Papers by Keyword: Bars

Abstract: The article provides the results of a statistical research of the relation of mechanical properties and chemical composition of Ø 15-rolled, forged, and pressed bars made of various modifications of the Ti-6Al-4V titanium alloy. The authors studied the correlation of mechanical properties and the content of alloying elements, impurities, bar diameter, and post-annealing (using various industrial modes) structural parameters, on the basis of the analysis of production data, and established regression dependencies for estimating average values of mechanical properties of bars on aluminum and molybdenum strength equivalents of alloying elements and impurities.

Abstract: A procedure has been developed for calculating the geometric, kinematic and energy-power parameters of helical rolling, which allows a comparative analysis of the processes carried out in stands of various designs. Based on the results of this analysis, a helical rolling mill was designed and manufactured which allows to roll materials with high deformation resistance at high temperatures. The results of the study of the mechanical characteristics of molybdenum bars and wires made by new technology are presented.

Abstract: This paper presents the results of statistical tests, carried out to identify the mechanical properties of Ø 16-150 mm VT6 titanium alloy bars, as a function of their post-annealing chemical composition and structure. It is shown that the high variation of mechanical properties may be, due to fluctuations in the grade composition and structure type. 50% to 60% of variations in strength properties are due to composition + structure co-effects. To improve the stability of such properties, the paper identifies maximum permissible total fluctuations in the chemical composition in terms of aluminum/molybdenum equivalents of alloying elements and impurities. The research team has fitted the regression dependencies for evaluating the mean values of the mechanical properties of Ø 16-60 mm VT6 bars, as a function of the structure type and aluminum/molybdenum equivalents of the alloying elements and impurities.

Abstract: The article provides the results of statistical research on the dependence of the mechanical properties of bars with a 14 mm diameter, made of the titanium alloy VT22, on the heat treatment modes and the chemical composition on the basis of the analysis of experimental, literature and manufacturing data. The authors study the correlation between mechanical properties and the content of alloying elements, admixtures, heat treatment modes. The research finds out regression dependences to evaluate the average values of the mechanical properties of the bars 14х14 mm of the alloy VT22 on the annealing temperature (within an hour, furnace cooling up to 400⁰С, and further air cooling) and the equivalents of alloying elements and admixtures on aluminium and molybdenum.

Abstract: This paper proposes a new solution to recognize and segment adhering bars. A support vector machine (SVM) is constructed according to the feature vectors of training samples to recognize the adhesions type of bars. The geometric feature values and moment feature values based on Blob regions in the image are extracted, which are the input feature vectors of support vector machine. The trained classifier is used for identifying the adhesions type of bars in the image. Finally, classification and recognition are realized by support vector machine. The experimental result shows that the recognition accuracy based RBF kernel achieves 100%. The method is feasible and effective for the recognition and segmentation of the adhering bars.

Abstract: During the last 90 years, a lot of works have been published about rolling theories for the two-roll rolling process (2RP). In the last decades, the three-roll process (3RP) has become a significant technique in the production of wire rod and bars, as it allows to cover a wide range of finished dimensions with one pass design, or to realize very close tolerances, depending on the pass design method used (free size rolling or high precision rolling). Horihata and Motomura [2] made use of the upper bound theorem to construct a method for spread calculation, but up to now, a straightforward mathematical method for calculation of stress distribution, roll forces, torques and forward slip is still missing. The present paper aims at a transfer of the slab method, which is well-known and established for the 2RP, to the 3RP. After the rolling theory for flat passes is introduced, Lendl’s equivalent pass method is transferred to the 3RP, which allows the calculation of section passes. Computational results show, that roll forces, torques and forward slips can be calculated under inclusion of elastic stand feedback and interstand tensions. Therefore the model can be used for roll speed set-up to minimize interstand tensions, which is of great importance for the rolling industry.

Abstract: Dynamic buckling of bars under step load was studied by considering the stress wave effect. Straight bars without axial inertia were taken as an example when deformation was small. The buckling solution satisfying the boundary conditions was given by the semi-analytic method. The buckling solution was substituted to the dynamic buckling governing equations. The unified expression of dynamic buckling critical load was obtained by discussing the character of the solution. The dynamic buckling critical load was obtained by calculating the value of when the stress wave propagated to the critical length . The value of dynamic buckling load was 2.5 times the one’s of static buckling load with corresponding equivalent length.

Abstract: This paper presents a new computer program called DIFAR (or dynamic incremental failure analysis of rock) that can simulate fracture process of brittle rocks under dynamic impacts. The program is based on a linear elastic finite element method incorporated with a failure criterion for damage checking. Modulus is reduced once the failure criterion is satisfied. In addition, Weibull distribution of the modulus and strength of the elements are used for modeling the mesoscopic heterogeneity. The failure criterion is a Mohr-Coulomb type of condition with a tensile cut-off, in which strength parameters are functions of the strain rate. More importantly, the whole fracture process of rock fragmentation can be simulated, including initiation, propagation, and coalescence of microcracks. The program DIFAR has been used to simulate elastic wave propagation and nonlinear fragmentation, and validity and efficiency of this program is demonstrated. The program can be considered as a dynamic counterpart of the RFPA, a failure analysis program for static loads, developed at Northeastern University, China.