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Article
Publication date: 1 May 2001

J.F. Molinari, M. Ortiz, R. Radovitzky and E.A. Repetto

This paper is concerned with the calibration and validation of a finite‐element model of dry sliding wear in metals. The model is formulated within a Lagrangian framework capable…

1732

Abstract

This paper is concerned with the calibration and validation of a finite‐element model of dry sliding wear in metals. The model is formulated within a Lagrangian framework capable of accounting for large plastic deformations and history‐dependent material behavior. We resort to continuous adaptive meshing as a means of eliminating deformation‐induced element distortion, and of resolving fine features of the wear process such as contact boundary layers. Particular attention is devoted to a generalization of Archard’s law in which the hardness of the soft material is allowed to be a function of temperature. This dependence of hardness on temperature provides a means of capturing the observed experimental transition between severe wear rates at low speeds to mild wear rates at high speeds. Other features of the numerical model include: surface evolution due to wear; finite‐deformation J2 thermoplasticity; heat generation and diffusion in the bulk; non‐equilibrium heat‐transfer across the contact interface; and frictional contact. The model is validated against a conventional test configuration consisting of a brass pin rubbing against a rotating steel plate.

Details

Engineering Computations, vol. 18 no. 3/4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 24 September 2010

M. Grujicic, G. Arakere and T. He

This paper aims to conduct a combined Eulerian/Lagrangian fluid/solid transient non‐linear dynamics computational analysis of the interaction between a single planar blast wave…

1203

Abstract

Purpose

This paper aims to conduct a combined Eulerian/Lagrangian fluid/solid transient non‐linear dynamics computational analysis of the interaction between a single planar blast wave and a human head in order to assess the extent of intra‐cranial shock wave generation and its potential for causing traumatic brain injury.

Design/methodology/approach

Two levels of blast peak overpressure were selected, one corresponding to the unprotected lung‐injury threshold while the other associated with a 50 percent probability for lung injury caused death. Collision of the head with a stationary/rigid barrier (at an initial collision velocity of 5 m/s) was also analyzed computationally, since blunt‐object impact conditions may lead to mild traumatic brain injury (mTBI), i.e. concussion.

Findings

A comparison between the two blast and the single blunt‐object impact cases with the corresponding head‐to‐head‐collision results showed that, while the von Mises stress‐based head‐to‐head collision mTBI thresholds are not exceeded under blast‐loading conditions investigated, the high blast‐induced peak‐pressure levels within the intra‐cranial cavity may lead to mTBI.

Practical implications

While concussion is not generally considered as life altering/threatening, the associated temporary loss of situational awareness or consciousness may have devastating consequences in the case of common military tactical and battle‐field scenarios. This suggests that the head‐protection gear (primarily, the helmet) which are currently designed to withstand blunt‐object and ballistic impacts, should be redesigned in order to obtain the necessary level of head protection with respect to blast impact.

Originality/value

The paper provides a comprehensive computational investigation of impact on a human skull/brain assembly.

Details

Multidiscipline Modeling in Materials and Structures, vol. 6 no. 3
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 25 November 2019

Rohit Pethe, Thomas Heuzé and Laurent Stainier

The purpose of this paper is to present a variational mesh h-adaption approach for strongly coupled thermomechanical problems.

48

Abstract

Purpose

The purpose of this paper is to present a variational mesh h-adaption approach for strongly coupled thermomechanical problems.

Design/methodology/approach

The mesh is adapted by local subdivision controlled by an energy criterion. Thermal and thermomechanical problems are of interest here. In particular, steady and transient purely thermal problems, transient strongly coupled thermoelasticity and thermoplasticity problems are investigated.

Findings

Different test cases are performed to test the robustness of the algorithm for the problems listed above. It is found that a better cost-effectiveness can be obtained with that approach compared to a uniform refining procedure. Because the algorithm is based on a set of tolerance parameters, parametric analyses and a study of their respective influence on the mesh adaption are carried out. This detailed analysis is performed on unidimensional problems, and a final example is provided in two dimensions.

Originality/value

This work presents an original approach for independent h-adaption of a mechanical and a thermal mesh in strongly coupled problems, based on an incremental variational formulation. The approach does not rely on (or attempt to provide) error estimation in the classical sense. It could merely be considered to provide an error indicator. Instead, it provides a practical methodology to adapt the mesh on the basis of the variational structure of the underlying mathematical problem.

Details

Engineering Computations, vol. 37 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 20 December 2018

Soheil Bazazzadeh, Arman Shojaei, Mirco Zaccariotto and Ugo Galvanetto

The purpose of this paper is to apply the Peridynamic differential operator (PDDO) to incompressible inviscid fluid flow with moving boundaries. Based on the potential flow…

435

Abstract

Purpose

The purpose of this paper is to apply the Peridynamic differential operator (PDDO) to incompressible inviscid fluid flow with moving boundaries. Based on the potential flow theory, a Lagrangian formulation is used to cope with non-linear free-surface waves of sloshing water in 2D and 3D rectangular and square tanks.

Design/methodology/approach

In fact, PDDO recasts the local differentiation operator through a nonlocal integration scheme. This makes the method capable of determining the derivatives of a field variable, more precisely than direct differentiation, when jump discontinuities or gradient singularities come into the picture. The issue of gradient singularity can be found in tanks containing vertical/horizontal baffles.

Findings

The application of PDDO helps to obtain the velocity field with a high accuracy at each time step that leads to a suitable geometry updating for the procedure. Domain/boundary nodes are updated by using a second-order finite difference time algorithm. The method is applied to the solution of different examples including tanks with baffles. The accuracy of the method is scrutinized by comparing the numerical results with analytical, numerical and experimental results available in the literature.

Originality/value

Based on the investigations, PDDO can be considered a reliable and suitable approach to cope with sloshing problems in tanks. The paper paves the way to apply the method for a wider range of problems such as compressible fluid flow.

Details

Engineering Computations, vol. 36 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 June 2002

C.A. Powell, Savage and J.T. Guthrie

A Lagrangian finite element algorithm is described for solving two‐dimensional, time‐dependent free surface fluid flows such as those that occur in industrial printing processes…

679

Abstract

A Lagrangian finite element algorithm is described for solving two‐dimensional, time‐dependent free surface fluid flows such as those that occur in industrial printing processes. The algorithm is applied using a problem specific structured meshing strategy, implemented with periodic remeshing to control element distortion. The method is benchmarked on the problem of a stretching filament of viscous liquid, which clearly demonstrates the applicability of the approach to flows involving substantial free surface deformation. The model printing problem of the transfer of Newtonian liquid from an upturned trapezoidal trench (3‐D cavity with a large transverse aspect ratio) to a horizontal substrate, which is pulled perpendicularly downwards from the cavity, is solved computationally using the Lagrangian scheme. The idealized 2‐D liquid motion is tracked from start‐up to the point where a thin sheet forms – connecting the liquid remaining in the cavity to a “sessile” drop on the moving substrate. The effect of varying substrate separation speed is briefly discussed and predictions are made for approximate drop volumes and “limiting” domain lengths.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 July 2006

Guillaume Houzeaux and Ramon Codina

To develop a numerical methodology to simulate the lost foam casting (LFC), including the gas back‐pressure effects.

619

Abstract

Purpose

To develop a numerical methodology to simulate the lost foam casting (LFC), including the gas back‐pressure effects.

Design/methodology/approach

Back‐pressure effects are due to the interactions of many physical processes. The strategy proposed herein tries to model all these processes within a simple formula. The main characteristic of the model consists of assuming that the back‐pressure is a known function of the external parameters (coating, temperature, gravity, etc.) that affects directly the heat transfer coefficient from the metal to the foam. The general framework of the simulation is a finite element model based on an arbitrary Lagrangian Eulerian (ALE) approach and the use of level set function to capture the metal front advance.

Findings

After experimental tunings, the model provides a way to include the back‐pressure effects in a simple way.

Research limitations/implications

The method is not completely predictive in the sense that a priori tuning is necessary to calibrate the model.

Practical implications

Provides more realistic results than classical models.

Originality/value

The paper proposes a theoretical framework of a finite element method for the simulation of LFC process. The method uses an ALE method on a fixed mesh and a level‐set function to capture metal front advance. It proposes an original formula for the heat transfer coefficient that enables one to include back‐pressure effects.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 26 September 2023

Lang Li, Jiahui Li, Fan Zhang, Fusen Jia and Lei Li

Sandwich structures with well-designed cellular cores exhibit superior shock resistance compared to monolithic structures of equal mass. This study aims to develop a comprehensive…

126

Abstract

Purpose

Sandwich structures with well-designed cellular cores exhibit superior shock resistance compared to monolithic structures of equal mass. This study aims to develop a comprehensive analytical model for predicting the dynamic response of cellular-core sandwich structures subjected to shock loading and investigate their application in protective design.

Design/methodology/approach

First, an analytical model of a clamped sandwich beam for over-span shock loading was developed. In this model, the incident shock-wave reflection was considered, the clamped face sheets were simplified using two single-degree-of-freedom (SDOF) systems, the core was idealized using the rigid-perfectly-plastic-locking (RPPL) model in the thickness direction and simplified as an SDOF system in the span direction. The model was then evaluated using existing analytical models before being employed to design the sandwich-beam configurations for two typical engineering applications.

Findings

The model effectively predicted the dynamic response of sandwich panels, especially when the shock-loading pulse shape was considered. The optimal compressive cellular-core strength increased with increasing peak pressure and shock-loading impulse. Neglecting the core tensile strength could result in an overestimation of the optimal compressive cellular-core strength.

Originality/value

A new model was proposed and employed to optimally design clamped cellular-core sandwich-beam configurations subjected to shock loading.

Details

Multidiscipline Modeling in Materials and Structures, vol. 19 no. 6
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 1 December 2001

Jaroslav Mackerle

Gives a bibliographical review of the finite element meshing and remeshing from the theoretical as well as practical points of view. Topics such as adaptive techniques for meshing…

1907

Abstract

Gives a bibliographical review of the finite element meshing and remeshing from the theoretical as well as practical points of view. Topics such as adaptive techniques for meshing and remeshing, parallel processing in the finite element modelling, etc. are also included. The bibliography at the end of this paper contains 1,727 references to papers, conference proceedings and theses/dissertations dealing with presented subjects that were published between 1990 and 2001.

Details

Engineering Computations, vol. 18 no. 8
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 August 2001

Jaroslav Mackerle

Gives a bibliographical review of the error estimates and adaptive finite element methods from the theoretical as well as the application point of view. The bibliography at the…

1686

Abstract

Gives a bibliographical review of the error estimates and adaptive finite element methods from the theoretical as well as the application point of view. The bibliography at the end contains 2,177 references to papers, conference proceedings and theses/dissertations dealing with the subjects that were published in 1990‐2000.

Details

Engineering Computations, vol. 18 no. 5/6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 September 2012

M. Grujicic, A. Arakere, B. Pandurangan, A. Grujicic, A. Littlestone and R. Barsoum

Polyurea falls into a category of elastomeric co‐polymers in which, due to the presence of strong hydrogen bonding, the microstructure is of a heterogeneous nature and consists of…

364

Abstract

Purpose

Polyurea falls into a category of elastomeric co‐polymers in which, due to the presence of strong hydrogen bonding, the microstructure is of a heterogeneous nature and consists of a compliant/soft matrix and stiff/hard nanometer size hard domains. Recent investigations have shown that the use of polyurea as an external or internal coating/lining had substantially improved ballistic‐penetration resistance of metallic structures. The present work aims to use computational methods and tools in order to assess the shock‐mitigation ability of polyurea when used in the construction of different components (suspension‐pads, internal lining and external coating) of a combat helmet.

Design/methodology/approach

Shock‐mitigation capability of combat helmets has become an important functional requirement as shock‐ingress into the intra‐cranial cavity is known to be one of the main causes of traumatic brain injury (TBI). To assess the shock mitigation capability of polyurea, a combined Eulerian/Lagrangian fluid/solid transient non‐linear dynamics computational analysis of an air/helmet/head core sample is carried out and the temporal evolution of the axial stress and particle velocities (for different polyurea augmented helmet designs) are monitored.

Findings

The results obtained show that improvements in the shock‐mitigation performance of the helmet are obtained only in the case when polyurea is used as a helmet internal lining and that these improvements are relatively small. In addition, polyurea is found to slightly outperform conventional helmet foam, but only under relatively strong (greater than five atm) blastwave peak overpressures.

Originality/value

The present approach studies the effect of internal linings and external coatings on combat helmet blast mitigation performance.

Details

Multidiscipline Modeling in Materials and Structures, vol. 8 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

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