Search Results (168)

This study presents a robust numerical framework for evaluating the upper-bound ultimate bearing capacity of shallow foundations in cohesive and C-phi soils using a self-developed finite element method. The model incorporates multi-segment zero-thickness interface elements to accurately simulate soil discontinuities and progressive failure mechanisms, based on the Mohr–Coulomb failure criterion. In contrast to optimization-based methods such as discontinuity layout optimization (DLO) or traditional finite element limit analysis (FELA), the proposed approach uses predefined failure mechanisms to improve computational transparency and efficiency. A variety of geometric failure mechanisms are analyzed, including configurations with triangular, circular, and logarithmic spiral slip surfaces. Particular focus is given to the transition zone, which is discretized into multiple blocks to enhance accuracy and convergence. The method is developed for two-dimensional problems under the assumption of elastic deformable-plastic behavior and homogeneous isotropic soil, with limitations in automatically detecting failure mechanisms. The proposed approach is validated against classical theoretical solutions, demonstrating excellent agreement. For friction angles ranging from 0° to 40°, the computed bearing capacity factors N_c and N_q show minimal deviation from the analytical results, with errors as low as 0.04–0.19% and 0.12–2.43%, respectively. The findings confirm the method’s effectiveness in capturing complex failure behavior, providing a practical and accurate tool for geotechnical stability assessment and foundation design. Full article

Aiming at the engineering problems of the severe wear and limited service life of mandrels during the hole extrusion strengthening of critical aerospace components, this study proposes a surface modification strategy for mandrels based on the anti-friction mechanism of micro-textures. Based on the Lame stress equation and the Mises yield criterion, a plastic strengthening stress distribution model of the hole wall was developed. Integrating Bowden’s adhesive friction theory, a parameterized numerical model was constructed to investigate the influence of micro-texture morphology on interfacial friction and wear behavior. An elastic–plastic contact model for micro-textured mandrels during hole extrusion strengthening was established using ANSYS. The effects of key parameters such as the micro-texture depth and area ratio on the contact pressure field, friction stress distribution, and strengthening performance were quantitatively analyzed. The results show that a circular micro-texture with a depth of 50 μm and an area ratio of 20% can reduce the fluctuation and peak value of the contact pressure by 41.0% and 29.7%, respectively, and decrease the average friction stress by 8.1%. The interfacial wear resistance and the uniformity of the residual compressive stress distribution on the hole wall are significantly enhanced, providing tribological insight and surface optimization guidance for improving the anti-wear performance and extending the service life of mandrels. Full article

Cracks due to stress corrosion cracking in stainless steels are becoming a problem not only in boiling water reactors but also in pressurized water reactor nuclear plants. Stress improvement measures have been implemented mainly for large-bore welded piping, but in the case of small-bore welded piping, post-welding stress improvement measures are often not possible due to dimensional restrictions, etc. Therefore, knowing the actual welding residual stresses of small-bore welded piping regardless of reactor type is essential for the safe and stable operation of nuclear power stations, but there are only a limited number of examples of measuring the residual stresses. In this study, austenitic stainless steel pipes with an outer diameter of 100 mm and a wall thickness of 11.1 mm were butt-welded. The residual stresses were measured by the strain scanning method using neutrons. Furthermore, to obtain detailed residual stresses near the penetration bead where the maximum stress is generated, the residual stresses near the inner surface of the weld were measured using the double-exposure method (DEM) with hard X-rays of synchrotron radiation. A method using a cross-correlation algorithm was proposed to determine the accurate diffraction angle from the complex diffraction patterns from the coarse grains, dendritic structures, and plastic zones. A quantum beam hybrid method (QBHM) was proposed that uses the circumferential residual stresses obtained by neutrons and the residual stresses obtained by the double-exposure method in a complementary use. The residual stress map of welded piping measured using the QBHM showed an area where the axial tensile residual stress exists from the neighborhood of the penetration bead toward the inside of the welded metal. This result could explain the occurrence of stress corrosion cracking in the butt-welded piping. A finite element analysis of the same butt-welded piping was performed and its results were compared. There is also a difference between the simulation results of residual stress using the finite element method and the measurement results using the QBHM. This difference is because the measured residual stress map also includes the effect of the stress of each crystal grain based on elastic anisotropy, that is, residual micro-stress. Full article

Wood–plastic composites (WPCs) have emerged as a sustainable and cost-effective material for construction, particularly in low-cost housing solutions. However, designing WPC panels that meet structural, serviceability, and manufacturing constraints remains a challenge. This study focused on optimizing the cross-sectional shape of WPC roof panels using evolutionary algorithms to minimize material usage while ensuring compliance with deflection and stress constraints. Two evolutionary algorithms—the genetic algorithm (GA) and particle swarm optimization (PSO)—were employed to optimize sinusoidal and trapezoidal panel profiles. The optimization framework integrated finite element analysis (FEA) to evaluate structural performance under uniformly distributed loads and self-weight. The modulus of elasticity of the WPC material was determined experimentally through three-point bending tests, ensuring accurate material representation in the simulations. The trapezoidal profile proved to be the most optimal, exhibiting superior deflection performance compared with the sinusoidal profile. A comparative analysis of GA and PSO revealed that PSO outperformed GA in both solution optimality and convergence speed, demonstrating its superior efficiency in navigating the design space and identifying high-performance solutions. The findings highlight the potential of WPCs in low-cost housing applications and offer insights into the selection of optimization algorithms for similar engineering design problems. Full article

At the microscale, the three-dimensional morphological features of contact surfaces have a significant impact on the performance of electrical contacts. This paper aims to reconstruct the microscopic contact state of contact groups and to deeply study the effect of contact morphological features on electrical contact performance. To fully obtain multimodal data such as the three-dimensional micro-morphological features and chemical composition distribution of contact surfaces, this paper proposes a contact surface feature-matching method based on entropy rate superpixel seed point adaptive morphological reconstruction. This method can adaptively retain meaningful seed points while filtering out invalid seed points, effectively solving the problem of over-segmentation in traditional superpixel segmentation method. Experimental results show that the proposed method achieves a segmentation accuracy of 92% and reduces over-segmentation by 30% compared to traditional methods. Subsequently, on the basis of the moving and static contact group difference plane model and the W-M model, this paper constructs a three-dimensional surface fractal contact model with an irregular base. This model has the ability to layer simulate multi-parameter elastic and plastic and to extract fractal parameter point cloud height, which can more accurately reflect the actual contact state of the contact group. The model demonstrates a 15% improvement in contact area prediction accuracy and a 20% reduction in contact resistance estimation error compared to existing models. Finally, this paper compares and verifies the theoretical feasibility of the model, providing a new theoretical contact model for the study of the impact of three-dimensional micro-morphology on the electrical contact reliability. Full article

Instability in the hole wall of bored pile may cause serious environmental problems. Therefore, using the small hole expansion theory and elastic–plastic theory, we studied the instability mechanism of the hole wall of bored pile, determined the stress expansion solution of the soil layer after the excavation of pile holes in the semi-infinite elastic soil layer, and established a mechanical model. Then, the stability of the hole wall of bored pile in the cohesive soil layer and sandy soil layer was analyzed, and a formula for calculating pile hole wall stability was obtained. Finally, the stability of the hole wall of bored pile under the action of mud slurry was calculated, and the stress on the pile hole wall was analyzed when local instability and overall instability occurred, respectively. The results show that in a sandy soil layer, the safety factor of the hole wall of bored pile has no connection with the depth of the pile hole but is related to the density of mud slurry in the pile hole. In unstable soil layers, the pile hole wall was prone to instability, and the stability of the hole wall could be improved by appropriately increasing the gravity of mud slurry. With the increase in pile diameter, the lateral displacement and deformation of the hole wall increase, and the displacement of the soil layer increases when the hole wall is unstable, increasing the possibility of forming variable cross-section piles correspondingly. Full article

In order to consider the effect of fabric anisotropy in the analysis of geotechnical boundary value problems, this study proposes a modified model based on a fabric-based modified Cam-clay model, which can account for the anisotropic response of soil. The major modification of the original model aims to simplify the equations for numerical implementation by replacing the SMP strength criterion with the Lade’s strength criterion. This model comprehensively considers the inherent anisotropy, induced anisotropy, and three-dimensional strength characteristics of soil. The model is first numerically implemented using the elastic trial–plastic correction method, and then it is encapsulated into the FLAC^3D 6.0 software, and tested through conventional triaxial, embankment loading, and tunnel excavation experiments. Numerical simulation results indicate that considering anisotropy and three-dimensional strength in geotechnical engineering analysis is necessary. By accounting for the interaction between microstructure and macroscopic anisotropy, the model can more accurately represent soil behavior, providing significant advantages for geotechnical analysis. Full article

Accurate analyses of contact problems for rough surfaces are important but complicated. Some assumptions, namely that all asperities can be approximated by a hemisphere with the same radius and assuming a Gaussian distribution of the asperity heights, are convenient but may lead to less accurate results. The purpose of this work is to investigate these assumptions and analyze the conditions under which they are valid. The finite element method is used to construct spherical asperity contact models with different radii and materials. The validity of the assumptions is assessed by comparatively analyzing the results of four models in terms of contact loads, contact radii, and average contact pressures under different yield strengths. The results show that these assumptions are fully applicable under elastic deformation. For plastic cases, the lower yield strength of the two contacting bodies is the dominant factor affecting the contact results. Assuming the same lower yield strength, the ratio of the yield strengths of two spheres has an influence on contact characteristics in the range from 1.2 to 3, but a negligible influence when the ratio is greater than 3. With an equivalent yield strength and yield ratio, the plastic contact of asperities can be analyzed in detail, which be conducive to clarifying the application scope of the above assumption. The work reported in this study provides some theoretical basis for an accurate contact model of rough surfaces. Full article

The collapsibility of aeolian sand has hindered the development of oil and gas resources and the construction of oil and gas stations in the Mu Us Desert. This study considered aeolian sand on the southern edge of the Mu Us Desert as the research object. Based on a water immersion load test, standard penetration test, and indoor geotechnical test, four evaluation indicators were selected, the water content, dry density, void ratio, and saturation. Combined with the support vector machine method, we established a method for evaluating the collapsibility of aeolian sand based on basic physical indicators. The results showed the following: (1) The degree of collapsibility was slight, with a small portion showing no collapsibility. And the load-settlement curve (P-s) was divided into three stages: the linear elastic deformation stage, the elastic–plastic deformation stage, and the collapsible deformation stage. (2) There was a strong relationship between the collapsibility coefficient and the four evaluation indicators for aeolian sand. Based on these indicators, we could accurately predict and evaluate the collapsibility coefficient. (3) Machine learning methods, such as the support vector machine, can effectively solve prediction and evaluation problems between variables when there is no clear mathematical relationship between multiple independent variables and a single dependent variable. Full article

Polyvinyl chloride (PVC) belongs to the most widely used group of thermoplastics. Most of the market for PVC products belongs to plasticized compositions. Plasticizers are the most demanded additives in the polymer industry. Environmental problems and the identified toxicity of the plasticizer di(2-ethylhexyl) phthalate (DEHP) stimulate the restriction of its use and contribute to the development of alternative plasticizers. As a possible replacement for phthalates, esters of dicarboxylic acids are known to provide reduced toxicity and high frost resistance to the resulting compositions. In this regard, esters of dicarboxylic acids and ethoxylated alcohols were obtained and their compatibility with polyvinyl chloride was investigated. The plasticizing effect of the esters obtained was evaluated. The thermomechanical characteristics of PVC compositions containing the developed plasticizers were studied, the glass transition temperature was determined, and the areas of the glassy and highly elastic state of the plastics were identified. It was shown that the chemical structure of dicarboxylate used as a plasticizer determines the important technological and operational characteristics of the PVC plastics obtained. Dibutoxyethyl sebacate (DBES) has the best plasticizing effect among the synthesized esters. The expansion of the highly elastic state area for PVC samples containing this ester exceeded the industrial plasticizers DEHP and di(2-ethylhexyl) adipate (DOA). The indicators of the critical temperature of dissolution of PVC in the esters under study suggest ensuring their low migration from PVC plastics. Full article

Single-layer steel reticulated shell structures have a long history and are widely distributed. As their service life increases, corrosion in these structures becomes an increasingly prominent problem. However, currently, there is nearly no research available on the static behavior of corroded steel reticulated shell structures. Therefore, taking the single-layer steel reticulated shell structure as the research object, an accelerated corrosion test was first carried out on Q345, a commonly used steel for this structure, and an equivalent conversion calculation method was proposed. Then, a Python program (version 3.5.0) for single-layer reticulated shells considering component dimensions, joint stiffness, and random corrosion was written, and numerical simulation analysis was carried out on the static behavior of single-layer steel reticulated shell structures after corrosion. Finally, based on parametric analysis, the random corrosion influence coefficient and joint stiffness influence coefficient were derived, and a calculation method for the elastic–plastic ultimate bearing capacity of the structure was established, which could enhance the current design methods for steel reticulated shells by taking corrosion effects into account. The research results will provide specific and programmed references for the damage identification and safety assessment of single-layer steel reticulated shell structures during their service life in strongly corrosive environments along the coast and offshore, holding important engineering significance and scientific value. Full article

Solder joints strongly determine the lifetime of electronic components subjected to temperature fluctuations. The lifetime predictions obtained by finite element analysis (FEA) are uncertain due to the significant variation in solder geometry. It is unclear how realistic a geometric model is needed for problems of impartial complexity. A balance must be found between modeling effort and simulation accuracy. Six geometric models of the solder joint of a gullwing lead were built with different complexity, from the simplest to the most realistic, including a realistic reference model obtained by the Surface Evolver simulation software. The FEA results considering linear elastic and plastic material models were compared for the different solder geometries. We conclude that manually created solder geometry is a sufficient alternative to physics-based realistic geometries. Full article

A numerical tool for simulating the detection signals of electromagnetic nondestructive testing technology (ENDT) is of great significance for studying detection mechanisms and improving detection efficiency. However, the quantitative analysis methods for ENDT have not yet been sufficiently studied due to the absence of an effective constitutive model. This paper proposed a new magneto–mechanical model that can reflect the dependence of relative permeability on elasto–plastic deformation and proposed a finite element–infinite element coupling method that can replace the traditional finite element truncation boundary. The validity of the finite element–infinite element coupling method is verified by the experimental result of testing electromagnetic analysis methods using TEAM Problem 7. Then, the reliability and accuracy of the proposed model are verified by comparing the simulation results under elasto–plastic deformation with experimental results. This paper also investigates the effect of elasto–plastic deformation on the transient magnetic flux signal, a quantitative hyperbolic tangent model between Bz_pp (peak–peak value of the normal component of magnetic flux signal) and elastic stress, and the exponential function relationship between Bz_pp and plastic deformation is established. In addition, the difference and mechanism of a magnetic flux signal under elasto–plastic deformations are analyzed. The results reveal that the variation of the transient magnetic flux signal is mainly due to domain wall pinning, which is significantly affected by elasto–plastic deformation. The results of this paper are important for improving the accuracy of quantitative ENDT for elasto–plastic deformation. Full article

Synthetic fibers are widely used in daily life due to their durability, elasticity, low cost, and ease of use. The textile industry is the primary source of synthetic microfibers, as these materials are mostly used in production processes. Globally, plastic pollution has been identified as a major environmental threat in this era, since plastics are not degradable but break down into smaller particles such as mesoplastics, microplastics, and microfibers. Synthetic microfiber pollution is a significant issue in aquatic ecosystems, including oceans and rivers, with laundry wastewater being a major source. This problem is particularly pressing in cities like Galle, Sri Lanka, where numerous tourist hotels are located. Despite the urgency, there has been a lack of scientific and systematic analysis to fully understand the extent of the issue. This study addresses this gap by analyzing the generation of microfibers from laundry activities at a selected hotel and evaluating the efficiency of a laundry wastewater filtration system. This study focused on a fully automatic front-loading washing machine (23 kg capacity) with a load of 12 kg of polyester–cotton blend serviettes (black and red). Samples (1 L each) were taken from both treated and untreated wastewater during four wash cycles, with a total of 100 L of water used for the process. The samples were filtered through a 100 μm sieve and catalytic wet oxidation along with density separation were employed to extract the microfibers, which were then collected on a membrane filter paper (0.45 μm). Microfibers were observed and analyzed for shapes, colors and sizes under a stereo microscope. Results revealed that untreated laundry wastewater contained 10,028.7 ± 1420.8 microfibers per liter (n = 4), while treated wastewater samples recorded 191.5 ± 109.4 microfibers per liter (n = 4). Most of the microfibers observed were black and white/transparent colors. Further analysis revealed that 1 kg of polyester–cotton blend fabric can generate 336,833 microfibers per wash, which was reduced to 6367 microfibers after treatment. The filtration unit recorded an impressive efficiency of 98.09%, indicating a remarkably high capacity for removing microfibers from wastewater. These findings highlight the potential of such filtration techniques to significantly reduce microfiber emissions from laundry wastewater, presenting a promising approach to mitigating environmental pollution from microfibers. Full article

As the most widely used building material, cement has attracted the attention of scholars because of its large carbon emission. To alleviate the problems of carbon emission and limited resource use caused by cement production, this study focuses on the performance of mortar after carbonization curing by regulating the composition of ternary binders. Testing involved mechanical parameters, carbon shrinkage, water absorption, hydration product, microstructure, adsorption of carbon dioxide, calcium carbonate content, and carbonization degree of mortar, as well as comparisons with the effect of calcium carbide slag and sintered red mud. We carried out several studies which demonstrated that carbonization curing and adjusting the content of calcium carbide slag and sintered red mud were beneficial to improve the mechanical properties, peak load displacement, slope, elastic energy, plastic energy, carbon shrinkage, carbon dioxide adsorption, calcium carbonate content, and carbonization degree of mortar, while the addition of calcium carbide slag and sintered red mud increased the water absorption of mortar, and the greater the dosage, the greater the water absorption. Meanwhile, adding 25%–50% calcium carbide slag and sintered red mud still had negative effects on the mechanical properties of mortar. But carbonation curing and the addition of calcium carbide slag and sintered red mud could promote the hydration reaction and consume calcium hydroxide formed by hydration to form calcium carbonate. When the dosage was 50%, the carbon dioxide adsorption capacity, calcium carbonate content, and carbonization degree of calcium carbide slag mortar were higher than those of sintered red mud mortar, which increased by 29.56%, 102.73%, and 28.84%, respectively. By comparison, calcium carbide slag and sintered red mud still showed superior carbon sequestration capacity, which was higher than fly ash and Bayer red mud. From the experiment, we came to realize that adjusting the composition of cementitious materials could realize the carbon sequestration of cement-based materials and promote the road toward low-carbon sustainable development of cement. Full article