemical equilibrium analysis.

Numerical Simulation of Shaped Charge Jet Using Multi-Phase SPH Method

Since the jets and detonation gaseous products are separated by sharp interfaces, the traditional smoothed particle hydrodynamics (SPH) method is difficult to avoid the computational instability at interfaces. The multi-phase SPH (MSPH) method was applied to improving the stabil-ity, which smoothes the particle density and makes pressure continuous at interfaces. Numericalexamples of jet forming process were used to test capability of the MSPH method. The results show that the method remains algorithm stability for large density gradient between the jets and gaseous products and has potential application to both the explosion and the jet problems. The effect of initiation ways of the shaped charge was discussed as well.

Digitalization Modeling System for Constitutive Relation of Geomaterial

A digital modeling system method is put forward for modeling constitutive relation of geomaterial including digital image subsystem for deformation measurement, numerical modeling subsystem and numerical simulation subsystem. A non-contact measurement method based on digital image processing is introduced to improve measurement of specimen deformation. Based on the method, a series of conventional tri-axial compression tests under diverse stress paths are done. Then an elasto-plastic constitutive model of soil is acquired through the numerical method of modeling constitutive law for geomaterial. Two examples of specimen deformation and ground subsidence are presented and discussed. It indicated that this method can rationally simulate the stress-strain relationship of soil, which reflects the effect of stress path on soil stress-strain relationship.

3D modeling and deformation analysis for electromagnetic sheet forming process

Electromagnetic forming （EMF） is a high-speed forming method which can be quite effective in increasing the forming limits of metal sheet. However, the EMF process is complicated due to magnetic-structure coupling analysis. Numerical simulation offers an opportunity to overcome the problem. Nevertheless, most present models for EMF process are limited to 2D axisymmetric model. So, a three-dimensional （3D） finite element model was established to analyze the electromagnetic sheet bulging. The contact between the sheet and the die and the effect of sheet deformation on the magnetic field analysis were both taken into consideration during the forming process. The simulation results of deflection at the sheet center and 20 mm away from the center were in agreement with the experimental ones. The plastic strain energy and plastic strain were analyzed.

Numerical Simulation of Viscous Flow Through Spherical Particle Assemblage with the Modified Cell Model

The cell model developed since 1950s is a useful tool forexploring the behavior of particle assemblages, but it demandsfurther careful development of the outer boundary conditions so thatinteraction in a particle swarm is better represented. In this paper,the cell model and its development were reviewed, and themodifications of outer cell boundary conditions were suggested. Atthe cell outer boundary, the restriction of uniform liquid flow wasremoved in our simulation conducted in the reference frame fixed withthe particle.

Numerical simulation and experimental verification of large-sized Zr-based bulk metallic glass ring-shaped parts in casting process

An outer ring of 29320 self-aliging roller bearing was used in an experimental study on the casting of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloy.Numerical simulations of mold filling and solidification processes were carried out to determine the velocity fields and temperature fields of the alloy melt during mold filling process as well as the temperature fields and temperature gradient fields in the course of the solidification.According to the results,a cast with a complete shape can be obtained at 1200℃under the condition that the cooling rate is greater than the critical cooling rate.The ring-shaped part with a thickness of 25 mm,an equivalent diameter of 22 mm,and a mass of 1.32 kg was prepared by gravity casting in a copper mold.X-ray diffraction and differential scanning calorimetry data revealed that the produced cast had the amorphous structure.