Mechanical Performance Analysis Research Articles

Rice husk ash and recycled sand as synergistic substitutes in ultra-high performance concrete: Microstructural, mechanical performance, and eco-economic analysis

Quartz sand and silica fume (SF), commonly used in UHPC production, are costly and contribute to dust pollution and significant carbon emissions. In this work, we explored the preparation of an environmentally friendly ultra-high performance concrete (e-UHPC) by substituting SF and quartz sand with rice husk ash (RHA) in ratios of 10 %, 20 %, and 30 %, and recycled building sand (RS) in ratios of 25 %, 50 %, and 75 %. We assessed the impact of these substitutions on workability, mechanical strength, hydration products, and the micromechanical characteristics of the interfacial transition zone. In addition, an environmental and economic assessment index for e-UHPC was introduced. Results showed that while RHA and RS reduced the flowability of e-UHPC, RHA helped mitigate the compressive strength loss due to RS (3.9 %-9.7 %). RHA accelerated early hydration, and improved densification in the transition zone, enhancing late hydration and refining the pore structure of e-UHPC. Notably, a 10 % RHA replacement rate optimally improved early hydration efficiency and minimized CH content. The combination of 10 % RHA and 25 % RS proved most effective in optimizing the interfacial transition zone and improving the pore structure of e-UHPC. Importantly, e-UHPC reduces the carbon footprint at a lower cost and offers significant environmental and economic advantages over traditional UHPC. The results of this study will promote the incorporation of construction and agricultural wastes into concrete.

Mechanical Performance Analysis Method for Ribbed H-Section Aluminum Alloy Members with Initial Curvature and Torsion Angle

In this study, an experimental investigation was conducted on the axial compression performance of ribbed H-section aluminum alloy members with initial curvature and torsion angle under varying boundary conditions, including one end hinged with the other rigidly connected, and both ends rigidly connected. Ultimate bearing capacity and failure modes were identified under real loads and subsequently compared with previous findings from our research group on members with hinged ends. To account for initial imperfections introduced during processing and transportation, 3D scanning technology was utilized to capture the precise geometrical dimensions, constructing an accurate numerical simulation model. The experimental results were corroborated with numerical simulations, leading to the proposal of an analytical method for members with initial curvature and torsion angle. Furthermore, extensive parametric analysis elucidated the impact of initial curvature, torsion angle, and slenderness ratio on the ultimate bearing capacity, culminating in the formulation of the stability factor and calculated length factor based on numerical outcomes. The study discovered significant variances in bearing capacity under different boundary conditions, with one-end hinged and one-section rigidly connected, and two-end rigidly connected conditions exhibiting 1.4 and 2.1 times the capacity of the hinged-at-both-ends scenario. Under different boundary conditions, the axial compression members were subjected to flexural-torsional buckling failure. Moreover, when the ultimate bearing capacity was reached, the lower flange of the member and the web near the lower flange appeared obvious buckling phenomenon. The numerical analysis aligned well with experimental data, validating the simulation method's reliability and revealing the stress distribution and evolution during member failure. These findings offer vital theoretical insights and technical support for engineering design and practical applications.

Annealing impact on mechanical performance and failure analysis assisted with acoustic inspection of carbon fiber reinforced poly‐ether‐ketone‐ketone composites under flexural and compressive loads

AbstractThis study investigates the effect of the annealing treatment for carbon fiber reinforced Polyether‐ketone‐ketone (CF/PEKK) composite structures under flexural and compressive loadings through reference, pre‐damaged, and annealed sample sets. Significant recovery of pre‐existing damage is observed after the annealing process, following both flexural and compressive loading. Acoustic emission (AE) inspection is employed to monitor the failure behavior and assess the impact of pre‐damage and annealing on CF/PEKK composite. Initially, AE inspection reveals that the reference CF/PEKK material exhibits a notable fiber‐related failure with 85% of cumulative AE counts under flexural load, whereas matrix‐related failures are more pronounced with 92% cumulative AE counts under compressive load. Pre‐damages in the matrix alter the cumulative count percentages and initiation time that are related to matrix, interface, and fiber‐related failures, under flexural and compressive loadings. After annealing, each cumulative AE count percentages are comparable to reference sample values, due to changes in microstructure and relieving of residual stresses. The annealing effect is further validated through dynamic scanning calorimetry (DSC) analysis results with increased glass transition temperature (Tg) and degree of crystallization (Xc). Overall, these findings indicate that annealing treatment effectively restores structural integrity and improves the mechanical performance of CF/PEKK composites.Highlights Annealing aims for damage recovery in CF/PEKK under flexural and compressive loads. Significant damage recovery in CF/PEKK is seen after annealing. Annealing raises Tg and crystallinity, and enhances CF/PEKK structural integrity.

Multi-scale modeling and mechanical performance analysis of finger seals with plain woven C/C composite

The application of carbon fibers reinforced carbon matrix (C/C) composite can solve the local wear of metallic finger seals effectively. However, the performance of C/C composite finger seal is complex and variable, which further decreases the sealing performance and life. Therefore, a method of multi-scale modeling and mechanical performance analysis for plain woven C/C composite finger seals was conducted. The circumferential finger beams of C/C composite were modeled by multi-scale structural analysis and weaving simulation. The radial static and dynamic stiffness characteristics of finger beams were investigated. The results showed that the radial static stiffness of the finger beam with three layers was about 3 times that with single layer. The radial stiffness of circumferential finger beams presented a periodic distribution pattern with a period of 90°. The radial dynamic stiffness of C/C composite finger beams increased with the excitation displacement amplitude and rotor speed. But the magnitude and fluctuation degree of dynamic stiffness were greater than those of static stiffness. A large difference in radial stiffness will lead to local wear and hysteretic leakage. This study lays a foundation for the analysis and optimization of the hysteresis and wear characteristics of C/C composite finger seals.

Statistical analysis of natural and mechanical ventilation performance in improving indoor air quality, thermal comfort, and perceived air quality in a healthcare facility

Ventilation strategies in healthcare facilities are mainly directed towards mechanical systems. Due to patients’ preferences or the necessity of terminal reheat/recool, Air Handler Units are often turned off or windows are opened when mechanical systems are active. This leads to poor IAQ, nosocomial infections, and energy loss. Besides, ventilation systems are not typically intended to optimize user satisfaction. Using field measurements in 140 spaces, survey studies, and statistical analysis, this study compares ventilation strategies in providing IAQ, thermal comfort, and Perceived Air Quality as an indicator of user satisfaction. 315 samples were collected for air velocity, air temperature, relative humidity, PAQ, odor intensity, and VOC concentrations. Lowest to highest pollutant concentrations were observed respectively in mechanical ventilation with two open windows, mechanical ventilation with one open window, natural ventilation with two open windows, mechanical ventilation with closed windows, natural ventilation with one open window, and nonventilated spaces. There was no evidence of an effect of ventilation strategies on environmental parameters and user satisfaction. Users’ thermal comfort and air quality satisfaction were not guaranteed even when ventilation rate, pollutant concentrations, and environmental parameters were within the permissible range. Findings support the efficient performance of natural ventilation in providing acceptable air quality.

Design and Mechanical Performance Analysis of Ti6Al4V Biomimetic Bone with One-Dimensional Continuous Gradient Porous Structures

Design and Mechanical Performance Analysis of Ti6Al4V Biomimetic Bone with One-Dimensional Continuous Gradient Porous Structures

Mechanical simulation and electrical performance analysis of high current connectors

Abstract Automotive high-current connectors are one of the key components in new energy vehicles, used for transmitting high currents within the vehicle. However, vibration is unavoidable during the actual operation of connectors. This vibration directly affects the contact pressure between the connector’s contact points, thereby influencing the electrical contact performance of the connector. This paper simplifies the contact components of the electrical connector using a cantilever beam model and conducts theoretical calculations of the contact pressure. Utilizing Ansys Workbench simulation software, the study investigates the contact pressure of the electrical connector under static and various sinusoidal vibration conditions, followed by sinusoidal frequency sweep vibration experiments. The research findings indicate that under vibration conditions, the contact pressure is lower than that under static conditions, and the electrical resistance fluctuates during the vibration process.

Reinforcing dental restoration material PMMA with SS 316L nanoparticles for mechanical performance analysis

Reinforcing dental restoration material PMMA with SS 316L nanoparticles for mechanical performance analysis

Protruding Boron Nitride Nanotubes on the Al2O3 Surface Enabled by Tannic Acid-Assisted Modification to Fabricate a Thermal Conductive Epoxy/Al2O3 Composite.

Over the past few years, the ability to efficiently increase boron nitride nanotube (BNNT) production has opened up ample research possibilities. BNNT has garnered significant attention for diversifying its industrial applications. However, the problem of poor processability resulting from agglomeration and uneven distribution has emerged as a major challenge to integrating BNNT into the polymer matrix for composite material formation. Utilizing noncovalently attached molecules with various reactive sites can be a logical method to enhance the compatibility of BNNT with different polymers. The present study explored a simple approach to protruding BNNT onto the surface of Al2O3 through tannic acid (TA)-assisted generation of alkyl chains (octadecylamine, ODA) to fabricate Al2O3@ODA-BNNT. The subsequent compounding of Al2O3@ODA-BNNT with epoxy polymer generates interconnected thermal conduction pathways, thereby improving the thermal conduction and mechanical performance of the composites. The current research approach allows for the even distribution of BNNT throughout the polymer matrix, as demonstrated by optical characterization, mechanical performance analysis, and isotropic thermal conductivity analysis. The fabricated epoxy composite by incorporating a 2 wt % (BNNT = 1.3 wt % and ODA = 0.7 wt %) ODA-BNNT exhibited 5.117 W/mK thermal conductivity and 7.43 MPa mechanical stress. Thermal conductivity improved by 2528, 76.56, and 54.7%, while mechanical stress enhanced by 270, 221, and 34% compared to neat polymers without BNNT and virgin BNNT epoxy composites, respectively.

Analysis and Simulation of Permanent Magnet Adsorption Performance of Wall-Climbing Robot

In response to problems such as insufficient adhesion, difficulty in adjustment, and weak obstacle-crossing capabilities in traditional robots, an innovative design has been developed for a five-wheeled climbing robot equipped with a pendulum-style magnetic control adsorption module. This design effectively reduces the weight of the robot, and sensors on the magnetic adsorption module enable real-time monitoring of magnetic force. Intelligent control adjusts the pendulum angle to modify the magnetic force according to different wall conditions. The magnetic adsorption module, using a Halbach array, enhances the concentration effect of the magnetic field, ensuring excellent performance in high-load tasks such as building maintenance, bridge inspection, and ship cleaning. The five-wheel structural design enhances the stability and obstacle-crossing capability, making it suitable for all-terrain environments. Simulation experiments using Maxwell analyzed the effects of the magnetic gap and the angle between the adsorption module and the wall, and mechanical performance analysis confirmed the robot’s ability to adhere safely and operate stably.

Determining the mechanical properties of biomaterial-based economic thermoplastic composites reinforced with hemp fibres

In this study, continuous reinforcement materials of hemp fibres and matrix polymers (staple polylactic acid (PLA), staple bicomponent PLA) were carded in a conventional carding machine. Various proportions of the hemp fibre reinforcement material, ranging from 20%, 30%, 40%, 50%, and 60% were used in the production of biocomposite structures. We have further studied the effect of several carding passages (up to 3 passages) on the strength performance of both the staple PLA and the staple bicomponent PLA matrix. To obtain composite samples, the carded webs were further consolidated in the hot press machine. Further mechanical performance analysis was carried out in both the cross direction as well as parallel to the machine direction. It was observed that the introduction of reinforcing hemp fibre shows an increase in tensile strength up to the critical fibre loading amount and a decrease in tensile strength after the critical fibre loading amount. The highest tensile strength of 35.84 MPa was obtained for (40HEMP / 60PLA / M / P3), applied to the composite structures in the machine production direction, while the lowest value was 14.70 MPa (60HEMP / 40BPLA / M / P1), respectively.

From microchips to microneedles: semiconductor shear testers as a universal solution for transverse load analysis of microneedle mechanical performance

Abstract Microneedles are a promising technology for pain-free and efficient pharmaceutical delivery. However, their clinical translation is currently limited by the absence of standardized testing methods for critical quality attributes (CQAs), such as mechanical robustness, which are essential for demonstrating safety and efficacy during regulatory review. A key aspect of mechanical robustness is transverse load capacity, which is currently assessed using diverse, non-standardized methods, which have limited capability to measure transverse failure forces at different heights along a microneedle. This is critical for understanding mechanics of potential failure modes during insertion after skin penetration. In this work we utilize a wire bond shear tester, a piece of test equipment widely used in the semiconductor industry, to measure the transverse load capacities of various microneedle designs. This approach is compatible with diverse microneedle types, geometries, and materials, and offers high-throughput and automated testing capabilities with high precision. We measure transverse failure loads with micron-scale control over the test height and have established comprehensive profiles of mechanical robustness along the length of different microneedle designs, which is a capability not previously demonstrated in literature for polymeric and metal microneedles. Transverse failure forces were 10±0.3 gf to 128±12 gf for wire bonded gold and silver microneedles, 11±0.7 gf to 480±69 gf for conical and pyramidal polymeric microneedles, and 206±80 gf to 381±1 gf for 3D printed conical stainless steel microneedles. Additionally, we present standardized definitions for microneedle structural failure modes resulting from transverse loads, which can facilitate root cause failure analysis and defect detection during design and manufacturing, and aid in risk assessment of microneedle products. This work establishes a standardized approach to evaluating a significant CQA of microneedle products, which is a critical step towards expediting their clinical adoption.

Design and mechanical performance analysis of T-BCC lattice structures

The Body-Centered Cubic (BCC) lattice structure is commonly used in high-end equipment fields, such as aerospace, due to its superior mechanical properties, lightweight characteristics, and ease of processing. However, there is a need to improve the performance-to-weight ratio of the traditional BCC lattice structure. This study utilizes topology optimization to design a T-BCC lattice structure based on the BCC unit cell, with the aim of maximizing stiffness. A model proposing the characterization of the Young's modulus of BCC lattice structures is presented. The model is based on calculations of cell porosity and beam stress analysis, assuming a large cell. This approach indirectly enables the calculation of the Young's modulus of T-BCC lattice arrays in multiple dimensions. Simulation and experimental comparison were used to analyze the compressive performance and load-bearing modes of T-BCC lattice structures, revealing the mechanisms of compressive deformation and failure modes. The accuracy of the characterization model for Young's modulus was found to be 93.1%. Compared to BCC lattice structures designed by traditional methods, T-BCC lattice structures designed via topology optimization can increase the Young's modulus by up to 36% and yield strength by 37.2%. This suggests that T-BCC lattice structures are a more lightweight and efficient solution for designing components in high-end equipment fields.

Experimental design, mechanical performance and mechanism analysis of C30 phosphogypsum-based concrete

The present study aimed to increase the utilization of phosphogypsum and reduce cement consumption. Single-factor experiments were designed to the effects of water-cement ratio (0.45–0.30), silica fume (1 %∼7 %), cement dosage (0 %∼20 %), and the RPG/HPG (20/80–0/100) on mechanical properties of phosphogypsum-based concretes (PGBCs). A new phosphogypsum-based concrete was prepared to meet the compressive strength requirement of C30 grade. The maximum 28d compressive strength of this PGBC reached 45.1 MPa. Simultaneously, the effect mechanisms of above four factors on the mechanical properties of PGBCs were discussed by combining XRD and SEM results. Moreover, the volume stability, elastic parameters, and compressive constitutive model of this PGBC with compressive strength above 30 MPa were investigated. This PGBC used more than 80 % phosphogypsum and 10∼20 % cement, exhibiting well economy and environmental friendliness. Moreover, the constitutive model was established to well predict the compressive behavior of PGBC with different RPG/HPG relative ratios. This PGBC had better volume stability and weaker deformation resistance than cement-based concrete. The present results can provide more theoretical and technical supports for the large utilization of PG.

Mechanical performance study of PVA fiber-reinforced seawater and sea sand cement-based composite materials

Due to the swift progress in the construction sector, there is a global concern about the potential scarcity of river sand and freshwater resources. The development of new construction materials is considered an inevitable trend for industry growth. PVA fibers, known for their strong corrosion resistance, cost-effectiveness, and high toughness, have the potential to enhance the corrosion resistance and seismic performance of structures in marine environments. However, their mechanical properties and durability in the seawater and sea sand environment are not well understood. Therefore, the investigation of the impact of seawater and sea sand on the mechanical properties and durability of PVA fiber-reinforced cement composites is considered crucial. A mechanical performance analysis of PVA fiber-reinforced seawater and sea sand fiber cement composites was conducted in this study. PVA fiber volume fractions of 0%, 0.75%, and 1.5%, cement composite matrix strength grades of C30 and C50, and curing periods of 28 days, 90 days, and 180 days were examined, investigating their influence on the bending toughness of PVA fiber-reinforced seawater and sea sand cement composites. Specific conclusions include the addition of fibers increased the peak bending load, had a less corrosive effect in seawater, and improved the flexural toughness of the material. The most significant improvement was observed at 1.5% fiber content, where the load-deflection curve was fuller and the energy absorption capacity of the material increased by 33–109%, maintaining good bending toughness. Furthermore, higher fiber contents are required for high-strength cementitious composites to improve flexural toughness and durability. The formulation of calculation formulas for predicting bending strength and corresponding deflection, which fit well with the experimental results; and the development of a calculation model for the bending toughness index of PVA fiber-reinforced seawater and sea sand cement composites, providing an effective prediction of material bending toughness.

Analysis and structural optimization of tree-type dynamic pressure groove mechanical seal performance

Abstract This study investigates the influence of the order and groove ratio of a tree-shaped groove on the sealing performance of a mechanical seal system using numerical simulations. A three-dimensional geometric model of the tree-shaped groove is established using SOLIDWORKS, and the mesh is divided in ANSYS Meshing before being imported into Fluent software for analysis. The single-factor experimental method is employed to evaluate the impact of different parameters on the opening force and leakage rate by varying one parameter while keeping others constant. The simulation results reveal that in the low-speed range, the tree-shaped groove with a groove ratio of 3:4:5 exhibits a larger opening force. Conversely, in the high-speed range, the three-stage tree-shaped groove with a groove ratio of 1:1:1 demonstrates a lower leakage rate and a larger opening force. The findings highlight the significant impact of the order and groove ratio of the tree-shaped groove on the sealing performance of the non-contact mechanical seal. The three-stage tree-shaped groove outperforms the second and fourth stages in terms of mechanical sealing performance, particularly in regard to the opening force. This study provides valuable insights into optimizing the design of tree-shaped grooves in mechanical seal systems to enhance their overall performance and efficiency.

Mechanical performance analysis of functionally graded triply periodic minimal surfaces

To address the issue of a single gradient direction in the gradient design of triply periodic minimal surfaces, two functional gradient schemes, trapezoidal and W-shaped, were proposed based on the stress distribution range of the uniform thickness porous structure model using the primitive minimal surface porous structure. These structures were manufactured using a photosensitive resin through stereolithography additive manufacturing technology. Through finite element analysis and experimental validation, it was observed that as porosity decreases, the bending resistance of the uniform thickness model increases. The designed functional gradient porous structures were compared with the uniform thickness model. The results show that the designed gradient porous structure has a higher strength and bending stiffness than the uniform thickness porous structure. The proposed design can improve the bending performance of the porous structure. The W-shaped gradient porous structure with fine control of porosity variation range had better ability to improve structural bending performance than the trapezoidal gradient design.

Mechanical performance and anisotropic analysis of rubberised 3D-printed concrete incorporating PP fibre.

The research investigates the effects of substituting sand with rubber particles derived from waste tyres-up to 40% by volume-and the inclusion of polypropylene (PP) fibres. Unlike steel fibres, which can cause operational challenges and surface irregularities in the printing process, PP fibres' flexibility integrates well within the concrete matrix. This integration ensures smooth extrusion and a high-quality surface finish, enhancing the printability of the concrete. The study's findings reveal that including rubber particles and PP fibres impacts the concrete's properties, showing a general decline in compressive and flexural strengths as the rubber content increases. Nevertheless, the PP fibre-enhanced mixtures maintain sufficient structural strength, demonstrating an anisotropic compressive strength above 30MPa and a flexural strength of 4MPa. These results underscore the feasibility of using rubberised 3D-printed concrete with PP fibres in sustainable construction practices, aligning with standards (ACI 318:2018) and contributing to eco-friendly and innovative construction methodologies.

Mechanical performance analysis of double-dovetail joint applied to furniture T-shaped components

T-shaped mortise and tenon members are the main structure of traditional Chinese furniture. In this paper, the double-dovetail joint used for face-to-face joint of rubber wood (Hevea brasiliensis Muell. Arg) is transformed into a new type of double-dovetail joint and rounded double-dovetail joint for T-shaped members of point joint structure. The ultimate pull-out test and bending strength test were carried out on the two structures and three structures of oval mortise, round rod mortise and right angle mortise. The results show that the ultimate pull-out force of the round double-dovetail joint is 39% higher than that of the double-dovetail joint, and the bending resistance capacity is 8.9% higher, and the strength and stability are better than those of other split mortises and tenons, which proves that this structure can be used in actual production, and also proves that the mortise and tenon connected by the surface has the possibility of transforming into a point connection structure. The concave structure of the rounded double-dovetail joint makes the mortise and tenon fit well, the tenon squeezed tight, and a good bonding effect was achieved. This structure can also provide greater friction and resistance, delay rubber adhesive failure and improve the stability.

Polyaluminum enhanced dehydrated cement paste activated slag: Mechanical performance and microstructural analysis

Dehydrated cement paste (DCP) activated slag offer a promising sustainable alternative to traditional Portland cement, but their inadequate mechanical strength limits practical applications. This study investigates the potential of polyaluminum chloride (PAC) to enhance the performance of DCP activated slags, utilizing multi-scale characterization methods. Results demonstrate that PAC incorporation significantly promotes strength development, enabling the binder to meet requirements for most engineering applications. PAC accelerates Ca(OH)2 consumption, and facilitates additional hydration product formation that refines the pore structure, leading to the densification of samples. These improvements in strength and microstructure are attributed to the modified slag dissolution and the enhanced polymerization of the C-A-S-H gel. Furthermore, the underlying role of PAC on the hydration, mechanical performance and microstructural development of DCP activated slags are discussed.