Strojniski Vestnik-journal of Mechanical Engineering 

About: Strojniski Vestnik-journal of Mechanical Engineering is an academic journal. The journal publishes majorly in the area(s): Machining & Surface roughness. Over the lifetime, 828 publications have been published receiving 8135 citations.

Focus Variation – a Robust Technology for High Resolution Optical 3D Surface Metrology

Abstract: This article describes and evaluates the focus variation method, an optical 3D measurement technique. The goal is to analyse the performance of the method on a series of typical measurement tasks including roughness measurements, form and wear measurements. First, a comparison of roughness measurements between the proposed method and a tactile device on a newly developed roughness standard is made. Results show that both systems deliver Ra values that are comparable to each other with differences of a few nanometers. Afterwards form measurements are performed on a calibration standard with hemi-spherical calottes, showing a repeatability of sphere measurements < 100 nm. Finally, two typical engineering applications are provided. The first is wear measurement of cutting tools, the second the inspection and classification of welding spots. Both applications demonstrate the ability of the method to measure steep surface flanks up to 80° and surfaces with difficult reflectance behaviour.

Auxetic Cellular Materials - a Review

Abstract: Auxetic cellular materials are modern materials which have some unique and superior mechanical properties. As a consequence of the structural deformation of their internal cellular structure they exhibit a negative Poisson’s ratio, i.e. they significantly increase in volume when stretched and vice versa. The effect of negative Poisson’s ratio is useful in many applications to enhance certain physical properties such as the density, stiffness, fracture toughness, energy absorption and damping. These properties can be further tailored by using variable cell geometry and density distribution, which can be achieved with functionally graded porosity of auxetic materials. This review paper provides the state-of-the-art overview of the auxetic materials, their development, most common geometries, fabrication methods, mechanical properties, applications and further possibilities for their development.

Signal Model-Based Fault Detection and Diagnosis for Induction Motors Using Features of Vibration Signal in Two- Dimension Domain

Abstract: In this paper, we propose an approach for vibration signal-based fault detection and diagnosis system applying for induction motors. The approach consists of two consecutive processes: fault detection process and fault diagnosis process. In the fault detection process, significant features from vibration signals are extracted through the scale invariant feature transform (SIFT) algorithm to generate the faulty symptoms. Consequently, the pattern classification technique using the faulty symptoms is applied to the fault diagnosis process. Hence, instead of analyzing the vibration signal to determine the induction motor faults, the vibration signal can be classified to the corresponding faulty category, which presents the induction motor fault. We also provide a framework for the pattern classification technique that is applicable to SIFT patterns. Moreover, a comparison with two other approaches in our previous work is also carried out. The testing results show that our proposed approach provides significantly high fault classification accuracy and a better performance than previous approaches.

Application of Ultrasonic C-Scan Techniques for Tracing Defects in Laminated Composite Materials

Abstract: In this paper practical ultrasonic C-scan techniques for NDT of laminated composite materials are developed and applied, with an aim to trace specific artificial defects. Two types of materials are examined; an advanced carbon/epoxy system and a typical marine type glass/polyester system. Both were constructed with two manufacturing methods (Hand Lay-Up and Vacuum Infusion). Several artificial defects were embedded into the test plates, varying in shape, magnitude and through thickness position. Test plates were C-scanned using ULTRAPAC II ultrasonic system with ULTRAWIN software and typical examination techniques (layer to layer examination, full width examination, etc.) were used to determine and characterize defects. In addition, appropriate software tuning procedures and examination strategies were applied, which further developed and optimised tthe scanning procedure. These efforts resulted in effective C-scan images, allowing the determination of the position and even the shape of the defects in some cases. Finally, precise determination of specimens’ thickness was achieved.

Calculation of the Combined Torsional Mesh Stiffness of Spur Gears with Two- and Three-Dimensional Parametrical FE Models

Abstract: The torsional mesh stiffness is one of the most important characteristics of spur gears. This paper presents the development of detailed two- and three-dimensional finite element models which can be used to calculate the torsional mesh stiffness. Using the parametrical design language of the FE software ANSYS the models offer the possibility to generate various different pairs of spur gears and include an adaptive meshing algorithm for the contact zones. Due to the short computation times the 2D model is well suited to simulate a variety of different gear pairs in a short time period. The more complex 3D model features more options in terms of investigating tooth face modifications for further studies. The resulting values of the torsional stiffness can be used – for example – in multi body simulations of gearboxes. The results from the 2D FEA are used to derive a simple formula for the combined torsional stiffness of spur gears in mesh. The results presented are based on the individual stiffness of the three main components – body, teeth and contact. Hence, the introduced formula uses these three parts to determine the overall stiffness for a wide range of gears and gear ratio combinations. Finally, the results from both the two- and three-dimensional finite element model and the derived formula are compared and the results from the 3D model are checked against results obtained by analytical equations.