Search Results (5,634)

This study proposes and evaluates a prefabricated steel-fiber-reinforced concrete (SFRC) wall-panel system for flexural performance. Material tests were used to calibrate and validate a compression stress–strain model for SFRC with good predictive accuracy. Finite element analyses quantify the panels’ flexural capacity and the effects of wythe thickness, connector spacing, and connector layout. Results show that adding glass-fiber grids produces synergy with steel fibers, improving the composite wall system’s flexural performance. Relative to plain-concrete panels, SFRC panels exhibit 29.5% lower peak strain and 27.2% higher peak stress. FE analyses indicate that shortening the connector length reduces flexural capacity. Within the studied range, a 200 mm connector spacing delivers the best structural performance. A full-height connector layout is recommended to ensure structural integrity. Full article

As oil and gas field development enters mid and late stages, steel pipeline corrosion becomes more severe, driving the adoption of non-metallic pipes. This study tested non-metallic composite pipe HDPE inner-layer materials in simulated produced water at 60 °C and 70 °C, analyzing surface structure, mechanical properties, and chemical composition via systematic analytical methods. The findings indicate that the surface roughness Ra of the sample remains stable following immersion, with no voids observed; the tensile strength of the material decreases by 8.94% and 15.36% at temperatures of 60 °C and 70 °C. Infrared research indicated that the material’s structure remained stable at both temperatures, with no occurrence of oxidation or chain scission. The environmentally corrected lifetime (24.3 years) provides a practical framework for operators in analogous Sichuan Basin conditions, bridging the gap between idealized laboratory predictions and field performance. Full article

Improving the operational parameters of machinery necessitates the use of materials with higher mechanical characteristics. Strength characteristics, particularly fracture toughness, are strongly linked to the material’s microstructure. This article presents the results of a study examining the effect of microstructure on the mechanical properties and fracture toughness of G17CrMo5-5 cast steel in its basic and rare-earth modified variants. The addition of rare-earth elements (REEs) to the melt resulted in a reduction and homogenization in grain size, as well as a reduction in the size and shape of non-metallic inclusions. For modified cast steel, there were no grains with a chord size above 120 μm and inclusions with a diameter above 5.5 μm. Changes in the microstructure of modified cast steel resulted in a slight increase in strength properties. It significantly increased the fracture toughness: for unmodified cast steel at a temperature of −20 °C, the fracture toughness increased from 94 kN/m to 416 kN/m for modified cast steel. Fracture fractographic analysis using non-contact microroughness measurement techniques or measuring the width of the stretch zone allowed for the calculation of fracture toughness without the need for a conventional test. Fracture toughness calculated based on fractographic analysis can be determined for brittle fracture and brittle fracture preceded by plastic growth. Numerical simulations of the loading of specimens tested for fracture toughness allowed us to determine the effect of the REE steel modification on the stress field distribution ahead of the crack front. The modification resulted in a change in the opening stress distribution and the location of its maximum at each temperature. The use of REE modification is an effective approach for homogenizing the microstructure and increasing the fracture toughness of cast steel, especially when the material operates at temperatures in the interval of the fracture mechanism change. Full article

In response to the issue of local damage to mountainous bridges easily caused by rockfall impacts, carbon fiber cloth and steel plate strengthening methods were adopted to deeply study the impact of the width of carbon fiber cloth and steel plates on the strengthening effect. This study investigates the strengthening effectiveness of Carbon Fiber-Reinforced Polymer (CFRP) wraps and steel jackets on circular bridge piers, utilizing the ABAQUS finite element method. The analysis focuses on the effects of varying load conditions and confinement widths ranging from 100 to 200 cm, with a specific case study of a bridge pier in Nanchuan District, Chongqing. The research results show that the width of carbon fiber cloth and steel plates has a significant impact on the bridge pier’s impact resistance and damage resistance. There exists an optimal strengthening width that maximizes the strengthening effect. The stress distribution and displacement changes under different load conditions are affected by the width of the steel plate; the wider the steel plate, the better the strengthening effect, but the effect is not strictly linear. A comprehensive analysis method integrating multi-directional stress and displacement data was developed, incorporating weighting factors based on structural safety relevance. For both strengthening methods, a set of fitted formulas for widths between 100 cm and 200 cm was derived. This study provides systematic insights and practical guidance for the design of impact-resistant strengthening systems for bridge piers. Full article

A microalloyed (MA) steel, combined with titanium diboride (TiB₂), was utilised to create a unique steel matrix composite (SMC), enhancing the modulus of the MA steel while also improving its strength. Through thermomechanical processing stages, including hot rolling and plane-strain compression (PSC) testing, followed by various final cooling methods, a cooling rate of 0.1 °C/s was identified as the most effective for achieving a ferrite–pearlite microstructure, which is suitable for toughness and ductility. With TiB₂ reinforcement successfully incorporated via Fe-Ti and Fe-B additions during vacuum induction melting (VIM), it was observed that the TiB₂ particles were homogeneously dispersed in both 5% and 7.5% nominal volume fraction additions, exhibiting faceted and hexagonal morphology. TiB₂ was found to exert a grain-pinning effect on recrystallised austenite at 1050 °C, as evidenced by the retention of grain orientation from hot rolling, in contrast to the MA steel deformed without the composite reinforcement. Increasing the volume fraction of TiB₂ improved the stiffness and strength of both composite alloys, verified through mechanical testing. Full article

The ultimate strength of the hull girder represents one of the key criteria in the design of large thin-walled steel structures such as ships and aircrafts. For large ship structures, the hull girder’s ultimate strength is expressed as the maximum internal vertical bending moment that the hull structure can absorb before collapse. In this paper, a progressive collapse analysis of the hull girder has been performed for several different variants of large steel thin-walled box girders, taken from the literature as benchmark cases, using the nonlinear finite element method (NLFEM), considering both material and geometrical nonlinearity. Results from the performed calculations were compared to the numerical results of other researchers published in the literature, as well as the results of our physical experiment. The influence of initial geometrical imperfection on the value of the ultimate bending moment achieved with NLFEM has been investigated. Full article

In this paper, the effects of 3D printing parameters on the metallurgical and mechanical properties of 3D-printed 25CrMo4 steel are presented. Using laser-based powder bed fusion of metals (PBF-LB/M), samples were fabricated under varying conditions of laser power, scan speed, and layer thickness. The study examined how variations in volumetric energy density (VED) and linear energy density (LED) influence the material’s performance. The results show a strong correlation between the printing parameters and key properties such as hardness, porosity, bending strength, compressive strength, and tensile strength. Appropriate VED and LED improved density, reduced defects, and enhanced mechanical performance, whereas excessive energy inputs introduced brittleness. These findings support the advancement of additive manufacturing technologies for high-strength steels and broaden their potential applications in the aerospace, automotive, and construction sectors. Full article

To achieve carbon neutrality goals, offshore wind power combined with a hydrogen energy storage system (OWP-HESS) is critical for integrating intermittent renewables. This study applied a “cradle-to-grave” process-based life cycle assessment (PLCA) to evaluate a 77.4 MW offshore wind farm coupled with a 45.0 MW electrolysis cell system, covering manufacture, transportation, construction, operation and maintenance, and decommissioning phases. It focuses on two hydrogen production routes, alkaline electrolysis (AEL) and proton exchange membrane (PEM), and covers 12 environmental indicators. Moreover, considering optimal economic efficiency, to adapt to the characteristic of “electricity–hydrogen cogeneration”, as well as to facilitate reflecting the efficiency differences between the two electrolysis technologies, the functional unit is defined as “0.4 kWh green electricity + corresponding green hydrogen”. Results show that offshore wind’s environmental impacts mainly come from manufacture (79.00%, driven by concrete/steel), while hydrogen storage impacts focus on operation/maintenance (66.03% for AEL and 96.61% for PEM, driven by electricity). PEM’s green hydrogen global warming potential (GWP) (0.96 kg CO₂-eq/kg) is much lower than AEL’s (1.81 kg CO₂-eq/kg) and China’s fossil-based hydrogen (≈40 kg CO₂-eq/kg). With an initial system lifespan of 25 years, a wind farm capacity factor of 41.30%, and a hydrogen production efficiency of 68.72% (AEL) and 69.89% (PEM), extending system lifespan by 5 years, raising wind farm capacity factor to 43%, and enhancing hydrogen production efficiency to 71% reduce emissions by 16.67%, 4.00%, and 2.16%, respectively. This study clarifies OWP-HESS’s environmental characteristics, confirms PEM’s low-carbon advantage, and provides support for its sustainable development. Full article

In the manufacturing of iron core for high-power transformers, a cutting stock problem arises where large-width silicon steel coils must be cut into narrower coils, known as strips. Typically, the required length of each strip far exceeds that of a single coil. Therefore, the problem necessitates additional consideration of how to split the strips and arrange them on the large coils, with the goal of minimizing the total number of strips. In this paper, we propose a discrete artificial bee colony algorithm to address this problem. The algorithm replaces the stochastic roulette wheel with biased selection in the onlooker bee phase and introduces partially mapped crossover in both the onlooker and scout bee phases. These enhancements facilitate more effective utilization of information from high-quality solutions, thereby improving the algorithm’s stability and its capacity to obtain higher-quality results. Experimental results show that compared to existing methods reported in the literature, the proposed approach reduces the total number of strips by an average of over 3.9% and 7.6% for Set 2 and Set 3, respectively, while also exhibiting a faster convergence rate than other competitive algorithms. Full article

During the laser cladding process for composite coatings, significant differences exist in the physical and mechanical properties between the substrate and the composite coating materials. Therefore, a systematic analysis of the mechanical properties is necessary to mitigate issues such as cracking and deformation caused by performance mismatch. This study investigated the mechanical properties (microhardness, wear resistance, tensile strength) of composite coatings formed by laser cladding IN718 alloy onto an EA4T steel substrate. Given the critical influence of scanning strategies on cladding layer quality, this study also examined the relationship between the tensile direction and scanning direction. By analyzing mechanical responses under different orientations, it revealed the patterns of influence on tensile properties and anisotropy characteristics of the cladding layer, providing a theoretical basis and process guidance for achieving high-performance cladding layers. Tensile tests conducted at different angles on the IN718 cladding layer indicate that when a thin cladding layer is required, selecting a scanning speed direction parallel to the primary tensile direction yields superior results. Conversely, for applications demanding a thicker cladding layer, aligning the scanning direction perpendicular to the tensile direction better leverages the cladding layer’s performance. Full article

Current research on tower crane control lacks high-fidelity models and fails to account for the coupling effects between the tower crane structure and the hoisting and luffing systems. A new dynamic analysis platform based on the flexible multibody system theory is proposed in this investigation for the tower crane which contains a large-scale steel structure and hoisting mechanisms undergoing large displacements and large deformations. The Arbitrary Lagrangian–Eulerian–Absolute Nodal Coordinate Formulation (ALE–ANCF) cable element was employed to model the varying length of the steel rope in the hoisting mechanisms. Nonlinear kinetic equations were used to describe the motion of a luffing trolley. The solving strategy of the system’s dynamical equations are presented. Two different trajectories were tested. Simulation results demonstrate the feasibility and rationality of the proposed dynamic analysis platform. The primary conclusion is that this platform serves as a reliable and high-fidelity testbed for developing and evaluating advanced control algorithms under realistic dynamic conditions, thereby providing a dependable tool for both research and engineering applications. Full article

This study examines the response of a composite material protection plate with an asymmetrical sandwich structure under low-velocity impact. The protection plate with an asymmetrical sandwich structure is constructed with materials such as polypropylene/glass fiber composites (PP/GFs), a steel plate, and a regular hexagonal honeycomb Al plate (Al honeycomb). The effects of the steel plate and Al honeycomb’s strength and thickness on the deformation behavior of the protection plate, as well as the influence of contact strength on the energy absorption of the Al honeycomb, were studied by combining models and experiments. A finite element model was established using Abaqus/Expliced software (2018), and the mechanical property parameters of each layer were simulated to analyze the greatest impact resistance of the protection plate. The experimental results show that the higher strength of the Al honeycomb can effectively improve the impact resistance of the protection plate. The energy absorption of the steel plate and the Al honeycomb accounted for 34.30% and 20.90%, respectively, and the damage area was more concentrated, making the protection plate more durable. Full article

The seismic design of aluminum alloy structures requires specific attention due to the material’s distinct mechanical properties compared to steel, which renders direct application of steel joint design methods inappropriate. This study investigates the seismic behavior of T-shaped aluminum alloy beam–column bolted connections, which consist of 6061-T6 aluminum alloy beams and columns connected by S304 stainless steel connectors via high-strength bolts. A finite element model, incorporating a mixed hardening constitutive model for accurate cyclic response, is established and validated against low-cycle cyclic loading tests. Parametric analyses evaluated the influence of L-shaped connector dimensions on hysteresis response, skeleton curves, stiffness degradation, energy dissipation, and ductility. Results demonstrate that increasing the thickness of the short leg of the L-shaped connector between the beam flange and column flange significantly enhances the ultimate bending moment, with an increase of up to 36.7% per 2 mm increment, alongside improved energy dissipation and ductility. Stiffness degradation follows a natural exponential decay, with residual stiffness between 23.85% and 32.57% at ultimate deformation. An efficiency analysis identifies the most cost-effective measures for seismic design. The primary novelty of this work lies in the successful application and validation of a mixed hardening model for simulating the complex cyclic behavior of T-shaped aluminum alloy connections, coupled with a systematic efficiency-oriented parametric study. The findings offer practical, quantitative guidelines for designing aluminum alloy bolted connections in seismic-prone regions. Full article

The aim of the research was to analyse the impact of peening each of the beads on the properties of a butt joint made of S960QL steel welded with ceramic backing on a robotic workstation using the 135 (MAG) method, and to determine the impact of pneumatic needle peening on the stress level. This analysis was based on a comparison of three butt joints: in the as-welded state, with each weld bead peened and post-weld heat treatment—stress relief annealing—performed. High-frequency peening (90 Hz) of each weld was performed to reduce stresses in the welded joint by introducing tensile stresses into it. A Weld Line 10 pneumatic hammer from PITEC GmBH was used for this purpose. The test joints obtained were tested in accordance with the requirements of EN ISO 15614-1. In order to determine the state of residual stresses, stress measurements were carried out using the Barkhausen effect based on the testing procedure of the technology supplier, NNT. This meter measures the intensity of the Barkhausen effect using a standard probe (with a single core). In order to verify the stress measurement using the Barkhausen method, stress measurements were performed using the XRD sin 2ψ technique based on the X’Pert Stress Plus program, which contains a database of material constants necessary for calculations. Structural studies, including phase analysis and crystallographic grain orientation, were performed using the backscattered electron diffraction method with a high-resolution scanning electron microscope and an EBSD (Electron Backscatter Diffraction) detector, as well as EDAX OIM analysis software. In addition, X-ray diffraction testing was performed on a Panalytical X’Pert PRO device using filtered cobalt anode tube radiation (λ = 1.79021 A). Qualitative X-ray phase analysis of the tested materials was performed in a Bragg–Brentano system using an Xcelerator strip detector. The tests showed that the high-frequency peening of each bead did not cause negative results in the required tests during qualification of the S960QL plate-welding technology compared to the test plates in the as-welded and post-stress-relief heat treatment states. Interpass peening of the weld face and HAZ resulted in a reduction in residual stresses after welding at a distance of 15 mm from the joint axis compared to the stress measurement result for the sample in the as-welded condition. This allows for a positive assessment of peening in terms of reducing the crack initiator in the form of the concentration of tensile stresses in the area of the fusion line and HAZ. Full article

Steel moment-resisting frames rely on strength and ductility to perform under seismic loads. Conventional techniques such as reduced beam section (RBS) and reduced web section (RWS) improve ductility by relocating plastic hinges but can suffer from local buckling, fabrication challenges, and costly post-earthquake repairs. This study proposes a sacrificial steel sleeve fuse system for bolted endplate connections, designed to concentrate inelastic deformation within a replaceable sleeve while preserving the primary structural components. Experimental tests included standalone sleeve compression, bolted sleeve assemblies, and T-stub connections with and without sleeves, all validated with finite element models. A parametric study evaluated two sleeve geometries—circular wave (CW) and U-shaped (US)—and compared the sleeve fuse system’s monotonic performance with RWS and standard connections. Results indicate that properly designed sleeve fuses significantly enhance ductility and energy dissipation without compromising initial stiffness or strength, achieving up to 1.8 times the ductility and 25.9% higher energy absorption relative to RWS connections. The findings highlight the sleeve fuse as an innovative, easily replaceable, and resilient solution for seismic applications, offering a practical path for both retrofitting existing frames and designing new structures. Full article