Mechanics Research Articles

Composites with Immobilized Bioactive Spirulina on an Inorganic Substrate (Yellow Clay, Hydroxyapatite, SiO2, TiO2, ZnO).

In order to improve the structural properties of clays and composites of powdered spirulina, clay, nanosilica, hydroxyapatite, TiO2 and ZnO were used as an additive for mechanical processing. As a result, composites with natural nanostructured materials (NNM) are prepared with improved structural properties and bioactivity. The mixtures based on NNM with crystalline kaolinite, clays and admixtures were processed in a knife mill. The materials were characterized using FTIR spectroscopy, nitrogen adsorption and desorption, SEM release of bioactive components (anthocyanin 0,004-0,07 mg/g; chlorophyll 20-29 mg/g), composite toxicity level (below 25%), particle size measurement and surface charge density, zeta potential. Adsorption enthalpies during the formation of an intermolecular complex during the interactions of an anthocyanin molecule with the appropriate component of the composite were also calculated. There are regularities in the characteristics depending on the type of NNM, particle morphology and textural features of solids. The morphological and structural properties of the components changed slighty in the blends because the processing was conducted under relatively low mechanical stress. The morphological, textural and structural characteristics of the composites as well as the transformation to a nanostructured state, assume great bioactive activity of the composites, interesting for practical applications in medicine and cosmetics.

About this title - The Bowland Shale Formation, UK: Processes and Resources

This volume showcases recent geological, geophysical and geochemical research on the UK Mississippian Bowland Shale Formation. Here, the Bowland Shale and equivalent units are described and interpreted in terms of sedimentary, geochemical, and mechanical properties and processes, basin-forming events, hydrocarbon prospectivity, mineralization, and heat and fluid flow in the subsurface.

Production of Glass Foam in a Microwave Oven Using Agro-Industrial Waste as Raw Material

Climate change is characterized by shifts in temperature and climate patterns. Constructing new high-rise environments using materials that incorporate agro-industrial waste can help mitigate this impact without compromising technological properties. This study produced vitreous foams intended to replace natural aggregates in lightweight concrete partially. These foams were sintered in a microwave oven at temperatures of 750 °C, 800 °C, and 850 °C, utilizing glass powder and sugarcane bagasse ash as raw materials. The homogenization and preparation of these materials were conducted through a mechanical pelletization process, employing a constant rotation engine at approximately 40 rpm. The efficacy of microwave sintering was assessed by comparing the outcomes with those from sintering in a conventional electric muffle furnace under identical conditions. The results indicated that the microwave-sintered vitreous foams exhibited the following values for apparent density (≤0.30 g/cm3), porosity (86% to 94%), and compressive strength (0.48 MPa to 0.58 MPa), which align with the global standards for commercial vitreous foams. The microwave sintering route proved to be economically feasible by reducing sintering time and, consequently, energy costs, without sacrificing technological properties. The materials produced in this study offer a promising solution to minimize the environmental impact associated with constructing new buildings, particularly tall structures. Additionally, they support the circular economy by converting waste into valuable by-products.

High-performance static formation of methane hydrate in fixed bed constructed by incorporating expanded graphite into polyimide foam

Hydrate has been endowed with great potential in energy storage and transportation. However, the kinetics of its formation process has been a challenge, often requiring dynamic mechanical processes that are energy-intensive and cumbersome to operate. Herein, a well-designed expanded graphite (EG)/polyimide (PI) foam was first explored as fixed bed for the formation of methane hydrate. The results demonstrate that the EG/PI fixed bed exhibits a remarkable performance in hydrate formation under static conditions, with a high gas storage capacity of 149 V/V, a short induction time and a rapid formation rate of 13.1 V·V−1·min−1 at 6 MPa and −2 °C, and excellent recyclability, which are attributed to its stable micro/macro structures. Thereinto, the pores of EG serves as gas adsorption and reaction sites, initialing the formation with extremely short induction time. The three-dimensional framework of PI foam supports the uniform dispersion of EG particles and enables the efficient formation of hydrate under static condition. The EG/PI fixed bed decreases the water freezing point and leads to a high supercooling that facilitates the rapid nucleation of hydrate. Meanwhile, the fixed bed provides extensive mass-transfer channels, sufficient growing space, and superior heat conductivity, which contribute to the hydrate growth under static condition. This work not only offers a novel strategy for fabricating high-performance fixed bed, but also provides an insight into its promotion mechanism in hydrate formation.

The Impacts of Micro‐Porosity and Mineralogical Texture on Fractured Rock Alteration

AbstractGeochemically driven alterations of fractures in multi‐mineral media can create altered layers (ALs) at the fracture‐matrix interface. Spatial variations in the AL significantly influence mass transfer across the interface, and the hydraulic and mechanical properties of the fractured medium. A real‐rock based microfluidic experiment reported spatial variations in AL thickness despite the initially smooth fracture surface, suggesting potential effects of matrix heterogeneity on AL development. However, the respective contribution of structural and mineralogical characteristics is still poorly understood. Using the microfluidic experimental data and a micro‐continuum reactive transport model, we systematically evaluated how micro‐porosity and initial mineral texture impact AL development and thus the overall reactive transport behaviors. Our simulation results confirmed that the extent of AL spatial variations, mainly controlled by mineralogical texture, influences the evolution of reaction and permeability in different ways. Accounting for spatial heterogeneity in mineral distribution produces “channeling” structures in ALs and lower overall reaction (by up to 35.6%), but larger permeability increase (by up to 9.8%). The characteristic length of the reactive mineral cluster was observed to dominate the internal texture of ALs. Whereas the presence of micro‐porosity can enhance mineral accessibility via improving connectivity for flow and transport, and lead to both higher bulk reaction, that is, thicker ALs, and permeability enhancement. Considerations of surface roughness with characteristic length on the same order of magnitude as mineral texture did not change the overall development of AL, which further highlights the importance of accounting for rock matrix properties in predicting long‐term evolution of fractured media. The resulting spatial variations of ALs and their impacts on bulk properties, however, are expected to be further complicated by the coupling of chemical and mechanical processes, and may trigger matrix disaggregation, erosion and other mechanisms of fractured media alteration.

Experimental and numerical analysis of NdFeB magnets under static and dynamic loading conditions

Neodymium iron boron (NdFeB) magnets, known for their superior magnetic properties, are pivotal in various high-performance applications, ranging from electric motors to wind turbines. The durability and reliability of these devices significantly depend on the mechanical integrity of NdFeB magnets under various stress conditions. In this work, the mechanical behavior and failure processes of NdFeB magnets are experimentally studied by in-door tests. We specifically examine the failure behavior of these magnets when subjected to dynamic loads, employing the Split Hopkinson Pressure Bar test both with and without initial loading perpendicular to the pressure bar direction. Furthermore, to complement the experimental findings, the experiments are numerically reproduced with a hybrid finite-discrete element method titled Continuous-Discontinuous Element Method (CDEM). Within the CDEM framework the Johnson-Holmquist 2 constitutive model is considered for the material under high strain rate loading conditions. Most material parameters are determined by experimental data and theoretical analysis. This research not only enhances our understanding of the properties of NdFeB magnets but also provides valuable insights for engineers and researchers aiming to improve the material’s resilience and durability.

Information content and optimization of self-organized developmental systems

A key feature of many developmental systems is their ability to self-organize spatial patterns of functionally distinct cell fates. To ensure proper biological function, such patterns must be established reproducibly, by controlling and even harnessing intrinsic and extrinsic fluctuations. While the relevant molecular processes are increasingly well understood, we lack a principled framework to quantify the performance of such stochastic self-organizing systems. To that end, we introduce an information-theoretic measure for self-organized fate specification during embryonic development. We show that the proposed measure assesses the total information content of fate patterns and decomposes it into interpretable contributions corresponding to the positional and correlational information. By optimizing the proposed measure, our framework provides a normative theory for developmental circuits, which we demonstrate on lateral inhibition, cell type proportioning, and reaction-diffusion models of self-organization. This paves a way toward a classification of developmental systems based on a common information-theoretic language, thereby organizing the zoo of implicated chemical and mechanical signaling processes.

Co-Assembly of Soft and Hard Nanoparticles into Macroscopic Colloidal Composites with Tailored Mechanical Property and Processability.

Colloidal composites, translating the great potential of nanoscale building bricks into macroscopic dimensions, have emerged as an appealing candidate for new materials with applications in optics, energy storage, and biomedicines. However, it remains a key challenge to bridge the size regimes from nanoscopic colloidal particles to macroscale composites possessing mechanical robustness. Herein, a bottom-up approach is demonstrated to manufacture colloidal composites with customized macroscopic forms by virtue of the co-assembly of nanosized soft polymeric micelles and hard inorganic nanoparticles. Upon association, the hairy micellar corona can bind with the hard nanoparticles, linking individual hard constituents together in a soft-hard alternating manner to form a collective entity. This permits the integration of block copolymer micelles with controlled amounts of hard nanoparticles into macroscopic colloidal composites featuring diverse internal microstructures. The resultant composites showed tunable microscale mechanical strength in a range of 90-270MPa and macroscale mechanical strength in a range of 7-42MPa for compression and 2-24MPa for bending. Notably, the incorporation of soft polymeric micelles also imparts time- and temperature-dependent dynamic deformability and versatile capacity to the resulting composites, allowing their application in the low-temperature plastic processing for functional fused silica glass.

Chemical mechanical polishing for copper films in integrated circuit wiring layers using an advanced slurry

In the chemical mechanical polishing process of integrated circuits (IC) copper (Cu) wiring layer, it is difficult to balance between material removal rate (RR) and surface quality. To solve this problem, a novel slurry composed of dodecylbenzene sulfonic acid (DBSA), 2-aminobenzimidazole (2-ABI) and multi-walled carbon nanotubes (MWCNTs) was proposed. The Cu surface roughness of 0.63 nm with RR of 5290 Å/min had been achieved. Polishing, electrochemical experiments and molecular dynamics simulations revealed that when DBSA: 2-ABI= 1: 4, the strongest inhibition effect was obtained. Quantum chemical calculations showed that the strong interaction force of hydrogen bonding between 2-ABI and DBSA greatly enhanced the inhibition efficiency. Surface morphology testing showed that the addition of MWCNTs could effectively reduce scratches.

Multi-stage manufacturing process parameter optimization method based on improved marine predator algorithm

Product quality is a critical factor in manufacturing industry competition, and mechanical processing technology has been widely applied in manufacturing, directly affecting product quality. Therefore, it is very important to find the appropriate optimal parameters to improve the impact of processing on product quality. However, modern production processes are characterized by complex mechanisms and the mutual influence of multiple processes, which poses higher challenges for optimizing processing technology parameters. In this regard, the thesis proposes a method for optimizing process parameters in multi-process manufacturing based on an improved marine predator algorithm, aiming to optimize and improve process parameters in multi-process manufacturing processes. Firstly, a multi-process modeling strategy is adopted to explore the nonlinear relationship between process parameters and quality indicators based on multi-gene genetic planning, establishing a multi-process parameter optimization objective model. This effectively solves the problem of modeling difficulty caused by severe coupling of multiple processes. Then, to improve the efficiency of solving the optimization objective model, an improved marine predator algorithm is proposed, utilizing reverse learning strategies and mixed control parameters to enhance optimization capability, thereby obtaining the global optimal solution. Finally, using production process data from a certain factory as an example, the feasibility of the proposed method is verified, achieving the goal of multi-process process parameter optimization and ensuring the stability of product quality.

Crashworthiness analysis and optimization of brain-coral-inspired multilayer sandwich structures under axial crushing

Inspired by brain corals and cuttlebone, this study employed 3D printing technology to fabricate a novel bio-inspired multilayer sandwich structure based on the Hilbert space-filling curve (named BHSS). The mechanical behavior and deformation process of the BHSS were compared through quasi-static axial crushing experiments and finite element (FE) simulations. The energy absorbing characteristics of the BHSS with different layers were compared through FE simulations, and the results indicated that the 4-layer BHSS displayed superior crashworthiness. Then, parametric studies were conducted to investigate the influence of layer-height gradient and wall-thickness gradient on the energy absorption performance and deformation modes of the BHSS. It was confirmed that the double gradient designs significantly reduced the initial peak force and improved the specific energy absorption of the BHSS. Finally, the multi-objectives optimization based on response surface method and the non-dominated sorting genetic algorithm (NSGA-II) was employed to optimize the geometric parameters of the BHSS, aiming at the optimal configuration for better crashworthiness. Compared to the original design structure, the SEA of the optimized knee point structure was increased by 21.8% and the IPF was reduced by 72.6%. These findings provided valuable guidelines for the brain-coral-inspired design of multilayer sandwich structures with superior energy-absorbing performance.

Advancing sustainability in mechanical engineering: Integration of green energy and intelligent manufacturing

Efficient energy utilization and waste reduction are imperative for sustainable mechanical engineering practices. This paper explores the integration of green energy sources and intelligent manufacturing techniques to enhance sustainability in the mechanical engineering sector. Through quantitative analysis and case studies, the efficacy of energy-efficient technologies, waste reduction strategies, and the adoption of green energy sources are examined. Additionally, the role of smart process automation and digital twin simulation in optimizing resource utilization and operational efficiency is discussed. The findings underscore the potential of integrating sustainable practices into mechanical engineering processes, contributing to environmental conservation, cost savings, and competitiveness.

Application of the FMECA method on the electro-hydraulic system for drilling machine type NKH45

This article focuses on the implementation of a preventive maintenance strategy, responding to a major challenge: the search for optimization in minimizing downtime of the radial drilling machine (NKH45). Crucially positioned at the heart of the mechanical manufacturing process, this machine holds significant influence on overall production performance and availability. In consideration of the strategic importance of this equipment within the framework of the mechanical manufacturing activity, an advanced methodology, in particular FMECA (Failure Mode Effects and Criticality Analysis), is implemented. FMECA represents one of the most recommended approaches in this context, based on reliability, allowing the meticulous identification of the main causes of functional failures of equipment. FMECA is a risk prevention method. It is used to improve the reliability of a product, a process or even a means of production. It makes it possible to assess the criticality of potential failures in a system. According to the recommendations of the maintenance department of the company specializing in the construction of agricultural equipment, this study will focus on a subsystem of the electro-hydraulic part of the NKH45 radial drilling machine, we use the FMEA Analysis method (Failure Mode Effects and Criticality Analysis). Thanks to this approach, it is possible to identify the main reasons for equipment breakdowns that affect production and to classify these breakdowns in order to develop an optimal maintenance strategy aimed at: reducing the number of breakdowns, preventing breakdowns, improving the preventive maintenance, reduce downtime, improve corrective maintenance, therefore the ultimate objective of this approach is to design an optimal maintenance action plan in order to significantly minimize downtime, which slows down production flow.

Effect of milling atmosphere on stability and surface properties of ZnO/vermiculite hybrid nanocomposite powders

The zinc acetate dihydrate and anhydrous zinc chloride were used as precursors for the sonochemical preparation of the zinc oxide/vermiculite and organically modified zinc oxide/vermiculite_chlorhexidine nanocomposite materials. The nanocomposites were mechanically processed via a high-energy ball milling for 30 min at 300 rpm using two types of atmospheres an air or a nitrogen. Changes in temperature and pressure inside the grinding vessels were measured during mechanical processing in an air atmosphere. The ZnO(Cl)/V_30/300 sample reached the highest pressure (1161 mbar) and temperature (30.3 °C) in the milling vessels and for the ZnO(ac)/V_CH_30/300 sample the highest temperature difference was measured at the beginning and at the end of the milling (7 °C). The phase transformation, chemical composition and particle size of the hybrid nanocomposite materials were investigated using X-ray diffraction method, Fourier-transform infrared spectroscopy, X-ray fluorescence spectroscopy, carbon phase analysis and particle size distribution analysis. Changes in morphology and particle arrangement were characterised using scanning electron microscopy. The effect of mechanical processing in a protective atmosphere on surface properties such as specific surface area, surface conductivity and ζ-potential were demonstrated in relation to the type of precursor used for the preparation of ZnO nanoparticles in the structure of hybrid nanocomposite materials.

Investigation of speed and temperature effects in mechanical nano-patterning of GaAs via molecular dynamics simulation

Speed and temperature are two key parameters governing GaAs mechanical nano-patterning process. For the first time, this study evaluates the effects of pressing speed and nanoimprinting temperature on the deformation behavior and mechanical properties of GaAs in the mechanical nano-patterning process. Simulation results reveal that high pressing speed and high nanoimprinting temperature facilitate the nano-pattern formation on GaAs. For the pressing speed effect, the maximum force, residual stress, and cubic diamond atomic friction decrease with the elevated pressing speed, while the surface pile-up is minimally influenced by the pressing speed during the nanoimprinting process. Moreover, the morphological accuracy of the nano-patterns is enhanced with increasing pressing speed. For the temperature effect, simulation results reveal that amorphization and plastic activity exhibit a positive correlation with increasing nanoimprinting temperature, whereas the maximum force and residual stress demonstrate a roughly inverse relationship with nanoimprinting temperature. Additionally, the elevated temperature also exerts a substantial influence on the dislocation density, morphological accuracy, and surface pile-up. This study contributes to a comprehensive understanding of the effects of these two key factors on the mechanical properties and deformation behavior of GaAs in mechanical nano-patterning.

INFLUENCE OF COOLING MEDIUM ON MICROSTRUCTURE AND MECHANICAL PROPERTIES IN FRICTION STIR PROCESSING OF MAGNESIUM ALLOY — A REVIEW

Friction stir processing (FSP) is used for changing the microstructure and material properties improvement. In modern years, special attention is exposed by governing the temperature level, and is applied by various coolants spraying on the top surface of the sample during FSP. This review paper explores the impact of several cooling mediums such as normal water, cold water, hot water, and cryogenic on the temperature distribution, grain refinement, mechanical characteristics, and superplastic deformation behavior of FSP using various grades of magnesium (Mg) alloys. It also includes the corrosion rate and wear behavior of FSP on Mg alloys. Through the systematic review, it has been observed that refined grains were formed and the generation of intermetallic compounds was suppressed after FSP in underwater and cryogenic conditions, leading to a notable increase in strength. The higher tensile strength and elongation are exhibited while using cryogenic compared to water medium. This is due to a rapid cooling process, where the high temperature was short for the newly-formed grains to fully develop. This review not only concludes the key findings of the preceding research but also suggests future recommendations.

Characteristics of Sizing Materials Used in Persian Medieval Manuscripts: Physical, Optical, Spectral Imaging, and Fungicidal Properties

ABSTRACT In this study, we investigated the diverse range of materials used for sizing in Iranian paper manuscripts during the Timurid (fifteenth century) to Safavid (sixteenth century) and Qajar (nineteenth century) periods. Our approach combined historical analysis with scientific examination of reconstructed sizings. We reconstructed 15 sizing materials based on identified Persian historical recipes and analysed their physical, optical, and spectral characteristics. Additionally, we assessed their behaviour against the mould fungus Aspergillus flavus. The results revealed distinctive properties for each sizing material, shedding light on their potential applications in paper preservation. Furthermore, our investigation demonstrated variations in hygroscopicity, thickness, grammage, and ash content post-sizing. The sizing materials also exhibited different effects on paper reflectance properties. Additionally, our study revealed insights into the impact of sizing on burnished papers, indicating that the mechanical process of burnishing did not significantly alter the chemical composition or spectral properties of the paper, with only minor changes in brightness observed in specific cases. All tested sizing materials supported varying levels of mould growth, indicating potential implications for paper conservation. Our findings provide valuable insights into the historical practices of Iranian paper sizing and offer practical considerations for the preservation of paper manuscripts.

Recent progress in enzymatic degradation and recycling of polyurethanes

The widespread production of polymeric materials has precipitated severe environmental challenges, prompting a pressing need for effective solutions. Among these materials, polyurethanes (PUs) stand out significantly due to their versatility in synthetic approaches, manufacturing, properties, and applications. This versatility has led to a high demand for PUs, resulting in significant waste accumulation at the end of their lifecycle. Along with that, the PU’s inherent chemical stability prevents the occurrence of natural hydrolytic processes. Consequently, there is a critical need for sustainable recycling methods, particularly those capable of recovering reusable monomers. Recycling is a leading way to manage waste by reducing plastic pollution and its environmental impact, which can be performed through mechanical, chemical, and biological processes. Biological degradation occurs through the action of enzymes and microbes that can potentially convert the polymers into monomers or other valuable chemicals. This approach presents an opportunity to establish a sustainable and circular economy within the PUs industry while considerably reducing the environmental impact. This review highlights enzymatic degradation as a promising solution for PU recycling by discussing the types of enzymes utilized in the process, potential biochemical pathways for PU degradation, recent achievements, and future remarks for this process.

A Wearable Fingertip Force Feedback Device System for Object Stiffness Sensing.

Virtual reality technology brings a new experience to human-computer interaction, while wearable force feedback devices can enhance the immersion of users in interaction. This paper proposes a wearable fingertip force feedback device that uses a tendon drive mechanism, with the aim of simulating the stiffness characteristics of objects within virtual scenes. The device adjusts the rotation angle of the torsion spring through a DC motor, and then uses a wire to convert the torque into a feedback force at the user's index fingertips, with an output force of up to 4 N and a force change rate of up to 10 N/s. This paper introduces the mechanical structure and design process of the force feedback device, and conducts a mechanical analysis of the device to select the appropriate components. Physical and psychological experiments are conducted to comprehensively evaluate the device's performance in conveying object stiffness information. The results show that the device can simulate different stiffness characteristics of objects, and users can distinguish objects with different stiffness characteristics well when wearing the force feedback device and interacting with the three-dimensional virtual environments.

Plastically Deformed Tubes Subjected to Mechanical Expansion Processes.

In engineering, the stress state of expanded tubes is crucial for ensuring structural integrity and preventing stress corrosion cracking. The analysis of stresses and strains in tubes subjected to mechanical expansion using an ogive bullet is essential, yet existing theoretical methods for estimating the stress distributions, especially with spherical and ogive shapes, are sparse. This study explores the expansion of 3/8 inch copper and stainless-steel tubes using an expanding bullet, where tangential and longitudinal strains are measured. A novel analytical approach is introduced to evaluate the stresses and strains, segmenting the tube into three zones, each analyzed with a distinct theory. Validation is achieved through an axisymmetric finite element model that employs a multi-linear kinematic hardening material behavior. The analytical model also estimates the expanding mandrel's push force, which is then compared with the results from numerical simulations and experimental data, showing good agreement across methods.