Search Results (141)

High-strength steel has high strength and low thermal conductivity, and its thin-walled parts are very susceptible to residual stress and deformation caused by cutting heat during the drilling process, which affects the machining accuracy and quality. High-strength steel thin-walled components are widely used in aerospace and other high-end sectors; however, systematic investigations into their temperature fields during drilling remain scarce, particularly regarding the evolution characteristics of the temperature field in thin-wall drilling and the quantitative relationship between drilling parameters and these temperature variations. This paper takes the thin-walled parts of AF1410 high-strength steel as the research object, designs a special fixture, and applies infrared thermography to measure the bottom surface temperature in the thin-walled drilling process in real time; this is carried out in order to study the characteristics of the temperature field during the thin-walled drilling process of high-strength steel, as well as the influence of the drilling dosage on the temperature field of the bottom surface. The experimental findings are as follows: in the process of thin-wall drilling of high-strength steel, the temperature field of the bottom surface of the workpiece shows an obvious temperature gradient distribution; before the formation of the drill cap, the highest temperature of the bottom surface of the workpiece is distributed in the central circular area corresponding to the extrusion of the transverse edge during the drilling process, and the highest temperature of the bottom surface can be approximated as the temperature of the extrusion friction zone between the top edge of the drill and the workpiece when the top edge of the drill bit drills to a position close to the bottom surface of the workpiece and increases with the increase in the drilling speed and the feed volume; during the process of drilling, the highest temperature of the bottom surface of the workpiece is approximated as the temperature of the top edge of the drill bit and the workpiece. The maximum temperature of the bottom surface of the workpiece in the drilling process increases nearly linearly with the drilling of the drill, and the slope of the maximum temperature increases nearly linearly with the increase in the drilling speed and feed, in which the influence of the feed on the slope of the maximum temperature increases is larger than that of the drilling speed. Full article

The Southern Lhasa Terrane, as the southernmost tectonic unit of the Eurasian continent, has long been a focal area in global geoscientific research due to its complex evolutionary history. The Yeba Formation exposed in this terrane comprises an Early–Middle Jurassic volcanic–sedimentary sequence that records multiphase tectonic deformation. This study applies structural analysis to identify three distinct phases of tectonic deformation in the Yeba Formation of the Southern Lhasa Terrane. The D₁ deformation is characterized by brittle–ductile shearing, as evidenced by the development of E-W-trending regional shear foliation (S₁). S₁ planes dip northward at angles of 27–87°, accompanied by steeply plunging stretching lineations (85–105°). Both south- and north-directed shear-rotated porphyroclasts are observed in the hanging wall. ⁴⁰Ar-³⁹Ar dating results suggest that the D₁ deformation occurred at ~79 Ma and may represent an extrusion-related structure formed under a back-arc compressional regime induced by the low-angle subduction of the Neo-Tethys Ocean plate. The D₂ deformation is marked by the folding of the pre-existing shear foliation (S₁), generating an axial planar cleavage (S₂). S₂ planes dip north or south with angles of 40–70° and fold hinges plunge westward or NWW. Based on regional tectonic evolution, it is inferred that the deformation may have resulted from sustained north–south compressional stress during the Late Cretaceous (79–70 Ma), which caused the overall upward extrusion of the southern Gangdese back-arc basin, leading to upper crustal shortening and thickening and subsequently initiating folding. The D₃ deformation is dominated by E-W-striking ductile shear zones. The regional shear foliation (S₃) exhibits a preferred orientation of 347°∠75°. Outcrop-scale ductile deformation indicators reveal a top-to-the-NW shear sense. Combined with regional tectonic evolution, the third-phase (D3) deformation is interpreted as a combined product of the transition from compression to lateral extension within the Lhasa terrane, associated with the activation of the Gangdese Central Thrust (GCT) and the uplift of the Gangdese batholith since ~25 Ma. Full article

The Sidi Aissa Pb-Zn-(Ag) District, located within the Nappe Zone of northern Tunisia, has been reinterpreted as a typical intermediate-sulfidation (IS) epithermal mineralization system based on field observations and lithogeochemical analyses. Previously described as vein-style Pb-Zn deposits, the local geological framework is dominated by extensional normal faults forming half-grabens. These faults facilitated the exhumation of deep Triassic autochthonous rocks and the extrusion of 8-Ma rhyodacites and Messinian basalts. These structures, functioning as pathways for magmatic-hydrothermal fluids, facilitated the upward migration of acidic fluids, which interacted with the surrounding wall rocks, forming a subsurface alteration zone. The mineralization, shaped by Miocene extensional tectonics and magmatic activity, occurred in three stages: early quartz-dominated veins, an intermediate barite-rich phase, and late-stage supergene oxidation. Hydrothermal alteration, characterized by silicification, argillic, and propylitic zones, is closely associated with the deposition of base metals (Pb, Zn) and silver. The mineral assemblage, including barite, galena, sphalerite, and quartz, reflects dynamic processes such as fluid boiling, mixing, and pressure changes. Full article

Polymer co-extrusion experiments are described simulating the dynamics of two different magmas (e.g., silicic and mafic having different viscosities) flowing simultaneously in a vertical volcanic pipe or conduit which results in the effusion of composite lava domes on the surface. These experiments, involving geologically realistic conduit length-to-diameter aspect ratios of 130:1 or 380:1, demonstrate that co-extrusion of magmas having different viscosities can explain not only the observed normal zoning observed in planar dikes and the pipelike conduits that evolve from dikes but also the compositional layering of effused lava domes. The new results support earlier predictions, based on observations of induced core-annular flow (CAF), that dike and conduit zoning along with dome layering are found to depend on the viscosity contrast of the non-Newtonian (shear-thinning) magmas. Any magma properties creating viscosity differences, such as crystal content, bubble content, water content and temperature may also give rise to the CAF regime. Additionally, codependent flow behavior involving the silicic and mafic magmas may play a significant role in modifying the nature of volcanic eruptions. For example, lubrication of the flow by an annulus of a more mafic, lower-viscosity component allows a more viscous but more volatile-charged magma to be injected rapidly to greater vertical distances along a dike into a lower pressure regime that initiates exsolving of a gas phase, further assisting ascent to the surface. The rapid ascent of magmas exsolving volatiles in a dike or conduit is associated with explosive silicic eruptions. Full article

This study investigates strategies to enhance the structural integrity of 3D-printed orthopedic transtibial exoskeleton sockets by integrating non-planar reinforcement with structured prepreg rods composed of continuous carbon fibers, leveraging multi-axis additive manufacturing techniques. A prototype of a cylindrical polyamide 3D-printed exoskeleton socket is examined. Numerical modeling using progressive failure analysis, incorporating material property degradation models, successfully simulated damage accumulation in the studied 3D-printed structures. Numerical simulations revealed that crack formation initiates in the socket’s distal section, aligning with physical test observations. Targeted localized reinforcement with carbon rods effectively strengthened the high-load regions of the prosthetic devices. A method to improve product strength by optimization of the internal architecture of the embedded reinforcements in the local stress concentrator zones is proposed. The results demonstrate a reduction in stress concentrations within prostheses when using carbon fiber reinforcements. Multi-axis dual extrusion non-planar additive manufacturing techniques were used to produce the developed prototypes. Surface morphology was examined, and optimal process parameters were determined to enhance printing quality. The developed approach enables precise reinforcement of custom-shaped sockets with complex geometries. Full article

Asymmetric deformation has been observed along the Altyn Tagh Fault (ATF), the northern boundary of the Tibetan Plateau. Several mechanisms have been proposed to explain this asymmetry, including contrasts in crustal strength, lower crust/upper mantle rheology, deep fault dislocation shifts, and dipping fault geometry; however, the real scenario remains debated. This study utilizes a time series Interferometric Synthetic Aperture Radar (InSAR) technique to investigate spatially variable asymmetries across the western section of the ATF (83–89°E). We generated a high-resolution three-dimensional (3D) crustal velocity field from Sentinel-1 data for the northwestern Tibetan Plateau (~82–92°E; 33–40°N). Our results confirm that pronounced greater deformations within the Tibetan Plateau occur only along the westernmost section of the ATF (83–85.5°E). We propose this asymmetry is primarily driven by a splay fault system within a transition zone, bounded by the ATF in the north and the Margai Caka Fault (MCF)–Kunlun Fault (KLF) in the south, which accommodates an east–west extension in the central Tibetan Plateau while transferring sinistral shear to the KLF. The concentrated strain observed along the ATF and MCF–KLF lends more support to a block-style eastward extrusion model, rather than a continuously deforming model, for Tibetan crustal kinematics. Full article

Eccentric camshaft components serve as critical elements in emergency pump systems for commercial vehicle steering mechanisms. To optimize material utilization efficiency, reduce production costs, and enhance manufacturing throughput, this investigation implemented a vertical upsetting extrusion forming methodology for camshaft forging production. Initial trials revealed defect formation in forged components. By analyzing the causes of the defects, an improved process method was developed to eliminate them. The chemical composition, macroscopic and microscopic morphologies of defects, forging process, and metal streamlines were analyzed and studied by means of a direct reading spectrometer, high-resolution camera, metallographic microscope, DEFORM finite element analysis software, and chemical etching. Findings indicate that the observed defects constitute forging-induced cracks, with subsequent normalizing heat treatment exacerbating decarburization phenomena in defect-adjacent microstructures. During the forging process of the forgings, the metal continuously extruded into the die cavity, and the inflowing metal pulled the dead zone metal downward, causing the flow lines aligned with the contour to bend into S-shaped metal streamlines. Cracks formed when the tensile stress in the dead zone metal exceeded the material’s critical tensile stress. An improved process was proposed: adopting a vertical upsetting extrusion forming method with a 40° diversion angle at the junction between the first step and the thin rod in the die cavity. Numerical simulations confirmed complete elimination of deformation dead zones in the optimized process. Experimental verification demonstrated crack-free forgings. Therefore, the eccentric camshafts formed by the initial process exhibited forging cracks, and the proposed improved method of vertical upsetting extrusion forming with a diversion angle effectively eliminated the forging cracks. Full article

To analyze the dynamic characteristics of single-tooth rock-cutting behavior, this paper proposes that the height of the extrusion zone (h_c) is not constant and does not equal the cutting depth in real rock-cutting behavior, and introduces a new dynamic cutting model (NDCM). By analyzing the single-tooth rock-cutting process, the concepts of the single cutting process and cutting frequency (f_c) are defined. A method for determining f_c based on the tangential cutting force (F_c^t) is also proposed. A series of single-tooth rock-cutting tests were conducted using numerical simulation, and the influence of rake angle (a), cutting speed (v), and cutting depth (h) on f_c was analyzed. The geometric difference coefficient (GDC) is introduced in the new dynamic cutting model, defined as the ratio of h_c to h. The determination method of GDC and its relationship with cutting parameters are explored from both theoretical and experimental perspectives. The results show that the cutting frequency corresponds to the main frequency of the tangential cutting force. f_c is linearly proportional to v and decreases nonlinearly with increasing h, while the rake angle has little effect on cutting frequency within the range of 10–20°. h_c exhibits a nonlinear relationship with h: when the cutting depth is small, GDC is close to 1.0; as h increases, GDC gradually decreases and eventually stabilizes, which aligns with experimental findings. The results of this study provide valuable insights for engineers to better understand the dynamic characteristics of tool–rock interaction in single-tooth rock cutting and offer new perspectives for applying cutting force and optimizing rock-cutting models. Full article

To reveal the influence of ultra-close coal seams mining on surrounding rock disturbance, PFC^2D is introduced to establish a simplified particle flow model of strata in the deeply buried mine, the damage and stress evolution characteristics of the surrounding rock were studied based on double coal seam mining. The results show that after the model excavation, the fracture length of the rock strata reached an accuracy of 97% compared with the theoretical calculation results, showing a good match with the theoretical calculations and the initial stress level obtained by the subsequent model monitoring is consistent with the measured value. The primary and secondary key layers are broken as a result of mining the higher coal seam, the siltstone interlayer is unaffected while the bottom coal seam is partially harmed, and there is noticeable extrusion damage between the rocks. Meanwhile, the damage to the rocks inside the gob is only becoming worse as a result of mining the lower coal seam. While the surrounding rock of the upper coal seam mining exhibits clear stress redistribution features in three zones, the lower coal seam mining creates a local and multi-point high-stress distribution. The siltstone interlayer’s stress variation is essentially identical to that of the surrounding rock. The extrusion state among rocks is related to the porosity of the shattered surrounding rock area. The siltstone interlayer is pressured during the upper coal seam mining, but it maintains its integrity, only collapsing during the lower coal seam mining. Though the siltstone interlayer can retain the necessary integrity of support before the lower coal seam mining, its internal stress is unstable which should be paid attention to when designing the support scheme during the mining period. Full article

This study employs structural information and stratigraphic lithology as constraints to conduct balanced restoration on seismic profiles from the Yinggehai Basin (YGB) and the Beibu Gulf Basin (BGB). The reconstruction indicates that the evolutionary periods of the YGB can be classified into five distinct stages: rift stage (56–36 Ma), fault depression stage (36–23 Ma), depression stage (23–15.5 Ma), inversion stage (15.5–5.3 Ma), and depression stage (5.3–0 Ma). In contrast, the evolutionary stages of the BGB are categorized into four stages: rift stage (66–56 Ma), fault depression stage (40–32 Ma), fault-depression transition stage (32–23 Ma), and depression stage (23–0 Ma). The BGB did not experience a tectonic inversion phase similar to that of the YGB, but both have undergone a fault depression stage under the same tectonic background. The rotational extrusion of the Indochina block has accelerated the opening of the rift basins along the northern and western margins of the South China Sea (SCS). The dual subduction processes of the Proto-SCS has led to the opening of the SCS Basin. Within the BGB, a significant increase in the dilatation strain rate (DSR) can be observed over a large area. The transition in the strike-slip nature of the Red River Fault Zone is evidenced by tectonic inversion in the stratigraphy. The tectonic mechanism of the YGB is primarily controlled by the convergence of the India-Eurasia plate, while the evolution of the BGB is governed by the subduction of the Pacific plate, the convergence of the India-Eurasia plate, and the dual subduction of the Proto-SCS. Full article

This study presents the formulation and comprehensive characterization of compatibilized polyamide 6 (PA6)/cyclic olefin copolymer (COC) blends with the aim of developing a self-healing matrix for thermoplastic structural composites. Rheological analysis highlighted the compatibilizing effect of ethylene glycidyl methacrylate (E-GMA), as evidenced by an increase in viscosity, melt strength (MS), and breaking stretching ratio (BSR), thus improving the processability during film extrusion. E-GMA also decreased COC domain size and improved the interfacial interaction with PA6, which was at the basis of a higher tensile strength and strain at break compared to neat PA6/COC blends. E-GMA also significantly boosted the healing efficiency (HE), measured via fracture toughness tests in quasi-static and impact conditions. The optimal healing temperature was identified as 160 °C, associated with an HE of 38% in quasi-static mode and 82% in impact mode for the PA6/COC blends with an E-GMA content of 5 wt% (PA6COC_5E-GMA). The higher healing efficiency under impact conditions was attributed to the planar fracture surface, which facilitated the flow of the healing agent in the crack zone, as proven by fractography analysis. This work demonstrates the potential of E-GMA in fine-tuning the thermomechanical properties of PA6/COC blends. PA6COC_5E-GMA emerged as the formulation with the best balance between processability and self-healing efficiency, paving the way for advanced multifunctional self-healing thermoplastic composites for structural applications. Full article

Cassava is a crucial food and economic crop in tropical regions globally. In response to challenges in fertilizer use efficiency for cassava cultivation, which is traditionally compromised by extensive leaching and broad root zone distribution, a novel large-particle slow-release fertilizer (LPF) was developed in this study. This fertilizer was synthesized through solution polymerization using non-metallic minerals and seaweed extract. Compared to conventional SFs that release 99% of nutrients within 1 min, the LPF prolonged the release duration to 51 min under optimal synthesis conditions: drying temperature of 80 °C, total extrusion force of 40 t, drying air pressure of −0.40 bar, auxiliary mineral proportion of 50%, and water content of 15%. Microbeam characterization (e.g., FTIR) and kinetic modeling revealed that the superior performance of LPF resulted from mineral crystal enrichment in the outer layer of fertilizer granules, facilitating intra-particle diffusion processes and imposing boundary layer limitations on nutrient release (e.g., N, P, and K). Field experiments validated the slow-release performance of the fertilizer. Notably, soil treated with LPF exhibited superior nutrient retention in the topsoil layer (0–20 cm) both horizontally and vertically. Even with two-thirds of the nutrient content relative to conventional fertilizers, LPF also displayed significant improvements in crop yield, partial factor productivity, and agronomic efficiency by 33.56%, 200.01%, and 513.84%, respectively. These results indicate that LPF presents a promising solution for sustainable cassava cultivation. Full article

Taking the tunnels crossing active faults in China’s Sichuan–Tibet Railway as the research background, experimental studies were conducted using a custom-developed split model box. The research focused on the cracking characteristics of the surrounding rock surface under the action of strike-slip faults, the progressive failure process of the tunnel model, and the mechanical response of the tunnel lining. In-depth analyses were performed on the tunnel damage mechanism under strike-slip fault action and the mitigation effects of combined anti-dislocation measures. The results indicate the following: Damage to the upper surface of the surrounding rock primarily occurs within the fault fracture zone. The split model box enables the graded transfer of fault displacement within this zone, improving the boundary conditions for the model test. Under a 50 mm fault displacement, the continuous tunnel experiences severe damage, leading to a complete loss of function. The damage is mainly characterized by circumferential shear and is concentrated within the fault fracture zone. The zone 20 cm to 30 cm on both sides of the fault plane is the primary area influenced by tunnel forces. The force distribution on the left and right sidewalls of the lining exhibits an anti-symmetric pattern across the fault plane. The left side wall is extruded by surrounding rock in the moving block, while the right side wall experiences extrusion from the surrounding rock in the fracture zone, and there is a phenomenon of dehollowing and loosening of the surrounding rock on both sides of the fault plane; the combination of anti-dislocation measures significantly enhances the tunnel’s stress state, reducing peak axial strain by 93% compared to a continuous tunnel. Furthermore, the extent and severity of tunnel damage are greatly diminished. The primary cause of lining segment damage is circumferential stress, with the main damage characterized by tensile cracking on both the inner and outer surfaces of the lining along the tunnel’s axial direction. Full article

Additive manufacturing is an attractive technology due to its versatility in producing parts with diverse properties from a single material. However, the process often generates plastic waste, particularly from failed prints, making sustainability a growing concern. Recycling this waste material presents a potential solution for reducing environmental impact while creating new, functional parts. In this study, the feasibility of creating printable filaments from recycled polylactic acid (PLA) waste and virgin PLA pellets was explored. Filaments were manufactured in the lab using a single-screw desktop extruder with four temperature zones, with compositions ranging from 100% virgin PLA to 100% recycled PLA in 10% composition increments. Test samples were 3D printed using a Material Extrusion 3D printer and subjected to tensile testing in conjunction with digital image correlation to evaluate their ultimate tensile strength, yield strength, Young’s modulus, ductility, toughness, and strain distribution. The results indicated that the optimal mechanical properties were observed in specimens made from 100% virgin PLA, 100% recycled PLA, and a 50% virgin/50% recycled PLA blend. Additionally, comparisons with a commercially produced PLA filament revealed that 100% virgin and 100% recycled blends have a 50.33% and 48% higher tensile strength than commercial filament, respectively. However, commercial filaments exhibited higher ductility and toughness than the lab-made extruded filament. Full article

A large number of MIG welding tests were carried out on a 3 mm thick 7075 aluminum alloy plate prepared by the self-developed jet forming–extrusion–drawing process of 7075 high-strength aluminum alloy welding wire, and the welding process of the welding wire and the change in the performance of the welded joint after T6 heat treatment were studied. The results show that the self-developed wire has a good forming joint and a wide welding process window: the welding speed is 5–7 mm/s, and the welding current is 100–150 A. The main precipitated phases in the joint were η(MgZn₂), S(CuMgAl₂), Mg₂Si, and Al₁₃Fe₄, which were continuously distributed at the grain boundaries in the form of coarse networks or long strips, which was an important reason for the weak performance of the joints. After the heat treatment of T6, the precipitated phase in the joint was greatly reduced, the element segregation phenomenon was improved, and the residual precipitated phase was mainly Al₁₃Fe₄ and a small amount of insoluble phase Fe and Si, and the recrystallization size of the heat-affected zone was refined. Through heat treatment, the average microhardness of the joint was increased from 110 HV to 150.24 HV, and the tensile strength was increased from 326 MPa to 536 MPa, reaching 97.5% of the strength of the base metal, indicating that the softening phenomenon was significantly improved after heat treatment, and the joint had excellent performance. Full article