Strojniski Vestnik-Journal of Mechanical Engineering最新文献

{"title":"Wall roughness influence on the efficiency characteristics of centrifugal pump.","authors":"A. Lipej, S. Muhič, D. Mitruševski","doi":"10.5545/SV-JME.2017.4526","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4526","url":null,"abstract":"Many different machines are developed in industry and in terms of energy conversion, their efficiency is one of the most important parameters. A lot of theoretical, experimental and numerical analyses are done in the development process in order to obtain required characteristics. Computational fluid dynamics (CFD) analyses are a very important part of the development process. To obtain accurate results it is important to pay attention to geometry definition, usage appropriate numerical model, quality of the computational grid, realistic boundary conditions and all of the other parameters regarding fluid and solid material properties. A very important issue is usually the correct selection of the turbulence model. In most CFD analyses, only smooth surface is taken into account without considering any wall roughness. Besides the usage of different physical and mathematical models and all required parameters, the wetted surface roughness can also be one of the important origins of the numerical results inaccuracy. In the paper, the analysis of the influence of different parameters such as the sandgrain equivalent parameter is presented. The influence of y+ on the accuracy of the flow analysis with different absolute roughness of the surfaces is also analyzed. For basic relations, the flow in simple geometries like flow over flat plate and flow in circular pipe has been analyzed. The conclusions of the preliminary research work are used in the case of efficiency prediction of centrifugal pump with rough walls. The final numerical results are compared with the experimental ones and show better agreement in comparison with the flow over smooth walls.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"53 1","pages":"529-536"},"PeriodicalIF":1.7,"publicationDate":"2017-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89105325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Effect of the Thickness-to-Die Diameter Ratio on the Sheet Metal Blanking Process","authors":"K. E. Engin, O. Eyercioglu","doi":"10.5545/SV-JME.2016.4272","DOIUrl":"https://doi.org/10.5545/SV-JME.2016.4272","url":null,"abstract":"The blanking process has a wide range of usage in the sheet metal production industry. The effectiveness of the process rests on the balance between the surface quality of the blanks and energy conservation during the process. The effects of different process parameters on surface quality and energy efficiency have been studied by researchers, but there is a gap concerning the effect of the thickness-to-die diameter ratio on surface quality and energy efficiency. In this study, four different thickness-to-die diameter ratios (t/Dm=1/5, t/Dm=1/10, t/Dm=1/30 and t/Dm=1/50) with five different clearances (1 %, 3 %, 5 %, 10 %, and 20 % of thickness) were used to blank 2-mm-thick round workpieces made of AISI 304 stainless steel. Both experimental and FEM studies were accomplished. A special die set was manufactured and a hydraulic press was used for experimental studies. For FEM studies, Deform-2D was used. Investigations were made on the effects of different thickness-todie diameter ratios on the blanking force, cutting energy crack propagation angles, and zone distribution related to surface quality. Results gathered from FEM simulations and experimental studies were coherent with each other.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"17 1","pages":"501-509"},"PeriodicalIF":1.7,"publicationDate":"2017-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90050675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Effect of Process Parameters on the Microstructure and Mechanical Performance of Fiber Laser-Welded AA5182 Aluminium Alloys","authors":"C. Yuce, Mumin Tutar, F. Karpat, N. Yavuz, Gokhan Tekin","doi":"10.5545/SV-JME.2017.4442","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4442","url":null,"abstract":"The laser welding of aluminium alloys is an important industrial technology but many challenges remain. The objective of this research is to investigate the effect of laser welding parameters on the quality of the fiber laser lap welded AA5182 aluminium alloy. The influences of the laser power, welding speed and focal point position on the mechanical and microhardness properties of the joints were experimentally investigated. The mechanical properties of the joints were evaluated by performing tensile tests. From the experimental results, optimum process parameters were determined, and microstructural examination and microhardness tests were conducted to better understand the performance of the joints. It was found that there is a correlation between the tensile shear loads of the joints and heat input per unit length. At the optimized parameters, the welded joint showed good weld appearance without macro defects, and the joint had an adequate tensile \u0000shear load.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"24 1","pages":"510-518"},"PeriodicalIF":1.7,"publicationDate":"2017-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74173765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Yield-Point Phenomenon and Cyclic Plasticity of the Console Beam","authors":"A. Žerovnik, I. Prebil, R. Kunc","doi":"10.5545/SV-JME.2017.4499","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4499","url":null,"abstract":"In the paper, the influence of the yield-point phenomenon (YPP) on cyclic plasticity of the console beam is presented with the objective to demonstrate the impact of the YPP on the local cyclic plasticity. The influence of the YPP and its dependence on cyclic material hardening or softening was studied through experiments and numerical simulations. Console beams are made from the low-alloy EN 42 CrMo 4 steel in its normalized state (184 HV), which exhibits cyclic hardening, and in its tempered state (296 HV), which is subject to cyclic softening. Numerical simulations were performed on constitutive model of cyclic plasticity taking into account the kinematic hardening, isotropic hardening or softening and formulations of the YPP which are based on the change of the elastic region surface in the stress space at first transition into the stress plateau. Analysis of the results shows the importance of taking into account the YPP equations in constitutive models of cyclic plasticity as well as the influence of the YPP on cyclic plasticity of the console beam.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"8 1","pages":"479-488"},"PeriodicalIF":1.7,"publicationDate":"2017-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85406350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Joint Clearance on Motion Accuracy of Robotic Manipulators","authors":"Selçuk Erkaya","doi":"10.5545/SV-JME.2017.4534","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4534","url":null,"abstract":"Robots have been introduced in many industrial and medical areas where high accuracy, repeatability, and operation stability are desired. These are key features for robots. Some error sources in robots originate from assemblage, servo actuator resolution, reducer backlash, and joint clearances [1]. These errors reduce the accuracy of the robot and must be controlled to ensure the quality of the desired movement. In this regard, increased importance has been given to the accuracy of robots through various contributions in the relevant literature [2] to [5]. In comparison to machine tools, industrial robots are flexible and relatively cheaper in terms of cost. At the same time, such robots are susceptible to errors from many sources due to their serial structure. To ensure the positioning accuracy of a robot end effector as well as to reduce the manufacturing cost of the robot, it is necessary to quantify the influence of the uncertain factors and optimally allocate the tolerances. A novel and simple approach to identify the positional and directional errors due to the joint clearance of linkages and manipulators based on a geometrical model was introduced [6]. A general probability density function of the endpoint of planar robots with joint clearance was established to derive the distribution functions for any position tolerance zone and any joint distribution type [7]. Some errors arising from link stiffness and clearances were considered to predict the accuracy of the parallel devices [8]. By considering the positional and directional errors of the robot hand and the manufacturing cost, the optimal allocation of joint tolerances was investigated. Interval analysis was used to predict the errors in the manipulator performance [9]. Singularity analysis and modelling of the joint clearance effects on the parallel robot’s accuracy were conducted. An analytical model was presented to easily predict the pose error for a given external load, a nominal pose and the structural parameters [3]. A procedure to calculate the positional error in parallel manipulators due to both clearances and elastic deformations was proposed [10]. For analysing the location of the discontinuities, a methodology was presented and the advantages of approach were analysed using a 5R planar mechanism [11]. The effect of joint flexibility on the dynamic performance of a serial spatial robot arm with rigid links was studied by using three developed models [12]. A novel method based on trajectory planning to avoid detachment of the joint elements of a manipulator with clearances was presented. An improved detachment criterion for the different joint types was proposed [13]. The clearance effects on an industrial robot were studied during 2D welding operations. The kinematics and Effects of Joint Clearance on the Motion Accuracy of Robotic Manipulators Erkaya, S. Selçuk Erkaya* Erciyes University, Engineering Faculty, Mechatronics Engineering Department, Turkey","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2017-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91296882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methodology To Facilitate Successful Lean Implementation","authors":"T. Berlec, M. Kleindienst, Christian Rabitsch, C. Ramsauer","doi":"10.5545/SV-JME.2017.4302","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4302","url":null,"abstract":"The implementation of lean production in a company is a transformation of the whole company’s culture. To achieve such a lean culture, the role and support of management are decisive. This paper introduces a newly defined model and methodology with an interview guide which helps to distinguish a supportive from a non-supportive management team when introducing lean production, and helps to decide if a step needs to be repeated, improved, or the next step can be initiated. The methodology is especially suitable for small and medium-sized enterprises (SME’s), because of their lack of human resources, where this model was also tested.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"93 1","pages":"457-465"},"PeriodicalIF":1.7,"publicationDate":"2017-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76394699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal Optimization and Comparison of Geometric Parameters of Rectangular and Triangular Fins with Constant Surfacing","authors":"Florent Bunjaku, R. Filkoski, Naser Sahiti","doi":"10.5545/SV-JME.2016.4276","DOIUrl":"https://doi.org/10.5545/SV-JME.2016.4276","url":null,"abstract":"This paper presents an optimization model of fins of rectangular and triangular profiles, based on a constant value of the transverse cutting surface, as well as the optimization of the ratio of efficiency of both fin profiles. The optimization model is based on the analytical and numerical simulation of the heat flux through fins in order to derive relevant thermo-physical parameters of the investigated fin profiles. The optimization of both fin profiles is carried out for different fin materials based on constant heat transfer coefficient and for different fin materials based on variable heat flux. The efficiency of fins as relevant fin goodness parameter is also analysed and the optimal values of the ratio of fin efficiency of both profiles is graphically presented and the optimal value estimated. Numerical simulation of fin models is carried out by using ANSYS/Fluent software.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"49 1","pages":"439-446"},"PeriodicalIF":1.7,"publicationDate":"2017-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80690488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling Study on Stiffness Characteristics of Hydraulic Cylinder under Multi-Factors","authors":"H. Feng, Q. Du, Yuxian Huang, Y. Chi","doi":"10.5545/SV-JME.2017.4313","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4313","url":null,"abstract":"For a complex mechanical system driven by hydraulic cylinders, the dynamic response characteristics of the mechanical system are significantly affected by the stiffness characteristics of hydraulic cylinders. This paper comprehensively studies the impacts of various factors on the stiffness characteristics of the hydraulic cylinders, including the oil bulk modulus, the air content in the hydraulic oil, the axial deformation of the piston rod, the volume expansion of the cylinder barrel, the volume expansion of the metal pipes and the flexible hoses, and the deformation of the hydraulic cylinder sealing. By combining the theoretical analysis and the experimental results, the level of each impacting factor was quantified, and the stiffness model of the hydraulic cylinder was established. Finally, comparative analysis of the stiffness was conducted by taking the experimental hydraulic cylinder as an example; it was verified that the calculated results of the proposed hydraulic cylinder stiffness model approximated the experimental results. Compared with stiffness models presented in current literature, the average accuracy was improved by more than 15 %.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"23 1","pages":"447-456"},"PeriodicalIF":1.7,"publicationDate":"2017-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74464169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LBM Analysis of Micro-Convection in MHD Nanofluid Flow","authors":"A. K. Sunil, Rakesh Kumar","doi":"10.5545/SV-JME.2016.4248","DOIUrl":"https://doi.org/10.5545/SV-JME.2016.4248","url":null,"abstract":"The lattice Boltzmann-Bhatnagar-Gross-Krook method was used to simulate Al2O3-water nanofluid to find the effects of Reynolds, Rayleigh and Hartmann numbers, slip coefficient, nanoparticle volume fraction and axial distance on forced convection heat transfer in MATLAB. The ranges of studied Reynolds number, Rayleigh number, magnetic field strength, nanoparticle volume concentration and slip coefficient include 200 ≤ Re ≤ 4000; 103 ≤ Ra ≤ 106; 0 ≤ Ha 90; 0 ≤ φ ≤ 2%; 0.005 ≤ B ≤ 0.02, respectively. The results show that increasing Reynolds number and nanoparticle volume fractions improve heat transfer in the 2D microtube under laminar, turbulent, slip and temperature jump boundary conditions. Decreasing the values of slip coefficient decreases the temperature jump and enhances the Nusselt number. A critical value for the Rayleigh number (105) and magnetic field strength (Ha 10) exists, at which the impacts of the solid volume fraction and slip coefficient effects are the most pronounced. The pressure drop shows a similar type of enhancement in magnitude, as observed in the case of the Nusselt number. However, application of nanofluids for low Reynolds numbers is more beneficial, and the effect of volume fractions are more pronounced in comparison to slip coefficient, though the effects are marginal.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"93 1","pages":"426-438"},"PeriodicalIF":1.7,"publicationDate":"2017-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85653620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Absolute Nodal Coordinate Formulation in a Pre-Stressed Large-Displacements Dynamical System","authors":"Luka Skrinjar, J. Slavič, M. Boltežar","doi":"10.5545/SV-JME.2017.4561","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4561","url":null,"abstract":"The design process for dynamical models has to consider all the properties of a mechanical system that have an effect on its dynamical response. In multi-body dynamics, flexible bodies are frequently modeled as rigid, resulting in non-valid modeling of the pre-stress effect. In this research a focus on the pre-stress effect for a flexible body assembled in a rigid-flexible multibody system is presented. In a rigid-flexible assembly a flexible body is modeled with an absolute nodal coordinate formulation (ANCF) of finite elements. The geometrical properties of the flexible body are evaluated based on the frequency response and compared with the experimental values. An experiment including the pre-stress effect and large displacements is designed and the measured values of the displacement are compared to the numerical results in order to validate the dynamical model. The pre-stress was found to be significant for proper numerical modeling. The partially validated numerical model was used to research the effect of different parameters on the dynamical response of a pre-stressed, rigid-flexible assembly.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"58 1","pages":"417-425"},"PeriodicalIF":1.7,"publicationDate":"2017-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75694357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}