In order to make the TiNi shape memory alloy (SMA) with arbitrary shape couture, the lost wax fine casting and self-propagating high-temperature synthesis (SHS) method can be applied. However, the SMA produced by these methods donot carries out some process. Thus the shot peening process is applied to improve the mechanical properties of SMA instead of cold roll process. In this study, we investigated the effect of the shot peening process for the improvement of the properties of SMA.

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Nitinol shape memory alloys (SMAs) are attracting considerable attention as core materials for medical guidewires because of their excellent flexibility and shape retention. However, since Nitinol guidewires possess low rigidity, the pushability and torquability of the guidewires are insufficient. On the other hand, although stainless steel guidewires have high pushability, plastic deformation easily occurs. We have developed a new class of superelastic guidewires with functionally graded properties from the tip to the end by using new SMA core materials such as Cu-Al-Mn-based or Ti-Mo-Sn SMAs. The tip portion of the guidewire shows excellent superelasticity (SE), while the body portion possesses high rigidity. These functionally graded characteristics can be realized by microstructural control. These guidewires show excellent pushability and torquability and are considerably easier to handle than conventional guidewires. Moreover, a metallic catheter using a Ni-free Ti-based SMA with high biocompatibility is introduced.

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Extrusion and intrusion were investigated by many researches but stress field in the first stage was not investigated. Therefore in this study using notched specimen stress field in initial crack occurrence at notch was investigated. Stress field at notch was measured by pasting strain gage on the notch and by measuring the change of stress field at notch the mechanism of crack occurrence was investigated.

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The fatigue properties are studied in detail on the high-tension steel sheets that are used in automobile structures and components. Safety, durability and stability, as well as good press formability for complicated shapes in automobile industries are necessary for this type of steel sheets. The materials used in this study are 4 types of high-tension steel sheets. The materials are designated as A, Q, T1 and T2 in term of as-rolled sheet, direct quench process and different tempering temperature, respectively. The results show that the fatigue limit is at the highest in material A followed by materials T2, T1 and Q. Compared to material A, the surface hardness in all materials are increased and tensile strength are improved in materials Q and T1 but not in T2. Surface fatigue crack initiation and propagation was studied by the replica methods and their morphology was observed by a scanning electron microscope.

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The present paper investigates distributions of α' martensitic phase on fatigue fracture surfaces in SUS 304 stainless steel specimens having through- and part-through-thickness cracks. The volume fraction V_α' of the α' phase transformed on fracture surfaces in the two types of specimens was measured after specimens had been fractured. The measurements were made with ferrite scope. On fracture surfaces, the contour maps of V_α' reflect the distributions of the maximum values of the stress intensity factor K_<max>. The contour maps look similar to crack shapes imprinted on fracture surfaces in the two types of specimens. The contour maps on through-thickness cracks have nearly rectangular shapes, whereas those on part-through-thickness cracks have semi-elliptical shapes. The values of V_α' measured on crack surfaces can be correlated with K_<max> values calculated at the measurement positions. The resultant V_α' vs. K_<max> plots fall within narrow bands whose upper and lower bounds are expressed as quadric curves. These results suggest that quantitative post-fracture analysis can be maid by measurement of V_α' on fracture surfaces with ferrite scope.

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In the present study, elasto-plastic analysis on the thick-walled filament-wound carbon fiber reinforced plastic (FW-CFRP) hybrid composite pipes subjected to internal pressure was proposed. The analysis is based on the Hencky relation and Ludwick's strain-hardening function. In order to evaluate the availability, the distributions of stress and strain based on the present analysis and finite element method were compared. Burst strength of the FW-CFRP hybrid composite pipes and residual strength after impact were predicted based on the maximum strain criterion. The analytical predictions are in good agreement with the experimental results.

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