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Abrasive waterjet (AWJ) peening has been proposed as a viable method of surface treatment for metal orthopedic devices. In this study the influence of AWJ peening on the compressive residual stress, surface texture and fatigue strength of a stainless steel (AISI 304) and titanium (Ti6Al4V) alloy were studied. A design of experiments (DOE) and an analysis of variance (ANOVA) were used to identify the primary parameters contributing to the surface texture and magnitude of surface residual stress. The influence of AWJ peening on the fatigue strength of the metals was evaluated under fully reversed cyclic loading. It was found that AWJ peening results in compressive residual stress and is primarily influenced by the abrasive size and treatment pressure. The residual stress of the AISI 304 ranged from 165 to over 460 MPa. Using the optimum treatment parameters for maximizing the residual stress, the endurance strength of Ti6Al4V was increased by 25% to 845 MPa. According to results of this study AWJ peening is a viable method of surface treatment for applications that require an increase in surface roughness and maintenance or increase in fatigue strength, qualities that most often are not available from a single process. 相似文献
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改善焊接接头疲劳强度超声冲击法的试验研究 总被引:2,自引:0,他引:2
利用自行研制的超声波冲击试验装置,对几种典型焊接结构用钢(Q235B和16Mn)的对接和十字接头(熔透)实施冲击处理.然后进行焊态与冲击处理态的弯曲与拉伸两种加载方式的疲劳对比试验.分别获得了各种情况冲击处理前后的σ-N曲线及条件疲劳极限(2×106周次).结果表明超声冲击处理后,Q235B对接接头条件疲劳极限(2×106周次)提高了57%(拉伸),十字接头(4点弯曲)提高了64%,能够提高疲劳寿命40~60倍左右.16Mn对接接头条件疲劳极限(2×106周次)提高了90%(拉伸),十字接头(拉伸)提高了67%,能够提高疲劳寿命多达30~100倍.超声冲击处理对16Mn疲劳强度与寿命的改善程度高于Q235B. 相似文献
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提高焊接接头疲劳强度的超声冲击法与TIG熔修法之比较 总被引:3,自引:0,他引:3
采用Q2 35B十字接头试件 ,就改善焊接接头疲劳强度的超声冲击法与TIG熔修法进行了全面对比。结果表明 :超声冲击处理对焊趾区硬度的影响不如TIG熔修明显 ;TIG熔修对焊趾几何外形的改善程度好于超声冲击法 ;TIG熔修处理工艺在焊趾区引入了残余拉应力 ,而超声冲击在焊趾区形成了较大数值的压缩应力。Q2 35B十字焊接接头经TIG熔修后 ,其疲劳强度 (2× 10 6 )提高 5 1% ,低于超声冲击处理对相同试件的疲劳强度 (2× 10 6 )改善程度 (6 4% )。 相似文献
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超声冲击处理焊接接头疲劳设计若干问题的探讨 总被引:1,自引:0,他引:1
对大量超声冲击处理焊接接头的试验结果进行分析总结,探讨超声冲击焊接接头疲劳设计与原始焊接接头的差异,并得到下述结论:①材料强度对超声冲击方法改善焊接接头疲劳性能的处理效果有一定影响,随着接头材料强度的提高改善效果也越好,因此采用低强钢超声冲击处理焊接接头的疲劳试验结果得到疲劳设计S—N曲线是安全的。②超声冲击处理焊接接头试件S—N曲线的斜率m远大于3(6~23),不能将试验结果硬性规定按m=3.0进行统计处理,推荐取m=10。③经过超声冲击处理后其疲劳强度不再与所外加的平均应力无关,而是随着应力比R的增加,接头所能够承受的疲劳应力幅度有所降低。因此建议采用最大应力对超声冲击处理焊接接头进行疲劳设计。④当采用最大应力对超声冲击处理焊接接头进行疲劳设计时,外载荷中所含平均应力与超声冲击处理焊接接头在FAT(200万次循环次数下的特定疲劳强度,将其定为疲劳级FAT)下的疲劳强度(应力范围)之间.的关系为:F(R)=1.25-0.5R,-1≤R≤0.5。 相似文献
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Balaji Sadasivam 《Machining Science and Technology》2013,17(1):71-95
Abrasive Waterjet Peening (AWJP) has emerged as a potentially viable method of surface treatment for components requiring compressive residual stress and a rough surface texture. In the present investigation the residual stress distributions resulting from AWJP of Ti6Al4V with load and displacement control flexure pre-stress were compared. An experimental evaluation was conducted to quantify the variations in the residual stress characteristics (magnitude and depth) as a function of boundary conditions over a pre-stress ranging from 0 to 75% of the material's yield strength. In addition, a finite element model for indentation-based surface treatments was developed to investigate the mechanisms contributing to the observed trends in experimental results. Overall, AWJP of the Ti6Al4V resulted in a surface residual stress ranging from approximately 800 to 1600 MPa. Load control pre-stress resulted in a larger surface residual stress (up to 50% greater) than that achieved under displacement control treatments. Although the maximum surface residual stress was obtained at the largest applied pre-stress, the difference between load and displacement control treatments decreased with pre-stress magnitude. Boundary conditions had limited influence on the depth of residual stress achieved, but were important to the depth of plasticized zone beneath the treated surface. 相似文献
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超声冲击法提高低碳钢焊接接头疲劳强度的研究 总被引:13,自引:1,他引:13
焊接结构中,焊接接头的疲劳强度远远低于母材的疲劳强度。大量的实验表明,疲劳裂纹主要起源于接头焊趾处,因此处理焊接接头焊趾将会提高接头的疲劳强度。文中利用自行研制的超声波冲击实验装置,对提高低碳钢焊接接头疲劳强度进行了研究。 相似文献
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超声波冲击与TIG熔修复合强化改善高强钢焊接接头的疲劳性能 总被引:2,自引:1,他引:2
研究表明超声波冲击方法与TIG熔修方法在提高焊接接头疲劳性能机理方面存在着很强的互补性。提出一种对接头焊趾先进行一遍TIG熔修处理,然后再实施超声波冲击的复合处理新方法用来改善焊接接头的疲劳性能。对比疲劳试验结果显示:①在一定的应力范围内,超声波冲击处理试件与原始焊态试件相比,疲劳强度提高95%左右,疲劳寿命延长3.6-62倍。②TIG熔修试件与原始焊态试件相比,疲劳强度的改善程度高达34%左右;在较高应力范围内,疲劳寿命没有提高:在低应力范围内,延长疲劳寿命约为0.4—1.3倍。③超声波冲击+TIG熔修复合强化试件与原始焊态试件相比,疲劳强度提高120%左右,疲劳寿命延长28—125倍。④TIG熔修+超声波冲击复合处理能够在TIG熔修和超声波冲击处理的基础上,进一步改善焊接接头的疲劳性能;与单纯的超声波冲击相比,在高应力区域内,TIG熔修+超声波冲击复合处理一定程度上克服了单纯的超声波冲击对所处理的焊接接头疲劳性能改善程度大幅度降低的缺点。 相似文献
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由于焊趾部位存在有应力集中和残余拉伸应力,焊接接头的疲劳强度远低于基体金属,超声冲击和低相变点焊条的应用是近年来发展的提高焊接接头疲劳强度方法。通过对横向对接焊接接头和纵向角接板焊接接头试件的疲劳试验,在2×106循环次数下与普通E5015焊条焊态试件相比,超声冲击处理的两种型式接头的疲劳强度分别提高50%和71%,低相变点焊条焊接的两种型式接头的疲劳强度分别提高11%和41%,相应接头的疲劳寿命也有大幅度的提高。试验结果说明,两种方法都是提高焊接接头疲劳强度的有效方法,其中超声冲击方法的提高程度较高,而由于免去了焊后加工处理工序,低相变点焊条方法更适合于具有高值残余拉伸应力纵向焊缝焊接接头疲劳强度的改善。 相似文献
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环面蜗杆副疲劳强度的校核 总被引:2,自引:0,他引:2
提出了采用赫兹公式计算环面蜗杆副接触应力的方法:将蜗轮齿面沿接触线微分成无数细段,在每一段上应用赫兹公式。再对接触线进行积分,即可求出此条接触线上作用力与齿面强度的关系。根据环面蜗杆副的结构特点和空间啮合原理的研究成果,推导出了计算蜗轮齿面接触应力的计算公式。公式中含有蜗轮的齿面特征参数和几何参数,明确地表达了它们与接触应力之间的数学关系。为了解它们之间规律,改善环面蜗杆副的工作条件,提高其使用寿命,提供了科学的依据。并结合工程设计的特点,对计算公式进行了简化,建立了实用的校核环面蜗轮齿面疲劳强度和使用寿命的计算公式,从大量的计算结果中总结出有关系数,使环面蜗杆副的承载能力及使用寿命的计算校核有了一个专用的方法。应用推导出的公式成功地对蜗轮的承载能力进行与圆柱蜗杆副的对比核算。 相似文献
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ABRASIVE MACHINING OF GLASS-CERAMICS WITH A DENTAL HANDPIECE 总被引:1,自引:0,他引:1
X. Dong L. Yin S. Jahanmir L. K. Ives E. D. Rekow 《Machining Science and Technology》2000,4(2):209-233
Dental restorations are commonly prepared from machinable glass-ceramics using modern dental CAD/CAM systems. Unfortunately, little is understood about the influence of machining parameters on material removal rates and any damage which could be introduced into the restoration during the abrasive machining processes employed with these systems. These effects are investigated for three experimental machinable glass-ceramics with varying microstructure and one closely related commercial material. Abrasive machining is performed with dental burs containing coarse and fine diamond particles. The results show that the microstructure of the glass-ceramic, the size of diamond grit in the burs, and the load applied to the burs during machining have significant effects on the machining behavior. By increasing the size of the mica platelets within the glass-ceramics or by increasing the load on the burs, material removal rate increases. However, chipping damage at groove edges increases as either the load is increased or as the size of the mica platelets is decreased. The use of coarse burs does not necessarily result in high material removal rates but increases the extent of chipping damage. Surface roughness is found to be relatively independent of the microstructure or applied load but is strongly dependent upon coarseness of the diamond particles in the burs. 相似文献
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变幅载荷下超声冲击处理焊接接头的疲劳行为 总被引:4,自引:3,他引:1
为研究变幅载荷作用下超声冲击处理焊接接头的疲劳行为,采用非承载纵向角接接头进行了Q235B及16Mn钢原始焊态与超声冲击处理态的对比疲劳试验。试验结果表明:①在变幅载荷作用下,Q235B超声冲击处理试件与原始焊态试件相比,疲劳强度提高69%左右,疲劳寿命延长5.7~19.0倍。②在变幅载荷作用下,16Mn超声冲击处理试件与原始焊态试件相比,疲劳强度提高80%左右,疲劳寿命延长2.5~17.0倍。③在变幅载荷作用下,超声冲击处理焊接接头与原始焊态试件的疲劳性能均有所下降:Q235B超声冲击处理焊接接头的疲劳寿命约为恒幅载荷作用时的1/3,原始焊态的疲劳寿命约为恒幅载荷作用时的70%;16Mn超声冲击处理焊接接头的疲劳寿命约为恒幅载荷作用时的1/3,原始焊态的疲劳寿命约为恒幅载荷作用时的75%。④超声冲击处理焊接接头在承受强烈的变幅载荷时依然具有很高的疲劳强度。 相似文献
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通过对金属材料表面微单元体疲劳损伤随机演化的分析,建立了一种基于表面微单元体串联概率失效模型的构件概率疲劳强度估算方法。利用本方法对构件疲劳强度、疲劳寿命分布规律、疲劳尺寸系数等疲劳试验结果进行的验证计算表明,计算具有较高的估算精度。 相似文献
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An experimental investigation is presented to increase the depth of cut in abrasive waterjet (AWJ) cutting of alumina ceramics by introducing a new cutting technique combining multipass operations with controlled nozzle oscillation. Plausible trends of the depth of cut per pass and total depth of cut with respect to the number of passes and the parameters in each pass are discussed. It shows that cutting with nozzle oscillation can significantly increase the depth of cut in the single-pass cutting mode, while further gains in the depth of cut can be made by using multipass cutting with nozzle oscillation. While multipass cutting can be used to increase the total depth of cut for machining thicker materials, it has been found that an average increase of 50.8% in the total depth of cut can be expected by using multipass cutting with nozzle oscillation as compared to single-pass cutting without nozzle oscillation within the same cutting time. Recommendations are finally made as a practical guide for the selection of process parameters in multipass AWJ cutting of alumina ceramics with controlled nozzle oscillation. 相似文献