共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
The paper presents results of an investigation of the low-cyclic fatigue strength of titanium alloys 3V (3.5 – 5% Al. 1.2–2.5%V) and 7M (1.8–2.6% Al, 2–3% Zr, 0.1% C).Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 33 – 34, April, 1996. 相似文献
4.
A. Hynnä V.- T. Kuokkala J. Laurila P. Kettunen 《Journal of Materials Engineering and Performance》1993,2(4):531-535
The high-temperature cyclic behavior of oxide dispersion-strengthened superalloy MA 760 was studied at different temperatures
and specimen orientations. The cyclic hardening curves at different strain am-plitudes were determined at 650, 900, and 950
°C, and the stress-strain response of the material was sub-stantiated by detailed fractographical scanning electron microscopy
(SEM) and microstructuralJoptical microscopy, STEM) observations. During cycling, MA 760 did not exhibit marked hardening
or soften-ing, and also the final fracture occurred very rapidly without a significant decrease in the cyclic strength of
the material. The “brittle” nature of deformation behavior of MA 760, especially at lower test tempera-tures, as well as oxidation-induced
secondary cracking along grain boundaries, was clearly revealed by microscopical studies of the fracture surfaces. At 650
°C, evidence of dislocation cutting of γ was ob-served in transmission micrographs, but at higher temperatures, dislocation
climb and by-passing of γ particles were found to become more prominent features. At all test temperatures, dislocation climb
over yttria particles, as well as the departure side pinning effect of dislocations at nonshearable particles, was frequently
observed. 相似文献
5.
A.G. Evans M.Y. He A. Suzuki M. Gigliotti B. Hazel T.M. Pollock 《Acta Materialia》2009,57(10):2969-2983
A model capable of characterizing oxidation-assisted low-cycle fatigue is described. It involves the following steps. After a few strain cycles, because of creep, a tensile stress develops during the de-straining phase of the cycle. This stress opens cracks present in the material and exposes the surfaces to the atmosphere, causing thermally grown oxide (TGO) growth. Dilatation takes place upon converting the alloy to oxide, with an associated strain rate that induces a compressive growth stress. Thereafter, during the re-straining phase of the cycle, transverse extension of the substrate induces in-plane tension in the TGO, which “pushes” the TGO into the substrate along the crack front. Finite element simulations of this process have been presented that predict crack growth per cycle, da/dN, comparable with experimental measurements. Trends in da/dN with the TGO dilatation rate and the creep strength of the superalloy have been elucidated. 相似文献
6.
Uniaxial ratcheting and low-cycle fatigue failure behaviors of hot-rolled AZ91D magnesium alloy were studied by uniaxial cyclic stress-controlling tension deformation experiments. The effects of stress amplitude, mean stress and stress rate on the uniaxial ratcheting response and fatigue life of the hot-rolled AZ91D magnesium alloy were analyzed. Results show that (1) the ratcheting strain and ratcheting strain rate of the hot-rolled AZ91D magnesium alloy both increase with the increase of stress amplitude or mean stress; (2) increasing stress rate will decrease the ratcheting strain and ratcheting strain rate of the hot-rolled AZ91D magnesium alloy; (3) the increase of stress amplitude and mean stress can both reduce the fatigue life of the hot-rolled AZ91D magnesium alloy, while the fatigue life will be prolonged with the increase of stress rate. 相似文献
7.
研究了高应力水平下不同加载波形对TC17钛合金疲劳损伤的影响,结果表明,对于在峰值应力处保载120S的加载波形,TC17钛合金的保载疲劳寿命低于无保载加载波形试验的寿命,在相同的保载疲劳条件下,片层组织的保载疲劳敏感性较等轴组织的疲劳敏感性低。断口分析表明,保载疲劳试样裂纹源出现在样品表面和亚表面处,常规疲劳试样裂纹源出现在试样表面处,保载疲劳断口较常规疲劳断口附近小平面平坦,保载条件并未从根本上改变断裂模式。 相似文献
8.
9.
T. Branza F. Deschaux-Beaume V. Velay P. Lours 《Journal of Materials Processing Technology》2009,209(2):944-953
The multi-pass weld-repair of heat-resistant cast steels is carried out using an automated shielded metal arc welding (SMAW) process, with various filler materials and pre-heating at 400 °C. Specimens weld-repaired with a filler material more resistant than the heat-resistant cast steel (over-matching) generally crack within the base metal following the tenth filling pass, whereas specimens buttered with a soft alloy prior to welding remain free of cracks.The high temperature strain-controlled fatigue lifetime of material weld-repaired without buttering is lower than that of bulk initial material. This is due to an increase of the stress amplitude as a result of the so-called over-matching. In the case of material welded following a prior buttering, the fatigue lifetime is reduced because of the stress tri-axiality generated in the thin soft layer which prevents its plastic flow. As a consequence, it is concluded that even though buttering prevents cracking efficiently during welding, it is not acceptable as far as fatigue performance, especially lifetime, is concerned. 相似文献
10.
11.
Fretting fatigue is an adhesive wear mechanism caused by repetitive tangential micro-oscillation between two contacting materials
pressed together under cyclic load. Bioimplants, such as hip joints and bone plates, are prone to undergo fretting fatigue
failures during their service within the body. This article presents the fretting fatigue damage characterization of physical
vapor deposition (PVD) TiN-coated biomedical titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) subjected to cyclic loads. The PVD
TiN layer delayed the damage because of superior tribological properties compared with uncoated alloys. Delamination and abrasive
wear damage of TiN at contact caused failure of the alloy. Friction coefficient curves of the PVD TiN-coated pair showed an
irregular pattern caused by the influence of wear particulates and Ringer fluid at the contact. 相似文献
12.
This study investigated the cyclic and static fatigue properties of 10 μm thick, deep reactive ion etched, monocrystalline silicon films. Stress–life fatigue curves and fatigue degradation rates vs. stress curves were generated at both 4 and 40 kHz, at 30 °C, 50% relative humidity (RH). A significant frequency effect was observed, with shorter fatigue lives and faster damage accumulation rates at 4 kHz. Static fatigue was also observed with shorter static lifetimes at 80 °C, 90% RH than at 30 °C, 50% RH. Fracture surface evaluation did not reveal any major difference between cyclically and statically fatigued devices. These experimental results confirm that the fatigue of micron-scale silicon is not purely mechanical. The study also proposes a fatigue scenario based on time-dependent subcritical crack growth to account for the low-cycle fatigue regime. 相似文献
13.
Sang Chul Seo Hyun Jung Kim Byung Ho Park Kwang Suk Son Sung Keun Lee Sun Bae Kang Donggyu Kim 《Metals and Materials International》2006,12(3):273-277
In a continuous casting steelmaking operation, the surface of a slab is under a condition that can be characterized as high-temperature,
low-cycle fatigue in which the tensile and compressive stress is repeatedly developed. For this reason, for the evaluation
of the hot ductility of a slab, considering the fatigue deformation is more feasible before a tensile or compressive test.
In this study, the effects of low-cycle fatigue on the hot ductility of steels with a carbon content of 0.06–0.8 wt.% are
investigated at various temperatures. For a carbon content of 0.06%, there were no significant differences between the RA
values from a simple tensile test and those from a tensile test after fatigue deformation. The tendency of ductility deterioration
with fatigue deformation is evident in 0.1 %C steel, and is due to the deformation-induced ferrite film that forms around
the prior austenite grain. Conversely, high carbon steel containing 0.8 %C did not show a recovery of hot ductility in a low
temperature region, and the specimen on which the tensile was measured after fatigue showed a higher hot ductility in the
low temperature region, which is thought to result from the pearlite refinement effects. As the results obtained in this work
showed noticeable differences in the hot ductility of carbon steel through the test conditions, it is suggested that for more
accurate data, fatigue deformation be adopted in which the temperature range in an unbending operation is determined in the
steelmaking factory. 相似文献
14.
15.
16.
A. Ya. Chernyak É. A. Kosakovskii A. A. Mezhlum'yan 《Metal Science and Heat Treatment》1978,20(1):63-65
Conclusions Isothermal hardening improves the ductility and increases the static fatigue strength of alloy 01420 by 9–12%.Tashkent Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 59–61, January, 1978. 相似文献
17.
A. A. Gol'denberg A. N. Chekhovoi L. N. Antipova 《Metal Science and Heat Treatment》1989,31(2):129-133
1. | One of the causes of failure during low-cycle fatigue of type 0Kh4V2S2MFNYuT die steel is the formation of defective spaces around the carbide inclusions. This type of damage is evidently associated with the development of stresses at the boundary of the matrix and the inclusion during external cyclic loading. |
2. | The effective radius of the carbide inclusions linearly increases with increase of the logarithm of their sizes. |
3. | During cyclic loading at a frequency of f=1 Hz and c = +2400 to –300 N/mm2 the defective spaces are observed in steel 8Kh4V2S2MFNYuT around particles of size greater than 0.3 m. |
4. | During metallurgical production, one should avoid the accumulation of large carbides in the structure of die steels to be used for cold working. |
18.
19.
B. A. Lerch R. D. Noebe K. B. S. Rao 《Journal of Materials Engineering and Performance》1998,7(2):205-213
The effect of a 0.1 at. % alloying addition of Zr on the low-cycle fatigue behavior of polycrystalline NiAl was determined
at 1000 K and compared to that of binary NiAl. Samples of binary NiAl and the Zr-doped alloy were processed by either HIP
consolidation or extrusion of prealloyed intermetallic powders. The cyclic stress response, cyclic stress-strain behavior,
and strain-life relationships were all significantly influenced by the microalloying addition of Zr, regardless of the processing
technique. A detailed examination of the post-tested low-cycle fatigue (LCF) samples was conducted by optical and electron
microscopy to determine variations in fracture and deformation modes and to characterize any microstructural changes that
occurred during LCF testing. Differences in LCF behavior due to the Zr addition are attributed to the strong effect that Zr
has on modifying the deformation behavior of the intermetallic. 相似文献