Assessment of Thorax Finite Element Model Response for Behind Armor Blunt Trauma Impact Loading Using an Epidemiological Database

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
D. S. Cronin ◽  
M. C. Bustamante ◽  
J. Barker ◽  
D. Singh ◽  
K. A. Rafaels ◽  
...  
Keyword(s):  
Finite Element ◽  
Blunt Trauma ◽  
Injury Risk ◽  
Element Model ◽  
Rib Fractures ◽  
Pulmonary Contusion ◽  
Element Mesh ◽  
High Deformation ◽  
Ballistic Impacts ◽  
Back Face

Abstract Nonperforating ballistic impacts on thoracic armor can cause blunt injuries, known as behind-armor blunt trauma (BABT). To evaluate the potential for this injury, the back face deformation (BFD) imprinted into a clay backing is measured; however, the link between BFD and potential for injury is uncertain. Computational human body models (HBMs) have the potential to provide an improved understanding of BABT injury risk to inform armor design but require assessment with relevant loading scenarios. In this study, a methodology was developed to apply BABT loading to a computational thorax model, enhanced with refined finite element mesh and high-deformation rate mechanical properties. The model was assessed using an epidemiological BABT survivor database. BABT impact boundary conditions for 10 cases from the database were recreated using experimentally measured deformation for specific armor/projectile combinations, and applied to the thorax model using a novel prescribed displacement methodology. The computational thorax model demonstrated numerical stability under BABT impact conditions. The predicted number of rib fractures, the magnitude of pulmonary contusion, and injury rank, increased with armor BFD, back face velocity, and input energy to the thorax. In three of the 10 cases, the model overpredicted the number of rib fractures, attributed to impact location positional sensitivity and limited details from the database. The integration of an HBM with the BABT loading method predicted rib fractures and injury ranks that were in good agreement with available medical records, providing a potential tool for future armor evaluation and injury assessment.

Elasto-Plastic Coupled Temperature-Displacement Finite Element Analysis of Two-Dimensional Rolling-Sliding Contact With a Translating Heat Source

1991 ◽  
Vol 113 (1) ◽  
pp. 93-101 ◽  
Author(s):  
S. M. Kulkarni ◽  
C. A. Rubin ◽  
G. T. Hahn
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Plastic Material ◽  
Element Model ◽  
Rolling Contact ◽  
Two Dimensional ◽  
Element Analysis ◽  
Element Mesh ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The present paper, describes a transient translating elasto-plastic thermo-mechanical finite element model to study 2-D frictional rolling contact. Frictional two-dimensional contact is simulated by repeatedly translating a non-uniform thermo-mechanical distribution across the surface of an elasto-plastic half space. The half space is represented by a two dimensional finite element mesh with appropriate boundaries. Calculations are for an elastic-perfectly plastic material and the selected thermo-physical properties are assumed to be temperature independent. The paper presents temperature variations, stress and plastic strain distributions and deformations. Residual tensile stresses are observed. The magnitude and depth of these stresses depends on 1) the temperature gradients and 2) the magnitudes of the normal and tangential tractions.

Finite Element Mesh Generator Applying Constraints’ Propagation and Isoparametric Mapping

1991 ◽  
Author(s):  
J. Rodriguez ◽  
M. Him
Keyword(s):  
Finite Element ◽  
Mesh Generation ◽  
Element Model ◽  
Finite Element Mesh ◽  
Fe Model ◽  
Element Analysis ◽  
Element Mesh ◽  
Mesh Generator ◽  
Generation Algorithm ◽  
Essential Input

Abstract This paper presents a finite element mesh generation algorithm (PREPAT) designed to automatically discretize two-dimensional domains. The mesh generation algorithm is a mapping scheme which creates a uniform isoparametric FE model based on a pre-partitioned domain of the component. The proposed algorithm provides a faster and more accurate tool in the pre-processing phase of a Finite Element Analysis (FEA). A primary goal of the developed mesh generator is to create a finite element model requiring only essential input from the analyst. As a result, the generator code utilizes only a sketch, based on geometric primitives, and information relating to loading/boundary conditions. These conditions represents the constraints that are propagated throughout the model and the available finite elements are uniformly mapped in the resulting sub-domains. Relative advantages and limitations of the mesh generator are discussed. Examples are presented to illustrate the accuracy, efficiency and applicability of PREPAT.

The Dynamic Strength of a Representative Double Layer Prismatic Core: A Combined Experimental, Numerical, and Analytical Assessment

2010 ◽  
Vol 77 (6) ◽  
Author(s):  
Enrico Ferri ◽  
V. S. Deshpande ◽  
A. G. Evans
Keyword(s):  
Finite Element ◽  
Double Layer ◽  
Dynamic Compression ◽  
Dynamic Strength ◽  
Element Model ◽  
Free Standing ◽  
The Core ◽  
Impulsive Loads ◽  
Back Face ◽  
Out Of Plane

Dynamic out-of-plane compressive testing was used to characterize the dynamic strength of stainless steel prismatic cores with representative double layer topology to be employed in sandwich panels for blast protection. Laboratory-scaled samples of the representative core unit cell were manufactured (relative density of 5.4%) and tested at constant axial impact velocities (ranging from quasi-static to 140 ms−1). The dynamic strength was evaluated by measuring the stresses transmitted to a direct impact Hopkinson bar. Two-dimensional, plane strain, finite element calculations (with a stationary back face) were used to replicate the experimental results upon incorporating imperfections calibrated using the observed dynamic buckling modes. To infer the response of cores when included in a sandwich plate subject to blast loading, the finite element model was modified to an unsupported (free-standing) back face boundary condition. The transmitted stress is found to be modulated by the momentum acquired by the back face mass and, as the mass becomes larger, the core strength approaches that measured and simulated for stationary conditions. This finding justifies the use of a simple dynamic compression test for calibration of the dynamic strength of the core. An analytical model that accounts for the shock effects in a homogenized core and embodies a simple dual-level dynamic strength is presented and shown to capture the experimental observations and simulated results with acceptable fidelity. This model provides the basis for a constitutive model that can be used to understand the response of sandwich plates subject to impulsive loads.

scholarly journals Finite Element Modeling of Orthogonal Machining of Brittle Materials Using an Embedded Cohesive Element Mesh

2019 ◽  
Vol 3 (2) ◽  
pp. 36
Author(s):  
Behrouz Takabi ◽  
Bruce L. Tai
Keyword(s):  
Finite Element ◽  
Cutting Force ◽  
Cohesive Zone ◽  
Manufacturing Industry ◽  
Brittle Materials ◽  
Element Model ◽  
Relative Difference ◽  
Unstable Crack ◽  
Element Mesh ◽  
Regular Elements

Machining of brittle materials is common in the manufacturing industry, but few modeling techniques are available to predict materials’ behavior in response to the cutting tool. The paper presents a fracture-based finite element model, named embedded cohesive zone–finite element method (ECZ–FEM). In ECZ–FEM, a network of cohesive zone (CZ) elements are embedded in the material body with regular elements to capture multiple randomized cracks during a cutting process. The CZ element is defined by the fracture energy and a scaling factor to control material ductility and chip behavior. The model is validated by an experimental study in terms of chip formation and cutting force with two different brittle materials and depths of cut. The results show that ECZ–FEM can capture various chip forms, such as dusty debris, irregular chips, and unstable crack propagation seen in the experimental cases. For the cutting force, the model can predict the relative difference among the experimental cases, but the force value is higher by 30–50%. The ECZ–FEM has demonstrated the feasibility of brittle cutting simulation with some limitations applied.

The Implementation of Inter-Element Model for Crack Growth Simulation

2004 ◽  
Vol 261-263 ◽  
pp. 687-692 ◽  
Author(s):  
Ahmad Kamal Ariffin ◽  
Syifaul Huzni ◽  
Nik Abdullah Nik Mohamed ◽  
Mohd Jailani Mohd Nor
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Problem ◽  
Adaptive Mesh ◽  
Element Model ◽  
Error Norm ◽  
Element Analysis ◽  
Element Mesh

The implementation of inter-element model to simulate crack propagation by using finite element analysis with adaptive mesh is presented. An adaptive finite element mesh is applied to analyze two-dimension elastoplastic fracture during crack propagation. Displacement control approach and updated Lagrangean strategy are used to solve the non-linearity in geometry, material and boundary for plane stress crack problem. In the finite element analysis, remeshing process is based on stress error norm coupled with h-version mesh refinement to find an optimal mesh. The crack is modeled by splitting crack tip node and automatic remeshing calculated for each step of crack growth. Crack has been modeled to propagate through the inter-element in the mesh. The crack is free to propagates without predetermine path direction. Maximum principal normal stress criterion is used as the direction criteria. Several examples are presented to show the results of the implementation.

Growth Behavior of Two Interacting Surface Cracks of Dissimilar Size (Comparison for Tensile and Bending Load)

2010 ◽  
Author(s):  
Masayuki Kamaya ◽  
Masanori Kikuchi ◽  
Eiichi Miyokawa
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Growth Behavior ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Element Mesh ◽  
Loading Direction ◽  
Parallel Surface ◽  
Bending Load ◽  
The Difference

When multiple cracks approach one another, the stress intensity factor is likely to change due to the interaction of the stress field. This causes change in growth rate and shape of cracks. In particular, when cracks are in parallel position to the loading direction, the shape of cracks becomes non-planar. In this study, the complex growth of interacting cracks is evaluated by using the S-Version finite element method, in which local detailed finite element mesh (local mesh) is superposed on cores finite element model (global mesh) representing the global structure. In this study, two parallel surface cracks are subjected to two types of loading; tensile and bending load. Comparisons are made on the growth behavior under two types of loading. It is shown that the smaller crack stop growing due to the interaction when the difference in size of two cracks is large. This tendency is more significant for the bending load. The procedure for evaluating crack growth for Fitness-for-Service assessment is discussed.

UNCERTAINTIES OF IMPACT CONFIGURATION FOR NUMERICAL REPLICATIONS OF REAL-WORLD TRAUMA: A FE ANALYSIS

2016 ◽  
Vol 16 (08) ◽  
pp. 1640018 ◽  
Author(s):  
MICHÈLE BODO ◽  
SÉBASTIEN ROTH
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Real World ◽  
Injury Risk ◽  
Body Position ◽  
Free Fall ◽  
Experimental Tests ◽  
Element Model ◽  
The Body ◽  
Thoracic Injury

This study deals with free fall accident analysis involving adults, and their numerical replications using a finite element model of the human thorax. The main purpose is to determine the role of body position at impact in the thorax injury risk appearance. For this study, cases of real-world free-fall provided by an emergency department were selected and investigated. These cases involved both male and female with an age range of 20 to 63 years, who sustained accidental free-fall with both injured and uninjured cases. The examination of the patients' medical record provided helpful information to accurately perform numerical replications with the finite element model HUByx (Hermaphrodite Universal Biomechanical yx model) which was already validated for various experimental tests in the field of automobile, ballistic impacts and blast. The results of simulations at different impact location allowed highlighting the crucial influence of the body orientation in the risk of thoracic injury occurrence.

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