The deformation microstructure produced by heavy cold rolling (from 70 % to 95 % reduction) of pearlitic structure with various amounts of rolling and the tensile strength of the cold rolled sheets were studied in the plain carbon steels with various carbon contents (0.6, 0.76, and 1.0 mass%C). The deformation microstructure was classified into the following three types; 1) Irregularly Bent Lamella (IBL): lamellae originally inclined with large angles to the rolling plane and irregularly bent after deformation, 2) Coarse Lamella with Shear band (CLS) : the rhomboidal blocks of weakly deformed lamellae bounded by shear band, 3) Fine Lamella (FL): heavily deformed lamellae aligned parallel to the rolling direction with fine interlamellar spacings. As rolling reduction increases, the proportion of FL increases.The tensile strength of cold rolled specimens increases with rolling reduction. Work hardening with respect to true strain by cold rolling is similar to that obtained by wire drawing. After 92 % cold rolling of 1.0 mass%C steel, the tensile strength over 2 500 MPa was achieved.

Kinetics and crystallography of intragranular pearlite nucleated at the surface of (MnSϩVC) complex precipitate were studied in hypereutectoid Fe-Mn-C steels. The incoherent MnS embedded in the austenite does not act as a strong nucleation site of pearlite unless the transformation time is prolonged. The intragranular pearlite transformation is promoted effectively by the addition of vanadium (V). EPMA analysis showed that the intragranular pearlite nucleates on the (MnSϩVC) complex precipitate in the V-added alloy. As the transformation temperature decreases, the intragranular pearlite formation occurs more frequently. A single intragranular pearlite is composed of several colonies, indicating that multiple pearlite colonies nucleate on a (MnSϩVC) complex precipitate for intragranular pearlite transformation. There is no specific orientation relationship (OR) between ferrite in intragranular pearlite and austenite matrix while there is a specific OR (Pitsch-Petch OR) between pearlitic ferrite and cementite in the intragranular pearlite.

Background Fall prevention in older adults is an important task. Lower extremity function is a main focus in fall prevention. There are few previous studies focusing on core stability. The purpose of this study was to investigate the relationship between fall risk and core stability. Methods The study participants were 33 community-dwelling older adults (mean age: 65±17 years old; 5 men, 28 women). The fall risk was assessed using the Fall Risk Index-21 (FRI-21). Core stability measured the retention time of Side Bridge (SB) and Front Bridge (FB). Secondary outcome measures included lower extremity muscle strength (knee extension, hip abduction) and physical function (two-step test). Statistical analysis investigated the correlation between the measurement items. Results We found a significant negative correlation between FRI-21 and SB (r = -0.51, p<0.01) and FRI-21 and FB (r = -0.47, p<0.01). We also found a correlation between FRI-21 and the two-step test (r = -0.40, p<0.05). There was no significant correlation between FRI-21 and lower extremity muscle strength. Discussion FRI and Core stability showed moderate correlation. It suggests that the core and hip muscle functions involved in posture retention are involved with fall. Conclusion The risk of falls in older adults was related to core stability. If the core stability of older adults improves, it may help to reduce the risk of falling. Therefore, it is useful to consider core stability in the assessment of fall risk.

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