Collapse Behavior of Pipe-Framed Greenhouses with and without Reinforcement under Snow Loading:A 3-D Finite Element Analysis

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.

Finite Element Analysis of Coronal Shear Fractures of the Femoral Neck: Displacement of the Femoral Head and Effect of Osteosynthetic Implants

Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.

Stress Distributions Created by Short and Regular Implants Placed in the Anterior Maxilla at Different Angles: A Finite Element Analysis

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.

Modal and Thermal Analysis of a Modified Connecting Rod of an Internal Combustion Engine Using Finite Element Method

The connecting rod is one of the most important moving components in an internal combustion engine. The present work determined the possibility of using aluminium alloy 7075 material to design and manufacture a connecting rod for weight optimisation without losing the strength of the connecting rod. It considered modal and thermal analyses to investigate the suitability of the material for connecting rod design. The parameters that were considered under the modal analysis were: total deformation, and natural frequency, while the thermal analysis looked at the temperature distribution, total heat flux and directional heat flux of the four connecting rods made with titanium alloy, grey cast iron, structural steel and aluminium 7075 alloy respectively. The connecting rod was modelled using Autodesk inventor2017 software using the calculated parameters. The steady-state thermal analysis was used to determine the induced heat flux and directional heat flux. The study found that Aluminium 7075 alloy deformed more than the remaining three other materials but has superior qualities in terms of vibrational natural frequency, total heat flux and lightweight compared to structural steel, grey cast iron and titanium alloy.

Study on Development of Light Aluminum Step by Using Finite Element Analysis

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.

A New Isogeometric Finite Element Method for Analyzing Structures

High-performance finite element research has always been a major focus of finite element method studies.This article introduces isogeometric analysis into the finite element method and proposes a new isogeometric finite element method.Firstly,the physical field is approximated by uniform B-spline interpolation,while geometry is represented by non-uniform rational B-spline interpolation.By introducing a transformation matrix,elements of types C^(0)and C^(1)are constructed in the isogeometric finite element method.Subsequently,the corresponding calculation formats for one-dimensional bars,beams,and two-dimensional linear elasticity in the isogeometric finite element method are derived through variational principles and parameter mapping.The proposed method combines element construction techniques of the finite element method with geometric construction techniques of isogeometric analysis,eliminating the need for mesh generation and maintaining flexibility in element construction.Two elements with interpolation characteristics are constructed in the method so that boundary conditions and connections between elements can be processed like the finite element method.Finally,the test results of several examples show that:(1)Under the same degree and element node numbers,the constructed elements are almost consistent with the results obtained by traditional finite element method;(2)For bar problems with large local field variations and beam problems with variable cross-sections,high-degree and multi-nodes elements constructed can achieve high computational accuracy with fewer degrees of freedom than finite element method;(3)The computational efficiency of isogeometric finite element method is higher than finite element method under similar degrees of freedom,while as degrees of freedom increase,the computational efficiency between the two is similar.

Finite element failure analysis of continuous prestressed concrete box girders

In order to analyze the load carrying capacity of prestressed concrete box girders, failure behaviors of in-situ deteriorated continuous prestressed concrete box girders under loading are experimentally observed and a finite failure analysis method for predicting behaviors of box girders is developed. A degenerated solid shell element is used to simulate box girders and material nonlinearity is considered. Since pre-stressed concrete box girders usually have a large number of curve prestressed tendons, a type of combined element is presented to simulate the prestressed tendons of box girders, and then the number of elements can be significantly reduced. The analytical results are compared with full-scale failure test results. The comparison shows that the presented method can be effectively applied to the failure analysis of in-situ continuous prestressed concrete box girders, and it also shows that the studied old bridge still has enough load carrying capacity.

Finite element analysis of stress at implant-bone interface of dental implants with different structures

The effect of structure,elastic modulus and thickness of lower modulus layer in porous titanium implants on the stress distribution at the implant-bone interface was investigated.Three-dimensional finite element models of different titanium implants were constructed.The structures of the implants included the whole lower modulus style （No.1）,bio-mimetic style （No.2）,the whole lower modulus style in cancellous bone （No.3） and the whole dense style No.4.The stress distributions at bone-implant interface under static loading were analyzed using Ansys Workbench 10.0 software.The results indicated that the distribution of interface stress is strongly depended on the structure of the implants.The maximum stresses in cancellous bone and root region of implant No.2 are lower than those in the other three implants.A decrease in the modulus of the low modulus layer facilitates the interface stress transferring.Increasing the thickness of the low modulus layer can reduce the stress and induce a more uniform stress distribution at the interface.Among the four implants,biomimetic style implant No.2 is superior in transferring implant-bone interface stress to surrounding bones.

Finite element simulation and optimal analysis of surfacing on steel orthotropic bridge deck

To analyze the stress state of steel orthotropic deck pavement and provide reference for the design of the overlay, the inner stress state and strain distribution of surfacing under the load of the deformation of the whole bridge structure and tyre load are analyzed by the finite element method of submodeling. Influence of surfacing modulus on the strain state of the overlay is analyzed for the purpose of the optimal design of the overlay structure. Analysis results show that the deformation of the whole bridge structure has no evident influence on the stress state of the overlay. The key factor of the overlay design is the transverse tensile strain in the overlay above the upper edge of web plate of rib. The stress state of the overlay is influenced evidently by the modulus of rigidity transform overlay. And the stress state of the overlay can be optimized and lowered by increasing the modulus and thickness of rigidity transform overlay, The fatigue test has been done to evaluate the fatigue performance and modulus of different deck pavement materials such as epoxy asphalt, SBS modified asphalt, rosphalt asphalt which can provide reference for deck pavement structure design.

Finite element analysis of the Taizhou Water Station Site

The Taizhou Water Station Site is an ancient masonry structure ruin built in the Southern Song Dynasty. The main structure was severely damaged. In order to understand its current structural properties and provide a scientific basis for protection design nonlinear finite element analysis and parameter analysis are carried out.The crack patterns deformations and stresses of the main structure under four load cases are analyzed by nonlinear finite element analysis and the effect of the backfill bulk density and modulus on the maximum principal tensile stress and maximum compressive stress are studied by parameter analysis.The results show that the most unfavorable condition for the foundation is the combination of weight＋backfill soil pressure＋additional load the most unfavorable load case to the main structure is weight ＋backfill soil pressure ＋water pressure＋additional heap load the maximum principal tensile stress of the main structure is very sensitive to the changes in the bulk density of the backfill soil.

Modeling Technology in Finite Element Analysis of Electrostatic Proximity Fuze Problem

In order to analyze the electrostatic field concerned with electrostatic proximity fuze problem using the available finite analysis software package, the technology to model the problem with a scale reduction object and boundary was presented. The boundary is determined by the maximum distance the sensor can detect. The object model is obtained by multiplying the terms in Poisson's equation with a scale reduction factor and the real value can be reconstructed with the same reverse process after software calculation. Using the finite element analysis program, the simulation value is close to the theoretical value with a little error. The boundary determination and scale reduction method is suitable to modeling the irregular electrostatic field around air targets, such as airplane, missile and so on, which is based on commonly used personal computer (PC). The technology reduces the calculation and storage cost greatly.

Analysis of Si/GaAs Bonding Stresses with the Finite Element Method

In conjunction with ANSYS,we use the finite element method to analyze the bonding stresses of Si/ GaAs. We also apply a numerical model to investigate a contour map and the distribution of normal stress,shearing stress, and peeling stress, taking into full consideration the thermal expansion coefficient as a function of temperature. Novel bonding structures are proposed for reducing the effect of thermal stress as compared with conventional structures. Calculations show the validity of this new structure.

Computer model of the human head-neck and finite element analysis

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.

Seismic performance of double-skin steel-concrete composite box piers: Part Ⅱ—Nonlinear finite element analysis

An accurate finite element （ FE） model was constructed to examine the hysteretic behavior of double-skin steel-concrete composite box （ DSCB） piers for further understanding the seismic performance of DSCB piers; where the local buckling behavior of steel tubes, the confinement of the in-filled concrete and the interface action between steel tube and in-filled concrete were considered. The accuracy of the proposed FE model was verified by the bidirectional cyclic loading test results. Based on the validated FE model, the effects of some key parameters, such as section width to steel thickness ratio, slenderness ratio, aspect ratio and axial load ratio on the hysteretic behavior of DSCB piers were investigated. Finally, the skeleton curve model of DSCB piers was proposed. The numerical simulation results reveal that the peak strength and elastic stiffness decrease with the increase of the section width to steel thickness ratio. Moreover, the increase of the slenderness ratio may result in a significant reduction in the peak strength and elastic stiffness while the ultimate displacement increases. The proposed skeleton curve model can be taken as a reference for seismic performance analyses of the DSCB piers.

STIFFNESS ANALYSIS OF THE MAIN MODULE FOR PARALLEL MACHINE TOOLS BY FINITE ELEMENT ANALYSIS

With the aid of commercial finite element analysis software package ANSYS,investigations are made on the contributions of main components to stiffness of the main module for parallel machine tools,and it is found that the frame is the main contributor.Then,influences of constraints,strut length and working ways of the main module have also been investigated.It can be concluded that when one of the main planes of the frame without linear drive unit is constrained,the largest whole stiffness can be acquired.And,the stiffness is much better when the main module is used in a vertical machine tool instead of a horizontal one.Finally,the principle of stiffness variation is summarized when the mobile platform reaches various positions within its working space and when various loads are applied.These achievements have provided critical instructions for the design of the main module for parallel machine tools.

Finite element analysis of stress distribution and burst failure of SiC_f/Ti-6Al-4V composite ring

A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.

Three-dimensional Finite Element Analysis of the Mechanical Properties of Helical Thread Connection

Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.

Finite element analysis of multi-piece post-crown restoration using different types of adhesives

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.

Nonlinear Bend Stiffener Analysis Using A Simple Formulation and Finite Element Method

Flexible marine risers are commonly used in deepwater floating systems. Bend stiffeners are designed to protect flexible risel against excessive bending at the connection with the hull. The structure is usually analyzed as a cantilever beam subjected to an inclined point load. As deflections are large and the bend stiffener material exhibits nonlinear stress-strain characteristics, geometric and material nonlinearities are important considerations. A new approach has been developed to solve this nonlinear problem. Its main advantage is its simplicity; in fact the present method can be easily implemented on a spreadsheet. Finite element analysis using ABAQUS is performed to validate the method. Solid elements are used for the bend stiffener and flexible pipe. To simulate the near inextensibility of flexible risers, a simple and original idea of using truss elements is proposed. Through a set of validation studies the present method is found to be in a good agreement with the finite element analysis. Further, parametric studies are performed by using both methods to identify the key parameters and phenomena that are most critical in design. The most important finding is that the common practice of neglecting the internal steel sleeve in the bend stiffener analysis is non-conservative and therefore needs to be reassessed.

Influence of Various Materials on Biomechanical Behavior of Endocrown-Restored, Endodontically-Treated Mandibular First Molar: A 3D-Finite Element Analysis

To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Three different materials （composite resin, ceramage and ceramic） were studied and two loading conditions （vertical and oblique load） were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.