Effect Of Thermal Cycling Research Articles

Experimental investigation of the effect of quenching cycles on the physico-chemical properties of granites

In this study, the physicochemical properties of granitic rocks subjected to quenching cycles were studied experimentally. Four granites of similar mineralogy but with different degrees of initial weathering (porosity between 1 and 6%) were slowly preheated at two peak temperatures (200 and 400 °C) and then quenched 35 times.To study the effect of thermal cycling on the physical properties, non-destructive tests were used such as water porosity, capillary water absorption tests, P- and S- wave propagation velocities, nuclear magnetic resonance relaxometry, and X-ray micro-tomography. Chemical analysis of the granites was performed using X-ray fluorescence, which provided information on the major and trace elements. Water-granite interactions were followed using inductive plasma mass spectrometry (ICP-MS).The variation of all the measured parameters indicates the creation of cracks with thermal fatigue. The porosity, water uptake, size, and volume of cracks increased while P- and S- wave velocity and Young's modulus decreased. At 200 °C, the changes were progressive up to ten cycles, from which the stress threshold was reached and only small readjustments took place. At 400 °C, the greatest damage was observed during the first five cycles. These changes were a direct consequence of the propagation of the microcracks induced by the strong gradient during the quenching tests. For both temperatures, the changes depended on the initial weathering conditions of the granites. Initially, weathered granites showed crack development or crack closure during quenching, meanwhile the damage on the sound rocks was characterized by the creation of intragranular microcracks.The analysis of the experimental fluids showed enrichment in K, Na and Ca in the solution as consequence of the dissolution of K-feldspar, plagioclase and the degradation of mica and clays, independently of the physical and mechanical modifications.

Flow serrations of rejuvenation behaviour through cryogenic thermal cycling for Zr-based bulk metallic glass

ABSTRACT Effects of cryogenic thermal cycling (CTC) on mechanical properties and serrated flow of the Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass were studied. The improved plasticity, a slightly reduced yield stress and abundant small serrations could be signs of rejuvenation. The high disorder degree result from rejuvenation increases the volume of shear transformation zones (STZs), and thus leads to the enhancement of plasticity. The larger plasticity of BMGs is realised through the superimposed effect of two favourable factors (CTC treatment and strain rate). In this case, the experimental failure threshold is far below the theoretical value. It provides a new idea for designing ductile BMGs.

Characterization of Solar-Aged Porous Silicon Carbide for Concentrated Solar Power Receivers.

Porous silicon carbide is a promising material for ceramic receivers in next-generation concentrated solar power receivers. To investigate its tolerance to thermal shock, accelerated ageing of large coupons (50 × 50 × 5 mm) was conducted in a solar furnace to investigate the effects of thermal cycling up to 1000 °C, with gradients of up to 22 °C/mm. Non-destructive characterization by computed X-ray tomography and ultrasonic inspection could detect cracking from thermal stresses, and this informed the preparation of valid specimens for thermophysical characterization. The effect of thermal ageing on transient thermal properties, as a function of temperature, was investigated by using the light-flash method. The thermophysical properties were affected by increasing the severity of the ageing conditions; thermal diffusivity decreased by up to 10% and specific heat by up to 5%.

Thermal shock response behaviour of carbon fibre reinforced silicon carbide matrix composites prepared by chemical vapour infiltration at different heating rates

The present work investigated the effects of thermal cycles in air on the tensile properties of a two-dimensional carbon fibre reinforced silicon carbide composite (2D C/SiC) prepared by chemical vapour infiltration at different heating rates. The composite was exposed to different cycles of thermal shock between 20 °C and 1300 °C in air. The damage mechanisms were investigated by AE online monitoring and fractured morphology offline analysis. The tensile strength of 2D-C/SiC decreases with increasing thermal cycles. However, the modulus only decrease within 40 cycles. Due to oxidation, with the decrease in heating rate, the residual properties of the material decrease more obviously. Meanwhile, the results of AE online monitoring and fracture analysis show that the matrix damage is more serious at higher heating rate and that more delamination occours in tensile fractures. The above results indicate that for the thermal shock of 2D C/SiC composites in air, oxidative damage plays a key role in the residual properties.

Effect of thermal cycles on rock cliff deformation. Monitoring and interpretation

Climatic actions are one of the factors controlling the evolution of slopes, this paper is devoted to a specific effect, relatively little studied, related to the effect of climate-driven temperature changes on rock massif deformation. The particularity of the study is to focus on permeable rocks and Temperatures varying in a range which discards freeze/thaw effects. Research has been carried out in relation with the analysis of the real case of a limestone cliff located in the Périgord region, the massif was highly instrumented, results show a slow cyclic accumulation of deformations with time, essentially synchronic with thermal cycles. An advanced constitutive model, specifically developed to capture rock degradation due to the differential expansion of the main minerals composing the rock, has been developed. It has been calibrated on experimental results obtained in the laboratory on block samples tested in a climatic chamber for a long series (several months) of daily thermal cycles. Deformation and shear wave velocity were monitored during the test. Model shows a good agreement with laboratory measurements.

Comparative thermal fatigue behavior of AlSi7Mg alloy produced by L-PBF and sand casting

By increasing the demand for additively manufactured Al parts for industrial applications, the knowledge about their thermal and mechanical behavior in service environments becomes highly required. Since Al alloys are widely used for the production of lightweight structures in transportation industry including several engine components, their thermo-mechanical behavior deserves special attention, considering the thermal and mechanical load fluctuations experienced in parts like cylinder heads, pistons, brake disks and calipers. In the present study, a comparative research has been carried out on the thermal fatigue (ThF) behavior of an AlSi7Mg (A357) alloy processed either by sand casting or laser powder bed fusion (L-PBF). Both alloy conditions were cycled within three temperature intervals with a lower temperature of 100 °C and upper limits of 200, 240 and 280 °C, in presence of a constant uniaxial tensile load. Three tensile loads of 110, 120 and 150 MPa were applied for each temperature range in order to explore the effect of both thermal cycling and concurrent tensile load on thermal fatigue resistance. Both alloys showed a similar ThF lifetime when exposed to temperature cycles from 100 to 200 °C under all the three tensile loads investigated, while the L-PBF A357 alloy tested to the highest temperature limits of 240 °C and 280 °C comparatively revealed an improved ThF resistance than the cast counterpart. Microstructural analyses on the cross-sections of both samples revealed that a large amount of strain was accumulated close to the fracture regions and several micropores and microcracks were developed in these areas. Microcracks preferentially nucleated at eutectic Si and Fe-bearing coarse intermetallics in the ThF tested cast alloy, while micropores nucleated from the fragmented silicon network in L-PBF samples on exposure to thermal cycling.

New insights into thermomechanical fatigue behavior of AISI Type 316 LN SS weld joint

AbstractCyclic deformation and fracture behavior of a type 316 LN austenitic stainless steel (SS) weld joint (WJ) were investigated under thermomechanical fatigue (TMF) and isothermal low cycle fatigue (IF) cycling at the maximum temperature (Tmax) of TMF. A higher cyclic stress response (CSR) and reduced cyclic softening were observed under TMF compared with IF tests. In‐phase (IP) TMF resulted in lower lives compared with IF cycling at the Tmax and out‐of‐phase (OP) TMF, which was attributed to the more pronounced creep‐induced intergranular damage. Characterization of microstructural features and microhardness variations revealed that the accumulation of damage and associated failure depends on the strength and microstructural gradient, together with the deformation incompatibility. The crack propagation is found to depend on the individual and synergistic interactions of the microstructural transformations, creep, and oxidation, depending on the type of fatigue cycle (IF and IP/OP TMF), strain amplitude, and thermal cycling effects.

Thermal induced residual stress and microstructural constituents of dissimilar S690QT high-strength steels and 316L austenitic stainless steel weld joints

The effect of thermal cycle on the residual stress, microstructural constituents, and alloying elements composition of dissimilar S690QT and 316L austenite stainless steel was studied. Finite element model (FEM) using ANSYS 19.1 software and an experimental investigation using gas metal arc welding (GMAW) process with fully austenite filler wire were applied to developed thermal cycle and evaluate residual stress in the heat-affected zone of both materials. The experimental data were recorded using a thermal-cycle sensor (TCS) and x-ray diffraction technique. A microstructural investigation was done using Scanning electron microscopy (SEM) and Energy-Dispersive x-ray Spectroscopy (EDS). The thermal cycle showed the maximum temperature (T max) in the HAZ of 316L side (850 °C) at a distance of 7 mm away from the centreline of the weld compare to S690QT side. The magnitude of tensile residual stresses in the 316L side decreased as welding heat input increased. The maximum residual stresses were observed on the S690QT side (700 MPa). Microstructural investigations revealed the formation of Bainite, and some retained of austenite at the temperature of 800 °C in the coarse grain heat-affected zone (CGHAZ) of S690QT. On 316L side, some grain boundary austenite (GBA), intragranular austenite (IGA), and carbides were observed in the CGHAZ. Compared to the initial microstructure of both materials, a slightly increase of Mn, Cr, and Si were observed at the respective values of 1.90%, 1.25%, and 0.40% on the S690QT side compared to the BM. For 316L side, it indicated an increase of Cr (26%), Mo (5.69%), and Ni (17%) in the alloying element composition compared to the BM. Applying 10 kJ cm−1 of heat input produced an excellent mechanical property and reduced the formation of carbide, inter-granular corrosion in the microstructure of 316L side.

Effect of the Welding Thermal Cycles Based on Simulated Heat Affected Zone of S1300 Ultrahigh Strength Steel

In the automotive industry there is an increasing demand for the wider application of high strength steels due to their favourable mechanical properties. The steel producers continuously developing new generations of high strength steels to insure higher strength and toughness properties. Since in most cases these steels are joined in welded structures, great attention must be taken to their weldability. The weldability of high strength steels has still challenges which are as follows: cold cracking sensitivity; reduction of strength and toughness of heat affected zone (HAZ); filler metal selection. Because the mechanical properties of ultrahigh strength steels are provided by using various alloying elements, micro alloys, and by different metallurgical methods, the steels may lose their outstanding properties during welding. In real welded joints the critical parts of the HAZ have small extent so their properties can be limitedly analysed by conventional material testing methods. With the help of physical simulators, the different parts of the heat affected zone can be produced in an adequate size for subsequent tests. In our research work the weldability, especially the HAZ properties of an ultrahigh strength structural steel (Rp0.2 = 1300 MPa) were investigated on thermal simulated samples with the help of Gleeble 3500 physical simulator. Three relevant technological variants for gas metal arc welding (GMAW), t8/5 = 5 s, 15 s and 30 s were applied during the HAZ simulations in the selected coarse-grained (CGHAZ), intercritical (ICHAZ) and intercritically reheated coarse-grained (ICCGHAZ) zones. Both the microstructure was studied by optical microscope and the mechanical properties were analysed by Vickers hardness tests and Charpy V-notch impact tests at -40 °C. According to the results the investigated ultrahigh strength steel was softened on account of the welding heat cycles, besides that the strength of the investigated ultrahigh strength steel can be better with the application of shorter t8/5 cooling time.

High-temperature Pumping of Silicon for Thermal Energy Grid Storage

As the cost of renewable energy falls below fossil fuels, the key barrier to widespread sustainable electricity has become availability on demand. Energy storage can enable dispatchable renewables, but only with drastic cost reductions compared to current batteries. One electricity storage concept that could enable these cost reductions stores electricity as sensible heat in an extremely hot liquid (>2000 °C) and uses multi-junction photovoltaics (MPV) as a heat engine to convert it back to electricity on demand, hours or days later. This paper follows previously reported technoeconomics and liquid containment, examining equipment that would be needed to exchange heat between resistive heaters, a molten silicon storage tank above 2000 °C, and a heat engine. Herein, we report on a pump that was designed and tested to circulate the liquid silicon between these three regions and the effect of spatial thermal cycling was simulated in models and experiments. While the pump successfully circulated silicon between 1800 and 2080 °C for 10 h, circulation with a temperature gradient caused it and other non-isothermal experiments to dissolve significantly due to the temperature dependent solubility of not only carbon, but also silicon carbide which otherwise protected the graphite infrastructure. Methods to reduce dissolution and an alternative embodiment are presented.

Enhancement of plasticity by cryogenic thermal cycling on Fe80P13C7 bulk amorphous alloy

The effect of cryogenic thermal cycling on the plasticity of Fe80P13C7 bulk amorphous alloy was investigated. The plastic strain increases from 1.7% of the as-cast samples to 5.4% of the cryogenic thermal cycling treated ones, while the yielding strength does not have an obvious deterioration. The enhancement of plasticity can be ascribed to the rejuvenation induced more disordered high-energy states in structure, which corresponds to a creation of excess free volume and therefore helps to the formation of multiple shear bands. This work provides an effective method for the modification of plasticity of Fe-based bulk amorphous alloys.

Effects of Repetitive Freeze-Thaw Thermal Cycles on the In-Plane Effective Thermal Conductivity of a Gas Diffusion Layer in Polymer Electrolyte Membrane Fuel Cells

As the fundamental components of polymer electrolyte membrane fuel cells, the thermal properties of gas diffusion layers (GDLs) play a significant role in influencing their overall heat conduction and management. We have experimentally characterized the temperature dependence of the in-plane thermal conductivity of a commercial carbon paper GDL, including the progressively in-plane thermal degradation of GDLs through a series of repetitive freeze-thaw thermal aging cycles. Even though the thermal properties of carbon fibers are crucial for the thermal performance determination of GDLs, the temperature-dependent in-plane thermal conductivity of pristine GDLs depends mainly on the thermal characteristics of the binder that connects carbon fibers and the polytetrafluoroethylene (PTFE) coated on the microporous layer. The microstructural failure of aged GDLs (breakage of carbon fibers, delamination, adhesive failure of binder, and PTFE cracks) caused by the freeze-thaw thermal aging treatment dominantly affects the in-plane effective thermal degradation at different thermal aging phases. Overall, the breakage of carbon fibers positively contributes, and delamination, adhesive failure of binder, and PTFE cacks negatively contribute to the in-plane effective thermal conductivity of GDLs. In particular, the in-plane thermal conductivity of aged GDLs through 300 cycles reaches a peak.

Effect of thermal cycles in electron beam welding of aluminium 1570 alloy on mechanical properties of welded joints

The Paton Welding Journal, 2021, №05. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Effect of thermal cycling on microstructure and mechanical properties of 2A97 Al–Li alloy fabricated by direct laser deposition

Direct laser deposition (DLD) is a potential approach to prepare large-scale metal component. This work focuses on understanding microstructural characteristics and mechanical properties along deposition direction of 2A97 Al–Li alloy fabricated by direct laser deposition. As-deposited sample showed coarse equiaxed grains at top and columnar crystals at middle and bottom. Growth texture of as-deposited sample along <001> was relatively obvious, value of which increased first and then decreased from bottom to top. Thermal cycle led to different kinds and distribution of precipitated phases along deposition direction, which affected microhardness and tensile strength. T1 phase and a small amount of T2, TB phase precipitated at top. Effect of thermal cycle from top to bottom gradually increased, resulted in δ′, T2, TB phase coarsened. As a result, microhardness decreased from top (99 HV) to bottom (75HV). The sample in bottom showed an ultimate tensile strength (UTS) of 232.9 ± 4.3 MPa, and elongation of 9.5 ± 1.4%. While, ultimate tensile strength was increased to 268.5 ± 5.2 MPa, and elongation was 12.5 ± 0.9% in middle part, which was close to that of sample at top.

Effect of hybrid thermal cycling and shock on flexural properties of nanoclay/glass/epoxy nanocomposites

In present research, the flexural properties of glass/epoxy composites reinforced by nanoclay particles (3, 5 and 7 wt.%) under various hybrid thermal cycling and shock loadings (15 and 30 thermal cycles at immediate −70°C and +100°C temperatures) have been investigated. It was found that the flexural strength of 5 wt.% nanoclay/glass/epoxy nanocomposites under 15 and 30 hybrid thermal loadings was enhanced by 19.35% and 20.78%, respectively. Also, after 15 hybrid thermal loadings, the flexural stiffness of 5 wt.% clay/glass/epoxy nanocomposites increased by 9.30% compared to static conditions. More importantly, after 30 hybrid thermal loadings, by adding more filler contents, the flexural stiffness was increased. For instance, at 7 wt.% clay/glass/epoxy nanocomposites, the flexural stiffness enhanced 17.97% compared to neat composite. FESEM morphology images confirmed that presence of optimum filler contents changed the composites inherent properties. Therefore, the outcome of this research can show various remarkable advantages for researchers to apply nanoclay as nanofillers to reinforce composites structures under hybrid thermal cycling and shock applications.

­Effect of sintering treatment time on the sintering behaviour and thermal shock resistance of Li2O-Al2O3-SiO2 glass-ceramics

ABSTRACT In order to determine the correlation of flexural strength and thermal shock resistance properties, the sintering behavior of Li2O-Al2O3-SiO2 (LAS) glass-ceramics at different sintering treatment times and the effect of thermal shock cycles on LAS glass-ceramics were investigated. The LAS glass-ceramics were isothermally treated at 1100°C from 1.5 to 4.5 h. Phase transformation of major crystalline of β-spodumene and minor crystalline of ZrTiO4 revealed unchanged as sintering treatment time increased. The physical properties of LAS glass-ceramics that were sintered for 3.5 h demonstrated an increased density (2.45 g/cm3) and less porosity percentage (0.62%). The prolonged sintering treatment affected the microstructure whereby the mean grain size increased from 0.55 to 0.67 µm which also demonstrated the increase of microhardness in the range between 3.90 and 5.47 GPa. The flexural strength of LAS glass-ceramics revealed an enhancement of 158 MPa when sintered for 3.5 h. The thermal shock resistance properties were assessed at 500°C from one to seven cycles via thermal shock tests. After four thermal shock cycles, LAS glass-ceramics showed an improvement of 82% of residual strength from its original strength, due to a decrease in the formation of pores and an increase in the crystallinity and percentage of β-spodumene.

Analysis of reliability based on thermal cycle and aging effect in electron devices

This paper concentrates on the estimation of reliability of an automotive electronic power device using thermal cycle, aging effect and accumulated damage. Thermal model has been developed for analysing the factors of power loss. A look-up table has been constructed to calculate the power loss and finite-element modelling was used to find out the aging effect. Thermal model was developed by using FLOTHERM. It is in the form of either Foster or Cauer network. Comparison of results from the thermal model has been done. Preprocessing of data by filtration and spectrum truncation was also explored. Reliability can also be estimated by calculating the accumulated damage with the help of Pagoda Roof method and Miner’s rule. Finally, a method was proposed of using Ga NFET instead of MOSFET to calculate power dissipation.

Effect of thermal cycling on microstructure and hardness of carbon steel

The present investigation deals with design of thermal cycling schedule to enhance hardness of 0.26%C carbon steel using thermo-mechanical simulator Gleeble® 3800. The specimens were thermal cycled at 775°C for 3 and 7 cycles. Optical micrographs, scanning electron micrographs, X-Ray diffraction patterns of as received steel specimen as well as thermal cycled specimens were reported. The thermal cycling heat treatment causes the refinement of microstructure and is responsible for enhancement in hardness of steel specimen.

Determination the Corrosion Rate of Carbon Steel (0.4%C) Due to Thermal Cycling, Oil Cooled

The effect of thermal cycling was carried out on steel bars (0.4 C %). A single run was performed at a lower temperature of 32℃ and an upper temperature of 500℃ cooled in water, seawater (previous results) and oil (new results). For several numbers of cycles up to 30 cycles for an accurate determination of heating and cooling times. The effect of thermal cycling on the corrosion rate was evaluated. The effect of thermal cycling on the following properties was evaluated the corrosion rate. The comparison between the effect of thermal cycling on carbon steel (0.4 C %) seawater and water-cooled (previous results as shown in references [1, 2]) and the effect of thermal cycling on carbon steel (0.4 C %) water-cooled (new results) has been studied. From the obtained test results (previous and in this paper, it was found that: the type of corrosion is uniform attack; corrosion rate of the first stage gradually increases with the number of thermal cycling up to 15 cycles, then it takes steady-state up to 30 cycles. It was found that the rate of corrosion (previous results, seawater and water-cooled) is more than the rate of corrosion of the new results, oil-cooled respectively.

Modeling and experimental study on the mechanical behavior of glass/basalt fiber metal laminates after thermal cycling

In the present study, the effect of thermal cycling and stacking sequence on the tensile behavior of fiber metal laminate (FML) composites containing glass and basalt fibers was investigated. To fabricate the FML samples, fibers reinforced epoxy composite were sandwiched between two layers of 2024-T3 aluminum alloy sheet. 55 thermal cycles were implemented at a temperature range of 25–115°C for 6 min. The tensile tests were carried out after the thermal cycling procedure, and the results were compared with non-thermal cycling specimens. Scanning electron microscopy (SEM) was employed for the characterization of the damage mechanisms. The FMLs containing four basalt fibers’ layers showed higher values of tensile strength, modulus, and energy absorption. On the other hand, the lowest strength and fracture energy were found in the asymmetrically stacked sample containing basalt and glass fibers, due to weak adhesion between composite components (basalt and glass fibers). The lowest tensile modulus was found in the sample containing glass fibers that was due to the low modulus of the glass fibers compared to basalt fibers. In the case of the samples exposed to thermal cycling, the highest and the lowest thermal stabilities were observed in basalt fibers samples and asymmetrically stacked samples, respectively. In accordance with the experimental results, a non-linear damage model using the Weibull function and tensile modulus was employed to predict the stress-strain relationship. The simulated strain–strain curves presented an appropriate agreement with the experimental results.