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1.
G. Madhusudhan Reddy P. Mastanaiah K. Sata Prasad T. Mohandas 《Transactions of the Indian Institute of Metals》2009,62(1):49-58
The influence of friction stir welding on the microstructure development and its role on residual stress distribution in the
weldment and mechanical properties has been investigated. The study also focused on the impact of post weld heat treatment
on the microstructure and mechanical properties as well as on residual stress distribution. The weld nugget region contained
fine equiaxed grains as a result of thermo-mechanical working. Hardness survey showed that nugget region is soft due to precipitates
dissolution. Weld joint exhibited lower strength as compared to the parent metal. Post weld Solution Treatment and Aging (STA)
of longitudinal welds resulted in strength and ductility equivalent to that of parent metal while transverse weld tensile
strength and ductility were lower than that of parent metal even after post weld STA. Residual stress distribution profiles
across the weld region are asymmetric with respect to weld centerline, with the largest residual; stress gradients occurring
on the advancing side of the weld. Within the region inside the shoulder diameter, residual stress is entirely compressive.
Welds exhibited tensile residual stresses in post weld STA condition 相似文献
2.
3.
Craig A. Brice William H. Hofmeister 《Metallurgical and Materials Transactions A》2013,44(11):5147-5153
Additive-manufactured aluminum alloy deposits were analyzed using neutron diffraction to characterize the effect of intermediate stress relief anneal heat treatment on bulk residual stresses in the final part. Based on measured interplanar spacing, stresses were calculated at various locations along a single bead, stacked wall deposit. A comparison between an uninterrupted deposited wall and an interrupted, stress-relieved, and annealed deposited wall showed a measureable reduction in residual stress magnitude at the interface with a corresponding shift in stress character into the deposit. This shift changes the interface stresses from purely compressive to partially tensile. The residual stress profile varied along the length of the deposit, and the heat-treatment procedure reduced the overall magnitude of the stress at the interface by 10 through 25 MPa. These results are interpreted in terms of thermal gradients inherent to the process and compared with prior residual stress-characterization studies in additive-manufactured metallic structures. 相似文献
4.
Residual stress measurements by x-ray diffraction in the ferritic-austenitic interface weldment 总被引:1,自引:0,他引:1
N. Sarafianos 《Metallurgical and Materials Transactions A》1993,24(9):2095-2106
A mathematical model of calculating residual stresses at the weld interface of ferritic-austenitic steels has been developed.
The Kurdjumov-Sachs orientation relationship (110)bcc[111]// (11 l)fcc[011] was determined at the interface of the transition joint. The resultant bcc-fcc lattice misfit gives rise to significant
residual stresses. The performed X-ray analysis establishes macro- and microstress profiles extending up to 22 mm and 55 μm,
respectively. The profiles indicate the development of compressive and tensile stresses on either side of the weld interface.
With respect to this, tensile stresses in increasing sequence were computed from the parent metal toward the interface and
compressive stresses were determined from the interface inward toward the weld bead in decreasing sequence. A remarkable stress
discrepancy between the two profiles was observed, with the macrostresses falling in the range of +185 to −245 MPa and the
microstress level ranging between +340 and −420 MPa. While the developed interfacial residual stresses are due to the difference
in the bcc-fcc lattice parameters, the discrepancy observed in the determined stress level has its origin in the varying percentage
of the two phases involved within a narrow mixing zone at the weld interface. 相似文献
5.
Textures, stresses, and strains, as well as the overall so-called real structure, are crucial for properties of thin films deposited by different methods and can have both positive and negative effects depending on the film and its application. They were studied by a combination of different X-ray diffraction (XRD) techniques for several ZnO films. The films prepared by pulsed laser deposition (PLD) on MgO and sapphire single-crystalline substrates and amorphous-fused silica showed different kinds of strong preferred orientation and also different stresses that could be estimated only from the analysis of quite narrow, nonzero intensity regions of diffraction spots. XRD line broadening was analyzed by a combination of different asymmetric scans. Fiber (0001) texture and tensile residual stresses were found on fused silica, while domains with local epitaxy and huge compressive stress were detected on MgO substrate, and surprisingly, very strong local epitaxy but not parallel to the (0001) sapphire substrate was observed. No residual stress was detected there. Some methodological aspects of the XRD studies of thin nanocrystalline films with strong preferred orientation are discussed. 相似文献
6.
Induction Heat Treatment of Sheet‐Bulk Metal‐Formed Parts Assisted by Water–Air Spray Cooling
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Hans‐Bernward Besserer Andrej Dalinger Dmytro Rodman Florian Nürnberger Philipp Hildenbrand Marion Merklein Hans Jürgen Maier 《国际钢铁研究》2016,87(9):1220-1227
In order to produce components with massive secondary functional elements from sheet metal bulk forming operations, termed sheet‐bulk metal forming, can be applied. Owing to high, three‐dimensional stress and strain states present during sheet‐bulk metal forming, ductile damage occurs in the form of micro‐voids. Depending on the material flow properties, tensile residual stresses can also be present in the components' formed functional elements. During service, the components are subjected to cyclic loading via these functional elements, and tensile residual stresses exert an unfavorable influence on crack initiation and crack growth, and therefore on the fatigue life. Following the forming process, temperature and microstructurally related compressive residual stresses can be induced by local heat treating of the surface. These residual stresses can counteract potential crack initiation on the surface or in the subsurface regions. In the present study, the adjustability of the residual stress state is investigated using a workpiece manufactured by orbital cold‐forming, which possesses an accumulation of material in its edge region. Based on residual stress measurements in the workpiece's edge region using x‐ray diffractometry, it is possible to verify the compressive residual stresses adjusted by varying the cooling conditions. 相似文献
7.
Xiaoya Dai Wenlong Zhang Ping Gao Shaozong Zhang Mingyuan Gu Hua-Xin Peng 《Metallurgical and Materials Transactions A》2014,45(3):1559-1566
The relationship between pretension and residual stress of an aluminum wire reinforced with 45 vol pct continuous Nextel? 610 alumina fibers is investigated. It is shown that as pretension stress increases, the matrix residual stress decreases. A transition in matrix residual stress from tension to compression occurs at a pretension stress of about 80 MPa. The initial rapidly decreased residual stress caused by pretension at relatively low pretension stresses is a result of matrix elastic compressive deformation; while the later gradually decreased residual stress at higher pretension stresses comes from matrix plastic compressive deformation. As the matrix yield stress and hardening exponent increase, the decrease in matrix residual stress with pretension stress is more rapid and the absolute value of matrix residual stress increases. An analytical model suitable for fiber-reinforced metal matrix composites (MMCs) with strong interfacial bonding is developed to describe the relationship between pretension and matrix residual stress and is shown to be in good agreement with the experimental and finite-element calculated results. The pretension-dependent matrix residual stress phenomenon suggests that the mechanical properties of fiber-reinforced MMCs associated with matrix residual stress may be effectively improved by applying tensile loads. 相似文献
8.
利用逐层钻孔法测试了直接淬火和水淬+空冷+水淬2种冷却工艺下的残余应力,分析了2种工艺下残余应力对裂纹产生和扩展的影响。结果表明:直接淬火工艺下,切向残余拉应力为229~281 MPa,轴向残余拉应力为191~237 MPa;水淬+空冷+水淬工艺下,切向残余应力为压应力,范围为-422~-185 MPa,轴向残余应力为拉应力,范围为90~190 MPa。与直接淬火工艺相比,优化冷却工艺使钢管切向应力变为压应力,轴向残余应力仍为拉应力但数值上减小,随孔深增加,轴向应力减小幅度趋于平缓,进而降低和缓解了钢管内微裂纹产生和扩展趋势。 相似文献
9.
J. B. Bai N. JI D. Gilbon C. Prioul D. François 《Metallurgical and Materials Transactions A》1994,25(6):1199-1208
The effect of an applied tensile stress on the hydrides morphology in ZIRCALOY-4 was studied. To this end, the residual stresses
around the hydride caused by the hydride precipitation was first evaluated. Considering the disability to predict hydride
transformation stresses by ordinary macroscopical mechanical calculation in previous studies, X-ray diffraction (XRD) profile
analysis and transmission electron microscopy (TEM) observations were carried out to quantify the microstructural evolution
in hydrided ZIRCALOY-4. The residual microstrains and microstresses in the matrix and around the hydride were thus estimated.
The big discrepancy between our results and the existing studies were explained by the major self-accomodation of phase transformation
deformation remaining inside the hydrides and the local plastic accommodation of ZIRCALOY-4. In order to study the stress
effect on hydride orientation and to estimate the hydride orientation threshold stresses, hydrogen was introduced into the
specimens under tensile stress. A quantitative technique was used to evaluate the susceptibility to perpendicular hydride
formation under the influence of texture, residual stresses, and externally applied tensile stresses, following an improved
approach that had been first developed by Sauthoff and then applied to Zr-H system by Puls. Both analytical and experimental
results indicate that the threshold stress for producing perpendicular hydrides varies with the microstructural features,
the yield strength, and the residual stresses. 相似文献
10.
The thermal residual stresses that develop in spray atomized and codeposited functionally graded and layered 6061 Al/SiC metal-matrix
composites (MMCs) during cooling from the codeposition temperature to ambient temperature were studied using thermo-elastoplastic
finite element analysis. In an effort to investigate the effect of layered and graded structures on the residual stress distribution,
the composites with homogeneous distribution of SiC particulates were also analyzed. The effect of SiC volume fraction in
the SiC-rich layers and the effect of SiC-rich layer thickness on the residual stresses were investigated. Based on the present
study, it was found that the residual stress distribution is very distinct for the aluminum and the SiC-rich layers in the
layered materials. As the volume fraction of SiC increases in the SiC-rich layer, the magnitude of residual stresses also
increases. The radial stress was found to be tensile in the aluminum layers and compressive in the SiC-rich layers. It was
also found that, as the thickness of the SiC-rich layer increases, the magnitude of radial stress in the aluminum layers increases,
and that in the SiC-rich layers decreases. In the graded material, the lower region of each layer exhibits tensile radial
stress, and the upper region of each layer shows compressive radial stress in order to maintain continuity between layers
during cooldown. In general, the layered and the graded materials have greater residual stresses and more complicated stress
distribution, as compared with those in the composite materials with homogeneous distribution of SiC particulates. 相似文献
11.
《Acta Metallurgica Materialia》1991,39(10):2255-2266
Elastoplastic finite element analyses of realistic models of short-fiber-reinforced composites were extended to include the effects of prior thermal treatments on predictions of subsequent mechanical properties. Two three-dimensional models were used, one in which the fiber ends were transversely aligned and another in which they were staggered. Both models were found to be necessary for accurate predictions of the behavior of higher volume fraction composites. The temperature dependence of the yield stress of the matrix material was explicitly included in the analysis. The spatial and temporal history of calculated. The room temperature residual stresses were also predicted. Both the plastic deformation and the residual stresses in the matrix were spatially non-uniform and varied rapidly from the regions near the ends of the fiber to those near the midpoint. Predictions of subsequent tensile stress-strain properties were in good quantitative agreement with experiments. The presence of residual stresses and locally deformed regions caused the tensile behavior to differ from the compressive behavior. These differences were complex and depended on the volume fraction and aspect ratio of the reinforcement. The analyses provide detailed insight into the deformation mechanisms of these composites. 相似文献
12.
《Acta Metallurgica Materialia》1992,40(2):309-323
The generation of tensile and compressive stress by the annihilation and production of vacancies which are subject to driving forces due to electromigration and due to the developing stress gradient is calculated. The rate of the stress changes is related to the deviation of the vacancy concentration from its equilibrium concentration. Depending on the magnitude of the rate constant different mechanisms of annihilation and production of vacancies (i.e. in the grain boundary itself, in adjacent grain boundaries or at dislocations) are covered. The resulting differential equations are solved numerically and analytically for some limiting cases. A quasi steady state concentration profile is established witin a short initial period of time, which is determined by one of the three processes diffusion, electromigration or rate of vacancy annihilation. During the quasi steady state the stresses increase linearly with time. When stresses are large enough to change the equilibrium vacancy concentration deviation from the linear increase occur and a rather long period follows where the true steady state is approached. If the time to failure, tf, of an Al-line is defined as the time necessary to reach a critical stress, tf is proportional to j−n where the current exponent changes from 1 at low critical stresses to 2 at higher stresses. The theoretical results are in excellent agreement with recent measurements of compressive stresses both with respect to the dependence on time and position. 相似文献
13.
14.
D. C. Brillhart A. G. Preban Paul Gordon 《Metallurgical and Materials Transactions B》1970,1(4):969-978
OFHC copper explosively deformed at pressures between 75 and 435 kbars is characterized by high residual stresses, compressive near the surface and tensile further in. Annealing after this deformation takes place in three some what overlapping stages. Property changes associated with these stages and possible interpretation of the effects are discussed in detail. Contrary to the annealing behavior of conventionally deformed metals, the first stage of annealing is accompanied by adecrease in density and anincrease in electrical resistivity. It is postulated that these changes are due to stress relief and microcrack growth. Also, unlike most conventionally deformed materials, the major softening stage is found to have recovery rather than recrystallization characteristics. The data in this stage are quantitatively consistent with a mechanism involving dislocation annihilation. 相似文献
15.
M. Karadge B. Grant P. J. Withers G. Baxter M. Preuss 《Metallurgical and Materials Transactions A》2011,42(8):2301-2311
This article describes an experimental study aimed at characterizing the extent of residual stress relaxation during thermal
treatment of inertia friction-welded alloy 720Li nickel-based superalloy welded tubular rings. In the as-welded condition,
yield level tensile hoop stresses were found by neutron diffraction in the weld region along with axial bending stresses (tensile
toward the inner diameter (ID)/compressive toward the outer). The evolution of these residual stress levels during postweld
heat treatment (PWHT) was mapped experimentally over the weld cross section. After 8 hours of PWHT, the axial stresses relaxed
by 70 pct, whereas the hoop stresses reduced by only 50 pct. Some scatter of residual stress evolution was found between samples,
particularly for the axial stress direction. This was attributed to substandard tooling to grip the rings. The results on
subscale samples were transferred to a full-scale aeroengine (650-mm diameter) compressor drum assembly that was postweld
heat treated for 8 hours. It was found that the residual stresses, particularly in the axial direction, were noticeably lower
in this full-scale weld component compared to the subscale weld heat treated for the same time. The differences seem to be
best rationalized by the different standards of jigging used during joining these two types of welds. 相似文献
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17.
����ξ ����ϣ ʯ�� �˲� 《钢铁研究学报》2013,25(9):24-29
MS980 is one of advanced high-strength steels, which has a great potential for producing square tubes. Residual stress plays a significant role in determining roll-formed members?? behavior and strength. An experimental study on transverse residual stress of roll-formed shape with square section was conducted via X-ray diffraction method. The distribution of transverse residual stresses at different position in sections was measured and studied, and influence of cold-rolled-sheet and hot-rolled-sheet, different fillet radius, different processes, and different pickling time on circumferential residual stress distribution for square section was investigated. The experimental results show the transverse residual stresses are compressive stress in the corner portion and the tensile stress in the straight edge. Fillet radius, sheet, and process have a significant impact on the distribution of residual stress, but the conventional pickling hardly affects residual stress. 相似文献
18.
基于残余应力测试新方法与先进电化学测试技术的进展, 围绕残余应力类型和大小对金属材料点蚀以及应力腐蚀行为的作用机理进行了总结和归纳. 研究发现, 尽管残余压应力对腐蚀行为的抑制作用得到了大量实验的证实, 但是在不同条件下其作用方式以及机理不尽相同, 并且与材料的结构特点以及腐蚀产物等密切相关. 同时, 残余拉应力的作用尚不明确, 受到材料类型和其他因素耦合的严重影响. 另外, 在某些环境下, 影响腐蚀行为的关键是残余应力梯度或残余应力的某个临界值. 但是对有色金属的研究表明残余拉应力和压应力均会导致基体中位错和微应变等结构缺陷增加, 进而促进点蚀敏感性, 降低材料服役性能. 最后, 对目前研究存在的局限进行了讨论和展望. 相似文献
19.
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
20.
LIU Zhao SUN Guang- ai WANG Hong QIN Hai- long YANG Zu- kun BI Zhong- nan 《钢铁研究学报》2018,30(9):729-724
The quenching process is indispensable for manufacturing the superalloys. However, high residual stress is inevitably induced by the large heat gradient, which influences the mechanical properties of the alloys. Therefore, it is of great significance to accurately characterize the internal residual stress of the super alloy and establish an effective finite element modeling. The quench- induced residual stresses of GH4169 super alloy were measured using neutron diffraction stress instrument. The results show that the center of the workpiece is subjected to tensile stress in three directions (hoop, radial and axial), which is about 400MPa. The rims of workpiece are subjected to compressive stress in one or two directions (hoop or axial), which is from -300MPa to -400MPa. The temperature and strain/stress fields of the GH4169 super alloy workpiece during quenching process were simulated by a 3D finite element model. The calculated residual strain/stress at the center and rim of the workpiece are compared to those by neutron diffraction, which shows good correspondence. These data provide reliable evidences to the formation of the residual stress during quenching. 相似文献