Explore the vast range of titles available.

This paper analyzes the fracture strength of ring-cut V-notched bearing steel under impact loading through numerical simulation. It systematically investigates how V-notch parameters—opening angle, root radius, and relative notch depth—influence the peak impact force. Furthermore, the study optimizes the V-notch parameters of the specimen. The results show that: the grooving depth has the largest impact on the peak impact force, the root radius is the second largest, and the opening angle has the smallest impact. Through the optimization of the parameters to obtain the opening angle θ = 30°, the root radius R = 0.25 mm, and the relative grooving depth of h = 0.3 of this set of optimal V-notch dimensions, from the quantitative point of view, it gives a more reasonable key process parameters.

The main goal of this study is to present an alternative method of pretreating metal surfaces, entitled mechanical grooving, for metal-polymer joining by friction stir spot welding (FSSW). This pretreatment consists of the successive passage of a rotating engraving tip on the metal surface, creating a multilinear textured pattern, being an innovative pretreatment for the production of hybrid structures by FSSW. Mechanical grooving results in the creation of a well-defined serrated profile that, when interacting with the polymer during welding, promotes the mutual anchoring of the dissimilar materials. Mechanically grooved and grinded aluminium were joined to polyamide 6 by FSSW, and the welds were characterised based on cross-section morphology, fractography, tool axial force, and tensile-shear testing. FTIR-ATR characterization demonstrated that the chemical degradation is not significant during welding and that at the metal/polymer interface, there is adhesion between the materials. The axial force during the plunging stage of welds produced with the mechanically grooved aluminium is around 900 N, while for the welds produced with grinded aluminium is close to 1900 N. Furthermore, the resulting meso-mechanical interlocking mechanism provides superior mechanical performance (4.00 kN ± 82 N) compared to welds executed using grinded aluminium (3.02 kN ± 420 N). Finally, different fracture modes were observed depending on the surface pretreatment used. For instance, while adhesive failure was observed in the grinded aluminium welds, a mixed adhesive-cohesive failure was observed in the mechanically grooved aluminium welds. The cohesive failure is mainly attributed to the good performance of the interlocking mechanism.

Rifling depth is a very important parameter of howitzer barrel design, which has great influence on howitzer firing performance and security. At present, there are two types of barrel rifling depth design, which are 1.27mm depth rifling and 2.3mm depth rifling. This paper studies the extrusion stress between top surface of rifling land and bearing band of projectile and the rifling depth of projectile. This paper studies the extrusion stress between top surface of rifling land and bearing band of projectile and rotating driving side force when deep rifling howitzer and shallow rifling howitzer are used. This paper studies the extrusion stress between top surface of rifling land and bearing band of projectile and rotating driving side force when deep rifling howitzer and shallow rifling howitzer fires unguided projectiles and guided projectiles. It can be found by comparison that shallow rifling howitzer does better. It can be found by comparison that shallow rifling howitzer does better that deep rifling howitzer in barrel life and guided projectile firing security. Research of this paper will produce an important meaning to our nation’s next generation howitzer.

Although cemented carbides have been manufactured by the powder metallurgy (P/M) technology for over a century now, systematic developmental efforts are still underway. In the present study, tool life improvements in metal grooving applications are the key objective. Four PVD-coated cemented carbides compositions, dedicated to groove steel, stainless steel, cast iron, and aluminium alloys, have been newly designed, along with their manufacturing conditions. Physical, mechanical and chemical characteristics—such as sintered density, modulus of elasticity, hardness, fracture toughness, WC grain size, and the chemical composition of the substrate material, as well as the chemical composition, microhardness, structure, and thickness of the coatings—have been studied. A series of grooving tests have also been conducted to assess whether modifications to the thus far marketed tool materials, tool geometries, and coatings can improve cutting performance. In order to compare the laboratory and application properties of the investigated materials with currently produced by reputable companies, commercial inserts have also been tested. The experimental results obtained indicate that the newly developed grooving inserts exhibit excellent microstructural characteristics, high hardness, fracture toughness, and wear resistance and that they show slightly longer tool life compared to the commercial ones.

The recoilless rifle with rifled barrels is a type of high-powered individual infantry weapon, boasting an effective firing range of up to 3,000 meters. Experiments have found that with the increase of firing range, the spin drift of spin-stabilized projectiles fired by recoilless rifle has seriously affected their shooting accuracy. In this paper, we study the influence of the drift effect of spin-stabilized projectiles on the impact point in the Recoilless rifle. The aerodynamic parameters of spinning projectiles were calculated using computational fluid dynamics method, and corresponding trajectory model was established to calculate drift. The reliability of ballistic model calculation was proved by comparison with experimental results. Combined with linearized swerving motion theory, some factors affecting drift were analyzed. The research results show that for low-speed spinning Projectile fired by recoilless rifles with Rifling, the influence of drift effect on impact point cannot be ignored. In addition, drift increases exponentially with dimensionless flight distance of Projectiles, and overturning moment coefficient and lift coefficient have significant effects on spin drift. The research outcomes will facilitate the effective completion of firing tables, thereby improving the shooting accuracy of recoilless rifle.

Bamboo–wood composites have found extensive applications in the container flooring, furniture, and construction industries. However, commonly utilized bamboo units such as four-side-planed rectangular bamboo strips and bamboo scrimber suffer from either low utilization rates or high adhesive content. The recently developed bamboo-flattening technology, which employs softening methods with saturated high-pressure steam, may improve the utilization rate and reduce the adhesive content, but its complex processes and high cost restrict its widespread application. This study introduces a novel bamboo–wood composite utilizing high-utilization, easy-to-manufacture bamboo units processed through a straightforward flattening-and-grooving method. However, the stress concentration introduced by the grooving treatment may affect the mechanical properties and stability of the bamboo–wood composites. In order to optimize the mechanical properties and bonding performance, response surface methodology based on a central composite rotatable design was used to map the effects of hot-pressing parameters (time, temperature, and pressure) on the mechanical properties. The bamboo-woodbamboo–wood composites prepared with optimized conditions of 1.18 min/mm pressing time, 1.47 MPa pressure, and a 150 °C temperature had a 121.51 MPa modulus of rupture and an 11.85 GPa modulus of elasticity, which exhibited an error of only ~5% between the experimental and model predictions. Finite element analysis revealed that, in comparison to homogeneous flat bamboo composites, grooved bamboo composites exhibited distinct tensile ductility and toughness due to discontinuous stress fields and alternating rigid–soft layers, which alter the stress transmission and energy dissipation mechanisms. Additionally, grooving treatment not only effectively improved the surface wettability of the bamboo plants, thus enhancing the permeability of the adhesive, but also facilitated adhesive penetration into parenchymal cells and fibers. This led to the formation of a more robust glue–nail structure and chemical bonding.

Retrofitting seismically deficient beam-column joints (BCJs) in reinforced concrete (RC) structures is crucial to preventing collapse during high-intensity earthquakes. Fiber reinforced polymer (FRP) composites have proven effective for retrofitting these components, but debonding of the FRP from concrete surfaces remains a challenge. Recently, the grooving method (GM) has emerged as a promising solution to mitigate this issue, enhancing the bond between FRP and concrete. This paper presents a numerical investigation of BCJs retrofitted with FRP composites using the GM, focusing on various design parameters. The study utilized finite element models developed in ABAQUS, incorporating the concrete damage plasticity (CDP) model to simulate the nonlinear behavior of concrete. The interface between the concrete and FRP was modeled as a perfect bond, simulating the strong adhesion provided by the GM. The numerical results were validated against experimental data from two BCJ specimens, showing good agreement in terms of load-displacement behavior, peak loads, and failure modes. Key parameters studied include the beam longitudinal reinforcement ratio, column axial load ratio, and joint aspect ratio. The findings reveal that these parameters significantly affect the shear capacity of retrofitted joints, impacting the efficiency of the retrofitting.

Although ultra-precision fly grooving (UPFG) is widely applied to fabricate micro-structured surfaces, few studies have focused on the cutting force model of UPFG. The unique kinematics of UPFG leads to the trans-scale variation of undeformed chip thickness from nanoscale to microscale, in which case the influence of material microstructure and size effect is prominent. This study proposes an analytical cutting force model for UPFG with full consideration of the kinematics, chip formation mechanism, material microstructure, material elastic recovery, size effect, and tool geometry. Specifically, by correlating micro-forming theory to crystal plastic theory, a hybrid slip-line model (HSLM) is developed to determine the flow stress in primary deformation zone, which can quantify the influence of size effect and microstructure, such as grain size, grain boundary, dislocation density, and crystal anisotropy, on flow stress. Then, the normal cutting force and frictional cutting force are estimated by analyzing the stress distribution and frictional states at tool-chip interface. The rubbing force induced by material elastic recovery is determined based on indentation theory. Finally, the models are experimentally validated by fly cutting of polycrystalline copper with different machining parameters, and it is also demonstrated that the proposed HSLM can capture the periodic transformation of cutting mechanism in UPFG from ploughing (compressive stress) to shearing (tensile stress) with tool rotation.

Spray pyrolysis deposition has been successfully applied to fabricate CTS thin films onto glass substrates that maintained at 300°C, via the homemade fully computerized system. A mixture aqueous solution of thiourea and dihydrate chloride of Sn (II) and Cu (II) were used for the spraying process. Structural, optical, and morphological properties of CTS films were examined. XRD endorses a monoclinic crystallinity. XRD pattern has diffraction peaks at 2θ = 28.39°, 33.02°, 47.34° and 56.39°, respectively. The FTIR examination certified the vibration mode of Cu-S and Sn-S bonds. The crystallite size was noted about 78 nm, where measured by debye-Scherrer's formula. Both absorption and transmission spectra were recorded in the wavelength range of 300-800 nm. The surface morphology of the fabricated CTS films exposed a uniform coating on the substrate with an applicable distribution. Laser grooving process was applied to grove the fabricated film. The groove width was found about 37 μm, etched via 500 mW blue laser source.