Maximum Recovery Strain Research Articles

Effect of Ta addition on shape memory behavior of Ti–22Nb alloy

Effect of Ta addition on microstructure and shape memory behavior of a Ti–22 at.%Nb alloy was investigated in order to improve the shape memory and superelastic properties. The mechanical properties and shape memory behavior of Ti–22 at.%Nb–(0–8 at.%)Ta alloys were investigated by tensile tests at various temperatures and thermal cycling tests under various constant stresses. The shape memory effect with the maximum recovery strain of 2.7% was observed at room temperature in the Ti–22Nb alloy. The martensitic transformation temperature of the Ti–22Nb alloy decreased by 30 K per 1 at.% addition of Ta. The superelastic strain increased with increasing Ta content. Almost perfect superelastic behavior was observed until 2% tensile strain in the Ti–22Nb–(6–8)Ta alloys. The apparent yield stress decreased with increasing Ta content reaching a minimum yield stress around 4 at.%, and then the yield stress increased by further addition of Ta. The critical stress for slip increased with increasing Ta content. A higher critical stress for slip and a lower stress for inducing martensitic transformation resulted in a larger shape recovery strain above 3.0% in the Ti–22Nb–(4–6)Ta alloys.

Effects of Chemical and Enzymatic Modification on Dough Rheology and Biscuit Characteristics

ABSTRACT: The effect of addition of sodium meta-bisulfite and a commercial protease on dough rheological properties and biscuit characteristics was studied on 7 biscuit wheat cultivars. Sodium meta-bisulfite (SMS) (360 mg/kg flour) or protease (300 mg/kg flour) was added to semisweet biscuit dough. Rheological studies included creep recovery and shear oscillation. SMS and protease increased maximum strain, recovery strain, and phase tan Δ, and lowered storage modulus, G′, and the relative recovery, % recovery. The effects varied among cultivars and between SMS and protease. Biscuit eccentricity (width/length) was significantly reduced by addition of SMS or protease, but the effect varied among the cultivars, and between SMS and protease. Partial least squares regression analysis of the rheological parameters and the dimensional characteristics showed that biscuit contraction and spread were mostly correlated to % recovery of the dough, and protein and gluten content of the flour. Correlations between predicted and measured contraction and spread were r= 0.70 and r= 0.43, respectively.

「スマートマテリアル」 低温結晶化させた非晶質Ｔｉ‐Ｎｉ薄膜の形状記憶特性と内部組織

The shape memory properties of sputter-deposited Ti-Ni thin films crystallized from amorphous at low-temperatures, 60-90 K lower than the crystallization peak temperature measured by differential scanning calorimetry (DSC), were investigated. The Ti-47.7 at%Ni (Ti-rich) and Ti-51.6 at%Ni (Ni-rich) thin films were fabricated by a r.f. magnetron sputter-deposition method. Heat-treatment temperature was varied from 643 to 693 K and heat-treatment time was varied from 3.6 to 360 ks. Thin plate precipitates were formed on {100}B2 in the Ti-rich thin films heat-treated at 653 K. Maximum recovery strain (εAmax) of the Ti-rich thin films increased up to 5.4% with increasing heat-treatment time. But it started to decrease after reaching the maximum value. The decrease in εAmax was caused by the decrease of the critical stress for slip (σs) with increase of heat-treatment time because of the growth of thin plate precipitates. Ti3Ni4 precipitates were formed in the Ni-rich thin films heat-treated at 673-693 K. εAmax of the Ni-rich thin films increased with increasing heat-treatment time. But, the εAmax reached only 2.9%, since the martensitic transformation and the growth of martensites were strongly suppressed by Ti3Ni4 precipitates. The martensitic transformation temperature (Ms) of the Ti-rich and Ni-rich thin films increased with increasing heat-treatment time.

Creep‐Recovery of Wheat Flour Doughs and Relationship to Other Physical Dough Tests and Breadmaking Performance

ABSTRACTMeasurements of creep‐recovery of flour‐water doughs were made using a dynamic mechanical analyzer (DMA) in a compression mode with an applied probe force of 50 mN. A series of wheat flour and blend samples with various breadmaking potentials were tested at a fixed water absorption of 54% and farinograph optimum water absorption, respectively. The flour‐water doughs exhibited a typical creep‐recovery behavior of a noncross‐linked viscoelastic material varying in some parameters with flour properties. The maximum recovery strain of doughs with a fixed water absorption of 54% was highly correlated (r = 0.939) to bread loaf volume. Wheat flours with a large bread volume exhibited greater dough recovery strain. However, there was no correlation (r = 0.122) between maximum creep strain and baking volume. The maximum recovery strain of flour‐water doughs also was correlated to some of the parameters provided by mixograph, farinograph, and TA‐XT2 extension.

Effect of Pre-Strain on Mechanical Propertiec of Ni-Ti-Nb Shape Memory Alloy.

A shape memory alloy (SMA) is intended to be used as structural elements at elevated temperatures. The mechanical and transformation properties of Ni Ti-Nb SMA were examined at room temperature and 561 K. The chemical composition of Ni-Ti-Nb SMA is 51 wt.% Ni, 38 w.% Ti and 11 wt.% Nb. The tensile strength, the 0.2% proof stress and the vickers hardness are increasing with increasing pre-strain below 14%, but the elongation, the reduction of area and the charpy impact absorption are decreasing with increasing pre-strain below 14%. The SMA is found to have sufficient mechanical strength for structural elements at elevated temperature. Maximum recovery strain due to the shape memory effect was about 5.5%. This value was obtained when 12% pre-strain was added. This means that a pre-strain of 12% is desirable when the Ni-Ti-Nb SMA is used for pipe coupling, etc.

Transformation and Deformation Behavior in Sputter-Deposited Ti-Ni-Cu Thin Films

Ti-Ni-Cu thin films were prepared by RF magnetron sputtering. Their compositions were determined by EPMA to be ranging in Cu-content from 0 to 18.0at%. All the thin films were solution-treated at 973K for 3.6ks followed by quenching into water. Transformation and deformation characteristics and lattice constants in the thin films have been investigated systematically by means of differential scanning calorimetry(DSC), constant load thermal cycling tests and X-ray diffractometry, respectively. The martensite transformation temperatures of all the thin films were around 323K ; they decreased only slightly with increasing Cu-content in the range within 9.5at%, while they slightly increased in the range beyond 9.5at%. The temperature hysteresis associated with the transformation showed a strong dependence on Cu-content, i.e., it decreased from 27K to 10K with increasing Cu-content from 0at% to 9.5at%. In the 9.5at%Cu specimen, a two-stage transformation appeared and it was determined as B2↔Orthorhombic↔Monoclinic by the X-ray diffractometry. Perfect shape memory effects were observed corresponding to these transformations. By the addition of Cu, the maximum recovery strain decreased from 3.9% to 1.1% and the critical stress for slip greatly increased from 55MPa to 350MPa with increasing Cu-content.