Dassault Systemes Research Articles

Biomechanical evaluation of six zygomatic implants versus four zygomatic implants combined with dental implants in the treatment of different maxillary defects

BackgroundThis study aims to compare the biomechanics of six zygomatic implants (ZIs) and dental implants (DIs) combined with four ZIs with different maxilla defects.MethodsThree-dimensional constructs of the ZIs, DIs human skulls, and maxillary prostheses were created using SolidWorks Software (Version 2015, Dassault Systems SolidWorks Corporation, Waltham, MA, USA). Eight finite element models of the skull with four different alveolar defect types (0–4) were constructed. Type 0: No defect; Type 1: Bilateral posterior defects; Type 2: Right posterior defect; Type 3: Anterior and left posterior defects; Type 4: Bilateral posterior and anterior defects. In two models with the same defect type (for defect types 0–2), six ZIs or two DIs combined with four ZIs were inserted into the maxilla. Six ZIs were inserted in the maxilla models with defect types 3 and 4. Vertical (150 N) and masseteric (300 N) loads were simulated on the prosthesis. The maximum Von Mises stress in the implants/surrounding bone and bone deformation were evaluated.ResultsThe maximum Von Mises stresses in bone/implant were found highest in the defect type 2 model with four ZIs combined with two DIs. The lowest maximum Von Mises stress for bone was detected in the model with defect type 0 and with six ZIs.ConclusionAmong the four types of defects, the posterior unilateral defect caused the highest stress value.

Stress distribution by parafunctional loading on tooth–implant, implant–implant, and tooth–tooth-supported prosthesis: A comparative three-dimensional finite element analysis

Aim: The study’s objective was to evaluate the stress distribution in tooth-implant, implant-implant, and tooth-tooth supported prostheses under parafunctional loading in axial and oblique directions employing a 3D finite element analysis in the mandibular posterior region which had D3 bone (porous cortical bone and fine trabecular bone). Setting and Design: In vitro study, Finite element analysis. Meterials and Methods: Cone-beam computed tomography data was used by Mimics software (Materialize Mimics 19) to create a three-dimensional finite element simulation of the jaw. Solid Works 2018 (Dassault Systems) was used to produce a geometric 3D model of the three systems. Each model consisted of a bone, an implant, and teeth (Model I tooth-tooth supported, Model II tooth-implant supported and Model III implant-implant supported). The three models’ geometrical models were transferred to Ansys Workbench (19.2 software) for the analysis portion. A load that mimicked masticatory force was delivered in both axial and oblique directions. Statistical Analysis Used: In the present study, statistical analysis was not required because 3D finite element analysis uses deterministic numerical methods to simulate physical behavior and stress distribution patterns. Result: The results demonstrated that under the parafunctional combined loading process, the implant- implant supported prosthesis showed significantly higher stress concentrations in the bone. It was found that the cortical bone around the crestal region had the highest stresses. Conclusion: Within the constraints of this investigation, we could draw the following conclusion: Of the three models, the tooth-tooth supported prosthesis exhibited the least amount of stress distribution, which was also least when functional loading was applied in the axial direction.

Influence of Framework Material and Abutment Configuration on Fatigue Performance in Dental Implant Systems: A Finite Element Analysis.

Background and Objectives: This study uses finite element analysis to evaluate the impact of abutment angulation, types, and framework materials on the stress distribution and fatigue performance of dental implant systems. Materials and Methods: Three-dimensional models of maxillary three-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Two different framework materials were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The distribution of stress and fatigue performance were then assessed, considering the types of restoration frameworks used and the angles of the abutments in three distinct locations. The simulation aspect of the research was carried out utilizing Abaqus Software (ABAQUS 2020, Dassault Systems Simulation Corp., Johnston, RT, USA). Results: In all models, fatigue strengths in the premolar region were higher than in the molar region. Maximum stress levels were seen in models with angled implants. In almost all models with the zirconia framework, fatigue performance was slightly lower. Conclusions: According to the findings of this study, it was concluded that the use of metal-framework multi-unit restorations with minimum angulation has significant positive effects on the biomechanics and long-term success of implant treatments.

Numerical analysis of stresses on angular contact ball bearing under the static loading with respect to race thickness and housing stiffness

A 3-dimensional model of the angular contact ball bearing (ACBB) was modeled using Abaqus/standard (Dassault systems- version 2017) to investigate the influence of race thickness on the bearing performance. It was found that the ability to support higher contact stress increased with race thickness. However, large deformations were found to occur on outer race with thickness of 3.3 mm and only small deformations were observed on outer race with a thickness of 9.9 mm. The large deformations induce higher shear stresses on thin races than on thick races. These stresses cause spall growth in bearings and propagate into a network of cracks. As a result of these findings, thin races are prone to failure compared with thick races.

A Comparative Evaluation of Stress Distribution Around Different Widths of Implant and Bony Interface in Function During Axial and Non-axial Loading: A Finite Element Analysis.

The study employed three-dimensional (3D) finite element analysis (FEA) and examined how implant diameters affect stress distribution across the implant-bone contact and how stress transmission through this interface changes during axial and non-axial loading. A 3D mandibular model was created using cone beam CT of a patient with implants inserted into the first mandible molar. Nobel Biocare implants (Nobel Biocare, Switzerland) with specific dimensions of 3.5 mm, 4.3 mm, 5.0 mm, and 6.0 mm were chosen. Models were created in CATIAV5R19 (Dassault Systemes, France) from threaded titanium implant dimensions. Implants were finite element-modeled utilizing ANSYS Workbench v11.0 (Ansys, Inc, Pennsylvania, USA). The analysis involved applying 100 N axial, 50 N buccolingual, and 50 N mesiodistal loads. In a lower first molar bone segment, the implant top surface was loaded in 100 N axial, 50 N buccolingual, and 50 N mesiodistal orientations. The cortical bone proximal to the implant neck had the most von Mises stress, regardless of model or stress scenario. In Model I cortical bone, maximal stress was centered at the implant neck. Most stress was on lingual bone plates, lesser on buccal, and least on mesial and distal. Less than half of the implant stress was transmitted to the cortical bone. The stress transferred from the implant to the cortical bone in Model II was less than half of the implant stress. The same was true for Models III and IV. In Model I cancellous bone, stress was concentrated in the implant's coronal half and minimal in the apical half. The stress patterns under axial loading were distributed favorably. Therefore, it can be inferred that an augmentation in the diameter of the implant enhances the even distribution of stress at the interface between the bone and the implant by offering a larger surface area for the dispersion of stress. Furthermore, it was determined that applying force along an implant's axis was a beneficial loading direction and did not negatively impact its lifespan.

Numerical model of aneurysm formation in vascular grafts

Background. Using numerical modeling to study biomechanics of implantable devices for cardiovascular healthcare can help specialists understand underlying mechanisms of clinical complications caused by these devices.Aim: To describe the results of numerical modeling of aneurysm formation in vascular grafts based on the simulation of degradation of their mechanical properties.Material and Methods. The simulation was carried out using a three-dimensional computer model obtained by high-resolution computed tomography of the vascular graft “KemAngioProtez” (CJSC “NeoKor”, Russia). Using the 3D model obtained with a specialized script in the Abaqus/CAE environment (Dassault systems, USA), we have simulated the decrease in the elastic modulus (from 100 to 10%) with post-threshold stresses in the material and the accumulation of plastic strain.Results. Undergoing 150 loading cycles, the vascular wall in the model swelled up to 0.7 mm in the radial direction, and its mechanical properties degraded significantly (by 90% compared to baseline) due to prolonged pressure exposure. The value of maximum plastic deformation was 0.55%.Conclusion. Numerical modeling of graft mechanical properties degradation can assist in qualitative and quantitative assessment of the areas of aneurysm formation. The method makes it possible to visualize the swelling areas and can be used as a valuable tool to complement the existing approaches to studying vascular grafts, and biografts in particular.

A finite element analysis study on different angle correction designs for inclined implants in All-On-Four protocol

BackgroundThe aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol.MethodsTwo (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction) .While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components).ResultsWhen applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 μm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant.ConclusionWithin the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level.

A hemodynamic analysis of energy loss in abdominal aortic aneurysm using three-dimension idealized model.

Objective: The aim of this study is to perform specific hemodynamic simulations of idealized abdominal aortic aneurysm (AAA) models with different diameters, curvatures and eccentricities and evaluate the risk of thrombosis and aneurysm rupture. Methods: Nine idealized AAA models with different diameters (3cm or 5cm), curvatures (0° or 30°) and eccentricities (centered on or tangent to the aorta), as well as a normal model, were constructed using commercial software (Solidworks; Dassault Systemes S.A, Suresnes, France). Hemodynamic simulations were conducted with the same time-varying volumetric flow rate extracted from the literature and 3-element Windkessel model (3 EWM) boundary conditions were applied at the aortic outlet. Several hemodynamic parameters such as time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), endothelial cell activation potential (ECAP) and energy loss (EL) were obtained to evaluate the risk of thrombosis and aneurysm rupture under different conditions. Results: Simulation results showed that the proportion of low TAWSS region and high OSI region increases with the rising of aneurysm diameter, whereas decreases in the curvature and eccentric models of the corresponding diameters, with the 5cm normal model having the largest low TAWSS region (68.5%) and high OSI region (40%). Similar to the results of TAWSS and OSI, the high ECAP and high RRT areas were largest in the 5cm normal model, with the highest wall-averaged value (RRT: 5.18 s, ECAP: 4.36 Pa-1). Differently, the increase of aneurysm diameter, curvature, and eccentricity all lead to the increase of mean flow EL and turbulent EL, such that the highest mean flow EL (0.82W · 10-3) and turbulent EL (1.72W · 10-3) were observed in the eccentric 5cm model with the bending angle of 30°. Conclusion: Collectively, increases in aneurysm diameter, curvature, and eccentricity all raise mean flow EL and turbulent flow EL, which may aggravate the damage and disturbance of flow in aneurysm. In addition, it can be inferred by conventional parameters (TAWSS, OSI, RRT and ECAP) that the increase of aneurysm diameter may raise the risk of thrombosis, whereas the curvature and eccentricity appeared to have a protective effect against thrombosis.

NUMERICAL INVESTIGATION OF THE VALVE MODEL FOR PRIMARY SUTURELESS IMPLANTATION

HighlightsThe presented numerical model of the bioprosthesis support frame for sutureless fixation needs to be optimized to reduce the amplitude of the von Mises stresses.The presented setup of numerical modeling has been validated using the study of commercial analogs. AbstractAim. To assess the stress-strain state of three computer models of TAVI prosthesis support frames during crimping and shaping to the delivery configuration.Methods. The study included three models of stent-like support frames for balloon-expandable devices, which are intended to serve as a foundation for the subsequent development of a domestic aortic valve prosthesis: two models of commercial bioprostheses and one experimental. The objects were evaluated numerically under the conditions of stress-strain state that arises in the stent support frames, simulating two loads: crimping and shaping to the delivery configuration. The study was conducted using the numerical modeling complex Abaqus/CAE (“Dassault Systemes”, France). The key indicators for evaluation were the von Mises stress, as a strength criterion, and its distribution over the frame; the presence and proportion of elastic recoil.Results. It was shown that all samples are capable of reaching the required diameter without excessive material. A quantitative investigation of the Von Mises stress showed that commercial models display amplitudes below the material`s strength limit (892.4 and 916.8 MPa), whereas the proprietary model exceeds this limit, reaching 991.4 MPa, requiring geometry optimization. Shaping to the delivery configuration indicates that all models provide safe expansion up to 26 mm, with a Von Mises stress level in the range of 882.4–914.1 MPa, which is below the strength limit of the cobalt-chrome alloy. Moreover, we have noted heterogeneous stress distribution, with concentration in the lamella junction areas.Conclusion. Thus, it has been demonstrated that numerical modeling and the finite element method can be effectively applied to assess the stress-strain state of sutureless prostheses. Geometry optimization and further development of this project – the development of a Russian minimally invasive aortic valve prosthetic system, may contribute towards increasing the accessibility of this treatment method.

Enhancing decellularized vascular scaffolds with PVDF and PCL reinforcement: a fused deposition modeling approach

BackgroundDecellularized xenogenic scaffolds represent a promising substrate for tissue-engineered vascular prostheses, particularly those with smaller diameters (<6 mm). Despite their benefits, a notable limitation presents itself during decellularization, namely, the diminished mechanical strength that introduces the risk of aneurysmal dilations in the early post-implantation period. This study introduces a strategy for modification the mechanical properties of these biological scaffolds through the forming of an external polymeric reinforcement via thermal extrusion.MethodsThe study utilized scaffolds fabricated from bovine internal mammary arteries through decellularization and preservation. The scaffolds were divided into subgroups and reinforced with polymeric helices made of Polyvinylidene fluoride (PVDF) and Polycaprolactone (PCL), n = 5 for each. An experimental setup for external reinforcement coating was designed. Computed microtomography was employed to obtain accurate 3D models of the scaffolds. Mechanical properties were evaluated through in vitro uniaxial tension tests (Z50, Zwick/Roell, Germany), compliance evaluation and numerical simulations (Abaqus/CAE, Dassault Systemes, France) to investigate the effect of external reinforcement on aneurysm growth.ResultsUsing a double-layer helix for the reinforcement significantly enhanced the radial tensile strength of the scaffolds, increasing it up to 2.26 times. Yet, the comparison of vessel's compliance between two reinforced and the Control scaffolds within the physiological pressures range did not reveal any significant differences. Numerical simulation of aneurysm growth showed that thin-walled regions of the Control scaffold developed aneurysmal-type protrusions, bulging up to 0.7 mm, with a substantial degradation of mechanical properties. In contrast, both PVDF and PCL reinforced scaffolds did not exhibit significant property degradation, with deformations ranging 0.1–0.13 mm depending on the model, and a maximum decrease in the modulus of elasticity of 23%.ConclusionThe results of the study demonstrated that the external polymer helical reinforcement of decellularized scaffolds via thermal extrusion enables a controlled modification of mechanical properties, notably enhancing radial strength while maintaining sufficient compliance within the physiological pressure range. A series of in vitro tests demonstrated the consistency and potential of this approach for decellularized xenogenic scaffolds, a concept that had not been explored before.

New Creep Crack Growth Prediction Model for the Life Assessment of Stainless-Steel Material Using Computational Modeling

The limitations of the established and existing creep failure models have inspired the development of a new creep prediction model. Models like Norton–Bailey and Omega are unable to model the tertiary creep curve for engineering materials. Kachanov–Rabotnov, Theta Projection, and Sine hyperbolic models rely on specific material properties for accurate damage predictions. In order to overcome these weaknesses, a new creep model combining the Norton–Bailey and Kachanov–Rabotnov models has been further devised for the creep life prediction of metallic materials. The model combination helps in covering the limitations of one model over another and to benefit from each other’s strengths. A technique of user subroutine scripting was adapted to implement the new creep model in finite element (FE) software of ABAQUS, manufactured by Dassault Systemes, version 2020. The new model was tested on an FE dog bone stainless steel 304 specimen; the analysis showed excellent agreement with the experimental creep deformation data at 600 °C to 700 °C. The creep strain rate curves obtained by the method of user subroutine scripting were found to be 90.69% accurate to the 1000 h experimental creep strain rate curve. Similarly, while comparing with the 336 h experimental creep test, the new model accuracy was found to be 92.66% for the creep strain rate curve. The new model’s precision was 91.56% when compared with the Omega and Norton–Bailey models for creep strain rate for the same conditions. The quantitative accuracy of the new creep model is better as compared to the existing creep models and can be an improved source of alternatives to existing creep models for the deformation predictions.

The Effect of Preparation Design on Stress Distribution in Lithium Disilicate Laminate Veneer using 3D Finite Element Analysis.

Background: A layer of ceramic bonded to the facial surfaces of prepared teeth to create a ceramic esthetic veneer, also known as a laminate veneer. Objective: This study aimed to examine the effect of preparation design on the stress distribution in lithium disilicate veneer at different angulations of masticatory loading. Methods: The finite element approach assessed the structure stress distribution. So, Exocad dental CAD was used to obtain the models, which consist of an upper central incisor in three dimensions (3D), and prepare them with the same software for an indirect veneer. The models were imported into software (SolidWorks; Dassault Systems) to construct solid models. The external load used in this study was 100 N at 60 degrees (intercuspal) and 125 degrees (protrusive) in the palatal surface, two mm below the incisal edge. The models were restored using e-max laminate veneers with different tooth preparation designs (palatal chamfer and window preparation designs). Analysis and calculations were performed on the stress distributions and maximum stress values of the tooth structures, cement layer, and laminate veneer. Results: With a window preparation design, the maximum stress values in the tooth and laminate veneer were higher. In the palatal chamfer design, stresses were dispersed more consistently through the cement layer and laminate veneer. Higher stress was generated by protrusive movement than by intercuspal movement. Conclusion: Compared to window preparation, the palatal chamfer design for lithium disilicate laminate veneer showed a more favourable stress distribution. Regardless of the preparation design, maximum stress values were observed in the cervical and incisor areas of the tooth structure.

The Effect of Preparation Design on Stress Distribution in Lithium Disilicate Laminate Veneer using 3D Finite Element Analysis.

Background: A layer of ceramic bonded to the facial surfaces of prepared teeth to create a ceramic esthetic veneer, also known as a laminate veneer. Objective: This study aimed to examine the effect of preparation design on the stress distribution in lithium disilicate veneer at different angulations of masticatory loading. Methods: The finite element approach assessed the structure stress distribution. So, Exocad dental CAD was used to obtain the models, which consist of an upper central incisor in three dimensions (3D), and prepare them with the same software for an indirect veneer. The models were imported into software (SolidWorks; Dassault Systems) to construct solid models. The external load used in this study was 100 N at 60 degrees (intercuspal) and 125 degrees (protrusive) in the palatal surface, two mm below the incisal edge. The models were restored using e-max laminate veneers with different tooth preparation designs (palatal chamfer and window preparation designs). Analysis and calculations were performed on the stress distributions and maximum stress values of the tooth structures, cement layer, and laminate veneer. Results: With a window preparation design, the maximum stress values in the tooth and laminate veneer were higher. In the palatal chamfer design, stresses were dispersed more consistently through the cement layer and laminate veneer. Higher stress was generated by protrusive movement than by intercuspal movement. Conclusion: Compared to window preparation, the palatal chamfer design for lithium disilicate laminate veneer showed a more favourable stress distribution. Regardless of the preparation design, maximum stress values were observed in the cervical and incisor areas of the tooth structure.

Multi-objective numerical optimization of 3D-printed polylactic acid bio-metamaterial based on topology, filling pattern, and infill density via fatigue lifetime and mass.

Infill parameters are significant with regard to the overall cost and saving material while printing a 3D model. When it comes to printing time, we can decrease the printing time by altering the infill, which also reduces the total process extent. Choosing the right filling parameters affects the strength of the printed model. In this research, the effect of filling density and infill pattern on the fatigue lifetime of cylindrical polylactic acid (PLA) samples was investigated with finite element modeling and analysis. This causes the lattice structure to be considered macro-scale porosity in the additive manufacturing process. Due to the need for multi-objective optimization of several functions at the same time and the inevitable sacrifice of other objectives, the decision was to obtain a set of compromise solutions according to the Pareto-optimal solution technique or the Pareto non-inferior solution approach. As a result, a horizontally printed rectangular pattern with 60% filling was preferred over the four patterns including honeycomb, triangular, regular octagon, and irregular octagon by considering the sum of mass changes and fatigue lifetime changes, and distance from the optimal point, which is the lightest structure with the maximum fatigue lifetime as an objective function with an emphasis on mass as an important parameter in designing scaffolds and biomedical structures. A new structure was also proposed by performing a structural optimization process using computer-aided design tools and also, computer-aided engineering software by Dassault systems. Finally, the selected samples were printed and their 3D printing quality was investigated using field emission scanning electron microscopy inspection.

BIO3: Advancement of a Novel Polymeric Transcatheter Aortic Valve as an Alternative to Tissue-based Valves

Background: Transcatheter aortic valve replacement (TAVR) is a minimally invasive alternative to surgical valve replacement, originally targeted to elderly patients with aortic stenosis (AS), now increasingly utilized in younger lower risk AS patients. With growth of TAVR the shortcomings of current tissue-based valves are becoming prevalent, namely limited durability and thromboembolic risk. To address these, a polymeric TAV named PolyV-2 (27 mm, PolyNova Cardiovascular Inc, Stony Brook, NY) was designed, optimized, and further tested. Methods: The design of the PolyV-2 (Figure A) was achieved with a battery of in silico simulations including the use of finite element analysis (FEA, Abaqus 2020, Dassault Systems, Providence, RI) to optimize the radial force of the stent frame and minimize leaflet stresses during the cardiac cycle. The PolyV-2 employs a sutureless design via coating the stent with polymer, bypassing problematic hand suturing manufacture of tissue valves. The PolyV-2 utilizes a thermoplastic elastomer polymeric material which was tested in vitro with accelerated wear durability testing according to ISO 5840-3 (2015) with periodic performance testing, evaluated against tissue-based surgical and TAV devices for platelet activation rate (PAR) in a pulsatile flow loop, and evaluated for calcification risk with similar wear testing in a pro-calcific medium. To assess the deposition of calcifications in the valves, both µCT and ICP spectroscopy were used. Results: The optimization process of the PolyV-2 leaflets (Figure B) was able to greatly lower the peak and mean stresses throughout over the cardiac cycle by employing a variable thickness across the entire leaflet. With success of this in silico optimization process, the leaflets were then tested in vitro (Figure C) in accelerated wear testing, performing 1Billion cycles w/o failure – correlating to 25 years of efficacy in vivo, exceeding the 250 million minimum required by the FDA. The material also demonstrated favorable hemocompatiblity as to PAR (Figure D) with activation significantly lower than a commercial tissue TAVR device, more comparable to a surgical device. The pro-calcific wear testing demonstrated no deposition of calcific salts within the polymer leaflet (µCT image, Figure E) compared to the tissue valve and minimal calcium detected with ICP spectroscopy. Conclusion: To mitigate the persistent complications of tissue-based TAV devices, the polymeric PolyV-2 valve was optimized through a battery of in silico and in vitro trials to offer superior hemodynamics, performance, and durability. Proper design and material considerations are essential to ensure successful translation, demonstration of enhanced bio/hemocompatibility and advance of the PolyV-2 through in vivo animal trials.

A structural analysis of the rail unit of an indoor assistive mobility system.

Individuals with gait disturbances, such as that post-stroke, are discharged home to undergo outpatient rehabilitation. Rehabilitation in the community is not as effective as that in hospital, due to long travel times and short program duration. This study analyzed rail unit structure, with the aim of assisting home indoor assistive mobility system (HIAMS) development, allowing patients to undergo gait-related rehabilitation training at home. The HIAMS consists of a mobile rail running around the whole room, a turn-table for movement between rails, and a weight-supporting component. Structural analysis was performed using the Abaqus/CAE solution (Version 6.14, Dassault systems, Inc.) to verify device safety, according to the load applied to the rail and turn-table units. The load was applied vertically at 150 kg to reflect the weight of potential users. Structural analysis was performed on the weight-supporting components, which was consist of turn-table case, bearing components (center, left), connective bracket and rail rollers. The safety factors of each components were estimated as 1.31, 5.39 (bearing, center), 8.45 (bearing, left), 1.43 and 3.61 in sequence. We demonstrated a safety factor of ⩾ 1.3 for the key system units, suggesting this technology is safe for use in the home rehabilitation training of individuals with gait impairment post-ICU stay.

P-Y Curve Correction of Shallow Seabed Formation Containing Hydrate

With the continuous growth in global energy demand, the exploration and development of hydrates has been the focus of increasing attention, and the accurate evaluation of the mechanical properties of hydrate layers has become particularly important. In this study, using a self-developed hydrate sample preparation device and hydrate triaxial seepage test platform, triaxial shear tests were carried out using the in situ synthesis method for hydrate sediment in the laboratory, and the stress–strain curves of hydrate sediment with different levels of saturation were obtained. By analyzing the stress–strain curve, the mechanical parameters of hydrate sediment were calculated and simulated using ABAQUS (2021, Dassault systemes, Vélizy Villacoublay France) finite element software. Several p-y curves were calculated and compared with the simulation results, and the p-y curve correction method of the hydrate layer in a shallow seabed was obtained. It was found that the strength of the hydrate sediment increased with an increase in saturation. At the same time, an increase in confining pressure and a decrease in temperature also increased the strength of hydrate deposits. Through comparison with the existing API (American Petroleum Institute) standard p-y curve, it was found that its strength is low because the existence of the hydrate improves the formation strength.

Biomechanical Profiling in Real-Life Abdominal Aortic Aneurysms in Different Clinical Scenarios

The aim of this study was to demonstrate the biomechanical properties in different abdominal aortic aneurysm (AAA) presentations of real-life patients. We used the actual 3D geometry of the AAAs under analysis and a realistic, nonlinearly elastic biomechanical model. Three patients with different clinical scenarios (R: rupture, S: symptomatic, and A: asymptomatic) with infrarenal aortic aneurysms were studied. Factors affecting aneurysm behavior such as morphology, wall shear stress (WSS), pressure, and velocities were studied and analyzed using steady state computer fluid dynamics using SolidWorks (Dassault Systems SolidWorksCorp., Waltham, Massachusetts). When analyzing the WSS, Patient R and Patient A had a decrease in the pressure in the bottom-back region compared with the body of the aneurysm. In contrast, WSS values appeared to be the most uniform across the entire aneurysm in Patient S. Furthermore, Patient A had focal small surface regions with high WSS values. The overall WSS in the unruptured aneurysms (Patient S and Patient A) were a lot higher than in the ruptured 1 (Patient R). All 3 patients showed a pressure gradient, being high at the top and low at the bottom. All patients had pressure values 20 times smaller in the iliac arteries compared with the neck of the aneurysm. The overall maximum pressure was similar between Patient R and Patient A, higher than the maximum pressure of Patient S. Computed fluid dynamics was implemented in anatomically accurate models of AAAs in different clinical scenarios for obtaining a broader understanding of the biomechanical properties that determine the behavior of AAA. Further analysis and the inclusion of new metrics and technological tools are needed to accurately determine the key factors that will compromise the integrity of the patient's aneurysms anatomy.

Influence of Philippine Halloysite on Thermal and Mechanical Performance of Poly(Lactic Acid) Filament for FDM Printing Applications

Additive manufacturing can be utilized to harness developments in polymer research. This study aims to investigate the effect of Philippine halloysite on poly(lactic acid) (PLA) filament for 3D printing using Fused Deposition Modeling (FDM). PLA-based filaments with halloysite powders were prepared by melt-compounding using a twin-screw extruder. The chemical composition and morphology of the halloysite powder was determined using XRD and SEM, respectively. Composite filament with 3% halloysite (PLA/HSC) was developed and characterized. The thermal properties of pure PLA and PLA/HSC were measured using DSC and TGA. CAD files for XRD analysis and tensile tests were generated using SolidWorks computer software (Dassault Systemes). Printability of pure PLA and the composite filament was observed by using Ultimaker S5 3D printer. The effect on chemical composition and mechanical performance of the 3D printed specimens was evaluated using XRD and UTM, respectively. XRD result confirmed the presence of dehydrated halloysite clay mineral. SEM image revealed the spherical morphology of the halloysite powder with average particle size of 72.472 nm. DSC analysis showed that incorporation of halloysite powder filaments had slightly decreased the glass transition of pure PLA matrix. This could be attributed to the enhanced mobility of polymeric chains by plasticization. Moreover, the melting temperature of PLA/HSC composite has slightly higher value than pure PLA filament owing to increased crystallinity imparted by the halloysite particles. With high stability of halloysite at elevated temperatures, the thermal stability of PLA/HSC filament was also enhanced. Mechanical performance of pure PLA was also improved with addition of halloysite. The tensile strength and elastic modulus of pure PLA matrix increased by 180.32% and 143.96%, respectively which could be due to the formation of hydrogen bonds between PLA matrix and halloysite particles. Digital micrographs of the fractured surface reveal that tensile pieces predominantly ruptured by brittle fracture.

Symmetries of Scan Patterns of Laser Scanners with Rotational Risley Prisms

Laser scanners with rotational Risley prisms produce scan patterns that can be classified as a type of rhodonea curve, because of their symmetry. The present study builds upon the novel, graphical method that we have developed to simulate and analyze such patterns using a commercially available mechanical design program, CATIA V5R20 (Dassault Systems, Paris, France). This graphical method has both the advantage of simplicity (regarding analytical methods) and of generating exact scan patterns (in contrast to approximate methods). The aim of this work is to utilize this method to study symmetry properties of scan patterns produced by a pair of rotational Risley prisms. A multi-parameter analysis is performed, considering the characteristic parameters of the approached scanner: refractive indexes and angles of the prisms, as well as their rotational velocities. Furthermore, Marshall’s parameters are considered: ratios of the rotational velocities and of the prism angles. Because the symmetries are identical for scan patterns generated by all the four possible configurations of a pair of prisms (and only their dimensions are different), the shape of these patterns is studied only for one of these configurations. Therefore, without losing generality, the symmetries of the patterns produced by such scanners are determined, as well as some of their characteristic dimensions. Rules-of-thumb were obtained to be able to generate patterns that are appropriate for a specific application. Moreover, we demonstrated that the existing symmetries simplify the process of obtaining the scan patterns by identifying repetitive parts (defined as structures of symmetry) of a pattern.