Influence of Thermomechanical Processing on the Martensitic Transformation Temperatures of NiTi SMA Wire

2010 ◽  
Vol 643 ◽  
pp. 43-48 ◽  
Author(s):  
Leonardo Kyo Kabayama ◽  
Odair Doná Rigo ◽  
Jorge Otubo
Keyword(s):  
Martensitic Transformation ◽  
Thermomechanical Processing ◽  
Cold Drawing ◽  
Wire Drawing ◽  
Mechanical Processing ◽  
Drawing Process ◽  
Intermediate Annealing ◽  
Transformation Temperatures ◽  
Area Reduction ◽  
Niti Sma

Most of the applications of NiTi SMA are as a wire form. In this sense it is important to know the effects of thermo-mechanical processing such as reduction per pass and intermediate annealing on the wire drawing process. For this work they were produced wire by cold drawing using 15 % area reduction per pass with and without intermediate annealing. The starting ingot was produced by VIM process. The influence of thermo-mechanical processing will be related to the martensitic transformation temperatures.

Optimization of Die design to abolish surface defect on Telescopic Front Fork (TFF) Tube

2021 ◽  
Vol 01 ◽  
Author(s):  
Asit Kumar Choudhary ◽  
Braj Bihari Prasad
Keyword(s):  
Outer Surface ◽  
Transverse Crack ◽  
Axial Stress ◽  
Substantial Reduction ◽  
Cold Drawing ◽  
Wire Drawing ◽  
Die Design ◽  
Drawing Process ◽  
Die Geometry ◽  
Area Reduction

Background: The telescopic fork is mainly used for suspension purposes in the different devices to absorb the vibration and disturbances from the road or mechanical devices. Factors such as die angle, drawing velocity, lubrication, and area reduction per pass significantly affect the drawing loads and residual stresses formed in the drawn tube during the tube marking process. Objective: Instantaneous transverse crack was found on the pipe's outer surface during the drawing process in the current work, and the key challenges were to reduce the percentage of pipe rejection. Methodology: In this work, optimum drawing die designs were proposed by using the finite element method (FEM). A FEM solving tool called Abaqus has been used for simulating and solving the cold-rolled process. The FEM model of the cold drawing process is generated in Abaqus with the same boundary condition (Axial load and constrain) as using on the actual wire drawing machine. Result: There was a substantial reduction in the area; axial stress (Tensile) along the die side is 672 MPa which is 23 % lower than the current die axial stress value of 877 MPa. A 48 % plastic strain was found along the purposed die side, which was 17 % lower than the existing strain of 64%. Finally, reduced the area by changing the die geometry from ~52% to 35 to 40 %. Conclusion: It was possible to abolish transverse crack on the pipe's outer surface to reduce the area reduction (35 to 40 %) in the output tube and strain (17 %). As part of the optimization of the FEM work process, this work gives us encouraging results. Further research will be considered for future positions.

Deformation Law of Cold Drawing Process of High Strength Bridge Cable Steel

2021 ◽  
Vol 1035 ◽  
pp. 801-807
Author(s):  
Xiao Lei Yin ◽  
Jian Cheng ◽  
Gang Zhao
Keyword(s):  
Strain Path ◽  
High Strength ◽  
Cold Drawing ◽  
Wire Drawing ◽  
Radial Deformation ◽  
Steel Bridge ◽  
Drawing Process ◽  
Single Pass ◽  
Potential Relationship ◽  
The Wire

High-strength cable-steel bridge is the “lifeline” of steel structure bridges, which requires high comprehensive mechanical properties, and cold-drawing is the most important process to produce high-strength cable-steel bridge. Therefore, through the ABAQUS platform, a bridge wire drawing model was established, and the simulation analysis on the process of stress strain law and strain path trends for high-strength bridge steel wire from Φ 12.65 mm by seven cold-drawing to Φ 6.90 mm was conducted. The simulation results show that the wire drawing the heart of the main axial deformation, surface and sub-surface of the main axial and radial deformation occurred, with the increase in the number of drawing the road, the overall deformation of the wire was also more obvious non-uniformity. In the single-pass drawing process, the change in the potential relationship of each layer of material was small, and multiple inflection points appeared in the strain path diagram; the change in the seven-pass potential relationship was more drastic, which can basically be regarded as a simple superposition of multiple single-pass pulls.

Influence of the Die Bearing Length on the Hydrogen Embrittlement of Cold Drawn Wires

2013 ◽  
Vol 577-578 ◽  
pp. 553-556 ◽  
Author(s):  
Jesús Toribio ◽  
Miguel Lorenzo ◽  
L. Aguado ◽  
Diego Vergara ◽  
Viktor Kharin
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
Cold Drawing ◽  
Wire Drawing ◽  
Wire Radius ◽  
Drawing Process ◽  
Strain Fields ◽  
Characteristic Value ◽  
The Wire ◽  
Definition Of

Prestressing steels, obtained by cold drawing, are highly susceptible to hydrogen embrittlement (HE) phenomena. Stress and strain fields produced by cold drawing play an essential role in this process since they affect hydrogen diffusion. Therefore, variations of such fields due to changes in drawing conditions could modify life in-service of these structural components. In this work the effect on HE of a parameter of the wire drawing process, thebearing length, is analyzed by means of diverse numerical simulations by the finite element method (FEM). The results of this work allow the definition of acharacteristic valueof the die bearing length equal to the wire radius, and demonstrate that the effects of stress-strain fields produced by wire drawing on HE are reduced when the bearing length exceeds such a characteristic value, so that the optimum cold drawing process is that with a bearing length higher than the wire radius.

Pushing The Limit to Achieve NiTi SMA Actuating Members that are Dimensionally Stable and have High Transformation Temperatures

1991 ◽  
Vol 246 ◽  
Author(s):  
Paul E. Thoma ◽  
Alexander M. Blok ◽  
Ming-Yuan Kao
Keyword(s):  
Mechanical Properties ◽  
Thermal Cycling ◽  
Axial Stress ◽  
Thermal Transformation ◽  
Mechanical Processing ◽  
Annealed Condition ◽  
Transformation Temperatures ◽  
Niti Sma ◽  
Stress Relieving ◽  
Stress Levels

AbstractIn binary NiTi shape memory alloys (SMA), the highest martensite (M) and austenite (A) transformation temperatures (TT) occur in the annealed condition. The highest TT also occur in near equiatomic NiTi alloys that have an excess of Ti. However, the NiTi alloy composition and condition that have the highest TT produce actuating elements that are generally short lived, have poor mechanical properties, and plastically deform (creep) under low stress levels. Cold working the SMA followed by a memory imparting stress relieving heat treatment (HT) produces actuating elements that are long lived, have good mechanical properties, and are resistant to creep under moderate stress levels. However, in obtaining these desirable properties through thermal-mechanical processing, the M and A TT are significantly decreased, which limits the upper ambient temperature in which the actuating element can operate.A dimensionally stable actuating member with high TT can be achieved by thermal cycling (under stress) a NiTi SMA wire that has received prior thermal-mechanical processing. Cycling under an applied axial stress can increase the M TT of a SMA wire. Data showing the influence of thermal cycling on the TT of axially stressed SMA wires, that were cold drawn followed by HT at different memory imparting temperatures, are presented and discussed. For a NiTi SMA wire (A finish TT = 111 °C in the annealed condition) having approximately 40% cold reduction in area, 400°C for 1 hour memory imparting HT, and 10 Ksi axial stress, the M start TT (Ms) and A finish TT (Af) increase from 26°C and 79°C respectively after 10 thermal transformation cycles to 62 °C and 83.5 °C respectively after 10,000 thermal transformation cycles.

scholarly journals Thermomechanical Analysis of an Electrically Assisted Wire Drawing Process

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Antonio J. Sánchez Egea ◽  
Hernán A. González Rojas ◽  
Diego J. Celentano ◽  
Jordi Jorba Perió ◽  
Jian Cao
Keyword(s):  
Mechanical Response ◽  
Cold Drawing ◽  
Wire Drawing ◽  
Thermomechanical Analysis ◽  
Drawing Process ◽  
Thermomechanical Model ◽  
Electron Backscattered Diffraction ◽  
Hardening Law ◽  
Electrically Assisted ◽  
Material Tests

Electrically assisted (EA) wire drawing process is a hybrid manufacturing process characterized by enhancement of the formability, ductility, and elongation of the wire drawn specimen. A thermomechanical model to describe the change of the mechanical response due to the thermal contribution is proposed in this work. Additionally, a numerical simulation was conducted to study the potential and limitations of this hybrid process by using two different hardening laws: a phenomenological and a dislocation-based hardening laws. The results show how the flow stress, the effective plastic strain, and residual stresses behave under the electroplusing effect. In addition, electron backscattered diffraction was used to study the electropulsing treatments on the microstructure during cold drawing. It is observed a decrease of the high- and low-angle grain boundaries (LAGB) for samples deformed with electropulsing. This detwinning process has a strong influence on the strain hardening by improving the material formability. It was shown that the two proposed hardening laws adequately describe the EA wire drawing process showing a similar mechanical behavior. Nevertheless, the dislocation-based hardening law has the potential to be generalized to many other material and process configurations without extensive number of material tests as the phenomenological hardening law would require.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

Variation of Residual Stresses in Drawn Copper Tubes

2008 ◽  
Vol 571-572 ◽  
pp. 21-26 ◽  
Author(s):  
Adele Carradò ◽  
D. Duriez ◽  
Laurent Barrallier ◽  
Sebastian Brück ◽  
Agnès Fabre ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Residual Stresses ◽  
Material Flow ◽  
Cold Drawing ◽  
Axisymmetric Deformation ◽  
Tube Length ◽  
Inhomogeneous Deformation ◽  
Drawing Process ◽  
Process Step ◽  
Residual Strains

Seamless tubes are used for many applications, e.g. in heating, transport gases and fluids, evaporators as well as medical use and as intermediate products for hydroforming and various mechanical applications, where the final dimensions normally are given by some cold drawing steps. The first process step – piercing of the billet, for example by extrusion or 3-roll-milling - typically results in ovality and eccentricity in the tube causing non-symmetric material flow during the cold drawing process, i.e. inhomogeneous deformation. Because of this non-axisymmetric deformation and of deviations over tube length caused by moving tools, this process step generates residual stresses. To understand the interconnections between the geometrical changes in the tubes and the residual stresses, the residual strains in a copper tube had been measured by neutron diffraction.

New Interpretation of the Electrical Resistivity Measurements for Obtaining NiTi SMA Stress-Free Transformation Temperatures

2012 ◽  
Author(s):  
Cristina Urbina ◽  
Silvia De la Flor ◽  
Francesc Gispert-Guirado ◽  
Francesc Ferrando
Keyword(s):  
Electrical Resistivity ◽  
Rietveld Refinement ◽  
Martensite Transformation ◽  
Weight Fraction ◽  
Transformation Process ◽  
Transformation Temperatures ◽  
Resistivity Measurements ◽  
Niti Sma ◽  
New Interpretation ◽  
New Criterion

The objective of this study is to clarify and to improve the interpretation of the ER measurements used to obtain NiTi SMA stress-free transformation temperatures for the austenite to martensite transformation process. To achieve this objective, the transformation temperatures of NiTi SMA wires are measured by ER using the Ling and Kaplow interpretation and are compared and complemented by weight fraction diagrams. The weight fractions are obtained from XRD profiles using the Parametric Rietveld refinement and adequate software. As a result of comparing both techniques, a new interpretation of the ER curves is proposed. This new interpretation is based on the shape of NiTi ER curve, which depends on the quantity of R-phase in the NiTi SMA. The quantity of the R-phase is obtained by weight fraction diagrams. According to the findings presented here, a new criterion for R-phase and martensite transformation temperatures is proposed.

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