Mechanical Characterization Research Articles

Simulating atherosclerotic plaque mechanics using polyvinyl alcohol (PVA) cryogel artery phantoms, ultrasound imaging and inverse finite element analysis.

The aim of this study is to demonstrate the potential of polyvinyl alcohol phantoms to simulate atherosclerotic features. In addition, a testing and simulation framework is developed for full PVA vessel material characterization using ring tensile testing and inflation testing combined with non-invasive ultrasound imaging and computational modelling. Strain stiffening behavior was observed in PVA through ring tensile tests, particularly at high (n=6) freeze-thaw cycles. Inflation testing of bi-layered phantoms featuring lipid pool inclusions demonstrated high strains at shoulder regions. The application of an inverse finite element framework successfully recovered boundaries and determined the shear moduli for the PVA wall to lie within the range 27 kPa to 53 kPa. The imaging-modelling framework presented facilitates the use and characterization of arterial mimicking phantoms to further explore plaque rupture. It also shows translational potential for non-invasive mechanical characterization of atherosclerotic plaques to improve the identification of clinically relevant metrics of plaque vulnerability.

Mechanical Characterization of Main Minerals in Carbonate Rock at the Micro Scale Based on Nanoindentation

The mechanical characterization of carbonate rock is crucial for the development of a hydrocarbon reservoir and underground gas storage. As a kind of natural composite material, the mechanical properties of carbonate rock exhibit multiscale characteristics. The macroscopic mechanical properties of carbonate rock are determined by the mineral composition and structure at the micro scale. To achieve a mechanical investigation at the micro scale, this study designed a scheme for micromechanical characterization of carbonate rock. First, scanning electron microscope observation and energy dispersive spectroscopy analysis were combined to select the appropriate micromechanical test areas and to identify the mineral types in each area. Second, the selected test area was positioned in the nanoindentation instrument through the comparison of different-type microscopic images. Finally, quasi-static nanoindentation was carried out on the surface of different minerals in the selected test area to obtain quantitative mechanical evaluation results. A typical carbonate rock sample from the Huangcaoxia gas storage was investigated in this study. The experimental results indicated apparent micromechanical heterogeneity in the carbonate rock. The Young’s modulus of pyrite was over 200 GPa, while that of clay minerals was only approximately 50 GPa. In addition, the proposed micromechanical characterization scheme was discussed based on experimental results. For minerals with an unknown Poisson’s ratio, the maximum error introduced by the 0.25 assumption was lower than 15%. To discuss the effectiveness of the nanoindentation results, the characterization abilities constituted by lateral spatial resolution and elastic response depth were analyzed. The analysis results revealed that the nanoindentation measurement of clay was more susceptible to influence by the surrounding environment as compared to other kinds of minerals with the experimental setup in this study. The micromechanical characterization scheme for clay minerals can be optimized in future research. The mechanical data obtained at the micro scale can be used for the interpretation of the macroscopic mechanical features of carbonate rock for the parameter input and validation of mineral-related simulation and for the construction of a mechanical upscaling model.

Experimental determination of the mechanical and hydrolytic properties of chitosan/rice husk ash composite membranes

Chitosan-based membranes are promising alternatives to synthetic membranes in a number of specialized use cases, including water purification and electrochemical devices. In application, excessive swelling when hydrated can lead to poor mechanical integrity, necessitating modifications to the polymer to counter this effect. Embedding inorganic fillers within an organic polymer matrix is one method of combining excellent mechanical stability with good performance. This study investigated the effect of rice husk ash (RHA) on the mechanical and hydrolytic properties of chitosan-based composite membranes. We incorporated varying amounts of RHA into a chitosan solution and prepared thin film membranes via solution casting. We performed structural, chemical, and mechanical characterizations on the ash and membranes, observing 82.84 % water uptake in the 1.5 wt% (wt%) RHA-doped membrane and 13.93 MPa tensile strength in the 2.0 wt% loaded composite. As the RHA content increased, the swelling ratio of the composites with RHA loadings greater than 1.0 wt% decreased, indicating an enhancement in mechanical strength. The observed results demonstrate that combining improved mechanical strength with increased water absorption and reduced swelling can lead to optimal membrane characteristics.

Biomimetic three-dimensional scaffolds with aligned electrospun nanofibers and enlarged pores for enhanced cardiac cell colonization

Among the wide range of biomimetic scaffolds, those made of aligned nanofibers represent an important class for tissue engineering applications, and particularly for cardiac repair. Electrospinning is a powerful technique allowing the fabrication of scaffolds with aligned nanofibers. However, the resulting morphology is characterized by low porosity and small pore size due to the formation of a compact structure of aligned fibers preventing cell colonization inside the scaffold. In the present work, supported by numerical simulation, it is demonstrated that when optimal electrostatic interactions occur during the simultaneous deposition of electrospun nanofibers and electrosprayed microparticles on a collector rotating at high speed, a 3D structured scaffold is obtained. Thanks to a self-organization mechanism, islands of microparticles intercalate inside a network of loosely packed and highly aligned nanofibers. In the case of poly(lactic acid) electrospinning and poly(glycerol sebacate)/cyclodextrin electrospraying, the resulting 3D biomimetic scaffold, deeply investigated by X-ray microtomography and mechanical characterization, shows an open porosity with enlarged interconnected pores with a mechanical behavior mimicking that of cardiac tissue. Finally, after functionalizing the fiber surface using laminin, it is shown an efficient 3D colonization of cardiac cells through a network of aligned nanofibers.

Bone regeneration in rabbit cranial defects: 3D printed polylactic acid scaffolds gradually enriched with marine bioderived calcium phosphate

ObjectiveThis study aimed to evaluate the in vivo biocompatibility, mechanical performance and osteoconductive potential of 3D-printed polylactic acid (PLA) scaffolds enriched with marine bioderived calcium phosphate (bioCaP) for bone tissue engineering. Materials and MethodsPLA-bioCaP composite scaffolds were specifically designed for the rabbit cranial defect model by 3D printing, with a uniform distribution of open square-shaped pores and contributions in bioCaP. Physicochemical and mechanical characterization and the evaluation of biological response are presented. ResultsThe scaffolds demonstrated mechanical properties comparable to human bones, integration with the host bone, and osteoconductive behavior promoting cell ingrowth from the defect edge. Strong mineralized tissue ingrowth through the scaffolds’ pores was observed, providing notable support to the host bone. In quantitative terms, micro-CT and histomorphometry analysis post-implantation revealed no significant differences in bone regeneration across all groups. ConclusionThe 3D-printed scaffolds with perpendicular patterning, open porosity, and proposed composition displayed satisfactory mechanical properties, biocompatibility, and osteoconductive response. The scaffolds promoted bone regeneration at similar levels as the PLA. The highest contribution of bioCaP promoted a positive influence in certain histomorphometric parameters; however, it did not significantly improve their osteogenic capability. Further research is required to optimize scaffold composition and enhance their osteogenic potential. Clinical RelevanceThis study presents a significant advancement in bone tissue engineering through the development of personalized composite scaffolds for bone-related applications. The clinical implications of this research are profound, especially considering the increasing demand for functional bone regeneration technologies capable of producing cost-effective producing cost-effective customized scaffolds.

Quantitative mechanisms for the Cd2+ adsorption increased by sewage-sludge biochar but decreased by rice-straw biochar after melamine modification

To explore the relative contributions of different mechanisms to Cd2+ adsorption by melamine (C3H6N6) modified biochars, the adsorption characteristic experiments including adsorption kinetics, isotherms and thermodynamics were performed, and the qualitative and quantitative characterization of adsorption mechanisms were further analyzed by SEM-EDS, XRD, FTIR, XPS and the calculation, respectively. When initial pH increased from 1.0 to 7.0, the adsorption capacities were increased, and began to decline after reaching maximum capacities at pH of 5.0 for both modified biochars. After C3H6N6-modification, the maximum adsorption capacity of sewage-sludge biochar (SSB) increased from 64.20 to 126.75 mg/g, but the maximum capacity of rice-straw biochar (RSB) decreased from 52.03 to 25.65 mg/g. For both pristine biochars, the adsorption process was better described by pseudo-second-order kinetic and Langmuir isotherm models, whereas it did not change the applicability of the adsorption models after modification. The thermodynamics confirmed that all the adsorptions were endothermic process under different temperatures of 293, 303 and 313 K, suggesting higher temperature was more conducive to the adsorption. Such an enhancement was supported by more aromatic structure in modified SSB (N-SSB) compared to SSB, which was qualitatively confirmed by FTIR and XPS observation, and the enhancement was fundamentally caused by the increases in the importance of Cπ-coordination mechanism, accounting for 20.30 % (SSB) to 41.12 % (N-SSB) of total adsorption. While for modified RSB (N-RSB), the reduction was primarily explained by the decreased contribution of cation-exchange mechanism to total adsorption, since the contribution proportion was reduced from 80.16 % to 55.65 % after modification. The present analyses would shed light on the mechanisms underlying the adsorption by similar modified adsorbents, and the application of rice-straw biochar by C3H6N6-modification for the Cd2+ adsorption should be investigated prudently in future.

Air leakage mechanism and hole sealing technology in directional long-drilled perimeter rock-borehole composite fissures: for gas enrichment in varying coal-seam thickness change areas

The issue of gas enrichment in the tectonic zone of coal seams, which poses significant threats to coal mine safety and leads to gas disasters, is primarily addressed through borehole extraction. The quality of this extraction is notably influenced by air leakage and sealing technologies used during drilling. To tackle the problem of gas leakage in directional long boreholes within the floor, a composite fissure leakage model for the surrounding rock and borehole is developed. This model inverts the characteristics of coal seam thickness variations and abnormal gas enrichment through heterogeneous geostatistical modeling. It enables the quantitative characterization of the air leakage mechanism in directional long boreholes of the bottom plate and proposes an effective sealing process. Due to damage and disturbance, fissures and irregular plastic zones form around the excavated roadway, which are major contributors to air leakage. Over time, the air content in the coal and rock seams gradually increases while the gas content and concentration decrease continuously. Compared to the polyurethane "two plugs and one injection" sealing process, the multi-stage grouting and sealing process provides a more stable gas extraction concentration and flow rate in the sealed drill holes. This process effectively seals the fissure zones of the roadway, reduces air leakage from the boreholes, and improves gas extraction concentration.

Approach to Design Sustainable Alkali-Activated Slag Recycled Aggregate Concrete: Mechanical and Microstructural Characterization

There is a steep increase in demand for concrete as the need for infrastructure is increasing with a rapid increase in urbanization. Consequently, there has been a surging demand for cement across the globe. By using alkaline concrete activated with ground granulated blast furnace slag (GGBS), cement usage can be eliminated in concrete, which addresses the issue of CO2 emissions concerned with the cement manufacturing process and promotes the use of industrial by-products as sustainable building materials. The current study focuses on proposing a methodology to design sustainable GGBS-based alkali-activated concrete incorporated with 100% coarse recycled coarse aggregates (RCA) recovered from construction and demolition (C&D), for various strengths by optimizing the mix proportions and verifying the same through experiments. From the current study, it is evident that this mix design procedure can be adopted to design alkali-activated slag recycled aggregate concrete (AASRAC) mixes for strengths ranging from 44MPa to 85MPa. The optimum values of alkalinity factor (λ) and NaOH concentration (M) i.e., 1.5 and 12, have a significant role in the development of high strengths which is attributed to the formation of hydrotalcite. Micrographs captured using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) studies reveal that the alkaline binders promote the development of a denser and stronger interfacial transition zone (ITZ) that enhances the strength of lower AA/B concretes at the microstructural level as Ca/Si ratio is higher for lower AA/B concretes. Global warming potential (GWP) analysis reveals that the alkali-activated concretes have significantly lower GWP compared to conventional OPC-based concrete by approximately 2.5 times. The mix-design chart proposed in this study may pave the way to designing structural grade AASRAC with enhanced performance for the desired strength, which may find its application in fast-track construction and manufacturing of prefabricated elements.

Mechanical and spectroscopic characterization of functionalized g-C3N4 fillers loaded epoxy reinforced banana natural Fiber composite for PCB applications

Mechanical and spectroscopic characterization of functionalized g-C3N4 fillers loaded epoxy reinforced banana natural Fiber composite for PCB applications

Mechanical and Tribological Characterization of Microporous Low Density Polyethylene Films Obtained in Blown Extrusion

Mechanical and Tribological Characterization of Microporous Low Density Polyethylene Films Obtained in Blown Extrusion

Effect of theoretical volume fraction (TVF) of reinforcements on Al5083/SiC and Al5083/ZrB2 surface composites produced by friction stir processing

This study focuses on the effects of theoretical volume fraction (TVF) on the microstructure and mechanical properties of silicon carbide (SiC) and zirconium diboride (ZrB2) ceramic reinforced Al5083 surface composites (SC). Al5083-H111 was used as the base material (BM), SiC and ZrB2 were used as reinforcement materials, and TVFs were determined as 5, 10, 15, and 20% for SCs produced by the friction stirring process (FSP). Macrostructure, microstructure, X-ray diffraction (XRD) analysis and mechanical properties such as microhardness, tensile strength (UTS), and wear behaviour were characterised. When the TVF and AVF values of SiC and ZrB2 particles were compared, it was found that the AVFs were lower than the TVFs. Significant decreases in the changes in the SZ areas of SiC and ZrB2 particle SCs were detected depending on the reinforcement size. In the time-dependent axial load graphs of SiC and ZrB2 reinforced samples, load values ranging from 7800 to 8200 N were obtained and it was determined that these values were sufficient for friction heat, hydrostatic pressure, and plasticization in FSP. As a result of mechanical characterisation processes, the microhardness values and wear rates of ZrB2 reinforced SCs in the stir zone (SZ) were higher than SiC reinforced SCs. When the reinforcement particles were compared, it was observed that ZrB2 reinforced SCs exhibited higher microhardness and wear resistance than SiC reinforced SCs. As a result of all tests and investigations, it was determined that the ideal TVFs were 15% for SiC reinforced SCs and 5% for ZrB2 reinforced SCs. The microhardness value of ZrB2 reinforced SC with 20% TVF was 119.6 HV, while the UTS and volume loss values of ZrB2 reinforced SC with 5% TVF were found to be the highest values with 305.86 MPa and 1.83 mm3, respectively. Compared to BM, these values showed significant improvements in mechanical test results, especially in wear behavior. The results obtained showed an improvement of 55% in microhardness, 3.3% in UTS values, and 309% in wear behavior.

Economic and Sustainable UHPC at Scale: Material Variability Study and Application to Full Axial Columns

The high cost of robust UHPC of a proprietary nature and expensive constituents hinders mass production and expansion into full structural applications. This study provides experimental research and validation to support new initiatives in scalable, economical UHPC of a semi-proprietary nature that leverages local and sustainable materials and explores the use of raw recycled tire fibers. The study provides comprehensive material trials and mechanical characterization validated through the fabrication and testing of five full-scale axial UHPC columns with varying reinforcement ratios, fiber ratios, and types of fibers. Overall, the result shows that incorporating local and sustainable components into proprietary mixtures does not compromise the mechanical properties of UHPC with compressive strength of more than 150 MPa and modulus of elasticity ranging from 41.8-43.4 GPa. In addition, the axial strength capacity of economical UHPC columns, designed accordingly with ACI, performed better than non-ACI-compliant columns by up to 26.8%.

Buckling Analysis of Thin-Walled Structures Based on Trace Theory: A Simple and Efficient Approach for Mechanical Characterization of GFRP Members

Buckling Analysis of Thin-Walled Structures Based on Trace Theory: A Simple and Efficient Approach for Mechanical Characterization of GFRP Members

Free–free resonance method for the mechanical characterization of lime-stabilized rammed earth specimens

Rammed earth is a historical construction technique found in a large number of structures spread throughout the world. To conduct thorough and secure studies on these structures, it is necessary to know the mechanical characteristics of the material. Due to the heritage value of many structures built with this technique, testing techniques that may damage or alter them cannot be applied, so the use of non-destructive testing (NDT) is required in such characterization. Among these non-destructive techniques are those based on the propagation of elastic waves in the material, as they are completely harmless to the elements to be characterized. In this paper, the non-destructive technique of free–free resonance (FFR) is applied to specimens of rammed earth stabilized with different lime dosages in order to determine the dynamic modulus of elasticity of the material, marking the first time this technique is applied to specimens of this material. The values obtained with the free–free resonance method are compared with those obtained using another non-destructive test such as ultrasonic pulse velocity (UPV). This test has been used by a large number of researchers, providing reliable results. The percentage of lime influences the parameters obtained due to the effects of the different carbonation velocities of the specimens. It is demonstrated that the FFR method is applicable to rammed earth specimens and is shown to be an effective test for identifying specimens with internal damage. The values obtained during the investigation for both methods range from 1.25 for the samples with a higher amount of lime, with a 3:1 ratio, to 1.26 for the specimens made with a lower amount of lime, with a 4:1 ratio.

Mechanical Characterization and Modeling of Large-Format Lithium-Ion Battery Cell Electrodes and Separators for Real Operating Scenarios

This study presents a novel application-oriented approach to the mechanical characterization and subsequent modeling of porous electrodes and separators in lithium-ion cells to gain a better understanding of their real mechanical operating behavior. An experimental study was conducted on the non-linear stiffness of LiNi0.8Co0.15Al0.05O2 and graphite electrodes as well as PE separators, harvested from large-format lithium-ion cells, using compression tests. The mechanical response of the components was determined for different operating conditions, including nominal stress levels, mechanical loading rates, and mechanical cycles. The presented work describes the test procedure, the experimental setup, and an objective evaluation method, allowing for a detailed summary of the observed mechanical behavior. A distinct nominal stress level and mechanical cycle dependency of the non-linear stiffnesses of the porous materials were found. However, no clear dependency on compression rate was observed. Based on the experimental data, a poroelastic mechanical model was utilized to predict the non-linear behavior of these porous materials under real mechanical operating scenarios with a normalized root-mean-squared error less than 5.5%. The results provide essential new insights into the mechanical behavior of porous electrodes and separators in lithium-ion cells under real operating conditions, enabling the accelerated development of high-performing and safe batteries for various applications.

Mechanical characterization of intact rock under polyaxial static-dynamic stress states

Accurate assessment of mechanical behaviour of rock is essential for safe and efficient design of structures on or within rock mass particularly under harsh in-situ stress conditions. Insights from rock engineering practices have revealed that rockbursts can occur at various scales and at any time during mining activities. These violent failure phenomena can be triggered by quasi-static stress redistribution resulting from mining activities as well as dynamically induced loads from seismic events. Moreover, the mechanical behaviour of rock has proven to differ under static and dynamic stress conditions, showing rate-dependent characteristics. Hence, this study aims to thoroughly investigate the triggers that can lead to rockburst events and provide insights into the brittle fracturing process under various stress conditions. To achieve this, a comprehensive set of static and dynamic laboratory tests was conducted on coal samples. The static experiments were conducted under uniaxial and triaxial conditions where the samples were tested at the confining pressures up to 20 MPa. For the dynamic tests, the samples were first pre-stressed uniaxially, biaxially and polyaxially at different ranges of static stresses up to 30 MPa hydrostatically and non-hydrostatically. Then, the high impact velocity up to 21.5 m/s was applied along the maximum stress direction to provide dynamic loading. The influences of loading condition, strain rate and confinement on the mechanical behaviour of coal were investigated. The fracturing process of samples based on their uniaxial, biaxial and polyaxial pre-stressing conditions and various strain rates were analysed to confirm the significant role of loss of confinement and strain rate in severe high-energy fragmentation of coal or so-called “rockburst” under both static and dynamic loadings.

Mechanical and tribological characterization of wire and multi-wire arc additive manufactured thin-walled TC11 component

Multi-wire arc additive manufacturing (MWAAM) has higher deposition efficiency and material utilization than traditional wire arc additive manufacturing (WAAM), but its droplet transition mode is more complex and sensitive, which affects not only the forming quality but also the metallurgical quality. Therefore, it is necessary and urgent to explore and optimize its process. In this study, the macroscopic component formation mechanism and microstructure influence mechanism of WAAM and MWAAM processes were studied, and TC11 titanium alloy was taken as the target alloy considering its huge application prospect in the aerospace field. In addition, the effects of different processes on the morphology, microstructure, phase composition, mechanical properties and wear properties of the deposited samples were systematically studied through the deposition experiments controlled by different heat source velocities. The results show that the thin-walled TC11 components deposited by MWAAM exhibit good mechanical properties and excellent wear resistance. This study is of great significance for the intelligent and industrialized development of MWWAM technology.

Experimental investigation and mechanical characterization of Al 5051 with nickel/titanium powder metal matrix composites using stir casting

Experimental investigation and mechanical characterization of Al 5051 with nickel/titanium powder metal matrix composites using stir casting

Sericin improves alginate-gelatin hydrogels’ mechanical properties, porosity, durability and viability of fibroblast in cardiac spheroids

Biofabrication of cardiac patches is a challenging strategy proposed as an alternative to transplantation for end-stage heart failure patients. The optimization of the bioink used for this aim can be limited by costs, properties and biocompatibility of its building blocks. Lately, sericin has emerged within a wide range of natural proteins thanks to its bioadhesive and biocompatibility potential. In this study, we assessed for the first time the effects of adding silk sericin on alginate-gelatin hydrogels, proposed for cardiac applications. To this aim, we first biofabricated sericin-containing hydrogels with increasing protein concentrations. Thus, we characterized hydrogels’ mechanical behaviour, porosity and structure through rheology, Brillouin microspectroscopy and SEM. Then, we bioprinted the formulated hydrogels and evaluated their effects on human cardiac spheroids (CSs) in vitro. Our mechanical characterisation demonstrated that adding sericin significantly enhanced the elasticity and the viscosity of alginate-gelatin hydrogels. Sericin also modified hydrogels’ swelling behaviour and their pore size, increasing by 20%, 62%, and 92% in Ser1%, Ser2% and Ser3%, respectively. Although Ser1% did not exhibit significant effects on CSs, Ser2% and Ser3% enhanced cardiac cell viability for up to 14 days compared to the sericin-free hydrogel by acting on the fibroblast population. Sericin-based bioinks showed better printability and durability with +33% and +28% intact patches after 28 days of culture at 37°C compared to alginate-gelatin. Altogether our results validated the use of sericin as a promising component for the optimization of bioink intended for cardiac applications.

Characterization of acetolactate synthase genes and resistance mechanisms of multiple herbicide resistant Lolium multiflorum

Combining imidazolinone-tolerant wheat with imazamox presents an effective solution to combat weed resistance. However, Lolium multiflorum, a troublesome resistant weed infesting wheat fields, may have developed resistance to imazamox, and the potential resistance mechanisms are intriguing. In this study, we explored the susceptibility of L. multiflorum to imazamox and investigated the resistance mechanisms, including the contribution of the target enzyme acetolactate synthase (ALS) to resistance and the presence of non-target-site resistance (NTSR). Eight L. multiflorum populations suspected of being resistant to imazamox were collected, and six populations exhibited resistance, ranging from 2.45-fold to 16.32-fold. The LmALS1 gene from susceptible population D3 plants and multiple copies of the LmALS gene (LmALS1, LmALS2, LmALS2α, LmALS3, LmALS3α, LmALS3β) from resistant populations D5 and D8 plants were separately amplified. Two mutations (Pro/Gln197 to Thr, Trp574 to Leu) were found in LmALS1 in the resistant populations. Compared to D3, LmALS1 was overexpressed in D5 but not in D8. The presence of LmALS1 mutants (LmALS1-Thr197 and LmALS1- Leu574), along with LmALS2, LmALS3, and their subunits, contribute to the resistance phenotype by increasing bonding energies, weakening hydrogen bonds, or decreasing protein binding pocket volumes and surface area. Additionally, D5 and D8 populations exhibited multiple resistance (>40-fold) to three other ALS inhibitors: pyroxsulam, flucarbazone-sodium, and mesosulfuron-methyl. Pre-treatment with malathion and 4-chloro-7-nitrobenzoxadiazole (cytochrome P450 monooxygenase and glutathione S-transferase inhibitors respectively) reversed the resistance of the D8 population and partially reversed the resistance of the D5 population to imazamox. This study characterizes ALS genes and extends our knowledge into the ALS resistance mechanisms involved in L. multiflorum. It also deepens our understanding of the complex diversification resistance mechanisms, thereby facilitating advances in weed resistance management strategies in wheat fields.