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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.

The Al alloy and carbon fiber reinforced polymer (CFRP) hybrid structures, incorporating the performance advantages of the two materials, have been attracting more attention in high-end manufacturing fields. In the current investigation, the flat friction spot joining (FSJ) was employed in joining the AA6061-T6 alloy and CFRP sheets. The significance of temperature distribution in influencing joint quality was highlighted through analyzing interface microstructural features, weld defect formation as well as fractography. To understand the role of thermal energy generation and conduction in the process comprehensively, a 3D thermal-mechanical coupling finite element model was established. The interfacial temperature was characterized by an uneven distribution behavior due to the inhomogeneous heat distribution. The peak temperatures on the top surface and Al alloy to CFRP interface at 1500 rpm rotational speed with 0.1 mm/s plunging speed were 498 °C and 489 °C, respectively. The peak interface temperature was reduced to 286 °C at 250 rpm, which produced an extremely small melted area. Compared with the plunging speed, rotational speed was found to be the predominant parameter for determining the joint property, which could be optimized to simultaneously realize the avoidance of thermal decomposition of CFRP, the sufficient melting duration time, and the wide enough melted area. Simulated thermal histories and melted area profiles were in agreement with experimental ones. The findings could be utilized to provide some feasible guidance for process optimization of dissimilar FSJ of metals and composites.

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.

It is of great importance to further investigate grain selection mechanism for the production of single crystal (SX) turbine blade because a single crystal with optimized crystal orientation will enhance service performance of the blade severely. In this paper, single crystals with different deviation angles, i.e. 6°, 12° and 29°, were obtained using directional solidification under the same casting conditions. It has been found that the grain selection in spiral selector is a coupling process where high order dendrites branch in the front side and primary dendrites disappear in the back side based on the metallographic analysis and electron back scatter diffraction (EBSD). Considering the development of liquid/solid interface by numerical simulation, a combination effect with space expansion, geometrical restriction and grain competition was proposed for spiral grain selection. The space expansion mechanism dominates the process as it provides growth space and driving force for high order dendrites advancing. Thereby, the smaller the take-off angle (θ) is, the larger space and the stronger driving force high order dendrites will get, and the higher efficient the selector will be. The competitive growth between the secondary dendrites plays more contribution than that of primary dendrites, i.e. grain with preferred secondary dendrites instead of preferred primary dendrites could outcompete during grain selection, and this is the reason why spiral grain selector cannot optimize the orientation of the primary dendrites. These findings provide experimental evidence for spatial control of SX growth, and benefit the sophistic casting fields such as turbine blade casting for improved yield.

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.

60NiTi alloy is highly promising for aerospace bearings and mechanisms. Shock load that is inevitably generated during launching process brings about an quick loading process and transient load duration, and may further results in an unnoticed but detrimental creep deformation. On this account, the nanoindentation creep behavior of solution-treated 60NiTi alloy at room temperature and the corresponding influencing mechanism were studied. The results show that creep displacement was dominated by strain rate at the very beginning of holding stage. Strain rate and flow stress at the very beginning of holding stage were increased with an increased loading rate but declined with increasing holding load or with simultaneously increasing loading rate and holding load. The underlying mechanisms were provided as nucleation and absorption of geometrically necessary dislocations (GNDs) associated with strain gradient plasticity theory rather than the model based on the consumption of creep deformation at loading stage.

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.

The consequence of coupling wear (erosion/abrasion) and corrosion is not just simply the sum of wear in the absence of corrosive medium and corrosion in absence of wear. The so-called synergistic effect implies that corrosion is accelerated due to the removal of the passivating layer because of wear. On the other hand, corrosion can accelerate abrasion when the electrochemical dissolution yields a brittle surface layer which can be subsequently removed by abrasion. The synergism between wear and corrosion is complex and the interaction between mechanical and chemical factors governing tribocorrosion is not yet fully understood. This review aims at providing a general and thorough summary of the wear-corrosion interaction focused on stainless steels due to the technological relevance of these materials. It is taken into consideration the influence of the key parameters affecting wear-corrosion, such as the stainless steel type, slurry characteristics (temperature, pH, solid concentration), the erodent properties (particle size and shape), etc. The different models to describe wear-corrosion and the most used apparatus for tribocorrosion testing are also reviewed.

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.

We conceive a model of nanosystems where Co is uniformly, randomly distributed into a CoFe2O4 (CFO) matrix, and study the influences of composition and CFO antiferromagnetic exchange coupling (JCFO) on zero-field-cooled/field-cooled magnetization behavior and the dependencies of exchange bias field (HE) and coercivity (HC) on Co/CFO interfacial coupling (JCo/CFO), composition and cooling field (HFC), based on a modified Monte Carlo method. With decreasing temperature, the zero-field-cooled and field-cooled magnetization curves are overlapped and increasing initially, and then splitting at a critical temperature (TP), below which the field-cooled magnetization continues increasing while the zero-field-cooled magnetization exhibits a peak and drops, indicating a magnetically frozen state. A larger JCFO induces an elevated TP and a reduced magnetization, while the opposite results are obtained by a higher Co occupation fraction (PCo). On the other hand, HE is nonmonotonic with JCo/CFO and the peak decreases and shifts to a lower JCo/CFO value for a larger PCo. HC increases monotonically with increasing JCo/CFO. Moreover, HE is inversely proportional to PCo when PCo varies from 0.11 to 0.30, indicating the exchange bias is still an interfacial effect. Finally, for a nonzero JCFO, HE may be suppressed and accompanied by the recovery of HC with increasing HFC. Otherwise, HC for zero JCFO becomes high and insensitive to HFC. It is ascribed to the uniform contact between Co and CFO, leading to the Co magnetization reversal and the CFO magnetization precisely controlled by HFC. This work opens a new avenue to control the exchange bias in nanosystems through interfacial randomization.

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.

The influence of initial cracks on the buckling performance of square steel tubular (SST) columns, widely used in civil engineering, is an aspect that has not been studied in detail. Thus, an experimental investigation was conducted on SST columns with initial crack defects. A total of 111 specimens (12 single-crack, 48 double-crack, 48 three-crack, and 3 no-crack SST columns) were tested under axial compression loading, and the failure modes, initial stiffness, bearing capacity, ultimate displacement, and strain strength of each specimen were reported. Combined with the experimental data, a finite element analysis of the validated model was conducted to evaluate the effect of the main influencing factors. A reduction coefficient was obtained via statistical analysis and introduced into the prediction formula to accurately estimate the ultimate bearing capacity of multicracked steel tubes. It was found that avoiding crack propagation in practical engineering is crucial. The initial cracks accelerated the local buckling and changed the bearing and deformation capacities of the SST columns. The ultimate loads of the steel tubes increased gradually with an increase in the tube thickness and decreased slightly with an increase in the crack length. Furthermore, the effect of crack number and crack spacing on the bearing capacity was found to be complex, and there was a coupling relationship with the tube thickness; therefore, the tube thickness of the component should be reasonably selected, or appropriate anti-cracking measures should be employed to avoid the joint action of material uneven stress and initial crack.

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.

A composite material is created by combining at least two materials to create a unique combination of qualities, one of which comprises stiff, long strands and the other of filaments. And it is mainly concerned with improving ordinary fibre composites to explore the extra possibilities of use. Such typical fibre composites in the accommodation and building areas are suitable as wood alternatives. Many large loads of different yields are supplied, but much of their squandering has no practical use. Horticultural squandering incorporates a variety of dry natural resources and the influence of silanee coupling agents on mechanical characteristics like bending strength, tensile strength, and impact intensity in sugar cane baggage and PP (polypropylene) composites discussed in this Research. The reinforcing material was treated with a 0 percent coupling agent, 10 percent, and 20 percent. This substance was present for the production of composite boards via compression molding. The influence on mechanical parameters such as stress, bending, and impact strengths of the composites were analyzed by the silanee coupling agent.

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.

Rock granular flow is a kind of rock debris aggregate produced by landslides, which can be greatly destructive due to its high velocity, long distance and large impact force. In this paper, dynamic responses and energy dissipation capacities of different shapes rigid retaining walls (rectangle, angular, arc-shaped) under the impact of rock granular flow were investigated. The experiments primarily focused on the influences of granular flow mass and slope angle on motion characteristics of rock granular flow and impact force of retaining wall. In addition, the relationship between the energy dissipation capacity and the structural form of the retaining wall were explored through quantitative analysis peak acceleration of different shapes retaining wall. According to the experimental results, substantial increases both in the impact velocity of rock granular flow and in the maximum resultant of impact force of retaining wall with increasing rock granular flow mass and slope angle were observed under the coupling effects of the granular flow mass and slope angle. Moreover, the impact force at different height of the rectangle retaining wall varied evidently with slope angle, but was mainly concentrated in the lower half of the retaining wall. In addition, the energy dissipation capacity of arc-shaped retaining wall was the best among those rigid retaining walls. This study can contribute to a better understanding of the flow-structure interaction and provide guidelines for the engineering application of the new retaining wall.

To improve the performance of the superfine-tailings cemented paste backfill (SCPB) and thus improve the utilization rate of superfine tailings, a blended binder (BB, containing high-volume mineral admixtures) and superplasticizer (SP) were employed. BB was designed based on the proposed model that coupled wet packing method and compressible packing model (CPM). The fluidity, the mechanical and microstructure properties of SCPB with various dosages of BB and SP were evaluated. Moreover, the coupling mechanism of BB and SP on the fluidity of fresh SCPB was also discussed. The results showed that the proposed coupling model could accurately predict the packing density of the multi-mixed cementitious system. The addition of BB and SP can improve the fluidity and strength of SCPB, and the coupling mechanism that affects the fluidity mainly by changing water film thickness (WFT). Therefore, using BB and SP is an effective method for improving the performance of SCPB.

Due to the complex effects of combined loadings on complete steel structures, the combined effects of high-velocity projectile impact and heat radiation due to a pool-fire on a vertical Q345 steel tank have not been generally considered. In this study, a consecutive coupling approach is established. The combined effects of projectile perforation and heat radiation on the failure modes and fire resistance of a vertical steel tank are investigated. Additionally, the effects of the projectile size, projectile shape, and separation distance are analyzed. The results indicate that compared with a fixed-roof tank without impact, the perforation results in stress concentrations in the plastic deformation zone. The stress level of the perforated tank is higher, and the fire resistance of the perforated tank is lower. Additionally, as the perforation size increases, the stress level triggering the thermal buckling of the perforated tank decreases outside of the plastic deformation zone. Additionally, the fire resistance decreases. Moreover, as the separation distance decreases, the stress level of the cylindrical shell increases. The fire resistance of the perforated tank decreases dramatically. By understanding the failure mode, this study is able to suggest fire and explosion protection measures in petrochemical industries to decrease or eliminate the domino effect risk and incident damage. Additionally, the fire resistance data can help improve guidelines and understanding for fire and rescue services, which would undoubtedly play a vital part in emergency response and rescue, and enhance the process safety level overall.

Monoblock prestressed concrete sleepers are the most dominant type of sleepers in ballasted railway tracks. As such, it is important to provide optimized designs to the concrete sleepers and the associated fastening systems to ameliorate railway safety and to save both capital and maintenance funds. Therefore, a three-dimensional finite element railway model was created and verified. The response of both concrete sleepers and fastening components to coupling vertical and lateral loading was quantified. Such loading form typically occurs at horizontal railway sections causing damage to the railway track components. The influences of the sleeper spacing, elastic modulus of the rail pad, and friction coefficient at the contact surfaces of the rail and sleeper with the rail pad under varied lateral loadings were investigated. The interaction influence between parameters was thoroughly discussed. Among the studied parameters, the finite element model outcomes showed that the elastic modulus of the rail pad and the coefficient of friction are the most critical parameters with respect to the lateral load path and the local response of concrete sleeper and fastening system, especially at high lateral loadings. By using a relatively soft rail pad (elastic modulus = 100 MPa), the concrete material remained below the compressive and tensile fatigue limits even under high lateral loadings provided that the coefficient of friction remains limited to 0.3. By contrast, for a given lateral to vertical loading ratio, a continuous increase in the developed stresses of the concrete material and rail pad was detected as the elastic modulus changed from 100 MPa to 2000 MPa and the coefficient of friction increased from 0.3 to 0.9. The influence of sleeper spacing on the behaviour of railway tracks is only tangible on the distribution of the vertical wheel load. Lastly, the peak stress magnitudes of the ballast bed could be increased by 50% as the lateral to vertical loading ratio reached 0.6 compared to the case where the lateral load is absent. The experience gained from this article would help to formulate specific recommendations to improve the design of concrete sleepers, fastening systems, and ballast bed.

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.

Degradation of a metallic film under harsh thermal-mechanical-electrical coupling field conditions determines its service temperature and lifetime. In this work, the self-heating degradation behaviors of Pt thin films above 1000 °C were studied in situ by TEM at the nanoscale. The Pt films degraded mainly through void nucleation and growth on the Pt-SiNx interface. Voids preferentially formed at the grain boundary and triple junction intersections with the interface. At temperatures above 1040 °C, the voids nucleated at both the grain boundaries and inside the Pt grains. A stress simulation of the suspended membrane suggests the existence of local tensile stress in the Pt film, which promotes the nucleation of voids at the Pt-SiNx interface. The grain-boundary-dominated mass transportation renders the voids grow preferentially at GBs and triple junctions in a Pt film. Additionally, under the influence of an applied current, the voids that nucleated inside Pt grains grew to a large size and accelerated the degradation of the Pt film.

In order to investigate the seismic behavior of the hybrid coupled partially encased composite (PEC) wall system, two 2/3-scale three-story specimens with different elastic coupling ratios (CRelastic) were tested under cyclic loading. The results showed that the hysteretic curves of the two specimens were full and stable, indicating their robust cyclic performance and excellent energy dissipation capacity. Under reversed cyclic lateral loading, the specimens exhibited a two-stage yielding energy dissipation mechanism, in accordance with theoretical expectations. Both specimens dissipated a large amount of energy during loading, with the equivalent viscous damping ξeq reaching 0.32 and 0.35 at the maximum displacement level, respectively. Based on the experimental results, the refined finite element model for the hybrid coupled PEC wall was established in ABAQUS and validated. A parametric analysis demonstrated that the CRelastic and the design axial compression ratio (n) had significant influences on the seismic behavior of the hybrid coupled PEC wall. With increasing CRelastic, the lateral stiffness, strength, and yield displacement of the hybrid coupled PEC wall gradually increased, while its ductility deteriorated. Moreover, the ductility of the hybrid coupled PEC wall decreased with increasing n owing to the strong coupling action of the steel coupling beams. In order to ensure the good seismic performance and form a reasonable failure mode, the CRelastic and n in the hybrid coupled PEC wall should not exceed 65% and 0.5, respectively.

The unsatisfactory solar light absorption of WO3 and poor charge separation of BiVO4 are main limits for their use in photoelectrochemical (PEC) water oxidation. Coupling WO3 with BiVO4 has been considered as a feasible way to improve PEC performance by taking complementary advantages of them. In this work, we obtained nanoflake-structured WO3 by hydrothermal growth with post-annealing. The effect of process variables on morphology and resultant performance were investigated. Electrodeposition growth was utilized to deposit BiVO4 onto WO3 forming WO3/BiVO4 heterojunction thin films. Porous BiVO4 with wormlike morphology was tightly coupled and well-distributed onto WO3 nanoflakes. The optimized best-performing WO3/BiVO4 photoanode exhibits higher photocurrent density than that summation of bare WO3 and BiVO4 over entire range of applied potential. This enhancement is mainly attributed to the effective charge separation at WO3/BiVO4 interface, which is confirmed through electrochemical impedance spectra (EIS) measurements, respectively. Our work provides a referable approach for the growth of WO3/BiVO4 heterojunction photoanode with enhanced PEC performance.

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.

A three-dimensional numerical model coupling the macrosegregation and magnetohydrodynamic simulations was developed to investigate the effects of electromagnetic stirring (EMS) on the macrosegregation. The results show that a significant swirling flow was induced by the in-mold EMS, which further changed the shape of the solidification shell and homogenized the solute elements in mold. However, the effects were only confined to the initial billet shell. The improvement in centerline segregation was observed with the usage of the final EMS (F-EMS), which led to the forced convection at the final solidification stage. The solute elements in the mushy zone were significantly even, with the maximum segregation degree of solute C reducing from 1.311 to 1.237. In addition, the effects of the stirrer positions and currents of F-EMS on the macrosegregation alleviation were numerically studied. Different values of centerline segregation were predicted with various stirrer positions and currents, and there is an optimum stirrer parameter to obtain the best macrosegregation alleviation. In the experimental conditions, the optimum position was about 7 m away from meniscus, and the optimum current was 300 A.

For the non-destructive interrogation purpose, the present work studies the flexural wave propagation characteristics in submerged pipes conveying viscous flowing fluid. The internal fluid-pipe and external fluid-pipe coupling effects are both considered. The internal fluid is assumed to be viscous, irrotational, and isotropic; and the external fluid is treated as ideal and irrotational. The pressures exerted on the pipe by the internal and external fluid can be derived via the Navier–Stokes equation. The pipe is modeled based on the first-order shear deformation shell theory. The motion equations of the submerged fluid-conveying pipe are given by the Hamilton’s Principle. The coupled equations of wave motion of the pipes are obtained based on the first-order shear deformation shell theory. The wave propagation relations of submerged pipes conveying viscous flowing fluid are given. Increasing internal fluid velocity, external fluid velocity, or reducing internal fluid mass density can result in an increase in phase velocity of the first flexural mode. In addition, the phase velocities of the first three flexural modes are almost constant under a large axial wave number.

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.

Geometric parameters present varying degrees of coupling effects on different performance indexes including slip resistance, preload force, and steel plate stress of friction high-strength bolts, resulting in mutual restraint relationships among these indexes. Design parameters and performance assessing indicators, in the current code, are relatively simple mentioned, which have few relevant investigations on the influences of different parameters to the mechanical performance of high-strength bolts by a more comprehensive evaluating method. This paper has systematically studied the influences of geometric parameters on the overall performance of friction-type high-strength bolts through four performance evaluation indexes based on finite element method and multi-objective optimization technology. The obtained results showed that the preload force loss of bolt slip was maintained within 5% and part dimension had a major impact on the stress distribution performance of bolt connection. The performance indexes of slip resistance, preload force, steel plate stress, and friction stress were mainly affected by cover plate thickness, middle plate thickness, hole diameter, and nut diameter. From the optimization results, the recommended value range of cover plate to medium plate thickness ratio verified the correctness of existing specifications, and aperture and nut diameter had a narrow value range for the stable performance of high-strength bolts keeping.

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.

To study the effect of nonuniform heat transfer on the grain structure of shells in molds, a micro and macroscopic model coupling heat transfer with dendritic growth was established based on the measured heat flux. Dendritic growth was modeled by using a cellular automaton technique and by considering solutal transport. The quasi-instantaneous nucleation model was introduced to address heterogeneous nucleation, which might occur at the mold wall and in the bulk of the liquid. The temperature field of the billet under the measured heat flux in the mold was calculated, and the initial solidification process and grain structure evolution of four domains at different angles from the inner arc were simulated. The effect of circumferential nonuniform heat transfer on the grain structure of the chill zone and columnar grains of the shell was discussed in detail. The relationship between the distribution of the primary dendrite spacings in different domains and locally measured heat flux was analyzed.

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.

The influence of the severe plastic deformation via high-speed high-pressure torsion (HSHPT) on the structural and magnetic properties of the Zr13Co87 alloys is investigated. Moderate applied deformation promotes the growth of the rhombohedral hard magnetic phase leading to the increase of the sample’s hardness and magnetic coercivity. A higher degree of deformation affects the samples morphology leading to a critical value of the grain size under which the exchange coupling of the soft phase is less effective. Additionally, it produces a random alignment of the anisotropy axes, which are both detrimental to the hard magnetic properties.

Achieve high-efficiency dewatering and purification of emulsion is not always feasible using conventional single method. A centrifugal separator embedded in electric field can achieve efficient dem...

New results about the influence of a small iron borided layer (~ 36 µm) obtained by the powder-pack boriding process (PPBP) and diffusion annealing post-process (DAP) were evaluated. Dry sliding wear tests on PPBP, PPBP + DAP and untreated AISI 1018 steel were performed under the pin-on-disc configuration, and balls of Al2O3 and WC were used as a counterpart at different sliding distances. Also, the contact pressures of the layer/substrate system were evaluated using the finite element model with the aid of the ABAQUS software. The results showed that the Al2O3 ball presented the major coupling (ball-disc), and the PPBP + DAP reduces the specific wear rate around ~ 304 times related to the untreated AISI 1018 steel to 500 m under severe sliding conditions.

Kilometer-deep mines have become the new norm in coal mining. To study the influence of high stress-high ground temperature coupling conditions in deep mines on the oxidative exothermic characteris...

The movement characteristics of yarn in the profiled reed groove of an air-jet loom can have a great impact on the performance of the fabric. Unstable yarn movement tends to lead to weft defects, as short wefts or weft breaks may occur, which could deteriorate the quality of the final fabric. In this paper, the characteristics of the yarn movement in a profiled reed groove are numerically studied. The arbitrary Lagrangian–Eulerian method is used to solve the two-way airflow–yarn interaction and the yarn is simulated with the ball–socket model. A fluctuation ratio is defined to characterize the unsteadiness of the yarn movement. Our simulation first investigates the effect of the gap ratio of the profiled reed groove (β) on the yarn movement then compares the movements of different yarn kinds. The simulation results indicate that a larger β not only decreases gas leaks (thus saves gas consumption), but also stabilizes the yarn movement. Our simulation results also show that the movement of the yarn of polypropylene is more stable than the other two weft-yarn materials. An experiment is also conducted to validate our numerical results, which shows a favorable agreement between them. Our numerical results of the yarn movement in the profiled reed groove can provide a valuable insight into the optimization of the weft insertion system of the air-jet loom.

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 dynamic response of a hollow cylinder subjected to a hygrothermal coupled shock is studied. The memory-dependent differential is introduced into the heat transfer equation and the diffusion equ...

Landslide tsunamis are complex fluid–solid coupling processes that often cause enormous catastrophes. In this study, the smooth particle hydrodynamics (SPH) and discrete element method (DEM) coupling algorithms are used to simulate the tsunami which was induced by the 1963 Vajont landslide, Italy. In order to simulate the failure process of the landslide, a DEM numerical model is constructed based on the geological structure of the landslide, and contact parameters for the DEM particles are inverted according to the laboratory tests. Based on the numerical results, the whole process of the tsunami by the Vajont landslide is reproduced in detail. Comparisons show that the simulated motion and accumulating characteristics of the landslide, the climb-up and peak overtopping flow of the tsunamis, and the load on the dam by the tsunamis agree well with the published results. The simulation also indicates that the right bank slope of Vajont Dam is the major spillway of the flood, thereby significantly reducing the flow directly over the dam, which is helpful to stabilize the dam; and the concrete of the left abutment is damaged by the mixture flow of water and geomaterials with a higher velocity (approx. 35 m/s at the max.). The overtopping depth decreases from the north bank to the south bank. The maximum depth on the right abutment and the left abutment is approximately 80 and 65 m, respectively, lower than the reported estimation of ~ 150 m. This study shows that the coupled SPH–DEM method and the developed code—CoSim—work well for the analysis and research on landslide tsunami.

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...