Search Results (216)

Fused Filament Fabrication (FFF) enables the manufacturing of complex polymer components. However, surface finish and dimensional accuracy remain key limitations for their integration into functional assemblies. This study explores the potential of conventional turning as a post-processing strategy to improve the geometric and surface quality of PLA reinforced with carbon fiber (CF) parts produced by FFF. Machinability was evaluated through the analysis of cutting forces, thermal behavior, energy consumption, and surface integrity under varying cutting speeds, feed rates, and specimen slenderness. The results indicate that feed is the most influential parameter across all performance metrics, with lower values leading to improved dimensional accuracy and surface finish, achieving the most significant reductions of 63% in surface roughness (Sa) and 62% in cylindricity deviation. Nevertheless, the surface roughness is higher than that of metals, and deviations in geometry along the length of the specimen have been observed. A critical shear stress of 0.237 MPa has been identified as the limit for interlayer failure, defining the boundary conditions for viable cutting operation. The incorporation of CNC turning as a post-processing step reduced the total fabrication time by approximately 83% compared with high-resolution FFF, while maintaining dimensional accuracy and enhancing surface quality. These findings support the use of machining operations as a viable and efficient post-processing method for improving the functionality of polymer-based components produced by additive manufacturing. Full article

Abrasive waterjet technology is a promising sustainable and green technology for cutting underground structures. Abrasive waterjet usage in demolition promotes sustainable and green construction practices by reduction of noise, dust, secondary waste, and disturbances to the surrounding infrastructure. In this study, a numerical framework based on a coupled Smoothed Particle Hydrodynamics (SPH)–Finite Element Method (FEM) algorithm incorporating the Riedel–Hiermaier–Thoma (RHT) constitutive model is proposed to investigate the damage mechanism of concrete subjected to abrasive waterjet. Numerical simulation results show a stratified damage observation in the concrete, consisting of a crushing zone (plastic damage), crack formation zone (plastic and brittle damage), and crack propagation zone (brittle damage). Furthermore, concrete undergoes plastic failure when the shear stress on an element exceeds 5 MPa. Brittle failure due to tensile stress occurs only when both the maximum principal stress (σ₁) and the minimum principal stress (σ₃) are greater than zero at the same time. The damage degree ($\chi$) of the concrete is observed to increase with jet diameter, concentration of abrasive particles, and velocity of jet. A series of orthogonal tests are performed to analyze the influence of velocity of jet, concentration of abrasive particles, and jet diameter on the damage degree and impact depth (h). The parametric numerical studies indicates that jet diameter has the most significant influence on damage degree, followed by abrasive concentration and jet velocity, respectively, whereas the primary determinant of impact depth is the abrasive concentration followed by jet velocity and jet diameter. Based on the parametric analysis, two optimized abrasive waterjet configurations are proposed: one tailored for rock fragmentation in tunnel boring machine (TBM) operations; and another for cutting reinforced concrete piles in shield tunneling applications. These configurations aim to enhance the efficiency and sustainability of excavation and tunneling processes through improved material removal performance and reduced mechanical wear. Full article

This paper proposes a method for determining the contact temperature in the secondary shear zone. The input data include the results of the experimental tests of the orthogonal turning of a Ti-6Al-4V titanium workpiece using uncoated WC-Co tools with a flat rake face. The cutting force components were recorded using a piezoelectric dynamometer, a thermovision camera was used to record the temperature in the cutting zone, and a high-speed camera was used to record the chip-forming process. The independent variables included machining parameters, feed rate, cutting speed, and rake angle. A dual-zone thermomechanical cutting process model that accounted for the sticking and sliding areas was adapted for the identification of the heat flux in the chip–rake face contact zone. Then, based on the Shaw approach, the partition coefficients were determined for the contact temperature on the chip–tool tip contact. In addition, the results of the experimental tests allowed the determination of the relationship among the process parameters, friction coefficients, and the length of the contact of the chip with the tool rake face. A graphical visualization of the temperature distribution on the tool rake face was performed using the MATLAB PDE 3.9 software package. Although the application of the dual-zone model has been well presented in the literature, the results provided in this paper may be helpful in analyzing and modeling thermal phenomena in the secondary shear zone. Full article

Rainfall can easily cause local sliding and collapse of carbonaceous mudstone deep road cut slopes. In order to study the strength characteristics of carbonaceous mudstone under different water environments, large-scale horizontal push shear tests were conducted on carbonaceous mudstone rock masses in their natural state and after immersion in saturated water. The push shear force–displacement relationship curve and fracture surface shape characteristics of carbonaceous mudstone samples were analyzed, and the shear strength index of carbonaceous mudstone was obtained, and numerical simulations on the stability and support effect of carbonaceous mudstone slopes were conducted. The research results indicate that carbonaceous mudstone can exhibit good structural properties and typical strain softening characteristics under natural conditions. The fracture surface, shear strength, and shear deformation process of carbonaceous mudstone samples will undergo significant changes after being soaked in saturated water. The average cohesion decreases by 33% compared to the natural state, and the internal friction angle decreases by 15%. The numerical simulation results also fully verify the attenuation of mechanical properties of carbonaceous mudstone after immersion, as well as the effectiveness of prestressed anchor cables and frame beams in supporting carbonaceous mudstone slopes. The research results provide an effective method for understanding the shear performance of carbonaceous mudstone and practical guidance for evaluating the stability and reinforcement design of carbonaceous mudstone slopes. Full article

Advanced high-strength steels (AHSSs) are used as lightweight solutions for vehicles, mainly focusing on the Body-in-White. However, the implementation of such steels for chassis parts requires a profound knowledge of the key design parameters for these components, particularly those concerning fatigue performance. Manufacturing of chassis parts include mechanical cutting operations. Therefore, the deformation and damage induced at the cut edge may affect the fatigue resistance of the parts in service. To characterize and study this critical area, damage and micromechanical properties have been evaluated at the cut edge for three different AHSS grades, CP800, CP980, and DP600, analyzing the impact of cutting parameters and post-processing treatments, such as sandblasting. Large high-speed nanoindentation maps of 400 × 200 µm² have been carried out along the cut edge in the three different target zones: burnish, fracture, and burr. In the hardness maps, the deformation lines and the gradient of hardness with increasing distance from the cut edge are perfectly observed. Residual stresses at the target zones of the cut edges were measured using the FIB-DIC method for CP980 to complement the micromechanical study in these critical areas. The results found show that reduced cutting clearance leads to larger hardened zones and favorable compressive stress distributions, correlating with improved fatigue resistance. Hardened zones extending up to 100 µm from the cut edge and compressive residual stresses exceeding −300 MPa were observed at low clearance. These findings are consistent with numerical simulations and previous fatigue tests, highlighting the potential of combining high-speed nanoindentation and local stress analysis for optimizing shear cutting processes in AHSS components. Full article

This study investigates shear cutting of high-strength steel sheets, a process known to negatively impact the forming and fatigue properties of the material. The localized deformation near the cut edges imposes sheared-edge damage, especially in advanced high-strength steels where severe shear deformation occurs in the very vicinity of the cut edge. In this work, an extensive experimental investigation was carried out on punched holes of thin sheets, using light optical microscopy and metallographic techniques for sheared-edge damage assessment. These methods provided detailed insights into the sheared-edge damage and offer a thorough understanding of the deformation behavior in the shear-affected zone. Advanced engineering cut-edge investigation methods have been developed based on 2D and 3D stereo light microscopy for non-destructive panoramic cut-edge parameters and cut-edge profile determination along cut-hole circumference. Such methods provide an efficient evaluation instrument for challenging close-cut holes, with the possibility of industrial in-line monitoring and machine learning applications for Industry 4.0 implementation. Additionally, the study compares grain shear angle measurement and Vickers indentation for deformation assessment of the cut edge. It concludes that grain shear angle offers higher resolution. This parameter is therefore postulated as relevant for assessing the sheared-edge zone. The findings contribute to a deeper understanding of sheared-edge damage and improve evaluation methods, potentially enhancing the use of high-strength steels in automotive and safety-critical applications. Full article

Sand mold milling plays a critical role in digital mold-free casting, but it is prone to damage such as corner collapse, collapse, and cracks during the machining process. To address this issue, ultrasonic vibration was used for sand mold milling in this study. By incorporating the solid–liquid transition model for sand mold cutting and considering the deformation characteristics of the shear zone, a prediction model for ultrasonic milling forces in sand mold was developed and experimentally validated. The results demonstrate that increasing the spindle speed and decreasing the feed rate lead to a decrease in cutting force. At high speeds, there is a 15% error between the dynamic milling force model and experimental values. Compared with conventional processing methods, ultrasonic processing reduces cutting force by 19.5% at a frequency of 25.8 kHz and amplitude of 2.97 μm, minimizes defects like sand particle detachment pits on the surface of sand mold, significantly improves surface quality, and enables precise, stable, high-precision, and efficient sand mold processing. Full article

In zooarchaeological research, animal bone fractures can result from various processes including slaughtering, dismemberment, marrow/grease extraction, craft processing, carnivore gnawing/trampling, sediment compression, bioturbation, and recovery bias. These fractures are further influenced by bone freshness/dryness and environmental temperature. The animal bones analysed in this study, excavated from Han dynasty tombs in the Xinxiang Plain New District, China, represent ritual offerings. These specimens exhibit distinct truncation features—chop surfaces, rough planes, and fracture traces—created by ancient iron tools for culinary purposes such as stewing preparation or consumption facilitation. These characteristics differ significantly, from the V-shaped butchery marks produced by stone/bronze tools and fracture patterns from marrow/grease extraction to post-depositional breakage formed during burial processes. In this study, steel tools were employed in the rocking slicing and rolling slicing of animal bones, complemented by techniques such as breaking to sever bone shafts. Subsequently, the marks on the cross-sections were observed using a stereomicroscope, and the results were compared and analysed with the materials from Han dynasty tombs unearthed at Xinxiang city, Henan Province. From the comparison between experimental observation results and archaeological materials, it is evident that the fine processing of meat-bearing bone materials mainly involved the use of rocking and rolling slicing methods. The cross-sections of the slices revealed shearing surfaces, rough patches, bone splinters, and sliced ends. The shearing surfaces in particular exhibited numerous visible trace characteristics, with the types and quantities of these traces varying with different cutting tools. This study holds significant reference value for exploring cutting tools and techniques in antiquity. Full article

Metalworking fluids (MWFs) are crucial in the manufacturing industry, playing a key role in facilitating various production processes. As each machining operation comes with distinct requirements, the properties of the MWFs have to be tailored to meet these specific demands. Understanding the properties of different MWFs is fundamental for optimizing processes and improving performance. This study centered on characterizing the thermal behavior of various cutting oils and water-based cutting fluids over a wide temperature range and sheds light on the specific tribological behavior. The results indicate that water-based fluids exhibit significant shear-thinning behavior, whereas cutting oils maintain nearly Newtonian properties. In terms of frictional performance, cutting oils generally provide better lubrication at higher temperatures, particularly in mixed and full-fluid film regimes, while water-based fluids demonstrate greater friction stability across a wider range of conditions. Among the tested fluids, water-based formulations showed a phase transition from solid to liquid near 0 °C due to their high water content, whereas only a few cutting oils exhibited a similar behavior. Additionally, the thermal conductivity and heat capacity of water-based fluids were substantially higher than those of the cutting oils, contributing to more efficient heat dissipation during machining. These findings, along with the reported data, intend to guide future researchers and industry in selecting the most appropriate cutting fluids for their specific applications and provide valuable input for computational models simulating the influence of MWFs in the primary and secondary shear zones between cutting tools and the workpiece/chiplet. Full article

The current work records for the first time the rare-metal pegmatites with mixed NYF-LCT located at Wadi Sikait, south Eastern Desert of the Egyptian Nubian Shield. Most of the Sikait pegmatites are associated with sheared granite and are surrounded by an alteration zone cross-cutting through greisen bodies. Sikait pegmatites show zoned and complex types, where the outer wall zones are highly mineralized (Nb, Ta, Y, Th, Hf, REE, U) than the barren cores. They consist essentially of K-feldspar, quartz, micas (muscovite, lepidolite, and zinnwaldite), and less albite. They contain a wide range of accessory minerals, including garnet, columbite, fergusonite-(Y), cassiterite, allanite, monazite, bastnaesite (Y, Ce, Nd), thorite, zircon, beryl, topaz, apatite, and Fe-Ti oxides. In the present work, the discovery of Li-bearing minerals for the first time in the Wadi Sikait pegmatite is highly significant. Sikait pegmatites are highly mineralized and yield higher maximum concentrations of several metals than the associated sheared granite. They are strongly enriched in Li (900–1791 ppm), Nb (1181–1771 ppm), Ta (138–191 ppm), Y (626–998 ppm), Hf (201–303 ppm), Th (413–685 ppm), Zr (2592–4429 ppm), U (224–699 ppm), and ∑REE (830–1711 ppm). The pegmatites and associated sheared granite represent highly differentiated peraluminous rocks that are typical of post-collisional rare-metal bearing granites. They show parallel chondrite-normalized REE patterns, enriched in HREE relative to LREE [(La/Lu)_n = 0.04–0.12] and strongly negative Eu anomalies [(Eu/Eu*) = 0.03–0.10]. The REE patterns show an M-type tetrad effect, usually observed in granites that are strongly differentiated and ascribed to hydrothermal fluid exchange. The pegmatite has mineralogical and geochemical characteristics of the mixed NYF-LCT family and shows non-CHARAC behavior due to a hydrothermal effect. Late-stage metasomatism processes caused redistribution, concentrated on the primary rare metals, and drove the development of greisen and quartz veins along the fracture systems. The genetic relationship between the Sikait pegmatite and the surrounding sheared granite was demonstrated by the similarities in their geochemical properties. The source magmas were mostly derived from the juvenile continental crust of the Nubian Shield through partial melting and subsequently subjected to a high fractional crystallization degree. During the late hydrothermal stage, the exsolution of F-rich fluids transported some elements and locally increased their concentrations to the economic grades. The investigated pegmatite and sheared granite should be considered as a potential resource to warrant exploration for REEs and other rare metals. Full article

Owing to potential inaccuracies in the current stress–strain curve used for constructing the Johnson–Cook (JC) constitutive model of amorphous alloys, the parameters of the JC constitutive equation were derived using Oxley’s cutting theory, negative chamfer theoretical mechanics modelling, and the particle swarm optimisation algorithm. A two-dimensional finite element cutting model was subsequently established using AdvantEdge software. The optimised constitutive model was used to simulate the main cutting force (Fz) and the backward force (Fy), which resulted in average errors of 12.461% and 9.161%, respectively. Based on the optimised constitutive model in which the JC constitutive equation parameters were derived using Oxley’s method, the variations in temperature, strain rate, and stress in the deformation zone during the cutting process were analysed. The chip microstructures revealed the transformation of lamellar chips into serrated chips resulting from a combination of plastic deformation, adiabatic shear, and shear slip. Full article

The cutting of leaf stems is a critical step in the mechanized harvesting of tuber mustard (Brassica juncea L.). This study focuses on the calibration of parameters for the discrete element model of mustard leaf stems to visualize the cutting process and facilitate numerical simulations. Intrinsic material properties were measured based on mechanical testing, and EDEM2022 simulation software was utilized to calibrate the model parameters. The Hertz–Mindlin (no-slip) model was employed to simulate the stacking angle of mustard leaf stems, and the contact parameters for the discrete element model were determined using a combination of two-level factorial design, steepest ascent, and CCD (central composite design) tests. The results showed that the coefficient of restitution, coefficient of static friction, and coefficient of rolling friction for the leaf stems were 0.45, 0.457, and 0.167, respectively, while for interactions between the leaf stems and the working parts, these values were 0.45, 0.55, and 0.175, respectively. Based on the Hertz–Mindlin with bonding model, the primary bonding parameters were calculated, and a BBD (Box–Behnken design) test was applied for optimization. The comparison between the simulation and experimental results showed that the relative error in the maximum shear force was within 5%, indicating that the calibrated model can serve as a reliable theoretical reference for the design and optimization of tuber mustard harvesting and cutting equipment. Full article

The increasing demand for sustainable and cost-effective manufacturing solutions has led to the development of innovative approaches to enhance the durability and reliability of cutting tools. This study presents a novel method for manufacturing shearing tools utilizing interchangeable modular elements loaded by deposition welding with covered electrodes. Using Weibull distribution modeling, a comparative reliability analysis between conventionally manufactured shear tools and the proposed modular design demonstrates a significant increase in the mean time to failure (MTTF). The least squares method (LSM) estimation was used in order to determine the shearing tools’ lifetime, expressed by reliability indices. Experimental results confirm that the modular tools achieve more than double the lifetime of traditional counterparts, with improved resistance to wear and mechanical stress. These findings highlight the potential for widespread industrial application, optimizing tool performance and sustainability in manufacturing processes. Full article

The cutting force exerted on steel bars plays a crucial role in determining tunneling parameters for shield tunneling, especially when cutters are used to cut through existing pile foundations. This research focuses on the cutting force during the initial phase of the cutting process. Using 2D finite element analysis, this study examines the early stage of orthogonal cutting with negative rake angle cutters, exploring the formation of a slip plane mode. By combining slip line theory with the shear band model, a computational model is developed to calculate the cutting force for negative rake angle cutters when cutting a circular steel bar cross-section at various depths. In addition, with the incorporation of the Johnson–Cook model, this study models cutting forces under various conditions, taking into account factors such as material strength, strain rate sensitivity, and temperature effects. The steels studied include AISI 1040, AISI 4340, and AISI 304, which are commonly used in construction, with attention given to how their mechanical properties, such as strength and hardness, affect the cutting forces. While this study acknowledges the steels’ manufacturing conditions, the primary focus remains on the cutting process and its impact on force predictions. The model’s calculated horizontal cutting force is compared to numerical simulations, showing a maximum absolute error of 33.85% and an average error of 14.23%. The vertical cutting force calculations are less accurate, with a maximum error of 64.2% and an average error of 14.06%. The analysis further reveals that chip accumulation significantly impacts the horizontal cutting force, while the variation in average stress along the slip line has a smaller effect. This study also examines how factors like material properties, initial temperature, low friction coefficients, and steel bar radius contribute to the model’s accuracy and reliability. Full article

The exploitation of immersive simulation platforms to improve traditional training techniques in the agricultural industry sector would enable year-round accessibility, flexibility, safety, and consistent high-quality training for agricultural operators. An innovative workflow in virtual simulations for training and educational purposes includes an immersive environment in which the operator can interact with plants through haptic interfaces, following instructions imparted by a non-playing character (NPC) instructor. This study allows simulating the pruning of a complex case study, a hazelnut tree, reproduced in very high detail to offer agricultural operators a more realistic and immersive training environment than those currently existing. The process of creating a multisensorial environment starts with the integrated survey of the plant with a laser scanner and photogrammetry and then generates a controllable parametric model from roots to leaves with the exact positioning of the original branches. The model is finally inserted into a simulation, where haptic gloves with tactile resistance responsive to model collisions are tested. The results of the experimentation demonstrate the correct execution of this innovative design simulation, in which branches and leaves can be cut using a shear, with immediate sensory feedback. The project therefore aims to finalize this product as a realistic training platform for pruning, but not limited to it, paving the way for high-fidelity simulation for many other types of operations and specializations. Full article