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1.
When cutting metallic materials, the magnitude and the variation of the amplitude of the cutting force and the quality of the treated surface are of major importance. During the fine turning of alloys that have similar mechanical properties, differences will show both in the roughness of the machined surface and in the magnitude of the cutting forces measured, which can be attributed to the influence of the microstructure of the workpiece material.This paper deals with the influence of the microstructure of Al alloys containing different amounts of silicon on the variation of the amplitude of the signal of the dynamic component of the main cutting force during fine turning. An analysis of the energy spectra and the auto-correlation functions of the amplitude of the dynamic component of the cutting force confirmed the relationship between the latter and the size of the phases in the microstructure of the workpiece material. It was confirmed that the microstructural changes were directly related to the amplitude of the cutting-force variation in the cutting zone. The microstructural changes and the cutting force can be considered as random phenomena; therefore, they may be described by statistical parameters such as the mean value, the standard deviation, and the coefficient of variation. The values calculated for the individual alloys differed considerably and confirmed a close relationship between the statistical values of the intercept lengths of the phases in the microstructure and the dynamic component of the cutting force. 相似文献
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Based on the phenomenological crystallographic theory of martensitic transformations, the following crystallographic characteristics of the tetragonal martensite in high-carbon steel have been calculated: orientation relationships between the crystal lattices of the bct martensite and fcc austenite; the magnitude and direction of the macroscopic shear; the habit plane; the angle and the axis of rotation of the crystal lattice of the martensite. The calculation was performed for three variants of lattice deformation: Bain deformation; two-shear Kurdjumov-Sachs deformation; and the deformation we suggested upon the analysis of the fcc-bcc transformation. In the last variant, a minimum rotation of the crystal lattice of martensite is required; consequently, this variant is closest to the real mechanism of the martensitic transformation. An expression has been derived that describes the interrelation between the degree of tetragonality of the crystal lattice of martensite and the magnitude of the shear deformation of the lattice. It has been shown that the 12 crystal-lographically equivalent variants of shear upon the formation of the lattice of the tetragonal martensite form three groups in each of which the martensite has the same tetragonality axis. For each variant of the shear, we have two equivalent variants of deformation of the martensite with invariant lattice. This results in 24 variants of orientation relationships. 相似文献
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数值模拟技术在汽车覆盖件成形中的应用 总被引:13,自引:18,他引:13
金属薄板成形的数值模拟技术在汽车覆盖件生产及其模具设计制造中起着十分重要的作用。数值模拟技术的广泛应用可以帮助模具设计人员显著地减少模具开发时间、试模周期和费用。为此,详细介绍了应用Dynaform软件模拟覆盖件成形过程的一般步骤,并以某汽车覆盖件的拉深为例,对其成形过程进行了数值仿真。通过对模具零件的运动、板料的成形,以及板料厚度的变化,应力应变分布,成形极限预测等结果的分析,进一步弄清了板料形状,压料筋布置以及压边力大小等工艺参数对汽车覆盖件质量的影响。在案例分析的基础上,针对覆盖件坯料拉深过程中可能出现的起皱现象,给出了相应的拉深工艺优化和模具方案优化。 相似文献
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A.D. Razmyshlyayev M.V. Mironova S.V. Yarmonov P.A. Vydmysh 《Welding International》2013,27(4):296-300
Physical modelling of arc welding with a wire shows that the flow speed of liquid metal, directed into the tail part of the pool and induced by the constant transverse magnetic field, increases with the increase of current and the transverse component of induction of the field. Experimental results show that the distribution of the flows is determined by the distribution of the density component of the current spreading in the liquid metal of the weld pool. The results can be used in the determination of the optimum frequency of the transverse magnetic field for controlling the dimensions of the penetration zone of the metal and the process of solidification of the weld pool metal in arc surfacing and welding. 相似文献
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Study on heat efficiency of laser-TIG double-side welding 总被引:1,自引:0,他引:1
A series of laser-TIG double-side welding experiments for aluminum alloys were carried out to investigate the heat efficiency of the process. The melting efficiency was introduced to evaluate quantitatively the degree of the mutual effect of the laser and the arc. The results showed that the melting efficiency of laser-TIG double-side welding exceeded the sum of the laser and the arc taken separately. With the increase of heat input, the weld depth and melting efficiency of the laser and the arc were increased signifwantly. This, in fact, implies the strong mutual effect of the laser and the arc as heat sources joined simultaneously in the process. Comparatively, the higher efficiency of the laser constituent of heat sources plays the main role in the increase of the process efficiency. The phenomena of arc column convergence, increased laser absorptivity and the formation of heat accumulation region are the causes of the improvement of heat efficiency. 相似文献
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对厚板HQ785T1低合金高强钢填充HS-70焊丝激光—电弧复合焊接头根部化学成分分析及元素线扫描分析,结果表明,焊缝部位主要元素的含量介于母材和焊丝之间,焊缝从上部到根部,随着深度的增加,焊缝元素组成越接近母材,根部焊缝组成以母材成分为主,焊丝成分所占比例较小;焊缝根部冲击韧性低于焊缝上部, 增大坡口钝边,焊缝根部的冲击韧性降低;金相显示根部焊缝中心组织为粒状贝氏体组织,随着钝边尺寸的增加,碳化物析出量减少,组织略显粗大,组织脆性增加. 相似文献
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为了验证Ar-N2混合气体对焊缝中各元素含量和焊缝铁素体数(FN值)的影响,对SS304L奥氏体不锈钢进行了4种比例的Ar-N2混合气体GTAW多层多道焊接试验,研究了4种Ar-N2比例对焊缝金属中各元素含量的影响,以及每条焊缝中各元素含量随着焊道层数的变化趋势。结果表明,不同保护气体类型的11种焊缝化学元素中,只有N元素随着保护气体中氮气比例的升高而明显增加,其它元素则没有明显的影响;经过汇总分析,认为由于稀释率的原因,导致各元素含量在同一保护气体焊缝中的规律为:C元素含量随着层数的增加而下降;Si,P,S和Nb元素含量随着层数的增加无明显上升或下降趋势;Mn,Ni,Cr,Mo和Cu元素含量随着层数的增加而上升;而N元素在纯氩气保护SG-A时的含量随着层数的增加而稍微下降,在SG-AN-0.5,SG-AN-1,SG-AN-1.5 3种保护气体中N元素含量随着层数的增加而上升;分析结果也表明,Creq/Nieq值和FN值有相同的变化趋势,都与氮气含量呈现反比关系。
创新点: 采用了阶梯式的多层多道焊,保留了各层焊缝的原始信息,验证了GTAW焊接方法在保护气体中添加氮气对奥氏体不锈钢焊缝各种化学元素成分的影响,为Ar-N2混合气体GTAW焊接奥氏体不锈钢在工程中的应用提供了可参考的试验数据。 相似文献
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The present paper describes the effect of the half apex angle of the cone-frustum on the motion trajectory under simultaneous five-axis motion and the effect of the sensitive direction of the ball bar when the motion trajectory is measured along the three-dimensional circular conical path. In the present paper, simulation of the measurement by means of a ball bar instrument is mainly conducted using a motion simulator developed previously. In particular, a precise mathematical model was developed to express the pitch errors of the axes of rotation of the five-axis machining center having a tilting rotary table driven by worm gears. In the experiment and simulation, primarily the center position and half apex angle of the cone-frustum were varied. In addition, two sensitive directions of the ball bar were investigated. The motion simulator incorporating the pitch error model can express the detailed trajectories obtained by the ball bar, even if the half apex angle and center position of the cone-frustum and the sensitive direction of the ball bar were changed. Then, the influence of the frictional force of the linear axes of motion, and the backlash and pitch error of the axes of rotation on the circular trajectories were analyzed. In particular, for the case of a half apex angle of 45°, the trajectory due to the errors of the axis of rotation is strongly affected by the sensitive direction of the ball bar. 相似文献
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为了进一步研究铁道车辆热铆连接过程,基于热固耦合有限元理论建立铆钉和铆接件的有限元模型,模拟热铆连接过程,并结合试验进行验证。将热铆连接变形过程分为6个阶段,分析铆钉在热铆连接过程中的受力和变形情况,并通过改变铆钉钉杆长度和镦头高度,分析不同参数对热铆连接的影响,并得到最佳热铆参数。结果表明:铆钉的最大应力集中在铆钉镦头和与铆接件边缘相接触的中心部位,最大应变集中在镦头靠近铆接件边缘的位置;钉杆长度小于一定值时,铆钉的最大应力均发生在铆钉镦头顶部和镦头与铆接件边缘相接触的中心部位,超过该值时,应力集中位置只出现在铆钉镦头顶部;铆钉的最大应力随镦头高度总体呈下降趋势。 相似文献
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针对风电叶片静力加载试验过程中牵引支架滑轮与钢丝绳易出现过度磨损问题,采用虚拟样机模型与正交试验相结合的方法来研究钢丝绳-滑轮在风电叶片静力试验中的磨损规律,进一步完成对其参数的优化匹配。采用虚拟样机技术建立钢丝绳滑轮卷绕过程的动力学模型,模拟仿真得到滑轮表面接触应力;结合正交试验,选取滑轮D_1表面压应力作为试验指标,结合极差分析与方差分析对全部仿真试验的结果进行数据分析,表明滑轮槽底直径对滑轮表面磨损影响最为显著,进而筛选出钢丝绳滑轮的最优结构参数组合;对这组优化参数进行数值仿真,仿真结果表明:当滑轮直径为330 mm、滑轮槽底直径为31 mm、钢丝绳偏角为3°时得到滑轮表面应力为6.09 MPa,此时试验指标值最小,验证了正交试验结果的准确性,对之后整体牵引支架的优化设计具有指导意义。 相似文献
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The results of investigations of the stress state of welded specimens prior to and after heat treatment using the method of magnetic memory (MMM) of the metal are presented. The relationship between the changes of the stress state of the welded joint and the strength of the intrinsic magnetic scattering field, formed in welding in the conditions of a weak geomagnetic field, is described. A method for the efficient determination of the zones of heterogeneity of the stress state of the welded joints by the MMM and the evaluation of the changes of after heat treatment is proposed. 相似文献
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为了获取直升机救助模拟器支撑横梁在模拟器激励运动下的振动响应,为进一步研究缓解横梁振动提供参考,在ANSYS Workbench中建立支撑横梁的有限元模型,通过模态分析以及随机振动响应分析获取了横梁的随机振动特性。建立了横梁固有频率的数值模型,并利用ANSYS 的预应力模块,对考虑集中质量的横梁进行模态分析,将横梁固有频率的仿真结果与数值建模的计算值进行比较,两者误差在1%以内。在模态分析基础上,利用ANSYS随机振动响应模块进一步建立了考虑直升机救助模拟器动力学的天车横梁的ANSYS仿真模型,包括横梁激振力模型以及横梁动态响应模型,得到了在直升机模拟器无规律负载作用下天车横梁的振动状态。并与试验结果对比分析,验证了模型的正确性。结果显示:应用 ANSYS求解得到的振动响应曲线与试验测得的曲线吻合良好,验证了该方法求解横梁随机振动响应的适应性,为今后解决柔性基座对运动平台的干扰问题提供参考。 相似文献
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目的 探究大排量柱塞泵滑靴副因底面尺寸大的特点所产生的不同于常规柱塞泵滑靴副的摩擦学性能。方法 首先,在考虑大底面滑靴高速旋转时形成线速度差的基础上,结合热楔效应以及热传导关系,建立一种在剩余压紧力状态下大排量柱塞泵滑靴副摩擦力的数学模型。其次,仿真分析柱塞腔压力、主轴转速以及油液温度对滑靴副摩擦力的影响。最后,搭建滑靴副摩擦力测试装置,并测量滑靴副所受摩擦力,验证所建立的滑靴副摩擦力数学模型的准确性。结果 滑靴副的总摩擦力由黏性摩擦力和犁沟力2部分组成。随着转速的升高,滑靴副的总摩擦力会降低,犁沟力的占比逐渐增大,当转速由800 r/min上升至1 800 r/min时,犁沟力所占比例由3.4%上升至11.9%。随着压力的升高,滑靴副的总摩擦力上升,犁沟力所占比例增大,当压力由3 MPa上升至9 MPa时,犁沟力所占比例由0%上升至21.5%。随着油液温度的升高,滑靴副的总摩擦力上升,犁沟力所占比例增大,当油温由25℃上升至55℃时,犁沟力所占比例由4.0%上升至17.1%。结论 研究揭示了黏性摩擦力在滑靴副所受摩擦力中的主导作用和犁沟力对摩擦力变化趋势的影响作用,仿真和试验结果的一... 相似文献
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O. V. Sobol’ A. D. Pogrebnyak V. M. Beresnev 《The Physics of Metals and Metallography》2011,112(2):188-195
Regularities of the formation of the phase and structural state and mechanical characteristics of vacuum-arc coatings produced
by the evaporation of Zr-Ti-Si-N targets in a reactive nitrogen atmosphere have been studied. For the targets of compositions
Zr 92.0 wt %, Ti 3.9 wt %, Si 4.1 wt %, and Zr 64.2 wt %, Ti 32.1 wt %, Si 3.7 % at a working pressure of the nitrogen atmosphere
of 0.1-0.8 Pa and a potential at the substrate of −100 and −200 V, the formation of a single-phase crystalline state of the
coatings (nitride of the solid solution of the components of the target) has been established. The size of crystallites is
in the nanometer range (25–85 nm). An increase in the size of crystallites in the direction of the incidence of the film-forming
particles (perpendicular to the growth plane) is favored by an increase in the bias potential from −100 to −200 V. The low
heat conductivity of the metallic (Ti and Zr) components of the target leads to a significant content of a droplet phase when
using the direct-flow regime of the vacuum-arc deposition and requires the employment of a technological scheme with a separation
of the film-forming beams to increase the homogeneity of the high mechanical properties of the coatings. The use of film-forming
beams separated from the droplet phase makes it possible to increase the homogeneity of the surface morphology of the coatings
with the retention of a large index of plasticity (H/E = 0.8–0.9) and high hardness (33–37 GPa) of the material of the coating. 相似文献
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