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Number of results: 5
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Abstract

Automation of machining operations, being result of mass volume production of components, imposes more restrictive requirements concerning mechanical properties of starting materials, inclusive of machinability mainly. In stage of preparation of material, the machinability is influenced by such factors as chemical composition, structure, mechanical properties, plastic working and heat treatment, as well as a factors present during machining operations, as machining type, cutting parameters, material and geometry of cutting tools, stiffness of the system: workpiece – machine tool – fixture and cutting tool. In the paper are presented investigations concerning machinability of the EN AC-AlSi9Cu3(Fe) silumin put to refining, modification and heat treatment. As the parameter to describe starting condition of the alloy was used its tensile strength Rm. Measurement of the machining properties of the investigated alloy was performed using a reboring method with measurement of cutting force, cutting torque and cutting power. It has been determined an effect of the starting condition of the alloy on its machining properties in terms of the cutting power, being indication of machinability of the investigated alloy. The best machining properties (minimal cutting power - Pc=48,3W) were obtained for the refined alloy, without heat treatment, for which the tensile strength Rm=250 MPa. The worst machinability (maximal cutting power Pc=89,0W) was obtained for the alloy after refining, solutioning at temperature 510 o C for 1,5 hour and aged for 5 hours at temperature 175 o C. A further investigations should be connected with selection of optimal parameters of solutioning and ageing treatments, and with their effect on the starting condition of the alloy in terms of improvement of both mechanical properties of the alloy and its machining properties, taking into consideration obtained surface roughness.
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Abstract

The machinability and the process parameter optimization of turning operation for 15-5 Precipitation Hardening (PH) stainless steel have been investigated based on the Taguchi based grey approach and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). An L27 orthogonal array was selected for planning the experiment. Cutting speed, depth of cut and feed rate were considered as input process parameters. Cutting force (Fz) and surface roughness (Ra) were considered as the performance measures. These performance measures were optimized for the improvement of machinability quality of product. A comparison is made between the multi-criteria decision making tools. Grey Relational Analysis (GRA) and TOPSIS are used to confirm and prove the similarity. To determine the influence of process parameters, Analysis of Variance (ANOVA) is employed. The end results of experimental investigation proved that the machining performance can be enhanced effectively with the assistance of the proposed approaches.
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Abstract

Development of mineral deposits located at significant depth may be carried out by means of vertical shafts. Shaft sinking technology usually requires a number of works to be carried out, including the selection of appropriate excavating techniques adapted to geological and hydrological conditions, including natural hazards. The production technology and the machines used determine the level of sinking costs and execution period. The article discusses the excavating technologies currently used across the world. Then the assumptions, concept and construction of a new generation of shaft sinking system were presented. The proposed new solution of the system and the excavating technology allow for parallel execution of key processes related to winning, loading, transport and shaft wall-side lining, which significantly increases the progress of sinking. The shaft sinking system was created by scientists from AGH in cooperation with KOPEX – Przedsiębiorstwo Budowy Szybów S. A. and Instytut Techniki Górniczej KOMAG.
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Abstract

The study aimed to apply the protection from damage to engineering facilities located near a planned underwater aggregate extraction. The analysis was conducted in compliance with mining regulations and expert opinions. The study also aimed to assess the precision and correctness of the extraction, due to economic aspects. To reach the goals, in-situ research of the mining area was conducted, with the help of an advanced bathymetric device, based on the USV methodology. The instrument – named by the author as Smart-Sonar-Boat – was especially designed for underwater surveys in open-pit aggregate mines. The study analyzed the “Dwory” open-pit mine, located in southern Poland in the city of Oświęcim. The bathymetric results obtained contributed to improving the observation of changes in the bottom during the extraction. The applied USV method allowed for conducting the reliable evaluation of the mining work.
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Abstract

The paper consists the problem of developing a scientific toolkit allowing to predict the thermal state of the ingot during its formation in all elements of the casting and rolling complex, between the crystallizer of the continuous casting machine and exit from the furnace. As the toolkit for the decision making task the predictive mathematical model of the ingot temperature field is proposed. Displacement between the various elements of the CRC is accounted for by changing the boundary conditions. Mass-average enthalpy is proposed as a characteristic of ingot cross-section temperature state. The next methods of solving a number of important problems with the use of medium mass enthalpy are developed: determination of the necessary heat capacity of ingots after the continuous casting machine for direct rolling without heating; determination of the rational time of alignment of the temperature field of ingots having sufficient heat capacity for rolling after casting; determination of the total amount of heat (heat capacity) required to supply the metal for heating ingots that have insufficient amount of internal heat.
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