Search Results (159)

Numerical simulations of the forming limit diagram (FLD) for SUS430/Al1050/TA1 laminated metal composites (LMCs) are conducted through the crystal plasticity finite element (CPFE) model integrated with the Marciniak–Kuczyński (M–K) theory. Representative volume elements (RVEs) that reconstruct the measured crystallographic texture, as characterized by electron backscatter diffraction (EBSD), are developed. The optimal grain number and mesh density for the RVE are calibrated through convergence analysis by curve-fitting simulated stress–strain responses to the uniaxial tensile data. The established multi-scale model successfully predicts the FLDs of the SUS430/Al1050/TA1 laminated sheet under two stacking sequences, namely, the SUS layer or the TA1 layer in contact with the die. The Nakazima test results validate the effectiveness of the proposed model as an efficient and accurate predictive tool. This study extends the CPFE–MK framework to multi-layer LMCs, overcoming the limitations of conventional single-layer models, which incorporate FCC, BCC, and HCP crystalline structures. Furthermore, the deformation-induced texture evolution under different loading paths is analyzed, establishing the relationship between micro-scale deformation mechanisms and the macro-scale forming behavior. Full article

This research examined the development and testing of hot-melt adhesives incorporating metallic (Al and Fe powders averaging 800 nm) and ferrite additives, designed for reversible bonding technology of polyolefins through electromagnetic energy. The experimental models with Al displayed smooth particles that were fairly evenly distributed within the polymer matrix. Experimental models with Fe suggested that Fe nanopowders are more difficult to disperse within the polymer matrix, frequently resulting in agglomeration. For ferrite powder, there were fewer agglomerations noticed, and the dispersion was more uniform compared to similar composites containing Fe particles. Regarding water absorption, the extent of swelling was greater in the composites that included Al. Because of toluene’s affinity for the matrices, the swelling measurements stayed elevated even with reduced exposure times, and the composites with ferrite showed the lowest swelling compared to those with metallic particles. A remarkable evolution of the dielectric loss factor peak shifting towards higher frequencies with rising temperatures was observed, which is particularly important when the materials are exposed to thermal activation through electromagnetic energy. The reversible bonding experiments were performed on polyolefin samples which were connected longitudinally by overlapping at the ends; specialized hot-melts were employed, using electromagnetic energy at 2.45 GHz, with power levels between 140 and 850 × 10³ W/kg and an exposure duration of up to 2 min. The feasibility of bonding polyolefins using homologous hot-melts that include metallic/ferrite elements was verified. Composites with both matrices showed that the hot-melts with Al displayed the highest mechanical tensile strength values, but also had a relatively greater elongation. All created hot-melts were suitable for reversible adhesion of similar polyolefins, with the one based on HDPE and Fe considered the most efficient for bonding HDPE, and the one based on PP and Al for PP bonding. When bonding dissimilar polyolefins, it seems that the technique is only effective with hot-melts that include Al. According to the reversible bonding diagrams for specific substrates and hot-melt combinations, and considering the optimization of energy consumption in relation to productivity, the most cost-effective way is to utilize 850 × 10³ W/kg power with a maximum exposure time of 1 min. Full article

The ball mill is a critical size reduction equipment in industries such as mining and metallurgy. However, the sustainable reliability modeling of the entire system is challenging due to its complex service conditions. This paper presents a systematic framework for the reliability analysis of ball mills based on Stress–Strength Interference Theory (SSIT). Based on a reliability block diagram (RBD), this study establishes a system-level reliability model for the ball mill. Within this framework, the cylinder model is developed using the energy conservation principle between impact energy and strain energy; the gear model comprehensively considers both contact and bending fatigue failure modes; and the bolt model is constructed through mechanical analysis in conjunction with Hooke’s law. In the case study, a laboratory-scale mill (Φ5.5 × 2.6 m shell, effective grinding chamber: 5.3 m inner diameter × 2.376 m length) operating at 14 RPM under dry grinding conditions is analyzed. The reliability of individual components and the entire system is computed using Monte Carlo simulation. The results indicate that the overall system reliability increases when one of the following three conditions is met: the surface hardness of the gear is higher and the tangential force is lower; the impact velocity on the cylinder is lower and the impacted area is larger; or the tensile force on the bolt is reduced. Full article

Growing concern about the environmental impact of traditional packaging has driven the development of biodegradable edible films made from natural and functional biopolymers. Various by-products generated during harvesting can be subjected to valorization. Potato, a tuber with high starch content, and carrot, rich in β-carotene, represent important sources of polymeric matrix and bioactive compounds, respectively. Similarly, the use of biodegradable plasticizers such as pectin and polysaccharides derived from nopal mucilage is a viable alternative. This study assessed the physical and chemical properties of edible films composed of potato starch (PS), cactus mucilage (NM), carrot extract (CJ), citrus pectin (P), and glycerin (G). The films were produced by means of casting, with three mixtures prepared that had different proportions of CJ, P, and PS. The experiments were adjusted to a simple mixture design, and the data were analyzed in triplicate, using Pareto and Tukey diagrams at 5% significance. Results showed that adding CJ (between 5 to 6%), P (between 42 to 44%) and PS (between 43 to 45%) significantly affects all of the evaluated physical and chemical properties, resulting in films with luminosity values greater than 88.65, opacity ranging from 0.20 to 0.54 abs/mm, β-carotene content up to 26.11 μg/100 g, acidity between 0.22 and 0.31% and high solubility with a significant difference between treatments (p-value < 0.05) and low water activity (around of 0.47) (p-value > 0.05). These characteristics provide tensile strength up to 5.7 MPa and a suitable permeability of 1.6 × 10⁻² g·mm/h·m²·Pa (p-value < 0.05), which ensures low diffusivity through the film. Similarly, increasing the CJ addition enables the functional groups of the other components to interact. Using carrot extract and potato starch is a promising approach for producing edible films with good functional qualities but with high permeability. Full article

Formability testing is a fundamental method for determining sheet metal’s susceptibility to deep drawing operations. This article presents the results of formability analysis of several batches of 0.7 mm thick cold-rolled DX56D+Z100-M-C-O steel sheets. As part of the preliminary tests, mechanical properties of the tested steel sheets were determined. The ARAMIS digital image correlation system was used to determine the formability of sheet metal during the hemispherical punch stretching test. The stretching tests were conducted over a wide range of strain rate variations between 2 mm/min and 17 mm/min. A total of 540 individual geometry measurements were taken to analyze the test material’s formability. It was observed that with increasing strain rate, the strength properties increased, while the plastic properties decreased. From the perspective of formability, the margin of plasticity (the ratio of yield strength to tensile strength) deteriorated with increasing strain rate in tensile tests. Forming limit curves revealed that at higher strain rates, the metal sheet’s formability decreased. A reduction in the safety margins with an increasing hemispherical punch stretching test speed was also observed. Full article

The study establishes key patterns in the influence of pre-applied impact-oscillatory loading (IOL) of varying intensity—realizing dynamic non-equilibrium processes (DNP)—in liquid nitrogen on the mechanical properties and structural state of stainless steel X10CrNi18-8. Static tensile deformation was investigated at room temperature following impulsive strain levels of ε_imp = 0.06–2.69%. A wave-like mechanical response of the steel to DNP was observed within this ε_imp range, most pronounced at ε_imp = 0.11% and ε_imp = 2.69%. After DNP at ε_imp = 0.11%, despite a maximum increase in ultimate strength by 5.25%, the relative elongation of the specimen increased to 10.3%. The scatter in ultimate tensile strength specimens across all loading regimes was within 6.38%, while the variation in ductility reached up to 21.25%. In contrast, after ε_imp = 2.69%, the stress–strain diagram resembled that of the steel in its initial state. Metallophysical investigations and X-ray diffraction analysis were conducted to explain the observed effects. At ε_imp > 2.7%, the high-strength but low-ductility X10CrNi18-8 steel undergoes brittle failure under impulsive loading. At the same time, the total fraction of the more brittle martensitic phase in the steel microstructure reaches approximately 22%. Full article

The enrichment laws and key controlling factors of coalbed methane (CBM) in the Xishanyao Formation of the Hedong mining area remain unclear, restricting exploration progress. Based on well data and experimental analyses, this study investigates CBM enrichment characteristics and geological controls using genetic identification diagrams. Results demonstrate that CBM exhibits a “high in northwest and low in southeast” planar distribution. Vertically, CBM content is extremely low above 360 m due to weathering oxidation and burnt zone effects, increases within the 360–950 m interval (peaking at 750–950 m), and declines from 950 to 1200 m because of limited gas contribution. Genetic analysis indicates predominantly primary biogenic gas, with a minor component of early thermogenic gas. Enrichment is controlled by structure and hydrogeology: the medium-depth range (358–936 m) on the northern syncline limb and western part of the northern monoclinal zone forms a high-efficiency enrichment zone due to compressive stress from reverse faults and high mineralization groundwater (TDS > 8000 mg/L). While the southern limb, characterized by high-angle tensile fractures and active groundwater runoff, suffers gas loss and generally low gas content (<3.5 m³/t). This study clarifies CBM enrichment laws and enrichment mechanisms, supporting exploration of low-rank CBM in the Hedong mining area. Full article

High-strength oil and gas pipeline girth welds exhibit significant material and geometric discontinuities with high susceptibility to defects, making them a critical weak link in oil and gas pipelines. Researching the fracture assessment technology pipeline’s girth welds is essential for enhancing the pipeline’s inherent safety and protection levels. Key issues and research progress related to fracture assessment technology are systematically addressed from the perspectives of pipeline fracture behavior and fracture assessment methods in this paper. The core focus of fracture behavior research is determining the crack driving force at the girth weld and the material’s fracture toughness. Fracture assessment methods include failure assessment diagrams and limited tensile strain capacity models. The development of single-parameter and multi-parameter fracture mechanics theories in establishing the relationship between in-plane and out-of-plane constraints and material fracture toughness is reviewed. Four commonly used methods for calculating crack driving forces in pipelines are presented. Moreover, the usage scenarios of various failure assessment diagrams in pipeline fracture assessment are analyzed. A comparison of the parameter ranges and applicability of commonly used international tensile strain capacity models is also provided. The paper highlights existing issues in current research on the fracture assessment of high-strength pipelines and outlines directions for further study. Lastly, this paper aims to provide theoretical and technical support for improving the inherent safety level of high-strength pipeline girth welds. Full article

Tensile tests of AlMg4.5 alloy were carried out at six strain rates to study the Portevin–Le Chatelier (PLC) effect. The measured engineering stress–time and engineering stress–engineering strain curves were evaluated by direct peak detection and reference function approximation. The waiting and decay times of the PLC effect, and the related stress jumps and drops, were determined. It was shown that, as a function of strain rate, the quotient of the decay and the waiting time forms a curve with a decreasing slope after an initial rapid rise; the same can be stated about the time derivative of the stress jumps. These relationships are suitable for identifying serrations that vary depending on the strain rate, in full harmony with the stress serration amplitudes observed in the tensile test diagrams. Full article

The effect of the chemical composition of two low-carbon steels, C18E and 22MnB5, on their behavior after forming by fine blanking was investigated. A specific tool, adaptable to a tensile testing machine, was designed to replicate an industrial half-cutting process. This tool allows for the production of samples with simple geometries and easy modification of the processing conditions. Residual elements in the raw material, concentrated in segregation bands, appear to play a key role in crack initiation within the shear zone during the blanking process. The role of non-metallic inclusions is discussed to explain the presence of large cracks in C18E, while 22MnB5 only shows damage nucleation. After fine blanking, a carbonitriding heat treatment process was performed to modify the initial microstructure and achieve the required mechanical properties in the final parts. Continuous cooling transformation diagrams were created for both steels to guide this process. The results of this study demonstrate the better formability of 22MnB5 by fine blanking, compared to that of C18E. Full article

Some common conductive polymers are polyfuran, polyacetylene, polythiophene, and poly-pyrrole. Since their discovery, many researchers have been exploring and evaluating their conductive and electronic properties. Various applications have been developed for conductive materials. Their biocompatibility offers a new alternative for studying and solving complex problems, such as cellular activity, or, more recently, for use as neural implants and as an alternative to spinal cord regenerative tissue. This is particularly true for the use of poly pyrrole. The main obstacle lies in estimating some of the mechanical properties, such as Young’s or shear modulus values for poly pyrrole, since these vary depending on the type of synthesis used. This article outlines a composite methodology for characterizing the elastic modulus according to ASTM D882 and the shear modulus according to E143 standards. It is specifically designed and applied for 3D composite samples involving PLA and PPy, where the PPy was processed by plasma oxidation. As a result, an increase of 360.11 MPa in the modulus of elasticity is observed on samples coated with poly pyrrole. The results are evaluated through a numerical test using COMSOL Multiphysics software 6.2 version, finding a similar behavior in the elastic zone, as indicated by the stress–strain diagram. The statistical analysis yields consistent data for tensile and shear results, with low to moderate variability. Full article

Current understanding of the load-transfer mechanism in the skeletal contact state of asphalt mixtures and its influence on macroscopic mechanical properties remains insufficient. This knowledge gap leads to difficulties in accurately predicting the performance of designed mixtures, thereby restricting the service life of asphalt pavements and the sustainable development of road engineering. This study investigated the skeletal contact characteristics, coarse aggregate movement, and crack propagation of three asphalt mixture types—Stone Mastic Asphalt (SMA), Asphalt Concrete (AC), and Open-Graded Friction Course (OGFC)—under loading. The methodology incorporated Computed Tomography (CT) technology, a Voronoi diagram-based skeletal contact evaluation method, and discrete element numerical simulation. The research aimed to elucidate the influence mechanisms of different skeletal structures on macroscopic performance and to validate the efficacy of the skeletal contact evaluation method. The findings revealed that under splitting load, the tensile stress contact force chains within the asphalt mixture’s skeleton were predominantly distributed along both sides of the specimen’s central axis. For all three gradations, compressive stress contact force chains (points) accounted for over 65% of the total, indicating that the asphalt mixture skeleton primarily bore and transmitted compressive stresses. The interlocking structure formed by coarse aggregates significantly enhanced the stability of the asphalt mixture skeleton, reduced its displacement under load, and improved the mixture’s resistance to cracking. In the three gradations, shear stress-induced cracks outnumbered those caused by tensile stress, with shear stress cracks accounting for over 55% of the total cracks. This suggests that under splitting load, cracks resulting from shear failure were more prevalent than those from tensile failure. SMA-20 demonstrated the best crack resistance, followed by AC-20, while OGFC-20 performed the poorest. These conclusions are consistent with the results of the Voronoi diagram-based skeletal contact evaluation, confirming the correlation between the contact conditions of the asphalt mixture skeleton and its mechanical performance. Specifically, inadequate skeletal contact leads to a significant deterioration in mechanical properties. The research results elucidate the influence of skeletal contact characteristics with different gradations on both mesoscopic features and macroscopic mechanical behavior, providing a crucial basis for optimizing asphalt mixture design. Full article

This paper, based on the Johnson–Cook damage model, investigates the damage mechanism of high-strength steel tailor welded blanks (TWBs) (Usibor1500P and Ductibor500) during the forming process. Initially, specimens with varying notch sizes were designed and fabricated to perform uniaxial tensile tests to determine their mechanical properties. Then, the deformation process of the notched specimens was simulated using finite element software, revealing the distribution and variation of stress triaxiality at the fracture surface. By combining both experimental and simulation data, the parameters of the Johnson–Cook (J–C) damage model were calibrated, and the effects of temperature, strain rate, and stress triaxiality on material fracture behavior were further analyzed. Based on finite element analysis, the relevant coefficients for stress triaxiality, strain rate, and temperature were systematically calibrated, successfully establishing a J–C fracture criterion for TWB welds, Usibor1500P, and Ductibor500 high-strength steels. Finally, the calibrated damage model was further validated through the Nakajima-type bulge test, and the simulated Forming Limit Diagram (FLD) closely matched the experimental data. The results show that the analysis based on the J–C damage model can effectively predict the fracture behavior of tailor welded blanks (TWB) during the forming process. This study provides reliable numerical predictions for the damage behavior of high-strength steel laser-customized welded sheets and offers a theoretical basis for engineering design and material performance optimization. Full article

The objective of this paper is to evaluate the capability of various steel rope manufacturers to maintain the desired variability within the strength class of wires used in the production of steel ropes. From a service life perspective, it is optimal to achieve the narrowest possible strength class interval for wires integrated into steel ropes. However, the applicable EN 12385 standards permit a relatively wide interval of allowable strength class dispersion. The analysis encompasses 112 steel ropes tested over the period from 2000 to 2025. For the purpose of evaluating rope quality in terms of wire strength variability, the ropes were categorized into four quality classes. The assessment of wire strength was conducted using statistical quality control methods, specifically through the application of control charts. Based on these methods, the stability and capability of wire strength within each rope were verified. The results highlight the differences in wire strength performance across the evaluated quality classes. Full article

This paper tackles the important issue of the flexural strength of continuous fiber-reinforced ceramic composite. Estimates of the flexural strength of 2D woven SiC/SiC composite are extracted from symmetric and asymmetric 3-point bending test results using three independent approaches: (1) the equations of elastic beam theory for homogeneous solids, (2) finite element analysis of the stress state, (3) stress–strain relations in the tensile outer surface of specimens. Furthermore, the flexural strength is predicted from the ultimate tensile strength using a bundle failure model based on the fracture of the critical filament. It is shown that the equation of elastic beam theory significantly overestimates the flexural strength of the 2D SiC/SiC (620 MPa), while the alternate approaches and the predictions from the ultimate tensile strength converged to ≈340 MPa. The variability of strength data was approached using the construction of p-quantile diagrams that provide an unbiased assessment of the normal distribution function. Pertinent Weibull parameters are derived using the first moment equations. Important trends in the effects of the size, stress gradient, tension–flexure relations, strength of critical filament in a tow, and populations of critical flaws are established and discussed. Full article