Defect Analysis in Microgroove Machining of Nickel-Phosphide Plating by Small Cross-Angle Microgrooving

Crystalline nickel-phosphide (c-Ni-P) plating is a newly developed mold material for precision glass molding (PGM) to fabricate microgrooves. In the ultraprecision cutting process of the c-Ni-P plating material, the neighboring microgrooves are required to adjoin with each other to ensure acute microgroove ridges and miniaturize the microgroove size. Generally, defects of burrs and fracture pits can easily occur on the ridges when the plating layer is grooved. Burrs appear when tears dominate in material removal with a large adjacent amount. With the change of the adjacent amount, the removed material is sheared out from the workpiece, and when the cutting depth of the groove ridge is over the brittle-ductile transition thickness, fracture pits arise. To restrict these defects, a small cross-angle microgrooving method is proposed to test the critical adjacent amount range efficiently. It is found that an acute ridge of the microgroove is formed with a small enough adjacent amount; when this amount is in the range of 570 nm~720 nm in the microgroove machining process, fracture pits begin to arise on the gradient edge. High-quality microgrooves can be obtained based on this methodology

A Mathematical Modeling to Predict the Cutting Forces in Microdrilling

In microdrilling, because of lower feed, the microdrill cutting edge radius is comparable to the chip thickness. The cutting edges therefore should be regarded as rounded edges, which results in a more complex cutting mechanism. Because of this, the macrodrilling thrust modeling is not suitable for microdrilling. In this paper, a mathematical modeling to predict microdrilling thrust is developed, and the geometric characteristics of microdrill were considered in force models. The thrust is modeled in three parts: major cutting edges, secondary cutting edge, and indentation zone. Based on slip-line field theory, the major cutting edges and secondary cutting edge are divided into elements, and the elemental forces are determined by an oblique cutting model and an orthogonal model, respectively. The thrust modeling of the major cutting edges and second cutting edge includes two different kinds of processes: shearing and ploughing. The indentation zone is modeled as a rigid wedge. The force model is verified by comparing the predicted forces and the measured cutting forces

Unraveling the Photocatalytic Mechanisms on TiO2 Surfaces Using the Oxygen-18 Isotopic Label Technique

During the last several decades TiO2 photocatalytic oxidation using the molecular oxygen in air has emerged as a promising method for the degradation of recalcitrant organic pollutants and selective transformations of valuable organic chemicals. Despite extensive studies, the mechanisms of these photocatalytic reactions are still poorly understood due to their complexity. In this review, we will highlight how the oxygen-18 isotope labeling technique can be a powerful tool to elucidate complicated photocatalytic mechanisms taking place on the TiO2 surface. To this end, the application of the oxygen-18 isotopic-labeling method to three representative photocatalytic reactions is discussed: (1) the photocatalytic hydroxylation of aromatics; (2) oxidative cleavage of aryl rings on the TiO2 surface; and (3) photocatalytic decarboxylation of saturated carboxylic acids. The results show that the oxygen atoms of molecular oxygen can incorporate into the corresponding products in aqueous solution in all three of these reactions, but the detailed incorporation pathways are completely different in each case. For the hydroxylation process, the O atom in O2 is shown to be incorporated through activation of O2 by conduction band electrons. In the cleavage of aryl rings, O atoms are inserted into the aryl ring through the site-dependent coordination of reactants on the TiO2 surface. A new pathway for the decarboxylation of saturated carboxylic acids with pyruvic acid as an intermediate is identified, and the O2 is incorporated into the products through the further oxidation of pyruvic acid by active species from the activation of O2 by conduction band electrons

The effect of cutting fluid on high strain rate dynamic mechanical property and cutting force of ultra-high-strength steel

Due to the different composition of cutting fluid will affect the failure stress of the material in the shear deformation area, so the rational use of cutting fluid can optimize the cutting force and the surface integrity of parts. Four kinds of hat-shaped samples with shear band widths were designed. The effects of different cutting fluids on mechanical properties of ultrahigh strength steel at different shear strain rates were studied in this paper by SHPB, and verified by cutting experiments. The stress–strain curve, shear failure stress, fracture morphology and cutting force were studied systematically. Experimental results show that the stress remains stable for a period of time with the increases of strain after strain hardening at γs= 10.03 × 104 1/s. All shear fracture is ductile fracture and at γs<1 0.03 ×104 1/s, the dimple will be elongated with the increase of the strain rate. When the shear bandwidth is reduced from 100 μm to 50 μm, size effect occurs, and the failure stress is increased by nearly 30%. The Rehbinder effect of TRIM E709 is more significant, the shear failure stress is the smallest, Fx, Fy and Fz decreases by 23.93%, 33.08% and 50.29% compared with HY-103. This research can guide the high-quality machining of ultra-high strength steel and may also evaluate and develop new cutting fluids to improve cutting performance

On Multi-Objective Based Constitutive Modelling Methodology and Numerical Validation in Small-Hole Drilling of Al6063/SiCp Composites

Discrepancies in capturing material behavior of some materials, such as Particulate Reinforced Metal Matrix Composites, by using conventional ad hoc strategy make the applicability of Johnson-Cook constitutive model challenged. Despites applicable efforts, its extended formalism with more fitting parameters would increase the difficulty in identifying constitutive parameters. A weighted multi-objective strategy for identifying any constitutive formalism is developed to predict mechanical behavior in static and dynamic loading conditions equally well. These varying weighting is based on the Gaussian-distributed noise evaluation of experimentally obtained stress-strain data in quasi-static or dynamic mode. This universal method can be used to determine fast and directly whether the constitutive formalism is suitable to describe the material constitutive behavior by measuring goodness-of-fit. A quantitative comparison of different fitting strategies on identifying Al6063/SiCp’s material parameters is made in terms of performance evaluation including noise elimination, correlation, and reliability. Eventually, a three-dimensional (3D) FE model in small-hole drilling of Al6063/SiCp composites, using multi-objective identified constitutive formalism, is developed. Comparison with the experimental observations in thrust force, torque, and chip morphology provides valid evidence on the applicability of the developed multi-objective identification strategy in identifying constitutive parameters

An Enhanced Reconfiguration for Deterministic Transmission in Time-Triggered Networks

The emerging momentum of digital transformation of industry, i.e. Industry 4.0, poses strong demands for integrating industrial control networks, and Ethernet to enable the real-time Internet of Things (RT-IoT). Time-triggered (TT) networks provide a cost-efficient integrated solution while RT-IoT arouses the reconfiguration challenges: the network has to be flexible enough to adapt to changes and yet provides deterministic transmission persistently during network reconfiguration. Software defined network benefits the flexible industrial control by configuring the rules handling frames. However, previous reconfiguration mechanisms are mostly oriented to the context of data centers and wide area networks and thus do not consider the deterministic transmission in TT networks. This paper focuses on the reconfiguration (i.e., updates) for the deterministic transmission. To minimize the overhead during updates, namely the minimum number of loss frames and the minimum duration time of updates, we first establish an update theory based on the dependence relationship derived by the conflicts during updates. In addition then the reconfiguration problem is modeled with the dependence graph built by the relationship. On such a basis, we present a reconfiguration mechanism and its implementation to solve the problem. Finally, we evaluate the proposed reconfiguration mechanism in two real industrial network topologies. The experimental results demonstrate that compared with previous methods, our mechanism significantly reduces the number of loss frames and achieves zero loss in almost all cases

Determining the TiO₂‑Photocatalytic Aryl-Ring-Opening Mechanism in Aqueous Solution Using Oxygen-18 Labeled O₂ and H₂O

The molecules O₂ and H₂O dominate the cleavage of aromatic sp² C–C bonds, a crucial step in the degradation of aromatic pollutants in aqueous TiO₂ photocatalysis, but their precise roles in this process have remained elusive. This can be attributed to the complex oxidative species involved and to a lack of available models for reactions with a high yield of direct products. Here, we used oxygen-18 isotope labeled O₂ and H₂O to observe the aromatic ring-opening reaction of the model compound 3,5-di-<i>tert</i>-butylcatechol (DTBC), which was mediated by TiO₂ photocatalysis in an aqueous acetonitrile solution. By analyzing the primary intermediate products (∼75% yield), especially the seven-membered ring anhydrides that were formed, we obtained direct evidence for the oxygen atom of dioxygen insertion into a C–C bond of the aromatic ring. This indicates that molecular oxygen is the ultimate ring-opening agent in TiO₂ photocatalysis and that it undergoes single O atom incorporation rather than the previously proposed molecular oxygen 1,2-addition processes. The ratio of intradiol to extradiol products depends on the particle size of TiO₂ catalysts used, which suggests that the O₂ activation is correlated with the available coordination sites on the TiO₂ surface in the photocatalytic cleavage of the aromatic ring

Nanocoiled Assembly of Asymmetric Perylene Diimides: Formulation of Structural Factors

Nanocoiled assemblies of organic π-conjugated molecules have attracted intense attention because of their various practical applications. Herein, the assembly of highly fluorescent monolayer and bilayer nanocoils from asymmetric perylene diimide (PDI) molecules is reported. Through systematic investigation of 21 asymmetric PDI derivatives, some critical molecular structural parameters for the formation of nanocoils, involving the position of methoxy substituents at the phenyl moiety on one side and the appropriate linker that attaches the phenyl moiety to the PDI core, are formulated. The J-aggregate nature of the helical π-stacking geometry within the nanocoil is demonstrated by optical characterization. All of the nanocoils are highly emissive, with a fluorescence quantum yield greater than 25%. Furthermore, all of the nanocoils exhibited a NIR emission with a band maximum greater than 710 nm. This new class of highly NIR fluorescent nanostructures offers promising applications in areas such as optoelectronics, fluorescent sensors, and biological imaging