Thermal and mechanical behavior of casting copper alloy wheel during wheel and belt continuous casting process

To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting process.The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail.In each rotation,the casting wheel passes through four different spray zones.The results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,respectively.The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.

Characterization and Analysis of Inconel 718 Alloy Ground at Different Speeds

Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the workpiece.In this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel.The relationship between grinding speed,SQ and subsurface damage(SSD)was well studied.With increasing grinding speed,surface roughness decreased,and SQ was greatly improved.Meanwhile,the microhardness of the grinding surface declined as the grinding speed increased.The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding speeds.It was attributed to the mechanical-thermal synergistic effect in the grinding process.The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy.The conclusion in the work may also provide insight into processing other hard-to-machining materials.

Dechlorination of pentachlorophenol by grinding at low rotation speed in short time

In order to apply grinding method for degradation of pentachlorophenol(PCP) to an industrial scale,the proportion of different materials[CaO,SiO_2 and CO(NH_2)_2]and the size of grinding balls were examined.For saving energy and increasing dechlorination efficiency,the rotation speed and grinding time were maintained at relatively low values.At a mass ratio of grinding balls to materials(40:1),PCP was added into a big steel jar(300 ml) with other materials to grind at 300 r ·min^(-1)for 5 h.The results indicated that when PCP was mixed with CaO and SiO_2in a molar ratio of 1:60:60,the best dechlorination of 58.4%was achieved.CO(NH_2)_2 could not be used as hydrogen donor in the dehalogenation by mechanochemical reaction,since it restrained the dechlorination process.The size of grinding balls has significant effect on the reaction.The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction,while steel balls of 10 and 15 mm could give better dechlorination reaction.It indicates that dechlorination depends on the mass of balls and fill rate.

Heat Transfer Characteristics outside the Condenser of a Rotating Heat Pipe Grinding Wheel with a Lateral Air Impinging Jet

This study numerically analyzed the heat transfer characteristics outside the condenser of a rotating heat pipe grinding wheel(RHP-GW).The goal of this investigation is to determine the optimal structure and parameters for the condenser section of RHP-GW.Different fin height(f=0-7 mm),rotational Reynolds number(Rer=1602-6408)and jet Reynolds number(Rej=42379-108302)were analyzed under input heat flux of 4000 W/m2.A fully developed flow was imposed at the outlet of the nozzles.Results showed that the optimal heat transfer rate was obtained for fin height of 5 mm,which improved the average Nusselt number by 84%compared to the structure without fins.A critical Rej for each Rer that the impinging jet can reach the condenser section was found.The critical Rej value increases with Rer,which is in the range from 42379 to 61215 and 61215 to 80050 for Rer=6408 and Rer=9610,respectively.

Sensitivity analysis of the surface integrity of monocrystalline silicon to grinding speed with same grain depth-of-cut

Mechanisms for removal of materials during the grinding process of monocrystalline silicon have been extensively studied in the past several decades.However,debates over whether the cutting speed significantly affects the surface integrity are ongoing.To address this debate,this study comprehensively investigates the effects of cutting speed on surface roughness,subsurface damage,residual stress,and grinding force for a constant grain depth-of-cut.The results illustrate that the changes in the surface roughness and subsurface damage relative to the grinding speed are less obvious when the material is removed in ductile-mode as opposed to in the brittle-ductile mixed mode.A notable finding is that there is no positive correlation between grinding force and surface integrity.The results of this study could be useful for further investigations on fundamental and technical analysis of the precision grinding of brittle materials.

Comparative investigation on high-speed grinding of TiCp/Ti–6Al–4V particulate reinforced titanium matrix composites with single-layer electroplated and brazed CBN wheels

In order to develop the high-efficiency and precision machining technique of TiCp/Ti - 6Al-4V particulate reinforced titanium matrix composites （PTMCs）, high-speed grinding experiments were conducted using the single-layer electroplated cubic boron nitride （CBN） wheel and brazed CBN wheel, respectively. The comparative grinding performance was studied in terms of grinding force, grinding temperature, grinding-induced surface features and defects. The results display that the grinding forces and grinding temperature obtained with the brazed CBN wheel are always lower than those with the electroplated CBN wheel. Though the voids and microcracks are the dominant grinding-induced surface defects, the brazed CBN wheel produces less surface defects compared to the electroplated wheel according to the statistical analysis results. The max mum materials removal rate with the brazed CBN wheel is much higher than that with the electroplated one. All above indicate that the single-layer brazed CBN super-abrasive wheel is more suitable for high-speed grinding of PTMCs than the electroplated counterpart.

风电轴承大尺寸钢球光球加工技术

针对国内现有风电轴承大尺寸钢球光球机加工精度低,加工效率低的问题,对钢球在光球机动、静磨盘沟道内的运动规律、受力特点和磨削机理进行分析,光球时钢球受到的磨削力与动、静磨盘沟道深度比有关,并基于ADAMS仿真得到最佳动、静磨盘沟道深度比为7∶3,去两极和环带、成形、走圆工序最佳动磨盘转速分别为90,120,90 r/min。样机试验结果表明,改进后光球机的光球效率提高了30%,球形误差至少提高了0.2 mm,表面粗糙度Ra值至少减小了0.03 mm。

CFRP砂轮高速外圆磨削稳定性分析

为分析不同影响因素对CFRP砂轮高速外圆磨削稳定性的影响,采用铁木辛柯梁理论对具有阶梯特征的工件进行动力学分析,结合锤击试验测得砂轮动态特性,对高速磨削过程中的砂轮-工件两自由度系统进行了磨削稳定性分析。在对阶梯工件进行动力学分析的过程中,发现阶梯特征对于动态特性的影响较小,误差小于2%。在稳定性分析中发现,不同的砂轮转速和不同的工件磨削位置均会影响磨削稳定性。磨削位置越靠近工件中心,工件刚度越弱,磨削稳定性降低易诱发颤振;而在靠近顶尖支撑的位置,由于工件刚度增强,该位置的磨削稳定性将同时受到工件和砂轮的动力学性能的影响。通过磨削试验验证了分析方法的有效性,试验结果表明,工件磨削位置的刚度差异将会影响加工表面质量,由磨削失稳导致的粗糙度增幅可达51.6%。

基于五轴平台的枞树型轮槽铣刀加工工艺分析

轮槽成型铣刀是加工汽轮机轮毂槽的重要工具,其结构复杂且加工困难。为提高加工效率和精度,以某型高速钢轮槽铣刀为例,提出基于五轴平台的加工工艺方法。使用UG软件基于五轴车铣复合机床规划粗加工刀具路径,并采用专用后置处理器生成数控加工程序,通过虚拟机床进行仿真验证;采用NUMROTO软件规划精加工路径,获得磨削NC代码并进行虚拟加工验证;进行实际切削验证,通过DOOSAN PUMA SMX2600ST车铣复合加工中心对刀具进行粗加工后,在SAACKE UWIF五轴工具磨床上完成刀具的精加工。实验结果证明,该工艺方法不仅能保证产品质量符合工艺设计要求,而且制造效率提高了20%。

轴承内圈沟道磨削热应力场有限元仿真分析

针对轴承套圈滚道磨削加工时过大的热应力会导致滚道表层产生热损伤的问题,联合ABAQUS及Hyper-Mesh建立B7008C角接触球轴承内圈沟道磨削热应力场有限元模型,开发DFLUX子程序减少模型分析步的数量,克服了网格数量庞大导致磨削热源无法沿沟道整周移动的问题,揭示了内圈沟道磨削热应力场的形成机制与演化规律,得到了内圈沟道表层产生残余拉应力的临界温度,并分析了工艺参数对内圈沟道残余拉应力分布的影响,结果表明:只有当磨削热应力超过材料的屈服强度时,内圈沟道表层才会产生残余拉应力,产生残余拉应力的临界温度约为420℃;随着热流密度的增大及工件转速的减小,内圈沟道表层的残余拉应力和分布深度增大。

旋转热管砂轮冷凝端单翅片对流换热仿真研究

为优化旋转热管砂轮冷凝端结构,在冷凝端添加翅片,增大散热面积,实现有效散热,从而提高换热能力。应用FLUENT软件对旋转热管砂轮冷凝端单翅片进行对流换热仿真研究,通过建模分析翅片高度、翅片厚度、冷风条件、转速对冷凝端换热性能的影响。研究表明,当翅片高度为6 mm,翅片厚度为1 mm时,冷凝端外壁面的平均对流换热系数最大,平均温度最低。当冷风压力为0.6MPa时,冷凝端换热性能较好。随着旋转速度的加快,冷凝端外壁面平均对流换热系数增大,表明换热能力不断提高。仿真研究结果为旋转热管砂轮冷凝端结构优化及后续磨削试验提供了参考,具有较高的实际工程应用价值。

内圆环氧胶配置优化平面砂布轮自动施胶技术研究

为了实现平面砂布轮内圆环氧填缝胶自动化施胶,使用增塑剂P、沸石粉、增韧剂Q对其共混改性。讨论了加入不同含量增塑剂P和沸石粉、增韧剂Q的适用期、拉伸性能、固化样红外分析,以及相应砂布轮内圆光泽性、回转强度和磨削性能的影响。结果表明,加入3%的增塑剂P时,适用期从原1 h延长至4 h,光泽性好,砂布轮回转强度达到22300 r/min,磨削性能良好,完全满足自动施胶工艺所要求的胶的性能。加入10%的增塑剂P同时加入沸石粉、增韧剂Q时,适用期从原1 h延长至9 h,砂布轮回转强度达到23800 r/min,磨削性良好,满足光泽性要求不高的砂布轮产品夏季自动施胶要求。

无压烧结碳化硅超精密磨削工艺参数优化

【目的】为降低碳化硅陶瓷材料表面粗糙度值,以优化磨削工艺参数为目标设计正交磨削试验。【方法】首先结合回归模型方差分析砂轮转速、进给速度、工件转速3个因素对磨削加工质量的影响程度;然后绘制响应曲面图,通过响应曲面图确定各参数对表面粗糙度的影响。【结果】当无压烧结碳化硅陶瓷材料用脆性去除方式时,砂轮转速对其表面粗糙度影响最大,在一定范围内砂轮转速越大,表面粗糙度值越小;求解得到最佳磨削参数组合为砂轮转速42000 r/min、进给速度1 mm/min、工件转速100 r/min,在此工艺参数下获得碳化硅陶瓷的表面粗糙度值为61.3 nm,可有效提高碳化硅陶瓷材料的加工质量。【结论】本研究结果可为降低无压烧结碳化硅陶瓷材料表面粗糙度值提供参考。

钢轨打磨仿真试验台测试条件对试验结果的影响

利用钢轨打磨仿真试验台,对打磨试验中砂轮转速、打磨功率、打磨时间、工件转速对试验结果的影响进行了综合研究,并对试验数据及现象进行了定性分析,得出了科学的打磨仿真试验测试条件。试验结果表明:单独提高砂轮转速时,打磨压力减小,工件磨削量减小,砂轮磨耗率减小,砂轮温升和工件温升下降;单独增大打磨功率时,打磨压力先快速增大后趋于缓慢,工件磨削量在13.50~14.25 kW时突然剧烈增加,砂轮磨耗率在10.50~11.25 kW和13.50~14.25 kW处突然剧烈增加,工件温升和砂轮温升先增大后趋于稳定;单独增加打磨时间时,打磨压力基本稳定,工件磨削量增加,砂轮磨耗率、砂轮温升和工件温升先增加后趋于平稳;单独提高工件转速时,工件磨削量减小,砂轮磨耗率减小。综合考虑现场实际工况和实验室内模拟效果,将打磨仿真试验台的测试条件定为打磨功率7.50~11.25 kW,打磨时间16 min,砂轮转速2400 r/min,工件转速10.85 km/h。

磨胶辊机的发展与应用

为提高胶辊磨砺的质量和效率,介绍磨胶辊机从手动到全自动的发展历程;以纺C 7.3 tex纱为例,对比分析传统手动磨胶辊机和全自动磨胶辊机磨砺胶辊上机成纱质量指标,提出对全自动磨胶辊机的改进建议及维护保养措施,并展望全自动磨胶辊机的发展方向。指出:全自动磨胶辊机具有磨砺效率高、工艺参数设置方便、磨砺效果好、能减轻工人劳动强度等优点,但也存在砂轮易损坏、不适应倚丽胶辊组合件磨砺等问题,可通过加装砂轮自动紧急制停装置、注重磨胶辊机维护与保养、加强技术创新等,优化设备性能,提高其适用性。

金刚石砂轮的磨削整形法研究

为研究金刚石砂轮修整的工艺,采用绿碳化硅砂轮对金刚石砂轮进行磨削整形法修整。通过改变修整量、修整速比、切削进给量、工作台速度得出修整参数对砂轮磨削性能的影响规律。研究结果表明,工件表面粗糙度随着修整量增加而增大,修整量增加到一定次数时粗糙度变化不大;修整速比增大时,工件表面粗糙度值增大;切削进给量增大时,工件磨削表面粗糙度增大;工作台速度增大时,工件表面粗糙度增大。所得结论为绿碳化硅砂轮修整金刚石砂轮的工艺参数选取提供了切实有效的参考价值。

钢轨铣磨技术在高速铁路小半径曲线的应用

为解决高速铁路进出站或临近管界的小半径曲线钢轨表面疲劳伤损问题,修复钢轨廓形,结合现场调查数据,分析了小半径曲线地段钢轨廓形质量、轨面状态、钢轨廓形偏差和轮轨接触关系。从轮轨关系角度分析了轨面疲劳伤损产生原因,提出了利用钢轨铣磨车和道岔打磨车的综合整治方案。结果表明:铣磨打磨作业后钢轨廓形质量和轨面状态得到明显改善;轮轨接触点分布位置更加合理,分布范围更加均匀,有效避免了轨面应力集中问题;动检车横向加速度明显减小,轮轨接触关系得到改善。

一种基于独立轮对车辆主动导向控制方案的可行性研究

世界各国轨道交通行业竟相开发对环境、线路和乘客“友好”的高速列车,兼备左右车轮独立旋转和可取消公共车轴特点的独立轮对为这种设计理念提供了新的解决方案。独立轮对车辆理论上可完美通过曲线,同时可兼顾乘坐便利性和经济友好性等特点。但独立轮对自身结构特点导致其缺乏导向能力。因此,文章研究了独立轮对导向控制的发展现状,分析了独立轮对导向控制的局限性和可行性,并在独立轮对两轴转向架车辆的基础上,提出了一种基于左右车轮转速差的导向控制方案。该方案采用经典PID控制方法,根据不同的车速、缓和曲线长度和曲线半径优选控制增益。此外,由于车辆结构限制,独立轮对两轴转向架车辆的理论控制目标与实际结果存在偏差。文章在优选控制增益的基础上,对控制目标进行了优化。结果表明,采用优选的控制增益和控制目标可为独立轮对两轴转向架车辆提供良好的导向控制效果。

超高速磨削技术在机械制造领域中的应用

概述了超高速磨削加工的起源、发展历程和现状·总结了超高速磨削的优越性和若干特点·介绍了高效深磨、超高速精密磨削、难磨材料的超高速磨削在机械制造领域的应用和超高速磨削的绿色加工特性·高速和超高速磨削是提高磨削效率、降低工件表面粗糙度和提高零件加工质量的先进加工技术·超高速磨削能越过磨削'热沟',减少传入工件的磨削热,从而避免或减少工件表面磨削'烧伤',产生残余压应力的加工表面·超高速磨削可以对硬脆材料实现延性域磨削加工,对高塑性、高强度等难加工材料也有良好的磨削性能·

不锈钢超高速磨削试验研究

为避免不锈钢磨削中发生砂轮堵塞,减轻磨削烧伤的程度,提高加工效率,优化加工工艺,对不锈钢进行超高速磨削试验研究。在高速/超高速磨削条件下,研究了不同砂轮线速度、工件进给速度和进给量对不锈钢磨削的磨削力、表面粗糙度和表面形貌的影响作用,并检测了不同工况下的砂轮表面状态。研究结果表明,不锈钢在超高速磨削状态下,选择合理的工作台速度和磨削深度能有效提高加工效率,同时又能保证磨削质量。