Josipa Mrša

Mathematical Modeling and Computer Simulation of Fatigue Properties of Quenched and Tempered Steel

The engineering and economical aspects of the optimization of steel shaft quenching and tempering were investigated. The mathematical model and method of computer simulation for the prediction of fatigue properties of quenched and tempered steel were developed. Computer simulation of the fatigue properties of quenched and tempered steel was applied in the optimization of quenching and tempering of steel shafts. The proper heat treatment process was accepted based on economical analysis. Fatigue properties of quenched and tempered steel were predicted based on microstructure composition and yield strength. Microstructure composition and yield strength were predicted based on as-quenched hardness. The distribution of as-quenched hardness in the workpiece was predicted through computer simulation of steel quenching using a finite volume method. The as-quenched hardness was estimated based on time of cooling and on Jominy test results. It was taken into account that the mechanical properties of quenched steel directly depend on the hardness, degree of hardening, and microstructural constituents. Using a numerical simulation of microstructure and mechanical properties, it was found out that the investigated shaft has the best fatigue properties in cases when the shaft was machined or formed on proper geometry before proper quenching and tempering. Through economical analysis of the investigated shaft manufacturing, it was found out that the most suitable shaft manufacture process is to manufacture the shaft from the quenched and tempered bar. But in this case, heterogeneous microstructures of ferrite, perlite, bainite, and martensite with very low fatigue limits could appear at some critical locations.

Measuring quality related costs

The cost aspect of heat treatment quality management has been presented. Quality management cannot be successful without quality cost management. The activity of heat treatment quality system as cost centers have been defined. The heat treatment quality costs have been classified in categories.

Interaction of Net Present Value, Cash Flow and Financial Statements

Adjustment of the specific national economic system to the economic system of the European countries implies abandoning traditional economic methods and implementation of the standards used in EU. It equally applies to economic, market, financial and other standards among which are the accounting standards.This fact is important from the financial analysis` point of view, because financial indicators cannot be compared nor can be necessary analysis conducted without application of international accounting standards. Those financial indicators and analysis form the basis for making business decisions. The application of international financial reporting standards changes presented financial position on a large scale, that is investment potential, net present value and application of cash flow. This is discussed in the paper on the examples from Croatia and Bosnia and Herzegovina.Applying different accounting standards results in changes in presented business results, in terms of profitability, financial opportunities and capabilities, assessment of credit-worthiness and other indicators of financial position and profitability.The paper elaborates the application of the present value method with the present value serving as goal value in net assets valuation, showing the difference in data obtained with traditional historical cost.

Time Lag Error of Inventory in Inflation

An algorithm of real value of inventory in inflation has been made. The model is made taking into consideration International Accounting Standards. In this point of view this model is based on maintenance of financial capital principle. The computer program for simulation of real value of inventory is made for modern process planning of engineering components manufacture. The program is an autonomous entity, but it can be part of one general program. Mathematical model of inventory was made from historical costs analyze. For the big inflation rate real value of inventory outflow has to be calculated by using precise methods.