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Demountable steel–concrete composite structures have attracted much attention from researchers because of its fast construction, demountability and environmental friendliness. Using ultra-high performance concrete (UHPC) in the hogging moment regions of demountable steel–concrete composite structures might improve their crack resistance and flexural performance. In this study, the cracking behavior, failure mode, stiffness, ultimate strength and relative slip of demountable steel-UHPC composite slabs with different stud spacings and longitudinal reinforcement ratios under hogging moment were experimentally investigated. A welded steel-UHPC composite slab was also tested to compare its behavior with the demountable slabs. The test results show the demountable steel-UHPC composite slabs have excellent crack control ability under hogging moment due to the slip of threaded headed stud and the strain hardening behavior of UHPC; the relative slip is directly associated with the stud spacing and controlled by the friction and shear force of threaded headed studs. As compared to the welded composite slab, the demountable composite slab can be easily separated after loading, the flexural capacity is slightly smaller, while the crack control ability is better and the ductility is higher. A constitutive model considering the reduction of tensile strength of UHPC after reinforcement was adoptedl the design formulas were developed to predict the elastic limit and the ultimate moment, and the bending stiffness of the demountable composite slabs under hogging moment. The test results verify the applicability of the proposed constitutive model of UHPC and design formulas. [ABSTRACT FROM AUTHOR]

A novel reinforced concrete (RC) vertical bent frame structure system consisting of a RC frame structure and RC bent structure has been proposed for the development of large-scale thermal power plants. To better understand the seismic performance of RC bent columns in vertical bent frame structures, a 1/5-scale representative component selected from a common vertical bent frame structure was tested by quasi-static testing (QST). The failure mode hysteretic characteristics, ductility, energy dissipation capacities of RC bent columns were investigated. Based on the experimental results, finite element models for the bent frame columns and vertical bent frame structures were developed and the nonlinear dynamic analyses were carried out. The results of finite element analysis indicate that the axial pressure ratio has significant effects on the seismic behaviour of RC bent columns. The relationship of drift angle for bent frame column under frequent earthquake and infrequent earthquake are investigated. The limitation values of axial compression ratios and the inter-storey drift angle for RC bent columns in vertical bent frame structures are suggested. [ABSTRACT FROM AUTHOR]

The joining of Ti6Al4V and Inconel 718 constitutes a great challenge, due to the TixNiy, Ti-Cr, and Ti-Fe brittle phases’ formation. For the solution of this problem, niobium was selected as an interlayer and the pulsed laser welding-induced eutectic reaction technology was proposed. Two metallurgical bonding zones based on two different bonding mechanisms were identified for the Ti6Al4V/Inconel718 dissimilar joint. When the laser beam was positioned at the Ti6Al4V/Nb interface, the Ti6Al4V and the Nb sheet were partially melted, for the Ti6Al4V and niobium to be joined through fusion welding, while the atomic interdiffusion and the eutectic reaction were responsible for the joining at the Nb/Inconel 718 interface. No TixNiy, Ti-Cr, or Ti-Fe intermetallics were detected in the weld, demonstrating that the unmelted Nb interlayer acted as a diffusion barrier between the Ti6Al4V and the Inconel 718. The eutectic reaction layer formed at the Nb/Inconel 718 interface with the main microstructure of the Ni-Nb system intermetallics. The welded joints fractured at the reaction layer at the maximum tensile strength of 145 MPa and the fracture mode was cleavage fracture. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to evaluate the effect of microstructure heterogeneity on the tensile and low cycle fatigue properties of electron beam welded (EBW) Ti6Al4V sheets. To achieve this goal, the tensile and low cycle fatigue property in the EBW joints and base metal (BM) specimens is compared. During the tensile testing, digital image correlation technology was used to measure the plastic strain field evolution within the specimens. The experimental results showed that the tensile ductility and low cycle fatigue strength of EBW joints are lower than that of BM specimens, mainly because of the effect of microstructure heterogeneity of the welded joint. Moreover, the EBW joints exhibit the cyclic hardening behavior during low fatigue process, while BM specimens exhibit the cyclic softening behavior. Compared with the BM specimens with uniform microstructure, the heterogeneity of microstructure in the EBW joint is found to decrease the mechanical properties of welded joint. [ABSTRACT FROM AUTHOR]

The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young's modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α′ and the application of TC-1 welding rods in the TIG-welded joint. [ABSTRACT FROM AUTHOR]

The present work is aimed at comparatively studying fatigue damage evolution of a pulsed Nd:YAG laser beam-welded (LBW) joint and the base metal (BM) of Ti6Al4V alloy subjected to cyclic loading. To reveal crack nucleation and propagation during the fatigue process, in situ fatigue was generated using infrared measurement methods. The results indicate that the rate of damage accumulated in the LBW joint was higher than in the BM specimens during a fatigue test, which decreased the fatigue life of the LBW joint. This observation is attributable to the LBW joint fusion zone microstructure, which has a higher void nucleation and growth rate compared with the BM microstructure. [ABSTRACT FROM AUTHOR]

In this study, the influence of weld cross-sectional profiles and microstructure, under different welding conditions, was investigated on the mechanical properties of pulsed Nd:YAG laser-welded joint of Ti6A14V alloy. The V- and H-shaped weld cross-section profiles were obtained under low and high heat input, respectively. The microstructure in the fusion zone (FZ) of V- and H-shaped welded joint consisted of a fine acicular martensitic α′ solidification structure within the prior-β grains, responsible for the maximum hardness in the FZ. Tensile tests revealed that the V-shaped welded joint fractured at the near heat-affected zone (HAZ)/base metal (BM) interface, but the H-shaped welded joint fractured in the BM. Furthermore, the tensile strength of the V-shaped welded joint was lower than that of the H-shaped welded joint. This was attributed to the fact that the heterogeneity of strain distribution at the interface of HAZ and BM of the V-shaped welded joint was greater than that of the H-shaped welded joint during tensile process. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by extracellular accumulation of amyloid deposits. Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor whose levels have been shown to be decreased in AD brains. BDNF supplementation can offer improvement in the course of AD. However, the means of assessment are still relatively limited. In the present study, 1H-MRS was used to evaluate the therapeutic effects of bilateral intraventricular BDNF infusion into Alzheimer's disease APP/PS1 double transgenic mice. For comparison to the 1H-MRS observations, Fluoro-Jade B staining and immunofluorescence for beta amyloid peptides (Aβ), glial fibrillary acidic protein, and tropomyosin-related kinase B (TrkB) were also performed. Our results showed that N-acetylaspartate (NAA) levels increased and myoinositol levels decreased in the BDNF group compared with the PBS group. However, the BDNF group NAA level was still lower than the control group at 6 weeks after infusion. These changes correlated with increased immunoreactivity for TrkB, decreased compact Aβ peptide containing plaques, and decreased Fluoro-Jade B-positive cells in the BDNF-infused mice compared to vehicle controls. These findings demonstrate that 1H-MRS may be a promising means of evaluating the therapeutic effects of BDNF on AD. [ABSTRACT FROM AUTHOR]