scholarly journals Dynamics and Stability of Stepped Gun-Barrels with Moving Bullets

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Mohammad Tawfik
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Stability Region ◽  
Element Model ◽  
Simple Eigenvalue ◽  
Bernoulli Beam ◽  
Stability Boundaries ◽  
The Stability ◽  
Euler Bernoulli Beam ◽  
Lowest Eigenvalue

The stability of an Euler-Bernoulli beam under the effect of a moving projectile will be reintroduced using simple eigenvalue analysis of a finite element model. The eigenvalues of the beam change with the mass, speed, and position of the projectile, thus, the eigenvalues are evaluated for the system with different speeds and masses at different positions until the lowest eigenvalue reaches zero indicating the instability occurrence. Then a map for the stability region may be obtained for different boundary conditions. Then the dynamics of the beam will be investigated using the Newmark algorithm at different values of speed and mass ratios. Finally, the effect of using stepped barrels on the stability and the dynamics is going to be investigated. It is concluded that the technique used to predict the stability boundaries is simple, accurate, and reliable, the mass of the barrel on the dynamics of the problem cannot be ignored, and that using the stepped barrels, with small increase in the diameter, enhances the stability and the dynamics of the barrel.

A Multi-Scale Approach to the Analysis of Ultra Deepwater Unbonded Flexible Risers

2009 ◽  
Author(s):  
Ali Bahtui ◽  
Giulio Alfano ◽  
Hamid Bahai
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Large Scale ◽  
Element Model ◽  
Constitutive Law ◽  
Beam Model ◽  
Bernoulli Beam ◽  
Multi Scale ◽  
Non Linear ◽  
Euler Bernoulli Beam

The results of a detailed, non-linear finite-element analysis of a small-scale (i.e. 1.7m long) six-layer unbonded flexible riser, accounting for interlayer contact and frictional slip, are used to calibrate a novel, simplified constitutive model for a 3D, non-linear Euler-Bernoulli beam model suitable for large scale analyses (hundreds of meters in length where water depth is more than 1000m). The detailed finite element model contains all the layers, each modeled separately with contact interfaces between them. The finite element model includes the main features of the riser geometry with very little simplifying assumptions made. The detailed finite element model is formulated in the framework of a novel, multi-scale approach potentially suitable for ultra deepwater applications. A simple, three-dimensional Euler-Bernoulli beam element, suitable for large scale analyses, is developed based on a non-linear constitutive law for the beam cross-section relating bending curvatures to the conjugate stress resultants.

scholarly journals Modeling inflatable fabric with undevelopable surfaces by motion folding method

2019 ◽  
Vol 14 ◽  
pp. 155892501988640
Author(s):  
Xiao-Shun Zhao ◽  
He Jia ◽  
Zhihong Sun ◽  
Li Yu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Numerical Study ◽  
Technical Problem ◽  
Three Dimensional ◽  
Element Model ◽  
Model Errors ◽  
Folding Model ◽  
Study Results ◽  
The Stability

At present, most space inflatable structures are composed of flexible inflatable fabrics with complex undevelopable surfaces. It is difficult to establish a multi-dimensional folding model for this type of structure. To solve this key technical problem, the motion folding method is proposed in this study. First, a finite element model with an original three-dimensional surface was flattened with a fluid structure interaction algorithm. Second, the flattened surface was folded based on the prescribed motion of the node groups, and the final folding model was obtained. The fold modeling process of this methodology was consistent with the actual folding processes. Because the mapping relationship between the original finite element model and the final folding model was unchanged, the initial stress was used to modify the model errors during folding process of motion folding method. The folding model of an inflatable aerodynamic decelerator, which could not be established using existing folding methods, was established by using motion folding method. The folding model of the inflatable aerodynamic decelerator showed that the motion folding method could achieve multi-dimensional folding and a high spatial compression rate. The stability and regularity of the inflatable aerodynamic decelerator numerical inflation process and the consistency of the inflated and design shapes indicated the reliability, applicability, and feasibility of the motion folding method. The study results could provide a reference for modeling complex inflatable fabrics and promote the numerical study of inflatable fabrics.

Analysis of the Stability of Thawing Slopes by Random Finite Element Method

2019 ◽  
Vol 2673 (10) ◽  
pp. 465-476 ◽  
Author(s):  
Shaoyang Dong ◽  
Xiong (Bill) Yu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Element Model ◽  
Frozen Soil ◽  
Silty Clay ◽  
Local Factor ◽  
The Stability ◽  
Random Finite Element

A significant number of landslides occur in cold regions because of freezing and thawing cycles. The instability of thawing slopes can cause serious damage to transportation infrastructure and property, and even loss of human life. This type of landslide is difficult to analyze by the traditional limit-equilibrium methods, however, because of the complicated multi-physics processes involved. This paper describes a holistic microstructure-based random finite element model (RFEM) to simulate the stability of a thawing slope. The RFEM model is developed to simulate the bulk behaviors of frozen and unfrozen soils based on the behaviors of individual phases. The phase coded image of a frozen silty clay is first custom built and then converted into a finite element model. The mechanical behaviors of individual phases of the frozen soil are calibrated by uniaxial compressive test. The triaxial test is then simulated by RFEM to obtain the shear strength parameters of frozen and unfrozen soils. Coupled thermal-mechanical REFM models are developed to simulate the effects of temperature on the displacement field and stress field in the slope. From the results, the local factor of safety field can be determined. The development of local factor of safety and potential failure surface associated with the thawing process over a typical year are simulated by this new model. The variations in the stability of thawing slopes predicted by this model are consistent with field observations as well as the global-wise slope stability analysis.

scholarly journals Vibration Control of an Unbalanced Single-Side Cantilevered Rotor System with a Novel Integral Squeeze Film Bearing Damper

2019 ◽  
Vol 9 (20) ◽  
pp. 4371 ◽  
Author(s):  
Yipeng Zhang ◽  
Lidong He ◽  
Jianjiang Yang ◽  
Fangteng Wan ◽  
Jinji Gao
Keyword(s):  
Finite Element ◽  
Energy Distribution ◽  
Finite Element Model ◽  
Vibration Control ◽  
Element Model ◽  
Rotor System ◽  
Squeeze Film ◽  
Single Side ◽  
The Stability ◽  
Stability Energy

In this paper, vibration control of an unbalanced single-side cantilevered rotor system using a novel integral squeeze film bearing damper in terms of stability, energy distribution, and vibration control is analyzed. A finite element model of such a system with an integral squeeze film bearing damper (ISFBD) is developed. The stability, energy distribution, and vibration control of the unbalanced single-side cantilevered rotor system are calculated and analyzed based on the finite element model. The stiffness of the integral squeeze film bearing damper is designed using theoretical calculation and finite element model (FEM) simulation. The influence of installation position and quantity of integral squeeze film bearing dampers on the vibration control of the unbalanced cantilevered rotor system is discussed. An experimental platform is developed to validate the vibration control effect. The results show that the installation position and quantity of the integral squeeze film bearing dampers have different effects on the stability, energy distribution, and vibration control of the unbalanced cantilevered rotor system. When ISFBDs are installed at both bearing housings, the vibration control is best, and the vibration components of the time and frequency domains have good vibration control effects in four working conditions.

Study on the Stability of the Bearing Capacity of Wedge Connected Scaffold

2015 ◽  
Vol 17 ◽  
pp. 24-29
Author(s):  
Shi Hui Zhou ◽  
Guo Dong ◽  
Zheng Ji Li
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Finite Element Model ◽  
Bearing Capacity ◽  
Theoretical Basis ◽  
Element Model ◽  
Theoretical Support ◽  
The Stability ◽  
Technical Regulations ◽  
Step Distance

Experimental data obtained from full-scale experiments determines the stiffness of wedge connected of scaffold.A finite element model is developed using semi-rigid scaffold node mode.And a reasonable combination of longitudinal span,transverse span and step distance is obtained.The results accords with the relevant standard of vertical load.It provides a theoretical support for the application of wedge connected scaffold.Additionally,the study explores the safety height of the wedge connected scaffold with or without bridging.It provides a theoretical basis for technical regulations.

scholarly journals Analysis on the design of steel wire wound extrusion containers for hot extrusion process

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401771241
Author(s):  
Changyong Liu ◽  
Renji Zhang ◽  
Yongnian Yan ◽  
Changshi Lao
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Steel Wire ◽  
Hot Extrusion ◽  
Element Model ◽  
Extrusion Process ◽  
Stability Factor ◽  
Improved Design ◽  
The Stability ◽  
The Finite Element Model

Extrusion container is the most important tooling for steel hot extrusion process. Conventional design using large castings and forgings is very difficult to execute due to high cost and risk. Steel wire wound containers have many advantages over conventional designs. However, conventional wire wound containers are developed for use at room temperature which are not applicable to steel hot extrusion process. In this article, the impacts of preheating on the design of steel wire wound containers are discussed in detail. A finite element model was established to examine the preheating temperature distribution, and a 1:10 scaled extrusion container was manufactured to verify the effectiveness of the finite element model. Based on the finite element model–computed temperature field, thermal stress analysis was performed. The thermal impacts on the stress of extrusion container and steel wire were obtained. Results showed that insufficient stability of internal cylinder and greatly enhanced steel wire stress may lead to the failure of extrusion container. To solve the problems, an improved design was put forward by increasing the stability factor of internal cylinder, reducing the prestress factor and lowering the allowable stress of steel wire. Results showed that the improved design can meet the requirements and counteract the thermal impacts.

Finite Element Analysis of Flexible Pipes Under Compression: Influence of the Sample Length

2015 ◽  
Author(s):  
Eduardo Ribeiro Malta ◽  
Clóvis de Arruda Martins
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
High Strength ◽  
Element Model ◽  
Sample Length ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Flexible Pipes ◽  
The Stability

In order to study the compressive behavior of flexible pipes, a nonlinear tridimensional finite element model was developed. This model recreates a five layer flexible pipe with two tensile armor layers, an external polymeric sheath, an orthotropic high strength tape and a rigid inner nucleus. Using this model, several studies are being conducted to verify the influence of key parameters on the wire instability phenomenon. The pipe sample length can be considered one of these parameters and its variation causes significant change at the stability response of the tensile layers. This article includes a detailed description of the finite element model itself and a case study where the length of the pipe is changed. The procedure of this analysis is here described, along with the results.

scholarly journals PROBABILISTIC MODELING OF ABOVEGROUND STORAGE TANKS UNDER SURGE AND WAVE LOADS

2018 ◽  
pp. 4
Author(s):  
Carl Bernier ◽  
Jamie Padgett
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Regression Model ◽  
Probabilistic Models ◽  
Element Model ◽  
Wave Loads ◽  
Storm Events ◽  
Hydrodynamic Loads ◽  
The Stability ◽  
Hydrodynamic Effects

This study presents the development of probabilistic models to assess the structural performance of a typical aboveground storage tank (AST) subjected to storm surge and wave loads. First, a finite element model is developed and validated against experimental results to determine hydrodynamic loads on the AST. This finite element model is then employed to derive a regression model of the hydrodynamic loads across ranges of surge and wave parameters using an Artificial Neural Network. This regression model is used as a surrogate of the finite element model to facilitate the investigation of the structural behavior of the case study AST. Finally, the buckling behavior of the AST and the stability of the tank to dislocation (uplift, overturning, or siding) are assessed for various AST modeling parameters and load conditions in order to develop fragility models. Two distinct fragility models are derived, one for dislocation and one for buckling. Key insights on the influence of surge and wave loads are obtained from these models. Results indicate that wave loads and hydrodynamic effects are significant, and neglecting them could underestimate the probability of dislocation or buckling of the AST by up to 30%. Overall, this paper proposes a rigorous yet efficient methodology for the fragility modeling of ASTs during storm events and opens the path for future investigations of the performance of ASTs with a range of design details and exposure conditions.

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