前混合水射流喷丸强化表面力学特性及疲劳寿命试验

为获得前混合水射流喷丸强化增益效果,研究前混合水射流喷丸对2A 11铝合金和45钢的表面显微硬度、表面残余压应力和疲劳寿命的影响.采用显微硬度计和X射线应力分析仪分别测定喷丸表面显微硬度和表面残余应力,利用扫描电镜观察疲劳断口形貌,获得喷丸表面显微硬度和表面残余压应力随喷丸压力、扫描速度及靶距的变化规律,指出射流喷丸可以大幅度地提高2A11铝合金和45钢的疲劳寿命,当2A11铝合金和45钢的应力振幅分别为155.7 MPa和282MPa时,喷丸试样疲劳寿命比未喷丸试样疲劳寿命分别提高25.31倍和18.56倍,且未喷丸试样疲劳裂纹萌生于试样表面,喷丸试样疲劳裂纹有的萌生于试样表面,有的萌生于试样内部,当疲劳源在试样内部时,裂纹在夹杂物处萌生.因此,前混合水射流喷丸是一种提高金属零构件疲劳寿命的有效方法.     

高压水射流喷丸降低焊接残余应力有限元分析

焊接不可避免产生残余应力,对结构完整性造成很大影响。提出利用高压水射流喷丸技术降低焊接残余应力,并利用有限元法进行计算模拟。分别开发了模拟焊接的移动双椭球热源子程序及模拟高压水射流喷丸的移动压力载荷子程序,得到了经高压水射流喷丸处理前后焊接残余应力分布的变化规律。计算结果表明,经高压水射流喷丸处理后,焊缝和热影响区存在的焊态残余应力得到降低,在焊缝区已经产生压缩应力。证明高压水射流喷丸具有降低焊接残余应力的效果。     

小孔喷丸加工喷射运动装置的结构设计

讨论了小孔内壁喷丸强化加工装置的喷射运动机构的设计研究，提出了依据孔内壁全区域喷丸强度的均衡性的要求，确定喷丸装置和反射装置运动速度的设计思想，并给出了两种类型的结构设计。     

空化水喷丸中空泡云动态演变及靶距优化研究

空化水喷丸是利用空化水射流中空泡云溃灭的能量冲击金属零件表面,使其表面产生强化效果的一种新工艺,但目前靶距选择缺少依据。利用高速相机开展了空化水射流试验,采用帧间差分法(Frame-difference method,FDM)分析了空泡云动态演变规律,得出空泡集中溃灭范围。同时,以2A12铝合金为例,基于不同直径d的喷嘴,进行空化水喷丸验证试验,研究了不同靶距对材料表面性能的作用规律。结果表明,空泡云具有明显的初生-发展-脱落-溃灭的周期性,空泡集中溃灭范围为60d～75d;空化水喷丸的最佳靶距为60d～67.5d,但当d=1.8mm、靶距为120mm时产生过喷现象;提出了根据靶距空化水射流可分为液滴作用区、混合作用区和空化作用区。     

小孔喷丸加工反射装置的运动结构研究

主要讲述了小孔内壁喷丸强化加工装置的喷射运动机构的设计研究,提出了"依据孔内壁全区域喷丸强度均衡性的要求,以确定喷/反射装置运动速度"的设计思想,并给出了两种结构设计.     

前混合水射流多弹丸喷丸模型及残余应力场的数值模拟

针对前混合水射流的液固湍动特性与喷丸过程多重非线性耦合作用行为,提供一种射流喷丸强化残余应力场的有限元分析法。采用液固两相流动理论与计算流体动力学方法分析喷嘴内流特性,建立射流多弹丸喷丸模型;基于弹丸速度冲击载荷加载制度,利用多线性各向同性强化弹塑性模型,应用动态接触对称罚函数法,运用ABAQUS软件模拟不同弹丸数量作用下射流喷丸在45钢材料表层产生的残余应力场,获得残余应力场的分布规律及残余应力沿深度的变化规律;得出射流喷嘴内流呈均质流流型,不同弹丸数量射流喷丸在材料表层产生的径向残余应力沿深度的变化规律相同,但在材料表面产生的径向残余压应力值受喷丸模型影响较大,对弹丸分三层排列、相邻弹丸之间径向和周向中心距离均为弹丸半径的多弹丸喷丸模型,数值模拟获得的表面径向残余压应力值与射流喷丸试验数据基本吻合。     

小孔喷丸加工反射装置的运动结构研究

主要讲述了小孔内壁喷丸强化加工装置的喷射运动机构的设计研究，提出了“依据孔内壁全区域喷丸强度均衡性的要求，以确定喷／反射装置运动速度”的设计思想，并给出了两种结构设计。     

前混合水射流强化技术及发展

介绍了前混合水射流强化技术的基本原理、磨料供给系统及优点,并对前混合水射流强化技术的未来发展进行了展望.     

高压水射流切割技术在反恐中的应用研究

介绍了高压水射流切割技术的主要原理,重点介绍了磨料高压水射流在反恐行动中的应用,并研究设计了一种在反恐行动中适用的前混合磨料高压水射流装置,为反恐行动的顺利进行提供一种行动上的保障。     

后混合水射流供料系统的改进设计

供料系统是后混合水射流设备中不可或缺的组成部分,极大地影响着后混合技术在实践中的作业效率和精度。本文通过归纳传统后混合水射流设备所采用的几种供料方式和供料装置特点,分析其存在的不足。并结合计算机模拟仿真手段,研究了气流在输送管道内的运动规律,提出了两种在现有装置条件下改进的供料系统设计方案,具有极好的运用前景。     

高强度钢喷丸强化处理的试验研究

喷丸强化是一种以小而硬的弹丸连续高速撞击金属零件表面而进行的一种特殊加工方法,零件通过喷丸可以大大提高材料的疲劳性能和抵抗应力腐蚀的能力。针对某型飞机上的喷丸强化零件,选取材料牌号为16Co14Ni10Cr2Mo高强度钢为研究对象,对两种厚度的试样进行不同喷丸强度的喷丸强化,对不同喷丸强度的试样进行疲劳寿命和残余应力场对比分析。     

斯太尔连杆喷丸强化工艺攻关试验

在我国引进了斯太尔发动机制造技术,其重要运动部件连杆由于承受交变载荷,必须进行表面喷丸强化处理,该文着重介绍了喷丸强化的原理,喷丸强度的计算和控制程序,以及根据国内条件研制的喷丸介质与喷丸设备。     

Numerical Calculation and Experimental Research on Residual Stresses in Precipitation-hardening Layer of NAK80 Steel for Shot Peening

Shot peening can improve fatigue strength of materials by creating compressive residual stress field in their surface layers,and offers a protection against crack initiation and propagation,corrosion,etc.And fatigue fracture and stress corrosion cracking of NAK80 steel parts are improved effectively.Currently there lacks in-depth research in which the beneficial effect of the residual stress may be offset by the surface damage associated with shot peening,especially in terms of the research on the effective control of shot peening intensity.In order to obtain the surface residual stress field of NAK80 steel after shot peening,the samples are shot peened by pneumatic shot peening machine with different rules.The residual stress in the precipitation-hardening layer of NAK80 steel is measured before and after a shot peening treatment by X-ray diffraction method.In order to obtain true residual stress field,integral compensation method is used to correct results.By setting up analytical model of the residual stress in the process of shot peening,the surface residual stress is calculated after shot peening,and mentioning the reason of errors occurred between calculated and experimental residual stresses,which is mainly caused by the measurement error of the shoot arc height.At the same time,micro hardness,microstructure and roughness in the precipitation-hardening layer of NAK80 steel before and after shot peening were measured and surveyed in order to obtain the relation between shot peening strength and surface quality in the precipitation-hardening layer.The results show that the surface quality of NAK80 steel is significantly improved by shot peening process.The over peening effect is produced when the shot peening intensity is too high,it is disadvantageous to improve sample’s surface integrity,and leading to reduce the fatigue life.When arc high value of optimal shot peening is 0.40 mm,the surface quality is the best,and the depth of residual stress in the precipitation-hardening layer reaches to about 450 μm.Numerical calculation is very useful to define the process parameters when a specific residual stress profile is intended,either to quantify the benefits on a specific property like fatigue life or to help on modeling a forming process like shot peen forming.In particular,the proposed parameter optimization in the progress of shot peening and effective control of the surface texture provide new rules for the quantitative evaluations of shot peening surface modification of NAK80 steel.     

喷丸强化残余应力对疲劳性能和变形控制影响研究进展

作为机械表面强化技术之一,喷丸强化使工件表层发生形变硬化,引入较高的残余压应力,减少了疲劳应力作用下微裂纹的萌生并抑制其扩展,从而显著提高零件的抗疲劳断裂和抗应力腐蚀开裂的能力。基于喷丸残余应力解析计算模型,从余弦函数模型、接触应力模型和球腔膨胀模型三个方面介绍喷丸强化残余应力的产生,进而对喷丸残余应力的仿真预测及影响规律进行论述。为了提高试件疲劳强度而引入的残余压应力会带来影响形位精度的变形,基于此阐述了喷丸残余应力对疲劳性能的影响及其在疲劳过程中的演化,同时论述了喷丸残余应力变形预测及控制的研究现状,最后对喷丸残余应力未来的研究内容与发展方向进行展望。     

喷丸与激光喷丸强化高强度钢对比试验

为了考察和对比喷丸(SP)和激光喷丸(LSP)2种表面强化技术对金属零件的强化效果,以30CrMnSiNi2A钢为试样,进行喷丸和激光喷丸强化处理试验。试验结果显示,2种强化试样的残余压应力和硬度都有较大的提高。分别测定了喷丸强化和激光喷丸强化试样在同一应力水平下的疲劳寿命,并运用扫描电镜分析了两者的疲劳断口。试验结果表明,激光喷丸强化试样中值疲劳寿命是喷丸强化试样的1.11~2.75倍,激光喷丸强化比喷丸强化在提高金属零件表面性能方面的效果更佳。     

Finite element analysis of shot-peening effect on fretting fatigue parameters

Shot peening is widely used to improve the fretting fatigue strength of critical surfaces. Fretting fatigue occurs in contacting parts that are subjected to fluctuating loads and sliding movements at the same time. This paper presents a sequential finite element simulation to investigate the shot peening effects on normal stress, shear stress, bulk stress and slip amplitude, which are considered to be the controlling parameters of fretting damage. The results demonstrated that among the modifications related to shot peening, compressive residual stress has a dominant effect on the fretting parameters.     

喷丸处理对汽车变速箱齿轮疲劳强度影响的研究

分析了汽车变速箱齿轮经喷丸处理后对疲劳强度的影响，通过喷丸强度试验，表面覆盖率试验确定了合理的喷丸处理工艺，通过疲劳试验，得出了喷丸处理对弯曲疲劳强度和接触疲劳强度的影响程度。结果表明：喷丸处理能极大地提高齿轮的疲劳强度，从而提高齿轮的使用寿命。     

激光冲击强化与喷丸提高不锈钢疲劳性能对比研究

对不锈钢材料1Cr11Ni2W2MoV进行了激光冲击强化和喷丸强化后表面粗糙度和残余应力测试分析,与喷丸相比,激光冲击强化对试件表面形貌和表面粗糙度的影响更小,产生的残余压应力更大。对光滑试件和2种强化后试件的振动疲劳对比试验表明,激光冲击强化能显著提高不锈钢材料振动疲劳寿命,是喷丸的2倍以上。     

金属材料超声滚压表面强化的研究进展

超声滚压表面强化技术具有良好的光整特性,能够实现对被处理材料的表面改性,提高其综合性能,不同程度地克服了滚压、喷丸等传统工艺的缺陷,具有广阔的发展前景。本文介绍了超声滚压技术的加工原理,总结了目前国内外超声滚压技术的研究进展,指出其重点研究方向是将该技术应用于工程部件的表面强化与修复,并对超声滚压表面强化技术的研究趋势进行了展望。     

Kinematic modeling and deformation mechanics in shot peening of functional ceramics

The applications of functional ceramics are significantly limited by the brittleness and low reliability. Recent studies have shown that compressive residual stress can be created in ceramics by shot peening, which improves the contact strength and fatigue of ceramic components. However, the formation mechanism of residuals stress in shot peening is yet to understand. In this study, a pressure-dependent plasticity model has been incorporated into a finite element simulation model of shot peening to understand the process mechanism underpinning the residual stress formation. Since shot velocity is the key process parameter to dominate the impact energy which determines the deformation state of the peened surface and the resultant residual stress, a new kinematic model of shots has also been developed by incorporating air drag and travel distance inside and outside the peening nozzle. The results have shown that the shot velocity model can be used to predict shot velocity. The experiment-based model may help understand the process mechanism underpinning the residual stress formation.