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《锻压技术》2015,(7)
挤压速度是铝型材挤压过程中的一个重要工艺因素,对挤压力、生产率和挤压产品的质量等具有直接影响。以某轨道车辆用6N01铝合金型材为例,在Hyper Xtrude商业软件平台上,采用不同的挤压速度对其稳态挤压成形过程进行数值模拟仿真,获得了挤压过程的挤压力、温度场及速度场的变化情况。结果表明:随着挤压速度的增大,挤压力、金属的出口温度及不均匀性增大。根据数值模拟结果与理论分析,确定了该规格6N01铝合金型材在150 MN挤压机上的合理挤压速度范围为0.6~0.9 mm·s-1。在实际试模生产中,采用数值模拟优化的工艺参数进行挤压,挤出合格的型材,验证了数值模拟的可行性。 相似文献
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《塑性工程学报》2016,(5):29-35
应用HyperXtrude有限元模拟软件,对大宽厚比ZK60镁合金型材正挤压成形过程进行了数值模拟,优化了模具结构,研究了不同挤压速度对型材成形效果的影响。对模拟得到的速度、位移、应变和温度场进行分析,优化了挤压工艺。在挤压温度为350℃,挤压速度为20mm·s-1下进行正挤压试验,成功挤出宽度225mm,厚6mm的ZK60镁合金型材。型材横截面微观组织为动态再结晶组织,晶粒沿变形方向被拉长,变形中的温度场和金属流动方向是影响微观组织的主要因素。对该型材采用不同热处理工艺处理后进行力学性能测试。结果表明,该型材经250℃保温2h的退火工艺可以获得较高的综合力学性能。 相似文献
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应用Hyper Xtrude有限元分析软件,考察了带长悬臂结构空心截面铝型材挤压时的焊合角α和焊合室深度h对其挤压成形质量的影响。结果表明:当α在15°~45°时,型材悬臂处及空心部位四周分流桥下金属的流动速率较大,开始焊合的时间早,焊合历程长;当α增加到60°时,相应区域金属的流动速率明显降低,焊合推迟;在α达到90°时,该情况最为严重,焊合历程变短。α为45°时,模芯最大偏移量达到最小值0.045 mm。随着h的增加,焊合面静水压力最小值与上模最大等效应力及模芯最大偏移量均逐渐增大。综合考虑各因素的影响,确定该型材挤压模具的最佳焊合角和焊合室深度分别为45°与20 mm,并将其用于挤压模具设计,试模发现模拟结果与试模结果吻合较好,挤出型材的综合质量较高。 相似文献
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《锻压技术》2015,(10)
采用有限元软件,对一非对称截面列车上侧梁型材挤压分流、焊合直至稳态挤出的整个非稳态过程进行了数值模拟。着重研究了挤压成形过程中变形体的速度、温度、应变速率等物理场量的分布与变化情况,以及模具应力分布情况。针对模拟过程中出现的挤出物前端存在严重变形的问题,对模具的二级焊合室尺寸、阻流块高度以及工作带尺寸作出优化。模具结构优化后模孔出口截面速度均匀性得到明显改善,其速度差从22 mm·s-1减小到7 mm·s-1。通过分析等效应变速率与温度分布的关系,发现坯料温度升高所需的热量主要来源于坯料变形产生的塑性变形能。通过模具应力分析得知模具在各挤压阶段的应力分布情况。 相似文献
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带I型纵筋薄壁构件的结构复杂、壁厚不均,在挤压过程中容易发生金属流动不均匀现象,导致型材发生翘曲变形。针对该问题,采用Hyper Xtrude有限元分析软件,研究了挤压速度、坯料初始温度和模具初始温度等工艺参数对挤压成形效果的影响规律,发现坯料初始温度的增大会使金属流速更加均匀,而过大的挤压速度和模具初始温度会加大金属流速的不均匀性。通过正交试验获得最佳成形工艺参数组合:挤压速度为2 mm·s~(-1),坯料初始温度为480℃,模具初始温度为440℃。最后进行了相应的挤压试验,并成功获得高精度带I型纵筋薄壁构件样品。该研究工作为此类构件的挤压成形工艺及模具的优化设计提供了理论参考。 相似文献
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Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang 《金属学报(英文版)》2019,32(6):684-694
In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone. 相似文献
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After nearly two years'tense construction the first phase of industrialized base of Shenyang Research Institute of Foundry 《中国铸造》2008,5(1):63-64
After nearly two years' tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry (SRIF), located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation. 相似文献
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Z. Sun S.L. Zheng Y. Zhang 《金属学报(英文版)》2007,20(3):187-192
Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process. 相似文献
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R. González-Martínez 《金属学报(英文版)》2007,20(4):235-240
The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke. 相似文献
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The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C). 相似文献
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This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
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Chao Yang He-Fei Huang Massey de los Reyes Long Yan Xing-Tai Zhou Tian Xia De-Liang Zhang 《金属学报(英文版)》2015,28(7):809
Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties. 相似文献
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Lei Li Bo Xu Wei-Ping Tong Hui Zhang Chun-Yan Ban Li-Zi He Zhi-Hao Zhao Yu-Bo Zuo Qing-Feng Zhu Jian-Zhong Cui 《金属学报(英文版)》2015,28(6):725
A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed. 相似文献
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The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel. 相似文献
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综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。 相似文献