Search Results (9)

Intertidal habitat heterogeneity can shape macrobenthic communities, but its links to assembly processes and network stability remain uncertain. Macrobenthos were surveyed at 22 sites across muddy sediment (MA), oyster farming (OF), eastern rocky reef (EA), and southern rocky reef (SA) habitats around Nan’ao Island. Habitat type explained 25.5% of compositional variation, whereas observed richness and evenness showed no consistent among habitat differences. Mean between-habitat Bray-Curtis dissimilarity (0.730) and turnover (0.623) exceeded their within-habitat values (0.634 and 0.555), indicating that species replacement, rather than nested species loss, dominated community differentiation. Functional richness differed among habitats, whereas most other functional indices remained comparatively stable. Neutral-model fits were stronger in EA and SA (R² = 0.501 and 0.475, respectively) than in MA and OF, and null-model partitioning indicated undominated processes in MA and OF but greater homogenizing dispersal in rocky habitats. SA contained the largest co-occurrence network (24 nodes, 81 edges), although robustness was highest in OF. Exploratory PLS-SEM showed positive associations between habitat heterogeneity and environmental filtering (β = 0.591, p = 0.004) and between turnover and potential network stability (β = 0.593, p = 0.022), whereas the assembly–stability association was nonsignificant (β = 0.044, p = 0.856). These cross-sectional associations support a conceptual pathway linking habitat-related environmental gradients, species turnover, assembly shifts, and network reorganization. Full article

Accurate prediction of slab temperature during the continuous casting and rolling process is essential for optimizing reheating furnace scheduling and achieving energy savings and emission reductions in steel production. However, because of the dynamic boundary conditions caused by the complex transport processes, obtaining precise temperature data for slabs remains challenging. These difficulties lead to issues such as low hot charging rates, mixing of hot and cold slabs in reheating furnaces, and excessive heat loss from slabs after cutting. To address these challenges, this study develops a mathematical model to calculate slab temperatures during the continuous casting and rolling process, providing a foundation for production scheduling optimization. The model accounts for the coupled heat transfer effects induced by dynamic slab stacking and the stacking heat transfer effects resulting from slabs with varying cross-sectional dimensions. Validation against experimental data demonstrated the model’s accuracy and reliability. Key findings highlighted that neglecting dynamic stacking effects or simplifying slab dimensions introduces errors. These results enhance slab temperature tracking in complex processes and advance related theoretical understanding. Full article

Brittle intermetallic compounds (IMCs) at the interface of dissimilar materials can seriously affect the mechanical properties of the dissimilar components. Introducing external assisted fields in the fabrication of dissimilar components is a potential solution to this problem. In this study, an alternating magnetic field (AMF) was introduced for the first time in the additive manufacturing of Ti6Al4V/AA2024 dissimilar alloy components by laser-directed energy deposition (L-DED). The effect of the AMF on the interfacial IMCs’ distribution was studied. The results indicate that the contents of the IMCs were different for different magnetic flux densities and frequencies, and the lowest content was obtained with a magnetic flux density of 10 mT at a frequency of 40 Hz. When an appropriate AMF was applied, the IMC layer was no longer continuous at the interface, and the thickness was notably decreased. In addition, the influence of the AMF on the temperature distribution and fluid flow in the melt pool was analyzed through numerical simulation. The simulation results indicate that the effect of the AMF on the temperature of the melt pool was not significant, but it changed the flow pattern inside the melt pool. The two vortices inside the cross-section that formed when the AMF was applied caused different orientations of club-shaped IMCs inside the deposition layer. A sudden change in the streamline direction at the bottom of the longitudinal cross-section of the melt pool can affect the formation of the IMC layer at the interface of dissimilar materials, resulting in inconsistent thickness and even gaps. This work provides a useful guidance for regulating IMCs at dissimilar material interfaces. Full article

Mechanical property changes in friction stir welding can directly affect the rebalance of the stress field in friction stir welding. This means that it reveals a high relevance with the residual states of friction stir welding. Here, we propose a subregion model in which the mechanical property changes are considered to predict the residual states in friction stir welding of dissimilar metals. Results indicate that the accuracy of the predicted distortion can be greatly increased when the different mechanical properties are considered in friction stir welding of 2024-T3 and 6061-T6. The final mechanical property is determined by the mixture of the materials at retreating and advancing sides. The final mechanical property in the stirring zone can be increased to 171 MPa for yield strength and 194 MPa for tensile strength when the strength of the advancing side material is higher. The shrinkage of material in the stirring zone during the cooling stage is the key reason for the formation of the tensile residual stress and the V-shape distortion on the cross-section in the as-weld state. Full article

Magnetic pulse welding of overlapping dissimilar metallic sheets is an emerging technique and usually employs flat electromagnetic coils with rectangular-, H-, I-, and E-shaped cross-sections. The asymmetric cross-section of these coils results in a non-uniform electromagnetic field and in a non-uniform connection in the interface between the overlapping sheets. In this article, the use of a novel O-shaped flat coil is proposed to join an aluminium flyer sheet with a target steel sheet. A finite element-based numerical model is developed to calculate the electromagnetic field, flyer velocity, and its gradual impact onto the target, and the deformations of the sheet assembly. The calculated results with the O-shaped coil show a high-intensity electromagnetic field, the concentration of which decreases radially outwards in a uniform manner. The numerically computed and experimentally measured flyer velocity are found to be in fair agreement. The calculated results show a regularly decreasing impact behaviour between the flyer and target and their resulting deformation. The measured results show the formation of an annular ring-shaped joint profile that is generally found to be stronger compared to that obtained with flat coils with a rectangular cross-section. Full article

GFRP sections with filler concrete material form promising structural components for structures; therefore, the structural performance of them has been investigated with increasing popularity. However, the performance of these composites degrades when fully composite action cannot be developed at the interface in where the literature hosts limited knowledge. Different techniques, such as abraded and sand-bonded surface treatments, were investigated experimentally to improve the bond-slip behavior between GFRP and concrete; however, there is a need to define shear mechanism at the interface of the numerical models. In this study, first, the average frictional bearing strengths were extracted for the treated and untreated inner surfaces using experimental results; then, the coulomb friction model was utilized to transfer the shear stresses between two dissimilar materials. Numerical models were verified by the experimental results, and different parametric studies were investigated by varying the amount and shape of GFRP in the cross section, compressive strength of concrete including the non-linear material behavior and interface frictional contact models. The findings showed that the interface strength can improve the flexural capacity of the concrete-filled GFRP beams by about 15.4%. Square GFRP box sections can be suggested for the construction of hybrid beams instead of rectangular sections, whereas the 10% areal ratio in a square cross section reached 103% load capacity improvement. The increased nominal compressive strength of concrete in hybrid beams can increase the hollow GFRP beams’ nominal load capacities and elastic stiffness of the hybrid beams in between; however, the relative gain is reduced due to increased compressive strength of concrete. Full article

In this paper, the effect of different shapes of tool pin on the plastic flow of 2024-T6 aluminum alloy during friction stir welding was studied. In order to observe the plastic flow of materials more clearly, we chose the method of friction stir welding of dissimilar materials, considering the different corrosive characteristics of aluminum alloys made of different materials when exposed to the same corrosive liquid. By studying and comparing the temperature field, macro and microstructure, microhardness and tensile properties of welded joints, the results indicated that the metal in the weld nugget zone (WNZ) mainly came from the base metal of the advancing side, the thread being the driving force of the downward movement of the FSW plastic metal. The deep groove thread tool pin had the strongest ability to drive the metal downward. The conical cam thread tool pin had the strongest stirring effect on materials and the best metal fluidity. The macroscopic morphology, microstructure, mechanical properties and fracture morphology of different joints were analyzed, and the results showed that all joints could form an excellent union, with an onion ring pattern appearing in cross-section. The minimum grain size of the WNZ formed by the conical cam thread stirring head was 7~12 μm; the hardness was least at the junction of the heat affected zone (HAZ) and the thermo-mechanically affected zone (TMAZ). However, the hardness of the weld formed by the conical cam thread at this point was higher than that of other stirring heads; the tensile strength of all joints was more than 80% of the BM, and the maximum tensile strength of the joint welded by the conical cam thread tool pin was 364.27 MPa, accounting for 86.73% of the base metal (BM). The elongation after break was 14.95%. Tensile fracture morphology analysis showed that all joints were fractured by plastic fracture. Full article

The aim of this study was to identify and analyze the fatigue fracture characteristics of dissimilar Al 6061 to Cu (UNS C11000) lap joints made with ultrafast electromagnetic pulse welding (EMPW) via fractography, stress analysis and finite element simulation. It was observed that EMPW generated an annular (or ring-shaped) bonding area, with weld zones and a central non-weld zone when viewed from the cross section. Two types of failure modes occurred in relation to the cyclic loading levels: base metal fracture or transverse through-thickness (TTT) crack growth at a higher loading level, and joint interfacial failure at a lower loading level. In the interfacial failure, fatigue crack initiated from the outer edge of annular welding area, and propagated to form an approximate elliptical boundary. Fatigue crack propagation was characterized by fatigue striations existing in discrete areas on the fracture surface. This was attributed to a coupled role of shear and normal stresses present in a tensile lap shear sample due to the bending moment caused by the inherent misalignment. The final rapid fracture started from elliptical boundary with elongated shear dimples. Both theoretical stress analysis and finite element model revealed the maximum stress and stress concentration along the outer edge, where fatigue crack initiation occurred. Full article

Dissimilar Al/steel butt joints of 6.0 mm thick plates have been achieved using fiber laser keyhole welding autogenously. The cross sections, interface microstructures, hardness and tensile properties of Al/steel butt joints obtained under different travel speeds and laser beam offsets were investigated. The phase morphology and thickness of the intermetallic compound (IMC) layers at the interface were analyzed by scanning electronic microscopes (SEM) using the energy-dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD) techniques. The results show that travel speeds and laser beam offsets are of considerable importance for the weld shape, morphology and thickness of IMC layers, and ultimate tensile strength (UTS) of Al/steel butt joints. This proves that the IMC layers consist of Fe₂Al₅ phases and Fe₄Al₁₃ phases by EBSD phase mapping. Increasing laser beam offsets from 0.3 mm to 0.7 mm significantly decreases the quantity of Fe₄Al₁₃ phases and the thickness of Fe₂Al₅ layers at the interface. During tensile processing, the Fe₂Al₅ layer with the weakest bonding strength is the most brittle region at the interface. However, an intergranular fracture that occurred at Fe₂Al₅ layers leads to a relatively high UTS of Al/steel butt joints. Full article