Experimental and Numerical Study of Pressure Intensity in Detachable Joints of D Series Pumps

The object of study is a single-stage double-suction axially split volute casing centrifugal pump. Background. In the design process of pumps, the problems associated with ensuring the tightness of the axial joint of a pump casing being under the effect of mechanical and temperature loads, are being solved. During the study of axial joint tightness, numerical calculation methods are used to estimate the pressure intensity on the contacting surfaces. A detachable joint under the external load satisfies the criterions of the tightness if the pressure intensity on the sealing surfaces is higher than values of the specific pressure prescribed by regulations. However, inability to experimentally determine the pressure intensity on the contacting surfaces has so far prevented to assess the accuracy of results obtained by the numerical calculation methods. Objective. In order to verify the numerical results obtained by mathematical models, an experiment was carried out using a special Prescale film that registers the magnitude of the contact pressure on the joint of the specimen model of the flange fragment. Based on the experimental results, an analysis of the pressure intensity distribution was conducted. Methods. To conduct the experiment, there was developed a method for determining the pressure intensity on the contacting surfaces according to the proposed scheme of the specimen of the flange fragment. Results. A comparative analysis of the solving results obtained for the contact problem on the finite-element models of the flange fragment and the zone of the pump casing joint in the discharge chamber area showed a good coincidence of the results. Analysis of results obtained experimentally on the specimen of flange fragment and results of the numerical calculation on the flange fragment model also showed a good agreement. Conclusions. Therefore, results of the calculation of the pressure intensity in the detachable joints on mathematical models have been experimentally confirmed.

Thermal physical processes during forming of biocompatible Ca-P coatings by detonation spraying

Carbon-carbon composites with calcium phosphate (Ca-P) coatings (with a thickness up to of ≈100 μm) are considering as prospective grafts for defect bone substitution. Detonation spraying of Ca-P layers allows to fulfil a deposition mode with relative low temperature loads (up to a temperature of the processed surface of ≈850…1100 K) under a pulsed pressure of ≈2…6 bar. Such deposition conditions could promote to minimal thermal decomposition of feedstock HAp.

Modification of Variance-Based Sensitivity Indices for Stochastic Evaluation of Monitoring Measures

In complex engineering models, various uncertain parameters affect the computational results. Most of them can only be estimated or assumed quite generally. In such a context, measurements are interesting to determine the most decisive parameters accurately. While measurements can reduce parameters’ variance, structural monitoring might improve general assumptions on distributions and their characteristics. The decision on variables being measured often relies on experts’ practical experience. This paper introduces a method to stochastically estimate the potential benefits of measurements by modified sensitivity indices. They extend the established variance-based sensitivity indices originally suggested by Sobol’. They do not quantify the importance of a variable but the importance of its variance reduction. The numerical computation is presented and exemplified on a reference structure, a 50-year-old pre-stressed concrete bridge in Germany, where the prediction of the fatigue lifetime of the pre-stressing steel is of concern. Sensitivity evaluation yields six important parameters (e.g., shape of the S–N curve, temperature loads, creep, and shrinkage). However, taking into account individual monitoring measures and suited measurements identified by the modified sensitivity indices, creep and shrinkage, temperature loads, and the residual pre-strain of the tendons turn out to be most efficient. They grant the highest gains of accuracy with respect to the lifetime prediction.

Optimal Allocation of Design Margins in Additive Remanufacturing

Often, coping with changing requirements results in substantial overdesign, because of the ways in which design margins are allocated at the beginning of the design process. In this paper, we present a design optimization method for minimizing overdesign using additive manufacturing. We use recently defined constituents of design margins (buffer and excess) as metrics in a design optimization problem to minimize overdesign. The method can be used to obtain optimal design decisions for changing requirements. We demonstrate our method by means of a turbine rear structure design problem where changes in the temperature loads are met by depositing different types of stiffeners on the outer casing. The optimal decisions obtained by optimization minimize overdesign but ensure that requirements are met throughout the product’s lifecycle.

Study of the Behavior of the Fire-Retardant Seals Under Thermal Exposure

The results are presented concerning the experimental studies of the behavior of fire-retardant seals produced by the Ogneza group of companies under thermal exposure up to 1000 °C, obtained by the method of synchronous thermal analysis (thermogravimetry together with the differential scanning calorimetry). Incombustible properties of the M-СORE (NG) seal were confirmed, which showed a decrease in the mass of the material when heated to 1000 °C by 11%, which is due to the mineral composition of the sample (a silica-based material). High thermal stability was shown by the fire-fighting seal M-CORE, the decrease in the mass of the sample of which, after reaching a temperature of 555 °C, stops at 37 %, which indicates the formation of an ash residue. Thermal sealing tape LTU, as a result of the temperature heating starting from a mark of 192 °C, uniformly was losing mass up to a total value of 82 %. The experiment established the sealant swelling. According to the experimental data obtained, the samples M-CORE (NG) confirmed the fire-retardant properties declared by the manufacturer. For the selection of heat-resistant materials that can withstand significant temperature loads during the operation of units and mechanisms, for electrical and thermal insulation, for fire protection of air ducts, equipment, structures, the advantages, and reliability of these seals are obvious. The results of the study (the temperature of the beginning of an intensive decrease in mass, the temperature of the onset of thermal effects accompanying a decrease in mass, the behavior of materials under thermal exposure) can be considered when designing heat and electrical insulation, fire protection of production processes, as well as when determining the level of fire risk of the production facilities.

Optimization of Design Margins Allocation When Making Use of Additive Remanufacturing

Coping with changing requirements by means of introducing design margins may result in overdesign. In this paper, we present a design optimization method for minimizing overdesign by exploiting additive remanufacturing. Our problem formulation makes use of recently defined constituents of design margins: buffer and excess. The proposed method can be used to obtain a set of design decisions for different changing requirement scenarios. We demonstrate it using a turbine rear structure design problem where changes in the temperature loads are met by depositing different types of stiffeners on the outer casing. The results of the case study are visualized in a tradespace, which allows for comparison between sets of optimal, flexible, and robust designs. Results show that the optimized set of design decisions balances flexibility and robustness in a cost-effective manner.