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

Shuo Wang, Jinhua Chi, Yanting Wang et al.

Vitrectomy is a common clinical treatment for fundus disease. Due to the non-renewable nature of the vitreous, artificial vitreous are usually required to replace natural vitreous to perform functions post operation. Silicone oil and gas, as the most commonly used vitreous substitutes, have obvious drawbacks, which may lead to postoperative posture maintenance, visual impairment, cataract formation and secondary surgery. In this study, an in situ cross-linked bionic hydrogel (OAHA-CDHA/Col) based on hyaluronic acid (HA) and collagen (Col) with available gelling time for clinical operation, excellent self-healing and fatigue resistance, as well as suitable mechanical and optical properties is constructed. The compatibility and degradability of OAHA-CDHA/Col hydrogel are verified, as well as the feasibility as vitreous substitute in rabbit vitrectomy model. Notably, the hydrogel demonstrates improved intraocular tolerance compared with silicone oil, with no cataracts, endophthalmitis, fundus lesions and other complications observed. These findings position the OAHA-CDHA/Col hydrogel as a promising candidate for an ideal vitreous substitute.

Shibin Li

This study examines the crystallization kinetics of Ni _50−x Mn _39 Sn _11 Fe _x (x = 0, 0.5, 2, 4 at.%) amorphous thin films prepared by DC magnetron sputtering. SEM and XRD confirm their amorphous structure. Non-isothermal DSC results show that the crystallization peak temperature increases from 542.7 K to 568.0 K as Fe content rises, while the apparent activation energy increases from 96.69 to 152.93 kJ mol ^−1 , indicating enhanced resistance to crystallization. Isothermal analysis yields Avrami exponents of 1.15–1.41 (average ≈1.2), corresponding to diffusion-controlled one-dimensional growth. Local activation-energy evaluation further reveals composition-dependent differences in nucleation and growth during various stages. These quantitative kinetic parameters clarify the role of Fe in altering crystallization behavior and support the optimization of annealing conditions for Ni-Mn-Sn-based functional thin films.

Sergei A. Shyshko, N. Ishin, A. Goman et al.

The paper considers scientific and engineering aspects of design, optimization, calculation, construction and ensuring manufacturability of production of drive axles of heavy-duty quarry dump trucks. A new method of engineering analysis has been developed for express assessment and limitation of the selection area of the main parameters of gear transmissions of drive axles of BELAZ quarry dump trucks: gear module; number of gear teeth; load on input (output) shafts; maximum rotation frequency of input (output) links; maximum dynamic factor. Distribution of the drive axle gear ratio uвм is made according to the principle of maximizing the torque in the final stage, i.e. in the planetary wheel transmission, which reduces the loads on the differential and axle shafts and their dimensions. When distributing gear ratios, it is necessary to take into account the limitations of ensuring the technological possibility of cutting teeth of bevel gears with a circular tooth of the main transmission on the equipment available at the enterprise. For the first time, the Bbha scheme of a single-row planetary wheel reduction gear with a double-crown satellite has been used on BELAZ extra-large-capacity quarry dump trucks. The adopted design provides an increase in the gear ratio by 1.7...1.8 times compared to a single-row classic Abha planetary reduction gear.

Beniyel Muthuraj, Sivapragash Murugesan, Rajesh Rajamony et al.

This study uses an artificial neural network (ANN) model to predict the wear rate and friction coefficient of the magnesium alloy AZ91D, based on experimental data from a pin-on-disc tribometer. The model includes three essential process parameters: sliding velocity (m/s), applied load (kg), and sliding distance (km), in addition to the chamber temperature (°C). A total of 27 experimental designs were devised using a Box-Behnken design. The ANN model was trained utilizing the Bayesian regularization approach with one hidden layer of 10 neurons. The developed ANN models for predicting wear rate and coefficient of friction were used as goal functions in a multi-objective Pareto-based genetic algorithm to maximize tribological performance. The ideal solution indicates a sliding velocity of 2 m/s, a load of 5 kg, a sliding distance of 1.5 km, and a chamber temperature of 143°C, yielding a minimal wear rate of 1.7891 mm3/kg·km and a coefficient of friction of 0.1435. Energy Dispersive Spectroscopy and Scanning Electron Microscopy analyses of worn surfaces show that the wear rate decreases with increasing load and sliding velocity at higher temperatures. The oxide layer that forms at high temperatures enhances wear resistance, even under high loads and sliding speeds.

Chuanzhe Wang, Jie Lv, Mengyi Yang et al.

Cardiovascular diseases (CVD) are the leading global threat to human health. The clinical application of vascular stents improved the survival rates and quality of life for patients with cardiovascular diseases. However, despite the benefits stents bring to patients, there are still notable complications such as thrombosis and in-stent restenosis (ISR). Surface modification techniques represent an effective strategy to enhance the clinical efficacy of vascular stents and reduce complications. This paper reviews the development strategies of vascular stents based on surface functional coating technologies aimed at addressing the limitations in clinical application, including the inhibition of intimal hyperplasia, promotion of re-endothelialization. These strategies have improved endothelial repair and inhibited vascular remodeling, thereby promoting vascular healing post-stent implantation. However, the pathological microenvironment of target vessels and the lipid plaques are key pathological factors in the development of atherosclerosis (AS) and impaired vascular repair after percutaneous coronary intervention (PCI). Therefore, restoring normal physiological environment and removing the plaques are also treatment focuses after PCI for promoting vascular repair. Unfortunately, research in this area is limited. This paper reviews the advancements in vascular stents based on surface engineering technologies over the past decade, providing guidance for the development of stents.

Deyang Zhang, Binhe Feng, Wenbo Guo et al.

Abstract A cost-effective and large-scale method for synthesizing ZnCo2O4 nanoflowers with surface oxygen vacancies as electrode materials for supercapacitors is presented. The existence of oxygen vacancies on the surface of the ZnCo2O4 nanoflowers has been confirmed through X-ray photoelectron spectroscopy (XPS). The energy bands and density of states (DOS) of ZnCo2O4 are examined using density functional theory, revealing that treatment with NaBH4 reduces the band gap of ZnCo2O4 while increasing the DOS near the Fermi level compared to pristine ZnCo2O4. Furthermore, the specific capacitance of reduced ZnCo2O4 is nearly double that of its unmodified counterpart. This straightforward and practical approach significantly enhances both conductivity and specific capacitance in metal oxides, making it applicable to other similar materials.

Shanwei Zhang

A. Belevich, Artem V. Charapok, Oleg P. Vysotskiy et al.

The current stage in the development of unmanned transport vehicles is characterized by a shift from public mobility to specialized applications in controlled environments. This article analyzes promising directions in the development of unmanned technologies in mechanical engineering. Modern achievements in the automation of three key sectors are systematized: agriculture, mining, and construction. Based on a comparative analysis of international experience and literature sources, characteristic features of each sector are identified: in agriculture, there is a transitional stage from automatic driving systems to full autonomy; in the mining industry, successful industrial implementation of unmanned systems with proven economic efficiency is demonstrated; and in construction, a significant potential for integrating robotic complexes with BIM technologies is revealed. Special attention is paid to legal and infrastructural limitations hindering the widespread adoption of autonomous transport in logistics and passenger transportation. The article presents research results and practical developments in creating unmanned transport vehicles for restricted-access sectors, carried out by specialists of the Joint Institute of Mechanical Engineering of the NAS of Belarus. The research outcomes justify focusing efforts on developing robotic complexes for applications in restricted environments, representing a strategic interest for the development of domestic mechanical engineering.

S. Kosytsyn, V. Akulich, Leonid N. Osetinskii

A numerical analysis of the stress-strain state of intersecting cylindrical shells has been performed taking into account various types of nonlinearities (physical, contact, and structural). Intersecting cylindrical shells are considered as part of a large-scale three-dimensional “shell - soil” system. The study identified the most stressed areas of intersecting shells that require special attention during the modeling process. It should be noted that the particular complexity of these models lies in their high computational dimensionality since they include both the structure under consideration and its surrounding soil, which imposes additional requirements on the software packages used to solve such problems. Using modern methods of numerical analysis can significantly improve the quality of modeling and increase the accuracy of the results obtained. In particular, by considering the nonlinear properties of materials, it is possible to more accurately assess the actual behavior of shells under different external influences. In addition, the analysis shows that accounting for construction stages has a significant impact on the distribution of stresses in the intersecting shells. This underscores the need to consider the sequence of construction works, which in turn can contribute to increasing the overall reliability of the structure. Future prospects involve testing and validating the developed numerical analysis techniques on real “shell - soil” systems. The application of the obtained results to the design of load-bearing structures in real underground construction projects is also envisaged.

S. Krivoshapko

An analysis of a number of published materials regarding four types of developable surfaces with two director (supporting) algebraic curves of the second order lying in parallel or in intersecting planes has been conducted. Three types of developable surfaces are shortly described with references to sources, and visualizations of each type of developable surface are presented. For the developable surfaces with two supporting curves with intersecting axes in intersecting planes, the construction technique and the method of obtaining parametric equations are given. This method is illustrated with three examples. It is established that to date, there are no studies on the strength of thin shells in the form of the presented developable surfaces defined in curvilinear conjugate non-orthogonal coordinates that coincide with the external contour of the shells. It is shown that there are suggestions of application of the studied surfaces in architecture, shipbuilding, and agricultural machine engineering.

M. Enescu, A. Negrea, D. Ungureanu et al.

Abstract This paper presents the study of the mechanical behavior of polytetrafluoroethylene (PTFE) during tensile tests performed at different strain rates, using standard samples. Test pieces are measured using a non-contact video extensometer. This procedure is particularly precise, as large deformities are involved. The results are compared with a mathematical model to predict the mechanical behavior observed in the experiments. The main objective is to predict the stress-strain curve at different strain rates (6.0 × 10−4, 7.7 × 10−2, 9.2 × 10−2 and 1.3 × 10−1 s−1) using model equations that combine enough mathematical simplicity to allow their use in engineering problems with the ability to describe complex nonlinear mechanical behavior. The material constants (PTFE) that appear in the model equations can be easily identified from tests performed at constant and different strain rates. The virtual studies were carried out using the FEM program under the Solidworks software (Simulation) in which a virtual material was created with the mechanical properties of the analyzed material. The studies contain simulations of tensile, bending and impact tests according to standardized standards.

Bin Wang, Gongxing Yan, Adham E. Ragab

Abstract Proper consideration should be given to the stability of new concrete in order to assure the quality of building engineering, while also demanding its excellent flowability. The inadequate initial state stability negatively impacts the long-term durability of reinforced concrete structures, although this issue has not been well addressed. This work focuses on assessing the aerodynamic response of concrete ceilings reinforced with advanced functionally graded nano-materials. As the reinforcement of the current concrete structure, graphene oxide powders (GOPs) are used with improved material properties than other types of reinforcement. For mathematical modeling of the current structure, Reddy’s Higher-order Shear Deformation Theory is used to model the current work’s displacement fields. Also, the perturbation aerodynamic force is mathematically described using the Bernoulli equation for potential flow. After that using a method that involves separating variables, we may get the answer for the aerodynamic pressure in its ultimate form. Haber-Schaim foundation made of auxetic material in the Cartesian coordinate system is used to model the foundation of the current work with high accuracy. After obtaining the governing equations and associated boundary conditions, a meshless approach with weighted orthogonal basis and Kronecker delta-based shape functions are used to solve the equations. Finally, some suggestions for improving the aerodynamics and flutter velocity of airflow of the presented concrete plate reinforced by GOPs are presented for related aerodynamics industries.

Huanhuan Xu, Jiali Li, Khalid A. Alnowibet

Guo-qiang Xu, Wei Zhang, Si Chen et al.

To investigate the impact of sulfate corrosion on the performance of shaft lining concrete under sustained compressive loads, this study immersed samples in a 10 % sodium sulfate solution after subjecting to sustained compressive loads of 0.2fcand 0.4fc. The variation in compressive strength, ultrasonic velocity, and dynamic elasticity modulus with corrosion age were examined. The corrosion mechanisms were analyzed using field emission scanning electron microscope and energy dispersive spectrometer. The impact tendency of concrete was also evaluated. The results indicated that under sustained compressive loads of 0.2fcand 0.4fc, the compressive strength, ultrasonic velocity, and dynamic elasticity modulus are all increased with age, in the order of 0.2fc> 0.4fc>no-load. When exposed to a 10 % sodium sulfate solution under sustained compressive loads, these properties initially increased and then decreased, peaking at 90 days of corrosion age, and the order was 0.2fc> no-load > 0.4fc when the corrosion age was longer than 240 days.The shaft lining concrete exhibited weak impact tendency, with the brittleness index increasing as the corrosion age progressed. The outcome of this work might provide a reference for the further research on the design of shaft lining concrete materials.

A. Kotlov, E. A. Shcherbakov, B. Ovsyannikov

Kamensk-Uralsky Metallurgical Works JSC (KUMZ JSC, Sverdlovsk Region) celebrates its 80th anniversary. On May 5, 1944, the first stage of the works was launched; this date is considered the birthday of KUMZ (then Works No. 268). Historically, the enterprise, its manufacturing base, and intellectual resources were focused on the needs of high-tech industries, namely aerospace, construction, shipbuilding, nuclear energy, oil and gas industry, transportation engineering.

Xin Chen

Soil mechanics plays a pivotal role in the success of dam construction projects, providing essential data that influences all phases from design to execution. This paper examines how modern advancements in soil mechanics have been integrated into dam construction practices, assessing both the benefits and ongoing challenges. Through a comprehensive review of recent developments in the field, the study highlights the innovative techniques and materials that have transformed dam construction and identifies critical areas where further research is needed.

D. Buranova, E.A. Atashev, S. Matchanov et al.

David Cajamarca-Zuniga, O. Kabantsev, Daniel Campos

In Ecuador, about 95.9% of dwellings are built with masonry, however the local production of bricks does not meet technical standards and there is no scientific research on its geometric characterization and the technical state of their production. The geometric characterization of bricks is essential for the standardization of materials and constructions and allows the design of structures with a higher degree of accuracy. This research, conducted in 12 provinces of the 3 continental regions of the country, where 79% of the buildings are concentrated, studies for the first time the geometric characteristics of solid clay bricks in Ecuador. The results show that 67% of the brick production in Ecuador is artisanal and 98% of the factories do not comply with the technical standards for brick production. The authors present the characteristic dimensions of solid bricks produced in different regions of Ecuador. The results show a high variation in brick dimensions depending on the region, and even in a same province the dimensions depend on the factory, since its production does not comply with any standard. Ecuadorian standards regulating brick geometry need to be updated taking into account the real characteristics of the national brick production.

V. Topilnytskyy, Volodymyr Vyshatytskyy

In the article, a mathematical model of the oscillating motion of a vibrating separator is constructed. The methods of nonlinear mechanics and the calculation scheme of the vibration separator with an eccentric and a spring suspension, which is presented in the form of a flat mechanical system with four degrees of freedom, were used for its construction. The amplitude of oscillations of the vibration separator capacities in the vertical plane is greater than the amplitude of its oscillations in the horizontal plane. It is believed that the containers of the vibroseparator move only in the vertical plane, that is, they are in planar motion. The obtained mathematical model makes it possible to investigate the influence of the separator parameters with their arbitrary combination on the productivity of its work with the aim of its optimization.

Jian Yang, Lei Zhang, Jun Zhang et al.

In this study, the mechanical models of a multilayer combined extrusion cylinder and a steel-wire-winding extrusion cylinder were established and compared using a finite element simulation and existing experimental cases. This work provides theoretical support for the selection of an ultrahigh-pressure extrusion cylinder. Comparative analysis of an ultrahigh-pressure extrusion structure was carried out. The mathematical optimization model is established based on the mechanical model, and the ultimate bearing capacities of the schemes are compared. Additionally, the winding mode and the number of core layers of the extrusion cylinder are compared and analyzed, which provides a theoretical basis for the parameter design of the steel-wire-winding ultrahigh-pressure extrusion cylinder. This work holds good theoretical significance and practical value for the promotion and application of ultrahigh-pressure hydrostatic extrusion technology.