In this work, the optimal combinations of Al – Si in cast iron for cast parts for machine-building purposes were determined with the aim of subsequent selection of rational modes of modification and alloying, and the possibility of their implementation under industrial smelting conditions was checked. The graphical dependence Si=f (Al) is obtained, which is a set of optimal combinations of the content of Al and Si in cast iron, providing the maximum ultimate tensile strength UTS≈245 ... 334 MPa. The technological audit of the results of serial industrial smelting included the analysis of actual indicators, the calculation of sample distribution functions (mathematical expectation and dispersion) of the Al and Si content in the alloy, as well as the UTS value. The correspondence of the indicators of the content of Al and Si and the value of σ to the optimal values was assessed by testing the statistical hypotheses: H: M(Al)=Alopt, M(Si)=Siopt, M(σв)=σвopt.On the basis of the obtained results of the assessment of statistical characteristics and verification of hypotheses, it was established that at the chosen significance level α=0.05, the technological process of smelting satisfies the requirements of optimality in terms of the Si content, but in terms of the Al content, the technological process does not meet the requirements of optimality. The proposed procedure for choosing the optimal combinations of Al and Si makes it possible to choose the amount of correcting additives depending on the actual indicators of the chemical composition during the smelting process. To do this, it is necessary to assess the closeness of the actual composition to the optimal curve Si=f(Al) and choose the one that most satisfies the criteria of rationality. The latter can be the cost of ferroalloys, through which Al and Si are introduced

This paper reports a study into the main parameters of long-term contracts for the maintenance of roads. Weaknesses in existing methods and models of substantiation of the initial characteristics of contracts have been identified. It is established that the main reason for the transition to long-term contacts in the road sector is the need to improve the efficiency and effectiveness of road asset management. This determines the main goal to maintain the operational condition of all components of roads at a level that ensures the satisfaction of user requirements and contributes to the preservation of assets. A simulation model for substantiating the parameters of long-term contracts for road maintenance has been built, which makes it possible to simulate forecast assessments of the characteristics of contracts. Underlying this study is the Monte Carlo method, as well as the triangular law of distribution, models of deterioration and restoration of the condition of road elements. Taking into consideration these models, it was established that the error in justifying the parameters of long-term contracts according to the devised method is up to 10 %. The devised model was tested by applying the developed original LTCsimula program using an example of the section of a motorway with a length of 87.3 km with an average level of requirements. According to the results of the test, the assessment of the laws of distribution of value, as well as the amount of deductions and profits of a long-term contract, was carried out. The calculation results demonstrated the model’s capability to determine the strategies for the maintenance of roads, taking into consideration the risk of implementing a contract with an error of up to 3.9 %. The practical use of the devised simulation model makes it possible to improve the efficiency of operational maintenance of roads, as well as to save from 10 % to 40 % of the cost of road maintenance

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