喷丸强化对轿车用新型齿轮钢表面应力状态影响的研究

应用单变量及正交试验,并配经X射线应力仪等系统地研究的喷丸工艺参数（丸粒速度、密度及喷丸时间）对工件表面残余应力及其分布的影响规律,试验结果表明：随着三种喷丸工艺参数值的提高,工件表面残余应力增大,尤其是在工件次表层峰值应力增大更明显,且内移,但当丸粒速度接近设备所产生的最大值时,则工件表层应力值几乎不再增加,并讨论了有关机理。     

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。     

A numerically low-cost and high-accuracy periodic FE modeling of shot-peened 34CrNiMo6 and experimental validation

This paper proposed a numerically low-cost 3D FE modeling method for multi-shot shot peening. The low computation cost and high prediction accuracy of shot peening are realized at the same time by the incorporation of random multi-shot with defined spacing between the adjacent simultaneously impinging shots, periodicity, and coverage rate of 100%. With this modeling method, one-step and dual-step multi-shot peening of 34CrNiMo6 steel target is modeled and the produced residual stress is predicted. In order to make the predicted residual stress depth profile more comparable with the measured one by XRD method, the redistribution of residual stress due to the layer removal by electrochemical polishing is simulated using Model Change technique. And the comparison between the prediction and experiment indicates that this improved 3D periodic FE modeling of multi-shot impingement provides very accurate simulation models for one-step and dual-step shot peening. It can substitute for the costly and time-consuming optimization experiments of the shot peening process, especially the multi-step shot peening process. Finally, the evolution of residual stress depth profile in dual-step shot peening process is investigated by using the simulation model and a variation of residual stress towards a more uniform distribution on the finished surface taking place in the second step is discovered by RMS analysis.     

喷丸三维残余应力场的有限元模拟

运用大型有限元计算软件ABAQUS建立了模拟喷丸残余应力场的三维有限元模型,预测了在相同喷丸强度下玻璃丸和钢丸两种类型弹丸喷射所产生的残余应力场。模拟过程中,分析了线性减缩积分单元的沙漏参数、材料的应变硬化率、喷丸覆盖率以及初始残余拉应力等因素对304不锈钢靶材残余应力分布的影响。从计算结果可以看出,钢丸喷丸产生的残余压应力层较深,但在高覆盖率时,玻璃喷丸产生的残余压应力的平均值比钢丸喷丸处理后产生的大。在有初始残余拉应力(250 Mpa)存在的情况下,两种类型的喷丸处理均能使304不锈钢靶材表面形成残余压应力层,这说明喷丸工艺可以提高奥氏体不锈钢焊接构件的抗应力腐蚀开裂能力。本研究成果为进一步探讨喷丸强化不锈钢焊接头抗应力腐蚀性能的机理奠定了基础。     

TiB_2/Al复合材料喷丸后微区残余应力的有限元模拟

采用ANSYS/LS-DYNA有限元分析软件建立了颗粒增强TiB2/Al复合材料的喷丸模型,并对喷丸后残余应力分布进行了预测;然后对复合材料进行了喷丸试验,对残余应力进行了检测;将试验结果与模拟结果进行了对比。结果表明:该复合材料喷丸后残余应力分布的试验结果与模拟结果基本相符;喷丸后最表层部分增强体呈拉应力状态,在材料残余压应力场内,由于增强体和基体材料力学性能的差异,增强体的残余应力值普遍大于基体中的。     

Shot peening simulation based on SPH method

Shot peening is a complex surface-treating process which is usually employed to improve the fatigue strength of metallic part or members. In dealing with shot peening simulation, existing literatures apply finite element method (FEM) to establish only a single shot or several shots models, thus the effect of a mass of shots impacting repeatedly and the interaction among adjacent shots are ignored. To overcome these defects of FEM models, smoothed particle hydrodynamics (SPH) coupled FEM modeling is presented, in which the shots are modeled by SPH particles and the target material is modeled by finite elements. Contact algorithm is used to simulate the interaction between shots and target. Utilizing this model, material model for shots is established, the relationships between compressive residual stress and peening frequencies, coverage, and velocities are analyzed. Steady compressive residual stress can be gotten by multiple peening; higher coverage can improve the compressive residual stress; faster velocities can induce greater and deeper maximum residual stress in target subsurface. The simulation results agree well with the existing experimental data. The study will not only provide a new powerful tool for the simulation of shot peening process, but also be benefit to optimize the operating parameters.     

Simulation on Residual Stress of Shot Peening Based on a Symmetrical Cell Model

The symmetrical cell model is widely used to study the residual stress induced by shot peening. However, the correlation between the predicted residual stresses and the shot peening coverage, which is a big challenge for the researchers of the symmetrical cell model, is still not established. Based on the dynamic stresses and the residual stresses outputted from the symmetrical cell model, the residual stresses corresponding to full coverage are evaluated by normal distribution analysis. The predicted nodal dynamic stresses with respect to four corner points indicate that the equi-biaxial stress state exists only for the first shot impact. Along with the increase of shot number, the interactions of multiple shot impacts make the fluctuation of the nodal dynamic stresses about an almost identical value more and more obvious. The mean values and standard deviations of the residual stresses gradually tend to be stable with the increase of the number of shot peening series. The mean values at each corner point are almost the same after the third peening series, which means that an equi-biaxial stress state corresponding to the full coverage of shot peening is achieved. Therefore, the mean values of the nodal residual stresses with respect to a specific transverse cross-section below the peened surface can be used to correlate the measured data by X-ray. The predicted residual stress profile agrees with the experimental results very well under 200% peening coverage. An effective correlation method is proposed for the nodal residual stresses predicted by the symmetrical cell model and the shot peening coverage.     

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。     

喷丸残余应力场有限元模拟研究进展

喷丸强化处理工艺可以显著提高金属材料的抗疲劳和抗应力腐蚀等性能,这与喷丸后在金属表面层形成的残余应力场紧密相关,因此对喷丸残余应力的大小及分布进行预测具有重要意义.对近年国内外喷丸残余应力场的有限元模拟进行评述,总结出6种典型的残余应力分析模型,分别是二维轴对称模型、四对称面模型、三对称面模型、双对称面模型、单对称面模...     

Numerical simulation of Almen strip response due to random impacts with strain-rate effects

Almen intensity is used in the shot peening industry as a standard measure of the residual stress during shot peening and it is employed to ensure the quality of the peening of identical parts. However, relating the intensity to the residual stresses in the strip needs to be established with confidence by realistic simulations. An improved FEM-based approach that simulates the actual process of Almen strip peening is presented in this paper. This approach has some unique features such as employing randomly located shots impacting on a slice of Almen strip and the inclusion of strain-rate dependent target material properties and the lateral deflection of the strip for improved accuracy. The intensity, the corresponding residual stresses and roughness match well with available experimental results. Further, it is shown in this study that the Almen intensity can be correlated well with the residual compressive stresses of the target material using a parameter that depends on the relative dynamic yield strength of the target material.     

喷丸强化在新能源汽车轴齿上的应用

针对某新能源输入轴上仿真安全因子偏低的齿轮进行喷丸强化,结合其喷丸强化重点区域进行了有效的工装和喷丸饱和曲线工艺设计。同时,对喷丸后的齿面粗糙度以及规定位置进行了残余应力测试。喷丸后的输入轴应力合格及满足整车耐久测试要求,确认合理的喷丸能有效改善轴齿的应力状态,提高其弯曲和接触安全系数。     

Numerical investigation of surface topography and residual stress after abrasive water jet sequential peening (AWJSP)

Abstract

This article reveals the formation mechanism of surface topography and the formation and coupling mechanism of residual stress field (RSF) after abrasive water jet sequential peening (AWJSP) that can sequential peening on the material surface at a certain distance interval, and proposes a mathematical model of surface dimple characteristic verified by simulation results. In addition, the influences of shot velocity v₀, shot radius R and the distance between the center of adjacent shots D_C on surface topography and RSF were also investigated. Results show the surface dimple forms resulting from the material plastic strain, and the residual stress (RS) is mainly induced by the unrecovered elastic strain resulting from the hindering of plastic strain. Decreasing v₀, R or D_C can decrease the surface roughness R_t, while increasing v₀ and R is beneficial to induce a large and deep compressive RS layer. D_C influences the whole distribution of compressive RS layer directly.     

1Cr12Ni2W1Mo1V铣削过程参数对残余应力影响研究

针对汽轮机末级动叶片在实际应用中的抗疲劳性能问题,文章通过对1Cr12Ni2W1Mo1V不锈钢进行不同参数下的加工试验,研究了过程参数对叶片表面残余应力的影响机理及规律。将不同组间的试验数据进行对比得出了结论,并对产生原因进行了分析,认为提高主轴转速有利于残余压应力的加大,而温度热应力对残余拉应力起着主导作用。可在不同加工参数条件下提高叶片表面的残余压应力,减少了后续的喷丸表面处理工序。     

FEM of residual stress and surface displacement of a single shot in high repetition laser shock peening on biodegradable magnesium implant

Laser shock peening (LSP) is one of the prominent surface processing techniques to improve the mechanical characteristics by inducing compressive residual stress on the specimen surface. Generally, LSP is performed using high energy, low repetition pulsed laser. Recently, High repetition laser shock peening (HRLSP) on biodegradable magnesium alloys has been reported. Increased speed and reduced operating costs are the key highlights of HRLSP. This work is aimed towards understanding of the residual stress profile beneath the specimen surface, where a Finite element method (FEM) has been proposed to show the ability of a tightly focussed nanosecond laser pulse for peening magnesium. The depth of maximum compressive residual stress of 48 MPa at 28 mm beneath surface was the result of the simulation. Also the Von Misses stress was analytically found to be 31.5 MPa, which is similar to the value from FEM at 30 MPa. Furthermore, the plastic displacement of FEM at 4.02 µm compares reasonably well with the experimental result at 3.698 µm, thereby validating the Finite element model. If increase in CRS can be created by single shot of laser pulse, it can be concluded that the same can be done beneath the entire magnesium surface using appropriate scanning protocols.

     

喷丸强化因素对钛合金固体粒子冲蚀抗力的影响

探讨了喷丸强化(SP)因素(残余压应力引入、表面粗糙度增大和表面加工硬化等)对Ti6Al4V钛合金固体粒子冲蚀(SPE)行为的影响和作用机制,为充分发挥SP改进航空发动机零部件服役性能的潜力提供依据。结果表明:Ti6Al4V合金表面直接喷丸处理,其SPE抗力无明显改变;SP处理后进行表面抛光,Ti6Al4V合金SPE抗力明显增加。SP造成的表面粗糙度增大导致了钛合金在大小冲击攻角下的SPE抗力的下降;SP引入的表面残余压应力对提高钛合金在90°大攻角下的SPE抗力起了重要作用,原因是SP残余压应力增加了裂纹闭合力和抑制了疲劳裂纹早期扩展;SP引起的表面加工硬化作用对提高钛合金在30°小攻角下的SPE抗力有重要贡献,这归于加工硬化提高了材料表面在小攻角下的微犁削抗力。     

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.     

Residual stress behaviors induced by laser peening along the edge of curved models

Laser peening (LP) induces high-magnitude compressive residual stresses in a small region of a component. The compressive residual stresses cause plastic deformation that is resistant to fatigue fracture. Fatigue cracks are generally nucleated at critical areas, and LP is applied for those regions so as to delay the crack initiation. Many critical regions are located on the edge of the curved portion of structures because of stress concentration effects. Several investigations that are available for straight components may not give meaningful guidelines for peening curved components. Therefore, in this paper, we investigate residual stress behaviors induced by LP along the edge of curved models. Three curved models that have different curvatures are investigated for peening performance. Two types of peening configurations, which are simultaneous corner shot and sequential corner shots, are considered in order to obtain compressive residual stresses along an edge. LP simulations of multiple shots are performed to identify overlapping effects on the edge portion of a curved model. In addition, the uncertainty calculation of residual stress induced by LP considering laser pulse duration is performed.     

考虑残余应力的螺旋锥齿轮接触疲劳裂纹萌生-扩展寿命计算方法研究

考虑渗碳、磨齿、喷丸等工艺产生的齿面残余应力,建立齿面接触应力与残余应力的复合应力场,提出一种螺旋锥齿轮接触疲劳裂纹萌生-扩展寿命计算方法。构建齿轮有限元接触分析模型,计算多轴交变接触应力场。考虑空间螺旋曲面残余应力分布的复杂性,将变曲率齿面离散为网状节点;测量各节点表面与次表面的残余应力,建立齿面残余应力场。基于Dang Van多轴疲劳准则,构建齿面裂纹萌生模型;计及残余应力与裂纹闭合效应,构建齿面裂纹扩展模型。计算复合应力场下齿轮接触疲劳寿命,研究残余应力对齿面裂纹萌生-扩展寿命的影响规律。结果发现：复杂齿面空间变曲率会影响喷丸等工艺产生的残余应力分布,中心区域的残余压应力高出齿面边缘区域约20%;复合应力场下齿面裂纹萌生位置与寿命主要取决于接触应力,残余应力会改变齿面节点平均应力进而影响疲劳寿命;齿面裂纹扩展寿命约占全寿命的10%,表征齿轮接触疲劳快速失效至迅速断裂。上述研究对于高性能齿轮传动的长寿命、高可靠性设计具有一定的参考价值。     

Effect of shot peening on the fretting wear of Ti–6Al–4V

In this paper, we report on the fretting wear behaviour of polished and shot peened Ti–6Al–4V specimens. For fretting experiments, due to micro-displacements at the interface between two contacting surfaces, two types of damage can be observed: crack initiation and debris formation. Shot peening, which is already well known for improving fatigue resistance of titanium alloys, is shown to have a beneficial effect on the crack initiation and propagation under fretting wear loading, as cracks observed on specimens after cylinder-on-flat fretting tests are shorter in shot peened specimens than in polished ones. It is also demonstrated that shot peening decreases the friction coefficient only at the beginning of the test, as long as the asperities induced by shot peening are not worn-off. The effects of displacement amplitude, normal force and test duration on the wear volume have been investigated: in all cases, shot peening has no significant impact on the wear process. The same amount of debris are formed and ejected for both polished and shot peened specimens. Moreover, it is found that, for both types of specimens, the linear relation, developed for steels and hard coatings, between wear volume and cumulated dissipated energy is not valid in the present case as different wear volumes are measured for the same cumulated dissipated energy, depending on the experimental conditions (normal force, displacement amplitude). Using the test duration as the variable parameter, energy wear coefficients are calculated for different experimental conditions.     

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.