Reduce Stress Concentration Research Articles

Revolutionizing polymethyl methacrylate toughness: Achieving 190% improvement with nanocellulose reinforcement while maintaining optical clarity

Polymethyl methacrylate (PMMA) is widely used in applications requiring high transparency and durability, such as optical lenses and protective coatings. However, its inherent brittleness limits its application in high-impact environments. This study investigates the incorporation of cellulose nanocrystals (CNCs) into PMMA to significantly enhance its toughness without compromising its optical clarity. By reinforcing PMMA with CNCs, the nanocomposites exhibited a remarkable 190% increase in toughness while maintaining 90% optical transparency. The innovation lies in achieving a balance between toughness and transparency through controlled CNC dispersion within the PMMA matrix, which minimizes excessive bonding that could lead to brittleness. Proper CNC dispersion was achieved through in-situ polymerization, allowing the nanocrystals to interact with the polymer matrix through van der Waals forces rather than covalent bonds. This approach reduces stress concentration and mitigates the formation of defects in the polymer matrix, ultimately leading to a tougher, more flexible material. In addition to enhancing mechanical properties, this study underscores the importance of controlling CNC content to preserve the intrinsic optical transparency of PMMA. These findings open new possibilities for CNC-reinforced PMMA in advanced applications that demand high mechanical performance coupled with excellent optical properties, extending its use in fields such as medical devices, protective coatings, and transparent structural materials.

Facile Construction of Polypropylene Foam with Dense Oriented Cell Structure and Enhancing-ductility Mechanism

Common polypropylene (PP) foam exhibited intrinsic inferior ductility and mechanical strength, which restricted its application as lightweight structural parts. To improve the ductility and mechanical strength of PP foam, the highly oriented PP component with fibrillar structure (cold-drawn fiber, CDF) was blended with isotropic PP resin to prepare PP/CDF foam via a facile foam injection molding process. During foaming at 170°C, CDF was not melted completely. Then, the remaining fibrils acted as shish structure and induced the crystallization of PP chains on its surface to form oriented kebab crystals, and the viscoelasticity and melt strength of the system were significantly improved, which promoted the nucleation of the bubble and the elongation of the cells, constructing a dense oriented cell structure with a large number of slender cylindrical cell walls for the foam. Such cell wall structure was prone to large plastic deformation and continuous elongation under load, which reduced stress concentration and absorbed a significant amount of tensile energy. As a result, a ductile and strong PP/CDF foam was successfully constructed, which exhibited roughly 465% increase in strain at break and 15% increase in tensile strength, respectively compared with PP foam.

Strength and plasticity coordination improvement mechanism in network structure TiBw/TA15 composite via multi-DOF forming

TiBw/TA15 composite with network TiB whisker (TiBw) reinforcement architecture, exhibits high strength but limited plasticity, presenting a significant challenge in enhancing the plasticity of TiBw/TA15 composites. In the current work, strength and plasticity coordination improvement of TiBw/TA15 composite is achieved through the application of multi-degrees of freedom forming (multi-DOF forming) technology. The α phase spheroidization behaviour and strength-plasticity coordination improvement mechanisms are investigated. The results elucidate that increasing deformation amount through multi-DOF forming leads to more pronounced α phase spheroidization and refinement. This effect is attributed to the generation of substantial strain along the deformation path, particularly in the regions where hard TiBw particles rotate (i.e., the tips of TiBw). Additionally, the impediment of dislocation movement by TiBw causes dislocations to accumulate along these rotation regions via single slip and cross slip mechanisms, thereby accelerating the α phase spheroidization process. Furthermore, with increasing deformation amount, the strength and plasticity are coordinately improved. The tensile strength and elongation increase linearly from 972 MPa to 1239 MPa (increased by 27.5 %) and from 5.6 % to 7.9 % (increased by 41.1 %) as the deformation condition advanced from the sintered state to the 40 % deformation condition, respectively. Improved plasticity can be attributed to the refinement of grains and TiBw, promoting more uniform plastic deformation and reducing stress concentrations during tensile testing. The strengthening mechanisms encompass load transfer strengthening facilitated by TiBw, grain refinement strengthening and dislocation pinning effect caused by TiBw.

Structural Analysis of the Geometric Alternatives of Double-Bottom Floor Plates of a Panamax-Class Container Ship

To reduce weight and simplify maintenance, ship structures frequently include openings and cutouts. While these features offer practical advantages, they can weaken the structural integrity of key components. This study explores the effects of these geometric discontinuities on the double-bottom floor plates of a Panamax-class container ship under axial and transverse loads. Through numerical simulations and experimental testing, we analyzed different cutout configurations and stiffening strategies to assess their impact on stress distribution, plate thickness, and fatigue behavior. The results reveal that side cutouts significantly increase stress, particularly under transverse loads, while central openings have less impact. Additionally, increasing plate thickness consistently reduces stress levels across all models, improving structural durability. Fatigue analysis shows that certain stiffening configurations, particularly those with longitudinal stiffeners in the bottom plates, enhance fatigue life. These findings offer critical design insights for optimizing hull structures, balancing weight reduction with strength improvement. This study provides valuable recommendations for reducing stress concentrations and extending the fatigue life of ship components, contributing to more efficient and safer ship designs.

Top Coal Weakening by Pulse Hydraulic Fracturing and Roof Cutting by Directional Hydraulic Fracturing for Control of Hanging Roof in the Face End of Fully Mechanized Top Coal Caving

Abstract Due to the supporting effect of the coal pillar on the side of the roadway, there is often a problem of the top coal and roof in the working face end not collapsing in time. The single directional hydraulic fracturing method cannot directionally cut off the top coal of the working face end. To overcome the above shortcomings, this article first proposes a method of controlling top coal and roof in the working face end by pulse and directional hydraulic fracturing. The method of using pulse hydraulic fracturing to weaken the top coal and directional hydraulic fracturing to cut off the roof to induce rock pressure to break the coal is used to control the timely collapse of the top coal and roof in the working face end. When the vertical stress on the top coal is greater than the strength of the weakened top coal, the top coal and roof begin to collapse. The vertical displacement of the weakened top coal and the cut roof gradually decreases from low to high, and the caving top coal and roof finally fill the goaf. The maximum reduction in stress concentration of coal pillar is about 75%. Then, the principles for determining the parameters of this method were provided. Finally, the industrial experiment was conducted in the coal mine. The construction water pressure of the roof is between 30 and 40 MPa. The construction water pressure of top coal ranges from 8 to 16 MPa, with an amplitude of approximately 4 MPa. Directional crack is formed within an area of 3.3 m in the direction of the adjacent roof borehole. A crack network is formed within a 4 m area near the top coal borehole. After hydraulic fracturing, the top coal and roof in the working face end collapse with mining.

Topology optimization framework of multiple-phase materials with stress and dynamic constraints under self-weight loads

This work aims to optimize the multi-material structures subjected to self-weight loading for the first time. Ignoring the self-weight loads results in less reliable designs, and to enhance the strength of optimized designs, stress-constrained multi-material topology optimization (MMTO) is considered with body forces. Two stress constraint aggregation schemes are employed and comparable, such as the K-S and p-norm aggregation schemes. Both of these schemes are effective with respect to stress constraints due to local stress issues. Moreover, eigenvalue constraints (MMTO) are introduced in this study with self-weight loading and stress constraints. Thus, the optimized results not only ensure self-weight load criteria but also reduce stress concentration and improve stability due to free vibration of structures. The proposed approach is an alternating-active-phase algorithm (AAPA) for dealing with the problems considered in this work. Results show that the results caused by self-weight loads are totally different from optimized results when they are not considered with self-weight loads using multi-materials.

Optimization of Filling Material Ratio in Yellow Phosphorus Slag Mine.

Yellow phosphorus slag has been considered as a potential cement substitute for mine filling material due to its cementing activity; however, its slow setting and low early strength have limited broader use. This study investigates the grading, compactness, and strength of yellow phosphorus slag combined with tailing sand. Using yellow phosphorus slag as an aggregate, cement as a binder, and mixing tailing sand in different ratios, this study evaluates its feasibility as a coarse aggregate in mine backfill. The key findings are as follows. (1) The grading index of tailing sand was 0.5, aligning with Fuller grading, but it required mixing with coarse aggregates to enhance strength and reduce cement consumption. Yellow phosphorus slag, with a grading index of 0.97, does not match Fuller's curve and thus benefits from mixing with tailing sand. (2) For mixtures of waste rock and tailings, the 5:5 ratio aligned closely with Fuller's theory, showing optimal packing density and strength. Mixtures of yellow phosphorus slag and tailings at ratios of 3:7, 4:6, and 5:5 had R2 values of 0.73, 0.80, and 0.85, respectively, confirming reliable fit. The 5:5 mixture provided the best packing density and strength. (3) A new strength prediction model, accounting for aggregate, cement, and water effects, suggests that a 5:5 ratio with a 71% mass concentration and 1/7 ash-sand ratio meets industrial strength requirements. FLAC3D simulations indicated that cemented backfill reduces stress concentrations caused by excavation and supports stability during mining while also absorbing energy through compaction, creating favorable conditions for safe mining operations.

Study on the nano-cutting mechanism of monocrystalline silicon material with an amorphous layer by molecular dynamics simulations

Monocrystalline silicon is prone to brittle fracture during the nano-cutting process. Surface modification through ion implantation to create an amorphous layer on monocrystalline silicon significantly enhances its processability. This paper conducted molecular dynamics simulations to deeply reveal the nanometric cutting mechanism for monocrystalline silicon with an amorphous layer. The influence of the amorphous layer on material removal, subsurface damage, cutting forces, stress distribution, and temperature profiles was analyzed and thoroughly discussed. The calculating results reveal that primary material removal mode transitions from shearing to extrusion under the influence of the amorphous layer. The presence of an amorphous layer can efficiently reduce stress concentration and defects in the nanometric machining process. When the thickness of the amorphous layer equals the cutting depth of the tool, subsurface damage is reduced to approximately 2 nm, indicating that an optimal surface quality is achieved. When the thickness of the amorphous layer reaches more than cutting depth, the hydrostatic stress of the monocrystalline silicon part is significantly lower than the phase transition threshold of 12 GPa, which greatly reduces the occurrence of phase transition. Furthermore, the formation and evolution of shear bands are the primary reasons for the fluctuations in cutting force. The cutting temperature is closely related to structural transformations. The heat generated by shear slip in monocrystalline silicon material is higher than the heat generated by plastic deformation of material in the amorphous layer. Moreover, the heat energy produced by plastic deformation of amorphous layer atoms exceeds that generated by structural transformation of monocrystalline silicon atoms. This work reveals the nanometric cutting behavior of the monocrystalline silicon material with amorphous layer surfaces based on phase transformation. It can provide effective references for the preparation of amorphous layer thickness and selection of cutting parameters in nanometric cutting process of the monocrystalline silicon with amorphous layer surfaces.

Experimental study and numerical simulation of the effect of different fiber types on the basic mechanical properties of shotcrete

This study analyzed the enhancement effects and mechanisms of steel, glass, and polypropylene fibers on the mechanical properties of concrete, aiming to guide the selection of suitable fiber types and dosages for shotcrete projects. Through laboratory tests, numerical simulations, and field experiments, it investigated the enhancement laws of flexural and compressive strengths of concrete with different dosages of these three fibers. Results showed: (1) After 28 days of curing, flexural strength peaked with 2.0% steel, 1.5% glass, and 2.0% polypropylene fibers, increasing by 118.6%, 42.86%, and 138.6%, respectively, over plain concrete. Compressive strength increased by 2.13%, 10%, and 18.3% at optimal dosages of 0.5%, 1.0%, and 2.0% for steel, glass, and polypropylene fibers. Fiber effects on compressive strength were less significant than on flexural strength, with polypropylene fibers outperforming the others. (2) Based on ABAQUS numerical simulations, microscopic analysis indicates that fibers, due to their high yield capacity, enhance the connections between concrete elements, reduce stress concentration, and improve the mechanical properties of concrete. (3) For shotcrete, 2.0% polypropylene fibers were preferred due to high flexural strength and reduced agglomeration. (4) The optimal dosage was applied to a mine’s wet shotcrete support, effectively controlling tunnel deformation. These findings provide practical guidance for shotcrete applications.

Study on the impact of grouting reinforcement on the mechanical behavior of non-penetrating fracture sandstone

The grouting reinforcement technology is an essential method to enhance the mechanical performance of fractured rock masses and the effectiveness of reinforcement varies with different grouting materials. To further understand the mechanical improvement capabilities of each grout and the reinforcement mechanisms at the grout-rock interface, this study prepared samples with different grouting materials (sulphoaluminate cement (SAC), ultra-fine cement (UFC), and epoxy resin (EPR)) and the uniaxial compression tests were conducted. Based on these tests, the macro and micro mechanical characteristics of different grouting samples were revealed using particle image velocimetry (PIV), acoustic emission (AE), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). The results indicate that grouting helps improve the mechanical performance and deformation resistance of fractured rock masses. It effectively limited lateral displacement of the samples, reduced stress concentration at fracture tips, enhanced shear effects during sample fracture, and altered the crack propagation process and failure modes. Compared to the fractured samples, the peak strength of SAC, UFC, and EPR samples increased by 17.8 %, 23.4 %, and 28.3 %, and the elastic modulus increased by 14.3 %, 7.9 %, and 24.8 %, respectively. Among these, the EPR samples exhibited a similarity in parameter indicators to intact samples of over 85 %, making EPR the optimal grouting material. The degree of grout-rock fusion is the primary factor influencing grouting reinforcement effectiveness. SAC is covering-type cement, UFC is embedded cement, EPR is a fusion material, and the fusion-type materials are more beneficial for improving the mechanical performance of fractured rocks.

Achieving enhanced high-temperature strength in Ti-48Al-1Fe alloy sheets by direct hot pack-rolling of powder-sintered billets without cogging

The TiAl alloy is a novel lightweight high-temperature structural material that exhibits exceptional performance. The brittleness and mechanical properties of the material can be enhanced by improving the microstructure via rolling. The Ti-48Al-1Fe alloy with high density was produced using powder compaction and pressure-less sintering. Subsequently, the TiAl alloy sheet was formed via hot pack rolling. This study examined the sheet formability of PM Ti-48Al-1Fe alloy sheets at various temperatures, as well as the microstructure and mechanical properties at varied levels of rolling deformations. The microstructure of the powder metallurgy (PM) TiAl alloy sheet has a unique duplex structure, consisting of α2/γ lamellar colonies and a composite structure. The rolling deformation process generates spherical recrystallized grains, which effectively reduce stress concentration. The enhanced composite structure is mostly localized at the interfaces between grains, creating a robust obstacle for the movement of dislocations at high temperatures. This results in the desired outcome of reinforcing the mechanical properties of the material at high temperatures through grain boundary strengthening. This study demonstrates that the ultimate tensile strength (UTS) of PM TiAl sheet tensile specimens in the rolling direction at room temperature is 443 MPa with 1 % elongation, whereas at 800 °C, the UTS rises to 548 MPa with 2.5 % elongation. This study proposes a novel process for the efficient production of Ti48Al1Fe sheets with good high-temperature mechanical properties. This technique entails the hot rolling of high-density sintered powder metallurgy billets, offering an innovative approach for the economical and swift production of TiAl alloy sheets during practical manufacturing process.

The effect of low-temperature heat treatment on hydrogen embrittlement of sheared edge in advanced high-strength steels

Hydrogen embrittlement (HE) has become an important issue in ultra-strong automotive steel applications. This study investigated the HE mechanism of the sheared edge in complex phase (CP) steel and examined the HE improvement achieved via low-temperature soaking (150 °C). To this end, changes in the microstructures of both the steel matrix and sheared edge were analyzed, and various mechanical properties were evaluated before and after soaking. In addition, the HE resistances of the steel and sheared edges were evaluated using slow-strain-rate tensile and immersion tests, respectively. Before soaking, the CP microstructure comprised of tempered martensite and lath bainite with island-shaped polygonal bainite. After soaking, the overall microstructure remained largely unchanged, the yield strength and fracture toughness increased, and uniform localized nanohardness was achieved through carbon redistribution. The intrinsic resistance to HE is enhanced by carbon clustering or carbide precipitation, which impedes hydrogen diffusion. Immersion tests revealed that HE occurred only in the sheared edge with a burr upward, indicating the cut-edge condition significantly affected HE susceptibility. H-induced cracks in the CP microstructure before soaking propagated along interfaces between the island bainite and the matrix, where stress concentration occurred because of large differences in nanohardness. After soaking, cracks penetrated the island bainite, suggesting a reduced stress concentration caused by the more uniform nanohardness across phases. Overall, soaking improved the HE resistance of the sheared edge by altering crack propagation behavior. The enhanced fracture toughness improved damage tolerance to pre-existing defects and enhanced the resistance to HE, along with reduced H diffusivity.

Dynamic response analysis of pipelines in gas distribution stations under seismic loads

Seismic loads in earthquake-prone regions significantly affect the structural integrity of pipelines at urban natural gas distribution stations, compromising safety. This study analyzes the dynamic response of pipelines in gas distribution stations under seismic loading and proposes effective measures to mitigate stress concentration. A numerical model of the pipeline in the gas distribution station, based on actual cases, was established. The material’s constitutive relationship was derived from tensile tests. The seismic response spectrum, obtained from ground motion data, was introduced to analyze the pipeline’s mechanical behavior. The dynamic response analysis identified critical stress concentration locations in the pipeline under operational conditions. Based on displacement analysis, the study recommended seismic measures. Results indicated that under seismic loading, higher stress values occurred primarily in pipeline sections with intricate flow pattern variations. The manifold connection was the most vulnerable point, with its average stress being 3.37 times that of the system’s average stress. The proposed seismic measures effectively reduced stress concentration at these critical points, mitigating the earthquake’s impact on the gas distribution station. This study establishes a theoretical framework for improving the seismic design and maintenance of natural gas distribution stations, enhancing their seismic resilience and operational safety.

A finite element based approach for nonlocal stress analysis for multi-phase materials and composites

AbstractThis study proposes a numerical method for calculating the stress fields in nano-scale multi-phase/composite materials, where the classical continuum theory is inadequate due to the small-scale effects, including intermolecular spaces. The method focuses on weakly nonlocal and inhomogeneous materials and involves post-processing the local stresses obtained using a conventional finite element approach, applying the classical continuum theory to calculate the nonlocal stresses. The capabilities of this method are demonstrated through some numerical examples, namely, a two-dimensional case with a circular inclusion and some commonly used scenarios to model nanocomposites. Representative volume elements of various nanocomposites, including epoxy-based materials reinforced with fumed silica, silica (Nanopox F700), and rubber (Albipox 1000) are subjected to uniaxial tensile deformation combined with periodic boundary conditions. The local and nonlocal stress fields are computed through numerical simulations and after post-processing are compared with each other. The results acquired through the nonlocal theory exhibit a softening effect, resulting in reduced stress concentration and less of a discontinuous behaviour. This research contributes to the literature by proposing an efficient and standardised numerical method for analysing the small-scale stress distribution in small-scale multi-phase materials, providing a method for more accurate design in the nano-scale regime. This proposed method is also easy to implement in standard finite element software that employs classical continuum theory.

Study on the mechanism of crystal-induced plasticity enhancement in Ni-Zr crystal/amorphous composites by molecular dynamics simulation

The industrial applications of metallic glass (MGs) are limited by poor plasticity, which crystal/amorphous composites (CACs) can effectively address. This study simulates the compression of Ni-Zr MGs with embedded fcc crystal phases by molecular dynamics to elucidate the mechanism of crystal-induced plasticity enhancement. The plasticity of CACs improves with larger crystal sizes. Atoms at the crystal-amorphous interfaces (CAIs) are classified as CAIfcc and CAIMGs for fcc and MGs, respectively. The transformation of CAIfcc to CAIMGs at the CAIs is crucial for plastic flow during compression. The connection between CAIfcc and CAIMGs clusters is less stable than that of fcc, making it more prone to damage and leading to multiple shear bands (SBs). These SBs offer additional pathways for plastic flow, reducing stress concentration and enhancing material plasticity. This research provides an atomic-level understanding of crystal-induced plasticity in CACs, offering valuable insights for designing high-performance CACs.

Appropriate sagittal positioning of femoral components in total knee arthroplasty to prevent fracture and loosening.

This study aimed to investigate the optimal sagittal positioning of the uncemented femoral component in total knee arthroplasty to minimize the risk of aseptic loosening and periprosthetic fracture. Ten different sagittal placements of the femoral component, ranging from -5 mm (causing anterior notch) to +4 mm (causing anterior gap), were analyzed using finite element analysis. Both gait and squat loading conditions were simulated, and Von Mises stress and interface micromotion were evaluated to assess fracture and loosening risk. During gait, varied sagittal positioning did not lead to excessive Von Mises stress or micromotion. However, under squat conditions, posterior positioning (-4 and -5 mm) resulted in stress exceeding 150 MPa at the femoral notch, indicating potential fracture risk. Conversely, +1 mm and 0 mm sagittal positions demonstrated minimal interface micromotion. Slightly anterior sagittal positioning (+1 mm) or neutral positioning (0 mm) effectively reduced stress concentration at the femoral notch and minimized interface micromotion. Thus, these positions are deemed suitable to decrease the risk of aseptic loosening and periprosthetic femoral fracture.

High-Performance Flexible Pressure Sensor with Micropyramid Structure for Human Motion Signal Detection and Electromagnetic Interference Shielding.

Flexible pressure sensors have a wide range of applications in the field of human motion signal detection, but the electromagnetic radiation generated during the monitoring process has become an unavoidable problem. Nowadays, it is still a challenge to develop high-performance pressure sensors with excellent electromagnetic interference (EMI) shielding performance. Herein, the Ti3C2TX MXene/carbon fiber/multiwalled carbon nanotube/polydimethylsiloxane (MXene/CMP) films with a micropyramidal structure were developed by the technology of vacuum high-temperature hot pressing and spray deposition. Benefiting from the dielectric loss of the conductive fillers and the presence of the microstructure, the MXene/CMP film exhibits excellent EMI shielding performance, and the EMI shielding efficiency (SE) can reach 49.37 dB. Besides, the introduction of CF effectively improves the mechanical properties of the MXene/CMP films, and the MXene nanosheets deposited on the surface of the film can reduce stress concentration, which in turn delays the expansion of cracks. Furthermore, the MXene/CMP sensor exhibits high sensitivity (89.76 kPa-1) and fast response/recovery time (61/60 ms). The deformation of microstructure and the construction of conductive networks enable the sensor to realize the monitoring of human motion signals (such as finger bending, knee bending, wrist bending, etc.). Meanwhile, the sensor maintains sensing stability even after 2000 pressure cycles, which can be attributed to the improvement in mechanical properties. In summary, the developed high-performance flexible pressure sensor with micropyramid structure has great application prospects in wearable devices and healthcare.

Investigating the effects of powder feeding rate on microstructure transformation in linear laser beam additive manufactured thick-walled structures

The coarse columnar crystals that grow through multiple layers are commonly observed in laser additive manufactured structures, with fractures tending to occur in regions where there are abrupt changes in grain morphology. This can lead to a degradation of the mechanical properties of the samples. In this study on laser additive manufacturing, thick-walled structures made of 304 stainless steel were created using a linear beam spot with a rectangular powder feeding nozzle. By adjusting the powder feeding rate to influence the thermal cycling characteristics during the laser additive manufacturing process, a hierarchical grain structure that combines coarse and fine equiaxed grains was achieved, enhancing the forming efficiency and overall mechanical performance of the structure. The results from the thermal cycling characteristics and microstructure analysis indicate that increasing the powder feeding rate during the additive manufacturing process can decrease the hierarchical cooling rate, temperature gradient, and heat accumulation effect. This reduction in turn decreases the grain size and facilitates the transformation of columnar crystals into equiaxed crystals. Furthermore, the transformation of low-angle grain boundaries into high-angle grain boundaries in the interlayer region helps to reduce stress concentration, weaken anisotropic tendencies, and mitigate intergranular fracture tendencies, ultimately improving the mechanical properties of the overall structure. In actual engineering applications, the powder flow can be adjusted to control the temperature gradient and cooling rate of the deposition layer, thereby altering the grain morphology and optimizing the mechanical properties of additive manufacturing parts.

Effect of porous defects on mechanical behavior of functionally graded materials

Porous defects in functionally graded materials (FGMs) significantly change their mechanical behavior, in particular, affecting the displacement of the neutral plane and stress distribution. Defects such as porosity reduce material bending strength while enhancing compression strength and can lead to significant transverse effects. The purpose of this study is to clarify the influence of porosity on transverse effects based on new kinematic model. This research consider in detail a particular case of this model, that allows take into account two Poisson`s effects separately. This study examines the influence of porosity on FGM, highlighting the critical role of changes in Poisson’s ratio through thickness. The theory used for analytical solution satisfies the nullity of the shear stresses at the upper and lower surfaces of the plate without using the shear correction factor. The network of pores proposed to be empty or filled with low-pressure air and material properties graded by thickness according to power-law and exponential models. Navier solution method is used to solve the governing differential equations of equilibrium. The concentration of porosity at the center of the plate or in separate layers results in a reduction in normal tensile stresses along the longitudinal coordinate, suggesting that strategic placement of porosity can be used to reduce stress concentrations, potentially enhancing the structural integrity and performance of functionally graded materials under mechanical loading.

Overloaded Vertebral Body Following Consecutive Three-Level Hybrid Surgery Comparing with Anterior Cervical Discectomy and Fusion.

Based on the varying number and relative positions of cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF) procedures, three-segment hybrid surgery (HS) presents a diverse structural approach. Currently, the potential differential effects of HS with different segment combinations and surgical procedures on overloaded vertebral body (OVB) occurrence remain unexplored. The purpose of this retrospective study is to compare the clinical and radiological outcomes of HS and ACDF in treating cervical degenerative disc disease (CDDD), aiming to provide further insights into OVB. This study included patients with three-level CDDD who underwent ACDF or HS at our institution. Eligible patients were divided into three groups: Type I (one-level CDR and two-level ACDF), Type II (two-level CDR and one-level ACDF), and ACDF (three-level ACDF). For radiographic analysis, patients were further divided into the Replacement Segment Group and the Nonreplacement Segment Group based on the presence of replacement segments above and below the OVB. Clinical outcomes were evaluated using visual analog scale (VAS) scores for neck and arm pain, Japanese Orthopedic Association (JOA) scores, and neck disability index (NDI) scores. The cervical radiological parameters assessed included (1) vertebral cross-sectional area (CSA), (2) wedge angle (WA), (3) anterior vertebral height (AH), (4) posterior vertebral height (PH), and (5) Hounsfield unit (HU) values. Statistical methods included paired t-test, ANOVA test, and chi-square test. Independent samples t-test, Mann-Whitney U test, and Wilcoxon signed-rank test were used to compare the differences between two groups according to the results of normal distribution test. A total of 123 patients, evenly distributed among three groups, were included and were well matched in terms of demographic characteristics. The likelihood of vertebral body collapse (VBC) was notably higher in the ACDF group (41.5%) compared with the Type I (17.9%) and Type II (8.9%) groups (p < 0.01). Following surgery, both at 3 and 6 months, the ACDF group demonstrated higher VAS neck scores and NDI scores compared with the Type I and Type II groups (p < 0.01). Additionally, the WA and AH values of the upper and lower adjacent OVB were consistently lower in the ACDF group than in the Type I and Type II groups at 6 and 12 months and at the final follow-up (p < 0.01). Notably, in the Nonreplacement Segment Group, WA significantly decreased at 12 months postoperatively and at the final follow-up compared with the Replacement Segment Group (p < 0.01). Three levels of HS appear to reduce stress concentrations and alleviate morphological changes in OVB. The occurrence of more VBC patients with OVB was associated with the use of Zero-P or Zero-P VA implants.