Determination of Thin NiTi Wires' Mechanical Properties during Phase Transformations.

The modern industrial and consumer applications in accordance with the concepts of Industry 4.0 and the Internet of Things are characterized by autonomy and self-sufficiency. This has led to an increase in the interest for the so-called smart materials, capable of combining the functionalities of sensors, actuators and, in some applications, control systems. An important group of smart materials are shape-memory alloys, among which nickel-titanium (NiTi) alloys are the most known. In this article, the influence of phase transformation on the mechanical properties of thin NiTi alloy wires was investigated. During the test, the influence of the heating currents on the displacement and the force generated by the thin NiTi wires were analyzed. The temperature of the wires during heating was measured by a thermographic camera. This study proved the maximum value of the wires' displacement was related to the value of the heating current. During the research, the dependence of the transformation dynamics on the value of the heating currents was also proved. In addition, the influence of the surface inhomogeneity of the thin NiTi alloy wires on the accuracy of the thermographic measurements was analyzed. For the experimental research described in this article, we used the NiTi alloy whose trade name is Flexinol, produced by DYNALLOY (Inc. 2801 McGaw Ave. Irvine, CA, USA).

Change in Electrical Resistance of SMA (NiTi) Wires during Cyclic Stretching.

In this article, the use of Nickel Titanium (NiTi) alloy as a sensor is examined. A cyclic stretching test, that has various elongations (0.5 and 1%), is administered to NiTi wires with various diameters and lengths. It is assumed that the elongation enables an observation of the change in electrical resistance of the NiTi wires, due to martensite reorientation. During the test, the stretching force, the displacement, and the electrical resistance of the NiTi wires are measured. Following the test, the resistance of all the tested samples differed compared to the starting position. Conducted research indicates that NiTi wires are very sensitive to resistance change when they are deformed. A large difference in NiTi electrical resistance was visible in all samples during the first stretching cycle. For longer wires, with a smaller diameter, resistance change was visible during almost all of the stretching cycles. However, the observed changes were very small. Based on the obtained results, it can be justifiably stated that NiTi wires could be used to build deformation sensors, which operate both online and offline. Moreover, NiTi wires with a small diameter could be used to create cyclic loading sensors. Such sensors can be used in self-sensing applications or in structural health monitoring.

The Mechanical and Tribological Properties of Epoxy-Based Composites Filled with Manganese-Containing Waste.

Waste from large-scale production processes is a growing environmental problem that can potentially be solved by using this waste as fillers in polymeric composites to improve the mechanical and tribological properties of polymeric matrixes. This paper presents research concerning how the introduction of fillers in the form of manganese residue and manganese(II) oxide changes the mechanical and tribological properties of epoxy composites produced by gravity casting. The research was carried out for composites with 2.5 wt.%, 5 wt.%, and 10 wt.% of fillers. Properties such as the density, hardness, resilience, flexural strength, deflection, flexural modulus, tensile strength, elongation at break, and Young's modulus were determined. Moreover, based on the ball-on-plate test, the wear volume and friction coefficients of the tested materials were determined. Microscopic images of the abrasion profiles were also obtained. The geometry of the wear paths was measured with a profilometer, and the results showed that introducing fillers reduced the abrasive wear of the composites; however, in all cases, the fillers decreased the strength of the tested materials.

Assessment of SMA Electrical Resistance Change during Cyclic Stretching with Small Elongation.

In this article, changes in NiTi alloy (Flexinol) electrical resistance during cyclic stretching with small elongation were investigated. A dedicated test stand consisting of motorized vertical test stand, force gauge, and electric resistance measuring device with an accuracy of 0.006 Ω was developed. A dedicated control algorithm was developed using LabVIEW software. Changes in electrical resistance were investigated for the 0.1 mm Flexinol wire with length of 120 mm. Testing was performed in the elongation range between 0.25% and 1.5% in martensite phase. Tested samples were subjected to 30 stretching cycles with a movement speed of 10 mm/min. Obtained results show that the cyclic stretching of Flexinol wire reduces its electrical resistance with each stretching cycle. Moreover, it was noted that changes in Flexinol electrical resistance during cycling stretching depend on the assumed elongation and number of the already performed stretching cycles. The observed electrical resistance change decreases with each stretching cycle. Thus, the observed changes are greater during the first stretching cycles. For elongations exceeding 1%, the Flexinol electrical resistance in the first stretching cycle increases. In each subsequent cycle, electrical resistance decreases, as in the case of the smallest value of assumed elongation. In almost all tested cases (except in the case with 1.5% of assumed elongation), Flexinol electrical resistance after 30 stretching cycles was smaller than before the test.

Determination of Mechanical and Tribological Properties of Silicone-Based Composites Filled with Manganese Waste.

High-tonnage industrial processes generate high amount of waste. This is a growing problem in the whole world. Neutralizing such waste can be time consuming and costly. One of the possibilities of their reuse is to use them as fillers in polymer composites. Introduction of the filler in polymer matrix causes change in its mechanical and tribological properties. In the article, the effect of introducing fillers from post-production waste, and its effect on changing the physical properties of silicone-based composites filled with manganese (II) oxide and waste manganese residue was investigated. The composites were made by gravity casting. Composites with 2.5, 5, 7.5, and 10 wt% of the fillers were examined. The composite materials were subjected to tests such as: density, hardness, resilience, tensile test, abrasion resistance, and ball-on-disc. Microscopic images showed that, the particles of the fillers are uniformly distributed in silicone matrix with the formation of smaller agglomerates. Such agglomerates introduced a discontinuity in the structure of the polymer material, which caused a decrease in the tensile strength and elongation at break for all tested compositions in comparison with the mechanical properties of the silicone used as the matrix. However, it was found that all silicone-based composites filled with manganese (II) oxide and manganese residue showed a reduction in abrasive wear, compared to the reference sample.

The Influence of Zinc Waste Filler on the Tribological and Mechanical Properties of Silicone-Based Composites.

Silicones are often used for various types of coatings, but due to their poor mechanical properties, they often require modification to meet specific requirements. At the same time, various production processes throughout the world generate different types of waste, the disposal of which is harmful to the environment. One possible solution is to use production waste as a filler. In this paper, the authors investigated how the use of metallurgical production waste products as fillers changed the mechanical properties of silicone composites prepared by casting. Composite samples were characterized using tensile tests, resilience, pin-on-disc, Schopper-Schlobach abrasion, hardness, and density measurements. Based on the obtained results, the authors assessed the effect of each of the fillers used in different weight proportions. The results showed that the silicone composite filled with 5 wt% zinc dust showed the lowest decrease in tensile strength and Young's modulus, with a simultaneous significant reduction in abrasion compared with the reference sample. This research shows that zinc waste can be successfully introduced into a silicone matrix in cases where it is important to reduce abrasive wear.

Low Velocity Impact Response and Tensile Strength of Epoxy Composites with Different Reinforcing Materials.

This paper presents the results of research concerning multilayered epoxy composites reinforced with different materials. The strength of multilayered composites depends, to a large extent, on the reinforcing material. The authors decided to compare the low velocity impact response and perform tensile strength tests on several composites, to ascertain the mechanical properties of the prepared composites. Five different reinforcing materials were provided for the research (two fabrics made from aramid fibers, two fabrics made from carbon fibers and one fabric made from polyethylene fibers). The composites were manufactured by the vacuum supported hand laminating method. The low velocity impact response tests were conducted with the use of a pneumatic launcher. Three strikers with different geometry (conical striker, hemispherical striker and ogival striker) were used. A comparison of the resulting damage to the composites after the impact of the strikers was based on the images obtained using an optical microscope; tensile tests were also performed. The experimental investigation showed significant differences in the mechanical properties of the composites, depending on the applied reinforcing material. It was found that, as a result of the impacts, less damage occurred in the composites which were characterized by a lower Young's modulus and a higher tensile strength.