In this paper the effect of soldering technique and thermal shock test were investigated on SAC 305 solder joints, produced by two different solder method. The solder joints were subjected to different cycle numbers up to 5000 thermal shock tests with two different thermal profiles of –30/+110°C and –40/+125°C. Microstructural properties of the tested joints were examined with the focus on intermetallic layer thickness and crack formation/propagation. Thickness of the scallop shaped Cu6Sn5 intermetallic layer was increased with increasing cycle number for both THRS and multiwave joints, but the thickening was more effective for the THRS joints. Cracks typically formed at the solder alloy/ PTH barrel and the solder alloy/pin interfaces and propagated along grain boundaries and precipitations of intermetallic compound.
The study presents a concept of generation of micro-cracks (or cracks) in metal specimens in order to assess their material with respect to the thermal shock resistance. Both the method of conducting the experiment and the criteria of the assessment of the material resistance to the rapid temperature changes are discussed. The schematic diagram of the research stand used for repeated heating and rapid cooling of specimens, constructed in the Foundry Institute of the Częstochowa University of Technology, is presented. The proposed solution enables to maintain constant conditions of the experiment. The tests were held for flat specimens 70 mm long, 20 mm wide, and 5 mm thick, tapered over a distance of 15 mm towards both ends. The specimens were induction heated up to the specified temperature and then, in response to the signal produced by a pyrometer, dipped in the tank containing the cooling medium. The thermal shock resistance of the material can be assessed on the basis of either the total length of the micro-cracks arisen at the tapered parts of a specimen after a specified number of heating-and-cooling cycles, or the number of such cycles prior to the total damage of a specimen, or else the number of thermal cycles prior to generation of the first crack. The study includes an exemplary view of the metal specimen after the thermal shock resistance tests, as well as the illustrative microstructure of the vermicular cast iron which reveals a crack propagating from the edge towards the core of the material.
This paper presents the results of studies concerning the production and characterization of Al-SiC/W and Cu-SiC/W composite materials with a 30% volume fraction of reinforcing phase particles as well as the influence of corrosion and thermal shocks on the properties of selected metal matrix composites. Spark plasma sintering method (SPS) was applied for the purpose of producing these materials. In order to avoid the decomposition of SiC surface, SiC powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. The obtained results were analysed by the effect of the corrosion and thermal shocks on materials density, hardness, bending strength, tribological and thermal properties. Qualitative X-ray analysis and observation of microstructure of sample surfaces after corrosion tests and thermal shocks were also conducted. The use of PVD technique allows us to obtain an evenly distributed layer of titanium with a constant thickness of 1.5 µm. It was found that adverse environmental conditions and increased temperature result in a change in the material behaviour in wear tests.
Ladle plays an important role in the metallurgical industry whose maintenance directly affects the production efficiency of enterprises. In view of the problems such as low maintenance efficiency and untimely maintenance in the current ladle passive maintenance scheme, the life prediction mechanism for ladle composite structures is established which bases on the stress analysis of steel shell and ladle lining in the production process, combining conventional fatigue analysis and extended fracture theory. The mechanism is accurate and effective according to the simulation results. Through which, the useful life of steel shell can be accurately predicted by detecting the crack length of it. Due to the large number of factors affecting the life of the lining of the ladle, it is difficult to accurately predict the life of the ladle lining, so a forecasting mean based on the thermal shock method is proposed to predict the service life of the ladle lining in this paper. The life prediction mechanism can provide data support and theoretical guidance for the active maintenance of the ladle, which is the prerequisite for scientifically formulating ladle initiative maintenance program.
Constantly developing production process and high requirements concerning the quality of glass determine the need for continuous improvement of tools and equipment needed for its production. Such tools like forms, most often made of cast-iron, are characterized by thick wall thickness compared to their overall dimensions and work in difficult conditions such as heating of the surface layer, increase of thermal stresses resulting from the temperature gradient on the wall thickness, occurrence of thermal shock effect, resulting from cyclically changing temperatures during filling and emptying of the mould. There is no best and universal method for assessing how samples subjected to cyclic temperature changes behave. Research on thermal fatigue is a difficult issue, mainly due to the instability of this parameter, which depends on many factors, such as the temperature gradient in which the element works, the type of treatment and the chemical composition of the material. Important parameters for these materials are at high temperature resistance to thermal shock and thermal fatigue what will be presented in this paper.
In this article, the fracture behavior of functionally graded thick-walled cylinder under thermo-mechanical shock is investigated. For this purpose, classical coupled thermoelastic equations are used in calculations. First, these equations are discretized with extended finite element method (XFEM) in the space domain and then they are solved by the Newmark method in the time domain. The most general form of interaction integral is extracted for axially symmetric circumferential crack in a cylinder under thermal and mechanical loads in functionally graded materials and is used to calculate dynamic stress intensity factors (SIFs). The problem solution has been implemented in MATLAB software.
The paper presents a detailed analysis of the material damaging process due to lowcycle fatigue and subsequent crack growth under thermal shocks and high pressure. Finite Element Method (FEM) model of a high pressure (HP) by-pass valve body and a steam turbine rotor shaft (used in a coal power plant) is presented. The main damaging factor in both cases is fatigue due to cycles of rapid temperature changes. The crack initiation, occurring at a relatively low number of load cycles, depends on alternating or alternating-incremental changes in plastic strains. The crack propagation is determined by the classic fracture mechanics, based on finite element models and the most dangerous case of brittle fracture. This example shows the adaptation of the structure to work in the ultimate conditions of high pressure, thermal shocks and cracking.