Mechanical Engineering

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Research Topic Summary.

Research and development of flexible highly responsive transducers (actuators, sensors and micro energy harvesters) with embedded lead-free electroactive polymers (EAPs) is currently a dynamic research area in the field of smart materials and (bio)mechatronics. There is a pressing need to replace traditional rigid, brittle and lead-containing piezoceramic transducers with the flexible and tough ones in order smart devices could effectively operate in large-deformation modes and ensure safe interaction with damage-sensitive environment (e.g. body parts, organs, tissues). Lightweight, flexible and robust mechanical sensors or micro energy harvesters, which safely interact with biological tissues, are considered as key components in next-generation mechatronic orthopedic devices (instrumented prostheses or orthoses) and various biomedical devices intended for monitoring of physiological and biomechanical signals (heart or respiration rate, blood pressure, muscle activity, etc.). Further progress in this field is closely linked to advancement of technologies for 3D printing-assisted fabrication of lead-free EAPs such as piezoelectric polymers and composites (e.g. based on PVDF). Fabrication of highly responsive, flexible and mechanically robust EAP transducers by exploiting 3D printing is one of the largest challenges in this field. ... For detailed information please contact the supervisor of the topic.

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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...... For detailed information please contact the supervisor of the topic.

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Research Topic Summary.

3D printing of flexible (compliant) multifunctional structures by using high-performance stimuli-responsive (active) nanocomposite polymer filaments is an extensively pursued research field of additive manufacturing (AM) and smart materials, which also includes research on 4D printing. Nanocomposite polymer filaments that can respond to electrical, magnetic, thermal or other stimuli are under development in various research labs worldwide. AM encompasses different technologies with the fused deposition modelling (FDM) being among the most popular, affordable and versatile ones. Development of extrusion-based technology for fabrication of stimuli-responsive thermoplastic nanocomposite filaments (e.g. polymeric-ceramic) opens wide possibilities in continuous manufacturing of freeform-shaped flexible smart structures with tailored mechanical properties (e.g. toughness, stiffness and/or dissipative characteristics) and additional functionality (e.g. mechanical sensing or micro energy harvesting). Worldwide research activities on fabrication of stimuli-responsive nanocomposite polymer filaments and their FDM printing are in early stages, which implies vast application potential in the future within diverse industrial sectors such as biomedical and healthcare, aerospace, automotive, etc. ... For more detailed information please contact the supervisor of the topic.

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Research Topic Summary.

Relevance During operation of structure, structural damage can occur causing disintegration of material which can progress, resulting in certain scenarios to permanent failure or collapse. For this reason, many NDT techniques are studied and implemented. However, most of them can be used only on a scheduled maintenance basis e.g. due to long measurement time, required disassembly, etc. This situation motivated to perform research in the field of SHM systems. The intention of such a system is permanent integration with the structural element and delivering current status of its “health”. Another possibility is actuators integration into the composite structure for the active control of the components. Scientific problem Development of smart composite structures containing arrays of different sensors (e.g. piezoelectric, optical) or actuators (e. g. piezoelectric) could be useful for novel structural health monitoring or active control systems. Variuos sensors (actuators) interated into hybrid structures are very promising in different applications, but their characteristics have not been analysed in details, yet. For detailed information 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). ... For detailed information please contact the supervisor of the topic.

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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 w'ith 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.

The work would be done in partnership with Chipper Blades Center, a company that would consult, supply samples and implement a new steel grade for its products. Five years ago, standard steel for blades, DIN 1.2360, was found to have its shortcomings, although the blades perform the basic function of wood chipping, i.e., resistance to cyclic loads is insufficient. When chipping wood, especially with a variety of abrasive impurities, the blades are influenced by impacts, causing the blade to become less sharp, they break and no longer perform their function. During the initial study, it was noticed that the possible main cause of brittleness was chromium in the steel, and attempts were made to reduce it from 8-9% to 5-5.5%. The molybdenum content was increased from 1.10-1.50% to 2.3-2.4% and the carbon content was increased from 0.45-0.55% to 0.60% in order not to reduce the carbide content. In addition, the steel is micro-alloyed with 0.04-0.06% niobium and 0.2-0.3% nickel. 8 batches of blades were tested using this chemical composition. According to a customer survey, blades made of new chemical steel cut 25 to 30% more raw material compared to the blades with standard chemical composition..... For detailed information please contact the supervisor of the topic.

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Research Topic Summary.

Relevance. The trend toward miniaturization of mass-produced products motivates the development of microtechnologies which is currently a very relative topic. Micropart manipulation is a very important step in manufacturing microassemblies. Microtechnologies are also rapidly expanding into the field of medicine by significantly improving capabilities of diagnostic, surgical, implantable equipment, and the like. Currently, research of microparts manipulation is of the utmost importance in most field of sciences and industries, especially related to new and high technologies. Scientific research problem. During manipulation of microparts, van der Waals, electrostatic and capillary forces become more dominant than inertial and gravity forces between the micro parts and, therefore, adhesion occurs between the parts and tools causing problems in with the precision and efficiency of alignment. The unwanted effect of the adhesion forces can be avoided by applying vibratory techniques and proper medium in the contact zone in this fashion creating the conditions for proper conveying and alignment of the microparts as well as ensuring the required manipulation precision and efficiency. The aim of the research is to analyse the dynamics of vibratory microparts manipulation and propose a new efficient methodology for vibratory manipulation. for detailed information please contact the supervisor of the topic.

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Research Topic Summary.

Classical continuum mechanics models and computational methods (e.g., FEM) are based on local stress-strain theories, and cast into Partial Differential Equations (PDE) systems. However, PDE-based local methods suffer to properly include certain mechanical phenomena such as influence of gradients, microscale size effects, discontinuities generated by fracture paths, strain localization due to softening. Therefore, they require special treatment to address these limitations. Alternatively, newly developed nonlocal continuum theories (e.g., peridynamics) remove such shortcomings, and enable the solution of multiscale problems including damage and fracture. The proposed phd topic addresses the applications of the non-local peridynamics theory to computational damage mechanics of composite materials and structures. Which would allow for addressing specific problems of composite structures computational damage analysis without encountering the issues (e.g., spurious mesh dependency, stress oscillations, strain localization) with the common damage mechanics tools (e.g, VCCT, CZM, CDM, XFEM) implemented in current FEA codes. For detailed information please contact the supervisor of the topic.

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Research Topic Summary.

The determination of fatigue curves is expensive, time consuming, it is difficult to implement the experiment in component environment (high or low temperatures, internal pressure and etc.). Therefore, finite element method can be helpful for material investigation to evaluate the behaviour of steel specimen during fatigue. The test matrix for fatigue testing can be developed on results of fatigue modelling by finite element method. The aim of this research is the numerical modelling of the low cycle fatigue behaviour of steels at different loadings. The finite element method will be used for numerical simulation of fatigue. The parameters necessary to describe the material softening/hardening for numerical simulation will be estimated from experimental data. One aspect of the novelty is the development of the methodology for numerical investigation of the low cycle fatigue behaviour of steels at tension-compression and rotation loadings. The scientific novelty of this research is the estimation of the steel parameters to describe the material softening/hardening during fatigue. It will be developed material model to describe material behaviour at cyclic loading. The numerical simulation results will be validated with the results of the experimental tests data. Tasks: - Overview of the literature and understanding of low cyclic fatigue problems, find out influence of cyclic loading to the material softening/hardening - Find out application of finite element methodology for modelling of fatigue; - The development of the methodology for numerical investigation of the low cycle fatigue of the steels at tension-compression and rotation loadings; - Estimation of the steel parameters necessary to describe the material softening/hardening for numerical simulation according experimental data at different loading; - The numerical simulation of the low cycle fatigue of the steels and validation of the simulation results according experimental data.

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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 detailed information please contact supervisor of the topic.