F. Dammak

NONLINEAR DYNAMICS ANALYSIS OF FGM SHELL STRUCTURES WITH A HIGHER ORDER SHEAR STRAIN ENHANCED SOLID-SHELL ELEMENT

IN THIS PAPER, NON-LINEAR DYNAMICS ANALYSIS OF FUNCTIONALLY GRADED MATERIAL (FGM) SHELL STRUCTURES IS INVESTIGATED USING THE HIGHER ORDER SOLID-SHELL ELEMENT BASED ON THE ENHANCED ASSUMED STRAIN (EAS). WITH THIS ELEMENT, A QUADRATIC DISTRIBUTION OF THE SHEAR STRESS THROUGH THE THICKNESS IS CONSIDERED IN AN ENHANCING PART. MATERIAL PROPERTIES OF THE SHELL STRUCTURE ARE VARIED CONTINUOUSLY IN THE THICKNESS DIRECTION ACCORDING TO THE GENERAL FOUR-PARAMETER POWER-LAW DISTRIBUTION IN TERMS OF THE VOLUME FRACTIONS OF THE CONSTITUENTS. PERFORMANCE AND ACCURACY OF THE PRESENT HIGHER ORDER SOLID-SHELL ELEMENT ARE CONFIRMED BY COMPARING THE NUMERICAL RESULTS OBTAINED FROM FINITE ELEMENT ANALYSES WITH RESULTS FROM THE LITERATURE.

Friction and Wear Behavior of Steels under Different Reciprocating Sliding Conditions

The friction and wear behavior of ISO 100Cr6 steel ball sliding against conventionally hardened carbon and low-alloy steels was studied. The effect of hardness, hardening capacity, normal load, and sliding speed on the coefficient of friction and friction energy was investigated. Friction tests were carried out, without lubrication and under ambient conditions, on a reciprocating friction tester in which a ball-on-flat contact configuration was adopted. The results showed that there is a relative tendency for the friction properties to decrease with increased hardening capacity and decreased hardness. The results showed that increasing normal load decreases the coefficient of friction for the two steel nuances. However, increasing sliding speed increases the coefficient of friction of low-alloy steel and decreases the coefficient of friction of carbon steel. The oxidation of wear debris influences the wear mechanisms and friction behavior.

NUMERICAL ANALYSIS OF GEOMETRICALLY NON-LINEAR BEHAVIOR OF FUNCTIONALLY GRADED SHELLS

IN THIS PAPER, A GEOMETRICALLY NONLINEAR ANALYSIS OF FUNCTIONALLY GRADED MATERIAL (FGM) SHELLS IS INVESTIGATED USING ABAQUS SOFTWARE. A USER DEFINED SUBROUTINE (UMAT) IS DEVELOPED AND IMPLEMENTED IN ABAQUS/STANDARD TO STUDY THE FG SHELLS IN LARGE DISPLACEMENTS AND ROTATIONS. THE MATERIAL PROPERTIES ARE INTRODUCED ACCORDING TO THE INTEGRATION POINTS IN ABAQUS VIA THE UMAT SUBROUTINE. THE PREDICTIONS OF STATIC RESPONSE OF SEVERAL NON-TRIVIAL STRUCTURE PROBLEMS ARE COMPARED TO SOME REFERENCE SOLUTIONS IN ORDER TO VERIFY THE ACCURACY AND THE EFFECTIVENESS OF THE NEW DEVELOPED NONLINEAR SOLUTION PROCEDURES. ALL THE RESULTS INDICATE VERY GOOD PERFORMANCE IN COMPARISON WITH REFERENCES.

Experimental Investigation of the Interface Behavior of Balanced and Unbalanced E-Glass/Polyester Woven Fabric Composite Laminates

The aim of this work is to study the influence of weave structure on the crack growth behavior of thick E-glass/polyester woven fabric composites laminates. Two different types of laminates were fabricated: (i) balanced: plain weave (taffetas T)/chopped strand mat weave (M) [T/M]6 and (ii) unbalanced: 4-hardness satin weave (S)/chopped strand mat weave [S/M]7. In order to accurately predict damage criticality in such structures, mixed mode fracture toughness data is required. So, the experiments were conducted using standards delamination tests under mixed mode loading and pure mode loading. These tests were carried out in mode II using End Load Split (ELS) tests and in mixed-mode I+II by Mixed Mode Flexure (MMF) tests under static conditions. The test methodology used for the experiments will be presented. The experimental results have been expressed in terms of total strain energy release rate and R-curves. The fracture toughness results show that the T/M interface is more resistant to delamination than the S/M interface.

Geometrically nonlinear analysis of elastoplastic behavior of functionally graded shells

A geometrically nonlinear analysis of elastoplastic ceramic/metal functionally graded material (FGM) shells is investigated in this paper based on the first-order shear deformation theory. The elastoplastic behavior of the ceramic particle-reinforced metal matrix FGM shell is assumed to follow Ludwik hardening law. The elastoplastic material properties are assumed to vary smoothly through the thickness of the shells. The Mori–Tanaka model and self-consistent formulas of Suquet are employed to locally evaluate effective elastoplastic parameters of the ceramic/metal FGM composite. The homogenization formulation and numerical algorithms are implemented into ABAQUS/Standard via a user material subroutine (UMAT) developed to study the FG shells in large displacements and rotations. With the aim of demonstrating the accuracy of the present method, current numerical results are compared to experimental and numerical ones considering geometrically nonlinear elastoplastic FGMs and show very good agreement. The overall robustness of the new developed solution taking into account both geometric and material nonlinearities is demonstrated through several non-trivial benchmark problems taken from the literature. The effect of the constituent distribution on the deflections is analyzed.

Friction and wear behaviour of induction hardened ISO 42CrMo4 low-alloy steel under reciprocating sliding conditions

Tribological behaviour of induction hardened ISO 42CrMo4 low alloy steel was evaluated under unlubricated sliding conditions. The effect of hardening depth and test conditions on the friction and wear properties was investigated. The tribological tests were carried out on a reciprocating tribometer. Cylinder-on-flat contact configuration was adopted. The results showed that varying the hardened depth, normal load or sliding speed influences the friction coefficient, the friction energy, the wear volume and the wear coefficient. It was found, also, that a change in the wear behaviour occurs when a critical value of normal load is exceeded.

The Extended Finite Element Method for Cracked Incompressible Hyperelastic Structures Analysis

This paper aims to examine the contribution of the extended finite element method (XFEM) in finite strain fracture mechanics problems. A generalized neo-Hookean hyperelastic material is considered in an incompressible plane stress approximation. The accuracy of the implementation is demonstrated by a series of numerical tests.

Low Velocity Impact Behavior of Glass Fibre-Reinforced Polyamide

The low velocity impact behavior of composites made of polyamide (PA) as matrix and glass fibre as reinforcement has been investigated. The assessment of the impact behavior has driven the need to perform tensile tests to determine the elasto-plastic behavior of the composites. The specimens were manufactured by injection molding techniques for the experimental tensile testing. ABAQUS/EXPLICIT for finite element modeling is employed in order to predict the impact behavior of glass fibre-reinforced polyamide. The determinations of the impact force history and elasto-plastic structure deflection are the most important objectives in impact engineering structures design.

Tribological behaviour of carbon and low alloy steels: effect of mechanical properties and test conditions

Abstract In this paper, the effects of mechanical properties and test conditions on the tribological behaviour of ISO C45 carbon steel and ISO 42CrMo4 low alloy steel were studied. The tribological tests were carried out, without lubrication, on a reciprocating friction tester. Cylinder on flat contact configuration was adopted. The results showed that there is no obvious relationship between the mechanical properties and the friction ones. However, the variation in the coefficient of friction depends on the test conditions. In contrary to normal load, the effect of sliding speed on the coefficient of friction is not the same for the two steel nuances. The tribological properties are dependent, however, on the nature of wear debris.

Effect of hygrothermal aging on mechanical and tribological behaviors of short glass-fiber-reinforced PA66

Mechanical and tribological behaviors of polyamide 66 reinforced by various weight fractions of short glass fiber were investigated. All studied materials were subjected to accelerated hygrothermal aging tests. Three-point bending flexural tests were carried out to determine the mechanical behavior. Reciprocating tribotester was employed to determine friction and wear behaviors. Tribological tests were carried out, without lubrication and under ambient conditions. Ball on flat contact configuration was adopted for friction tests. Wear tests were carried out against an abrasive counterface. Results showed that flexural strength and elastic modulus increased when increasing glass fiber rate for all tested materials. In the contrary, the coefficient of friction and the wear resistance decreased. Results showed that the hygrothermal aging decreased the flexural features and increased the coefficient of friction. The effect of hygrothermal aging on the wear resistance depends on the reinforcement rate.