| Concrete is a heterogeneous,quasi-brittle composite material,and is widely used in defense and civil engineering.However,under the high-speed impact and explosion load,concrete is prone to brittle failure,causing splashing of debris.Therefore,finding engineering protective materials and structures that better resist impact and explosion load has become the focus of current research.Ultra high toughness cementitious composite(UHTCC)is a new type of material with high tensile toughness.Reactive Powder Concrete(RPC)is a cement-based composite material with ultra-high strength.High Strength-Ultra High Toughness Cementitious Composites(HS-UHTCC)not only inherits the high tensile toughness of UHTCC but also possesses the ultra-high compressive strength of RPC,which are all considered good protective engineering materials.Therefore,it is necessary to carry out experimental research and numerical simulation research on the dynamic response of UHTCC,RPC,and HS-UHTCC components subjected to different impact and explosion loads.The specific work is as follows:1)This chapter aims at studying the multiple penetration resistance of Reactive Powder Concrete(RPC)and Ultra High Toughness Cementitious Composites(UHTCC).A 14.5 mm ballistic gun was used to investigate multiple penetration tests on RPC and UHTCC.The test results showed that RPC had excellent resistance against penetration by projectiles.However,UHTCC had excellent resistance to cratering and cracking.Multiple penetrations will increase the crater area of concrete,while reducing the crater area of UHTCC and RPC.With the increase of penetration times,the penetration resistance of concrete decreased more greatly,while the penetration resistance of UHTCC and RPC decreased less.2)Present chapter studies the dynamic characteristics,damage characteristics and failure laws of concrete,UHTCC and RPC targets subjected to blast by embedded explosives.The content of the test includes the blast resistance test of high-strength concrete(HSC),UHTCC and RPC targets by changing the explosive embedding depth.The test results show that the RPC and UHTCC targets have stronger seismic collapse resistance,better integrity and less splashed debris than the HSC targets.3)Present paper mainly calibrates the K&C constitutive model of UHTCC and RPC based on the existing static and dynamic mechanical test data of UHTCC and RPC.Then,using the restarting method to simulate the projectile repeatedly penetrating the UHTCC and RPC targets.In addition,UHTCC and RPC targets subjected to blast by embedded explosives is also simulated.The accuracy of the calibrated K&C model parameters is verified.by adjusting the parameters related to the compressive strength,tensile strength and tensile toughness in the modified K&C model,the damage patterns of the UHTCC targets with different compressive and tensile strengths and tensile toughness were predicted.It is found that enhancing the toughness of UHTCC can effectively prevent the target from undergoing overall damage,increasing the tensile strength of UHTCC can reduce the cratering diameter on the blasting surface,and increasing the compressive strength of the material has no obvious effect on reducing the cratering size.4)To study the blast resistance of HS-UHTCC plate subjected to contact blast load,a 1 kg TNT contact explosion test of the HS-UHTCC plate with 2000×2000×200 mm was carried out.And compared with UHTCC,RPC and reinforced of concrete under the same test conditions.The test results show that the HS-UHTCC plate has the best resistance to spalling and collapse,and the crater area on the blast face is the smallest.In addition,a constitutive model that can reflect HS-UHTCC is calibrated.Then,the improved model was used to simulate the failure mode and damage distribution of the HS-UHTCC plate.Lastly,the HS-UHTCC plate subjected to multiple blast was simulated at the same position by the restart method,and it was found that the HSUHTCC plate could withstand three explosions of 1kg TNT at the same position without the plate being brached.5)This paper studies the damage law,failure characteristics and penetration resistance performance of high strength-ultra high toughness cementitious composites(HS-UHTCC)and reactive powder concrete(RPC)subjected to the impact of largecaliber projectiles.The penetration resistance tests of the concrete,HS-UHTCC and RPC with a 125 mm caliber howitzer at a projectile velocity of 430 m/s.The test results show that RPC has better resistance to projectile penetration,while HS-UHTCC has better resistance to cratering and cracking.At the same time,the K&C model was used to simulate the failure mode and damage distribution of the HS-UHTCC and RPC targets subejected to the impact of the above-mentioned projectile.The simulation results are basically consistent with the test results,and the whole process of the projectile penetrate into the HS-UHTCC and RPC target is reproduced.6)In this study,a dynamic constitutive model of UHTCC was established,which comprehensively considered damage evolution,shear expansion,strain rate,strain hardening and strain softening of such materials.Then,a comprehensive element test was carried out on the new model,and compared with the commonly used concrete models,it was found that the new model could better reflect the mechanical properties of UHTCC.Finally,a set of experimental tests of the UHTCC subjected to high-speed impact and contact blast loads were simulated.It was found that the numerical prediction results were in good agreement with the experimental results.In addition,the dynamic response of HS-UHTCC targets subjected to impact and contact explosion is simulated with the new model,and the simulation results are consistent with the test results.In present paper,experimental research,verification of K&C model parameters,numerical simulation,and constitutive model establishment are carried out,aiming to provide design guidance for the application of UHTCC,RPC and HS-UHTCC materials in protection engineering. |
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