Abstract This article presents the process of designing a robot with a magnetic pressure pad for inspections of ferromagnetic ventilation ducts. In compliance with the assumptions, the CAD design of the robot was developed in a 3D programming environment. The designing process brought about a mathematical model of the robot with one pair of magnetic drive modules, including simulation in a MATLAB/Simulink environment. The model accounted for parameters such as rolling resistance force, transverse resistance moment, magnetic attraction force, solid moment of inertia, and other factors. The magnetic pressure pad allowed for moving the robot in magnetic ventilation systems irrespective of slopes and shapes of ducts.
{"title":"Modeling the inspection robot with magnetic pressure pad","authors":"K. Kurc, A. Burghardt, D. Szybicki, J. Giergiel","doi":"10.2478/mme-2019-0007","DOIUrl":"https://doi.org/10.2478/mme-2019-0007","url":null,"abstract":"Abstract This article presents the process of designing a robot with a magnetic pressure pad for inspections of ferromagnetic ventilation ducts. In compliance with the assumptions, the CAD design of the robot was developed in a 3D programming environment. The designing process brought about a mathematical model of the robot with one pair of magnetic drive modules, including simulation in a MATLAB/Simulink environment. The model accounted for parameters such as rolling resistance force, transverse resistance moment, magnetic attraction force, solid moment of inertia, and other factors. The magnetic pressure pad allowed for moving the robot in magnetic ventilation systems irrespective of slopes and shapes of ducts.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41365357","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}
Abstract In petroleum and mine industries, the centrifugal pumps were used for transferring solid particles with water. This method is preferable to other methods because of its user friendly and economic issues. In this article by selecting a proper pump and designing test circuit, we conducted hydraulic tests for water and water mixture with solid particles. For this purpose, an experimental set-up of centrifugal pump with only water and water with solid particles was developed. Then by analyzing the test results and efficiency equation, optimal coefficients of head loss is provided to improve the pump efficiency during hydraulic transmission of solids. The experimental results of power consumption, head, and pressure difference measurements in solid–liquid systems are presented. The experimental set-up results are compared with simulation and numerical one, which show a good agreement with them. It reveals that by adding the solid particles and increasing the fluid density up to 15%, the consumed power increases by about 20%, which result in dropping the efficiency of hydraulic system up to 6%. Finally, the optimal components for developed cycle presented for evaluation the various configuration and hydraulic analysis of pure flow and flow with solid particles in various applications to enhance the most achievable efficiency.
{"title":"Experimental Investigation of a Centrifugal Pump Hydraulic Performance in Hydraulic Transmission of Solids","authors":"Reza Barmaki, M. B. Ehghaghi","doi":"10.2478/mme-2019-0035","DOIUrl":"https://doi.org/10.2478/mme-2019-0035","url":null,"abstract":"Abstract In petroleum and mine industries, the centrifugal pumps were used for transferring solid particles with water. This method is preferable to other methods because of its user friendly and economic issues. In this article by selecting a proper pump and designing test circuit, we conducted hydraulic tests for water and water mixture with solid particles. For this purpose, an experimental set-up of centrifugal pump with only water and water with solid particles was developed. Then by analyzing the test results and efficiency equation, optimal coefficients of head loss is provided to improve the pump efficiency during hydraulic transmission of solids. The experimental results of power consumption, head, and pressure difference measurements in solid–liquid systems are presented. The experimental set-up results are compared with simulation and numerical one, which show a good agreement with them. It reveals that by adding the solid particles and increasing the fluid density up to 15%, the consumed power increases by about 20%, which result in dropping the efficiency of hydraulic system up to 6%. Finally, the optimal components for developed cycle presented for evaluation the various configuration and hydraulic analysis of pure flow and flow with solid particles in various applications to enhance the most achievable efficiency.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41373096","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}
S. Sai Venkatesh, T. Ram Kumar, A. P. Blalakumhren, M. Saimurugan, K. Marimuthu
Abstract Machining is the most widely used process in manufacturing, and tool wear plays a significant role in machining efficiency and effectiveness. There is a continuous requirement to manufacture high-quality products at a lower cost. Many past researches show that variations in tool geometry affect the cutting forces significantly. The increase in cutting forces leads to excessive vibrations in the system, giving a poor surface finish to the machined product. In this work, a 2D coupled thermo-mechanical model is developed using Abaqus/Explicit to predict the cutting forces during turning of mild steel. Johnson–Cook material model along with damage model has been used to define the material behavior. Coulomb’s friction model is considered for defining the interaction between the tool and the work piece. Metal cutting process is simulated for different sets of cutting conditions and compared with experimental results. The finite element method results correlate well with the experimental results.
{"title":"Finite element simulation and experimental validation of the effect of tool wear on cutting forces in turning operation","authors":"S. Sai Venkatesh, T. Ram Kumar, A. P. Blalakumhren, M. Saimurugan, K. Marimuthu","doi":"10.2478/MME-2019-0040","DOIUrl":"https://doi.org/10.2478/MME-2019-0040","url":null,"abstract":"Abstract Machining is the most widely used process in manufacturing, and tool wear plays a significant role in machining efficiency and effectiveness. There is a continuous requirement to manufacture high-quality products at a lower cost. Many past researches show that variations in tool geometry affect the cutting forces significantly. The increase in cutting forces leads to excessive vibrations in the system, giving a poor surface finish to the machined product. In this work, a 2D coupled thermo-mechanical model is developed using Abaqus/Explicit to predict the cutting forces during turning of mild steel. Johnson–Cook material model along with damage model has been used to define the material behavior. Coulomb’s friction model is considered for defining the interaction between the tool and the work piece. Metal cutting process is simulated for different sets of cutting conditions and compared with experimental results. The finite element method results correlate well with the experimental results.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42179779","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}
Abstract Drilling is a cutting process that uses a drill bit to cut a circular profile in workpiece. Forces acting on the drill bit reduce its life expectance. Analysis of forces acting on the drill bit during drilling prevents the tool from failing prematurely because of wear and excess feed rate. Excess feed rate can induce excessive internal stress on both the tool and workpiece. This paper aims to study the effects of reaction force acting on a drill bit during drilling of Al6061-T6. A numerical finite element simulation study is performed with commercially available software called Abaqus. Simulation results depend on the right choice of material property such as Johnson–Cook material property and Johnson–Cook damage property. Validation of material property is achieved by comparison of experimental results with simulative results. Reaction force acting against the drill bit during drilling is compared.
{"title":"Numerical Validation of Drilling of Al6061-T6 with Experimental Data","authors":"P. Elango, K. Marimuthu","doi":"10.2478/mme-2019-0038","DOIUrl":"https://doi.org/10.2478/mme-2019-0038","url":null,"abstract":"Abstract Drilling is a cutting process that uses a drill bit to cut a circular profile in workpiece. Forces acting on the drill bit reduce its life expectance. Analysis of forces acting on the drill bit during drilling prevents the tool from failing prematurely because of wear and excess feed rate. Excess feed rate can induce excessive internal stress on both the tool and workpiece. This paper aims to study the effects of reaction force acting on a drill bit during drilling of Al6061-T6. A numerical finite element simulation study is performed with commercially available software called Abaqus. Simulation results depend on the right choice of material property such as Johnson–Cook material property and Johnson–Cook damage property. Validation of material property is achieved by comparison of experimental results with simulative results. Reaction force acting against the drill bit during drilling is compared.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45972441","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}
Abstract The objective of this paper is to assess the inplane shear buckling of a steel foam sandwich panel that relies on elastic Pasternak foundation. The panel is a combination of solid steel face sheets and foamed steel cores. Foamed steel, that is steel with internal voids, provides enhanced bending rigidity and energy dissipation, and also, the potential to reduce local buckling. The Classic plate theory is employed where their governing equations are solved by the Rayleigh–Ritz method. Uniformly distributed in-plane shear loads are applied to the two opposite edges of the panel and all the four edges of the panel are simply supported. Finally, the effects of the panel parameters, such as the existence of a Pasternak foundation, aspect ratios, and central fraction of the steel foam core, are presented. The results showed that the optimum central fraction of the steel foam core would be 65%, so that the maximum critical shear buckling load has taken place.
{"title":"Shear buckling of steel foam sandwich panel resting on Pasternak foundation","authors":"Ebrahim Nazarimofrad, Mehdi Barang","doi":"10.2478/mme-2019-0025","DOIUrl":"https://doi.org/10.2478/mme-2019-0025","url":null,"abstract":"Abstract The objective of this paper is to assess the inplane shear buckling of a steel foam sandwich panel that relies on elastic Pasternak foundation. The panel is a combination of solid steel face sheets and foamed steel cores. Foamed steel, that is steel with internal voids, provides enhanced bending rigidity and energy dissipation, and also, the potential to reduce local buckling. The Classic plate theory is employed where their governing equations are solved by the Rayleigh–Ritz method. Uniformly distributed in-plane shear loads are applied to the two opposite edges of the panel and all the four edges of the panel are simply supported. Finally, the effects of the panel parameters, such as the existence of a Pasternak foundation, aspect ratios, and central fraction of the steel foam core, are presented. The results showed that the optimum central fraction of the steel foam core would be 65%, so that the maximum critical shear buckling load has taken place.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47300978","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}
Abstract To analyse the effects of cylindrical- and row-trenched cooling holes with an alignment angle of 90 degrees on the film-cooling effectiveness near the combustor end wall surface at a blowing ratio of 3.18, the current research was done. This research included a 3D representation of a Pratt and Whitney gas turbine engine, which was simulated and analysed with a commercial finite volume package FLUENT 6.2.26. The analysis was done with Reynolds-averaged Navier–Stokes turbulence model on internal cooling passages. This combustor simulator was combined with the interaction of two rows of dilution jets, which were staggered in the streamwise direction and aligned in the spanwise direction. In comparison with the baseline case of cooling holes, using row-trenched hole near the end wall surface increased the film-cooling effectiveness 44% in average.
{"title":"A Detailed Study of Row-Trenched Holes at the Combustor Exit on Film-Cooling Effectiveness","authors":"E. Kianpour, N. Sidik","doi":"10.2478/mme-2019-0033","DOIUrl":"https://doi.org/10.2478/mme-2019-0033","url":null,"abstract":"Abstract To analyse the effects of cylindrical- and row-trenched cooling holes with an alignment angle of 90 degrees on the film-cooling effectiveness near the combustor end wall surface at a blowing ratio of 3.18, the current research was done. This research included a 3D representation of a Pratt and Whitney gas turbine engine, which was simulated and analysed with a commercial finite volume package FLUENT 6.2.26. The analysis was done with Reynolds-averaged Navier–Stokes turbulence model on internal cooling passages. This combustor simulator was combined with the interaction of two rows of dilution jets, which were staggered in the streamwise direction and aligned in the spanwise direction. In comparison with the baseline case of cooling holes, using row-trenched hole near the end wall surface increased the film-cooling effectiveness 44% in average.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45198004","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}
Dheepakram Laxmimala Barathwaaj, Sujay Yegateela, V. Vardhan, V. Suresh, Devarajan Kaliyannan
Abstract In this paper, closed-form optimal parameters of inerter-based variant dynamic vibration absorber (variant IDVA) coupled to a primary system subjected to base excitation are derived based on classical fixed-points theory. The proposed variant IDVA is obtained by adding an inerter alone parallel to the absorber damper in the variant dynamic vibration absorber (variant DVA). A new set of optimum frequency and damping ratio of the absorber is derived, thereby resulting in lower maximum amplitude magnification factor than the inerter-based traditional dynamic vibration absorber (traditional IDVA). Under the optimum tuning condition of the absorbers, it is proved both analytically and numerically that the proposed variant IDVA provides a larger suppression of resonant vibration amplitude of the primary system subjected to base excitation. It is demonstrated that adding an inerter alone to the variant DVA provides 19% improvement in vibration suppression than traditional IDVA when the mass ratio is less than 0.2 and the effective frequency bandwidth of the proposed IDVA is wider than the traditional IDVA. The effect of inertance and mass ratio on the amplitude magnification factor of traditional and variant IDVA is also studied.
{"title":"Effect of Inerter in Traditional and Variant Dynamic Vibration Absorbers for One Degree-of-Freedom Systems Subjected to Base Excitations","authors":"Dheepakram Laxmimala Barathwaaj, Sujay Yegateela, V. Vardhan, V. Suresh, Devarajan Kaliyannan","doi":"10.2478/mme-2019-0002","DOIUrl":"https://doi.org/10.2478/mme-2019-0002","url":null,"abstract":"Abstract In this paper, closed-form optimal parameters of inerter-based variant dynamic vibration absorber (variant IDVA) coupled to a primary system subjected to base excitation are derived based on classical fixed-points theory. The proposed variant IDVA is obtained by adding an inerter alone parallel to the absorber damper in the variant dynamic vibration absorber (variant DVA). A new set of optimum frequency and damping ratio of the absorber is derived, thereby resulting in lower maximum amplitude magnification factor than the inerter-based traditional dynamic vibration absorber (traditional IDVA). Under the optimum tuning condition of the absorbers, it is proved both analytically and numerically that the proposed variant IDVA provides a larger suppression of resonant vibration amplitude of the primary system subjected to base excitation. It is demonstrated that adding an inerter alone to the variant DVA provides 19% improvement in vibration suppression than traditional IDVA when the mass ratio is less than 0.2 and the effective frequency bandwidth of the proposed IDVA is wider than the traditional IDVA. The effect of inertance and mass ratio on the amplitude magnification factor of traditional and variant IDVA is also studied.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45259008","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}
M. Dennison, Sivaram N M, Debabrata Barik, S. Ponnusamy
Abstract The objective of this study is to analyse the effect of tool-work interface temperature observed during the turning of AISI 4340 cylindrical steel components in three machining conditions, namely flooded, near-dry and dry conditions with three separate CNMG-PEF 800 diamond finish Titanium Nitride (TiN) coated carbide cutting tool. The machining parameters considered in this study are cutting velocity, feed rate and depth of cut. The experiments were planned based on full factorial design (33) and executed in an All Geared Conventional Lathe. The tool-work interface temperature was observed using a K-type tool-work thermocouple, while the machining of steel, and subsequently, a mathematical model was developed for the tool-work interface temperature values through regression analysis. The significance of the selected machining parameters and their levels on tool-work interface temperature was found using analysis of variance (ANOVA) and F-test. The results revealed that machining under near-dry condition exhibited lesser temperature at the tool-work interface, which is the sign of producing better quality products in equivalence with the machining under flooded condition.
{"title":"Turning operation of AISI 4340 steel in flooded, near-dry and dry conditions: a comparative study on tool-work interface temperature","authors":"M. Dennison, Sivaram N M, Debabrata Barik, S. Ponnusamy","doi":"10.2478/mme-2019-0023","DOIUrl":"https://doi.org/10.2478/mme-2019-0023","url":null,"abstract":"Abstract The objective of this study is to analyse the effect of tool-work interface temperature observed during the turning of AISI 4340 cylindrical steel components in three machining conditions, namely flooded, near-dry and dry conditions with three separate CNMG-PEF 800 diamond finish Titanium Nitride (TiN) coated carbide cutting tool. The machining parameters considered in this study are cutting velocity, feed rate and depth of cut. The experiments were planned based on full factorial design (33) and executed in an All Geared Conventional Lathe. The tool-work interface temperature was observed using a K-type tool-work thermocouple, while the machining of steel, and subsequently, a mathematical model was developed for the tool-work interface temperature values through regression analysis. The significance of the selected machining parameters and their levels on tool-work interface temperature was found using analysis of variance (ANOVA) and F-test. The results revealed that machining under near-dry condition exhibited lesser temperature at the tool-work interface, which is the sign of producing better quality products in equivalence with the machining under flooded condition.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43529820","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}
Abstract In this paper, an iterative finite element model updating method in structural dynamics is proposed. This uses information matrices and element connectivity matrices to reconstruct the corrected model by reproducing the frequency response at measured degrees of freedom. Indicators have been proposed to quantify the mismodelling errors based on a development in Lagrange matrix interpolation. When applied on simulated truss structures, the model gives satisfactory results by detecting and quantifying the defaults of the initial model.
{"title":"Finite element model updating using Lagrange interpolation","authors":"F. Asma","doi":"10.2478/mme-2019-0030","DOIUrl":"https://doi.org/10.2478/mme-2019-0030","url":null,"abstract":"Abstract In this paper, an iterative finite element model updating method in structural dynamics is proposed. This uses information matrices and element connectivity matrices to reconstruct the corrected model by reproducing the frequency response at measured degrees of freedom. Indicators have been proposed to quantify the mismodelling errors based on a development in Lagrange matrix interpolation. When applied on simulated truss structures, the model gives satisfactory results by detecting and quantifying the defaults of the initial model.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43993275","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}
Abstract This research is concerned with the study of mechanical disturbances due to presence of ultra-short laser pulse as input heat source in a microstretch thermoelastic medium with microtemperatures. The medium is subjected to normal and tangential forces. The solution of the problems is developed in terms of normal modes. Mathematical expressions have been obtained for normal stress, tangential stress, microstress and temperature change. The numerically computed results are shown graphically. A mathematical model has been developed and various stress quantities have been analyzed. Some particular cases are also derived from the present investigation.
{"title":"Elastodynamical disturbances due to laser irradiation in a microstretch thermoelastic medium with microtemperatures","authors":"Arvind Kumar, D. Singh","doi":"10.2478/mme-2019-0015","DOIUrl":"https://doi.org/10.2478/mme-2019-0015","url":null,"abstract":"Abstract This research is concerned with the study of mechanical disturbances due to presence of ultra-short laser pulse as input heat source in a microstretch thermoelastic medium with microtemperatures. The medium is subjected to normal and tangential forces. The solution of the problems is developed in terms of normal modes. Mathematical expressions have been obtained for normal stress, tangential stress, microstress and temperature change. The numerically computed results are shown graphically. A mathematical model has been developed and various stress quantities have been analyzed. Some particular cases are also derived from the present investigation.","PeriodicalId":53557,"journal":{"name":"Mechanics and Mechanical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48587268","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：