磨料喷射喷嘴的应力分析及FGM模型设计

分析表明磨料喷射加工中喷嘴承受的应力在喷嘴入口最大、出口次之、中间区域相对较小。试验显示喷嘴的冲蚀磨损在喷嘴入口最严重、出口次之、中间区域相对较小。试验结果与应力分析结果一致,得出磨料喷射加工中喷嘴入口、出口处承受的高拉应力是造成其冲蚀磨损严重的主要原因的结论。针对提高均质陶瓷材料喷嘴抗冲蚀磨损能力的力度有限,提出运用梯度功能材料(Function gradient material,FGM)理论于喷嘴材料的设计和制造中,研发新型非均质的陶瓷喷嘴材料,将梯度功能陶瓷喷嘴制备中产生的残余压应力引入喷嘴入口、出口,使其减缓磨料喷射加工中喷嘴承受的拉应力,以提高喷嘴抗冲蚀磨损能力。结合喷嘴的冲蚀磨损特点、结构特点及陶瓷喷嘴材料制备工艺性等,建立了梯度陶瓷喷嘴物理模型和成分分布模型。根据本模型设计结果,研制出梯度 SiC／(W,Ti)C陶瓷喷嘴。结果表明,相同条件下制各的梯度SiC／(W,Ti)C陶瓷喷嘴的抗冲蚀磨损能力高于非梯度 SiC／(W,Ti)C陶瓷喷嘴。     

喷嘴抗冲蚀磨损研究及梯度模型设计

分析喷嘴冲蚀磨损特点，指出喷嘴的不同部位同时受到不同角度的冲击；磨料颗粒在喷嘴内部加速运动，喷嘴沿长度方向的磨损程度不同，喷嘴人口磨损最严重，出口次之，而中间区域磨损相对较轻。阐述陶瓷喷嘴冲蚀磨损机理，说明陶瓷喷嘴两端承受以高冲击角为主的冲蚀，磨损机理以应力疲劳断裂和脆性断裂为主；喷嘴中部承受低角冲蚀，微切削冲蚀磨损为其主要磨损机理，得到喷嘴磨损属于多冲蚀磨损机理并存的结论。在此基础上，提出均质材料难以适应喷嘴冲蚀磨损特点，不易满足喷嘴高抗冲蚀磨损性能要求的观点。基于梯度功能技术思想首次提出梯度功能喷嘴设计方法，并建立梯度功能喷嘴设计模型。     

新型陶瓷喷砂嘴的制备及其应用

分析了喷砂嘴材料和结构的发展情况,采用热压烧结工艺制备出了B4C/(W,Ti)C新型陶瓷喷砂嘴,结果表明随(W,Ti)C含量的增加,陶瓷喷嘴材料的致密度显著增加,晶粒显著细化,保温时间大大缩短,抗弯强度和断裂韧性大大提高;以SiC为冲蚀磨料进行的喷砂冲蚀试验证明了新型陶瓷喷砂嘴的抗冲蚀磨损能力远高于金属、硬质合金和其它陶瓷喷嘴。     

陶瓷喷砂嘴应力的有限元分析

根据喷砂工作情况和一种具体陶瓷喷砂嘴结构,建立了单粒子冲蚀模型,利用有限元软件模拟陶瓷喷砂嘴冲蚀过程,研究了喷砂嘴材料在冲蚀过程中的破坏状态以及不同时刻的应力、能量分布情况,为进一步研究陶瓷喷砂嘴冲蚀磨损的动态过程及冲蚀磨损机理提供了有力依据.     

基于离散相模型的水力喷砂射孔器优化设计

针对常用水力喷砂射孔器冲蚀磨损严重、使用寿命短的问题,运用数值模拟软件的离散相模型,分析了常用水力喷砂射孔器的冲蚀磨损规律,提出了工具结构和喷嘴结构的优化设计方案;并对新型水力喷砂射孔器的射流性能和耐冲蚀性能进行验证。研究结果表明：常用水力喷砂射孔器的冲蚀磨损主要集中在工具内腔喷嘴入口处、喷嘴内流道和工具外壁喷嘴出口处,且射孔器结构、射孔液运动特性、管柱振动和工作环境是造成冲蚀磨损的4个主要原因;相同条件下,相比于常用水力喷砂射孔器,所提出的新型水力喷砂射孔器的射流速度更大,上下层喷嘴间的速度差更小,耐冲蚀性能更佳。     

高压对高压管汇冲蚀磨损的影响

针对现有的高压管汇冲蚀磨损理论,缺乏考虑高压力载荷对其冲蚀磨损的影响。通过对高压管汇冲蚀磨损的分析,得出当弯头受到内压作用时,产生的环向应力即拉伸应力明显大于轴向应力的结论。利用实验室自主研发的可施加拉伸应力的冲蚀磨损试验机,开展在不同拉伸应力作用下,冲击角为30°时,高压管汇材料40CrMo冲蚀磨损性能的实验研究。结果表明:随着应力的增大,40CrMo的冲蚀磨损率增加,抗冲蚀能力减弱。     

高压对高压管汇冲蚀磨损结果的影响

针对现有的高压管汇冲蚀磨损理论,缺乏考虑高压力载荷对其冲蚀磨损的影响。通过对高压管汇冲蚀磨损的分析,得出当弯头受到内压作用时,产生的环向应力即拉伸应力明显大于轴向应力的结论。利用实验室自主研发的可施加拉伸应力的冲蚀磨损试验机,开展在不同拉伸应力作用下,冲击角为30°时,高压管汇材料40CrMo冲蚀磨损性能的实验研究。结果表明：随着应力的增大,40CrMo的冲蚀磨损率增加,抗冲蚀能力减弱。     

新型抗冲击磨损扇形喷嘴的设计研究

从磨损机理出发,指出扇形喷嘴的主要磨损形式.分析造成扇形喷嘴磨损快、寿命短的原因,指出传统喷嘴结构上的缺陷,提出新型喇叭型出口结构的扇形喷嘴,并进行了磨损对比试验.结果表明:喇叭型出口结构可增加喷孔颈部的厚度,增强喷孔的抗冲蚀能力,可有效地减少喷嘴的磨损、延长喷嘴的寿命.     

冲蚀与气蚀复合磨损试验装置及其试验研究

在分析典型含沙水流的冲蚀、气蚀磨损试验设备和方法的基础上,针对我国水力机械和水工建筑的特殊损伤破坏形式提出了基于射流的水下冲蚀与气蚀复合磨损试验设备和方法。实验室泥沙冲蚀与气蚀复合磨损模拟试验结果表明,该试验装置设计合理,可以在较短时间内获得试验数据。对2种典型的耐磨不锈钢材料进行了冲蚀磨损试验研究,发现2种材料在冲蚀磨损过程中伴随有气蚀作用机制,材料损伤的实质是冲蚀与气蚀的复合磨损。     

拉应力作用下冲蚀速度对35CrMo钢冲蚀磨损行为的影响

研究拉应力作用下冲蚀速度对35CrMo钢冲蚀磨损行为的影响。采用自制的喷射型冲蚀磨损试验机,模拟管汇承受105 MPa应力,在30°冲蚀角度下,用携砂液对试样进行冲刷试验,研究携砂液冲蚀速度对冲蚀磨损的影响,并使用扫描电子显微镜(SEM)对试验后试样表面形貌进行分析。试验结果表明,在拉伸应力105 MPa和冲蚀角度30°下,在携砂液总量一定的情况下,随着冲蚀速度的增加,35CrMo钢的冲蚀磨损量呈指数形式增加;冲蚀坑深度随着冲蚀速度的增加而增大;不同冲蚀速度下35CrMo钢冲蚀磨损机制相同,主要为切削磨损。     

陶瓷喷砂嘴结构参数对冲蚀磨损的影响

根据喷砂工作原理和喷枪结构特征建立了引射段的自由射流模型。研究了喷砂嘴结构参数(粗糙度、内径、长度)变化时,喷砂嘴和喷枪内的气固两相流场性质和变化过程。并结合陶瓷材料的冲蚀磨损机理,分析了流场对磨料运动和冲蚀磨损的影响。结果表明,合理选择喷砂嘴的结构参数对减轻喷砂嘴的冲蚀磨损,提高其使用寿命具有重要作用。该结论对进行喷砂嘴的耐磨结构设计具有重要的指导意义。     

Wear behaviors of ceramic nozzles with laminated structure at their entry

Laminated ceramic nozzles (GN1, GN2, and GN3) with different architecture and composition at the constituent layers were produced by hot pressing. The mechanical properties of the constituent layers of the laminated materials were measured, the microstructure was examined. The wear behaviors of these laminated nozzles were investigated and compared with an unstressed reference nozzle (CN). Results showed that the surface layer (nozzle entry) possessed higher hardness and fracture toughness than those of other layers of the laminated nozzles, and is greatly improved over the stress-free nozzle. The laminated nozzles had superior erosion wear resistance to that of the stress-free one, especially at the nozzle entry. The mechanism responsible was explained as the formation of compressive residual stresses at the entry of the laminated nozzles during fabricating processes. The erosion wear resistance of the laminated nozzles was influenced not only by the volume fraction of the constituent layers, but also by the difference in composition between adjacent layers. The GN2 nozzle with 2% difference of (W,Ti)C content between adjacent layers exhibited higher erosion wear resistance over the GN1 and GN3 nozzles. Surface mechanical properties improvement at the entry area was found to be the main reason for the increase of erosion wear resistance of the GN2 nozzle.     

Wear of ceramic nozzles by dry sand blasting

Monolithic B₄C, Al₂O₃/(W,Ti)C and Al₂O₃/TiC/Mo/Ni ceramic composites, which provided a reasonably wide range of mechanical properties and microstructure, were produced to be used as nozzles materials. The erosion wear of the nozzle caused by abrasive particle impact was compared with dry sand blasting by determining the cumulative mass loss of the nozzles made from these materials. Results showed that the hardness of the nozzle material plays an important role with respect to its erosion wear. On the nozzle entry bore section, the B₄C nozzle appears to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While the erosion mechanism of Al₂O₃/TiC/Mo/Ni nozzle appeared to be a preferential removal of the metal binder followed by pluck out of the undermined Al₂O₃ and TiC grains under the same test conditions. On the nozzle center bore zone, the B₄C nozzle fails in a highly brittle manner, and there are lots of obvious micro-cracks and small pits located on this area. While the primary wear mechanisms of Al₂O₃/TiC/Mo/Ni nozzle is plowing and micro-cutting by the abrasive particles. Both types of material removal model seem to be occurred for the Al₂O₃/(W,Ti)C nozzle.     

Nozzle wear during the flow of a gas-particle mixture

An experimental study of nozzle wear during gas-solid particle flow is presented. The experiments were carried out on a specially designed erosion tester where the input parameters could be precisely controlled. The results indicate that the nozzle length, nozzle diameter, entrance angle, mixture ratio and grain size have a significant influence on nozzle wear. These results are discussed on the basis of existing erosion models.     

An experimental investigation into the wear of the cylinder liner-piston ring in engines

In order to meet the demands of different engines, various kinds of material are used for the cylinder liners and piston rings. This paper describes a method and the results of wear tests for various liners and rings. These experiments were carried out on a FGM-1 wear simulation testing machine. The results help contribute to the rational selection and pairing of the liners and the rings.     

Development of a method for selecting technical ceramics for protection against abrasive erosion

The paper deals with the solution of a topical problem of selecting protective ceramic materials to improve the service life of parts of gas-and-oil and other equipment that experience abrasive erosion. The available theoretical and experimental methods of specifying protective materials are analyzed. The author discusses the potential of the energy concept of the abrasive erosion process and uses this concept together with system approach methodology to propose new numerical characteristics. The possibility of determining these characteristics for ceramic materials by the calculation-experimental method involving a developed technique and device is shown. The availability of adequate numerical characteristics of the abrasive-containing flow and the ceramic material forms the basis for selecting a ceramic material using the criterion of its minimal wear intensity in the contaminated flow of a working fluid.