entific Con i c S fe l a r n e o n i c t e a 2 n r e t n I ISC 2011 Proceeding of the International Conference on Advanced Science, Engineering and Information Technology 2011 Hotel Equatorial Bangi-Putrajaya, Malaysia, 14 - 15 January 2011 ISBN 978-983-42366-4-9 ISC 2011 International Conference on Advanced Science, Engineering and Information Technology ICASEIT 2011 Cutting Edge Sciences for Future Sustainability Hotel Equatorial Bangi-Putrajaya, Malaysia, 14 - 15 January 2011 S R I E A V I U N I T N I E S E D K O B I N N R A G J A A L S A A E N P M N A A U T S R E P N O I T A I Organized by Indonesian Students Association Universiti Kebangsaan Malaysia Proceeding of the Ogive Nose Hard Missile Penetrating Concrete Slab Numerical Simulation Approach Qadir Bux alias Imran Latif#, Ismail Abdul Rahman#, Ahmad Mujahid Ahmad Zaidi* # Faculty of Civil & Environmental Engineering, UTHM Parit Raja, Johor, 86400, Malaysia +60197013878, E-mail: imranqazi37@gmail.com *Department of Mechanical, Faculty of Engineering, UPNM Kem Sungai Besi, Kuala Lumpur, 57000, Malaysia +60174783139, E-mail: mujahid@upnm.edu.my Abstract— Great demand exists for more efficient design to protect delicate and serious structures such as nuclear plants, Power plants, Weapon Industries, weapons storage places, water retaining structures, & etc, against impact of kinetic missiles generated both accidentally and deliberately such as dynamic loading, incident occurs in nuclear plants, terrorist attack, Natural disasters like tsunami and etc., in various impact and blast scenarios for both civilian and military activities. In many cases, projectiles can be treated as rigid bodies when their damage and erosion are not severe. Due to the intricacy of the local impact damages, investigations are generally based on experimental data. Conclusions of the experimental observations are then used to guide engineering models. Local damages studies normally fall into three categories, i.e. empirical formulae based on data fitting, idealised analytical models based on physic laws and numerical simulations based on computational mechanics and material models. In the present study, 2D asymmetrical numerical simulation have done on concrete slab against the impact of ogive nose hard missile of 26.90mm and 76.20mm diameter with CRH ratio 2.0 and 6.0 respectively, for penetration by using Concrete Damaged Plasticity Model, and ABAQUS/Explicit dynamic analysis in ABAQUS. It is found that the strains/stresses are induced in the concrete slab and a very nicely propagation of the stresses inside the concrete slab in the form of waves, which is a clear indication for vibrations of the concrete. The lack of failure criterion in concrete damaged plasticity model does not allow the removal of elements during the analyses. This means that spalling, scabbing, and perforation cannot be modelled with the Concrete Damage Plasticity Model. The penetration depth results shows that the deeper penetration requires higher critical impact kinetic energies, and comparison shows the simulation results are more accurate than other formulae predicted results. Keywords— Penetration, concrete, local impact, Kinetic energy, Numerical simulation, Ogive Nose, Hard Missile, CRH. I. INTRODUCTION Over the years, concrete is commonly used construction material for the defensive and civil applications, to protect structures from local and explosive impact loads. For the designing of high-quality protective structures it is crucial to have a good knowledge about behaviour of concrete against impact or explosive loading conditions. Projectile exists in a long range with variation in sizes, shapes, velocity, weight, density, hardness, such as aircraft crashes, fragments generated by accidental explosions and other events (e.g., failure of a pressurized vessel, failure of a turbine blade or other high speed rotating machines), flying objects due to natural forces (tornado, meteoroid), bullets, fragments, etc. The projectile may be classified as ‘Hard’ and ‘Soft’ depending upon deformability of projectile with respect to target’s deformation. Deformation of hard missile is considerable smaller or negligible compared with target’s deformation ([1], [2], [12]). Almost in all cases hard missiles are considered as non – deformable or rigid. However, ‘Soft’ missile deforms itself considerably well as compared to target’s deformation ([1], [2], [12]). Local impact effect is briefly sub-divided in below explained processes: Radial Cracking: When projectile colloids with concrete target with certain velocity, it results radial cracks originated from the point of impact within the target in every direction [2]. 586

Spalling: The ejection of material of target from front face (impacted face) due to impact of hard projectile is called spalling. Spalling produces spall crater in the surrounding area of impact. Spall crater is the total damaged portion of peeling off material from target on impacted face ([1], [2]). Penetration: Penetration is defined as the digging of missile into the target body afar from the thickness of spall crater. The lengthwise measurement of dig is called penetration depth ([1], [2]). Cone cracking & Plugging: During penetration missile colloids with rear border of target and generates curved shear cracks in the shape of bell plug is called cone cracking. And than missile continues penetrating through target, it forces plug and shears-off the surrounding material of target is called plugging. This process generates rapid change into the behaviour of target [2]. Scabbing: Ejection of target material from back face of target is called scabbing ([1], [2]). Perforation: Perforation means complete passage or complete crossing of projectile through the target. It causes missile to extend penetration hole through scabbing crater and exit from the rear face of target ([1], [2]). Fig.1. Explains the local impact phenomena caused by hard projectile [2]. (a) Penetration, (b) Cone cracking and Plugging, (c) Spalling, (d) Radial cracking, (e) Scabbing, (f) Perforation, and (g) Global phenomena. In general, the local impact effect of hard missile on concrete structures can be studied in three ways, (i). Empirical Studies (predict empirical formula based on experimental data), (ii). Analytical Studies (create formula based on physical laws), and (iii), Numerical Simulation (based on computer based material model). Numerical simulation study is fast developed approach to calculate the dynamic behaviour of concrete against local impact effects, and it become more reliable and economical because of its rapid growth. In this paper a numerical simulation study is conducted to overcome the shortcomings of other modes of studies, and to provide a better understanding of ABAQUS Explicit dynamic analysis based on concrete damaged plasticity model with the analysis of required critical impact kinetic energies for maximum penetration. II. LITERATURE REVIEW The effects of the local impact of hard missile on concrete structures have been studied since the mid of 17th century because of continuous military interest in designing of high performance missiles and high performance protective barriers [2]. A review of previous research work exposed that peak studies on concrete structures against dynamic loading were conducted from the early 1940s [5]. However, most of the research work ceased shortly after World War – II and were not resumed until 1960s [5]. The intensive study on concrete targets against local impact effects of hard missiles in the nuclear industry re-initiated since five decades ago. Kennedy (1976) provided an early review of the concrete response against local impact effects of hard missile for nuclear industries and recommended impact force time history theory [2]. Various studies were conducted to specify the local impact effects of hard missile on concrete structures, a review of these studies were discussed intensively in previous publications, Kennedy (1976), Bangash (1993), Williams (1994), Corbett et al. (1996) [2]. With the rapid developments of computational tools, computational mechanics and material constitutive models, the numerical simulation of local missile impact effects becomes more reliable and economical. The major differences between a quasi-static constitutive model and a dynamic one of concrete are encapsulated by the needs to understand inertia effects and the effects of strain rate on the deformation and failure of the concrete target. Extensive simulation studies were conducted in past to analyse local impact effects of hard missile on concrete structures. T.L Teng et. al. (2004) simulates 2D local impact effects of ogive nose missile impacted on reinforced concrete walls perpendicularly, and impacted at 50o oblique with the equivalent inclusion method considering reinforced concrete as homogeneous material. He suggested the equivalent matrix for homogenized material and equivalent material moduli for finite element analysis by using Mori – Tanaka’s average strain theory. The FEM proposed model simulates very close results as compared to the experiment considering residual velocity and ricochet limit of projectile [6]. C.Y. Tham (2005) investigated the penetration and perforation of reinforced concrete with 3D hydro-code in AUTODYN and examined the influence of constant-yield strength, pressure- dependent yield strength, and pressure-dependent yield strength + damage + strain-rate hardening. Except for the low velocity regime, the results for the case of the constitutive model with pressure-dependent yield function exhibit strong correlation with experimental residual velocities, and the result from the constitutive model that includes strain-rate and damage with a pressure-dependent yield surface showed relatively good agreement with the experimental residual velocities. The damage contours at the impact and exit surface from the simulation were also consistent with the post-test damage results [9]. Z. L. Wang et. al. (2006) improved and implemented the Taylor-Chen-Kuszmaul (TCK) continuum damage model into the dynamic finite element code, LS – DYNA, with erosion algorithm. The results of impact, exit crater (scabbing), and as well as residual velocity shows good understanding with experimental data. In addition the effect of CRH ratio of ogive 587