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Characterization of hot deformation behavior of Ti-6Al-4V-0.5Ni-0.5Nb titanium alloy was investigated through isothermal compression at various temperatures from 750 to 1 050 °C and strain rate from 0.01 to 10 s−1. The isothermal compression experiment results showed that the peak stress of Ti-6Al-4V-0.5Ni-0.5Nb titanium alloy decreased with the temperature increasing and the strain rate decreasing. The softening mechanism was dynamic recovery below Tβ and changed to dynamic recrystallization above Tβ. The arrhenius-type relationship was used to calculate the constitutive equation of Ti-6Al-4V-0.5Ni-0.5Nb alloy in two-phase regions. It was found that the apparent activation energies were 427.095 kJ·mol−1 in the α+β phase region and 205.451 kJ·mol−1 in the β phase region, respectively. On the basis of dynamic materials model, the processing map is generated, which shows that the highest peak efficiency of power dissipation of 56% occurs at about 1 050 °C/0.01 s−1. It can be found in the processing maps that the strain had significant effect on the peak region of power dissipation efficiency of Ti-6Al-4V-0.5Ni-0.5Nb alloy. Furthermore, optimized hot working regions were investigated and validated through microstructure observation. The optimum thermo mechanical process condition for hot working of Ti-6Al-4V-0.5Ni-0.5Nb titanium alloy was suggested to be in the temperature range of 950–1 000 °C with a strain rate of 0.01–0.1 s−1. [ABSTRACT FROM AUTHOR]

The Antarctic Bottom Water formation site Vincennes Bay, East Antarctica is experiencing a substantial intrusion of modified Circumpolar Deep Water (mCDW), which may inhibit the formation of Dense Shelf Water (DSW) and drive basal melting of the ice shelves. Based on hydrographic data obtained from March to November in 2012, we evaluated the spatial spread of mCDW over the continental shelf region of Vincennes Bay and the associated temporal evolution of water properties, as well as the sea ice formation effect on water column in the coastal polynya. Results show that two branches of mCDW occupied the deep layers of the continental shelf, distinguished by the potential density (smaller than 27.8 kg/m3 or not) when potential temperature θ=−0.5 °C in the θ-salinity space. The warmer and less dense branch observed on the east plateau, accessed the eastern ice shelves in the coastal polynya to drive basal melting of ice shelves. In contrast, the other colder and denser branch in the mid-depression reached the western Underwood Ice Shelf. DSW formation was detectable in the coastal polynya during September–November, proving the occurrence of deep convection. Surface heat loss and brine rejection during the intensive sea ice formation contributed to the destratification of the water column in the coastal polynya. It was estimated that at least 1.11±0.79 TW heat carried by mCDW into the inner part of the polynya. [ABSTRACT FROM AUTHOR]

Purpose: [18F]-FDG PET/CT and brain MRI are common approaches to detect metastasis in patients of lung cancer. Current guidelines for the use of PET/CT and MRI in clinical T1-category lung cancer lack risk-based stratification and require optimization. This study stratified patients based on metastatic risk in terms of the lesions' size and morphological characteristics. Methods: The detection rate of metastasis was measured in different sizes and morphological characteristics (solid and sub-solid) of tumors. To confirm the cut-off value for discriminating metastasis and overall survival (OS) prediction, the receiver operating characteristic (ROC) analysis was performed based on PET/CT metabolic parameters (SUVmax/SUVmean/SULpeak/MTV/TLG), followed by Kaplan–Meier analysis for survival in post-operation patients with and without PET/CT plus MRI. Results: 2,298 patients were included. No metastasis was observed in patients with solid nodules < 8.0 mm and sub-solid nodules < 10.0 mm. The cut-off of PET/CT metabolic parameters on discriminating metastasis were 1.09 (SUVmax), 0.26 (SUVmean), 0.31 (SULpeak), 0.55 (MTV), and 0.81 (TLG), respectively. Patients undergoing PET/CT plus MRI exhibited longer OS compared to those who did not receive it in solid nodules ≥ 8.0 mm & sub-solid nodules ≥ 10.0 mm (HR, 0.44; p < 0.001); in solid nodules ≥ 8.0 mm (HR, 0.12; p<0.001) and in sub-solid nodules ≥ 10.0 mm (HR; 0.61; p=0.075), respectively. Compared to patients with metabolic parameters lower than cut-off values, patients with higher metabolic parameters displayed shorter OS: SUVmax (HR, 12.94; p < 0.001), SUVmean (HR, 11.33; p <0.001), SULpeak (HR, 9.65; p < 0.001), MTV (HR, 9.16; p = 0.031), and TLG (HR, 12.06; p < 0.001). Conclusion: The necessity of PET/CT and MRI should be cautiously evaluated in patients with solid nodules < 8.0 mm and sub-solid nodules < 10.0 mm, however, these examinations remained essential and beneficial for patients with solid nodules ≥ 8.0 mm and sub-solid nodules ≥ 10.0 mm. [ABSTRACT FROM AUTHOR]

In accordance with the bending deformation of titanium alloy profile generated by hot extrusion, the hot stretch straightening assisted by resistance heating is an effective strategy to improve the straightness accuracy. In order to reveal the heat transfer behavior and deformation mechanism of titanium alloy profile during hot straightening, this study focuses on Ti-6.5Al-2Zr-1Mo-1 V alloy thin-walled T-shaped profile with unequal thicknesses. The flow stress curves of profile within temperatures from 400 to 800 ℃, strain rate at 5·10−4 s−1 were obtained by uniaxial tensile tests. The thermal boundary conditions between profile and air were determined by using inverse analysis experiment. Then, the thermal-electrical–mechanical multi-field coupling numerical simulation model was established. The temperature distribution, stress distribution, and deformation of profile were investigated systematically. The results show that the non-uniform temperature field with low temperature in thinner wall region and high temperature in thicker wall region would form during resistance heating. The stress distribution of stretch straightening process was determined by the temperature distribution and the initial bending shape of profile jointly, thereby affecting the springback deflection and direction after unloading. The established numerical simulation models, which have been verified by process experiments, could lay foundation for the prediction and process optimization in hot stretch straightening of titanium profile. [ABSTRACT FROM AUTHOR]

The effect of Al addition on ω precipitation and age-hardening behavior of Ti-9.2Mo-2Fe and Ti-2Al-9.2Mo-2Fe alloy during aging treatment was investigated. The results showed that athermal and isothermal ω phase formation in Ti-2Al-9.2Mo-2Fe alloy was suppressed to a certain extent due to Al addition. In addition, a small amount of athermal ω phase was observed in the β matrix with a size of about ~5 nm during water quenching from above the β transus temperature for both alloys. Isothermal ω formation was also found during aging at temperatures ranging from 573 K to 773 K (300 °C to 500 °C) in both alloys, although it had a limited time of stability at 773 K (500 °C). The hardening due to isothermal ω precipitation exhibited no over-aging as long as ω phase existed in both alloys, and ω phase played a more important role in hardening than α phase. And the ω phase in 50 to 100 nm size exhibited the best hardening effect in Ti-9.2Mo-2Fe alloy. Similarly, α phase with 100 to 200 nm in length showed better hardening effects in Ti-2Al-9.2Mo-2Fe alloy. Both the alloys showed stronger age hardening at an intermediate temperature of 673 K (400 °C) and in the first aging stage at a higher temperature of 773 K (500 °C) due to the sufficiently fine size (50 nm), while they exhibited weaker age hardening at a lower temperature of 573 K (300 °C) and long period aging at a higher temperature of 773 K (500 °C) due to incomplete ω formation and/or coarsening of α phase. No over or peak aging stage was found at 573 K and 673 K (300 °C and 400 °C) during the aging for 72 hours, while the peak hardness values of both alloys aged at 773 K (500 °C) were obtained in the first stage of aging. The hardness of the alloys was very sensitive to size and volume fraction of ω phase, which depends on aging temperature, time, and composition of the involved alloys. [ABSTRACT FROM AUTHOR]

In this paper, a developed multi-fingered dexterous hand with flexible tactile skin is described. The dexterous hand has 5-fingers with 6-DOFs and each finger is equipped with a small harmonic drive gear and a fine high-power mini actuator. To achieve the goal of grasping with high accuracy, each fingertip is covered with the tactile array sensors for determination of the force between the finger and the grasped object. Some preliminary experiments are conducted to illustrate the performance of the grasping of the developed dexterous hand. [ABSTRACT FROM AUTHOR]

Titanium and titanium alloys have several advantages, but the cost of titanium alloys is very expensive compared with the traditional metal materials. This article introduces two new low-cost titanium alloys Ti-2.1Cr-1.3Fe (TCF alloy) and Ti-3Al-2.1Cr-1.3Fe (TACF alloy). In this study, we used Cr-Fe master alloy as one of the raw materials to develop the two new alloys. We introduce the microstructure and tensile properties of the two new alloys from β solution treated with different cooling methods. Optical microscopy (OM), X-ray diffractometry (XRD), and transmission electron microscopy (TEM) were employed to analyze the phase constitution, and scanning electron microscopy (SEM) was used to observe the fracture surfaces. The results indicate that the microstructures consist of β grain boundary and α′ martensite after water quenching (WQ), β matrix and α phase after air cooling (AC) and furnace cooling (FC), respectively. Also, the microstructure is the typical basketweave structures after FC. Of course, athermal ω is also observed by TEM after WQ. The strength increases with decreasing cooling rates and the plasticity is reversed. Because of the athermal ω, the strength and ductility are highest and lowest when the cooling method is WQ. The strength of TACF alloy is higher than the TCF alloy, but the plasticity is lower. The fracture surfaces are almost entirely covered with dimples under the cooling methods of AC and FC. Also, we observe an intergranular fracture area that is generated by athermal ω, although some dimples are observed after WQ. [ABSTRACT FROM AUTHOR]

Human-robot control interfaces have received increased attention during the past decades for conveniently introducing robot into human daily life. In this paper, a novel Human-machine Interface (HMI) is developed, which contains two components. One is based on the surface electromyography (sEMG) signal, which is from the human upper limb, and the other is based on the Microsoft Kinect sensor. The proposed interface allows the user to control in real time a mobile humanoid robot arm in 3-D space, through upper limb motion estimation by sEMG recordings and Microsoft Kinect sensor. The effectiveness of the method is verified by experiments, including random arm motions in the 3-D space with variable hand speed profiles. [ABSTRACT FROM AUTHOR]

Ti-62A alloy plates with three different types of microstructure, fully equiaxed, bimodal, and Widmanstätten, were obtained by various heat treatments to investigate the effects of microstructure on the tensile and fracture properties at room temperature. The results reveal that Widmanstätten microstructure exhibits good damage tolerance behavior considering strength, fracture toughness, and fatigue crack growth behavior, while the bimodal microstructure shows good comprehensive properties considering the plasticity synthetically. Optical microscopy (OM) and scanning electron microscopy (SEM) microstructure analyses on fracture and fatigue crack path demonstrate that the dependence of mechanical properties and fatigue crack growth behavior on microstructural feature are attributed to the α lamellae width and the α colony size. [ABSTRACT FROM AUTHOR]

The addition of 3%∼9% Zr on the martensitic transformation of Ti-18Nb(at.%) alloy was investigated. The results of microstructure and X-ray diffraction (XRD) analysis show that the phase constitution of as-quenched Ti-18Nb-9Zr(at.%) alloy consists of the retained β matrix and α″ martensite, while that of the other three alloys is single α″ martensite. No trace of athermal ω phase was found in any of the as-quenched alloys. Unlike the effect of Nb addition on the martensitic transformation start temperature M of Ti-18Nb(at.%) alloy, M decreased nonlinearly as increasing the Zr addition from 3% to 9% and M decreased much more sharply as increasing the Zr addition. The M of as-quenched Ti-18Nb-9Zr alloy was around room temperature. The effect of Zr addition on the β phase stabilizing in the Ti-18Nb(at.%) alloy was briefly discussed. [ABSTRACT FROM AUTHOR]

The dynamic fracture toughness of TA15ELI alloy with two types of microstructures was studied by instrumented impact test. Charpy specimens with both the 0.2 mm U-notch and the a/W = 0.2 pre-crack were adopted to compare notch sensitivity in the two microstructures. The result shows that the specimen with Widmanstätten microstructure exhibits a better dynamic fracture toughness and lower notch sensitivity than that with lath-like microstructure. Fracture surfaces in the case of the two microstructures are analyzed to have a ductile and brittle mixed feature under dynamic loading. The fracture surface of lath-like microstructure is composed of dimples and tear ridges, while that of Widmanstätten microstructure is covered with rough block-like facets and dimples and tear ridges. The α phase boundaries and α/β interfaces act as locations for void nucleation and crack arrest and deviation. The decrease in width of α phase lamellae leads to the increase in the amount of boundaries and interfaces, which causes the increase in the consumption of impact energy and results in the improvement in dynamic fracture toughness. [ABSTRACT FROM AUTHOR]

The dynamic fracture behavior of TA15ELI alloy with lath-like microstructure was studied by caustics method. Specimens with double-side pre-notch were tested under the plane-stress condition at mode-II loading with a drop hammer system. Caustics information recorded in films illustrated the histories of both crack length and stress intensity factor. The dynamic fracture toughness and crack growth velocity of TA15ELI with lath-like microstructure were determined to be 279 MPa·m1/2 and 32.6 m/s, respectively. SEM fractograph analysis showed a mixed feature of mainly plastic mode for TA15ELI alloy in dynamic mode-II fracture. Shear localization was observed in the vicinity of the crack initiation area. [ABSTRACT FROM AUTHOR]

The Ti-Al-Sn-Zr-Cr-Mo-V-Si (Ti-62A) alloy, an alpha-beta alloy with high strength and fracture toughness, is currently used as an advanced structural material in aerospace and non-aerospace applications. Thermo-mechanical processes can be used to optimize the relationship between its strength and fracture toughness. A Ti-62A alloy bar can be machined through a transus β-forged plus α+β solution treated and aged specimen with a lamellar alpha microstructure. The effects of heat treatment on the mechanical properties were discussed. Heat treatment provided a practical balance of strength, fracture toughness, and fatigue crack growth resistance. A comparison of the Ti-62A alloy with the Ti-62222S alloy under the same thermo-mechanical processing conditions showed that their properties are at the same level. [ABSTRACT FROM AUTHOR]