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。     

喷丸强化提高齿轮寿命

本文叙述了喷丸强化的作用,原理与使用范围。     

齿轮喷丸强化与疲劳寿命试验

本文介绍齿轮喷丸强化延长疲劳寿命的机理及喷丸工艺参数对残余应力的影响,并经上海汽车齿轮厂应用验证。     

表面喷丸工艺提高金属材料疲劳性能试验分析

在航空航天等领域,疲劳失效甚至占到所有零件失效的80％～90％,金属材料的表面强化技术,例如表面喷丸工艺成本较低且适用场景广泛而被工业界和研究人员关注.介绍了ZK60镁合金、Ti60钛合金以及0Cr13Ni8Mo2Al钢在喷丸处理前后疲劳寿命的对比,说明了喷丸技术对多种金属构件的疲劳性能的提升具有非常显著的效果.通过喷丸等表面强化技术可以很好地提高材料的疲劳寿命,从而避免危险事故的发生,节约经济成本.     

圆柱螺旋弹簧的喷丸强化研究

本文对弹簧喷丸强化后的表面残余应力及其在疲劳过程中的松弛，以及喷丸强化对疲劳性能的影响等进行了研究。结果指出，在适宜的喷丸强化工艺下，喷丸弹簧可达到国际上公认的２．３×１０＾７次数的疲劳寿命。     

喷丸强化提高齿轮寿命

本文叙述了喷丸强化的作用,原理与使用范围.     

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。     

300M超高强度钢喷丸强化工艺中的打磨问题

文中指出300M钢喷丸强化工艺中打磨对喷丸效果(残余应力及疲劳性能)的影响问题;通过X射线应力测定,研究喷丸及打磨后试样的残余应力分布及变化的特点;通过三点弯曲疲劳试验,研究喷丸后打磨对试样疲劳性能的影响;在此基础上,分析喷丸标准中规定喷丸后打磨去除量不可以超过阿尔门(Almen)强度值的1/10的原因.     

喷丸强化技术对弹簧疲劳寿命的影响

本文从喷丸对弹簧疲劳寿命影响的机理进行了从试验到理论的论述，从各个角度分析了喷丸的作用，并介绍了试验方法。     

喷丸强化对2024铝合金疲劳性能的影响分析

以2024铝合金材料为研究对象,开展了表面喷丸处理对材料疲劳性能的影响研究。采用试验方法对比分析了2024铝合金试件在喷丸强化前后的疲劳性能。在此基础上采用ABAQUS有限元软件模拟分析了喷丸强化后试件的残余应力分布规律。两组疲劳试验数据对比分析表明:喷丸强化后2024铝合金材料的疲劳寿命可以提高(1.53~2.55)倍。有限元分析结果表明:喷丸强化在材料表层引入了残余压应力,从而提高了材料的疲劳性能。分析结果为定量研究喷丸强化对材料疲劳性能的影响提供了参考。     

弹丸束喷丸有限元模型数值模拟及试验研究

喷丸工艺是一种有效提高工件表面疲劳抗力的表面处理工艺,被广泛应用在航空、汽车、动力机械等重要领域。喷丸数值模拟是制订喷丸工艺方案、评估喷丸后工件表面疲劳抗力的主要理论工具。目前,现有的喷丸数值模型主要有单弹丸模型、阵列弹丸模型等形式,在这些模型中,弹丸的撞击位置是固定的,忽略了真实的喷丸过程中弹丸位置的随机性。采用有限元计算软件ABAQUS提供的python语言开发一种弹丸在空间位置随机分布的弹丸束喷丸模型,在此模型基础上研究喷丸工艺参数与残余应力间的分布规律,进一步讨论喷丸工艺对工件表面粗糙度的影响,模拟喷丸强度的饱和过程,并通过Q235钢喷丸试验对弹丸束喷丸模型进行验证,为喷丸工艺的精确控制提供了科学依据和理论基础。     

The effects of laser peening and shot peening on fretting fatigue in Ti-6Al-4V coupons

This paper describes testing of Ti-6Al-4V coupons in fretting fatigue and compares the effects of mechanical surface treatments on performance. Fretting fatigue tests were performed using a proving ring for fretting load, bridge-type fretting pads, and applied tension-tension cyclic fatigue stress. As-machined (AM), shot peened (SP), and laser peened (LP) coupons were evaluated, and data generated to compare residual stress, surface condition, lifetime, and fractographic detail encountered for each. Near-surface residual stress in SP and LP coupons was similar. The layer of compressive residual stress was far deeper in LP coupons than in SP coupons and, consequently, subsurface tensile residual stress was significantly greater in LP coupons than in SP coupons. SP coupons exhibited a rough surface and had the greatest volume of fretting-induced wear. LP coupons exhibited a wavy surface and had a small volume of wear localized at wave peaks. SP coupons had the greatest fretting fatigue lifetime, with significant improvement over AM coupons. Lifetimes of LP coupons were similar to those for SP coupons at high fatigue stress, but fell between AM and SP coupons at lower fatigue stress. Fractographic evaluation showed that fractures of AM samples were preceded by initiation of fretting-induced cracks, transition of a lead fretting crack to mode-I fatigue crack growth, and crack growth to failure. SP and LP samples exhibited behavior similar to AM samples at high fatigue stress, but in coupons tested at low stress the lead crack initiated subsurface, near the measured depth of maximum tensile residual stress, despite the presence of fretting-induced cracks. The level of fatigue stress above which lead cracks were initiated by fretting was higher for LP than for SP, and was predicted with good accuracy using an analysis based on linear elastic fracture mechanics, the fatigue crack growth threshold stress intensity factor range, and superposition of measured residual stress and applied fatigue stress.     

An inverse approach to determination of residual stresses induced by shot peening in round bars

In this paper an analysis is presented to determine the distribution of a residual stress field from a limited incomplete set of measurements obtained from shot-peened round steel bars. Using an Airy stress function as the primary unknown the axisymmetric stress equations are solved directly. In this new method there exists the flexibility to impose physical conditions that govern the behavior of residual stress to achieve a meaningful complete stress field. This new method aims to achieve the best agreement between the model prediction and limited measured stress components in the sense of least squares approximation. The power of this new method is demonstrated by analyzing experimental data and achieving a good agreement between the model prediction and the results obtained from residual stress measurement.     

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.     

Influence of shot peening on the surface durability of thermomechanically treated En 24 steel spur gears

En steel, in untreated and thermal treated conditions, with and without shot peening, were tested in a back-to-back gear test rig. Their contact fatigue characteristics were studied and S–N curves have been established. Contact fatigue strength of shot peened gears for a given life showed an improvement in relation to unpeened gears.     

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.     

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...     

A non-local fatigue approach to quantify Ti-10V-2Fe-3Al fretting cracking process: Application to grinding and shot peening

This paper presents an experimental study on the tribological behaviour and cracking response of a Ti-10V-2Fe-3Al titanium alloy under fretting loading with a cylinder on plane configuration. Three types of surfaces were investigated: a polished one considered as the reference, a ground one and a shot peened surface. Surfaces were compared with respect to residual stress, hardness and roughness. The first step of this study was to determine sliding conditions and coefficient of friction of the three contact types. Next, fretting tests under stabilized partial slip regime were carried out to investigate crack nucleation and propagation. Results show that whatever surface roughness or residual stress in the material, tribological behaviour is the same. These latter confirm that sliding condition and coefficient of friction in partial slip regime is due to material effect and not to roughness or surface hardness. Then, residual stress induced by grinding or shot peening have no influence on the crack nucleation threshold under fretting solicitation because crack nucleation is only induced by a sufficient tangential loading. The crack nucleation threshold is formalized by applying the Crossland criterion taking into account the stress gradient and the ensuing “size effect”. As expected, cracks propagation is influenced by residual stress under the surface. Compared to the reference case, for a same loading parameters set, residual stress induced by grinding is not sufficient to decrease the crack length reached whereas effects of shot peening decrease highly these latter. So, there is a threshold of residual stress from which residual stresses are useful against cracking.     

Effect of shot peening on rolling contact fatigue and lubricant film thickness within mixed lubricated non-conformal rolling/sliding contacts

The effect of shot peening on rolling contact fatigue (RCF) and lubricant film thickness within non-conformal rolling/sliding contacts operated under mixed lubrication conditions was observed in this study. Rolling contact fatigue tests and film thickness measurements were carried out using specimens with modified surface topography by shot peening process using glass beads having diameter between 0.07 and 0.11 mm. It has been shown that the effect of shot peening on RCF has no positive effect even if shot peened surface of the roller exhibited somewhat higher hardness in contrast to the grounded surface. The reduction of RCF may be caused due to asperities interactions because after shot peening the surface roughness of the roller was increased. Film thickness measurements confirmed that the contact is realized actually only between asperity peaks of shot peened ball and smooth disc.Conversely, no negative effect on RCF was observed when the shot peened surface of the roller was polished. The polish of asperity peaks causes the creation of lands and micro-cavities, which may be employed as lubricant micro-reservoirs. From film thickness measurements it has been observed that lubricant emitted by shallow micro-cavities can provide the local increase in lubrication film thickness, which thereby reduces asperities interactions. Similar results were obtained for start-up conditions where the squeeze lubricant enlarges film thickness and reduces surface interactions.From the obtained results, it can be suggested that properly designed surface topography modification could help to increase the efficiency of lubrication films leading to the enhancement of contact fatigue life of non-conformal mixed lubricated rolling/sliding contacts.