Values Of Normal Stress Research Articles

Effect of ultrasound geometry on the production efficiency of damaged starch: Determining rheology parameters, and non-isothermal reaction kinetics

Present study investigates the effects of probe size geometry on thermodynamic kinetics, rheology, and microstructure of wheat and tapioca starch. Ultrasound treatment using different probe diameters (20 mm and 100 mm) significantly influenced the gelatinization process. Results showed reduced enthalpy (ΔH) and Gibbs energy (ΔG), indicating enhanced gelatinization efficiency. According to the results, using a 20 mm and 100 mm probe leads to a reduction of 52.7 % and 68.6 % in reaction enthalpy for wheat starch compared to native starch, respectively. Microstructure analysis revealed structural changes, with ultrasound treatment leading to granular fractures and a sheet-like structure with air bubbles. The rheological behavior of the starches is found to exhibit shear thinning behavior, with the Casson model providing the best fit for the experimental data. Moreover, rheology modeling using Herschel-Bulkley and power law models showed increased viscosity and shear stress in larger probes. Numerical simulation data demonstrated that probe size influenced ultrasonic pressure, sound pressure level, and thermal power dissipation density, affecting fluid motion and velocity field components. Moreover, the maximum dissipated power decreases from 8.43 to 0.655 mW/m3 with an increase in probe diameter from 20 to 100 mm. The average yield shear stress values are calculated as 3.36 and 3.14 for wheat and tapioca starches, respectively. The larger probe diameter leads to greater entropy increases, with tapioca starch showing a 4.72 % increase and wheat starch a 4.97 % increase, compared to 2.56 % and 3.11 %, respectively, with the smaller probe. Additionally, the Keller-Miksis model provided insights into bubble dynamics, revealing increased pressure and temperature with higher pressure amplitudes.

Identification of Water Hyacinth Fiber (Eichornia Crassipes) and Polyethylene Terephthalate Waste as an Alternative Material

Synthetic fiber is reinforcing material made and developed by human involving chemical reactions to change the structure or strengthen certain material. Synthetic fiber has high temperature resistance and is sturdy, strong, and elastic. Although synthetic fiber has good properties, it poses a serious problem of non-organic waste. Thus, it encourages changes in composite technology to pay more attention to natural fiber that are enviromentally friendly. This research used water hyacinth fiber and plastic waste as filler and polyester resin as matrix, to determine the mechanical properties of tensile test. The research employed hand lay-up method by arranging the fiber randomly at the composition of fiber variations of 10%, 20%, and 30% of the stress, strain, and modulus elasticityof the composite. The research finding were described in each fiber variations, where the average stress value at fiber variations of 10% 48,556 Mpa, strain was 1,4% and modulus elasticity was 36,264 Mpa. In addition, the fiber variation of 20% contained an average stress value of 44,178 Mpa, strain of 1,3% and modulus elasticity of 35,037 Mpa. Lastly, the fiber variation 30% contained an average stress value of 54,556 Mpa, strain of 1,2% and modulus elasticity of 46,811 Mpa. In the meantime, the tensile strength of 30% fiber variation owned the largest value compared the other fiber variations. While the 10% fiber variation strain owned the largest value compared the other fiber variations. Additionally, the elastic modulus of 30% fiber variation owned the largest value compared to the other fiber variations.

The Effect of Welding Current on Shear Test and Microstructure TIG Brazing of Cemented Carbide and Steel

The need for good welding results as knowledge in the process of welding different types of materials is needed in the community, and this res- earch is to determine the effect of variations in welding currents of different types of metals on cemented carbide and carbon steel using the TIG brazing method. For the base metal, YG6 cemented carbide and SS400 carbon steel with CuSi filler metal are used. The sample method is made by connecting different types of materials with the welding process using variations in current of 60 ampere; 80 ampere, and 100 ampere. The mechanical properties of this material connection were tested using the Hydraulic Universal Testing Machine, while for the microstructure examination, a microstructure test tool with a magnification of 100 x was used. The results of the tests revealed that the highest average compressive strength was 22.2 kN at a welding current variation of 60 A, and the lowest average value was 10.2 kN at a welding current variation of 100 A. Furthermore, for the average value of shear stress, the highest value at 60 A variation is 148 N/mm2 and the lowes t value is at 100 A welding current, which is 67 N/mm2. The res ults of testing the microstructure of the connection area s how that the higher the current strength, the more enriched the Cu content and will affect the size and spacing of Si grains.

Simulasi Pengaruh Jumlah Palang Rim Sepeda Motor Terhadap Equivalent von Mises stress dan Safety Factor Menggunakan Software Ansys

Rim or wheels have various types of model designs and the number of spokes. Therefore, those wheels can have a different response on each rim model when subjected to loads such as impact loads. In this simulation, impact load testing is carried out on the rim, with variations of 4 types of geometry where this geometry differs in the design of the number of spokes. By finding the Safety Factor value on each rim, the most optimal rim design can be determined. Explicit Dynamics can solve this problem because the impact on the simulation occurs in a very short time. In this study, the design of a cast wheel type motorcycle rim with spokes number of 5, 6, 10 and 12 with a uniformly applied impact speed of 10 km/h. The rim material used was aluminum 6061 T6 and the projectile material used was aluminum alloy. The designed rim has a diameter of 35.56 cm and a width of 4.01 cm and a mass of 2415 gram. Solidworks and Ansys software based on the finite element method were used to make it easier to design cast wheel rims. By using this software, the rim can be designed so that it can be analyzed for stresses and strains that occur when simulating impact loads on the rim plane. The simulation results show that rims with spoke 10 and 12 are categorized as safe because they have a lower average stress value than rims 5 and 6 and have a Safety Factor value above 1. In other words, rims with 10 and 12 number of spokes are the optimal design in terms of cost and strength.

Анализ напряженно-деформированного состояния узловых соединений высотных зданий при учете климатических воздействий

Purpose: to analyze the design solutions of the junctions of floors with external walls in buildings erected using monolithic technology. To identify defects and damages that occur on facades and overlaps with perforations for thermal pads during construction and operation. To investigate by numerical methods the stress-strain state of the overlap disk at the junction with the outer wall, taking into account temperature influences. Materials and methods: the standard version of the nodal connection of a monolithic building of various storeys is considered. The fragment of the junction joint of the overlap disk with the wall was modeled in the Ansys and SCAD software complexes. The model consisted of an anisotropic material — concrete and reinforcement rods included in it. The behavior of the stress-strain state under various temperature influences was studied. Results: numerically, taking into account geometric parameters and temperature loads, the patterns affecting the nature of changes in the values of normal stresses in the characteristic sections of the perforated plate are revealed and the existing types of design solutions are evaluated. The locations of stress concentration zones and their impact on performance are determined. Practical significance: it is shown that the most dangerous cross-section in perforated discs of overlaps takes place at the key joints. It is determined that vulnerability in such compounds is caused by the influence of alternating cyclic temperatures. Patterns leading to an increase in normal stresses at stress concentration sites have been established. Fundamentally new design solutions have been proposed, protected by utility model patents, which allow to reduce stress values and thereby ensure higher performance in monolithic buildings, including high-rise ones.

Barriers and facilitators for oral health screening among tobacco users: a mixed-methods study

ObjectivesTobacco consumption adversely affects general and oral health and is considered one of the significant public health burdens globally. The present study aims to assess the barriers and facilitators for attending oral and dental health screening among tobacco users who seek cessation advice.MethodologyThe present mixed-methods study used group concept mapping (GCM) to identify the facilitators/barriers to attending oral health screening among young adults attending face-to-face and virtual Tobacco Cessation Clinic at King Saud University (Riyadh, Saudi Arabia) between September 2022 and April 2023. Study investigators included healthcare social workers, dental interns, and oral and maxillofacial medicinists. Information about demographics, general health, oral/dental health and tobacco use were collected using self-completed questionnaires. The barriers and facilitators were assessed following GCM by brainstorming, sorting, rating, and interpretation activities. Descriptive, multidimensional scaling and hierarchical cluster analysis were used to describe the study participants and produce concept maps of the generated statements.ResultsThe study included 148 participants who generated 67 statements summarised into 28 statements as facilitators or barriers. Based on a 5-point importance scale, the participants indicated the importance of facilitators under health-related cluster [e.g. when I feel pain] as the highest, followed by personal [e.g. to maintain my mouth hygiene], social [e.g. the quality of treatment] and financial clusters [e.g. the reasonable cost]. Concerning barriers, financial factors [e.g. high cost] acted as the highest-rated barrier, followed by personal [e.g. lack of dental appointments] and health-related [e.g. worry that dental problems will worsen]. The social factors were the least considerable barrier [e.g. lack of time]. Clustering these facilitators/barriers on the concept map indicated their conceptual similarity by an average stress value of 0.23.ConclusionPain was the most important facilitator to attending oral health screening by young adults seeking tobacco cessation advice. Notable barriers included the high cost of dental treatment and the lack of scheduled appointments. Thus, oral health care providers need to consider scheduling periodic and timely dental check-ups to prevent and reduce the burden of tobacco-associated and pain-causing oral diseases.

Finite element method analysis of bone stress for variants of locking plate placement

This study investigates the optimal placement of locking plate screws for bone fracture stabilization in the humerus, a crucial factor for enhancing healing outcomes and patient comfort. Utilizing Finite Element Method (FEM) modeling, the research aimed to determine the most effective screw configuration for achieving optimal stress distribution in the humerus bone. A computer tomography (CT) scan of the humerus was performed, and the resulting images were used to create a detailed model in SOLIDWORKS 2012. This model was then analyzed using ANSYS Workbench V13 to develop a finite element model of the bone. Four different screw configurations were examined: 4 × 0°, 4 × 10°, 4 × 20°, 2 × 20°; 2 × 0°. These configurations were subjected to bending in the XZ and YZ planes, as well as tension and compression along the Z axis. The research identified the 2 × 20°+2 × 0° configuration as the most beneficial, with average stress values below 30 MPa and peak stress values below 50 MPa in 3-point bending at the first screw. This configuration consistently showed the lowest stress values across all loading scenarios. Specifically, stress levels ranged from 20 MPa to 50 MPa for bending in the XZ plane, 20 MPa–35 MPa for bending in the YZ plane, 20 MPa–30 MPa for extension in the Z-axis, and 18 MPa–25 MPa for compression in the Z-axis. The 4 × 10° and 4 × 20° configurations also produced satisfactory results, with stress levels not exceeding 70 MPa. However, the 4 × 0° configuration presented considerable stress during bending and compression in the Z-axis, with stress values exceeding 100 MPa, potentially leading to mechanical damage. In conclusion, the 2 × 20°; 2 × 0° screw configuration was identified as the most effective in minimizing stress on the treated bone. Future work will involve a more detailed analysis of this methodology and its potential integration into clinical practice, with a focus on enhancing patient outcomes in bone fracture treatment.

A Combined Computational and Experimental Analysis of PLA and PCL Hybrid Nanocomposites 3D Printed Scaffolds for Bone Regeneration.

A combined computational and experimental study of 3D-printed scaffolds made from hybrid nanocomposite materials for potential applications in bone tissue engineering is presented. Polycaprolactone (PCL) and polylactic acid (PLA), enhanced with chitosan (CS) and multiwalled carbon nanotubes (MWCNTs), were investigated in respect of their mechanical characteristics and responses in fluidic environments. A novel scaffold geometry was designed, considering the requirements of cellular proliferation and mechanical properties. Specimens with the same dimensions and porosity of 45% were studied to fully describe and understand the yielding behavior. Mechanical testing indicated higher apparent moduli in the PLA-based scaffolds, while compressive strength decreased with CS/MWCNTs reinforcement due to nanoscale challenges in 3D printing. Mechanical modeling revealed lower stresses in the PLA scaffolds, attributed to the molecular mass of the filler. Despite modeling challenges, adjustments improved simulation accuracy, aligning well with experimental values. Material and reinforcement choices significantly influenced responses to mechanical loads, emphasizing optimal structural robustness. Computational fluid dynamics emphasized the significance of scaffold permeability and wall shear stress in influencing bone tissue growth. For an inlet velocity of 0.1 mm/s, the permeability value was estimated at 4.41 × 10-9 m2, which is in the acceptable range close to human natural bone permeability. The average wall shear stress (WSS) value that indicates the mechanical stimuli produced by cells was calculated to be 2.48 mPa, which is within the range of the reported literature values for promoting a higher proliferation rate and improving osteogenic differentiation. Overall, a holistic approach was utilized to achieve a delicate balance between structural robustness and optimal fluidic conditions, in order to enhance the overall performance of scaffolds in tissue engineering applications.

Micromechanical simulation of interfacial fracture behavior using cohesive zone modeling for TRIP steel composite with ceramic particles

ABSTRACT In this work, ceramic particle and metal matrix interfacial delamination in transformation-induced plasticity steel composite reinforced with magnesium partially stabilized zirconia particles is investigated using a parametric modeling approach. The global behavior of the composite is modeled using elastic and Johnson-Cook plasticity models for the ceramic particles and the austenite matrix. Interfacial degradation is implemented through a cohesive zone model with a traction-separation law. Both perfect and damaged models are considered in the global stress-strain curve analysis. In the damaged model, the plastic region is characterized by softening and hardening stages, corresponding to unstable and stable crack propagation, respectively. To comprehensively identify the interfacial evolution, parameters such as normal contact strength, normal separation and stiffness degradation are evaluated along the particle/matrix interface. From a statistical perspective, the mechanical behavior of the system is analyzed through the kernel distribution plots for both the particles and the matrix. As the strain level increases, right- and left-skewed distributions are observed in the particles and matrix, respectively, particularly under high-strain conditions. Consequently, in the plastic hardening region, the median value exceeds the mean value, indicating that relying solely on the average stress value results in an underestimation during significant delamination.

Визначення запасу міцності деталей при нестандартній зміні напружень

In modern mechanical engineering, the search for machines, mechanisms, machine tools and other equipment that works under variable loads is widely conducted. During work from the actions of variable loads in machine parts according to the result and changes in stress. Incorrectly defined margin of safety of parts with non-standard changes will lead to breakdowns and destruction, as well as machine accidents. Thus, a more precisely defined safety margin is required in parts in which the maximum stress cycles vary according to a step law. The purpose of the article is to study the processes of a non-standard mode of voltage change, which change according to a step law and receive the number of cycles after which the destruction of the part occurs. The task takes place in the investigated values of the equivalent stress, according to the parameters of which the coefficient of production of the safety margin under the action of non-standard stresses. When performing the calculations of the parts, ultimately, the margin of safety during simultaneous action is changed to the value of normal and tangential stresses, which have different characteristics of stress cycles. These calculations are valid in the case when the amplitude changes do not vary over time, that is, for the established or stationary mode. However, in a number of reports, one can encounter such a situation when changes in the amplitude of stress cycles over time do not remain constant, that is, the so-called non-stationary regimes. Therefore, in a more detailed study, there is a margin of safety for non-standard stress changes. As a result of theoretical studies, the number of cycles after which parts are destroyed under the action of a load, characteristic of non-stationary modes of operation, is calculated and the coefficients of the safety margin of durability are determined.

CALCULATION OF SHELLS BASED ON THE MIXED FEM VARIANT WITH TENSOR-VECTOR APPROXIMATION OF THE DESIRED VALUES

An algorithm for calculating thin shells based on the mixed finite element method (FEM) in a two-dimensional formulation is proposed. To correctly take into account possible displacements of the shell as a rigid body, the algorithm implements the developed tensor-vector form of the interpolation procedure of the desired values, which were chosen as the tensors of deformations and curvature at the point of the middle surface and the displacement vectors of this point. The discretization element was a quadrangular fragment of the middle surface with unknown nodes in the form of location and their first derivatives, as well as components of strain and curvature tensors among the inner surface at the nodes of the finite element. After minimizing the modified mixed functional, a 36?36 finite element stiffness matrix is formed. In order to verify the developed algorithm, a number of test problems were solved for calculating a fragment of an elliptical cylinder with an analytical solution, as well as for calculating a shell with spring supports that allow the ellipsoidal shell to move as an absolutely rigid body. Analysis of the obtained results showed that when calculating a fragment of an elliptical cylinder, the calculation scheme of which makes it possible to obtain an analytical solution, the numerical values of bending moments and normal stresses completely coincide with the values calculated from the condition of static equilibrium. An analysis of the calculation results for an ellipsoidal shell with spring supports led to the conclusion that the developed tensor-vector interpolation procedure in the mixed FEM version allows one to correctly take into account the displacements of shells as solids and obtain an adequate assessment of their stress-strain state.

EXPERIMENTAL STUDY OF ADHESION BETWEEN FRAMEWORK IN RONIER WOOD (BORRASSUSAETHIOPUM) AND LATERITE CONCRETE

In todays world, the environment and the economy, are becoming more and more important, especially in the field of construction. As a result, many researches are beginning to emerge in order to find alternatives to the usual reinforced concrete. In this article, research is focused on constructions using local materials, more specifically on laterite concrete reinforced with plant reinforcement made of rônier wood. The main goal was to study the adhesion between these wooden reinforcements and the laterite concrete in order to submit this structural material to construction stresses. The average value of the adhesion stress obtained is 3.521±0.668 MPa for the reinforcements without serrations and 3.828±0.437 MPa for those with serrations. Rebars with serrations achieved a gain of about 09% to 20% over the surface rebar without serrations. These reinforcements with circular section with or without crenellation and with octagonal section incorporated in the laterite concrete beams considerably increased the resistance of the laterite concrete. This increase is close to 335.86% of the breaking stress for the beams reinforced with two reinforcements of circular section, 386.96% for the beams reinforced with two reinforcements of circular section with crenellation and 353.78% for the beams reinforced with two reinforcements of octagonal section. This study made it possible to show that reinforcements with a circular section with crenellation are better reinforcements in laterite concrete.

Анализ грейферной выемки волокнистого торфяного сырья

The purpose of the study was to confirm the possibility of implementing the operations of the working cycle of mining equipment with the determination of the range of forces required to introduce the elements of the grab into the deposit and close the jaws in the massif, taking into account the design features of the grab. Research methodology. A series of field studies was carried out using full-scale models of the working bodies of a fork grab in the conditions of a peat deposit to confirm the possibility of implementing the process of extracting raw materials of a low degree of decomposition. Results. It has been established that the average value of the force required overcoming the resistance to the introduction of the grab model: on the site with magellanicum peat – 44.4 kN, with fuscum-peat – 61.5 kN. The average value of the normal stress when immersed in an array of a clamshell equipment element, taking into account the end surface area, is 89 kPa for: magellanicum peat, 123 kPa for fuscum-peat. The average value of the total deformation modulus in the natural occurrence of a peat deposit is 116 kPa for magellanicum peat and 126 kPa for fuscum-peat. The rational distance between the teeth of the jaw model of the fork grab has been determined. With a distance between the teeth of the grab jaw model l=0.25 m, a single drawing body is formed when the captured area of the material is shifted. Conclusion. With the determination of the effort ranges for the implementation of the two main operations of the excavation process, as well as the establishment of the design features of the grab for surface excavation, it was concluded that it is possible to use grab equipment for the surface extraction of fibrous peat raw materials.

Effect of maximum applied cyclic stress on fretting fatigue stress distribution of flat-on-flat modified 9Cr-1Mo steel contact: Finite element analysis

Fretting fatigue experiments were conducted on a modified 9Cr-1Mo (P91) steel under flat-on-flat contact with maximum applied cyclic stress (σmax) levels of 450 MPa, 500 MPa and 550 MPa at a stress ratio of 0.3 and a contact pressure of 100 MPa. A decrease in the cyclic life was observed with an increase in σmax. Chaboche model with isotropic and kinematic hardening was employed in finite element analysis to evaluate the stress distribution near the contact pad and along the contact surface under fretting fatigue conditions. In addition, the contact-related parameters such as contact pressure, contact shear stress and relative tangential motion were also assessed. The relative tangential motion was found to increase with increasing σmax. Besides, the peak values of normal stress (parallel to the applied loading direction) and maximum principal stress were observed around the leading and trailing edges of the contact pad at the σmax. The amplitude of relative tangential motion and slip zone increases with σmax. The orientations of the principal plane and shear plane to the applied cyclic loading direction are −89.5° and −134.5°, irrespective of the σmax. The fracture surface of the failed specimen revealed that the direction of the crack was nearly perpendicular to the applied stress. Smith-Watson-Topper parameter was used for estimating the crack initiation life with σmax. It has been noticed that the fraction and dominance of crack initiation or propagation phase depend on the imposed cyclic condition for the steel.

Evaluation of peel resistance of paint coatings depending on the roughness of the cement substrate

The object of the study is paint and varnish coatings of cement concrete. The goal is to evaluate the stress-strain state of coatings under the action of temperature depending on the geometry of the substrate roughness relief. The results of calculating the distribution of stresses over the cross section of the coatings and the possibility of their peeling are presented. The SCAD Office software module was used for the calculation. Heavy concrete was considered as the substrate. Polyvinyl acetate cement PVAC paint was used as a paint composition. The calculations were carried out for the conditions of Moscow. A comparison is made of the stresses in the coating on a smooth and rough surface. I has been found that an increase in the relief angle of the substrate surface roughness does not cause a significant change in the magnitude of stresses. The stress concentration in the zone of contact between the coating and the rough surface of the cement substrate has been established. A diagram of the distribution of stresses in the PVAC coating is presented. It was revealed that at some distance from the zone of the microdepression of the substrate surface relief, an increase in stresses is observed, which, depending on the angle of inclination of the relief, are s х = (1.007-1.021) MPa. At the peak of the relief, the stress values in the contact zone are less and amount to 0.403-0.441 MPa. The influence of the substrate roughness has practically no effect on the values of normal stresses on the coating surface, which are 0.835-1.001 MPa. The probability of peeling off the coating is estimated. The possibility of peeling of the coating has been established, tk. stress values are less than the adhesion strength, which is 0.9-1.1 MPa. It is recommended that in order to increase the resistance of coatings to peeling, strive to create a uniformly distributed roughness of the substrate surface.

Experimental study of interface performance between calcareous sand and steel pile with different surface roughness and temperatures

The shear characteristics of calcareous sand, a typical deposit in the South China Sea, could significantly influence the safety and stability of marine structures. Previous studies showed that many factors, such as temperature and surface roughness, could affect the mobilized shear strength between the calcareous sand and steel surface. Therefore, studies on the shear behaviors of the steel-sand interface under various thermal conditions are necessary. In this study, a new multifunctional sediment shear system has been developed and employed to investigate the shear performance. For this purpose, steel plates with different surface roughness were tested under various normal stress values, shear displacement rates and temperatures. Shear strength and deformation were analyzed using test data to reveal the relationships between several factors and the shear strength of the steel-sand interface. Results from test demonstrate that the interfacial shear strength on rough steel interfaces will be 1.45–3.15 times higher than that on the smooth steel interface. Besides, the shear strength of the interface rises significantly with the roughness of the steel plate. The peak friction angle increases rapidly at the start and then tends to stabilize with the increase of normalized roughness. The interfacial shear strength could be enhanced in low-temperature environments but would reduce in high-temperature environments, e.g. the energy pile, particularly under low normal stress. The shear displacement rate also has a positive effect on the interface shear strength for most cases in this study. Finally, a new nonlinear function is proposed to describe the peak friction angle ratio of foundation interface to consider the effect of temperature and shear displacement rate reasonably.

Stress Analysis of Graphite Anode under Various Binder Conditions in a Multiparticle Model through Multiscale Simulation and Experimental Verification

Quantifying and analyzing the stress of the battery system at different levels are important for ensuring battery stability and performance. Herein, a three‐dimensional multiparticle model to evaluate the stress generated within the active material particles of battery due to the particle–particle and particle–binder interactions is developed. Variations in binder conditions, such as binder distribution, thickness, and radius, as well as Young's modulus, are introduced to investigate their effects on the mechanical stress of graphite particles in the battery. Herein, it is demonstrated that larger binder distributions, lower thicknesses, and smaller Young's moduli and radii reduce the maximum particle stress of graphite. Moreover, smaller binder distributions and Young's moduli along with larger thicknesses and radii reduce the maximum and average binder stress values. The interfaces between the particle–particle and particle–current collector are the typical maximum stress locations. The average stress data obtained are applied at the electrode level for comparison with the experimental stress value. The experimental and the model average stresses are comparable, indicating the credibility of our model. These findings have considerable implications for minimizing the mechanical stress and probability of electrode fracture in the battery electrode operation and fabrication processes.

Preliminary exploration of the biomechanical properties of three novel cervical porous fusion cages using a finite element study

BackgroundPorous cages are considered a promising alternative to high-density cages because their interconnectivity favours bony ingrowth and appropriate stiffness tuning reduces stress shielding and the risk of cage subsidence.MethodsThis study proposes three approaches that combine macroscopic topology optimization and micropore design to establish three new types of porous cages by integrating lattices (gyroid, Schwarz, body-centred cubic) with the optimized cage frame. Using these three porous cages along with traditional high-density cages, four ACDF surgical models were developed to compare the mechanical properties of facet articular cartilage, discs, cortical bone, and cages under specific loads.ResultsThe facet joints in the porous cage groups had lower contact forces than those in the high-density cage group. The intervertebral discs in all models experienced maximum stress at the C5/6 segment. The stress distribution on the cortical bone surface was more uniform in the porous cage groups, leading to increased average stress values. The gyroid, Schwarz, and BCC cage groups showed higher average stress on the C5 cortical bone. The average stress on the surface of porous cages was higher than that on the surface of high-density cages, with the greatest difference observed under the lateral bending condition. The BCC cage demonstrated favourable mechanical stability.ConclusionThe new porous cervical cages satifies requirements of low rigidity and serve as a favourable biological scaffold for bone ingrowth. This study provides valuable insights for the development of next-generation orthopaedic medical devices.

Optimization methods for the distortion of thin-walled box girders and investigation of distortion effects

To investigate the distortion process of thin-walled box girders, three commonly used methods based on energy variational calculus and static balance analysis are optimized. A generalized analytical formula for box-girder distortion research is derived, and a fourth-order distortion control differential equation is obtained. Typical numerical examples are used to verify and compare the three methods. The results show that the value of distortional warping normal stress calculated by the optimized methods is slightly different from the literature values and that the maximum error between methods does not exceed 5.39%. The calculation results of Method 2 and Method 3 are similar. The values of the geometric distortion characteristics calculated by the three methods are related to the cross-sectional form of the box girder and the distortion analysis process, and the calculated values are not unique. The absolute value of the peak normal stress of distortion on the top plate of a thin-walled box girder with a cantilever plate is smaller than that on the bottom plate. Under a concentrated distortion load, the distribution of the distortion deformation along the length of a simply supported box girder with only end diaphragm is not consistent, and there is reverse deformation near the beam end.

Plasma-Treated Electrospun PLGA Nanofiber Scaffold Supports Limbal Stem Cells

The corneal epithelial layer is continuously replaced by limbal stem cells. Reconstructing this layer in vitro using synthetic scaffolds is highly needed. Poly-lactic-co-glycolic acid (PLGA) is approved for human use due to its biocompatibility and biodegradability. However, PLGA is hydrophobic, preventing cell adherence to PLGA membranes. PLGA scaffolds were prepared by electrospinning on a custom-made target drum spinning at a rate of 1000 rpm with a flow rate of 0.5 mL/h and voltage at 20 kV, then treated with oxygen plasma at 30 mA using a vacuum coater. Scaffolds were characterized by SEM, mechanically by tensile testing, and thermally by DSC and TGA. In vitro degradation was measured by weight loss and pH drop. Wettability was assessed through water uptake and contact angles measurements. Human limbal stem cells (hLSCs) were isolated and seeded on the scaffolds. Cell attachment and cytotoxicity assay were evaluated on day 1 and 5 after cell seeding. SEM showed regular fiber morphology with diameters ranging between 150 nm and 950 nm. Tensile strength demonstrated similar average stress values for both plasma- and non-plasma-treated samples. Scaffolds also showed gradual degradability over a period of 7–8 weeks. Water contact angle and water absorption were significantly enhanced for plasma-treated scaffolds, indicating a favorable increase in their hydrophilicity. Scaffolds have also supported hLSCs growth and attachment with no signs of cytotoxicity. We have characterized a nanofiber electrospun plasma-treated PLGA scaffold to investigate the mechanical and biological properties and the ability to support the attachment and maintenance of hLSCs.