Mechanical Engineering

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Research Topic Summary.

In the development of modern biosensors, it is important to develop a bioactive composite and to use its active properties in such micromechanical devices that create nano / micro spaces into which biodparties performing a diagnostic function are positioned. Therefore, it is important to develop micromechanical systems with nano / micro spaces at the nano / micrometric level that can be used to develop nano / micro biodparticle traps and storages and biosensors operating on this basis. The main idea of the project includes the development of devices and technologies that would lead to the further development of modern biosensors based on the single molecule principle. This will be achieved by synthesizing a bioactive nanocomposite, evaluating its mechanical, electrical, hydrophobic and dynamic properties, and developing technology for the formation of nano / microspaces and microstructures in a piezoelectric nanocomposite.

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Research Topic Summary.

3D printing of multifunctional structures and devices by using eco-friendly piezoelectric nanocomposite materials (piezocomposites) is an emerging and highly promising research avenue in additive manufacturing (AM), which is related to a new fabrication paradigm referred to as 4D printing. AM is one of the strategic technological drivers of Industry 4.0, hence it is essential to expand portfolio of printable materials by including various smart materials. Specifically, there is a pressing need to replace traditional rigid, brittle and lead-based piezoceramics with nontoxic or less toxic flexible and resilient piezocomposites. Their 3D printing via fused deposition modelling is a technically and economically viable AM approach. Implementing fabrication of 3D printing filaments using thermoplastic lead-free piezocomposites (e.g. polymeric-ceramic ones) will open wide possibilities to develop freeform-shaped flexible multifunctional structures with tailored mechanical properties (stiffness, energy absorption, etc.) and integrated smart functionalities such as mechanical sensing and micro energy harvesting. Worldwide research activities on fabrication of lead-free piezocomposite filaments and 3D printing of next-generation sensorial and energy harvesting devices are in early stages. This indicates vast application potential in development of advanced self-monitoring and energy-autonomous systems used in the bio-medical/mechatronics and soft robotics domains. For more details please contact the supervisor of the topic.

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Research Topic Summary.

Composite structures are very widely used in various industries such as medicine, aviation, renewable energy, defence and etc. It is obvious that area of usage of composites is expanding and such tendencies can be seen in the science and industry too. Additive manufacturing (AM) technologies allows to produce very complex products, minimize wastes, and decrease production cycle time. AM of innovative products from composite materials takes more important role in the global manufacturing environment. Existing technologies are continuously improving however new AM technologies emerge in the market with potentiality to use new materials. Therefore, many challenges are meet here because usage of new material in the AM environment requires a lot of consistent research and experimentations. Especially this is important then composite materials are used, because compatibility of materials needs to be considered. Proposed topic of PhD thesis is dedicated for solving of above-mentioned challenges. During the studies new additive manufacturing technology for production of high performance structures will be developed. Influence of manufacturing parameters on mechanical properties of composite structures will be analysed. Developed technology will allow producing high performance structures with optimal mass to strength ratio.

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Research Topic Summary.

The development of advanced transport, aerospace, wind turbines and other structural components of fibre reinforced polymer composites is constantly growing due to perfect combination of their high stiffness, strength and low density. During in-service life these composite structures are subjected to impact and fatigue loads, causing a localized damage such as matrix cracking, delamination and fibre breakage, which leads to the degradation of the mechanical properties. These damages are usually invisible and the prediction of the required maintenance intensity, ensuring the cost efficiency avoiding a catastrophic failure is a very difficult task. Structural health monitoring for the damage detection is essential to enhance in-service reliability and lifetime of composite structures. Many types of sensors, vibration, wave propagation techniques have been developed for damage sensing. Despite their advantages, these techniques also have a number of disadvantages, for instance, integrated sensors can cause the increase of stress concentration in a part, contactless methods are often difficult to use due to sophisticated equipment. The aim of this study is to develop novel electrically conductive fibre reinforced polymer composites with excellent mechanical properties and self-diagnostic function. The objectives for this aim are the following  optimisation of hybrid-hierarchical composite microstructure to ensure extraordinary electrical properties of the material without losing excellent strength and stiffness;  experimental-numerical analysis of complex damage processes of new composite with optimized structure under fatigue and impact loading;  modelling of the correlation between electrical parameters and damage propagation;  development and validation of structural health monitoring methods based on the correlation between electrical parameters and damage propagation.

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Research Topic Summary.

Idea of proposed topic: To design a controlled shoulder joint trainer that can be controlled by a signal from the person's own muscles. Aim: The aim of this study is to develop an intelligent MR trainer that would use surface electromyographic signals to evaluate shoulder joint movement patterns and provide an opportunity to train in an isokinetic mode. The novelty and originality of the idea and experience in the field of the research is that is offered the solution to develop and test a shoulder joint trainer that is user-friendly, easily adaptively controlled using an electromyography (EMG) model. EMG is a diagnostic procedure that aims to assess the condition of nerves, muscles and the nerve cells that control them (motor neurons). EMG will be used to assess the electrical activity of the muscles (i.e., the total action potential) on the skin surface, both when the muscles are relaxed and when they tightened at different intensities. Upon detection of movement from the processed EMG signal, a control signal will be generated, which will be transmitted to the executing components of the trainer so that the corresponding movement of the trainer can be performed together with the movement of the shoulder joint. It is planned to create a self-learning - based on artificial intelligence methods, an algorithm operating on the principle of EMG tracking. This algorithm will select the most optimal individualized workout modes for each trainer user. Current state of the research. It has been shown that EMG signals can be used in the human interface, such as prostheses and limbs. Surface EMG can also be measured with electrodes attached to the skin. In addition, when the muscles contract and generate a displacements, an EMG signal is generated, so this displacement can be estimated from the EMG signal. Therefore, will be used the EMG signal to control the simulator.

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Research Topic Summary.

This work deals with new approach in design and investigation of the precision positioning systems with some degrees-of-freedom, based on developing active piezoelectric I and III class kinematic pairs (1 and 3 degrees-of-freedom), in which transformation of multi-directional resonant oscillations of piezoelectric actuators into continuous or start-stop motion of moving link is taking place. The frequency of oscillations lies in the range of 20 kHz to 200kHz, amplitude up to 5µm, and that enable to realize high nano-scale resolution, combined with high speed of the motion control. Few modifications of two and five degrees-of-freedom, covering wide range of the controlled dynamic parameters will be developed. Detailed investigation of their advantages and specifics for this application will be carried on. It is planned to develop the theory of I and III class piezoelectric active kinematic pairs, combined with mathematical modeling and experiments.

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Research Topic Summary.

The structural integrity of components of environmentally hazardous enterprises must be ensured under normal operating conditions and in hazardous conditions. Nuclear power plants, thermal power plants, chemical industry companies, oil industry companies, gas pipelines, heating networks, etc. can be classified as hazardous. Metal structures and pipelines in the above-mentioned companies may cause metal degradation due to higher temperature, more aggressive working environment exposure, and thus their integrity will be vulnerable. One of the main mechanisms of degradation is metal fatigue, which may lead to structural fracture. Nowadays in the energetic, transport, chemical and metallurgic industry, structural features and facilities, because of the high power, speed and overloads or sometimes purposely reduced weight of the facility, the plastic deformation is caused, which exceeds the proportional limit of the material and plastic strain starts, which results the hysteresis loop of the plastic strain and reduces the fatigue life of the material. In most mechanisms and devices (especially in air and missile engineering, various type motors, transport and other equipment) under loading the elastic-plastic strain appears in the stress concentration areas, near the sudden change of the shape, e.g. in key seats, near the shafts diameter changing places, as a result of the incorrectly chosen fillet radius, in welded joints, because of the various welding defects and etc. Under cyclic elastic-plastic loading, after hundreds or thousands of cycles, the fatigue crack appears, which commonly causes the failures with hardly predictable outcomes. For more details please contact the supervisor of the topic.

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Research Topic Summary.

One of the modern metal products industries is the welding of metal parts. In addition to traditional welds used in the past: electric arc, plasma gas flow, conventional spot welding and many other welds, new, progressive welding methods are increasingly being used: laser, friction welding. Welding using these methods can be done more precisely, more efficiently, it is possible to weld materials that are difficult or even impossible to weld in traditional ways. The most important welding parameter is the seam reliability. The thread must meet the operational design requirements. It is affected by the metal composition, welding method and mode. When welding with conventional technology, good weldability is considered when the joint strength obtained is equal to the strength of the base metal. Frictional Welding (FSW) is a thermomechanical solid state welding process that works by generating frictional heat between a rotating tool and a material (the tool is harder than the material). During it, there is a generally rotary cylinder shaped tool which slowly penetrates in the metal. Friction is formed between the surface of the abrasion-resistant tool and the welded metal, which makes the metal become plastic, but does not reach the melting temperature. This creates a partial metallurgical bond. For more details please contact the supervisor of the topic.

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Research Topic Summary.

Composite materials and structures are becoming more and more important due to modern lightweight design strategies imposed by the need of material, fuel consumption and costs reduction; especially in key industries like automotive, aerospace, wind energy. However, the lightweight design strategy brings the requirement of well understanding and mastering the complex multi-modes damage behavior of composite structures; as well as associated SHM methods and systems to assure the safety requirements of the lightweight composite structure under severe and long term loading conditions. On this background, the goal of the research is the development of a new Structural Health Monitoring (SHM) method for lightweight composite structures; based on a combined experimental and computational approach. The experimental method of non-contact photogrammetry will be deployed for damage detection; in conjunction with the computational method of Finite Element model updating for damage identification (i.e., localization, characterization). Special attention in terms of both theoretical formulation and computational implementation will be given to the new nonlocal peridynamics theory for composite damage mechanics analysis. The research idea is mainly motivated by the advantages offered by the non-contact feature of the proposed SHM method; eliminating thus the need of complex sensor networks attached to the structure for damage detection; and eliminating thus some of the main disadvantages of the attached/embedded SHM sensing systems: pre-defined known locations for sensors placement, possibility of sensors damage, sensitivity of the sensor baseline measurements to environmental conditions, complex wiring and data acquisition systems, high implementation and operation costs. For more details please contact the supervisor of the topic.

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Research Topic Summary.

Currently, great attention is paid to ecology and the reduction of negative impacts on the environment, therefore, one of the priority areas is the development and research of new materials that are environmentally friendly and fully recyclable using renewable natural resources. The aim of the proposed work is to develop natural fibre reinforced polymer composites exhibiting enhanced mechanical properties. In order to create a suitable composite microstructure and provide other factors that determine the desired mechanical properties, a micromechanical numerical modelling methodology will be developed for the research of the composite response to mechanical loading. To calibrate the developed model, experimental tests will be carried out. It is expected that the research will be carried out within the framework of research projects planned to be implemented at the university.

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Research Topic Summary.

This topic is related to the University's research topics – "Mechatronic and micromechanical systems” and “Creation and development of efficient mechanical technologies”. The aim is to create a mechatronic device – a small-dimensional magnetorheological actuator (gear) for adaptive hand-rotational movement or braking. By changing the intensity of magnetic field, which crossing the magnetorheological fluid, changes the fluid viscosity, and at the same time will be changed brakes functional parameters. Such devices can be used in various prostheses (for example, arms, legs) for adaptive (controlled) motion transmission and braking. This facilitates the process of healing the arm or leg. For the development of the device is intended to be used magnetorheological fluids and piezoelectric materials, by exploiting their direct piezoelectric effect and inverse piezoelectric effect. To determine the functional parameters of device with magnetorheological fluid, the numerical modelling methodology will be created by using SolidWorks Flow Simulation flow analysis and ANSYS CFX software.

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Research Topic Summary.

Composite materials and structures are becoming more and more important due to modern lightweight design strategies imposed by the need of material, fuel consumption and costs reduction; especially in key industries like automotive, aerospace, wind energy. However, the lightweight design strategy brings the requirement of well understanding and mastering the complex multi-modes damage behavior of composite structures; as well as associated SHM methods and systems to assure the safety requirements of the lightweight composite structure under severe and long term loading conditions. On this background, the goal of the research is the development of a new Structural Health Monitoring (SHM) method for lightweight composite structures; based on a combined experimental and computational approach. The experimental method of non-contact photogrammetry will be deployed for damage detection; in conjunction with the computational method of Finite Element model updating for damage identification (i.e., localization, characterization). Special attention in terms of both theoretical formulation and computational implementation will be given to the new nonlocal peridynamics theory for composite damage mechanics analysis.

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Kita informacija.

The research idea is mainly motivated by the advantages offered by the non-contact feature of the proposed SHM method; eliminating thus the need of complex sensor networks attached to the structure for damage detection; and eliminating thus some of the main disadvantages of the attached/embedded SHM sensing systems: pre-defined known locations for sensors placement, possibility of sensors damage, sensitivity of the sensor baseline measurements to environmental conditions, complex wiring and data acquisition systems, high implementation and operation costs. Consequently, the research results and the SHM method proposed here can have direct applicability and can be of high-interest for advanced industrial application such as aeronautical and wind energy lightweight composite structures. The impact of the research is expected under multiple aspects of scientific (new knowledge, research, and innovation capacity), economic (condition based maintenance, reduced inspection down time), and societal (increased safety and security for structures and public) benefits.