저자명 염기선 
년도 2013 

Polymer-bonded explosive(PBX) is an energetic material in which small explosive crystals are bonded in a polymer matrix which occupies typically 5−10 % by weight. PBX is used in a wide variety of weapon applications ranging from rocket propellants to the main explosive charge in conventional munitions and weapon systems. It is important to characterize the mechanical properties of PBX and to accurately model their response behavior because unwanted external stimuli could cause accidental detonation during manufacturing, transportation or handling. The mechanical properties of PBX are similar to those of particle-filled elastomers which are known to exhibit highly nonlinear behaviors such as the stress softening phenomenon (known as the Mullins effect), hysteresis under cyclic loading, residual strain after unloading, and frequency dependant responses. The characterization of the Mullins effect and hysteresis under cyclic loading is considered in this paper. It is well known that the initial material properties of unstretched specimens of particle-filled elastomers are varied after the specimen has been subjected to loading. This phenomenon was observed by Mullins and his coworkers and has become widely known as the "Mullins effect".

Ogden and Roxburgh proposed a pseudo-elastic phenomenological model in order to consider the Mullins effect observed in particle-filled elastomers. In this model, a single continuous damage parameter is incorporated into the theory in order to modify the strain energy function so that the material response then differs in the loading from a point on the primary loading path. The model, however, is not adequate to PBX because the PBX exhibit highly nonlinear behavior such as a stress softening, hysteresis, and residual strain effects. The stress softening, residual strain and hysteresis are the most important inelastic phenomena for PBX. This paper introduces a new pseudo-elastic phenomenological model for the Mullins effect based on the strain energy functions of isotropic, incompressible hyperelastic, time-independent PBX simulant materials. The damage function is suggested by modification of an existing model. To develop a new damage function, the error function which is employed in the Ogden-Roxburgh model is replaced with hyperbolic tangent function and ratio of current strain to prior maximum strain is additionally introduced. As for hysteresis under cyclic loading, it is observed that second loading stress is located between first loading curve and first unloading curve. However Ogden-Roxburgh model do not represent hysteresis under cyclic loading because this model follow first unloading curve in case of unloading and reloading. Therefore this paper introduces additional term that follows gradually first reloading curve in case of reloading and first unloading curve in case of unloading.

For safety and cost reasons, two types of inert PBX simulants were adopted as the mechanical simulant. Compressive uniaxial loading-unloading and simple shear tests were conducted at quasi-static states in order to evaluate prediction accuracy of the proposed pseudo-elastic model. In the experiments, stress-strain relations of two kinds of PBX simulants with different particle sizes are observed at the strain rate of 10-3 /sec with various maximum strains. In the results of the experiments, two PBX simulants show different stress-strain relations however the amount of stress softening consistently tends to increase with larger strain applied to the specimen. Stress-strain relations obtained from the experiments are approximated with Ogden-Roxburgh and proposed pseudo-elastic models and applicability is evaluated. Proposed damage function provides stress-strain relation which shows smoother change of slope than Ogden-Roxburgh model and Prediction with the new model shows a good correspondence to the experimental data demonstrating that the model properly describes the Mullins effect and the hysteresis of PBX simulant. Moreover, the proposed pseudo-elastic model only requires three material parameters to be determined and is constructed based on a theoretical framework of energy function. Judging from the results, the proposed damage variable and pseudo-elastic model are predicted to provide enhanced results in applications of PBX simulants.

번호 제목 저자명 날짜 조회 수
27 Anisotropic Fracture Limit for the Failure Prediction of Advanced High-Strength Steel Sheets (고강도 강판의 파괴 예측을 위한 이방성 파괴 한계에 관한 연구) 박남수  2017.06.07 362
» A Study on the Nonlinear Behaviors of Polymer-Bonded Explosives Considering Stress Softening Effect(응력연화현상을 고려한 복합화약의 비선형 거동에 관한 연구) 염기선  2013.09.08 4883
25 Rate-Dependent Hardening Model for Polymer-Bonded Explosives Considering a Wide Range of Strain Rates (광범위한 변형률속도를 고려한 복합화약의 변형률속도 의존 경화모델) 박충희  2013.08.30 3654
24 Dynamic Failure Criteria of a Laser-welded Region under Combined Loading Conditions for Auto-body Crash Analyses (차체용 부재의 충돌해석을 위한 복합하중조건에서 레이저 용접부의 동적 파단조건 연구) 하지웅  2013.04.14 7409
23 Rate Dependent Hardening Model for Pure Titanium Considering the Effect of Deformation Twinning (쌍정의 영향을 고려한 티타늄의 변형률속도 의존 경화 모델) 안광현  2012.12.12 17139
22 Strain-Rate Dependent Anisotropic Yield Criteria for Auto-body Steel Sheets (자동차용 강판의 변형률속도 의존 이방성 항복함수에 관한 연구) 허지향  2012.12.11 17976
21 A New Ductile Fracture Criterion for the Formability Prediction of Steel Sheets and Its Application to Finite Element Analysis (강판의 성형성 예측을 위한 새로운 연성 파괴 조건 및 유한 요소 해석에의 응용) [1] Yanshan Lou  2012.12.10 20981
20 Measurement Uncertainty Evaluation for High Strain Rate Tensile Properties of Auto-body Steel Sheet (자동차용 강판 고속인장물성 데이터의 측정불확도 산출) 정세환  2012.12.10 17705
19 A Study on a Continuum Damage Yield Function to Predict Ductile Fracture of Materials (재료의 연성파단을 예측하기 위한 연속체 손상 항복 함수에 관한 연구) 고윤기  2012.12.10 14565
18 A Study on the Tension/Compression Hardening Behavior of Auto-body Steel Sheets Considering the Pre-strain and the Strain Rate (초기 변형률 및 변형률 속도를 고려한 차체 강판의 인장/압축 경화 거동에 관한 연구) [1] 배기현  2011.01.11 20279
17 Forming Limit Diagram of Auto-body Steel Sheets at High Strain Rates for Sheet Metal Forming and Crashworthiness (박판성형 및 충돌성능 향상을 위한 고변형률속도에서의 차체강판 성형한계도) 김석봉  2010.07.13 21585
16 Evaluation of a cast-joining process of dual metal crankshafts for heavy-duty engines with ductile cast iron and high strength forged steel(구상흑연주철과 고강도 단조강의 주조접합 이종금속을 이용한 중대형 엔진 크랭크샤프트의 평가) 한 신  2010.07.13 17829
15 A Study on Material Properties of OFHC Copper Film at High Strain Rates using High-Speed Micro Material Testing Machine (고속마이크로재료시험기를 이용한 무산소동 박판의 고변형률속도 재료물성치 연구) 김진성  2010.07.13 20162
14 Microscopic investigation of the strain rate hardening for auto-body steel sheet(차체강판 변형률속도 경화의 미시적 관찰) 윤종헌  2010.07.13 16891
13 Analysis of Elasto-Plastic Stress Waves by a Time Discontinuous Variational Integrator of Hamiltonian with a Second-Order Integration Scheme of the Constitutive Model (해밀토니안의 시간 불연속 변분적분기와 구성방정식의 2차 정확도 적분법을 이용한 탄소 조상순  2008.12.15 21646
12 A Study on the Dynamic Failure Model of a Spot Weld under Combined Loading Conditions for Auto-body Crash Analyses (차체용 부재의 충돌해석을 위한 복합하중조건에서 점용접부의 동적 파단모델 연구) [1] 송정한  2008.07.24 18512
11 Study on Dynamic Tensile Tests of Auto-body Steel Sheet at the Intermediate Strain Rate for Material Constitutive Equations (차체강판의 중변형률 속도에서의 동적 인장시험 및 물성 구성방정식에 관한 연구) 임지호  2005.11.29 25432
10 Dynamic Formulation of Finite Element Limit Analysis for Impact Simulation of Structural Members (구조부재의 충돌해석을 위한 유한요소 극한해석의 동적 수식화) 김기풍  2005.11.29 17726
9 Finite Element Inverse Approach and Initial Guess Generation for Sheet Metal Forming Analysis of Complicated Auto-body Members (복잡한 차체부재의 박판성형공정을 위한 유한요소 역해석 및 초기추측치 계산) 김승호  2005.11.29 19051
8 Development of a Nonlinear Degenerated Shell Element with the Drilling Degree of Freedom by the Cubic Polynomial Interpolation and the Assumed Strain Method (드릴링 자유도의 삼차 근사법과 대체변형률법을 이용한 비선형 감절점 쉘 요소의 개발) 이형욱  2005.11.29 17662