There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Microstructures and properties of high-entropy alloys

Mechanical properties of nanocrystalline materials

Principles of equal-channel angular pressing as a processing tool for grain refinement

On the origin of dynamic strain aging in twinning-induced plasticity steels

On the room temperature deformation mechanisms of a Mg–Y–Zn alloy with long period stacking ordered structures

Modern car design puts an increasing emphasis on the notion that a material used in building the body-in-white (BIW) should be selected on the basis of how well it helps achieving specific engineering targets such as low vehicle weight, high passive safety, stability, stiffness, comfort, acoustics, corrosion, and recycling. Steel is at present still the material of choice for car bodies, with 99% of the passenger cars having a steel body, and 6070% of the car weight consisting of steel or steel-based parts. The automotive industry is however continuously making excursions in the area of light materials applications. At present, most car makers are routinely testing multi-materials concepts, which are not limited to the obvious use of light materials for closures, e.g. the use of Al for the front lid or thermosetting resins for trunk lids. The steel industry has made a sustained effort to innovate and create advanced steels and original steel-based solutions and methods in close collaboration with the manufacturers by an early involvement in automotive projects, but also by involving automakers in their own developments. Carmakers have increasingly built passenger cars with body designs which emphasize passenger safety in the event of a collision, and most passenger cars currently achieve high ratings in standardized crash simulations such as the EURO NCAP or the North American NHST tests. The safety issue directly related to the BIW materials is passive safety. High impact energy absorption is required for frontal crash and rear collision, and anti-intrusion properties are required in situations when passenger injury must be avoided, i.e. during a side impact and in case of a roll over, with its associated roof crush. Increased consumer expectations have resulted in cars which have steadily gained in weight as illustrated in figure 1. This weight spiral is a direct result of improvements in vehicle safety, increased space, performance, reliability, passenger comfort and overall vehicle quality. This trend has actually resulted in an increased use of steel in car body manufacturing in absolute terms, and this increase may in certain cases be as high as 25%. The weight issue is therefore high on the agenda of BIW design, as it is directly related to environmental concerns, i.e. emissions of CO2, and the economics of the gas mileage. Reports on weight saving resulting from the use of Advanced High Strength Steels (AHSS) are difficult to evaluate as these tend to focus on the use of advanced steels and improved designs for a single part, rather than the entire car body. The use of Dual Phase (DP) and Transformation-Induced Plasticity (TRIP) steels has been

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High Mn TWIP Steels for Automotive Applications

Effect of Al on the stacking fault energy of Fe–18Mn–0.6C twinning-induced plasticity

Pre-equal-channel-angular-pressing (ECAP) solution treatment combined with post-ECAP aging treatment has been found to be effective in enhancing the room-temperature strength of 6061 aluminum alloy. The largest increase in ultimate tensile strength (UTS) (=460 MPa) and yield stress (YS) (=425 MPa) is obtained in post-ECAP aged 6061 Al with six pressings. The strength increases by a factor of 1.4 when compared to T6 treated commercial 6061 Al. The strength of 6061 Al obtained in the present research is higher than that of ECA-pressed 6061 Al with pre-ECAP peak-aging treatment studied by other investigators. The more effective strengthening of post-ECAP low-temperature aging may be linked with the higher dislocation accumulation rate in the solutionized matrix and the presence of higher density particles in the aged matrix. Modest low-temperature (523 K) and high-temperature (813 K) superplasticity is observed in the ECAP 6061 Al, which may be a result of increased grain bundary area from grain refinement.

Jin-Kyung Kim

Papers

On the origin of dynamic strain aging in twinning-induced plasticity steels

On the room temperature deformation mechanisms of a Mg–Y–Zn alloy with long period stacking ordered structures

High Mn TWIP Steels for Automotive Applications

Effect of Al on the stacking fault energy of Fe–18Mn–0.6C twinning-induced plasticity

Enhancement of strength and superplasticity in a 6061 Al alloy processed by equal-channel-angular-pressing