Contact stresses and deformations in thrust ball bearing

The aim of this paper is to determine deformations and stresses in the statically loaded thrust ball bearing subjected to a centric external axial load. In this case, all balls in the bearing are equally engaged in the transmission of the operational load. The influence of the load on the stresses and deformations in the bearings of different series has been analysed. The obtained results are the basis for further research of the load distribution in an eccentrically loaded axial ball bearing in order to determine the reduction of the static load bearing capacity in relation to the values determined in appropriate standard and also to the values prescribed by manufacturers' catalogues

Acceptability of Residual Stresses Measurement Methods of Butt Weldments and Repairs

The joints made by fusion of materials are exposed to the influence of residual stresses induced by welding thermal cycles. Residual stresses were measured on butt welded plates made of NIOMOL 490K, before and after reparation. The objective of this paper is to compare three methods of residual stress measurement (hole-drilling method, x-ray diffraction and directional effective permeability) induced by two welding processes (Submerge Arc Welding and Transferred Ionized Molten Energy) of V-butt welded plates. The residual stresses values are higher after reparation than before reparation of welded joints

Modification of the Dynamics Characteristics using a Reanalysis Procedures Technique

The present paper deals with the problem of dynamic improving characteristics for a sub-structure (bucket wheel excavator) of a complex mining structure. The procedure used in this paper is concerned with the analysis of the distribution of potential and kinetic energy in every element of structure, which gives prediction for which elements need reanalysis. Reanalysis technique can be done for the structure using finite element methods. Therefore, some information like material, size, and boundary conditions should be prepared before FE model is constructed. Because the optimum structure design has high natural frequency, the main aim of dynamic modification is to increase natural frequencies and to increase the difference between them

Acceptability of Residual Stresses Measurement Methods of Butt Weldments and Repairs

The joints made by fusion of materials are exposed to the influence of residual stresses induced by welding thermal cycles. Residual stresses were measured on butt welded plates made of NIOMOL 490K, before and after reparation. The objective of this paper is to compare three methods of residual stress measurement (hole-drilling method, x-ray diffraction and directional effective permeability) induced by two welding processes (Submerge Arc Welding and Transferred Ionized Molten Energy) of V-butt welded plates. The residual stresses values are higher after reparation than before reparation of welded joints

Experimental Determination of the Critical Value of the J-Integral that Refers to the HSLA Steel Welded Joint

Fracture mechanics, as a scientific discipline dealing with the study of cracks in welded structures, has defined parameters and introduced new test methods in order to better determine the tendency to crack growth, critical conditions for rapid fracture development, material resistance to rapid crack propagation and better definition of other parameters for assessing the behaviour of the material and the safety of the structure in the presence of cracks. In this paper, the focus is on determination of the parameter of elastic-plastic mechanics of J-integral, more precisely, on examination of the critical value of J-integral (JIc) of the welded joint of HSLA steel. The position of the tip of the fatigue crack and the properties of the region where fracture propagation occurs are main indicators of influence of the heterogeneity of the NN-70 welded structure and mechanical properties. Resistance to cracking in the welded joint shows that the heterogeneity has a major impact on the resistance to crack initiation and propagation, in elastic as well as in the plastic region

Determination of the Coffin-Manson equation under low-cycle fatigue conditions

The cycle loading of a material results in the modification of its properties and so in this paper is presented the behaviour of the fatigue life using low-cycle fatigue parameters. By applying the Coffin-Manson equation in fatigue loading of the tested specimens, the crack initiation has been computed. The stabilized hysteresis loop is a characteristic of all hystereses and it is used to determine all of the parameters for the low cycle fatigue (LCF) assessment. The experimental results have given us important information on the understanding of fatigue behaviour of high strength low-alloyed steel (HSLA) and its welded joints

Identification of low cycle fatigue parameters of high strength low-alloy (hsla) steel at room temperature

Low cycle fatigue test was performed in ambient atmosphere at room temperature. cycle loading of material, in case of High strength low-alloy steel, entails modifications of its properties and in this paper is therefore shown behavior of fatigue life using low cycle fatigue parameters. Mere precisely, crack initiation life of tested specimens Was computed using theory of Coffin-Manson relation during the fatigue loading. The geometry Of the stabilized hysteresis loop of welded joint HSLA steel, marked as Nionikral 70, is also analyzed. This stabilized hysteresis loop is very important for determination of materials properties

Finite element modelling of creep process - steady state stresses and strains

Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C* integral evaluation

Methodology for determining the region of stabilization of low-cycle fatigue

In present paper, the behaviour of high-strength low-alloyed (HSLA) steel under conditions of low-cycle fatigue (LCF) has been experimentally tested and analyzed. Based on the experimental results obtained in the programme EXCEL, characteristic regions of low-cycle fatigue of steel NIONIKRAL 70 (NN-70) have been determined, the most important being the region of stable behaviour of materials, so-called "the region of stabilization". From this region, on the basis of pre-defined requirements, characteristic stabilized hysteresis have been isolated for each strain level, based on which the Indicators of low-cycle fatigue of steel NN-70 have been identified