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Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, Ti/Al3Ti laminated composites were prepared by "explosive welding + heat treatment". On this basis, the microstructure and the fracture failure process of the laminated composites were analyzed using SEM and the in situ tensile test. The results show that no pure aluminum remains in the laminate composites and the bonding interfaces of the laminate composites still exhibit wavy-like bonding. When the Ti/Al3Ti laminated composites are subjected to continuous horizontal stress, cracks appear in the brittle layers first, and cracks begin to appear in the ductile layers after all the brittle layers fail. And the cracks generated in the brittle Al3Ti layers are diverse, making the Al3Ti layers absorb more horizontal stress. Cracks in the ductile layers will constantly propagate and deflect, thus increasing the toughness of the material. Therefore, the fracture failure mechanism of Ti/Al3Ti laminated composites is the combined action of brittle Al3Ti layers and ductile Ti layers. [ABSTRACT FROM AUTHOR]

Cracks of varying lengths may occur in galleries throughout dam construction, operation, and management processes. This study investigates the influence of age and crack length on the fracture parameters of gallery concrete, which is crucial for understanding the mechanisms and risks associated with gallery cracking and for developing appropriate treatment measures. Wedge-splitting tests were performed on gallery concrete specimens with varying crack lengths and at different ages. It was found that the fracture parameters measured at different ages all decrease with the increase of crack length. Based on the test results, size-independent material constants such as fracture toughness and the effective length of the fracture process zone were derived and modeled using an exponential function to reflect their time-varying characteristics. A fracture model was proposed and validated, which can accurately predict the fracture behavior of gallery concrete across varying ages and crack lengths, and is applicable in practical dam gallery crack analysis for assessing crack stability and evaluating the effectiveness of treatment measures.

In the oil and gas industry, the selection of tubing and casing materials is required to follow international standard ISO 15156. However, it does not provide guidance on selecting stainless steel materials for H2S-containing wells above 232 °C, which raises uncertainty about the suitability of 13Cr steel. This work focuses on investigating the mechanical degradation and failure mechanisms of 13Cr stainless steel exposed to high-temperature conditions and proposed a creep constitutive model. Then, the corrosion and cracking mechanisms of 13Cr stainless steel at temperatures ranging from 150 °C to 350 °C were elucidated. Results show that 13Cr stainless steel meets the current material selection criteria (GB/T34907-2017) for mechanical properties and creep resistance. In the range of 150–250 °C, the localized corrosion is dominant, and stress-oriented hydrogen-induced cracking occurs at 150 °C. As the temperature increases from 250 °C to 350 °C, although the maximum value of uniform corrosion rate is as high as 0.2960 mm/a, the cracking does not happen. Therefore, with the implementation of suitable protective measures, 13Cr stainless steel can be utilized in wells that the temperatures ranging from 250 °C to 350 °C and H2S partial pressures up to 0.17 MPa. This aligns with the global carbon-neutral agenda.

The output gear shaft of the main gearbox for polypropylene granulator main gearbox breaks during operation.Fracture reasons of the output gear shaft are investigated through fracture analysis, physical and chemical inspection, and strength check. The results show that the output gear shaft has early fretting tear, due to instantaneous impact caused by fracture of the corresponding screw shaft. Under the compound alternating load of the torque and the bending moment, the early crack initiates and propagates along the journal. When the effective bearing area of the output gear shaft reduces to the critical point that it cannot withstand the torsional torque generated by normal operation, the fracture of the output gear shaft occurs. It is easy to form stress concentration at the cutter back groove of the output gear shaft journal, which is also one of the cracking inducement.

The connecting bolt of a blowout preventer oil circuit filter SCM435 broke during use, causing the filter to fail to work normally. In order to find out the failure causes of connecting bolts, the microstructure, chemical composition, hardness, mechanical properties and fracture morphology of fractured and unfractured bolts were studied by means of metallographic microscope, tensile testing machine, impact testing machine, microhardness tester, scanning electron microscope and energy dispersive spectrometer. The results show that the microstructure of fractured and unbroken bolts are tempered cordite and ferrite, the fractured bolts have more inclusions, high carbon content, and the hardness and mechanical properties of the fractured bolts are lower than those of unbroken bolts. The fracture bolt fracture is in the two sections of parallel and oblique 45° angle, manifested as a mixed fracture form of ductile fracture and brittle fracture, the fracture source originates from the inside. It can be seen that the fracture bolt is due to the uneven distribution of brittle phases such as internal carbides. Under the action of continuous external force, the crack source is preferentially formed, and the bolt finally breaks with the expansion of the crack. [ABSTRACT FROM AUTHOR]

Copyright of Automobile Technology & Material is the property of Automobile Technology & Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the merits of low carbon emission and energy consumption, cement bitumen emulsion mixture (CBEM) is more and more preferred in the construction and rehabilitation of pavement engineering. However, CBEM has a high risk of cracking damage due to the inappropriate addition of cement. To deeply know and then reasonably design the cracking resistance of CBEM, the fracture behaviour of CBEM is studied by a semi-circular bending test, and the global displacement and strain of the specimen during the whole loading process are measured through digital image correlation (DIC). The results indicate that the three fracture stages of CBEM (i.e. crack initiation, crack propagation and failure) can be accurately identified by DIC data. The maximum value of the mean global horizontal strain, representing that the specimen affords the maximum tension energy, is proposed to identify the fracture failure point for the accurate calculation of fracture parameters. The fracture energy, J integral and fracture toughness of CBEM increase and then decrease with the increasing cement dosage. To obtain a good comprehensive fracture behaviour for CBEM, it is recommended that cement dosage can be between 2% and 3%, and the optimum cement dosage is 2.6%. [ABSTRACT FROM AUTHOR]

Abstract With the development of the rail transit industry, more attention has been paid to the passive safety of rail vehicles. Structural damage is one of the main failure behaviors in a rail vehicle collision, but it has been paid little attention to in past research. In this paper, the quasi-static fracture experiments of SUS301L-MT under different stress states were carried out. The mechanical fracture properties of this material were studied, and the corresponding finite element simulation accuracy was improved to guide the design of vehicle crashworthiness. Through the tests, the fracture behavior of materials with wide stress triaxiality was obtained, and each specimen's fracture locations and fracture strains were determined. Parameters of a generalized incremental stress state dependent damage model (GISSMO) of the material were calibrated, and the model's accuracy was verified with test results from a 45° shear specimen. The GISSMO failure model accurately reflected the fracture characteristics of the material. The mesh dependency of this model was modified and discussed. The results show that the simulation agrees well with experimental data for the force-displacement curve after correction, but the strain distribution needs to be further studied and improved.

Semiflexible pavement (SFP) is gradually gaining more attention for its excellent rutting resistance and high load-bearing capacity. However, cracking damage is one of the most challenging distresses in SFP due to the brittle behavior of cement paste (CP) and insufficient adhesion between porous asphalt matrix (PAM) and hardened CP. In this study, the cement asphalt emulsion paste (CAEP) was introduced as a grouting material for SFP to overcome the shortcomings of CP. Therefore, the effect of CAEP on the cracking resistance of the SFP was studied by conducting a semicircular bending test and obtaining the full-field displacement and strain of the specimen during the whole loading process through digital image correlation (DIC). The maximum average value of full-field tensile strain was proposed to accurately determine the specimens' fracture failure point for calculating fracture parameters. Results indicated that DIC data could identify the three fracture phases of SFP materials (i.e., crack initiation, crack propagation, and failure) precisely. In addition, incorporating the asphalt emulsion in the cement grout significantly improved the SFP material's fracture performance by increasing the fracture energy, J-integral (Jc), and cracking resistance index (CRI) values on average by 48%, 76.1%, and 43% in SFP with CAEP20 and by 13.4%, 45.7%, and 87% in SFP with CAEP40, respectively. Overall, CAEP with an asphalt emulsion content between 20% and 40% by weight of cement is recommended as the best grout in SFP to obtain the best cracking resistance. [ABSTRACT FROM AUTHOR]

In order to study the effect of different surface crack parameters on the fracture failure of steel plate, the model was established by FEM. The results showed that the edge surface crack has the greatest influence on the fracture failure of the steel plate, and for non-edge surface cracks, the central surface crack has the greatest influence on the fracture failure of the steel plate. The larger the a/t and the smaller the a/c, the easier the steel plate fracture failure occurs. The a/c has a certain influence on the variation law of K and the position where Kmax appears. [ABSTRACT FROM AUTHOR]

Fracture failure of super 13Cr can occur in complex and harsh environments such as high temperature, high pressure, and corrosive gas wells, which damages the economic benefit of oil and gas development and also poses a great threat to wellbore integrity. Therefore, it is urgent to study the corrosion mechanism of super 13Cr tubing in oil and gas wells, and this study performed an on-site experimental analysis on failed super 13Cr tubing, employing the microarea electrochemical scanning Kelvin probe (SKP) method to investigate the causes of corrosion of super 13Cr material. In addition, the thermodynamics of the mechanism by which pits turn into cracks was examined in light of the experimental findings on the nucleation and development of pitting corrosion. The findings reveal scale and clear pits on the surface of the failed super 13Cr tubing and that CaCO3 as well as FeCO3 are the scale's primary constituents. According to the SKP scan results, the super 13Cr tubing has a risk of pitting under wells, and the galvanic cell with microcorrosion is the primary cause of pitting corrosion, which also shows that the potential difference between the anode area and the cathode area of the super 13Cr material gradually increases with the increase in immersion time. Under the autocatalytic effect of the occlusive corrosion cell and the applied load, the corrosion pits and cracks of super 13Cr tubing propagate, eventually leading to tubing breaks and failure. [ABSTRACT FROM AUTHOR]

With the development of the rail transit industry, more attention has been paid to the passive safety of rail vehicles. Structural damage is one of the main failure behaviors in a rail vehicle collision, but it has been paid little attention to in past research. In this paper, the quasi-static fracture experiments of SUS301L-MT under different stress states were carried out. The mechanical fracture properties of this material were studied, and the corresponding finite element simulation accuracy was improved to guide the design of vehicle crashworthiness. Through the tests, the fracture behavior of materials with wide stress triaxiality was obtained, and each specimen's fracture locations and fracture strains were determined. Parameters of a generalized incremental stress state dependent damage model (GISSMO) of the material were calibrated, and the model's accuracy was verified with test results from a 45° shear specimen. The GISSMO failure model accurately reflected the fracture characteristics of the material. The mesh dependency of this model was modified and discussed. The results show that the simulation agrees well with experimental data for the force-displacement curve after correction, but the strain distribution needs to be further studied and improved. [ABSTRACT FROM AUTHOR]

The dynamic mechanical properties and the damage prediction are critical for 3003 aluminum alloy during its safety application on lightweight automobile. Dynamic tensile properties at strain rate from 1 to 500 s−1 were analyzed, and the damage behavior was simulated by using the GISSMO model based on original and modified Johnson–Cook (JC) constitutive equation. The experimental results demonstrated that 3003 alloy exhibited significant strain rate sensitivity in the yield strength and fracture prolongation. JC model was modified based on the GISSMO damage parameter. A damage behavior of 3003 aluminum alloy was predicted accurately by using the modified JC equation. The reliability of the modified JC model was verified by using the cupping experiment and the simulation. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage. [ABSTRACT FROM AUTHOR]

The cracking of bitumen pavement in seasonal frozen areas has direct and significant influences on its properties. In order to study the compressive and tensile fracture failure features of basalt fiber-reinforced asphalt mix after freeze–thaw (F-T) treatment, the load–displacement curves under the compression and tensile modes of asphalt mixture after F-T conditions were tested. As a real-time detection means, acoustic emission (AE) was used for testing asphalt mix under compression and tensile load modes. X-ray computed tomography (CT) was employed to represent and evaluate the interior void in F-T conditions. The results showed that, as F-T conditions continue, the compressive and tensile strength of the specimens at different temperatures decreases. The amplitude and count of AE signals with the time history of load level show different characteristics of change in various intervals. AE signal indirect parameters reveal that under compressive and tensile load modes there is a gradual deterioration of performance for asphalt mix due to the coupling interactions between tensile and shear cracks. The asphalt mixtures have different behavior in F-T conditions, which are attributable to interior meso-void characteristics based on CT analysis. This study is limited to the type and loading mode of asphalt mixture in order to quantitatively predict the performance of asphalt mixture. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wax deposition reduces the transportation capacity of oil pipelines and brings major safety hazards to oil production. Heating crude oil with a coil type heater can prevent wax deposition. To study the failure mechanism of the connection between the coil pipe and the gathering pipe and then find optimization methods, the microstructures of the welded joint are observed by scanning electron microscopy, and the mechanical properties of the materials are tested. A mechanical model of the interaction between crude oil and coil pipe is constructed for simulation calculations. The relations between mechanical properties and structural parameters are obtained, and the influence of inclination angle of coil pipe on heat transfer performance is found opposite to that on static performance. Based on the comprehensive analysis of heat transfer rate and stress-strain of multi groups of coil pipes, the methods to optimize the overall performance of the coil heater from the aspects of material, structure and processing technology are proposed. The maximum equivalent (von-Mises) stress and shear stress of bell end coil pipe are reduced by 14.81% and 3.22% respectively, and the heat transfer rate is increased by 7.36 kW compared with that of the original structure under the same working condition.

• A thermodynamic strength model considering elastic and plastic behavior of single fiber is established. • Single fiber and fiber bundle experiments are designed and carried out. • All experimental data points of fiber bundle are within the range predicted by theoretical model. • Key parameters which regulate mechanical behavior of single fiber are investigated theoretically. In order to analyze the mechanical behavior of plastic fiber bundle, a theoretical model considering elastic and plastic behavior of single fiber is established. Based on uniaxial tensile tests of polythene single fiber, elastoplastic mechanical properties, such as elastic modulus and plastic modulus, are obtained. Moreover, distributions of yield strength and breaking strength of single fiber are determined. The stress–strain curve of polythene fiber bundle is predicted by theoretical model. The correctness of this theoretical model is verified by uniaxial tensile test of polythene fiber bundle. All experimental data points are within the range predicted by theoretical model. Some key parameters which regulate mechanical behavior of single fiber are investigated theoretically. Results show that Weibull parameters of yield strength and breaking strength of single fiber have great effect on mechanical performance of fiber bundle. The concentration of distribution area of breaking strength can improve the overall fracture strength of fiber bundle. Results and conclusions in this investigation can extend and perfect fiber bundle model in terms of plastic behavior. [ABSTRACT FROM AUTHOR]

• Perform a failure analysis of the traction transformer oil pump flange. • Use a combination of physical, chemical, and finite element analysis. • The flange failure is characterized by overload fracture. A flange fracture occurred during the installation of a traction transformer oil pump. The causes of the flange fracture were analyzed using physical, chemical, and finite element methods. The fracture surface shows expanded edges and a linear fracture source, indicating an overload fracture. No significant defects such as pinholes, looseness, or cracks were found in the internal structure, which contains elongated Si phases. The Si, Ti, and Zn content in the failure part does not meet standard specifications. The hardness of the failure part is HBW107.8, meeting standards, but the elongation at break is at the lower limit, suggesting higher material brittleness. Finite element analysis revealed a maximum tensile stress of 241.5 MPa on the flange, close to the yield strength, indicating a small safety margin. The flange fracture is related to high material brittleness and potential assembly anomalies. To prevent similar incidents, strict control of raw material quality, regular inspection of mechanical properties, and finite element analysis for structural optimization are necessary. [ABSTRACT FROM AUTHOR]

• Tensile deformation of lamellar γ-TiAl alloy is investigated by MD simulation. • PT interface has stronger release of strain energy to retard crack extension. • RB interface retard and resist crack extension by blunting crack tip. • Temperature suppresses dislocation propagation while strain rate is opposite. • FCC-to-BCC phase transition occurs at high strain rate and low temperature during the incipient plasticity. Crystalline interface plays a significant role in strengthening lamellar γ-TiAl alloys through reconciling the strength and ductility. Herein, the effects of temperature and strain rate on the tensile deformation of three lamellar γ-TiAl interface models are investigated by molecular dynamics simulations. The three interfaces, pseudo twin (PT), rotational boundary (RB), and true twin (TT), exhibit different tensile responses due to the different interface effects: TT interface only acts as a barrier of dislocation traversing to facilitate crack extension; PT interface acts as both dislocation barrier and emission source and has a stronger release of strain energy than TT interface, retarding the crack extension; RB interface can retard and resist crack extension due to the blunting and deflection of the crack tip and the best interface geometry compatibility. The defect evolution indicates that the elevated temperature suppresses dislocation propagation at low strain rate, while the high strain rate causes small lamellar stacking faults and slit-shaped holes along tensile direction at low temperature. In addition, the dual conditions of high strain rate and low temperature induce the phase transition from FCC to BCC and then BCC to HCP. These findings provide a specific insight to understand the atomistic mechanism of interface-mediated deformation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the problem of the frequent hub axle breakage of passenger vehicle hub axle at the end customer’s use, the fracture causes of hub axle was analyzed and investigated, and the hub axle loading capability under different heat treatment process conditions was further studied. First, the cause of the fracture of the existing passenger vehicle hub axle was systematically analyzed, the fracture mode was evaluated, and the optimization direction was proposed. Then trial production and performance measurement of the hub axle samples under four type heat treatment conditions were carried out. Finally the static pressure, impact, stiffness, fatigue strength comparative test and analysis of the hub axle loading capacity under four type heat treatment conditions were carried out. The study results show that: compared with the hub axle whose surface is quenched and tempered, static load bearing capacity of the hub axle without surface quenching and tempering is increased by 60%, and impact resistance is increased by at least 26%, and dispersion of fatigue strength life is decreased, at the same time, the technical requirement of no plastic deformation under 1.2 G load conditions can be meet. After the process improvement is carried out, the fracture safety accident is completely eliminated in practical applications. [ABSTRACT FROM AUTHOR]

Based on the inclusion theory, the calculation formula of additional water pressure caused by the change of external stress state of fracture water in rock mass is deduced, and its rationality and correctness are verified by numerical experiments. Then, using the rock fracture process analysis system RFPA2D-flow and considering the influence of additional water pressure, the failure process of rock mass with multiple (2, 3, and 4 fractures) parallel fractures (dip angles of 0°, 30°, 45°, 60°, and 90°) under the coupling action of stress and seepage is numerically simulated, and the conclusions are as follows: (1) When the number of fractures is small (2 and 3 fractures), for fractured rock mass with fracture dip angles of 30°, 45°, and 60°, fracture failure finally occurs along its internal fractures. Each fracture is independent of each other, and the wing fractures formed are also parallel to each other. When the fracture dip angle is 0°, the additional water pressure has the least effect on the fracture strength of fractured rock mass, and finally the overall shear failure occurs. When the fracture dip angle is 90°, the additional water pressure has the greatest influence on the fracture strength of rock mass, and the specimen finally forms tension and shear failure. For the peak strength, the rock mass with 0° and 90° fractures is significantly higher than that with 30°, 45°, and 60° fractures, and the rock mass with 45° fracture dip angle is the lowest. In addition, with the same dip angle, the rock mass strength decreases slightly with the increase of the number of fractures. (2) When there are a large number of fractures (4 fractures), for fractured rock mass with fracture dip angles of 30°, 45°, and 60°, due to the reduction of fracture spacing, the strength of rock bridge decreases, and each fracture connects with each other, resulting in fracture failure. When the fracture dip angle is 0° and 90°, the whole shear failure of fractured rock mass occurs. With the increase of the number of fractures, the damage degree of rock mass gradually increases, the range is larger and larger, and the strength decreases rapidly. (3) When the fracture dip angle is the same, the additional water pressure in the fracture decreases gradually with the increase of the number of fractures in the rock mass. [ABSTRACT FROM AUTHOR]

Arterial tissue delamination, manifested as the fracture failure between arterial layers, is an important process of the atherosclerotic plaque rupture, leading to potential life-threatening clinical consequences. Numerous models have been used to characterize the arterial tissue delamination fracture failure. However, only a few have investigated the effect of cohesive zone model (CZM) shapes on predicting the delamination behavior of the arterial wall. In this study, four types of CZMs (triangular, trapezoidal, linear–exponential, and exponential–linear) were investigated to compare their prediction of the arterial wall fracture failure. The Holzapfel–Gasser–Ogden (HGO) model was adopted for modeling the mechanical behavior of the aortic bulk material. The CZMs optimized during the comparison of the aortic media delamination simulations were also used to perform the comparative study of the mouse plaque delamination and human fibrous cap delamination. The results show that: (1) the numerical predicted the relationships of force–displacement in the delamination behaviors based on the triangular, trapezoidal, linear–exponential, and exponential–linear CZMs match well with the experimental measurements. (2) The traction–separation relationship results simulated by the four types of CZMs could react well as the corresponding CZM shapes. (3) The predicted load–load point displacement curves using the triangular and exponential–linear CZMs are in good agreement with the experimental data, relative to the other two shapes of CZMs. All these provide a new method combined with the factor of shape in the cohesive models to simulate the crack propagation behaviors and can capture the arterial tissue failure response well.

Fracture failure of super 13Cr can occur in complex and harsh environments such as high temperature, high pressure, and corrosive gas wells, which damages the economic benefit of oil and gas development and also poses a great threat to wellbore integrity. Therefore, it is urgent to study the corrosion mechanism of super 13Cr tubing in oil and gas wells, and this study performed an on-site experimental analysis on failed super 13Cr tubing, employing the microarea electrochemical scanning Kelvin probe (SKP) method to investigate the causes of corrosion of super 13Cr material. In addition, the thermodynamics of the mechanism by which pits turn into cracks was examined in light of the experimental findings on the nucleation and development of pitting corrosion. The findings reveal scale and clear pits on the surface of the failed super 13Cr tubing and that CaCO3 as well as FeCO3 are the scale’s primary constituents. According to the SKP scan results, the super 13Cr tubing has a risk of pitting under wells, and the galvanic cell with microcorrosion is the primary cause of pitting corrosion, which also shows that the potential difference between the anode area and the cathode area of the super 13Cr material gradually increases with the increase in immersion time. Under the autocatalytic effect of the occlusive corrosion cell and the applied load, the corrosion pits and cracks of super 13Cr tubing propagate, eventually leading to tubing breaks and failure.

In this study, 35VB high-strength bolts used in subtropical, humid climate were tested to determine the causes of fracture failure. Simulated working conditions of a stress corrosion experiment were carried out on bolt #S1. The fracture macromorphology, micromorphology, and phase composition of corrosion products of failed bolt #D1 and simulated stress corrosion bolt #S1, the metallographic structure of the new bolts #N1, #D1, and #S1, and the mechanical properties of #N1 and #S1 were compared and analyzed. It was concluded that the microstructure of #D1 was defective and there were cracks in the crack source region and the crack propagation region. Stress loading and environmental corrosion led to the occurrence of fracture synergistically. It was speculated that the coupling of the environment with stress produced little damage to the bolt in the stress corrosion test, but the environment and stress accelerated the impact on fracture failure. [ABSTRACT FROM AUTHOR]

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage.

This paper investigates the effect of wet-blasting pressure on the surface integrity and tool cutting performance of hybrid CVD-TiN/TiCN/α-Al 2 O 3 /TiN coated tools. The hybrid TiN/MT-TiCN/α-Al 2 O 3 /TiN multilayer coating was deposited on the surface of the cemented carbide inserts by chemical vapor deposition (CVD) technique. Then the coated inserts were subjected to wet-blasting by aluminum oxide with varying pressure. The coatings were characterized by scanning electron microscopy, white light surface profiler, and X-ray residual stress diffractometer. The results indicate that the average residual tensile stress of the α-Al 2 O 3 layer on the rake face of CVD-coated inserts gradually decreased with the increase of wet-blasting pressure. When the wet-blasting pressure reached 0.24 MPa, the residual tensile stress was transformed into compressive stress. It was accompanied by increased cutting edge roughness and cutting edge radius, reduced cutting edge coating thickness, and a change in rake face surface roughness. To understand the effect of the surface integrity change on the cutting performance of CVD-coated inserts, a case study designed for AISI 4340 steel machining under continuous and intermittent cutting conditions is performed. When the Al 2 O 3 layer on the cutting edge is not peeled off by wet-blasting, the change of residual stress from tensile to compressive in the rake face of CVD-coated inserts can effectively improve the fracture failure resistance of inserts in continuous and intermittent cutting processes. When the Al 2 O 3 layer on the cutting edge is peeled off by wet-blasting, the fracture failure resistance during intermittent cutting will be significantly reduced. • The roughness on the cutting edge rises with the increase in blasting pressure. • Fracture failure is improved as the residual compressive stress is obtained. • The peeling of the Al2O3 layer doesn't worsen the continuous turning performance. • The peeling of the Al2O3 layer exerts a negative impact on the intermittent cutting. [ABSTRACT FROM AUTHOR]

The fracture failure of flawed coal has always been a problem in underground engineering. Therefore, it is necessary to monitor crack propagation and damage evolution during coal fracture. In this study, the split Hopkinson pressure bar (SHPB) and digital image correlation (DIC) were combined to analyze the impact failure electric potential (EP) of flawed coal samples. The multi-dimensional joint response characteristics of coal EP time–frequency-field under dynamic load were studied and the differential expression and multi-fractal characteristics of EP responses at different measuring points were analyzed. Based on the EP signals, the evolution of damage to the coal was calculated. The results show that the time series evolution of EP and stress–strain curves during coal failure is consistent. The generation of fracture zones will excite the high-value area of local EP, and the spectral distribution of EP signals in this area shows the characteristics of low frequency and high amplitude. Each channel's EP signal and the degree of deformation at the corresponding place are perfectly matched. The multi-fractal spectrum of the EP signal close to the fracture zone has a higher Δ α and a lower Δ f , which demonstrates the dominance of the large-scale EP signal produced in this region by the destruction of sample. Theoretical study indicates that the main causes of the anomalous distribution of the EP field are crack tip potential, diffusion potential, etc. The results can provide theoretical basis for the evaluation of coal fracturing by EP technology. [ABSTRACT FROM AUTHOR]

• Size and age effects on fracture parameters of dam gallery concrete are studied simultaneously. • Size-independent double-K fracture parameters and scale parameters are extrapolated from test results. • Equations for predicting the concrete fracture failure of any age and size are established based on Boundary Effect Model. • Double-K fracture parameters of dam gallery concrete specimens of any age and size are solved by Fracture Extreme Theory. Cracking-associated problems may occur in the construction and operation periods of dam galleries, necessitating attention to the fracture characteristics of gallery concrete. The fracture parameters of concrete exhibit size effects and also change with age. A correct evaluation of the cracking risk or crack stability of gallery structures at any given time requires a comprehensive understanding of both the size effect and time-variant characteristics of the gallery concrete fracture parameters. In the present study, 75 wedge-splitting specimens, with effective heights ranging from 200 mm to 600 mm, were cast using gallery concrete produced by the concrete mixing system at the Baihetan Dam construction site. Subsequently, fracture tests were conducted on these specimens at curing ages spanning from 7 days to 90 days. According to the test results, the fracture parameters of concrete with a specific size exhibited an increasing trend with age within 90 days, while the fracture parameters of concrete at specific ages show a significant size effect, tending to stabilize as the effective depth of specimens gradually increases. The boundary effect model was utilized for analyzing the fracture test results of concrete specimens at different ages, yielding the size-independent double-K fracture parameters and scale parameters for concrete at each age, along with their time-varying patterns. Subsequently, equations for predicting the failure loads of concrete specimens of any age and size were established. Based on the prediction results of failure loads, the double-K fracture parameters of concrete specimens of any age and size were solved by the fracture extreme theory. The predicted failure loads and fracture parameters were in good agreement with the experimental results. The findings of this study can be applied to the full lifecycle crack risk analysis or crack stability assessment of Baihetan Dam gallery structures. [ABSTRACT FROM AUTHOR]

In the long-term overheating operation condition, the boiler high temperature superheater is easy to cause the deterioration of materials and the decline of material structure and performance, and causes the pipe explosion accident. The causes of burst tube of final-stage superheater tube in a power plant boiler were analysed through macroscopic examination, Brinell hardness test, tensile strength test and metallographic structure test. The analysis results show that final-stage superheater tube operates at high temperature and pressure for a long time, resulting in the carbide enrichment at grain boundary and weaken the grain boundary strength. Under the action of tensile stress, creep cavities and creep cracks occur at grain boundary, resulting in the decrease of durable strength and tensile strength of pearlite heat-resistant steel, and finally the fracture failure occurs.

The cracking of bitumen pavement in seasonal frozen areas has direct and significant influences on its properties. In order to study the compressive and tensile fracture failure features of basalt fiber-reinforced asphalt mix after freeze–thaw (F-T) treatment, the load–displacement curves under the compression and tensile modes of asphalt mixture after F-T conditions were tested. As a real-time detection means, acoustic emission (AE) was used for testing asphalt mix under compression and tensile load modes. X-ray computed tomography (CT) was employed to represent and evaluate the interior void in F-T conditions. The results showed that, as F-T conditions continue, the compressive and tensile strength of the specimens at different temperatures decreases. The amplitude and count of AE signals with the time history of load level show different characteristics of change in various intervals. AE signal indirect parameters reveal that under compressive and tensile load modes there is a gradual deterioration of performance for asphalt mix due to the coupling interactions between tensile and shear cracks. The asphalt mixtures have different behavior in F-T conditions, which are attributable to interior meso-void characteristics based on CT analysis. This study is limited to the type and loading mode of asphalt mixture in order to quantitatively predict the performance of asphalt mixture.

Aiming at the problem of the diaphragm coupling is affected by snap loads which lead to diaphragm fatigue broken and fracture failure， the structural and dynamic performance of the redundant diaphragm coupling are carried out. The overall structure of the redundant diaphragm coupling is designed， and the finite element analysis model of diaphragm disk is established， the optimum thickness of the diaphragm meets the design requirement is obtained by calculating. Then， the safety factor of the redundant structure is verified based on the strength analysis of redundant structure of diaphragm coupling， and the transmission of the torque can be realized. Finally， the frequency response curve is obtained based on the dynamic performance research of the diaphragm coupling. The results can provide the effective basis for the analysis of mechanical transmission devices in this field.

Featured Application: It is an important trend that Pb-free materials in electronic devices/components are used in the aerospace field. Several reliability issues associated with this kind of material characteristic occurred and need in-depth studies. One of the issues is that Sn-rich material's characteristic changes under low-temperature. This change may cause components/device failure and has an influence on their reliability. This work of failure analysis provides an actual case of electronic components with failure when under harsh environments, such as extreme cryogenic temperature in space. It makes reliable use of Pb-free material under extremely cryogenic temperature conditions to be taken seriously, brings up an analysis process for this kind of failure, and suggestions for operating temperatures are put forward. To verify the reliability of a typical Pb-free circuit board applied for space exploration, five circuits were put into low temperature and shock test. However, after the test, memories on all five circuits were out of function. To investigate the cause of the failure, a series of methods for failure analysis was carried out, including X-ray detection, cross-section analysis, Scanning Electron Microscope (SEM) analysis, and contrast test. Through failure analysis, the failure was located in the Pb-free (Sn-3.0Ag-0.5Cu) solder joint, and we confirmed that the failure occurred because of the low temperature and change of fracture characteristic of Sn-3.0Ag-0.5Cu (SAC305). A verification test was conducted to verify the failure mechanism. Through analyzing data and fracture surface morphology, the cause of failure was ascertained. At low temperature, the fracture characteristic of SAC305 changed from ductileness to brittleness. The crack occurred at solder joints because of stress loaded by shock test. When the crack reached a specific length, the failure occurred. The temperature of the material's characteristic change was −70–−80 °C. It could be a reference for Pb-free circuit board use in a space environment. [ABSTRACT FROM AUTHOR]

Sleeve plate of clutch disk is studied in this paper,according to the fracture problems of sleeve plate by carbonitriding and phosphating treatment,the fractured sleeve plate was analyzed by means of fracture macroscopic analysis,fracture microscopic analysis,metallographic analysis,hardness testing and chemical composition analysis of material. The results show that the fracture of sleeve plate occurs before surface phosphating treatment,crack starts at left part of round window for sleeve plate,and it extends to run through the fracture in the process of production. In addition,due to cylindrical section is smaller and the surface area adopts hardening treatment,when the surface area is subjected to abnormal impact,it is very easy to cause the cracking of sleeve plate,especially the coarse structure leads to the increase of brittleness and it increases the probability of cracking of the parts.