Theoretical Stress Analysis of Intersecting Cylindrical Shells Subjected to External Forces on Nozzle

2005 ◽  
Vol 128 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Ming-De Xue ◽  
Qing-Hai Du ◽  
Dong-Feng Li ◽  
Keh-Chih Hwang
Keyword(s):  
Cylindrical Shell ◽  
Stress Analysis ◽  
Branch Pipe ◽  
Three Dimensional ◽  
Present Solution ◽  
Mechanical Models ◽  
Applicable Range ◽  
External Forces ◽  
3D Finite Element Method ◽  
Theoretical Stress

The stress analysis based on thin shell theory is presented for a cylindrical shell with a normally intersecting nozzle subjected to three kinds of branch pipe forces, which are tension and two shear forces. The basic mechanical models for the three load cases are presented in order to obtain the solutions independent of the length of the main shell and branch pipe. The applicable range of the present solution is expanded up to d∕D⩽0.8 and λ=d∕DT⩽12 by means of the accurate cylindrical shell equations and continuity conditions and the improved numerical method. The theoretical results are verified by test and three-dimensional (3D) finite element method (FEM) results. The maximum stress for tension force case are in good agreement with WRC Bulletin No. 297 when λ is small. The comparison between the present results and WRC Bulletin No. 107 shows that the latter needs improvement.

A Stress Analysis Method for Cylindrical Shells With Nozzles Subjected to Internal Pressure, External Forces and Moments

2006 ◽  
Author(s):  
Ming-De Xue ◽  
Qing-Hai Du ◽  
Dong-Feng Li ◽  
Keh-Chih Hwang
Keyword(s):  
Internal Pressure ◽  
Stress Analysis ◽  
Thin Shell ◽  
Cylindrical Shells ◽  
Branch Pipe ◽  
Three Dimensional ◽  
Theoretical Solution ◽  
Analysis Method ◽  
External Forces ◽  
Three Dimensional Finite Element

An identical stress analysis method based on the thin shell theory is carried out for cylindrical shells with normally intersecting nozzles subjected to internal pressure and six kinds of external branch pipe loads involving axial tension, two kinds of transverse shear forces, longitudinal and circumferential bending and torsion moments. The thin shell theoretical solution is obtained based on the Morley equation instead of the Donnell shallow shell equation. The accurate continuity conditions at the intersecting curve, which is a complicated space curve, are adopted. The presented results are verified by three-dimensional finite element method (FEM). The theoretical solution can be applied to d/D ≤ 0.8, λ = d/DT ≤ 12 and d/D ≤ t/T ≤ 2 successfully. The solutions are in good agreement with WRC Bulletin 297 when diameter ratio is small. In the paper some typical design curves calculated by the theoretical solutions are presented and their applicable ranges are greatly expanded in comparison with current design methods.

scholarly journals Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins

Geology ◽  
2021 ◽  
Author(s):  
Nicholas Schliffke ◽  
Jeroen van Hunen ◽  
Frédéric Gueydan ◽  
Valentina Magni ◽  
Mark B. Allen
Keyword(s):  
Continental Margin ◽  
Three Dimensional ◽  
Oceanic Lithosphere ◽  
Spreading Center ◽  
Continental Margins ◽  
Mechanical Models ◽  
External Forces ◽  
Back Arc ◽  
Orogenic Belts ◽  
Stress Buildup

Continental collisions commonly involve highly curved passive plate margins, leading to diachronous continental subduction during trench rollback. Such systems may feature back-arc extension and ophiolite obduction postdating initial collision. Modern examples include the Alboran and Banda arcs. Ancient systems include the Newfoundland and Norwegian Caledonides. While external forces or preexisting weaknesses are often invoked, we suggest that ophiolite obduction can equally be caused by internal stress buildup during collision. Here, we modeled collision with an irregular subducting continental margin in three-dimensional (3-D) thermo-mechanical models and used the generated stress field evolution to understand resulting geologic processes. Results show how tensional stresses are localized in the overriding plate during the diachronous onset of collision. These stresses thin the overriding plate and may open a back-arc spreading center. Collision along the entire trench follows rapidly, with inversion of this spreading center, ophiolite obduction, and compression in the overriding plate. The models show how subduction of an irregular continental margin can form a highly curved orogenic belt. With this mechanism, obduction of back-arc oceanic lithosphere naturally evolves from a given initial margin geometry during continental collision.

Theoretical Stress Analysis in Wrist Joint – Neutral Position and Functional Position

2000 ◽  
Vol 25 (3) ◽  
pp. 292-295 ◽  
Author(s):  
E. GENDA ◽  
E. HORII
Keyword(s):  
Rigid Body ◽  
Stress Analysis ◽  
Wrist Joint ◽  
Three Dimensional ◽  
Force Distribution ◽  
Neutral Position ◽  
Spring Model ◽  
Triangular Fibrocartilage ◽  
Theoretical Stress ◽  
Functional Position

A three-dimensional rigid body spring model (3D-RBSM) was used to analyse force distribution through the wrist joint. In the neutral position, 48% of the force was transmitted through the radioscaphoid fossa, 40% through the radiolunate fossa, and 12% through the triangular fibrocartilage complex. In the functional position, the wrist joint was slightly extended, resulting in significantly increased force through the lunate (53%). The lunate appears to bear more load than has been reported previously.

scholarly journals Origin and Application of the Twinned Calcite Strain Gauge

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 296
Author(s):  
Richard H. Groshong
Keyword(s):  
Stress Analysis ◽  
Strain Gauge ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Constant Strain Rate ◽  
Axis Orientation ◽  
Order Of Magnitude ◽  
Rate Experiment ◽  
Strain Axis ◽  
Expected Values

This paper is a personal account of the origin and development of the twinned-calcite strain gauge, its experimental verification, and its relationship to stress analysis. The method allows the calculation of the three-dimensional deviatoric strain tensor based on five or more twin sets. A minimum of about 25 twin sets should provide a reasonably accurate result for the magnitude and orientation of the strain tensor. The opposite-signed strain axis orientation is the most accurately located. Where one strain axis is appreciably different from the other two, that axis is generally within about 10° of the correct value. Experiments confirm a magnitude accuracy of 1% strain over the range of 1–12% axial shortening and that samples with more than 40% negative expected values imply multiple or rotational deformations. If two deformations are at a high angle to one another, the strain calculated from the positive and negative expected values separately provides a good estimate of both deformations. Most stress analysis techniques do not provide useful magnitudes, although most provide a good estimate of the principal strain axis directions. Stress analysis based on the number of twin sets per grain provides a better than order-of-magnitude approximation to the differential stress magnitude in a constant strain rate experiment.

scholarly journals A critical look at the prediction of the temperature field around a laser-induced melt pool on metallic substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi Shu ◽  
Daniel Galles ◽  
Ottman A. Tertuliano ◽  
Brandon A. McWilliams ◽  
Nancy Yang ◽  
...  
Keyword(s):  
Laser Beam ◽  
Constant Velocity ◽  
Three Dimensional ◽  
Laser Beams ◽  
Poor Control ◽  
Metallic Substrates ◽  
Melt Pool ◽  
Mechanical Models ◽  
Transport Effects ◽  
Thermal Histories

AbstractThe study of microstructure evolution in additive manufacturing of metals would be aided by knowing the thermal history. Since temperature measurements beneath the surface are difficult, estimates are obtained from computational thermo-mechanical models calibrated against traces left in the sample revealed after etching, such as the trace of the melt pool boundary. Here we examine the question of how reliable thermal histories computed from a model that reproduces the melt pool trace are. To this end, we perform experiments in which one of two different laser beams moves with constant velocity and power over a substrate of 17-4PH SS or Ti-6Al-4V, with low enough power to avoid generating a keyhole. We find that thermal histories appear to be reliably computed provided that (a) the power density distribution of the laser beam over the substrate is well characterized, and (b) convective heat transport effects are accounted for. Poor control of the laser beam leads to potentially multiple three-dimensional melt pool shapes compatible with the melt pool trace, and therefore to multiple potential thermal histories. Ignoring convective effects leads to results that are inconsistent with experiments, even for the mild melt pools here.

scholarly journals Biomechanical Effects of Torquing on Upper Central Incisor with Thermoplastic Aligner: A Comparative Three-Dimensional Finite Element Study with and Without Auxillaries

2021 ◽  
pp. 030157422097434
Author(s):  
V Sandhya ◽  
AV Arun ◽  
Vinay P Reddy ◽  
S Mahendra ◽  
BS Chandrashekar ◽  
...  
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Three Dimensional ◽  
Central Incisor ◽  
Dimensional Finite Element ◽  
Attachment Model ◽  
Three Dimensional Finite Element ◽  
3D Finite Element Method ◽  
Root Movement ◽  
Maxillary Dentition

Background and Objectives: This study was conducted to determine the effective method to torque the incisor with thermoplastic aligner using a three-dimensional (3D) finite element method. Materials and Methods: Three finite element models of maxilla and maxillary dentition were developed. In the first model, thermoplastic aligner without any auxiliaries was used. In the second and third models, thermoplastic aligner with horizontal ellipsoid composite attachment and power ridge were used, respectively. The software used for the study was ANSYS 14.5 FE. A force of 100 g was applied to torque the upper right central incisor. The resultant force transfer, stress distribution, and tooth displacement were evaluated. Results: The overall tooth displacement and stress distribution appeared high in the model with power ridge, whereas the root movement was more in the horizontal ellipsoid composite attachment model. The model without any auxillaries produced least root movement and stress distribution. Conclusion: Horizontal ellipsoid composite attachment achieved better torque of central incisor than the model with power ridge and model without any auxillaries.

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