• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2828-2835
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• 2000

This paper presents the fatigue behavior of composite materials with impact-induced damage. The impact damage parameter is proposed to evaluate the effect of impact damage on fatigue life. Subsequently, a new model is developed to predict the fatigue life of impacted composite materials. Also, a stochastic model is proposed to describe the variation of fatigue life due to the material nonhomogeneity. For these models, the fatigue tests were performed on the unimpacted and impacted composite materials, The effect of impact damage on fatigue life can be characterized by the impact damage parameter. Additionally, the results by the present fatigue life prediction model agree will with experimental results regardless of applied impact energy. Also, the variation of fatigue life can be described by the present stochastic model and is reduced with applied impact energy.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.225-230
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• 2000

This paper presents the fatigue behavior of composite materials with impact-induced damage. The impact damage parameter is proposed to evaluate the effect of impact damage on fatigue life. Subsequently, a new model is developed to predict the fatigue life of impacted composite materials. Also, a stochastic model is proposed to describe the variation of fatigue life due to the material nonhomogeneity. For these models, the fatigue tests were performed on the unimpacted and impacted composite materials. The effect of impact damage on fatigue life can be characterized by the impact damage parameter. Additionally, the results by the present fatigue life prediction model agree well with experimental results regardless of applied impact energy. Also, the variation of fatigue life can be described by the present stochastic model and is reduced with applied impact energy.

• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.31-39
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• 2021

To investigate numerically the effect of all parameters on the outcome of an aircraft impact into robust engineering structures like nuclear power plant containments is a tedious task. In order to reduce the problem to a manageable size, we propose a single dimensionless parameter, the damage potential, to characterize the main features of the impact. The damage potential, which is the ratio of the initial kinetic energy of the aircraft to the work required to crush it, enables us to find the crucial parameter settings that need to be modelled numerically in detail. We show in this paper that the damage potential is indeed the most important parameter of the impact that determines the time-dependent reaction force when either finite element (FE) modelling or the Riera model is applied. We find that parameters that do not alter the damage potential, like elasticity of the target, are of secondary importance and if parameters are altered in a way that the damage potential remains the same then the course of the impact remains similar. We show, however, that the maximum value of the reaction force can be higher in case of elastic targets than in case of rigid targets due to the vibration of the target. The difference between the Riera and FE model results is also found to depend on the damage potential.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1089-1096
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• 2001

This paper presents the fatigue behavior of composite materials with impact-induced damage under 2 level block loading. For this purpose, the 2 level block loading fatigue tests were performed on the impacted composite laminate. The fatigue life of the laminate under the block loading is greatly influenced by the impact damage; the effect of impact damage can be characterized by the present impact damage parameter. Based on this parameter, the model is developed to predict the fatigue life under block loading and the results by this model agree well with experimental results regardless of applied impact energy. Also, stochastic model is established to describe the variation of cumulative damage behavior and fatigue life due to the material nonhomogeneity.

• Wind and Structures
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• v.13 no.2
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• pp.95-108
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• 2010

This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon Impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.

• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.12-16
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• 2009

The laminated sequence and thickness of a composite structure is an important design parameter which affect the strength and impact damage. In this study, it was investigated the residual strength of carbon fiber laminate after impact damage by the experimental investigation. The tensile strength test and compressive strength test were used to find the mechanical properties, previously. Impact test was performed using low-velocity drop-weight test equipment. The impact damages were finally assessed by the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the impact damage.

• Geomechanics and Engineering
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• v.20 no.2
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• pp.113-120
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• 2020

Rock damage is the main cause of accidents in underground engineering. It is difficult to predict rock damage accurately by using only one parameter. In this study, a rock failure prediction model was established by using stress, energy, and damage. The prediction level was divided into three levels according to the ratio of the damage threshold stress to the peak stress. A classification predicting model was established, including the stress, energy, damage and AE impact rate using Bayesian method. Results show that the model is good practicability and effectiveness in predicting the degree of rock failure. On the basis of this, a multi-parameter classification predicting deterioration model of rock failure was established. The results provide a new idea for classifying and predicting rockburst.

• Structural Engineering and Mechanics
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• v.70 no.1
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• pp.33-41
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• 2019

The influence of two parameters on fatigue damage predictions of a variably loaded cantilever beam has been examined. The first parameter is the geometry of the cantilever beam and the weld connecting it to a rear panel. Variables of the geometry examined here include the cantilever length, the weld width on the critical cross-section and the angle of the critical cross-section. The second parameter is the safety factor, as set out by the Eurocode 3 standard. An analytical approach has been used to calculate the stresses at the critical cross-section and standard rainflow counting has been used for the extraction of the load cycles from the load history. The results here suggest that a change in the width and angle of the critical cross-section has a non-linear impact on the fatigue damage. The results also show that the angle of the critical cross-section has the biggest influence on the fatigue damage and can cause the weld to withstand fatigue better. The second parameter, the safety factor, is shown to have a significant effect on the fatigue damage calculation, whereby a slight increase in the endurance safety factor can cause the calculated fatigue damage to increase considerably.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3148-3154
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• 2010

This paper presents the probabilistic analysis for fatigue life of Glass/Epoxy laminates with impact-induced damage. For this, a series of impact tests were perfomed on the Glass/Epoxy laminates using instrumented impact testing machine. Then, tensile and fatigue tests carried out so as to generate post-impact residual strength and fatigue life. Two Parameter Weibull distribution was used to fit the residual strength and fatigue life data of Glass/Epoxy composite laminates. The residual strength was affected by impact energy and their variance decreased with increasing of impact energy. The fatigue life of impacted laminates was greatly reduced by impact energy and this trend depended on applied stress amplitude. Additionally, the variation of fatigue life was gradually decreased with the applied stress amplitude.

• Composites Research
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• v.34 no.2
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• pp.115-122
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• 2021

SMC(Sheet molding compound) composite is mainly used for forming of vehicle's body. Considering the car accident, it is essential to research the impact behavior and characteristics of materials. It is difficult to identify them because the impact process is completed in a short time. Therefore, the impact damage analysis using FE(finite element) model is required for the impact behavior. The impact damage analysis requires the parameters for the damage model of SMC composite. In this paper, ANN(artificial neural network) technique is applied to obtain the parameters for the damage model of SMC composite. The surrogate model by ANN was constructed with the result in LS-DYNA. By comparing the absorption energy in drop weight test with the result of ANN model, the optimized parameters were obtained. The acquired parameters were validated by comparing the results of the experiment, the FE model and the ANN model.