Abstract: A constitutive model for isotropic damage of geomaterial is put forward, and its numerical
computation procedure is given also. The calculated results for a simple example could highlight our
understanding about the mechanism of geomaterial damage, and several useful conclusions can be
drawn: The series assumption can not be used to synthesis mode of stress and strain for complexus
theory of geomaterials damage; strictly speaking, the parallel assumption can not be used to that of
geomaterials damage also; the complexus stress-strain behavior like that of ideal natural geomaterial
under small stress, and like that of reconstituted soil under large stress.
Abstract: Crack propagation tests were conducted with CCT specimens made by 2024-T3 Aluminum
alloy in benign and corrosive environments to investigate the stochastic characteristics of crack
growth. A random variable probability crack growth model, base on the modified form of Paris law,
was used to characterize the stochastic performance. Distribution significance test has been done,
which shows that the random variable X can be considered reasonably to follow log-normal
distribution in all the 4 kind of environments. Variance analysis indicates that the scatter in wet air is
greater than that in laboratory air significantly. Expressions for the probability distribution of crack
size at any given loading cycle and the probability distribution of the random fatigue life at which a
given crack size is reached were discussed. The corresponding calculations for the crack length
distribution and P-a-N curves with certain reliability were carried out. The comparisons with
experimental data indicate the validity of the proposed method.
Abstract: In this paper, the method of Green’s function is used to investigate the problem of
dynamic stress concentration of circular lining and interior linear crack impacted by incident
SH-wave. The train of thought for this problem is that: Firstly, a Green’s function is constructed for
the problem, which is a fundamental solution of displacement field for an elastic space possessing a
circular lining while bearing out-of-plane harmonic line source force at any point in the lining. In
terms of the solution of SH-wave’s scattering by an elastic space with a circular lining, anti-plane
stresses which are the same in quantity but opposite in direction to those mentioned before, are
loaded at the region where the crack existent actually, we called this process “crack-division”.
Finally, the expressions of the displacement and stress are given when the lining and the crack exist
at the same time. Then, by using the expressions, some example is provided to show the effect of
crack on the dynamic stress concentration around circular lining.
Abstract: Based on Dankert’s et al.  initial model for the elastic-plastic evaluation of fatigue
crack growth in sheets providing elliptical notches, a generalized procedure enabling an improved
evaluation of the effective ranges of the crack driving force (i.e. the J-Integral) as well as the
application to arbitrary notched components has been developed . The present paper presents the
basic topics of the calculation model as well as its verification using experimental results from
notched specimens with various notch shapes subjected to cyclic loading with various load ratios.
Abstract: This paper attempts to critically review some numerical methods for fatigue strength
assessment of welded joints by means of stress analysis tools (usually FE models). In particular, it
focuses on the significance of geometrical model, by distinguishing beams from shells and solids,
more than distinguishing among nominal, structural and notch stress type. In addition, basing on
continuous mechanics theories, a distinction between “local” and “non-local” stress approaches is
proposed. Finally the advantages of notch stress approaches are showed by commenting also
problems connected to multiaxiality and three-dimensionality of stress states.
Abstract: In this paper, RFPA－dynamic numerical simulation system was adopted to simulate the
entire process of the three–point bending specimen with off–center edge-crack propagation to the
specimen macroscopic crack which under the dynamic load function. And showed the whole process
of the cement mortar specimen crack propagation which under the dynamic load function, as well as
the whole field stress distribution picture, and has carried on analysis the specimen destruction
process, has pointed out the influence of the no dimension quantity a/L change to crack expansion
path and the destruction form.
Abstract: Rotating bending fatigue tests up to 108 cycles were carried out to investigate the
effects of shot peening on the fatigue strength and the fracture mechanism in an 18 % Ni
maraging steel by using shot particles of various sizes or hardness. Fatigue strength was
increased markedly by shot peening in the wide region of fatigue life. The S-N curves showed
duplex S-N properties because of the transition of fracture origin from the specimen surface in
the short life region to the subsurface in the long life one. Double shot peening by using
super-hard fine particles was effective to improve the fatigue strength for surface fracture,
though the fatigue strength for an internal fracture was hardly influenced. These results were
discussed from the points of view of effects of surface roughness, residual stress and work
hardening on the fatigue strength.
Abstract: Rotating bending fatigue tests were carried out to investigate the influence of grain size
on the resistance to crack growth of Ni-base super alloy, Inconel 718, using the materials with grain
sizes of about 20, 50,100 and 200 たm, at room temperature. The larger grain size, the smaller crack
growth rate, though the static strength was decreased with increase in grain size. The growth rate of
a small crack was uniquely determined by the term ja
na (Small crack growth law), where ja and a
are the stress amplitude and the crack length, respectively, and n is a constant. The resistance to
crack growth among materials was evaluated based on the law and showed a good correlation with
tensile strength jB, meaning that fatigue life can be predicted by using only j B BB.
Abstract: Temper embrittlement and fracture control method based on both non-equilibrium
grain-boundary segregation (NGS) theory and grain refinement technique are studied in this paper.
Grain refinement technique by deformation induced phase transformation in low-alloy steels,
12Gr1MoV and 2.25Gr1MoNb, is investigated. A single-pass hot rolling process by using a
Gleeble-1500 system is performed. Experimental results show that steel strength and toughness may
be controlled and improved by grain refinement, and that the grain sizes were affected by the
deforming temperature, strain reduction, and strain rate. According to the NGS theory, a control
method of brittle fracture along grain-boundary is proposed so that some catastrophically brittle
fracture failure may be averted. Grain refinement may decrease both the concentration of
phosphorus at grain boundaries and the critical time. With the grain refinement technique, the
temper embrittlement of steel may be improved, and the critical time may be shortened. The cost of
heat treatment for fracture control will therefore be reduced.
Abstract: When failure occurs in material, it is often occurs by fracture along some grain boundaries
and often by the micro-segregation of embrittling impurity to the grain boundaries. In the present
work, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temper
embrittlement at the same solution treatment and different isothermal holding temperature in steel
2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature
（1050 oC ）and different isothermal holding temperature (540 oC and 600 oC) are given. Experimental
results provide a direct evidence of NGS kinetic model and show that the grain boundary segregation
concentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600
oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC are
also higher than those at 600 oC. It is therefore concluded that the lower the isothermal holding
temperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and also
the higher the degree of embrittlement.