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.     

Relation between roughness and processing conditions of AISI 316L stainless steel treated by ultrasonic shot peening

This article assessed the roughness induced by ultrasonic shot peening. Surface properties of AISI 316L steel specimens were modified through the variation of ultrasonic shot-peening parameters (shot material, shot diameter, sonotrode amplitude vibration and coverage). Each surface was characterized using fifty surface roughness parameters and two types of robust Gaussian filter (low pass and high pass) associated with twenty one cut-off lengths. For each type of processing parameter, the most relevant roughness parameter and its corresponding length scale and filter were found. A linear relationship was identified between the four ultrasonic shot-peening parameters and the mean density of furrows with a coefficient of determination equal to 0.97.     

Relation between surface hardening and roughness induced by ultrasonic shot peening

This paper is focused on the identification of a relation between surface hardening and roughness induced by ultrasonic shot peening. A method that dissociates the influence of roughness from the value of the true macroscopic hardness is applied to AISI 316L stainless steel specimens treated using different processing conditions. The true macroscopic hardness is identified and used to determine the surface roughness parameter and scale that give the best relation between hardness and roughness. A relation is identified between the five point pit height S_5V roughness parameter (local depth of roughness) and hardness using a high-pass filter with a cut-off of 100 µm. This power function was identified at a scale that corresponds to the size of the shot impacts.     

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。     

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。     

Experimental investigation of shot peening: correlation of pressure and shot velocity to Almen intensity

The International Journal of Advanced Manufacturing Technology - Shot peening is a mechanical surface enhancement process that is extensively used in various industries to increase fatigue life of...     

超声喷丸中级联式变幅杆的动力学特性研究

超声强化能有效地提高工件的疲劳极限,延长其疲劳寿命.丸粒速度是影响超声喷丸强化效果的重要因素,而变幅杆振幅的提高可以显著地提高丸粒速度.以提高变幅杆振幅为目的,用解析法设计了级联式变幅杆;在此基础上,用ANSYS软件对其进行了动力学分析,得到了比单一变幅杆更大的振幅放大比.     

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.     

基于ANSYS/LS-DYNA的受控喷丸工艺过程仿真

将喷丸过程简化为丸粒撞击工件的模型,丸粒看作刚性体,运用ANSYS/LS-DYNA软件进行了数值模拟,分析了覆盖率对残余压应力分布的影响,得出在不完整喷丸覆盖率下工件表面会产生残余拉应力.在单个丸粒模型中,将丸粒的材料改为塑性硬化材料,分析丸粒的速度对残余压应力分布的影响,得出丸粒的材料参数一定时,存在最优喷丸速度,丸速过高会导致丸粒的变形能增加,而使工件表层的最大压应力值和应力层深度下降.     

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.     

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.     

Impact of surface hardening treatment generated by shot peening on the fatigue life of brass alloy

Brass alloy is widely used because of some attractive properties such as high electrical and thermal conductivity. But its fatigue performance after surface treatment is not very well explored in literature. Thus, in the present work, particular emphasis was given to the influence of surface treatment by shot peening on the fatigue life of brass alloy, throughout surface roughness and microstructural evolution. Fatigue tests were performed on unpeened, peened and peened then polished specimens. Various times of surface hardening treatment as 30, 60 and 120 min were considered. Experimental results reveal that the fatigue life of peened brass alloy decrease for all studied hardening treatment conditions. Surface roughness and microstructural properties showed large sensitivity to the shot peening process of brass alloy.     

AZ31B镁合金激光喷丸强化后疲劳裂纹扩展的数值模拟研究

激光喷丸(LSP)是一种先进的材料表面强化工艺,能有效提高零件的机械性能及其使角寿命.建立了以有限元软件ABAQUS和MSC.Fatigue为平台,面向抗疲劳制造的激光喷丸工艺有限元分析模型.结果表日月激光喷丸可以有效抑制疲劳裂纹扩展,延长疲劳寿命,喷丸次数的增加在一定程度上增大残余应力及疲劳寿命.残余应力抑制疲劳裂纹扩展的原因归结为最终断裂尺寸的增大以及裂纹扩展速度的减小.研究结果为LSP抗疲劳效果的预测提供了有效的方法,对于优化工艺参数,减少试验次数,降低成本具有指导意义.     

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...     

Energy saturation of metal parts in surface plastic deformation (shot peening)

A new algorithm simulating the change in surface plastic deformation during shot peening is described. Using this algorithm, metallic panels with specified curvature may be produced.     

Surface durability of shaved gears

Gears have become very vital positive transmission elements, finding numerous applications in small, medium and large machinery. With increasing demands for high strength materials for numerous applications, designers have found it necessary to develop new techniques to enhance the life of gears made of even low strength materials. Addendum correction, processing techniques and surface treatments are some of the techniques used for the above purpose. One of the faster and most economical of the above methods is gear shaving. Sufficient data on the performance characteristics of shaved gears are not available. The present paper highlights the performance characteristics of shaved gears, so far unpublished, from tests conducted on Forschungsstelle für Zahnräder und Getriebe apparatus. Scanning electron micrographs indicate that the pitting of shaved gears is occurring around oxides and other inclusions and is accompanied by delamination.Spectral analysis of the gear flanks shows that, apart from pitting, the entire wear profile follows the fatigue process.     

Empirical modeling of shot peening parameters for welded austenitic stainless steel using grey relational analysis

The attempt of this paper is to present an effective approach for the optimization of the shot peening process of welded AISI 304 austenitic stainless steel with multi performance characteristics using Grey relational analysis (GRA) based on Taguchi orthogonal array. Twenty-seven experimental runs are performed to determine best process parameters level. An analysis of variance (ANOVA) is carried out to identify significant peening parameters. The response tables are obtained for analyzing the optimal levels of shot peening parameters and major factors that affect the quality function. The multiple performance characteristics including tensile strength, surface hardness and surface roughness are the quality functions considered for the optimization. Further mathematical models are developed using regression analysis for the tensile strength, surface hardness and surface roughness. It will be very helpful to the engineers in deciding the levels of the shot peening parameters for desired performance characteristics.     

Some investigations into development of nozzle and suction system for air blast shot peening machine

Shot peening is an important surface enhancement process, which helps in assuring satisfactory fatigue life and reliability of the automotive, aerospace and marine components. One of the most important factors affecting shot peening performance is the type of shot peening machine. This paper presents an innovative design of a laboratory-based air blast shot peening machine. This machine has a vertical nozzle suction system to take the advantage of gravity feed as well as the feed created by suction of the pressurized air. Special attention was paid to the design of the nozzle and the mixing chamber so as to obtain adequate suction of shots. The performance of the machine was evaluated by carrying out various shot peening tests on AISI 1045 steel specimens. The tests included microscopic examination of coverage with ×10 magnification lens, fatigue and wear resistance. The wear resistance of the peened AISI 1045 material increased by 3.5 times the unpeened one. The fatigue tests showed improvement in fatigue life of the workpiece up to about four times. Besides, there was an increase in yield and torsional strength of the workpiece by about 1.5 times.     

Effect of shot peening coverage on fatigue limit in round bar of annealed medium carbon steel

Shot peening is an effective and economical technique for improving the fatigue strength of metallic components by inducing compressive residual stress and hardening the layer near the surface. The effect is generally evaluated by main two parameters: coverage and peening intensity. However, the valuable coverage for improving the fatigue strength depends on the shape of the target material. In this study, the effect of coverage on fatigue limit in round bar of annealed medium carbon steel was experimentally studied. The fatigue limits for shot peened round bar specimens with 140–2300% coverage increased 14–25% by comparing those for non-peened round bar specimens. The valuable range of coverage was 280–60% in the used material and shot peening condition for improving the fatigue limit in short time. The result indicates that the valuable coverage of the round bar material is higher than full coverage to improve the fatigue limit of the material due to the effect of incident angle on round bar, even though the degree depends on the materials and shot peening conditions.