共查询到20条相似文献,搜索用时 750 毫秒
1.
S. Anand Kumar S. Ganesh Sundara Raman T. S. N. Sankara Narayanan 《Transactions of the Indian Institute of Metals》2014,67(1):137-141
This work deals with the influence of surface mechanical attrition treatment (SMAT) duration on fatigue lives of Ti–6Al–4V. The SMAT process was carried out in vacuum with SAE 52100 steel balls of 5 mm diameter for 30 and 60 min at a vibrating frequency of 50 Hz. SMAT treated surface was characterized by electron microscopy. Surface roughness, nano-indentation hardness, residual stress, and tensile properties of the material in both SMAT treated and untreated conditions were determined. SMAT enabled surface nanocrystallization, increased surface roughness, surface hardness, compressive residual stress and tensile strength but reduced ductility. Samples treated for 30 min exhibited superior fatigue lives owing to positive influence of nanostructured surface layer, compressive residual stress and work hardened layer. However, fatigue lives of the samples treated for 60 min were inferior to those of untreated samples due to presence of microdamages or cracks induced by the impacting balls during the treatment. 相似文献
2.
T. Balusamy Satendra Kumar T. S. N. Sankara Narayanan 《Transactions of the Indian Institute of Metals》2011,64(4-5):507-511
Stainless steels are widely used as orthopedic implant materials. The main problems with these implant materials are fatigue fracture, fretting fatigue, wear and corrosion. Surface mechanical attrition treatment (SMAT) is a newly developed method to improve the materials properties and performance. In the present study, AISI 304 SS was subjected to SMAT using 2, 5 and 8 mm ? 316L SS balls for 15, 30, 45 and 60 min at 50 Hz under vacuum. SMAT of 304 SS increased the surface roughness, induced the formation of mechanical twins, strain induced martensite phase, and increased the defect density, which is a function of the size of the balls and treatment time. SMAT using 5 and 8 mm ? balls significantly decreased the corrosion resistance whereas treatment using 2 mm ? balls enabled an anodic shift in Ecorr and a marginal decrease in icorr. However, increase in surface roughness leads to the formation of a defective passive film and a decrease in breakdown potential. 相似文献
3.
Charudatta Pathak Prathamesh Dodkar 《Transactions of the Indian Institute of Metals》2020,73(3):571-576
This paper investigates the effect of shot blasting and shot peening parameters on residual stresses induced in connecting rod. Compressive residual stresses are induced using shot peening to increase fatigue life of connecting rod. Shot peening is also responsible for increase in surface roughness. Surface roughness is detrimental for fatigue life of the connecting rod. This necessitates shot blasting to reduce surface roughness. Shot peening and shot blasting processes are analysed to find optimum process parameters which will induce required value of compressive residual stress on the surface of connecting rod. Compressive residual stresses induced in the connecting rod specimen have been experimentally measured using X-ray stress analyser. The experimental results have been analysed using grey relational analysis to find optimum values of process parameters for target value of compressive residual stress and surface roughness. The experimental investigation and the analysis of it have resulted in achieving the desired value of compressive residual stress, which is 10.5% higher over the existing connecting rod. Surface roughness also decreases to 3.84 Ra which is 8.5% lesser than specified value to achieve better fatigue life. 相似文献
4.
S. Ganesh Sundara Raman B. Rajasekaran 《Transactions of the Indian Institute of Metals》2008,61(6):465-471
The present study compares the performance of alumina coatings prepared by two different methods (micro arc oxidation (MAO)
and detonation gun (D-gun) spray) on AA 6063 (Al alloy) fatigue test samples under plain fatigue and fretting fatigue loading.
While MAO coating had comparable proportions of γ-Al2O3 and α-Al2O3, D-gun sprayed coating contained γ-Al2O3 with minimal quantities of α-Al2O3. MAO coating was relatively harder than D-gun sprayed coating. As both types of coated samples were ground, they exhibited
almost the same surface roughness. D-gun sprayed alumina coated samples exhibited slightly higher magnitude of surface residual
compressive stress compared with MAO coated specimens. Both types of coated samples experienced almost the same friction force.
D-gun spray coated samples exhibited superior plain fatigue and fretting fatigue lives compared with MAO coated specimens.
This may be attributed to layered structure of the D-gun sprayed coating. 相似文献
5.
采用扫描电镜、显微硬度仪、X射线应力测量仪及透射电镜等对激光冲击强化Ti6Al4V合金的表面完整性进行了分析,采用MTS疲劳试验机测试了疲劳性能,并采用扫描电镜分析了疲劳断口,探讨了激光冲击强化机制。结果表明:经功率密度为15.9 GW/cm^2的激光处理后,其四点弯曲中值疲劳寿命较未处理试样提高了4.2~23.5倍;激光功率密度越大,试样的中值疲劳寿命越长。激光冲击强化表现出比喷丸强化更优的疲劳寿命增益效果。经激光冲击强化后,Ti6Al4V合金表面形成了深度为600~1400μm的残余压应力场,表面硬度比未强化区域提高了约10%,且亚表层内部的位错密度也有显著提高。 相似文献
6.
M. Burak Toparli Niall Smyth Michael E. Fitzpatrick 《Metallurgical and Materials Transactions A》2017,48(4):1519-1523
Two 2.0-mm-thick aluminum sheets were laser peened and the resulting residual stresses were measured using incremental hole drilling, surface X-ray diffraction, and synchrotron X-ray diffraction techniques. Laser peening was applied to two samples using the same laser peening parameters, but one of the samples has a larger peened area. The aim of this research was to discover the effect of peen area on residual stress, for application in aerospace structures for fatigue life enhancement. It was found that a larger peened area has higher and deeper compressive stresses in the crack-opening direction, leading to greater enhancement of fatigue life. 相似文献
7.
《Baosteel Technical Research》2010,4(4):8-12
Dissolution of cementite was found in the surface layer of 1.0C-1.5Cr steel plates during the process of surface mechanical attrition treatment(SMAT),and its evolution was characterized by transmission electron microscope(TEM),three-dimensional atom probe(3DAP)and Mssbauer spectroscopy.The average grain size contained in the top surface of SMAT specimen was 10nm,and no diffraction ring corresponding to cementite grain was identified in the selected area election diffraction(SAED)pattern,which indicated the disappearance of cementite.3DAP analysis showed the average carbon concentration in ferrite(0.75 at%)after SMAT,which was almost 100 times higher than that in matrix(0.008 at%),which suggested cementite dissolve in the process of SMAT.The results of Mssbauer spectroscopy indicated that partial cementite dissolved in the process of SMAT,the saturation of cementite dissolution is about 47%.Evolution of cementite involved three sub-stages:①inoculation stage,in the first 5 min of treated duration,cementite fraction is reduced only by 0.4%;②dissolution stage,within the following 25 min cementite fraction significantly is reduced from 14.6% to 8.4%;③saturation stage,when treatment exceeds 30 min,the fraction of cementite nearly remains the same. 相似文献
8.
A nanocrystalline layer was synthesized on the surface of TWIP steel samples by surface mechanical attrition treatment (SMAT) under varying durations. Microhardness variation was examined along the depth of the deformation layer. Microstructural characteristics of the surface at the TWIP steel SMATed for 90 min were observed and analyzed by optical microscope, X-ray diffraction, transmission and high-resolution electron microscope. The results show that the orientation of austenite grains weakens, and α-martensite transformation occurs during SMAT. During the process of SMAT, the deformation twins generate and divide the austenite grains firstly; then α-martensite transformation occurs beside and between the twin bundles; after that the martensite and austenite grains rotate to accommodate deformation, and the orientations of martensite and between martensite and residual austenite increase; lastly the randomly oriented and uniform-sized nanocrystalline layers are formed under continuous deformation. 相似文献
9.
Chunsheng Wen Ph.D. Zi Chen Baoxu Huang Ph.D. Yonghua Rong 《Metallurgical and Materials Transactions A》2006,37(5):1413-1421
A nanostructured surface layer was formed in Fe-30 wt pct Ni alloy by surface mechanical attrition treatment (SMAT). The microstructure
of the surface layer after SMAT was investigated using optical microscopy, X-ray diffraction, and transmission electron microscopy.
The analysis shows that the nanocrystallization process at the surface layer starts from dislocation tangles, dislocation
cells, and subgrains to highly misoriented grains in both original austenite and martensite phases induced by strain from
SMAT. The magnetic properties were measured for SMAT Fe-30 wt pct Ni alloy. The saturation magnetization (M
s
) and coercivity (H
c
) of the nanostructured surface layers increase significantly compared to the coarse grains sample prior to SMAT. The increase
of M
s
for SMAT Fe-30 wt pct Ni alloy was attributed to the change of lattice structure resulting from strain-induced martensitic
transformation. Meanwhile, H
c
was further increased from residual microstress and superfined grains. These were verified by experiments on SMAT pure Ni
and Co metal as well as liquid nitrogen-quenched Fe-30 wt pct Ni alloy. 相似文献
10.
为研究微晶刚玉砂轮成型磨削20CrMnTi齿轮的表面完整性,开展了20CrMnTi齿轮成型磨削试验,分析了砂轮线速度、轴向进给速度及径向进给量对齿面粗糙度、表层/次表层显微硬度、微观组织和残余应力的影响规律,探讨了由磨削引起的磨削烧伤、微观裂纹等损伤缺陷的形成机理,结果表明:径向进给量对表面粗糙度的影响最显著,砂轮线速度次之,轴向进给速度最不显著;磨削温度过高会导致磨削烧伤,淬火烧伤使得表面硬度提高5%~20%,回火烧伤则导致表面硬度不同程度地下降;表层组织从外至内分别为白层、暗层和基体组织,白层主要由致密的马氏体+碳化物+残余奥氏体组成;砂轮线速度和径向进给量的增大使得由磨削引起的残余拉应力增大,表面残余压应力下降并逐渐向拉应力转变,当表面最终残余拉应力大于材料的断裂强度时,表面产生微观裂纹. 相似文献
11.
Reversed-bending fatigue tests of quenched and tempered AISI 6150 steel were conducted in dry air and in aqueous 3 pct NaCl.
The 3 pct NaCl environment drastically reduced fatigue life but two different shot peening treatments were found to improve
the corrosion fatigue life over that of unpeened samples. Multiple fatigue crack initiation occurred at very distinct locations
in both the unpeened and the peened specimens fatigued in 3 pct NaCl. Fatigue crack propagation from each initiation site
occurred first on flat facets normal to the stress axis and then by a more ductile mechanism after the initiation facets had
linked. The average size of the corrosion fatigue initiation facets in the peened specimens was much smaller than that of
the unpeened specimens; however, the number of initiation sites was greater in the peened specimens. It is believed that the
beneficial effect of the shot peening results from significantly reduced early fatigue crack propagation rates in the compressive
residual stress layer at the surface.
Formerly Research Assistant, Materials Department, University of Wisconsin-Milwaukee 相似文献
12.
H. C. F. Rozendaal E. J. Mittemeijer P. F. Colijn P. J. Van Der Schaaf 《Metallurgical and Materials Transactions A》1983,14(2):395-399
On nitriding iron specimens nitrogen concentration profiles within the specimens are built up. A numerical method for the
calculation of such concentration profiles was developed. The results calculated were compared with experimental data. It
was found that during nitriding the nitrogen surface concentration approached relatively slowly the equilibrium value. This
effect strongly influenced the development of the nitrogen concentration profile. The model predicted correctly the incubation
time for compound(i. e., iron nitride) layer formation at the surface. If the fatigue resistance is strongly dependent on the (compressive) residual
surface stress, the present treatment allows calculation of anoptimum nitriding time by determining when the maximum (compressive) residual surface stress occurs. 相似文献
13.
B. B. Bartha J. Zawadzki S. Chandrasekar T. N. Farris 《Metallurgical and Materials Transactions A》2005,36(6):1417-1425
High-precision machining such as hard turning changes the surface and the material properties of steel alloys. The near-surface
material properties have been predicted from the known hard-turning cutting conditions. The effect of the predicted hard-turned
surface and material properties on wear performance was analyzed in detail to develop a process-performance model. A sliding
block-on-cylinder wear tester was used for the purpose of testing the wear performance of AISI 52100 bearing steel. The microstructure,
surface roughness, residual-stress field, and loading conditions from each wear test were used to develop the process-performance
model. The effect of microstructure on the wear performance of hard-turned steel showed that the white layer and overtempered
martensite (OTM) had a higher wear resistance than martensite. The wear-mechanism dependence on the surface hardness was attributed
to this increase in wear performance. The near-surface residual stress of the material was shown to become more compressive
as the material wore down. The applied normal loads affected the surface roughness, residual stresses, and, in turn, the wear
performance of the material. A process-performance model was developed to predict the wear performance of hard-turned steels,
which considers the machining process and the operating conditions in sliding wear. 相似文献
14.
The stress-failure (S-N) curves for ferritic irons, pearlitic irons, and austempered ductile irons (ADIs) have been determined
under tension-tension loading with a stress ratio of 0.1. The effects of Ti contents of up to 0.10 wt pct (resulting from
the deliberate use of Ti-containing steel scrap) on fatigue behavior were investigated. It was found that ferritic and pearlitic
ductile irons can contain up to 0.10 wt pct Ti without any adverse effect on fatigue behavior. In ADIs, fatigue properties
deteriorate at such high Ti contents. Tests were also conducted to investigate the effects of microstructural features on
fatigue properties. It was found that the effect of the graphite nodule count (the number of graphite particles on a unit
area of a polished surface) on the fatigue limit is significant only in ADIs. Scanning electron microscope (SEM) analysis
has shown that cracks usually initiate from surface dross-type defects. However, in ADIs, fatigue cracks can also initiate
at shrinkage cavities and at surface or subsurface locations. An offset bilinear S-N curve behavior (the linear S-N curve
at higher stress levels is separated from the linear S-N curve at lower stress levels) has been observed in ADIs. This is
attributed to surface residual compressive stresses, which prohibit fatigue crack initiation from surface positions at lower
applied stress levels. In ferritic and pearlitic ductile irons, the offset bilinear S-N curve behavior is not observed because
of the rapid relaxation of the residual compressive stresses. 相似文献
15.
ZHANG Junbao WANG Aixiang and ZHANG Yujun Advanced Technology Division Research Institute Baoshan Iron & Steel Co. Ltd. Shanghai China 《Baosteel Technical Research》2010,4(4):17-21
Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are characterized by means of X-ray diffraction(XRD)and transmission electron microscopy(TEM).The friction and wear properties are also investigated by a UMT-2 friction and wear tester.Experimental research has indicated that the average diameter of nanocrystalline grains in the surface layer after being treated for 15 min is in the range of 10-20 nm,and ferrite and cementite grains can not be identified by their morphologies.The wear-resistance of the specimen treated for 15 min has been doubled,compared with that of the matrix due to the grain refinement to a nano-sized scale.The lowest friction coefficient is 0.27,which is for the specimen treated for 30 min,resulting from the dissolution of the cementite phase and the formation of a relative homogenous structure.The SMAT technique for enhancing the wear-resistance of the 1.0C-1.5Cr steel has an optimum processing time,which is in the range of 15-30 min.The dominant wear mechanism of the specimen treated for 15 min changes from adhesive wear into particle wear. 相似文献
16.
17.
The present work was aimed at evaluating the effects of shot-peening on the high cycle fatigue performance of the age-hardening aircraft alloy Al 2024 at different almen intensities. Shot-peening to full coverage (100 pct) was performed using spherically conditioned cut wire (SCCW 14) with an average shot size of 0.36 mm and at almen intensities of 0.1, 0.2, and 0.3 mmA. After applying the various mechanical surface treatments, the changes in the surface and near-surface layer properties such as microhardness, residual stress-depth profiles, and surface roughness were determined. The microhardness, surface roughness, and the residual stresses increased proportionally with the almen intensity. Electropolitically polished conditions were used as reference in the mechanically surface treated specimens. A significant improvement was seen in the fatigue performance of the 0.1 mmA. 相似文献
18.
Changwoo Jeon Chang Young Son Choongyun Paul Kim Sunghak Lee 《Metallurgical and Materials Transactions A》2012,43(2):471-478
In this study, the fatigue properties of a shot-peened Zr-based amorphous alloy containing ductile crystalline particles were
investigated, and fatigue processes were analyzed and compared with those of a non–shot-peened (as-cast) alloy. The microstructural
analysis results of the shot-peened alloy surface indicated that the flexion and microstructural deformation were observed
as the hot-peening time or pressure increased. However, the compressive residual stress formed on the shot-peened surface
was approximately half of the ultimate tensile strength and was not varied much with shot-peening time or pressure. The fatigue
limit and fatigue ratio of the shot-peened alloy were 368 MPa and 0.24, respectively, which were considerably higher than
those of the as-cast alloy. This was because the compressive residual stress formed by the shot peening induced the initiation
of fatigue cracks at the specimen interior instead of the specimen surface and, thus, enhanced the overall fatigue limit and
fatigue life. These findings suggested that the shot peening was useful for improving fatigue properties in amorphous alloys. 相似文献
19.
Hideki Yamagishi Mikio Fukuhara Hiroaki Matsumoto Akihiko Chiba 《Metallurgical and Materials Transactions A》2010,41(8):2151-2161
Nondestructive evaluation of cyclic-tension fatigue in a rolled magnesium alloy, Mg-3Al-1Zn, was performed using vertically
polarized shear wave (SV) reflection and shear horizontal wave (SH) transmission methods. Internal friction measured by SV
reflection increased rapidly in the early stages of the fatigue and finally saturated, showing dominating interactions of
movable dislocations and twinning boundaries with the waves as acoustic nonlinearities. The propagation time and logarithmic
damping ratio in the SH transmission method followed a repeated increase and subsequent sudden decrease pattern, and finally
converged toward fatigue failure due to acoustoelasticity, which represents the interaction with residual stresses. The wave
and phase data were determined using an optical microscope, a scanning electron microscope, a surface roughness tester, and
X-ray diffraction. The results demonstrated that during the fatigue process, residual stress accumulated on the compressive
side of the specimen, despite the applied cyclic-tension loading. Brittle cracks that originated in inclusions provided sudden
relief from the residual stress. 相似文献
20.
Thomas K. Hirsch Alexandre Da S. Rocha Fabiano D. Ramos Telmo R. Strohaecker 《Metallurgical and Materials Transactions A》2004,35(11):3523-3530
Plasma nitriding of tool materials is common practice to improve the wear resistance and lifetime of tools. Machining-induced
compressive residual stresses in shallow layers of some tenths of microns are observed accompanied by other characteristic
properties of machined surfaces in these high-strength materials. After plasma nitriding of M2 high-speed steel, previously
induced compressive residual stresses remain stable and the depth of diffusion layers decreases with increasing compressive
residual stresses. This article reports investigations of plasma nitrided samples with different levels of residual stresses
induced prior to the nitriding process. For comparison, experiments with bending load stresses during plasma nitriding have
also been carried out. The plasma nitriding treatment was performed at constant temperature of 500 °C with a gas mixture of
5 vol pct N2 in hydrogen. Nitriding time was varied from 30 to 120 minutes. All samples were characterized before and after plasma nitriding
concerning microstructure, roughness, microhardness, chemical composition, and residual stress states. Experimental results
are compared with analytical calculations on (residual) stress effects in diffusion and show a clear effect of residual and
load stresses in the diffusion of nitrogen in a high-strength M2 tool steel. 相似文献