微孔砂轮射流冲击内外冷却技术在钛合金磨削中的应用研究

论述了钛合金材料理化特性和导致磨削加工困难的原因;阐述了冷却液在磨削中的基本作用;描述了微孔砂轮射流冲击内外冷却机理;给出了微孔砂轮射流冲击内外冷却磨削钛合金零件表面质量和砂轮表面形貌电子扫描分析报告;指出微孔砂轮射流冲击内外冷却新工艺最大限度地发挥了冷却液的冷却、润滑和冲淋作用,有效地解决了磨削钛合金零件表面产生拉伤、烧伤和夥轮表面粘结等工艺难题.     

微孔砂轮射流冲击内外冷却技术在钛合金磨削中的应用研究

论述了钛合金材料理化特性和导致磨削加工困难的原因;阐述了冷却液在磨削中的基本作用;描述了微孔砂轮射流冲击内外冷却机理;给出了微孔砂轮射流冲击内外冷却磨削钛合金零件表面质量和砂轮表面形貌电子扫描分析报告;指出微孔砂轮射流冲击内外冷却新工艺最大限度地发挥了冷却液的冷却、润滑和冲淋作用,有效地解决了磨削钛合金零件表面产生拉伤、烧伤和砂轮表面粘结等工艺难题.     

WS-20磨削液

在机械加工中,冷却液主要是起冷却、润滑、防锈和清洗作用。合理的选用冷却液,可以有效地减少加工过程中摩擦热的产生,改善散热条件,从而降低功率消耗,切削、磨削温度,延长刀具寿命,提高加工精度和表面质量。随着科学技术和机械工业的不断发展,磨削加工原来只能用精加工,由于高速磨削、强力磨削和高速强力磨削等高效磨削工艺的相继出现,也可以     

基于Fluent的高速磨削风冷结构设计与流场分析

研究采用高速空气作为冷却介质的一种新型高速磨削冷却方案,提出利用高速磨床主轴带动涡扇叶片结构作为风冷结构产生高速气流,高速气流经风冷砂轮内部空腔喷射至磨削工作表面进行强制对流散热,进而实现绿色高速磨削的目的。通过三维软件Pro/Engineer对新型砂轮结构进行造型设计,将设计内部结构导入Fluent软件并完成流场环境建模,通过反复流场模拟实验,确定出高速气流到达磨削工作表面时的流场分布特性。结果表明,压缩比为1.3的轴流压气结构产生的气流能够顺利突破高速气流屏障到达磨削区域,与传统的冷却液内冷式砂轮结构的磨削相比,冷却效果相当,验证了常温空气作为高速磨削冷却介质的可行性,并为其他切削加工提供一种新的冷却思路。     

80米/秒高速磨削冷却液的磨削试验

提高磨削加工的生产效率和加工质量,是我国机械工业当前迫切需要解决的主要课题之一。高速磨削就是提高磨削效率和加工质量,降低砂轮消耗的重要途径之一,也是当前磨床发展的主要趋向。高速磨削加工,必须使用合适的冷却液,才能有效地提高磨削效率和降低砂轮消耗。我们根据一机部指示,进行了新型高速磨削冷却液的研究。在实验室通过大量的配方评定和常数测定,按照高速磨削的特点,我们选用了冷却和清洗为主的水溶性离子型冷却液。在上海机床厂M131W 型改装的80米/秒高速外圆磨床上进行了三次高速磨削试验,现将各次试验结果归纳总结如下:     

不锈钢高速磨削加工冷却工艺分析

针对不锈钢高速磨削加工时产生的质量问题,通过对磨削区温度特性分析和几种冷却工艺对比,提出实现不锈钢产品高速、环保、高效磨削加工的关键是采用低压除尘冷却液与高压冷风组合的冷却新工艺.     

应用低温高压喷雾冷却控制磨削烧伤

介绍了磨削烧伤的危害、影响因素以及一般的预防措施。重点介绍了磨削加工中低温高压喷雾冷却技术的应用。喷雾冷却技术就是利用一定压力的压缩空气将冷却液雾化后,喷向磨削区,对磨削区进行冷却和冲洗,带走灰尘和脱落的磨粒,能极大改善磨削状况。试验证明相比较于传统的冷却方法,喷雾冷却具有经济性好,降温效果好,有利于控制磨削烧伤以及提高磨削加工表面质量,可对难加工材料的磨削提供借鉴。     

磨削过程中磨削液的有效利用及其实现技术

在磨削加工过程中,一般都是利用向磨削区供给充分冷却液的方法来抑制零件表面温度升高和解决热损伤。但是由于砂轮的高速旋转,会在砂轮的表面形成一个高压空气边界层,阻止磨削液有效的进入磨削区,使加工条件恶化,磨削区温度升高,影响了工件的表面质量和完整性。通过合理的选择供液压力、流量和供液方式及喷嘴形式来提高进入磨削区有效磨削液的比例,进而更好的发挥磨削液的冷却作用,降低磨削区温度,保证工件表面质量和表面完整性,同时也有利于实现绿色磨削加工。     

加压内冷却砂轮的研制及磨削性能研究

针对高温合金材料在磨削加工过程中存在磨削烧伤问题,为避免气障效应并强化冷却液在磨削弧区的换热效果,提出采用加压式内冷却断续磨削方法。利用数值模拟方法和3D打印技术对砂轮基体、加压内冷却系统和密封结构等进行设计和验证,制备了用于平面磨削的加压内冷却开槽CBN砂轮。在相同的磨削加工参数条件下,使用加压内冷却方法与外部喷射冷却方法进行镍基高温合金磨削对比试验,分析了砂轮速度、磨削深度和工件进给速度等加工参数对磨削温度、加工表面粗糙度和表面形貌的影响规律,验证了加压内冷却断续磨削方法对磨削弧区的强化换热效果。结果表明：在相同试验参数条件下磨削镍基高温合金,加压内冷却法比外部喷射冷却法的换热效率更高,得到的磨削温度更低,表面粗糙度更小,加工表面更为光滑细腻。     

QM高速强力磨削冷却液

为配合推广高速强力磨削工艺,我所研制了适用于多种钢材切入强力磨削用的QM176冷却液,和适用于强力磨削合金冷硬铸铁凸轮轴的QM186冷却液。该项目曾获机械部科研成果二等奖和新产品银质奖。 QM高速强力磨削冷却液具有良好的加工性能。用于切入强力磨削钢件时,比苏联420磨削液增加磨削量36％,磨削比提高60％,功率消耗降低42％,砂轮耐用度提高40％。QM186冷却液在强力磨削冷硬铸铁时,磨削     

Temperature field model and experimental verification on cryogenic air nanofluid minimum quantity lubrication grinding

Considering the poor lubricating effect of cryogenic air (CA) and inadequate cooling ability of nanofluid minimum quantity lubrication (NMQL), this work proposes a new manufacturing technique cryogenic air nanofluid minimum quantity lubrication (CNMQL). A heat transfer coefficient and a finite difference model under different grinding conditions were established based on the theory of boiling heat transfer and conduction. The temperature field in the grinding zone under different cooling conditions was simulated. Results showed that CNMQL exerts the optimal cooling effect, followed by CA and NMQL. On the basis of model simulation, experimental verification of the surface grinding temperature field under cooling conditions of CA, MQL, and CNMQL was conducted with Ti–6Al–4V as the workpiece material. Simultaneously, CNMQL exhibits the smallest specific tangential and normal grinding forces (2.17 and 2.66 N/mm, respectively). Further, the lowest grinding temperature (155.9 °C) was also obtained, which verified the excellent cooling and heat transfer capabilities of CNMQL grinding. Furthermore, the experimental results were in agreement with theoretical analysis, thereby validating the accuracy of the theoretical model.     

A study on a cooling method for bone grinding using diamond bur for minimally invasive surgeries

Miniature ball-end diamond wheels are widely used for bone grinding in endoscopic surgeries. During bone grinding, a considerable amount of heat is generated, which can cause thermal injuries to the tissues adjacent to bone, including nerves. In our previous studies, it was revealed that the strong adhesion of bone chips on the wheel surface promotes heat generation. To prevent adhesion, a surface-treated wheel was proposed, and it reduced the temperature elevation. However, we found that the proposed wheel cannot stably suppress the temperature elevation because the wheel effect depends on the coolant supply rate. In this study, a bone grinding method that stably suppresses temperature elevation was investigated. Based on the obtained findings, a cooling method using cold air was developed, and the temperature elevation was stably suppressed under a cold air supply.     

Experimental investigation on high-efficiency grinding of Inconel 718 with heat pipe grinding wheel

Grinding heat is a significant problem for grinding difficult-to-machine materials such as nickel-based superalloys, which restricts their applications. A majority of existing cooling methods ensure cooling by simply increasing the volume of coolant. However, lubricants often lose efficacy due to film boiling and have adverse health and environment effects. To dissipate grinding heat in the contact zone and guarantee workpiece surface quality, a novel cooling method that dissipates grinding heat assisted by forming rotating heat pipe inside the grinding wheel (HPGW) is proposed. Tests were performed to determine its heat transfer capacity in high-efficiency grinding of Inconel 718 alloy. The results show that grinding with HPGW leads to lower grinding temperatures and lower thermal damages to the workpiece when compared to grinding with non-HPGW. Better heat transfer capacity of HPGW is explained by heat transfer resistance analysis for both grinding wheels. The analysis proves that the value of HPGW is one order of magnitude lower than non-HPGW. Furthermore, in-depth studies of the ground surface showed no changes in microstructure or microhardness for the workpiece when using HPGW, whereas different degrees of burn were seen as indicated by different temper colors and corresponding changes in microstructure and microhardness.     

Cooling by sub-zero cold air jet in the grinding of a cylindrical component

This paper investigates the cooling effect when using an air jet at sub-zero temperature of ?15 °C in the plunge grinding of a cylindrical component made of high strength steel EN 26. A three-dimensional finite element heat transfer model with a moving heat source was developed to reveal the complexity of the heat transfer mechanism involved. It was found that the use of cold air does not significantly reduce the temperature rise in grinding and that the cooling effectiveness is mainly limited by the following facts: (a) the air jet is difficult to penetrate into the grinding zone, (b) the heat transfer coefficient provided by an air jet is small and (c) cooling is limited by the time which the rotating workpiece surface can be exposed to the jet impingement. The study also showed that the present modelling method can be used as a first tool to assess the feasibility of a new cooling medium for grinding operations.     

以载荷作用次数为寿命度量指标下的零件可靠性建模

提出了以随机载荷作用次数为寿命度量指标框架下的零件可靠性建模方法,分别给出了强度不退化和强度退化时随机载荷多次作用下的零件可靠度与失效率计算模型,研究了不同情况下零件可靠度与失效率随载荷作用次数的变化规律。研究表明,即使零件强度不退化,零件的可靠度与失效率也会随着随机载荷作用次数的增加而逐渐减小,且失效率曲线具有浴盆曲线“早期失效期”和“偶然失效期”的特征。强度随载荷作用次数退化时,随着载荷作用次数的增加,零件的可靠度降低较为明显,失效率先减小后增大具有“浴盆曲线”的全部特征。     

Investigation of a heat pipe cooling system in high-efficiency grinding

The high grinding temperature is one of the problems restricting on the further development of high-efficiency grinding due to the workpiece burnout and excessive wheel wear. An original method about enhancing heat transfer in the contact zone based on heat pipe technology is put forward to reduce the grinding temperature in this paper. Drawing on the structure of rotation heat pipe, one heat pipe cooling system, heat pipe grinding wheel (HPGW) applied to high-efficiency grinding, is developed and its heat transfer principle is illustrated. Besides, the cooling effect in the contact zone using HPGW is simulated through a three-dimensional heat transfer model in grinding, and the influence of different parameters of the wheel speed, cooling condition, and heat flux input on the grinding temperature is analyzed. Eventually, preliminary grinding experiments with HPGW were carried out to verify the cooling effect by comparing with non-HPGW in grinding of 0.45 wt.% C steel and titanium alloy Ti-6A1-6V. Results show that using HPGW can significantly reduce the grinding temperature and prevent the burnout.     

磨削液的加注方式对冷却效果的影响及其对策

分析了现有各种磨削液加注方式对唐削弧区的冷却效果的影响，从冷却机理方面，对其存在问题及改进方向进行了探讨，并在此基础上，提出了一项射流冲击强化磨削弧区换热的新技术。实验结果表明，该项技术是降低磨削温度、提高磨削弧区换热效率的有效方法，将在解决难加工材料磨削烧伤方面具有广阔的应用前景。     

不同冷却工况下的磨削钛合金温度场模型及验证

为克服普通纳米流体微量润滑在磨削区换热能力不足的技术瓶颈,提出了低温风冷+纳米流体微量润滑的新工艺,并建立了温度场有限差分模型.对低温风冷+纳米流体微量润滑、低温风冷、纳米流体微量润滑三种冷却方式下的磨削温度场进行了数值仿真,结果表明低温风冷+纳米流体微量润滑的换热能力最强,低温风冷次之,纳米流体微量润滑最弱.在三种不...     

磨削温度对刀剪刃口的影响

砂轮磨削刀剪材料的过程中产生的磨削热是影响刀剪表面质量的重要因素。对磨削热的产生进行了分析 ,讨论了磨削温度对刀剪产品质量的影响 ,提出了正确选择磨削刀剪时的砂轮、冷却方式及磨削量等 ,以确保刀剪产品的磨削质量。