A Nonlinear Analytical Model for Flexible Pipe Crushing Analysis

2012 ◽  
Author(s):  
Celso P. Pesce ◽  
Guilherme R. Franzini ◽  
Marcos A. Rabelo ◽  
Roberto Ramos ◽  
Rodolfo T. Gonçalves ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Analytical Model ◽  
Analytical Modeling ◽  
Present Model ◽  
Analytical Models ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Plastic Analysis ◽  
Nonlinear Analytical Model ◽  
Combined Action

This paper discusses a nonlinear analytical model for flexible pipe crushing analysis, improving analytical models previously published in OMAE2003, 2010 and 2011. Following that path, and still based on the concept of equivalent pipes and rings, the present model discusses a strategy to cope with an elastic-to-plastic analysis. Such a model considers the combined action of squeezing and concentrated loads applied as representing those due to the caterpillar shoes. Experimental results and finite element analysis are used to assess the pertinence of analytical modeling hypotheses.

Effect of Ply Stacking Sequence on Structural Response of Symmetric Composite Laminates

2014 ◽  
Author(s):  
Mosfequr Rahman ◽  
Saheem Absar ◽  
F. N. U. Aktaruzzaman ◽  
Abdur Rahman ◽  
N. M. Awlad Hossain
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Analytical Model ◽  
Composite Laminates ◽  
Structural Response ◽  
Laminated Composite ◽  
Analytical Models ◽  
Orthotropic Materials ◽  
Stacking Sequence ◽  
Element Analysis

In this work, the effect of ply stacking sequence on the structural response of multi-ply unidirectional fiber-reinforced composite laminates was evaluated using finite element analysis. The objective of this study was to develop a computational model to analyze the stress response of individual plies in a composite laminate for a given stacking sequence. A laminated composite plate structure under tensile loading was modeled in ANSYS. Stress profiles of the individual plies were obtained for each lamina. An Epoxy matrix with both unidirectional Graphite and Kevlar fibers was considered for the model. Three dimensional sectioned shell elements (SHELL181) were used for meshing the model. Several sets of stacking sequences were implemented, symmetrical to the mid-plane of the laminate. Symmetric stacking configurations of 6 layers stacked in ply angles of [0/45/-45]s, [0/60/-60]s, [0/45/90]s, and an 8-layered arrangement of [0/45/60/90]s were modeled for the analysis. The layer thickness was maintained at 0.1 mm. The results were compared against an analytical model based on the generalized Hooke’s law for orthotropic materials and classical laminate theory. A numerical formulation of the analytical model was implemented in MATLAB to evaluate the constitutive equations for each lamina. The stress distributions obtained using finite element analysis have shown good agreement with the analytical models in some of the cases.

Design of a cutting head for a crosscutting machine

2016 ◽  
Vol 231 (1) ◽  
pp. 5-17 ◽  
Author(s):  
D Croccolo ◽  
M De Agostinis ◽  
S Fini
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Analysis ◽  
Dynamic Behavior ◽  
Analytical Model ◽  
Analytical Models ◽  
Rectangular Section ◽  
Element Analysis ◽  
Cutting Head ◽  
Numerical Finite Element

The present paper deals with the structural analysis and the re-design of a cutting head for an automatic crosscutting machine. The machine is already marketed, and can process rectangular section wooden slats. The principal goal of this work is to develop a new mechanism capable of enhancing the productivity of the machine by around 80%. The work has been carried out by means of both numerical finite element analysis tools and analytical models. In fact, a secondary aim of the research is to define an analytical model which can capture the dynamic behavior of the device: this tool will be helpful to the design engineer in order to save costs associated with the development of future head designs.

Updating of Non-Conservative Systems Using Inverse Methods

1997 ◽  
Author(s):  
Ladislav Starek ◽  
Milos Musil ◽  
Daniel J. Inman
Keyword(s):  
Analytical Model ◽  
Degrees Of Freedom ◽  
Ad Hoc ◽  
Natural Frequencies ◽  
Eigenvalue Problems ◽  
Model Updating ◽  
Analytical Models ◽  
Mode Shapes ◽  
Element Analysis ◽  
Modal Data

Abstract Several incompatibilities exist between analytical models and experimentally obtained data for many systems. In particular finite element analysis (FEA) modeling often produces analytical modal data that does not agree with measured modal data from experimental modal analysis (EMA). These two methods account for the majority of activity in vibration modeling used in industry. The existence of these discrepancies has spanned the discipline of model updating as summarized in the review articles by Inman (1990), Imregun (1991), and Friswell (1995). In this situation the analytical model is characterized by a large number of degrees of freedom (and hence modes), ad hoc damping mechanisms and real eigenvectors (mode shapes). The FEM model produces a mass, damping and stiffness matrix which is numerically solved for modal data consisting of natural frequencies, mode shapes and damping ratios. Common practice is to compare this analytically generated modal data with natural frequencies, mode shapes and damping ratios obtained from EMA. The EMA data is characterized by a small number of modes, incomplete and complex mode shapes and non proportional damping. It is very common in practice for this experimentally obtained modal data to be in minor disagreement with the analytically derived modal data. The point of view taken is that the analytical model is in error and must be refined or corrected based on experimented data. The approach proposed here is to use the results of inverse eigenvalue problems to develop methods for model updating for damped systems. The inverse problem has been addressed by Lancaster and Maroulas (1987), Starek and Inman (1992,1993,1994,1997) and is summarized for undamped systems in the text by Gladwell (1986). There are many sophisticated model updating methods available. The purpose of this paper is to introduce using inverse eigenvalues calculated as a possible approach to solving the model updating problem. The approach is new and as such many of the practical and important issues of noise, incomplete data, etc. are not yet resolved. Hence, the method introduced here is only useful for low order lumped parameter models of the type used for machines rather than structures. In particular, it will be assumed that the entries and geometry of the lumped components is also known.

Characterization and Modeling of Elastomeric Joints in Miniature Compliant Mechanisms

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Dana E. Vogtmann ◽  
Satyandra K. Gupta ◽  
Sarah Bergbreiter
Keyword(s):  
Analytical Model ◽  
Compliant Mechanisms ◽  
Analytical Models ◽  
Accurate Analysis ◽  
Element Analysis ◽  
Fea Model ◽  
Torsional Spring ◽  
Tension Tests ◽  
In Series ◽  
Efficient Exploration

Accurate analysis models are critical for effectively utilizing elastomeric joints in miniature compliant mechanisms. This paper presents work toward the characterization and modeling of miniature elastomeric hinges. Characterization was carried out in the form of several experimental bending tests and tension tests on representative hinges in five different configurations. The modeling portion is achieved using a planar pseudo rigid body (PRB) analytical model for these hinges. A simplified planar 3-spring PRB analytical model was developed, consisting of a torsional spring, an axial spring, and another torsional spring in series. These analytical models enable the efficient exploration of large design spaces. The analytical model has been verified to within an accuracy of 3% error in pure bending, and 7% in pure tension, when compared to finite element analysis (FEA) models. Using this analytical model, a complete mechanism—a robotic leg consisting of four rigid links and four compliant hinges—has been analyzed and compared to a corresponding FEA model and a fabricated mechanism.

An Experimental and Numerical Investigation of the Effect of Axial Thermal Gradients in Flexible Pipes

2017 ◽  
Author(s):  
Dag Fergestad ◽  
Frank Klæbo ◽  
Jan Muren ◽  
Pål Hylland ◽  
Tom Are Grøv ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cross Section ◽  
Measurement Techniques ◽  
Full Scale ◽  
Model Complexity ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Flexible Pipes ◽  
Full Scale Testing

This paper discusses the structural challenges associated with high axial temperature gradients and the corresponding internal cross section forces. A representative flexible pipe section designed for high operational temperature has been subject to full scale testing with temperature profiles obtained by external heating and cooling. The test is providing detailed insight in onset and magnitude of relative layer movements and layer forces. As part of the full-scale testing, novel methods for temperature gradient testing of unbonded flexible pipes have been developed, along with layer force- and deflection-measurement techniques. The full-scale test set-up has been subject to numerous temperature cycles of various magnitudes, gradients, absolute temperatures, as well as tension cycling to investigate possible couplings to dynamics. Extensive use of finite element analysis has efficiently supported test planning, instrumentation and execution, as well as enabling increased understanding of the structural interaction within the unbonded flexible pipe cross section. When exploiting the problem by finite element analysis, key inputs will be correct material models for the polymeric layers, and as-built dimensions/thicknesses. Finding the balance between reasonable simplification and model complexity is also a challenge, where access to high quality full-scale tests and dissected pipes coming back from operation provides good support for these decisions. Considering the extensive full scale testing, supported by advanced finite element analysis, it is evident that increased attention will be needed to document reliable operation in the most demanding high temperature flexible pipe applications.

Finite Element Analysis of Flexible Pipes Under Compression

2014 ◽  
Author(s):  
Eduardo Ribeiro Malta ◽  
Clóvis de Arruda Martins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Strength ◽  
Element Model ◽  
Large Displacements ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Flexible Pipes ◽  
Compressive Loads ◽  
Surface Vessel

Axial compressive loads can appear in several situations during the service life of a flexible pipe, due to pressure variations during installation or due to surface vessel heave. The tensile armor withstands well tension loads, but under compression, instability may occur. A Finite Element model is constructed using Abaqus in order to study a flexible pipe compound by external sheath, two layers of tensile armor, a high strength tape and a rigid nucleus. This model is fully tridimensional and takes into account all kinds of nonlinearities involved in this phenomenon, including contacts, gaps, friction, plasticity and large displacements. It also has no symmetry or periodical limitations, thus permitting each individual wire of the tensile armor do displace in any direction. Case studies were performed and their results discussed.

The Application of ABAQUS in Cast-Steel Joints Elastic-Plastic Analysis

2013 ◽  
Vol 351-352 ◽  
pp. 854-859 ◽  
Author(s):  
Fan Wang ◽  
Zhi Feng Luo ◽  
Sheng Hao Mo
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cast Steel ◽  
Element Analysis ◽  
Elastic Plastic ◽  
The Finite Element Analysis ◽  
Plastic Analysis ◽  
Reticulated Shell Structure ◽  
Steel Joints ◽  
Cast Steel Joint

The article introduces the application of the large universally used finite element analysis software ABAQUS in elastic-plastic analysis of the cast-steel joints in building structure. Using the cast-steel joint of a large reticulated shell structure in Shenzhen as an example, the article explains how to import the joint model into ABAQUS and start the finite element analysis, and finally get the elastic-plastic analysis results, thus provide the reference for engineering design, analysis and optimize design of cast-steel joints.

A 2-legged XY parallel flexure motion stage with minimised parasitic rotation

2014 ◽  
Vol 228 (17) ◽  
pp. 3156-3169 ◽  
Author(s):  
Guangbo Hao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Design Approach ◽  
Analytical Models ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Motion Range ◽  
Cross Axis

XY compliant parallel manipulators (aka XY parallel flexure motion stages) have been used as diverse applications such as atomic force microscope scanners due to their proved advantages such as eliminated backlash, reduced friction, reduced number of parts and monolithic configuration. This paper presents an innovative stiffness centre based approach to design a decoupled 2-legged XY compliant parallel manipulator in order to better minimise the inherent parasitic rotation and have a more compact configuration. This innovative design approach makes all of the stiffness centres, associated with the passive prismatic (P) modules, overlap at a point that all of the applied input forces can go through. A monolithic compact and decoupled XY compliant parallel manipulator with minimised parasitic rotation is then proposed using the proposed design approach based on a 2-PP kinematically decoupled translational parallel manipulator. Its load–displacement and motion range equations are derived, and geometrical parameters are determined for a specified motion range. Finite element analysis comparisons are also implemented to verify the analytical models with analysis of the performance characteristics including primary stiffness, cross-axis coupling, parasitic rotation, input and output motion difference and actuator nonisolation effect. Compared with the existing XY compliant parallel manipulators obtained using 4-legged mirror-symmetric constraint arrangement, the proposed XY compliant parallel manipulators based on stiffness centre approach mainly benefits from fewer legs resulting in reduced size, simpler modelling as well as smaller lost motion. Compared with existing 2-legged designs with the conventional arrangement, the present design has smaller parasitic rotation, which has been proved from the finite element analysis results.

Allowable Limit and Finite Element Analysis of Pipes With Local Wall Thinning Subjected to Bending Moment

2004 ◽  
Author(s):  
Seok Hwan Ahn ◽  
Ki Woo Nam ◽  
Koji Takahashi ◽  
Kotoji Ando
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Failure Modes ◽  
Bending Test ◽  
Element Analysis ◽  
Allowable Limit ◽  
Pipe Surface ◽  
Wall Thinning ◽  
Plastic Analysis ◽  
Local Wall Thinning

Fracture behaviors of pipes with local wall thinning are very important for the integrity of power plant piping system. In this study, monotonic bending tests without internal pressure are conducted on 1.91-inch diameter Schedule 80 STS370 full-scale carbon steel pipe specimens. Fracture strengths of locally wall thinned pipes were calculated by elasto-plastic analysis using finite element method. The elasto-plastic analysis was performed by FE code ANSYS. We simulated various types of local wall thinning that can be occurred at pipe surface due to coolant flow. Locally wall thinned shapes were machined to be different in size along the circumferential or axial direction of straight pipes. We investigated fracture strengths and failure modes of locally wall thinned pipes by four-point bending test. From the test results, failure modes could be divided three types, ovalization, local buckling and crack initiation. And, the allowable limit of pipes with local wall thinning was investigated. In addition, we compared the simulated results by finite element analysis with experimental data. The failure mode, fracture strength and fracture behavior obtained from the tests showed well agreement with analytic results.

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