The present paper first investigates the collapse behavior of a conventional pipe-framed greenhouse under snow loading based on a 3-D finite element analysis,in which both geometrical and material non-linearities are ...The present paper first investigates the collapse behavior of a conventional pipe-framed greenhouse under snow loading based on a 3-D finite element analysis,in which both geometrical and material non-linearities are considered.Three snow load distribution patterns related to the wind-driven snow particle movement are used in the analysis.It is found that snow load distribution affects the deformation and collapse behavior of the pipe-framed greenhouse significantly.The results obtained in this study are consistent with the actual damage observed.Next,discussion is made of the effects of reinforcements by adding members to the basic frame on the strength of the whole structure,in which seven kinds of reinforcement methods are examined.A buckling analysis is also carried out.The results indicate that the most effective reinforcement method depends on the snow load distribution pattern.展开更多
The biomechanical effects of acetabular revision with jumbo cups are unclear.This study aimed to compare the biomechanical effects of bionic trabecular metal vs.titanium jumbo cups for the revision of acetabular bone ...The biomechanical effects of acetabular revision with jumbo cups are unclear.This study aimed to compare the biomechanical effects of bionic trabecular metal vs.titanium jumbo cups for the revision of acetabular bone defects.We designed and reconstructed American Academy of Orthopaedic Surgeons(AAOS)type I–III acetabular bone defect models using computed tomography scans of a man without acetabular bone defects.The implantation of titanium and trabecular metal jumbo cups was simulated.Stress distribution and relative micromotion between the cup and host bone were assessed using finite element analysis.Contact stress on the screws fixing the cups was also analyzed.The contact stress analysis showed that the peak contact stress between the titanium jumbo cup and the host bone was 21.7,20.1,and 23.8 MPa in the AAOS I–III models,respectively;the corresponding values for bionic tantalum jumbo cups decreased to 4.7,6.7,and 11.1 MPa.Analysis of the relative micromotion showed that the peak relative micromotion between the host bone and the titanium metal cup was 10.2,9.1,and 11.5μm in the AAOS I–III models,respectively;the corresponding values for bionic trabecular metal cups were 17.2,18.2,and 31.3μm.The peak contact stress on the screws was similar for the 2 cup types,and was concentrated on the screw rods.Hence,acetabular reconstruction with jumbo cups is biomechanically feasible.We recommend trabecular metal cups due to their superior stress distribution and higher relative micromotion,which is within the threshold for adequate bone ingrowth.展开更多
Although short implants are seen as alternative treatments that require additional surgical techniques in posterior region, they can be applied to anterior maxilla and various studies are required on this subject. The...Although short implants are seen as alternative treatments that require additional surgical techniques in posterior region, they can be applied to anterior maxilla and various studies are required on this subject. The purpose of this study was to examine and compare the peak von Mises stress distributions in the crown, implant and abutment by using finite element analysis (FEA). Besides, a comparison of the implant-abutment connection types in the short implant with the FEA method was established. A short implant (4 × 5 mm) with a taper-lock connection and a regular implant (4 × 9 mm) with a screw connection were used in maxillary central incisor tooth area. Three different titanium abutments with 0?, 15? and 25? angles were used for abutments. In addition, in order to determine whether the stress change in short implants is due to the length of the implant-abutment connection, a screw was designed for a short implant and it was also evaluated in the same three angles. A total of three groups and nine models were generated. 114.6N load was applied to the cingulum area of the crown at an angle of 135? to the long axis of the crowns. A torque load of 25 Ncm was applied to the regular and short implant screw. Von Mises stress distributions of implants, abutments and crowns were evaluated by using FEA. Increased angle in implants increased von Mises stress values of implant, abutment and crown. Screw connection was found higher at all angles in short implants. Close values were found at different angles in taper-lock short implant crowns. The length and the angle in the bone of implant with the type of implant-abutment connection results in the accumulated stress values. Clinical Implications Taper implant-abutment connection system was found to be more promising in terms of stress accumulation in crowns. Although the amount of stress on the abutment increased due to the length of the implant in short implants, taper implant-abutment connection system slightly reduced related to this increase.展开更多
In order to ensure the safe operation of the escalator,the step as a part of transporting passengers,the design will consider a high safety factor,which will increase the weight,the manufacturing cost,and the energy c...In order to ensure the safe operation of the escalator,the step as a part of transporting passengers,the design will consider a high safety factor,which will increase the weight,the manufacturing cost,and the energy consumption of the steps band operation.Therefore,in order to reduce the weight and ensure the strength and stiffness of the step,through the optimization design,the number of reinforcing rib supports of the step tread plate and riser plate is increased,and the thickness of the step tread plate and riser plate is moderately reduced,so as to achieve the purpose of reducing the weight of the step and reducing the manufacturing cost and operating energy consumption.Through the finite element analysis and testing of the new type step design,Its strength and stiffness fully meet the requirements of GB 16899-2011 and EN 115-1:2017 standards,and the breaking force also meets the industry standards,so that the manufacturing and operating costs of the product can be reduced to improve the competitiveness of the product market.展开更多
The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure...The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure building units to construct a Hierarchical Papillary microrough Structure(HPS)on a ceramic surface.The effects of the spatial distribution of HPS on the abrasion resistance and mechanical stability of hydrophobic coatings were investigated.Furthermore,for each HPS,the falling sand abrasion process was analyzed using finite element fluid mechanics analysis.A denser or more two-dimensional HPS implied that more area was impacted by the falling sand and that the abrasion amount and rate were higher.This is contrary to the common belief that when there are more wear-resistant substances on the surface,the abrasion resistance is better;thus,abrasion resistance does not necessarily depend entirely on the concentration of wear-resistant substances on the surface,but it is also influenced by the abrasion mode and the spatial distribution structure of the wear-resistant substances.The 3D stacked HPS(3D-HPS)with excellent abrasion resistance and rich pore structure considerably enhanced the mechanical stability of the hydrophobic coatings.These findings provide novel insights and a theoretical basis for designing spatial structures on high abrasion-resistant superhydrophobic ceramic surfaces.展开更多
To prevent dense chromium oxide covers from cracking during firing,such as internal cracking,surface cracking and fracture,the firing process of dense chromium oxide products was simulated,and the performance paramete...To prevent dense chromium oxide covers from cracking during firing,such as internal cracking,surface cracking and fracture,the firing process of dense chromium oxide products was simulated,and the performance parameters at several specific temperatures before and after densification of chromium oxide green bodies were tested.The temperature difference and the stress difference of chromium oxide green bodies were calculated by Finite Element Software at heating and cooling rates of 10,20,30 and 40℃·h^(-1),respectively.The results show that large temperature difference and thermal stress difference are the main causes of internal cracking,surface cracking and fracture of the brick.Suitable heating rates reduce or avoid internal cracking of the brick.When the heating rate is 30℃·h^(-1) below 1450℃and 10℃·h^(-1) above 1450℃,the temperature difference and the thermal stress difference in the brick are below 4℃and 4 MPa,respectively,and there is no internal crack in the brick after firing.The initial cooling stage is the key stage that causes cracking or fracture of bricks.When the cooling rate is 20℃·h^(-1) above 1450℃,the thermal stress difference in the brick is less than 4 MPa,which can significantly reduce the surface cracks and fracture of the brick.展开更多
Nonlinear time‐history analysis can be used to determine the liquefiable behaviors of the tunnel-sand-pile interaction(TSPI)model with the consideration of sand anisotropy.This study presents the nonlinear response o...Nonlinear time‐history analysis can be used to determine the liquefiable behaviors of the tunnel-sand-pile interaction(TSPI)model with the consideration of sand anisotropy.This study presents the nonlinear response of the TSPI model with the existence of liquefaction under seismic excitation.The analysis reveals that tunnel and pile behave as isotropic elements,while sand shows isotropic,orthotropic,and anisotropic characteristics.Three constitutive models including UBC3D‐PLM(two yield surfaces associated with the hardening rule),NGI‐ADP(yielding with associated plastic potential function),and a user‐specified constitutive model are adopted to evaluate the isotropic,orthotropic,and anisotropic behaviors of sand.On this basis,two finite element‐based codes(ETABS 18.1.1 and Plaxis 3D)are used to evaluate sand behaviors and responses.Responses of the tunnel,sand,pile,and excess pore pressure ratio are recorded in the interaction zone by varying the pile diameter,tunnel diameter,and tunnel-pile clearance.Compared with the orthotropic and isotropic conditions,lower variations of results are found in the anisotropic condition,except for the case of generation of excess pore pressure.In addition,the present reanalysis results are in agreement with previous analytical and case study results,which further indicates the effectiveness of the finite element‐based numerical codes.展开更多
Artificial cementation is a method commonly used to enhance and improve soil properties. This paper investigates the effect of using different amounts of cement on soil strength parameters and soil bearing capacity, u...Artificial cementation is a method commonly used to enhance and improve soil properties. This paper investigates the effect of using different amounts of cement on soil strength parameters and soil bearing capacity, using the finite element method. Experimental tests are conducted on soil samples with different amounts of Portland cement. A 2-D numerical model is created and validated using the numerical modelling software, COMSOL Multiphysics 5.6 software. The study finds that the cohesion, and the angle of the internal friction of the soil samples increase significantly as a result of adding 1%, 2%, and 4% of Portland cement. The results demonstrate that the stresses and strain under the strip footing proposed decrease by 3.24% and 7.42%. Moreover, the maximum displacement also decreases by 1.47% and 2.97%, as a result of adding cements of 2% and 4%. The bearing capacity values obtained are therefore excellent, especially when using the 2% and 4% cement. The increase identified is due to the increased values of the bearing capacity factors. It is concluded that from an economic viewpoint, using 2% cement is the best option.展开更多
This paper describes the structure of the base,on which two working arms are installed simultaneously.To ensure structura safety,the fatigue failure analysis and statics analysis are finished using the finite element ...This paper describes the structure of the base,on which two working arms are installed simultaneously.To ensure structura safety,the fatigue failure analysis and statics analysis are finished using the finite element method.The calculation can make sure that the structure of the base meets the design standard,and the material can be reduced one grade.展开更多
The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques.Various types of adhesives have different material properties that affect restoration.Therefore,the c...The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques.Various types of adhesives have different material properties that affect restoration.Therefore,the choice of adhesive is particularly important for patients.However,the effect of different kinds of adhesives was not too precise by experimental methods when concerning about individual differences of teeth.One tooth root can only be restored with one type of adhesive in experiment.After the mechanical test,this tooth root cannot be restored with other adhesives.With the help of medical imaging technology,reverse engineering and finite element analysis,a molar model can be reconstructed precisely and restored using different types of adhesives.The same occlusal and chewing loads were exerted on the same restored residual root models with different types of adhesives separately.Results of von Mises stress analysis showed that the adhesives with low Young’s modulus can protect the root canal effectively.However,a root canal concentration is apparently produced around the root canal orifice when chewing.Adhesives with large Young’s modulus can buffer the stress concentration of the root canal orifice.However,the root canal tissue may be destroyed because the adhesive is too hard to buffer the load.展开更多
The static dent resistance performance of the aluminum alloy double-curved panel formed using viscous pressure forming (VPF)was studied by finite element analysis,which mainly considers the forming process conditions....The static dent resistance performance of the aluminum alloy double-curved panel formed using viscous pressure forming (VPF)was studied by finite element analysis,which mainly considers the forming process conditions.The whole simulation consisting of three stages,i.e.,forming,spring-back and static dent resistance,was carried out continuously using the finite element code ANSYS.The influence of blank holder pressure(BHP)and the drawbead on the stiffness and the static dent resistance of the panels formed using VPF was analyzed.The results show that the adequate setting of the drawbead can increase the plastic deformation of the double-curved panel,which is beneficial to the initial stiffness and the static dent resistance.There is an optimum BHP range for the stiffness and the static dent resistance.展开更多
Porous structure in orthopedic prosthesis may reduce micromotion and increase the service life of implants.The purposes of this study were to compare the influence of the tibial stems with solid and porous structures ...Porous structure in orthopedic prosthesis may reduce micromotion and increase the service life of implants.The purposes of this study were to compare the influence of the tibial stems with solid and porous structures in Total Knee Arthroplasty(TKA)on knee joint and prostheses,and to improve the mechanical stability of the host bone by seeking favorable structure for the tibial stem.The Finite Element(FE)models of TKA knee with four different structures in the middle segment of the tibial stem(i.e.,solid,cubic,truncated cubic,and octahedral structures)were constructed.The distributions of von Mises stress in the knee joint,tibial prosthesis and proximal tibia,and the compressive stresses of the tibial prosthesis and ultra-high-molecular-weight polyethylene for the four FE models were analyzed.The results showed that the tibial stem filled with the octahedral structure has the best mechanical performance among the above four types of tibial stems.It could effectively reduce the stress concentration and stress shielding effects,and provide an improved mechanical environment for knee joint after TKA.This study would shed some lights on the design and fabrication of porous implants targeted to biomedical applications.展开更多
Adjacent vertebral fractures are common in patients with osteoporotic vertebral compression fractures(OVCFs) after kyphoplasty.This finite element study was to examine whether short segment pedicle screw fixation(PSF)...Adjacent vertebral fractures are common in patients with osteoporotic vertebral compression fractures(OVCFs) after kyphoplasty.This finite element study was to examine whether short segment pedicle screw fixation(PSF) with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae after kyphoplasty for OVCFs.By simulating cement augmentation with or without short segment pedicle screw fixation(PSF),two tridimensional,anatomically detailed finite element models of the T10–L2 functional spinal junction were developed.The insertion of pedicle screws into the intact vertebra apparently decreased the stress distribution of the treated vertebra in vertical compression and other load situations.The stress distribution in the bone structures of the intact vertebra adjacent to the intact-screwed vertebra was much less than that in the one adjacent to the treated vertebra.The insertion of pedicle screws into the intact vertebra greatly decreased the maximum displacement of the cortical bones and cancellous bones of the vertebrae.Our results indicated that short segment PSF with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae in the management of OVCFs.展开更多
Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic ads...Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic adsorption model was established by coupling equations of mass,momentum and energy balance,and solved by finite element analysis.The simulation breakthrough curves fit well with the low-concentration CO_(2) adsorption experimental data,indicating the reliability of the established model.The distributions of concentration and temperature field in the column for CO_(2) adsorption and separation from CO_(2)/N_(2) were obtained.The sensitivity analysis of the adsorption conditions shows that the operation parameters such as feed flow rate,feed concentration,pellet size,and column height-to-diameter ratio produce a significant effect on the dynamic adsorption performance.The multi-physics coupled 2D axisymmetric model could provide a theoretical foundation and guidance for designing CO_(2) fixed-bed adsorption and separation processes,which could be extended to other mixed gases as well.展开更多
A new type of soft actuator material-ionic liquid gel(ILG),which consists of HEMA,BMIMBF4,and TiO_2,can be transformed into gel state under the irradiation of ultraviolet(UV)light.In this paper,Mooney–Rivlin hyperela...A new type of soft actuator material-ionic liquid gel(ILG),which consists of HEMA,BMIMBF4,and TiO_2,can be transformed into gel state under the irradiation of ultraviolet(UV)light.In this paper,Mooney–Rivlin hyperelastic model of finite element method is proposed for the first time to study the properties of the ILG.It has been proved that the content of TiO_2 has a great influence on the properties of the gel,and Young’s modulus of the gel increases with the increase of its content,despite of reduced tensile deformation.The results in this work show that when the TiO_2 content is 1.0 wt%,a large tensile deformation and a strong Young’s modulus can be obtained to be 325%and 7.8 k Pa,respectively.The material parameters of ILG with TiO_2content values of 0.2 wt%,0.5 wt%,1.0 wt%,and 1.5 wt%are obtained,respectively,through uniaxial tensile tests,including C_(10),C_(01),C_(20),C_(11),C_(02),C_(30),C_(21),C_(12),and C_(03)elements.In this paper,the large-scaled general finite element software ANSYS is used to simulate and analyze the ILG,which is based on SOLID186 element and nonlinear hyperelastic Mooney–Rivlin model.The finite element simulation analysis based stress-strain curves are almost consistent with the experimental stress–strain curves,and hence the finite element analysis of ILG is feasible and credible.This work presents a new direction for studying the performance of soft actuator for the ILG,and also contributes to the design of soft robot actuator.展开更多
The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system(LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching(F...The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system(LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching(FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30–50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis(FEA)approach. An intact murine tibia was first re-constructed from micro CT images into a three-dimensional(3D)linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform(FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex.Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces(shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.展开更多
This paper is concerned with the numerical prediction of the burst pressure of a radial truck tire. Even though relatively rare, the tire fracture or failure brings up a big accident. Especially, the tire burst or rup...This paper is concerned with the numerical prediction of the burst pressure of a radial truck tire. Even though relatively rare, the tire fracture or failure brings up a big accident. Especially, the tire burst or rupture is a rapid loss of inflation pressure of a truck and bus tire leading to an explosion. The tire burst pressure, under this extreme loading condition, can be predicted by identifying the pressure at which the cord breaking force of the composite materials is attained. Recently, the use of finite element analysis in tire optimal design has become widely popular. In order to determine the burst pressure of a radial truck tire, an axisymmetric finite element model has been developed using a commercial finite element code with rebar element. The numerical result shows that the bead wire among the various layers modeled the rebar element breaks off first in the radial truck tire. The finite element modeling with the rebar element on the bead wire of a radial truck tire is able to well predict the tire burst pressure identifying the pressure at which the breaking force of steel bead wires is reached. The model predictions of tire burst pressure should be correlated with test data, in which case the tire is hydro-tested to destruction. The effect of the design change with the different bead structure on the tire burst pressure is discussed.展开更多
This paper presents a constitutive framework for finite element analysis of the truck beam end cutting process.For this purpose,a finite strain anisotropic elasto-plastic model,which takes nonlinear kinematic and isot...This paper presents a constitutive framework for finite element analysis of the truck beam end cutting process.For this purpose,a finite strain anisotropic elasto-plastic model,which takes nonlinear kinematic and isotropic hardening into account,is presented.Three factors are investigated to determine the effect on cutting quality:radius of cutting tools,strength of materials and relative clearance in cutting.The recommendations made herein are based on the simulation results.展开更多
The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically...The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically modeling of Mimics software and the RE technology of Geomagic software. Then the finite element model of the head-neck which is close to the real one is set up by the preprocessor of the FEM soft ware ANSYS. After the transient finite element analysis is performed on the model,the historical response of the displacement of the head is obtained. The result is validated by the result of the existed experiment. The stress,as well as the deformation,of nodes in the head and the cervical spine at any time benefits a lot to the clinic study on the injure to the head and neck caused by the impacts. And all the analysis is done by limited computer available.展开更多
There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loo...There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loosened,which causes safety risks.In order to eliminate this security issue,the finite element modeling is proposed to analyze the relationship between the force generated by the connector type A or type B during the step band running and the assembly clearance or the assembly mode.So as to find out the root cause of fixing bolt loosening phenomenon,by redesigning the assembly clearance between the connector shaft and the chain hole,the fixing bolt of the connector is prevented from loosening during the step band running,ensuring the safe operation of escalators to avoid injury accidents.展开更多
基金financially supported by the Steel Structure Research and Education Promotion Project of the Japan Iron and Steel Federation in FY2016.
文摘The present paper first investigates the collapse behavior of a conventional pipe-framed greenhouse under snow loading based on a 3-D finite element analysis,in which both geometrical and material non-linearities are considered.Three snow load distribution patterns related to the wind-driven snow particle movement are used in the analysis.It is found that snow load distribution affects the deformation and collapse behavior of the pipe-framed greenhouse significantly.The results obtained in this study are consistent with the actual damage observed.Next,discussion is made of the effects of reinforcements by adding members to the basic frame on the strength of the whole structure,in which seven kinds of reinforcement methods are examined.A buckling analysis is also carried out.The results indicate that the most effective reinforcement method depends on the snow load distribution pattern.
基金This work was supported by funding from China Postdoctoral Science Foundation(No:2020M670863)Jilin Scientific and Technological Development Program(No:20230203089SF).
文摘The biomechanical effects of acetabular revision with jumbo cups are unclear.This study aimed to compare the biomechanical effects of bionic trabecular metal vs.titanium jumbo cups for the revision of acetabular bone defects.We designed and reconstructed American Academy of Orthopaedic Surgeons(AAOS)type I–III acetabular bone defect models using computed tomography scans of a man without acetabular bone defects.The implantation of titanium and trabecular metal jumbo cups was simulated.Stress distribution and relative micromotion between the cup and host bone were assessed using finite element analysis.Contact stress on the screws fixing the cups was also analyzed.The contact stress analysis showed that the peak contact stress between the titanium jumbo cup and the host bone was 21.7,20.1,and 23.8 MPa in the AAOS I–III models,respectively;the corresponding values for bionic tantalum jumbo cups decreased to 4.7,6.7,and 11.1 MPa.Analysis of the relative micromotion showed that the peak relative micromotion between the host bone and the titanium metal cup was 10.2,9.1,and 11.5μm in the AAOS I–III models,respectively;the corresponding values for bionic trabecular metal cups were 17.2,18.2,and 31.3μm.The peak contact stress on the screws was similar for the 2 cup types,and was concentrated on the screw rods.Hence,acetabular reconstruction with jumbo cups is biomechanically feasible.We recommend trabecular metal cups due to their superior stress distribution and higher relative micromotion,which is within the threshold for adequate bone ingrowth.
文摘Although short implants are seen as alternative treatments that require additional surgical techniques in posterior region, they can be applied to anterior maxilla and various studies are required on this subject. The purpose of this study was to examine and compare the peak von Mises stress distributions in the crown, implant and abutment by using finite element analysis (FEA). Besides, a comparison of the implant-abutment connection types in the short implant with the FEA method was established. A short implant (4 × 5 mm) with a taper-lock connection and a regular implant (4 × 9 mm) with a screw connection were used in maxillary central incisor tooth area. Three different titanium abutments with 0?, 15? and 25? angles were used for abutments. In addition, in order to determine whether the stress change in short implants is due to the length of the implant-abutment connection, a screw was designed for a short implant and it was also evaluated in the same three angles. A total of three groups and nine models were generated. 114.6N load was applied to the cingulum area of the crown at an angle of 135? to the long axis of the crowns. A torque load of 25 Ncm was applied to the regular and short implant screw. Von Mises stress distributions of implants, abutments and crowns were evaluated by using FEA. Increased angle in implants increased von Mises stress values of implant, abutment and crown. Screw connection was found higher at all angles in short implants. Close values were found at different angles in taper-lock short implant crowns. The length and the angle in the bone of implant with the type of implant-abutment connection results in the accumulated stress values. Clinical Implications Taper implant-abutment connection system was found to be more promising in terms of stress accumulation in crowns. Although the amount of stress on the abutment increased due to the length of the implant in short implants, taper implant-abutment connection system slightly reduced related to this increase.
文摘In order to ensure the safe operation of the escalator,the step as a part of transporting passengers,the design will consider a high safety factor,which will increase the weight,the manufacturing cost,and the energy consumption of the steps band operation.Therefore,in order to reduce the weight and ensure the strength and stiffness of the step,through the optimization design,the number of reinforcing rib supports of the step tread plate and riser plate is increased,and the thickness of the step tread plate and riser plate is moderately reduced,so as to achieve the purpose of reducing the weight of the step and reducing the manufacturing cost and operating energy consumption.Through the finite element analysis and testing of the new type step design,Its strength and stiffness fully meet the requirements of GB 16899-2011 and EN 115-1:2017 standards,and the breaking force also meets the industry standards,so that the manufacturing and operating costs of the product can be reduced to improve the competitiveness of the product market.
基金supported by the National College Students Innovation and Entrepreneurship Training Program(No:202110895003,China)Pingxiang City Science and Technology Plan Project(No:2021C0102,China)National Natural Science Foundation of China(Nos.5217020839,52001175,China).
文摘The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure building units to construct a Hierarchical Papillary microrough Structure(HPS)on a ceramic surface.The effects of the spatial distribution of HPS on the abrasion resistance and mechanical stability of hydrophobic coatings were investigated.Furthermore,for each HPS,the falling sand abrasion process was analyzed using finite element fluid mechanics analysis.A denser or more two-dimensional HPS implied that more area was impacted by the falling sand and that the abrasion amount and rate were higher.This is contrary to the common belief that when there are more wear-resistant substances on the surface,the abrasion resistance is better;thus,abrasion resistance does not necessarily depend entirely on the concentration of wear-resistant substances on the surface,but it is also influenced by the abrasion mode and the spatial distribution structure of the wear-resistant substances.The 3D stacked HPS(3D-HPS)with excellent abrasion resistance and rich pore structure considerably enhanced the mechanical stability of the hydrophobic coatings.These findings provide novel insights and a theoretical basis for designing spatial structures on high abrasion-resistant superhydrophobic ceramic surfaces.
文摘To prevent dense chromium oxide covers from cracking during firing,such as internal cracking,surface cracking and fracture,the firing process of dense chromium oxide products was simulated,and the performance parameters at several specific temperatures before and after densification of chromium oxide green bodies were tested.The temperature difference and the stress difference of chromium oxide green bodies were calculated by Finite Element Software at heating and cooling rates of 10,20,30 and 40℃·h^(-1),respectively.The results show that large temperature difference and thermal stress difference are the main causes of internal cracking,surface cracking and fracture of the brick.Suitable heating rates reduce or avoid internal cracking of the brick.When the heating rate is 30℃·h^(-1) below 1450℃and 10℃·h^(-1) above 1450℃,the temperature difference and the thermal stress difference in the brick are below 4℃and 4 MPa,respectively,and there is no internal crack in the brick after firing.The initial cooling stage is the key stage that causes cracking or fracture of bricks.When the cooling rate is 20℃·h^(-1) above 1450℃,the thermal stress difference in the brick is less than 4 MPa,which can significantly reduce the surface cracks and fracture of the brick.
文摘Nonlinear time‐history analysis can be used to determine the liquefiable behaviors of the tunnel-sand-pile interaction(TSPI)model with the consideration of sand anisotropy.This study presents the nonlinear response of the TSPI model with the existence of liquefaction under seismic excitation.The analysis reveals that tunnel and pile behave as isotropic elements,while sand shows isotropic,orthotropic,and anisotropic characteristics.Three constitutive models including UBC3D‐PLM(two yield surfaces associated with the hardening rule),NGI‐ADP(yielding with associated plastic potential function),and a user‐specified constitutive model are adopted to evaluate the isotropic,orthotropic,and anisotropic behaviors of sand.On this basis,two finite element‐based codes(ETABS 18.1.1 and Plaxis 3D)are used to evaluate sand behaviors and responses.Responses of the tunnel,sand,pile,and excess pore pressure ratio are recorded in the interaction zone by varying the pile diameter,tunnel diameter,and tunnel-pile clearance.Compared with the orthotropic and isotropic conditions,lower variations of results are found in the anisotropic condition,except for the case of generation of excess pore pressure.In addition,the present reanalysis results are in agreement with previous analytical and case study results,which further indicates the effectiveness of the finite element‐based numerical codes.
文摘Artificial cementation is a method commonly used to enhance and improve soil properties. This paper investigates the effect of using different amounts of cement on soil strength parameters and soil bearing capacity, using the finite element method. Experimental tests are conducted on soil samples with different amounts of Portland cement. A 2-D numerical model is created and validated using the numerical modelling software, COMSOL Multiphysics 5.6 software. The study finds that the cohesion, and the angle of the internal friction of the soil samples increase significantly as a result of adding 1%, 2%, and 4% of Portland cement. The results demonstrate that the stresses and strain under the strip footing proposed decrease by 3.24% and 7.42%. Moreover, the maximum displacement also decreases by 1.47% and 2.97%, as a result of adding cements of 2% and 4%. The bearing capacity values obtained are therefore excellent, especially when using the 2% and 4% cement. The increase identified is due to the increased values of the bearing capacity factors. It is concluded that from an economic viewpoint, using 2% cement is the best option.
文摘This paper describes the structure of the base,on which two working arms are installed simultaneously.To ensure structura safety,the fatigue failure analysis and statics analysis are finished using the finite element method.The calculation can make sure that the structure of the base meets the design standard,and the material can be reduced one grade.
文摘The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques.Various types of adhesives have different material properties that affect restoration.Therefore,the choice of adhesive is particularly important for patients.However,the effect of different kinds of adhesives was not too precise by experimental methods when concerning about individual differences of teeth.One tooth root can only be restored with one type of adhesive in experiment.After the mechanical test,this tooth root cannot be restored with other adhesives.With the help of medical imaging technology,reverse engineering and finite element analysis,a molar model can be reconstructed precisely and restored using different types of adhesives.The same occlusal and chewing loads were exerted on the same restored residual root models with different types of adhesives separately.Results of von Mises stress analysis showed that the adhesives with low Young’s modulus can protect the root canal effectively.However,a root canal concentration is apparently produced around the root canal orifice when chewing.Adhesives with large Young’s modulus can buffer the stress concentration of the root canal orifice.However,the root canal tissue may be destroyed because the adhesive is too hard to buffer the load.
文摘The static dent resistance performance of the aluminum alloy double-curved panel formed using viscous pressure forming (VPF)was studied by finite element analysis,which mainly considers the forming process conditions.The whole simulation consisting of three stages,i.e.,forming,spring-back and static dent resistance,was carried out continuously using the finite element code ANSYS.The influence of blank holder pressure(BHP)and the drawbead on the stiffness and the static dent resistance of the panels formed using VPF was analyzed.The results show that the adequate setting of the drawbead can increase the plastic deformation of the double-curved panel,which is beneficial to the initial stiffness and the static dent resistance.There is an optimum BHP range for the stiffness and the static dent resistance.
基金the National Natural Science Foundation of China(Nos.11872095,11702110)the Natural Science Foundation of Jilin Province(No.20200201260JC)the Graduate Innovation Fund of Jilin University(No.101832018C194)for financial support.
文摘Porous structure in orthopedic prosthesis may reduce micromotion and increase the service life of implants.The purposes of this study were to compare the influence of the tibial stems with solid and porous structures in Total Knee Arthroplasty(TKA)on knee joint and prostheses,and to improve the mechanical stability of the host bone by seeking favorable structure for the tibial stem.The Finite Element(FE)models of TKA knee with four different structures in the middle segment of the tibial stem(i.e.,solid,cubic,truncated cubic,and octahedral structures)were constructed.The distributions of von Mises stress in the knee joint,tibial prosthesis and proximal tibia,and the compressive stresses of the tibial prosthesis and ultra-high-molecular-weight polyethylene for the four FE models were analyzed.The results showed that the tibial stem filled with the octahedral structure has the best mechanical performance among the above four types of tibial stems.It could effectively reduce the stress concentration and stress shielding effects,and provide an improved mechanical environment for knee joint after TKA.This study would shed some lights on the design and fabrication of porous implants targeted to biomedical applications.
基金supported by the National High Technology Research and Development Program("863"Program)of China(No.SS2012AA022811)the Science and Technology Program of Guangzhou(No.201508020253)the Special Project on the Integration of Industry,Education and Research of Guangzhou(No.158100062)
文摘Adjacent vertebral fractures are common in patients with osteoporotic vertebral compression fractures(OVCFs) after kyphoplasty.This finite element study was to examine whether short segment pedicle screw fixation(PSF) with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae after kyphoplasty for OVCFs.By simulating cement augmentation with or without short segment pedicle screw fixation(PSF),two tridimensional,anatomically detailed finite element models of the T10–L2 functional spinal junction were developed.The insertion of pedicle screws into the intact vertebra apparently decreased the stress distribution of the treated vertebra in vertical compression and other load situations.The stress distribution in the bone structures of the intact vertebra adjacent to the intact-screwed vertebra was much less than that in the one adjacent to the treated vertebra.The insertion of pedicle screws into the intact vertebra greatly decreased the maximum displacement of the cortical bones and cancellous bones of the vertebrae.Our results indicated that short segment PSF with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae in the management of OVCFs.
基金supported by the National Natural Science Foundation of China(21776028)Key Research and Development Projects of Liaoning Province(2017308004)。
文摘Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic adsorption model was established by coupling equations of mass,momentum and energy balance,and solved by finite element analysis.The simulation breakthrough curves fit well with the low-concentration CO_(2) adsorption experimental data,indicating the reliability of the established model.The distributions of concentration and temperature field in the column for CO_(2) adsorption and separation from CO_(2)/N_(2) were obtained.The sensitivity analysis of the adsorption conditions shows that the operation parameters such as feed flow rate,feed concentration,pellet size,and column height-to-diameter ratio produce a significant effect on the dynamic adsorption performance.The multi-physics coupled 2D axisymmetric model could provide a theoretical foundation and guidance for designing CO_(2) fixed-bed adsorption and separation processes,which could be extended to other mixed gases as well.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51538009 and 51605334)the Natural Science Foundation of Shanghai Municipality,China(Grant No.08002360285)
文摘A new type of soft actuator material-ionic liquid gel(ILG),which consists of HEMA,BMIMBF4,and TiO_2,can be transformed into gel state under the irradiation of ultraviolet(UV)light.In this paper,Mooney–Rivlin hyperelastic model of finite element method is proposed for the first time to study the properties of the ILG.It has been proved that the content of TiO_2 has a great influence on the properties of the gel,and Young’s modulus of the gel increases with the increase of its content,despite of reduced tensile deformation.The results in this work show that when the TiO_2 content is 1.0 wt%,a large tensile deformation and a strong Young’s modulus can be obtained to be 325%and 7.8 k Pa,respectively.The material parameters of ILG with TiO_2content values of 0.2 wt%,0.5 wt%,1.0 wt%,and 1.5 wt%are obtained,respectively,through uniaxial tensile tests,including C_(10),C_(01),C_(20),C_(11),C_(02),C_(30),C_(21),C_(12),and C_(03)elements.In this paper,the large-scaled general finite element software ANSYS is used to simulate and analyze the ILG,which is based on SOLID186 element and nonlinear hyperelastic Mooney–Rivlin model.The finite element simulation analysis based stress-strain curves are almost consistent with the experimental stress–strain curves,and hence the finite element analysis of ILG is feasible and credible.This work presents a new direction for studying the performance of soft actuator for the ILG,and also contributes to the design of soft robot actuator.
基金supported by grants from NIH (P30GM103333 and RO1AR054385 to LW)China CSC fellowship (to LF)DOD W81XWH-13-1-0148 (to XLL)
文摘The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system(LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching(FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30–50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis(FEA)approach. An intact murine tibia was first re-constructed from micro CT images into a three-dimensional(3D)linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform(FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex.Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces(shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.
文摘This paper is concerned with the numerical prediction of the burst pressure of a radial truck tire. Even though relatively rare, the tire fracture or failure brings up a big accident. Especially, the tire burst or rupture is a rapid loss of inflation pressure of a truck and bus tire leading to an explosion. The tire burst pressure, under this extreme loading condition, can be predicted by identifying the pressure at which the cord breaking force of the composite materials is attained. Recently, the use of finite element analysis in tire optimal design has become widely popular. In order to determine the burst pressure of a radial truck tire, an axisymmetric finite element model has been developed using a commercial finite element code with rebar element. The numerical result shows that the bead wire among the various layers modeled the rebar element breaks off first in the radial truck tire. The finite element modeling with the rebar element on the bead wire of a radial truck tire is able to well predict the tire burst pressure identifying the pressure at which the breaking force of steel bead wires is reached. The model predictions of tire burst pressure should be correlated with test data, in which case the tire is hydro-tested to destruction. The effect of the design change with the different bead structure on the tire burst pressure is discussed.
文摘This paper presents a constitutive framework for finite element analysis of the truck beam end cutting process.For this purpose,a finite strain anisotropic elasto-plastic model,which takes nonlinear kinematic and isotropic hardening into account,is presented.Three factors are investigated to determine the effect on cutting quality:radius of cutting tools,strength of materials and relative clearance in cutting.The recommendations made herein are based on the simulation results.
文摘The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically modeling of Mimics software and the RE technology of Geomagic software. Then the finite element model of the head-neck which is close to the real one is set up by the preprocessor of the FEM soft ware ANSYS. After the transient finite element analysis is performed on the model,the historical response of the displacement of the head is obtained. The result is validated by the result of the existed experiment. The stress,as well as the deformation,of nodes in the head and the cervical spine at any time benefits a lot to the clinic study on the injure to the head and neck caused by the impacts. And all the analysis is done by limited computer available.
文摘There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loosened,which causes safety risks.In order to eliminate this security issue,the finite element modeling is proposed to analyze the relationship between the force generated by the connector type A or type B during the step band running and the assembly clearance or the assembly mode.So as to find out the root cause of fixing bolt loosening phenomenon,by redesigning the assembly clearance between the connector shaft and the chain hole,the fixing bolt of the connector is prevented from loosening during the step band running,ensuring the safe operation of escalators to avoid injury accidents.
