Stress Analysis of Near Optimal Surface Notches in 3D Plates

2004 ◽  
Vol 127 (6) ◽  
pp. 1173-1183 ◽  
Author(s):  
R. Wescott ◽  
B. Semple ◽  
M. Heller
Keyword(s):  
Three Dimensional ◽  
Peak Stress ◽  
Finite Element Analyses ◽  
3D Finite Element ◽  
Aspect Ratios ◽  
Damage Repair ◽  
Elementary Methods ◽  
Notch Length ◽  
Optimal Surface ◽  
The Given

This paper presents a method of using two-dimensional (2D) optimal notch shapes to create near optimal surface notches with various depth and aspect ratios in uniaxially loaded three-dimensional (3D) plates. Axisymmetric and elongated surface notches are created by rotating 2D optimal notch shapes about two types of fixed axes, a major reason being to enable the surface notches to be manufactured by elementary methods. Stresses in the surface notches are determined using intensive 3D finite element analyses. Axisymmetric notches show small reductions in local peak stress relative to spherical notches with the same bounding dimensions. Local peak stresses in elongated notches are reduced by up to 26% relative to comparable spherical notches. The given method and results are transferable for the initial design, re-shaping, and damage repair of components manufactured from any commonly used metal. In damage removal applications a significant advantage of both notch types over spherical notches is that they allow more material to be extracted for the same notch length and maximum depth.

Enhanced Collapse Resistance of Compressed Steel Pipes

2014 ◽  
Author(s):  
Venkat R. Krishnan ◽  
David A. Baker
Keyword(s):  
Experimental Testing ◽  
Three Dimensional ◽  
External Pressure ◽  
Combined Loading ◽  
Finite Element Analyses ◽  
Forming Process ◽  
3D Finite Element ◽  
Steel Pipes ◽  
Collapse Resistance ◽  
Sensitivity Studies

Pipe collapse is a primary design consideration for deep water locations and offshore areas with sharp seabed curvatures or spans, where bending reduces collapse resistance due to ovalization. Previous numerical and experimental work has shown that collapse resistance of steel pipes can be enhanced significantly by using compression instead of expansion during the final stage of the pipe forming process. ExxonMobil has recently undertaken a rigorous numerical modeling and experimental testing program to investigate the collapse resistance of compressed (JCOC) steel pipes under combined loading of external pressure and bending, and this paper presents the main results from the program. The first part of the paper presents results of sensitivity studies from three dimensional (3D) finite element analyses (FEA) of the pipe forming process, and the second part focuses on the collapse modeling under combined loading as well as a comparison of the numerical results with the experiments. The results indicate that the collapse envelope for steel pipes under combined external pressure and bending can be enhanced by up to 35% by adopting pipe compression rather than expansion as the final step of the forming process.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

Stabilized hp-DGFEM for Incompressible Flow

2003 ◽  
Vol 13 (10) ◽  
pp. 1413-1436 ◽  
Author(s):  
D. Schötzau ◽  
C. Schwab ◽  
A. Toselli
Keyword(s):  
Boundary Layer ◽  
Discontinuous Galerkin ◽  
Incompressible Flow ◽  
Discontinuous Galerkin Methods ◽  
Stokes Problem ◽  
Three Dimensional ◽  
Stability Result ◽  
Approximation Order ◽  
Galerkin Methods ◽  
Aspect Ratios

We consider stabilized mixed hp-discontinuous Galerkin methods for the discretization of the Stokes problem in three-dimensional polyhedral domains. The methods are stabilized with a term penalizing the pressure jumps. For this approach it is shown that ℚk-ℚk and ℚk-ℚk-1 elements satisfy a generalized inf–sup condition on geometric edge and boundary layer meshes that are refined anisotropically and non quasi-uniformly towards faces, edges, and corners. The discrete inf–sup constant is proven to be independent of the aspect ratios of the anisotropic elements and to decrease as k-1/2 with the approximation order. We also show that the generalized inf–sup condition leads to a global stability result in a suitable energy norm.

Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection

2021 ◽  
Author(s):  
Susanne Horn ◽  
Peter J. Schmid ◽  
Jonathan M. Aurnou
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Mean Flow ◽  
Large Scale Circulation ◽  
Convective Systems ◽  
Aspect Ratios ◽  
Mode Decomposition ◽  
Coherent Flow Structure

Abstract The large-scale circulation (LSC) is the most fundamental turbulent coherent flow structure in Rayleigh-B\'enard convection. Further, LSCs provide the foundation upon which superstructures, the largest observable features in convective systems, are formed. In confined cylindrical geometries with diameter-to-height aspect ratios of Γ ≅ 1, LSC dynamics are known to be governed by a quasi-two-dimensional, coupled horizontal sloshing and torsional (ST) oscillatory mode. In contrast, in Γ ≥ √2 cylinders, a three-dimensional jump rope vortex (JRV) motion dominates the LSC dynamics. Here, we use dynamic mode decomposition (DMD) on direct numerical simulation data of liquid metal to show that both types of modes co-exist in Γ = 1 and Γ = 2 cylinders but with opposite dynamical importance. Furthermore, with this analysis, we demonstrate that ST oscillations originate from a tilted elliptical mean flow superposed with a symmetric higher order mode, which is connected to the four rolls in the plane perpendicular to the LSC in Γ = 1 tanks.

An Inverse Inviscid Method for the Design of Quasi-Three-Dimensional Turbomachinery Cascades

1993 ◽  
Vol 115 (1) ◽  
pp. 121-127 ◽  
Author(s):  
E. Bonataki ◽  
P. Chaviaropoulos ◽  
K. D. Papailiou
Keyword(s):  
Differential Equation ◽  
Three Dimensional ◽  
Test Cases ◽  
Elliptic Type ◽  
Flow Angle ◽  
Blade Shape ◽  
Closure Conditions ◽  
Type Boundary ◽  
Absolute Frame ◽  
The Given

The calculation of the blade shape, when the desired velocity distribution is imposed, has been the object of numerous investigations in the past. The object of this paper is to present a new method suitable for the design of turbomachinery stator and rotor blade sections, lying on an arbitrary axisymmetric stream-surface with varying streamtube width. The flow is considered irrotational in the absolute frame of reference and compressible. The given data are the streamtube geometry, the number of blades, the inlet flow conditions and the suction and pressure side velocity distributions as functions of the normalized arc-length. The output of the computation is the blade shape that satisfies the above data. The method solves an elliptic type partial differential equation for the velocity modulus with Dirichlet and periodic type boundary conditions on the (potential function, stream function)-plane (Φ, Ψ). The flow angle field is subsequently calculated solving an ordinary differential equation along the iso-Φ or iso-Ψ lines. The blade coordinates are, finally, computed by numerical integration. A set of closure conditions has been developed and discussed in the paper. The method is validated on several test cases and a discussion is held concerning its application and limitations.

Calculation of Complete Three-Dimensional Flow in a Centrifugal Rotor With Splitter Blades

1988 ◽  
Author(s):  
Liu Dian-Kui ◽  
Ji Le-Jian
Keyword(s):  
Mass Flow ◽  
Three Dimensional ◽  
Present Calculation ◽  
Flow Ratio ◽  
Three Dimensional Flow ◽  
Stream Surface ◽  
Dimensional Flow ◽  
Flow Capacity ◽  
The Given ◽  
Mass Flow Ratio

The flow within a centrifugal rotor has strong characteristics of three-dimensional effect. A procedure called “stream-surface coordinates iteration” for the calculation of complete three dimensional flow in turbo-machinery is first described. Splitter blade techniques have been used in many rotors, especially in centrifugal compressors and pumps with high flow capacity. The difficulty of the calculation of the flow field for this type of rotor lies on that the mass flow ratio between the two sub-channels is unknown for the given total flow capacity. In the second part of this paper, an assumption about how to determine this mass flow ratio and a procedure to calculate the complete three-dimensional flow are presented. Finally, some design criteria about the splitter blades are put forward. Experimental data from two centrifugal pump impellers equipped with different splitter blades are also given to demonstrate the availability of the present calculation method.

Modeling and Optimization of Ultra High Pressure Vessel With Self-Protective Flat Steel Ribbons Wound and Tooth-Locked Quick-Actuating End Closure

2008 ◽  
Author(s):  
Xin Ma ◽  
Zhongpei Ning ◽  
Honggang Chen ◽  
Jinyang Zheng
Keyword(s):  
High Pressure ◽  
Fatigue Life ◽  
Pressure Vessel ◽  
Design Method ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Peak Stress ◽  
High Pressure Vessel ◽  
Ultra High Pressure ◽  
Flat Steel

Ultra-High Pressure Vessel (UHPV) with self-protective Flat Steel Ribbons (FSR) wound and Tooth-Locked Quick-Actuating (TLQA) end closure is a new type of vessel developed in recent years. When the structural parameters of its TLQA and Buttress Thread (BT) end closure are determined using the ordinary engineering design method, Design by Analysis (DBA) shows that the requirement on fatigue life of this unique UHPV could hardly be satisfied. To solve the above problem, an integrated FE modeling method has been proposed in this paper. To investigate the fatigue life of TLQA and BT end closures of a full-scale unique UHPV, a three-dimensional (3-D) Finite Element (FE) solid model and a two-dimensional (2-D) FE axisymmetric model are built in FE software ANSYS, respectively., Nonlinear FE analysis and orthogonal testing are both conducted to obtain the optimum structure strength, in which the peak stress in the TLQA or BT end closure of the unique UHPV is taken as an optimal target. The important parameters, such as root structure of teeth, contact pressure between the pre-stressed collar and the cylinder end, the knuckle radius, the buttress thread profile and the local structure of the cylinder, are optimized. As a result, both the stress distribution at the root of teeth and the axial load carried by each thread are improved. Therefore, the load-carrying capacity of the end closure has been reinforced and the fatigue life of unique UHPV has been extended.

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