Abstract: In this paper, combined the micromechanical and the thermodynamic theory, a three phase
model for the SMA composite is developed, in which the composite is considered as the austenitic
phase, the product phase (martensite) and the matrix phase. In the present model, the interaction
among the three phases is analyzed. From the micromechanical analysis, the macroscopic free energy
function is found. Then macroscopic transformation strain, effective elastic compliance, macroscopic
constitutive model are derived.Compared with the traditional two-phase method, non-linearity of
SMA need not be considered. The method is not only simply but also the interaction among the three
phases is considered. As an application of above model, we consider the case of a composite with
NiTi/epoxy, illustrate the predicted stress-strain response of it under isothermal loading and
unloading conditions and analyses the effects of temperature and fiber volume on macroscopic
mechanical property. By comparing with references, it is shown that the results are credible. It is
helpful to design the intelligent composite.
Abstract: The corrosion, corrosion fatigue and fracture failure process of aircraft structure is
directly concerned with combined effect of many factors, such as load, material characteristics,
corrosive environment and so on. The process is very complicated, and there is typical randomness.
Based on probabilistic fracture mechanics, with consideration of the limitation of the conventional
probabilistic approaches for prediction of corrosion fatigue life of aircraft structure at present, and a
new reliability approach under loading spectrum was proposed, in which corrosion damage and
fatigue crack damage was united as a same damage parameter. Short crack and long crack growth
behavior was separately discussed, and influence of short crack aspect ratio on structure life was
discussed. The Advanced First-Order Reliability Method, Importance Sampling Method and
iteratively advanced Second-Order Reliability Method were used to compute the fracture failure
probability. The results show that the model is feasible. By sensitivity analysis of random parameter,
the important parameter was obtained, which helped to monitor the structure fatigue life.
Abstract: In this paper, a numerical code, Realistic Failure Process Analysis code (RFPA), was
used to perform a microscopic analysis of a crack in a fiber-reinforced ceramic, when the crack
length is the same order of magnitude as the fiber spacing. The numerical results performed in the
paper shown the failure process of fiber-reinforced ceramic subjected to tension loading, which
indicate that the reinforcing fibers in a ceramic composite have a significant effect in inhibiting
crack propagation even during the stages of the development of crack. Moreover, the fiber evidently
increased the load-carrying capacity.
Abstract: Fracture along an interface between materials plays a major role in failure of material. In
this investigation, finite element calculations with Kachanov–Rabotnov damage law were carried
out to study the creep damage distribution near the interface cavity in bimaterial specimens. The
specimens with central hole were divided into three types. The material parameters of K-R law used
in this paper were chosen for a brittle material and ductile material. All calculations were performed
under four load cases. Due to the difference between elastic moduli of the bounded materials, the
elastic stress field as a function of the Young’s modulus ratio (R=E1/E2) was determined. At the
same time, the influence of model type on elastic stress distribution near the cavity was considered.
Under the same conditions, the material with larger modulus is subjected to larger stress. The creep
damage calculations show that the location of the maximum damage is different for each model.
The distributions of creep damage for all three models are dependent on the material properties and
Abstract: This article provides a theoretical and numerical treatment of a crack subjected to an
anti-plane shear loading in an infinite strip of FGMs. The crack situated in the mid-plane of strip
moves at a constant velocity. It is assumed that the shear moduli varies continuously in the
thickness direction and is to be of exponential form. The mixed boundary value problem is reduced
to a pair dual integral equations by means of nonlocal elasticity theory and integral transform
method. The stress field and displacement field for the strip are solved near the tip of the crack by
using Schmidt’s method. Then the influences of the characteristic length, graded parameters and
crack velocity on the stress at crack tip are studied. Unlike the classical elasticity solution, the
magnitude of stress at the crack tip is finite, and it is found that the maximum stress increases with
the crack velocity as the strip length is decreased, and the maximum stress decreases with the
characteristic length as the graded parameters is increased.
Abstract: The low cycle fatigue behavior and energy dissipation capacity around the weak axis of the
welded I-section bracing members are investigated by 35 pinned-pinned bracing specimen tests under
the axial cyclic loading with different characteristics. Particular attention is paid to the effects of
loading amplitude, loading history and geometry properties of these members. It is found that the
fatigue damage propagating to fracture in the flanges of the bracing members can be divided into 3
stages involving the macroscopic surface crack initiation, the penetrated crack formation and the
penetrated crack propagation. Some empirical formulas to estimate the fatigue life and cyclic energy
dissipation capacity of the bracing members are also presented based on the experimental data. The
statistical analysis indicates that the fatigue life to surface crack initiation significantly depends on the
inelastic local buckling and will increase with decreasing width-thickness ratio of the flanges and
increasing slenderness ratios of the bracing members. Besides, it is found that the low cycle fatigue
and energy dissipation of these members also depends on loading amplitude and loading history, and
the effects of overloads and mean compression amplitude can improve the fatigue performance of
bracing members. The test results show that the bracing members with better low-cycle fatigue
resistance have the better energy dissipation capacities.
Abstract: Using of a safe life approach is necessitated by the small critical crack sizes and rapid crack
growth rates resulting from the severe vibratory environment of rotorcraft. However Based on the
success of damage tolerance initiative for airframe structure, a crack growth based on damage
tolerance approach is being examined for implementation into the design and management of
dynamic components. In this paper the crack growth behavior in low cycle fatigue (LCF) and high
cycle fatigue (HCF) are compared and the accuracy of several damage tolerance analysis methods in
determining the crack growth life from an initial detectable crack size 1.25 mm to 12 mm for a
rotorcraft main rotor yoke are investigated. The real rotorcraft materials measured by experiment and
the fatigue load mean frequency spectrum based on statistical usage spectrum are adopted. The crack
growth equations used in the programs are discussed to provide a basis for understanding the results.
The results show that the load less than the safe fatigue limit has an important effect on crack
growth life and it is reasonable for the material that the cut-off stress ratio for the threshold stress
intensity factor range is set 0.7.
Abstract: Virtual life testing is becoming a widely accepted methodology for predicting the life
span of products. In this method, reliable models are important to predict different aspects of design
performance, one of which is wear. Wear and has been a subject of numerous scientific and
empirical investigations. Due to the complex and dynamic nature of the phenomena, there is no
general wear model, which can be adopted for all wear problems. A systematic approach to the
modelling of dry sliding wear using analytical time domain models is presented in this paper. Given
the sliding distance, the model is capable of predicting wear status in transient (running-in) and
steady-state operating conditions. The validity of the modelling approach is demonstrated by
comparing the predicted results of wear experiments, with that actually measured. For simplicity,
the model is based on sliding distance as input variable, while other factors like temperature, load,
surface conditions are treated as constant. A simple geometry of sliding polymer-based contacts is
used for establishing of wear model.
Abstract: With the concepts of the confidence interval, a random parameter can be transformed into
an interval number in the mesco ductile fracture. Hence analyses of the random isolated void model
can be used in the interval analysis method. Based on the macro- and mesco-experimental results of
four steels, 30CrMnSiA, 40CrNiMoA, No.45 and No.20, the probabilistic fracture characteristics of
the four steels are given. Finally the interval isolated void models in the four steels are discussed.