scholarly journals The fracture behavior transitions in cold dwell fatigue of Ti-6Al-4V

2020 ◽  
Vol 321 ◽  
pp. 11085
Author(s):  
Tomomichi Ozaki ◽  
Yutaro Ota ◽  
Keiji Kubushiro ◽  
Kokichi Sano
Keyword(s):  
Grain Size ◽  
Fracture Surface ◽  
Dwell Time ◽  
Fracture Behavior ◽  
Fatigue Tests ◽  
Fracture Elongation ◽  
Fine Grain ◽  
Dwell Fatigue ◽  
Billet Material ◽  
Short Time

Ti-6Al-4V forged materials which had fine grain size and commercial billet which had moderate grain size and micro texture were prepared. Cold dwell fatigue tests were conducted using both materials, and dwell time condition was up to 1800s. Fracture cycles and elongation were almost same on each specimen. Number of cycle to failure decreased with increase of dwell time. Fracture elongation increased up to dwell time of 10s, and it was constant in over 10s. Fracture surface were observed. In short time dwell condition up to 2s, fracture surface showed fatigue type. Fracture surfaces changed to dimple in over 10s dwell. In billet material, facets were observed in inner area of fracture surface.

The Texture Effect on the Dynamic Fracture Properties of Magnesium Alloy AZ31B

2016 ◽  
Vol 715 ◽  
pp. 74-79
Author(s):  
Xia Yu ◽  
Yu Long Li ◽  
Tao Li
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Fracture Surface ◽  
Dynamic Fracture ◽  
Texture Evolution ◽  
Crack Tip ◽  
Image Correlation ◽  
Coarse Grain ◽  
Alloy Plate ◽  
Fine Grain

In this work, Mode I dynamic fracture experiments are conducted on pre-cracked three point bending specimens by using modified split-Hopkinson pressure bar. Two sets of specimens with different initial textures are considered here: one set of the specimens are machined from a hot rolled AZ31B Mg alloy plate with a bigger grain size. The others are treated by four pass of equal channel angular pressing (ECAP) after they are cut from the initial material. They are with the finer grain size. Digital image correlation (DIC) technique is used to determine the strain contours around the crack tip and electron back scatter diffraction (EBSD) is employed to analyze the texture evolution after tests. It is found that the dynamic fracture toughness of finer grain specimen is higher than that of coarse grain specimen. The fracture toughness of both sets of specimens is enhanced by increasing the loading rates. Texture analysis shows the formation of tensile twinning in the ligament ahead of the crack tip in the coarse grain specimen but no sign in fine grain specimen. The brittle features e. g. cleavage planes and twinning lamellas are observed on the fracture surface of coarse grain specimen by scanning electron microscope (SEM). However, the relative ductile features such as micro-voids surrounding by tear ridges present on the fracture surface of fine grain specimen.

Temperature-Dependent Dwell-Fatigue Behavior of Nanosilver Sintered Lap Shear Joint

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yansong Tan ◽  
Xin Li ◽  
Yunhui Mei ◽  
Gang Chen ◽  
Xu Chen
Keyword(s):  
Shear Stress ◽  
Dwell Time ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Maximum Shear Stress ◽  
Fatigue Tests ◽  
Shear Strain Rate ◽  
Lap Shear ◽  
Shear Joint ◽  
Dwell Fatigue

A series of dwell-fatigue tests were conducted on nanosilver sintered lap shear joint at elevated temperatures from 125 °C to 325 °C. The effects of temperature and loading conditions on dwell-fatigue behavior of nanosilver sintered lap shear joint were systematically studied. With higher temperature and longer dwell time, creep played a more important part in dwell-fatigue tests. Creep strain accumulated during maximum shear stress hold was found partly recovered by the subsequent cyclic unloading. Both the fracture mode and silver particle growth pattern were characterized by X-ray tomography system and scanning electron microscope (SEM). The mean shear strain rate γ˙m synthesized the effects of various factors, such as temperature, shear stress amplitude, mean shear stress, and dwell time, by which the fatigue and dwell-fatigue life of nanosilver sintered lap shear joint could be well predicted within a factor of two.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

A fractographic study exploring the fracture surface topography of S355J2 steel after pseudo-random bending-torsion fatigue tests

Measurement ◽  
2021 ◽  
Vol 178 ◽  
pp. 109443
Author(s):  
W. Macek ◽  
Z. Marciniak ◽  
R. Branco ◽  
D. Rozumek ◽  
G.M. Królczyk
Keyword(s):  
Fracture Surface ◽  
Surface Topography ◽  
Fatigue Tests ◽  
Fractographic Study

Study on the Fine Grain size and the Micro‐Hardness at the Interface of AZ31/Mg‐Y Composites

2021 ◽  
Author(s):  
Yihong Xian ◽  
Weijun He ◽  
Wenhuan Chen ◽  
Zejun Chen ◽  
Bing Jiang ◽  
...  
Keyword(s):  
Grain Size ◽  
Micro Hardness ◽  
Fine Grain

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

scholarly journals Study on the erosion of Mo/ZrO2 alloys in glass melting process

2020 ◽  
Vol 39 (1) ◽  
pp. 595-598
Author(s):  
Cui Chaopeng ◽  
Zhu Xiangwei ◽  
Li Qiang ◽  
Zhang Min ◽  
Zhu Guangping
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Powder Metallurgy ◽  
Hydrothermal Synthesis ◽  
Grain Boundaries ◽  
Electrode Material ◽  
Glass Melting ◽  
Melting Process ◽  
Fine Grain ◽  
Conventional Electrode

AbstractThe Mo/ZrO2 electrode was prepared by combining hydrothermal synthesis with powder metallurgy, and this new electrode material has a totally different microstructure from the conventional electrode. The grain size of the new electrode was fine, and the size of ZrO2 in the alloy reached 200 nm. According to the results, the Mo–ZrO2 electrode has better performance, because the erosion occurs along the grain boundaries. Meanwhile, the new electrode, based on its fine grain, can effectively improve the corrosion resistance of the electrode.

Fracture Behavior of Ceramics Used in Multilayer Capacitors

1986 ◽  
Vol 72 ◽  
Author(s):  
Theresa L. Baker ◽  
Stephen W. Freiman
Keyword(s):  
Crack Growth ◽  
Fracture Behavior ◽  
Ceramic Materials ◽  
Fatigue Tests ◽  
Internal Stresses ◽  
Crack Growth Behavior ◽  
Multilayer Capacitors ◽  
Materials Used ◽  
Aging Phenomena

AbstractThis study involved the determination of the effects of composition and microstructure on the fracture toughness and susceptibility to environmentally enhanced crack growth of several ceramic materials used in multilayer capacitors. Indentation-fracture procedures were used to measure KIC as well as to assess the possible effects of internal stresses on the fracture behavior of these materials and to correlate dielectric aging phenomena with strength. The environmentally enhanced crack growth behavior of these materials was determined by conducting dynamic fatigue tests in water.

Sign in / Sign up

Export Citation Format

Share Document