Low Temperature Fracture Research Articles

RETRACTED ARTICLE: Influence of crumb rubber particle sizes on rutting, low temperature cracking, fracture, and bond strength properties of asphalt binder

The present study aimed at evaluating the effect of Crumb Rubber (CR) particle size on rutting, low temperature cracking, fracture, and bond strength properties of asphalt binder. Three different CR particle sizes (#10–20, #30–40, and #60–80) were considered in this research work. Rutting performance was evaluated using Multiple Stress Creep Recovery (MSCR) tests. Although the addition of CR was found to improve the rutting performance, asphalt binder combination with higher CR particle size exhibited better performance compared to asphalt binder combination with lower CR particle size. Similarly, low temperature cracking properties were evaluated using Bending Beam Rheometer (BBR). It was found that the addition of CR has positive impact on the low-temperature performance of asphalt binder. Fracture property was evaluated using Double Edge Notch Tension (DENT) test and found to be improving with the increase in CR particle size. Finally, the effect of CR particle size on moisture damage resistivity potential was evaluated using the recently developed Bitumen bond strength (BBS) test. Although the addition of CR was found to have deteriorating impact on bond strength behavior, the degree of impact was found to be lower for asphalt binder containing the lowest considered CR particle size.

Deterioration of HAZ toughness by residual Sn and Determination of its Allowable Content for Electric Furnace Steels

One promising direction in steelmaking to respond to global climate change issue is to increase the use of electric furnace manufacturing methods using zero-carbon electricity, which have received more and more attention recently. Considering the replacement from blast furnace steel, the temper embrittlement problem induced by some tramp elements, which is unique behavior for electric furnace methods, must be resolved.Sn is considered as a tramp element that cannot be removed in steel refining process, and it has been reported that the toughness of the base metal and the welded heat affected zone can be significantly degraded. In the case of electric furnace steels with degraded toughness, segregation of Sn is observed at grain boundaries and the resulting fracture mode shifts to intergranular fracture mode. In this study, in order to quantify the allowable amount of Sn added to thick steel plates that is used for large-heat input welding, experiments were conducted on specimens with different amounts of Sn and heat-treated for different holding times at 400℃, which is a typical embrittlement temperature and investigated the effect of the amount of Sn on the change in low-temperature fracture toughness. As a result of fracture toughness tests, clear evidence of temper embrittlement was observed. Apart from previous famous study by McMahon, there was no intergranular fracture in fracture surface but transgranular and cleavage fracture was observed. Therefore, the mechanism by which Sn tends to cause cleavage fracture in the weld heat affected zone was proposed. Based on our newly proposed mechanism, a model was developed to estimate the transition temperature change for various conditions of tempering time, tempering temperature and Sn content.Finally, the authors propose allowable maximum content of Sn based on the model for the establishment of the rational ore sorting system from scraps in near future society.

Low temperature fracture resistance of cement emulsified asphalt mortar under mixed mode I/III loading

Having asphalt in Cement Emulsified Asphalt Mortar (CEAM), this composition has higher toughness and ductility but also higher thermal sensitivity than conventional cement mortar. This study was aimed at investigating the fracture behavior of CEAM under out-of-plane shear and tensile loadings (Mode I, I/III, III) at low temperature. This investigation was performed by testing Edge Notched Disc Bending (ENDB) specimens with different asphalt-to-cement and water-to-cement ratios at three temperatures. Scanning Electron Microscopy technique (SEM was also employed to evaluate the effect of asphalt-to-cement and water-to-cement ratios on the structure of CEAMs. The findings revealed that for CEAM, the fracture toughness attains its highest value at pure tensile mode I, decreases as the share of out-of-plane shear in the mixed-mode I/III loading increases, and reaches its lowest value in the pure out-of-plane shear mode III. Furthermore, a multiple regression model was extracted for the relationship between each critical stress intensity factor (KC) and asphalt-to-cement ratio (A/C), water-to-cement (W/C), and temperature (T). The analyses showed -at the 95% confidence level- that A/C have a significant impact on KC in all examined modes and also the fracture toughness of CEAM decreases with increasing A/C. Changes in W/C also had a significant impact on the pure shear mode and mixed tensile-shear mode (I/III) stress intensity factors. Temperature changes in the studied range only affected the pure tensile mode stress intensity factor.

Fracture Behavior of Permeable Asphalt Mixtures with Steel Slag under Low Temperature Based on Acoustic Emission Technique.

Acoustic emission (AE), as a nondestructive testing (NDT) and real-time monitoring technique, could characterize the damage evolution and fracture behavior of materials. The primary objective of this paper was to investigate the improvement mechanism of steel slag on the low-temperature fracture behavior of permeable asphalt mixtures (PAM). Firstly, steel slag coarse aggregates were used to replace basalt coarse aggregates with equal volume at different levels (0%, 25%, 50%, 75%, and 100%). Then, the low-temperature splitting test with slow loading was used to obtain steady crack growth, and the crack initiation and propagation of specimens were monitored by AE technique in real time. From the low-temperature splitting test results, SS-100 (permeable asphalt mixtures with 100% steel slag) has the optimal low-temperature cracking resistance. Therefore, the difference of fracture behavior between the control group (permeable asphalt mixtures without steel slag) and SS-100 was mainly discussed. From the AE test results, a slight bottom-up trend of sentinel function was founded in the 0.6–0.9 displacement level for SS-100, which is different from the control group. Furthermore, the fracture stages of the control group and SS-100 could be divided based on cumulative RA and cumulative AF curves. The incorporation of 100% steel slag reduced the shear events and restrained the growth of shear cracking of the specimen in the macro-crack stage. Finally, the considerable drops of three kinds of b-values in the final phase were found in the control group, but significant repeated fluctuations in SS-100. In short, the fracture behavior of PAM under low temperature was significantly improved after adding 100% steel slag.

Laminated composites using potassium doped tungsten

Abstract Highly deformed tungsten (W) thin foils could show excellent low temperature ductility, even at room temperature. A laminated composite using pure W foils has been proposed for the application to the plasma-facing material of divertors, which is a composite material consisting of stacked pure W thin foils and interlayer materials. However, the degradation of low temperature ductility attributed to the recrystallization and neutron irradiation of pure W foils is one of the concerns of the laminated composite using pure W foils. Potassium (K) doping is known as one of the methods to suppress recrystallization and to improve neutron irradiation resistance, in addition to improving the low temperature fracture toughness. Therefore, a laminated composite using K-doped W foils was developed in the present study, which has the possibility to show improved mechanical properties even after the neutron irradiation compared to the pure W foil laminated composite. The K-doped W foil laminates using an interlayer made of pure cupper (Cu) and pure vanadium (V) were fabricated at 900 and 1250 °C in the present study. An enough ductility at room temperature was observed in these laminates, even after the fabrication at 1250 °C.

Study of Low-Temperature Performance of Short Fiber–Reinforced Asphalt Seal Band

Abstract To study the low-temperature performance of short fiber–reinforced asphalt seal band, different experiments were set by changing the content, length, and type of fibers. Their low-temperature performance was analyzed by low-temperature tensile tests as well as stress relaxation experiments, and the fracture morphology was analyzed using a scanning electron microscope; elastic modulus, ultimate tensile stress, low-temperature tensile fracture energy, and relaxation index are reported. Furthermore, a new evaluation scheme was given according to an entropy evaluation method. Results indicate that fibers effectively improve the low-temperature performance of the asphalt seal band. Specifically, in terms of the mechanical properties of the asphalt seal band during the tensile process, it is the best to infuse a 0.3 % volume fraction of 6-mm basalt fiber into the matrix, while according to the evaluation system established in this research, it is the best to use a 0.3 % volume fraction of 6-mm polyester fiber.

An experimental investigation on FPZ evolution of concrete at different low temperatures by means of 3D-DIC

The three-point bending tests of concrete specimens at different temperature levels (20 ℃, 0 ℃, −20 ℃, and −40 ℃) were performed using a low-temperature fracture test system. The 3D digital image correlation (3D-DIC) technique was employed to measure the surface deformations of the beams during fracture process. Combined with the displacement fields obtained from 3D-DIC, the crack propagation lengths and crack widths at different loading points were determined, providing information for the fracture process zone (FPZ) evolution in concrete at different temperatures. The results revealed that temperature has significant effect on the crack propagation, i.e. the average FPZ length in the later stage of unloading and the critical crack length ac decrease with decreasing temperature. In addition, the FPZ length for specimens at 0 ℃, −20 ℃ and −40 ℃ decreases slowly in the initial stage and then decreases significantly when the crack extends to the specimen boundary.

Acoustic Emission-Based Reinforcement Evaluation of Basalt and Steel Fibers on Low-Temperature Fracture Resistance of Asphalt Concrete

AbstractThis study aims to adopt the acoustic emission (AE) technique to evaluate the reinforcing effect of basalt and steel fibers on the fracture resistance of asphalt concrete (AC) under indirec...

Evaluation of tension softening curve of concrete at low temperatures using the incremental displacement collocation method

The three-point bending tests of concrete beams at different temperatures (20 °C, 0 °C, −20 °C, and −40 °C) were carried out by using a low-temperature fracture test system. The digital image correlation technique was utilized to measure the surface displacement and strain fields of the specimens. The crack characteristics, including the crack propagation length and the crack opening displacement profile were determined. The tension softening curves (TSCs) of concrete were obtained using the incremental displacement collocation method. The developed TSCs were verified through the comparisons of the displacements determined by finite element method and by clip gauge as well as the fracture energy. In addition, based on the double-K fracture criterion, the deviations of two fracture toughness were analyzed, and again the accuracy of the TSCs was verified. Finally, the results of characteristic length and damage scale were also presented in this paper.

Prediction of fracture toughness of SA738Gr.B steel in the ductile-brittle transition using master curve method and bimodal master curve method

The low temperature fracture toughness of SA738Gr.B steel is as important as its strength, but the low temperature fracture toughness tends to be more complicated due to some deterministic and random inhomogeneity, such as sampling locations. In this paper, the fracture toughness of the 60 mm thick SA738Gr.B sheet in DBT region from the surface to the center was characterized by MC method and BMC method. Considering the sampling position, a distinct trend is found that the toughness of the surface is significantly higher than that of the center and T0 is lower from center to the surface due to the faster quenching rate. Special attention was paid on the discussion of the applicability of China-produced SA738Gr.B steel to the master curve (MC) method. It was found that the inhomogeneity caused the actual distribution of the experimental data to deviate from the three-parameter weibull distribution, and the weibull slope was lower than the theoretical value of 4. Characterizing the fracture toughness of materials containing heterogeneous components by the MC method can overestimate the fracture toughness and may pose a potential hazard. The BMC method can effectively solve the problem of material inhomogeneity. It is an evaluation method based on the actual toughness distribution of materials. The BMC method takes into account the influence of material inhomogeneity on the toughness estimation, and more accurate assessment of material scatter than the standard MC method yields a slightly conservative but more appropriate prediction.

Regularities of Low-Temperature Deformation and Fracture of Polyimide Films of Kapton H Type of Different Thickness

The mechanical characteristics (limit of forced elasticity σforc, fracture stress σfr, relative deformation to failure εfr) of polyimide films of kapton H type under uniaxial tension conditions along the direction of drawing in the temperature range (4.2-293 K), deformation rates (10-5 - 10-3 s-1) and film thicknesses (25, 75 and 125 μm) were investigated. It is discovered, that the forced-elastic state remains for all films up to 4.2 K of all strain rates - σfors<σfr. In this case, the reserve of elasticity significantly depends on the thickness of the film with a decrease in temperature. A sharp decrease in εfr occurs in films: 125 μm thick - at 77 K, 75 μm thick - at 4.2 K. Two variants of deformation curves are possible in a 25 μm thick film at 4.2 K: with a short nonlinear stage or with a long one proceeding jumpily. The working surface of the samples that have undergone jump deformation is covered with a deformation relief, partially representing a delayed highly elastic deformation. The σfors limit is most sensitive to the strain rate. The nature of the strain rate sensitivity σfors(έ) depends on the temperature and film thickness. The change to the opposite in the character of σfors(έ) and σfr(έ) with a decrease in temperature to 4.2 K in 75 and 125 thick films was found for a first time. Change in the character of σfors(έ) is not observed in 25 μm thick film which retains the maximum reserve of elasticity at 4.2 K

Low-Temperature Fracture of Low-Alloy Steel after Severe Plastic Deformation

Low-Temperature Fracture of Low-Alloy Steel after Severe Plastic Deformation

Effects of warm mix additives on the thermal stress and ductile resistance of asphalt binders

The application of warm mix additives to asphalt was studied to analyze their influence on the low-temperature fracture performance of asphalt materials. To this end, a set of warm mix asphalt binders (WMABs) were prepared by mixing a hot mix asphalt binder (HMAB), PG 64-28 with two different types of warm mix additives (one being Sasobit and the other ET-3100). A bending beam rheometer test and a double edge notched tension test were performed to characterize the thermal stress and ductile resistance of the HMAB and WMABs, respectively. Fourier transform infrared spectroscopy (FTIR) was employed to study the modification mechanism during the application of the warm mix additives. The test results showed that the addition of Sasobit deteriorates the low-temperature fracture properties of the asphalt, with higher thermal stress, linearly increasing critical cracking temperature, and lower crack tip opening displacement. ET-3100 showed little effect on the low-temperature fracture properties of the bitumen, regardless of the added amount. The FTIR results showed that there was basically no chemical reaction in the modification process and both types of warm mix additives were physically modified.

Study on the Fracture Properties of HTPB Propellant at Low Temperature

AbstractIn order to study the fracture behaviour of hydroxyl‐terminated polybutadiene (HTPB) propellant, the low temperature fracture toughness experiment of HTPB propellant was carried out by using centrally cracked sheet tensile specimens. The fracture toughness values of HTPB propellant with mode I crack at different temperature and loading rate were obtained, and the effect of specimen thickness on the fracture toughness was investigated. The experimental results show that the fracture toughness value continuously increases with the decreasing of temperature and the increasing of loading rate, and a linear relationship exists between the fracture toughness and the logarithm of loading rate. The effect on the fracture toughness by the change in loading rate is more notable at a lower temperature. Both at 25 °C and −40 °C, the fracture toughness of thick specimens is higher than that of thin specimens, and at low temperature the change is more obvious. A master curve of quadratic function for the fracture toughness was obtained. The influence of temperature on the fracture toughness is more obvious than that of the strain rate with double factor analysis of variance.

Effect of Silicone Oil on Dispersion and Low-Temperature Fracture Performance of Crumb Rubber Asphalt

Low-temperature cracking is one of the major pavement distresses in cold regions. To reduce the prevalence of such cracks, crumb rubber modified asphalt (CRMA) has been applied for a long time. However, CRMA experiences compatibility and segregation problems with asphalt. Silicone oil has long been seen to improve compatibility and segregation problems of polymers in asphalt, but its benefits on low temperature performance of crumb rubber asphalt have not been explored. Furthermore, silicone oil can be obtained as virgin or recycled from industrial transformers; however, the recycled silicone oil’s influence on low-temperature crack performance of asphalt has also not been explored. Therefore, the purpose of this study was to investigate the effect of recycled silicone oil (SO) on dispersion and low-temperature fracture performance of crumb rubber asphalt. The fracture mechanics-based single-edge notch beam (SENB) test was performed at temperatures of −12°C, −18°C, and −24°C. In addition, fluorescence microscopy (FM), atomic force microscopy (AFM), and Fourier-transform infrared (FTIR) experiments were also conducted. Results show that the addition of SO to CRMA increases displacement, fracture energy, and fracture toughness at low temperature while it decreases stiffness which reduces cracking. In addition, AFM results show that surface roughness increases with the addition of SO which indicates that bonding of asphalt and rubber particles had also improved. FM also confirmed that dispersion of rubber particles had improved with addition of silicone oil. FTIR results revealed that asphalt samples with SO treatment were hydrophobic which potentially repels water ingress and delays the freezing of asphalt. Lastly, statistical analysis revealed that the influence of silicone oil on low-temperature performance of rubber asphalt was significant. Therefore, the study concluded that fracture cracking resistance is improved by addition of silicone oil to crumb rubber asphalt.

Improved microstructure heterogeneity and low-temperature fracture toughness of C–Mn weld metal through post weld heat treatment

The Crack Tip Opening Displacement (CTOD) test was used to investigate the effect of post-weld heat treatment (PWHT) on the low-temperature fracture toughness of C–Mn weld metal. The microstructure observations, instrumented nano-indentation test and microstructure-based finite element simulation were conducted to analyze the toughening mechanisms. The study found that the CTOD value increased significantly from 0.241 mm to 1.754 mm after PWHT. The hardness and strength between acicular ferrite (AF) and proeutectoid ferrite (PF) both get closer, which improves the extent of microstructure heterogeneity. The simulation indicated that the distributions of the strain and stress on AF and PF are homogenized with the improvement of microstructure coordination after PWHT, making the level of plastic strain localization within PF decreased and the stress concentration on the interphase of AF and PF lessened. As a result, the resistance of crack initiation and propagation increases, and the low-temperature fracture toughness is improved. Moreover, the dislocation densities in AF and PF both decrease, the dislocation morphology evolves from dislocation tangles into movable dislocation lines, and amounts of fine carbides precipitate and spheroidize, which also contribute to the toughening of microstructures.

A method to determine minimum design metal temperature of pressure vessels made from ferritic steel by Master Curve approach

The four impact exemption curves in ASME are convenient to estimate the minimum design metal temperature (MDMT) of ferritic steel. However they can’t distinguish low temperature fracture toughness of ferritic steel well. Materials with similar fracture toughness, divided into different impact exemption curves will have different MDMT and conservative degree. And the MDMT of ferritic steel are estimated by the steel grade. There are differences in toughness for steel with same steel grade from different factories and different heats and batches of the same factory. In this paper, the seven MDMT curves, identified with labels I, II, III, IV, V, VI and VII are proposed based on assumed yield strength and seven reference temperatures, (T0MC = 20 °C, 0 °C, −20 °C, −40 °C, −60 °C, −80 °C and −100 °C) which can cover the temperature range for commonly used pressure vessels made from ferritic steel. The MDMT for a ferritic steel can be determined once the reference temperature and yield strength are measured. SA508-3 and Q345R, as a representative of ferritic steel are used to illustrate the applicability of the MDMT curves.

Evaluation of performance properties of 50% recycled asphalt mixtures using three types of rejuvenators

In this study Cyclogen, Rapiol and waste cooking oil was used as rejuvenators to improve properties of aged bitumen. The effects of these rejuvenators on asphalt mixtures containing 50% of reclaimed asphalt pavement specimens was evaluated using dynamic creep, resilient modulus, low temperature fracture energy and moisture susceptibility tests and the results was compared to recycled mixtures without rejuvenator and control HMA mixtures. The results showed that the rejuvenators are effective in alleviating the aging effect of RAP bitumen. Waste cooking oil performed better than other studied rejuvenators followed by Cyclogen and Rapiol. However, moisture resistance was impaired when rejuvenators were used.

The Role of Retained Austenite Stability on Low-Temperature Mechanical Behaviors of a Quenching and Partitioning Steel

Low-temperature deformation and fracture behaviors are studied for a quenching and partitioning (Q&P) steel by interrupted tensile tests and X-ray diffraction (XRD). The austenite stability decreases significantly from 298 K to 223 K, while further cooling to 77 K does not cause greater instability. The yielding, work hardening, and fracture behaviors are found to change under the influence of austenite stability at low temperatures.

Practical Approach to Mix Design with High Binder and Aggregate Replacement in Iowa using Fractionation

A laboratory study was conducted to examine the effect of fractionated reclaimed asphalt pavement (FRAP) materials on the performance of a standard surface hot mix asphalt (HMA), as well as a HMA crack relief interlayer. The surface mix contained a PG58-28S binder, 3.3% of a bio-rejuvenator (0.12% by total mix weight), and 50% FRAP containing 30% fine fraction and 70% coarse fraction. The interlayer mix contained a polymer modified PG76-28 binder, 3.5% of the bio-rejuvenator (0.16% by total mix weight), and 50% FRAP containing 100% fine fraction. The surface mix was evaluated for HMA rutting resistance, moisture susceptibility, and low temperature fracture resistance, while the interlayer mix was evaluated for interlayer fatigue resistance. The rejuvenated FRAP surface mix performed better than the control FRAP surface mix in rutting and moisture susceptibility (stripping inflection point of 19,582 versus 17,805 for the control), and had a 100% improvement in low temperature fracture (768 J/m2 versus 354 J/m2 for the control) all due to the addition of 0.12% of a bio-rejuvenator by total mix weight. From the interlayer test there was a 57.7% and 33.6% improvement in number of cycles to failure and cumulative dissipated energy due to the addition of 0.16% of a bio-rejuvenator by total mix weight. Neither the FRAP control nor rejuvenated FRAP interlayer mixtures passed the interlayer test criteria. There is room for further improvement in the future, however, and the bio-rejuvenator is shown to improve performance substantially for mixtures with high asphalt binder and high aggregate replacement.