{"title":"Investigation of the Bending Properties of Ex situ Functional Metal Foams","authors":"Gábor Pados, A. Kemény, D. Károly, I. Orbulov","doi":"10.3311/ppme.23707","DOIUrl":"https://doi.org/10.3311/ppme.23707","url":null,"abstract":"In each industry, compromises have to be made when choosing materials. Lower-density materials have a significant advantage in the automotive sector, especially due to rising fuel prices, since weight reduction can lower overall fuel consumption. The advantageous properties of metal foams, such as low density, high specific strength, and excellent energy absorption, should be researched and exploited in as many areas and ways as possible. This research aims to perform and evaluate the bending tests of ex situ functional metal foams: aluminum alloy matrix (AlSi7Mg) was used, which was filled with Ø2.5–3.0 mm lightweight expanded clay aggregate particles and surrounded by thin-walled aluminum tubes (AlMgSi0.5) with a wall thickness of 2 mm and an outer diameter of Ø32 mm. Empty tubes, foam-filled tubes (with and without structural epoxy adhesive) and metal matrix syntactic foams were compared based on their flexural strength and energy absorption capacity. Quasi-static three-point bend tests were carried out up to 25 mm deflection. The foam-filled tubes with epoxy adhesive showed an average of 6% increase in flexural strength compared to the foam-filled tubes without adhesive and a 145% increase compared to the metal matrix syntactic foams.","PeriodicalId":513310,"journal":{"name":"Periodica Polytechnica Mechanical Engineering","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139597086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Investigation of Spinodal Decomposition in Isothermally Heat Treated LDX 2101 type Duplex Stainless Steel at 475 °C","authors":"T. Berecz, István Mészáros, P. Jenei","doi":"10.3311/ppme.23385","DOIUrl":"https://doi.org/10.3311/ppme.23385","url":null,"abstract":"Spinodal decomposition of the ferritic phase, a thermally induced phase transformation process is studied in an LDX 2101 type lean-duplex stainless steel by different examination methods. This phase transformation in duplex stainless steels has special importance because it is responsible for the so called \"475 °C embrittlement\". This deterioration process causes a decrease in toughness and corrosion resistance. Fe-Cr alloys, thus several stainless steels, are susceptible to the spinodal decomposition at intermediate and low temperatures (<600 °C). Therefore, it is important to study this phenomenon in novel lean-duplex stainless steels as well. Our results revealed that spinodal decomposition occurs to a lesser extent in the studied type of lean-duplex stainless steel but its effect is not negligible in applications.","PeriodicalId":513310,"journal":{"name":"Periodica Polytechnica Mechanical Engineering","volume":"44 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139613238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Mechanical Studies of Subperiosteal Implants","authors":"Klaudia Kulcsár, I. Zsoldos","doi":"10.3311/ppme.23706","DOIUrl":"https://doi.org/10.3311/ppme.23706","url":null,"abstract":"When designing subperiosteal implants, mechanical testing of the implant and abutment is inevitable. Subperiosteal implants and their abutments are medical devices made to order, so each implant requires a separate design, since each patient has a different bone surface, for which the implant must be designed. For the mechanical testing of subperiosteal implants, a new test apparatus was constructed, on which mechanical simulations were carried out, the subperiosteal implants were tested together with their abutments. In addition to the finite element analysis simulation, the test apparatus can also be used to determine how much force is generated by the chewing force on the subperiosteal implant and its abutment as a result of the chewing mechanism.","PeriodicalId":513310,"journal":{"name":"Periodica Polytechnica Mechanical Engineering","volume":"11 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139616873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Predicting Concentration Fluctuations of Locally Emitted Air Pollutants in Urban-like Geometry Using Deep Learning","authors":"Bálint Papp, G. Kristóf","doi":"10.3311/ppme.23391","DOIUrl":"https://doi.org/10.3311/ppme.23391","url":null,"abstract":"The accurate quantification of concentration fluctuations is crucial when evaluating the exposure to toxic, infectious, reactive, flammable, or explosive substances, as well as for the estimation of odor nuisance. However, in the field of Computational Fluid Dynamics (CFD), the industry currently relies predominantly on steady-state RANS turbulence models for simulating near-field pollutant dispersion, which are only capable of producing the time-averaged concentration field. This paper presents a regression relationship for calculating the standard deviation of the local concentration based on the mean concentration and the downstream distance from a point source, over a city-like surface, in the case of the wind direction perpendicular to the streets. The desired peak values and other statistical characteristics can be predicted by assuming a gamma distribution which is fitted based on the average and standard deviation. To obtain the regression function, a deep neural network model was used. The model was trained using time-resolved concentration data obtained from wind tunnel experiments. The validation results show that the concentration fluctuations predicted by the DNN-based model are in satisfactory agreement with the measurement data in terms of the skewness, the kurtosis, the median, and the peak concentrations. Furthermore, the present paper suggests a workflow for estimating the concentration fluctuations based on RANS CFD results, as well as recommendations for generating further training data for specific applications.","PeriodicalId":513310,"journal":{"name":"Periodica Polytechnica Mechanical Engineering","volume":"34 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139443023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zuzana Straková, Jozef Vojtaššák, Ján Takács, Mária Kurčová, Pavol Štefanič, Samuel Malíšek
{"title":"Heat Recovery Variable Refrigerant Volume System Installation and Experiences from its Summer Operation","authors":"Zuzana Straková, Jozef Vojtaššák, Ján Takács, Mária Kurčová, Pavol Štefanič, Samuel Malíšek","doi":"10.3311/ppme.21907","DOIUrl":"https://doi.org/10.3311/ppme.21907","url":null,"abstract":"Variable refrigerant volume (VRV) systems operate on the principle of a cooling machine. They extract heat from one side and return it on the other, enabling them to function as a source of heat for both heating and hot water preparation, as well as a source of cold for cooling within a single building. These systems efficiently remove unnecessary excess heat outside and only introduce the required amount of heat from the outside into the building. With an appropriate configuration and setting, a VRV system can transfer heat in both directions within one system, eliminating the requirement for waste heat to be removed without use in the building. Instead, it is transferred to the desired locations where it is needed. This principle necessitates the adjustment of not only the refrigerant temperature but also its flow rate. Consequently, the VRV system can fulfil tasks that are otherwise handled by several individual systems in a building.A heat recovery VRV system was installed in a small retail store to extract waste heat generated by baking ovens during the baking process. This report provides a brief summary of electricity and energy consumption measurements taken during the summer period for cooling purposes. Sequential logic is observed and coherence is ensured, with active voice predominating for clearer and more direct communication. The parameters of interest include cooling setpoints, cooling outside of working hours, and capacity assessment.","PeriodicalId":513310,"journal":{"name":"Periodica Polytechnica Mechanical Engineering","volume":"31 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139388809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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