Search Results (8,638)

The mechanical performance of sewn seams is commonly evaluated using parameters such as seam strength and seam efficiency, which primarily describe the behavior of the seam at ultimate failure. However, these parameters provide only limited information about the initiation of structural deterioration that precedes rupture. An operational definition of the Seam Yielding Point (SYP) is proposed as an experimentally identifiable indicator of the onset of seam degradation during tensile loading. Nine woven fabric variants differing in structural characteristics were sewn using four polyester sewing threads with different linear densities. Seam tensile tests were performed according to the relevant international standard, while force–elongation curves were continuously recorded. The SYP was identified as the first local decrease in force observed on the force–elongation curve. Photographic documentation was used only for qualitative interpretation of the deformation process. The experimental results showed that the proposed SYP could be consistently identified in all tested specimens prior to ultimate seam failure. The corresponding yielding force and elongation depended on both the sewing thread properties and the fabric structure. In addition to conventional seam strength measurements, the proposed approach provides valuable information regarding the initiation of irreversible structural changes within the seam. Overall, the proposed operational definition of the SYP represents a useful complementary parameter for evaluating seam mechanical behavior and contributes to a more comprehensive assessment of seam performance. Full article

Thermoplastic polyurethane (TPU) is highly versatile yet inherently flammable, restricting its use in fire-safe applications. This study incorporates sodium antimonate (SA) into TPU via melt blending (0–10 wt%). Through a comprehensive suite of analytical techniques—including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), universal testing, and cone calorimetry—the effects of SA on the various properties of the material were investigated. Quantitative analysis reveals that 10 wt% SA delivers the best flame retardancy, reducing the peak heat release rate by ~50% (from 605 to 310 kW/m²) and total heat release by ~40% (from 32 to 19 MJ/m²), while increasing the char residue from 9.84% to 13.89%. However, to retain mechanical robustness, the SA content must be capped at ≤5 wt%. This ensures that the material retains 30% of its fracture elongation and a tensile strength of 1.7 MPa; higher loadings cause severe embrittlement due to particle agglomeration. Mechanistically, SA acts via a dual-phase mode—promoting a dense insulating char layer in the condensed phase and quenching reactive radicals in the gas phase. These findings establish a practical balance between fire safety and mechanical performance, offering a clear guideline for the rational design of flame-retardant TPU composites. Full article

Predicting the changes in the performance of polymer-based 3D printing materials over time under industrial operating conditions is of critical importance. In particular, the chemicals present in the environments to which these materials are exposed and the duration of exposure directly affect their structural integrity and durability. In this study, the structural changes occurring in 3D-printed PLA Pro material as a result of aging in different environments (three different coolants used in the manufacturing industry and Xenon arc exposure) were investigated. The experiments were conducted using various analysis methods, including tensile and flexural tests, hardness, gloss, surface roughness, color, and mass measurements. The initial mass uptake behavior during the first 24 h of immersion was also evaluated. Finally, the changes in tensile strength (UTS) and flexural force of 3D-printed PLA Pro samples exposed to three different coolants for four different durations, and also subjected to 600 h of Xenon Arc aging, were evaluated using ANOVA. As a result, changes in the mechanical properties were observed under the different aging conditions.. Compared with the reference specimen (41.9 MPa), the highest tensile strength was obtained for the specimens immersed in the water-based fully synthetic Rhenus TY108S coolant for two weeks (48.4 MPa), while the lowest tensile strength was observed for the specimens immersed in the semi-synthetic FU51 coolant for one week (39.9 MPa). Following Xenon arc aging, the tensile strength was determined to be 47.5 MPa. Regarding the maximum flexural force results, an increase was observed in the specimens aged under Xenon arc exposure, whereas a decrease was observed in the specimens aged in the coolants. Hardness generally decreased with increasing immersion time in the coolants; however, the hardness values remained higher than that of the reference PLA Pro specimen throughout the aging period. The highest color change occurred in the Xenon arc-aged specimens, while no significant color change was observed in the specimens exposed to the coolants. The surface gloss of all specimens was classified as matte to semi-matte. Surface roughness increased following exposure to the coolants, whereas it decreased after Xenon arc aging. The mass of the specimens was more strongly affected by coolant exposure. Full article

Centrifugally cast 35Cr45NiNb alloy has been widely employed in ethylene-cracking furnace tubes owing to its excellent carburization and creep resistance. However, the influence of microstructural degradation and temperature on its high-temperature tensile behavior remains poorly investigated. In this study, an accelerated aging method at 1200 °C for 230 h (A1) and 430 h (A2) was employed to simulate approximately 4 and 8 years of service at 1050 °C, based on the Larson-Miller parameter. The equivalence was validated by the nearly identical precipitate area fractions of the A1 specimen (16.6%) and an ex-service specimen (14.8%). Combined with SEM and EBSD characterization, tensile tests at 950, 1000, and 1050 °C were conducted to elucidate the relationship between microstructure and high-temperature tensile properties. During aging, the skeletal interdendritic M₇C₃ carbides transformed into blocky M₂₃C₆, NbC evolved into the brittle G-phase (Ni₁₆Nb₆Si₇), fine secondary M₂₃C₆ precipitates formed, and the initially continuous primary-carbide network progressively coarsened. Yield and ultimate tensile strengths decreased monotonically with increasing temperature, whereas aging produced pronounced hardening at the expense of ductility, as secondary-carbide precipitation strengthening outweighed the weakening of the primary carbide network. The fracture mode transitioned from mixed quasi-cleavage fracture at 950 °C, initiated by stress concentration at coarse phase interfaces, to ductile rupture at 1000 and 1050 °C. GND analysis further revealed an aging-dependent transition in the dominant deformation mechanism, from dislocation pile-up at the carbide network, to recrystallization after prolonged aging. Full article

MQ silicone resins are widely used reinforcing fillers for addition-curing liquid silicone rubber (LSR); however, establishing a quantitative composition–property relationship remains challenging because published data are fragmented across matrix chemistries, crosslinkers, catalyst systems and testing standards. Here we present a machine-learning-guided workflow integrating literature data mining, interpretable random-forest (RF) modelling and independent experimental validation for the design of MQ-reinforced LSR. An RF model trained on 55 curated literature points spanning RTV and LSR systems, using four physically motivated descriptors (MQ content, M/Q ratio, curing system and vinyl content), yielded leave-one-out coefficient of determination (R²) values of 0.741 for tensile strength (TS) and 0.730 for Shore A hardness (HA), with mean absolute errors of 0.63 MPa and 8.95 ShA, respectively. Feature-importance and partial-dependence analyses identified MQ content as the dominant descriptor. Guided by the model, seven LSR formulations (vinyl content 4 wt%, M/Q = 0.8, loading 5–35 wt%) were designed and fully characterised: the model reproduced the measured TS and HA for all seven formulations within the corresponding training mean-absolute-error tolerance, whereas elongation at break (EB), whose prediction is substantially weaker (LOO R² ≈ 0), was captured only as a qualitative trend with respect to MQ loading. This workflow demonstrates that a modest, curated literature dataset, mined by an interpretable ML model, can support formulation design and independent experimental validation—an efficient, low-cost alternative to trial-and-error optimisation. Full article

This study examined the reported splitting-tensile response of 17 concrete mixtures labeled by nominal rubber replacement levels of 5–20% and steel fibers at 0–1.5% by volume after 7 and 28 days of curing. The reported strength values were considered together with failure photographs, representative load-displacement curves, acoustic-emission (AE) energy records for three selected mixtures, and qualitative scanning electron microscopy (SEM) observations. Rubber addition was associated with lower splitting-tensile strength, whereas several rubber–fiber mixtures recovered or exceeded the ordinary-concrete value. Among the tested combinations, SF1RR5C had the highest reported strength (4.27 MPa at 28 days, 12.4% above the ordinary-concrete value). The load-displacement curves and post-failure photographs indicate delayed separation and residual load capacity in the fiber-containing specimens. The AE and SEM observations provide qualitative, mixture-specific evidence consistent with crack bridging; they do not independently quantify internal damage, porosity, or fiber-matrix bond strength. Full article

Growing environmental concerns associated with petroleum-based plastics have stimulated the development of renewable and biodegradable alternatives. In this study, corn-starch-based composite films were prepared with bacterial cellulose (BC), α-cellulose (α-C), or carboxylated cellulose nanofibers (CNC) in the presence of laponite and glycerol. The films were characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis, optical measurements at 600 nm, tensile testing, qualitative solvent-exposure tests, and thermally induced repair experiments. Among the films containing different cellulose types, the bacterial-cellulose-containing bioplastic (BC-BP) exhibited the highest tensile strength and Young’s modulus, reaching 4.47 and 0.229 MPa, respectively. The carboxylated-cellulose-nanofiber-containing bioplastic (CNC-BP) showed the highest elongation at break (100%) and the lowest thickness-normalized optical attenuation (0.38 mm⁻¹), whereas the α-cellulose-containing bioplastic (α-C-BP) exhibited the highest maximum degradation-rate temperature (approximately 315 °C). Increasing the BC content from 0.25 to 1.0 g increased tensile strength from 3.17 ± 0.13 to 7.78 ± 0.31 MPa and Young’s modulus from 0.260 ± 0.002 to 0.996 ± 0.009 MPa. This increase was accompanied by a reduction in elongation at break from 41 ± 1.6% to 16 ± 0.6%. The BC-BP films retained their visible integrity after exposure to selected organic solvents but underwent substantial changes under strongly acidic and alkaline conditions. Following thermally induced repair, the BC-BP film recovered approximately 55% of its tensile strength and 45% of its Young’s modulus while retaining an elongation at break close to that of the original film. These results demonstrate that cellulose type and BC content can be used to adjust the measured thermal, optical, mechanical, and repair properties of starch–cellulose–Laponite films. Further structural, barrier, migration, and food-contact safety evaluations are required to establish their suitability for packaging applications. Full article

In recent years, an increasing number of national major projects have focused on the physicochemical properties of materials and the structural integrity of components in cryogenic environments. In situ neutron non-destructive testing offers a distinct advantage for scientific research conducted under cryogenic conditions. With the progressive advancement of neutron sources and neutron diffraction techniques, neutron probes have become indispensable for the in situ observation of lattice strain, phase transformation behavior, and residual stresses in materials at cryogenic temperatures. Based on the energy-resolved neutron imaging instrument (ERNI) at Beamline 13 of the China Spallation Neutron Source (CSNS), we have developed a cryogenic loading frame for in situ neutron diffraction tensile tests. This paper presents a detailed description of the mechanical structural design, cooling and control system, strength and thermal analyses, and experimental validation of the device. The apparatus enables in situ neutron diffraction experiments over a wide temperature range of 6–473 K, with an axial loading capacity of 50 kN. Furthermore, the device was employed to conduct in situ neutron diffraction measurements on austenitic 304 stainless steel at both room and cryogenic temperatures. The experimental results confirm that this equipment exhibits stable loading capability and precise temperature control, ensuring the reliability of the experimental data. Full article

Friction stir welding (FSW) is a solid-state joining process widely used for aluminum alloys due to its low heat input, reduced distortion, and ability to produce high-quality joints. However, excessive tool forces generated during the welding process can increase machine loading, accelerate tool wear, and negatively affect the process efficiency. Therefore, understanding the relationship between welding parameters, tool forces, and the joint performance is essential for achieving high-quality welds while avoiding unnecessary mechanical loads. In this study, 4 mm thick AA5754 aluminum alloy plates were joined using the FSW process, and the feasibility of using tool force measurements for process optimization was investigated. A comprehensive experimental matrix consisting of nine different rotational speeds and ten different tool travel speeds was established based on preliminary studies and previous literature. During each welding operation, forces acting on the tool in the F_x, F_y, and F_z directions were continuously recorded. The welded joints were evaluated through tensile testing (Zwick Z300 universal testing machine, ZwickRoell, Ulm, Germany), hardness measurements, and microstructural characterization using scanning electron microscopy (SEM) (ZEISS Merlin scanning electron microscope, Carl Zeiss Microscopy GmbH, Oberkochen, Jena, and Göttingen, Germany). A Pearson correlation analysis and a two-way analysis of variance (ANOVA) were performed at a 95% confidence level to quantify the relationships and statistical significance of the process parameters. The results showed that F_z was the dominant force component during welding. The rotational speed had a statistically significant effect on the tensile strength, yield strength and hardness (p < 0.05), accounting for 99.39% of the total variation in hardness. For the mean tool force, both the rotational speed and the tool travel speed were statistically significant (p < 0.0001), contributing 38.48% and 47.16% of the total variation, respectively. The rotational speed also accounted for 81.55% of the variation in the maximum axial force. The Pearson correlation analysis showed a strong negative correlation between the rotational speed and hardness (r = −0.73), whereas the tool travel speed showed positive correlations with F_x (r = 0.61), F_z (r = 0.62), and the mean tool force (r = 0.68). Despite the increased tool loading associated with higher travel speeds, no corresponding improvement in the mechanical performance was observed. The results demonstrated that appropriately selected welding conditions produced joints with a yield strength and hardness exceeding 90% of the corresponding base material properties while maintaining relatively lower tool forces. SEM observations confirmed grain refinement in the stir zone. Overall, the combined correlation and ANOVA results demonstrate that real-time tool force monitoring can provide a quantitative basis for selecting FSW parameters that achieve an adequate mechanical performance while minimizing unnecessary machine and tool loading. Full article

To address the resource utilization of waste tires and the fire-safety concerns in engineering applications of rubber concrete (RC), this study systematically investigates the residual static and dynamic mechanical properties of RC after exposure to elevated temperatures and subsequent cooling to room temperature. Specimens are prepared by replacing fine aggregate with rubber particles at equal volume replacement ratios of 0%, 5%, 15%, and 30%. After undergoing gradient heating to target temperatures ranging from 20 °C to 300 °C, the specimens are naturally cooled to room temperature prior to testing. Subsequently, static compressive and splitting tensile tests, along with dynamic impact tests using a Split Hopkinson Pressure Bar (SHPB), are performed. These experiments are supplemented by scanning electron microscopy (SEM) to elucidate the microscale mechanisms. The results show that the residual static strength decreases monotonically with increasing rubber content and temperature. For the 30% rubber content mixture, the compressive strength decreased by approximately 40.6% from ambient temperature to 300 °C, and its strength is 64.6% lower than that of NC at 300 °C. Dynamic strength exhibits a pronounced strain-rate effect, with the strain-rate sensitivity of DIF being enhanced by higher rubber content. Energy dissipation increases substantially with strain rate; rubberized mixtures generally exhibit higher energy dissipation than NC at lower strain rates, though this effect becomes less evident at higher strain rates. These findings provide a theoretical foundation for the application of RC in complex thermo-mechanical loading scenarios, particularly in evaluating its post-fire residual load-bearing capacity. Full article

Ultra-high-performance concrete (UHPC) is characterized by exceptional compressive strength; however, its structural performance is primarily governed by tensile behavior, fracture resistance, and energy dissipation. This study presents a comprehensive mechanical characterization of a steel fiber-reinforced UHPC incorporating a slag–limestone powder-based binder system with a low water-to-binder ratio of 0.15 and steam curing at 90 °C for 48 h. The experimental program comprised compressive strength, flexural behavior, split and direct tensile response, impact energy absorption, ultrasonic pulse velocity, and an assessment of specimen size and geometry effects. The UHPC achieved mean compressive strengths of approximately 209 and 218 MPa at 7 and 28 days, respectively, in 75 × 150 mm cylindrical specimens, indicating only modest strength development after the initial steam-curing period. Smaller cube specimens exhibited higher nominal compressive strengths, reaching approximately 221 and 227 MPa at 7 and 28 days, respectively, demonstrating a measurable but limited specimen-size effect. Flexural testing produced an average strength of 33.1 MPa and a stable post-peak response, although no strain hardening in bending was observed. Split tensile strength reached approximately 16.1 MPa, exceeding that of conventional normal-strength concrete by more than four times. Direct tensile tests demonstrated an intrinsically ductile response, with tensile strengths above 10.9 MPa and strain capacities of 0.25–0.30%, including a pronounced strain-hardening regime. Under drop-weight impact loading, specimens absorbed more than 40 J of energy without catastrophic fragmentation. Ultrasonic pulse velocity averaged 5344 m/s, indicating a dense and well-integrated microstructure. Overall, the results confirm that the investigated UHPC functions as a fracture-resistant structural composite in which tensile capacity, fiber-controlled crack bridging, and energy dissipation govern performance across multiple loading modes. Full article

Titanium alloy bone scaffolds have been widely used in the clinical treatment of bone defects. However, conventional titanium alloy bone scaffolds exhibit a lack of porous structure and excessively high elastic modulus, resulting in poor osseointegration. In this study, mimicking the structural characteristics of human bone—namely dense exterior and porous interior—three types of bionic Gyroid titanium alloy bone scaffolds with a uniform porosity of 50% but distinct gradient properties were designed, including uniform lattice structure, linear gradient structure, and quadratic gradient structure. Process optimization of selective laser melting (SLM) and characterization of the as-fabricated microstructures were carried out. The tensile and compressive properties of additively manufactured titanium alloy bone scaffolds were investigated via mechanical testing and finite element analysis (FEA). The results demonstrate that optimized SLM parameters yield a matrix relative density of 98.56% for solid Ti-6Al-4V reference specimens. Using these parameters, bionic gradient-porosity Gyroid bone scaffolds were successfully manufactured. The bionic quadratic function gradient design achieves optimal modulus matching (10–30 GPa) and sufficient mechanical strength at the design level, satisfying the mechanical requirements for bone scaffolds and showing favorable application potential for load-bearing bone scaffolds. Full article

Unequal-wall-thickness X80-X60 girth welded joints used in pipeline transition sections exhibit strong local mechanical heterogeneity, while the wall-thickness transition also introduces a separate structural geometry effect. Conventional homogeneous or weld-metal-only descriptions may therefore be insufficient for interpreting the fracture response of single-edge-notched tension (SENT) specimens sampled from such joints. In this study, a constraint-driven fracture toughness assessment was conducted for single-edge-notched tension (SENT) specimens representing the X80 base metal, X80 heat-affected zone (HAZ), weld metal, X60 HAZ, and X60 base metal as five distinct material regions. Miniature tensile tests provided the local constitutive input for these regions. The numerical procedure was verified against published SENT force versus crack-mouth-opening-displacement (CMOD) data; because direct SENT fracture-toughness tests for the present X80-X60 target joint are not yet available, the literature comparison is treated as verification of the modeling procedure rather than direct validation of the target joint. Parametric analyses were then performed for an initial crack ratio of a₀/W = 0.10–0.30, a thickness-to-width ratio of B/W = 0.50–1.50, weld width = 10–30 mm, HAZ width = 1–9 mm, and different weld/HAZ strength combinations. The simulations show asymmetric crack-tip plastic deformation toward the lower-strength X60 side. Increasing the crack length increases crack-tip opening displacement (CTOD), whereas increasing B/W, weld width, or HAZ width generally reduces CTOD by increasing local constraint. The influence of weld strength is strongly coupled with the strength level of the adjacent HAZs. The results are therefore interpreted as numerical CTOD-response trends for a heterogeneous SENT specimen; direct experimental fracture-toughness measurements of the target X80-X60 joint remain an important subject of follow-up work. Full article

In the subsequent backfilling mining method, the composite structure formed by the ore pillar and the backfill is the key element in ensuring the stability of the working face. Its mechanical behaviour directly affects mining safety and ore recovery rates. In order to elucidate the mechanical response and failure mechanisms of rock-like backfill composite structures (RLBCS) under biaxial loading, specimens with different water-to-cement (W/C) ratios (0.5, 0.6, 0.7 and 0.8) for the rock-like backfill were prepared in this study. Biaxial loading tests were conducted, with digital image correlation (DIC) technology employed simultaneously to monitor the evolution of strain and displacement on the specimen surface. The results indicate that the biaxial strength of RLBCS decreases exponentially as the W/C increases. When the W/C exceeds 0.7, the strength reaches a plateau. The strength contribution of the backfill increases relatively. The axial stress–strain curve exhibits four distinct phases. A pronounced bimodal distribution is observed when the W/C exceeds 0.5. The evolution of lateral strain exhibits a transition point where compression is followed by expansion. The threshold for lateral expansion stress exhibits a non-monotonic variation. The modulus of elasticity decreases as the W/C increases. The apparent structural strain ratio exhibits a non-monotonic variation. The failure pattern exhibits marked asymmetry. The rock-like side shows tensile failure. Where the interface is present, this manifests as localised crushing at the top of the rock-like layer, cracking along the interface, and bulging of the backfill. The W/C ratio of the rock-like material governs the failure mechanism of RLBCS. The strain localisation modes in backfill materials are classified into two types: post-peak abrupt and pre-peak gradual. The evolution of interface strain exhibits four distinct stages: an initial abrupt change, cooperative deformation, crack initiation, and post-peak instability. The spatiotemporal evolution of interfacial delamination and the deformation of the backfill was quantified through displacement field analysis. The research findings provide a theoretical basis for the design of underground mining operations. Full article

Ultrasonic bonding offers a promising alternative to traditional sewing and other plastic bonding techniques, with several potential advantages. This paper comprehensively analyzes ultrasonic bond characteristics in PVC-coated hybrid textiles, prevalent in awnings and camping tents. Untreated samples were used as controls to compare the effects of ultrasonic bonding on various characteristics. Developed experimental designs were applied using a 12 mm welding width in a lapped seam, with carefully selected parametric levels to achieve higher bond strength based on preliminary test results. Mechanical properties (tensile, cyclic, and tear strength, including thickness reduction) were thoroughly examined to assess ultrasonic bond seam efficiency. The analysis covered thermal, chemical, morphological, and weight loss aspects before and after ultrasonic welding. Results showed that the weld seam tensile efficiency ranged from 68.27% to 96.13%, indicating enhanced durability. Cyclic efficiency exceeded 95%, tear efficiency surpassed 70%, and both treated and untreated samples showed strengths above standard thresholds. Thermal findings indicated a 3% increase in crystallinity after ultrasonic treatment, enhancing thermal stability with lower weight loss and causing shifts in glass transition and melting temperatures. FTIR spectra revealed that ultrasonic bonding had no significant impact on the material’s chemical properties. Morphological analysis identified pre-existing microvoids, with no significant increase in their number and/or size following ultrasonic treatment. Overall, the study demonstrates the efficacy of ultrasonic welding in improving the mechanical, chemical, and thermal properties of PVC-coated hybrid textiles, providing valuable insights for applications like awnings, camping tents, and roofing materials for short- and long-term use. Full article