Search results for "work hardening"
showing 9 items of 9 documents
Microstructural Characterization of Thermo-Mechanical Treated TRIP Steels
2007
The increasing demand for the reduction of automobiles CO2 emissions for environmental preservation leads the automotive industries towards the mechanical components weight reduction. Sheet steels with multiphase microstructures exhibit favourable combinations of strength and ductility. The so called TRIP steels have a metastable microstructure that consists of a continuous ferrite matrix containing a dispersion of hard second phases martensite and bainite. These steels also contain retained austenite, at room temperature, that represents the source of the TRansformation Induced Plasticity effect. When the material is subjected to deformation step, the retained austenite transforms itself i…
<title>Formation of dislocations and hardening of LiF crystals irradiated with energetic Au, Bi, Pb, and S ions</title>
2003
The irradiation of LiF crystals with Au, Pb, Bi, and S ions in the range of 400 - 2200 MeV leads to a remarkable increase of the hardness. The effect appears for Bi and Pb ions at fluences above 109 ions/cm2 and for S ions above 1010 ions/cm2. The increase of hardness follows the energy loss and is related to the formation of defects along the ion path. Defect complexes, clusters and aggregates with nanoscale dimensions serve as strong obstacles for dislocations and cause dispersion strengthening. Structural investigations reveal the generation of long-range stress in the adjacent non-irradiated part of the crystal. Close to the implantation zone, the stress exceeds the yield strength, caus…
Optimum design for work-hardening adaptation
1977
Abstract The finite element-linear programming approach and the work-hardening adaptation criterion are used to formulate a general theory of optimum design of rigid-work-hardening structures subjected to loads which vary statically within given limits. Self-weight, as well as some technological constraints, can be introduced into the framework of the optimization problem. The optimality conditions are discussed with the aid of geometrical descriptions as well, and a comparison is made with the standard limit design. Numerical applications are given for a plane truss and a plane frame with axial force-bending moment interaction.
Fatigue crack propagation from a cold-worked hole
2007
Abstract The cold expansion process is widely used to enhance the fatigue life of structures with fastener holes. Various studies assert that the cold expansion improves the fatigue strength of fastener holes; however, the improvement of fatigue life is difficult to quantify. Therefore, the influence on fatigue life of cold-worked process was studied by numerical and experimental tests. Then, a parametric study on material hardening behavior and Bauschinger’s parameter was performed for several loading conditions in order to determine their effect on crack growth propagation. The results of the numerical tests have exhibited a good prediction of the fatigue life of the component.
Depth profiles of hardening in lithium fluoride irradiated with swift58Ni ions
2004
The changes of hardness and dislocation formation in LiF crystals irradiated with 630-MeV 58Ni ions up to a dose of 20 MGy were studied by microindentation and dislocation etching techniques. Above the threshold fluence of 2 × 1010 ions/cm2, a marked effect of hardening, which is related mainly to damage processes in the track core, has been observed. Its magnitude depends on ion fluence and energy loss. To investigate the depth distribution of hardening, indentation tests on crystal cross sections cleaved parallel to ion flux were performed. It has been found that the hardness change along the ion path correlates with the ion energy loss and reaches the highest value at the Bragg maximum. …
Size effects in micro- and nanoscale indentation
2006
Abstract The indentation size effect (ISE) has been studied in single crystals, polycrystals and amorphous solids using the Vickers microhardness test. The ISE is clearly present in single crystals but is absent in fine-grained polycrystals. A size-dependent hardness for amorphous solids is observed only in the sub-micrometre surface layer. The behaviour of the ISE in single crystals for micro- and nanoindentation is compared. Estimates of the surface hardness are made by the extrapolation of the experimental hardness–indentation depth curves. The extrapolated hardness in the surface region reaches values corresponding to the theoretical shear strength. The results confirm the multifarious …
<title>Hardening and long-range stress effects in LiF caused by high-fluence irradiation with fast Bi, Ni, Kr, and S ions</title>
2005
The limits of the hardening, and the effects of ion-induced internal and long-range stresses in LiF crystals irradiated with Bi, Ni, Kr, and S ions, having a specific energy of the order of 10 MeV/u and the fluence up to 1013cm-2, are studied. A considerable hardness increase, bending of the crystals, formation of dislocations in distant nonirradiated parts of the crystals, and initiation of fracturing under the high-fluence irradiation are observed. It is shown that the irradiation with heavy ions (Bi) gives rise to dislocations and work hardening mainly in the region adjacent to the irradiated one. In the case of lighter ions (Ni and S), the work hardening takes place also inside the irra…
Influence of M23C6 carbides on the heterogeneous strain development in annealed 420 stainless steel
2020
Understanding the local strain enhancement and lattice distortion resulting from different microstructure features in metal alloys is crucial in many engineering processes. The development of heterogeneous strain not only plays an important role in the work hardening of the material but also in other processes such as recrystallization and damage inheritance and fracture. Isolating the contribution of precipitates to the development of heterogeneous strain can be challenging due to the presence of grain boundaries or other microstructure features that might cause ambiguous interpretation. In this work a statistical analysis of local strains measured by electron back scatter diffraction and …
Strain hardening in liquid-particle suspensions
2005
The behavior of a liquid-particle suspension induced to sheared motion was analyzed by numerical simulations. When the velocity (strain) of the suspension began to increase, its viscosity first stayed almost constant, but increased then rapidly to a clearly higher level. This increase in viscosity is shown to be related to formation of clusters of suspended particles. Clusters are shown to increase the viscosity by enhanced momentum transfer though clustered particles. This is the mechanism behind the strain-hardening phenomenon observed in small-strain experiments on liquid-particle suspensions.