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Wentian Shi, Yude Liu, Xuezhi Shi, Yanjun Hou, Peng Wang, Guohua Song
A 400 W high-power laser was used to fabricate 200-µm-thick Ti-6Al-4V samples to evaluate the effects of small (50 μm) and large (200 μm) beam diameter on density, microstructure and mechanical properties. A series of single-track experiments demonstrated that it was challenging for the small-beam laser to fabricate smooth and defect-free scan tracks. A larger beam diameter efficiently avoided process instability and provided a more stable and uniform melt pool. By increasing the beam diameter, the density of multilayer samples reached 99...
July 18, 2018: Materials
Jorge Salguero, Juan Manuel Vazquez-Martinez, Irene Del Sol, Moises Batista
One of the main criteria for the establishment of the performance of a forming process by material removal is based on cutting tool wear. Wear is usually caused by different mechanisms, however, only one is usually considered as predominant or the controller of the process. This experimental research is focused on the application of Pin-on-Disc wear tests, in which the tribological interference between UNS A92024-T3 Aluminum⁻Copper alloy and tungsten carbide (WC⁻Co) has been studied. The main objective of this study is focused on the determination of the predominant wear mechanisms involved in the process, as well as the characterization of the sliding and friction effects by using SEM and Energy Dispersion Spectroscopy (EDS) techniques, as applied to WC⁻Co (cutting tool material)/Al (workpiece material) which are widely used in the aerospace industry...
July 18, 2018: Materials
Jessica Shiels, David Harbottle, Timothy N Hunter
This study investigated dispersions analogous to highly active nuclear waste, formed from the reprocessing of Spent Nuclear Fuel (SNF). Non-radioactive simulants of spheroidal caesium phosphomolybdate (CPM) and cuboidal zirconium molybdate (ZM-a) were successfully synthesised; confirmed via Scanning Electron Microscopy (SEM), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy. In addition, a supplied ZM (ZM-b) with a rod-like/wheatsheaf morphology was also analysed along with titanium dioxide (TiO₂)...
July 18, 2018: Materials
Sukhyun Hwang, Shin Hye Chung, Jung-Tae Lee, Yong-Tae Kim, Yoo Jin Kim, Soram Oh, In-Sung Luke Yeo
This study investigated the influences of acidity, ethanol, and pigment on the optical properties, microhardness, and surface roughness (Ra ) of a nanohybrid dental composite resin. A total of 108 disc-shaped specimens were fabricated using a nanohybrid dental composite and allocated into 36 different storage solutions according to the levels of pH (2.0, 3.0, 4.0, and 5.5), ethanol (0%, 20%, and 40%), and anthocyanin pigment (0%, 2.5%, and 12.5%). Measurements of the colorimetric parameter and the amount of color change (ΔE), translucency parameter (TP), microhardness, and surface roughness (Ra ) were performed at 24 h (baseline), 1-, 2-, 3-, and 4-weeks...
July 18, 2018: Materials
Yue Guo, Mingxing Zhou, Xingdong Sun, Long Qian, Lijia Li, Yingjie Xie, Zeyang Liu, Di Wu, Liguo Yang, Tong Wu, Dan Zhao, Jinguo Wang, Hongwei Zhao
Effects of temperature and strain rate on the fracture behaviors of an Al-Zn-Mg-Cu alloy are investigated by isothermal uniaxial tensile experiments at a wide range of temperatures and strain rates, from room temperature (RT) to 400 °C and from 10-4 s-1 to 10-1 s⁻1 , respectively. Generally, the elevation of temperature leads to the increasing of elongation to fracture and the reduction of peak stress, while higher strain rate results in the decreasing of elongation to fracture and the increasing of peak stress...
July 18, 2018: Materials
Huihui Cao, Wangtu Huo, Shufang Ma, Yusheng Zhang, Lian Zhou
For the purpose of detecting the influence of grain structure of a Mg matrix on the microstructure and corrosion resistance of micro-arc oxidation (MAO) coating, prior to MAO processing, sliding friction treatment (SFT) was adopted to generate a fine-grained (FG) layer on coarse-grained (CG) pure Mg surface. It showed that the FG layer had superior corrosion resistance, as compared to the CG matrix, owing to the grain refinement; furthermore, it successfully survived after MAO treatment. Thus, an excellent FG-MAO coating was gained by combining SFT and MAO...
July 18, 2018: Materials
Dong Li, Zhou-Lian Zheng, Rui Yang, Peng Zhang
Orthotropic membrane materials have been applied in the numerous fields, such as civil engineering, space and aeronautics, and mechanical engineering, among others. During their serving lifespan, these membranes are always facing strong stochastic vibrations induced by the random impact load such as hail, heavy rain, and noise, among others. In this paper, the stochastic vibration problem of orthotropic membrane subjected to random impact load is investigated. The statistical characteristics of random impact load are initially obtained based on the stochastic pulse theory...
July 18, 2018: Materials
Lusha Tian, Yongchun Guo, Jianping Li, Feng Xia, Minxian Liang, Yaping Bai
The effects of cooling rate 0.15, 1.5, 15, 150, and 1.5 × 105 °C/s on the microstructures and mechanical properties of Al-13Si-4Cu-1Mg-2Ni cast piston alloy were investigated. The results show that with an increase of solidification cooling rate, the secondary dendrite arm spacing (SDAS) of this model alloy can be calculated using the formula D = 47.126v - 1/3. The phases formed during the solidification with lower cooling rates primarily consist of eutectic silicon, M-Mg₂Si phase, γ-Al₇Cu₄Ni phase, δ-Al₃CuNi phase, ε-Al₃Ni phase, and Q-Al₅Cu₂Mg₈Si₆ phase...
July 18, 2018: Materials
Meigui Yin, Wenjian Wang, Weifeng He, Zhenbing Cai
Outer particle collision with certain dynamic objects is not a pure impact wear behavior; it is typically accompanied by sliding wear phenomena. This study is aimed at investigating the impact-sliding wear performance of three different TC17 titanium alloys. One was untreated, and the other two were subjected to laser shock peening (LSP) by 5 and 7 J pulse energy, respectively. The wear test was performed on a novel impact-sliding wear testing rig, which can realize multiple impact-sliding motions by changing motion parameters in the x and z directions...
July 17, 2018: Materials
Ilaria Corsi, Andrea Fiorati, Giacomo Grassi, Irene Bartolozzi, Tiberio Daddi, Lucio Melone, Carlo Punta
Nanoremediation, which is the use of nanoparticles and nanomaterials for environmental remediation, is widely explored and proposed for preservation of ecosystems that suffer from the increase in human population, pollution, and urbanization. We herein report a critical analysis of nanotechnologies for water remediation by assessing their sustainability in terms of efficient removal of pollutants, appropriate methods for monitoring their effectiveness, and protocols for the evaluation of any potential environmental risks...
July 17, 2018: Materials
Safaa Lhadi, Maria-Rita Chini, Thiebaud Richeton, Nathalie Gey, Lionel Germain, Stéphane Berbenni
Near β titanium alloys can now compete with quasi-α or α/β titanium alloys for airframe forging applications. The body-centered cubic β-phase can represent up to 40% of the volume. However, the way that its elastic anisotropy impacts the mechanical behavior remains an open question. In the present work, an advanced elasto-viscoplastic self-consistent model is used to investigate the tensile behavior at different applied strain rates of a fully β-phase Ti alloy taken as a model material. The model considers crystalline anisotropic elasticity and plasticity...
July 17, 2018: Materials
Hyuk-Jun Kwon, Junyeob Yeo, Jae Eun Jang, Costas P Grigoropoulos, Jae-Hyuck Yoo
Wetting has been studied in various fields: chemical industry, automobile manufacturing, food companies, and even life sciences. In these studies, super-hydrophobic surfaces have been achieved through complex steps and processes. To realize super-hydrophobicity, however, we demonstrated a simple and single pass laser process for the fabrication of micro/nano hierarchical structures on the flexible polytetrafluoroethylene (PTFE, Teflon) surface. The fabricated hierarchical structures helped increase the hydrophobicity by augmenting the surface roughness and promoting air-trapping...
July 17, 2018: Materials
Shuai Hu, Zhenyu Chen, Xingpeng Guo
A novel and simple method to improve the corrosion resistance of copper by constructing a three-dimensional (3D) 1-dodecanethiol self-assembled monolayer (SAM) in 3.5% NaCl solution is reported in this study. Several drops of 1% H₃PO₄ solution are thinly and uniformly distributed on copper surface to form a 3D nanostructure constituted by Cu₃(PO₄)₂ nanoflowers. The anticorrosion properties of 1-dodecanethiol SAM on copper surface and on copper surface that is treated with H₃PO₄ solution were evaluated...
July 17, 2018: Materials
Driss Kenfaui, Moussa Gomina, Jacques Guillaume Noudem, Daniel Chateigner
The misfit-layered Ca₃Co₄O₉ oxide is being seen as a potential thermoelectric (TE) candidate for high-temperature power generation in air. Given the very small size and low strength exhibited by single crystals, grain-oriented Ca₃Co₄O₉ ceramics are worth elaborating to capitalize on their anisotropy. However, the usual textured pellets are too thin to probe the TE properties along their principal crystallographic directions. In this paper, we report on the anisotropy of TE properties in the 350⁻860 K range within thick textured Ca₃Co₄O₉ ceramics fabricated by moderately pressing at 1173 K stacks of pellets primarily textured using spark plasma sintering (SPS), spark plasma texturing (SPT), and hot pressing (HP)...
July 17, 2018: Materials
Hongbing Chen, Bin Xu, Yilung Mo, Tianmin Zhou
In this study, the numerical investigation of the detectability of concrete aggregate segregation in circular concrete-filled steel tubulars (CCFST) based on piezoelectric lead zirconate titanate (PZT) measurement is performed. The stress wave propagation in the concrete core of circular CCFST excited with a surface-mounted PZT actuator is studied with multi-scale and multi-physical field coupling analysis. The piezoelectric effect of PZT patches and its coupling effect with CFSTs are considered. Numerical concrete modeling technology is employed to construct the concrete core composed of randomly distributed aggregates with and without aggregate segregation at different levels, mortar, and an interfacial transition zone (ITZ)...
July 17, 2018: Materials
Yongsheng Lian, Xiaoting He, Sijie Shi, Xue Li, Zhixin Yang, Junyi Sun
In this study, we use a multi-parameter perturbation method to solve the problem of a functionally graded piezoelectric cantilever beam under combined loads, in which three piezoelectric coefficients are selected as the perturbation parameters. First, we derive the two basic equations concerning the Airy stress function and electric potential function. By expanding the unknown Airy stress function and electric potential function with respect to three perturbation parameters, the two basic equations were decoupled, thus obtaining the corresponding multi-parameter perturbation solution under boundary conditions...
July 16, 2018: Materials
Hongtao Wang, Ruifeng Du, Ruijuan Shi, Junlong Liu
In this study, Zr0.92 Y0.08 O2-α (8YSZ) powders were synthesized by the sol-gel method. The chemical physics changes and phase formation temperature of 8YSZ crystal were determined by thermogravimetry analysis and differential scanning calorimetry (TGA-DSC). 8YSZ-low melting point glass powder (8YSZ-glass) composite electrolytes with various weight ratios were prepared and calcined at different temperatures. The X-ray diffraction (XRD) patterns of the composite electrolytes were tested. The effects of synthesis temperature, weight ratio, test temperature, and oxygen partial pressure on the conductivities of 8YSZ-glass composite electrolytes, were also investigated at 400⁻800 °C...
July 16, 2018: Materials
Jesus-Maria Hernandez-Vazquez, Iker Garitaonandia, María Helena Fernandes, Jokin Muñoa, Luis Norberto López de Lacalle
Accurate finite element models of mechanical systems are fundamental resources to perform structural analyses at the design stage. However, uncertainties in material properties, boundary conditions, or connections give rise to discrepancies between the real and predicted dynamic characteristics. Therefore, it is necessary to improve these models in order to achieve a better fit. This paper presents a systematic three-step procedure to update the finite element (FE) models of machine tools with numerous uncertainties in connections, which integrates statistical, numerical, and experimental techniques...
July 16, 2018: Materials
Zhichao Zhang, Hu Tang, Yujiao Ke, Yu Li, Xiaochen Jiao, Changjian Geng, Yucheng Zhao, Mingzhi Wang
Nonstoichiometric TiC0.5 and (TiNb)0.5 powders were prepared by the mechanical alloying process using Ti, Nb, and TiC powders as raw materials. Furthermore, the as-prepared TiC0.5 and (TiNb)0.5 powders were used as initial materials to fabricate TiC0.5 and (TiNb)0.5 compacts under high pressures and high temperatures (HTHP) of 5.5 GPa and 1200⁻1550 °C for 5 min. Phase identification and microstructure of the mechanical-alloyed powders and the sintered TiC0.5 and (TiNb)0.5 compacts were realized by an X-ray diffractometer and scanning electron microscope...
July 16, 2018: Materials
Viet Q Vu, Yan Beygelzimer, Roman Kulagin, Laszlo S Toth
A new severe plastic deformation process, plastic flow machining (PFM), was introduced recently to produce sheet materials with ultrafine and gradient structures from bulk samples in one single deformation step. During the PFM process, a part of a rectangular sample is transformed into a thin sheet or fin under high hydrostatic pressure. The obtained fin is heavily deformed and presents a strain gradient across its thickness. The present paper aims to provide better understanding about this new process via analytical modelling accompanied by finite element simulations...
July 16, 2018: Materials
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