A simplified method was proposed for predicting the threshold value of small fatigue cracks, which is based on the concept of the cyclic resistance-curve (R-curve) method. In this simplified method, the resistance curve can be determined by using only one material data, either the hardness or the tensile strength. The threshold condition of crack initiation was given by the constant value of the effective stress intensity range, which is assumed to be equal to the threshold value for long cracks. The threshold value of the crack opening stress intensity factor was formulated as a function of the hardness, the applied stress and the amount of crack extension. The fatigue limits for the crack initiation and the fracture and the length of arrested crack were predicted. The predicted values agreed well with the experimental results.

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The fatigue crack propagation behavior from a tesile pre-crack under cyclic torsion combined with static or cyclic axial loading was predicted on the basis of the maximum tangential stress criterion. The prediction was compared with the experimental results obtained for a medium carbon steel. The direction of fatigue crack propagation follows the direction of the maximum of the total range of the tangential stress, Δσ_<θmax> near the crack tip and then gradually changes to the direction perpendicular to the maximum of the total range of the principal nominal stress. The mode II stress intensity factor range ΔK_<II> quickly gets close to zero after small amount of crack extension. The propagation rate was faster than the uniaxial data as cracks extended a long distance.

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This paper covers investigations of the effect of mean stresses normal to the crack plane on fatigue damage in uniaxial and torsional fatigue and of the effect of near yield stress overloads on fatigue damage in uniaxial and biaxial fatigue at various strain ratios. For uniaxial fatigue the results showed that the effective stress range at the fatigue limit was the same for all mean stresses. The fatigue limit stress range decreased linearly with increasing mean stress and crack opening stress until the point at which the crack opening stress fell below the minimum stress and the crack remained open. Then the fatigue limit stress range remained constant. A similar linear decrease of shear stress range, at a given fatigue life, with increasing mean stress normal to the crack was observed up to the mean stress at which the crack remained open. Again there was no further decrease in stress range beyond this point. Tests, in which overloads were inserted between smaller constant amplitude small cycles frequently enough to result in cracks that remained open at various biaxial strain ratios, resulted in strain-life curves identical to those obtained when high mean stresses were used to maintain open crack growth.

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It was verified that anodic polarization method is suitable to evaluate the sensitization degree of the stainless steel at passive region. Heat treated weldment and parent metal is more sensitized compared with the weldment and parent metal. Specially, heat treated weldment at 730℃, 4 hr holding time and cooling in furnace is most sensitized. Unstable passive film for the heated treated weldment was formed because of the Cr depleted zone at passive region. In case of the parent metal, time to failure in synthetic seawater is longer than that in air. However, time to failure for the weldment and heat treated weldment in synthetic seawater is shorter than that in air. In case of the heat treated weldment, corrosive damage is the most greatest among other specimens.

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The mechanisms of crack growth of pre-cracked materials under cyclic torsion with static axial load were investigated using 4340 steel, 1050 aluminum and polycarbonate. In the case of 4340 steel, branching of the main crack was observed. The length of the crack between the first branching points was dependent on the loading conditions, and it was found that friction between the crack surfaces prevented shear mode crack growth. Micro-cracks, which initiated in front of the main crack, were a factor in branching of the main crack. The initiation of micro-cracks was also observed in 1050 aluminum, though the main crack did not branch. The main crack in 1050 aluminum propagated by shear mode in all stages of crack propagation. It is well known that the crack growth behavior under cyclic load is related to the slip systems of the materials. To confirm the effect of the crystal structure on the crack growth mechanisms, the crack propagation behavior of a polycarbonate specimen, which is a non-crystalline material, was also investigated. From these observations, it was found that shear mode crack propagation is influenced by not only the crystal structure, but also the friction between crack surfaces.

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Recently studies concerning strength evaluation of very thin plates of metallic materials have become more important for safety design.Thin plates of metallic materials are applied to safety bursting rupture discs. A test specimen was made from bursting rupture discs of copper plate. Experiments were conducted using three shapes(disc, dome or annealed dome). The fatigue life was examined by test specimens of six materials (copper, aluminum, nickel, monel, inconel and stainless steel) for flat bursting rupture disc. The effect when excess cyclic pressures were generated and repeated numerous times was examined in stainless steel, and a very interesting result was obtained.

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This paper presents results from an experimental and numerical study on generating triaxial residual stresses in stainless steel. The residual stresses were introduced by water quenching of spheres and cylinders. A series of finite element simulations were carried out to determine how process conditions and dimensions of solid cylindrical bars and spherical balls influence the residual stress distributions. The results show that high compressive residual stresses occur around the surfaces of the cylinders and spheres. Near the centre of the samples the residual stresses are tensile. Spray water quenching experiments were conducted using solid cylinders and spheres of a stainless steel. The temperature during quenching compared well with the finite element simulations. Surface residual stresses were measured using the incremental centre-hole technique. Overall there is good agreement between the predicted and measured residual stresses. However, the level of triaxial stress is found to be sensitive to heat transfer coefficients. By controlling the cooling conditions and changing the dimensions of the steel samples differing triaxial residual stress states can be achieved in a controlled manner. This differs from other processes, such as welding, and shot peening, where the magnitudes and distributions of residual stresses are ill defined and the volume of material subjected to triaxial residual stresses is relatively small.

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The authors have proposed an analytical model to simulate the low cycle fatigue behavior of a degraded pipe against excessive seismic loading. A series of elasto-plastic analyses have been carried out in order to investigate the experimental behaviors of degraded elbows. It has been shown that the ovaling, ratcheting, buckling, and leak behaviors of locally thinned elbows can be simulated well by the proposed method.

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This method is based on data collected during previous expertise done on similar products. The objective is to predict reservoir and tube useful life and wall thickness using a minimum of field measurements. The method was initially developed for non-destructive inspection such as radiography and ultrasound. It can be described in eight steps: 1) Assessment of degradation severity 2) Determination of inspection method 3) Initial sample size calculation 4) Field testing 5) Results analysis 6) Probability and reliability calculations 7) Useful predictions and degradation pattern 8) Results presentation. Steps 4 to 7 can be recomputed to get a better confidence index. This method is fully computerized. Calculation and results presentation are customized based on a questionnaire fill by the project engineer.

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The author has investigated the subsurface crack growth of silicon nitride ball bearings from the view of fracture mechanics. It was discovered that the stress fields caused by the spherical Hertzian contact fulfill the mechanical conditions of a plate subduction boundary, and also that crack growth under rolling contact fatigue simulates the behavior of plate subduction boundary. Great similarities are found between the earthquake faults and subsurface cracks under rolling contact fatigue. In this paper the similarities are explained and the features of crack growth are described from the viewpoint of mechanics in earthquakes. Especially, based on the similarities, the mechanical relations between intraplate earthquakes and interplate earthquakes are explained.

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A series of 2-dimentionally randomaramid short fiber (AsF) FRP laminates have been prepared with a range of fiber fraction volume by reinforcing unsaturated polyester (UP) resin with aramid short fiber (3mm) sheets . Tensile, compressive and three-point bending test of aramid short fiber FRP laminates have been performed to study the mechanical behaviour on the fracture energy of the materials. It is expected that mechanical properties of the laminate may be much improved than directly reinforced FRP composite. On the other hand, its compressive strength is still unsolved. And the compressive destructed behavior is still not made clear even now. Originally, the difference between tensile strength and compressive strength is caused by the difference between their destructive mechanisms. The destruction will be completed in only a moment. It is difficult to get a detailed observation on the process of destruction because of the influence of test jig. And up to now, the reliable value of fracture energy of aramid short fiber FRP laminates has not been gotten. Therefore, we served our purpose of the research as the effect of fracture behaviour on the energy absorption properties of aramid short fiber sheet FRP laminate. Reasonable agreement has been achieved between the predictions and available experimental data.

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Fracture tests under the mixed I, II and III mode conditions with different mode ratios have been carried out, by adopting cylindrical notched specimens and introducing the initial crack by a cyclic axial loading. A special jig has been developed so that any mode ratio can be obtained by tensile and torsion loadings. Based on the effective maximum strain energy release rate and the experimental results, the fracture criterion of a crack under mixed I, II and III modes has been proposed. It is found that the fracture direction can be well predicted by the effective maximum strain energy release rate, and the fracture occurs when the effective maximum strain energy release rate reaches the fracture toughness G_C, which is related to K_<IC>. The relationship between K_<IC> and K_<IIIC> for a homogenous material has also been clarified theoretically and experimentally. Through the comparison of the elliptical criterion and the criterion proposed in this study, it is found that the experimental results agree better to the criterion based on the effective maximum strain energy release rate. Moreover, the criterion proposed is continuous with the σ_<θmax> criterion for the mixed I and II modes condition, and also contains the pure mode fracture criterion.

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The objectives of the present study were: (1) to investigate the influence of phase difference between combined axial and torsional loading on the fatigue strength of steel containing small defects, and (2) to develop a unified method for fatigue strength prediction for such loading conditions. The mat e-rial investigated was an annealed 0.37% carbon steel. As an artificial defect, a drilled hole of either 100μm or 500μm in diameter was introduced into round-bar specimens. Combined axial and torsional fatigue tests were performed at R=-1 under in-phase or 90° out-of-phase loading condition. Non-propagating cracks emanating from holes were observed at fatigue limit. On the assumption that the fatigue limit is determined by the threshold condition for propagation of a small Mode I crack, a single criterion was proposed, which accounted for the determination of the fatigue strength, regardless of phase difference of combined stresses . Under out-of-phase combined loading, a crack initiated at a hole is subjected to Mode I loading as well as Mode II loading with a 90° phase difference. The threshold level was slightly influenced by the Mode II loading.

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Two approaches were investigated for evaluating unreliability functions of failure events in steam turbine components. One is the parameter normalizing approach to establish the unique relationship between normalized hours or normalized cycles and unreliability for various classes of steam turbine output capacity. Another is the parameter adjustment approach to seek modifying coefficients as the functions of steam turbine design parameters for evaluating the specific unreliability functions from the common master curve. The cumulative hazard function method is applied to evaluate the actual field data fittings of those approaches for turbine rotor bowing and nozzle erosion events respectively. The data fittings through those approaches are good enough to apply the probabilistic risk analysis in the case of small sample size or number of units in the objective type of steam turbines. This procedure is applied in the PC based risk-based maintenance (RBM) system for practical utilization.

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We have examined reliability in the case of applying cables to a steering system which transmit steering torque to front wheel. As a current automobile steering system is constructed by a column shaft, an intermediate shaft and universal joints between a handle and a steering gear box, the shaft's reliability is ensured by ordinal mechanical design method. However, it is difficult to design cables by using the ordinal mechanical design method. After we clarified the subject in the case of applying the cable to front steering, we proposed the new structure of the cables. And we confirmed an ability to ensure the reliability by an ordinal mechanical design method by using the S-N diagram which is delivered from fatigue test of the new cables. As a first step, the reliability of cable was evaluated by FTA method. Then, the main factors controlling the reliability of cable system was made clear to be wear fatigue behavior of cable which contact with pulley. Therefore in this paper, fatigue behavior of cable used in the abovementioned front steering system was investigated, especially in relation to the wear characteristics of cable material. Fatigue tests were conducted under the condition of loading torque of 29.4 Nm using cable made of SWRH62A covered with plastic coating filled oil inside of coating. From these experiments, degradation behavior of cable made of SWRH62A under repeated bending fatigue condition was investigated, and effect of amount of oil supply upon wear behavior of was examined. As a result, acceleration fatigue damage by wear was indicated in the cable especially under insufficient oil supply conditions.

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Monotonic four-point bending tests were conducted using tee pipe specimens having local wall thinning. The effects of local wall thinning on the fracture behaviors of tee pipe were investigated. Local wall thinning was machined on the inside of pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area were l=100 mm in eroded axial length, d/t=0.5 and 0.8 in eroded ratio, and 2θ=90° in eroded angle. The area undergoing local wall thinning was subjected to either tensile or compressive stress. Fracture behaviors of the tee pipes were compared with those of straight pipes. It was found that fracture type could be classified into ovalization, local buckling, and crack initiation, depending on pipe shape, eroded ratio, and stress at the eroded area. Three-dimensional elasto-plastic analyses were also carried out using the Finite Element Method, which is able to accurately simulate fracture behaviors.

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A new damage-diagnosis system for gas turbines has been developed. One of the features of the system is a method of evaluating damage to the hot-gas-path components of gas turbines. The relationship between sensor signals installed in the gas turbine and the thermal boundary conditions of the hot-gas-path components was established. The local stress, strain and temperature of the components under operational conditions was calculated using finite element analyses within the framework of the experimental design. Damage induced by creep/thermal fatigue of the hot-gas-path components was accurately evaluated in real-time using sensor signals, and taking the variations that occur in real operating conditions into account. The use of our system to evaluate damage to a first-stage blade is described. The results of damage-diagnosis of the blade calculated using the system are compared with field data collected during in-service inspections.

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In order to characterize small mode III crack growth torsional fatigue tests were done using circumferentially notched prefatigue-cracked specimens. The change of the shape of hysteresis loop during crack growth was monitored in terms of two wire strain gauges mounted on the surface perpendicularly across the notch. Then, the change of compliance during fatigue crack growth was evaluated in terms of the hysteresis loop. Regarding to characteristic growth behavior of the small mode III fatigue crack, the small crack first grew in the coaxial plane. Then it gradually changed growth plane out of that coaxial plane. Finally the crack was propagated in the direction 45° inclined to the cross sectional plane. That means, the change of three dimensional crack plane was found to correspond to so-called factory roof pattern, common at the first stage of fatigue crack growth from the notch root in torsional fatigue condition. The fatigue crack growth rate varied in accordance with that mode change of small crack growth. In addition, the crack growth rate was considerably affected by the friction force acting on the crack surface. Increasing crack length in mode III crack growth condition decelerated the crack growth, which reflected increase in friction force. The change of compliance during crack growth was found suitable for estimating the effect of the friction force on crack growth rate. In lower ΔKeff region, the friction force was successfully characterized using a parameter of compliance. In case of large scale yielding condition, ΔJeff parameter including the effect of friction force-generated increase of torque was found to be a suitable parameter to estimate crack growth rate. The friction force acting on the unit area of crack plane was constant, irrespective of crack length and loading condition.

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The fatigue crack growth test under mode II dominant condition is conducted. It is found that the crack growth direction can not be predicted by the conventional method. By the fracture surface observation, it is also found that the three dimensional effect strongly affects this behavior. Three dimensional elastic-plastic FEM analyses are conducted for this problem considering the Bauschinger effect. The change of the crack tip field during fatigue crack growth is studied. The criteria to predict the fatigue crack growth direction is studied and a new criteria is discussed.

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Research work has been performed to determine the influence of the multiaxial stress state on failure especially in the creep range: the failure time and creep damage development of both multiaxial loaded specimens as well as component tests have been compared with standard uniaxially loaded creep specimens. It could be demonstrated that multiaxial stress state influences creep damage development, failure time and creep deformation capacity. For design purposes the influence of multiaxiality especially on creep strain limits could be described by using multiaxiality factors.

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The structural components used in power generating plants sometimes fail due to the corrosion fatigue. The corrosion fatigue cracks often initiate from the pits. In order to prevent the corrosion fatigue failure, 13Cr stainless steel is employed for the components used in the corrosive environments. Even if employing 13Cr stainless steel, the components failed by the fatigue and the corrosion pits were observed at the origins of fatigue cracks. In this study, the effect of surface finishing on the generation of corrosion pits was investigated using 13Cr stainless steel. The corrosive environment is pure water with chloride ion concentration. The initiation and growth of the corrosion pits are remarkably affected by the chloride ion concentration. So-called "One-third rule" was obtained and the aspect ratio, that means the ratio of pit depth to size on the surface, was estimated as about 1/4. The surface finishing affected the initiation and growth of corrosion pits. Especially they are reduced when the surface was finished to the mirror-like surface by the emery paper polishing. The fatigue tests were conducted in air at the ambient temperature and in de-oxygenated water at 463K. The fatigue strength decreased with the increasing the corrosion pits. The reduction of fatigue strength can be explained by the short crack theory. On the other hand, all the fatigue cracks initiated from the corrosion pits in the high temperature water. The surface observation of test specimens suggested that the corrosion pits were mainly originated from the manganese sulfide. This indicates that the corrosion fatigue strength could be improved by controlling the chemical compositions and the impurity atoms.

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At a tee junction point of piping system, hot water and cold water is mixed with each other in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on an inside surface of the pipe just after the connection point. The temperature fluctuation yields a cyclic thermal stress near the pipe surface and results in the crack initiation. In the previous study the thermal fatigue tests using disk specimens in simulated BWR environment were performed and the thermal fatigue crack initiation strength was compared with the mechanical fatigue strength. Furthermore the thermal fatigue crack arrest depth was analyzed using the linear fracture mechanics, and the arrest depth was found to be in proportion to the reciprocal root of the frequency of temperature fluctuation, and the experimental results agreed well with the analysis. In this study, the thermal stress distributions in the disk specimen were analyzed using the finite element method, and the thermal fatigue crack initiation behavior, the crack growth and the arrest behavior are discussed.

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The fatigue crack growth mechanism under Mode II and Mode III loadings and the threshold stress intensity factor ranges, ΔK_<IIth> and ΔK_<IIIth>, were investigated on an annealed 0.47% carbon steel (JIS S45C). The dependency of ΔK_<IIIth> on crack size was also investigated. The layers of microstructural change were observed in the vicinity of Mode II and Mode III fatigue cracks. The Vickers hardness of the layers was much higher than that of the original matrix (Mode II: HV=196→629, Mode III: HV=175→438). The layers consisted of very fine grains (Mode II: 102nm, Mode III: 64nm). Thus, the mechanism of Mode II fatigue crack growth is presumed to be essentially identical to that of Mode III fatigue crack growth. The Mode III fatigue crack growth threshold ΔK_<IIIth> had a dependency on crack size. For the large crack size, √<area>_p &ap; 4900μm, ΔK_<IIIth> (9.6 MPa√<m>) was higher than ΔK_<Ith> (7.8 MPa√<m>) and the factory roof morphology was formed after ΔK_<III> reached ΔK_<IIIth>. For small cracks of √<area>_p < 1000μm (√<area>_p &ap; 450 and 140μm), ΔK_<IIIth> (8.2 and 5.2 MPa√<m>) were approximately equal to ΔK_<Ith> (7.3 and 5.0 MPa√<m>, respectively), and the factory roof morphology was formed after ΔK_<III> reached ΔK_<IIIth>.

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The performance of repair welds on service-aged 2.25Cr-1Mo header using SMAW with post weld heat treatment was evaluated. The creep rupture strength of the repair-welded specimen was almost same as that of the new weldment and repair-welding extended the remaining life of service-aged component under creep condition. In creep-fatigue test with strain holding, the fully repair-welded specimen showed almost the same creep-fatigue life as that of the new weldment, however, the partially repair-welded specimen showed shorter creep-fatigue life. FEM analysis revealed that the deformation behavior of repair-welded specimen was quite different from that of new weldment and strain concentrated on softened aged metal.

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A simulation method for multi-site creep damage at the fine-grain heat-affected zone of welds involving high energy piping consisting of low alloy steel was proposed on the basis of the combination of elastic-creep FEM analysis and random fracture resistance modeling of the materials. First, the initiation and the growth driving forces of small defects taking into account the dependence on stress and temperature were concretely determined based on microscopic observation of the damage progress of the material. Then, a simulation procedure combining the stress distribution from elastic-creep FEM and the random fracture resistance model was proposed, and this procedure was applied to the simulation of the microscopic damage progress in a welded joint model test and in actual power piping. The results in terms of the simulated number density of small defects throughout the wall thickness matched well with the observed results.

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The boiling water reactor (BWR) includes many internals with complex welded parts. It is necessary to develop an in-service inspection rule for the internals based on fracture mechanics concepts. In this paper, the stress intensity factors of a surface crack in a pipe penetrating a thick plate with a stub tube were estimated. This geometry was chosen to model the control rod drive housing in a Boiling Water Reactor. Numerical and simplified methods were applied for the calculation of the stress intensity factors. The simplified methods were developed for the geometry of pipes and plates and gave comparable results to the numerical methods in some cases. In other cases the stress intensity factors estimated by the simplified methods were higher than by the numerical methods. To decrease the conservatism for the simplified method, a modification factor obtained by two-dimensional numerical analysis was proposed. By using the modification factor, the simplified methods gave close results to the numerical method.

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The mechanism of a disk cracking in a low-pressure steam turbine was investigated by finite-element and fracture mechanics analysis and, based on the results of the investigation, a life assessment method was derived. The disk cracking was found to be caused by growth of corrosion pits, superposition of multiple vibration modes, and an increase in the standard deviation of the natural frequency of grouped blades after long-term operation. Taking these findings into consideration, the authors then developed a life-assessment method for disk cracking composed of evaluations of (1) maximum corrosion pit size at the current situation, (2) corrosion pit growth after a certain term, and (3) failure-occurrence ratio for the estimated corrosion pit depth. Maximum corrosion-pit size is evaluated by extreme value statistical analysis using the data obtained by replica inspection. The failure-occurrence ratio is evaluated by Monte Carlo simulation considering two uncertainties, namely, the standard deviation of the natural frequency of grouped blades and the stimulus ratio. The values of both uncertainties were determined by the inverse problem analysis of the disk cracking. In light of these results, the authors found that replacing conventional tenon-shroud grouped blades with continuous-cover blades is effective from the view point of vibratory behavior.

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Fatigue tests of crack propagation from a circular notch in thin-walled tubular specimens made of a stainless steel (SUS 316NG) were performed under cyclic torsion with and without superposed static and cyclic axial loading. The propagation path of mode I fatigue cracks followed the direction perpendicular to the maximum direction of the total range of the normal stress. The propagation rate was faster than the uniaxial data when compared at the same range of the stress intensity factor or the effective stress intensity factor. The negative nonsingular stress induced excessive plasticity ahead of the fatigue crack, which accelerated the fatigue crack. The J-integral range was estimated from the relation between the torsional load and the crack center opening displacement which was obtained by a specially designed extensometer. The J-integral range was proved to be an appropriate parameter for crack propagation with excessive plasticity under combined loading.

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In this paper, materials aging and structural reliability are considered in the context of life-cycle engineering and management of engineered systems. The quality of assessments of structural reliability depends largely upon the accuracy in estimating the evolution and distribution of damage that result from materials aging (e.g., corrosion and cracking). For these estimates, a more robust predictive approach must be adopted to rely upon science based modeling that captures the influences of both external (e.g., loading) and internal (e.g., microstructural) variables. The approach is contrasted against the more traditional parametrically based statistical approaches that are in use. The proposed approach and its efficacy are illustrated through examples on corrosion and corrosion fatigue of airframe aluminum alloys, the linkage between crack growth and S-N response in fatigue and oxygen enhanced crack growth in nickel-based superalloys.

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The paper describes methods to characterise creep, fatigue and creep fatigue loading for modern martensitic steels used in advanced fossile fired power plants. To increase efficiency of fossile fired power plants the process parameters, in particular the temperature, have been increased more and more. There is a strong need to know the long time behaviour of materials and weldments in components. Numerical models based on unified constitutive equations developed by Chaboche and Ohno and Wang are used as well as conventional creep laws. Special emphasis is put on the modelling of different material properties in the different zones of a weldment (heat affected zones, weld metal and base metal) in order to describe stress redistribution, strain and damage behaviour and failure location. Feature tests with hollow cylinder, spinning cylinders as well as component tests on pipes and T-pieces partly containing welds are simulated in order to support the development of DBA methods and lifetime assessment methods for components including weldments.

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Austenitic stainless steel pipes made by centrifugal casting have been used as burner material for heat-treatment furnaces and other industrial furnaces. This material has a high heat resistance, but brittle fracture can occur earlier than expected. Brittle fracture may start in the final solidification layer with micro cavitated structure formed on the inner surface of centrifugally cast pipes during manufacturing. In the present study, the strength of the specimens of an austenitic stainless steel machined from centrifugally cast pipes was studied with attention to the final solidification layer on the inner surface of the pipe. The strength decreased with increasing area of the final solidification layer. In order to predict the fracture strength of pipes with solidification layers under a variety of yielding scales, two-parameter method was proposed based on the combination of the stress intensity factor criterion and the gross sectional yielding stress criterion.

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The durability, especially the fracture and fatigue characteristics, of smart materials including Ni-Ti-based shape memory alloys (SMAs) and piezoelectric ceramics, is presented. It is shown that these materials may suffer degradation in toughness, which must be duly considered in their intended applications. Composite structures with embedded superelastic SMA wires can be properly designed and fabricated in order to enhance their impact damage resistance against delamination and fibre breakage. Smart composite patches using SMA wires may also be used to repair cracked structures and hence control crack growth. Theoretical modelling and calculations for the design of such patches are given. Similarly, applications and analyses of piezoceramic wafers for shape and vibration control of structures, and piezo-electric active fibres for the arrest of crack growth in composites laminates using controllable closure stresses are illustrated. Finally, an artificial damage detection system and methodology for delamination and hole-type damages in composites structures is discussed and examples are given to demonstrate its applicability and usefulness.

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The behavior of nanostructured materials/small-volume structures and biological/bio-implantable materials, so-called "nano" and "bio" materials, is currently much in vogue in materials science. One aspect of this field, which to date has received only limited attention, is their fracture and fatigue properties. In this paper, we examine two topics in this area, namely the premature fatigue failure of silicon-based micron-scale structures for microelectromechanical systems (MEMS), and the fracture properties of mineralized tissue, specifically human bone.

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The present paper reviews some recent developments of the measurements of micro- and macro-stresses by diffraction using X-rays, synchrotron and neutrons especially in Japan. These three methods are based on the same principle of the diffraction of crystals, and have different advantages. The conventional X-rays detect the stress very near the surface, while the neutron diffraction takes the stress in the interior of the materials. High-energy X-rays from synchrotron sources have the penetration depth in between and are suitable for the measurement of subsurface stresses. After describing the developments of the fundamentals of the methods, the paper covers the recent applications of the diffraction methods to the residual stress analysis in textured thin films, the nondestructive determination of the subsurface distribution of residual stress in shot-peened materials, local stress measurements near the crack tip, the stress measurements of single crystals, micro- and macro-stress measurements in composites, and the determination of the internal distribution of the residual stress in welding joints.

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