Bauschinger Effect Of Material Research Articles

Study on the minimum transverse impact toughness required to resist cracking of non-API high grade steel casing

Abstract In Tarim oilfield of China, the non-API high grade steel casing (HGSC) is frequently used as the intermediate and production casing in ultra-deep well with true vertical depth (TVD) more than 6000 m. So far, no internationally accepted standard has been established for non-API high grade steel casing (HGSC) presently, although some obvious shortcomings exist, such as sensitivity to crack defects and service environment, so that the fracture failure accidents of non-API HGSC happens frequently in Tarim oilfield. Here, firstly, this paper deduces the unified algorithm of burst pressure of non-API HGSC based on twin shear unified strength theory and bilinear hardening model, which takes strain-hardening, Bauschinger effect of material and effect of intermediate principal stress into consideration. Secondly, the burst pressure formula of non-API HGSC has been presented based on weighting twin shear stress yield criterion. Thirdly, the calculation method which can calculate the minimum transverse impact toughness (TITmin) required to resist cracking of non-API HGSC, has been established based on the presented burst pressure formula and API/ISO standard, and the effects of four kinds of defects, factor of effective thickness and non-destructive examination (NDE) level on the TITmin required to resist cracking of pipe body under diffenrent internal pressures have been analyzed. Finally, the full-scale ductile burst test of non-API 140 casing have been conducted, by which the accuracy and reliability of burst pressure formula and calculation method of TITmin have been validated. Research results can provide an important reference for non-API HGSC design in ultra-deep well.

Basis for the Bauschinger effect in copper single crystals: changes in the long-range internal stress with reverse deformation

The long-range internal stresses (LRIS) associated with the Bauschinger effect were investigated using synchrotron X-ray microbeam diffraction and reversed deformation experiments. [100]-oriented Cu single crystals were deformed in compression to approximately − 0.3 true strain, followed by tension to a strain of approximately + 0.02. Two conclusions are arrived at from this work: First, the LRIS are confirmed in this work to be small relative to the applied stress both before and after reversal. Second, the LRIS persist after 2% reversed strain despite a significant drop in the overall dislocation density by dynamic recovery. This appears to satisfy the necessary condition for LRIS to significantly contribute to a Bauschinger effect in materials. The pronounced Bauschinger effect in Cu is probably best rationalized by a combination of both the LRIS and the Orowan–Sleeswyk model that relies on a non-uniform distribution of dislocation obstacles without a substantial LRIS.

Design of energy dissipating elastoplastic structures under cyclic loads using topology optimization

A topology optimization approach for designing structures with maximum energy absorption capacity under cyclic loads is proposed. To simulate the Bauschinger effect in materials under cyclic loads, Prager and the Armstrong-Frederick kinematic hardening rules are considered together with the von Mises plasticity in the optimization process. Path-dependent sensitivities are derived analytically using the adjoint method, which are further verified by the central difference method. Effectiveness of the proposed approach is demonstrated on several examples. Results show that the optimized designs with kinematic hardening are remarkably different from the ones obtained with isotropic hardening and are highly dependent on the loading patterns.

Analysis of Springback Simulation Based on Bauschinger Effect

Strain hardening of mental in one direction reduces the yield stress in the opposite direction, the existence of Bauschinger effect plays a unique role on the accuracy of the sheet metal forming simulation. Especially now extensive use of high strength steels and aluminum alloys, makes springback phenomenon an increasingly important issue, tool manufacturing of Auto-body forming put forward higher requirement for the accuracy of the finite element springback prediction. In order to improve the accuracy of springback prediction it is necessary to study the Bauschinger effect of materials. With a device tension-compression tests of DC06 and DP600 are carried out and the displacement-force relationship in different pretension strain are obtained. U-channel forming tests of DC06 and DP600 is carried out, with the simulation models are built, the magnitude of springback are calculated. The influence of different material models, which include the hardening laws of isotropic hardening, isotropic-kinematic hardening and kinematic hardening, on springback prediction is analyzed by comparing the simulation results, the factor of material model which influence the accuracy of springback prediction are also analyzed. The results show that there are differences between DC06 and DP600 on the size of Bauschinger effect, it is helpful to improve the accuracy of springback calculation when considering the Bauschinger effect, while the sensitivity of material constitutive model on the simulation of small curvature bending forming, limited the springback simulation accuracy.

Localization of Plastic Buckling Patterns under Cyclic Loading

This study investigates the theoretical aspects of the localization of plastic buckling patterns, which results in the strength deterioration of steel structures under cyclic loading. Because the localization phenomena is caused by the plastic bifurcation from the decreasing equilibrium path in the post-peak range, we first presented a method based on the finite-element method (FEM) to analyze the plastic bifurcation. Then, using the proposed method, we analyzed a multiply supported column and simply supported rectangular compression plates subject to repeated loading. As a result of numerical anlysis, it was confirmed theoretically that the localization of buckling patterns has a large influence on the strength deterioration under cyclic loading. Furthermore, it was observed from the numerical results that the occurrence of localization is accelerated by the accumulation of residual bending deformations as well as the Bauschinger effect of materials.

Hopkinson techniques for dynamic recovery experiments

Novel techniques are introduced to render the classical split Hopkinson bar apparatus suitable for dynamic recovery experiments, where samples can be subjected to a single pulse of pre-assigned shape and duration, and then recovered without any additional loading, for post-test characterization; i. e., techniques for fully controlled unloading in Hopkinson bar experiments. For compression dynamic recovery tests, the new design generates a compressive pulse trailed by a tensile pulse (stress reversal), travelling toward the sample. Furthermore, all subsequent pulses which reflect off the free ends of the two bars (incident and transmission) are rendered tensile, so that the sample is subjected to a single compressive pulse whose shape and duration can also be controlled. For tension recovery experiments, the new design provides for trapping the compression pulse reflected off the sample, and the tensile pulse transmitted through the sample. In addition, a sample can be subjected to compression followed by tension, and then recovered, allowing the study of, e. g. the dynamic Bauschinger effect in materials.

The elasto-plastic strain analysis of notched plate under cyclic loading—An application of plastic anisotropic hardening theory

In order to predict the life of engineering structures, it is necessary to investigate the strain distribution in notched members. In general, the Bauschinger Effect of materials under cyclic loading is not negligible, and so the anisotropic hardening model has been suggested. From the comparison between the calculated and experimental results in this paper, we can see that even the linear kinematic hardening model is quite suitable for strain analysis under cyclic loading.

Continuous dislocation distribution model of the Bauschinger effect

A model of the Bauschinger effect in materials containing heterogeneities is developed using the theory of continuous dislocation distributions on a plane. The effect of work hardening is considered. Energy losses per stress cycle are calculated as a function of maximum stress and a comparison is made with the fatigue studies of Lazan.