scholarly journals An Experimental and Numerical Study of Ballistic Impacts on a Turbine Casing Material at Varying Temperatures

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
B. Erice ◽  
F. Gálvez ◽  
D. A. Cendón ◽  
V. Sánchez-Gálvez ◽  
T. Børvik
Keyword(s):  
Finite Element ◽  
Thick Plate ◽  
Numerical Study ◽  
Shear Bands ◽  
Mesh Size ◽  
Complex Loading ◽  
Steel Plates ◽  
Explicit Finite Element ◽  
Ballistic Impacts ◽  
Turbine Casing

An experimental and numerical study of ballistic impacts on steel plates at various temperatures (700 °C, 400 °C and room temperature) has been carried out. The motivation for this work is the blade-off event that may occur inside a jet engine turbine. However, as a first attempt to understand this complex loading process, a somewhat simpler approach is carried out in the present work. The material used in this study is the FV535 martensitic stainless steel, which is one of the most commonly used materials for turbine casings. Based on material test data, a Modified Johnson-Cook (MJC) model was calibrated for numerical simulations using the LS-DYNA explicit finite element code. To check the mesh size sensitivity, 2D axisymmetric finite element models with three different mesh sizes and configurations were used for the various temperatures. Two fixed meshes with 64 and 128 elements over the 2 mm thick plate and one mesh with 32 elements over the thickness with adaptive remeshing were used in the simulations. Both the formation of adiabatic shear bands in the perforation process and the modeling of the thermal softening effects at high temperatures have been found crucial in order to achieve good results.

Micro-Damage Constitutive Modeling and Numerical Simulation of Perforation of Targets by Projectiles

2007 ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
George Z. Voyiadjis ◽  
Anthony N. Palazotto
Keyword(s):  
Finite Element ◽  
Shear Bands ◽  
Numerical Algorithms ◽  
Mesh Size ◽  
Steel Plates ◽  
Mapping Algorithms ◽  
Physical Description ◽  
Rate Dependent ◽  
Return Mapping ◽  
Effective Use

The effective use of existing Finite Element Codes in the direct simulation of hypervelocity impacts by projectiles is limited by the dependence of the size of localized failure regions on the mesh size and alignment. This gives rise to a non-physical description of the penetration and perforation processes. A micromechanical constitutive model that couples the anisotropic thermo-viscodamage mechanism with the thermo-hypoelasto-viscoplastic deformation will be presented as a remedy to this situation. Explicit and implicit microstructural length scale measures, which preserve the well-posed nature of the differential equations, are introduced through the use of the viscosity and gradient localization limiters. Simple and robust numerical algorithms for the integration of the constitutive equations will be also presented. The proposed unified integration algorithms are extensions of the classical rate-independent return mapping algorithms to the rate-dependent problems. A simple and direct computational algorithm is also used for implementing the gradient-dependent equations. This algorithm can be implemented in the existing finite element codes without numerous modifications as compared to the current numerical approaches for integrating gradient-dependent models. Model capabilities are preliminarily illustrated for the dynamic localization of inelastic flow in adiabatic shear bands and the perforation of Weldox 460E steel plates with various thicknesses by a deformable blunt projectile at various high impact speeds.

scholarly journals Experimental and Numerical Study on the Protective Behavior of Weldox 900 E Steel Plates Impacted by Blunt-Nosed Projectiles

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 141
Author(s):  
Yahui Shi ◽  
Ang Hu ◽  
Taisheng Du ◽  
Xinke Xiao ◽  
Bin Jia
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Fracture Criterion ◽  
Numerical Study ◽  
Mesh Size ◽  
High Strength ◽  
Element Model ◽  
Steel Plates ◽  
Protective Behavior ◽  
The Finite Element Model

To demonstrate the importance of incorporating Lode angle into fracture criterion in predicting the penetration resistance of high-strength steel plates, ballistic tests of blunt-nosed projectiles with a diameter of 5.95 mm impacted 4 mm thick Weldox 900 E steel plates were conducted. Impacting velocity range was 136.63~381.42 m/s. The fracture behavior and the ballistic limit velocities (BLVs) were obtained by fitting the initial-residual velocities of the projectiles. Subsequently, axisymmetric finite element (FE) models parallel to the tests were built by using Abaqus/Explicit software, and the Lode-independent Johnson–Cook (JC) and the Lode-dependent ASCE fracture criterion were incorporated into the finite element model for numerical simulation. Meanwhile, to verify the sensitivity of the mesh size in the numerical simulation, different mesh sizes were used in the shear plug area of the target. It can be found that Weldox 900 E steel has obvious mesh size sensitivity by comparing the experimental results and numerical simulation, and the JC fracture criterion and the ASCE fracture criterion predicted similar BLV for the same mesh size.

Finite Element Analysis of Plugging Failure in Steel Plates Struck by Blunt Projectiles

2009 ◽  
Vol 76 (5) ◽  
Author(s):  
A. Kane ◽  
T. Børvik ◽  
O. S. Hopperstad ◽  
M. Langseth
Keyword(s):  
Finite Element ◽  
Shear Bands ◽  
Mesh Size ◽  
Steel Plates ◽  
Temperature Fields ◽  
Target Strength ◽  
Ballistic Limit ◽  
Element Analysis ◽  
Mesh Sensitivity ◽  
The Impact

In this paper, the influence of mesh sensitivity on the fracture predictions during penetration and perforation of hardened blunt-nose cylindrical steel projectiles in plates of Weldox 460E, Weldox 700E, and Weldox 900E steel has been studied. The main objective is to try to describe the experimentally obtained trend of a decrease in ballistic limit velocity with increased target strength when the plates are impacted by blunt projectiles. This behavior is due to the occurrence of highly localized shear bands as the target strength increases. The impact tests are analyzed using the explicit solver of a nonlinear finite element code. A thermoelastic-thermoviscoplastic constitutive model with coupled or uncoupled ductile damage was used in the simulations. It was found that the residual velocity continuously increases when the element size is decreased from 125 μm to 15 μm in the shear zone, and that this increase is significantly stronger for impact velocities close to the ballistic limit. The ballistic limit decreases by up to 25% when the size of the element is decreased from 125 μm to 30 μm; the decrease being somewhat greater for the two steels with the highest strength. Even with the finest mesh, the experimental trend of a decreasing ballistic limit with increasing target strength was not predicted in the simulations, neither with coupled nor uncoupled damage. Nonlocal simulations based on smoothing of the damage and temperature fields, which are the two variables causing the softening, were carried out for the Weldox steels and a mesh size of 30 μm. These simulations indicate a reduction in the mesh sensitivity for both the coupled and uncoupled damage approaches when nonlocal averaging is employed.

An Experimental and Numerical Study to Analysis and Design of Sheet Hydroforming Process for an Automobile Fender Shell

2006 ◽  
Author(s):  
Mohammad Habibi Parsa ◽  
Payam Darbandi
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Fluid Pressure ◽  
Finite Element Program ◽  
New Approach ◽  
Explicit Finite Element ◽  
Sheet Hydroforming ◽  
Analysis And Design ◽  
Hydroforming Process ◽  
Element Program

A new approach for manufacturing of shell fender is proposed and has been examined numerically and experimentally. The new suggested method is based on sheet hydroforming process, which has a lot of advantages over conventional deep drawing process. After defining the shape of initial blank using an inverse finite element program, numerical evaluation of the proposed sheet hydroforming process for production of shell fender has been carried out using an explicit finite element code considering fluid pressure, boundary conditions and tools. Then experimental evaluation has been carried out using down sized specimen and the results have been compared with results of previous simulations. It has been shown that there are similar trends between finite element and experimental results.

scholarly journals An Efficient and General Finite Element Model for Double-Sided Incremental Forming

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Newell Moser ◽  
David Pritchet ◽  
Huaqing Ren ◽  
Kornel F. Ehmann ◽  
Jian Cao
Keyword(s):  
Finite Element ◽  
Incremental Forming ◽  
Mesh Size ◽  
Element Model ◽  
Explicit Finite Element ◽  
Fully Integrated ◽  
Shell Elements ◽  
Mass Scaling ◽  
Element Simulation ◽  
Element Type

Double-sided incremental forming (DSIF) is a subcategory of general incremental sheet forming (ISF), and uses tools above and below a sheet of metal to squeeze and bend the material into freeform geometries. Due to the relatively slow nature of the DSIF process and the necessity to capture through-thickness mechanics, typical finite element simulations require weeks or even months to finish. In this study, an explicit finite element simulation framework was developed in LS-DYNA using fully integrated shell elements in an effort to lower the typical simulation time while still capturing the mechanics of DSIF. The tool speed, mesh size, element type, and amount of mass scaling were each varied in order to achieve a fast simulation with minimal sacrifice regarding accuracy. Using 8 CPUs, the finalized DSIF model simulated a funnel toolpath in just one day. Experimental strains, forces, and overall geometry were used to verify the simulation. While the simulation forces tended to be high, the trends were still well captured by the simulation model. The thickness and in-plane strains were found to be in good agreement with the experiments.

scholarly journals Numerical Simulation of Blast Loaded CFRP Retrofitted Steel Plates

2021 ◽  
Vol 347 ◽  
pp. 00038
Author(s):  
Mujtaba M. Shuaib ◽  
Steeve Chung Kim Yuen ◽  
Gerald N. Nurick
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Structural Response ◽  
Steel Plates ◽  
Blast Load ◽  
Cylindrical Charge ◽  
Arbitrary Lagrangian Eulerian ◽  
Finite Element Software ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper reports on the results of a numerical study to simulate the response of carbon fibre reinforced polymer (CFRP) retrofitted steel plates to applied blast loads using finite element software, LS-DYNA. The results of the simulation were validated against plate response and magnitude of deformation obtained from previous experiments. The uniform blast load was generated in the experiment by detonating a cylindrical charge down the end of a square tube. The finite element code LS-DYNA was used to simulate the structural response of the respective blast structures. For the numerical model, the blast load was simulated using the mapping feature available in LS-DYNA for the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) elements which significantly reduced the size of the air domain in the model. The simulations showed a satisfactory correlation with the experiments for the blast results and post-failure deformations that occurred in CFRP retrofitted steel plates.

scholarly journals A Stochastic Galerkin Cell-based Smoothed Finite Element Method (SGCS–FEM)

2019 ◽  
Vol 17 (08) ◽  
pp. 1950054
Author(s):  
Tittu Varghese Mathew ◽  
Lars Beex ◽  
Stéphane PA Bordas ◽  
Sundararajan Natarajan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Free Vibration ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Numerical Study ◽  
Mesh Size ◽  
Statistical Characteristics ◽  
Smoothed Finite Element Method ◽  
Element Method

In this paper, the cell-based smoothed finite element method is extended to solve stochastic partial differential equations with uncertain input parameters. The spatial field of Young’s Modulus and the corresponding stochastic results are represented by Karhunen-Loéve expansion and polynomial chaos expansion, respectively. Young’s Modulus of structure is considered to be random for stochastic static as well as free vibration problems. Mathematical expressions and the solution procedure are articulated in detail to evaluate the statistical characteristics of responses in terms of the static displacements and the free vibration frequencies. The feasibility and the effectiveness of the proposed SGCS–FEM method in terms of accuracy and lower demand on the mesh size in the solution domain over that of conventional FEM for stochastic problems are demonstrated by carefully chosen numerical examples. From the numerical study, it is inferred that the proposed framework yields accurate results.

scholarly journals Effect of Mesh on Springback in 3D Finite Element Analysis of Flexible Microrolling

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Feijun Qu ◽  
Zhengyi Jiang ◽  
Haina Lu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Numerical Study ◽  
Mesh Size ◽  
Computational Time ◽  
Element Analysis ◽  
3D Finite Element ◽  
Forming Quality ◽  
The Finite Element Analysis ◽  
Optimal Mesh

In flexible microrolling, springback in thickness direction is a critical indicator to determine the forming quality. Accurate prediction of springback is one of the significant aspects in the finite element analysis of flexible microrolling. Meshing is a step of great importance in finite element analysis of manufacturing process as it directly determines the accuracy of the FEA results as well as the requested computational time. This paper presents a numerical study on revealing the mesh effects on the accuracy of springback estimation utilising ABAQUS/Standard for modelling and analyses. Two types of meshes with six mesh sizes for each mesh type are considered in this study and the optimal mesh type and mesh size have been found to obtain accurate value of springback while saving as much computational time as possible.

scholarly journals Experimental and Numerical Study of the Elastic SCF of Tubular Joints

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4220
Author(s):  
Mostafa Atteya ◽  
Ove Mikkelsen ◽  
John Wintle ◽  
Gerhard Ersdal
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Numerical Study ◽  
Mesh Size ◽  
Element Analysis ◽  
Tubular Joints ◽  
Fine Mesh ◽  
Comparison Results ◽  
Weld Profile ◽  
Safe Side

This paper provides data on stress concentration factors (SCFs) from experimental measurements on cruciform tubular joints of a chord and brace intersection under axial loading. High-fidelity finite element models were generated and validated against these measurements. Further, the statistical variation and the uncertainty in both experiments and finite element analysis (FEA) are studied, including the effect of finite element modelling of the weld profile, mesh size, element type and the method for deriving the SCF. A method is proposed for modelling such uncertainties in order to determine a reasonable SCF. Traditionally, SCF are determined by parametric formulae found in codes and standards and the paper also provides these for comparison. Results from the FEA generally show that the SCF increases with a finer mesh, 2nd order brick elements, linear extrapolation and a larger weld profile. Comparison between experimental SCFs indicates that a very fine mesh and the use of 2nd order elements is required to provide SCF on the safe side. It is further found that the parametric SCF equations in codes are reasonably on the safe side and a detailed finite element analysis could be beneficial if small gains in fatigue life need to be justified.

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