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The texture evolution of a near β-Ti alloy (Ti-55511) is investigated by hot compressive deformation experiments in β region. A visco-plastic self-consistent (VPSC) model is employed to elaborate the correlation between plastic deformation mechanisms and texture evolution. The experimental results show that the types of textures are insensitive to the deformation temperature and strain rate, while the true strain dramatically affects the type of textures. The developed textures include {001}<100>, {012}<100> and η-fiber textures. In VPSC model, the bi-plane and pencil slip modes are selectively activated to match the experimental textures at different deformation strains. With an increase in strain, there is a gradual transition in the slip mode from bi-plane slip to pencil slip. The common textures in β phase of Ti alloys are strongly correlated with the active {112}<111> slip ({112} slip) and {123}<111> slip ({123} slip) modes. Additionally, to explain the effect of initial orientation on texture formation, various initial orientations in Ti alloys are employed in VPSC simulations. The results reveal that starting with a random orientation initially promotes the formation of {110}<111>, {001}<100> and η-fiber textures, accompanied by an increase in texture intensity as the strain level increases. Moreover, {110}<110> orientation undergoes rotation leading to develop {110}<111> texture with a decrease texture intensity, while {110}<112> orientation undergoes rotation inducing {110}<223> texture with an increased texture intensity. • Texture evolution of a near β-Ti alloy is investigated by hot compressive deformation experiments in β region. • A visco-plastic self-consistent model is developed to elaborate the correlation between plastic deformation mechanisms and texture evolution. • Texture types are insensitive to the deformation temperature and strain rate, while the true strain dramatically affects the type of textures. • The common textures in β phase of Ti alloys are strongly correlated with the active {112} and {123} slip modes. • Starting with a random orientation initially promotes the formation of {110}<111>, {001}<100> and η-fiber textures. [ABSTRACT FROM AUTHOR]

Up to now, there are few reports on the yield behavior of Ni-based superalloy during plastic deformation. However, an accurate yield stress model is significant for simulating the plastic forming process by cellular automaton or finite element methods. Therefore, the yield behavior of a solution-treated Ni-based superalloy is studied by hot compression tests. In order to evaluate yield stresses from the measured flow stress curves, the yield process is analyzed in terms of dislocation theory. Then, yield stresses at different deformation temperatures and strain rates are clearly determined. The experimental results show that the yield stresses are highly sensitive to deformation temperature and strain rate. The determined yield stress almost linearly increases with the increase of the logarithm of strain rate or the reciprocal of deformation temperature. A yield stress model is developed to correlate the yield behavior of the studied solution-treated Ni-based superalloy with deformation temperature, strain rate, and strengthening effect of alloying elements. The developed model can well describe the yield behavior of the studied solution-treated Ni-based superalloy. [ABSTRACT FROM AUTHOR]

Two-stage creep-aging characteristics of an Al-Zn-Mg-Cu alloy under the extra compressive stress are investigated. The effects of the second-stage creep-aging temperature (SSCAT) and compressive stress on precipitates are discussed. It is found that the main precipitates are η′ and η phases in the two-stage creep-aged alloy. With the increase of SSCAT, the size of intragranular aging precipitates (IAPs) rapidly increases, while its density decreases. Meanwhile, the density of IAPs first increases and then decreases with the increase of compressive stress. Additionally, the grain boundary precipitates (GBPs) discontinuously distribute on grain boundaries. The size of GBPs and the width of precipitate free zones (PFZs) increase with increasing the SSCAT, and the total volume of GBPs increases with the increase of compressive stress. Moreover, the sizes of IAPs under compressive stress are bigger than those under tensile stress, while their density is relatively smaller. Furthermore, the compressive stress can effectively inhibit the growth of GBPs and the broadening of PFZs. Compared with the creep-aged alloys under tensile stress, the sizes of the GBPs are smaller, and the PFZs is narrower in the creep-aged alloys under compressive stress. [ABSTRACT FROM AUTHOR]

Two-stage stress-aging behaviors of an Al-Zn-Mg-Cu alloy are studied. The precipitates evolution during two-stage stress-aging is analyzed. It is found that the formation of precipitate nuclei mainly occurs in the first stage stress-aging. With increasing the first stage stress-aging temperature, the nuclei gradually grow up and partly transform from GP zones to η′ phases. Meanwhile, continuously-distributed aging precipitates appear along grain boundaries, and no obvious precipitate free zone can be detected. In the second stage stress-aging, aging precipitates (η′ and η phases) easily coarsen, but the density of intragranular aging precipitates highly depends on the first stage stress-aging temperature. Furthermore, discontinuously-distributed η phases appear along grain boundaries with a broadened precipitate free zone. Two-stage stress-aging processing can optimize the distribution of aging precipitates within grains and at grain boundaries. Additionally, when the external stress is enhanced, the diffusion kinetics of solute atoms could be accelerated through the interaction between dislocations and aging precipitates. Therefore, the formation and growth of stable aging precipitates are greatly promoted under large external stress. These important conclusions can be used for fabricating the complex shaped aluminum sheet components by combining both the mechanical forming process and aging treatment, such as creep-aging forming technology. [ABSTRACT FROM AUTHOR]

Generally, the obvious work hardening, dynamic recrystallization (DRX), and dynamic recovery behaviors can be found during hot deformation of Ni-based superalloys. In the present study, the classical dislocation density theory is improved by introducing a new dislocation annihilation item to represent the influences of DRX on dislocation density evolution for a Ni-based superalloy. Based on the improved dislocation density theory, the peak strain corresponding to peak stress and the critical strain for initiating DRX can be determined, and the improved DRX kinetics equations and grain size evolution models are developed. The physical framework and algorithmic idea of the improved dislocation density theory are clarified. Moreover, the deformed microstructures are characterized and quantitatively correlated to validate the improved dislocation density theory. It is found that the improved dislocation density-based models can precisely characterize hot deformation and DRX behaviors for the studied superalloy under the tested conditions. [ABSTRACT FROM PUBLISHER]

The effects of stress-aging processing on corrosion resistance of an Al–Zn–Mg–Cu alloy were investigated. It is found that the one-stage stress-aged alloy is strongly sensitive to the electrochemical corrosion. The poor corrosion resistance of the one-stage stress-aged alloy can be attributed to fine intragranular aging precipitates and continuous distribution of grain boundary precipitates. Meanwhile, the incomplete precipitation of solute atoms results in high electrochemical activity of aluminum matrix. However, when the alloy is two-stage stress-aged, the corrosion resistance is greatly improved. Furthermore, the corrosion resistance decreases firstly and then increases with increasing the first stage stress-aging temperature. Increasing external stress can enhance the corrosion resistance of the two-stage stress-aged alloy. These phenomena are mainly related to aging precipitates within grains and along grain boundaries. The coarse and relatively low-density intragranular aging precipitates, as well as the discontinuously distributed grain boundary precipitates can enhance the corrosion resistance of the stress-aged alloy. [ABSTRACT FROM PUBLISHER]

Two-stage stress-aging experiments of an Al–Cu–Mg alloy were performed over wide range of external stress. The effects of external stress on corrosion resistance of the two-stage stress-aged Al–Cu–Mg alloy are investigated by cyclic potentiodynamic polarization experiments, electrochemical impedance spectroscopy (EIS) tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. It is found that the external stress significantly affects corrosion resistance, which is ascribed to the evolution of aging precipitates. The corrosion resistance can be enhanced by two-stage stress-aging processing at the relatively low external stress. This is because the fine aging precipitates of the stress-aged alloy are more uniformly distributed than those of the as-received and stress-free aged alloys. However, the high external stress easily induces the obvious stress-orientation effects, and enlarges aging precipitates. The coarse precipitates increase the potential difference between aging precipitate and aluminum matrix, as well as the level of distortions of crystal lattice. Then, the corrosion resistance is deteriorated. Furthermore, the optimized external stress for the studied Al–Cu–Mg alloy is about 185 MPa within the tested conditions. [ABSTRACT FROM AUTHOR]

Two-stage stress-aging experiments of an Al–Cu–Mg alloy were performed. The effects of stress-aging temperature on corrosion resistance of the two-stage stress-aged Al–Cu–Mg alloy are discussed. It is found that the stress-aging temperature significantly affects corrosion resistance, which is ascribed to the evolution of aging precipitates. The aging precipitates uniformly nucleate in the first stage of two-stage stress-aging. Increasing stress-aging temperature can enhance the uniform distribution of precipitates, but precipitates easily become coarse in the second stage of two-stage stress-aging. The coarsen precipitates enlarge the potential difference between aging precipitate and aluminum matrix, and decrease the corrosion resistance. So, the corrosion resistance of the stress-aged alloy decreases with the increase of the second stage stress-aging temperature. Furthermore, the optimized stress-aging temperature is about 433 K within the tested conditions. [ABSTRACT FROM AUTHOR]

• The discrepancy of mechanical properties between ti and al layers evidences the slip bands with 45° to tensile direction in Al grains. • Morphology and/or crystallographic orientation changes in al grains of composite achieve a compatible deformation. • Heterogeneous deformation induced stress concentration facilitates the initiation of micro-crack and sequential failure at the interfacial zone. Laminated/bimetal composites can offer the advantage of combining constituent metals, but their heterogeneous microstructures exhibit different mechanical properties during subsequent remanufacturing process than those of the homogeneous counterparts. This study investigated the tensile properties, microstructural evolution and deformation behaviours of a new explosive welded TA1/5083 composite sheet using the in-situ characterisation. It is found that a wavy transition zone forms in the composite sheet, showing gradients in the element diffusion and micro-hardness adjacent to the interface. The slip bands with the tensile direction of 45° primarily occur in the 5083 side (rather than the TA1 side) with an increase in deformation. Although the dislocation density of the grains in the 5083 layer increases significantly, these grains are slightly elongated along the tensile direction without a significant orientation change. Three deformation stages and a subsequent crack initiation stage appear during the in-situ tensile process. The initiation of micro-cracks in the interfacial zone results from the internal stress concentration occurring at the bottom of interfacial wave structure. Once initial micro-cracks evolve into the intermetallic compounds (IMCs) of the interfacial zone, the high magnitude of stress concentrations of the TA1 and 5083 layers leads to necking and sequential fractures. This study can provide a reference for the design of high-quality Ti/Al composite components for industry. [Display omitted] [ABSTRACT FROM AUTHOR]

Hot deformation behaviors of a typical nickel-based superalloy are investigated by isothermal compression tests under the deformation temperature range of 920–1040 °C and strain rate range of 0.001–1 s −1 . Scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) technique and transmission electron microscopy (TEM) are employed to study the evolution of hot deformed microstructures. It is found that the fraction of low angle grain boundaries decreases with the increase of deformation temperature or the decrease of strain rate. This is related to the decrease of dynamic recrystallization degree under the low deformation temperature or high strain rate. The fraction of low angle grain boundaries shows a rapid increase at the relatively small deformation degree, and then a significant decrease due to the progress of dynamic recrystallization (DRX). The microstructural changes indicate that both continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) take place during hot deformation. However, the small fraction of low angle boundaries with 10–15° misorientation indicates that the CDRX plays a minor role on the nucleation of dynamic recrystallization. Discontinuous dynamic recrystallization (DDRX) characterized by grain boundary bulging is the dominant nucleation mechanism for the studied superalloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Corrosion resistance of Al–Zn–Mg–Cu alloy is sensitive to creep-aging processing. [•] The increase of applied stress can enhance the corrosion resistance. [•] The increased temperature first increases and then decreases corrosion resistance. [•] Discontinuous GB precipitate and narrow PFZ improve can corrosion resistance. [Copyright &y& Elsevier]

Abstract: Uniaxial tensile tests of a typical Ni-based superalloy are conducted under the deformation temperature range of 920–1010°C and strain rate range of 0.01–0.001s−1. The effects of initial δ phase (Ni3Nb) on the hot tensile deformation behaviors and fracture characteristics are discussed in detail. The results show that: (1) For the studied Ni-based superalloy with a large amount of δ phase, the flow stress curves are composed of three distinct stages, i.e., work hardening stage, flow softening stage and the final fracture stage. (2) The initial δ phase has significant effects on the deformation behaviors of the studied superalloy. δ phase can cause the obvious work hardening at the beginning of hot deformation, and then accelerates the flow softening by promoting the dynamic recrystallization with further straining. With the increase of initial δ phase, the strain rate sensitivity coefficient decreases firstly and then increases. (3) The combined effects of localized necking and microvoid coalescence cause the final fracture of specimens. The increase of initial δ phase increases the density of nucleus for the formation of microvoids, and promotes the nucleation and coalescence of microvoids. [Copyright &y& Elsevier]

The hot compressive deformation behaviors of a typical Ni-based superalloy are investigated over wide ranges of forming temperature and strain rate. Based on the experimental data, the efficiencies of power dissipation and instability parameters are evaluated and processing maps are developed to optimize the hot working processing. The microstructures of the studied Ni-based superalloy are analyzed to correlate with the processing maps. It can be found that the flow stress is sensitive to the forming temperature and strain rate. With the increase of forming temperature or the decrease of strain rate, the flow stress significantly decreases. The changes of instability domains may be related to the adiabatic shear bands and the evolution of δ phase(Ni3Nb) during the hot formation. Three optimum hot deformation domains for different forming processes (ingot cogging, conventional die forging and isothermal die forging) are identified, which are validated by the microstructural features and adiabatic shear bands. The optimum window for the ingot cogging processing is identified as the temperature range of 1010–1040°C and strain rate range of 0.1–1s−1. The temperature range of 980–1040°C and strain rate range of 0.01–0.1s−1can be selected for the conventional die forging. Additionally, the optimum hot working domain for the isothermal die forging is 1010–1040°C and near/below 0.001s−1. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low-cycle fatigue failure behaviors of hot-rolled AZ91 magnesium alloy are investigated. [•] The fatigue life increases with the increase of the strain ratio and decrease of the peak stress. [•] Increasing stress ratio and decreasing peak stress can decrease the amount of residual twins. [•] The residual twins kink with each other and deteriorate the grain boundary. [•] A modified stress-based fatigue life model is developed for hot-rolled AZ91 magnesium alloy. [ABSTRACT FROM AUTHOR]

Abstract: Uniaxial ratcheting and low-cycle fatigue failure behaviors of the hot-rolled AZ31B magnesium alloy are studied by uniaxial asymmetrical cyclic stress-controlled experiments at room temperature. The effects of mean stress, stress amplitude and stress rate on the uniaxial ratcheting response and ratcheting life of the studied magnesium alloy are analyzed. The microscopic observations near fracture surface are carried out. In addition, a fatigue parameter is introduced to describe the ratcheting damage and fatigue damage processes, and a new model is established to describe the relationship between the linear density of twins and the fatigue parameter. Results show that (1) the mean stress and stress amplitude has a great influence on the ratcheting strain and fatigue failure life. When the mean stress or stress amplitude is increased, the ratcheting strain and its rate rapidly increase. So, the fatigue failure life is reduced. (2) The increase of mean stress and stress amplitude can accelerate the generation of twins, which decreases the fatigue resistance and increases the ratcheting strain. However, the stress rate has little effect on the twinning. So, the effects of stress rate on ratcheting and low-cycle fatigue failure behaviors are not obvious under the tested conditions. This is because the studied magnesium alloy shows highly rate-independent property at room temperature within the tested strain rate range. (3) The established model can accurately describe the relationship between the linear density of twins and the fatigue parameter. Furthermore, the threshold fatigue parameter for twinning is found. [Copyright &y& Elsevier]

Abstract: Exposure of 2024-T3 Al alloy to an elastic loading, either for “creep age forming” and other manufacturing processes at relatively high temperature, may lead to the lasting creep deformation. The high-temperature creep behavior of 2024-T3 Al alloy was studied by the constant-stress uniaxial tensile creep experiments under the temperatures of 423, 448 and 473K. Constitutive models, based on the θ projection method, are established to describe the high-temperature creep behavior of 2024-T3 Al alloy. The material parameters of the established constitutive models are associated with the applied creep stress and temperature. The creep strains predicted by the proposed models well agree with experimental results, which confirm that the established creep constitutive models can give an accurate and precise estimate of the high-temperature creep behavior for 2024-T3 Al alloy. The evaluated power–law stress exponent n =3.405 and the activation energy for secondary creep Q =85.390kJmol−1 indicate that the creep processes of 2024-T3 Al alloy are controlled by the dislocation viscous glide mechanism. [Copyright &y& Elsevier]

Abstract: The uniaxial tensile creep tests of Al–Cu–Mg alloy were carried out over a wide range of temperature and applied stress. The effects of applied stress and creep aging temperature on the precipitation in Al–Cu–Mg alloy were discussed. It is found that the precipitation process is very sensitive to the applied stress and creep aging temperature, and S phase (CuMgAl2) is the main precipitate under the tested creep conditions. With the increase of applied stress and creep aging temperature, S phase easily grows up and becomes sparse. Meanwhile, the creep aging leads to the discontinuous distribution of precipitation phase in grain boundary, which can improve the corrosion-resistance of Al–Cu–Mg alloy. Because the lattice misfit of acicular exudation phase is far less than that of disk-shaped phase, the applied stress/strain fields will alert the competitive precipitation equilibrium between different strengthening phases. So, the large applied stress and high aging temperature easily make the preferential precipitation process as SSS→GPB→S″→S′→S. [Copyright &y& Elsevier]

Abstract: The dynamic recrystallization behavior in 42CrMo steel was investigated by hot compression tests. The effects of deformation temperature, strain rate, and initial austenite grain size on the dynamic recrystallization behavior were discussed. Based on the experimental results, the kinetic equations for the dynamic recrystallization behavior of 42CrMo steel were proposed. Results indicate that the effects of the deformation temperature, strain rate and initial austenitic grain size on the dynamic recrystallization behavior in 42CrMo are significant. The dynamic recrystallization in 42CrMo steel easily occurs at high deformation temperature, low strain rate and fine initial austenitic grain. A good agreement between the experimental and predicted results shows that the proposed kinetic equations can give an accurate estimate of the dynamic recrystallization behavior in hot deformed 42CrMo steel. [Copyright &y& Elsevier]

Abstract: The high-temperature creep behavior of Al–Cu–Mg alloy was studied by the constant-stress uniaxial tensile creep experiments under the temperatures of 473K, 503K and 533K. Constitutive models for describing the high-temperature creep behavior of Al–Cu–Mg were established based on the θ projection method. The material parameters of the established constitutive models are associated with applied creep stress and temperature. Results show that a good agreement between the experimental and predicted results is obtained, which confirms that the established creep constitutive models can give an accurate and precise estimate of the high-temperature creep behavior for the studied Al–Cu–Mg alloy. Additionally, the specimens at 533K failed by the intergranular creep fracture. [Copyright &y& Elsevier]

Abstract: The metadynamic recrystallization behaviors in deformed 2124 aluminum alloy were investigated by isothermal interrupted hot compressive tests, which were carried out at the deformation temperatures of (653–743) K, strain rates of (0.01–10) s−1 and inter-stage delay time of (30–180) s. A new approach, “peak stress method”, is proposed to calculate the softening fractions induced by the rapid metadynamic recrystallization. The kinetic equations were developed to predict the metadynamic recrystallization behaviors in hot compressed 2124 aluminum alloy. Both the experimental and predicted results show that the effects of deformation parameters, including strain rate, deformation degree and temperature, on the softening behaviors in the two-pass hot compressed 2124 aluminum alloy are significant. A good consistency between the experimental and predicted results indicates that the proposed kinetic equations can precisely estimate the softening behaviors and metadynamic recrystallization kinetics of the hot compressed 2124 aluminum alloy. [Copyright &y& Elsevier]

Abstract: In industrial forming processes, the metals and alloys are subject to complex strain, strain-rate, and temperature histories. Understanding the flow behaviors of metals and alloys in hot working has a great importance for designers of metal forming processes. In order to study the workability and establish the optimum hot formation processing parameters for some metals and alloys, a number of research groups have made efforts to carry out the thermo-mechanical experiments (compressive, tensile and torsion tests) over wide forming temperatures and strain-rates, and some constitutive equations were developed to describe the hot deformation behaviors. This paper presents a critical review on some experimental results and constitutive descriptions for metals and alloys in hot working, which were reported in international publications in recent years. In this review paper, the constitutive models are divided into three categories, including the phenomenological, physical-based and artificial neural network models, to introduce their developments, prediction capabilities, and application scopes, respectively. Additionally, some limitations and objective suggestions for the further development of constitutive descriptions for metals and alloys in hot working are proposed. [Copyright &y& Elsevier]

Abstract: Polymer-based conductive adhesive materials have become widely used in many electronic packaging interconnect applications. Uniaxial ratchetting behavior of anisotropic conductive adhesive film (ACF) was studied by uniaxial cyclic tension experiments. The effects of mean stress, stress amplitude and loading history on the ratchetting response of ACF material were analyzed. Results show that (1) the ratchetting strain amplitude and ratchetting strain rate of the ACF material increase with increasing stress amplitude or mean stress; (2) the ACF material has a strong memory of loading history. Prior stress cycling with higher mean stress or stress amplitude restrains the ratchetting strain in subsequent cycling with lower mean stress or stress amplitude. Prior stress cycling with higher stress rate will accelerate the plastic deformation of subsequent cycling with lower stress rate for the ACF material. [ABSTRACT FROM AUTHOR]

Abstract: The compressive deformation behaviors of 2124-T851 aluminum alloy were investigated over a wide range of temperature and strain rate on Gleeble-1500 thermo-simulation machine. The results show that the true stress–true strain curves exhibit a peak stress at a very small strain, after which the flow stresses decrease until high strains, showing a dynamic flow softening. The measured flow stress was modified by friction correction, and the corrected flow stresses are lower than the measured ones, which nicely reflect negative effects of the interfacial friction on the flow stress. A revised model is proposed to describe the relationships of the flow stress, strain rate and temperature of 2124-T851 aluminum alloy at elevated temperatures. The stress–strain values of 2124-T851 aluminum alloy predicted by the proposed model well agree with experimental results, which confirmed that the revised deformation constitutive equation gives an accurate and precise estimate for the flow stress of 2124-T851 aluminum alloy. [ABSTRACT FROM AUTHOR]

Abstract: Based on the experimental results from the hot compression tests of 42CrMo steel, the efficiencies of power dissipation and instability parameter were evaluated. The effects of strain on the efficiency of power dissipation and instability parameter of 42CrMo steel have been discussed in detail. Processing maps were constructed by superimposition of the instability map over the power dissipation map. The dynamic recrystallization domains and instable zones were identified in the processing map. The effects of strain on microstructural evolutions were correlated with the processing maps. According to the 3D processing maps, the optimum domain of hot deformation is in the temperature range of 1050–1150°C and strain rate range of 0.01–3s−1, with its peak efficiency of 32% at about 1140°C and 0.23s−1, which are the optimum hot working parameters. [Copyright &y& Elsevier]

Abstract: Dynamic recrystallization mathematical models of 42CrMo steel were derived based on the experimental results. The effects of deformation temperatures on the strain/stress distribution and microstructural evolution of 42CrMo steel during hot upsetting process were simulated by integrating the thermo-mechanica1 coupled finite element model. The results show that the distributions of the strain/stress and dynamic recrystallization grain sizes are inhomogeneous. The average volume fraction of dynamic recrystallization increases with the increase of deformation temperatures. The average dynamic recrystallization grain sizes become fine when the deformation temperatures decrease. A good agreement between the predicted and measured average grain sizes was obtained. [Copyright &y& Elsevier]

Abstract: In this research, we studied the effect of deflection on the characteristics of an indium tin oxide (ITO) film deposited on a flexible polyethylene terephthalate flexible substrate by pulse magnetron sputtering. The experimental results show that an increase in the ITO film thickness leads to an increase in the residual stress and a decrease in the adhesion. Under power of 80 W, pulse frequency of 10 kHz, pulse reverse time of 2 μs, and ITO film thickness of 100 nm, thin film with an optimized resistivity of 4.5×10−4 Ω-cm, visible light transmittance of more than 84%, and adhesion of class 5B/0 as per the ASTM/ISO standards. Micro-cracking was observed on the ITO film surface when the film thickness was greater than 100 nm and when the deflection was carried out for 100 times. Micro-cracking led to an increase in the residual stress and deterioration in the adhesion properties. [Copyright &y& Elsevier]

Abstract: In order to study the workability and establish the optimum hot forming processing parameters for 42CrMo steel, the compressive deformation behavior of 42CrMo steel was investigated at the temperatures from 850°C to 1150°C and strain rates from 0.01s−1 to 50s−1 on Gleeble-1500 thermo-simulation machine. Based on these experimental results, an artificial neural network (ANN) model is developed to predict the constitutive flow behaviors of 42CrMo steel during hot deformation. The inputs of the neural network are deformation temperature, log strain rate and strain whereas flow stress is the output. A three layer feed forward network with 12 neurons in a single hidden layer and back propagation (BP) learning algorithm has been employed. The effect of deformation temperature, strain rate and strain on the flow behavior of 42CrMo steel has been investigated by comparing the experimental and predicted results using the developed ANN model. A very good correlation between experimental and predicted result has been obtained, and the predicted results are consistent with what is expected from fundamental theory of hot compression deformation, which indicates that the excellent capability of the developed ANN model to predict the flow stress level, the strain hardening and flow softening stages is well evidenced. [Copyright &y& Elsevier]

Abstract: The mechanical integrity of in-service pressure piping is a matter of great importance for both economical and safety reasons. Considering the uncertainties in various internal operating loadings and external forces, flaw sizes, material properties, this paper presents a probabilistic assessment methodology for in-service pressure piping containing defects, which is especially designed for programming. A general sampling computation method of the stress intensity factor (SIF), in the form of the relationship between SIF and axial force, bending moment and torsion, is adopted in the probabilistic analysis methodology. Based on the European flaw assessment procedure, SINTAP, Integrity Assessment Expert System of In-service Pressure Piping Containing Flaws (IAESPP-SINTAP) is developed using the presented probabilistic methodology. A numerical example is given to show the application of IAESPP-SINTAP software. The failure probabilities of every defect and the whole piping can be obtained by using this software. [Copyright &y& Elsevier]

The reliability of pressure piping containing defects is important in engineering. The failure probability of pressure piping containing defects may be used as a guide to the most economic deployment of resources on maintenance, inspection and repair. This paper presents a probabilistic assessment methodology for in-service pressure piping containing defects, which is especially designed for programming. It is based on three assessment codes, BS 7910, R6 and SAPV-99, considering uncertainties in operating loadings, flaw sizes, material fracture toughness and flow stress. A general sampling computation method of stress intensity factor (SIF), in the form of the relationship between SIF and axial force and bending moment and torsion, is adopted. This relationship has been successfully used in developing software, Safety Assessment System of In-service Pressure Piping Containing Flaws (SAPP-2003), to assess planar and non-planar flaws. A numerical example is presented to illustrate the application of SAPP-2003 for calculating the failure probabilities of separate defects and for the assessed pressure piping. [Copyright &y& Elsevier]

For cracked structural rectangular thin-walled tubes, an exact and very simple method to determine the stress intensity factors has been proposed based on a new concept of crack surface widening energy release rate. Unlike the classical crack extension energy release rate, the crack surface widening energy release rate can be expressed by the G*-integral and elementary strength theory of materials for slender cracked structures. From present discussions, a series of new and exact solutions of stress intensity factors are derived for cracked rectangular and square tubes. The present method can also be applied to cracked polygon thin-walled tubes. [Copyright &y& Elsevier]

Total strain-controlled low cycle fatigue (LCF) tests of a nickel based superalloy were performed at 650 °C. Various hold times were introduced at the peak tensile strain to investigate the high-temperature creep-fatigue interaction (CFI) effects under the same temperature. A substantial decrease in fatigue life occurred as the total strain amplitude increased. Moreover, tensile strain holding further reduced fatigue life. The saturation phenomenon of holding effect was found when the holding period reached 120 s. Cyclic softening occurred during the LCF and CFI process and it was related to the total strain amplitude and the holding period. The relationship between life-time and total strain amplitude was obtained by combining Basquin equation and Coffin-Manson equation. The surface and fracture section of the fatigued specimens were observed via scanning electronic microscope (SEM) to determine the failure mechanism. [ABSTRACT FROM AUTHOR]