The Influence of Strain Rate on the Springback of Commercially Pure Titanium in a Stretch Forming Operation

2015 ◽  
Vol 639 ◽  
pp. 107-114 ◽  
Author(s):  
Alan G. Leacock ◽  
Shane Quinn ◽  
Gregor Volk ◽  
David McCracken ◽  
Desmond Brown

A common processing stress state used in the construction of sheet metal components is that of uniaxial tension/stretching. This work examines the stretching of CP-Ti over a rigid form tool using varying degrees of strain and strain rate. The degree of springback is shown to be influenced by the interaction of strain rate, strain magnitude and time following forming.

2020 ◽  
Vol 321 ◽  
pp. 04009
Author(s):  
Min-Su Lee ◽  
Yong-Taek Hyun ◽  
Tea-Sung Jun

In this study, we have investigated the effect of oxygen contents on strain rate senstivitiy (SRS) within Gr. 1 and 4 commercially pure titanium (CP-Ti). The SRS was evaluated in multi-scales using macro-scopic tensile test with constant strain rate (CSR) method and strain rate jump (SRJ) method, and nanoindentation test with SRJ method. Electron backscatter diffraction (EBSD) has been used to characterise crystallographic texture and individual grain orientation of samples. Slip and twin activities of each CP-Ti were compared by EBSD measurements and the associated Schmid factor (SF) analysis. The active slip system is anticipated to be different in each relation between loading directions and textures, but twin activity is much similar. The texture dependent global SRS is thus thought to be resulted from the different slip activity. Local SRS was dependent not only on the grain orientation but also on the oxygen contents, leading to the fact that the impact of oxygen contents is closely correlated in macro- and micro-scopic level.


Author(s):  
V.V. Skripnyak ◽  
◽  
K.V. Iokhim ◽  
V.A. Skripnyak ◽  
◽  
...  

In this work, the effect of a triaxiality stress state on the mechanical behavior and fracture of commercially pure titanium VT1-0 (Grade 2) in the range of strain rates from 0.1 to 1000 s−1 is studied. Tensile tests are carried out using a servo-hydraulic testing machine Instron VHS 40 / 50-20 on flat specimens with a constant cross-sectional area and on flat specimens with a notch. To study the effect of the complex stress state on the ultimate deformation before fracture, the samples with the notch of various radii (10, 5, 2.5 mm) are used in the experiments. Phantom V711 is employed for high-speed video registration of specimen’s deformation. Deformation fields in a working part of the sample are investigated by the digital image correlation method. It is shown that the effect of the strain rate on the ultimate deformations before fracture has a nonmonotonic behavior. An analysis of strain fields in the working part of the samples shows that the degree of uniform deformation of the working part decreases with an increase in the strain rate. At strain rates above 1000 s−1, the shear bands occur at the onset of a plastic flow. Commercially pure titanium undergoes fracture due to the nucleation, growth, and coalescence of damages in the bands of localized plastic deformation oriented along the maximum shear stresses. The results confirm that the fracture of commercially pure titanium exhibits ductile behavior at strain rates varying from 0.1 to 1000 s−1, at a triaxiality stress parameter in the range of 0.333 ≤ η <0.467, and at a temperature close to 295 K.


2012 ◽  
Vol 548 ◽  
pp. 174-178 ◽  
Author(s):  
Chong Yang Gao ◽  
Wei Ran Lu

By using a dislocation-based plastic constitutive model for hcp metals developed by us recently, the dynamic thermomechanical response of an important industrial material, commercially pure titanium (CP-Ti), was described at different temperatures and strain rates. The constitutive parameters of the material are determined by an efficient optimization method for a globally optimal solution. The model can well predict the dynamic response of CP-Ti by the comparison with experimental data and the Nemat-Nasser-Guo model.


1986 ◽  
Vol 72 (2) ◽  
pp. 321-328 ◽  
Author(s):  
Takehide SENUMA ◽  
Hiroshi YADA ◽  
Hirobumi YOSHIMURA ◽  
Hisaaki HARADA ◽  
Takuji SHINDO ◽  
...  

Author(s):  
Karibeeran Shanmuga Sundaram ◽  
Gurusami Kiliyappan ◽  
Senthil Kumaran Selvadurai

Laser shock peening (LSP) is one of the innovative technique that produces a compressive residual stress on the surface of metallic materials, thereby significantly increasing its fatigue life in applications where failure is caused by surface-initiated cracks. The specimens were treated with laser shock waves with different processing parameters, and characterization studies were made on treated specimens. The purpose of the present study was to investigate the influence of Nd:YAG laser on commercially pure titanium (CP-Ti) used in prosthetic dental restorations. The treatment influenced change in microstructure, micro hardness, surface roughness, and wear resistance characteristics. Though CP-Ti is considered as an excellent material for dental applications due to its outstanding biocompatibility, it is not suitable when high mastication forces are applied. In the present study, pulsed Nd:YAG laser surface treatment technique was adopted to improve the wear resistance of CP-Ti. The wear test pin specimens of CP-Ti were investment cast with centrifugal titanium casting machine. The wear properties of specimens were evaluated after LSP on a “pin-on-disc” wear testing tribometer, as per ASTM G99-05 standards. The results of the wear experiment showed that the treated laser surface has higher wear resistance, micro hardness, and surface roughness compared to as-cast samples. The improvement of wear resistance may be attributed due to grain refinement imparted by LSP processes. The microstructure, wear surfaces, wear debris, and morphology of the specimen were analyzed by using optical electron microscope, scanning electron microscope, and X-ray diffraction (XRD). The data were compared using ANOVA and post-hoc Tukey tests. The characteristic change resulted in increase in wear resistance and decrease in wear rate. Hence, it is evident that the more reliable and removable partial denture metal frameworks for dental prostheses may find its applications.


2005 ◽  
Vol 19 (2) ◽  
pp. 139-143 ◽  
Author(s):  
Wagner Sotero Fragoso ◽  
Guilherme Elias Pessanha Henriques ◽  
Edwin Fernando Ruiz Contreras ◽  
Marcelo Ferraz Mesquita

Commercially pure titanium (CP Ti) has been widely applied to fabricate cast devices because of its favorable properties. However, the mold temperature recommended for the manufacture of casts has been considered relatively low, causing inadequate castability and poor marginal fit of cast crowns. This study evaluated and compared the influence of mold temperature (430°C - as control, 550°C, 670°C) on the marginal discrepancies of cast CP Ti crowns. Eight bovine teeth were prepared on a mechanical grinding device and impressions were used to duplicate each tooth and produce eight master dies. Twenty-four crowns were fabricated using CP Ti in three different groups of mold temperature (n = 8): 430°C (as control), 550°C and 670°C. The gap between the crown and the bovine tooth was measured at 50 X magnification with a traveling microscope. The marginal fit values of the cast CP Ti crowns were submitted to the Kruskal-Wallis test (p = 0.03). The 550°C group (95.0 µm) showed significantly better marginal fit than the crowns of the 430°C group (203.4 µm) and 670°C group (213.8 µm). Better marginal fit for cast CP Ti crowns was observed with the mold temperature of 550°C, differing from the 430°C recommended by the manufacturer.


2010 ◽  
Vol 654-656 ◽  
pp. 2172-2175
Author(s):  
Kyosuke Ueda ◽  
Hajime Suto ◽  
Kaori Nakaie ◽  
Takayuki Narushima

The surface modification of commercially pure titanium (CP Ti) by pack cementation treatment at 973 K using tetracalcium phosphate (Ca4(PO4)2O, TTCP) slurry was investigated. An HAp phase and a CaTiO3 phase were observed on the reaction layer of the CP Ti substrate after pack cementation treatment at 973 K for 86.4 ks. TTCP powder decomposed to HAp and CaO, and CaO reacted with TiO2 to form CaTiO3. The reaction layer on the CP Ti substrate consisted of inner and outer layers and the particles were in the outer reaction layer. The pores observed on the reaction layer were formed by the detachment of particles from the outer layer. The bonding strength of the reaction layer was 68.1 MPa. Apatite completely covered the surface of the pack-cementation-treated CP Ti after immersion in Kokubo solution for 21.6 ks; such rapid apatite formation suggests that pack cementation treatment improves the biocompatibility of titanium.


2018 ◽  
Vol 53 (9) ◽  
pp. 6872-6892 ◽  
Author(s):  
S. Khayatzadeh ◽  
M. J. Thomas ◽  
Y. Millet ◽  
S. Rahimi

Author(s):  
F Reshadi ◽  
S Khorasani ◽  
G Faraji

This study investigated the surface characteristics of ultrafine-grain commercially pure titanium (UFG CP-Ti) substrates produced by equal channel angular pressing (ECAP), compared with those of coarse-grain commercially pure titanium (CG CP-Ti) and Ti–6Al–4V (Ti-64) substrates. All Ti surfaces were sandblasted and acid-etched (SLA-treated) to produce micro-rough surfaces. Tensile and microhardness tests were carried out to measure the mechanical properties of fabricated samples. Then the surface characteristics of samples including contact angle measurements, surface morphology and in vitro cell response were evaluated after polishing, sandblasting and acid etching procedures. The results showed that after applying four passes of ECAP, the average grain size of microstructure decreased from 25 µm to 170 nm, while the ultimate tensile strength increased from 545 ± 24 MPa to 971 ± 38 MPa. Investigation of surface morphologies carried out by scanning electron microscopy indicated that ECAP-processed substrate exhibits nano-topography compared with CG CP-Ti and Ti-64 substrates after applying SLA process. In addition, the contact angle of SLA-treated CG CP-Ti and UFG CP-Ti substrates decreased from 68.3° to 9.5° and 51.9° to 7.4°, respectively, indicating a significant improvement of surface wettability. The morphologies of MG63 cells cultured on the developed surfaces proved the potential superior osteoblast cell compatibility of the micro-roughened surface made of UFG CP-Ti substrates over CG CP-Ti and Ti-64 substrates.


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