The Use of Mixed Element FEA for Predicting Tubular Frame Behaviour

2002 ◽  
Author(s):  
Rodney Pinna ◽  
Beverley F. Ronalds
Keyword(s):  
Numerical Models ◽  
Pushover Analysis ◽  
Joint Stiffness ◽  
Beam Model ◽  
Element Analysis ◽  
Detailed Model ◽  
Robust Solution ◽  
Framed Structures ◽  
Detailed Modelling ◽  
Compression Member

Pushover analysis of offshore framed structures is usually performed on simplified structural models, using finite element analysis. To assess the typical assumptions made concerning joint and member behaviour, various numerical models of increasing complexity are considered in this paper. These range from simple beam models, to models including a detailed replica of the critical joint connected to a beam model, to a complete shell model of the critical compression member and end connections. Phenomenological models of member behaviour, in this case a Marshall Strut representation, are also examined. Numerical results are compared with experimental data from two studies [1, 2]. It is found that detailed modelling of the joint stiffness is sufficient to accurately model the peak frame response, while a detailed model of the complete compression member, which includes cross section distortion, is needed to match the residual strength of the frame. Marshall strut elements are found to provide a robust solution, provided that the variables which describe the model can be defined with sufficient accuracy. Detailed modelling of the frame is also found to be able to provide the required input data for such special purpose elements.

Parametric Equations Using Generic Representation of Joint Stiffness

2006 ◽  
Vol 129 (2) ◽  
pp. 131-137 ◽  
Author(s):  
A. Nazari ◽  
W. J. T Daniel ◽  
Z. Guan ◽  
H. Gurgenci
Keyword(s):  
Hot Spot ◽  
Joint Stiffness ◽  
Geometrical Parameters ◽  
Exact Nature ◽  
Beam Model ◽  
Tubular Structures ◽  
Element Analysis ◽  
Stress Concentration Factors ◽  
Generic Set ◽  
Generic Representation

For most design and recertification work on tubular structures, it is not practical to determine the joint hot spot stresses experimentally or using detailed finite element analysis. Therefore, parametric equations were developed in the past for various joint geometries to relate stress concentration factors around the joints to basic joint geometrical parameters. Such parametric equations have limited applications to reinforced joints because the nature of reinforcement varies and may be difficult to represent by a generic set of geometric parameters. In this paper, a new method is introduced to include local joint stiffness in the parametric equations represented by a generic characteristic of the joint determined by modal analysis. The parametric equations produced in this paper can be applied to any reinforced T-joint regardless of the nature of reinforcement. This is especially useful in those cases where the exact nature of reinforcement is not known, for example, hidden in the interior or deteriorated through age or fabrication error. The dimensionless joint stiffness parameter can be calculated by a simple modal test and a beam model without needing to know the nature and details of the reinforcement.

scholarly journals Finite element analysis of dovetail joint made with the use of CNC technology

2010 ◽  
Vol 58 (5) ◽  
pp. 321-328 ◽  
Author(s):  
Václav Sebera ◽  
Milan Šimek
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Numerical Models ◽  
Experimental Testing ◽  
Joint Stiffness ◽  
Bending Moment ◽  
Parametric Models ◽  
Cnc Machine ◽  
Element Analysis ◽  
Bending Load

The objective of the paper is the parametrization and the finite element analysis of mechanical pro­per­ties of a through dovetail joint made with the use of a specific procedure by a 3-axis CNC machine. This corner joint was used for the simulation of the bending load of the joint in the angle plane – by compression, i.e. by pressing the joint together. The deformation fields, the stress distribution, the stiffness and the bending moment of the joints were evaluated. The finite element system ANSYS was used to create two parametric numerical models of the joint. The first one represents an ideal­ly stiff joint – both joint parts have been glued together. The second model includes the contact between the joined parts. This numerical model was used to monitor the response of the joint stiffness to the change of the static friction coefficient. The results of both models were compared both with each other and with similar analyses conducted within the research into ready-to-assemble furniture joints. The results can be employed in the designing of more complex furniture products with higher demands concerning stiffness characteristics, such as furniture for sitting. However, this assumption depends on the correction of the created parametric models by experimental testing.

scholarly journals Diffusion Model of Preemptive-Resume Priority Systems and Its Application to Performance Evaluation of SDN Switches

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5042
Author(s):  
Tomasz Nycz ◽  
Tadeusz Czachórski ◽  
Monika Nycz
Keyword(s):  
Diffusion Approximation ◽  
Numerical Models ◽  
Software Defined Networks ◽  
Detailed Model ◽  
Preemptive Resume ◽  
Central Controller ◽  
Priority Systems ◽  
Primary Element ◽  
Preemptive Resume Priority ◽  
General Distributions

The increasing use of Software-Defined Networks brings the need for their performance analysis and detailed analytical and numerical models of them. The primary element of such research is a model of a SDN switch. This model should take into account non-Poisson traffic and general distributions of service times. Because of frequent changes in SDN flows, it should also analyze transient states of the queues. The method of diffusion approximation can meet these requirements. We present here a diffusion approximation of priority queues and apply it to build a more detailed model of SDN switch where packets returned by the central controller have higher priority than other packets.

Analysis of Heat Transfer through PVC Window Profile Reinforced with Ti6Al4V Alloy

2016 ◽  
Vol 687 ◽  
pp. 236-242 ◽  
Author(s):  
Piotr Lacki ◽  
Judyta Różycka ◽  
Marcin Rogoziński
Keyword(s):  
Heat Transfer ◽  
Titanium Alloy ◽  
Thermal Insulation ◽  
Numerical Models ◽  
Characteristic Temperature ◽  
Permanent Deformation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Ti6al4v Titanium Alloy ◽  
Characteristic Points

This requires the use of additional reinforcement in order to prevent excessive or permanent deformation of PVC windows. In the paper particular attention was devoted to space located in a corrosive environment exposed to chemical agents. For this purpose, proposed to change the previously used steel profiles reinforcements made of Ti6Al4V titanium alloy corrosion-resistant in the air, at sea and many types of industrial atmosphere. Analysis of the thermal insulation properties of PVC windows with additional reinforcement of profile Ti6Al4V titanium alloy was performed. PVC window set in a layer of thermal insulation was analyzed. Research was conducted using Finite Element Analysis. Numerical models and thermal calculations were made in the program ADINA, assuming appropriate material parameters. The constant internal temperature of 20 ̊ and an outer-20 ̊ was assumed. The course of temperature distribution in baffle in time 24 hours and graphs of characteristic points was obtained. The time of in which followed the steady flow of heat, as well as the course of isotherm of characteristic temperature in the baffle was determined. On the basis of numerical analysis obtained vector distribution of heat flux q [W/m2] and was determined heat transfer coefficients U [W/m2K] for the whole window with titanium reinforcement . All results were compared with the model of PVC windows reinforced with steel profile.

scholarly journals An Improved Analytical Solution for Process-Induced Residual Stresses and Deformations in Flat Composite Laminates Considering Thermo-Viscoelastic Effects

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2506 ◽  
Author(s):  
Chao Liu ◽  
Yaoyao Shi
Keyword(s):  
Differential Equation ◽  
Finite Element ◽  
Analytical Solution ◽  
Residual Stresses ◽  
Composite Laminates ◽  
Composite Structures ◽  
Numerical Models ◽  
Element Analysis ◽  
Current Time ◽  
Viscoelastic Effects

Dimensional control can be a major concern in the processing of composite structures. Compared to numerical models based on finite element methods, the analytical method can provide a faster prediction of process-induced residual stresses and deformations with a certain level of accuracy. It can explain the underlying mechanisms. In this paper, an improved analytical solution is proposed to consider thermo-viscoelastic effects on residual stresses and deformations of flat composite laminates during curing. First, an incremental differential equation is derived to describe the viscoelastic behavior of composite materials during curing. Afterward, the analytical solution is developed to solve the differential equation by assuming the solution at the current time, which is a linear combination of the corresponding Laplace equation solutions of all time. Moreover, the analytical solution is extended to investigate cure behavior of multilayer composite laminates during manufacturing. Good agreement between the analytical solution results and the experimental and finite element analysis (FEA) results validates the accuracy and effectiveness of the proposed method. Furthermore, the mechanism generating residual stresses and deformations for unsymmetrical composite laminates is investigated based on the proposed analytical solution.

scholarly journals Nonlinear Axial Stiffness Characteristics of Axisymmetric Bolted Joints

1990 ◽  
Vol 112 (3) ◽  
pp. 442-449 ◽  
Author(s):  
I. R. Grosse ◽  
L. D. Mitchell
Keyword(s):  
Finite Element ◽  
Linear Theory ◽  
Design Theory ◽  
Joint Stiffness ◽  
Bolted Joints ◽  
Axial Stiffness ◽  
Outer Diameter ◽  
Bolted Joint ◽  
Element Analysis ◽  
Stiffness Characteristics

A critical assessment of the current design theory for bolted joints which is based on a linear, one-dimensional stiffness analysis is presented. A detailed nonlinear finite element analysis of a bolted joint conforming to ANSI standards was performed. The finite element results revealed that the joint stiffness is highly dependent on the magnitude of the applied load. The joint stiffness changes continuously from extremely high for small applied loads to the bolt stiffness during large applied loads, contrary to the constant joint stiffness of the linear theory. The linear theory is shown to be inadequate in characterizing the joint stiffness. The significance of the results in terms of the failure of bolted joints is discussed. A number of sensitivity studies were carried out to assess the effect of various parameters on the axial joint stiffness. The results revealed that bending and rotation of the joint members, interfacial friction, and the bolt/nut threading significantly influence the axial stiffness characteristics of the bolted joint. The two-dimensional, axisymmetric finite element model includes bilinear gap elements to model the interfaces. Special orthotropic elements were used to model the bolt/nut thread interaction. A free-body-diagram approach was taken by applying loads to the outer diameter of the joint model which correspond to internal, uniformly distributed line-shear and line-moment loads in the joint. A number of convergence studies were performed to validate the solution.

scholarly journals Evaluation of Anterior Cruciate Ligament Surgical Reconstruction Through Finite Element Analysis

2021 ◽  
Author(s):  
Konstantinos Risvas ◽  
Dimitar Stanev ◽  
Lefteris Benos ◽  
Konstantinos Filip ◽  
Dimitrios Tsaopoulos ◽  
...  
Keyword(s):  
Finite Element ◽  
Anterior Cruciate Ligament ◽  
Reference Model ◽  
Numerical Models ◽  
Cruciate Ligament ◽  
Surgical Techniques ◽  
Surgical Reconstruction ◽  
Modeling Framework ◽  
Element Analysis ◽  
Anterior Cruciate

Abstract Anterior Cruciate Ligament (ACL) tear is one of the most common knee injuries. The ACL reconstruction surgery aims to restore healthy knee function by replacing the injured ligament with a graft. Proper selection of the optimal surgery parameters is a complex task. To this end, we developed an automated modeling framework that accepts subject-specific geometries and produces finite element knee models incorporating different surgical techniques. Initially, we developed a reference model of the intact knee, validated with data provided by the OpenKnee project. This helped us evaluate the effectiveness of estimating ligament stiffness directly from MRI. Next, we performed a plethora of “what-if” simulations, comparing responses with the reference model. We found that a) increasing graft pretension and radius reduces relative knee displacement, b) the correlation of graft radius and tension should not be neglected, c) graft fixation angle of 20 degrees can reduce knee laxity, and d) single-versus double-bundle techniques demonstrate comparable performance in restraining knee translation. In most cases, these findings confirm reported values from comparative clinical studies. The numerical models are made publicly available, allowing for experimental reuse and lowering the barriers for meta-studies. The modeling approach proposed here can complement orthopedic surgeons in their decision-making.

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