scholarly journals Finite element modelling versus classic beam theory: comparing methods for stress estimation in a morphologically diverse sample of vertebrate long bones

2013 ◽  
Vol 10 (79) ◽  
pp. 20120823 ◽  
Author(s):  
Charlotte A. Brassey ◽  
Lee Margetts ◽  
Andrew C. Kitchener ◽  
Philip J. Withers ◽  
Phillip L. Manning ◽  
...  
Keyword(s):  
Finite Element ◽  
Principal Stress ◽  
Beam Theory ◽  
Maximum Principal Stress ◽  
Long Bones ◽  
Element Analysis ◽  
Cross Sectional ◽  
Computed Tomographic ◽  
Slender Beams ◽  
Stress Behaviour

Classic beam theory is frequently used in biomechanics to model the stress behaviour of vertebrate long bones, particularly when creating intraspecific scaling models. Although methodologically straightforward, classic beam theory requires complex irregular bones to be approximated as slender beams, and the errors associated with simplifying complex organic structures to such an extent are unknown. Alternative approaches, such as finite element analysis (FEA), while much more time-consuming to perform, require no such assumptions. This study compares the results obtained using classic beam theory with those from FEA to quantify the beam theory errors and to provide recommendations about when a full FEA is essential for reasonable biomechanical predictions. High-resolution computed tomographic scans of eight vertebrate long bones were used to calculate diaphyseal stress owing to various loading regimes. Under compression, FEA values of minimum principal stress ( σ min ) were on average 142 per cent (±28% s.e.) larger than those predicted by beam theory, with deviation between the two models correlated to shaft curvature (two-tailed p = 0.03, r 2 = 0.56). Under bending, FEA values of maximum principal stress ( σ max ) and beam theory values differed on average by 12 per cent (±4% s.e.), with deviation between the models significantly correlated to cross-sectional asymmetry at midshaft (two-tailed p = 0.02, r 2 = 0.62). In torsion, assuming maximum stress values occurred at the location of minimum cortical thickness brought beam theory and FEA values closest in line, and in this case FEA values of τ torsion were on average 14 per cent (±5% s.e.) higher than beam theory. Therefore, FEA is the preferred modelling solution when estimates of absolute diaphyseal stress are required, although values calculated by beam theory for bending may be acceptable in some situations.

scholarly journals Influence of fibromucosa height and loading on the stress distribution of a total prosthesis: a finite element analysis

2021 ◽  
Vol 24 (2) ◽  
Author(s):  
Tarcisio José de Arruda Paes Junior ◽  
João Paulo Mendes Tribst ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Viviane Maria Gonçalves de Figueiredo ◽  
Alexandre Luiz Souto Borges ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Cortical Bone ◽  
Principal Stress ◽  
Maximum Principal Stress ◽  
Element Analysis ◽  
Total Displacement ◽  
Anterior Guidance ◽  
Mandibular Movements

Purpose: To evaluate the effect of fibromucosa height on the stress distribution and displacement of mandibular total prostheses during posterior unilateral load, posterior bilateral load and anterior guidance using the finite element analysis (FEA). Material and methods: 3D virtual models were made to simulate the stress generated during different mandibular movements in a total prosthesis. The contacts were simulated according to the physiology, being considered perfectly bonded between cortical and medullar bones; and between cortical bone and mucosa. Non-linear frictional contact was used for the total prosthesis base and fibromucosa, allowing the prosthesis to slide over the tissue. The cortical bone base was fixed and the 100 N load was applied as unilateral load, posterior bilateral load and anterior guidance simulation. The required results were for maximum principal stress (MPa), microstrain (mm/mm) and total displacement (mm). The numerical results were converted into colorimetric maps and arranged according to corresponding scales. Results: The stress generated in all situations was directly proportional to the fibromucosa height. The maximum principal stress results demonstrated greater magnitude for anterior guidance, posterior unilateral and posterior bilateral, respectively. Only posterior unilateral load demonstrated an increase in bone microstrain, regardless of the fibromucosa height. Prosthesis displacement was lower under posterior bilateral loading. Conclusion: Posterior bilateral loading is indicated for total prosthesis because it allows lower prosthesis displacement, lower stress concentration at the base of the prosthesis and less bone microstrain.   Keywords Finite element analysis; Occlusion; Total prosthesis.

Study on the Reduction Strategy of Machining-Induced Edge Chipping Based on Finite Element Analysis of In-Process Workpiece Structure

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Hu Gong ◽  
F. Z. Fang ◽  
X. F. Zhang ◽  
Juan Du ◽  
X. T. Hu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Principal Stress ◽  
Maximum Principal Stress ◽  
Machining Process ◽  
Element Analysis ◽  
Edge Chipping ◽  
Additional Support ◽  
The Relationship ◽  
Complex Parts

Edge chipping is one of the most serious issues during machining process of brittle materials. To find an effective method to reduce edge chipping, the relationship between the distribution of maximum principal stress and edge chipping is studied comprehensively based on 3D finite element analysis (FEA) model of in-process workpiece structure in this paper. Three-level influencing factors of edge chipping are proposed, which are helpful to understand the relationship between intuitive machining parameters and edge chipping at different levels. Based on the analysis, several experiments are designed and conducted for drilling and slotting to study the strategy of controlling edge chipping. Two methods are adopted: (a) adding additional support, (b) improving tool path. The result show that edge chipping can be reduced effectively by optimizing the distribution of the maximum principal stress during the machining process. Further, adding addtitional support method is extended to more complex parts and also obtain a good result. Finally, how to use adding additional support method, especially for complex parts, will be discussed in detail. Several open questions are raised for future research.

Effects of the Mechanical Properties of Veneering Porcelain on Stress Distribution of Dental Zirconia Layered Structure: A Finite Element Model Study

2012 ◽  
Vol 512-515 ◽  
pp. 1797-1801
Author(s):  
Yuan Fu Yi ◽  
Long Quan Shao ◽  
Chen Wang ◽  
Ning Wen ◽  
Bin Deng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Stress Distribution ◽  
Principal Stress ◽  
Layered Structure ◽  
Geometric Model ◽  
Middle Layer ◽  
Maximum Principal Stress ◽  
Element Analysis ◽  
Occlusal Contact

The purpose of this study was to study effects of the mechanical properties of veneering porcelain on stress distribution of dental zirconia layered structure by three-dimensional finite element analysis. A 3-D geometric model of the first maxillary molar was established, a tooth preparation was simulated by the Imageware software. A crown was designed and divided into three layers: core, middle layer and outer veneer layer. The elasticity modulus of the middle layer was 70GPa for the control model up to 175GPa for the tested models. Loads of 200N were applied over a 1 mm diameter area beneath the tip of the mesial-distal cusp, simulating typical occlusal contact areas, the stress distribution of the crown systems were analyzed. Results show that within the geometry of the crown configuration, one concentration district of maximum principal stress occurred on the occlusal surface closely proximal to the loading position, several sub-maximum principal stress area were observed, such as margin regions of the mesial face, lingual face, distal faces, buccal face and occlusal fossa. Middle layer with higher modulus can effectively disperse the stress concentration in the layered zirconia all-ceramic crown system.

The Role of Fluid Dynamics in Distributing Ankle Stresses in Anatomic and Injured States

2016 ◽  
Vol 37 (12) ◽  
pp. 1343-1349 ◽  
Author(s):  
Kamran S. Hamid ◽  
Aaron T. Scott ◽  
Benedict U. Nwachukwu ◽  
Kerry A. Danelson
Keyword(s):  
Finite Element ◽  
Synovial Fluid ◽  
Principal Stress ◽  
Maximum Stress ◽  
High Stress ◽  
Distal Tibia ◽  
Element Model ◽  
Maximum Principal Stress ◽  
Ankle Injuries ◽  
Element Analysis

Background: In 1976, Ramsey and Hamilton published a landmark cadaveric study demonstrating a dramatic 42% decrease in tibiotalar contact area with only 1 mm of lateral talar shift. An increase in maximum principal stress of at least 72% is predicted based on these findings though the delayed development of arthritis in minimally misaligned ankles does not appear to be commensurate with the results found in dry cadaveric models. We hypothesized that synovial fluid could be a previously unrecognized factor that contributes significantly to stress distribution in the tibiotalar joint in anatomic and injured states. Methods: As it is not possible to directly measure contact stresses with and without fluid in a cadaveric model, finite element analysis (FEA) was employed for this study. FEA is a modeling technique used to calculate stresses in complex geometric structures by dividing them into small, simple components called elements. Four test configurations were investigated using a finite element model (FEM): baseline ankle alignment, 1 mm laterally translated talus and fibula, and the previous 2 bone orientations with fluid added. The FEM selected for this study was the Global Human Body Models Consortium–owned GHBMC model, M50 version 4.2, a model of an average-sized male (distributed by Elemance, LLC, Winston-Salem, NC). The ankle was loaded at the proximal tibia with a distributed load equal to the GHBMC body weight, and the maximum principal stress was computed. Results: All numerical simulations were stable and completed with no errors. In the baseline anatomic configuration, the addition of fluid between the tibia, fibula, and talus reduced the maximum principal stress computed in the distal tibia at maximum load from 31.3 N/mm2 to 11.5 N/mm2. Following 1 mm lateral translation of the talus and fibula, there was a modest 30% increase in the maximum stress in fluid cases. Qualitatively, translation created less high stress locations on the tibial plafond when fluid was incorporated into the model. Conclusions: The findings in this study demonstrate a meaningful role for synovial fluid in distributing stresses within the ankle that has not been considered in historical dry cadaveric studies. The increase in maximum stress predicted by simulation of an ankle with fluid was less than half that projected by cadaveric data, indicating a protective effect of fluid in the injured state. The trends demonstrated by these simulations suggest that bony alignment and fluid in the ankle joint change loading patterns on the tibia and should be accounted for in future experiments. Clinical Relevance: Synovial fluid may play a protective role in ankle injuries, thus delaying the onset of arthritis. Reactive joint effusions may also function to additionally redistribute stresses with higher volumes of viscous fluid.

scholarly journals Evaluation of the stress distribution in the cortical bone caused by variations in implant applications in patients with bruxism: A three-dimensional finite element analysis

2021 ◽  
Vol 11 (Suppl. 1) ◽  
pp. 194-200
Author(s):  
Yakup Kantaci ◽  
Sabiha Zelal Ülkü
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Cortical Bone ◽  
Principal Stress ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Element Analysis ◽  
Minimum Principal Stress ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Aim: To evaluate the stress distribution in the cortical bone under parafunctional forces with different occlusal thicknesses, monolithic zirconia with different implant diameters, and number variations in implant-supported fixed prosthetic restorations applied in patients with bruxism. Methodology: The tomographic sections of the previously registered mandible were used in order to model the mandible. Modeled bone height is 30 mm, cortical bone thickness is 1.5 mm, and trabecular bone thickness is modeled as 13 mm. By placing two implants in the created bone model, a three-member main model (Group 1), the number of implants was increased, three implants supported the Group 2 models, the diameter of the implants was increased, and the Group 3 models were created. The created Group 1, 2, 3 models, the occlusal thickness was divided into subgroups with 1.0, 1.5, and 2.0 mm, respectively (Groups A, B, and C). The groups were applied in two directions: vertical and 30o oblique. Stress values under forces were analyzed by finite element stress analysis. Results: Under vertical loading, the maximum principal stress value in the cortical bone was found to be lowest in Group 2C, and the highest maximum principal stress value was found in Group 1A. The minimum principal stress value in the cortical bone was found to be the lowest in Group 3C, and the highest minimum principal stress value was found in Group 1A. Under oblique loading, the maximum principal stress value in the cortical bone was found to be the lowest in Group 3C and the highest maximum principal stress value was found in Group 1A. The minimum principal stress value in the cortical bone was found to be lowest in Group 3C, and the highest minimum principal stress value was found in Group1A. Conclusion: Stresses caused by oblique forces are more than vertical forces. Increasing the occlusal thickness of the implant fixed prosthesis material, implant diameter, and number reduce the minimum and maximum principal stress values in the cortical   How to cite this article: Kantaci Y, Ülkü SZ. Evaluation of the stress distribution in the cortical bone caused by variations in implant applications in patients with bruxism: A three-dimensional finite element analysis. Int Dent Res 2021;11(Suppl.1):194-200. https://doi.org/10.5577/intdentres.2021.vol11.suppl1.27   Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

scholarly journals Influence of Fiber Post Cementation Length on Coronal Microleakage Values in vitro and Finite Element Analysis

2014 ◽  
Vol 15 (4) ◽  
pp. 444-450 ◽  
Author(s):  
César Dalmolin Bergoli ◽  
Rodrigo Furtado de Carvalho ◽  
Ivan Balducci ◽  
Josete Barbosa Cruz Meira ◽  
Maria Amélia Máximo de Araújo ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Principal Stress ◽  
Maximum Principal Stress ◽  
Fiber Post ◽  
Element Analysis ◽  
Mechanical Cycling ◽  
Fiber Posts

ABSTRACT Aim This study aims to evaluate, the influence of different fiber posts cementation lengths by finite element analysis (FEA) and coronal microleakage. Materials and methods Fifty anterior bovine teeth were sectioned to obtain roots with 16 mm length. The coronal length of the post was 6 mm for all groups, while the radicular length were varied 6, 8, 10 or 12 mm. The fiber posts surfaces were cleaned with alcohol and silanized. Then the posts were cemented using a two steps total etch-and-rinse adhesive system + conventional resin cement. Forty teeth were submitted to mechanical cycling (45°; 2.000.000 cycles; 90N; 4Hz; 37°C) and ten teeth with radicular length of 12 mm was not submitted, serving as control. So, the experimental design was composed by different ratios of post coronal length/post radicular length and mechanical cycling (MC): Gr1- 1/1 + MC; Gr2- 3/4 + MC; Gr3- 3/5 + MC; Gr4- 1/2 + MC. All groups were immersed in a 1% toluidine blue solution. After 24 hours, the teeth were longitudinally sectioned and the microleakage scores was given by a blind operator. Data were submitted to Kruskal-Wallis test (p = 0.05). The experimental variables were simulated in twodimensional finite element analysis (2D-FEA). The maximum principal stress distributions were compared. Results No difference was observed in microleakage values between the cycled groups, whilst the control groups showed the lowest values. FEA analysis showed similar maximum principal stress distribution between the groups. Conclusion Mechanical cycling affected the values of coronal microleakage and different cementation length generated similar values of coronal microleakage and stress distribution. Clinical significance These results showed that from the microleakage point of view, more conservative cementation lengths have the same effect as longer cementation lengths. How to cite this article Bergoli CD, de Carvalho RF, Balducci I, Meira JBC, de Araújo MAM, Valera MC. Influence of Fiber Post Cementation Length on Coronal Microleakage Values in vitro and Finite Element Analysis. J Contemp Dent Pract 2014; 15(4):444-450.

scholarly journals Modelling of orbital deformation using finite-element analysis

2005 ◽  
Vol 3 (7) ◽  
pp. 255-262 ◽  
Author(s):  
Jehad Al-Sukhun ◽  
Christian Lindqvist ◽  
Risto Kontio
Keyword(s):  
Finite Element ◽  
Ct Scan ◽  
Principal Stress ◽  
Maximum Shear Stress ◽  
Element Model ◽  
Maximum Principal Stress ◽  
Blunt Injury ◽  
Shear Stresses ◽  
Element Analysis ◽  
Finite Element Software

The purpose of this study was to develop a three-dimensional finite-element model (FEM) of the human orbit, containing the globe, to predict orbital deformation in subjects following a blunt injury. This study investigated the hypothesis that such deformation could be modelled using finite-element techniques. One patient who had CT-scan examination to the maxillofacial skeleton including the orbits, as part of her treatment, was selected for this study. A FEM of one of the orbits containing the globe was constructed, based on CT-scan images. Simulations were performed with a computer using the finite-element software NISA (EMRC, Troy, USA). The orbit was subjected to a blunt injury of a 0.5 kg missile with 30 m s −1 velocity. The FEM was then used to predict principal and shear stresses or strains at each node position. Two types of orbital deformation were predicted during different impact simulations: (i) horizontal distortion and (ii) rotational distortion. Stress values ranged from 213.4 to 363.3 MPa for the maximum principal stress, from −327.8 to −653.1 MPa for the minimum principal stress, and from 212.3 to 444.3 MPa for the maximum shear stress. This is the first finite-element study, which demonstrates different and concurrent patterns of orbital deformation in a subject following a blunt injury. Finite element modelling is a powerful and invaluable tool to study the multifaceted phenomenon of orbital deformation.

Modeling and Finite Element Analysis of Drill Bit Vibrations

1989 ◽  
Vol 111 (2) ◽  
pp. 148-155 ◽  
Author(s):  
O. Tekinalp ◽  
A. G. Ulsoy
Keyword(s):  
Finite Element ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Helix Angle ◽  
Drill Bit ◽  
Element Analysis ◽  
Cross Sectional ◽  
Various Boundary Conditions ◽  
Drill Bits ◽  
Euler Bernoulli Beam

Drill bit vibrations are modeled using the Euler-Bernoulli beam theory. The model includes the most important properties of drill bits and of the drilling operation. These are: the drill bit cross sectional geometry, the drill helix angle, rotational speed of the drill bit, the thrust force, torque, and cutting forces generated during drilling. Equations of motion are derived in an inertial frame and then transformed to a rotating fluted frame for convenience in the solution. The transformed equations are discretized using finite element techniques. The finite element code developed is capable of solving the eigenvalue problem for various boundary conditions and drill cross sectional geometries. Finite element solutions are compared to known analytical, numerical, and experimental results from the literature and good agreement is obtained.

scholarly journals Folding photopolymerized origami sheets by post-curing

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Xiaodong He ◽  
Christopher-Denny Matte ◽  
Tsz-Ho Kwok
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Maximum Principal Stress ◽  
Second Step ◽  
Post Processing ◽  
Element Analysis ◽  
Digital Light Processing ◽  
Processing Step ◽  
Lower Maximum

AbstractThe paper presents a novel manufacturing approach to fabricate origami based on 3D printing utilizing digital light processing. Specifically, we propose to leave part of the model uncured during the printing step, and then cure it in the post-processing step to set the shape in a folded configuration. While the cured regions in the first step try to regain their unfolded shape, the regions cured in the second step attempt to keep their folded shape. As a result, the final shape is obtained when both regions’ stresses reach equilibrium. Finite element analysis is performed in ANSYS to obtain the stress distribution on common hinge designs, demonstrating that the square-hinge has a lower maximum principal stress than elliptical and triangle hinges. Based on the square-hinge and rectangular cavity, two variables—the hinge width and the cavity height—are selected as principal variables to construct an empirical model with the final folding angle. In the end, experimental verification shows that the developed method is valid and reliable to realize the proposed deformation and 3D development of 2D hinges.

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