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Editorial Office

University of Ljubljana
Faculty of Mechanical Engineering
Journal of Mechanical Engineering

Aškerčeva 6,

SI-1000 Ljubljana
Slovenia

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E: info@sv-jme.eu



The journal is subsidized by Slovenian Research Agency.

 
ISSN: 0039-2480

Journal of Mechanical Engineering 63 (2017) 9

 

 

 


 

The Yield-Point Phenomenon and Cyclic Plasticity of the Console Beam

Authors - Andrej Žerovnik* – Ivan Prebil – Robert Kunc


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

Keywords - yield-point phenomenon, cyclic plasticity, mechanical testing, FEM simulations

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 479-488, SI 71
DOI:10.5545/sv-jme.2017.4499

 

pdfThe Yield-Point Phenomenon and Cyclic Plasticity of the Console Beam (.pdf 1.2MB)

 


  

Application of a Force Model Adapted for the Precise Turning of Various Metallic Materials

Authors - Richárd Horváth* – Judit Lukács


Abstract

The knowledge of cutting forces is critical. They might affect the load of the machine and, in the case of fine turning, the deformation of thin and slim workpieces. The generated forces depend not only on material properties (hardness, tensile strength) and on cutting parameters, but also on the tool edge geometry, that strongly determines the geometry of the chip (thickness and width). This article deals with the application of a force model adapted for precise turning technology. Three different types of materials widely used in mass production were taken into consideration (C45 and KO36 steel types and AS12 die-cast aluminium alloy). The components of cutting force were measured in three directions (Fc , Ff, Fp) and the specific cutting forces were calculated. The main values of specific cutting forces were introduced for precision turning (k1, 0.1); using this, a new force model was constructed based on the theoretical parameters of the non-deformed chip cross-section (heq is equivalent chip thickness and leff effective length of the edge of the tool) in case of all three examined materials. Investigations revealed that the influence of leff on specific cutting force components is not negligible; however, it has the least effect on kc and is the most influential in case of kp. The errors of the constructed new force models follow Gaussian distribution with low values of standard deviation. Thereby, the models can be applied to estimate cutting force components during the technological process planning procedure with adequate accuracy.

Keywords - fine turning, force model, force measurement, specific cutting force

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 489-500, SI 72
DOI:10.5545/sv-jme.2017.4430

 

pdfApplication of a Force Model Adapted for the Precise Turning of Various Metallic Materials (.pdf 1.1MB)

 


 

The Effect of the Thickness-to-Die Diameter Ratio on the Sheet Metal Blanking Process

Authors - Kaan Emre Engin* – Omer Eyercioglu


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.

Keywords - blanking process, blanking parameters, shear zone, clearance

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 501-509, SI 73
DOI:10.5545/sv-jme.2016.4272

 

pdfThe Effect of the Thickness-to-Die Diameter Ratio on the Sheet Metal Blanking Process (.pdf 1.4MB)

 


 

The Effect of Process Parameters on the Microstructure and Mechanical Performance of Fiber Laser-Welded AA5182 Aluminium Alloys

Authors - Celalettin Yuce* – Mumin Tutar – Fatih Karpat – Nurettin Yavuz – Gökhan Tekin


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 shear load

Keywords - fiber laser welding, aluminium alloys, mechanical characterization, microstructural analysis


Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 510-518, SI 74
DOI:10.5545/sv-jme.2017.4442

 

pdfThe Effect of Process Parameters on the Microstructure and Mechanical Performance of Fiber Laser-Welded AA5182 Aluminium Alloys (.pdf 2.0MB)




Neural Network-Based High-Accuracy Motion Control of a Class of Torque-Controlled Motor Servo Systems with Input Saturation

Authors - Lei Liu – Jian Hu* – Yuangang Wang – Zhiwei Xie

Abstract

The torque-controlled motor servo system is widely used in many industrial applications. However, input saturation often occurs due to the limitation of the actuator output ability, which may worsen the system control performance. In this paper, in order to inhibit the impact of input saturation on the system, a single-hidden-layer neural network based observer is designed to estimate the value of input saturation, which could later be compensated in the proposed controller. In addition, an adaptive law is introduced to estimate the unknown parameters, and a nonlinear robust term is designed to overcome the time-varying disturbances and other compensation errors. The Lyapunov theorem is used to prove the stability of the proposed controller with the neural network-based observer. Extensive comparative experimental results are obtained to verify the high-performance of the proposed control strategy.

Keywords - torque-controlled motor, input saturation, adaptive robust control, neural network, disturbance

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 519-528, SI 75
DOI:10.5545/sv-jme.2016.4282

 

pdfNeural Network-Based High-Accuracy Motion Control of a Class of Torque-Controlled Motor Servo Systems with Input Saturation (.pdf 786KB)




Wall Roughness Influence on the Efficiency Characteristics of Centrifugal Pump

Authors - Andrej Lipej – Simon Muhič* – Duško Mitruševski

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.

Keywords - pump, CFD, wall roughness, turbulence

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 529-536 , SI 75
DOI:10.5545/sv-jme.2017.4526

 

pdfWall Roughness Influence on the Efficiency Characteristics of Centrifugal Pump (.pdf 1.7MB)




Electric-Thermo-Mechanical Analysis of Joule Heating in Dilatometric Specimens

Authors - Martin Herrejón-Escutia – Gildardo Solorio-Díaz – Héctor Javier Vergara-Hernández – Edgar López-Martínez – Gerardo Marx Chávez-Campos – Octavio Vázquez-Gómez*

Abstract

A mathematical model of Joule heating was developed for an AISI 304 stainless steel in a hollow cylinder dilatometric specimen. The model was developed by means of creating a balance of energy by coupling the generation term due to the Joule heating and the thermal expansion of the specimen. A Newtonian heating system was assumed for a volume element, and it was resolved by means of the finite differences method, generating its own computer code in the Scilab free-license software. The model considers the thermophysical and electrical properties of steel, depending on the temperature. Thermal interactions at the boundary and the linear thermal expansion coefficient were determined by solving the inverse heat conduction problem (IHCP) using the thermal profile and thermal expansion measured experimentally by means of a direct heating device. The model was validated by comparing the thermal response and experimental thermal expansion with simulated responses for different heating rates

Keywords - mathematical model, continuous heating, Joule effect, dilatometry, AISI 304 stainless steel

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)9, 537-547, SI 75
DOI:10.5545/sv-jme.2017.4320

 

pdfElectric-Thermo-Mechanical Analysis of Joule Heating in Dilatometric Specimens (.pdf 1.1MB)



 


Leaflet SV-JME


 

 

Journal of Mechanical Engineering

in digital form


SV-JME-9-2017


SV-JME-7-8-2017


SV-JME-6-2017


SV-JME-5-2017

 

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