基于热力非耦合数值模拟的轮胎模具结构优化

以1188型号轮胎模具为例,运用ANSYS软件对模具进行热分析与结构应力分析,得出模具热分析与结构应力分析的结果。以改善模具型腔内温度的均匀性和花纹块上的温度分布为模具结构的优化目标,提出了改变花纹块与弓形座之间接触方式的模具结构调整方案,并对改进后的模具结构进行应力分析与热分析。结果表明:改变花纹块与弓形座的接触方式后,花纹块上、下两端的温差由1.933℃减小为0.01℃,模具型腔温差由2.319℃减小至0.989℃,模具型腔温度均匀性好;同时,花纹块上、下两端拐角处的应力值明显减小,应力集中也有明显改善,有利于提高硫化轮胎的使用性能和延长其使用寿命。     

轮胎模具合体结构的设计与数值模拟

介绍了一种合体结构轮胎模具,主要说明其特点及应用场合,论述合体结构模具设计过程及应注意的问题。应用ANSYS软件对合体结构模具和原结构模具进行应力分析与热分析,依据分析结果与数据,从模具型腔应力分布、模具型腔温度分布的均匀性以及花纹块温度分布情况,模具质量与体积等方面对合体结构模具与原结构模具进行对比。结果表明,合体结构模具有利于提高轮胎产品的性能。     

底座滑板结构对花纹块温度分布的影响

轮胎模具型腔温度分布的均匀性对硫化轮胎质量非常重要,模具结构设计上的差异会使花纹块的温度分布出现较大的温差,这种温差将导致硫化轮胎的胎面质量不均匀,从而影响轮胎性能。利用ADINA有限元软件,针对全钢轮胎模具底座滑板结构,对花纹块温度分布进行了模拟分析,结果表明:底座滑板结构的变化,对12.00R20规格的轮胎模具结构影响较大。     

铝合金压铸模具温度场模拟与节点热应力分析

利用ProCAST软件对铝合金压铸模具进行温度场和流场的耦合模拟,动态展示了模具的充型过程和模具稳定工作时的温度场变化。利用温度场模拟结果,提取出模具型腔表面重要节点的温度场变化曲线,对节点温度进行分析并计算节点热应力,判断模具所受的热冲击。该模具型腔比较复杂,棱边处温度场变化很大,成型圆孔边缘上的节点温度变化尤为剧烈。节点上温差为200℃时,所受热应力可以达到600MPa以上,长期循环生产易使型腔表面出现热裂纹。     

轮胎活络模及花纹块顺序热力耦合分析

以X1188型号轮胎活络模为例,运用ABAQUS有限元软件进行顺序热力耦合分析,得到轮胎活络模整体及花纹块的等效应力和位移分布云图,并分析力的作用机理。通过结构优化的方法对比分析,得出花纹块腰带厚度增大,腰带下端面的等效应力减小,中间区域变化明显,应力分布均匀性降低;对花纹块肩部和底部倒角,花纹块整体等效应力降低,缓解应力集中情况。     

圆锥面与斜平面轮胎模具传热模拟分析

介绍了圆锥面与斜平面轮胎模具的结构特点,以Y1188壳体9.00R20、12.00R20的2种规格模具为例,利用Abaqus软件对2种规格的圆锥面与斜平面轮胎模具进行传热模拟分析。结果表明:9.00R20规格的轮胎模具型腔温度分布要优于12.00R20规格的轮胎模具,斜平面轮胎模具型腔温度分布要优于圆锥面轮胎模具,与斜平面轮胎模具相比,圆锥面轮胎模具升温快,9.00R20和12.00R20规格的圆锥面轮胎模具分别比对应的斜平面轮胎模具达到轮胎硫化要求温度的预热时间减少26 min和20 min,模拟结果为合理的选择轮胎模具进行轮胎硫化提供理论指导。     

轮胎活络模具温模过程的轴对称数值模拟分析

建立了9．00R20轮胎模具的轴对称传热模型,利用ABAQUS有限元软件对温模过程进行了传热模拟研究,得到温模过程中轮胎模具型腔壳体的温度场。并据此提出改进方案,达到了缩短模具预热时间的效果,同时使花纹块整体温度升高,整体温差缩小,轮胎的硫化效率与硫化质量均能得到提高。     

双色汽车车灯模具型腔分析

以汽车双色车灯装饰条注塑件为例，在裂纹风险位置点设置镶块，运用Moldflow-ABAQUS耦合的方法，采用全分体方案和部分拆分方案对镶块进行试验分析，同时完成注塑和结构的一射和二射应力分布云图和应变分布云图。模拟结果表明：型腔最大等效应力为515 MPa,最大变形为0.15 mm,符合车灯模具强度和刚度要求。该方法能够较为全面地反映车灯注塑模具在注塑成型过程中型腔的受力和变形情况，能为同类模具的开发提供有效技术支持。     

轮胎活络模具弓形座的参数优化设计与传热模拟分析

利用Solid Works和ANSYS Workbench构建的协同仿真优化平台,对轮胎模具的重要零件弓形座进行静力学分析。分析了弓形座在一定压力状态下的应变,找到其工作的危险部位;运用ANSYS Workbench软件平台的DOE模块,以弓形座的3个主要尺寸作为设计变量,以其质量、最大等效应力作为目标函数进行优化设计;将活络模具结构更新,进行传热模拟分析,得到模具型腔内部的温度分布。结果表明:在满足强度条件下,改进后的弓形座重量减轻,模具型腔内部温差减小,有利于轮胎硫化的质量。     

斜平面导向轮胎模具底座耐磨板结构性能分析

斜平面模具底座耐磨板在闭模时起到支撑弓形座的作用,底座耐磨板磨损过大会导致侧板与花纹圈结合处出现错台,影响硫化轮胎的表面质量,底座耐磨板的形状大小也会影响模具传热过程中型腔内部的温度均匀性。通过对底座耐磨板的磨损和传热模拟分析可知:当底座耐磨板结构为梯形时,模具工作1.5万次时闭模瞬间磨损量可达0.083 mm,且花纹块上下点温差较大;当底座耐磨板结构为矩形时,模具工作1.5万次时闭模瞬间磨损量为0.32 mm,模具磨损量较大,但硫化时花纹块的温差较小。     

焊接热循环过程中氢陷阱热释放的数值分析

基于焊接热循环过程的特点,分别提出了热循环的升温段和冷却段过程中氢陷阱的热释放的动力学模型,并运用数值分析的方法,对焊接热循环中氢陷阱的热释放过程进行了研究.结果表明,高强度低合金钢的多层多道焊中,前一焊道受后续焊道的热循环作用下,焊道中的氢陷阱存在热释放过程,且弱氢陷阱在热循环的升温段就基本完全被释放出去,而稳定性较...     

Improved thermal stress analysis for castings

Abstract

Three algorithms are presented to address three problems in stress analysis of castings: difficulties for enmeshment of complicated casting into finite element meshes, coupling of thermal and stress analysis, and determination of inverse deformation, respectively. An algorithm of conversion of finite difference meshes into finite element meshes is achieved by reformatting the data of meshes. An algorithm of the heat transfer coefficient at the casting/mould interface is presented and the coupling of thermal and stress analysis is realised with the feedback of stress and deformation to heat transfer. Machining allowance is applied as a criterion for deformation evaluation of castings. And insufficient machining allowance is transformed to inverse deformation which is fed back to the original casting design for recalculation of stress and deformation. Therefore, the design of casting with appropriate inverse deformation is obtained. Case studies about a cylinder block and a hydro turbine blade casting are illustrated.     

一水硬铝石的热分解反应动力学

根据一水硬铝石(α-AlOOH)分解前后的X射线衍射(XRD)谱, 判断其热分解后主要生成α-Al2O3. 分别用Coats-Redfern积分法和Kissinger方法处理了不同升温速率下一水硬铝石的差热曲线, 两种方法得到的热分解反应动力学参数非常接近, 计算所得的活化能分别为254.54 kJ/mol和244.08 kJ/mol, 并推断了反应的动力学模型和反应机理. 研究表明一水硬铝石的热分解符合Mample单行法则, 相对应的机理为随机成核和随后增长.     

Fabrication and analysis of nano-structured thermal spraying feeds

A kind of thermal spray nanostructured Al2O3 and TiO2 feeds fabricating technology was investigated.Agglomerated nanogranules prepared by spray drying were heat treated in order to be dense, and there were two sintering technologies used, i.e. high temperature electric furnace sintering and high velocity flame sintering, respectively. The results indicate feeds phase components using high temperature electric furnace sintering at 1 200 ℃,1 300 ℃ and 1 400 ℃ do not change, and grain sizes of nano-Al2O3 and TiO2 grow little at 1 200 ℃ and 1 300 ℃,while grain sizes of nano-Al2O3 and TiO2 grow obviously, and the grain size of nano-TiO2 is larger than 100 nm at 1400 ℃. Phase components of the feeds using high velocity flame sintering change, where α-Al2O3 changes to γ-Al2O3 and rutile TiO2 changes to brookite TiO2, though grain size of nano-Al2O3 does not grow and is less than 100 nm because cooling velocity is too quick. Compared with these two heat treatment technology, the technology using electric furnace to treat nanostructured Al2O3 and TiO2 feeds is more suitable.     

热模拟试验机试样热压缩数值分析

针对热模拟试验机(Gleeble 3500)热轧试样高温压缩试验的动态变形、材料内部应力、组织损伤、动态应变量及材料各部分塑性变形差异性等问题，利用Deform 3D软件数值仿真开展研究。结果表明：随着压缩的进行，试样表面积先减少后增加，约在5 s时表面积最小，下降率为4.1%，在8.4 s后剧烈增加，增加率为14.4%。在整个压缩阶段试样两端承受应力最大约为70 MPa。破坏性损伤Damage值为0.22，应变为1.43，顶部区域变形速率最大为1.19 mm/s。空冷和淬火冷却过程中，试样顶底边界面角部区域温度下降最快，高温区域变化趋势为由长方形向圆角长方形，再向椭圆形转变。     

手工自蔓延焊接热循环测试与分析

焊接过程是一个牵涉到传热传质、金属熔化与凝固的复杂过程,焊接能量分布、焊接熔池中的流体流动及其传热过程对焊接质量有着重要的影响。介绍了焊接热循环试验原理和试验设计,测试了手工自蔓延焊接热循环,并将测试结果与传统焊接热循环相比较,分析认为:在焊缝中心线上的温度循环中,距熔合线位置越远温度越低,在焊缝横截面上的温度循环随着布点距离的增大,温度下降;热循环在800℃以上停留时间过长,导致热影响区成为手工自蔓延焊接接头的薄弱区域,并提出了解决方案。     

差温无模锻造的三维FEM模拟与分析

为探索差温无模锻造技术在成形齿形类锻件中的应用,首先建立了差温加热的三维温度场有限元分析模型,并通过正交实验法确定了在两种不同加热方式下最佳温度场的工艺匹配,在此基础上进行了两种不同热加载方式的变形模拟.通过变形模拟分析可知:无论采用哪种热加载方式,镦粗锻件局部突出变形都不是特别大.利用差温无模锻造技术来成形具有多个较大局部突出的齿形类锻件有一定的难度,但可作为初锻的一种成形方法.     

Post-test corrosion analysis of high-temperature thermal energy storage capsules

Thermal energy storage capsules have been freeze-thaw cycled in vacuum at 1000 ± 100 K. The capsules were fabricated from Inconel 617^® (Inco Alloys International, Inc.) and contained eutectic fluoride mixtures of sodium, magnesium, lithium, and potassium. Samples that were thermal cycled for 20,000 and 30,000 hr were analyzed for corrosion effects. Radiography indicated neither flaws nor inhomogeneities, and there were no significant microstructural changes in the container alloy. The microstructural damage penetrating the inside surface was as deep as 120 m and that penetrating the outside surface was approximately 150 m. Microprobe results on the containers revealed a concentration gradient of alloying elements. The aluminum concentration was reduced from 1.34% in the original matrix to 0.4% at 10 m from the inside surface, and chromium was reduced from a nominal value of 23% to 10% at the outer surface. The depletion of aluminum and chromium from the outer surface was due to vacuum vaporization at elevated temperature. X-ray diffraction revealed the formation of possible protective films consisting of MgNaF₃ and MgF₂. The measured and theoretically predicted concentrations of aluminum and chromium were in good agreement. It was concluded that the corrosion process is a solid-state diffusion-dominated process and an expected lifetime of 5 to 7 years is a reasonable estimate.     

Numerical analysis of a high-velocity oxygen-fuel thermal spray system

The fluid and particle flow field characteristics of a high-velocity oxygen-fuel (HVOF) thermal spray (TS) system are analyzed using a two-phase flow model and simulated using computational fluid dynamics (CFD) techniques. The model consists of a conservation equation and constitutive relations for both gas and particle phases. Compressible, turbulent flow is modeled by ak-ɛ turbulent model. A Lagrangian formulation is used to model particle trajectory, and heat and momentum transfer. The fluid velocity fluctuations resulting from gas turbulence are simulated by a stochastic model and the particle motion in the turbulent flow is calculated in a Lagrangian Stochastic-Deterministic (LSD) method. Details of gas flow field, particle temperature and particle velocity histories, and particle temperature and velocity profiles in the system are presented. For the validation of the numerical analysis, the computed results are compared with available experimental measurement. Excellent agreement between simulations and measurements is obtained for both gas and particle flow fields. A parametric study is also conducted for different particle sizes and different nozzle barrel lengths. The flow phenomena for different flow parameters are analyzed and explained as the result of gas dynamics and heat and momentum transfer between the two phases. The developed methodology provides a means to analyze, design, and optimize the TS process. The numerical analysis presents a first comprehensive, fundamental quantitative analysis for the HVOF TS system.