Analysis of Rolling Force in Rolling Process of Thi...

Jo Jul 11, 2025

Cold pilger mills include a roll cold-pipe rolling mill and a roller cold-pipe rolling mill. As the roll cold-pipe rolling mill involves difficult roll processing, the roller cold-pipe rolling mill is now in wide use.

Determination of rolling force during periodic rolling in roller cold pilger mills is one of the important problems in determining the design parameters. In particular, the roller cold pilger mill is subject to periodic reciprocating motion so that the deformation zone and rolling force continue to change during one cycle, and thus it is important to determine the maximum rolling force.

Han Myong Jin, a researcher at the Faculty of Materials Science and Technology, has determined the average pressure and contact area between the rolling roller and the workpiece as one of the basic data for determination of the design parameters of two-row roller cold pilger mills, and investigated the rolling force.

First, he derived a formula of the maximum rolling force and performed a comparison using the finite element analysis tool Deform-3D. Then, he installed a force sensor under the inclined support plate and compared it with the measured results to confirm the accuracy of calculation.

When producing a copper tube of ϕ24mm×0.5mm in size from a workpiece of ϕ30mm×3mm in size in a two-row roller cold-pipe rolling mill, the rolling force analysis by the computer-coupled rolling force measuring device and the rolling force calculation confirmed that the rolling force formula is relatively accurate, with 3% in the first row and 0.73% in the second row. In the same way, the comparison of the rolling force by the simulation analysis data with Deform-3D and the rolling force determined by the rolling force formula showed that the rolling force formula is relatively accurate, with 2.8% in the first row and 1.96% in the second row.

Temperature Characteristics of Radial Cooling Rotor...

Jo Jul 10, 2025

A turbogenerator is one of the main equipment for large-capacity power stations such as nuclear power plants. In order to design a turbogenerator of high operational reliability, thermal characteristics should be analyzed exactly.

The direct gas-cooled rotor winding in large power turbogenerators is cooled by gas (hydrogen) that flows along the U-type or radial ventilation duct. Many researchers and experts have published their research results on the temperature characteristics of winding of direct gas-cooled rotor in large turbine generators larger than 1 000MW. However, the detailed research results on the cooling duct dimension at the radial cooling rotor windings are rarely mentioned in the literature.

An Se Gwang, a researcher at the Faculty of Electrical Engineering, has determined the reasonable cross section of an axial ventilation duct that makes the distribution of flow velocity uniform in the radial cooling slot of a 1 000MW 4-pole turbogenerator and the reasonable value of the width coefficient of cooling duct and segment length.

First, he proposed a mathematical model to analyze the temperature feature of radial cooling rotors and confirmed the range of practical value to determine the reasonable number and dimension of radial ventilation ducts.

Then, he proved that the gas velocity distribution has an equal value along the axial length when the input cross section of the axial ventilation duct is increased 1.67 times the output cross section, with the effect of revolution in consideration.

The research result is helpful for the design standard of large 4-pole turbine generators, and it can be applied to the design and building of 1 000 MW 4-pole turbine generators.

Specialty of Korea ― Kangso Mineral Water

Jo Jul 9, 2025

Kangso Mineral Water is not only unique in its taste but also efficacious for treating various diseases and protecting health.

Our people already started using Kangso Mineral Water hundreds of years ago.

“Kangsogunji”, published in 1936, says the following.

There was a mineral spring in Jonghwa ri of Kangso myon. Over 250 years ago, a crane which got hurt in the leg flew down to the spring to drink the water and wash its body with it every morning. After a few days, it was fully recovered and flew away. Thus, the mineral water was discovered to be of medicinal value.

It tastes refreshing and stimulates the tip of the tongue, which tastes just like a fizzy drink. In addition, habitual drinking of it helps cure many diseases including gastric disorder, anemia, constipation, inflammation of the bladder, etc.

This tells us that Kangso Mineral Water has hundreds of years of use history and it has been one of our country’s specialties well known from long ago for its unique taste and mysterious and marvelous medicinal effect.

On December 7, 1947, when he visited the Kangso Mineral Water spring, President Kim Il Sung said that Kangso Mineral Water had had a good reputation from olden times. Then, he set forth the detailed orientation of future development, saying that the gush amount should be increased further and rest centers and sanatoria for gastric diseases should be built so that working people could enjoy and recuperate themselves drinking the mineral water.

Today, the modern Kangso Mineral Water Factory near the spring is producing a huge amount of bottled mineral water to supply to every part of the country including Pyongyang City.