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

Hao Yang, Fujie Zhao, Junhui Zhang et al.

Thywill Cephas Dzogbewu, Deon Johan de Beer

Direct laser powder bed fusion (LPBF) of ceramics has experienced tremendous advancement and it is about to be metamorphosed from the laboratory research phase to the industrial scale. Nonetheless, several challenges need to be overcome before progressing to the next phase of manufacturing crack-free, large-size, and multimaterial ceramic products via the direct LPBF process with high surface quality and homogeneous mechanical integrity. Surprising the current challenges required automation of the in-process activities to control the high viscous ceramic molten pool and its solidification mechanisms to mitigate the building up of thermal stress, and crack formation to ensure the production of crack-free, large-size ceramic parts with high surface quality. The automation of the process would ensure consistency, reliability, and reproducibility of direct printing of ceramic products, which would speed up the development of a validation framework for the certification of direct printed ceramic products. The post-processing activities of the indirect ceramic printing process might not be the ideal approach for producing dense crack-free ceramic products, since it could increase the cost of the product by 70 % without any significant improvement as compared to the direct LPBF ceramic manufacturing route.

Pooja Singh, Lokendra Singh, Sameer Yadav et al.

A serious worldwide health concern, tuberculosis (TB) necessitates creative methods for quick and precise diagnosis. This paper presents the detection of Mycobacterium tuberculosis (mTB) using a two-way approach utilizing refractive index (RI) sensors and machine learning (ML) techniques. The approach is validated by adopting a Fano resonance (FR) sensor which consists of freshly prepared cerium oxide nanostructures (CNS) covered sensing slots. The CNS is prepared by using combustion technique and characterized through transmission electron microscopy (TEM) and x-ray diffraction (XRD). The RI values sensed through the sensor yield a high sensitivity and autocorrelation coefficient of 163 nm RIU ^−1 and ${R}^{2}=92.37\, \% $ , respectively. The microscopic sputum smear examination is used to detect mTB through five different ML classifiers. Among all, the random forest classifier provides the highest accuracy of 96%. According to preliminary findings, the suggested system provides a quick, affordable, and non-invasive diagnostic option with excellent accuracy, sensitivity, and specificity. The approach addresses important TB diagnostic problems and is more suitable for low-resource environments. This hybrid strategy can transform TB detection, enhance patient outcomes, and support TB control initiatives.

Chandrabhan Singh, Pramod Kumar Gupta

WANG Feng, GAO Meng-jie

With the development of petrochemical industry, the deep exploitation of domestic petroleum and the continuous increase of oil input from the Middle East, the sulfur content in raw materials is gradually increased. The corrosion of hydrogen sulfide on welded joints can lead to the failure of the whole component, bringing great threat to production safety. Researchers at home and abroad have paid great attention to the stress corrosion of high-strength low-alloy(HSLA) steel welded joints caused by hydrogen sulfide. In this paper, the mechanism of stress corrosion cracking of HSLA steel welded joints in service in a wet hydrogen sulfide environment was briefly described, and the factors that influencing stress corrosion of welded joints were discussed. Furthermore, different experimental methods for exploring stress corrosion were summarized and the stress corrosion was compared with that of carbon steel.

Davood Rahmatabadi, Kianoosh Soltanmohammadi, Mohammad Aberoumand et al.

Abstract Unmodified polyvinyl chloride (PVC) has low thermal stability and high hardness. Therefore, using plasticizers as well as thermal stabilizers is inevitable, while it causes serious environmental and health issues. In this work, for the first time, pure food‐grade PVC with potential biomedical applications is processed and 3D printed. Samples are successfully 3D printed using different printing parameters, including velocity, raster angle, nozzle diameter, and layer thickness, and their mechanical properties are investigated in compression, bending, and tension modes. Scanning electron microscopy is also used to evaluate the bonding and microstructure of the printed layers. Among the mentioned printing parameters, raster angle and printing velocity influence the mechanical properties significantly, whereas the layer thickness and nozzle diameter has a little effect. Images from scanning electron microscopy  also reveal that printing velocity greatly affects the final part's quality regarding defective voids and rasters’ bonding. The maximum tensile strength of 88.55 MPa is achieved, which implies the superiority of 3D‐printed PVC mechanical properties compared to other commercial filaments. This study opens an avenue to additively manufacture PVC that is the second most‐consumed polymer with cost‐effective and high‐strength features.

Kunal Singh, Ajit Khosla, Shilpa Gupta

Soft robotics, offering precise actions in complex environments, stands at the brink of transformative advancements across diverse fields. To realize this potential, the field must address five key challenges: creation of soft power and control mechanisms, emphasis on sustainability, cultivation of advanced intelligence, and the imperative for standardization. This perspective argues for solutions grounded in sensory feedback systems, aiming to fortify the foundation of soft robotics, ensure its sustainability, enhance adaptability in robot intelligence, and set the stage for scalable robot production. Addressing these challenges, we aim to pave the way for a more inclusive era of soft robotic technology.

Kh. Zamani, M. Tavoosi, A. Ghasemi et al.

In this study, the effect of partial addition of silicon on the structural behavior and electromagnetism of TiC/Ti3AlC2 ceramic matrix composites has been investigated. In this regard, the mechanical alloying and annealing processes were used for the synthesis of the desired composite. Structural and phase investigations were performed using scanning electron microscope, differential thermal analysis, and X-ray diffractometer, and electromagnetic behavior was investigated by network analyzer. The results showed that it was possible to synthesize TiC/Ti3AlC2 composite structure with in-situ partial addition of silicon. 2TiC-Al-Ti-0.2Si system showed the best absorption behavior of electromagnetic waves with reflection loss of about -30.10 dB at matching frequency of 15.1 GHz. It was found that the TiC/Ti3AlC2 composite structure obtained from the mechanical alloying was stable after annealing at 1400 °C. However, the electromagnetic absorption behavior was affected. Thus, the reflection loss of the annealed samples was obtained about -1dB.

Giampaolo Pitruzzello, Christoph G. Baumann, Steven Johnson et al.

Heterogeneous bacterial populations can display increased resistance to external threats, such as exposure to antibiotics. Despite the mounting clinical evidence supporting the importance of bacterial heterogeneity in acute infections, current antimicrobial susceptibility tests (ASTs) are typically insensitive to cell‐to‐cell differences as they only measure population‐wide averages. Herein, the use of single‐cell motility to address this issue is demonstrated. It is shown for the first time that antibiotic susceptibility detected as a change in single‐cell motility is an excellent proxy for polyclonal and monoclonal heteroresistance. It is also demonstrated that motility and growth are both inhibited by an antibiotic with strikingly similar patterns, thus enabling the quantification of minimum inhibitory concentration (MIC) using a high‐throughput, single‐cell motility assay. The method allows for the detection of heteroresistance in Escherichia coli and Salmonella typhimurium in 2 h or less and quantifies the MIC of an antibiotic in 1.5 h. The findings emphasize the need for characterizing bacterial heterogeneity, and they highlight the importance of single‐cell bacterial motility in assessing both antibiotic susceptibility and population‐wide heteroresistance.

Henan LIU, Biao QIN, Tingzhang WANG et al.

As the core device of the hemispherical resonator gyroscope (HRG), the processing accuracy and the surface quality of hemispherical resonator directly affect the working accuracy and the service life of HRG. To solve the problem of hemispherical resonator processing and improve the performance of HRG, the interference in the processing of hemispherical resonator is analyzed theoretically according to the structural characteristics of the hemispherical resonator. Then, the grinding trajectory is planned by using the characteristics of the grinding area distribution of the ball-end grinding wheel, and the optimal turning angle of the ball-end grinding wheel during different grinding processing sections of the hemispherical resonator is determined. Finally, grinding experiments of hemispherical resonator are conducted on the developed hemispherical resonator ultra-precision grinding machine tool. The surface roughness (Ra value) of hemispherical resonator is improved from 0.615 8 μm to 0.040 2 μm after ultra-precision grinding processing, while the profile accuracy (PV value) is improved from 4.590 4 μm to 0.339 0 μm. The surface roughness Ra of the hemispherical resonator is further improved to 0.003 2 μm after magnetorheological polishing. The research shows that the grinding process after trajectory planning can avoid the interference between the grinding wheel rod and the workpiece. High-quality hemispherical resonator component is produced by using the above grinding process.

Kai Zhu, Baiqing Xiong, Xiwu Li et al.

During the immersion quenching process, severe temperature changes and significant temperature differences between the core and superficial area can give rise to high residual stresses within the aluminum alloy thick plate to cause subsequent machining distortion of the thin-walled part. Reducing the residual stress within the thick plate can effectively minimize the distortion in part. In this research, ABAQUS software was adopted to simulate the internal temperature and stress fields of thick plates of Al7055 alloy during the quenching and pre-stretching processes, sequentially and respectively. In addition, the x-ray residual stress measurement method was used to measure and characterize the surface residual stress of the plates. The results indicate that the medium temperature affects residual stress inside the thick plate significantly during the immersion quenching process. The level of which inside the plate gradually increases as the medium temperature decreases. Further, the pre-stretching treatment can effectively reduce residual stresses within the thick plate, and the residual stress level gradually decreases with the pre-stretching ratio increasing. The experimental results verify the feasibility of numerical simulation to predict the status of quenching stress in thick plates. Subsequently, a simulation study for material removal processes was carried out based on the above studies. The results reveal that the thin-walled part’s machining distortion degree improves as the raw thick plate’s initial quench residual stress level decreases.

Antonios Kanellopoulos, Jose Norambuena-Contreras

Rohan Borade, Rohan Borade, Rohan Borade et al.

Increasing demand of human beings has a greater effect on the self-sustaining nature of Earth. New technologies facilitated the new generations but created a question mark on the existence of the next generation. The only way to remove this possibility is sustainable development. Through this paper review of evolution of various construction materials is drawn from sustainability aspects and various alternative solutions are highlighted. From the evolutionary history of construction materials, it is found that all other materials have some sustainability issue or construction issue and hence with the development of advanced material their use in construction is reduced. With this study it has been concluded that concrete has been a widely used construction material since the 19th century. With the advancement in concrete technology this will remain popular for a longer time and hence those aspects of concrete which create sustainability issues are to be resolved.

Masoud Ahmadi, Bekir Salgın, Bart J. Kooi et al.

Zn-Al-Mg coatings are important materials for the corrosion protection of steel sheets. However, susceptibility towards cracking limits the formability performance of these coatings. In this study, we focus on the effect of the underlying steel substrate on cracking behavior in these coatings. In order to elucidate this, a high-strength low-alloy (HSLA) steel substrate and an interstitial-free (IF) steel substrate are coated with two different ZnAlMg coatings with and without binary eutectic microstructures. Meticulous in-situ tensile and bending tests are conducted in a scanning electron microscope. To quantify the strain distribution and damage incidents, micro and macro digital image correlation techniques are utilized in order to illuminate the associated cracking causes across length scales. Furthermore, electron backscatter diffraction method is applied to study the role of crystallographic orientation on the cracking tendency. Crack opening and crack area fractions are correlated with the applied strain and bending angles. The findings denote that the discontinuous yielding (Lüders banding) of the HSLA steel substrate generates substantial surface roughening and heterogeneous deformation in the coatings that facilitates cracking. In contrast, the IF steel induces a more uniform deformation within the coatings leading to much reduced crack size and crack area fraction. This study has resulted in a key element of a guideline towards crack-resistant and formable Mg-alloyed zinc coatings.

Guangshe ZHAO, Chuntao ZHAO

Given the problem of three-sources uncertainty in aero engine degradation process and the assumption of normal distribution of measurement error in existing research, a Wiener process aero engine residual useful life time(RUL) prediction method with logistic distribution of measurement error was proposed. Firstly, the performance degradation model was established when the measurement error obeys the logistics distribution, and the accurate mathematical expression of the RUL distribution was given under the first arrival time. Secondly, in order to improve the utilization of monitoring parameters, a key parameter screening method based on Spearman coefficient was given. Lastly, in view of the lack of historical data and prior information, a parameter estimation method based on maximum entropy unscented particle filtering and conditional expectation maximization algorithm was adopted. Meanwhile after new performance degradation data was obtained, the model parameters could be adaptively updated. With MSE as the evaluation index, the experimental results show that the MSE value of this method is 13.25, and the MSE value is 16.12 lower than that of traditional method, which can effectively improve the prediction accuracy and the engine utilization and safety.

Xiaojun Tao, Siyu Mao, Qiufang Zhang et al.

Abstract Most Alzheimer’s disease drugs do not work efficiently because of the blood–brain barrier. Therefore, we designed a new nanopreparation (PS-DZP-CHP): cholesterol-modified pullulan (CHP) nanoparticle with polysorbate 80(PS) surface coverage, as donepezil (DZP) carrier to realize brain tissue delivery. By size analysis and isothermal titration calorimetry, we chose the optimal dosing ratio of the drug with nanomaterials (1:5) and designed a series of experiments to verify the efficacy of the nanoparticles. The results of in vitro release experiments showed that the nanoparticles can achieve continuous drug release within 72 h. The results of fluorescence observation in mice showed a good brain targeting of PS-DZP-CHP nanoparticles. Furthermore, the nanoparticle can enhance the drug in the brain tissue concentration in mice. DZP-CHP nanoparticles were used to pretreat nerve cells with Aβ protein damage. The concentration of lactate dehydrogenase was determined by MTT, rhodamine 123 and AO-EB staining, which proved that DZP-CHP nanoparticles had a protective effect on the neurotoxicity induced by Aβ25–35 and were superior to free donepezil. Microthermal perpetual motion meter test showed that PS-DZP-CHP nanoparticles have an affinity with apolipoprotein E, which may be vital for this nanoparticle targeting to brain tissue.

Nagesh R. Iyer

Xuemin Sun, Weiyuan Yu, Baolei Wu et al.

Ultrasonic-assisted soldering, as a type of new welding method, is widely used in the field of electronic packaging. This research used the immersion method to study the dissolution behavior of copper in liquid tin and the growth of IMC at 513, 543, and 573 K with/without ultrasonic waves. The amount of copper dissolved and IMC layer thickness were measured and the dissolution activation energy of Cu/Sn was calculated. Experimental results indicated that Without ultrasonic waves, the amount of copper dissolved increased nonlinearly with immersion time. However, with ultrasonic waves, the amount of copper dissolved increased linearly with immersion time. The amount of copper dissolved in liquid tin increased considerably with ultrasonic waves, and the dissolution rate increased by 7–8 times. The thickness of the IMC layer decreased as the ultrasonic time and ultrasonic power increased. Meanwhile, the ultrasonic waves reduced the dissolution activation energy of the Sn/Cu system.

S. Wang, N.L. Pomerantz, Z. Dai et al.

Highly selective and lightweight protective suits featuring excellent breathability, mechanical robustness, and catalytic degradation performance toward chemical warfare agents (CWAs) are highly desirable for first responders and the military. However, current multilayered state-of-the-art chemical/biological (CB) protective textiles containing activated carbon and separate aerosol-protective layers exhibit several drawbacks including high thermal burden and secondary contamination. Herein, we present for the first time, a highly sorptive, breathable, and mechanically strong aerosol-protective layered fabric with prominent catalytic degradation capability of CWA simulant, through novel material selection and engineering design. The electrospun polymer of intrinsic microporosity (PIM-1) fiber web with hierarchical porosity is used as a matrix material, preventing toxic gas penetration while providing pathways for air and water vapor molecules. Polyacrylonitrile (PAN) nanofibers assembled with PIM-1 fibers via a layer-by-layer electrospun-deposition approach are shown to achieve significantly enhanced mechanical integrity and filtration efficiency, due to the high polar chemical structure and small fiber diameter of PAN. The subsequent incorporation of UiO-66-NH2 particles, a Zr-based metal-organic framework (MOF), further enhances the sorption capacity while maintaining excellent filtration efficiency, mechanical strength, and breathability, and also endows the fiber web with remarkable catalytic degradation towards CWA simulants. The resulting PIM/PAN/MOF composite fiber mat demonstrates unprecedented integrated properties with water vapor transmission rate of 1,013 g/m2·24 h, surface area of 574 m2/g, increased tensile strength (more than 70 times compared to neat PIM-1 fiber web), and PM2.5 and PM10 filtration efficiency of 99.88% and 99.94%, respectively, comparable to commercial polypropylene (PP) non-woven textile. This facile and effective fabrication of such a multifunctional composite fiber mat is valuable for the design of protective garments in health care, personal protective gear, and law enforcement and military uniforms.

W.M. Sebastian, J. Mudie, G. Cox et al.