Thermomechanical Studies Research Articles

A 3D gravity and thermal model for the Barents Sea and Kara Sea

In the frame of this study, we investigate the lithosphere-scale 3D physical state of the Barents Sea and Kara Sea region. Therefore, we test an existing 3D structural model against the gravitational field by considering the heterogeneous upper mantle to further assess the structural and density configuration of the continental crystalline crust. The resulting 3D density configuration of the crust is discussed in terms of its relationships with the spatial distribution of tectonically different domains. In addition, it provides the base for a lithology-controlled parameterisation of the crust with thermal properties to calculate the 3D conductive thermal field. The deeper thermal field is controlled by the depth configuration of the lithosphere–asthenosphere boundary. Accordingly, deeper isotherms such as the 450°C isotherm deepen from below the rifted SW Barents Sea towards the intracratonic basins of the eastern Barents Sea and Kara Sea, indicating an increase of the lithospheric strength in the same direction. Temperature measurements of the upper 800m below the SW Barents Sea reveal an increased thermal gradient which cannot be reproduced by a steady-state 3D conductive model alone. Beside fault-induced fluid flow to be active there, an alternative scenario could involve a phase of subsidence long enough to increase the temperature of the upper 800m, followed by an uplift and erosion phase that prevented the positive thermal anomaly to propagate towards larger depths. The final lithosphere-scale 3D model is the first to integrate the geological, density and thermal configuration of the entire Barents Sea and Kara Sea region and hence provides an ideal base for future thermomechanical studies addressing, for instance, questions on the present-day, past and future relationships between lithospheric strength and deformation.

Rheological and rheokinetic properties of phosphazene-containing epoxy oligomers

The rheological and rheokinetic properties of a two-component binder consisting of epoxy-diane oligomers and the oligoepoxyphosphazenes PEO-1 (30 wt %) and PEO-2 (40 wt %) are studied. The viscosities of the initial oligomers at 40°C are 130 (PEO-1) and 270 (PEO-2) Pa s; the activation energies of viscous flow in the range 40–70°C are from 122 to 128 kJ/mol. The addition of equivalent amounts of curing agents, such as triethylenetetramine or iso-methyltetrahydrophthalic anhydride, reduces the initial viscosity of a composition, most strongly in the presence of the second curing agent (by a factor of 50–100). The activation energies of the cure process with triethylenetetramine in the range 45–95°C are 89 (PEO-1) and 125 (PEO-2) kJ/mol, and the gelation time at 55°C is 6 min for both oligomers. The time of gelation for the system PEO–iso-methyltetrahydrophthalic anhydride at 90°C is 475 min, and the glass-transition temperatures of the cured compositions are 238 (PEO-1) and 250°C (PEO-2), as evidenced by thermomechanical studies.

Thermomechanical Behavior of Molded Metallic Glass Nanowires.

Metallic glasses are disordered materials that offer the unique ability to perform thermoplastic forming operations at low thermal budget while preserving excellent mechanical properties such as high strength, large elastic strain limits, and wear resistance owing to the metallic nature of bonding and lack of internal defects. Interest in molding micro- and nanoscale metallic glass objects is driven by the promise of robust and high performance micro- and nanoelectromechanical systems and miniature energy conversion devices. Yet accurate and efficient processing of these materials hinges on a robust understanding of their thermomechanical behavior. Here, we combine large-scale thermoplastic tensile deformation of collections of Pt-based amorphous nanowires with quantitative thermomechanical studies of individual nanowires in creep-like conditions to demonstrate that superplastic-like flow persists to small length scales. Systematic studies as a function of temperature, strain-rate, and applied stress reveal the transition from Newtonian to non-Newtonian flow to be ubiquitous across the investigated length scales. However, we provide evidence that nanoscale specimens sustain greater free volume generation at elevated temperatures resulting in a flow transition at higher strain-rates than their bulk counterparts. Our results provide guidance for the design of thermoplastic processing methods and methods for verifying the flow response at the nanoscale.

Optimisation of thermal baffle for liquid metal injection nozzle

SADHANA is a test facility dedicated for the experimental demonstration of passive safety grade decay heat removal in the prototype fast breeder reactor. Experiments are planned in SADHANA to characterise the behaviour of this system followed by various reactor transients. For simulating the reactor transients of hot pool, cold sodium at 310°C has to be injected to the test vessel of SADHANA at 550°C temperature. Thermal baffle provided in the nozzle of test vessel was optimised to limit the peak local stress. This paper gives the thermo-mechanical studies conducted to optimise the nozzle geometry with thermal baffles.

Optimisation of thermal baffle for liquid metal injection nozzle

SADHANA is a test facility dedicated for the experimental demonstration of passive safety grade decay heat removal in the prototype fast breeder reactor. Experiments are planned in SADHANA to characterise the behaviour of this system followed by various reactor transients. For simulating the reactor transients of hot pool, cold sodium at 310°C has to be injected to the test vessel of SADHANA at 550°C temperature. Thermal baffle provided in the nozzle of test vessel was optimised to limit the peak local stress. This paper gives the thermo-mechanical studies conducted to optimise the nozzle geometry with thermal baffles.

Licos, a fuel performance code for innovative fuel elements or experimental devices design

This paper provides an overview of the Licos fuel performance code which has been developed for several years within the platform pleiades, co-developed by the French Alternative Energies and Atomic Energy Commission (CEA) and its industrial partners Électricité de France (EDF) and AREVA.CEA engineers have been using Licos to back multidimensional thermo-mechanical studies on innovative fuel elements design and experimental device pre-and post-irradiation computations. Studies made with Licos thus encompass a wide range of situations, including most nuclear systems used or studied in France in recent years (PWR, SFR or GFR), normal and off-normal operating conditions, and a large selection of materials (either for fuel, absorber, coolant and cladding).The aim of this paper is to give some insights about some innovative features in the design of Licos (dependency management, kriging, mfront, etc.). We also present two studies that demonstrate the flexibility of this code. The first one shows how Licos can be combined with the Germinal monodimensional fuel performance code to demonstrate the interest of a three dimensional modelling of the fuel relocation phenomenon in the Sodium Fast Reactor fuel pin. The second one describes how Licos was used to model the DIAMINO experiment.

Tetra-functional epoxy-acrylate as crosslinker for UV curable resins: Synthesis, spectral, and thermo-mechanical studies

Abstract UV-curable tetra-functional epoxy acrylate (EA4) was newly synthesized using 4,4′-methylenebis(N,N-diglycidylaniline). Effects of reaction temperature and epoxy/acrylic acid molar ratios on the reaction conversion were investigated. The conversion of epoxy to ester group was monitored by FTIR spectroscopy and the relative concentration of epoxy value and conversion of the reactions were calculated from FTIR data, in different intervals of the reaction time. EA4 curing under UV irradiation was studied, and the physicochemical characteristic of the cured resin was determined. DMTA, TGA and mechanical properties of the casted films were evaluated. Moreover, studies on effect of the synthesized EA4 content on properties of conventional epoxy acrylate (EA2) were carried out. According to TGA and DMTA studies, the UV-cured blend films of EA2 containing ≤9% EA4 presented film homogeneity, and improved thermal and mechanical properties. Thus, it can be used as a crosslinking agent in UV-curable formulations.

Improving Steel Processing Through Thermo-Mechanical Simulation Studies

Thermo-mechanical simulation studies can be effectively utilized for optimization of processing parameters apart from development of new alloys, quality/yield improvement and material characterization. Physical simulation, being very close to the real world process, can be very helpful in near exact reproduction of the process, and in turn, better results. Thermo-mechanical simulation studies using Gleeble System found extensive applications in steel research and its processing. It can help in careful design of alloy chemistry, proper continuous casting operation to produce defect-free casting, and optimization of hot rolling and post-cooling parameters to produce the desired microstructure and annealing process after cold rolling to achieve the desired microstructure and properties, welding for easy fabrication, etc. Each of these steps needs to be fine-tuned and optimized to achieve the maximum benefit towards reduction in alloy additions, as well as quality and yield improvement during steel processing. A number of studies like continuous casting simulation for production of Cr-alloyed rail steel, hot deformation simulation and phase transformation behavior to optimize hot rolling of difficult to process high boron steel, and hot deformation simulation to bring down the rolling load and annealing simulation to achieve the desired hardness in low nickel stainless steel, etc. undertaken, helped to improve the processing of these steels. Details of these studies, results obtained, and the way to improve processing were discussed.

Thermo-mechanical studies for the slit in the emittance measurements

A double-slit type monitor will be used in the emittance measurements at the exit of the first tank of the drift tube linac in the China Spallation Neutron Source where the H− ion energy is 21.67 MeV. The rapid energy deposition in the first slit may generate a rapid temperature rise and high thermal stress, which may damage the slit plate. This article presents detailed thermo-mechanical studies for the slit by Monte Carlo program and finite element analysis. The existence of Bragg peak of the stopping power introduces a thermal spike and stress peak in the slit plate, and both the peak values reach a quasi-steady-state after several beam pulses, moreover, they show different variation trends with changing the beam repetition rate and pulse width. The equilibrium peak temperature and stress are about 1605 K and 78 MPa, respectively, at beam pulse width of 100 μs and repetition rate of 5 Hz when the beam centered at the edge of slit, which does not exceed the corresponding threshold value of graphite, however, high cycling stress may bring about fatigue damage, so the beam parameters should be selected at suitable values according to the demands of actual measurements.

Effect of lignocellulosic fibers on mechanical, thermomechanical and hydrophilic studies of epoxy modified with novel bioresin epoxy methyl ester derived from soybean oil

Epoxy resin is modified with epoxy methyl soyate synthesized from soybean oil to toughen the matrix and reduce the viscosity of resin system. Unidirectional sisal fibers in mat form were incorporated at different orientations of [0/0] and [0/90] as reinforcement in epoxy blend having more toughened nature. Highly improved strength and modulus of the [0/0] laminated composite revealed strong interfacial region of matrix for binding the fibers. Further, notched impact strength of the composites was found to be more than 700% higher compared with modified epoxy blend. Dynamic mechanical analysis depicted an improvement in the storage modulus and higher damping factor of the [0/0] sisal fiber laminated composite, which confirms better damping properties under vibrating conditions. The fiber‐matrix interfacial adhesion in the composite was confirmed by scanning electron microscopic analysis of the fractured specimens. Contact angle and atomic force microscopic studies were carried out to reveal the hydrophilic nature. Copyright © 2015 John Wiley & Sons, Ltd.

Curing and thermo-mechanical studies of a modified thermosetting clearcoat containing OH-functional POSS nanocages

Abstract This paper attempts to study the chemical, thermo-mechanical and rheological properties of an acrylic/melamine clearcoat modified with a polyhedral oligomeric silsesquioxane (POSS) macromolecule. OH-functional groups of the linear acrylic resin were stoichiometrically substituted with those of the POSS. This modification resulted in a drop in viscosity compared with the pristine sample, mainly because of the globular compact structure of the modifier. This lowered the chain entanglements and provided more mobile functional groups during curing. FTIR spectroscopy, dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM) techniques were utilized to study the resultant clearcoats. It was illustrated that reduced viscosity facilitated curing reactions and lead to a more efficient and more extensive curing degree, leading to an enhanced cross-linking density in presence of the POSS nanostructure. It was also illustrated that compatibility of POSS and acrylic/melamine lead to a molecular-scale dispersion of POSS nanostructures within the matrix.

Mechanical properties of epoxy composites based on silver nanoparticles formed in situ

The mechanical and thermomechanical properties of metal-containing epoxy composite films based on silver nanoparticles synthesized in situ are investigated. There is a nonmonotonic dependence of the mechanical properties on the concentration of silver myristate used as a precursor. It is found for the first time that the breaking strength and elastic modulus increase by a factor of 1.8–1.5 relative to those of the unmodified matrix at a small concentration of precursor nanoparticles (on the order of 0.1 wt %). DSC and thermomechanical studies reveal that the glass-transition temperature decreases slightly (by 5–6°C) as the precursor concentration is increased to 0.5 wt %, thereby suggesting a weak plasticization of the modified epoxy matrix. On the basis of the spectrophotometry data measured in the region of surface plasmon resonance of silver nanoparticles (420–425 nm) and SEM data, it is inferred that the in situ strengthening of an epoxy nanocomposite based on epoxy resin ED-20, triethylamine, and silver myristate is attained because silver nanoparticles smaller than 20 nm in size and having a narrow particle-size distribution are formed during curing.

Facile preparation of highly exfoliated and optically transparent polycarbonate (PC)/clay mineral nanocomposites using phosphonium modified organoclay mineral

Here, we focus on the morphology, mechanical and optical properties of the polycarbonate (PC) in the PC/clay mineral nanocomposites prepared through both the melt and solution blending technique at two different loadings (0.5 phr and 1 phr) of propyl triphenyl phosphonium modified montmorillonite (PTPP-Mt). The modified organo-Mt was prepared by ion exchange reaction and verified through FTIR spectroscopy, EDS study and XRD analysis. The outstanding thermal stability of the PTPP-Mt at the processing temperature of PC (280°C) made it a suitable candidate for the preparation of optically transparent PC/Mt nanocomposites. The XRD analysis over the PC/PTPP-Mt nanocomposites revealed the destruction of ordered geometry of the clay mineral, whereas, the presence of some localised zones of Mt was evident from transmission electron microscopic (TEM) analysis. Thermal analysis indicated an increase in glass transition temperature (Tg) and thermal stability of PC in the nanocomposites. The strength and modulus of the nanocomposites were increased with increase in Mt loadings. An increase in storage modulus in the nanocomposites was evident from the thermomechanical studies. Finally, the optical transparency of PC was retained without generation of any colour in the PC/PTPP-Mt nanocomposites.

Application of high-speed video extensometry for high-temperature tensile characterization of boron heat-treated steels

The increased desire to use advanced, high-strength steels for lightweight automotive structural components requires better understanding of thermo-mechanical behavior and appropriate experimental data for developing constitutive models. Thermo-mechanical studies are particularly important for understanding and optimizing hot-stamping processes which produce both complex and high-strength components. The experimental setup presented herein is capable of characterizing the thermo-mechanical behavior of such steels with strain rates up to approximately 1 s–1 and temperatures as high as 850 °C. The main parts of the apparatus are a high-speed camera, a load frame, and a box furnace. For the determination of strain, a simple image-processing program was developed. The strain was determined in three sections that span the entire gauge length of the specimen. Thus, the onset of localization could be more accurately determined. Stress versus strain data for various strain rates and temperatures are presented.

Dry and wet mechanical properties of polylactic acid in the presence of canola oil

ABSTRACTPolylactic acid (PLA) is a compostable and biodegradable polymer obtained from renewable resources. They can be used in the packaging and medical industries. For our study, two grades of PLA resins were procured. One grade was procured from Cereplast, Inc., USA, (CPL) and other from NatureWorks LLC, USA, (NWPL). Mechanical, thermal, thermomechanical and morphological studies were carried out for PLA resins procured from both the sources. Virgin and modified canola oil (0.25–0.5% with respect to PLA) were mixed manually with CPL and NWPL to prepare injection‐moulded specimens. Mechanical, thermal, thermomechanical and morphological studies of injection moulded PLA samples in the presence of canola oil were then carried out. Results indicated that canola oil acted as a plasticizer for PLA specimens. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Thermomechanical design of a static gas target for electron accelerators

Gas targets are often used at accelerator facilities. A design of high-pressure gas cells that are suitable for hydrogen and helium isotopes at relatively high electron beam currents is presented. In particular, we consider rare gas targets, 3H2 and 3He. In the design, heat transfer and mechanical integrity of the target cell are emphasized. ANSYS 12 was used for the thermo-mechanical studies of the target cell. Since the ultimate goal in this study was to design a gas target for use at the Jefferson Laboratory (JLab), particular attention is given to the typical operating conditions found there. It is demonstrated that an aluminum alloy cell can meet the required design goals.

Development of a production target for FRIB: thermo-mechanical studies

One of the challenges for the Facility for Rare Isotope Beams (FRIB) is the development of a high power target capable of rare isotope production by projectile fragmentation and in-flight separation at primary beam powers of up to 400 kW and at beam energies of 200 MeV/u for uranium. A small beam spot is required to achieve a high resolution in fragment separation which implies high power densities in the target. For FRIB a multi-slice rotating solid carbon disk was selected as the technical baseline concept. This paper presents the results from a number of critical experimental studies on the thermo-mechanical behavior of such a target. These studies were accompanied by extensive simulations in support of the development of a single-slice target. As a final step, a multi-slice 50 kW target that is a prototype for the FRIB production target was designed, built, and mechanically tested prior to beam tests to be performed.

Synthesis, characterization and biodegradation studies of chain-coupled polyesters based on tartaric acid

A series of chain-coupled polyesters based on tartaric acid was synthesized and characterized following a two-step procedure. In the first step, tartaric acid based hydroxyl terminated polyesters with various alkane diols were prepared and then, in a second step, a chain-coupling approach using hexamethylene diisocyanate was employed on the synthesized polyesters to prepare a series of chain-coupled polyesters. The number-average molecular weights (Mn) of the polyesters were found to vary in the range (4.8 − 28.1) × 103 g mol−1. Thermomechanical studies demonstrate that the storage modulus of the chain-coupled polyesters decreases with increasing polymethylene chain length which is attributable to enhanced flexibility. The isolation of bacteria on medium containing polymer as the sole source of carbon indicates the ability of the synthesized polyesters to be taken up by microorganisms for growth. © 2013 Society of Chemical Industry

Thermomechanical and Rheological Studies of Copolymers of Methyl Methacrylate with a Series of Linear Vinyl Esters

A series of copolymers of methyl methacrylate (MMA) with linear vinyl esters (LVEs), including vinyl acetate (VA), vinyl propionate (VP), vinyl hexanoate (VH), and vinyl decanoate (VD), were synthesized by free radical copolymerizations at 60 °C. The LVE composition was varied from 3 to 41 mol % in the resultant copolymers. The glass transition (Tg) of the copolymers ranged from 60 to 108 °C. The storage moduli (E′) of the copolymers decreased as the LVE composition increased from 4 × 109 to 1.5 × 109 Pa. Copolymers containing VD exhibited a more obvious reduction in storage moduli and a larger shift of the tan δ peak. The rheological property analysis of the copolymers at different temperatures showed that the shear storage and loss moduli of poly(LVE-co-MMA) (G′ and G″) were mostly dominated by MWs. Short side chains did not have an obvious impact on the shear moduli and complex viscosities.

Effect of the composition of polyacrylimide-forming copolymers on their processing

Thermomechanical studies of thermosetting copolymers of acrylonitrile with methacrylic acid and acrylamide with acrylic acid that form similar polyacrylimide foam plastics during curing have been performed. The dependence of the glass-transition temperatures of the copolymers on the degrees of intramolecular imidization has been calculated and confirmed experimentally. Procedures to control the curing rate have been proposed. The influence of plasticizing additives on the glass-transition temperatures, imidization, and foaming of foam-forming compositions has been studied. Plasticized powdered foam-forming compositions with delayed imidization have been developed, and temperature conditions for their processing have been determined.