An Adaptive Growth Method for Shape Refinement: Methodology and Applications to Pressure Vessels and Piping

1992 ◽  
Vol 114 (1) ◽  
pp. 87-93 ◽  
Author(s):  
H. Azegami ◽  
A. Okitsu ◽  
T. Ogihara ◽  
A. Takami
Keyword(s):  
Dynamic Test ◽  
Pressure Vessels ◽  
Test Problems ◽  
Piping System ◽  
Simple Shape ◽  
Bulk Strain ◽  
Growth Method ◽  
Deformation Step ◽  
Adaptive Growth Method ◽  
Measure Distribution

A simple shape refinement technique for improving strength has been developed. The technique is to deform shapes with growth bulk strain which springs up in proportion with deflection of a strength measure to a basic value in all parts of a body. The scheme for the shape refinement consists of the iteration of the two steps with finite element method: 1) analysis step of a strength measure distribution, and 2) growth deformation step with the growth bulk strain. Numerical experiments on static and dynamic test problems and practical problems of pressure vessel and piping system indicate the effectiveness of this technique for improving strength.

Dynamic Characteristics of Structure With Bolted Joint Considering Some Factors

2004 ◽  
Author(s):  
Shigeru Aoki
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Random Excitation ◽  
Pressure Vessels ◽  
Bolted Joints ◽  
Piping System ◽  
Bolted Joint ◽  
Earthquake Excitation ◽  
Applied Torque

Bolted joints are widely used for pressure vessels and piping system. Many studies on strength and stiffness of bolted joint are carried out. However, few studies on the dynamic characteristics of structure with bolted joint are carried out. The dynamic characteristics are important for design of structure subjected to earthquake excitations. In this paper, the effect of bolted joints on dynamic characteristics of structure is examined. First, the damping ratio and the natural frequency of specimens with some types of bolted joints are measured. Those are obtained for some factors, amplitude of excitation, applied torque. Obtained results are compared with those for the specimen without bolted joint. It is found that the damping ratio increases and the natural frequency becomes lower. Next, modeling of the bolted joint is presented. The bolted joint is modeled using additional mass, stiffness and damping elements. Finally, using model of bolted joint, response of the structure with bolted joint subjected to earthquake excitation is examined. Earthquake excitation is modeled as stationary random excitation. Mean square values of the response are obtained. Standard deviation of the acceleration response of the structure with bolted joint are lower than those without bolted joint.

Pseudo-Dynamic Heterogeneous Testing With Dynamic Substructuring of a Piping System Under Earthquake Loading

2013 ◽  
Author(s):  
Md. Shahin Reza ◽  
Oreste S. Bursi ◽  
Giuseppe Abbiati ◽  
Alessio Bonelli
Keyword(s):  
Dynamic Test ◽  
Piping System ◽  
Earthquake Loading ◽  
Delay Compensation ◽  
Hybrid Testing ◽  
Heterogeneous Model ◽  
Dynamic Substructuring ◽  
External Forces ◽  
Bolted Flange ◽  
The University

In recent years, both pseudo-dynamic and real time heterogeneous testing with dynamic substructuring — hybrid testing — have gained significant popularity for their applicability to testing several types of nonlinear structures/systems. In a hybrid test, a heterogeneous model of the emulated system is created by combining a Physical Substructure (PS) with a Numerical Substructure (NS) that describes the remainder of the system. Nevertheless, an efficient implementation of this technique requires overcoming certain problems, e. g., proper dynamic substructuring, reduction of external forces and actuator delay compensation. This paper presents a pseudo-dynamic test campaign undertaken by the University of Trento, Italy, on a typical full-scale industrial piping system subjected to earthquake loading in order to investigate its seismic performance. Some challenges faced during the implementation are shown and strategies adopted to overcome these problems are illustrated. Experimental activities will be described and performances of different components of the piping system, i.e., elbows, tee-joints, bolted flange joints and straight pipes under earthquake loading with the presence of an internal pressure of 3.2 MPa will be presented and commented.

Brittle Fracture Assessments on Offshore Piping Systems

2013 ◽  
Author(s):  
Kannan Subramanian ◽  
Jorge Penso ◽  
Graham McVinnie ◽  
Greg Garic
Keyword(s):  
Low Temperature ◽  
Brittle Fracture ◽  
Stress Analysis ◽  
Pressure Vessels ◽  
Piping System ◽  
Piping Systems ◽  
Assessment Approach ◽  
Section Viii ◽  
System Information ◽  
Safe Operating

Offshore piping systems may be subject to low temperatures due to operation related scenarios and are cause for brittle fracture concern. The analyses included in this work consider probable events leading to low temperature conditions such as auto-refrigeration. In such circumstances, brittle fracture assessments of piping are typically carried out using API 579-1/ASME FFS-1, latest referred as API 579, procedures. The assessment of piping systems are in many cases very involved, requiring extended piping system information followed by stress analysis and MAT calculations depending on the material type, thickness of the piping analyzed, and stress levels. In addition, the component-by-component assessment approach recommended in API 579 leads to tedious calculations. In this paper, approaches used for static and dynamic low temperature scenarios are presented. Static cases involve constant pressures and temperatures. Dynamic cases involve varying pressures and temperatures as the low temperature events unfold (e.g., blowdown of a valve or a vessel). Dynamic cases warrant the requirement of a safe operating envelope or MAT curve similar to those developed for pressure vessels. Case studies involving the influence of the extent of the system analyzed and the restraint conditions on the results are also presented. In addition, the importance of separately assessing the rated components such as flanges and valves away from the stress analysis is discussed. Based on the assessments carried out, a discussion on the toughness rules defined in ASME Section VIII Divisions 1, 2, and the original piping code of construction is provided.

Elastic-Plastic Analysis of Thick-Walled Toroidal Pressure Vessels

2008 ◽  
Author(s):  
R. Adibi-Asl
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Toroidal Shell ◽  
Piping System ◽  
Straight Pipe ◽  
Element Analysis ◽  
Process Industries ◽  
Piping Systems

Piping systems in process industries and nuclear power plants include straight pipe runs and various fittings such as elbows, miter bends etc. Elbows and bends in piping systems provide additional flexibility to the piping system along with performing the primary function of changing the direction of fluid flow. Distinctive geometry of these toroidal shell components result in a structural behavior different from straight pipe. Hence, it would be useful to predict the behavior of these components with acceptable accuracy for design purposes. Analytical expressions are derived for stresses set up during loading and unloading in a toroidal shell subjected to internal pressure. Residual stresses in the component are also evaluated. The proposed solutions are then compared with three-dimensional finite element analysis at different locations including intrados, extrados and flanks.

Comparison of Fully Parameterized and Gradient Deficient Elements in the Absolute Nodal Coordinate Formulation

2017 ◽  
Author(s):  
Johannes Gerstmayr ◽  
Peter Gruber ◽  
Alexander Humer
Keyword(s):  
Finite Elements ◽  
Absolute Nodal Coordinate Formulation ◽  
Dynamic Test ◽  
Test Problems ◽  
Rotational Parameter ◽  
Absolute Nodal Coordinate ◽  
Beam Elements ◽  
Spatial Beams ◽  
Numerical Instabilities ◽  
The Absolute

The aim of the present paper is to evaluate six particular beam finite elements based on the absolute nodal coordinate formulation (ANCF). Specifically, accuracy, computational efficiency and numerical stability are compared for those beam finite elements. The finite elements under consideration are planar as well as spatial beams, which are formulated both for the Bernoulli-Euler case as well as for shear and cross-section deformation. While all of the investigated elements have been exposed to specific numerical tests already before, a comparative test has not been performed in the past. The numerical examples cover large deformation static and dynamic problems, which represent typical applications of such beam elements. Finally, the dynamic test problems show that the thin spatial beam formulation, which includes a rotational parameter, leads to well-known numerical instabilities.

Study of Dynamic Stresses in Pipe Networks and Pressure Vessels Using Fluid-Solid-Interaction Models

2007 ◽  
Author(s):  
Philip Diwakar ◽  
Lorraine Lin
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Traditional Approach ◽  
Fluid Model ◽  
Pressure Vessels ◽  
Piping System ◽  
Atmospheric Conditions ◽  
Flow Induced Vibration ◽  
Element Analysis ◽  
Fluid Solid Interaction

A lack of understanding of the fluid-structure interactions has resulted in a number of infamous structural failures in the past. For example, the collapses of the Tay Bridge in Scotland in 1879, the Tacoma Bridge in 1948 and three tall cooling towers in Ferrybridge/England in 1965 have been intrinsically related to fluid forces acting on the structure. Flutter, flow-induced vibration, divergence and related phenomena may be studied using the Fluid-Solid-Interaction (FSI) approach. This paper gives three examples of the FSI approach and shows the innovative application of state-of-the-art computational methods to improve realism and accuracy in engineering analyses. Case 1: Study of Hydrodynamic Sloshing Loads: The sloshing of liquid in large vessels under seismic loads is a timely topic. The movement of the free surface of the liquid is simulated using a two-phase volume of fluid model at various liquid heights. The transient forces generated by the fluid on the vessel wall and internals are superimposed as loads on a dynamic non-linear calculation and the fatigue and stresses are computed in an explicit finite element analysis. This approach calculates the local sloshing effects on internals as opposed to the traditional approach of using spring-mass elements. Case 2: Bending of Large Pipes due to Temperature Differentials: Pipe temperature differentials can be caused by either extremely cold liquids or hot liquids flowing at the bottom of a piping system while the top is exposed to atmospheric conditions. Differential expansion can cause pipe deformation resulting in pipe lift-off at its supports and failure at the weld locations and T-joints. Heat transfer from complex multi-phase flows was simulated using CFD. The predicted pipe wall temperatures were then input to an FEA grid and analyzed for heat transfer and thermal stresses. These stresses were compared to ASME standard allowable limits. Based on this analytical approach, a design guide for various diameters of flare header pipes, supports and tees has been established. Details of this paper were previously published in [Ref 1] and are not described in this paper. Case 3: Establishing velocity limits and line sizing criteria in pipes: The original guidelines in Fluid Flow Manuals were developed over the last fifty years based on project experience and economic and best practices technology of the time. The criteria have proven out as good, but overly conservative with regards to line size. Compressor discharge guidelines are based on the erosion velocity limits. Based on a dynamic analysis approach — using unsteady flow rates from compressors — stresses due to flow-induced vibration, noise and fatigue, hydraulic transients such as waterhammer effects for long lines (greater than 1000 feet), flashing and control valve cavitations may be studied. FSI was used to determine if the velocity limit guidelines hold in the current designs and use a parametric approach to mitigate the bottlenecking by supplying a simple fix to the problem. Furthermore the approach was used to define the correct velocity limit and establish optimal layout for the piping network.

Sign in / Sign up

Export Citation Format

Share Document