Subjects: Mechanics >> Applied Mechanics submitted time 2022-11-01 Cooperative journals: 《应用力学学报》
Abstract： With the increase of drilling depth,the compaction,strength and formation pressure of reservoir rock are also increasing,so it is necessary to use super-strong perforating projectile to penetrate the pollution zone,and the combination of super-strong projectile,super-strong target and high confining pressure will increase the difficulty of penetration analysis.In this paper,using LS-DYNA software,combined with ALE algorithm,taking an oilfield downhole perforation as an example,the HS45-5super-strong bullet-gun-liquid-casing-sandstone three-dimensional model is established without confining pressure and 50 MPa confining pressure.The interference of detonation wave on jet forming and effect is eliminated by establishing non-reflective boundary conditions.By adjusting the mesh density of key parts and optimizing the mesh coordination between different contact surfaces,the numerical distortion can be reduced,the analysis accuracy can be improved,and the machine time can be reduced.The results show that the peak value of jet energy reaches 60 kJ at 13 μs,accounting for 23% of the total energy,and then decays sharply and reaches zero at 850 μs.At 16 μs,the peak velocity of jet reaches 6 300 m/s.The penetration depth under 50 MPa confining pressure is 560 mm,which is 20% lower than that without confining pressure.The research in this paper can provide a reference for the simulation analysis of underground super-strong projectile penetration into super-strong targets with high confining pressure.
Subjects: Mechanics >> Basic Mechanics submitted time 2023-11-09 Cooperative journals: 《应用力学学报》
Abstract： Wormlike micellar fluids formed by dissolving surfactants in water have unique mechanical responsesdue to its high surfactivity and strong viscoelasticity.These properties enable wormlike micellar fluids rich and complicated flow behaviors.By considering the breakage of long chains and the reforming of short chains,a two species VCM model is introduced in this study to numerically investigate the effect of the chain scission on the flow instability.First,the rheological properties are obtained by directly solving the VCM constitutive equation set numerically.The fluid exhibits a strong nonlinear thickening-thinning-thickening phenomenon under the uniaxial tension.The flow passing by a confined cylinder is investigated.The flow becomes significantly unstable at very low Reynolds numbers(Re～0.01)when the Weissenberg number is larger than 1.The fluid velocity in the downstream wake of the cylinder presents a fluctuation with the time.The flow fluctuation is quasi-periodic according to the power spectrum analysis.The flow fluctuation becomes more irregular when the nonlinearity of the variation of the tension stress with the elasticity becomes stronger.A pair of symmetrical vortexes behind the cylinder changing with time are also observed,indicating that the elasticity promotes the flow separation on the cylinder surface.The flow instability is due to the strong nonlinear response of the tension stress within the bulk fluid to the elasticity of the fluid.
Subjects: Mechanics >> Basic Mechanics submitted time 2023-04-24 Cooperative journals: 《应用力学学报》
Abstract：
In order to study the seismic performance of weak joints of steel coupling beam-partially enclosed composite shear wall,a model specimen of the steel coupling beam-partially enclosed composite shear wall was designed,and the low-cycle reciprocating loading numerical simulation was carried out through the finite element software ABAQUS.The influences of factors such as concrete strength,the details horizontal stiffener and vertical stiffener,and span-to-height ratio of connecting beams on the seismic performance of joints are studied.The analysis results show that the steel coupling beam-partially enclosed composite shear wall joint has excellent seismic performance,the hysteretic curve is full and stable,the displacement ductility coefficient is greater than 3,the limit angle of the beam end of some specimens can reach 0.05 rad,and the specimen ductility is good.The increase of concrete strength can improve the initial stiffness of joint specimen.The setting of horizontal stiffeners and vertical stiffeners improves the restraint effect on the wall concrete and can effectively prevent the crack propagation speed.The setting of stiffener is an effective way of stress transfer in the joint area,which enables the stress in the joint area to be smoothly transferred to the adjacent area,reduces the load drop speed in the later stage of loading,and improves the seismic performance of the joint as the span-to-height ratio of the connecting beam increases When the span-to-height ratio of the connecting beam is greater than 3.8,the limit angle of the beam end is reduced from 0.05 rad to 0.03 rad.
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