Pressure Strain Rate Research Articles

A generalization of the shock invariant relationship

Shock invariant relationship, which was conceived for inert shock waves to derive the 4th power relationship between shock pressure and maximum strain rate, is generalized for reactive shock waves such as Chapman–Jouget detonation and shock-induced vaporization. The generalization, based on the first-order reaction models, is a power function relationship between overall dissipated energy (Δedis) and reaction time Δτ such that ΔedisΔτ1/α=constant, where the power coefficient α is found to be in the range of 2/3–4. Experimental data, though scarce, are consistent with the generalization. Implication of the generalization for inert shocks is also considered and suggests a broad range of the 4th power coefficient including an inequality equation that constrains the shock and particle velocity relationship.

Large-Eddy vs. Reynolds-Averaged Navier–Stokes Simulations of Flow and Heat Transfer in a U-Duct with Unsteady Flow Separation

Large-eddy simulation (LES) and Reynolds-Averaged Navier–Stokes (RANS) equations were used to study incompressible flow and heat transfer in a U-duct with a high-aspect-ratio trapezoidal cross section. For the LES, the WALE subgrid-scale model was employed, and its inflow boundary condition was provided by a concurrent LES of incompressible fully-developed flow in a straight duct with the same cross section and flow conditions as the U-duct. LES results are presented for turbulent kinetic energy, Reynolds stresses, pressure–strain rate, turbulent diffusion, turbulent transport, and velocity–temperature correlations, with a focus on how they are affected by the U-turn region of the U-duct. The LES results were also used to assess three commonly used RANS models: the realizable k-ε with the two-layer model in the near-wall region, the two-equation shear-stress transport model, and the seven-equation stress-omega Reynolds stress model. Results obtained show steady and unsteady RANS to incorrectly predict the effects of unsteady flow separation. The results obtained also identified the terms in the RANS models that need to be modified and suggested how turbulent diffusion should be modeled when there is unsteady flow separation.

A theoretical model for the oblique impact of fragments

A portion of the casing charge's fragments would strike the target plate and ricochet when it exploded close to or inside a steel structure, like a ship or manufacturing facility. Considering the high pressure, high temperature, and high strain rate during the impact, the kinematic characteristics of the ricochet fragment, such as ricochet velocities and ricochet angle, are challenging to describe using the existing methods. In this study, a novel theoretical model of ricochet fragment kinematics under oblique impact was proposed, and the corresponding initial assumptions and application conditions were presented. A series of oblique impact experiments was conducted to obtain the differences in kinematic characteristics under various impact velocities and impact angles. The parameters of the proposed theoretical model were determined. The accuracy of the theoretical model was verified by using 921A hull steel target plate. The average relative error and standard deviation of ricochet velocity were 7.4 % and 2.3 %, respectively, and the mean relative error and standard deviation of the ricochet angle are 11.2 % and 1.1 %, respectively. The results showed that the theoretical model can predict the ricochet velocity well, and the error of ricochet angle increased due to the different pile-up effect of different strength target plates, but it was still within the reasonable range. In addition, the effects of the impact velocity and angle on the ricochet velocity and angle were analyzed. When the impact angle was small, the ricochet angle and velocity were affected by both impact velocity and angle. When the impact angle increased to a certain Angle (>64.2°), the ricochet velocity only increased linearly with the impact velocity. The ricochet angle increased with the increase in the impact angle. When the impact velocity was less than 400 m/s, the ricochet angle increased with the increase in the impact velocity. When the velocity is greater than 400 m/s, the ricochet angle decreased with the increase in the impact velocity. When the impact angle was greater than 57° and the impact velocity was greater than 400 m/s, the ricochet angle was almost only related to the impact angle. The results indicate that the proposed model has good accuracy and can have high application value in terminal effects, safety engineering, and structural defense fields.

Compression Characteristics of Liquid Ring Compressors With Fixed and Freely Rotating Casings

Abstract Liquid ring compressors (LRC) are used for a wide range of compression and vacuum applications, including corrosive or flammable gases for which other compression technologies may not be feasible. The presence of a surrounding liquid ring may offer the possibility of polytropic compression due to incremental heat loss to the liquid. This aspect may play a critical role in compression (and expansion) processes of heat engine cycles toward approaching the targeted Carnot efficiencies. To date, published research addressing the physical phenomena behind LRC is highly limited. Experimentally studying these machines will result in a demonstration of aggregate performance. In order to improve our understanding of LRC with and without freely rotating casings and to be able to analyze the complex inner workings, a numerical approach using computational fluid dynamics (CFD) tools, supported by available experimental data for validation purposes, has been established. Physical parameters such as water–air interface, temperature, pressure, entropy production, vorticity, and shear strain rate are presented for a baseline geometry taken from the open literature. Finally, temperature-entropy paths and isothermal and isentropic efficiencies are presented. The significant performance gain from the freely rotating casing is highlighted. Detailed results present insights into work addition processes of such machines.

Effect of the Addition of Steel Fibers on the Bonding Interface and Tensile Properties of Explosion-Welded 2A12 Aluminum Alloy and SS-304 Steel

First of all, the explosion-welding method was adopted to prepare steel fiber-reinforced steel-aluminum composite plates. Secondly, the smooth particle hydrodynamic (SPH) method was used to investigate the effect of introducing steel fibers to a vortex region created at the bonding interface of the steel-aluminum composite plate. Thirdly, the following conclusions were drawn through an analysis of the vortex region with the assistance of scanning electron microscopy and energy-dispersive X-ray spectroscopy. A brittle intermetallic compound FeAl was produced in the vortex region in an environment characterized by high temperature, high pressure, and high strain rate, resulting in cracks, holes and pores. In addition, the hardness of the vortex area was less than the estimated value, which is mainly because the main element in the vortex area was 2A12 aluminum with low hardness, and there were cracks, holes, pores and other defects that caused hardness reduction. Although the addition of steel fibers caused defects at the bond interface, the addition of steel fibers was effective in improving the tensile resistance performance of steel-aluminum composite panels to a certain extent. In addition, the larger the fiber diameter, the more significant the increase in tensile resistance.

Numerical modeling of the effect of nozzle diameter and heat flux on the polymer flow in fused filament fabrication

A numerical model that fully account for the velocity of the traveling filament (push velocity) in the liquefier is presented in the current work to predict the pressure, temperature, outlet melt viscosity, strain rate, and velocity in the hot-end of a FFF system for printing tough-poly(lactic acid) (TPLA). The numerical model was thoroughly validated by comparing the model predictions with experimentally measured feeding force data. The predicted numerical results closely approximated the experimentally measured feeding force. Then the model was also validated with extrudate temperature, measured with a thermal imaging camera, and the results obtained are in good agreement. Outlet capillary diameter, feeding rate, and heat flux (quantified in terms of Nusselt number) were varied to determine the response of pressure field, temperature, velocity, viscosity, and strain rate in the liquefier. The results show that an increase in the nozzle outlet diameter decreases the extrusion pressure in the hot-end. The maximum pressure predicted for TPLA is 3.34, 2.91, and 2.04 MPa for the 0.4, 0.6, and 0.8 mm outlet diameters nozzles, respectively. Also, an increase in the nozzle outlet diameter decreases the central velocity at the outlet and decreases the shear rate with an increase in the viscosity of TPLA at the exit during material extrusion. The area-weighted averaged outlet temperature for TPLA decreases as the feeding rate increases for all three nozzle diameters. Elucidated from the simulation results, significant variation of the normalized velocity at the center of the nozzle outlet suggests that different printing speeds for TPLA material extrusion should be set for different nozzle diameters. Otherwise, the accuracy and precision of the gantry motion during layer deposition on the print will be compromised. The simulation results indicate that based on the 90% core melting temperature requirement, at a liquefier set temperature of 503 K, the TPLA should be printed below 80mm/min for all outlet diameters considered. A Nusselt number of 49.61 was observed to be the upper limit where an increase in the heat flux in the liquefier has no significant effect on the area-weighted averaged outlet temperature of TPLA.

Interface-unaware sub-scale dynamics closure model for multimaterial cells in cell-centered arbitrary Lagrangian-Eulerian hydrodynamics

We develop new interface-unaware sub-scale dynamics (IU-SSD) multimaterial cell closure models for the Lagrangian stage of cell-centered arbitrary Lagrangian-Eulerian method. The IU-SSD closure models do not require information about the interface in the multimaterial cell and consist of two stages. The first stage makes use of a constant volume fraction model, wherein the main ingredient is the construction of a nodal Riemann solver that is capable of handling multimaterial cells. This model provides the numerical flux at cell face and introduces the mechanism of velocity relaxation. The sub-scale interactions of the materials in a multimaterial cell are taken into account by incorporating the pressure relaxation model in the second stage. Two types of pressure relaxation models are designed utilizing the linear relation between viscous pressure and volume strain rate. The pressure relaxation models are implemented via a multi-step time marching procedure such that they satisfy the physically justified constraints: positivity of volume, positivity of internal energy and smooth relaxation of pressure. The performances of new IU-SSD models are demonstrated via a series of numerical tests involving both Lagrangian and arbitrary Lagrangian-Eulerian hydrodynamics calculations.

Pseudo-Static Simplified Analysis Method of the Pile-Liquefiable Soil Interaction considering Rate-Dependent Characteristics

The lateral pressure generated by liquefied soil on pile is a critical parameter in the analysis of soil-pile interaction in liquefaction-susceptible sites. Previous studies have shown that liquefied sand behaves like a non-Newton fluid, and its effect on piles has rate-dependent properties. In this study, a simplified pseudo-static method for liquefiable soil-pile interaction analysis is proposed by treating the liquefied soil as a thixotropic fluid, which considers the rate-dependent behavior. The viscous shear force generated by the relative movement between the viscous fluid (whose viscosity coefficient varies with excess pore pressure and shear strain rate) and the pile was assumed to be the lateral load on the pile. The results from the simplified analysis show that the distribution of bending moment is in good agreement with experiments data. Besides, the effects of various parameters, including relative density, thickness ratio of nonliquefiable layer to liquefiable layer, and frequency of input ground motion, on the pile-soil rate-dependent interaction were discussed in detail.

Dynamic response characteristics of adjacent tunnel lining under blasting impact in subway connecting passage

The connecting passage between two adjacent tunnels is conducive to the rescue and evacuation of subway tunnels when disasters occur. The blasting method is usually used in the construction of connecting passage. The vibration caused by blasting construction may endanger the safety of subway tunnel structure. As a result, the influence of blasting pressure on the stability of subway tunnel lining structure during the excavation of connecting passage is studied, and the safe blasting construction distance is proposed, which is crucial to the safety of adjacent subway tunnel lining. This study takes the connecting passage of Wuhan Metro Line 8 as an example. Using Finite element software ANSYS/LS-DYNA, an accurate numerical calculation model of construction site is established. The nonlinear elastoplastic mechanical characteristics of soil, rock, and tunnel lining are simulated by Drucker Prager, Plastic Kinematic, and Johnson Holmquist Concrete constitutive material models, respectively. The credibility of the three-dimensional numerical calculation model and material constitutive model was proved by contrasting the field measured data of the connecting passage with the numerical calculated results. Analysis of numerical results, the axial and radial PPV, frequency, and Von Mises stress of subway tunnel lining are obtained. The influence of subway tunnel lining under adjacent blasting can be obtained by analyzing the distribution law of PPV and Von Mises stress. Non-static tensile strength is needed considering the high pressure and high strain rate process of concrete during blasting. By fitting the relationship between PPV and dynamic tensile stress, and referring to DIF parameters, the safety range of PPV in subway tunnel lining blasting is determined. The critical safety distance between blasting construction and tunnel lining is obtained by Sadovsky vibration velocity attenuation formula, which is used to guide the subsequent blasting excavation of continuous tunnels.

Studying the strengthening mechanism and thickness effect of elastomer coating on the ballistic-resistance of the polyurea-coated steel plate

Experiments have shown that the ballistic performance of the steel plate improves significantly after coating polyurea at the impact face. However, the strengthening mechanism of the elastomer coating on the ballistic-resistance is not understood well until now. In this paper, the strengthening mechanism and thickness effect of the coating under fragment simulating projectiles (FSP) impact are studied through numerical and experimental analysis. Firstly, a viscoplastic constitutive model of polyurea is developed based on experimental characterization and thermodynamic equation of state. It can capture strongly nonlinear volumetric behavior and impact-induced shearing stiffening and strengthening considering the coupling of high pressure, high temperature, and high strain rate under ballistic impact. Then, by applying this newly developed viscoplastic model of polyurea, the underlying ballistic-resistant mechanism of the polyurea-coated steel plate is numerically studied. The analysis shows that the dynamic behavior of polyurea under ballistic impact and propagating regulation of impact wave jointly play the key role. One side, the impact-induced stiffening and strengthening of the polyurea change the failure modes of the steel plate and considerably improve the ballistic-resistance of the structure. The other side, increasing coating thickness can only provide the limited benefit for improving the ballistic-resistance of the structure, as obtained in experiments. For the impact-face-coated steel plate, the low-thickness polyurea coating suffering from FSP impact can increase the frequency of the compressive wave reflection-superposition on the high-impedance polyurea/steel interface before the energy transfer from the impacted location. This helps to improve the pressure level and enhance the instantaneous energy storage and dissipation of the polyurea per volume significantly. However, increasing coating thickness can make the pressure level and the specific energy density of polyurea decrease gradually during penetration. It is also found that the energy dissipation of FSP during penetration is reduced after increasing the coating thickness because of the erosion mitigation from the structure. The new insight on the strengthening mechanism of elastomer coating will be helpful for the light armor design.

Effect of Heat Treatment Process and Composition on Deformation and Damage Behavior of WHA under Detonation Loading

The excellent material properties of tungsten heavy alloy (WHA) make it widely used in the military field. When used as killing elements of weapons, its dynamic mechanical properties under detonation loading directly determine the damage effect of weapons, which makes the research on its mechanical behaviors under high pressure and high strain rate loads such as detonation loading of great significance. In this paper, several WHAs with different compositions and processes are selected, and the mechanical properties and deformation and damage behavior under static explosion test are analyzed by combining macro and micro study, so as to provide guidance for the subsequent optimization of the performance design of WHA.

Spalling modes and mechanisms of shocked nanocrystalline NiTi at different loadings and temperatures

Spalling damage is one of the typical forms of material dynamic failure, of which the damage modes and physical mechanisms are directly related to the design of material impact protection. NiTi alloys have already been used in some dynamic extreme environments. However, its dynamic failure behavior and mechanism under high pressure and high strain rate are still unclear. In this study, nonequilibrium molecular dynamics simulations (NEMD) were used to explore the spalling modes and physical mechanisms of shocked nanocrystalline NiTi (nc-NiTi) at different loadings and temperatures. The results show that its spalling modes include classical-spall without melting state, multi-spall with partial-melting or partial-disorder states and micro-spall with complete melting or disorder states according to the thermodynamic states and melting characteristics of the spall region. It was found that the multi-spall or micro-spall depends on the homogeneity of the main Voronoi polyhedrons (VPs) of the short-range order (SRO) under different shock stresses, and that the spall strength at T0=1000 K decreases more regularly than that of T0=300 K with the increase of shock loading velocity Up. Moreover, increasing the initial ambient temperature T0 from 300 K to 1000 K not only reduced the spall strength of nc-NiTi, but also reduced the critical stress required for different spalling modes. This is attributed to the temperature softening effect occupying a dominant position during the spalling, including the grain boundary diffusion and the change of the thermodynamic paths due to the increase of initial ambient temperature T0.

Effects of heat release on turbulence characteristics in a three-dimensional spatially developing supersonic droplet-laden mixing layer

By direct numerical simulations, the effects of heat release on turbulence characteristics are systematically investigated in a three-dimensional spatially developing supersonic droplet-laden mixing layer with the convective Mach number of 1.2. A one-step Arrhenius global reaction mechanism is employed for the combustion of n-decane and the liquid fuel is supposed to be fully atomized point droplets. The reactive and inert simulations are both conducted for comparison. The thermal-runaway ignition occurs in the transition region and the flame surfaces distribute at the upper and lower edges of the mixing layer. The diffusion combustion happens on the hot side, but the flame tends to extend towards the cold fuel layer with more vigorous chemical reactions, where the premixed combustion mode dominates. The combustion heat release makes the droplets gradually spread downwards and the tendency that the droplets accumulate in the low-temperature and high-density regions is augmented. Under the effects of chemical reactions, the mixing layer asymmetry is enhanced with the shear layer center further skewing towards the hot side and turbulence anisotropy is augmented due to the reduction of the pressure-strain rate. The fluctuations of temperature, density and species mass fractions are also augmented and two peaks appear at the positions of flame surfaces on the hot and cold sides, where the lower peak is more significant. However, the Reynolds stresses are attenuated, but exhibit the inflection points with larger magnitude on the cold side, which is attributed to the viscous transport and the enhancement of thermodynamic fluctuations.

Microstructural evolution of polyurea under hydrostatic pressure

Polyurea (PU) is a versatile high strain rate elastomeric polymer that has attracted significant interest due to its utility as a blast and ballistic resistant coating. Predictive design of PU materials, particularly with a focus on structure, is complicated by the occurrence of both high pressure and high strain rate effects in response to blast and ballistic impact. To help elucidate the behavior of PU under such conditions, we sought to characterize the microstructural evolution of PU under hydrostatic compression. To this end, we utilized a diamond anvil cell with in-situ X-ray scattering to monitor the compression-induced microstructural changes of two PU materials differing in their soft segment length. We found that regardless of soft segment length, the initially phase separated structure becomes increasingly mixed during hydrostatic compression up to ~1 GPa. Despite this increase in phase mixing, the interchain network between urea linkages formed through hydrogen bonds remains apparent at pressures well above 1 GPa. The mean spacing associated with the interchain hydrogen-bonded network within the hard segment domains contracts under hydrostatic compression and in some cases recovers upon load removal. Furthermore, the extent of both deformation and recovery depends upon the degree of microphase separation as dictated by the length of the soft segment, wherein PU with a longer soft segment deforms less and recovers more.

Thermo-Rheological Properties of the Ethiopian Lithosphere and Evidence for Transient Fluid Induced Lower Crustal Seismicity Beneath the Ethiopian Rift

Lower crustal earthquakes at plate boundaries and intraplate settings occur at depth where deformation is normally expected to occur in a ductile manner. Here we use the available earthquake catalogs and compute theoretical predictions for a range of conditions for the occurrence of lower crustal earthquakes beneath the Main Ethiopian Rift (MER) and adjacent north-western (NW) plateau. Yield strength envelops are constructed using information on geothermal gradient, strain rate, and composition constrained by geophysical observations. Our models suggest that away from the MER beneath the NW plateau the depth distribution of earthquakes in the lower crust is best explained by strong mafic lower crustal rheology and hydrostatic fluid pore pressure conditions. In the same region the effective elastic thickness is similar to seismogenic thickness showing that the lower crust has long-term strength and hence can physically support brittle deformation. On the contrary, in the central MER the seismogenic thickness is much larger than the effective elastic layer thickness implying that the lower crust has no long-term strength. Here our models show that both hydrostatic and near-lithostatic fluid pore pressures fail to explain the observed seismicity and instead a combination of near-lithostatic pore fluid pressure and transient high strain rate due to the movement of fluids provide a plausible mechanism for the occurrence of seismicity in the lower crust. Our interpretations are supported by occurrence of swarms of deep earthquakes beneath the MER, as opposed to more continuous background deep seismicity away from the rift. Using time-depth progression of earthquakes, we estimate permeability values of 5.9 × 10−15m2and 1.8 × 10−14m2at lower crustal depth. The range of permeability implies that seismicity can be induced by pore-pressure diffusion, likely from fluids sourced from the mantle that reactivate preexisting faults in the lower crust. Our thermo-rheological models explain the first order differences in lower crustal earthquakes both directly beneath and outboard of the rift valley.

Comprehensive investigation of microstructural inhomogeneity in the bonding zone of explosive-welded AISI 410S/A283GrD composite

ABSTRACT This study investigates the microstructural inhomogeneity in the bonding zone of AISI 410S/A283GrD explosive-welded plate by experiment and simulation. The interfacial microstructure and chemical components are investigated, and the difference of grain size across the peak and valley is studied separately. Due to severe plastic deformation and work hardening during the explosive welding process, the microhardness of the combination area adjacent to the interface is higher than that of parent plates. The wavy interface of the numerical simulation is in good agreement with the experimental observation. The numerical simulation results, such as distribution of shear stress, pressure, and effective plastic strain rate of the model are investigated, and the forming reason of interfacial microstructures, are explained by these results.

A simplified dynamic constitutive model for BFRCAC under confining pressure considering the coupling effect of fibre reinforcement and mechanical damage

To effectively characterise the dynamic mechanical properties of basalt fibre-reinforced coral aggregate concrete (BFRCAC) under confining pressure, a dynamic constitutive model of BFRCAC is presented through characterising the basalt fibre reinforcement by measuring the variation in elastic modulus and the mechanical damage by measuring the fracture probability of micro-crack propagation. The dynamic mechanical properties of BFRCAC under different confining pressures were investigated using a split Hopkinson pressure bar device with active confining pressure. A comparison of the theoretical results and experimental results indicates the good validity of the dynamic constitutive model. Analysis of damage development reveals that both strain rate and confining pressure have delayed effects on damage development. The addition of basalt fibre at an appropriate content reinforces the BFRCAC; consequently, the total damage is less than the mechanical damage in the early stage of deformation. As the deformation progresses, basalt fibre is gradually destroyed and its reinforcement effect gradually disappears, causing the total damage to gradually approach the mechanical damage. The bridging effect of basalt fibre helps restrain crack propagation; this not only slows the rate of damage in BFRCAC but also improves the confining pressure effect and strain rate effect of damage development.

Experimental Investigation and Modeling the Compressive Behavior of NEPE Propellant under Confining Pressure

AbstractIn order to study the effects of confining pressure and strain rate on the mechanical properties of the Nitrate Ester Plasticized Polyether (NEPE) propellant, compressive tests were conducted under various confining pressure conditions and strain rates using a new‐designed active gas confining pressure testing machine. The stress‐strain curves and mechanical properties of the NEPE propellant under varying confining pressure conditions and strain rates were obtained. The results show that the compressive mechanical properties of the NEPE propellant are remarkably influenced by the confining pressure and strain rate. The compressive strength under confining pressure is obviously larger than those without applied confining pressure. With the coupled effects of the confining pressure and strain rate, the compressive strength under 5.4 MPa and 6.67×10−2 s−1 is 2.17 times of its value at room condition and 6.67×10−4 s−1. Then, based on previous tensile results, the quantified comparisons of tensile and compressive mechanical properties under different experimental conditions were presented. Finally, a nonlinear constitutive model with damage was constructed to model the effect of pressure. The statistical damage model parameters were defined as ExpDec1 function of pressure P. The calibrated model can accurately predict the mechanical behaviour of the NEPE propellant under different confining pressure conditions and strain rates.

Experimental Study on Biaxial Dynamic Compressive Properties of ECC.

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

Long-Term Drained and Post-liquefaction Cyclic Behaviour of Offshore Wind Turbine in Silty Sand Using Element Tests

Offshore wind turbine (OWT) structure foundations and soil are subjected to long-term cyclic loading from wind and waves. Loads due to earthquake also act on the OWT system in seismically active areas. The long-term dynamic behaviour of the OWT is challenging due to the complex nature of dynamic loads. The soil stiffness changes due to the application of cyclic loading, which leads to a change in the natural frequency and response of the OWT system. Therefore, the assessment of long-term dynamic behaviour soil surrounding the foundation of the OWT structure is essential due to the operational condition and seismic event. In this study, element tests are conducted utilizing cyclic triaxial test apparatus to examine the long-term drained and post-liquefaction long-term cyclic behaviour of silty sand. Secant shear modulus and damping ratio are estimated under drained condition due to 10,000 load cycles. Silty sand behaviour at liquefied phase and post-liquefaction long-term cyclic behaviour phases are investigated at different effective confining pressure, relative density, and shear strain rate. Based on the element tests, a numerical model is proposed predicting the long-term fundamental frequency of OWT to avoid resonance.