Compound forming technology of outside 3D integral fin of copper tubes

Using rolling-ploughing-extrusion compound processing methods, a 3D integral-fin structure on outside surface of red copper tube with diameter of 16.0 mm and wall thickness of 1.5 mm was obtained. When both rolling depth and ploughing-extrusion (P-E) depth were 0.2 mm, rotating speed was 50 r/min, feed speed was 0.16 mm/r, 3D fin structures with height of 0.25 mm were gotten. Two different fin structures were obtained in grooves formed with rolling-ploughing-extrusion compound forming technology and observed by scanning electron microscope(SEM). One is the compound structure with V-shaped groove and U-shaped groove, and the other is the single structure with V-shaped grooves. Two kinds of groove structures obtained by rolling processing and ploughing extrusion processing are restricted together by groove interval and rolling depth, and pitch and P-E depth, respectively. Based on the analysis of interaction of rolling and P-E processing, it is found from the result that the outside 3D integral-fin can be achieved by rolling-ploughing-extrusion compound processing when single V-shaped groove structures are formed by both rolling and P-E processing.     

锯齿状翅片犁削-挤压成形翅高的有限元法预测

简要介绍了锯齿状翅片的犁削-挤压加工成形机制;基于有限元分析软件Deform-3D建立犁削-挤压成形翅片的有限元分析模型;对翅片成形过程进行了三维有限元模拟,获得了在不同刀具参数和切削用量下平均翅高的变化曲线;将模拟计算结果与试验进行了对比,具有较好的一致性。     

Thermo-mechanical coupled analysis of hot ring rolling process

A 3D rigid-plastic and coupled thermo-mechanical FE model for hot ring rolling（HRR） was developed based on DEFORM 3D software, then coupled heat transferring, material flow and temperature distribution of the ring in HRR were simulated and the effects of process parameters on them were analyzed. The results show that the deformation nonuniformity of ring blank increases with the increase of the rotational speed of driver roll and friction factor or the decrease of the feed rate of idle roll and initial temperature of ring blank. The temperature nonuniformity of ring blank decreases with the increase of the feed rate of idle roll or the decrease of initial temperature of ring blank and friction factor. There is an optimum rotational speed of driver roll under which the temperature distribution of ring blank is the most uniform. The results obtained can provide a guide for forming parameters optimization and quality control.     

翅片油箱换热性能的数值模拟

为提高液压外骨骼机器人油箱的换热性能,采用CFD数值模拟方法,对不同翅片结构的圆环形槽翅片油箱流动传热性能进行了三维数值模拟,得到了不同入口风速下翅片表面平均换热系数、进出口压降和综合评价系数JF因子随翅片结构变化的特性曲线。研究结果表明:翅片厚度在0.5~0.9 mm时,换热系数随翅片厚度的增加而减小,同时压降随厚度的增加而增大;翅片间距在2.1~2.9 mm时,换热系数随翅片间距的增大而增大,同时压降随间距的增大而减小;翅片高度在10.5~14.5 mm时,换热系数和压降都随翅片高度的增加而增大。研究结果表明:当翅片厚度为0.5 mm,翅片间距为2.9 mm,翅片高度为12.5 mm时,翅片单元整体综合换热性能最优,仿真结果为翅片油箱结构优化设计提供了参考。     

FE simulation and experimental research on cylindrical ring rolling

During the conventional ring rolling process, the ring mainly produces the incremental deformation of wall-thickness reduction and diameter expansion, which makes it difficult to manufacture the cylindrical ring with small diameter and large height. In this paper, a new method for manufacturing the cylindrical ring using a ring blank with smaller height, i.e. cylindrical ring rolling, is proposed and its feasibility is verified. For evaluating the cylindrical ring rolling process and to better understanding its deformation characteristics, a 3D elastic–plastic FE model of cylindrical ring rolling is first established. Then, the comparison between conventional ring rolling and cylindrical ring rolling is investigated using this 3D FE model. Finally, the effects of the process parameters, such as the feed rate of the idle roll, diameter of the idle roll and friction coefficient between the rolls and ring, on cylindrical ring rolling are numerically revealed. The experiment is carried out on a vertical NC ring rolling machine and the good agreements between the experimental and simulation results verify the validity of the established 3D FE model of the cylindrical ring rolling.     

Formation of integral fins function-surface by extrusion-ploughing process

1 Introduction The ever-increasing integrity of electronic chips results in high heat flow density, which makes the cooling become the ever more serious[1-5]. The traditional single-scale and simple figure surface heat-function macro-structure can not mee…     

Y型异径三通管热态内高压成形研究

基于Dynaform软件平台,建立了Y型异径三通管三维弹塑性有限元模型。运用数值模拟方法,研究了AZ31镁合金Y型异径三通管热态内高压成形过程、成形缺陷、等效应变分布。探讨了初始管坯长度、左右冲头轴向进给量与成形支管高度之间的关系;研究得到了相同支管长度下成形不同Y型夹角三通管所需的左右冲头进给量。结果表明：随着初始管坯长度减小,支管高度随之增加;在左右进给量相同的情况下,左侧金属流向支管阻力更小,支管高度增加明显;随着Y型夹角的增大,右侧冲头进给增加,轴向补料比减小,总补料比增加,当夹角为90°时,左右补料相同。     

Effect of different production phases on residual stress field in double-layer cast rolls

The aim of this investigation was to determine the effect of different production operations and parameters on residual stress level in double-layer cast rolls. Using a hole-drilling method, residual stress depth distribution in surface layer was measured around and along the body of the double-layer cast roll after casting, heat treatment, turning and grinding. Furthermore, using different turning and grinding parameters (speed, feed), and heat treatment parameters (temperature, time), influence of these parameters on residual stress level and distribution was determined.Results of the investigation show that the conditions in the casting pit have an influence on the residual stress field generated in double-layer cast rolls, with surfaces exposed to faster cooling rates in general showing higher residual stress values. Very critical phase in rolls production is coarse grinding, which if not carried out properly will generate very high tensile stresses in the roll surface and cause surface cracking or even roll fracture. Heat treatment on the other hand results in uniform compressive residual stress field in the roll's surface. However, reduction in tempering time and especially increase in hardening temperature lead to increased residual stress level in the roll surface. Final machining of the roll surface further influences residual stress level in the roll. Increase in turning speed of up to 40% results in compressive residual stress increase of up to 60%, while less than 30% increase in feeding rate gives almost 100% increase in residual stress level.     

3D laser investigation on micron-scale grain protrusion topography of truncated diamond grinding wheel for precision grinding performance

A grain tip (GT) truncation is proposed to truncate grain protrusion tips of #270 diamond grinding wheel in plunge grinding of hard and brittle material. In this study, a 3D laser microscopy was employed to measure the wheel working surface and parameterize its 3D grain protrusion topography. The objective is to investigate how micron-scale grain protrusion parameters influence grinding performance such as grinding force and surface roughness. First, the GT truncation was performed after dressing of diamond grinding wheel in grinding experiment of quartz glass; then its 3D grain protrusion topography was constructed by smoothing 3D measured noise, matching measured point cloud, transferring protrusion frame and extracting 3D diamond grains; finally, the grain protrusion parameters such as grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle, grain clearance angle, etc. were investigated in connection with ground surface and grinding force. It is shown that GT truncation averagely decreases grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle and grain clearance angle by about 44%, 74%, 75%, 24% and 70% on whole wheel surface, respectively. However, it greatly increases active grain number by about 32 times and active grain volume by about 181 times in actual grinding with the depth of cut in 1 μm, thus leading to a decrease (about 80%) in surface roughness and an increase (about 40 times) in grinding force. It is also found that truncated diamond grain tips are mostly shaped with nanometer-scale tip wedges along grain cutting direction, leading to about 75% very large negative grain rake angles and about 75% large grain clearance angles, thus contributing to ductile-mode grinding. It is confirmed that the active grain number and active grain volume for the actual depth of cut may be regarded as main grain protrusion parameters to evaluate and predict the precision grinding performance of a coarser diamond grinding wheel.     

面向高速钢轧辊材质磨削的磨床电解磨削装置控制系统研发

针对高速钢轧辊材质的修复问题,展开高速钢轧辊材质电解磨削装置控制系统研发工作。基于普通外圆磨床的机床,以S7 200 SMART系列PLC为控制器对阴极进给系统、电解液供液系统和加工系统进行控制。其次,展开高速钢轧辊材质电解磨削装置控制系统的硬件、软件以及人机交互设计,该控制系统具有自动对刀、故障检测等模块化功能。再者,对加工间隙控制提出了一种带修正因子的模糊控制器-PI双模控制方法,建立MATLAB/Simulink仿真模型,其结果表明该控制方法效果理想,鲁棒性强,可整定控制器增益参数,并将该算法编程于PLC中,最终可实现加工间隙控制过程稳态误差小、超调小、响应快、稳定性好。最后,展开预实验,探究了加工间隙以及温度对加工电流的关系,结果表明加工电流随加工间隙的增加而减小,随温度的升高而增加。     

整体翅片管的劈切—挤压加工

提出了一种新的本翅片管的机械加工方法,即劈切－挤压加工,实验观察发现,翅片的形成包括切入、挤压和成形3个阶段,实验结果表明,影响翅片形成的主要有刀具几何参数、挤压深度,进给量和劈切－挤压速度;对某一刀具,在选定挤压速度时,一定的挤压深度对应一个极限进人量,一定的进给量对应一个极限挤压深度。选择合理的参数可保证翅片加工的连续性和获得接近最佳形状的翅片。劈切－挤坟加工在普通车床上进行,设备简单易,翅片一次成形,材料利用率高,是一种能降低加工技术,提高生产率的加工方式。     

冷却速度对支承辊用Cr5钢显微组织与力学性能的影响

采用金相显微镜、维氏硬度计、拉伸试验机、夏比摆锤试验机等,研究了冷却速度对支承辊用Cr5钢显微组织与力学性能的影响。结果表明,随着冷却速度的降低,组织中珠光体含量不断增加,试样强度和硬度逐渐下降,塑韧性相近。冷却速度≥3 ℃/min时,组织中珠光体体积分数≤30%,抗拉强度≥1025 MPa、屈服强度≥750 MPa、硬度≥45 HS、冲击吸收能量≥40 J。生产试验表明,采用强风冷冷却的热处理可使辊颈表面至一定深度处的力学性能达到油冷的效果,完全满足支承辊辊颈的力学性能要求。     

A New Model for Grinding Force Prediction and Analysis

In the present paper a new grinding force model is developed by incorporating the effects of variable coefficient of friction and ploughing force. This is based on the fact that chip formation during grinding consists of three stages: ploughing, cutting and rubbing. Equations for the total normal and tangential force components per unit width of the grinding, during these three stages, were established. These components were expressed in terms of the experimental coefficients and process parameters like wheel speed, table feed and depth of cut. All the coefficients were determined experimentally by performing grinding tests at specified conditions. The variation of the friction coefficient with process parameters such as wheel speed and work feed has been taken into consideration while calculating the frictional force components. The ploughing force components were modelled by performing single-grit tests. During these tests the grinding forces were measured by duplicating the cutting mechanism of grinding wheel using a dummy aluminium wheel and a diamond indenter. The predicted normal and tangential grinding forces were compared with those experimentally obtained and the results show reasonable agreement quantitatively. From the total force values the contributions of each component of force were obtained.     

锥形环锻件预轧坯设计方法研究

锥形环锻件是一种典型的异形截面环件。在轴向高度、锥角和体积相等的情况下,不同壁厚的锥形环锻件水平横截面积分布差异很大,所以利用锥形毛坯直接轧制成形锥形环锻件将十分困难。以典型的大高度锥形环锻件为实例,在考虑轧制稳定性、轴向金属体积流动等工艺条件的基础上,利用增大锥形环锻件大端壁厚的方法对锥形环锻件预轧件进行了设计。以有限元模拟软件Abaqus为平台,对锥形环锻件的轧制过程进行了模拟,模拟结果表明:锥形环锻件预轧件设计方法是合理的。     

Characterization of the transition from ploughing to cutting in micro machining and evaluation of the minimum thickness of cut

When the machining process is miniaturized two process mechanisms, ploughing and chip formation, are essential and a critical cutting thickness needs to be exceeded so that not only ploughing will occur but chips will also be formed. The ploughing effect thereby influences the chip formation process, workpiece surface roughness, burr formation and residual stress state after processing and is therefore of great interest. In order to optimize the machining process a better understanding of the minimum thickness of cut is crucial.The changes in surface topography along the cutting track occurring during machining with a constant feed rate of the cutting tool were analyzed. The influence of the built-up edge phenomena on the micro machining process was investigated for normalized AISI 1045 using confocal white light microscopy and scanning electron microscopy. Furthermore the sin²ψ-method was applied in order to study the residual stress state in the workpiece surface induced by the machining process. Both surface layer properties investigated, surface roughness and residual stresses, show a characteristic transition indicating a change in the dominating process mechanisms. Based on these results a model is developed to determine the minimum thickness of cut. The minimum thickness of cut is found to significantly decrease with higher cutting velocities and to moderately increase with higher cutting edge radii. In addition a propagation of error for the values obtained with the model was performed, proving the quality of the model developed.     

Nondestructive analysis of pitting corrosion characteristics on EN AW-2024-T3 using 3D optical pattern profilometry

High-strength age-hardenable aluminium alloys are susceptible to localised corrosion. It is vital to monitor the evolution of the corrosion depth in order to prevent a critical degradation of the mechanical properties. This study presents the application of 3D optical pattern profilometry for the analysis of the pitting corrosion behaviour of the aluminium alloy EN AW-2024-T3. Therefore, measurements were conducted using a 1?M NaCl solution at different exposure times. The measurements are compared to the results of optical microscopy investigations of metallographic specimens as well as laser scanning microscopy measurements. In immersion bath tests, the 3D pattern profilometry shows a high measurement accuracy of the pitting corrosion. Regarding the pit characteristics, corroded metal sheets exhibit an increase in the pit depth, volume and area with an increasing exposure time of up to 312?h and then decrease. Moreover, a higher increase in the width in rolling direction than perpendicular to it is noticeable.     

旋轮参数对异型薄壁壳体强力旋压成形的影响

异型薄壁壳体强力旋压是一种复杂的塑性成形过程,研究旋轮参数对该过程的影响,可为相关成形参数的确定和优化设计提供理论依据.采用基于ABAQUS/Explicit平台建立的异型薄壁壳体强力旋压三维有限元模型,研究揭示了旋轮圆角半径、旋轮安装角、旋轮进给比对该成形过程中的切向和周向应力及壁厚的影响规律：减小旋轮圆角半径或进给率、增大其安装角,均可减弱甚至消除旋轮前方的金属堆积,从而使工件壁厚分布更均匀.     

氧化锆陶瓷旋转超声加工脆塑转变特性研究

目的揭示旋转超声振动对硬脆材料脆塑转变特性及工艺参数对材料脆塑转变临界切削深度的影响规律。方法以氧化锆陶瓷为研究对象,在硬脆材料压痕断裂试验基础上,从理论上分析了超声振动加工硬脆材料脆塑转变的临界条件,并进行了纵向振动及纵扭共振形式的旋转超声振动划痕与普通划痕对比试验。结果在相同试验条件下,超声振动划痕较普通划痕有较高的材料脆塑转变临界切削深度。适当地增大超声能量,纵扭共振比纵向振动具有更大的脆塑转变临界切削深度值;而随着进给速度的增大,纵向振动比纵扭共振具有更大的材料脆塑转变临界切削深度。结论通过不同划痕条件的对比,超声振动能有效提高氧化锆陶瓷的脆塑转变临界切削深度,增大塑性域加工范围,提高材料表面加工质量,验证了理论分析的正确性。     

高体积分数SiCp/Al复合材料平面磨削实验研究

本文使用SiC砂轮和金刚石砂轮对颗粒尺寸大、体积分数高的SiCp/Al复合材料进行了平面磨削实验,研究了磨削深度和工件进给速度对磨削力的影响,并利用扫描电镜对已加工表面形貌进行了研究.结果表明:使用SiC砂轮加工时,磨削力随磨削深度的增加而增大;工件进给速度较低时,磨削力随工件进给速度增加而减小,当工件进给速度超过12...     

疏水/超疏水Ti合金表面液滴的运动特性

采用激光加工技术在Ti6Al4V合金表面构建点阵微结构,利用自组装分子膜技术在微结构表面沉积低表面能物质,制备疏水/超疏水表面。采用自制测试系统测试液滴在试样表面的静态接触角和滚动角,用高速摄像机拍摄液滴滴落到试样表面的运动过程。结果表明,经激光加工和低表面能修饰可构建Ti6Al4V疏水/超疏水表面,其最大接触角为151.4°,表面静态接触角随点阵间隔的增大而减小;液滴静态接触角与液滴滴落高度相关,同一表面上的液滴静态接触角由最后一次滴落高度决定。液滴滴落到水平试样表面的铺展系数由试样表面粗糙度和静态接触角决定,表面粗糙度和静态接触角越大,液滴铺展系数越小。当滴落高度从0 mm增大到20 mm时,铺展系数的增大幅度约为50%。