Stress Distribution Area Research Articles

(Digital Presentation) Stress and Electrochemical Reaction Prediction of the Particle Structure of All-Solid-State Batteries By Numerical Simulation and Machine Learning

All-Solid-State Battery (ASSB), which is nonflammable, safe, and high capacity, is expected to be commercialized for electric vehicle applications in the near future. However, the correlation between the electrode structure and the stress on the solid-solid contact surface is unknown, and no design theory has been established. However, the design theory has not been established because the correlation between the stresses on the electrode structure and the solid-solid contact surface is unknown. In this study, a stress distribution estimation method for complex electrode structures using machine learning was investigated.The stress estimation was performed using the discrete element method (DEM)¹⁾ . The average particle size of LCO was given as 9-12 ㎛, standard deviation as 0-2, and Young's modulus was given as 264 GPa²⁾. The LGPS particles were fixed at 1 ㎛ in diameter, with Young's modulus of 26.7 GPa, Poisson's ratio of 0.32, and density of 1.988 g/cm³. The distribution of the stresses on each particle was calculated from the DEM calculation results and confirmed to be approximately Gaussian.A convolutional neural network (CNN)³⁾ was used as the model for machine learning, and various structural parameters, including the stress on each particle calculated by DEM, were identified to create a dataset. Five hundred images were used for training, 320 of which were used for training, 80 for validation, and 100 for testing. The coefficient of determination (R²) of the standard deviation of the stress on each particle was AM_0.861, SE_0.936, and SE_0.936, confirming that the stress distribution can be predicted by the machine learning model. The contact area of the electrochemical reaction interface, AM-SE, was calculated from the stress on the contact surface calculated by DEM and Hertzian contact theory⁴⁾. The total interfacial area was also predicted well with a coefficient of determination of 0.921.Thus, it was possible to predict the stress distribution and effective contact area in the electrode layer of the all-solid-state battery. Next, we will verify the validity of the electrode structure and stress distribution by simultaneously measuring the in-situ stress distribution and Li concentration distribution during charging and discharging using X-ray spectroscopy and atomic force microscopy. In addition, a machine learning model of crack formation during charging and discharging will be developed. By linking machine learning and measurement, we will connect to the structural design of electrode layers to improve charge-discharge and cycle characteristics, and aim to establish fundamental technology that will contribute to the early commercialization of all-solid-state batteries.

Deformation Stability Response of Adjacent Subway Tunnels considering Excavation and Support of Foundation Pit

Abstract Since the safety and stability of the original tunnel structure are easily affected by the adjacent foundation pit excavation, it is strongly necessary to study the deformation evolution of tunnels during the adjacent foundation pit excavation. With regard to the two cases that tunnel is adjacently located at the right and bottom of foundation pit, the influence of different supporting methods, including pile support, bolt support, pile-bolt support, and shotcrete-bolt support, on the tunnel stability was investigated on the basis of the whole excavation process numerical simulation of deep foundation pit for determining the best foundation pit supporting beneficial to the stability of adjacent tunnel. The results indicate that both one-step excavation and multistep excavation have great influences on the displacement of adjacent tunnels, wherein the influences on the tunnel located at the right of foundation pit are greater than those at the bottom of foundation pit. Multistep excavation is recommended for the foundation pit adjacent to shallow tunnel. In the case of the tunnel located on the bottom of the foundation pit, the maximum stress generated around the tunnel is small, the maximum stress area is limited, and the displacement of tunnel monitoring points is also small. For the tunnel located at the right of the foundation pit, the pile-bolt supporting can effectively limit the displacement of soil between the tunnel and the foundation pit, reduce the maximum stress and the maximum stress distribution area, and effectively control the tunnel displacement.

Hemodynamic study of the effect of the geometric height of leaflets on the performance of the aortic valve under aortic valve reconstruction

BackgroundAlthough aortic valve reconstruction has become an alternative treatment for aortic valve disease, the design of the geometric parameters of the reconstructed leaflet still mainly depends on the experience of doctors. The present study investigates the effects of the height of the leaflets on the performance and biomechanical states of the reconstructed aortic valve.MethodsThis numerical study was carried out using the finite element approach and the lattice Boltzmann method. The dynamic and biomechanical characteristics of the leaflets were evaluated by using the finite element approach, while the blood flow in the aortic sinus was evaluated by applying the lattice Boltzmann method. Three types of leaflets with different heights were designed. Then the dynamic characteristics, stress distribution, and effective orifice area (EOA) of the aortic valve and flow pattern were calculated as the indicators.ResultsThe results demonstrated that the height of the leaflets could indeed regulate the performance and the biomechanical states of the aortic valve. The rapid valve opening times of the 3 types of leaflets gradually reduced along with the decrease of the height ratio (HR_0.8: 120 ms vs. HR_1.0: 68 ms vs. HR_1.2: 31 ms), while the rapid valve closing times (RVCTs) of the 3 types of leaflets were similar to each other (approximately 75 ms). Moreover, the radial displacement of the leaflet at the fully open time increased along with the decrease of the HR of the leaflets (HR_0.8: 8 mm vs. HR_1.0: 6 mm vs. HR_1.2: 4 mm). In addition, the stress level of the leaflets also increased with the increase of the height of the leaflets (max stress, HR_0.8: 0.5 MPa, vs. HR_1.0: 1.1 MPa, vs. HR_1.2: 1.8 MPa). Similarly, the low velocity region near the ascending aortic wall and the wall shear stress (WSS) level on the ventricular side of the leaflets also increased along with the increase of the HR of the leaflets.ConclusionsIn short, the height of the leaflets mainly affects the opening performance of the reconstructed aortic leaflets. The HR of the reconstructed leaflets for adults should be less than 1.0 to balance the opening and closing performance of aortic leaflets.

The responses of stitched ultra-high-molecular-weight polyethylene woven fabrics upon ballistic impact

This paper investigates the influence of thread stitching on the ballistic performance of plain weaves made of ultra-high-molecular-weight polyethylene multi-filament yarns. The inter-yarn friction is increased due to the constraint imparted by the sewing thread. The yarn pull-out test shows that the peak-load force of the sample with one stitching line is almost 10 times greater than that of the unstitched plain weave, and the maximum pull-out force increases with the loading rate. Ball-bearing impact tests are performed to characterize the ballistic performance of the stitched and the unstitched samples, and finite element simulation is used to study the underlying mechanisms of energy absorption. The ballistic penetration tests show that the stitched fabrics outperform the plain weave in terms of energy absorption. The most significant improvement in ballistic performance is observed in stitched panels where sample SL2T (a triple-ply plain fabric system stitched on every two yarns) exhibits a specific energy absorption over two times greater than that of multi-ply systems consisting of plain weaves. It is also found from the high-speed photography that thread stitching constrains the yarn displacement and therefore eliminates the possibility of yarn pull-out, enabling the primary yarns to be well-engaged with the projectile at low impact velocities and to be stretched to fail at high impact velocities. Numerical predictions show that thread stitching enlarges the area of stress distribution and widens the transverse deflection, making the stitched systems absorb more energy than the unstitched system shortly after impact.

The Ballistic responses of thread-quilted plain weaves with increased yarn–yarn​ friction

This paper investigates the influence of quilting on the ballistic performance of plain weaves. The friction between the fabric-forming yarns was increased due to the constraint imparted by thread quilting. Ballistic impact tests were performed to characterize the ballistic protection of the quilted and the un-quilted samples, and FE simulation was used to study the mechanisms of energy absorption. It was found that the quilted fabrics outperform the un-quilted plain weave in terms of energy absorption. The most significant improvement in energy absorption capability exhibits a specific energy absorption over two times greater than that of un-quilted plain weaves. In addition, it was found from the images obtained from the high-speed camera that yarn quilting is effective in resisting yarn pull-out during a ballistic event, enabling more energy to be absorbed by the fabric system. Numerical predictions showed that thread quilting enlarges the area of stress distribution and the transverse deflection, and consequently enable the quilted systems to absorb more energy than the unquilted system shortly after impact. When the constituent layers were quilted together in a panel, the system acted as integrity during the energy dissipation process even though the individual layers were damaged by the projectile.

Effect of different attributes of the mimic human lumbar spine biomechanics material structure change by finite element analysis

In this study, we compared stress changes and quantity effect relationships from 3D finite element models of normal and degenerative lumbar segments. We further defined the mechanisms causing alterations in mechanical stability the control of normal and degenerative lumbar segments using traditional Chinese medicine. The characteristics of the stress change and the quantity effect relationships of the three-dimensional finite element model of normal and degenerative lumbar segments were compared. The mechanism(s) leading to changes in mechanical stability and the intervention and balance between normal and degenerative lumbar segments of the traditional Chinese medicine was analyzed. The change trend of stress and strain was compared with the three dimensional finite element model under different motion states of normal lumbar vertebrae. A 3D-FEM of degenerative lumbar segments L4 ~ 5 of the human spine was established to simulate the physiological and pathological changes of the lumbar spine in response to flexion, extension, lateral bending and torsion. The stress changes in the normal and degenerative lumbar vertebrae were assessed through external force interventions and the response to TCM. Stress in the degenerative lumbar vertebrae changed according the external load. Stress and strain were compared in the FEM model under a range of motion states. Components of the human lumbar vertebrae including the cortical vertebrae, cancellous bone, endplates, fibrous rings, and facet articular processes were investigated. The elastic modulus of the nerve roots and the posterior marginal structures of the vertebral body increased with lumbar degeneration. Under stress trends in normal lumbar and different degrees of degenerative lumbar structures including cortical bone, loose bone, terminal plate, fiber ring, nucleus, small articular processes, nerve roots and posterior structures. In normal lumbar spine, 20%, 50%, 70% lumbar degeneration, 106 different lumbar anterior flexion 30 and posterior extension with different external forces showed that ANOVA F was between 3.623 and 11.381 and P changed between 0.001 and 0.05.It is clear that in the lumbar movement segments under different pressure intervention, the changes in the degree of degeneration are significantly different from each constituent structure, among which the trend of expected change between the constituent structures of the lumbar anterior flexion 30 is particularly obvious. The stress distribution in the intervertebral discs were influenced by TCM, and the space in the spinal canal enlarged so that nerve root stress decreased, vertebral body stress increased, and facet processes and pedicle stress in the posterior regions exceeded those of the anterior flexion position. The internal stress of the intervertebral disc increased in the flexion compared to the extension position, gradually increasing from top to bottom. The stress concentration point of the degenerative lumbar disc is significantly greater than the stress in the normal lumbar disc stress distribution area, and increases with the degree of degeneration. Compared with the load capacity of normal lumbar and mild (15% reduction), moderate (40% reduction) lumbar disc protrusion model in bending, extension, axial rotation, lateral bending, the results found that the load transmission of lumbar disc degeneration model to different degrees has also changed, so its compression stiffness, strain distribution and size are also different. TCM can improve and treat lumbar disc disease through its ability to regulate the mechanical environment of degenerative lumbar vertebrae. Compared to the FEM models of the lumbar vertebrae, lumbar degenerative changes could be assessed in response to alterations in the biomechanical environment. These findings provide a scientific basis for the popularization and application of TCM to prevent and treat spinal degenerative disease.

Stress distribution around short implants with different frictional joint designs: a photoelastic colorimetric analysis / Distribuição de tensão em torno de implantes curtos com diferentes designs de fricção: uma análise colorimétrica

Aim: To compare, biomechanically, two types of short implants with different frictional implant/abutment joint designs. Methods: Two groups (n = 10) were divided in straight platform (DSP, 5 x 5.5 mm) and angled platform (30°) (Kopp, 5 x 6.0 mm). The loads applied axially were 100 N, 200 N and 400 N. A photoelastic colorimetric analysis around the implants was performed, based on the magenta fringes, measured in pixels. The data were analyzed by the One-Way ANOVA with repeated measures, Tukey and Mann-Whitney U tests (p < 0.05). Results: The short implants demonstrated similar biomechanical behavior, but statistical difference occurred in the group Kopp, under the axial load of 400 N (p < 0.05). Conclusion: The implant design showed influence on the stress distribution around the locking taper short dental implants. In both groups, the area of greatest stress distribution was at the apical region.

Shear band evolution related with thermal annealing revealing ductile-brittle transition of Zr35Ti30Be27.5Cu7.5 metallic glass under complex stress state

The ductile-brittle transition (DBT) caused by thermal annealing was systematically investigated by means of small punch test (SPT), accompanied by finite element simulation, uniaxial compression and nanoindentation in Zr-based metallic glasses (MGs) annealed for 1 h in a wide temperature range, i.e., sub-Tg, Tg ∼ Tx and above-Tx. In multiaxial loading mode, three deformation mechanisms, i.e., (ⅰ) circumferential shear bands (CSBs) + radial shear bands (RSBs), (ⅱ) RSBs and (ⅲ) radial cracks (RCs), can be found separately on MGs annealed sub-Tg, Tg ∼ Tx and above-Tx, leading to a transition in deformation mode from ductility to brittleness. First, for MGs with sub-Tg, Tg ∼ Tx annealing, the reduction in the number of CSBs and RSBs, as well as the disappearance of CSBs, are responsible for the ductile-brittle transition, which is attributed to the annihilation of free volume caused by structural relaxation and the reduction of released elastic energy. Based on simulation results, the decrease in plasticity of MGs is accompanied by the reduction in stress distribution area, which is in agreement with the change in the number and distribution area of shear bands. The initiation of multiple shear bands and their strong interaction dramatically improve the plasticity of MGs under the synergistic effect of large stress distribution area and high content of free volume. Second, the embrittlement of MGs with above-Tx annealing is mainly attributed to the rapid formation and extension of RCs induced by the occurrence of crystallization. Meeanwhile, simulation results indicate that stress distribution area decreases gradually and facilitate the formation of stress concentration, leading to the rapid extension of RCs and the occurrence of catastrophic fracture of MGs. In addition, MGs with sub-Tg, Tg ∼ Tx and above-Tx annealing not only exhibit such DBT in uniaxial compression, but also show a soft-hard transition in nanoindentation test.

Stress distribution and displacement of three different types of micro-implant assisted rapid maxillary expansion (MARME): a three-dimensional finite element study

Background/objectiveUntil 2010, adults underwent surgical treatment for maxillary expansion; however, with the advent of micro-implant-assisted rapid maxillary expansion (MARME), the availability of less invasive treatment options has increased. Nevertheless, individuals with severe transverse maxillary deficiency do not benefit from this therapy. This has aroused interest in creating a new device that allows the benefit of maxillary expansion for these individuals. The aim of this study was to evaluate the efficacy of three MARME models according to tension points, force distribution, and areas of concentration in the craniofacial complex when transverse forces are applied using finite element analysis.Materials and methodsDigital modeling of the three MARME models was performed. Model A comprised five components: one body screw expander and four adjustable arms with rings for mini-implant insertion. These arms have an individualized height adjustment that allows MARME positioning according to the patient’s palatal anatomy, thereby preventing body screw expander collision with the lateral mucosa in severe cases of maxillary deficiency. Model B was a maxillary expander with screw rings joined to the body, and model C was similar to model B, except that model C had open rings for the insertion of the mini-implants. Through the MEF (Ansys software), the stresses, distribution, and area of concentration of the stresses were evaluated when transverse forces of 7.85 N were applied.ResultsThe three models maintained the following pattern: model C presented weak stress peaks with limited distribution and lower concentration area, model B obtained median stress peaks with better distribution when compared to that of model C, and model A showed better stress distribution and larger concentration area. In model A, tensions were located in the lateral lamina of the pterygoid process, which is an important site for maxillary expansion. The limitation of the present study was that it did not include the periodontal tissues and muscles in the finite element method evaluation.ConclusionsModel A showed the best stress distribution conditions. In cases of severe atresia, model A seems to be an excellent option.

Seismic Response Analysis of Deep Underground Roadways and Coal Pillars under the Influence of the Adjacent Goaf

In this work, a numerical study is conducted on the seismic response of deep-buried roadways in coal mines under the influence of goafs, and a 3D numerical model of the seismic response simulation of deep-buried roadways is established using the coupling model of the finite difference method and the distinct element method. This model simulates the seismic response of different coal pillar widths and the seismic conditions of the deep-buried roadways under the influence of the adjacent goafs. The deformation, stress distribution, and plastic area distribution of roadways and coal pillars are systematically studied, and the situations under the static load and the roadways, which are not affected by the goafs, are compared and analyzed. A reasonable width of the coal pillar is proposed on the basis of the stability of the roadway and the coal pillars. In the end, suggestions for the reasonable setting of coal pillars under seismic load are provided.

Finite element analysis of biomechanical effects of residual varus/valgus malunion after femoral fracture on knee joint.

Post-operative femoral shaft fractures are often accompanied by a residual varus/valgus deformity, which can result in osteoarthritis in severe cases. The purpose of this study was to investigate the biomechanical effects of residual varus/valgus deformities after middle and lower femoral fracture on the stress distribution and contact area of knee joint. Thin-slice CT scanning of lower extremities and MRI imaging of knee joints were obtained from a healthy adult male to establish normal lower limb model (neutral position). Then, the models of 3°, 5°, and 10° of varus/valgus were established respectively by modifying middle and lower femur of normal model. To validate the modifying, a patient-specific model, whose BMI was same to former and had 10° of varus deformity of tibia, was built and simulated under the same boundary conditions. The contact area and maximum stress of modified models were similar to those of patient-specific model. The contact area and maximum stress of medial tibial cartilage in normal neutral position were 244.36 mm2 and 0.64MPa, while those of lateral were 196.25 mm2 and 0.76MPa. From 10° of valgus neutral position to 10° of varus, the contact area and maximum stress of medial tibial cartilage increased, and the lateral gradually decreased. The contact area and maximum stress of medial meniscus in normal neutral position were 110.91 mm2 and 3.24MPa, while those of lateral were 135.83 mm2 and 3.45MPa. The maximum stress of medial tibia subchondral bone in normal neutral position was 1.47MPa, while that of lateral was 0.65MPa. The variation trend of medial/lateral meniscus and subchondral bone was consistent with that of tibial plateau cartilage in the contact area and maximum stress. This study suggested that varus/valgus deformity of femur had an obvious effect on the contact area and stress distribution of knee joint, providing biomechanical evidence and deepening understanding when performing orthopedic trauma surgery or surgical correction of the already existing varus/valgus deformity.

Biomechanical behavior of endocrowns vs fiber post-core-crown vs cast post-core-crown for the restoration of maxillary central incisors with 1 mm and 2 mm ferrule height: A 3D static linear finite element analysis.

To analyze the stress distribution of the maxillary central incisor with oblique fracture, repaired by different methods, using 3-dimensional finite element analysis. From the biomechanical point of view, it is expected to provide a reference for clinical selection of restoration method which is more conducive to stress distribution and preservation of dental tissue as much as possible.Use cone beam CT and finite element software to establish the finite element models of the maxillary central incisor with oblique fracture, and then create models according to 5 repairing methods(A. fiber post-core-crown group; B. cast post-core-crown group; C.3 mm deep endocrown; D.4 mm deep endocrown; E.5 mm deep endocrown)after root canal treatment, and analyze the Von Mises equivalent stress and maximum principal stress distribution and peak value of each model.When the height of dentin ferrule was fixed, the value of the Von Mises equivalent stress and the maximum principal stress in residual tooth tissue: group A was the highest, and there was no significant difference in group B, C, D and E. And the stress distribution area of 5 groups were the same. In prosthodontic layer: group B was the highest, while group A was the lowest, and the stress peak slightly increased with the increase of depth in group C, D and E. And the 5 groups were with the same stress distribution area as well. In adhesive layer: group A was the highest, while group B was the lowest, and there was little difference among group C, D and E. Group A was concentrated in 1/3 of the post tip, while group B,C,D and E were concentrated in 1/3 of the post and the post tips.Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 3 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown.

The structural effects on the impact response of ultra-high-molecular-weight polyethylene plain weaves

This paper investigates the penetration and energy absorption mechanisms of ultra-high-molecular-weight polyethylene plain weaves with different fabric properties. Impact tests along with finite element (FE) analysis were used to study the impact response of the fabrics. In this research, the impacting projectile did not cause any fiber or yarn failure on the samples. It was found that structural parameters determine the yarn pull-out behavior and the softness of the resultant fabrics. Fabrics formed by loosely interlaced yarns tend to exhibit higher softness and less resistance against yarn pull-out. When the projectile velocity is not sufficient to initiate yarn pull-out, material softness determines the depth of the backface signature on the clay witness. This trend is more pronounced in a multi-ply fabric system than in a single-ply system; when yarn pull-out occurs, the projectile-slowing mechanism depends on the frictional force between the warp and weft yarns. Therefore, fabric softness becomes less important, and the yarn pull-out behavior of the fabric plays a predominant role in energy absorption. FE prediction showed that tightly woven fabrics exhibit a larger area of stress distribution and material deformation than those with severe yarn pull-out and, consequently, these tight fabrics tend to absorb more kinetic energy and sustain higher impact load from a projectile.

Numerical simulation of the stability of deep roadway surrounding rock based on FLAC3D

In view of the problems such as roadway section deformation caused by the roadway’s violent bottom drum, causing the roadway transportation and maintenance difficulties, the numerical simulation calculation software FLAC3D was used, and the numerical calculation was obtained, which was the vertical stress, horizontal stress distribution and plastic area distribution of the surrounding rock after the excavation of the roadway, and the analysis obtained the mechanism of the roadway bottom drum: because the weak top plate of the coal layer was disturbed by the weak top plate of the coal layer closer to the bottom of the roadway. Then the underside rock pressure of the roadway because of the bottom drum and continuous dynamic redistribution, and gradually to the right and deep development, and eventually lead to the bottom drum gradually deterioration and show left and right asymmetrical characteristics.

Effects of tool edge radius on chip formation during the micromachining of pure iron

The smoothed particle hydrodynamics simulation model of micromachining of industrial pure iron was established to study the effect of tool edge radius on chip formation in this paper. The process of chip production was studied by particle displacement method, and cutting force and stress were analyzed. Meanwhile, the mechanism of chip formation was revealed. The simulation results show that the tool edge radius has significant effects on chip formation in micromachining. When the depth of cut is 0.16 times of the tool edge radius, the chips begin to produce. And the minimum cutting thickness decreases with the increase of the ratio of the cutting depth to the tool edge radius, which means that chips are more easily to be produced with the decrease of the tool edge radius. Meanwhile, the larger the tool edge radius is, the wider the stress distribution area is and the greater the fluctuation of the cutting force is. Finally, values of the minimum cutting thickness under different ratios obtained by the theoretical formula are basically consistent with the simulation results, verifying the correctness of the simulation results. This paper provided valuable insights into reasonable selection of tool parameters for improving machining precision.

Safety performance of self-expandable NiTi alloy stent

In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent's original diameter.

Illustrating hybrid effect and damage evolution of carbon/aramid braided composite under low-velocity impact

This study illustrates the hybrid effect and damage evolution of carbon/aramid braided composites under low-velocity impact, using a finite element model (FEM) of a complete braided structure. The model was established based on a real three dimensional (3D), five directional (5d) braided structure by taking the interior, surface, corner braided and axial yarns into consideration. Constitutive material modeling and failure criteria were introduced into the model. The degree of damage was determined by comparing the volumes of units removed on failure. Three hybrid structure types were adopted to investigate the relationships between stress distribution and damage evolution. The results showed that the impact response and failure morphology were significantly dependent on hybrid effects under different low-velocity impacts. The impact response curves of hybrid structures showed obvious toughness characteristics. The addition of aramid fiber as an axial yarn could prolong the overall impact response time and reduce failures. Moreover, the hybrid effect strongly influenced the stress distribution and damage evolution in different circumstances. Hybrid structures led to a large stress distribution area and a low stress level, which could reduce the material failure caused by stress concentration. This work provides a sound method for designing hybrid structures and expanding the application potential of 3D braided composites.

Transcatheter aortic valve implantation with the Portico and Evolut R bioprostheses in patients with elliptic aortic annulus.

To compare paravalvular leak (PVL) and device success rate of two self-expanding devices (Portico and Evolut-R) in patients with elliptic aortic annulus undergoing transcatheter aortic valve implantation (TAVI). This retrospective study included 374 patients submitted to TAVI with Portico (n=111) and Evolut-R (n=263), and available aortic annulus measurements at computed tomography angiography. Aortic annulus was defined elliptic if the index of eccentricity (IE=1-aortic annulus (minimum diameter)/(maximum diameter)) was >0.25. Device behavior to annulus eccentricity variations was measured by computational simulation in an idealized aortic root with three different IE (0, 0.25, and 0.5). An elliptic aortic annulus was found in 107 (28.6%) of 374 patients. Fewer rates of >moderate PVL were observed in Portico elliptic group compared to Evolut-R elliptic group (0.0% vs.15.2%; P=0.034). Device success in Portico elliptic group (100%) was significantly higher compared to that of Evolut-R elliptic group (84.8%; P=0.019). Eccentricity was a positive predictor of device success only in Portico patients (P=0.021). On computational simulation, Portico showed stable stent root interaction area, stress distribution, and regurgitant orifice area for IE=0.25 and 0.5. Portico showed good adaptability to annulus eccentricity variations and excellent PVL/device success rates in elliptic patients, compared to Evolut-R.

Computational Biomechanical Analysis of Postoperative Calcaneal Fractures with Different Placement of the Sustentaculum Screw

ObjectiveTo evaluate the computational biomechanical analysis of intra‐articular calcaneal fractures with different fixation status of the sustentaculum plate screw, when the finite element modeling of calcaneal fractures were fixed by the lateral locking plate.MethodsThe normal right foot of a male (age: 36 years; height: 174 cm; body weight: 65 kg) was scanned by the CT scanner. As the computational biomechanical study, the three‐dimensional finite element model of the simplified Sanders type‐II calcaneal fracture was built. Fixation with the lateral calcaneal locking plate and screws was simulated using a finite element software package according to clinical operation. According to the different placement of the sustentaculum plate screw, the models were categorized as the accurate fixation group, marginal fixation group, and non‐fixation group. The loading of 650 N with the vertical axial compression was applied to simulate the standing phase with single foot. The Von Mises stress distribution, maximal displacement, and contact area of the subtalar joint were analyzed among three groups.ResultsThe pressure distribution of the subtalar joint facet was inhomogeneous. The stress concentration of the calcaneus was located at the medial zone of the posterior subtalar joint facet. The peak Von Mises stress distribution in three groups was similar at the subtalar joint facet of 4.9 MPa, 5.1 MPa, and 5.4 MPa. In the accurate fixation group, the contact area on the posterior articular facet was 277.1 mm2; the maximal displacement was 0.18 mm. The contact area of the marginal fixation group was 265.3 mm2 on the posterior facet, where the maximal displacement was 0.23 mm. In the non‐fixation group, the contact area was 253.8 mm2; the maximal displacement was 0.25 mm. There was a slight change in the contact area of the subtalar joint and no prominent displacement of the calcaneus could be detected among the three groups.ConclusionsThe biomechanical results, including the peak stress distribution, contact area, and maximal displacement of subtalar joint, were similar whether the screw is placed exactly within the sustentaculum tali or not, when the calcaneal fractures were fixed by the lateral locking plate. The sustentaculum plate screw had less effect on the biomechanical performance of the calcaneus.

Design of bulkhead reinforcement of trimaran based on topological optimization

A design method of bulkhead reinforcement of trimaran based on topological optimization is proposed, which can reduce the mass of bulkhead and reinforcement as much as possible while ensuring that bulkhead has sufficient structural strength. Based on Rules for The Classification of Trimarans, seven structural strength checking conditions are designed. Stress distribution of trimaran bulkhead structure and reinforcement before and after optimization under different conditions are calculated by using finite element method and variable density topology optimization method. The results show that: The maximum stress distribution area of bulkhead and reinforcement occurs near the connecting bridge and the large opening. When the volume constraints are changed, the stress distribution and maximum stress of the optimized bulkhead and reinforcement will change accordingly. There is no positive correlation between the maximum stress and the volume reduction ratio of reinforcement. The maximum bulkhead stress cannot be reduced by increasing the volume retention ratio of the reinforcement. The distribution of the optimized reinforcement is similar to that of the real bulkhead. On the premise that the bulkhead has sufficient structural strength, the lightweight design of trimaran structure can be realized based on the topological optimization method.