Low-temperature Compression Research Articles

Experimental study on the low-temperature compression performance of 3D five-directional braided composites applied to extreme environments

• A low-temperature compression test method was designed for 3D5dB composites. • The effects of low-temperature on the compression strength and strain were revealed. • Results of the failure mode are guided for its application in extreme environments. 3D five-directional braided (3D5dB) composites with different braiding angles were designed and prepared, and their compressive properties in the longitudinal, out-of-plane and transverse directions were investigated at room temperature (RT) and liquid nitrogen temperature (LNT). The results of the stress-strain curves showed that the composites at LNT exhibited more pronounced brittle fracture failure and increased compressive strength in all directions compared to RT. The longitudinal compression strength decreased with increasing braiding angle, while the opposite effect was observed for transverse and out-of-plane. The effect of LNT on the failure of 3D5dB composites was mainly focused on the interfacial debonding of fibers and matrix, so the mechanical properties can generally be improved by modifying the fibers to increase the interfacial shear strength at low temperatures. 3D5dB composites with high mechanical strength at the temperature of LNT can be potentially used as cryogenic materials for aerospace applications.

Compression behaviours of aluminium alloy I-column at low temperatures

Aluminium alloys have been used in cold-region engineering constructions. To make more comprehensive understandings of aluminium material properties and structural behaviours at cold-region low temperatures (T), mechanical properties of aluminium alloy 6061-T6 at different T of −80 – 20 °C were investigated through tensile coupon tests. Then, seven aluminium alloy 6061-T6 I-columns were tested under axial compression and different T of 20, −30, −60, and −80 °C. The failure modes, load-shortening/strain behaviours of aluminium I-columns under low-temperature compression were detailed studied. These tests showed that the decreasing T increased the yield/ultimate strength of aluminium alloy 6061-T6 by 10%, and also increased the axial ultimate compression resistance (Pu) of I-column by 7% without reductions in their ductility. Finite element models (FEMs) were also developed by ABAQUS for simulating structural behaviours of aluminium I-columns using the obtained low-temperature material properties. Validations of FEM simulations showed its reasonable simulations on compression behaviours of aluminium I-columns. The code equations in Chinese code GB 50429 and Eurocode 9 were also checked to estimate Pu of aluminium I-columns at low temperatures. It shows that both codes provided conservative predictions on Pu of aluminium I-columns at low temperatures.

Aerobic oxidation of hydrocarbons using N-hydroxyphthalimide (NHPI) catalysts for cetane enhancement

Gasoline compression ignition (GCI) utilizes gasoline-like fuels in low temperature compression ignition (CI) engines. As a result, thermal efficiency is increased compared to that of a conventional spark ignition (SI) engine, while NOx and soot tailpipe emissions are reduced compared to those from a diesel engine. This combustion strategy requires gasoline fuel with a moderate ignition delay for cold start and high load demand conditions. This work proposes an approach to control the ignition characteristics of gasoline to widen GCI engine operation conditions. Aerobic oxidation of gasoline using N-hydroxyphthalimide (NHPI) catalyst has been suggested as an effective method to produce high cetane components, such as hydroperoxide. NHPI catalyzed oxidation reactions of toluene and market gasoline were studied at different reaction conditions using an autoclave batch reactor. The produced hydroperoxide (HP) was quantified by titration using triphenylphosphine (Ph3P) followed by Gas Chromatography (GC) analysis. In addition, an ignition quality tester (IQT) was used to estimate the derived cetane number (DCN) of the oxygenated product. The gasoline cetane number was enhanced by nine digits using gaseous oxygen at moderate conditions (10 bar, 110 °C for 3 h). Aerobic oxidation of gasoline using NHPI catalyst was found to be a promising approach to control the ignition characteristics of fuel and hence an enabler of the GCI engine concept.

Effect of low temperature and high strain rate compression on the microstructure evolution and mechanical behavior of Mg-2Y-0.6Nd-0.6Zr alloy

Mg-2Y-0.6Nd-0.6Zr alloy was implemented for compression test via split Hopkinson pressure bar under the conditions of low temperature and a high strain rate. The microstructure evolution and deformation mechanism of the processed material were characterized by optical microscopy (OM), electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) during the testing of low-temperature dynamic compression. As a result, Mg-2Y-0.6Nd-0.6Zr alloy exhibited a positive strain rate strengthening processed by low-temperature dynamic compression along the RD. In addition, the dynamic compressive strength and yield strength are significantly enhanced with the increasing strain rate, following the emerging of tension twins and a small amount of compression twins. The primary deformation mechanisms are the prismatic <a > slip system and {10[Formula: see text]2} tension twins. The Mg-2Y-0.6Nd-0.6Zr was fractured in a brittle manner at low temperature.

Investigation of bonding mechanism for low-temperature Cu[sbnd]Cu bonding with passivation layer

The bonding mechanism of low-temperature CuCu thermal compression bonding (TCB) with passivation layer has been investigated in this research. After the structures of Cu with Au passivation and Cu with Pd passivation were bonded at 180 °C, the analyses of transmission electron microscope (TEM) were performed for the bonded structures to explore the bonding behavior of passivated-Cu during different stages of the TCB process. The results indicate that grain boundary diffusion of Cu leads to formation of amorphous Cu at the bonding interface in the passivated-Cu structure. Furthermore, diffusion of Cu atoms and recrystallization of amorphous Cu into polycrystalline Cu can eliminate voids at the bonding interface during the TCB process. Comparing to conventional Cu direct bonding with high crystallinity Cu at the bonding interface, passivated-Cu bonding can be achieved by much lower energy, leading to high quality bonding results with low thermal budget.

Electrochemical deposition of indium from chloride bath for low-temperature microbump bonding

Indium chloride bath was characterized towards the application of low-temperature thermal compression bonding. The electrochemical behavior of the indium chloride bath was analyzed using the cyclic voltammetry method. Electrochemical deposition of indium was carried out at various deposition factors on different materials such as copper, nickel, and cobalt. Based on the results of indium deposition obtained from the blanket films, indium bumps were electrochemically fabricated inside a through-resist hole pattern at various current densities. In addition, stacked indium bumps with various metals (Cu/In, Cu/Ni/In, Cu/Co/In) were formed for a practical application of micro bump bonding. Moreover, the formation of the intermetallic compounds between indium and under bump metallization was investigated.

Application of Modified CNFs in High Energy Nitramine Gun Propellant

Modified nanocellulose fibers (MCNFs) were added to the high energy nitroamine gun propellant to explore its influence on the mechanical and energy properties of the gun propellant. In this paper, nanocellulose fibers (CNFs) and MCNFs with a content of 1% were added in the high energy nitroamine gun propellant formula. The mechanical properties, fracture surface structure and energy performance are characterized by the impact strength test equipment, universal material experiment machine, scanning electron microscope (SEM) and closed vessel test. The results show that in terms of low-temperature tensile properties, low-temperature compression properties, and low-temperature impact resistance, the MCNFs-containing propellant samples increased by 2.97%, 1.94%, and 20.4%, respectively, compared with the CNFs-containing propellant samples. The difference in energy properties between the two is not significant. Compared with CNFs, MCNFs can better combine with nitrocellulose matrix in microstructure.

Comparison of the phase transitions of high-pressure phases of ammonium fluoride and ice at ambient pressure

The phase diagrams of water and ammonium fluoride (NH4F) display some interesting parallels. Several crystalline NH4F phases have isostructural ice counterparts and one of the famous anomalies of water, the fact that the liquid is denser than ice Ih, is also found for NH4F. Here, we investigate the phase transitions of the pressure-quenched high-pressure phases of NH4F upon heating at ambient pressure with x-ray diffraction and calorimetry, and we compare the results with the corresponding ices. NH4F II transforms to NH4F Isd, which is a stacking-disordered variant of the stable hexagonal NH4F Ih polymorph. Heating NH4F III gives a complex mixture of NH4F II and NH4F Isd, while some NH4F III remains initially. Complete conversion to NH4F Isd is achieved above ∼220 K. The NH4F II obtained from NH4F III persists to much higher temperatures compared to the corresponding pressure-quenched NH4F II. Quantification of the stacking disorder in NH4F Isd reveals a more sluggish conversion to NH4F Ih for NH4F Isd from NH4F III. In general, the presence of stress and strain in the samples appears to have pronounced effects on the phase transition temperatures. NH4F shows a complete lack of amorphous forms at low temperatures either upon low-temperature compression of NH4F Ih or heating NH4F III at ambient pressure. The amorphous forms of ice are often used to explain the anomalies of water. It will, therefore, be interesting to explore if liquid NH4F displays more water-like anomalies despite the apparent lack of amorphous forms at low temperatures.

The sp2-sp3 transition and shear slipping dominating the compressive deformation of diamond-like carbon

The uniaxial compression tests of diamond-like carbon (DLC) films are conducted via molecular dynamics to investigate their mechanical properties and deformation mechanisms by considering different factors including strain rates, temperatures, void defects and compliance. It is found that during the compression, large sp3C clusters expand themselves by annexing neighboring sp2C atoms which experience sp2-sp3 transition. Moreover, the sp3C-sp3C bonds along the direction perpendicular to the compressive direction are elongated and the rupture of such bonds leads to the compressive failure of DLC films. Furthermore, the stress relief of DLC films is the result of competition between internal relative slip and diffusion relaxation. The relative slip is dominant with low temperature and high compression strain rate, which makes the DLC films own high strength and exhibit brittleness. However, with high temperature and low strain rate, these films become ductile and their strength are degraded due to the activation of diffusion relaxation.

Compression behaviours of concrete-filled Q690 high-strength steel tubular columns at low temperatures

Concrete-filled high-strength steel tubular columns (CFHSTCs) were developed using high-strength steel (HS) Q690 for cold-region engineering constructions. To study their compression behaviours at low temperatures, 15 CFHSTCs were tested under axial compression at different low temperatures within 20 ~ −90 °C. Including the influence of low temperatures, the effects of steel-tube wall thickness was also covered in this study. Compression test results showed that under the condition of low temperatures, local buckling of HS tube (HST), core crushing and weld fracture of HST occurred to the CFHSTCs. The CFHSTCs achieved the compression capacity as the crushing of concrete core, and HST local buckling at the recession working stage. Decreasing temperatures from 20 to −90 °C improved ultimate compression capacity and elastic stiffness of CFHSTCs. Moreover, enlarging the wall thickness of HST improved compression behaviours of CFHSTCs both at ambient and low temperatures. This paper also developed 3D finite element model (FEM) to simulate low-temperature compression behaviours of CFHSTCs. Validations of the FEM simulation results against 15 tests confirmed its capacity on simulating compression behaviours of CFHSTCs at both ambient and low temperatures.

Compression behaviour of stainless-steel stub square tubular columns at cold-region low temperatures

This paper studied the axial compression behaviour of stainless-steel stub square tubular columns (SSSSTCs) at low temperatures (T). Firstly, mechanical properties of stainless steel (SS) S30408 at −80–20 °C were experimentally studied. Test results revealed that decreasing low temperature significantly improved the strength of SS especially the ultimate strength, but reduced its ductility. Twenty SSSSTCs with varying wall thickness were tested at different T of −80–20 °C. Test results showed that inward and outward local buckling took place for SSSSTCs under low temperature-compression. The decreasing T value had significantly positive influence on strength and stiffness of SSSSTCs, but reduced the nonlinear branch of P-Δ curves and ductility of SSSSTCs. The increasing wall thickness significantly improves both strength and ductility of SSSSTCs at different low temperatures due to the reduced width-to-thickness ratio. This paper also developed finite element model (FEM) on simulating compression behaviour of SSSSTCs at different low temperatures that considered geometric imperfections and material nonlinearities. Different code prediction equations were also adopted for predictions of the ultimate low-temperature compression resistances of SSSSTCs. Their accuracies were checked by reported test results.

Axial compression behaviours of ultra-high performance concrete-filled Q690 high-strength steel tubes at low temperatures

This paper proposed the UHPC-filled high-strength steel tube (UHST) for cold-region buildings/bridges. The cold-region low-temperature environment was simulated in the laboratory using a cooling chamber with LNG. Then, low-temperature compression tests were performed on 23 stub UHSTs to study their low-temperature compression behaviour. The studied parameters included four low temperatures (T = −80, −60, −30, and 30 °C) and three width-to-thickness ratios (C/t ratio = 48.4, 33.5, 22.0). Test results showed that the P (load) −Δ (shortening) curves exhibited a four-stage manner. The UHPC crushing occurred at the ultimate load capacity and UHPC nonlinearities contributed to the nonlinear behaviour of UHSTs. Outward buckling of HSS tube and welding fracture occurred at the recession stage. The decreasing temperature from 30 °C to −80 °C improved the compression behaviour of UHSTs. As T decreases form 30 °C to −80 °C, the ultimate compressive resistance Pu (or initial stiffness K0) value of UHSTs with C/t ratio of 22.0 receives the increments of 20% (24%). With the same decrease of C/t ratio, the increments of peak load capacity decreased as T decreased from 30 °C to −80 °C. This paper also developed finite element models (FEMs) and theoretical models to simulate the axial compression behaviour of UHSTs at low temperatures. Validations of simulations against 23 test results proved that both the FEM and theoretical models provided reasonable simulations on axial low-temperature compression behaviours of UHSTs.

Introduction to the New Copolymer of Chloroprene and Acrylonitrile with Differentiated Properties

The random copolymer of chloroprene and acrylonitrile is a newly developed rubber whose features and value propositions are not scientifically explored yet. This article focuses on the basic characterizations and properties of acrylonitrile-chloroprene rubber. Qualitative analyses through infrared (FTIR) and nuclear magnetic resonance (1H-NMR) spectra confirm the presence of both the -Cl and -CN groups in the new rubber. As evidenced through differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), the single glass transition temperature of acrylonitrile-chloroprene rubber reflects its monophasic random microstructure. While compared against commercial grades of chloroprene rubber (CR) and nitrile rubber (NBR), the new rubber provides a distinctive combination of properties that are not available with either of the elastomer alone. Acrylonitrile-chloroprene rubber demonstrates slightly lower specific gravity, an improved low-temperature compression set, higher flex-fatigue resistance, and lower volume swelling in IRM 903 and Fuel C to chloroprene rubber. As compared to nitrile rubber, the new copolymer shows appreciably better heat aging and ozone resistance. Good abrasion resistance, low heat buildup, and remarkably high flex-fatigue resistance indicate excellent durability of the acrylonitrile-chloroprene rubber under dynamic loading. Based on the preliminary results, it is apparent that the new copolymer can be a candidate elastomer for various industrial applications which demand good fluid resistance, high heat and low-temperature tolerances, good weatherability, and durability under static and dynamic conditions.

Low-temperature compression behaviour of square CFST columns using Q960 ultra-high strength steel

This paper studied the low-temperature compression behaviours of concrete-filled Q960 ultra-high-strength-steel (UHSS) tubes (CFUT), which were developed for the high-performance Arctic engineering constructions. Fifteen stub CFUTs were tested at different low temperatures of 20, −30, −60, and −290 °C. The studied parameters in the testing program were low temperatures and thickness of Q960 UHSS tube. The low-temperature compression tests showed that the CFUTs failed in concrete crushing, outward local buckling and weld fracture at the corner of Q960 square UHSS tube. The Arctic low temperatures increased the compression capacity and stiffness, but reduced the ductility of CFUTs with Q960 UHSS tube. A 3D nonlinear finite element model (FEM) was built for simulations on the low-temperature compression behaviour of CFUTs with Q960 UHSS tube. Moreover, theoretical models on simulating load-shortening behaviours of CFUTs with Q960 UHSS tube at low temperatures were developed. Validations proved that the developed FEM and theoretical models predicted well compression behaviour of CFUTs with Q960 UHSS tube at low temperatures.

Performance evaluation and exergy analysis of a novel combined cooling, heating and power (CCHP) system based on liquid air energy storage

Liquid air energy storage (LAES) is a promising large-scale energy storage technology in improving renewable energy systems and grid load shifting. In baseline LAES (B-LAES), the compression heat harvested in the charging process is stored and utilized in the discharging process to enhance the power generation. Due to the low liquid air yield, a large amount of compression heat is wasted. In order to improve the round-trip efficiency (RTE) and extend the application field, a novel combined cooling, heating and power system based on the LAES (LAES-CCHP) is proposed and investigated. In the proposed system, an organic Rankine cycle (ORC) is employed to recover the high-temperature surplus compression heat to generate electricity and an absorption refrigeration system (ARS) is introduced to utilize the low-temperature compression heat to realize district cooling and heating. Based on a mathematical model, performance evaluation and exergy analysis of the system is performed. It is found that the effective and cascaded utilization of the compression heat could significantly improve the efficiency and performance of the system. With optimal operational parameters, the RTE and exergy efficiency of the LAES-CCHP could reach 69.64% and 57.02%, respectively, which are 37.66% and 12.71% higher than those of the B-LAES.

Analysis of Low Temperature Compression Characteristics of Rubber Seal Strip of Shelter based on ABAQUS

The extreme low temperature of the alpine region is easy to have a bad effect on the sealing performance of the rubber seal strip of the shelter. In this paper, ABAQUS software is used to simulate and analyse the compression characteristics of the seal strip of the shelter at 23°C and -55°C, the Von Mises stress and the surface contact stress at two different temperatures are obtained. The result shows that the compression performance of rubber seal strip is sensitive to the extreme low temperature, and it is prone to low-temperature failure. The simulation results in this paper can provide an important reference for the subsequent low-temperature environmental test, so as to more comprehensively analyse the low-temperature failure mechanism of the rubber seal strip of the shelter in the alpine region.

The impact of intake pressure on high exhaust gas recirculation low-temperature compression ignition engine combustion using borescopic imaging

In diesel engines, high levels of exhaust gas recirculation can be used to achieve low-temperature combustion, resulting in low emission levels of both nitrogen oxides (NO x) and particulate matter. This work studied the effects of varying the intake manifold pressure on in-cylinder combustion processes and engine-out emissions from a light-duty single cylinder diesel engine under conventional and high exhaust gas recirculation low-temperature combustion regimes. The work was conducted at a part-load cruise condition of 1500 r/min and at an indicated mean effective pressure of approximately 600 kPa. Exhaust gas recirculation rates were varied between 0% and 65% at absolute intake pressures of 100–150 kPa. Very low NO x emissions were achieved (<10 ppm, ∼0.05 g/kW h) for intake oxygen mass fractions below about 11%, independent of boost pressure. Smoke emission levels were lower than for non–exhaust gas recirculation combustion at oxygen mass fractions below ∼9%, depending on the boost pressure. High intake pressures reduced fuel consumption by 15% and combustion by-product emissions by 50%–60% compared to low boost. For the low intake boost case, little visible flame was apparent through borescope imaging. At higher boost pressures, intense flame luminosity was observed within the piston bowl early in the expansion stroke. Spatially averaged soot luminosity based on photomultiplier tube data showed that peak soot luminosity was five times greater and occurred 8 °CA earlier for high boost. This work demonstrates how the combination of appropriate boost pressures and exhaust gas recirculation rates can be used to mitigate the emissions and thermal efficiency penalties of high-dilution low-temperature combustion to achieve near-zero NO x operation.

The cryogenic mechanical property deviation of Ti-based bulk metallic glass composite induced by interstitial element

Although most bulk metallic glass composites (BMGCs) will undergo ductile-to-brittle transition at cryogenic temperature, significant low temperature compression and tensile ductility have been found in a BMGC with the composition of Ti48Zr20Nb12Cu5Be15. In present work, the cryogenic mechanical behavior of BMGCs containing interstitial element was studied for understanding the multiple reinforcement of BMGCs in low temperature environment and for explaining the differences in cryogenic properties of BMGCs. Results show that the Ti-based BMGC will be much more sensitive to impurity elements in cryogenic environment than that at room temperature. Besides, the increase in yield strength of BMGCs with the decrease of temperature is not simply due to the dislocations motion in the dendrites becomes more difficult. Low temperature environment can strengthen the glassy matrix as well as increase the strength of dendrites. Results imply Ti48Zr20Nb12Cu5Be15 BMGC can be a kind of promising materials for low-temperature applications.

Comparison and analysis of two processes for BOG re-liquefaction in LNG carrier with normal-temperature compressor

Two processes for boil-off gas (BOG) re-liquefaction of liquefied natural gas (LNG) carrier with normal-temperature compressor are proposed and compared: (1) the re-liquefaction system with the single mixed refrigerant process (SMRP), (2) the re-liquefaction system with the dual mixed refrigerant process (DMRP). The main thermodynamic parameters to be compared are specific energy consumption, exergy efficiency, coefficient of performance, heat transfer curves and exergy losses of main equipment in optimized case and base case. The result shows that the performance of the DMRP is better than that of the SMRP and the specific energy consumption of DMRP is 0.5635 kWh/kgLNG. In addition, by comparing the thermodynamic parameters of the re-liquefaction system with the normal-temperature compressor and the cryogenic compressor, it can be found that not only the cooling capacity of BOG is used effectively, but also the energy consumption is reduced and the efficiency is improved for the normal-temperature compressor system. Therefore, for the two mixed refrigerant re-liquefaction systems, the performance of the normal-temperature compression system is better than that of the low-temperature compression system.

A Thermoelectrochemical Converter Using High-Temperature Polybenzimidazole (PBI) Membranes for Harvesting Heat Energy

To meet the rising energy demand and efficiently utilize a larger amount of waste heat energy from various devices and systems, here we report an innovative thermo-electrochemical converter which utilizes the electrochemical potential of a hydrogen pressure differential applied across a proton conductive membrane. The amount of energy available to the external load is the difference in electrical potential between that generated during a high temperature expansion stage and that required during a low temperature compression stage. In this work, various phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes, DiOH-PBI, para-PBI, and m/p-PBI, are prepared via the poly(phosphoric acid) (PPA) process and investigated to understand how the membrane chemistry affected device performance. When operating a laboratory scale device at 20oC/200oC and a pressure ratio of 770, DiOH-PBI exhibited the best performance (maximum current density of 43mA/cm2, peak power density of 0.52mW/cm2, and net efficiency of 17.1...