Elastic-viscoplastic behaviors of polymer-blend geocell sheets:Numerical and experimental investigations

Polymer-blend geocell sheets(PBGS)have been developed as substitute materials for manufacturing geocells.Various attempts have been made to test and predict the behaviors of commonly used geogrids,geotextiles,geomembranes,and geocells.However,the elastic-viscoplastic behaviors of novel-developed geocell sheets are still poorly understood.Therefore,this paper investigates the elastic-viscoplastic behaviors of PBGS to gain a comprehensive understanding of their mechanical properties.Furthermore,the tensile load-strain history under various loading conditions is simulated by numerical calculation for widespread utilization.To achieve this goal,monotonic loading tests,short-term creep and stress relaxation tests,and multi-load-path tests(also known as arbitrary loading history tests)are performed using a universal testing machine.The results are simulated using the nonlinear three-component(NLTC)model,which consists of three nonlinear components,i.e.a hypo-elastic component,a nonlinear inviscid component,and a nonlinear viscid component.The experimental and numerical results demonstrate that PBGS exhibit significant elastic-viscoplastic behavior that can be accurately predicted by the NLTC model.Moreover,the tensile strain rates significantly influence the tensile load,with higher strain rates resulting in increased tensile loads and more linear load-strain curves.Also,parametric analysis of the rheological characteristics reveals that the initial tensile strain rates have negligible impact on the results.The rate-sensitivity coefficient of PBGS is approximately 0.163,which falls within the typical range observed in most geosynthetics.

Numerical Analysis of Hydrodynamic Behaviors of Two Net Cages with Grid Mooring System Under Wave Action

Based on rigid kinematics theory and lumped mass method, a mathematical model of the two net cages of grid mooring system under waves is developed. In order to verify the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and the experimental results, it can be found that the simulated and the experimental results agree well in each wave condition. Then, the forces on the mooring lines and the floating collar movement are calculated under different wave conditions. Numerical results show that under the same condition, the forces on the bridle ropes are the largest, followed by forces on the main ropes and the grid ropes. The horizontal and the vertical float collar motion amplitudes increase with the increase of wave height, while the relationship of the horizontal motion amplitude and the wave period is indistinct. The vertical motion amplitude of the two cages is almost the same, while on the respect of horizontal motion amplitude, cage B （behind cage A, as shown in Fig. 4） moves much farther than cage A under the same wave condition. The inclination angle of the floating system both in clockwise along y axis and the counter one enlarges a little with the increase of wave height.

Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

Numerical Analysis of Dynamic Behavior of RC Slabs Under Blast Loading

In order to reduce economic and life losses due to terrorism or accidental explosion threats, reinforced concrete （RC） slabs of buildings need to he designed or retrofitted to resist blast loading. In this paper the dynamic behavior of RC slabs under blast loading and its influencing factors are studied. The numerical model of an RC slab subjected to blast loading is established using the explicit dynamic analysis software. Both the strain rate effect and the damage accumulation are taken into account in the material model. The dynamic responses of the RC slab subjected to blast loading are analyzed, and the influence of concrete strength, thickness and reinforcement ratio on the behavior of the RC slab under blast loading is numerically investigated. Based on the numerical results, some principles for blast-resistant design and retrofitting are proposed to improve the behavior of the RC slab subjected to blast loading.

Numerical investigation of the mechanical behavior of the backfill–rock composite structure under triaxial compression

To ensure safe and economical backfill mining,the mechanical response of the backfill–rock interaction system needs to be understood.The numerical investigation of the mechanical behavior of backfill–rock composite structure(BRCS)under triaxial compression,which includes deformation,failure patterns,strength characteristics,and acoustic emission(AE)evolution,was proposed.The models used in the tests have one rough interface,two cement–iron tailings ratios(CTRs),four interface angles(IAs),and three confining pressures(CPs).Results showed that the deformation,strength characteristics,and failure patterns of BRCS under triaxial compression depend on IA,CP,and CTR.The stress–strain curves of BRCS under triaxial compression could be divided into five stages,namely,compaction,elasticity,yield,strain softening,and residual stress.The relevant AE counts have corresponding relationships with different stages.The triaxial compressive strengths of composites increase linearly with the increase of the CP.Furthermore,the CP stress strengthening effect occurs.When the IAs are45°and 60°,the failure areas of composites appear in the interface and backfill.When the IAs are 75°and 90°,the failure areas of composites appear in the backfill,interface,and rock.Moreover,the corresponding failure modes yield the combined shear failure.The research results provide the basis for further understanding of the stability of the BRCS.

Numerical Simulation of Motor Vehicles’ Courtesy Behavior on Crosswalk Based on Car-Following Model

In observing driver courtesy towards pedestrians at unsignalized crosswalks, a behavioral model was adopted in a simulation based on the GM Car-Following Model. The SIMI Motion Software was used to extract the vehicle operation data from Wenyi South Road and Hanyuan Road in Xi'an City. The parameters of the GM Car-Following Model were calibrated by genetic algorithm. The road simulation environment based on the Car-Following Model was constructed by MATLAB. In the case of no stopping, uniform deceleration avoidance with advance notice, emergency brake avoidance without advance notice, changes such as the displacement of the Car-Following queue, headway, speed, acceleration, and deceleration were analyzed by numerical simulation. The results show that when there is advance notice before the crosswalk, the minimum headway distances of Car1-Car2, Car2-Car3, Car3-Car4 and Car4-Car5 are 7.09 m, 7.38 m, 7.65 m, 7.91 m, and the average rates of change of the headway during deceleration are 0.78 m/s, 0.74 m/s, 0.71 m/s, 0.68 m/s respectively;in the absence of advance notice before the crosswalk, the minimum headway distances of Car1-Car2, Car2-Car3, Car3-Car4 and Car4-Car5 are 7.28 m, 7.75 m, 8.19 m, 8.59 m, and the average rates of change of the headway during deceleration are 1.57 m/s, 1.25 m/s, 1.04 m/s, 0.96 m/s, respectively. Therefore, in order to effectively prevent the occurrence of vehicle rear-end events, it's necessary to set traffic signs and markings on the preceding section of the intersection or road exhibiting behavioral comity.

Numerical study on the discharge characteristics and nonlinear behaviors of atmospheric pressure coaxial electrode dielectric barrier discharges

The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied.It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.

Numerical simulation of the behaviors of test square for prehistoric earthen sites during archaeological excavation

During the process of archaeological excavation in the regions of Southeast China, collapse of test square usually occurs due to poor site-specific conditions. In this paper, the fast Lagrangian analysis of continua in three dimensions（FLAC3D） is employed to reveal the behaviors of test square. Taking the archaeological works in Liangzhu prehistoric earthen sites as the research background, the paper first introduces the geological setting, excavation procedure and monitoring scheme of the studied test square. Then, the deformation of four sides of the test square is modeled using FLAC3D. By comparison, it shows that the numerical results are consistent with the results from field monitoring. The result suggests that the numerical simulation can be effectively applied to representing the actual behaviors of the test square,which is helpful for determination of excavation scheme and stability evaluation of the test square during archaeological excavation.

Experimental and numerical study on cyclic behavior of a UHPC-RC composite pier

Conventional reinforced concrete piers are vulnerable to severe compressive damage under strong earthquake conditions and are difficult to quickly rehabilitate.This paper develops a new type of composite pier,consisting of ultra-high-performance concrete(UHPC)and reinforced concrete(RC).This UHPC-RC composite pier uses a UHPC cover outside of an RC core to achieve a high load-carrying capacity and mitigate compressive damage.An experiment is performed to evaluate the performance of the UHPC-RC composite pier under cyclic deformation.The crack development,ultimate failure modes,and load-carrying capacities of the pier are observed.Because of the extraordinary compressive strength of UHPC,the composite pier suffers little compressive damage under large lateral deformations.The composite pier fails as a result of fracturing of the reinforcement.A numerical model is developed to reproduce the cyclic behavior of the composite pier.On the basis of the verified numerical model,a parametric analysis is used to investigate the influence of the thickness of the UHPC cover and the axial load ratio.Finally,an approach is recommended for designing composite piers.

Shear behavior of AZ80 Mg alloy using experimental, theoretical and numerical techniques

The shear punch test(SPT)is a suitable experiment for characterizing the shear behavior of various materials,especially where there are volume limitations.In the present investigation,the relations among various parameters such as clearance,die diameter and sample thickness,and the yield and ultimate shear strengths of AZ80Mg alloy were studied.Moreover,based on the Mohr-Coulomb theory,relatively optimum conditions were introduced for the shear punch test.With this regard,a range of2%-10%is found to be suitable for the clearance/sheet thickness ratio.To provide a simple shear stress state during a shear punch test,it is also necessary to select the die diameter/sheet thickness ratio between2:1and10:1.Based on the predictions of the Mohr-Coulomb theory,it is better to conduct a room-temperature shear punch test with a sample thickness of0.5mm,a clearance of25μm and a die diameter of2mm.Finally,the mean conversion factors to gain the tensile and compressive yield strengths of the cast AZ80from its shear one are found to be1.70and3.09,respectively.

Numerical simulation of thermal behavior during laser metal deposition shaping

Abstract: Based on the element life and death theory of finite element analysis(FEA), a three-dimensional multi-track and multi-layer model for laser metal deposition shaping(LMDS) was developed with ANSYS parametric design language(APDL), and detailed numerical simulations of temperature and thermal stress were conducted. Among those simulations, long-edge parallel reciprocating scanning method was introduced. The distribution regularities of temperature, temperature gradient, Von Mise’s effective stress, X-directional, Y-directional and Z-directional thermal stresses were studied. LMDS experiments were carried out with nickel-based superalloy using the same process parameters as those in simulation. The measured temperatures of molten pool are in accordance with the simulated results. The crack engendering and developing regularities of samples show good agreement with the simulation results.

Numerical Simulation of Mechanical Behaviors of the TiNi Shape Memory Alloy Welded Joints in the Precise Pulse Resistance Butt-Welding

The hysteresis unit system was introduced to mechanical structure behavior of the TiNi SMA joint based on the structure characteristics of the martensite variants in the joints, and some functions reflecting its inner structure characteristics and micro-behavior such as density function, phase transformation function were set up from micro-points. Finally, the structure behavior relationship and corresponding mathematic model reflecting the relationship among hysteresis strain, stress and phase transformation strain were provided, which could predict the stress-strain behavior of the TiNi SMA joint to large extent.

Heterogeneous individuals’behavioral biases model and numerical simulation

A model of the relationships between individual cognitive biases and individual decision-making based on the analysis of cognitive biases of bonded rationality individual,has been established in this paper by introducing a set of new variables called overconfidence coefficient and attribution bias coefficient to the sentiment model. The irrational expectation and irrational risk aversion as two inseparable aspects of bonded rationality are expressed in an unified model,and a method of measuring individual cognitive biases is proposed,which overcomes the shortcomings of traditional normative models that can not describe the differences of behaviors among heterogeneous individuals. As a result,numerical simulations show that individual cognitive risk is a positive interaction with overconfidence coefficient,and a negative interaction with attribution bias coefficient.

Long-time limit behavior of the solution to an atom's master equation

We study the long-time limit behavior of the solution to an atom＇s master equation. For the first time we derive that the probability of the atom being in the α-th （α = j ＋ 1 -jz, j is the angular momentum quantum number, jz is the z-component of angular momentum） state is {（1 - K/G）/[1 - （K/G）2j＋1]}（K/G）^α-1 as t → ＋∞, which coincides with the fact that when K/G 〉 1, the larger the a is, the larger the probability of the atom being in the α-th state （the lower excited state） is. We also consider the case for some possible generaizations of the atomic master equation.

Numerical analysis on seismic behavior of railway earth embankment: A case study

A numerical case study on the seismic behavior of embankment was carried out based on a prototype of earth embankment in Yun-Gui Railway （from Kunming City to Nanning City） in southwest of China. A full-scale model of earth embankment was established by means of numerical simulation with FLAC3D code. The numerical results were verified by shaking table test. The seismic behaviors of earth embankment were studied, including the horizontal acceleration response, the vertical acceleration response, the dynamic displacement response, and the block state of earth embankment. Results show that the acceleration magnification near the embankment slope is larger than that in internal earth embankment body. With the increase of input peak acceleration, the horizontal acceleration magnification presents a decreasing trend. The horizontal acceleration response at the top of embankment is more sensitive to the intensity of ground motion than that at the bottom of cmbankment. The embankment presents an obvious nonlinear-plastic characteristic when the input horizontal peak acceleration is larger than 0.3 g. The maximum residual deformation occurs in the middle of embankment slope surface instead of at the top of embankment. The upper part of embankment experiences tension failure without shear failure, and area at mainly presents shear failure under the earthquake loading. surface of earth embankment. the bottom of embankment around the symmetry-axis of embankment The tension failure and shear failure repeatedly occur along the slope

LONG-TIME BEHAVIOR OF TRANSIENT SOLUTIONS FOR CELLULAR NEURAL NETWORK SYSTEMS

By establishing concept an transient solutions of general nonlinear systems converging to its equilibrium set, long-time behavior of solutions for cellular neural network systems is studied. A stability condition in generalized sense is obtained. This result reported has an important guide to concrete neural network designs.

Analytical and numerical solutions for shear mechanical behaviors of structural plane

The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to describe the stress deformation characteristics of plastic structural plane and brittle structural plane.The relation of stress and strain to the failure mode of structural plane considering the effect of its shape was investigated,and a model which could reflect the relation between undulate angle and shear strength was built.The result indicates that structural plane presents nonlinear characteristics,specifically,the value of undulate angle,as well as corresponding shear strength,becomes larger as the normal stress decreases.

Numerical Investigations on the Transient Behavior of Sand Waves in Beibu Gulf Under Normal and Extreme Sea Conditions

In this study, a morphodynamic numerical model is established with the Regional Ocean Modeling System(ROMS)to investigate the transient behavior of sand waves under realistic sea conditions. The simulation of sand wave evolution comprises two steps: 1) a regional-scale model is configured first to simulate the ocean hydrodynamics, i.e., tides and tidal currents, and 2) the transient behavior of sand waves is simulated in a small computational domain under the time-variant currents extracted from the large model. The evolution of sand waves on the continental shelf in the Beibu Gulf is specifically investigated. The numerical results of the two-year evolution of sand waves under normal sea conditions compare well with the field survey data. The transient behavior of sand waves in individual months shows that the sand waves are more stable in April and October than that in other months, which can be selected as the windows for seabed operations. The effects of sediment properties, including settling velocity, critical shear stress and surface erosion rate, on sand wave evolution are also analyzed. Then, the typhoon-induced currents are further superimposed on the tidal currents as the extreme weather conditions. Sand waves with the average wavelength generally have more active behavior than smaller or larger sand waves. The characteristics of the evolution of sand waves in an individual typhoon process are quite different for different hydrodynamic combinations. For the storm conditions, i.e., the real combination and maximum combination cases, the sand waves experience a significant migration together with a damping in height due to the dominant suspended sediment transport. For the mild conditions, i.e., the pure tidal current and minimum combination cases, the sand waves migrate less, but the heights continue growing due to the dominant bedload transport.

Numerical investigation of fracture behavior of tunnel by excavation loading

A rock failure process analysis model, RFPA2D code, a two-dimensional numerical code, were proposed. The code not only satisfied the global equilibrium, strain consistent and nonlinear constitutive relationship of rock and soil materials but also took into account the heterogeneous characteristics of rock materials at macroscopic and microscopically level. The failure behavior of tunnel could be simulated by this numerical model. The model could realistically simulate the fracture behavior of tunnel by excavation loading, strength limits, and post peak response for both tension and compression. As the proposed method was used to conduct the stability analysis of tunnel, the safety factor of tunnel was defined as the ratio of actual shear strength parameter to critical failure shear strength parameter. Not only the safety factor of tunnel with specific physics meaning can be obtained, but also the overall failure process and the location of failure surface may also be determined at the same time.

Experimental and Numerical Investigation on the Mechanical Behaviors of the Velcro^(■) and Dual-Lock Fasteners

In order to characterize the mechanical behaviors of the Velcro~? and Dual-lock fasteners, a series of tests including the butt-joint(BJ) monotonic tensile and shear, mixed tensile-shear with various loading angles, the loading rates effects, the double cantilever beam(DCB) fracture and 180° peel experiments were performed. The tensile and shear tests results showed that the mechanical behaviors of Velcro~? fastener separation are analogous to ductile materials, and those of Dual-lock fasteners are more like brittle ones. The mixed tensile-shear with various loading angles tests results demonstrated that magnitudes of the peak stresses in 30°, 45°, and 60° have no significant differences, which are lower than those in the monotonic tensile or shear tests for the two fasteners. The effects of the loading rate tests show that the peak stresses of the Velcro~? fastener manifested good performance at the loading rate of 10 to 20 mm/min in the tensile and shear conditions, and the Dual-lock did it well around the loading rates of 10 to 20 mm/min in the tensile condition. The cohesive zone model(CZM) is employed to numerical predict the DCB fracture and the 180° peel tests. The CZM predictions results are proven to commendably capture the two tests separation processes, of the tow fasteners, and the numerical results agreed well with the peeling tests data of the Dual lock fasteners. The results and discussions in this study are expected to bring more understanding to engineers and designers about the performance of Velcro~? and Dual lock fasteners.