Solidification Of Material Research Articles

Modeling three-dimensional flow in a thermal energy tank: Numerical analysis of the impact of tank shape on the melting and solidification of phase change material

Modeling three-dimensional flow in a thermal energy tank: Numerical analysis of the impact of tank shape on the melting and solidification of phase change material

Preparation and reaction mechanism of low environmental load mud solidification agent from multivariate solid waste

Utilizing various industrial solid waste to replace cement to prepare mud solidification materials could achieve energy conservation, carbon reduction and sustainable development. This research conducted solidification mud (SM) experiments using solidification agent (SA) compounded by mixing five types of solid waste. The focus was on studying the performance of SA and SM in the presence of different activators, as well as the influence of different activators on the SA curing mechanism. The results indicate that the SA and SM specimens with 3.0% Na2SiO3 addition had the highest compressive strength values at 1 d and 28 d, respectively. In addition, the microscopic test analysis showed that when 3.0% Na2SiO3 was added, the hydration activity of SA was relatively high, and the continuous distribution of cluster gel in the hydration product made its overall structure more compact.

Research on Resilient Modulus Prediction Model and Equivalence Analysis for Polymer Reinforced Subgrade Soil under Dry-Wet Cycle.

The subgrade soil of asphalt pavement is significantly susceptible to changes in moisture content, and therefore many projects introduce polymer-based reinforcement to ensure soil performance. This paper aims to incorporate a variable representing the dry-wet cycle into the prediction model of resilient modulus of polymer reinforced soil. The polymer adopted is a self-developed subgrade soil solidification material consisting of sodium dodecyl sulfate and polyvinyl oxide. The current resilient modulus prediction model is improved, notably involving the effects of the dry-wet cycle. Combined with finite element method (FEM) analysis, the actual stress state of pavement and the coupling effect of dry-wet cycle and vehicle load on the resilient modulus are studied. The deterioration in resilient modulus with the variation in seasonal climate and load response is also investigated. Results show that the deviator stress is negatively correlated with the resilient modulus while the bulk stress has a linearly positive relation. The decreasing rate at low deviator stress is larger than that at the high level. Moreover, the dry-wet cycle can reduce the resilient modulus and the reducing amplitude is the largest at the first dry-wet cycle. FEM analysis shows that the middle position of the subgrade slope has the largest initial resilient modulus with decreasing amplitude in the first year of dry-wet cycles, while the upper position shows a smaller change. The variation in resilient modulus is closely related to the changes in cumulative volumetric water content. Considering that different positions of subgrade bear the external vehicle load, the equivalent resilient modulus is more realistic for guiding the subgrade design.

An adaptive clamp system for deformation control of aerospace thin-walled parts

The assembly and service of thin-walled parts are usually threatened by machining deformation. In this study, phase change material (Sn-Bi-Pb-Cd alloy with a melting point of 70 °C) was used to develop an adaptive clamp system, which could adjust the clamping position when the material was liquid to follow the stress-releasing deformation after rough machining. The material's solidification could re-clamp the workpiece, whose internal stress had been minimized. Afterwards, the workpiece deformation could be removed in finishing machining. Comparing to the counterpart using traditional vacuum fixture, the maximum deformation and the flatness tolerance of the web using the adaptive clamp system reduced by 82.0 % and 72.9 %, respectively, thus effectively improving the accuracy of thin-walled parts manufacturing.

Numerical study of debris bed formation behavior for severe accident in sodium-cooled fast reactor by using least square MPS-DEM method

During a Core Disruptive Accident (CDA) in a Sodium-cooled Fast Reactor (SFR), debris beds may form in the lower plenum of the reactor vessel as a result of the accumulation of discharged debris, which is formed from the solidification and fragmentation of core molten materials during their release due to interactions with the sodium coolant. Since the configuration of debris beds plays a vital role in their long-term coolability and neutronic subcriticality for achieving in-vessel retention, it is essential to understand and assess the Debris Bed Formation Behavior (DBFB). In this study, an advanced Moving Particle Semi-implicit (MPS) method, called least square MPS (LSMPS), is utilized and coupled with the Discrete Element Method (DEM) for the numerical investigations of DBFB characteristics in a two-dimensional liquid pool. The applicability and reliability of the proposed LSMPS-DEM method are validated by comparing simulation results with experiments using simulant materials. The LSMPS-DEM method is then employed to study DBFB in sodium. It is observed that debris properties significantly impact the sedimentation and accumulation processes of DBFB, leading to variations in the characteristics of the formed debris beds. The present study is expected to be useful for further investigations of DBFB under more realistic conditions and for the design improvement of safety devices to mitigate the consequences of CDA in SFR.

Twenty Years of Progress in Microstructure Modelling for Ultrasonic Testing, from Shielded Metal Arc Welding to Gas Tungsten Arc Welding: An Analysis for Future Developments

To ensure and to demonstrate the mechanical integrity of a welded structure, precise ultrasonic testing (UT) is often mandatory. The importance of the link between nondestructive testing (NDT) and the assessment of structural integrity is recalled. However, it is difficult to achieve great efficiency as the welding of thick and heavy structural part produces heterogeneous material. Heterogeneity results from the welding process itself as well as from the material solidification laws. For thick components, several welding passes are deposited, and temperature gradients create material grain elongation and/or size variations. In many cases, the welded material is also anisotropic, this anisotropy being due to the metal used, for example, austenitic stainless steel. At the early stages of ultrasonic testing, this kind of welded material was considered too unpredictable, and thus too difficult to be tested by ultrasounds without possible diagnosis errors and misunderstandings. At the end of the 1990s, an algorithmic solution to predict the material organisation began to be developed using data included in the welding notebook. This algorithm or modelling solution was called MINA. This present work recalls, in a synthetic form, the path followed to create this algorithm combining the use of solidification laws and the knowledge of the order of passes in the case of shielded metal arc welding (SMAW). This work describes and questions the simplifications used to produce a robust algorithm able to give a digital description of the material for wave simulation code. Step by step, advances and demonstrations are described as well as the limitations, and ways to progress are sketched. Recent developments are then explained and discussed for modelling in the case of gas tungsten arc welding (GTAW), in addition to discussions about 3D modelling for the future. The discussion includes alternative ways to represent the welded material and challenges to continue to produce more and more convincing weld material model to qualify and to make use of UT methods.

Effect of welding processes on ferrite content, microstructure and mechanical properties of super duplex stainless steel 2507 welds

Abstract Super duplex stainless steel (SDSS) plates of 6 mm thickness have been welded using tungsten inert gas, activated tungsten inert gas, electron beam welding and friction stir welding processes. Among these, in the first two, melting and solidification of material occurs slowly whereas, it is faster in electron beam welding process and no melting occurs in friction stir welding. Macro and microstructural studies, hardness surveys, tensile tests and percentage of ferrite content were compared for all the welds. The ferrite–austenite phase balance is 50 % each, with electron beam weld metal at about 65 % ferrite. This showed the hardness of the weld metal and heat affected zones to be higher than base metal. The weldment joint efficiencies are more than 90 %. The fracture location is found to be in the weld metal for tungsten inert gas and activated tungsten inert gas weld, in the nugget for friction stir welds and in the base metal for electron beam welds. The ductility of electron beam weld joints is 32 % while it is around 20 % for the others. The preferred order while choosing the welding process should be activated tungsten inert gas welding, tungsten inert gas welding, electron beam welding, and friction stir welding.

Study of microscopic properties and heavy metal solidification mechanism of electrolytic manganese residue-based cementitious materials.

Electrolytic manganese residue (EMR) is a solid waste that contains a significant amount of soluble manganese and ammonia nitrogen, which can pose risks to human health if improperly disposed of. This study aimed to prepare cementitious materials containing abundant ettringite crystals by mixing EMR with various proportions of granulated blast furnace slag (GBFS) and alkaline activators (CaO, Ca(OH)2, clinker, NaOH). The resulting cementitious material not only utilized a substantial amount of EMR but also exhibited comparable strength to ordinary Portland cement. The optimal ratios were determined through mechanical testing. Additionally, the leaching toxicity of cementitious materials was assessed using ICP-MS (inductively coupled plasma mass spectrometer) tests. The microscopic properties, hydration, and mechanism of heavy metal solidification in the cementitious materials were evaluated using XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy-dispersive spectrometer), FTIR (Fourier transform infrared spectroscopy), and TG (thermogravimetric) techniques. The results showed that the optimal ratio for the cementitious materials was 60% EMR, 36% GBFS, and 4% Ca(OH)2. The hardened mortar exhibited compressive strengths of 34.43 MPa, 41.3 MPa, and 50.89 MPa at 3 days, 7 days, and 28 days, respectively, with an EMR utilization rate of 60%. The hydration products of EMR-based cementitious materials were C-(A)-S-H, AFt, and ferromanganese compounds, which contribute to the mechanical strength. The Mn2+ and NH4+-N contents of raw EMR were 1220 and 149 mg/L, respectively. Nonetheless, the leaching of Mn2+ and NH4+-N in the alkali-EMR-GBFS system was significantly below the limits set by the Chinese emission standard GB8978-1996. Within this system, C-(A)-S-H and AFt could physically adsorb and displace heavy metals, Ca6Mn2(SO4)2(SO3)2(OH)12·24H2O could replace Al ions with Mn ions, and ferromanganese compounds Fe2Mn(PO4)2(OH)2·(H2O)8 and MnFe2O4 could chemically precipitate Mn2+.

Discharging performance evaluation and optimization of a latent heat thermal energy storage unit with helm-shaped fin

Latent heat thermal energy storage with phase change materials can help mitigate the imbalance between the energy supply and demand. Improving the discharging efficiency is crucial to the performance of thermal energy storage units. This paper explores the enhancement performance of helm-shaped fin on phase change materials solidification in a vertical shell-tube storage unit. Numerical model was built to examine the solidification performance of the thermal energy storage unit and its effectiveness was validated by experimental data from literature. The effect of the dimensionless offset (O, defined as the ratio of the minimum distance between the rectangular part of helm-shaped fin and the tube to the distance between the shell and the tube) on the thermal performance was firstly investigated. Results showed that an O of 0.458 is optimum, which shortens the solidification time by 23.9% compared to the O of 0. With this offset, the effects of volume, thickness and height ratios of the annular part to the rectangular part of the helm-shaped fin were further investigated. Results showed that the phase change materials solidification rate increases as the thickness ratio increases and height ratio decreases. The optimum thickness and height ratios are 8 and 0.473 respectively, which reduces the solidification and melting times by 54.5% and 22.1% respectively compared to the traditional annular fin at the same fin volume.

On the Possibility of Replacing Scheil-Gulliver Modeling with Machine Learning and Neural Network Models

Resource-efficient manufacturing is a foundation for sustainable and circular manufacturing. Semi-solid processing typically reduces material loss and improves productivity but generally requires a better understanding and control of the solidification of the cast material. Thermal analysis is commonly used in high-pressure die casting (HPDC) processes to determine casting process parameters, such as liquidus and solidus temperatures. However, this method is inadequate for semi-solid casting processes because the eutectic temperature is also a crucial parameter for successful semi-solid casting. This study explores the feasibility of using machine learning and artificial neural networks to predict fundamental values in Al-Si alloy casting. The Thermo-Calc 2022 software Scheil-Gulliver calculation function was used to generate the training and the test datasets, which included features such as melting temperature, alpha aluminium solidification temperature, eutectic temperature, and the solid fraction amounts at eutectic temperature. The results show that both models have a symmetric mean absolute percentage error (SMAPE) of less than 2 % with temperature prediction, with the machine learning model achieving a better accuracy of less than 1 %. A case study comparing practical measurements with prediction results is also discussed, demonstrating the potential of AI methods for predicting semi-solid casting processes.

Microstructure and crystal order during freezing of supercooled water drops.

Supercooled water droplets are widely used to study supercooled water1,2, ice nucleation3-5 and droplet freezing6-11. Their freezing in the atmosphere affects the dynamics and climate feedback of clouds12,13 and can accelerate cloud freezing through secondary ice production14-17. Droplet freezing occurs at several timescales and length scales14,18 and is sufficiently stochastic to make it unlikely that two frozen drops are identical. Here we use optical microscopy and X-ray laser diffraction to investigate the freezing of tens of thousands of water microdrops in vacuum after homogeneous ice nucleation around 234-235 K. On the basis of drop images, we developed a seven-stage model of freezing and used it to time the diffraction data. Diffraction from ice crystals showed that long-range crystalline order formed in less than 1 ms after freezing, whereas diffraction from the remaining liquid became similar to that from quasi-liquid layers on premelted ice19,20. The ice had a strained hexagonal crystal structure just after freezing, which is an early metastable state that probably precedes the formation of ice with stacking defects8,9,18. The techniques reported here could help determine the dynamics of freezing in other conditions, such as drop freezing in clouds, or help understand rapid solidification in other materials.

Fluidity and Strength of Loess-Based Quick Consolidated Backfill Material with One High-Water Content.

To study the flow and strength characteristics of loess-based backfill materials, orthogonal tests were used to design a cemented backfill material combining loess, high-water content materials, cement, and fly ash. By using the range, analysis of variance, and multi-variate regression analysis, influences of four key factors on the initial setting time, diffusivity, compressive strength, and shear strength of the backfill material were investigated. These four factors included the mass concentration of loess water (A), the content of high-water content materials (B), cement content (C), and content of fly ash (D). The results showed that the initial setting time, diffusivity, compressive strength, and shear strength of the backfill material were 13~33 min, 400~580 mm, 0.917-3.605 MPa, and 0.360-0.722 MPa, respectively, all distributed in wide ranges. For the initial setting time, the four factors were listed in descending order as A > D > B > C according to their influences; for diffusivity, the four factors were listed as A > B > C > D; for the compressive strength, the four factors were ranked as A > C > D > B; for the shear strength, the four factors were ranked such that A > C > D > B. With regard to the comprehensive index, the four factors were such that A > B > D > C. That is, the factors were listed in descending order as the mass concentration of loess water, cement content, the content of fly ash, and content of high-water content materials according to their significance in influencing characteristics of the loess-based backfill material. Comprehensive analysis indicated that the fluidity of the material was mainly influenced by the mass concentration of loess water, and the two were negatively correlated. The hydro-consolidation effect of materials with high-water contents accelerated material solidification. The strength of the backfill material was mainly influenced by the cement content while only slightly affected by contents of other materials. In this way, a prediction model for characteristic parameters, namely, fluidity and strength, of the loess-based backfill material under the action of various factors was established.

Politics of Memory, Heritage, and Diversity in Modern China

Interpretations and memorialisations of China's long history, in service of political aspirations of the present and towards the future, have long attracted scholarly attention. This special issue addresses how the curation, performance, and consumption of collective memory provide valuable insight into the interplay between the reconstruction of Chinese identity, cultural modernisation, and the shifting role of heritage and memory in Chinese domestic and international politics. Touching on issues around diversity in, for instance, personal/collective memory or community-based/state-led heritage, we consider how state–society relations inform local memory practices. Furthermore, the articles enclosed discuss pertinent and far-reaching impacts of China's cultural-material changes, transformations, and destructions in service of memory re-formation. Investigating the politicisation of heritage and the material solidification of strategically selected representations of the past, we consider how the notion of “memory infrastructure” contributes to an academic understanding of the interaction between history, memory, and politics.

Development of a Numerical Simulation Methodology for PCM-Air Heat Exchangers Used in Decentralised Façade Ventilation Units

This paper presents the development of a methodology for using simulation to test decentralised façade ventilation systems with PCM exchangers and its validation with experimental data. Two approaches were compared to simulate the operation of an exchanger filled with phase-change material. In Method A, the geometry consisted of an air domain and a phase-change material domain, located in the cylinders of the exchanger. In this method, the phase transition was not modelled, but the specific heat was made temperature-dependent, wherein within the limits of the melting point, the specific heat is increased to a level that mimics the amount of latent heat from melting and solidification of the phase-change material. In Method B, the geometry consisted only of the air domain, and the temperature was set on the cylinder wall surfaces at each time step using UDFs. When comparing the methods, the temperature difference at the individual measuring points was no greater than 1 K and the resulting exchanger efficiencies did not differ by more than 5%. It was noted that when the phase-change material was modelled in the software with Method A, the results provided better representation of the values obtained in the experiment. Validation of the models was carried out by comparing the experimental results from the real tests with the simulation results of methods A and B. It demonstrated that both models correctly reflected the operation of the exchanger, and that the efficiency results achieved did not differ by more than 6% compared to the experiment. A comparison of supply temperatures and exchanger efficiencies with numerical simulations using two methods is presented. Visual comparison of the temperature distribution in the flowing air and the temperature distribution on the cylinder walls is also presented. This article adds to existing scientific knowledge of computer simulation of exchangers used in façade ventilation units with phase-change material.

Stabilization of Road Embankments on Peat Soils Using Oil Shale Ash and Pozzolanic Additives

Using kukersite oil shale ash for the stabilization of organic-rich soils has been extensively studied but without much success. The main reason for this is the retarding effect of humic acids present in organic-rich soils on the formation of the C–S–H (calcium–silicate–hydrate) phase, which effectively prevents the solidification of cementitious materials in peat soils. Based on the studies performed at the University of Tartu, we have developed a novel method for the in situ mass stabilization of peat soils using waste materials (calcareous fly ash and silica fume). In this manner, the perfect hardening of peat–ash mixtures (to each 1 m3 of soil, 150–400 kg ash, 25–50 L pozzolanic additives, and 2.5–5 kaNaOH were added) can be achieved. A test road embankment was constructed under extremely hard conditions in a peat quarry that is currently in use.

Optimisation of Mechanical Characteristics of Alkali-Resistant Glass Fibre Concrete towards Sustainable Construction

Concrete is a worldwide construction material, but it has inherent faults, such as a low tensile strength, when not reinforced with steel or other forms of reinforcement. Various innovative materials are being incorporated into concrete to minimise its drawbacks while concurrently improving its dependability and sustainability. This study addresses the research gap by exploring and enhancing the utilisation of glass fibre (GF) concerning its mechanical properties and reduction of embodied carbon. The most significant advantage of incorporating GF into concrete is its capacity to reduce the obstruction ratio, forming clusters, and subsequent material solidification. The study involved experiments wherein GF was incorporated into concrete in varying proportions of 0%, 0.5%, 0.75%, 1%, 1.25%, 1.50%, 1.75%, and 2% by weight. Mechanical tests and tests for durability were conducted, and Embodied carbon (EC) with eco-strength efficiency was also evaluated to assess the material’s sustainability. The investigation found that the optimal percentage of GF to be used in concrete is 1.25% by weight, which gives the optimum results for concrete’s mechanical strength and UPV. Adding 1.25% GF to the material results in increases of 11.76%, 17.63%, 17.73%, 5.72%, and 62.5% in C.S, STS, F.S, MoE, and impact energy, respectively. Concrete blended with 1.25% of GF has the optimum value of UPV. The carbon footprint associated with concrete positively correlates with the proportion of GF in its composition. The optimisation of GF in concrete is carried out by utilising the response surface methodology (RSM); equations generated through RSM enable the computation of the effects of incorporating GF in concrete.

Special Issue on Recent Trends in Additive Manufacturing

Additive manufacturing (AM) has undergone rapid development in the past decade. Owing to its capacity to produce complex and functional parts in various industries, it has been recognized as a remarkable scientific and industrial technique. It is used to enhance weight-saving production and reduce the number of parts, with metal-based AM techniques in particular being recognized as the most promising AM techniques developed thus far. This is because of their high potential for direct production through the selective solidification of metal materials from three-dimensional, computer-aided design data. The medical, aerospace, and part molding industries are some of the many expected to reap particular benefit from the ability to produce high-quality models with reduced manufacturing costs and lead times. The objective of this special issue is to collect recent research works focused on recent trends in AM. This issue includes 7 papers covering the following topics: - Metal-based powder bed fusion using a laser beam (PBF-LB/M) - Wire and arc-based AM (WAAM) - Fused deposition modeling (FDM) This special issue is expected to help readers understand the recent trends in AM, leading in turn to further research on AM. We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.

The heat transfer with nanomaterial enhanced phase change materials in different container shapes

The heat transfer is studied during the melting and solidification of sp11 and sp24 phase change materials in different container shapes. The materials are further mixed with nano-alumina and nano CuO enhancements. We aim to identify the most favorable phase change material for free-cooling in summer and free-heating in winter. Ansys Fluent 20.2 is used to analyze the 2D models for the melting and solidification mechanisms of the phase change samples in cylindrical, square, rectangular, and elliptical-shaped capsules. The nanomaterial-enhanced phase change material improves the melting and solidification behavior over the base phase change material by as much as 9.8%. It is further observed that the nanomaterial-enhanced phase change material particularly in the rectangular-shaped containers has faster melting and solidification rates by over 43% compared to the others. The material sp24 with 4% nano-alumina in a rectangular profile has the shortest melting times ~70-100 mins, when the inlet temperatures are 313 and 318 K. The same material has the shortest solidification time of 426 mins, two times faster compared to the 928 mins observed with the cylindrical capsule under the same conditions. The Sp11 with the nano-alumina in a rectangular capsule also has a short melting time of 134 mins. The rectangular profile is found capable of achieving the highest temperature drop about 3.3 K during free cooling of inlet air using nano-enhanced sp24. A progress is realized in unmasking the potential of the thermal energy battery using hybrid geometry and nanomaterial enhancements.

Mechanical properties and soluble phosphorus solidification mechanism of a novel high amount phosphogypsum-based mortar

Phosphogypsum (PG) has great potential for recovery and utilization, but its effective utilization is greatly limited by the harmful impurities mainly composed of soluble phosphorus (SP). Based on excess-sulfate phosphogypsum slag cement (PPSC), a novel type of high amount phosphogypsum-based mortar (HAPBM) is proposed, which is an ideal solidification material. HAPBM has good compressive strength with the high amount PG. The mechanical properties of HAPBM and the solidification mechanism of phosphorus are studied and analyzed. With the changes in PG particle size and sand-cement (s/c) ratio, the influence of SP on the system is further explored. The solidification ability of HAPBM to phosphorus is further studied by adding different forms of SP. XRD analysis shows that in addition to the Brushite, there are also differences in the existences of insoluble phosphorus (ISP) formed by different forms of SP in HAPBM. The leaching results of SP indicate that through the solidification of HAPBM, all groups of leaching solution can meet the Class I (cI = 0.02 mg/L) or II (cII = 0.1 mg/L) limitation of national standard (GB 3838-2002). The microstructure is characterized in detail using SEM images, and the distribution of hydration products and ISP is elucidated through EDS and Mapping results. This study provides possibilities and references for the large-scale recovery and utilization of PG and the solidification of harmful impurities SP.

Study on the Performance and Solidification Mechanism of Multi-Source Solid-Waste-Based Soft Soil Solidification Materials

In this paper, ground granulated blast furnace slag, steel slag, red mud, waste ceramic powder, and desulfurization gypsum were used as raw materials to develop a kind of multi-source solid-waste-based soft soil solidification material. Three ratios and the strength activity index were used to determine the fractions of different solid wastes. The mineralogical and microstructural characterization was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis–differential scanning calorimetry (TG&DSC) tests. The results showed that the unconfined compressive strength of the three types of soft soil increases with an increase in the content of the solidifying agent. The failure strain of the stabilized soil decreases from 1.0–1.3% to 0.75–1.0%, and the failure mode gradually changes from plastic failure to brittle failure. The optimum content of the solidifying agent was determined to be 17% (the lime saturation factor (KH), silica modulus (SM), and alumina modulus (IM) of the solidifying agent were set to 0.68, 1.74, and 1.70, respectively), and the unconfined compressive strength (28 d) of the solidified soil (sandy soil, silty clay, and organic clay) was 3.16 MPa, 2.05 MPa, 1.04 MPa, respectively. Both measurements can satisfy the technical requirements for a cement–soil mixing pile, suggesting the possibility of using various types of solid waste as a substitute for cement.