半钢轮胎模具上盖刚度及疲劳寿命分析

通过轮胎模具在硫化工况下的上盖受力分析,根据板壳理论中圆形薄板计算理论,简化了半钢轮胎模具上盖受力模型,推导出半钢轮胎模具上盖刚度计算公式。通过计算不同上盖材料的最小厚度及其疲劳寿命,运用有限元数值模拟验证其刚度。根据上侧板材料和结构装配形式,运用有限元模拟计算其疲劳寿命,得到45锻钢比Q235材料疲劳寿命长以及整体式上盖上侧板结构比通过螺栓连接结构疲劳寿命长的结论。模拟结果能够指导上盖设计,掌握模具实时工作状态。     

轮胎活络模具开滑板摩擦模拟分析

为保证轮胎模具硫化后平稳开模,对上盖开滑板进行受力分析,并通过有限元模拟的方法研究了开滑板的传热和磨损。结果表明:模具的预热过程有利于提高开滑板的使用周期;不同规格下的轮胎模具开滑板的磨损情况不同,开滑板的磨损主要受载荷的影响。由此可见,合理设计模具结构、减少T型块等部件的自重对减轻开滑板的磨损具有重要意义。     

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。     

轮胎模具预热温度分析及结构优化

探讨有限元分析在轮胎活络模具中的应用,通过有限元模拟分析轮胎硫化过程中的传热升温情况,对模具的结构进行优化,增加传热面积,缩小模具内部零件之间的间隙,提高轮胎硫化质量和效率。通过对模具结构进行优化,减少热量损失,提高轮胎硫化过程中蒸汽热量利用率,达到节能减排,绿色制造的目的。     

轮胎模具中套有限元分析

中套作为轮胎模具中的重要零件,在轮胎硫化过程中发挥着不可或缺的作用。运用力学知识,对中套进行了受力分析,并通过有限元分析软件对中套进行了热力耦合模拟分析,得出中套的位移变化趋势及不同材料和导向角的改变对中套的应力、位移的影响。中套材料为40Cr时的最大等效应力和U_1方向上的位移均小于中套材料为45钢和Q235的最大等效应力。在中套材料为45钢不变的情况下,中套导向角越大,所受的最大等效应力与U_1方向上的位移就越大。     

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。     

轮胎模具滑板使用周期的模拟研究

为防止硫化后轮胎出现胶边问题,以铜基石墨合金的轮胎模具滑板为研究材料,借助扫描电子显微镜以及能量分析谱仪分别观察光滑表面石墨的分布及摩擦表面沟槽特点,发现摩擦表面脱落颗粒及剥落块直接影响不同阶段材料的磨损率。通过往复式摩擦磨损试验确定滑板在试验载荷下的磨损率,修正Archard磨损模型的系数,得到铜基石墨合金的合理的磨损模型,设定载荷模拟计算滑板在锁模瞬间的磨损率。结果表明,滑板在锁模的瞬间磨损量决定了滑板的使用周期。     

活络模具结构影响轮胎温度场的模拟分析

建立9.00R20轮胎模具的三维模型,为分析活络模具结构对轮胎温度场的影响,通过应用ANSYS Workbench有限元软件对轮胎活络模具温模过程进行了数值模拟分析,获得轮胎胎面的温度场分布,并据此提出改进模具的结构,解决轮胎胎面存在温差的现象.结果表明:与原模型相比,不同模具结构对轮胎温度场的影响不同,通过改进模具结构,使轮胎胎面的温差减小,同时缩短轮胎的硫化时间,节约能耗,降低成本.     

轮胎模具结构研究现状及分析

从轮胎模具的发展与研究现状介绍了轮胎两半模具与活络模具的结构,对比了斜平面式活络模具和圆锥面式活络模具的结构和装配特点,模具零件变形和磨损对硫化后轮胎的外观影响,说明了模具热板式和蒸锅式的加热方式在轮胎硫化过程中的热传导路线。还论述了模具结构有限元分析的步骤,从减轻模具质量、缩小模具体积、缩短模具温模时间、改善模具型腔温度分布均匀性、解决轮胎表面胶毛和轮胎胶边与错花外观质量等方面,介绍了轮胎模具结构改进的方法,以期对后续的轮胎模具研究工作有一定的借鉴和启发作用。     

轮胎模具花纹块温模过程传热分析

通过模拟分析X1188型号轮胎活络模具的温模过程，研究了模具整体的热传导规律以及花纹块内表面的温度分布情况，利用优化模具结构的方法获得更优的温度场分布，为轮胎的生产工艺与轮胎的硫化成型提供理论指导。     

超声辅助对共沉淀法制备富锂锰基正极材料Li[Li_0.144Ni_0.136Co_0.136Mn_0.544]O₂性能影响的研究

通过超声辅助共沉淀法成功制备了富锂锰基正极电极材料,研究了不同的超声时间对材料形貌、结构和电化学性能的影响。研究发现,超声辅助能够使材料颗粒更加均匀,结构更合理,有利于材料电化学性能的提升。当合成前躯体材料超声时间为8h时,复合材料的放电比容量最好,在0.1C的初始放电比容量为327.8 mAh g_-1,均高于未超声的复合材料的265.2 mAh g_-1,1C下循环50圈后放电容量为181.6 mAh g_-1,保持率为84.8%。通过循环伏安法测试和电化学交流阻抗测试,发现超声后的复合材料还原氧化峰电流更大,电荷转移阻抗更小,具有较好的倍率性能。     

Investigation of the microwave dielectric properties of Ca1−xMgxLa4Ti5O17 ceramics for application in coplanar patch antenna

In this paper, the dielectric properties of Ca_1−xMg_xLa₄Ti₅O₁₇ ceramics at microwave frequency have been studied. The diffraction peaks of Ca_(1−x)Mg_xLa₄Ti₅O₁₇ ceramics nearly unchanged with x increasing from 0 to 0.03. Similar X-ray diffraction peaks of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic were observed at different sintering temperatures. A maximum density of 5.3 g/cm³ can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. A maximum dielectric constant (_r) and quality factor (Q × f) of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h are 56.3 and 12,300 GHz (at 6.4 GHz), respectively. A near-zero temperature coefficient of resonant frequency (τ_f) of −9.6 ppm/°C can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. The measurement results for the aperture-coupled coplanar patch antenna at 2.5 GHz are presented. With this technique, a 3.33% bandwidth (return loss <−10 dB) with a center frequency at approximately 2.5 GHz has been successfully achieved.     

High-speed deposition of Y-Si-O films by laser chemical vapor deposition using Nd:YAG laser

Y-Si-O films were prepared by laser chemical vapor deposition (LCVD) with a Nd:YAG laser using TEOS (tetraethyl orthosilicate) and Y(dpm)₃ precursors. The effects of laser power (P_L), deposition temperature (T_dep) and total chamber pressure (P_tot) on the phase, microstructure and deposition rate of Y-Si-O films were investigated. At P_L < 102 W (T_dep < 1140 K), amorphous Y-Si-O films were obtained independent of P_tot. At P_tot = 0.6 kPa, mixture phase films of Y₂SiO₅ (the X1 phase) and Y₂Si₂O₇ (the α, β, δ and y phases) were obtained at P_L = 102 W (T_dep = 1210 K), while single phase X1-Y₂SiO₅ films were prepared at P_L > 139 W (T_dep > 1280 K). Y₂Si₂O₇ mixture phase films were obtained at P_tot = 3.5 kPa and Y₂Si₂O₇ and Y₂SiO₅ (the X2 phase) mixture phase films were obtained at P_tot = 7.5 kPa independent of T_dep. Amorphous Y-Si-O films showed a dense, glassy microstructure. Faceted columnar grains grew on the Y-Si-O films at P_tot = 0.6 kPa, whereas rounded cauliflower-like grains grew at P_tot = 7.5 kPa. The R_dep increased with increasing P_L and T_dep and reached a maximum of 430 μm h⁻¹ at P_tot = 0.6 kPa, P_L = 186 W and T_dep = 1310 K.     

Structure, microstructure and electrical properties of (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBi0.5Li0.5TiO3 lead-free piezoelectric ceramics

The ternary system (1 − x − y)Bi_0.5Na_0.5TiO₃–xBi_0.5K_0.5TiO₃–yBi_0.5Li_0.5TiO₃ (abbreviated to BNKLT-x/y) was synthesized by conventional oxide-mixed method. The phase structure, microstructure, and dielectric, ferroelectric and piezoelectric properties of the ceramics were investigated. The X-ray diffraction patterns showed that pure perovskite phase with rhombohedral structure can be obtained in all the ceramics. The grain size varied with x and y. The temperature dependence of dielectric constant and dielectric loss revealed there were two phase transitions which were from ferroelectric (tetragonal) to anti-ferroelectric (rhombohedral) and anti-ferroelectric to paraelectric (cubic). Either increasing x or y content can make T_m (the temperature at which dielectric constant _r reaches the maximum) increase. With the addition of Bi_0.5K_0.5TiO₃, the remanent polarization P_r increased but the coercive field E_c decreased. With the addition of Bi_0.5Li_0.5TiO₃, P_r increased obviously and E_c increased slightly. Due to the stronger ferroelectricity by modifying Bi_0.5K_0.5TiO₃ and Bi_0.5Li_0.5TiO₃, the piezoelectric properties were enhanced at x = 0.22 and y = 0.10, which were as follows: P_r = 31.92 μC/cm², E_c = 32.40 kV/cm, _r = 1118, tan δ = 0.041, d₃₃ = 203 pC/N and K_p = 0.31. The results show that the BNKLT-x/y ceramics are promising candidates for the lead-free materials.     

Microwave dielectric properties and its compatibility with silver electrode of Li2MgTi3O8 ceramics

The effects of BaCu(B₂O₅) (BCB) additions on the sintering temperature and microwave dielectric properties of Li₂MgTi₃O₈ ceramic have been investigated. The pure Li₂MgTi₃O₈ ceramic shows a relative high sintering temperature (∼1000 °C) and good microwave dielectric properties as Q × f of 40,000 GHz, ?_r of 27.2, τ_f of 2.6 ppm/°C. It was found that the addition of a small amount of BCB can effectively lower the sintering temperature of Li₂MgTi₃O₈ ceramics from 1025 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 0.5 wt% BCB added Li₂MgTi₃O₈ ceramic sintered at 900 °C for 2 h exhibited good microwave dielectric properties of Q × f = 36,200 GHz (f = 7.31 GHz), ?_r = 26 and τ_f = −2 ppm/°C. Compatibility with Ag electrode indicates this material can be applied to low temperature-cofired ceramics (LTCC) devices.     

Mg-substituted ZnNb2O6-TiO2 composite ceramics for RF/microwaves ceramic capacitors

Microstructure and microwave dielectric properties of Mg-substituted ZnNb₂O₆-TiO₂ microwave ceramics were investigated. Mg acted as a grain refining reagent and columbite phase stabilization reagent. With an increasing Mg content, the amount of ixiolite (Zn, Mg) TiNb₂O₈ decreased, and the amount of (Zn_0.9Mg_0.1)_0.17Nb_0.33Ti_0.5O₂ and columbite increased. ZnO-Nb₂O₅-1.75TiO₂-5 mol.%MgO exhibited excellent dielectric properties (at 950 °C): ?_r = 35.6, Q × f = 16,000 GHz (at 5.6 GHz) and τ_f = −10 ppm/°C. The material was applied successfully to make RF/microwaves ceramic capacitor, whose self-resonance frequency was 19 GHz at low capacitance of 0.13 pF.     

Dielectric function and the crystal structure of MeV ion implanted LiNbO3

The behavior of the dielectric functions of MeV ion-implanted LiNbO₃ was studied using THz spectroscopy. Single crystal LiNbO₃ specimens were implanted with 3 MeV Au ions at four different levels of ion fluence (1 × 10¹², 1 × 10¹³, 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2). The optical spectra of the specimens were then measured in two ranged values: (1) reflectance THz range spectra from 40 to 700 cm^− 1 and (2) reflectance ultraviolet, visible, and near-infrared spectra from 250 to 2000 nm. The THz spectra were analyzed by fitting with the dielectric function model proposed by Brendel. The dielectric function model explained well the experimental spectra of the ion-implanted LiNbO₃. The dielectric function shows that the ion-implanted layers were amorphous phase at the fluence of 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2, whereas the layers at 1 × 10¹² and 1 × 10¹³ cm^− 2 maintained the crystal phase but significantly suppressed the phonon resonances. The volume of ion-implanted layers expanded about 8% with the fluence of 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2, i.e. after amorphization, These results show that the ion implantation significantly affected the lattice vibration mode and the structure even at very low ion fluence.     

Ultraviolet and violet upconversion luminescence in Ho-doped Y2O3 ceramic induced by 532-nm CW laser

Ultraviolet and violet upconversion luminescence spectra of holmium-doped Y₂O₃ were produced under the excitation of a compact continues-wave 532 nm solid-state laser. Emissions around 306, 362, 412, 390 and 428 nm can be assigned to the transitions of ³D₃ → ⁵I_J (J = 8, 7, 6), ⁵G₄ → ⁵I₈ and ⁵G₅ → ⁵I₈, respectively. Power dependence and upconversion dynamics analysis demonstrated that both the energy transfer upconversion (ETU) and the excited state absorption (ESA) processes were involved in the population of ³D₃ state via the coupled intermediate states ⁵S₂/⁵F₄. Fluorescence spectra in the visible and infrared ranges showed that ⁵G₄ and ⁵G₅ states were populated by the ESA process from ⁵I₆ and ⁵I₇ states, respectively, while the ⁵I₆ and ⁵I₇ states were radiatively populated from the excited ⁵S₂/⁵F₄ states. Upconversion mechanisms have been evaluated based on a rate equation model.     

Relationships between Zr substitution for Ti and microwave dielectric properties in Mg(ZrxTi1−x)O3 ceramics

The influence of Zr substitution for Ti on the microwave dielectric properties and microstructures of the Mg(Zr_xTi_1−x)O₃(MZ_xT) (0.01 ≤ x ≤ 0.3) ceramics was investigated. The quality factors of Mg(Zr_xTi_1−x)O₃ ceramics with x = 0.01-0.05 were improved because the solid solution of a small amount of Zr⁴⁺ substitution in the B-site could increase density and grain size. An excess of Zr⁴⁺ resulted in the formation of a great deal of secondary phase that declined the microwave dielectric properties of MZ_xT ceramics. The temperature coefficient of resonant frequency (τ_f) of Mg(Zr_xTi_1−x)O₃ ceramics slightly increased with increasing Zr content, and the variation in τ_f was attributed to the formation of secondary phases.     

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glasses

Cu₄₆Zr_47−x Al₇M _x (M = Ce, Pr, Tb, and Gd) bulk metallic glassy (BMG) alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability (GFA), thermal stability, and mechanical properties of Cu₄₆Zr_47−x Al₇M _x were investigated. The GFA of Cu₄₆Zr_47−x Al₇M _x (M = Ce, Pr) alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu₄₆Zr_47−x Al₇Tb _x (x = 2, 4, and 5) amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu₄₆Zr_47−x Al₇Gd _x (x = 2, 4, and 5) increases with increasing Gd. T _x and T _p of all decrease. T _g is dependent on the rare-earth element and its content. ΔT _x for most of these alloys decreases except the Cu₄₆Zr₄₂Al₇Gd₅ alloy. The activation energies ΔE _g, ΔE _x, and ΔE _p for the Cu₄₆Zr₄₂Al₇Gd₅ BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respectively. The Cu₄₆Zr₄₅Al₇Tb₂ alloy presents the highest microhardness, Hv 590, while the Cu₄₆Zr₄₃Al₇Pr₄ alloy presents the least, Hv 479. The compressive strength (σ _c.f.) of the Cu₄₆Zr₄₃Al₇Gd₄ BMG alloy is higher than that of the Cu₄₆Zr₄₃Al₇Tb₄ BMG alloy.