Thermo-Mechanical Transient Analysis and Conceptual Optimization of a First Stage Bucket

2008 ◽  
Author(s):  
A. Campos-Amezcua ◽  
Z. Mazur ◽  
A. Gallegos-Mun˜oz
Keyword(s):  
Transient Analysis ◽  
Computational Models ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Element Analysis ◽  
Simulation Techniques ◽  
Start Up ◽  
Three Dimensional Models ◽  
Almost All

This paper presents a thermo-mechanical analysis of a first stage bucket during a gas turbine start-up. This analysis uses two simulation techniques, Computational Fluid Dynamics (CFD) for the conjugate heat transfer and flow analysis, and Finite Element Analysis (FEA) for the thermo-structural analysis. Computational three dimensional models were developed using two commercial codes, including all elements of the real bucket, to avoid geometric simplifications. An interface was developed to transfer the three-dimensional behavior of bucket temperatures during turbine start-up from CFD analysis to subsequent FEA analysis, imposing them as a thermal load. This interface virtually integrates the computational models, although they have different grids. The results of this analysis include temperature evolution and related stresses, as well as the thermo-mechanical stresses and zones where they are present. These stresses are dominated by thermal mechanisms, so a new temperature start-up curve is proposed where the maximum calculated stress decline around 100 MPa, and almost all stresses are lower throughout the transient analysis. The results are compared to experimental data reported in the literature obtaining acceptable approximation.

Thermomechanical Transient Analysis and Conceptual Optimization of a First Stage Bucket

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Alfonso Campos-Amezcua ◽  
Zdzislaw Mazur-Czerwiec ◽  
Armando Gallegos-Muñoz
Keyword(s):  
Transient Analysis ◽  
Computational Models ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Thermomechanical Analysis ◽  
Element Analysis ◽  
Simulation Techniques ◽  
Calculated Stress ◽  
Three Dimensional Models ◽  
Almost All

This paper presents a thermomechanical analysis of a first stage bucket during a gas turbine startup. This analysis uses two simulation techniques, computational fluid dynamics (CFD) for the conjugate heat transfer and flow analysis, and finite element analysis (FEA) for the thermostructural analysis. Computational three-dimensional models were developed using two commercial codes, including all elements of the real bucket to avoid geometric simplifications. An interface was developed to transfer the three-dimensional behavior of bucket temperatures during turbine startup from CFD analysis to subsequent FEA analysis, imposing them as a thermal load. This interface virtually integrates the computational models, although they have different grids. The results of this analysis include temperature evolution and related stresses, as well as the thermomechanical stresses and zones where they are present. These stresses are dominated by thermal mechanisms, so a new temperature startup curve is proposed where the maximum calculated stress decline around 100 MPa, and almost all stresses are lower throughout the transient analysis. The results are compared with experimental data reported in the literature obtaining acceptable approximation.

scholarly journals Numerical aspects for efficient welding computational mechanics

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 139-148
Author(s):  
Tarek Aburuga ◽  
Aleksandar Sedmak ◽  
Zoran Radakovic
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Mechanical Analysis ◽  
Tensile Test Specimen ◽  
Integrity Assessment ◽  
Mass Scaling ◽  
Three Dimensional Models ◽  
Thermal Mechanical Analysis

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

scholarly journals Comparative Evaluation of Biomechanical Performance of Titanium and Stainless Steel Mini Implants at Different Angulations in Maxilla: A Finite Element Analysis

2019 ◽  
Vol 53 (3) ◽  
pp. 197-205
Author(s):  
Kshitij Hemant Sabley ◽  
Usha Shenoy ◽  
Sujoy Banerjee ◽  
Pankaj Akhare ◽  
Ananya Hazarey ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Titanium Implant ◽  
Titanium Implants ◽  
Element Analysis ◽  
Mini Implants ◽  
The Difference ◽  
Tractional Forces ◽  
Three Dimensional Models

Objective: To assess and compare the tensions and deformations (stresses and strains) generated after application of two types of forces (traction and torsion) in miniscrews of two different materials (titanium and stainless steel) placed at five different angulations. Materials and Methods: Three-dimensional models of the posterior maxillary area and the mini-implants were constructed using computer-aided design software program (CATIA P3 V5-6 R2015 B26 / 2016; Dassault Systèmes). Titanium and stainless steel materials were used for miniscrews. The area constructed was in between the maxillary second premolar and first molar. The models with mini-implants were inserted at five different angulations (30°, 45°, 60°, 75° and 90°). Torsional and tractional forces were applied on these implants, and the models were solved using ANSYS 10.0. Stress generated in implant and in the cortical and cancellous bones was evaluated and compared at all the five angulations. Results: Stress generated in stainless steel mini-implant during torsional and linear force application was less when compared with titanium mini-implant. Also, stress generated in implants of both materials increased as the angle increased from 30° to 90°. Difference in stress generated by stainless steel implant in the cortical bone for both linear and torsional forces was less when compared with titanium implant, whereas for cancellous bone, the difference was insignificant at all the angles. Conclusion: Irrespective of angles, difference in stress generated in stainless steel implants and titanium implants for both the forces was not significant, and hence, stainless steel implants can be used effectively in a clinical setting.

scholarly journals Effect of apical portion of T-, sloped L-, and reversed L-closing loops on their force systems

2016 ◽  
Vol 87 (1) ◽  
pp. 104-110 ◽  
Author(s):  
Paiboon Techalertpaisarn ◽  
Antheunis Versluis
Keyword(s):  
Three Dimensional ◽  
Vertical Force ◽  
Element Analysis ◽  
Force System ◽  
Apical Portion ◽  
Beam Elements ◽  
Force Ratio ◽  
Force Systems ◽  
Three Dimensional Models ◽  
Apical Loop

ABSTRACT Objective: To investigate the effect of the position of the apical portion of closing loops on the force system at both loop ends. Materials and Methods: T-loops were compared with backward-sloped L-loops (SL) and reversed L-loops (RL). SL-loops were directed toward the anterior side; RL-loops were directed toward the posterior side. Loop response to loop pulling was determined with finite element analysis at six positions of the apical loop portion for 12-mm interbracket distance and 8-mm loop length and height. Three-dimensional models of the closing loops were created using beam elements with the properties of stainless steel. Loop responses (horizontal load/deflection, vertical force, and moment-to-force ratio) at both loop ends were calculated as well as at 100 g and 200 g activation forces. Results: T-, SL-, and RL-loops with the same position of the apical portion showed approximately the same force system at both loop ends. This behavior was found across the investigated range through which the loops were moved (interbracket center to posterior bracket). Conclusions: The center of the apical portion determined the force system of the closing loops regardless of the position of the loop legs. The centers of the apical portion of the T-, SL-, and RL-loops acted like V-bend positions.

scholarly journals Field Variable Associations With Scratch Orientation Dependence of UHMWPE Wear: A Finite Element Analysis

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Matthew C. Paul ◽  
Liam P. Glennon ◽  
Thomas E. Baer ◽  
Thomas D. Brown
Keyword(s):  
Finite Element ◽  
Computational Models ◽  
Three Dimensional ◽  
Element Model ◽  
Field Variable ◽  
Orientation Dependence ◽  
Normal Strain ◽  
Stress Strain ◽  
Element Analysis ◽  
Local Direction

Scratches on the metal bearing surface of metal-on-polyethylene total joint replacements have been found to appreciably accelerate abrasive/adhesive wear of polyethylene, and constitute a source of the considerable variability of wear rate seen within clinical cohorts. Scratch orientation with respect to the local direction of relative surface sliding is presumably a factor affecting instantaneous debris liberation during articulation. A three-dimensional local finite element model was developed, of orientation-specific polyethylene articulation with a scratched metal counterface, to explore continuum-level stress/strain parameters potentially correlating with the orientation dependence of scratch wear in a corresponding physical experiment. Computed maximum stress values exceeded the yield strength of ultra-high molecular weight polyethylene (UHMWPE) for all scratch orientations but did not vary appreciably among scratch orientations. Two continuum-level parameters judged most consistent overall with the direction dependence of experimental wear were (1) cumulative compressive total normal strain in the direction of loading, and (2) maximum instantaneous compressive total normal strain transverse to the sliding direction. Such stress/strain metrics could be useful in global computational models of wear acceleration, as surrogates to incorporate anisotropy of local metal surface roughening.

Noninvasive In Vivo Characterization of Pediatric Human Spine: 3-D Finite Element Study

2011 ◽  
Author(s):  
Elizabeth S. Doughty ◽  
Nesrin Sarigul-Klijn
Keyword(s):  
Finite Element ◽  
Computational Model ◽  
Muscle Activation ◽  
Computational Models ◽  
Three Dimensional ◽  
Pediatric Spine ◽  
Element Analysis ◽  
Spine Stabilization ◽  
Surgical Tool

There are no full three-dimensional computational models of the pediatric spine to study the many diseases and disorders that afflict the immature spine using finite element analysis. To fully characterize the pediatric spine, we created a pediatric specific computational model of C1-L5 using noninvasive in vivo techniques to incorporate the differences between the adult and pediatric spines: un-fused vertebrae, lax ligaments, and higher water content in the intervertebral discs. Muscle follower loads were included in the model to simulate muscle activation for five muscles involved in spine stabilization. This paper is the first pediatric three-dimensional model developed to date. Due to a lack of experimental pediatric spinal studies, this 3-D computational model has the potential to become a surgical tool to ensure that the most appropriate technique is chosen for treating pediatric spinal dysfunctions such as congenital abnormalities, idiopathic scoliosis, and vertebral fractures.

scholarly journals Effects of Different Positions and Angles of Implants in Maxillary Edentulous Jaw on Surrounding Bone Stress under Dynamic Loading: A Three-Dimensional Finite Element Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Xiaqing Liu ◽  
Fang Pang ◽  
Ying Li ◽  
Hui Jia ◽  
Xiaohua Cui ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Dynamic Loading ◽  
Three Dimensional ◽  
Element Analysis ◽  
Posterior Teeth ◽  
Dimensional Finite Element ◽  
Three Dimensional Models ◽  
Three Dimensional Finite Element ◽  
Edentulous Jaws ◽  
Surrounding Bone

Purpose. To evaluate the effects of different placements of mesial implants and different angles of distant implants in maxillary edentulous jaws on the stress on the implant and the surrounding bone tissue under dynamic loading. Materials and Methods. Cone beam computed tomography was used to acquire images of maxillary edentulous jaws. Using Mimics 17.0, Geomagic, and Unigraphics NX8.5 software, three-dimensional models were established: two mesial implants were placed vertically in the anterior region of the maxilla (bilateral central incisor, lateral incisor, and canine), and two distant implants were placed obliquely in the bilateral second premolar area at different inclined angles (15°, 30°, and 45°). The established models were designated I–IX. The models were subjected to dynamic load using Abaqus 6.12, with the working side posterior teeth loading of 150 N and simulation cycle of 0.875 s. Results. During the second to fourth phases of the mastication cycle, the stress was mainly concentrated on the neck of the distal implant. The stress of the distal implants was greater than that of mesial implants. Stress levels peaked in the third stage of the cycle. The stress of the distal cortical bone of distal implant of Model I reached the maximum of 183.437 MPa. The stress of the distal cortical bone and cancellous bone of distal implant of Model VIII represented the minima (62.989 MPa and 17.186 MPa, respectively). Conclusions. Our models showed optimal stress reductions when the mesial implants were located in the canine region and the distal implants tilted 30°.

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