Індекс рубрикатора НБУВ: К642.572 + К642.78

Рубрики:

Різання металів з використанням плазмового струменя (плазмове різання)

Різання металів променем лазера

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

Індекс рубрикатора НБУВ: К643-31

Рубрики:

Паяння металів

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

This paper reports the experimental study carried out to establish the dependence of the thermal conductivity of polypropylene-based nanocomposites filled with carbon nanotubes on the main parameter of the temperature regime of their manufacturing - the level of overheating a polymer melt relative to its melting point. The study has been conducted for nanocomposites that were manufactured by applying a method based on the mixing of components in the polymer melt applying a special disk extruder. During the composite manufacturing process, the level of melt overheating varied from 10 to 75 K, with the mass share of filler ranging from 0,3 to 10,0 %. It is shown that increasing the overheating of a polymer melt causes an increase in the thermal conductivity of the composites. However, when the overheating has reached a certain value, its further growth does not increase the thermal conductivity of nanocomposites. Based on the established pattern, the rational level of this overheating has been determined. That resolves the tasks of manufacturing highly heat-conducting nanocomposites and implementing appropriate energy-saving technology. Data have been acquired on the effects of the impact of the amount of polymer melt overheating on the values of the first and second percolation thresholds for the examined nanocomposites. It is established that the value of the first percolation threshold is more sensitive to the specified amount of overheating. The dependences of the density of the examined composites on the level of polymer melt overheating have been derived. The correlation between a given dependence and the nature of a corresponding change in the thermal conductivity of the composites has been established. Applying the proposed highly heat-conducting nanocomposites is promising for micro and nanoelectro nics, energy, etc.

Індекс рубрикатора НБУВ: К644.51-1 + К644.57-1

Рубрики:

Електродугове наплавлення металів

Інші види електричного наплавлення металів

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

Індекс рубрикатора НБУВ: К644.77

Рубрики:

Наплавлення у виробництві біметалів

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

This paper reports a series of experimental studies to establish regularities of the integrated effect exerted on the specific heat capacity of polymer nanocomposites by such factors as the temperature regime of their production, the value of the mass fraction of the filler, and the temperature of the composite material. The studies were conducted for nanocomposites based on polypropylene filled with carbon nanotubes. When obtaining composites, the method of mixing the components in the melt of the polymer was used. During the studies, the temperature of nanocomposites varied from 295 to 455 K, the mass fraction of the filler - from 0,3 to 10 %. The basic parameter of the technological mode for obtaining composite materials, the value of overheating the polymer melt relative to its melting point, varied in the range of 10 - 75 K. It is shown that the temperature dependence of the specific heat capacity of the considered composites is sensitive to changes in the overheating of the polymer melt only in the region maximum values of the specific heat capacity. Concentration dependences of the specific heat capacity of the considered nanocomposites at different values of their temperature and the level of overheating of the polymer melt have been built. The studies have been carried out to identify the effects of the influence of the above parameters on the coefficient of thermal diffusivity of nanocomposites. It has been established, in particular, that an increase in the level of overheating the polymer could lead to a very significant increase in the coefficient of thermal diffusivity, which is all the more significant the higher the proportion of filler and the lower the temperature of the composite material. It is shown that the level of overheating the polymer melt relative to its melting point is a parameter that can be used as the basis for the creation of polymer composite materials with specified thermophysical properties.

Індекс рубрикатора НБУВ: К641,331 + К233.107.5

Рубрики:

Зварювання металів

Вплив зварювання на структуру та властивості алюмінію і його сплавів

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

A set of experimental studies has been carried out to establish the effect of the mixing time of components of nanocomposite materials on their thermal conductivity, specific heat, and density. The physical properties of polypropylene-carbon nanotube composites were to be studied. During the experiments, the duration of mixing of the components in the melt of the polymer varied from 5 to 52 minutes, the mass fraction of the filler - in the range of 0,3 - 10 %, and nanocomposite temperature - from 290 K to 475 K. It was found that an increase in the mixing time of components of nanocomposite materials could lead to a significant (more than 70 times) increase in their thermal conductivity. It is also shown that the influence of the specified time is limited to its value equal to 27 minutes, above which the change in the thermal conductivity of nanocomposites can be neglected. It was found that the sensitivity of the thermal conductivity of nanocomposites to the time of mixing of their components decreases with a decrease in the mass fraction of the filler. Temperature dependences of the specific heat capacity of the studied composites were obtained by varying the mixing time of their components and the mass fraction of the filler. It was found that with an increase in the specified time, there is a decrease in the heat capacity of nanocomposites, which is significantly manifested only in the region of temperatures close to the melting point of the composite matrix. It is shown that the dependence of the density of nanocomposites on the mixing time of their components in qualitative terms is similar to the corresponding dependence for their thermal conductivity. The obtained data can be used to choose the mixing time of components of nanocomposite materials in the development of appropriate technology for their production.

The object of this study is the thermophysical properties of polymer micro- and nanocomposites, as well as the dependence of their heat conductivity with structural characteristics when using different types of fillers. A set of experimental studies of heat conductivity and specific heat capacity of polymer micro- and nanocomposite materials for polyamide 6 and carbon nanotubes, copper and aluminum as matrix and fillers was carried out. When obtaining composites, a method was used that is based on the mixing of components in the polymer melt. The content of fillers varied from 0,3 to 10 %, and the temperature of composite materials - from 305 to 500 K. Experimental dependences of heat conductivity coefficients of the studied composites on the content of the filler were derived. It was established that according to the value of these coefficients in order of their reduction, these composite materials are ranked as follows: composites with fillers with carbon nanotubes, copper, and aluminum. It was found that only one percolation threshold is observed, when using a polyamide 6 matrix. The regularities of changes in the specific heat capacity of the composites under consideration on their temperature when varying within the above limits of the filler content were investigated. The analysis of the influence of the content of fillers on the degree of crystallinity of the polymer matrix of the investigated composite materials was carried out. It is shown that with an increase in the content of fillers, the degree of crystallinity decreases. The relationship between the thermally conductive properties of the composites under consideration and the specified degree of crystallinity has been established. Higher values of heat conductivity of composites correspond to lower values of the degree of crystallinity. The reported results can be widely used in the development of highly heat conductive composites for various engineering applications.

The object of this study is determining the stressed-strained state (SSS) of a welded article by applying quantitative non-destructive testing. The relevance of the study is associated with the need to devise a universal methodology for the non-destructive quantification of SSS using the simplest approaches and means of provision. To solve this task, an estimation-experimental procedure has been developed. This procedure is based on comparing digital stereo images of the individual sections (spatial primitives) of an article before and after its welding, followed by computer processing. To validate the developed procedure, the SSS of a cylindrical article made of aluminum alloy 7005, at the end of which two flanges were welded laserly with ring seams, was determined. It was established that after performing four diametrically opposed point tacks, the residual deformations of the ends of the article can reach 0,02 - 0,05 mm, and after performing continuous ring seams - to decrease to 0,01 - 0,02 mm. The calculation showed that the residual deformations of the end of the article after welding a ring seam are at the level of 0,02 mm, and the residual stresses in the same zone - in the range of 50 - 60 MPa. The deviation in the coincidence of residual deformations is in the range of 10 - 20 %, which is a satisfactory result and can be considered as an error in the results of determining SSS in general. Based on the developed methodology for determining SSS, an experimental industrial complex has been created that allows TIG and PAW to perform welding of objects from steels and alloys with the ability to determine the resulting stressed-strained state of these objects. The procedure devised and the equipment designed can be used for to non-destructively determine SSS of spatial structures made of steels and alloys.

Індекс рубрикатора НБУВ: Л51-1

Рубрики:

Загальна технологія палива

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

Індекс рубрикатора НБУВ: К663.223-18

Рубрики:

Залізнення (насталювання) металів

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ 

Шифр НБУВ: Ж24320 Пошук видання у каталогах НБУВ