The Johnson-Mehl-Avrami Model Applied to Martensitic Kinetics in Ausformed Cooper Based Shape Memory Alloy

CuAlNi shape memory alloys which are used as sensors and actuators have also been investigated recently as materials for medicine devices. This study shows the influence of the thermo – mechanical treatments in CuAl13Ni4 shape memory alloy on martensitic transformation kinetics and microstructures. While maintaining a constant 20% degree of deformation, deformation temperature was varied between 800 oC and 1000 oC. The alloy was investigated by differential scanning Calorimetry (DSC) and optical microscopy. The validity of JMA model to the kinetics analysis was checked. The changes in the microstructure and kinetic transformations have been linked to the evolution of the rolling temperature that introduced high density dislocations in initial phase and changes fraction and interaction between the β1’ (18R) and γ1’ (2H) martensite coexisting in this shape memory alloy

Structural characteristics of multilayered ni-ti nanocomposite fabricated by high speed high pressure torsion (Hshpt)

47PCCDI/2018 MANUNET 3 PN3-P3-302 grant number 99-2019It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength.publishersversionpublishe

Embedded fiber sensors to monitor temperature and strain of polymeric parts fabricated by additive manufacturing and reinforced with NiTi wires

POCI-01-0145-FEDER-016414 (FIBR3D) BI/UI96/6642/2018 BI/UI96/6643/2018 PD/BD/128265/2016 UID/CTM/50025/2019 UIDB/00667/2020 FCT-SFRH/BD/146885/2019 UIDB/50025/2020 UIDP/50025/2020This paper focuses on three main issues regarding Material Extrusion (MEX) Additive Manufacturing (AM) of thermoplastic composites reinforced by pre-functionalized continuous Nickel–Titanium (NiTi) wires: (i) Evaluation of the effect of the MEX process on the properties of the pre-functionalized NiTi, (ii) evaluation of the mechanical and thermal behavior of the composite material during usage, (iii) the inspection of the parts by Non-Destructive Testing (NDT). For this purpose, an optical fiber sensing network, based on fiber Bragg grating and a cascaded optical fiber sensor, was successfully embedded during the 3D printing of a polylactic acid (PLA) matrix reinforced by NiTi wires. Thermal and mechanical perturbations were successfully registered as a consequence of thermal and mechanical stimuli. During a heating/cooling cycle, a maximum contraction of ≈100 µm was detected by the cascaded sensor in the PLA material at the end of the heating step (induced by Joule effect) of NiTi wires and a thermal perturbation associated with the structural transformation of austenite to R-phase was observed during the natural cooling step, near 33.0◦ C. Regarding tensile cycling tests, higher increases in temperature arose when the applied force ranged between 0.7 and 1.1 kN, reaching a maximum temperature variation of 9.5 ± 0.1◦ C. During the unload step, a slope change in the temperature behavior was detected, which is associated with the material transformation of the NiTi wire (martensite to austenite). The embedded optical sensing methodology presented here proved to be an effective and precise tool to identify structural transformations regarding the specific application as a Non-Destructive Testing for AM.publishersversionpublishe

Continuous Flux Thermal Treatments for Improving the Resistance at Alternate Bending of Medium to High Strength Steel Strips

The research was focused on obtaining medium to high strength steel strips for strapping heavy products by applying continuous flux thermal treatments on common grades, cheap carbon steels. For steel strapping the behavior at alternate bending is an important issue, thus an objective of the research was to make sure that the treated products withstand a critical number of alternate bending cycles and further more an improvement of the resistance at alternate bending by applying thermal treatments in continuous flux was pursued. The paper presents the results of the alternate bending test, SEM fractographs, optical analysis of the fracture surface and surface of the strip in the vicinity of the fracture surface after breaking by alternate bending using a stereo-microscope and optical analysis on etched and un-etched samples in transversal section along the rolling direction in the vicinity of the fracture surface using a metallographic optical microscope; for the following samples: the raw material in strain-ardened state, samples subjected to continuous flux quenching from 900 °C and tempering by passing through the furnace maintained at 600 °C, and samples subjected to quenching from 900 °C and tempering by passing through the furnace maintained at 700 °C

Experimental analysis of niti alloy during strain-controlled low-cycle fatigue

PTDC/CTM-CTM/29101/2017- POCI-01-0145-FEDER-029101 UIDB/EMS/00285/2020 UIDB/50025/2020-2023The interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission electron microscopy (TEM), before and after the tensile cycles. This gives rise to an overall increase of the resistivity values up to the maximum deformation. Therefore, the research suggests that shape memory alloy wire has great potential as a stress sensor inside bulk materials.publishersversionpublishe

Characterization of the file-specific heat-treated ProTaper Ultimate rotary system

Funding Information: FMBF acknowledges the funding of CENIMAT/i3N by national funds through the FCT‐Fundação para a Ciência e a Tecnologia, I.P., within the scope of Multiannual Financing of R&D Units, reference UIDB/50025/2020‐2023. Publisher Copyright: © 2022 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd on behalf of British Endodontic Society.Aim: To compare design, metallurgy and mechanical performance of the ProTaper (PT) Ultimate system with instruments of similar dimensions from the ProGlider, PT Gold and PT Universal systems. Methodology: New PT Ultimate instruments (n = 248) were compared with instruments of similar dimensions from ProGlider (n = 31), PT Gold (n = 155) and PT Universal (n = 155) systems regarding their number of spirals, helical angle, blade symmetry, tip geometry, surface finishing, nickel/titanium ratio, phase transformation temperatures and mechanical performance. One-way anova and nonparametric Mood's median tests were used for statistical comparison (α = 5%). Results: All instruments had symmetrical blades without radial lands or flat sides, similar surface finishing and an almost equiatomic nickel/titanium ratio, whilst the number of spirals, helical angles and the tip geometry were different. PT Ultimate instruments showed 3 distinct heat treatments that matched with the colour of their metal wire. Slider and ProGlider instruments had similar R-phase start (Rs) and R-phase finish (Rf) temperatures. SX, F1, F2, F3 and Shaper instruments showed equivalent heat treatments (Rs ~45.6°C and Rf ~28.3°C) that were similar to their PT Gold counterparts (Rs ~47.9°C and Rf ~28.2°C), but completely distinct to the PT Universal ones (Rs ~16.2°C and Rf ~−18.2°C). Amongst the PT Ultimate instruments, the lowest maximum torques were observed in the SX (0.44 N cm), Slider (0.45 N cm) and Shaper (0.60 N cm) instruments, whilst the highest was noted in the FXL (4.90 N cm). PT Ultimate Slider and ProGlider had similar torsional (~0.40 N cm) and bending loads (~145.0 gf) (p = 1.000), whilst the other PT Ultimate instruments showed statistically significantly lower maximum torque, higher angle of rotation and lower bending load (higher flexibility) than their counterparts of the PT Universal and PT Gold systems. Conclusions: The PT Ultimate system comprises instruments with 3 distinct heat treatments that showed similar phase transformation temperatures to their heat-treated analogues. PT Ultimate instruments presented lower torsional strength and superior flexibility than their counterparts, whilst maximum torque, angle of rotation and bending loads progressively increased with their sizes.publishersversionpublishe

Research Regarding the Possibility of Obtaining Nitinol by Powder Metallurgy

In the paper the obtaining of nitinol by pressing and sintering of a mixture of nickel and titanium powders is presented. The fabrication of NiTi alloys by powder metallurgy allows avoiding the usual problems related to classical casting obtaining methods (problems related to defects caused by segregation or excessive growth of the grains), it also assures an exact control of the chemical composition and offers the possibility of manufacturing a variety of components very close to their final shape. Although the advantages of manufacturing products by powder metallurgy are certain, the first research presented in this paper in the case of nickel and titanium powders have showed some unwanted aspects related to powder metallurgy processing which are yet to be resolved, that is, the high oxide content, the high content of secondary phases, also the difficulty of obtaining dense materials. The main conclusion is that it is imperative to do the sintering in a protecting system (if possible in vacuum), because of the high content of oxygen observed in the measured sintered products

MAMMALS IN PORTUGAL : A data set of terrestrial, volant, and marine mammal occurrences in P ortugal

Mammals are threatened worldwide, with 26% of all species being includedin the IUCN threatened categories. This overall pattern is primarily associatedwith habitat loss or degradation, and human persecution for terrestrial mam-mals, and pollution, open net fishing, climate change, and prey depletion formarine mammals. Mammals play a key role in maintaining ecosystems func-tionality and resilience, and therefore information on their distribution is cru-cial to delineate and support conservation actions. MAMMALS INPORTUGAL is a publicly available data set compiling unpublishedgeoreferenced occurrence records of 92 terrestrial, volant, and marine mam-mals in mainland Portugal and archipelagos of the Azores and Madeira thatincludes 105,026 data entries between 1873 and 2021 (72% of the data occur-ring in 2000 and 2021). The methods used to collect the data were: live obser-vations/captures (43%), sign surveys (35%), camera trapping (16%),bioacoustics surveys (4%) and radiotracking, and inquiries that represent lessthan 1% of the records. The data set includes 13 types of records: (1) burrowsjsoil moundsjtunnel, (2) capture, (3) colony, (4) dead animaljhairjskullsjjaws, (5) genetic confirmation, (6) inquiries, (7) observation of live animal (8),observation in shelters, (9) photo trappingjvideo, (10) predators dietjpelletsjpine cones/nuts, (11) scatjtrackjditch, (12) telemetry and (13) vocalizationjecholocation. The spatial uncertainty of most records ranges between 0 and100 m (76%). Rodentia (n=31,573) has the highest number of records followedby Chiroptera (n=18,857), Carnivora (n=18,594), Lagomorpha (n=17,496),Cetartiodactyla (n=11,568) and Eulipotyphla (n=7008). The data setincludes records of species classified by the IUCN as threatened(e.g.,Oryctolagus cuniculus[n=12,159],Monachus monachus[n=1,512],andLynx pardinus[n=197]). We believe that this data set may stimulate thepublication of other European countries data sets that would certainly contrib-ute to ecology and conservation-related research, and therefore assisting onthe development of more accurate and tailored conservation managementstrategies for each species. There are no copyright restrictions; please cite thisdata paper when the data are used in publications.info:eu-repo/semantics/publishedVersio

Mammals in Portugal: a data set of terrestrial, volant, and marine mammal occurrences in Portugal

Mammals are threatened worldwide, with ~26% of all species being included in the IUCN threatened categories. This overall pattern is primarily associated with habitat loss or degradation, and human persecution for terrestrial mammals, and pollution, open net fishing, climate change, and prey depletion for marine mammals. Mammals play a key role in maintaining ecosystems functionality and resilience, and therefore information on their distribution is crucial to delineate and support conservation actions. MAMMALS IN PORTUGAL is a publicly available data set compiling unpublished georeferenced occurrence records of 92 terrestrial, volant, and marine mammals in mainland Portugal and archipelagos of the Azores and Madeira that includes 105,026 data entries between 1873 and 2021 (72% of the data occurring in 2000 and 2021). The methods used to collect the data were: live observations/captures (43%), sign surveys (35%), camera trapping (16%), bioacoustics surveys (4%) and radiotracking, and inquiries that represent less than 1% of the records. The data set includes 13 types of records: (1) burrows | soil mounds | tunnel, (2) capture, (3) colony, (4) dead animal | hair | skulls | jaws, (5) genetic confirmation, (6) inquiries, (7) observation of live animal (8), observation in shelters, (9) photo trapping | video, (10) predators diet | pellets | pine cones/nuts, (11) scat | track | ditch, (12) telemetry and (13) vocalization | echolocation. The spatial uncertainty of most records ranges between 0 and 100 m (76%). Rodentia (n =31,573) has the highest number of records followed by Chiroptera (n = 18,857), Carnivora (n = 18,594), Lagomorpha (n = 17,496), Cetartiodactyla (n = 11,568) and Eulipotyphla (n = 7008). The data set includes records of species classified by the IUCN as threatened (e.g., Oryctolagus cuniculus [n = 12,159], Monachus monachus [n = 1,512], and Lynx pardinus [n = 197]). We believe that this data set may stimulate the publication of other European countries data sets that would certainly contribute to ecology and conservation-related research, and therefore assisting on the development of more accurate and tailored conservation management strategies for each species. There are no copyright restrictions; please cite this data paper when the data are used in publications