The main goal was to demonstrate the possibility of investigating martensitic transformation induced by plastic strain, especially including the kinetics of this transformation, using selected cross effects. It is commonly known that this type of transformation is a basic “mechanism” occurring in shape memory materials and metastable austenitic steels strengthened with martensite separations. The motivation behind the research was also to follow and visualise the transformation on line, during cyclic loading (fatigue process), without the necessity to use, for example, roentgenographic (destructive) or microscopic methods. The application of the magneto-mechanical effect (the Villari effect) and the thermomechanical effect (the Kelvin/Thomson effect) turned out to be particularly useful because they significantly change with martensite initiation and then accumulate in austenite. Therefore, the goal was to develop the non-destructive methods of investigating martensite transformation, which could then be used on real constructions made of metastable austenite steel. In the case of the magneto-mechanical method, the goal was to additionally visualise the magnetic field transformations along a sample in the function of a loading cycle and the index of this period. To achieve this, high-resolution phase maps were used, which also allowed image processing methods known from machinery visioning (MV) or digital image correlation (DIC) techniques to be used.
Part of the book: Austenitic Stainless Steels
This chapter presents the methodology of designing and testing wideband actuators and energy harvesters which can be treated as one device called a mechanical resonator. In order to obtain described effects, the magnetostriction phenomenon was used. This effect enables the construction of resonators in selected frequency bands, including the ultrasonic range. Cores made of giant magnetostrictive materials (GMM) were used for the construction. Considerable attention was given to composite cores to reduce the weight of pure Terfenol-D. The influence of the volume fraction of Terfenol-D powder, the size of its grains, and the direction of polarization on the value of magnetostriction in a wide frequency band were investigated. The magnetostriction of composite cores and solid Terfenol-D samples was also compared. The structure and the use of magnetostrictive cores containing a combination of NdFeB magnets and pure Terfenol-D are also presented. An important issue was also the development of our own methodology of magnetostriction testing, including the use of fiber optic sensors (Fiber Bragg Grating sensors, FBGs), Hall’s sensors, and the original measuring system for magnetic field visualization (Magscanner). The chapter also discusses several own designs of actuators and energy harvesters, including shock harvester, resonant harvester, and energy transmission system.
Part of the book: Actuators
This work is focused on the development of new kind of energy harvesters that could be used in various applications including industrial, aerospace, or customer markets. The main aspect to consider is transformation of different sources of energy (that in normal conditions is wasted such as temperature, vibration, shock, etc.) into the usable electric power. The goal was to prepare wireless subsystem based on energy-harvesting technology which will aid different areas. The energy-harvesting devices are shown as small harvesting devices with power output from 10 mW up to 5 W. Proposed solutions might be used in applications such as low-power microprocessor systems, ultrasonic continuous power supply for low-power wireless network systems, and multi-node harvester systems that allow to collect more electrical power for critical structural health monitoring (SHM) applications. The main purpose was to obtain from harvesters the sufficient values for supplying the chosen 32-bit microcontroller systems. Additionally possible application in mechanic for the other than magneto-based solid harvesters is described.
Part of the book: Small-Scale Energy Harvesting