Fatigue life improvement for cruciform welded joint by mechanical surface treatment using hammer peening and ultrasonic nanocrystal surface modification*

For the improvement of the fatigue strength for welded structures, mechanical posttreatments have been applied in various industrial fields and in most cases have been found to give substantial increases in their fatigue lives. These methods, generally, consist of the modification of weld toe geometry and the introduction of compressive residual stresses. In mechanical surface treatments, for example, PHP (pneumatic hammer peening) and UNSM (ultrasonic nanocrystal surface modification), the weld profile is modified due to removed or reduced minute crack‐like flaws, and compressive residual stresses are also induced. In this study, a PHP procedure and a UNSM device were introduced, and a quantitative measure of fatigue strength improvement was performed. The fatigue strength at 2 × 10⁶ cycles of hammer‐peened and UNSM treated on a non‐load‐carrying cruciform welded joint shows 220 and 260 MPa, respectively, which are more than two times higher than that of as‐welded specimen. Especially, the surface layer in the vicinity weld toe treated by the UNSM provides nanocrystal structure created by an ultrasonic cold forging and introduces very high welding residual stress in compression.     

Damage and penetration behavior of aluminum foam at various impacts

In this work, the damage and penetration behavior of aluminum foam at various types of impact were examined through experiments. The impact energy of a striker was applied on the fixed aluminum foam having a thickness of 25 mm while increasing its impact by 2 J at each strike from 6 J to 16 J. The results show that the impact energies from 6 J to 12 J could not penetrate aluminum foam. However, the aluminum foam applied with the impact energy of 12 J incurred severe damages on its lower part. Finally, the aluminum foam applied with the impact energy of 14 J was penetrated. The striker having the impact energy of 6 J could penetrate aluminum foam around 10 mm. At this moment, aluminum foam could absorb the impact energy of around 9 J. When the impact energy of 14 J was applied on the aluminum foam, the aluminum foam was penetrated and it absorbed the impact energy of around 17.2 J. It is possible to create the safer structure against impact using the results of this work. The simulation results for the verification of the experimental results imply that the results for all the experiments in this work are reliable. It is possible to predict the structural safety of the aluminum foam for an impact if the impact behavior of aluminum foam performed in this work is utilized.     

Experimental Study of Material Removal Process of Fused Silica Glass Using MR Jet Polishing System

Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitable means of polishing complex shapes is to use a jet of abrasive fluid.However,aerodynamic disturbances and radial spreading are generated by the unstable polishing process of the jet on the surface of the workpiece when it is being polished.A method of jet stabilization has been proposed in which the original nozzle form of a jet of magnetorheological(MR)fluid contains abrasive particles that are magnetized using a magnetic.This paper details the design of an MR jet polishing system that uses an electromagnet,a nozzle,and a hydraulic unit to stabilize a slurry jet based on MR fluid,Second,for silica glass,the polishing spot and section profile are analyzed and the effect of the MR fluid jet polishing process is evaluated.The results of the experiment show that the removal profile is W-shaped and that,in this case,a stable can be proof of a distance of several tens of millimeters from the nozzle.Such results show the possibility of applying the proposed polishing method using MR fluids in ultra-precision micro and optical parts production processes.MR jet polishing shows great potential for use as a new type of precision surface polishing technology.In particular,this is a highly valuable process for the polishing of complex shapes such as micro parts,concaves parts,and cavities.     

KINETIC MECHANISM OF PYROPHOSPHATE-DEPENDENT PHOSPHOFRUCTOKINASE FROM PROPIONIBACTERIUM FREUDENREICHII AT EXTREMELY HIGH CONCENTRATION (> 0.5 mM) OF PYROPHOSPHATE

ABSTRACT A new region for enzyme activity of inorganic pyrophosphate-dependent phosphofructokinase from Propionibacterium freudenreichii was detected at extremely high concentration (>0.5 mM) of pyrophosphate, where the maximum velocity increased about 3 times. At a relatively low concentration (<0.1 mM) of pyrophosphate, the kinetic mechanism is rapid equilibrium random sequential with E:F6P:Pi, E:MgPPi:Pi and E:FBP:MgPPI being dead-end complexes. However, the data from initial velocity and product inhibition patterns at extremely high concentration of pyrophosphate are consistent with a ping-pong mechanism with E:MgPPi:Pi as a dead-end complex, where MgPPi binds first.     

Chemical Characterization of Sardine Meat Powder Produced by Dehydration with High Osmotic Pressure Resin and Defatting with High Pressure Carbon Dioxide

Oils and fishy odor were extracted from the minced sardine meat with liquid carbon dioxide after dehydration with high osmotic pressure resin. This treatment resulted in higher quality minced sardine meat usable as “Surimi.” The lipids of the minced sardine meat defatted with liquid carbon dioxide was half that of undefatted meats; residual lipids were mainly composed of polar lipids such as phospholipids. Although soluble nitrogen and ATPase activity in sardine meat were decreased by dehydration and defatting, the Kamaboko-forming ability was present, and its flavor was improved after defatting. Moreover, sardine meat defatted with liquid carbon dioxide had good stability against protein deterioration and lipid peroxidation.     

Development of Ubiquitous Simulation Service Structure Based on High Performance Computing Technologies

The simulation field became essential in designing or developing new casting products and in improving manufacturing processes within limited time, because it can help us to simulate the nature of processing, so that developers can make ideal casting designs. To take the prior occupation at commercial simulation market, so many development groups in the world are doing their every effort. They already reported successful stories in manufacturing fields by developing and providing the high performance simulation technologies for multipurpose. But they all run at powerful desk-side computers by well-trained experts mainly, so that it is hard to diffuse the scientific designing concept to newcomers in casting field. To overcome upcoming problems in scientific casting designs, we utilized information technologies and full-matured hardware backbones to spread out the effective and scientific casting design mind, and they all were integrated into Simulation Portal on the web. It professes scientific casting design on the NET including ubiquitous access way represented by ＂Anyone, Anytime, Anywhere＂ concept for casting designs.     

STUDY OF SOLIDS LEACHED DURING RICE COOKING USING THE TRANSMITTANCE AT 650 NM

The objective of this research was to develop a method to predict the amount of total solids leached during rice cooking using light transmittance at 650 nm with an ultraviolet-visible spectrometer. Rice was cooked in excess water for different durations, the transmittance was measured, and the solids were determined gravimetrically after evaporation of the water. Results of leached solids obtained gravimetrically showed a good correlation with the logarithm of the transmittance ( R ²  =  0.9731), thus indicating the feasibility of the method. As a result, calibration curves were developed using rice starch and rice flour as standards. Calibration curves generated with rice starch has shown to overpredict the amount of solids leached. When rice flour was used, the method predicted that the solids leached with an average error of 2.3%, with a minor tendency towards underprediction.

PRACTICAL APPLICATIONS

During the industrial production of instant rice, important amounts of solids leach out from the rice, producing yield loss and high biochemical oxygen demand (BOD) waste streams. A quick method to estimate the leaching potential of different rice varieties would be important to adjust processing parameters and minimize leaching. The results presented in this study show that the transmittance at 650 nm can be used to estimate the solids leached during rice cooking. Still, the successful implementation of this method depends on the finding of suitable standards.     

Heating energy savings potential from retrofitting old apartments with an advanced double-skin façade system in cold climate

Apartments account for over 60% of total residential buildings and consume a significant portion of primary energy in South Korea. Various energy efficiency measures have been implemented for both new apartment constructions and existing apartment retrofits. Old apartment structures have poor thermal performances, resulting in a high energy consumption. The South Korean government initiated retrofitting projects to improve the energy efficiency in old apartments. Apartment owners typically replace old windows with high-performance windows; however, there is still a demand for better and more innovative retrofit methods for a highly improved energy efficiency. This paper proposes an advanced double-skin façade (DSF) system to replace existing balcony windows in old apartments. Considering the cold climate conditions of Seoul, South Korea, it mainly discusses heating energy savings. Three case models were developed: Base-Case with existing apartment, Case-1 with typical retrofitting, and Case-2 with the proposed DSF system. The EnergyPlus simulation program was used to develop simulation models for a floor radiant heating system. A typical gas boiler was selected for low-temperature radiant system modeling. The air flow network method was used to model the proposed DSF system. Five heating months, i.e., November to March, and one representative day, i.e., January 24, were selected for detailed analysis. The main heat loss areas consist of windows, walls, and infiltration. The results reveal that the apartment with the DSF retrofit saves 38.8% on the annual heating energy compared to the Base-Case and 35.2% compared to Case-1.