Papers by Keyword: Temperature

Abstract: On the basis of large changes in temperature during the welding process technology, there is a shape change or welded parts of tensions. Stress and deformation of the welded material formed as a result of heat delivered to the weld zone and its surroundings. Uneven heating or cooling, and fixed mounting welded parts may cause the formation of stress in welded material during the welding process. Causing local, or overall deformation of welded parts. That is why it is necessary to know the temporal distribution of temperature and stress generated during welding. Stress or strain cycle is the result of welding thermal cycles. It is possible to determine the time courses of thermal cycles with different methods. The most commonly used method are experimental, analytical and numerical. Currently most often to predict stresses and deformations using the methods of the modeling and numerical simulation used FEM. Which any application methods for solving specific problems in the field of welding, it is possible to obtain such results. Such as residual thermal stress and deformation of welded materials or changes in the structure of the different phases of the material in the heat affected zone (HAZ). The residual thermal stress and deformation, changes of phase structure of the material in the heat affected zone have a great impact on the quality and strength of the weld joint.

Abstract: The article is focused to the temperature measurement and methodology of computer modeling of laser cutting process on stainless steel plate. Microstructure of stainless steel and dimension of the kerf width was obtained. The temperature was measured with two K-type thermocouples by digital convertor NIUSB9211. Obtained temperature dependences were used for simulation 2D and 3D models creation by ANSYS software. The results of the model application with SHELL and SOLID elements are shown. Numerical simulation showed effect of nitrogen gas on heat dissipation and is also one of the reason why isn't total energy received in the material. Author considered 3D model with impinging jet flow whose proposal is in the article as the model closest to reality.

Abstract: The palygorskite or attapulgite is a mineral clay that has a fibrous morphology with porous crystalline structure, hydrated of type 2:1, which is constituted by layer-shaped strips with two tetrahedral layers connected by a central octahedral layer through the sharing of common oxygens [. It presents in its structure low surface charge, high magnesium content and high specific surface area. This mineral clay together with the sepiolite belong to the class of fibrous clay minerals [.

Abstract: A two-dimensional numerical model was built for the typical shallow reservoir with serious thermal pollution in the North China Plain. After calibration and validation, four scenarios were developed to study the impacts of water transfer on thermal structure. Model results showed that the hydrodynamic and water temperature could be well simulated. The effects of water transfer on thermal structure showed in decreasing temperature rises, which was more remarkable for regions far away from the releasing point of thermal discharge. In terms of reducing temperature, 45.5 m³/s was the most efficient inflow rate among the four representative flow rates. This study provides useful information for reservoir sustainable management. Keywords: water transfer, temperature, numerical simulation, Douhe reservoir.

Abstract: A microstructural model of surface layer of machine elements from a nonuniform material is developed. With using of this model a calculation scheme that includes basic structural elements is created. Each element is characterized by the following properties: density, elastic modulus, thermal conductivity, linear expansion coefficient and Poisson's ratio. A mathematical model of surface layer of machine elements from a sintered nonuniform material is formulated on the basis of solution of two-dimensional heat-conduction and elasticity problems by the finite-element method. The created algorithms for solution of these problems are used for formation of an automated system for thermal strength calculations. This system is surrounded with some original techniques which provide the investigation of the stress-strain state of surface layer of machine elements from a sintered nonuniform material.

Abstract: The shear interaction of laminated glass belongs to the essential characteristics of this material. The impact of the increased temperature on deformation properties was tested within investigation of basic mechanical properties of laminated glass panes. The specimens of laminated glass with the size of 120 x 1100 mm loaded by four-point bending load were exposed to the effect of the gradually increasing temperature up to approximately 65 °C in a thermal chamber. The progress of the deformation was continuously monitored by a measuring device during both temperature rise and subsequent cooling. Four kinds of interlayers were tested in total. In this paper the obtained experimental results are compared to numerical FE analysis and also the degree of an interaction of particular interlayer is evaluated.

Abstract: Square cup drawing experiments were performed on an AZ31 sheet at various temperatures (T) ranging from room temperature to 200°C with three different punch travel speeds (V) of 3, 30 and 300mm/min. From the experiment, the highest drawability was observed either at T=175°C with V= 30mm/min or at T=200°C with V= 300mm/min. The effects of temperature and forming speed on the formability were discussed by comparing the result of drawing experiment with the high temperature tensile properties of the material. The forming limits were well predicted by FE simulation using a temperature and rate dependent constitutive model.

Abstract: Grinding is one of the most difficult processes in machining operations. Normally, the flood coolant method was used as a cooling agent in the grinding process. The most common defects using flood coolant are higher grinding friction, higher heat generation, and thermal damage. Therefore, the minimum quality lubricant (MQL) was introduced to minimize the defects. The main objective of this project is to compare the performance of MQL and flood coolant techniques in terms of grinding temperature, grinding force and specific energy. Three levels of cutting speeds, three levels of feed rate and depth of cut are adopted in the evaluation. The experiments were conducted on a thin plate of mild steel AISI 1020. The result shows that the MQL technique was effectively supplied to the grinding contact zone. This research revealed that the MQL technique exhibited an advantages on the surface temperature compared to the flood coolant.

Abstract: The paper presents recent studies in simulation of thin profile extrusion technology with the emphasis on interaction between the material flow and the state of the tooling set. To take into consideration die deflection and gradient of the temperature across the die and mandrel during the entire process cycle a transient coupled thermo-mechanical model has been built on the basis of QForm-Extrusion program. The paper explains the background for this model and some tests to verify its accuracy. Practical implementation of this model at several die making and extrusion companies has shown it to be of higher accuracy compared to the results of rigid die simulation.

Abstract: To investigate the transfer of PBDEs from products into the aqueous media, experiments and analysis were carried out by contacting TV housing plastics with distilled and dissolved humic solution (DHS) in brown bottles in the artificial climate box. The leaching test conditions were a liquid-to solid ratio of 100:1, and a contact period of 1, 2, 4, 7, 10, 13, 16 and 20 day (s), with pH of 3, 5, 7, 9 and temperature of 15, 20, 25 °C. The leaching concentrations of PBDE increased with DHS rather than distilled water, and were found to be remarkably enhanced when TOC of DHS increased. Despite no detection of most of the lower BDEs in distilled water, most homologues could be detected in DHS, and their solubility increased according to the contact time; those of highly BDEs increased to 10 times their maximum solubility in distilled water. Temperature had limited influence for the limited range investigated. Lower pH generally resulted in higher transfer of PBDEs to aqueous phase.