High Strength Research Articles

Elevated temperature material properties of cold-formed advanced high strength steel channel sections

Fire safety remains a paramount concern in the design and application of cold-formed structures, making the understanding of mechanical properties of advanced high strength steel (AHSS) at elevated temperatures essential. This paper presents a comprehensive experimental investigation into the mechanical properties of cold-formed AHSS channel sections and their virgin material at elevated temperatures. A total of 60 coupon specimens were extracted from the middle of web element, the corner-flat adjunction of web element, as well as the middle of flange element of the cold-formed AHSS channel sections. Moreover, 20 additional coupon specimens were extracted from the cold-rolled AHSS sheets, which is the virgin material. Elevated-temperature tensile coupon tests were carried out by using steady-state test method under 10 different temperatures up to 800 °C. Full range of stress-strain curves were obtained for the virgin material and three locations of the cold-formed AHSS channel sections. Key mechanical properties including elastic modulus, yield stress and ultimate strength were obtained. Differences in the mechanical properties of coupons with different thicknesses and from various cutting positions were investigated. The obtained reduction factors of the studied AHSS were compared with existing design rules, including European, American, and Australian specifications, as well as predictive models from related research work. New design curves were proposed to provide an accurate and conservative estimation of the reduction in mechanical properties at elevated temperatures, and constitutive stress-strain models were also proposed.

High-strength polyvinyl alcohol/gelatin/LiCl dual-network conductive hydrogel for multifunctional sensors and supercapacitors

The synthesis of conductive hydrogels with high mechanical strength, toughness, optimal fracture growth rate and the capability to detect diverse human body movements poses a significant challenge in the realm of flexible electronics. In this study, a one-pot technique utilized effectively to fabricate conductive materials by doping LiCl into a mixture of polyvinyl alcohol (PVA) and gelatin. The PVA/gelatin/LiCl0.3(PGL) conductive hydrogel demonstrates exceptional robustness, flexibility, and resistance to deformation, enabling the monitoring of various physiological signals such as temperature and humidity. Additionally, the PGL demonstrates exceptional elongation properties (up to 1111.32 %), high lifting capacity (up to 25 kg), resistance to deformation, and sustained stability of peak signals even after 300 cycles at 50 % strain. The hydrogel electrolyte exhibits a conductivity of 2.114 S/m at 25 °C and a specific capacitance of up to 48.75 F/g, along with favorable mechanical and electrochemical characteristics. These findings suggest that the PVA/gelatin/LiCl0.3 hydrogel supercapacitor (PGLSC) conductive hydrogel shows significant potential for integration into flexible electronics and wearable technology devices.

Ultra-high performance concrete with high strength, workability, loading durability and low curing maintenance for applications in airport pavement

With the rapid development of the aviation industry, airport pavement is subjected to ever-increasing loads, posing urgent and higher demands on the mechanical performance and durability of pavement materials. This study develops a novel Ultra-High Performance Concrete (UHPC) with outstanding mechanical properties, good workability, low curing maintenance, and excellent performance in sustaining long-term load to specially designed for its potential application in airport pavement. The as-developed UHPC contains a mixed portion of fine and coarse aggregate, assuring its workability and avoiding the early-age shrinkage crack for the potential on-site construction. With a 7-day compressive strength of 140MPa, compressive strength of 155.1MPa, flexural strength of 25.4MPa at 28 days, and a wear loss per unit area of 0.043kg/m2, the mechanical properties of UHPC well outperform those of conventional C30 airport pavement concrete. Finite element simulation analysis reveals that a 10cm thick UHPC surface layer demonstrates durability and safety under aircraft taxiing and landing impact loads, with a maximum tensile stress of 4.12MPa well below its tensile strength limit of 8.75MPa. Furthermore, it is predicted that a 10cm thick UHPC overlay could support a load cycle lifespan 1014 times longer than that of conventional C30 concrete of 30cm thickness, indicating its potential to significantly extend the service life of airport pavement. This research provides a theoretical basis for the applications of UHPC in airport pavement and presents innovative perspectives on into material and structural design of airport pavement materials for the future.

Study on damage performance of high strength casing by shaped charge jet assisted window sidetracking method

This paper explores the penetration of high-strength casings by metal jets to reduce the milling workload of windowing drill bits, thereby improving the efficiency and success rate of window sidetracking in high-strength thick-walled casings. The numerical simulation model of shaped charge penetration casing was established based on Autodyn software. The penetration effects of shape charge structure, charge liner material and charge quantity on casing were studied from the angles of casing damage degree, penetration volume, metal jet kinetic energy and mechanical specific energy (MSE). The results show that trumpet shaped liner has better reaming ability, has the largest effective damage area, the largest penetration volume, and the lower MSE, and the hole shape is more suitable for window sidetracking. The larger the charge diameter, the better the penetration effect on the casing. The charge combination of 70-1(charge diameter D=70mm and charge length=1D) causes more effective damage in the hole edge of the casing, and has a larger penetration volume and the smallest MSE. When the material density of the top section is greater than that of the curve section, the jet head velocity is larger; otherwise, the jet head velocity is smaller. The penetration volume of the titanium-tungsten charge liner increased by 110.6% compared with titanium material charge liner, but the MSE increased by only 24.26%, indicating that combination material charge liners can significantly enhance the penetration effect of the metal jet on the casing. The titanium-tungsten charge liner has the largest penetration volume and good damage effect on the casing, with a low MSE, making it suitable for window sidetracking. In summary, under standoff distance of 1D and the 70-1 charge combination, the trumpet-shaped liner with titanium-tungsten material combination exhibits the best penetration performance on the casing. This study provides valuable insights into the application of metal jet-assisted window sidetracking techniques.

Stability analysis of the false roof made of cemented tailings backfill in deep mine: A case study

The overall stability of cemented tailings backfill (CTB) false roof, as an important support structure in the quarry, is of great significance for realizing the safe recovery of the ore body. This paper aims at the practical problem of ore body mining under the condition of deep broken rock mass. By analyzing the typical process characteristics of underhand cut-and-fill mining method, the dangerous mechanical state of CTB false roof is determined, and the CTB false roof strength model based on the maximum tensile stress failure criterion and deep mining coefficient is established. Based on the measured load value of CTB false roof, the minimum required strength of CTB false roof is obtained. Through the performance tests of CTB under different proportioning schemes, the mechanical strength of CTB false roof (UTS：0.43MPa, UCS：6.22MPa) is designed，the proportioning parameters of CTB with "high strength, high fluidity, quick setting and low cost" are put forward. Finally, based on FLAC3D numerical simulation and field monitoring, the stability of CTB false roof with recommended ratio parameters is analyzed. The results show that the CTB false roof has not been violently displaced and destabilized in the process of service ore body mining, has good strength reserve, and is able to provide a safe workspace for mining, verifies the reliability and reasonableness of the CTB false roof proportioning parameter, and provides a new way for the study of false roof stability.

Sustainable stabilization/solidification of electroplating sludge using a low-carbon ternary cementitious binder

Electroplating sludge (ES), due to its high dosages of heavy metals (HMs), is classified as hazardous waste, presenting risks to both health and environment. Stabilization/solidification (S/S) technology is extensively applied in ES treatment. This study designs a low-carbon ternary cementitious binder, limestone calcined clay cement (LC3), for S/S treatment of ES and investigates the immobilization mechanism of HMs in the crystalline products and calcium alumino-silicate hydrate (C-A-S-H) within LC3. Results show that CrO42- and Cd2+ are primarily stabilized in aluminate crystalline products by replacing SO42- and Ca2+ in the double-layered plate structure, respectively. The remaining CrO42- is captured by the (SiOOH)2AlCa⁺ groups in C-A-S-H generated from substitution of aluminum tetrahedra to bridging silicon tetrahedra. For positively charged Cd2+, it is mainly stabilized through ion exchange with Ca2+ on the C-A-S-H chains. The pozzolanic reaction of calcined clay increases the Al/Ca and Si/Ca atomic ratios in C-A-S-H, enhancing the immobilization efficiency of C-A-S-H to CrO42- and Cd2+. The synergistic effect of calcined clay and limestone, along with the dissolution of aluminosilicates in calcined clay, changes the structure and composition of hydration products, facilitating the chemical binding of CrO42- and Cd2+ by aluminate products. Moreover, the extra hydration products generated by the pozzolanic reaction and the formation of numerous carboaluminate phases strengthen the physical encapsulation performance to HMs. Regarding actual S/S performance, multi-scale evaluation results show that the designed LC3 binder achieves sustainable S/S of ES with high strength, low carbon emission, low cost, and low energy consumption.

An improved prediction of high-performance concrete compressive strength using ensemble models and neural networks

Traditional methods for proportioning of high-performance concrete (HPC) have certain shortcomings, such as high costs, usage constraints, and nonlinear relationships. Implementing a strategy to optimize the mixtures of HPC can minimize design expenses, time spent, and material wastage in the construction sector. Due to HPC's exceptional qualities, such as high strength (HS), fluidity and resilience, it has been broadly used in construction projects. In this study, we employed Generalized Regression Neural Network (GRNN), Nonlinear AutoRegressive with exogenous inputs (NARX neural network), and Random Forest (RF) models to estimate the Compressive Strength (CS) of HPC in the first scenario. In contrast, the second scenario involved the development of an ensemble model using the Radial Basis Function Neural Network (RBFNN) to detect inferior performance of standalone model combinations. The output variable was the 28 Days CS in MPa, while the input variables included slump (S), water-binder ratio (W/B) %, water content (W) kg/m3, fine aggregate ratio (S/a) %, silica fume (SF)%, and superplasticizer (SP) kg/m3. An RF model was developed by using R Studio; GRNN and NARX-NN models were developed by using the MATLAB 2019a toolkit; and the pre- and post-processing of data was carried out by using E-Views 12.0. The results indicate that in the first scenario, the Combination M1 of the RF model outperformed other models, with greater prediction accuracy, yielding a PCC of 0.854 and MAPE of 4.349 during the calibration phase. In the second scenario, the ensemble of RF models surpassed all other models, achieving a PCC of 0.961 and MAPE of 0.952 during the calibration phase. Overall, the proposed models demonstrate significant value in predicting the CS of HPC.

Grain size dependent deformation microstructure evolution and work-hardening in CoCrNi medium entropy alloy

This study clarified the grain size dependence of the deformation microstructure evolution and work-hardening behavior in CoCrNi medium entropy alloy. We fabricated fully recrystallized specimens with coarse-grained (CG) and ultrafine-grained (UFG) specimens by severe plastic deformation and subsequent annealing processes. Tensile deformation was applied to the specimens at room temperature. The UFG specimen exhibited both high strength and high ductility compared to conventional UFG metals due to the high work-hardening ability. In the CG specimen, three distinct types of deformation microstructures consisting of dislocations and deformation twins developed depending on grain orientations, similar to the single-crystalline specimens. In the UFG specimen, widely extended stacking faults and randomly-tangled dislocations were found to coexist in most grains. Deformation twins were found to nucleate without evidence of dislocation reactions regardless of grain orientations, implying abnormal nucleation mechanisms of deformation twins in the UFG specimen. Dislocation densities quantified by in-situ synchrotron XRD measurements during tensile deformation were higher in the UFG specimen than those in the CG specimen and conventional UFG metals. Our analysis showed that the work-hardening behavior of the specimens was primarily controlled by increases in dislocation density as well as the introduction of planar defects during deformation. Through comparisons with the CG specimen and conventional UFG metals, we concluded that the excellent work-hardening ability of the UFG specimen was mainly due to the evolution of unique deformation microstructures and rapid increase in dislocation density, which could be due to inhibited dynamic recovery in the MEA.

A green inorganic binder for material extrusion of ultra-low shrinkage and relatively high strength metakaolin ceramics at low sintering temperature

Ultra-low shrinkage and relatively high strength metakaolin ceramics printed by material extrusion were innovatively fabricated using inorganic aluminum dihydrogen phosphate (Al(H2PO4)3) as a binder and low sintering temperature. The optical microscopy, scanning electron microscopy (SEM), electronic vernier caliper, three-point bending test, Archimedes method and X-ray diffraction (XRD) were used to measure and evaluate the surface morphology, microstructure, dimensional shrinkage, flexural strength, porosity and phase composition of the printed ceramics sintered at different temperatures. The results showed that when the mass ratio of metakaolin, Al(H2PO4)3 and deionized water was 17:6:2, the rheological characteristic of the purely green inorganic ceramic slurry was very suitable for material extrusion additive manufacturing, and the corresponding printed ceramic green bodies possessed high-quality formability. The ceramic samples sintered at 750 °C possessed the best whiteness, the lowest shrinkage (<2%), relatively high flexural strength (9.02 MPa). As the sintering temperature increased, Al(H2PO4)3 transformed to aluminum metaphosphate Al(PO3)3, and then decomposed into aluminum phosphate (AlPO4) and phosphorus pentoxide gas (P2O5), which caused pores and reduced strength, and alumina oxide (Al2O3) and silicon oxide (SiO2) in metakaolin gradually transformed to mullite and cristobalite with more stable structure and higher strength.

Preparation of carboxylated-silk nanofibers by the one-pot method of maleic acid hydrolysis.

In this study, a maleic acid (MA) hydrolysis one-pot method is proposed to prepare carboxylated silk nanofibers (MA-SNFs). The MA concentration, hydrolysis temperature, and processing time were optimized. Combined with high-pressure homogenization, MA-SNFs with a carboxyl content of 0.617±0.019mmol/g and length of 333±116nm were obtained with a yield of 54.90±1.98% at the optimal conditions: 50wt% of MA concentration, 110°C of hydrolysis temperature and 120min of processing time. The morphology, chemical structure, and crystal structure of raw silk fibroin (SF), acid-hydrolyzed silk fibroin and nanofibers were studied. Furthermore, MA was reused several times with a recovery rate of >94% and maintained almost the same treatment effect. Finally, due to the presence of carboxyl groups, MA-SNF hydrogels were successfully prepared by an acetic coagulation vapor bath which exhibited excellent self-supporting ability and mechanical properties as well as a more sensitive pH response compared with regenerated silk fibroin solution and other non-carboxylated silk nanofibers. The MA-SNF aerogels had the characteristics of light weight, high strength and porous with cross-linked nanostructures.

Behavior of Hybrid Natural Fiber Reinforced Polymers Bars Under Uniaxial Tensile Strength and Pull-Out Loads with UHPC

This study evaluated the uniaxial tensile strength and bond performance of natural hybrid reinforcement bars. Hybrid FRP combines multiple fibers and matrixes, resulting in a desirable performance. Two types of hybrid bars were tested: one with natural fibers surrounded by glass fiber, and the other with a steel core surrounded by natural fiber and then glass fiber. Thirteen samples were used to assess tensile behavior, with four groups including glass fiber, flax, sisal, and jute fibers. Pull-out behavior testing was conducted on twelve samples, divided into four groups of fiberglass, flax, sisal, and jute. Each group used three types of concrete: normal, high strength, and ultra-high-performance concrete (UHPC). The results refer to flax samples that had a higher tensile strength and elastic modulus of 143MPa and 38GPa, respectively, than samples made of sisal and jute fibres. The hybrid bars with a steel core exhibited a significant improvement in elastic modulus of 206% in compared to samples made solely from glass, sisal, and jute fibers. On the other hand, the samples with UHPC showed the highest bond strength. The sample U-GFRP with ultra-high-performance concrete showed the highest bond strength 9.32MPa, while the sample N-GFRP with normal concrete showed the lowest bond strength 5.87MPa, respectively. However, this study suggests that hybridizing natural fibers can be a cost-effective and eco-friendly alternative to synthetic fibers.

The control of fully equiaxed microstructure in laser welding Al-mg-Er-Zr alloy

The Al-Mg-Er-Zr alloy with higher strength and thermal stability was focused on as promising candidate in shipbuilding field. However, when this material was joined and manufactured with high-efficiency laser welding technology, the unmelted strengthening Al3(Er,Zr) particles segregated in weld bead and formed the discontinuous fine equiaxed and column grain zone simultaneously which decreased the joint strength. In order to solve the segregation behavior of precipitates and obtain the fully equiaxed microstructure of weld seam, the transverse scanning adjustable-ring-mode laser technology was employed. The stirring effect in the molten pool pushed the unmolten Al3(Er,Zr) dispersoids from the fusion line to the weld center. At the same time, the temperature distribution of weld seam was more homogeneous as inhibited the growth of column grain. Finally, the homogeneously distributed Al3(Er,Zr) particles as well as higher supercooling degree in the molten pool refined the microstructure. The optimal weld joint was obtained, which displayed remarkable mechanical performance with tensile strength of 389 ± 1 MPa, up to 93.3 % of base metal.

Effect of Ti addition on the microstructure and corrosion behavior of laser cladding AlCoCrFeNi high-entropy alloy coatings

AlCoCrFeNi high-entropy alloys (HEAs) has higher strength and wear resistance but poorer corrosion resistance. In the present investigation, the AlCoCrFeNi HEAs containing titanium(Ti) were fabricated via laser cladding to enhance the corrosion resistance properties of the coating and the influence of the Ti content on the microstructure of the coatings was investigated. The results show that the microstructure of the coating changed from a single BCC phase to a BCC+B2 phase with the addition of Ti. The Laves phases appeared within the coating when the Ti content was beyond 0.5 mol ratio. As an excellent corrosion-resistant element, Ti promoted the formation of a passive film and enhanced the corrosion resistance of the HEAs coating. The corrosion resistance of the coating first increased and then decreased with the addition of Ti, and the AlCoCrFeNiTi0.5 coating exhibited optimal corrosion resistance.

Investigation of tensile deformation behavior of a TWIP/TRIP metastable β titanium alloy at typical temperature part Ⅰ: Room temperature

The tensile behavior and deformation mechanism of Ti-10Mo alloy at room temperature (298 K) were investigated. The results show that the alloy has an ultimate tensile strength (UTS) of 744 MPa and a high yield strength (YS) of 662 MPa, as well as an excellent elongation (El) after fracture of 38 %, outperforming Ti-15Mo alloy under the same conditions. The superior strength and plasticity of Ti-10Mo alloy at 298 K are attributed to the activation of both {332}〈113> twinning and SIM α“ during deformation. The sequence of different deformation mechanisms is as follows: in the initial stage of deformation, dislocation slip can be extensively activated and continues to occur during subsequent deformation; in the middle stage of deformation, primary and secondary {332}〈113〉 twinning and SIM α” are activated simultaneously, resulting in a continuous increase in work hardening rate; in the later stage of deformation, the alloy can further deform through {1 1 1}α“ twinning. The higher YS may be due to the optimal quantity and size of athermal ω phase in Ti-10Mo alloy, which increases the YS without significantly affecting plasticity. Meanwhile, Quenching vacancies can also increase the YS of the alloy. The three stages of the work hardening rate curve correspond to the activation of the dislocation slip mechanism, the activation of the {332}〈113〉 twinning and SIM α” and the stop of the {332}〈113〉 twinning and SIM α“.

A one-step polyvinyl alcohol/polyacrylamide/polyacrylic acid/dimethyl sulfoxide/CaCl2 hybrid hydrogel enabling anti-fatigue, anti-freeze and anti-dehydration for wearable strain sensor

Hydrogel with fatigue resistance, freezing tolerant and dehydration resistance are peculiarly attractive in strain sensors. The hydrogel soaked in organic solvent is an effective strategy to improve freezing resistance and dehydration resistance, while this may result in poor conductivity. Moreover, ion-incorporation is considered to be the most feasible method for solving above concern, while high concentration of salt ions will result in weak mechanical properties. Therefore, the facile preparation of anti-freezing and anti-dehydration hydrogels with excellent fatigue resistance remains a challenge. Herein, a polyvinyl alcohol/polyacrylamide/polyacrylic acid/dimethyl sulfoxide/CaCl2 hybrid hydrogel was designed and fabricated through a facile one-step method to balance a variety of outstanding properties. On account of the hybridization design of multi-materials, the hybrid hydrogel exhibited high ionic conductivity (∼0.2 S/m), strength (∼0.36 MPa) and stretchability (∼825 %). Meanwhile, the hybrid hydrogel demonstrated prominent freezing resistance, dehydration resistance and fatigue resistance. The mechanical properties almost no deterioration after 1000 stretching cycle at 100 % strain, exposure to environment for 30 days or freeze at low temperature. Besides, the hybrid hydrogel-based stain sensor showed a linear sensitivity (GF = 1.12 over 0–400 % strain), quickly responsivity (200 ms), and could monitor various human activities steadily, demonstrating distinguished potential for use in wearable health monitoring and flexible electric skins.

Novel orientation relationships and mechanical properties of in situ synthesized Ti5Si3-reinforced TiAl composite via electron beam-directed energy deposition

Titanium aluminide (TiAl) alloys, known for their light weight and high specific strength, hold promising potential for aerospace applications. Recent studies have focused on improving their properties through composite strengthening. An in situ synthesized Ti5Si3-reinforced TiAl composite with excellent performance was successfully fabricated via a dual-wire electron beam-directed energy deposition (EB-DED) process. The microstructure of the as-deposited Ti5Si3/TiAl composite consisted of primary Ti5Si3 rods, eutectic Ti5Si3 needles, and lamellar TiAl+Ti3Al structures. The phase transformation during the EB-DED process was L→Ti5Si3+L→Ti5Si3+(α+Ti5Si3)Eutectic→Ti5Si3+(Ti3Al+TiAl)Eutectoid. The expanded Blackburn orientation relationships among the ternary phases emerged from the eutectic reaction of L→α+Ti5Si3 with an undercooling exceeding 136°C and the subsequent eutectoid reaction with ordering transformation and were expressed as <112¯0>Ti3Al//<101¯0>Ti5Si3//<11¯0]TiAl and {0001}Ti3Al//{0001}Ti5Si3//{111}TiAl. The Ti5Si3 phase had a greater hardness than did the lamellar structures and enhanced the mechanical properties of the matrix. The compressive yield strengths at room temperature and 750°C were 1221±51 and 1034±34 MPa, respectively, whereas the tensile yield strength was 347.4±12.7 MPa at 950°C, surpassing those of other TiAl alloys. The calculated strength with different strengthening mechanisms was 1056.4 MPa, and the greatest improvement in strength was attributed to the decreased interlamellar spacing. This work provides critical insight into the design of TiAl composites with superior mechanical properties and aids in understanding the microstructural evolution of as-deposited Ti5Si3/TiAl composites.

Optimization design of multi-scale TPMS lattices based on geometric continuity fusion and strain energy driven

3D lattice structure is a kind of advanced metamaterial structure with excellent performance, such as lightweight, high specific strength and stiffness, shock damping, heat dissipation, and electromagnetic shielding capabilities. With the development of additive manufacturing technology, it has been widely concerned and developed rapidly in recent years. In order to further integrate the performance of lattice structures with mesoscale units into multi-scale optimization, this paper proposes an optimization design method for the multi-scale TPMS (Triply Periodic Minimal Surfaces) lattices based on geometric continuity fusion and strain energy driven. Regarding the challenge of geometric continuity problem of complex transition boundaries in multi-TPMS lattices, interface interpolation and density factor optimization methodologies are studied. At the same time, the mapping mechanism between lattice configuration and mechanical properties of multi-TPMS lattices is discussed in view of the requirements of multi-scale design from macro to micro configurations. Then, the multi-TPMS lattice density and configuration fields in the design domain are co-designed with the strain energy driven. Simulation and experimental results show that the mechanical properties of the multi-scale TPMS lattice designed by the proposed method are significantly improved compared with the traditional single-configuration gradient lattice, including the stiffness of the cantilever beam optimized structure is improved by 20.5% and the flexural stiffness of the three-point flexural beam optimized structure is improved by 51.3%.

High-temperature mechanical properties and thermal shock resistance of an alumina-fiber-reinforced alumina ceramic matrix composite

An alumina-fiber-reinforced alumina ceramic matrix (Al2O3/Al2O3) composite is fabricated by a slurry infiltration process in this study. The slurry contains Al2O3 powders with broad particle size distribution (d10=0.35 μm, d50=0.57 μm, d90=1.90 μm). The resultant Al2O3/Al2O3 composite exhibits a density of 2.95 ± 0.02 g/cm3 and porosity of 25 ± 1%. Mechanical properties are assessed via three-point flexural tests, revealing a high flexural strength of 400 ± 8 MPa at room temperature. The high-temperature mechanical properties and thermal shock resistance are further examined. The flexural strength remains stable from room temperature to 1100°C, while temperatures up to 1200°C induces superplastic behavior. After thermal shock tests (5, 10 and 20 cycles at 1100°C), the composite maintains a stable microstructure and flexural strength. The Al2O3 powders with broad particle size distribution are beneficial to the high-temperature mechanical properties and thermal shock resistance of the Al2O3/Al2O3 composite.

Experimental study of rotational friction damper for seismic response control: friction material comparison and configuration optimization

Rotational friction dampers (RFDs) can be incorporated into structures flexibly as energy-dissipation devices for seismic response control. However, the basic primary form of RFD has three main challenges and objectives in enhancing its performance: (1) avoiding strength fluctuation and jittering, namely, improving the stability of the performance, (2) enhancing the strength, and (3) relieving the basic assumption that the clamping pressure is uniformly distributed on the friction pads and ensuring the accuracy of the theoretical equation. To address these issues, this study proposes four potential approaches: (1) selecting a friction material with a stable performance, (2) increasing the friction coefficient, (3) increasing the clamping force, and (4) optimizing key configurations. Based on these concepts, two sets of experimental studies, including 27 friction pad material comparison tests and 17 lug plate and clamping bolt configuration optimization tests, were conducted. According to the test results, the fiber-reinforced resin-based composite (FRRC) material was found to be better than H62 brass and 7075 aluminum alloy in realizing a high friction coefficient and stable performance, as well as achieving uniformly distributed pressure. The four-bolt lug plate and six-bolt lug plate with stiffening ribs were found to be effective in realizing a high clamping force and, thus, a high RFD strength, as well as in achieving a uniformly distributed pressure. In contrast, the single-bolt lug plate could not realize a high clamping force because of the tightening torque limit. A six-bolt lug plate can cause pressure concentration and edge damage to the friction pad.

Effect of isomeric polysaccharides on heteroaggregation of nanoplastics in high ionic strength conditions: Synergies of morphology and molecular conformation

Polysaccharides with various molecular structures and morphology may influence the aggregation kinetics of nanoplastics. This study used various characterization methods to elucidate the heteroaggregation mechanism of polystyrene nanoplastics (PSNPs) in the presence of polysaccharides (ionic strength (IS) 1-800mM NaCl and 0.01-60mM CaCl2). The results showed that under high IS, cellulose (CL) accelerated the heteroaggregation of PSNPs, and the aggregation rate of PSNPs increased by approximately 62.05%, while amylose (AM) had little effect (10.38%). Compared with AM (43.2nm), the morphology of the CL (78.4nm) gully had improved surface roughness, leading to its decisive role in the heteroaggregation of PSNPs. Quantum chemistry calculations indicated that van der Waals forces of PSNPs-CL systems (-217.28kJmol-1) were stronger than those of PSNPs-AM systems (-184.62kJmol-1) based on the subtle molecular conformation differences between CL and AM (opposite and same sides of OH groups in CL and AM, respectively). The morphology and molecular conformation of polysaccharides collaboratively controlled the heteroaggregation of PSNPs. Because the morphology of polysaccharides was based on their molecular conformation, the latter is the most critical factor. These findings provide new insights into the effects of PSNPs stability in the environment.