Abstract: Reducing structural weight is one of the major ways to improve aircraft performance.
Lighter and/or stronger materials allow greater range and speed and may also contribute to reducing
operational costs. Nowadays composite materials are widely used in “primary” structural
components such as fuselage, for which contrasting requirements like lightness and structural
strength are required, so particular attention is necessary during its design. In this paper a composite
front bulkhead, subjected to ultimate pressure load, was examined. The front bulkhead is made of a
composite skin, stiffened with seven vertical stiffeners linked through metallic fittings; the whole
system is joined to the fuselage by rivets. A Finite Element model was established: the used
elements were four nodes shells, simulating composite layers, and two nodes bar elements,
simulating rivets; the structure was clamped and a pressure load was applied to the skin. A linear
static stress analysis was performed to calculate strains in particular points in which strain gauges or
rosettes are placed: the numerical results, compared with experimental ones, show a good degree of
correlation. Stress calculations were performed in order to verify the front and rear bulkhead
Abstract: A few years ago we showed that the Theory of Critical Distances (TCD) and the Crack
Modelling Method (CMM) could be used to predict the behaviour of welded joints of various
geometries, in both steel and aluminum alloys. However we found that there were certain kinds of
joints for which our methods, and also other methods which are commonly used, consistently underpredicted
the fatigue strengths. Some explanations are suggested for this problem. Finally, mention
is made of some of failure investigations in which the author has been involved, to illustrate the
complexities which arise in real-world situations.
Abstract: This paper presents some ideas on incorporating output from advanced synchrotron and
neutron scanning strain methods in improved assessment of the influence of weld process
parameters on residual strains at welds and on their fatigue performance. It very briefly outlines two
different cases involving synchrotron diffraction strain scanning of friction stir welds in a strain
hardened aluminium alloy and neutron diffraction strain scanning of MIG welds in high strength
Abstract: Some recently developed variants of local concepts for assessing the fatigue strength and
structural durability of welded joints are reviewed. These comprise structural stress, notch stress or
strain and fracture mechanics concepts. New variants of the structural stress concept are Dong’s
gradient stress approach and Xiao-Yamada’s ‘one millimetre stress’ approach. FE meshing rules
have been developed for welded joints in thin sheet structures. The concept of fictitious notch
rounding is now better substantiated for aluminium alloys. The small-size notch concept is
applicable to thin sheet lap joints. The new notch stress intensity factor concept is based on the
singular stresses at the sharp weld toe notch. Advanced fracture mechanics concepts combine crack
initiation at the seam weld root or nugget edge and crack propagation over the plate thickness
resulting in endurable FK values as function of cycles per unit thickness, N/t.
Abstract: Wear and rolling contact fatigue interaction in rolling/sliding contact is an important
topic in the research on structural integrity of rails and railway wheels. Wear is in competition with
rolling contact fatigue, as it removes surface material layers, reducing cracks length and hindering
their propagation. Cracks nucleate by accumulation of cyclic unidirectional plastic strain
(ratcheting). In this paper a model for ratcheting assessment is discussed and applied to the UIC
900A steel, after a calibration based on experimental results. The experimental tests allow also a
characterization of the crack formation condition for this material. By this model, a computer
program is developed in order to simulate in a very short time the effect of a large number of load
cycles, providing a tool for predicting crack formation and propagation rates.
Abstract: Structural details of ship structures are prone to fatigue damage mainly due to high-cycle
wave load and low-cycle cargo loading/unloading. Full stochastic fatigue analysis of selected
structural details on an oceangoing 6500 cbm LPG ship is presented. A critical Y-joint of
longitudinal bulkhead and bilobe tank shell as well as double-bottom girder details are selected due
to different reasons. The eccentricity of the Y-joint, leads to significant stress concentration. Saddle
supports of gas tanks cause stress concentration in ship double bottom due to weight and dynamic
loads. Wave load on ship structure is calculated using linear strip theory for ship in ballast condition
and full ship. Wave load is transferred to ship finite element model and notch structural stresses are
determined using finite element analysis. Stochastic fatigue analysis is then performed, taking into
account sailing route and other ship operational parameters. Finally, fatigue damage summation is
done and results are discussed.
Abstract: This work presents the investigation of the mechanical behavior of composite materials
strengthened with short fibers and particles. A simple model is presented, with the purpose of
predicting the fracture strength of this class of composite material. The model consists of the
modification of the rule of mixtures, by the introduction of a correction factor, which corresponds to
the adhesion of the resin to the fiber and the particles. The experiments were performed on three
different composite materials having the same raw material but different mixture ratios. The
composite materials produced were tested by the three-point flexural method, according to ASTM
standard, in order to determine their mechanical properties. The comparison between theoretical and
experimental results were also performed and found to be in reasonable agreement. Other relevant
parameters will also be discussed.
Abstract: In the present paper, a new method for inserting cracks with out-of-plane features is presented.
Starting point is an arbitrary reference structure and a crack of any shape. The final cracked
structure is represented by hexahedral elements in the crack-front region and tetrahedral elements in
the remaining structure domain. The tetrahedron is employed to take advantage of the versatile
meshing capabilities and the collapsed quarter-point hexahedron gives good crack-tip behaviour.
Stress intensity factors are calculated from the asymptotic stress field, retrieved from the integration
points near the crack-tip.
Abstract: The aim of the presentation is to highlight the influence of the kink, developing at the
beginning of mixed-mode crack growth, on the propagation behavior of the crack. Le et al.  have
shown that the variational principle of a body containing a crack results in the principle of
maximum energy release rate incorporating the stress intensity factors of the kinked crack. Here the
influence of the kink and the kinking angle, resulting in a singular field around the corner, on the
crack growth is analyzed. The generalized stress intensity factors at the kinks corner are computed
with the help of a FEM strategy. The influence of these on the T-stresses and the plastic energy
dissipated at the kink is determined using a small scale yielding approach. The impact of these
results on mixed-mode crack propagation is discussed.
Abstract: Due to their microstructure, quasi brittle materials present rough cracks. Under sliding of
the crack lips, this roughness involves in one hand induced opening and in the other hand some apparent
plasticity which is due to the interlocking of the crack lips combined with Coulomb’s friction.
The proposed model is written under the irreversible thermodynamics framework. Micromechanics
uses the Del Piero and Owen’s structured deformation theory. Opening of the crack depends upon
the crack shape and the relative sliding of the crack lips. The thermodynamic force associated to the
sliding has the mechanical meaning of the force acting in order to make the crack slide. Yield surface
is defined as a limitation of this force with respect to the Coulomb’s friction and the Barenblatt cohesion.
The crack orientation is defined as the one for which the criterion is reached for the lowest stress
level. A decreasing cohesion, respect to sliding is supposed. Tension and compression reference cases