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Vegetable fields are often contaminated by heavy metals, and Spodoptera exiguais a major vegetable pest which is stressed by heavy metals mainly by feeding. In this study, cadmium accumulation in the tissues of S. exiguaexposed to cadmium and its effects on the growth and development of the parents and the offspring were investigated. Under the stress of different concentrations of cadmium (0.2, 3.2, and 51.2 mg kg–1), the cadmium content in each tissue of S. exiguaincreased in a dose-dependent manner. At the larval stage, the highest cadmium accumulation was found in midgut in all three cadmium treatments, but at the adult stage, the highest cadmium content was found in fat body. In addition, the cadmium content in ovaries was much higher than in testes. When F1S. exiguawas stressed by cadmium and the F2generation was not fed a cadmium-containing diet, the larval survival, pupation rate, emergence rate and fecundity of the F2generation were significantly reduced in the 51.2 mg kg–1treatment compared to the corresponding F1generation. Even in the F2generation of the 3.2 mg kg–1treatment, the fecundity was significantly lower than in the parental generation. The fecundity of the only-female stressed treatment was significantly lower than that of the only-male stressed treatment at the 3.2 and 51.2 mg kg–1cadmium exposure levels. When only mothers were stressed at the larval stage, the fecundity of the F2generation was significantly lower than that of the F1generation in the 51.2 mg kg–1treatment, and it was also significantly lower than in the 3.2 and 0.2 mg kg–1treatments. The results of our study can provide useful information for forecasting the population increase trends under different heavy metal stress conditions and for the reliable environmental risk assessment of heavy metal pollution.

Purpose: The electrical properties of piezoelectric vibrators have a crucial influence on the operating state of ultrasonic motors. In order to solve the problem that the current piezoelectric vibrator generates a large amount of heat during vibration to degrade its performance, which in turn affects the normal operation of ultrasonic motors, this paper prepares a novel piezoelectric vibrator and tests its maximum vibration velocity under the working condition, which is more than twice as much as that of the current commercial PZT-8. Design/methodology/approach: The crystal structures of the samples were analyzed by using an X-ray diffractometer. For microstructure observation, samples were observed by scanning electron microscope (SEM). The quasi-static piezoelectric coefficient meter (ZJ-3AN) was used for piezoelectric measurement. Dielectric properties were measured by utilizing an impedance analyzer (Agilent 4294A) with a laboratory heating unit. Ferroelectric hysteresis loops were obtained using a ferroelectric analyzer (Radiant, Multiferroic 100). A Doppler laser vibrometer (Polytec PSV-300F, Germany) and a power amplifier were used for piezoelectric vibration measurements, during which the temperature rise was determined by an infrared radiation thermometer (Victor 303, China). Findings: The ceramics exhibit enhanced piezoelectric performance at 0.1–0.4 mol% of Yb doping contents. The ceramic of 0.4 mol% Yb reaches the maximal internal bias field and presents a larger mechanical quality factor of 1,692 compared with that of 0.2 mol% Yb-doped ceramic, in spite of a slightly decreased dielectric constant of 439 pC/N, the unit of the piezoelectric constant, which is the ratio of the local charge (pC) to the frontal force (N) and electromechanical coupling coefficient of 0.63. The vibrator with this large mechanical quality factor ceramic displays a vibration velocity of up to 0.81 m/s under the constraint of 20 °C temperature rising, which is much higher than commercial high-power piezoelectric ceramics PZT-8. Originality/value: The enhanced high-power properties of the piezoelectric vibrator by Yb doping may provide a potential application for the high-performance USM and offer the possibility of long-term stable operation under high power for special equipment like USM. In the subsequent phase of research, the novel PZT-based high-power piezoelectric vibrator can be utilized in the USM, and the motor's performance will be evaluated under aerospace conditions to objectively assess the reliability of the piezoelectric vibrator.

The plunger component is a key part of the plunger pump in the aircraft hydraulic system. Neck-spinning process is commonly used to fabricate plunger components, of which the quality of the spinning process significantly affects the performance of plunger pumps. One of the bottlenecks faced by the industry in the spinning process is to choose a suitable neck-spinning process so as to ensure the quality of plunger components. It is necessary to propose a reliable method to optimize the process parameters which affect the neck-spinning quality of plunger components. In this study, a calculable finite element analysis (FEA) model is established to simulate the three-roller neck-spinning process of the plunger component, which includes six typical slipper structures, two roller structures, and two spinning parameters. The FEA model is then validated by comparing the simulated spinning forces with the corresponding experimental results. The influence of the process conditions on the neck-spinning quality is investigated. And the orthogonal simulation results are analyzed by a combination of range method and fuzzy mathematical analysis method to recommend a reasonable slipper structure, roller structure and neck-spinning parameters. This study provides a promising method to improve the manufacturing quality of the typical plunger components.

Compared with Conventional Grinding (CG), the Ultrasonic Vibration-Assisted Grinding (UVAG) is more competitive for the machining of difficult-to-cut materials. In this article, a novel ultrasonic vibration plate sonotrode that enables the special longitudinal full-wave and transverse half-wave vibration modes was proposed. The vibration characteristics of the proposed sonotrode was theoretically studied based on the apparent elasticity and Rayleigh methods, achieving a single longitudinal workpiece ultrasonic vibration with an amplitude of 7.6 μm. A superior vibration uniformity was achieved, as indicated by the coupling coefficient of 0.5. Based on the proposed method, the normal and tangential grinding forces decreased by 35 % and 39 % in comparison with the CG, and an improved machined surface was obtained in the UVAG of Ti-6Al-4V, with the following characteristics: vibration amplification of 7.6 μm; a cut depth of 0.1 mm; a workpiece feed rate of 100 mm/min; and a grinding speed of 30 m/s.

Aiming at the unclear knowledge of the effect of the axial grain separation distance ΔZvon the interference, the double diamond grains grinding tests and finite element (FE) simulations were carried out to understand the interference of diamond grains generated in SiC grinding process. A double-grains grinding device with rotational holder was first developed, which could adjust ΔZvconveniently. The experimental results demonstrate that the normal grinding force is more sensitive than the tangential grinding force to ΔZvat agmax = 0.3 and 1 μm. The grinding forces and cross-section profiles of the grinding grooves show the same trend to increase initially and then decline with the expansion of ΔZv. The critical value of ΔZvis determined at 309 μm based on the variations of grinding forces and cross-section profiles in the grinding experiments. The surface morphologies and surface/subsurface Von Mises stress fields were also analyzed with a 3D FE model. The interference arising from adjacent diamond grains results in the severity of the stress field in the central region of the two grooves. A critical ΔZvbetween adjacent rows is determined at 300 μm when the severity of the overlap stress field reaches the maximum value, which coincides well with the experimental results.

Ti2AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in aeronautic and automotive engines due to its excellent mechanical properties and high strength retention at elevated temperature. The aim of this work is to present a fast and reliable methodology of inverse identification of constitutive model parameters directly from cutting experiments. FE-machining simulations implemented with a modified Johnson-Cook (TANH) constitutive model are performed to establish the robust link between observables and constitutive parameters. A series of orthogonal cutting experiments with varied cutting parameters is carried out to allow an exact comparison to the 2D FE-simulations. A cooperative particle swarm optimization algorithm is developed and implemented into the Matlab programs to identify the enormous constitutive parameters. Results show that the simulation observables (i.e., cutting forces, chip morphologies, cutting temperature) implemented with the identified optimal material constants have high consistency with those obtained from experiments, which illustrates that the FE-machining models using the identified parameters obtained from the proposed methodology could be predicted in a close agreement to the experiments. Considering the wide range of the applied unknown parameters number, the proposed inverse methodology of identifying constitutive equations shows excellent prospect, and it can be used for other newly developed metal materials.

A state-of-the-art review on monolayer electroplated and brazed cubic boron nitride (CBN) superabrasive wheels for grinding metallic materials has been provided in this article. The fabrication techniques and mechanisms of the monolayer CBN wheels are discussed. Grain distribution, wheel dressing, wear behavior, and wheel performance are analyzed in detail. Sample applications of monolayer CBN wheel for grinding steels, titanium alloys, and nickel-based superalloys are also provided. Finally, this article highlights opportunities for further investigation of monolayer CBN grinding wheels.

As one kind of key anti-fatigue manufacture approaches with simplicity and effectiveness, the hole cold expansion technology satisfies the increasing needs for light weight and durability of aircraft structures. It can improve the fatigue life by several times at no additional weight conditions. The hole cold expansion technology has been widely used in manufacturing and repairing of both fighters and commercial aircraft, and has become a research hotspot in the strengthening technology. In recent years, hole cold expansion process methods, residual stress around expanded holes, the behavior of fatigue crack initiation and propagation, and fatigue lives after cold expansion are researched extensively through lots of experiments and finite element simulations. A review on the hole cold expansion technology research status in the last twenty years is presented in this paper. Via the analysis of the current characteristics and defects of the hole cold expansion technology, combined with the actual needs in design and manufacture of new-generation aircraft, development trends and novel research directions are presented for realizing precise and high-efficiency anti-fatigue manufacture.

(TiCp+TiBw)/Ti-6Al-4V titanium matrix composites (PTMCs) have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.

In order to understand chip formation mechanism during high speed grinding of nickel-based superalloy, grinding tests with single brazed diamond grit were performed with the wheel speed from 20 m/s to 150 m/s. The kinematic grit trace was geometrically optimised to meet the requirement of the real grinding process. The maximum undeformed chip thickness was kept at 1 μmm. Grooves and chips were observed and analysed by means of optical microscope and scanning electron microscope. The results obtained showed that, when the wheel speed was below 60 m/s, the serrated behaviour of the chips was not obvious. However, the typical serrated behaviour took place on the free surface in case of the wheel speed of above 60 m/s. The frequency of the chip segmentation was increased linearly with the increasing grinding speed from 60 m/s to 150 m/s.

Cu-Sn-Ti alloy, CBN grains and graphite particles were mixed, moulded and sintered to prepare the self-lubrication CBN abrasive composite blocks and grinding wheels. The mechanical strength of the composite blocks was measured. The fracture morphology and the interfacial microstructure of blocks were characterised. Dressing experiments were conducted. The graphite film was observed on the working surface. Finally, the grinding temperature of self-lubrication CBN grinding wheel was compared with that of the vitrified counterpart. The obtained results show that the bending strength of the composite blocks reaches 116 MPa in case of 5 wt.% graphite particles. Chemical joining has happened within the interface of CBN/Cu-Sn-Ti and graphite/Cu-Sn-Ti. Graphite film has been formed successfully and spread to the working layer surface after dressing. The grinding temperature of the self-lubrication CBN wheel is lower than that of the vitrified counterparts. All this indicates the potential of the graphite self-lubrication CBN grinding wheels in machining difficult-to-cut materials.