scholarly journals Buckling and Post-Buckling Behavior of Uniform and Variable-Density Lattice Columns Fabricated Using Additive Manufacturing

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3539 ◽  
Author(s):  
Aamer Nazir ◽  
Ahmad Bin Arshad ◽  
Jeng-Ywan Jeng
Keyword(s):  
Lattice Structure ◽  
Weight Ratio ◽  
High Strength ◽  
Variable Density ◽  
Buckling Load ◽  
Uniform Density ◽  
Lattice Structures ◽  
Critical Buckling Load ◽  
Buckling Behavior ◽  
Post Buckling

Lattice structures are known for their high strength-to-weight ratio, multiple functionalities, lightweight, stiffness, and energy absorption capabilities and potential applications in aerospace, automobile, and biomedical industry. To reveal the buckling (global and local) and post-buckling behavior of different lattice morphologies, both experimental and simulation-based studies were carried out. Additionally, a variable-density lattice structure was designed and analyzed to achieve the optimal value of critical buckling load. Latticed columns were fabricated using polyamide 12 material on multi jet fusion 3D printer. The results exhibited that the buckling in lattice columns depends on the distribution of mass, second moment of inertia I, diameter and position of vertical beams, number of horizontal or inclined beams, and location and angle of the beams that support the vertical beams. The number of horizontal and inclined beams and their thickness has an inverse relation with buckling; however, this trend changes after approaching a critical point. It is revealed that vertical beams are more crucial for buckling case, when compared with horizontal or inclined beams; however, material distribution in inclined or horizontal orientation is also critical because they provide support to vertical beams to behave as a single body to bear the buckling load. The results also revealed that the critical buckling load could be increased by designing variable density cellular columns in which the beams at the outer edges of the column are thicker compared with inner beams. However, post-buckling behavior of variable density structures is brittle and local when compared with uniform density lattice structures.

Critical Buckling Load for Lattice Column Elements with Variable Dimensions

2017 ◽  
Vol 2 (2) ◽  
pp. 84
Author(s):  
Ahmad Alghamdi ◽  
Martin Leary ◽  
Ma Qian ◽  
Wei Xu ◽  
Milan Brandt
Keyword(s):  
Carrying Capacity ◽  
Lattice Structure ◽  
Buckling Load ◽  
Digital Data ◽  
Lattice Structures ◽  
Load Carrying Capacity ◽  
Critical Buckling Load ◽  
Manufacturing Defects ◽  
Independent Variables ◽  
Load Carrying

<p>Lattice structures are used in a variety of high-value engineering applications; for example, in automobile, aerospace and biomedical applications, due to their light weight, high specific strength, stiffness, heat transfer control and energy absorption. Additive Manufacturing (AM) technologies, such as Selective Laser Melting (SLM), offer radical net-shape manufacturing solutions for metallic structures directly from digital data. The prediction of AM lattice structure mechanical properties prior to manufacture is both cost and time-consuming; particularly as existing models do not readily accommodate the effects of manufacturing defects and lattice node geometry on column buckling. The critical buckling load of columns was algebraically and numerically simulated for a full Design of Experiments (DOE) of independent variables, including column length, column radius, node radius and material type. This simulation data quantifies the effect of independent variables on critical buckling load and demonstrates the limitations of algebraically prediction. This research can be extended to allow the simulation of the load carrying capacity of entire lattice structures; and to accommodate the effect of manufacturing variation on the associated load carrying capacity of AM lattice structures.</p>

Determination of Optimal Unit-Cell Size of Homogeneous Conformal Unit-Cell Lattice Structure Using Solid Shape Matching

2016 ◽  
Author(s):  
Mahmoud A. Alzahrani ◽  
Seung-Kyum Choi
Keyword(s):  
Cell Size ◽  
Solid Body ◽  
Strain Energy ◽  
Lattice Structure ◽  
Weight Ratio ◽  
Unit Cell ◽  
Optimal Size ◽  
Lattice Structures ◽  
Unit Cell Size ◽  
Unit Cells

With rapid developments and advances in additive manufacturing technology, lattice structures have gained considerable attention. Lattice structures are capable of providing parts with a high strength to weight ratio. Most work done to reduce computational complexity is concerned with determining the optimal size of each strut within the lattice unit-cells but not with the size of the unit-cell itself. The objective of this paper is to develop a method to determine the optimal unit-cell size for homogenous periodic and conformal lattice structures based on the strain energy of a given structure. The method utilizes solid body finite element analysis (FEA) of a solid counter-part with a similar shape as the desired lattice structure. The displacement vector of the lattice structure is then matched to the solid body FEA displacement results to predict the structure’s strain energy. This process significantly reduces the computational costs of determining the optimal size of the unit cell since it eliminates FEA on the actual lattice structure. Furthermore, the method can provide the measurement of relative performances from different types of unit-cells. The developed examples clearly demonstrate how we can determine the optimal size of the unit-cell based on the strain energy. Moreover, the computational cost efficacy is also clearly demonstrated through comparison with the FEA and the proposed method.

Buckling and Post Buckling Behavior of a Transversely Stiffened Ship Hull Model

1964 ◽  
Vol 8 (04) ◽  
pp. 7-21
Author(s):  
H.G. Schultz
Keyword(s):  
Reasonable Agreement ◽  
Ship Hull ◽  
Buckling Load ◽  
Experimental Results ◽  
Postbuckling Behavior ◽  
Pure Bending ◽  
Box Girder ◽  
Buckling Behavior ◽  
Theoretical Investigations ◽  
Post Buckling

In the paper presented the behavior of a transversely formed box-girder model subjected to pure bending is discussed, where the deck plating of the model is loaded above the buckling load. The experimental results obtained are in reasonable agreement with theoretical investigations and show the influence of fabrication initiated plate deflections on the buckling and postbuckling behavior of the deck plating clearly. A method is suggested for determining the buckling load of plates having large initial deformations.

scholarly journals Benefits of 3D printing technologies for aerospace lattice structures

2021 ◽  
Vol XXIV (1) ◽  
pp. 8-16
Author(s):  
VOICU Andrei - Daniel
Keyword(s):  
3D Printing ◽  
Cell Structure ◽  
Weight Ratio ◽  
High Strength ◽  
Cellular Structures ◽  
Lattice Structures ◽  
Mass Reduction ◽  
Aerospace Sector ◽  
Potential Applications ◽  
Remote Operations

The article makes a brief presentation of the latest 3D printing methods that are used for manufacturing aerospace lattice structures. Most 3D printing technologies are not fully deployed on the industrial scale of aerospace sector, but are rather used for rapid prototyping of components. One of the main potential applications is for them to offer a rapid solution for remote operations, where it is difficult to supply parts. Additive manufactured lattice structures are cellular structures based on biomimicry (inspired from nature lattice structures such as bones, metal crystallography, etc.), that possess many superior properties compared to solid materials and are ideal for fabricating aerospace structures mainly due to the mass reduction they introduce and the high strength-to-weight ratio. Their mechanical properties are defined by the infill percentage, the geometry of the cell structure and the material used in the manufacturing process.

scholarly journals Buckling Behavior of Nanobeams Placed in Electromagnetic Field Using Shifted Chebyshev Polynomials-Based Rayleigh-Ritz Method

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1326 ◽  
Author(s):  
Subrat Kumar Jena ◽  
Snehashish Chakraverty ◽  
Francesco Tornabene
Keyword(s):  
Boundary Condition ◽  
Closed Form ◽  
Chebyshev Polynomials ◽  
Ritz Method ◽  
Closed Form Solution ◽  
Form Solution ◽  
Buckling Load ◽  
Mode Shapes ◽  
Critical Buckling Load ◽  
Buckling Behavior

In the present investigation, the buckling behavior of Euler–Bernoulli nanobeam, which is placed in an electro-magnetic field, is investigated in the framework of Eringen’s nonlocal theory. Critical buckling load for all the classical boundary conditions such as “Pined–Pined (P-P), Clamped–Pined (C-P), Clamped–Clamped (C-C), and Clamped-Free (C-F)” are obtained using shifted Chebyshev polynomials-based Rayleigh-Ritz method. The main advantage of the shifted Chebyshev polynomials is that it does not make the system ill-conditioning with the higher number of terms in the approximation due to the orthogonality of the functions. Validation and convergence studies of the model have been carried out for different cases. Also, a closed-form solution has been obtained for the “Pined–Pined (P-P)” boundary condition using Navier’s technique, and the numerical results obtained for the “Pined–Pined (P-P)” boundary condition are validated with a closed-form solution. Further, the effects of various scaling parameters on the critical buckling load have been explored, and new results are presented as Figures and Tables. Finally, buckling mode shapes are also plotted to show the sensitiveness of the critical buckling load.

Mechanical buckling of nanocomposites: Experimental and numerical investigations

2020 ◽  
pp. 096739112096844
Author(s):  
John Raphael ◽  
Arunkumar G Bhat ◽  
Jackson Siby ◽  
Blestin Dino Geevarghese ◽  
Nivish George ◽  
...  
Keyword(s):  
Flexural Modulus ◽  
Buckling Load ◽  
Experimental Results ◽  
Displacement Curve ◽  
Nonlinear Finite Element Method ◽  
Deflection Curve ◽  
Close Match ◽  
Critical Buckling Load ◽  
Buckling Behavior ◽  
Mechanical Buckling

The proposed research explores Multi-Walled Carbon Nanotube’s (MWCNT’s) effect on the mechanical buckling behavior of glass fiber-enhanced thermosetting composites using UTM and the load vs displacement curve is plotted. Using the inflection point method, the critical buckling load is obtained from the load vs displacement curve for beams with three different volume fractions of MWCNT. The nonlinear finite element method is used to numerically obtain the load vs deflection curve and the numerical results are compared with the experimental results, and a close match is found with the experimental results. It is observed that the nonlinearity associated with the structure can significantly reduce the critical buckling load. The critical buckling load is found to increase and reported a 27.4% increase in buckling load with 0.3 wt.% of MWCNT which could be accounted for the increase in flexural modulus of the material.

Initial Post-buckling Behavior of Thick Rings Under Uniform External Hydrostatic Pressure

1995 ◽  
Vol 62 (2) ◽  
pp. 338-345 ◽  
Author(s):  
Lei Fu ◽  
A. M. Waas
Keyword(s):  
Hydrostatic Pressure ◽  
Shear Deformation ◽  
Buckling Load ◽  
Deformation Analysis ◽  
Two Dimensional ◽  
Composite Ring ◽  
Buckling Behavior ◽  
Buckling Stability ◽  
Post Buckling ◽  
Beam Type

The initial post-buckling behavior of thick rings under external uniform hydrostatic pressure is investigated. In the analysis, no assumptions are placed upon the relative magnitudes of the elongations and rotations, and the ring is assumed to be elastic and extensional. The importance of including certain nonlinear terms in the initial post-buckling stability analysis and the effects of nonzero shearing strains on the buckling load and the initial post-buckling stability are examined. It is shown that the classical Kirchhoff assumptions, when employed for a ring lead to nonvanishing through thickness strains, εzz and εzθ, with the latter being proportional to the through thickness coordinate z. An approximate first order shear deformation analysis and a two-dimensional elasticity analysis (without beam-type kinematical assumptions) of the initial post-buckling behavior of thick rings are presented and the thickness effects on the buckling load and the initial post-buckling behavior are examined. The formulation for the composite ring was reduced to that of an isotropic ring and the results thus obtained were compared with published one-dimensional results in the literature. It is found from both the shear deformation and the two-dimensional analysis that the initial post-buckling behavior of the isotropic ring and the composite rings studied are stable. The influence of thickness on the degree of stability in the immediate post-buckling response is characterized.

A New Shape of Snaked-Lay Pipeline

2011 ◽  
Vol 250-253 ◽  
pp. 2829-2832
Author(s):  
Yu Xiao Liu ◽  
Tao Ge ◽  
Xin Li ◽  
Jing Zhou
Keyword(s):  
Finite Element ◽  
Nonlinear Finite Element ◽  
Buckling Load ◽  
Lateral Buckling ◽  
Critical Buckling Load ◽  
Post Buckling ◽  
The Moment

Snaked-lay pipeline is an effective method for control lateral buckling of pipeline, which is used widely. For design of snaked-lay pipeline the key is how to control lateral buckling of pipeline, namely, the lateral buckling is triggered at the designed location, the moment and strain of post buckling are acceptable. A new shape of snaked-lay pipeline is presented. Based on ANSYS, nonlinear finite element of pipeline is built. Comparisons show that the critical buckling load, moment and strain of post-buckling are all reduced for the new shape of snaked-lay pipeline.

Buckling Behavior of Horizontal Hydraulic Cylinder Articulated at Both Supports

2020 ◽  
Vol 20 (03) ◽  
pp. 2050033
Author(s):  
Ji Zhou ◽  
Duanwei Shi ◽  
Chengyun Di ◽  
Yang Zhang ◽  
Xionghao Cheng
Keyword(s):  
Numerical Calculation ◽  
Large Deflection ◽  
Beam Theory ◽  
Initial Boundary ◽  
Hydraulic Cylinder ◽  
Buckling Load ◽  
Stability Test ◽  
Practical Calculation ◽  
Critical Buckling Load ◽  
Buckling Behavior

The existing critical buckling load calculation methods of horizontal hydraulic cylinder failed to fully reflect the initial boundary conditions and some critical influence factors, resulting in an unjustified critical buckling load. A new method to analyze the buckling behavior of the horizontal hydraulic cylinder articulated at both supports is developed on basis of large deflection theory and Timoshenko beam theory. Friction at supports, self-weight and initial misalignment by clearances are taken into account. Friction moments of supports are built according to Hertz contact theory. Bending stiffness of cylinder-rod junction is figured out in terms of elastic deformation theory. Runge–Kutta and Newton–Raphson method are used in numerical calculation for the critical buckling load. Practical calculation and stability test are carried out to verify the necessity of considering large deflection and shear effect in the proposed method. Experimental work shows the critical buckling load by the proposed method can well match to that by stability test with 0.55% deviation. Moreover, the numerical calculation results demonstrate that the friction moment of the support at piston rod end is crucial for the buckling behavior. The critical buckling load rises increasingly as the friction coefficient [Formula: see text] rises. As the friction coefficients [Formula: see text] increases from 0 to 0.020, the rise rate of critical buckling load increases from 1.782% to 8.055% per 0.001. And the clearance at cylinder-rod junction is a minor factor on the critical buckling load. As the clearances increase by 10 times, the critical buckling load decreases by 3.542%.

Global Buckling Analysis of Stem Pipe During Side-Step in J-Lay Tower

2015 ◽  
Author(s):  
Bob (H. E. J.) van der Heijden ◽  
Richard Liu ◽  
Gabriel Vazquez Perez ◽  
Henk Smienk
Keyword(s):  
Bending Moment ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Free Standing ◽  
Critical Buckling Load ◽  
Environmental Loads ◽  
Analysis Methodology ◽  
Buckling Behavior ◽  
Step Procedure ◽  
Global Buckling

Within Heerema Marine Contractors’ (HMC) global installation analysis scope, the sidestep procedure of structures (e.g. in-line tee structure, 2nd end FLET structure or upper riser assembly structure) is identified that might require global buckling analysis. During a side-step procedure a structure is skidded out of the J-Lay tower while free-standing via the stem pipe on the hang off collar of the last hex-joint. While skidding the tower cannot support the structure vertically, only horizontally via a side step clamp higher up in the tower. Hence the stem pipe could buckle globally under the structure weight. The weight of the structure causes compression in the stem pipe and a center of gravity offset of the structure with respect to the pipe centerline causes a bending moment leading to potential global buckling. A global buckling analysis must be performed to check this load case. The purpose of this paper is to provide validation for the use of Flexcom for performing global buckling analysis for the side-step procedure of structures in the J-Lay tower. In order to prove that Flexcom can indeed model global buckling behavior with sufficient accuracy, the critical buckling load obtained is validated using the FE packages Abaqus and Ansys. This comparison serves as validation, not only for the use of Flexcom, but also for the method used to determine the critical buckling load in Flexcom. The analysis methodology used to assess a pipeline or riser for global buckling behavior is updated using the benefits of Flexcom. The use of Flexcom for global buckling analysis is more efficient, due to the ease and simplicity of modeling, and allows dynamic load cases, due to environmental loads and vessel motions, to be analyzed. Hence the potential benefit of performing global buckling analysis in Flexcom.

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