【作者】 吴平；

【导师】 徐世烺； 李庆华；

【作者基本信息】 浙江大学 ， 结构工程， 2022， 博士

【摘要】 混凝土是一种非均质、准脆性复合材料,且广泛地应用在国防和土木工程中。然而,混凝土在受到高速冲击和爆炸荷载作用下,极易发生脆性破坏,引起碎片的飞溅。因此,找到更好抵抗冲击和爆炸荷载的工程防护材料及结构成为当下研究的重点。超高韧性水泥基复合材料(Ultra High Toughness Cementitious Composites,简称为UHTCC)是一种高拉伸韧性的新型材料。活性粉末混凝土(Reactive Powder Concrete,简称为RPC)则是具有超高的强度水泥基复合材料。超高强-超高韧水泥基复合材料(High Strength-Ultra High Toughness Cementitious Composites,简称为HS-UHTCC)不仅继承了UHTCC高拉伸韧性同时还具备了RPC的超高压缩强度,它们都被认为是不错的防护工程材料。因此,有必要对UHTCC、RPC、HS-UHTCC构件在不同冲击和爆炸工况下的动力响应进行试验研究和数值模拟探究,具体工作如下:1)为了研究活性粉末混凝土(RPC)和超高韧性水泥复合材料(UHTCC)的抗多次侵彻性能。本文使用14.5 mm弹道枪对RPC和UHTCC靶体进行不同着弹点多次侵彻试验。试验结果表明,RPC具有出色的抗弹体侵彻能力,UHTCC在减小迎弹面开坑损伤和抗开裂方面更具优势。多次侵彻会让普通混凝土抗开坑能力降低,而让UHTCC和RPC抗开坑能力则会提高。随着侵彻次数增加,普通混凝土的抗侵彻阻力下降幅度较大,而UHTCC和RPC的侵彻阻力下降幅度较小。2)本文研究了UHTCC、RPC和高强混凝土(HSC)在内埋炸药爆炸作用下的动力特性、损伤特性和破坏规律。试验内容包括通过改变炸药埋置深度对UHTCC、RPC和HSC靶体进行抗爆测试。试验结果表明:相较于HSC,RPC和UHTCC靶体的抗震塌性能更强、整体性更好以及飞溅的碎片数量也更少。3)本文主要基于现有UHTCC和RPC的静态和动态力学性能试验数据标定了UHTCC和RPC的K&C本构模型。然后,利用重启动的方法模拟了弹体多次冲击UHTCC和RPC靶体的试验以及UHTCC和RPC的内埋爆炸试验,验证了标定后的K&C模型参数的准确性。最后,通过数值预测了不同抗压强度、抗拉强度以及拉伸韧性下UHTCC靶体的破坏状态,发现增强UHTCC的韧性可以有效防止靶体发生整体性破坏;增大UHTCC的抗拉强度可以减小靶体迎爆面的开坑直径;增大UHTCC的抗压强度对减小开坑直径效果不明显。4)为研究HS-UHTCC在接触爆炸荷载作用下的动力响应,本文对2000×2000×200 mm的HS-UHTCC靶板进行了在1 kg TNT的作用下的接触爆炸试验。并与在相同条件下的UHTCC,RPC和钢筋混凝土的试验结果进行对比。试验结果表明,HS-UHTCC板的抗震塌性能最好,并且迎爆面的开坑面积最小。另外,本文根据现有的试验数据校核了HS-UHTCC的K&C本构模型。然后,利用改进的模型参数模拟HS-UHTCC靶板的破坏模式和损伤分布。最后,采用重启动的方法对HS-UHTCC靶板进行同一位置的多次抗爆数值模拟,结果表明,厚度为200 mm的HS-UHTCC靶板可以承受3次1 kg TNT在同一位置爆炸而靶板不发生贯穿破坏。5)本文研究了超高强-超高韧水泥基复合材料(HS-UHTCC)和活性粉末混凝土(RPC)在大口径侵彻弹冲击下的损伤规律、破坏特征以及抗侵彻性能并与普通混凝土进行对比。试验采用125 mm口径的榴弹炮对C45混凝土、HS-UHTCC和RPC进行了430 m/s的弹体侵彻试验。试验结果表明:RPC具有更优秀的抗弹体侵彻能力,而HS-UHTCC则具有更优异的抗开坑开裂能力。同时,采用K&C模型模拟了在上述弹体冲击下HS-UHTCC和RPC靶体的破坏模式和损伤分布。模拟结果与试验结果基本一致,并且再现了弹体侵入HS-UHTCC靶体的全过程。6)最后,本文建立了UHTCC的动态本构模型,综合考虑了此类材料的损伤演化、剪切膨胀、应变率效应、应变硬化和应变软化、应变硬化的率效应。通过用户定义的界面将新模型嵌入到LS-DYNA软件中。同时,对新模型进行了全面单元测试,并与常用的混凝土模型进行了比较,发现新模型能够更好地反映UHTCC的各项力学特性。然后模拟了UHTCC在弹体高速冲击和接触爆炸载荷下的一组试验,发现数值预测结果与试验结果吻合较好。此外,还采用新模型模拟了HS-UHTCC靶体在弹体冲击和接触爆炸作用下的动力响应,得到了与试验结果相一致的模拟结果。全文进行了试验研究、K&C模型参数的校核、数值模拟、本构模型建立,旨在为UHTCC,RPC和HS-UHTCC材料在防护工程中的应用提供设计指导。更多还原

【Abstract】 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.更多还原