An analytical method for calculating the stress-strain state of PVC window profiles under thermal loading

Introduction. The practical operation of modern PVC windows in the climate of the Russian Federation has proven that due to thermally induced deformations of window elements cold air enters premises and window frames freeze. Presently, there is no engineering method for calculating the temperature deformations of windows, that takes account of the key features of their structure: the composite structure of window sections, the rigidity of insulating glass units, fittings, etc. An important task is to develop a method for calculating temperature deformations of PVC window elements, that takes account of nonlinear temperature distribution over their cross-sections. Materials and methods. A three-dimensional finite element model of a standard PVC window was developed using the COMSOL Multiphysics software, and its temperature field was calculated. The analysis of the calculation results allowed to identify the nature of the temperature distribution over the cross sections of PVC window profiles and propose a method for their analytical calculation. Using the basic equations of solid mechanics and methods of mathematical analysis, the bending of PVC window elements was described on the basis of their actual temperature fields. Results. The obtained equations were tested by comparing the results of the manual calculation with the results of the finite element modeling. Conclusions. The obtained equations, describing temperature deformations of individual window elements, serve as the starting point for an integrated method of calculating the structural behavior of PVC windows under thermal loading. The further development of the presented method will encompass the analysis of the influence of the reinforcing core on the structural behavior of PVC elements and the exploration of the structural behavior of the entire window structure.

Distortion of AISI 1020 steel substrate in the process of laser cladding of E-300 powder material

The results of experimental studies to determine the effect of power during laser powder cladding on temperature deformations of the substrate at a constant cladding rate and the mass flow rate of the powder are presented. Steel 1020 was used as the substrate material, from which samples of sizes 90x90 mm and a thickness of 8 mm were made. Laser powder cladding was performed by using a wear-resistant powder E-300 on a robotic complex with an ytterbium fiber laser and a coaxial powder feed. Single tracks were applied to the sample by laser powder cladding using various parameters of technological modes. The amount of deformation of the substrate was estimated taking into account the depth of the mixing layer. The cladding mode is selected, which provides minimal temperature deformations, with maximum process performance.

Features of the Propagation of Microwave Radiation in a Freshwater Ice Cover

When scanning fresh ice cover in the microwave range at a frequency of 13 GHz, the transmitted radiation power was investigated at four linear polarizations (vertical, horizontal, and polarizations rotated at an angle of +-45) for a long period of time. The measurements were carried out on the ice cover of the lake. Arakhley (Transbaikal region) at a distance of 120 m from the coast in March 2021. We also measured the external parameters of the studied environment, namely, the temperature of the ice cover, meteorological parameters (wind speed, air temperature, pressure). The distance between the generator and the receiver of electromagnetic radiation was 40 meters. The orientation of the instruments is West-East. As a result, variations in the power of the transmitted microwave radiation were detected. These variations are related to the temperature deformations of the ice cover, which were recorded using a deformation sensor installed in the ice cover. Also revealed a feature that was observed earlier in the spring. This is a different temporal behavior of the first Stokes parameter, which is determined by the sum of the powers of two orthogonal polarizations, namely, the sum of the received signals at the vertical and horizontal polarizations, and the sum of the received signals of the two polarizations rotated at an angle of +45 and -45. This difference is also associated with temperature deformations of the fresh ice cover in the spring. Keywords: microwave range, fresh ice cover, Stokes parameters, temperature deformation

The Correlation of Movements in the Technological System during Grinding Precise Holes

The article presents the results of the study of the quality parameters of the precise hole, depending on the size, spatial location and condition of the contacting surfaces, the parameters of the state of the contact zone, during finishing grinding. The correlation between the processing modes and the current parameters of the contact zone during internal grinding is established. Dependencies describe the flow cross-feed for the i-th turn increment of the depth of micro-cutting, compensation of radial material removal previous turn, deterioration of the wheel, the increment of the elastic and thermal strains. At the same time, the depth of micro-cutting and the increment of elastic and temperature deformations affect the values of the radial wear of the tool and the radial removal of the material. The equation of displacement balance is developed for discrete processes of hole processing with abrasive tools, during which the analyzed surface area comes into contact with the abrasive tool periodically.

Modeling of heat propagation processes during thermal metal cutting, taking into account the main provisions of the theory of welding deformations and stresses

The article describes the features of applying the main provisions of the theory of welding deformations and stresses to the thermal cutting of metal. The above calculation formulas allow us to pre-evaluate the temperature deformations of the sheet edges during separation heat cutting, as well as the size and configuration of the temperature field, to take into account the thermal effect on the metal and determine the size of the zone of thermal influence. These equations are considered by the authors as a basis for the development of a method for calculating thermal deformations and stresses during thermal cutting of metal, taking into account the transverse and longitudinal distribution of temperature over the sheet section, the ambient temperature and interaction with it, the parameters of the geometry of the cut sheet and its stiffness, heat capacity, thermal conductivity and other temperature characteristics.

The influence of ball screw drive positioning errors on the accuracy of part manufacturing

The article considers the components of the total error of mechanical processing that occur when positioning the working units of the machine: ball screw drive elements. The reasons for the loss of positioning accuracy of the machine drives are described. The accuracy of the positioning of the machine spindle in determining the axes of the holes to be processed is analyzed. The numerical estimation of the values of the errors of the temperature deformations of the lead screw is carried out on the example of drilling holes in the workpiece. The causes of heating of the ball screw drive of the machine are identified. The dependence of the unit heating on the speed of movement of the operating elements of the machine is described. The optimal trajectory of the tool movement when processing holes in the workpiece is presented. The criterion of optimality of this trajectory is described. The values of the deviations of each hole in the workpiece from the specified accuracy of their location are obtained. The scheme of accumulation of errors of linear displacements resulting from the temperature deformation of the lead screw of the CNC machine drive is presented. The value of the accumulated total error of the temperature deformations of the ball screw pair is obtained. The error associated with the movement of the machine drive carriage is considered. The geometric characteristics of the carriage orientation are given. The schemes of occurrence of the error caused by the change of the roll angle and the carriage tilt angle are presented. The maximum axial load of the lead screw at translational acceleration is calculated. The scheme of possible carriage deflection under the action of the maximum translational force of a ball screw pair is presented. The numerical estimation of the maximum possible roll angle of the carriage, as well as the maximum deviation from the specified accuracy of the carriage, at the maximum load on the lead screw, is carried out. As a result, it is concluded that the total error of the machine drives positioning can go beyond the tolerances of the linear dimensions of the processed holes, which significantly affects the accuracy of the part manufacturing.

Investigation of Temperature Deformations and Burning of Models from Polymers

The usage of 3D printing technology SLA and DLP is promising for obtaining casting models. The article presents the results of a study of temperature deformations, developing during the burning of models from polymers “Fun to Do Castable Blend”, “Oh-All! Red” and “Orange Fluor”. In the performance of the experiments, photopolymer models were exposed to an impact of isothermal at temperatures from 50 to 330 °C, and their linear dimensions measured; changes developing on their surface were noted. It is shown that, with an increase of the isothermal holding temperature, the models expand first and narrow later. It has been linked to temperature expansion and subsequent decomposition of the photopolymer. It is shown that the casting molds ,obtained with the usied thin-walled hollow casting models from these photopolymers, are destroyed at the stage of their burning.

Criteria for climatic applicability of modern window types

Currently, the assignment of the required values of the technical and operational windows characteristics (such as resistance to heat transfer, air permeability, sound insulation, etc.) is carried out based on the technological capabilities of the window industry, and not on the basis of scientifically substantiated requirements for ensuring the microclimate and energy buildings efficiency in the design practice of most countries (as it happens in the case of external walls which are in almost identical operating conditions with windows, for example). One of the most common types of windows in modern construction practice are single windows with insulated glass units and profiles made of PVC and aluminum alloys. They were originally developed for operation in Western Europe where they have proven themselves well over many years of operation. However, their widespread use in the climatic conditions of the Russian Federation and the countries of Eastern Europe showed a number of problems during operation which is expressed in a decrease in the technical and operational characteristics of windows due to temperature deformations of their profile elements. This circumstance testifies to the limited area of application of these structures in terms of climatic conditions. The authors of the work introduce the concept of “climatic applicability of windows” in order to determine the rational application areas of types of windows which would ensure the fulfillment of the specified requirements for the comfort of the microclimate of the premises in any operation period of the building. Based on the results of the analysis of the work of third-party researchers and the authors own works the authors have determined a set of criteria for the climatic applicability of modern types of windows based on winter operating conditions. Promising areas for further research were considered.

Fire Behavior of Continuous Assembled Monolithic Hollow-Ribbed Slabs

To further understand the fire behavior of assembled monolithic hollow-ribbed (AMH) slab floor, a fire test was performed on six small-scale continuous AMH slabs (two by three). In this paper, the special designed furnace and relevant experimental phenomena are briefly introduced. Detailed experimental results in the form of furnace temperatures, temperature distributions, vertical deflections, and failure criteria are presented. The test data indicate that almost all the AMH slabs showed upward displacements during the fire tests, which is very distinct with the isolated AMH slab under fire. As the edge girders transformed into the frame girders gradually, the edge girders would show displacement plateaus. The integrity of the AMH slab under elevated temperature should receive more critical role to serve as its failure criterion compared with the load bearing function. Except fire environment, boundary constraint conditions also have a considerable effect on the elevated temperature deformations of the structural elements. At last, several rational suggestions are provided to improve the fire resistance of the AMH slabs.