Examination of superplastic forming combined with diffusion bonding for titanium: Perspective from experience

Superplastic forming (SPF) combined with diffusion bonding (DB) has been used successfully for the fabrication of titanium aerospace hardware. Many of these applications have been for military aircraft, whereby a complex built-up structure has been replaced with monolithic parts. Several methods for applying the two- and four-sheet titanium SPF/DB processes have been devised, including the welding of sheets prior to forming and the use of silk-screened stop-off (yttria) to prevent bonding where it is undesirable. Very little progress has been made in the past few years toward understanding and modeling the SPF/DB process using constitutive equations and data by laboratory testing. Concerns that engineers face in designing for fatigue life, acceptable design loads, and damage tolerance are currently being studied, but the database is very limited. This is a summary of past work found in the literature and forms the foundation for additional research. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

Autonomous Magnetic Microrobots by Navigating Gates for Multiple Biomolecules Delivery

The precise delivery of biofunctionalized matters is of great interest from the fundamental and applied viewpoints. In spite of significant progress achieved during the last decade, a parallel and automated isolation and manipulation of rare analyte, and their simultaneous on‐chip separation and trapping, still remain challenging. Here, a universal micromagnet junction for self‐navigating gates of microrobotic particles to deliver the biomolecules to specific sites using a remote magnetic field is described. In the proposed concept, the nonmagnetic gap between the lithographically defined donor and acceptor micromagnets creates a crucial energy barrier to restrict particle gating. It is shown that by carefully designing the geometry of the junctions, it becomes possible to deliver multiple protein‐functionalized carriers in high resolution, as well as MCF‐7 and THP‐1 cells from the mixture, with high fidelity and trap them in individual apartments. Integration of such junctions with magnetophoretic circuitry elements could lead to novel platforms without retrieving for the synchronous digital manipulation of particles/biomolecules in microfluidic multiplex arrays for next‐generation biochips.     

Ternary MOF‑Based Redox Active Sites Enabled 3D‑on‑2D Nanoarchitectured Battery‑Type Electrodes for High‑Energy‑Density Supercapatteries

Designing rationally combined metal-organic frameworks(MOFs)with multifunctional nanogeometries is of significant research interest to enable the electrochemical properties in advanced energy storage devices.Herein,we explored a new class of binderfree dual-layered Ni-Co-Mn-based MOFs(NCM-based MOFs)with three-dimensional(3D)-on-2D nanoarchitectures through a polarityinduced solution-phase method for high-performance supercapatteries.The hierarchical NCM-based MOFs having grown on nickel foam exhibit a battery-type charge storage mechanism with superior areal capacity(1311.4μAh cm^−2 at 5 mA cm^−2),good rate capability(61.8%;811.67μAh cm^−2 at 50 mA cm^−2),and an excellent cycling durability.The superior charge storage properties are ascribed to the synergistic features,higher accessible active sites of dual-layered nanogeometries,and exalted redox chemistry of multi metallic guest species,respectively.The bilayered NCM-based MOFs are further employed as a battery-type electrode for the fabrication of supercapattery paradigm with biomass-derived nitrogen/oxygen doped porous carbon as a negative electrode,which demonstrates excellent capacity of 1.6 mAh cm^−2 along with high energy and power densities of 1.21 mWh cm^−2 and 32.49 mW cm^−2,respectively.Following,the MOF-based supercapattery was further assembled with a renewable solar power harvester to use as a self-charging station for various portable electronic applications.     

NiCo sensing layer for enhanced signals in planar hall effect sensors

NiCo alloy materials have been investigaged as a potential sensing layer for planar Hall effect (PHE) sensors in magnetic multilayer structures. In this study, the magnetoresistive performance of the NiCo alloy is compared with that of the NiFe alloy. With an optimum thickness of 10 nm, the increment of the PHE voltage (V _max ) for the NiCo-based sensor was approximately 1.5 times larger than that of the NiFe-based sensor. The field sensitivity of both sensor types appeared to be nearly equal. However, the dynamic field range for the NiCo sensor was increased by approximately 40% compared with that of the NiFe sensor. The measuring configuration was optimized in order to obtain higher field sensitivity in the sensor. The field sensitivity was measured to be at a maximum at a 20° angle between the easy axis of the sensor and the applied external field, which was approximately three times higher than that in the perpendicular direction.     

Strain energy density fracture criterion in elastodynamic mixed mode crack propagation

Sih's fracture criterion based on strain energy density, S, for mixed mode crack extension under static loading is extended to dynamic mixed mode, K_I and K_II, crack propagation. Influence of the second order term, σ_ox, which represents the non-singular constant stress acting parallel to the direction of crack propagation, on the S distribution surrounding the crack tip, is demonstrated. Numerical studies show that positive σ_ox enhances the fracture angle and negative σ_oxreduces the fracture angle irrespective of the sign of K_II/K_I, when S is measured at a critical distance r_c from the crack tip. This fracture criterion is verified by the crack curving results of dynamic photoelastic fracture specimens. Omission of σ_ox term leads to predicted fracture angles which are at variance with experimental data.     

An Integrated Approach Toward Renewable Energy Storage Using Rechargeable Ag@Ni0.67Co0.33S‐Based Hybrid Supercapacitors

Self‐powered charging systems in conjunction with renewable energy conversion and storage devices have attracted promising attention in recent years. In this work, a prolific approach to design a wind/solar‐powered rechargeable high‐energy density pouch‐type hybrid supercapacitor (HSC) is proposed. The pouch‐type HSC is fabricated by engineering nature‐inspired nanosliver (nano‐Ag) decorated Ni_0.67Co_0.33S forest‐like nanostructures on Ni foam (nano‐Ag@NCS FNs/Ni foam) as a battery‐type electrode and porous activated carbon as a capacitive‐type electrode. Initially, the core–shell‐like NCS FNs/Ni foam is prepared via a single‐step wet‐chemical method, followed by a light‐induced growth of nano‐Ag onto it for enhancing the conductivity of the composite. Utilizing the synergistic effects of forest‐like nano‐Ag@NCS FNs/Ni foam as a composite electrode, the fabricated device shows a maximum capacitance of 1104.14 mF cm^?2 at a current density of 5 mA cm^?2 and it stores superior energy and power densities of 0.36 mWh cm^?2 and 27.22 mW cm^?2, respectively along with good cycling stability, which are higher than most of previous reports. The high‐energy storage capability of HSCs is further connected to wind fans and solar cells to harvest renewable energy. The wind/solar charged HSCs can effectively operate various electronic devices for a long time, enlightening its potency for the development of sustainable energy systems.     

Human response to blast-induced vibration and air-overpressure: an Indian scenario

Ground vibration (V_max) and air-overpressure/noise (p) are some of the negative effects of blasting. The associated human annoyance and complaints are expected to show an increasing trend in the future as there is no economically viable alternative to blasting in mines in India.A study of the human response to blasting in four mining localities across India has shown that the response is not simply political, as frequently assumed. It has been found that irrespective of those questioned, a basic concern for the safety of property was the main response. There was a greater response from the middle-aged and middle-educated while fewer women than men responded. Assuming that a 100% negative response from the inhabitants will translate into complaints, a methodology is suggested to take account of the human response criteria when considering blasting within 400 m of habitations.     

Drilling of graphite/bismaleimide composite material

Drilling study of graphite/bismaleimide composite material was conducted by using different cutter materials (high-speed steel, carbide, and polycrystalline diamond) and drill geometries. It was found that polycrystalline diamond tools outperformed all other tools in terms of minimal surface damage, delamination, and fiber pullout. The drilling forces exerted in machining graphite/bismaleimide were recorded by using a dynamometer, and the morphology of drilled surfaces was evaluated with surface profilometry and optical and scanning electron microscopy. The drilling characteristics were evaluated in terms of cutting forces, tool wear, and surface morphology.     

Removal of Cr(VI) by thermally activated weed Salvinia cucullata in a fixed-bed column

The present study evaluates the feasibility of using a thermally activated fresh water weed in removing Cr(VI) from wastewater through column studies. The effect of flow rate, bed height and Cr(VI) concentration of the feed solution on the adsorption capacity of the activated weed was investigated. The adsorption capacity increased with decrease in both flow rate and bed height but increased with an increase in initial adsorbate concentration. Four different kinetic models, such as. Adams-Bohart, Bed Depth Service Time (BDST), Thomas and Yoon-Nelson models were first applied to the experimental data to predict the breakthrough curve and to determine the characteristic parameters of the column useful for designing large-scale column studies. Different statistical methods such as Sum of the Square of the Error (SSE), Sum of the Absolute Error (SAE), Average Relative Error (ARE), Average Relative Standard Error (ARS) and regression coefficient, were applied to evaluate the prominent and unique characteristic features of the experimental and predicted parameters under the respective models to find out the best fit. The performance stability of the adsorbent was tested by continuous adsorption-desorption studies.     

Influence of grain size and microstructure on oxidation rates in titanium alloy Ti-6Al-4V under superplastic forming conditions

Ti-6Al-4V (Ti-6-4) sheets of two different grain sizes were exposed to time and temperature conditions representative of superplastic forming (SPF). The influence of SPF conditions on oxidation rates was evaluated in terms of weight gain, α-case depth, and microhardness profile. Differences in the response are related to the difference in grain size between the two lots of Ti-6-4. Fine grain Ti-6Al-4V exhibits faster oxygen diffusion in all three areas examined in this study, weight gain, α-case thickness, and increased microhardness depth. The differences were found to be significant relative to diffusion analysis and processing during manufacturing. Results from this work support reduced temperature SPF using fine grain material and the accompanying benefits in manufacturing superplastic parts. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.