Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Zhenbang Sun, Jianping Liu, Maohua Du et al.

Accurate analysis of residual stress in aluminum alloy welds is essential for ensuring the quality and service life of joints. The mechanical properties of both as-received and softened high-strength aluminum alloy at different temperatures were determined at various temperatures through high-temperature tensile experiments on 11  mm-thick 7A52 plates. Furthermore, a material softening model for aluminum alloy was developed based on Lifshitz-Slyozov-Wagner (LSW) theory. The impact of weld joint softening on residual stress was investigated through VPPA–MIG hybrid welding simulations, with the results derived from the proposed softening model evaluated against a conventional modeling approach. The softening model predicts significantly lower residual stresses in the heat-affected zone (HAZ) adjacent to the weld, with maximum longitudinal and transverse tensile stresses reduced by 26.4 % and 25.2 %, respectively, while stresses outside the HAZ remain comparable to the conventional model. X-ray diffraction validation demonstrated closer agreement with the softening model’s predictions. The developed model accurately predicts residual stress distributions in aluminum alloy welds, supporting improved service reliability, process optimization, and structural integrity assessment in aerospace and automotive applications.

S. Ghuku, S. Naskar, T. Mukhopadhyay

Zeyu Kang, Yi Cao, Lu Liu et al.

Abstract Precise tuning of dielectric constants (εr) in oxide glasses is critical for high‐frequency devices in 5G/6G systems, where εr directly governs signal propagation efficiency. A machine learning framework combining data augmentation and physicochemical descriptor integration is developed to address data scarcity. Validated pseudo‐labels are generated via ensemble learning, expanding the dataset from 1503 to 11,029 compositions without distributional shift. The XGBoost model trained on the augmented dataset achieved superior accuracy, with an R2 of 0.96 and an MSE of 0.14. For prediction tasks on unseen data, it reduced the error rate by 48% compared to the non‐augmented model and improved generalization performance by 43% over GlassNet. B2O3 and SiO2 are identified as εr suppressors and BaO and TiO2 as enhancers through SHAP analysis, aligning with network former/modifier roles. Cation‐specific polarizabilities are derived via Clausius–Mossotti regression (R2 = 0.909). Integration of physicochemical descriptors (coordination number and bond strength) enables transferable predictions for Y2O3 and La2O3 containing glasses, with mean deviation 2.46%–4.76%. Crucially, structural descriptors dominate polarizability with 69.9% feature importance, establishing network engineering as the optimal design paradigm. A data‐driven pathway for rational dielectric glass development is thus established.

Jiaguo Yu, Liuyang Zhang, Quanjun Xiang et al.

D.A. Abdoh

Jingpei Liu, Wanchang Sun, Eryong Liu et al.

Double-layer Ni-P coatings with low phosphorus content in the inner layer and high phosphorus content in the outer layer and Ni-Mo-P composite coatings are successfully prepared on the surface of AZ91D magnesium alloy by chemical plating process. The microstructures, friction and corrosion resistance of double-layer Ni-P and Ni-Mo-P coatings are studied in comparison. Meanwhile, the deposition and corrosion resistance mechanism for the coatings are investigated. Results convey that both Ni-P and Ni-Mo-P coatings showcase an amorphous structure. The coating possesses denser and more homogeneous structure with the co-doping of Mo. The micro-indentation hardness (859.7 HV) and friction coefficient (0.58) of Ni-Mo-P coatings show that the ternary alloy coating is firmly bonded to the magnesium alloy substrate. Besides, the Ni-Mo-P coatings demonstrate exceptional wear resistance attributed to Mo co-deposition, fostering grain refinement and facilitating the growth of passivation films.

A. Navakoti, D.S. Chakram, M. Dasari

Lead Zirconium Titanate (PZT) is a potential piezoelectric material for sensor and transducer applications due to its outstanding piezoelectric coupling near the morphotropic phase boundary (MPB). This is because PZT can switch between tetragonal and rhombohedral phases. PZT is still considered to be one of the piezoelectric materials that has received the greatest amount of attention from researchers and is used the most frequently. Modification with Lithium will improve the piezoelectric properties. In this study, the structural properties and morphological studies of Lead zirconium titanate and Lead zirconium titanate with Lithium modification have been evaluated. Various Scherrer’s models and other models, such as the Williamson-Hall model and Size-strain plots model, were used to display the observed fluctuations in crystallite size. Morphological analysis was used to determine the particle size. Graphs showing the distribution of particle sizes were drawn.

Stirbescu Nicolae Mihail, Stirbescu Raluca Maria, Olteanu Radu Lucian et al.

Technique development for getting environmentally friendly nanomaterials was the paper's main goal. Spectroscopic techniques were utilized to characterize the plant extracts used in this work (UV-Vis, FTIR and Raman). In this case, plants from the Valea Voievozilor was processed in a dry state, was used at the ideal moment and at the plant's peak maturation period. Several analytical techniques (UV-Vis, FTIR, Raman analysis) have been used to analyze the nanoparticles (Ag) created with the aid of these plant extracts. Both the bioreduction of silver ions (Ag+ to Ag0) and the stability of silver nanoparticles are caused by the bioactive chemicals found in plant materials.

Belete Tessema, Girma Gonfa, Sintayehu Mekuria Hailegiorgis et al.

Silica has shown numerous applications in different fields such as environmental, biomedical, agriculture, and even in chemical processing. However, due to high energy-intensive and cost-effective issues, researchers show interest to replace the conventional methods with biobased environmentally-friendly techniques for biosilica production from renewable biomass sources. Generally, silica is found to be available in amorphous and crystalline structures. For commercial purposes, silica is produced from alkyl orthosilicates ore that consists of polyethlydiorthosilicate, tetraethyl ortothosilicate, and tetramethyl orthosilicate. Another form of silica, silica gel, is produced from the selected resources of biomass, such as palm tree, wheat straw, maize leaves, teff straw, sugarcane bagasse, rice husk, rice straw, sugarcane leaf, oat husk, bamboo leaf, and corn cob. The production of biobased silica gel from agricultural residues is found to be a sustainable which receives a significant attention that can be replaced with inorganic-based silica gel for environmental concerns. Based on this context, there is a huge look for developing a process to produce biobased silica and silica gel from biomass resources with low energy utilization as promising alternatives to conventional methods. Keeping in view, current trends and methods for synthesis, the characterization of biobased silica and silica gel, as well as its wide prognostic applications were focused on a comprehensive review.

Anna Pytel, Andrzej Nowotnik, Agnieszka Nalborczyk-Kazanecka

In the publication, tests were conducted on compressor turbine working blades made of EI-867 material, in accordance with the TU 14-1-402-72 standard, which were subjected to the gas non-contact aluminizing process. Metallographic analyses of the produced aluminide layer were undertaken, and the phase components of the aluminide layer microstructure were identified. This identification was achieved by analyzing the chemical composition in micro-areas using the EDS attachment in a scanning electron microscope and using X-ray diffraction. Additionally, hardness and creep resistance tests of the blades, after undergoing solution and aging processes, were performed over different durations. The research was aimed at exploring the feasibility of the aluminizing process using the "above the pack" method on parts made of EI-867 material and understanding the process's impact on the creep resistance of the part. Experimental research have shown that aluminizing turbine blades with EI-867 using the "above the pack" method to obtain a layer thickness in the range of 0.03-0.06 mm is possible within 10 hours at 950ºC. Aluminizing with the analyzed method results in the formation of an aluminized layer with a three-phase structure that ensures the appropriate strength of the coating. However, it has been shown that the aluminizing process using the "above the pack" method with the applied time of 10 hours causes a significant reduction in the creep resistance of the material. Based on the obtained results, it was shown that the non-contact aluminizing method for turbine blades made of EI 867 material does not meet aviation requirements for safe operation due to a significant reduction in mechanical properties.

Pu Zhang, Junmin Hu, Jixing Yu et al.

Mike Aurilio, Pejoohan Tavassoti, Michael Elwardany et al.

Shahid Adeel, Mahmood ul Hasan, Fatima Batool et al.

The ongoing age is the time of sustainability, where in the current pandemic scenario, which is getting worse, needs treatment with nature rather than chemical-based products. In this study, microwaves (M.W. rays) treatments as extraction mode for Esfand ( P. harmala ) have been revived for polyamide (nylon) dyeing. The water solubilized and acid solubilized filtrates and polyamide (nylon fabrics) were treated M.W. rays up to 10 min with an interval of 2 min. Mordanting with chemicals and plant extracts before and after dyeing was done at 60°C–80°C. It has been found the application of M.W. ray treatment for 4 min., to 30 mL of extract of 8 p H containing 4 g/100 mL of Table salt as leveling agent has given desired results when employed at 55°C for 55 min. Statistical analysis of dyeing variables through R.S.M., and two way-Anova shows that the effect of these variables has been observed highly significant. Experimentally it has been observed that the application of extract for dyeing of polyamide (nylon fabric) has given good results when chemical or bio-mordanted at selected conditions. Practically, Esfand seeds has ability for bio- coloration of surface modified polyamide fabric (nylon fabric), and utilization of pomegranate extract as bio-mordant and tannic acid as sustainable chemical mordant has furnished colorfast shades.

Kejin Zhang, Xusheng Qian, Jieshi Chen et al.

In this study, the structure and fatigue properties of a new type asymmetric round bar–plate rotary friction welding (RFW) joints with three kinds of welding time, 0.8 s, 1.2 s and 3.6 s, were investigated. The results show that the RFW processing evolves from the heat stage to the quasi-steady stage with a trade-off of dynamic recrystallization (DRX) and grain boundary sliding (GBS). From 0 s for the base metal (BM) to 3.6 s, the DRX intensity changes from strong to weak relative to the GBS intensity, resulting in the non-monotonic evolution of the microstructure, e.g., the texture, the average grain size and the geometrically necessary dislocation, with welding time. The evolution results in non-monotonic evolution of the fatigue properties: specimens with welding time of 0.8 s, 1.2 s and 3.6 s, have fatigue lives of approximately 150,000, 200,000, and 100,000 cycles, respectively. The microstructure evolves with the welding time through the texture strength, grain size, and dislocation density, affecting the dislocation and slip mobility. This evolution not only directly affects the rates of crack initiation and extension, but also makes the initiation point of fatigue crack change on the fillet, which affects the fatigue life.

Dongqing Zhang, Kai Zhao, Daoxiu Li et al.

In this work, novel TiC particles doped by trace amounts of B, referred to as TiCB, were introduced to an Al-Mn alloy with the Al-TCB master alloy. The effects of the TiCB particles on the solidification microstructure, extrusion behavior, and mechanical properties of the Al-Mn alloy were systematically studied. The results showed that TiCB particles could significantly refine α-Al grains by providing heterogeneous nucleation substrates and hindering the growth of α-grains. For example, when the amount of added TiCB particles was 0.5 wt%, average α-Al grain size could be refined to a minimum of 40.2 μm from 410.1 μm when no particles were added. After hot extrusion, TiCB particles and fractured α-Al(Fe, Mn)Si formed streamlines along the extrusion direction. More importantly, TiCB particles could inhibit the dynamic recrystallization process during hot extrusion and retain numerous geometrically necessary dislocations. Consequently, the mechanical properties of the Al-Mn alloy at room temperature (25 °C) and elevated temperature (350 °C) were significantly improved after adding TiCB particles. When the amount of added TiCB particles was 1.5 wt%, the ultimate tensile strengths at 25 °C and 350 °C were increased by 25.6% and 32.4%. This work sheds light on the grain refinement and strengthening of non-heat-treatable wrought Al-Mn alloys.

YIN Yan-li, YU He-long, ZHOU Xin-yuan et al.

Tribological properties of oleic acid modified natural serpentine ultrafine mineral powders as lubricating oil additive were investigated by a reciprocating sliding wear tester. The effects of the four factors including load, reciprocating frequency, sliding time and concentration of serpentine on the properties of serpentine additive were analyzed. Results indicate that the anti-wear and friction-reducing properties of the base oil are significantly improved by the addition of the modified serpentine powders. The order that affects the friction-reducing performance of the serpentine additive is:concentration, reciprocating frequency, load, sliding time, and the optimal tribological conditions are 100 N, 5 Hz, 180 min, 0.5%(mass fraction). While that affects the anti-wear property is:load, concentration, reciprocating frequency, sliding time, and the optimal conditions are 100 N, 50 Hz, 180 min, 0.3%. Serpentine minerals forms a tribofilm consisting of various oxides, graphite and organic compounds on the friction surface, which is the key to improving anti-wear and friction-reducing properties.

Yingli Li, Hongge Yan, Jihua Chen et al.

In this work, the influences of welding speed on microstructure and mechanical properties in friction stir welding (FSW) of the hot-rolled Al-9.2Mg-0.8Mn-0.2Zr-0.15Ti alloy plates has been investigated. Microstructures and mechanical properties of the joints are characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with electron dispersive spectroscopy (EDS), hardness and tensile testing. The results show that all the joints are free of volume defects at the welding speed of 25–100 mm min ^−1 and the fixed rotation rate of 1000 rpm. And all the nugget zones (NZs) are characteristics of fine grains with the high angle grain boundaries (HAGBs) fraction higher than 90% at the welding speed of 25–100 mm min ^−1 . The mean grain size in NZs and tensile properties of joints exhibit a parabolic relation with the welding speed. Furthermore, the optimal welding parameters are the welding speed of 50 mm min ^−1 and the rotation rate of 1000 rpm. The as-prepared joint at 50 mm min ^−1 , featured with the smallest grain size of 3.02 μ m and a uniform distribution of the fine second phase particles in NZ, exhibits the highest elongation to rupture about 45% higher than the base metal (22.2 ± 1.6%) and the highest ultimate tensile strength efficiency of 87.4%. It can be attribute to the synergetic effect of the fine-grain structure with the high HAGBs fraction and the small second phase particles with a uniform distribution.

Narine Pirumyan, Mihran Stakyan, Gagik Galstyan

A mathematical model has been proposed for processing data from tests of building materials and obtaining optimal links between the characteristics of the bearing capacity and technological parameters of building materials for the use of these connections in refined design and construction procedures for building structures. To improve the accuracy of the results obtained, a three-level optimization principle was applied using the least squares method and a computational algorithm was compiled that allows us to develop an additional computational subroutine expanding the capabilities of the corresponding standard computer programs.

Jianlin Xu, Bingxue Ma, Lei Niu et al.

To improve the flame retardancy of polybutylene terephthalate (PBT), PBT-based flame retardant composites containing antimony trioxide nanoparticles (nano-Sb 2 O 3 ) and brominated polystyrene (BPS) were investigated. Nano-Sb 2 O 3 , BPS, and PBT were dispersed by ball milling method to obtain composite powders, and the nano-Sb 2 O 3 /BPS-PBT samples were prepared by melt blending and injection molding methods. The flame retardancy of nano-Sb 2 O 3 /BPS-PBT composites was investigated. The results showed that nano-Sbs 2 O 3 can obviously improve the flame retardancy of PBT-based composites. When the nano-Sb 2 O 3 /BPS-PBT composite contains nano-Sb 2 O 3 with 5 wt% of mass fraction and BPS with 10 wt% of mass fraction, the nano-Sb 2 O 3 /BPS-PBT composite has excellent flame retardancy, in which the UL94 degree of flame retardancy achieves V-0 grade and the limit oxygen index is 28.3%.

YANG Fan, LIU XiaoNing, LIU Bing et al.

In order to increase the burst pressure of copper pipe,save the copper material under the premise of guaranteeing safety,overpressure enhancement of TP2 copper tube was tested at room temperature,the relationship between the burst pressure of copper tube and the pretreatment pressures was studied,the changes of TP2 material tensile strength was analyzed. Based on28 groups burst test of TP2 copper tubes under different pretreatment pressure at room temperature,studies have shown that: 1)If the enhancement pretreatment pressure of TP2 copper tube is equal to the yield pressure,the thermal effect of copper tubes brazing should be improved,copper tube burst pressure and TP2 material tensile strength should be strengthened to a certain extent. 2) Compared with non overpressure enhancement at room temperature,for the burst pressure and the tensile strength of TP2 copper tube used appropriate pressure pretreatment,the means of copper tube burst pressure and the TP2 material tensile strength are increased significantly,the standard deviation and coefficient of variation are decreased significantly,and the precision is improved obvious. For the burst pressure and the tensile strength of TP2 copper tube,the fluctuation range of the average,standard deviation and coefficient of variation are smaller,and the stability is become well.