Determination of residual macrostresses in surface layer of solid-rolled railway wheels disks by X-ray diffractometry

Residual stresses on the surface of disks of one-piece-rolled steel railway wheels, caused by their fi nishing (turning) with different tool feed rate and speed, are measured using the X-ray diffractometric method implemented using the DRP portable diffractometer. It is shown that the specifi ed fi nishing parameters have signifi cant infl uence on the level of surface residual stresses induced by fi nishing. The most favorable stress state (compressive stresses up to –200 MPa) on the surface of the disks is achieved under relatively small values of tool feed and speed. The results may serve as basis for improving of the fi nishing technology of solid-rolled wheels.

Components of Magnetic Anisotropy of Soft Magnetic Nanocrystalline Fe-Based Films

We present quantitative evaluation results of micromagnetic structure parameters of nanocrystalline Fe, Fe95Zr5, Fe90N10, and Fe85Zr5N10films obtained by magnetron sputtering. It is shown that quantities of magnetocrystallineK1, magnetoelasticKME, magnetostaticKMS, and surfaceKa,Sanisotropies are components of experimentally measured effective local anisotropyKeff. The shape of the hysteresis loops of the films is determined by the presence of two main macroscopic effective magnetic anisotropies, one of which is the anisotropy field of stochastic domains, and the other is the magnetoelastic anisotropy field due to residual macrostresses.

Residual Stresses in Cast Ni-Cr Alloys-Ceramics Joints with an Intermediate Layer

The results of residual stresses in biocompatible cast Ni-Cr alloys-ceramics joints with an intermediate layer with thickness of about 10μm are discussed. To the experiment were used specimens with dimensions of 45×3×10 mm and 45×4×10 mm made of Cr-Ni alloys-ceramics joint both with and without of application of an intermediate layer. The examinations were carried out by means of metallographical microscope, testing machine and X-ray diffractometer. The measurement of residual macrostresses was carried out by using sin2ψ method. The obtained experimentally values of residual macrostresses are in good agreement with results of numerical simulation performed by means of FEM ANSYS package. The researches have been shown that application of an intermediate ceramics layer influence on increase of strength properties of Ni-Cr alloys-ceramics joints.

The Measurement of Residual Stresses Using Neutron Diffraction

Residual stresses are common in engineering materials. They are elastic stresses that exist in the absence of external forces and are produced through the differential action of plastic flow, thermal contraction, and/or changes in volume created by phase transformations. Differential plastic flow can occur during the forming of a part. For example, the grinding of a surface will plastically extend a thin surface layer relative to the underlying material through frictional forces. This tends to throw the near-surface region into compression, which is balanced by a tensile stress through the bulk of the part. In such a situation, the requirements of force equilibrium lead to a rather high level of compressive stress in the near-surface region and a low level of tensile stress through the bulk. Differential thermal contraction often occurs during the nonuniform cooling of a large part, in the vicinity of welds, and between the matrix and reinforcement phases of a composite. Differential volume changes occur during the precipitation of second phases, i.e., the atomic volume of the precipitating phase generally differs from that of the host matrix. If it is larger, the second phase is placed in compression, with the matrix in tension, and vice versa.The residual stress states discussed in the previous paragraph are of two basic types: macrostress and microstress. Residual macrostresses are long-range relative to the scale of the microstructure––that is, they extend continuously across a part. Residual stresses arising from forming and joining are of this type. They generally vary with position and are extensive in nature. A plate with compressive residual stresses on the flat surfaces will deflect if the compressive region on one surface is removed. Destructive stress measurement techniques such as hole drilling or strain gauging and sectioning can be used to determine residual macrostresses.