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1
Anwar, Sohail. "Transient Stress and Strain Assessment of Marine Boiler : Fully Rigid Body Dynamics Coupled Finite Element Analyses." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-95440.
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Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations. In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.
2
Rahmanivahid, Pooyan. "Investigation on influence of dental implants." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/13789.
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Osseointegration is defined as the direct physical and practical relation between the living tissue and implant surface. Although, success rate of dental implants is high, implant failure occurs. Overloading implants from occlusal forces are known as one of the main reasons. In order to have successful implant, a dynamic balance must be provided between mechanical and biological elements (Isidor, Flemming 1996). Şimşek et al. reported bone quality, oral sanitation, host medical condition and biomechanical parameters as the main reasons for implants failure. Also, implant fixture micromotion and inappropriate stress in the bone implant interface is known as the potential reasons for early bone loss and implant failure (Şimşek, Barış 2006). Even so, implant position in jawbone, bone density; biomaterial properties of implant surface, treatment technique, loading history and patient clinical status are the influential factors in implant success (Brunski, J.B. 1999). Although there are many studies on stress distribution of implants in bone-implant interface, majority are limited to current implants in the market. However, current designs have been developed by marketing purposes rather than scientific considerations. Therefore, there is need to introduce and analyse new designs in order to optimize implant structure. Recent investigations have shown reliability of FEA method in simulating human jawbone situation. This research aims to develop a new dental implant with better life expectancies and introduce an optimized implant based on FEA stress analyses and experimental tests. Therefore, based on literature recommendations a series of new design factors are defined and analysed. In this study, a primary design is created in AutoCAD and yields to 3 different implants developed in SolidWorks. Branemark MK IV was selected as the bench model to play role of control group. Then, CT-scan images of human jawbone are imported to MIMICS to create a host bone model. Implant and jawbone models are assembled in 3-Matic and exported to Abaqus for final analyses. A series of loadings are defined to examine implant performance in different conditions. Branemark and C-3 implants are manufactured from Titanium for experimental analyses. Mechanical tests on sawbone foam blocks and cadavers are targeted to portray realistic performance. This research demonstrates C-3 model as the optimized dental implant, which presents a new design profile and better performance in low bone densities. The FEA and experimental results validate the benefit of the new design compare to the conventional ones. Furthermore, results can provide a basis for future designers to develop further optimizations.
3
Sarker, Pratik. "Investigation of the Quenching Characteristics of Steel Components by Static and Dynamic Analyses." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1942.
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Machine components made of steel are subjected to heat treatment processes for improving mechanical properties in order to enhance product life and is usually done by quenching. During quenching, heat is transferred rapidly from the hot metal component to the quenchant and that rapid temperature drop induces phase transformation in the metal component. As a result, quenching generates some residual stresses and deformations in the material. Therefore, to estimate the temperature distribution, residual stress, and deformation computationally; three-dimensional finite element models are developed for two different steel components – a spur gear and a circular tube by a static and a dynamic quenching analyses, respectively. The time-varying nodal temperature distributions in both models are observed and the critical regions are identified. The variations of stress and deformation after quenching along different pathways for both models are studied. The convergence for both models is checked and validations of the models are done.
4
Ribeiro, Marcelo Leite. "Programa para análise de juntas coladas: compósito/compósito e metal/compósito." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-19012011-122529/.
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O presente trabalho consiste basicamente no desenvolvimento de um programa de engenharia denominado SAJ (sistema de análise de juntas) capaz de realizar uma análise detalhada do comportamento de dois dos diversos tipos de juntas coladas existentes, a junta simples colada (\"single lap joint\") e a junta dupla colada (\"double lap joint\"). Sendo que foram analisadas juntas coladas com aderentes de material compósito ou, então, compostas de aderentes de compósitos e metal. O programa de engenharia desenvolvido possibilita o cálculo das tensões, dos esforços e dos deslocamentos nessas juntas. Para validar o referido programa, os resultados obtidos do mesmo foram confrontados com os resultados obtidos para condições semelhantes utilizando \"softwares\" comerciais de elementos finitos e de cálculo de juntas. Após a validação do programa, são apresentados alguns estudos de fatores que influenciam na resistência da junta colada, verificando a influência do comprimento de \"overlap\" (sobreposição), a rigidez do adesivo e a espessura da camada adesiva. Também é apresentada uma análise de falha dos aderentes de compósito evidenciando assim, as potencialidades e limitações desta ferramenta computacional para a área de desenvolvimento de produto.This work consists on the development of software called SAJ which can analyze a bonded joint behavior in detail, not only for single lap joint, but also, for double lap joint. These joints could be made of composite/composite materials or metal/composite as adherentes. The software developed can calculate the joints stresses, loads and displacements. The results obtained are compared to the results obtained using commercial software and the same problems proposed. After the validation of SAJ, some studies were performed in order to determine how some characteristics affect the joint stresses distribution as overlap length, adhesive elastic modulus, adhesive thickness and a failure analysis of composite adherents showing the potential and limitation of this computational tool for the product development area.
5
Gundeboina, Saidulu. "Finite Element Analysis of a Washing Machine Cylinder." Thesis, Högskolan i Skövde, Institutionen för teknik och samhälle, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-4863.
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In this thesis a finite element model of a household washing machine cylinder is built and analysed in ABAQUS 6.9-2. The aim is to help Asko appliances in conducting similar analysis for future manufacturing of high capacity cylinders by reducing experimentation. The analysis is mainly concerned with an evenly distributed load at a constant angular velocity. The load is applied with the help of lead plates instead of clothes. The cylinder is loaded with three thin (2 mm) lead plates weighing 2 kg each. The plates with dimensional 370x240x2 mm are mounted with one strip of double sided foam tape inside the cylinder. To estimate the behavior of the cylinder the strains are measured when the cylinder is rotating at 1620 and 2200 revolution per minute (rpm). To validate the model the numerical analyses are compared with experimental results. The results clearly show that the numerical strain values fit with experimental strain values.
6
Barrans, Simon Mark. "Enhancing finite element analysis boundary stress predictions." Thesis, University of Huddersfield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338613.
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7
Daniels, Michael John. "Accuracy improvements in finite element stress analysis." Thesis, Birmingham City University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327853.
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8
Pascoe, Steven Keith. "Contact stress analysis using the finite element method." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240266.
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9
Burstow, Mark C. "A combined boundary element and finite element method for elasto-plastic fracture analysis." Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387269.
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10
Guzelbey, Ibrahim H. "Finite and boundary element analysis of elasto-plastic finite strain contact problems." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335006.
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11
Oysu, Cuneyt. "Coupled finite and boundary element analysis of elastoplastic contact problems." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391437.
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12
Yueh, Sean. "Finite Element Analysis of Total Knee Arthroplasty." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2257.
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The total knee arthroplasty (TKA) has become one of the most successful procedures in all of medicine, with an average of over 966,000 operations performed a year. Since its introduction in 1968, the TKA’s surgical process and implant designs have continuously been improved to increase survivability. However, the need for a revision TKA – due to aseptic loosening – continues to be a problematic aspect of the procedure. Stress shielding induced by different design parameters of the implant has generated controversy in the determination of an ideal configuration. The purpose of this study is to investigate how implant design parameters – fixation technique, stem geometry, cement stiffness, and interface condition – affect the stress shielding within the tibia, and to find an optimal combination of designs that mitigates stress shielding. A CT scan of a tibia was used to simulate multiple configurations of TKAs for finite element analysis in ABAQUS. Stress shielding was assessed by taking the average minimum principal stress of different regions at interval cuts along the depth of the tibia. The results concluded a short, full-cement stem to be the ideal combination of stem length and fixation technique, high-stiffness cement to be ideal for hybrid cements, low-stiffness cement to be ideal for full cements, and a sliding friction interface to be ideal for all models.
13
Karasan, Mustafa Murat. "Residual Stress Analysis Of Riveting Process Using Finite Element Method." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608997/index.pdf.
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Rivets are widely used as a means of fastening in airframe construction industry. There are various types of riveted joints on an aircraft fuselage or on a helicopter body. Among the other types of fasteners riveted joints are preferred in such applications due totheir permanence after installation and their economical advantages. In a riveted joint, it is known that residual stresses are present as a result of the installation process. Furthermore, during the flight of an aircraft, the fuselage is loaded in one cycle and such cycles are repeated throughout the service life. As a result, the panels and the rivets are subjected to fatigue type loading. The integrity of the joint must be maintained against this combination of service loads and the residual stresses. Hence, the riveting process parameters which influence the residual stresses are utmost critical in terms of fatigue life of the hole body. In this study it is aimed to obtain an accurate numerical model of a single-lap riveted joint which is widely used in airframes. 2-D axisymmetrical and 3-D numerical models are generated using commercial finite element code ABAQUS/CAE and subsequent parametric studies are carried out on these models. The Results of both models are compared with those found in the literature. Clearance between hole and rivet shank is selected as the primary parameter to be inspected. The effects of hole clearance on the final residual stress field are examined on 2-D and 3D models. Furthermore, a through the thickness, crack on the inner panel which is initiated after installation is modeled. The crack is perpendicular to the direction of loading. It is placed to the residual tensile stress zone that surrounds the rivet hole. Hence, the effects of residual stresses are also taken into account. For a riveted joint subjected to fatigue loading, such a macroscopic crack could eventually form. In this thesis, stress intensity factors (SIF&rsquo
s) for this crack are calculated for various parameters such as clearance and crack length. These can be utilized in a subsequent fatigue crack growth analysis as the initial values or they can be used in a fracture analysis, to predict unstable crack growth due to overload (i.e. crack linking).
14
Groome, Isabelle Marie-Clement. "Finite element analysis of stress in prosthesis implanted canine femur." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/16990.
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15
Chau, Kam Shing Patrick. "A finite element model for stress analysis of underground openings /." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63962.
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16
Lek, Toh Cher. "Error estimates and adaptive meshing in finite element stress analysis." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359057.
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17
Rampilla, Lokamanya Siva Manohar. "A FINITE ELEMENT APPROACH TO STRESS ANALYSIS OF FACE GEARS." Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1337095318.
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18
Kingwill, Barry. "Ship structural analysis using finite element analysis and onboard stress monitoring methods." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/9734.
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Includes bibliographical references.This dissertation covers the application of finite element analysis and hull stress monitoring and measuring methods, in the current day design of, and/or the analysis of ship structures.
19
Tao, Chen. "Heterogeneous element : a new finite element method for the micro-stress analysis of composites /." Search for this dissertation online, 2003. http://wwwlib.umi.com/cr/ksu/main.
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20
Donaghy, Richard James. "Dimensional reduction of stress analysis models." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263368.
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21
Phillips, Donald Andrew. "Finite Element Analysis of a Shaft-Rotor System." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31450.
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The United States Air Force is in the process of developing a more electric aircraft. The development of an aircraft Integrated Power Unit and an Internal Starter/Generator will be instrumental in producing sufficient electrical power to run all non propulsive systems. Iron-cobalt alloys, such as Hiperco alloy 50HS, are high temperature, high strength magnetic materials ideal for these power applications. Design requirements and previous studies indicate that these materials need to survive in temperatures up to 1000F (810K), rotation speeds of about 55,000 rpm, and have strengths in excess of 80 ksi. Research conducted by Fingers provided the material and creep properties used in the analysis presented in this report. The finite element method was used to analyze a spinning rotor mounted to a circular shaft via an interference fit subjected to various operating environments. The power law creep model defined by Fingers was used to analyze three distinct rotor configurations. The first configuration was a constant temperature single lamina, mounted to a shaft of equal thickness, subject to temperatures between 727K and 780K, rotation speeds between 35,000 rpm and 60,000 rpm, and two different interference fits: 0.0015 inches and 0.003 inches. The results yield conservative predictions that indicate that these models could not survive the required operating conditions. The second configuration was a linear radial variation in temperature single lamina, mounted to a shaft of equal thickness, subjected to three temperature ranges, rotation speeds between 30,000 rpm and 55,000 rpm, and two different interference fits; 0.0015 inches and 0.003 inches. These results represent a more realistic model, which indicate that the â coolerâ inner portions of the rotor restrict the creep deformations of the â hotterâ outer portions resulting in higher possible operating temperatures and rotation speeds very near the required operating conditions. The third configuration was a lamina stack comprised of two rotor lamina, with a Coulomb friction surface interaction, and held together by a compressive axial force. These models represent a first step towards understanding the behavior of the entire rotor stack.Master of Science
22
McCune, Robert Willard. "Mixed dimensional coupling and error estimation in finite element stress analysis." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263494.
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23
Li, S. L. "Stress analysis in two dimensions by a 'mixed' finite element method." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233358.
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The development of mixed and hybrid models provides viable alternatives in finite element structural analysis which overcome the shortcomings of conventional displacement and force methods. In this thesis, a mixed triangular finite element model in two-dimensional stress analysis is studied. The mixed finite element model has several features which are distinct from those of conventional methods: (i) the use only of mid-side nodes; (ii) a global coordinate system is not required; (iii) nodal variables include both forces and displacements; (iv) the element matrix consists of a mixture of stiffness, flexibility, equilibrium and compatibility coefficients; (v) the ability to deal with incompressible materials; (vi) internal equilibrium and compatibility are satisfied; (vii) the entire stress field of the assembled structure is in equilibrium; (viii) formulation of element equations is not based on an extremum principle. The derivation of element matrix equations for small-strain, small-displacement linear-elastic analysis is discussed and a scheme for assmebling the final set of algebraic equations is presented. Accurate and balanced results for both stress and displacement are obtained for a number of problems in plane elasticity including thermal strain and body-force problems. The ability of the mixed element to deal with incompressible materials makes it useful for the computation of collapse loads in elastic-perfectly plastic analysis, for example in undrained soil mechanics problems. Ideal plastic behaviour is approximated by the use of an extremely soft incompressible material. This approximation enables an incremental plastic stress-strain matrix to be written down, relating a plastic strain-increment to an imposed stress-increment in the ideal plastic range. The performance of the mixed element in elastic-perfectly plastic analysis is studied and numerical results are compared with those obtained by analytical techniques and the displacement finite element method. The use only of mid-side nodes in the mixed model has the advantage that a global coordinate system is not required in the analysis. This makes it relatively simple to follow the behaviour of structures in large-deflection problems. Examples are studied to investigate how the mixed element works in small-strain, large-deflection problems.
24
Chen, Chi. "2-D Finite Element Modeling for Nanoindentation and Fracture Stress Analysis." Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/1897.
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In Chapter 1, a brief introduction of nanoindentation and finite element method is presented. General procedures have been developed based on FEM modeling of nanoindentation data to obtain the mechanical properties of thin films. Selected FEM models are illustrated in detail.
In Chapter 2, nanoindentation test is simulated using finite element method based on contact mechanics approach. The relationship between load and indentation depth is obtained. The numerical results show good agreement with experimental data. It is shown that FEM is an effective tool for simulation of nanoindentation tests of metallic films. However, limitations caused by simplification of models and assumptions should not be neglected.
In Chapter 3, finite element method is used to analyze bonded repair structure of aluminum plates with Multiple Site Damage (MSD). A 2-D 3-layer technique is used to deal with the damage area. A typical aluminum plate with multiple collinear twin cracks is taken as an example. The effects of relative position of two cracks, patch size, and patch thickness on stress intensity factors are studied in detail. The results reveal that the stress intensity factors at the tips of collinear twin cracks can be reduced greatly through bonded composite repair. In order to increase the performance of the patch repair, the adhesive properties, the patch length and thickness must be optimized.
In Chapter 4, finite element method is used for thermo-mechanical analysis of porous coatings in steel micro channels used for catalysis. Thermal stresses in the coating due to temperature changes are obtained. The effects of micro channel geometry on thermal stresses are studied in detail. The results reveal that in order to increase the mechanical performance of the coatings, film thickness and profile geometry must be optimized.
Chapter 5 summarizes major results and outlines future work.
25
Brew, Patrick Joseph. "Crack Initiation Analysis in Residual Stress Zones with Finite Element Methods." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84537.
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This research explores the nearly untapped research area of the analysis of fracture mechanics in residual stress zones. This type of research has become more prevalent in the field in recent years due to the increase in prominence of residual stress producing processes. Such processes include additive manufacturing of metals and installation procedures that lead to loads outside the anticipated standard operating load envelope.
Abaqus was used to generate models that iteratively advanced toward solving this problem using the compact tensile specimen geometry. The first model developed in this study is a two-dimensional fracture model which then led to the development of an improved three-dimensional fracture model. Both models used linear elastic fracture mechanics to determine the stress intensity factor (K) value. These two models were verified using closed-form equations from linear elastic fracture mechanics. The results of these two models validate the modeling techniques used for future model iterations. The final objective of this research is to develop an elastic-plastic fracture mechanics model. The first step in the development of an elastic-plastic fracture model is a three-dimensional quasi-static model that creates the global macroscale displacement field for the entire specimen geometry. The global model was then used to create a fracture submodel. The submodel utilized the displacement field to reduce the model volume, which allowed a higher mesh density to be applied to the part. The higher mesh density allowed more elements to be allocated to accurately represent the model behavior in the area local to the singularity. The techniques used to create this model were validated either by the linear elastic models or by supplementary dog bone prototype models. The prototype models were run to test model results, such as plastic stress-strain behavior, that were unable to be tested by just the linear elastic models. The elastic-plastic fracture mechanics global quasi-static model was verified using the plastic zone estimate and the fracture submodel resulted in a J-integral value.
The two-dimensional linear elastic model was validated within 6% and the three-dimensional linear elastic model was validated within 0.57% of the closed-form solution for linear elastic fracture mechanics. These results validated the modeling techniques. The elastic-plastic fracture mechanics quasi-static global model formed a residual stress zone using a Load-Unload-Reload load sequence. The quasi-static global model had a plastic zone with only a 0.02-inch variation from the analytical estimate of the plastic zone diameter. The quasi-static global model was also verified to exceed the limits of linear elastic fracture mechanics due to the size of the plastic zone in relation to the size of the compact specimen geometry. The difference between the three-dimensional linear elastic fracture model J-integral and the elastic-plastic fracture submodel initial loading J-integral was 3.75%. The J-integral for the reload step was 18% larger than the J-integral for the initial loading step in the elastic-plastic fracture submodel.Master of Science
26
Rajam, Sham Kumar. "Design and finite element analysis of the broaching tools." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177014495.
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Lai, Zhi Cheng. "Finite element analysis of electrostatic coupled systems using geometrically nonlinear mixed assumed stress finite elements." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-05052008-101337/.
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Karachalios, E. F. "Stress and failure analysis of adhesively bonded single lap joints." Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/72fde066-0a88-4b2b-83ea-c2c08f0ce0fc.
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Moita, Gray Farias. "Non-linear finite element analysis of continua with emphasis on hyperelasticity." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7943.
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Wong, Vui-Hong, and n/a. "Finite Element Analysis and Improvement of Impeller Blade Geometry." Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030825.150853.
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Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.
31
Golbasi, Onur. "Investigation Of Stress Distribution In A Dragline Bucket Using Finite Element Analysis." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612993/index.pdf.
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Overburden stripping is one of the essential activities in open-cast mines before starting the ore production. Due to the economic advantages, dragline is a widely utilized machinery in the overburden excavation. These earthmovers carry out the earthmoving process with dragging, hoisting and dumping actions of the bucket. Dragline excavator&rsquos efficiency is critically important, since poor performance of a dragline in the mine site directly affects the total efficiency of ore production. Therefore, productivity studies about dragline should be directed to decrease cycle time and increase payload, with avoiding catastrophic failure. In this regard, determination of stress distribution on the front-end components of dragline is meaningful to detect the external factors against dragline operation. In order to provide insight into the dragline bucket-formation interaction and stress distribution on the bucket, this research studies the simulation of horizontally moving dragline bucket where passive earth forces of the formation create resistance to the movement. Within the scope of simulation, (i) solid models of dragline bucket and the rigging mechanism were created in the Computer-Aided Drawing (CAD) environment, (ii) the model was transferred to the Finite-Element Analysis (FEA) software, (iii) two different case studies were simulated in the FEA virtual environment. One of the cases handled the stress investigation on the dragline bucket at the first interaction with the formation, while the other focused on the stress formations on a moving dragline bucket. Simulation results showed that overloading conditions occurred on bottom edges of the bucket lip for the first case, and drag hitch part and digging teeth for the second case. Moreover, a sensitivity analysis was carried out to measure the effects of formation specification changes on the stress values on the bucket. The analysis showed that stress values on the bucket elements were most sensitive to internal friction angle and least sensitive to density. Consequently, this thesis study discusses stress and deformation components on the dragline bucket during the interaction with formation. Since there is not enough number of research studies in the literature about the stress investigation on a moving dragline bucket, this thesis study is expected to provide benefit to understand the basis of dragline bucket actions.
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Cozzolino, Luis D. "Finite element analysis of localised rolling to reduce residual stress and distortion." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8428.
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Fusion welding processes cause residual stress due to the uneven heat distribution produced by the moving welding torch. These residual stresses are characterised by a large tensile component in the welding direction. Due to the self-equilibrated nature of the residual stress, compressive ones are present in the far field next to the weld seam, which can cause different kind of distortion such as bending or buckling. Welding residual stress can be responsible of premature failure of the components, such as stress crack corrosion, buckling, and reduction of fatigue life. Localised rolling is a stress engineering technique that can be used to reduce the residual stress and distortion caused by welding. It induces plastic strain in the rolling direction, counteracting the plastic strain produced during welding. In this thesis three techniques were investigated, pre-weld rolling, post-weld rolling, and in situ rolling. These techniques have been seldom studied in the past, particularly pre-weld rolling; consequently the mechanisms are poorly understood. Finite element models allow stress and strain development during both welding and rolling processes to be better understood, providing an improved understanding of the mechanisms involved and aiding process development. A literature survey was done to find the state of the art of the computational welding mechanics simulations, stress management, and the residual stress measurement techniques, as well as the knowledge gaps such as, the thermal losses through the backing-bar in the thermal simulation, the frictional interaction in the rolling process, and the material properties of the steel used in the models. In the literature not many models that investigate the management of welding residual stress were found. After this, the general considerations and assumptions for the welding thermal mechanical models presented in this thesis were discussed. The effect of different backing-bar conditions, as well as different material properties where investigated. Both influenced the residual stress profile to varying degrees. In particular, temperature dependent heat loss to the backing-bar was necessary to capture the improved heat loss near the weld. The distortion predicted by the model was investigated to determine whether it was due to bending or buckling phenomena. Lastly, the temperature distribution and residual stress predictions were validated against thermocouple and neutron diffraction measurements conducted by Coules et al. [1–3]. Pre-weld rolling was the first of the three rolling methods considered, in which rolling is applied to the plates before performing GMA butt-welds. The principle behind this technique consisted in inducing tensile residual stress in the weld region before welding; therefore, it is similar to mechanically tensioning the weld, which can significantly reduce the residual stress and distortion. However, there was no significant change in the tensile residual stresses. On the other hand, it was possible to achieve a small reduction in the distortion, when the plates were rolled on the opposite surface to the weld; rolling in this way induced distortion in the opposite direction to the distortion induced by welding, reducing the magnitude of the latter. These results were compared with experiments conducted by Coules et al. [1,4]. A subsequent investigation combined pre-weld rolling with post-weld heating. With this additional process the residual stress and distortion were significantly reduced, and flatter residual stress profile was achieved. The post-weld rolling and in situ rolling techniques were discussed afterwards. In the post-weld rolling models, rolling was applied after the weldment was cooled to room temperature. In in situ rolling the roller was applied on top of the weld bead at some distance behind the torch, while it was still hot. The principle behind these techniques consisted in applying positive plastic strain to the weld bead region by a roller, counteracting the negative plastic strains produced in the welding process. Two roller profiles were investigated, namely, grooved, and double flat rollers. The post-weld rolling on top of the weld bead models, which used the grooved roller, showed good agreement against experimental results, producing a large reduction of the residual stress and distortion. Some discrepancies were present when the weld toes were rolled with the dual flat roller. The former roller was more efficient for reducing residual stress and distortion. The influence of different friction coefficients (between the roller and weldment, and between the backing-bar and the weldment), were investigated. It showed significant dependency on the residual stress distribution when high rolling loads were used. The frictional interaction constrained the contact area inducing more compressive stress in the core of the weld bead; therefore it produced more tensile residual stress in the surface of the weldment. Additionally, the influence of rolling parameters on the through-thickness residual stress variation was investigated. Low loads only influence the residual stress near the surface, while high loads affected the material through the entire thickness. When the dual flat roller was used to roll next to the weld bead, significant compressive residual stress was induce in the weld bead; however, the residual stress reduction was very sensitive to the contact of the roller to the weld toes; therefore, when rolling a weld bead that varies in shape along the weld, the residual stress reduction is not uniform and varies along the length. On the other hand, the in situ rolling did not produced significant residual stress or distortion reduction in all the cases analysed. The rolling occurred when the material was still hot and the residual stress was subsequently formed as the material cooled to room temperature. Numerical modelling was a very useful tool for understanding the development of stress and plastic strain during the welding and rolling processes.
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Akers, Stephen Andrew. "Two-Dimensional Finite Element Analysis of Porous Geomaterials at Multikilobar Stress Levels." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/30070.
Full textAbstract:
A technique was developed for analyzing and developing mechanical properties for porous geomaterials subjected to the high pressures encountered in penetration and blast-type loadings. A finite element (FE) code was developed to verify laboratory test results or to predict unavailable laboratory test data for porous media loaded to multikilobar stress levels. This FE program eliminates a deficiency in the process of analyzing and developing mechanical properties for porous geomaterials by furnishing an advanced analysis tool to the engineer providing properties to material modelers or ground shock calculators. The FE code simulates quasi-static, axisymmetric, laboratory mechanical property tests, i.e., the laboratory tests are analyzed as boundary value problems. The code calculates strains, total and effective stresses, and pore fluid pressures for fully- and partially-saturated porous media. The time dependent flow of the pore fluid is also calculated. An elastic-plastic strain-hardening cap model calculates the time-independent skeletal responses of the porous solids. This enables the code to model nonlinear irreversible stress-strain behavior and shear-induced volume changes. Fluid and solid compressibilities were incorporated into the code, and partially-saturated materials were simulated with a "homogenized" compressible pore fluid. Solutions for several verification problems are given as proof that the program works correctly, and numerical simulations of limestone behavior under drained and undrained boundary conditions are also presented.Ph. D.
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Nishiyama, Kenta. "Analysis of Soil-Tire Interaction Using a Two-Dimensional Finite Element-Discrete Element Method." Kyoto University, 2019. http://hdl.handle.net/2433/245298.
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Maddela, Naveen. "Finite Element Analysis of Railway Track Wooden Sleeper." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
Railway sleepers have important roles within the complex railroad. Dynamic interaction among Rail, sleeper and ballast supports are vital for the construction of dynamic model track capable of predicting its responses to impact loads due to wheel flats, wheel burns, irregularities of the rail. Railway track deteriorates over time due to the dynamic loading of passing wheeled vehicle. to ensure the secure passing of trains, the track must well design and managed.The objective of this thesis is to determine the stress in wooden rail sleeper by the considering Ballast, Sub ballast, and soil with the help of well-known FEM Tool Ansys Workbench. Material models for wooden sleeper and subgrade are anisotropic elasticity and elasto plastic (Drucker Prager), respectively. To validate FEM results with analytical Zimmermann method, perform the 2D linear static analysis and 3D nonlinear static analysis. The numerical analysis results in Ansys Work bench are presented and discussed the model validation with analytical results. Even though simulation converged it does not mean this model could give results similar to reality. But in my opinion these results are not sufficient to study the behavior of wooden sleeper because limitations in soil mechanics (Soil Models in Ansys Workbench).
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Kapoor, Hitesh. "Isogeometric Finite Element Code Development for Analysis of Composite Structures." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50567.
Full textAbstract:
This research endeavor develops Isogeometric approach for analysis of composite structures and take advantage of higher order continuity, smoothness and variation diminishing property of Nurbs basis for stress analysis of composite and sandwich beams and plates. This research also computes stress concentration factor in a composite plate with a hole.Isogeometric nonlinear/linear finite element code is developed for static and dynamic analysis of laminated composite plates. Nurbs linear, quadratic, higher-order and k-refined elements are constructed using various refinement procedures and validated with numerical testing. Nurbs post-processor for in-plane and interlaminar stress calculation in laminated composite and sandwich plates is developed. Nurbs post-processor is found to be superior than regular finite element and in good agreement with the literature. Nurbs Isgoemetric analysis is used for stress analysis of laminated composite plate with open-hole. Stress concentration factor is computed along the hole edge and good agreement is obtained with the literature. Nurbs Isogeometric finite element code for free-vibration and linear dynamics analysis of laminated composite plates also obtain good agreement with the literature.
Main highlights of the research are newly developed 9 control point linear Nurbs element, k-refined and higher-order Nurbs elements in isogeometric framework. Nurbs elements remove shear-locking and hourglass problems in thin plates in context of first-order shear deformation theory without the additional step and compute better stresses than Lagrange finite element and higher order shear deformation theory for comparatively thick plates i.e. a/h = 4. Also, Nurbs Isogeometric analysis perform well for vibration and dynamic problems and for straight and curved edge problems.
Ph. D.
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Pimmarat, Marut. "Finite element analysis of the assembly process for two pipes." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175792842.
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Desborough, Michael. "The mathematical modelling of the structural integrity of cast enclosures in switchgear applications." Thesis, University of Sunderland, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309569.
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Cole, Garry. "Consistent co-rotational formulations for geometrically non linear beam elements with special ref to large rotations." Thesis, Kingston University, 1990. http://eprints.kingston.ac.uk/20535/.
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Husain, I. A. "Finite element and boundary element methods for elasto-plastic stress analysis of two-dimensional and axisymmetric problems." Thesis, Cranfield University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352947.
Full text
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Mahmood, Rashid. "Static and dynamic finite element stress analysis of layered composite plates and shells." Thesis, Cranfield University, 1989. http://hdl.handle.net/1826/4048.
Full textAbstract:
In this work an attempt has been made to develop
theories for finite element static and dynamic stress
analysis tailored for use with composite layered plates and
shells in this way it was hoped to provide accurate values
of the stresses particularly transverse shear stresses
through the thickness, and to perform accurate natural
frequency analysis by including non-linear effects such as
centrifugal stiffening.
Initial derivations were based upon first order facet
shell element analysis and first order curved shell element
analysis. Subsequently, derivations were produced for
higher order element analysis.
A programming package has been developed based upon
the above derivations, and containing a banded solver as
well as a frontal solver, capable of analysing structures
build up from uniform or variable thickness layers and with
a multiple number of layers having constant or variable
dimension.
Results obtained with the aid of the present package
have been compared with results derived from experimental
work as well as with results derived from available
analytical solutions. Investigations have been carried out
for existing compressor blades, made of isotropic material
and layered composite material, respectively. The results
obtained from the package have been compared with available
experimental results produced by RR or carried out at
Cranfield. It has been shown that the above mentioned
derivations produce comparable results and the package has
proved to be reliable and accurate.
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Huang, Yen Chieh, and 黃彥結. "Three-Dimensional Finite Element Stress Analyses of Proximal l Applications." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/48205484270702998069.
Full textAbstract:
碩士中原大學
醫學工程學系
83
The current study is focused on the finite element stress analyses of a proximal femur. It includes two clinical applic- tions:one is to analyze a femur with intertrochanteric fracture that was treated with an angle plate for internal fixation, the other one is to analyze a femur that was implanted with a newly -designed Cervico-Trochanter (C-T) hip prosthesis which was developed at the Department of Orthopaedics,Chang-Gung memorial hospital. Three-dimensional finite element models were created for the comparison of stress and strain patterns of a femur before and after implantation of an angle plate and two different types of hip prostheses respectively. A commercial finite element analysis package - ANSYS 5.0A was used to perform the stress analyses in this study. In the angle plate study, several factors were considered , such as: various degrees of osteoporosis, amount of bone cement used, states of healing of the fracture. Finite element analysis results showed that for patients with osteoporosis, fracture in the bone cement is more likely to happen than patients without osteoporosis. For patients treated with larger amount of bone cement, stresses in bone cement and angle plate were reduced simultaneously. In addition, simulations of falls following intertrochanteric fracture were performed and the minimum loadings for the onset of cement fracture were predicted for patients with and without osteoporosis. In the analysis of hip prostheses, stress and strain patterns of a proximal femur before implantation were compared with the same femur implanted with a C-T hip prosthesis and with a PCA hip prosthesis respectively. Results showed that the stress and strain patterns of the femur implanted with a C-T prosthesis are closer to the patterns shown in the intact femur than the femur implanted with a PCA prosthesis. In addi- tion, the stress shielding effect is less significant for the femur implanted with a C-T hip prosthesis than the femur with a
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Macho, Gabriele A., D. Shimizu, Y. Jiang, and I. R. Spears. "Australopithecus anamensis: a finite element approach to studying functional adaptations in extinct hominins." 2005. http://hdl.handle.net/10454/3625.
Full textAbstract:
NoAustralopithecus anamensis is the stem species of all later hominins and exhibits the suite of characters traditionally associated with hominins, i.e., bipedal locomotion when on the ground, canine reduction, and thick-enameled teeth. The functional consequences of its thick enamel are, however, unclear. Without appropriate structural reinforcement, these thick-enameled teeth may be prone to failure. This article investigates the mechanical behavior of A. anamensis enamel and represents the first in a series that will attempt to determine the functional adaptations of hominin teeth. First, the microstructural arrangement of enamel prisms in A anamensis teeth was reconstructed using recently developed software and was compared with that of extant hominoids. Second, a finite-element model of a block of enamel containing one cycle of prism deviation was reconstructed for Homo, Pan, Gorilla, and A. anamensis and the behavior of these tissues under compressive stress was determined. Despite similarities in enamel microstructure between A. anamensis and the African great apes, the structural arrangement of prismatic enamel in A. anamensis appears to be more effective in load dissipation under these compressive loads. The findings may imply that this hominin species was well adapted to puncture crushing and are in some respects contrary to expectations based on macromorphology of teeth. Taking together, information obtained from both finite-element analyses and dental macroanatomy leads us to suggest that A. anamensis was probably adapted for habitually consuming a hard-tough diet. However, additional tests are needed to understand the functional adaptations of A. anamensis teeth fully.
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Chao, Chen-Yen, and 趙偵言. "New Profile Geometric Design, Finite Element Analyses of Contact Stress, Flow Analyses and LIGA-like Fabrication of Roots Type Rotors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23040390292444398717.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
99
Nowadays, Roots type rotors are widely used in various industrial applications, such as rotary blower, pump, supercharger, and compressor, etc. The aim of this paper is to present a new profile geometric design of Roots type rotors, the compound profile of driving rotor is consisted of three-segment curves formed by cycloid-circular-cycloid and circular-cycloid-circular. Based on theory of gearing and continuous connected condition for compound curves, the profile of new Roots type rotors are derived. In order to avoid yielding during rotors rotation of micro Roots type pump, the contact stress of rotors for two-lobe, three-lobe and four-lobe were simulated separately by using the finite element analyses software ANSYS/Workbench. Otherwise, the pressure head of new Roots type pump of two-lobe, three-lobe and four-lobe were analyzed separately by using the computational fluid dynamics software FLUENT. From the analyses results of area efficiency and pressure head, it reveals that the proposed new Roots type rotors can provides more better pump efficiency than those of traditional Roots rotors. The new micro Roots type rotors were successfully fabricated by LIGA-like process and nickel70-cobalt30 electroforming process for the purpose of achieving the high aspect ratio new micro Roots type rotors.
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Yu-JungLu and 盧宥融. "The Three-Dimensional Finite-Element Analyses for Stress Intensity Factors of Semi-Elliptical Cracks at Fillet Weld Toes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/86554371902699530157.
Full textAbstract:
碩士國立成功大學
土木工程學系碩博士班
100
This thesis mainly employed a three-dimensional finite-element program to compute and analyze the stress intensity factors (SIFs) of semi-elliptical cracks at fillet weld toes in two types of joints. The first type of joint was the cruciform joint which was used to connect steel plates by fillet welds. The second type of joint was the T-shaped joint which was created to simulate the joint connecting a steel box-column and a steel plate by all-around fillet weld. A semi-elliptical crack was simulated in the fillet weld toe of each joint. This thesis developed three-dimensional finite-element models for two types joints, and, in each type of joint, a number of finite-element joint models were created by varying the key geometric parameters to investigate the influences of the key geometric parameters to the SIFs of semi-elliptical cracks at fillet weld toes. In addition to acquiring the SIFs directly from the three-dimensional finite-element program, this thesis also utilized the crack opening displacements (CODs) of the deepest point in the semi-elliptical crack that were simulated from the three-dimensional finite-element program, and then computed the SIFs of the deepest point by least-squares method. The simulation results showed that semi-elliptical cracks in the two types of joints were affected by tensile/opening mode (mode I) significantly. The SIFs at crack front decreased from the surface point to the deepest point. The SIFs of crack front at surface point were all greater than those at the deepest point. When the attachment plate of the T-shaped joint was applied with the tensile force, the weld toe semi-elliptical crack occurred only in the main plate yielded greater SIFs than the weld toe semi-elliptical crack occurred only in the attachment plate. When the attachment plate of the T-shaped joint was applied with the shear force of the same magnitude, the weld toe semi-elliptical crack occurred only in the attachment plate yielded greater SIFs than the weld toe semi-elliptical crack occurred only in the main plate.
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Wang, Jhe-Hong, and 王哲鴻. "Finite Element Analyses of Contact Stress and LIGA-like Fabrication of Rotors and Performance Test of Prototypes for a New Micro Gear Pump and a New Micro Internal Lobe Pump." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/35516415041004871684.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
96
Both of the traditional internal lobe pump with cycloid rotor and micro gear pump with involute rotor have the drawback of low volumetric efficiency. Accordingly, the goal of this thesis is to study the finite element analyses of contact stress and LIGA-like fabrication of the rotors and the performance test of the prototypes for both a new parabolic micro lobe pump and a new micro gear pump which have high volumetric efficiency. The first, how to design the profiles of rotors of two kinds of new micro gear pumps were introduced by applying the gear meshing theorem. Then, the contact stress of rotors for two kinds of new micro gear pump were simulated separately by using the finite element analyses software ANSYS/Workbench, and the von Mises stress of rotors of both micro gear pump were confirmed that smaller than the yield strength of the nickel70-cobalt30 alloy. The rotors of the new micro gear pump and the new micro lobe pump were fabricated by LIGA-like process and nickel70-cobalt30 electroforming process for the purpose of achieving the high aspect ratio mcirorotor. The profiles of fabricated rotors are measured by optical measuring microscope and E-MAX software to ensure the precision. Subsequently, the chamber and microchannel on the housings of the prototypes were fabricated on PMMA material by precision CNC machining technique. The prototypes of the new micro gear pump and the new micro lobe pump were composed by assembling the rotors, housings and the DC micromotor. Finally, the performance test of fluid transmission were experimented with various speeds of micromotor and the related data were obtained. Both of the proposed new parabolic micro lobe pump and new micro gear pump have big potential for application in some fields, such as biomedical technology, chemical processing, micro machinary, energy resources, etc.
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Chou, Cheng-Han, and 周政翰. "Finite Element Analysis of Thin Film Stress." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/85269848723873842334.
Full textAbstract:
碩士國立成功大學
土木工程學系碩博士班
94
In this work we employ the finite element software, ABAQUS, to simulate the stress evolution in film-substrate system subject to intrinsic mismatch strains. The mismatch strain could be origined from surface stress, different thermal expansion coefficients, and others. In pratical situations it is difficult to measure the stress in situ. The renowned Stoney formula provides a simple analytical connection between the internal stress and the curvature of the substrate, and thus could serve as a convenient tool to estimate stress through the measured curvature. However, the derivation of the Stoney formula was based on classical plate assumptions. In addition, the energy terms associated with the film deformation are all neglected. Naturally, this formula, though simple, could only be valid under certain conditions. Here we employ the finite element analysis to examine the range of validity of Stoney formula.
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Kocababuc, Berkay. "Finite element analysis of wellbore strengthening." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4694.
Full textAbstract:
As the world energy demand increases, drilling deeper wells is inevitable. Deeper wells have abnormal pressure zones where the difference between pore pressure and fracture pressure gradient, is very small. Smaller drilling margins make it harder to drill the well and result in high operation costs due to the increase of non-productive time. One of the major factors influence non-productive time in drilling operations is lost circulation due to drilling induced fractures. The most common approach is still plugging the fractures by using various loss circulation materials and there are several wellbore strengthening techniques present in the literature to explain the physics behind this treatment. This thesis focuses on development of a rock mechanics/hydraulic model for quantifying the stress distribution around the wellbore and fracture geometry after fracture initiation, propagation and plugging the fracture with loss circulation materials. In addition, fracture behavior is investigated in different stress states, for different permeability values and in the presence of multiple fractures. The following chapters contain detailed description of this model, and analysis results.text
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WU, YUAN SHIH, and 袁師武. "Finite Element Analysis for Stress Distribution of Orthodontics." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/63657206787101662331.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
The purpose of this thesis is to analyse stress distribution in Alveolar Bone and tooth movement during the process of orthodontics.That’s provide to work out with doctor , this’s finish by analysis individual tooth from Mandibular now .In this thesis that imitate analysis to simplify 2-D structure by individual tooth from Mandibular with CAE software ANSYS.The imitate analysis module that contours to build for dental distal aspect by WHEELER’S , Alveolar Bone to build for Mandibular picture , and input dental material number to software .In this thesis that use photoelasticity stress ansisyse to proof software .The analyse result that stress ansisyse answer is match by ANSYS and photoelasticity , that to reveal high accuracy of ANSYS.Beside , influence is very important on contour of Alveolar Bone and tooth movement；The low stress of Aligner during the process and successful of orthodontics , The stiffness factor of individual tooth on Mandibular will be find by tooth movement , that can be use of orthodontics in the future.
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李金聰. "Finite Element Stress Analysis of Nine Endosseous Dental Implants." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/01401562215260260561.
Full textAbstract:
碩士國防醫學院
牙醫學系
84
Utilizaton of dental implants in restoration of edentulous patients is the progress of dental science. Stress can induce resorption in the surrounding bone of implants, leading to gradual loosening and ultimately to complete loss of implants. Thus, the maintenance of periimplant bone structure plays an important role for long term success of osseointegrated implants. Previous study has used the finite element method to assess mechanical stresses occurring in bone surrounding dental implants. However, little has been done to related the calculated stress distributions to clinical situation. In this investigation, to avoid the limitations stated, we made axisymmetric finite element models of various bone qualities and loading directions to simulate clinical conditions. The aim of this investigation is to evaluate the effects of different implant shapes and bone qualities on stress distribution in bone. Nine different root-type endosseous implants are included in this study. Among them are seven commercial cortical-Schraube, Branemark, Screw-Vent, Steri-Oss, Minimatic, Pitt-Easy, and MicroVent), two self-designed implants (A1, and B1). Four types of bone are modeled for this study: homogenous cortical bone, homogenous cancellous bone, a cortical bone layer superior to cancellous bone, a cortical bone layer superior to cancellous bone and the other inferior. 100-newton loadings of an axial direction and a 30-degree oblique direction to the axis are applied over the top surface of each implant. The results indicate that the stress distribution pattern is determined by implant shape, bone quality, and loading condition. Implant surfaces with geometric discontinuities (serrated, grooved, and sharp geometries) lead to high-stress concentrations at the tips of the bony ingrowth. Moreover, a smooth, longer cylinder shape of implant head causes higher stresses than shorter shape under oblique loading. Oblique loading produces more greater maximun bone stress than vertical, and concentrated in the little volume of crestal bone. In this study, the cortical bone will be advantageous for the stress delivered to bone, since it produces a more uniform stress distribution than does cancellous bone. it suggests that bone model of a cortical bone layer superior to cancellous bone and the other inferior is a good selection for operation site of implant. However, additional researches, combining biological and clinical studies, were recommended for all commercially available dental implants.