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Based on the two-arc profile assumption, the expansion deformation and energy absorption of circular tubes compressed by conical-cylindrical dies were reconsidered. First, the deformation of the two arcs was analyzed independently and an improved model denoted as Model-I was established. Then, by further involving the coupling between the bending moment and membrane forces, a more elaborate model, i.e., Model-II was developed. Afterwards, experiments and simulations were conducted to verify the models, which show that, compared with previous theoretical models, Model-II could not only capture the prominent features of the deformation, but also improve the prediction accuracy of the steady driving force significantly. By means of this model, it was found that the critical semi-conical angle, which makes the driving force minimum, increases with the increase of the friction coefficient, expansion ratio as well as the radius/thickness ratio of the tube. And, the energy dissipation due to stretching is always greater than that of bending, while the friction dissipation can account for the largest proportion at small semi-conical angle or large friction coefficient. At a certain friction and die conditions, the specific energy absorption of expanded tubes can be much higher than that under progressive collapse mode.

The 3D visualization of the porosity in high-pressure die casting (HPDC) Mg alloys AZ91D and Mg4Ce2Al0.5Mn (EA42) was investigated by X-ray computed tomography. It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location. This difference resulted from the low valid time during intensified casting pressure conditions. Specimens of alloy EA42 exhibited a narrow pore distribution in the side view (∼0.5 mm) compared to the wide distribution (∼1.8 mm) of alloy AZ91D, which was mainly attributed to the formation mechanism of the defect band. The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3 phase segregated in the defect band during solidification. Additionally, an effective estimator (Z-Propagation) was introduced, which is proposed to predict the projected area fraction of the porosity (f) involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface. By coupling the Z-Propagation method with the critical local strain model, the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03% and 1.65% of the absolute value of the average relative error (AARE), respectively.

In underground rock engineering, water-bearing faults may be subjected to dynamic loading, resulting in the coupling of hydraulic and dynamic hazards. Understanding the interaction mechanism between the stress waves induced by dynamic loadings and liquid-filled rock joints is therefore crucial. In this study, an auxiliary device for simulating the liquid-filled layer was developed to analyze the dynamic response characteristics of liquid-filled rock joints in laboratory. Granite and polymethyl methacrylate (PMMA) specimens were chosen for testing, and high-amplitude shock waves induced by a split Hopkinson pressure bar (SHPB) were used to produce dynamic loadings. Impact loading tests were conducted on liquid-filled rock joints with different joint inclinations. The energy propagation coefficient and peak liquid pressure were proposed to investigate the energy propagation and attenuation of waves propagating across the joints, as well as the dynamic response characteristics of the liquid in the liquid-filled rock joints. For the inclination angle range considered herein, the experimental results showed that the energy propagation coefficient gently diminished with increasing joint inclination, and smaller coefficient values were obtained for granite specimens compared with PMMA specimens. The peak liquid pressure exhibited a gradually decreasing trend with increasing joint inclination, and the peak pressure for granite specimens was slightly higher than that for PMMA specimens. Overall, this paper may provide a considerably better method for studying liquid-filled rock joints at the laboratory scale, and serves as a guide for interpreting the underlying mechanisms for interactions between stress waves and liquid-filled rock joints.

s Feed-water valves (FWVs) are used to regulate the flow rate of water entering steam generators, which are very important devices in nuclear power plants. Due to the working environment of relatively high pressure and temperature, there is strength failure problem of valve body in some cases. Based on the thermo-fluid-solid coupling model, the valve body stress of the feed-water valve in the opening process is investigated. The flow field characteristics inside the valve and temperature change of the valve body with time are studied. The stress analysis of the valve body is carried out considering mechanical stress and thermal stress comprehensively. The results show that the area with relatively high-velocity area moves gradually from the bottom of the cross section to the top of the cross section with the increase of the opening degree. The whole valve body reaches the same temperature of 250 °C at the time of 1894 s. The maximum stress of the valve body meets the design requirements by stress assessment. This work can be referred for the design of FWVs and other similar valves.

Cu(I) catalysts were studied for the synthesis of a propargylamine via A3-coupling of aldehyde, amine, and alkyne, under solvent-free and low loading conditions, using batch microwave or flow thermal heating. We explored ultra-low loading conditions with Cu(I) salts as fast and active catalysts featuring turnover frequencies (TOFs) above 105 h−1. Well-defined octahedral and cubic Cu2O microcrystals were also successfully applied and compared with this reaction. Both types of microcrystals exhibited excellent catalytic activities within minutes, via in situ generation of low dose of Cu(I) ions within the reaction medium, to achieve TON beyond 2000 and recycling up to 10 times in a flow reactor. The study of the catalytic system demonstrated that the activity was surface-structure dependent and allowed for the design of low Cu contamination A3-coupling systems, affording a product at the decigram scale, with Cu contamination below FDA recommendations for drug synthesis, without the need for a purification procedure.

A floating air weapon system (such as airborne floating mines) plays an important role in modern air defense operations. This paper focuses on aerodynamic characteristics of airborne floating mine named inflated pillow. Firstly, the dynamic deployable process of the pillow and characteristics of the local instability of the edge are studied, and the evolution mechanism of wrinkles and kinks is analyzed. Secondly, in the cruising stage, the fluid-structural-thermal coupling analysis is performed on the pillow, and the aerodynamic characteristics are studied. Thirdly, the shape-preserving effect of the inflated pillow during the “negative pressure” slow landing stage is evaluated. It is found that when the wind velocity is higher, the pillow has a collapsed instability (surface extrusion and contact), and when the wind velocity is lower, snap-through instability occurs. Finally, for the collapsed instability, a carbon fiber skeleton is added to discrete the large global collapsed fold into small local folds, thus achieving shape-preserving effect of pillow. For snap-through instability, the critical internal pressure and different shape evolution under different wind velocity are evaluated. Through the analysis of the mechanical mechanism and control of the structural morphological evolution, it provides theoretical guidance for the application of the curved shell structure in floating air weapon system.

Natural gas hydrate (NGH) reservoirs consist of the types of sediments with weak cementation, low strength, high plasticity, and high creep. Based on the kinetics and thermodynamic characteristics of NGH decomposition, herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term drilling. The results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range, thus aggravating the plastic strain accumulation around the wellbore. Furthermore, the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress, as a result, the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ stress. The lower the pore pressure, the greater the stress concentration effects and the higher the plastic strain at the wellbore. Moreover, the lower the initial NGH saturation, the greater the initial plastic strain and yield range and the higher the equivalent creep stress. The plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.

Manufacture of a transition hybrid coupling from two different steels, medium carbon S355J2 and stainless 316L, has been demonstrated using two different solid-state joining routes, forge welding (FW) and rotary friction welding (RFW). An additional manufacturing route, electron beam welding (EBW), was also employed in investigating its feasibility for such application. Mechanical and microstructure properties of the final components manufactured from the three different routes have been compared. Finite element (FE) analysis was utilised to determine optimal geometries for the FW and the RFW preform rings and identify optimal parameters for both processes. Of the three manufacture routes, the FW produced an instant diffusion-like bond with a single forging stroke on a 2100T screw press with the thinnest weld interface and most uniform hardness distribution at either side of the joint. The RFW part, manufactured on a 125T RFW machine, also exhibited a very thin weld interface, yet slightly thicker compared to the FW case, with small variations in the hardness distribution at either side. The EBW produced markedly thicker weld interface compared to the two solid-state routes. The EBW part exhibited significant variation in hardness distribution across the weld exhibiting peak hardness in the weld indicating requirements for a post-weld heat treatment (PWHT). Both the FW and the RFW process routes exhibited very uniform micro-hardness and microstructures across the weld interface in contrast with the EBW process in as-manufactured condition.

A theoretical model is developed to investigate the influence of external mean flow on sound transmission loss (STL) through composite sandwich panels filled with porous materials. The equations of the motions for the composite laminate plates are established by adopting the first-order shear deformation theory. The porous materials in between the sandwich structures are characterized by an equivalent fluid model. Employing the fluid-structure coupling condition, the displacement continuity at fluid-structure interfaces is guaranteed. To validate the proposed theoretical model, a comparison among the present theoretical predictions, the existing theoretical and experimental results are executed, with overall agreements achieved. A systematical investigation is carried out to explore the influences of the external mean flow, incidence angle and laminate scheme on the coincidence frequency and sound transmission loss of the sandwich structures. This work provides a helpful guideline for the vibroacoustic design of composite sandwich structures.

The high reliability and extended life of seawater hydraulic components is dependent on the tribological properties of key friction pairs, more and more attention has been given to the performance degradation and lifetime of the friction pairs. In this paper, the wear process of Tungsten carbide (WC) with 6%wt of Ni (WC–6Ni)/SiC friction pair is studied through the tribological test under seawater lubrication. Considering the random effects and the complex wear mechanism of WC-6Ni/SiC, an efficient Inverse Gaussian (IG) process supported lifetime prediction model is established by coupling the multiple stresses under seawater lubrication, and the parameters in the proposed IG process model are derived. Two actual cases are used to validate the proposed method. The prediction model and experimental results show the high accuracy in time-varying lifetime prediction of WC-6Ni/SiC, which is of great significance to the evaluation of friction pair and the maintenance for seawater hydraulic components.

The heating capacity of air source heat pump increases with the increase of ambient temperature, coupled with the heating demand decreases, resulting in a prolonged partial load operation. The partial load operation of low ambient temperature air source heat pumps applied in cold region is particularly serious. With that also comes an efficiency degradation, taking into consideration that the characterization method of current product standards is not uniform in different countries. In this paper, the mechanism of partial load efficiency degradation was analyzed firstly, the explicit relationship between cycling losses and cyclic time was derived, and a partial load factor characterization method of air source heat pump by coupling start-up loss and stand-by loss was proposed. Secondly, the cycling losses of 3 sets of low ambient temperature ASHPs with different configurations were tested under different ambient conditions by using the intermittent ON-OFF cycles tests method. The magnitude of start-up loss is 2.0%∼17.3% for test ASHPs, and the stand-by loss rises sharply from 4.2% to 8.9% for the test ASHPs as the PLR drops from 0.2 to 0.1. The accuracy of the PLF characterization method was verified, and especially that of the load rate below 0.2 was improved.

To investigate the degradation mechanism of static tensile mechanical behaviors of marble containing dynamic damage, multiple impact loading tests were performed on the disc marble samples, and then static Brazilian tests were conducted for the damaged samples. Besides, coupling modeling technology of finite difference method (FDM)—discrete element method (DEM) was used to carry out the numerical investigation. The results show that after multiple impacts, more white patches appear on the surface, and some microcracks, macro-fractures as well as pulverized grains are found by optical microscopic. The static tensile strength decreases with the increase of the dynamic damage variable characterized by the ultrasonic wave velocity of sample. The interaction between grains in the damaged sample becomes intense in the subsequent static loading process, causing a relatively large strain. The volume of the fragments falling off around the loading points becomes larger as impact number increases. As the dynamic damage increases, the absorbed energy of sample during the static loading first decreases and then tends to be stable. Both the stress concentration and the breakage of the force chains are the root causes of the degradation of the static tensile strength.

Grouting is a typical HM (hydro-mechanical) coupling process between slurry and rock and widely used in underground engineering to reinforce the strength of fractured rock mass. In present work, based on numerical manifold method (NMM), an NMM-HM grouting model is proposed to investigate slurry flowing and analyze grouting efficiency. In this NMM-HM grouting model, the slurry flows in fractures and grouting pressure can cause fracture aperture variation and fracture propagation. Then, two numerical examples for central embedded crack and hydraulic fracturing are adopted to validate the presented model. Furthermore, grouting simulations are conducted on a multi-crack and a roadway with fracture networks. Results show that Grouting pressure in fractures can increase fracture aperture, which is beneficial for grouting efficiency. However, fluid pressure could also cause closure of neighboring fractures or even fracture propagation and failure of rock mass, which will weaken grouting effectiveness. Therefore, the coupled HM impacts on grouting efficiency and grouting pressure should be seriously considered and optimized to achieve the expected grouting performance in practice.

Nozzle flowmeter is widely used in industry. In this paper, in order to study the influence of different flow rates and inner wall temperatures on the thermal effect and flow field of the nozzle flowmeter, the fluid-solid coupling numerical calculation of the thermal effect and flow field of nozzle flowmeter is carried out under four different flow rates and five different inner wall temperatures. It is found that, with the increase of flow rate, the heat transfer effect of the nozzle flowmeter is weakened under different inner wall temperatures. The pressure distribution in the fluid domain, the dynamic stress, and fluid-induced vibration deformation generated by the fluid of the nozzle flowmeter are less affected by inner wall temperatures.

In this article, the explicit finite difference method is used to solve the magnetic-thermal coupling phenomenon of velocity skin effect (VSE), and the skin effect phenomenon at different velocities is analyzed. In order to reduce the VSE between the armature and the rail, the skin effect phenomena of the layered rail with graphite coating, the layered armature with Ti Mo Al metal, and the combined structure of the layered rail and the layered armature were studied, respectively. The results show that with the increase of velocity, the VSE gradually appears in the armature and rail, and the layered rail can weaken the adverse effect of the VSE. Although the layered armature can weaken the VSE, the physical properties of Ti Mo metal will cause the local temperature of the armature tail to be too high. Through the combination with the layered rail, the high temperature of the armature tail caused by the layered armature can be significantly improved.

Acid fracturing is an important means of reservoir stimulation, whose purpose is to form an incompletely closed acid-etched fracture as the flow channel for oil and gas during production. The length and conductivity of acid-etched fractures can be used to evaluate acid fracturing and directly impact production. To study their influence on the stimulation effect and final production, an acid fracturing coupling model including a fracture propagation model coupled with reservoir flow and temperature field models is established for the first time in this study based on an embedded discrete fracture model (EDFM), which can realize the coupling of fracture propagation and reservoir flow and simplify the solution of fracture and reservoir temperatures. The simulation results of the acid fracturing coupling model are introduced into the productivity model, which is also based on the EDFM to analyze and evaluate well productivity. The results show that: (1) the EDFM can easily couple fracture propagation and reservoir flow and can be used to rapidly solve the temperature fields in the fracture and reservoir successfully for the first time. (2) Reservoir flow impacts the propagation of fractures by increasing or decreasing the leak-off velocity of the working fluid. (3) Temperature diffusion is much weaker than pressure diffusion during acid fracturing and is limited near the acid fracture. The reaction between the acid and rock increases the local temperature around the acid fracture, and may even exceed the initial formation temperature. (4) Raising the injection rate reasonably enhances H+ diffusion, increases the effective length of acid-etched fractures, enlarges the drainage area of oil and gas, and benefits long-term well production.

For the newly deposited soil, the consolidation will occur under the self-weight and external load jointly if the soil is treated by the stack pre-pressure method. The soil stress caused by self-weight has a significant influence on its consolidation process no matter the soil is either saturated or unsaturated. However, the soil’s self-weight is ignored in the one-dimensional (1D) consolidation theory for unsaturated soils (Fredlund and Hasan, 1979). In this paper, we derived the semi-analytical solutions for excess pressures and normalized settlement in 1D dimensional consolidation of unsaturated soils considering self-weight. The analytical solutions were obtained by Crump’s method (Crump, 1976), through a computing program coupling the calculation of initial excess pore pressures with the inverse Laplace transform of the obtained solutions. Then, the proposed solutions are verified through a degradation case. Several 2D charts are presented to visualize the solutions, and various examples are employed to discuss the key factors that affect one-dimensional consolidation behavior of unsaturated soils when self-weight is considered. It can be found that the relative excess pore pressure will be restrained for the one-dimensional consolidation when considering self-weight.

The couple of radiation with convection heating owned advantages of less energy utilization, healthier and more comfortable indoor environment. However, local thermal discomfort was often induced by large vertical temperature difference and radiation asymmetry temperature. This work studied indoor thermal environment characteristics under different coupling ways of radiation and convection heating terminals through experiments and CFD simulation. The studied five scenarios were denoted as: (I) lateral air supply + adjacent side wall radiation, (II) lateral air supply + opposite side wall radiation, (III) lateral air supply + floor radiation, (IV) lateral air supply + adjacent side wall radiation + floor radiation, and (V) lateral air supply + opposite side wall radiation + floor radiation. The overall thermal comfort indices (including air diffusion performance index (ADPI), predicted mean vote (PMV), and predicted percent of dissatisfaction (PPD)) and local thermal comfort indices under different scenarios were investigated. For Scenarios I-III, the local dissatisfaction rates caused by vertical air temperature difference were 0.4%, 0.1%, and 0.2%, respectively, which belonged to "A" class according to the ISO-7730 Standard. While the vertical asymmetric radiation temperature of Scenario I/II was about 6.5 °C lower than that of Scenario III/IV/V. The ADPI for Scenarios III-V were about respectively 5.7%, 16.7%, and 21.0% higher than that of Scenarios I-II, indicating that a large radiation area and radiation angle coefficient could reduce the discomfort caused by radiant temperature asymmetry. The coupling mode improved local discomfort by decreasing vertical temperature difference and radiation asymmetry temperature wherefore improving the PMV from -1.6 to -1. The lateral air supply coupled with asymmetric radiation heating could potentially improve the thermal comfort of occupied area, while the comprehensive effect of thermal environmental improvement, energy-saving, and cost-effectiveness needes to be further investigated.

Although jute fiber-reinforced PLA composites show strong application prospects, their low mechanical properties limit their applications to some extent. In this paper, nano-SiO2 particles as well as nano SiO2 modified by coupling agents which can efficiently improve the strength and toughness of composite materials are introduced into the PLA matrix. The bending, stretching and thermal properties of designed jute/PLA nonwoven composites were studied. The study shows that the nano-SiO2 particles are beneficial to the interface performance between the PLA matrix and jute leading to improvement in the mechanical properties and thermal stability. Moreover, thermomechanical properties indicate that the addition of SiO2 can improve the jute/PLA interfacial adhesion and increase the glass transition temperature of the material. Finally, toughening mechanism of nano-SiO2 particles in the jute/PLA composite was analyzed.

The cutting process of titanium alloy Ti-6Al-4 V is a complex thermomechanical coupling process with high temperature and high strain rate. In this paper, the modified Johnson–Cook (JCM) constitutive model considering strain-temperature coupling and high temperature dynamic crystallization is established, and the modified JC constitutive model is compiled based on the user subroutine VUMAT of ABAQUS. The 3D milling finite element simulation model of titanium alloy frame thin-walled parts is established, and the stress field, temperature field, milling force, and workpiece deformation are simulated and analyzed. The results show that the modified JC constitutive model improves the simulation accuracy by 4.3% and can more accurately describe the mechanical behavior of Ti-6Al-4 V alloy thin-walled parts in the cutting process.

Liquid storage tanks are lifeline structures and strategically very important. Heavy damages or even collapse of these facilities subjected to strong earthquakes may cause disastrous consequences. In this paper, the seismic response of a multistage series liquid storage tank was simulated by a finite element method and verified by a scaled-down experiment. The structural flexibility of the tank and the liquid-structure coupling characteristics between the liquid and tank wall were considered in the research. A multimass-block and spring model was employed to be equivalent to the longitudinal vibration of the liquid in the storage tank. The relationships between the connection springs and the elements of the stiffness matrix were explicitly deduced. The seismic response analysis of a four-stage series liquid tank was carried out, and the acceleration response, the stress response of the tank, and the vertical vibration of the liquid were obtained. The experimental results are in good agreement with the simulation results, which verifies the effectiveness of the modeling method in this paper.

To accommodate special applications where installation space is limited and noise and vibration requirements are high, a new triple screw pump structure was proposed, which was integrated into a servo motor. The design optimizes the profile of the master and slave screws of the embedded triple screw pump. The temperature and pressure fields of the embedded triple screw pump, as well as the heat transfer and pressure distribution between the fluid in the pump and the screw, were investigated through a thermal-fluid-structure approach. The deformation and stresses of the screw were compared for three operating conditions: temperature loading, pressure loading, and thermal-fluid-structure coupling. The results show that the deformation and stresses in the screw tended to increase with increasing pressure and temperature and the pressure load caused more significant deformation and stresses in the screw than the temperature load. The screw deformation caused by pressure loading was found to be the main factor affecting the thermal-fluid-structure coupling. The screw deformation after coupling was smaller than the sum of the screw deformation caused by individual temperature and pressure loads, and the stress values were the same. The results indicate that the coupling action weakens the deformation and stresses in the master and slave screws.

The damage of the package structure, caused by the multi-stress coupling of various environmental factors, can lead to the failure of the electronic device. Therefore, through the finite element method, the reliability analysis of three kinds of lead-free Sn-Ag-Cu solders (SAC105, SAC305, SAC405) in ball grid array (BGA) packaging was conducted under the conditions of thermoelectric coupling and random vibration, respectively. The results indicate that, according to the modified Coffin–Mason model, SAC405 has the largest plastic strain range and the shortest fatigue lifetime under thermoelectric coupling. As a counterpart, SAC105 has the smallest plastic strain range and the longest lifetime. However, under random vibration load, by addressing the Miner linear damage rule, the empirical formula of Manson high cycle fatigue and Steinberg’s three band theory, the fatigue lifetime of SAC405 is the longest, which is twice as much as SAC105 and SAC305. Furthermore, based on the linear damage superposition approach, the fatigue lifetime is predicted as SAC305

The optimal design of laminates of interlayer hybrid lamination with multicouplings is significantly beneficial to enhance the mechanical properties and reduce the cost of composite structures. The...

In this study, a vertical twin-roll cast (TRC) thermal-fluid coupling model was established to determine a suitable roll-casting velocity. A slab of 0.9mm thick roll-cast Al-50 wt.% Si alloy with a two-phase zone width of 473°C was prepared at a velocity of 20m/min for the first time. In addition, the finite element simulation showed that the average heat transfer rate had a positive correlation with the roll-casting velocity. When the roll-casting velocity increased to 20m/min, the average heat transfer rate reached 1260K/s, at which point, the average size of the primary Si was merely 16.5μm. This was a decrease of approximately 90% when compared with the size of alloys cast with conventional methods. After carrying out semi-solid heating, an observation on the distribution of alloy elements identified a novel phenomenon of solute redistribution, i.e., inverse segregation. This inverse segregation process was highly significant in further controlling solute redistribution in the alloy. Additionally, it provided a new concept for improving roll-cast segregation.

This paper presents the experimental examination of an alternative lingual organ pipe construction that uses a free tongue which, in contrast with traditional lingual organ pipes, operates in a blown open manner. A possible advantage of the construction is that it can enable changing the windchest pressure and thus, achieving an extended dynamic range while keeping a constant pitch. Three experimental pipes with diverse resonator shapes are investigated in various setups. The three pipes also demonstrate the variety of timbres obtainable by different configurations of tongues and resonators. The analysis of the measurement results shows that the pipes exhibit a very good stability of the fundamental frequency and can have a dynamic range of 15 dB. At the same time, the timbre of the sound is found to change significantly as the windchest pressure is increased. Experiments performed with damping the resonator reveal the working principle of the tongue-resonator coupling in the alternative construction. Several sound recordings are presented as multimedia file attachments enabling the subjective comparison of the pipe sounds.

Curved ultra-thin glass is widely used in mobile electronic devices such as smartphones, and its market demand is gradually increasing. The ultra-thin glass molding process (UTGMP) is a new type of glass molding process with a short processing period and high precision. However, the UTGMP is restricted to the development of curved ultra-thin glass because of its low pass rate and high cost. In particular, surface defects, including cracks, microbubbles and water ripples result in poor surface integrity of curved ultra-thin glass. Therefore, the surface integrity of the curved ultra-thin glass was comprehensively studied and analyzed in this study. First, the principles and apparatus of the UTGMP are introduced. Second, a thermo-mechanical coupling model of ultra-thin glass is established to simulate the temperature and stress distribution of curved glass using the finite element method. The results demonstrate that close to the curved area and slot, the variation in the temperature gradient is significant, and the internal stress is clearly large and concentrated. A series of experiments are conducted to further study the respective effects of various UTGMP parameters on the breakage rate and the densities of microbubbles and water ripples. A comparison of the simulation and experiment results reveals that the molding temperature has a significant effect on the breakage rate and the densities of microbubbles and water ripples, while the molding pressure has a significant effect on the breakage rate. Based on a comprehensive analysis, an optimal molding temperature of 806 °C and a molding pressure of 0.45 MPa are selected. Under this condition, the breakage rate decreases from 67% to 0%, the density of microbubbles decreases from 1.03/mm2 to 0.89/mm2, and the water ripple phenomenon weakens. This study contributes to a better understanding and improvement of the surface integrity of high-precision glass molding processes for curved ultra-thin glass.

Aiming to study the stray losses and temperature distribution of power transformer ascending flange, a 1:1 test model is built, and the corresponding three-dimensional (3D) finite-element analysis (FEA) model is established. Then the influence of shielding on stray losses distribution is simulated by surface impedance method, and the 4mm copper shielding is selected as the optimized one. Besides, a mixed steel tank lid structure is proposed to limit the maximum loss density in the tank lid. Finally, the temperature field of ascending flange based on magneto-thermal coupling method is simulated, which can provide an effective guidance for allowable lead current and the related optimization.

In this study, an analytical model was established for calculating solute distribution pattern and precipitates of the Al-Mg-Si series alloys resistance spot welds. By coupling the model with a thermodynamic database, a volume element Ω was considered, then used to calculate the effective Mg and Si concentration in α-Al solid solution under different post-weld heat treatment. Resistance spot welding test of Aluminum alloys 6061 and 6082 was carried out, followed by sample characterization via transmission electron microscopy (TEM). Analysis of β-Mg2Si phase’s distribution revealed that Mg and Si were segregated at the inter-granular region after welding. Notably, the β-Mg2Si phase was dissolved during post-welding solid solution treatment, thereby making Mg and Si to diffuse into the inner-granular region. This solute redistribution process was consistent with C-fS curves evolution calculated by the analytical model. The calculated effective Mg and Si concentration set up a platform for further calculation of precipitate evolution curves. Precipitate mole fraction was positively correlated with the weld’s strength.

The fatigue life of drill pipe is a vital factor affecting the drilling process and safety, while severe fatigue failure of drill pipe under the condition of high temperature containing hydrogen sulfide have been reported frequently in recent years. Hence, a systematic methodology was proposed to investigate the fatigue behavior of different drill pipe under multi-factor environment. The present work aims to characterize the fatigue life and mechanism of G105, S135, V150 as well as the titanium alloy drill pipe. The hardness and tensile tests were initially performed to determine the material characterization of the different drill pipe. Then, a fatigue experimental system was specifically designed based on the experimental conditions to evaluate the fatigue property of the drill pipes. Experimental results reveal that in the air, drill pipe’s fatigue life could be longer with the increasing steel grade while in drilling mud, the fatigue performance of titanium alloy drill pipe is the best. The results of sensitivity analysis demonstrate that the coupling factor of H2S mud with temperature showed the greatest influence on the fatigue properties, followed by the single factor of H2S mud and the temperature respectively. The sensitivity to temperature and mud coupling factors is: V150 (65.2%) > S135 (58.1%) > Ti (51.6%) > G105 (40.3%). The sensitivity for H2S mud is: V150 (59.8%) > S135 (51.6%) > G105 (29.7%) > Ti (21.7%). The order of sensitivity to temperature is as follows: Ti (6.5%) > S135 (6.3%) > G105 (2.5%) > V150 (1.5%). The mechanisms underlying fatigue fracture were explored. Finally, according to the experimental results, the economical practicality of different drill pipes is analyzed and compared. The work presented in this paper can provide a technological basis for fatigue theory and service conditions of drill pipes.

As the first barrier of wellbore integrity, tubing string is an important guarantee for safety production. However, with the rapid consumption of oil and gas, the mechanical environment in wellbore is becoming more and more harsh, which poses a challenge to the safe service of tubing string. In order to systematically study the erosion of buckling tubing string in high temperature and high pressure (HTHP) ultra-deep wells, the researches on buckling deformation and erosion of tubing string are carried out gradually in this paper. There are three steps in the research process: (a) The tests including metallographic, mechanical properties and hardness of studied tubing material are carried out, and the test results are the basis of the next numerical simulation; (b) the finite element model (FEM) of whole section tubing sting-packer-casing is established to study the buckling deformation of tubing string due to the comprehensive effect including piston effect, ballooning effect, temperature effect, friction effect and buckling effect; (c) according to the buckling flow passage, FEM of tubing erosion is established based on erosion mode, fluid–solid coupling and impact of sand on each other. Finally, the erosion rule and failure region on tubing are obtained. The researches presented in this paper can provide reference and guidance for predicting erosion and protecting the tubing string.

In this study, we have obtained the corresponding relationship between SLM-NiTi alloy transition temperatures and energy density, and realized the accurate prediction and inverse prediction of SLM process parameters and NiTi alloy transition temperatures. And we verify the accuracy of the prediction model through DSC, XRD and SEM. Secondly, B19′NiTi and B2NiTi are successfully obtained through the prediction model. Finally, a composite gradient NiTi is established based on the idea of rigid-flexible coupling, which successfully achieved the simultaneous improvement of the strength and toughness of the SLM-NiTi alloy. The compressive fracture strength reached 2668 MPa, and the fracture strain reached 55.51%.

Thermal cracking widely exists in nature and engineering practices, attracting more and more attention nowadays. Understanding the failure mechanism of thermal cracking is critical to improving the efficiency and safety of engineering applications. Despite great efforts have been performed on the numerical modeling of thermal cracking, accurately representing and tracking a nonplanar three-dimensional (3D) cracking pattern is still a challenge. In this work, a novel thermo-mechanical coupling model (FEMM-TM), combining a heat transfer algorithm and the finite element-meshfree method (FEMM), is proposed to simulate the nonplanar 3D thermal cracking problems, involving the temperature transfer, thermal stress distribution, as well as the crack propagation and coalescence. The performance of the proposed FEMM-TM model is validated by numerical tests with analytical or numerical solutions. The nonplanar 3D thermal cracking problems under different thermal loading conditions are further investigated. Results show that the proposed method can be effectively deployed in the analysis of nonplanar 3D thermal cracking problems.

Air leakage around the in-seam borehole leads to a poor quality of gas extracted, thus gas outburst danger is difficult to eliminate but also may cause other disasters, such as coal spontaneous combustion and gas explosion. Moreover, the low concentration gas discharged into the atmosphere always possesses an intense greenhouse effect. To investigate multiphase and multifield coupling problem of gas extraction, a dual medium coupling model was developed in this study to describe the gas–air mixture flow by considering the influences of matrix shrinkage and effective stress on coal permeability. And the coupling model was calculated by the 3D numerical simulation and presented an ideal matching result with the field data. Then, the key factors affecting the gas extraction quality were also investigated with the model. It was found that the gas concentration elevated with the increase in the sealing length and borehole diameter, and reduced with the augmentation of extraction negative pressure and coal permeability. Therefore, we developed an improved sealing technology, which can fully seal the various fractures around the borehole for improving gas extraction. The field test indicated that the gas concentration by this improved sealing technology was 1.91 times that of the traditional sealing method, and still maintained a relatively high extraction level in the subsequent extraction stage with a superior application effect. The results of this work can help in optimizing the borehole sealing technology for improving gas extraction quality, which is of great significance to CBM exploitation and utilization, reduce greenhouse gas emission and ensure safe mining.

With the development of gas well exploitation, the calculation of wellbore with single-phase state affected by single factor cannot meet the actual needs of engineering. We need to consider the simulation calculation of complex wellbore environment under the coupling of multiphase and multiple factors, so as to better serve the petroleum industry. In view of the problem that the commonly used temperature and pressure model can only be used for single-phase state under complex well conditions, and the error is large. Combined with the wellbore heat transfer mechanism and the calculation method of pipe flow pressure drop gradient, this study analyzes the shortcomings of Ramey model and Hassan & Kabir model through transient analysis. Based on the equations of mass conservation, momentum conservation and energy conservation, and considering the interaction between fluid physical parameters and temperature and pressure, the wellbore pressure coupling model of water-bearing gas well is established, and the Newton Raphael iterative method is used for MATLAB programming. On this basis, the relationship between tubing diameter, gas production, gas–water ratio, and wellbore temperature field and pressure field in high water-bearing gas wells is discussed. The results show that the wellbore temperature pressure coupling model of high water-bearing gas well considering the coupling of gas–liquid two-phase flow wellbore temperature pressure field has higher accuracy than Ramey model and Hassan & Kabir model, and the minimum coefficients of variation of each model are 0.022, 0.037 and 0.042, respectively. Therefore, the model in this study is highly consistent with the field measured data. Therefore, the findings of this study are helpful to better calculate the wellbore temperature and pressure parameters under complex well conditions.

Drying-induced cracks are an important issue for bi-block ballastless track system consisting of foundation, precast sleepers, and cast-in-place track slab, which not only significantly affects the comfortableness and safety of rapid transit railway but also reduces the service life of ballastless track. In order to explore its damage mechanism, this work presents an evolution model of relative humidity (RH) in the CRTS I bi-block ballastless track system by considering the actual construction sequence and environmental conditions to simulate the crack propagation induced by nonuniform RH field. Firstly, based on the node coupling technique, a three-step transfer process of RH is designed to separately investigate the influence of the construction sequence on the early humidity field in the foundation, sleepers, and cast-in-place track slab, and then the nonuniform distribution of early humidity field in the ballastless track system is determined. Subsequently, the formation mechanism of shrinkage crack in the system is analyzed, and the crack propagation path is predicted by using the mixed-mode fracture criterion. The results show that the maximum relative humidity gradient (RHG) appears at the interface between the track slab and the sleeper after concreting the cast-in-place track slab, which causes the maximum principal stress due to the drying shrinkage property of concrete materials. When the maximum principal stress exceeds the tensile strength of the interface, an interface crack will be generated and converted to a splayed crack with an initial angle of about 45° at the sleeper corner, which will be further propagated under the action of drying shrinkage deformation and finally forms a transverse through-wall crack in the track slab. The simulated crack propagation path agrees with the observed one at the site well, and thus the results are beneficial to understand the formation mechanism of through-wall crack in the track slab and further guide the construction design of the bi-block ballastless track system.

In concrete mixing plan, we usually encounter a combination of aggregates including sand, the amount of cement, which is actually the criterion of concrete grade, and the volume of water consumed. Changes in the quality and quantity of these components actually create the usual types of concrete. But the attitude that formed the basis of this research is based on the change in the nature of the components of the concrete mixing design. Removal of water and cement from the mixing plan and replacement of polymeric materials as well as the use of mixed LECA aggregates instead of aggregates is the basis of this research. In this paper, by examining and selecting LECA grain style and pre-treatment (hydrophobicity and coupling), in a constant ratio of resin, concrete samples were selected from three dimensional categories. After making the samples, flexural strength test was performed on them and the results were analyzed. Various compounds and processes have so far been proposed in the lightweight concrete mixing scheme. The distinctive point of this study is the use of lightweight expanded clay concrete with heat-treated acrylic polymer (crosslinking constituents) and related coupling agents. It is also important to select and apply the right amount of hydrophobic nanoparticles for hydrophilic surface hydrophobicity. Hydrophobicity was possible due to the non-polar nature of the acrylic polymer and the use of hydrophobic nanomaterials.

With the tremendous development of additive manufacturing technology in recent years, porous infill structures with well-designed topology configurations have been widely used in various physical fields. The porous infill structure may be prone to thermo-mechanical buckling failure under certain extreme thermal conditions due to temperature gradient effects and delicate local details of the porous infill structure.Therefore, a topological optimization design method, which considers the influence of the thermo-solid coupling field on the buckling performance of the porous infill structure, is proposed by using the projection approach merged with the Solid Isotropic Material with Penalization (SIMP) method. Critical buckling load factors obtained with thermal-elastic equilibrium and linear buckling analysis are employed to measure the buckling performance of the structure. Numerical examples show that the proposed method can effectively improve the buckling performance of the porous infill structure under the thermo-mechanical environment.

Time and water-to-cement ratio have significant influences on rheology of cement grouts. In order to study effects of time and water-to-cement ratio on rheology of Bingham cement grouts, taking Bingham cement grouts widely used in practical engineering (cement grouts with water-to-cement ratio of 0.75–1.25) as research object, some rheological experiments of five cement grouts with water-to-cement ratio of 0.8, 0.9, 1.0, 1.1, and 1.25 were carried out at six moments of 0, 5, 10, 20, 30, and 60 minutes, respectively. Combining theoretical discussion with numerical analysis, influence of coupling effects of time and water-to-cement ratio on rheological properties of Bingham cement grouts was discussed. Results show that at the level of α = 0.05, time has a significant influence on plastic viscosity but has no significant influence on the yield stress of Bingham cement grouts. Water-to-cement ratio has a significant influence on both plastic viscosity and yield stress. Exponential models obtained by comprehensive analysis from statistical theory, practical applicability, and accuracy are the optimal models to describe quantitative change in the relationship of coupling effects of time and water-to-cement ratio on plastic viscosity and yield stress of Bingham cement grouts. The rheological equation considering coupling effects of time and water-to-cement ratio of Bingham cement grouts is constructed. Research achievements not only have certain theoretical significance to the development and improvement of fluid mechanics and theoretical system of penetration grouting but also provide theoretical support and technical reference for practical grouting engineering and also have certain practical significance for solving or improving the practical engineering problems.

Abstract The exotic properties of 2D materials made them ideal candidates for applications in quantum computing, flexible electronics, and energy technologies. A major barrier to their adaptation for industrial applications is their controllable and reproducible growth at a large scale. A significant effort has been devoted to the chemical vapor deposition (CVD) growth of wafer-scale highly crystalline monolayer materials through exhaustive trial-and-error experimentations. However, major challenges remain as the final morphology and growth quality of the 2D materials may significantly change upon subtle variation in growth conditions. Here, we introduced a multiscale/multiphysics model based on coupling continuum fluid mechanics and phase-field models for CVD growth of 2D materials. It connects the macroscale experimentally controllable parameters, such as inlet velocity and temperature, and mesoscale growth parameters such as surface diffusion and deposition rates, to morphology of the as-grown 2D materials. We considered WSe2 as our model material and established a relationship between the macroscale growth parameters and the growth coverage. Our model can guide the CVD growth of monolayer materials and paves the way to their synthesis-by-design. Graphic abstract

Steel materials employed in severe conditions including strong corrosion, high load and multi-factor coupling damages can easily cause incredible degradation until failure, and the protective CrN-based coatings should be one of promising candidates to relieve those damages for the steel equipment or components. In present paper, the monolayer CrAlN and multilayer Cr/CrAlN coatings were successfully deposited on steel substrates by multi-arc ion technology, and their microstructure, mechanical, tribological and corrosion performances were systematically investigated. The results show that the special multilayer Cr/CrAlN coating could possess much better load-bearing capacity and wear resistance than that of monolayer CrAlN coating, which was due to the facts that the multilayer architecture can effectively release the internal stress and inhibit the expansion of defects. Particularly, the multilayer interfaces could effectively prevent the aggressive medium in seawater infiltrating into the inside of coating, and thus the multilayer Cr/CrAlN coating could have higher corrosion resistance compared to monolayer CrAlN coating. As a result, this multilayer Cr/CrAlN coating could achieve excellent combined performances, indicating that it has greatly potential application as protective coating in seawater.

This study introduces a test system for microwave-induced fracturing of hard rocks under true triaxial stress. The test system comprises a true triaxial stress loading system, an open-ended microwave-induced fracturing system, a data acquisition system, an acoustic emission (AE) monitoring system, and an auxiliary specimen loading system. Microwave-induced surface and borehole fracturing tests under true triaxial stress were fulfilled for the first time, which overcomes the problem of microwave leakage in the coupling loading of true triaxial stress and microwave. By developing the dynamic monitoring system, the thermal response and fracture evolution were obtained during microwave irradiation. The monitoring system includes the infrared thermometry technique for monitoring rock surface temperature, the distributed optic fiber sensing technique for monitoring temperature in borehole in rock, the AE technique and two-dimensional digital speckle correlation technique for monitoring the evolution of thermal damage and the rock fracturing process. To validate the advantages of the test system and investigate the characteristics of microwave-induced fracturing of hard rocks, the study demonstrates the experimental methods and results for microwave-induced surface and borehole fracturing under true triaxial stress. The results show that thermal cracking presented intermittent characteristics (calm–active–calm) during microwave-induced surface and borehole fracturing of basalt. In addition, true triaxial stress can inhibit the development and distribution of thermal cracks during microwave-induced surface fracturing. When microwave-induced borehole fracturing occurs, it promotes the distribution of thermal cracks in rock, but inhibits the width of cracks. The results also prove the reliability of the test system.

This work deals with the coupling between a periodic homogenization procedure, and a damage process occurring in a Representative Volume Element (RVE) of inclusion composite materials. We mainly seek, on the one hand to determine the effective mechanical properties according to the different volume fractions, and forms of inclusions for a composite with inclusions at the macroscopic level. On the other hand, to explore the rupture mechanisms that can take place at the microstructure level. To do this; the first step is to propose a periodic homogenization procedure, to predict the homogenized mechanical characteristics of an inclusion composite. This homogenization procedure is applied to the theory based on finite element analysis, by the Abaqus calculation code. The inclusions are modeled by a random object modeler, and the periodic homogenization method is implemented by python scripts. It is then a matter of introducing the damage into the problem of homogenization, that is to say; once the homogenized characteristics are assessed in the absence of the damage initiated, by microcracks and micro cavitations. It is then possible to introduce damage models, by a subroutine (Umat) in the Abaqus calculation code. The verifications carried out focused on RVE of composite materials with inclusions

Based on laboratory direct shear tests and discrete element theory, the crack propagation mechanism and numerical simulation of rock-like specimens with preexisting flaws considering combined actions of internal hydraulic pressure and shear force were carried out in this paper. We completed the filling of the internal hydraulic pressure in the rock-like specimens with preexisting flaws, and performed direct shear tests on the specimens. Furthermore, we explored the crack propagation process of rock-like specimens with flaws under internal hydraulic pressure and shear load. In the numerical analysis, the pipe domain model in the two-dimensional particle flow code (PFC2D) was modified owing to the high brittleness and low permeability of the cement mortar particles in the numerical model. We modified the calculation rules of the interaction between the fluid and cement mortar particles, and proposed an improved fluid–solid coupling model which is more suitable for the crack propagation analysis in the high brittle cement mortar specimens. Under the action of internal hydraulic pressure, a tensile region existed at the tip of the preexisting flaws of the cement mortar specimen, which can also explain the crack initiation and propagation along the horizontal shear direction during the stage of crack initiation. When cracks progressively propagated, concentrated tensile stress and internal hydraulic pressure were released, leading to the appearance of a large number of tensile cracks, and the release of transverse shear force and internal hydraulic pressure resulted in the appearance of a large number of shear cracks. In the presence of internal hydraulic pressure, the increased number of pre-existing flaws would reduce the shear strengths of cement mortar specimens. Compared with the shear strength of the specimen with single flaw, the shear strength of the specimen with double flaws was reduced by 7.6%, and the specimen with triple flaws was reduced by 10.2%.

An integrated DEM-FEM coupling simulation approach is developed to simulate the real process of shot peening, and is validated by comparing the predicted in-depth residual stresses with the experimentally measured results. Two kinds of three-dimensional finite element models associated with the original surface roughness of Rα0 = 26.7μm and 50.1μm are respectively established by using Gaussian distribution in conjunction with the exponential autocorrelation function, and another target model without the original surface roughness is utilized for reference purposes. Taking advantage of the integrated DEM-FEM coupling simulations of shot peening processes based on the three kinds of target models, the effects of the original surface roughness, shot impact angle, and shot peening coverage on the shot-peened residual stresses and surface roughness are investigated in detail. The obtained results show that the larger original surface roughness of TC4 titanium alloy could be reduced by shot peening, and the reduction increases with the increasing shot peening coverage from 100 to 200%. In the target models associated with the original surface roughness, the distributions of shot-peened surface residual stresses tend to be more uniform than that in the target model without the original surface roughness, whereas both the in-depth residual stresses and surface roughness are not very sensitive to the changes of shot impact angle in the range from 60° to 90°.

In order to grasp the characteristics and mechanism of saline soil deformation under the coupling action of cooling and dynamic load, three types of subgrade fillings from the Qarhan-Golmud Highway in Qinghai-Tibet Plateau were selected as experimental soil samples for the experimental study. Firstly, the freezing temperature experiment was carried out on SS (sandy silt) and HS (high-sulfate silty clay). The test results showed that the freezing temperature of SS is -0.32°C, while that of HC (high-chloride silty clay) and HS will not freeze at -20°C, due to the presence of salt. Secondly, the three soil samples were subjected to deformation characteristic test under coupling action of cooling and dynamic load, respectively, and the time history curve of temperature gradient change, the time history curve of the change rate of deformation, and deformation rate were summarized. Finally, the model of deformation rate vs. time and the model of change rate of deformation vs. deformation rate under the coupling action of cooling and dynamic load are proposed. The test results found that (1) the cooling rate of the temperature gradient curve of the three soil samples showed a rapid cooling rate in the early stage, and it tends to stabilize in the later stage. The distance of the 0°C line from the top gradually decreases, which is affected by the freezing temperature and the salt content. (2) Affected by the freezing temperature and salt type, SS exhibits frost heave, and HS and HC appear to settlement. The final deformation is 1.0%, -0.73%, and -1.10%, respectively. (3) The model of deformation rate vs. time and the model of change rate of deformation vs. deformation rate under the coupling action of cooling and dynamic load were proposed and verified, which are helpful for the evaluation of engineering stability on saline soil subgrade fillings.

The thermo-mechanical-vibration coupling characteristics of the cutting system has always been an important research topic in the field of machining, and the material, states, and performance of cutting tools can directly affect these coupling characteristics. In this paper, a synchronous testing system is built to collect the cutting temperature and cutting vibration near the tip of three tools with different wear states: D1 (new blade), D2 (moderately worn blade), and D3 (severely worn blade). Based on the test data and the gray correlation theory, the coupling characteristics of cutting temperature rise and cutting vibration under different tool wear states are analyzed. Based on the experimental data and least square method, (1) the regression model of cutting temperature rise about cutting vibration and cutting parameters are established, (2) the regression model of cutting vibration about cutting temperature rise and cutting parameters are established. The undetermined parameters and correlation coefficients are obtained by MATLAB software programming. The research results show that for tools D1 and D2, the coupling of cutting temperature rise and cutting vibration is a one-way coupling, that is, cutting vibration and cutting parameters significantly affects cutting temperature, but cutting temperature rise and cutting parameters has little effect on cutting vibration, while for tool D3, the coupling of cutting temperature rise and cutting vibration is a bi-directional coupling.

Based on analysis of thermo-hydro-mechanical-chemical (THMC) coupling mechanism for brittle rock, THMC coupling indicator in terms of rock porosity was introduced to represent the influencing degree of THMC coupling field on stress field in order to establish THMC coupling fracture criterion. A novel real-time measurement method of permeability (related to porosity) was proposed to determine the THMC coupling indicator, and self-designed THMC coupling tests and scanning electron microscope tests were conducted on pre-cracked red sandstone specimens to study the macroscopic and microscopic fracture mechanism. Research results show that the higher the hydraulic pressure is, the smaller the crack initiation load is and the easier the Mode I fracture occurs. Test results are in good agreement with prediction results (crack initiation load and angle, and fracture mode), which can verify the effectiveness of the newly established THMC coupling fracture criterion. This new fracture criterion can be also further extended to predict THMC coupling fracture of multi-crack problem.

The coupling control of quenching rate and pre-aging and its positive effect on the age-hardening response of Al–Mg–Si–Cu–Zn–Fe–Mn alloy was systematically investigated. The larger and more stable solute clusters can be formed in alloy with fast age-hardening response by using the lower quenching rate (5.3 °C/min) and an appropriate pre-aging, in which the deterioration of natural aging also can be obviously suppressed. Additionally, the highest bake hardening increment of the alloy can reach 145.2 MPa, which is much higher than those of traditional Al–Mg–Si–(Cu) alloys (such as, 6016 and 6111 alloys). Based on the detailed precipitation behavior characterization of alloys with different quenching rates and the same pre-aging, the quenching rate change can result in the significant differences in the size, number density of precipitates in the both paint baking and peak aging states, but the type of precipitates basically keeps the same, i.e., Mg–Si precipitates, and no Mg–Zn precipitates can be observed. Finally, the related mechanisms of coupling control of quenching rate and pre-aging were also discussed in this paper. The developed coupling control method shows great potential and could significantly increase applications of Al–Mg–Si–Cu–Zn–Fe–Mn alloys with a fast age-hardening response.