Mechanical Engineering

---

Research Topic Summary.

Environmental issues have motivated researchers to replace synthetic fibres with natural fibres in the fabrication of polymer composites. However, natural fibres demonstrate weak mechanical or thermal properties which limit their different applications. It was sugested suggested fabrication of hybrid composites in order to improve the mechanical and thermal properties of natural fibre-based composites. Hybrid composites are made up by two or more fibres in one matrix or two polymer blends and with one natural fibre reinforcement. By hybridising one natural fibre with another natural fibre/synthetic fibre in one matrix, the resulting composite is a unique product (hybrid composites) that displays better mechanical and thermal properties in comparison with individual fibre-reinforced polymer composites. Hybrid composites are one of the emerging fields in mechanical engineering science which has attracted attention for their different engineering applications especially in biomechanics. That is why the main focus in future research will be done on creating new types of hybrid composite and their properties investigation and application in biomechanics.

---

Research Topic Summary.

For the development of functional microfluidic elements, the technologies of micro mechanical fluidic devices development as well as particle positioning and control technologies in them need to be available. When developing the mentioned technologies, it is necessary to form the nano/micro cavities to trap bio particles to be used for diagnostics function. With the application of piezoelectric nanocomposites such micromechanical systems with nano/micro cavities can be controlled at nano/micrometer level what can be used as particle traps and positioning places thus serving as the basic principle of sensors or filters development. Carrying out the research it is planned to make the microfluidic acoustophoresis device from piezoelectric nanocomposite for which micro scale level piezoelectric properties are characteristic what in turn would assist in more effective and higher precision generating of bulk acoustic waves thus ensuring higher effectiveness of microparticles manipulation and control. This will be achieved by synthesizing nano composite, evaluating its mechanical, electrical, hydrophobic and dynamic properties, and developing technologies for nano/micro cavities and microstructure formation in nano composite.

---

Research Topic Summary.

The general challenge in mechanical engineering is developing strong, damage tolerant, lightweight, and reliable materials and structures working under severe exploitation conditions (extreme mechanical loads, high humidity, rain erosion, etc.). Traditional glass fibre-reinforced plastic (GFRP) composites can be an excellent solution for such issues. However, with the increasing application of GFRP in multiple industrial sectors, a global need to recycle these plastic wastes emerges. Switching to environmentally friendly epoxies instead of traditional matrices is vital, but it often leads to poorer mechanical properties. Two ways that help to sustain mechanical properties are the modification of the matrix and the use of advanced fibres such as three-dimensional (3D) woven fabrics. These fabrics are becoming a preferred choice for manufacturing GFRP composites. They have several advantages over two-dimensional laminated composites, such as higher delamination resistance, higher impact strength and resistance to crack propagation. The aim of this research is to develop high-performance 3D woven GFRP composites based on the novel recyclable epoxy resin. This sustainable epoxy will be modified with environmentally friendly nanofillers to improve its mechanical, barrier and fire-retardant properties. It will be used both as a 3D woven GFRP composite matrix and after appropriate tailoring, as a protective coating. The use of 3D woven fabrics for GFRP composites will compensate the potential decrease of mechanical properties due to the eco-friendly epoxy.

---

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. The topic of the research is based on the ongoing international projects, therefore close cooperation, secondments and work with foreign academic and industrial partners is planned.

---

Research Topic Summary.

COVID-19 causes acute respiratory distress by damaging alveolar epithelial and endothelial cells in the lungs and results in the development of acute respiratory failure. The aim of the project is to develop a non-invasive ultrasound stimulation device that can modulate the effects of GYY4137, angiotensin receptor antagonists and amlodipine on inflamed pulmonary vessels, thus treating acute respiratory distress and delaying the need for artificial lung ventilation. Our proposed development of an external ultrasound stimulation device that can modulate the effects of GYY4137, amlodipine, or angiotensin receptor antagonists during inflammation currently has no analogues in the world. A non-invasive ultrasound stimulation device will provide the opportunity to improve lung function without additional intervention and locally enhance the effects of medications, delay the need for invasive lung ventilation, and improve treatment outcomes. After making sure that the effect of drugs in the inflamed vessel can also be enhanced by low-frequency ultrasound, a non-invasive ultrasound stimulation device will be modeled and tested in animal models of pulmonary hypertension and respiratory distress. The success in project will allow to focus on vasodilators as an alternative to COVID-19 treatment, as calcium channel blockers can improve blood flow through the alveolar-capillary block. Improved blood flow can better compensate for hypoxia, suppress inflammation, and repair vasoconstriction. In addition, improving blood transit due to vasodilation can help prevent blood clots from forming.

---

Research Topic Summary.

Developments in highly flexible additive (or hybrid) manufacturing systems through robot-assisted integration of different technological processes are highly relevant in the context of Industry 4.0 since they underpin faster adoption of smart manufacturing paradigm. Industrial robot manipulators can be reconfigured to perform complex multi-directional operations within large workspace and their integration with specialized end-of-arm tools (for 3D printing, process monitoring, etc.) may contribute towards higher process flexibility, efficiency and product quality as well as better use of resources and lower waste generation. Implementation of robotic 3D printing technology requires integration of several end-of-arm extruders that should be customized for deposition of specific materials (thermoplastics, pastes, etc.). Such robotic multi-material printing may expand functional capabilities of additive technology, provide more design freedom and enable rapid fabrication of complex-shaped, large-size and highly personalized products including multi-functional (smart) components. Major advancements in this field are related to various developments in flexible additive/hybrid manufacturing to enable efficient fabrication of high value-added components with embedded electrical, electronic/mechatronic functionalities (e.g. sensorized components). Structural configuration of many state-of-the-art flexible mechanical sensors is based on multi-layer designs that effectively combine dielectric, conductive and various functional/smart materials. Robotic multi-extrusion platform would be useful for 3D printing of multi-material sensorized structures, especially large-area ones. The main aim of the PhD project is to develop robotic 3D printing technology for rapid fabrication of multi-layer sensorized structures. A PhD student will work at KTU Institute of Mechatronics on such research tasks as design, adaptation and integration of end-of-arm extrusion tooling, implementation of robot arm printing and investigation of additive process parameters, characterization of mechanical and electrical properties of printed samples and sensorized structures.

---

Research Topic Summary.

3D printing of multifunctional structures and devices by using eco-friendly biopiezoelectric composites (biopiezocomposites) 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 biopiezocomposites. Extrusion-based AM (3D printing) is a technically and economically viable approach to manufacture complex-shaped biopiezocomposite structures. Implementation of technology for fabrication of printable biopiezocomposite filaments could open wide possibilities to develop various flexible multifunctional structures with tailored mechanical properties (e.g. stiffness) and integrated smart functionalities such as mechanical sensing and micro energy harvesting. Worldwide R&D activities in extrudable biopiezocomposites and 3D printing of eco-friendly sensorial and energy harvesting devices are in early stages. This indicates high innovation potential and vast application potential in development of advanced self-monitoring and energy-autonomous systems used in the bio-medical/mechatronics and soft robotics domains. The main aim of the PhD project is to fabricate extrudable biopiezocomposite and demonstrate 3D printing of sensorial and/or energy harvesting structures. A PhD student will work at KTU Institute of Mechatronics on such research tasks as biopiezocomposite fabrication, filament extrusion and printability studies, characterization of mechanical and electrical properties of printed samples, design, modeling, rapid prototyping and performance testing of biopiezocomposite-based sensor or energy harvester by considering a relevant application case.

---

Research Topic Summary.

The topic is related to the development of smart high-performance composites – additive manufactured (AM) carbon/ glass fibre reinforced polymers with integrated piezoelectric actuators. Piezoelectric actuators advantages (small dimensions and weight) allow to integrate them into structures without influence on the material durability. It allows development of active vibration control system increasing the safety of AM structures recently very popular in many industrial branches. Impact and potential benefits are related to developing method of manufacturing high strength performance composite materials with integrated piezoelectric actuators arrays. Such method can be applied for manufacturing of different elements in e.g. marine, cars, aircrafts, civil engineering structures.

---

Research Topic Summary.

Light metals account for an increasing share of the engineering industry, which is affected by a combination of materials research and market factors. There is currently no material more relevant to this topic than aluminium. Aluminium alloys have not been fully investigated and there is room for new challenges, especially in the field of non-destructive joints. Welding aluminium, compared to welding steel or other conventional materials, presents several exceptional challenges, especially in terms of chemical processes and susceptibility to cracking. In most cases, the welding of aluminium requires some special procedures and the following factors must be considered: the selection of the right filler metal, the right surface preparation, and the right welding technology. The alumina layer, which protects the material from external influences, becomes a barrier to the weld seam during the welding process. Therefore, it is common to use an alternating current that breaks through the higher melting point oxide layer. Moreover, thermal conductivity and factors related to porosity are the two biggest differences in aluminium welding compared to steel. A helium/argon shielding gas mixture may be used to combat alloy porosity if all other means have been tested. Autogenous welding of aluminium alloys can be performed using a direct current electrode (DCEN), but this is usually only possible by welding small cross sections with a pulsating arc. It should be noted that many experiments have to be performed before reliable results can be obtained, as the weldability of two batches of seemingly identical alloys is often very different.

---

Research Topic Summary.

In case of an internal or external accident due to dynamic effects in nuclear and thermal power plants, chemical and oil industry companies, gas and central heating pipelines and other strategical objects can cause dangerous consequences for human health and environment or at least can make big damage to technical equipment. Therefore, it is necessary to ensure structural integrity of components during whole their lifetime. Metal structures and elements often work at high temperatures and variable loads to aggressive environmental conditions. Operating factors lead to degradation of metal properties, which increases the probability of structural vulnerability. Degradation mechanisms can be reason for guillotine rupture of components. Therefore, for safe operation of nuclear, thermal power plant and chemical facilities it is very important evaluate degradation of steel of pressure vessel, piping system. For example, a guillotine breakup of one of the high-energy pipelines in the high-pressure system raises serious safety concerns due to the potential for major damage to surrounding pipelines and infrastructure. Due to the rupture, the fluid from the pipe escapes with high reactive forces resulting in the motion of the pipe. A pipe whip is a possible severe consequence of a postulated High Energy Line Break, which can occur after a sudden rupture of a pipeline under certain thermodynamic, structural, and geometrical conditions. In case of the dynamic loading it is very important evaluate of interaction of deformable bodies. The interaction between deformable bodies in case of dynamic loading event is danger for structural integrity of neighbouring components. Therefore, it is very important to estimate behaviour of solid bodies during impact. The transient behaviour of the structures in the case of impact loading is a complex phenomenon, due to various factors such as inertia effects, large deformations and inelastic behaviour. It is thus not possible to obtain analytical solutions for general cases, and hence sophisticated models are necessary for analysis. The finite element method (FEM) has been used extensively to simulate many applications for transient analysis. Alternatively, an experimental approach could be considered; however, this is not a practical approach because of the size of components and the impact speeds. The FE methodology is presently used for estimation of safety criteria (factors) for critical components. According this the finite element method can be helpful for numerical simulation to evaluate the behaviour of deformable bodies interaction. The finite element method will be used, as main numerical methods for development the methodology for numerical investigation of the deformable bodies in case of dynamic loads for this analysis. Also should be noted that in order to ensure that nuclear power plant buildings are reliable and safe in case of external loading, it is very important to evaluate uncertainties associated with loads, material properties, geometrical parameters, boundaries and other parameters. Therefore, a probability-based analysis will applied in this methodology as the integration of deterministic and probabilistic methods using existing state-of-the-art software‘s.

---

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 displacement, 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.

---

Research Topic Summary.

Complex geometric shapes and details of various purpose objects and figures are rapidly increasing nowadays in various fields of industry and everyday life. Despite the fact, that modern computer hardware and software greatly facilitates the creation of such objects/shapes during the design phase, the actual production of such objects is very complicated and expensive. For this reason, the incremental forming of sheets, mainly made from metals, is being investigated and used nowadays. This machining method allows a significant reduction in time and cost. Among other things, the incremental sheet forming allows the production of objects/shapes of extremely complex geometric shape which would be very difficult or even impossible to produce by traditional methods. Currently, a number of studies have been carried out around the world on the incremental sheet forming. In some of them, the incremental sheet forming is carried out using robots. The scientific literature revealed that the incremental sheet forming can be successfully applied in the polymer (plastic) sheet formation, but no further information on the process sequence and the parameters to be applied has been provided. Therefore, the aim of this project is to research and develop a technology for incremental sheet forming of polymer (thermoplastic). The aim of the research is to carry out theoretical and experimental research with the dual purpose of investigating the formation of a polymer (thermoplastic) sheet using a point contact tool and the selection of suitable temperature-forming modes and polymers. The aim of doctoral research is to develop and investigate a technology for the robotic incremental sheet forming of a polymer (thermoplastic) sheet. The research results obtained during the doctoral studies would be useful for companies in the plastics molding, processing and molding industries, which could increase their productivity using the developed technology and enable the market to offer more complex shapes that are difficult or impossible to produce with the current technology.

---

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. The particular operating regimes of the equipment may result the short-term overloads. In overload conditions the elastic-plastic strain causes the appearance of microcracks on the surface of the rotating element and so increases the accumulation of the damage. As a result of such an influence the lifetime of the parts may decrease, i.e. the low cycle fatigue may occur. The purpose of the research is to investigate the fatigue life and cyclic properties of metals used in energetic facilities and objects under multiaxial loading conditions and to determine the relationships between deformation and fracture properties. Scientific investigation is very important for prediction of the strength and fatigue life of the parts and structural elements under complex symmetric and asymmetric loading. Obtained investigation results will be applied to design a new machines, facility and modify the existing equipment, especially if aiming to increase the exploitation loads and fatigue life.

---

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. FSW is a fully coupled thermo-mechanical process which involves frictional and adiabatic heating of the workpiece, very large strain and strain rate, and very complex material flow during the welding process. Successful simulation of FSW process not only involves consideration of all essential elements (e.g., tool, backing plates, and clamps) but also demands for accurate material constitutive relationships, knowledge of variation of friction coefficients as a function of temperature, and condition of materials at tool-workpiece interface (stick or slip). In view of these conditions, it has been very challenging to carry out process modeling of even similar FSW processes. The purpose of the study is to make numerical simulation and experimental investigation of Friction Stir Welding (FSW) process of dissimilar materials and their alloys. The main industries using Friction Stir Welding are transport (cars, aircraft, ships, trucks, railways).

---

Research Topic Summary.

Fatigue damage is one of the main failure mechanisms in engineering structural elements. Up to 80-90% of in-service failures are caused by fatigue damage. Engineering companies seeking to avoid expensive fatigue tests and fatigue life prediction becoming an integral part of the modern design process of structures. In long operation cases the safety assessment based on combination of a safe-life design and damage tolerance concepts. Therefore, important is not only the accurate fatigue life prediction but also crack initiation and propagation mechanisms. Research objectives are to develop a verified combined experimental - computational tool to simulate crack initiation, propagation and failure mechanisms based on critical damage and quantified fracture mechanics parameters obtained from digital image correlation measurements. The project will develop the methodology for data?rich testing of samples subjected to fatigue loading to quantitively identify the damage initiation and propagation mechanisms, critical damage and fracture mechanics parameters such as the crack growing patch and rate, crack opening displacement, stress intensity factor, energy release rate etc. Experimentally obtained and evaluated data will be applied for novel fatigue simulation technique developed in the department capturing crack initiation, propagation and final failure. The application of digital image correlation (DIC) technique will be used to monitor the crack growth process during a cyclic fatigue test and to verify the mathematical model. The verified experimental-computational methodology will lead to the better understanding of the fatigue damage mechanisms; it will improve the confidence in designing lighter structures subjected to cyclic loading. The analysis of experimental DIC results using simulation technique with conjunction of inverse FEM may open possibility for new NDT approach for the detection of an early small-scale damage in composites and the assessment of damage tolerance. Experimental equipment: linear-torsion machine for fatigue testing; UTM for material characterisation; 3D digital image correlation (DIC) technique to monitor the crack growth process during a cyclic fatigue test and to characterise the material during the static test.

---

Research Topic Summary.

Taking ideas from nature i.e. biological systems is the promising way in order to develop of biomedical systems functioning effectively in interaction with the human body and capable of performing monitoring and stimulation tasks. The main idea of the current research is the development of active micro hydraulically actuated system with integrated sensing function. The research tasks are achieved by integrating flexible micro hydraulic element with piezo polymer. Thus the functional component capable of making flexural movements and having the integrated sensing function together with theoretical background of its design will be available.