scholarly journals The Effect of General Imperfections on the Buckling of Cylindrical Shells

1969 ◽  
Vol 36 (1) ◽  
pp. 28-38 ◽  
Author(s):  
Johann A´rbocz ◽  
Charles D. Babcock
Keyword(s):  
Axial Load ◽  
Circular Cylindrical Shell ◽  
Three Dimensional ◽  
Initial Imperfection ◽  
Buckling Load ◽  
Data Recording ◽  
Buckling Loads ◽  
Recording Process ◽  
Global Buckling ◽  
Experimental Values

An experimental and theoretical investigation of the effect of general imperfections on the buckling load of a circular cylindrical shell under axial compression was carried out. A noncontact probe has been used to make complete imperfection surveys on electro-formed copper shells before and during the loading process up to the buckling load. The data recording process has been fully automated and the data reduction was done on an IBM 7094. Three-dimensional plots were obtained of the measured initial imperfection surfaces and of the growth of these imperfections under increasing axial load. The modal components of the measured imperfection surfaces were also obtained. The theoretical solution located the limit points of the postbuckled states. A simplified imperfection model was used consisting of one axisymmetric and two asymmetric components. For global buckling the correlation between the theoretical buckling loads and the experimental values was found to be good.

scholarly journals Numerical Derivation of Buckling Knockdown Factors for Isogrid-Stiffened Cylinders with Various Shell Thickness Ratios

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Han-Il Kim ◽  
Chang-Hoon Sim ◽  
Jae-Sang Park ◽  
Keejoo Lee ◽  
Joon-Tae Yoo ◽  
...  
Keyword(s):  
Shell Thickness ◽  
Control Method ◽  
Computation Time ◽  
Initial Imperfection ◽  
Equivalent Model ◽  
Detailed Model ◽  
Buckling Loads ◽  
Global Buckling ◽  
Displacement Control Method ◽  
Factor Function

This study is aimed at providing a numerical derivation of the shell knockdown factors of isogrid-stiffened cylinders under axial compressive loads. The present work uses two different analysis models such as the detailed model with modeling of numerous stiffeners and the equivalent model without modeling of stiffeners for isogrid-stiffened cylinders. The single perturbation load approach is used to represent the geometrically initial imperfection of the cylinder. Postbuckling analyses using the displacement control method are conducted to calculate the global buckling loads of a cylinder. The shell knockdown factor is numerically derived using the obtained global buckling loads without and with the initial imperfection of the isogrid-stiffened cylinder. The equivalent model is more efficient than the detailed model in terms of modeling time and computation time. The present knockdown factor function in terms of the shell thickness ratio (radius to thickness) for the isogrid-stiffened cylinder is significantly higher than NASA’s knockdown factor function; therefore, it is believed that the present knockdown factor function can facilitate in developing lightweight launch vehicle structures using isogrid-stiffened cylinders.

Shear Deformation and Buckling of Columns

1991 ◽  
Vol 44 (11S) ◽  
pp. S160-S165 ◽  
Author(s):  
J. M. Kelly
Keyword(s):  
Shear Deformation ◽  
Axial Load ◽  
Buckling Load ◽  
Elastomeric Bearings ◽  
Buckling Loads ◽  
Sandwich Construction ◽  
Isolation Systems

It is shown that the prediction of buckling loads of columns that are very weak in shear is crucially dependent on the choice of direction for the axial load of the column in the buckled configuration. Examples are given showing the wide differences in buckling load predicted by different choices. The results are applicable to columns of sandwich construction, springs, and multilayer elastomeric bearings for isolation systems.

On Establishing Buckling Knockdowns for Imperfection-Sensitive Shell Structures

2018 ◽  
Vol 85 (9) ◽  
Author(s):  
S. Gerasimidis ◽  
E. Virot ◽  
J. W. Hutchinson ◽  
S. M. Rubinstein
Keyword(s):  
Cylindrical Shells ◽  
Strong Dependence ◽  
Elastic Shell ◽  
External Pressure ◽  
Buckling Load ◽  
Spherical Shells ◽  
Nonlinear Buckling ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Global Buckling

This paper investigates issues that have arisen in recent efforts to revise long-standing knockdown factors for elastic shell buckling, which are widely regarded as being overly conservative for well-constructed shells. In particular, this paper focuses on cylindrical shells under axial compression with emphasis on the role of local geometric dimple imperfections and the use of lateral force probes as surrogate imperfections. Local and global buckling loads are identified and related for the two kinds of imperfections. Buckling loads are computed for four sets of relevant boundary conditions revealing a strong dependence of the global buckling load on overall end-rotation constraint when local buckling precedes global buckling. A reasonably complete picture emerges, which should be useful for informing decisions on establishing knockdown factors. Experiments are performed using a lateral probe to study the stability landscape for a cylindrical shell with overall end rotation constrained in the first set of tests and then unconstrained in the second set of tests. The nonlinear buckling behavior of spherical shells under external pressure is also examined for both types of imperfections. The buckling behavior of spherical shells is different in a number of important respects from that of the cylindrical shells, particularly regarding the interplay between local and global buckling and the post-buckling load-carrying capacity. These behavioral differences have bearing on efforts to revise buckling design rules. The present study raises questions about the perspicacity of using probe force imperfections as surrogates for geometric dimple imperfections.

Flexural-Torsional Buckling of Pultruded Fiber-Reinforced Polymer Angle Beams under Eccentric Loading

2020 ◽  
Vol 982 ◽  
pp. 201-206
Author(s):  
Jaksada Thumrongvut ◽  
Natthawat Pakwan ◽  
Samaporn Krathumklang
Keyword(s):  
Buckling Load ◽  
Fiber Reinforced Polymer ◽  
Width Ratio ◽  
Fiber Reinforced ◽  
Torsional Buckling ◽  
Eccentric Load ◽  
Buckling Loads ◽  
Reinforced Polymer ◽  
Cross Sectional Dimension ◽  
Flexural Torsional Buckling

In this paper, the experimental study on the pultruded fiber-reinforced polymer (pultruded FRP) angle beams subjected to transversely eccentric load are presented. A summary of critical buckling load and buckling behavior for full-scale flexure tests with various span-to-width ratios (L/b) and eccentricities are investigated, and typical failure mode are identified. Three-point flexure tests of 50 pultruded FRP angle beams are performed. The E-glass fibre/polyester resin angle specimens are tested to examine the effect of span-to-width ratio of the beams on the buckling responses and critical buckling loads. The angle specimens have the cross-sectional dimension of 76x6.4 mm with span-to-width ratios, ranging from 20 to 40. Also, four different eccentricities are investigated, ranging from 0 to ±2e. Eccentric loads are applied below the horizontal flange in increments until beam buckling occurred. Based upon the results of this study, it is found that the load and mid-span vertical deflection relationships of the angle beams are linear up to the failure. In contrast, the load and mid-span lateral deflection relationships are geometrically nonlinear. The general mode of failure is the flexural-torsional buckling. The eccentrically loaded specimens are failed at critical buckling loads lower than their concentric counterparts. Also, the quantity of eccentricity increases as buckling load decreases. In addition, it is noticed that span-to-width ratio increases, the buckling load is decreased. The eccentric location proved to have considerable influence over the buckling load of the pultruded FRP angle beams.

Buckling characteristics of cut-out borne composite stiffened hyperbolic paraboloid shell panel

2021 ◽  
pp. 146442072110058
Author(s):  
Sarmila Sahoo
Keyword(s):  
Finite Element ◽  
Orientation Angle ◽  
Buckling Load ◽  
Benchmark Problems ◽  
Hyperbolic Paraboloid ◽  
Element Analysis ◽  
Load Effect ◽  
Global Buckling ◽  
Fiber Orientation Angle ◽  
Shell Panel

The present study investigates buckling characteristics of cut-out borne stiffened hyperbolic paraboloid shell panel made of laminated composites using finite element analysis to evaluate the governing differential equations of global buckling of the structure. The finite element code is validated by solving benchmark problems from literature. Different parametric variations are studied to find the optimum panel buckling load. Laminations, boundary conditions, depth of stiffener and arrangement of stiffeners are found to influence the panel buckling load. Effect of different parameters like cut-out size, shell width to thickness ratio, degree of orthotropy and fiber orientation angle of the composite layers on buckling load are also studied. Parametric and comparative studies are conducted to analyze the buckling strength of composite hyperbolic paraboloid shell panel with cut-out.

scholarly journals CFRP Origami Metamaterial with Tunable Buckling Loads: A Numerical Study

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 917
Author(s):  
Houyao Zhu ◽  
Shouyan Chen ◽  
Teng Shen ◽  
Ruikun Wang ◽  
Jie Liu
Keyword(s):  
Numerical Study ◽  
Buckling Load ◽  
Fe Modelling ◽  
Buckling Loads ◽  
Folding Angle ◽  
Mechanical Responses ◽  
Reinforced Plastic ◽  
Rate Of Increase ◽  
Practical Engineering ◽  
Identical Rate

Origami has played an increasingly central role in designing a broad range of novel structures due to its simple concept and its lightweight and extraordinary mechanical properties. Nonetheless, most of the research focuses on mechanical responses by using homogeneous materials and limited studies involving buckling loads. In this study, we have designed a carbon fiber reinforced plastic (CFRP) origami metamaterial based on the classical Miura sheet and composite material. The finite element (FE) modelling process’s accuracy is first proved by utilizing a CFRP plate that has an analytical solution of the buckling load. Based on the validated FE modelling process, we then thoroughly study the buckling resistance ability of the proposed CFRP origami metamaterial numerically by varying the folding angle, layer order, and material properties, finding that the buckling loads can be tuned to as large as approximately 2.5 times for mode 5 by altering the folding angle from 10° to 130°. With the identical rate of increase, the shear modulus has a more significant influence on the buckling load than Young’s modulus. Outcomes reported reveal that tunable buckling loads can be achieved in two ways, i.e., origami technique and the CFRP material with fruitful design freedoms. This study provides an easy way of merely adjusting and controlling the buckling load of lightweight structures for practical engineering.

Simulation of Three-Dimensional Stress Distribution in Compression Dies

2008 ◽  
Vol 575-578 ◽  
pp. 449-454
Author(s):  
Chu Yun Huang ◽  
Sai Yu Wang ◽  
Tao Yang ◽  
Xu Dong Yan
Keyword(s):  
Stress Distribution ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Distribution Model ◽  
Extrusion Dies ◽  
Maximum Value ◽  
Multiple Unit ◽  
Stress Freezing Method ◽  
Experimental Values ◽  
Aided Design

The stress fields of rectangular and T shape compression dies were simulated by three dimensional photo-elasticity of stress freezing method. The rules of stress distribution of σx, σy, σz on the surface of rectangular and T-shaped dies were discovered, and the rules were also found inside the dies. The results indicate that the stress distribution of rectangular die is similar to that of T shape die. Obvious stress concentration in corner of die hole was observed. σz rises from die hole to periphery until it achieves maximum value then it diminishes gradually, and σz between die hole and fix diameter zone is higher than it is in other position. At the same time, the equations of stress field of extrusion dies were obtained by curved surface fitting experimental values in every observed point with multiple-unit regression analysis method and orthogonal transforms. These works can provide stress distribution model for die computer aided design and make.

Three-Dimensional Seismic Response Analysis of Buried Continuous or Jointed Pipelines

1987 ◽  
Vol 109 (1) ◽  
pp. 80-87 ◽  
Author(s):  
S. Takada ◽  
K. Tanabe
Keyword(s):  
Seismic Behavior ◽  
Ground Motions ◽  
Three Dimensional ◽  
Response Analysis ◽  
Ground Deformations ◽  
Pipe Systems ◽  
Experimental Values ◽  
Earthquake Response Analysis ◽  
Nonlinear Behaviors ◽  
Torsional Properties

This paper presents a three-dimensional quasi-static analysis of continuous or jointed pipelines. Transfer Matrix Method was applied to the analysis providing for nonlinear behaviors of joints and soil frictions. An improved computer program ERAUL-II (Earthquake Response Analysis of Underground Lifelines-II) was developed for numerical computations. First, numerical response analyses were carried out for three-dimensional pipe systems with steel or cast iron pipe materials subject to large ground deformations or seismic ground motions. Analytical results show that torsional properties of pipes are also important factors for seismic behavior, which cannot be known by two-dimensional analyses. Second, experimental test data of three-dimensional steel pipe systems were simulated by using the ERAUL-II program. Simulated results agree well with the experimental values.

scholarly journals Numerical Simulation of Water Absorption and Swelling in Dehulled Barley Grains during Canned Porridge Cooking

Processes ◽  
2018 ◽  
Vol 6 (11) ◽  
pp. 230 ◽  
Author(s):  
Lei Wang ◽  
Mengting Wang ◽  
Mingming Guo ◽  
Xingqian Ye ◽  
Tian Ding ◽  
...  
Keyword(s):  
Moisture Absorption ◽  
Three Dimensional ◽  
Processing Conditions ◽  
Relative Deviation ◽  
Cooking Process ◽  
Proposed Model ◽  
Hygroscopic Swelling ◽  
3D Numerical Model ◽  
Barley Grains ◽  
Experimental Values

Understanding the hydration behavior of cereals during cooking is industrially important in order to optimize processing conditions. In this study, barley porridge was cooked in a sealed tin can at 100, 115, and 121 °C, respectively, and changes in water uptake and hygroscopic swelling in dehulled barley grains were measured during the cooking of canned porridge. In order to describe and better understand the hydration behaviors of barley grains during the cooking process, a three-dimensional (3D) numerical model was developed and validated. The proposed model was found to be adequate for representing the moisture absorption characteristics with a mean relative deviation modulus (P) ranging from 4.325% to 5.058%. The analysis of the 3D simulation of hygroscopic swelling was satisfactory for describing the expansion in the geometry of barley. Given that the model represented the experimental values adequately, it can be applied to the simulation and design of cooking processes of cereals grains, allowing for saving in both time and costs.

Obtaining the thermal resistance of air enclosed at the interface of multilayer fabrics by simulation

2018 ◽  
Vol 89 (15) ◽  
pp. 3178-3188 ◽  
Author(s):  
Hua Shen ◽  
Lexi Tu ◽  
Xiaofei Yan ◽  
Sachiko Sukigara
Keyword(s):  
Finite Element Method ◽  
Surface Roughness ◽  
Thermal Resistance ◽  
Three Dimensional ◽  
Estimating Equation ◽  
Experimental Result ◽  
Dimensional Finite Element ◽  
Experimental Values ◽  
Three Dimensional Finite Element ◽  
Method Model

An air layer enclosed at the interface was largely responsible for the insulation results of multilayer fabrics obtained from experiments. In this study, a three-dimensional finite element method model, in which the air layer enclosed at the interface of multilayer fabrics was ignored, was developed to calculate the fabric thermal resistance, and the result obtained from the fabric model was independent of the air. A Thermolab II Tester KES-F7 was also used to measure the thermal resistance of fabrics, and the experimental results were influenced by the air layer. By comparing the simulation and experimental result, the air layer thermal resistance was determined, and then an estimating equation, which can be used to estimate the fabric and air layer thermal resistance for multilayer fabrics, was proposed. The results suggested that the surface roughness of fabrics was strongly related to the air layer thermal resistance, with a linear relationship between them. Moreover, for multiple layers stacked by different fabrics, the air layer thermal resistance at the interface was mainly decided by the fabric with the rougher surface. An estimating equation was also developed to predict the thermal resistance of multilayer fabrics and good correlation between predicted and experimental values was observed.

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