The objective of the present study was to elucidate the cavity formation mechanism of Type IV failure in weldment of advanced high-Cr ferritic steels. A welded joint of Mod.9Cr-1Mo steel was creep ...tested at 650 °C under 83 MPa. The creep fracture mode was Type IV failure in the heat affect zone (HAZ). Microstructural characterization of the HAZ and the fracture location, were performed before and after the creep test. The Type IV cracking started in the inter-critical HAZ at a location having fine grain size and coarse M
23
C
6
precipitates. Moreover, the grain structure of the inter-critical HAZ, which is a mixture of soft α and hard α’ grains, plays an important role in the stage of cavity evolution into a crack along the grain boundary. This is due to the heterogeneity of local strain between the two kinds of grains. By a synergistic effect of the strain concentration, the coarse precipitates and heterogeneous strain distribution among grains in the inter critical HAZ, facilitates the nucleation and growth of creep cavities, resulting in premature failure of welded joints.
Static recovery of tempered lath martensite microstructures of strength enhanced ferritic steels has been investigated during very long-term aging up to 2
×
10
4
h at 650
°C for 3 steels containing 9 ...to 12% Cr. Static recovery of tempered lath martensite microstructure occurs after an incubation period for 1–2
×
10
3
h in the steels. The static recovery is controlled by the loss of strengthening due to M
23C
6 precipitates, and disappearance of MX carbonitrides cannot be the main cause of the static recovery.
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► The contribution of the static recovery of subgrains to creep deformation causes the breakdown of creep strength in Gr.91 steel. ► Loss of pinning force from M
23C
6 precipitates is ...responsible for the static recovery of subgrains. ► MX has nothing to do with the static recovery. ► The breakdown of creep strength is expected to happen in the time range a little longer than 10
5
h at 600
°C.
The cause of the breakdown of creep strength has been studied in Gr.91 steel. The results show that the contribution of the static recovery of subgrains to creep deformation causes the breakdown of creep strength. The subgrain boundaries are mainly stabilized by M
23C
6 and MX precipitates. MX precipitates are thermally stable even in the time range when coarsening of subgrains takes place. Whereas M
23C
6 precipitates are not thermally stable and the aggregation of M
23C
6 precipitates takes place in the time range when coarsening of subgrains happens. Therefore, loss of pinning force from M
23C
6 precipitates is responsible for the static recovery of subgrains. MX has nothing to do with the static recovery. The microstructural stability of Gr.91 steel in the time range longer than 10
5
h at 600
°C has also been assessed based on the creep data of Gr.91 steel tested up to 90,408
h at 600
°C and 22,900
h at 650
°C. The aggregation of precipitates and the coarsening of subgrains start to take place at round 10
5
h at 600
°C. Therefore, the breakdown of creep strength is expected to happen in the time range a little longer than 10
5
h at 600
°C.
Creep rupture life and microstructural degradation have been studied in two heats of Gr.91 steels. The coarsening of subgrains and precipitates, mainly M23C6 and MX, has been evaluated during static ...aging and creep. Hardness of head (static aging) and gauge (creep) portions of crept samples were measured to know their relation with microstructural degradation during long-term exposure. The correlation between subgrain size and spacing of precipitates and hardness has been equated. As an example, there is a close correlation between hardness value and inverse subgrains size in Gr.91 steels, regardless of aging or creep conditions. The appearance of three recovery mechanisms was found during long-term creep, namely: strain-induced recovery, pure static recovery and strain-assisted static recovery. By equated correlations between subgrain size, precipitates and hardness, the contribution of three recovery mechanisms to subgrain coarsening and hardness drop were calculated for two creep conditions at 700°C in long-term creep region, where breakdown of creep strength has happen. The calculated data accord well with experimental data obtained from aged and crept samples. The contribution of static recovery to the subgrain coarsening and consequent hardness drop during long-term creep increases with increasing creep time. The significant contribution of both static recovery mechanisms can result in the breakdown of creep strength in long-term creep region.
Larson-Miller (LM) and Orr-Sherby-Dorn (OSD) parameters are widely used when formulating and predicting creep rupture life tr. The LM constant C and the activation energy Q in the OSD parameter ...characterize temperature dependence of tr. Q = QLSD (QLSD: activation energy for lattice self-diffusion) and C = 20 are often assumed in the formulation. Creep rupture datasets of 11 heats of nickel alloy A617, 304H and 304J1 stainless steels, 6 heats of A3004N aluminum alloy and four Mg-Al alloys are formulated with the parameters for determining C and Q of each dataset. Based on the correlation between C and Q among similar materials, it is discussed what is the C value equivalent to Q = QLSD. It is also examined how the C value changes with melting temperature of the material. The value of C equivalent to Q = QLSD varies from 14 to 9.5 depending on average values of log(rupture life) and of reciprocal temperature of the dataset. These values of C point out that C = 20 is not equivalent to Q = QLSD. The equivalent C values are similar in all the materials independently of their melting temperatures.
Larson-Miller constant C is correlated to Orr-Sherby-Dorn constant Q by an equation.•C takes about 12 when Q is equal to activation energy for lattice diffusion.•C is proved to be insensitive to melting temperature of the material.•Q decreases to activation energy for lattice diffusion in long-term creep.
Background and purpose
Differential diagnosis of sporadic inclusion body myositis (s‐IBM) and polymyositis (PM)/dermatomyositis (DM) is difficult and can affect proper disease management. Detection ...of heterogeneous muscular involvement in s‐IBM by muscle sonography could be a unique diagnostic feature.
Methods
Sonography of the lower leg and forearm was performed in patients with s‐IBM, PM/DM and control subjects (n = 11 each). Echo intensities (EIs) of the adjacent muscles medial head of the gastrocnemius versus soleus and the flexor digitorum profundus (FDP) versus flexor carpi ulnaris (FCU) were scored by three blinded raters. The mean EIs of these muscles were compared using computer‐assisted histogram analysis.
Results
Both evaluation methods showed high echoic signals in the gastrocnemius of patients with s‐IBM. EIs were significantly different between the gastrocnemius and soleus in patients with s‐IBM, but not in those with DM/PM and the controls. In the forearm, although the EI of the FDP was higher in the s‐IBM group than in the other groups, the EI differences between the FDP and FCU did not differ significantly between disease groups. The difference in area under the curves to differentiate between s‐IBM and DM/PM was greatest between the gastrocnemius−soleus EIs (0.843; P = 0.006).
Conclusions
High echoic signals in the medial gastrocnemius compared with those of the soleus are suggestive of s‐IBM over PM/DM.
A large‐aperture radiotelescope called the Solar Wind Imaging Facility (SWIFT) has been developed at the Toyokawa Observatory of the Solar‐Terrestrial Environment Laboratory (STEL), Nagoya ...University. The SWIFT is dedicated to interplanetary scintillation (IPS) observations of the solar wind at 327 MHz, the same frequency as that of the existing STEL IPS system. The aim of this instrument is to improve the spatial and temporal resolutions of tomographic reconstructions from STEL IPS observations by increasing the number of usable lines of sight within a given time period. The SWIFT consists of a pair of asymmetric cylindrical parabolic reflector antennas with an aperture size of 108 m (N‐S) by 19 m (E‐W), and a 192‐element phased array receiver system which forms a single beam steerable between 60°S and 30°N with respect to the zenith. Since the antenna beam is fixed in the local meridian, IPS observations are taken around the time of meridian transit for each source. The performance of the SWIFT has been tested using preliminary observations for strong discrete sources and diffuse galactic background.
Key Points
A UHF radiotelescope dedicated to interplanetary scintillation observations
A unique design of the radiotelescope
A high sensitivity for radio astronomical observations
External low-frequency ultrasound (USD) in combination with microbubbles has been reported to recanalize thrombotically occluded arteries in animal models.
The purpose of this study was to examine ...the enhancing effect of thrombus-targeted bubble liposomes (BLs) developed for fresh thrombus imaging during ultrasonic thrombolysis.
In vitro: after the administration of thrombus-targeted BLs or non-targeted BLs, the clot was exposed to low-frequency (27 kHz) USD for 5 min. In vivo: Rabbit iliofemoral arteries were thrombotically occluded, and an intravenous injection of either targeted BLs (n = 22) or non-targeted BLs (n = 22) was delivered. External low-frequency USD (low intensity, 1.4 W cm(-2) , to 12 arteries, and high intensity, 4.0 W cm(-2) , to 10 arteries, for both the targeted BL group and the non-targeted BL group) was applied to the thrombotically occluded arteries for 60 min. In another 10 rabbits, recombinant tissue-type plasminogen activator (rt-PA) was intravenously administered.
In vitro: the weight reduction rate of the clot with targeted BLs was significantly higher than that of the clot with non-targeted BLs. In vivo: TIMI grade 3 flow was present in a significantly higher number of rabbits with USD and targeted BLs than rabbits with USD and non-targeted BLs, or with rt-PA monotherapy. High-intensity USD exposure with targeted BLs achieved arterial recanalization in 90% of arteries, and the time to reperfusion was shorter than with rt-PA treatment (targeted BLs, 16.7 ± 5.0 min; rt-PA, 41.3 ± 14.4 min).
Thrombus-targeted BLs developed for USD thrombus imaging enhance ultrasonic disruption of thrombus both in vitro and in vivo.
The AirWay Scope (AWS) is a fibreoptic device that allows for intubation without alignment of the oral, pharyngeal, and tracheal axes. It may be useful for patients with an unstable cervical-spine ...(C-spine) or when C-spine movement is undesirable. This study was conducted to fluoroscopically evaluate upper C-spine movement during tracheal intubation with the AWS and or the Macintosh laryngoscope with in-line stabilization (ILS).
Thirteen patients with a normal C-spine and scheduled for elective surgery agreed to simulation of an unstable C-spine and ILS. Two attempts at laryngoscopy were allowed. Laryngoscopy was performed with the Macintosh laryngoscope, then with the AWS, or vice versa. The movement of the upper C-spine during intubation was examined by measuring the angles formed by adjacent vertebrae from the occiput to C4. Time to achievement of intubation was also recorded.
The AWS significantly decreased median movement of the C-spine at the occiput/C1, C1/C2, and C3/C4 concentrations (P=0.041, 0.0079, and 0.0050, respectively), resulting in a significant decrease in cumulative upper C-spine movement (13.5° with the AWS compared with 30.5° with the Macintosh laryngoscope, P<0.01). Intubation time did not differ 23.8 (sd 16.7) s with the AWS; 17.9 (6.4) s with the Macintosh.
In comparison with the use of the Macintosh laryngoscope, the AWS decreased median upper C-spine movement during intubation under ILS in patients with normal C-spine.
The addition of zinc is effective in improving creep strength of Mg–Y solid solution alloys at temperatures 550–650 K because zinc suppresses the non-basal slip that operates predominantly at such ...temperatures. This suppression is caused by the formation of planar defects on the (0
0
0
1) plane and confinement of dislocations in the basal plane due to a decrease in stacking fault energy.
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