• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.671-674
• /
• 2001

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of the interface crack. This paper investigates the effects of the stiffness of interface defect(exist along the path of the crack propagation) on the dynamic interface crack propagation behavior by comparing the experimental isochromatic fringes to the theoretical stress fields.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.429-432
• /
• 2000

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of the interface crack. This paper investigates the effects of the hole (existed along the path of the crack propagation) shape on the dynamic interface crack propagation behavior by comparing the experimental isochromatic fringes to the theoretical stress fields.

• Structural Engineering and Mechanics
• /
• 제47권5호
• /
• pp.643-660
• /
• 2013

In the present work, the capacity ratings of steel truss bridges have been carried out incorporating dynamic effect of moving vehicles and its accumulating effect as fatigue. Further, corrosion in the steel members has been taken into account to examine the rating factor. Dynamic effect has been considered in the rating procedure making use of impact factors obtained from simulation studies as well as from codal guidelines. A steel truss bridge has been considered to illustrate the approach. Two levels of capacity ratings- the upper load level capacity rating (called operating rating) and the lower load level capacity rating (called inventory rating) were found out using Load and Resistance Factor Design (LRFD) method and a proposal has been made which incorporates fatigue in the rating formula. Random nature of corrosion on the steel member has been taken into account in the rating by considering reduced member strength. Partial safety factor for each truss member has been obtained from the fatigue reliability index considering random variables on the fatigue parameters, traffic growth rate and accumulated number of stress cycle using appropriate probability density function. The bridge has been modeled using Finite Element software. Regressions of rating factor versus vehicle gross weight have been obtained. Results show that rating factor decreases when the impact factor other than those in the codal provisions are considered. The consideration of fatigue and member corrosion gives a lower value of rating factor compared to those when both the effects are ignored. In addition to this, the study reveals that rating factor decreases when the vehicle gross weight is increased.

• Structural Engineering and Mechanics
• /
• 제14권6호
• /
• pp.661-677
• /
• 2002

The subject of this investigation is to study the buckling of cross-ply laminated orthotropic cylindrical thin shells with variable elasticity moduli and densities in the thickness direction, under external pressure, which is a power function of time. The dynamic stability and compatibility equations are obtained first. These equations are subsequently reduced to a system of time dependent differential equations with variable coefficients by using Galerkin's method. Finally, the critical dynamic and static loads, the corresponding wave numbers, the dynamic factors, critical time and critical impulse are found analytically by applying a modified form of the Ritz type variational method. The dynamic behavior of cross-ply laminated cylindrical shells is investigated with: a) lamina that present variations in the elasticity moduli and densities, b) different numbers and ordering of layers, and c) external pressures which vary with different powers of time. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question.

• International Journal of Precision Engineering and Manufacturing
• /
• 제3권3호
• /
• pp.69-75
• /
• 2002

Measuring dynamic fracture toughness of brittle and small ceramic specimen is very difficult in a SHPB (Split Hopkinson Pressure Bar). As a countermeasure to this difficulty, a dynamic fracture toughness measuring method by the Chevron-notch ceramic specimen was proposed. Tested chevron specimens were of Chevron notch angles of 90$^{\circ}$, 100$^{\circ}$ and 110$^{\circ}$. Through finite element analysis, shape parameters of the Chevron-notch specimens according to notch angles were calculated. And the static fracture tough1ess of the Chevron-notch alumina specimen was measured as 3.8MPa√m similar to that of CT specimen with a precrack. Dynamic fracture toughness was 4.5MPa√m slightly higher than the static one. It was shown in this study that the proposed Chevron-notch specimens are valid to measure dynamic fracture toughness of extremely brittle materials such as ceramic.

• 대한기계학회논문집A
• /
• 제26권7호
• /
• pp.1217-1222
• /
• 2002

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of the interface crack. This paper investigates the effects of the hole (existed along the path of the crack propagation) shape on the dynamic interface crack propagation behavior by comparing the experimental isochromatic fringes to the theoretical stress fields.

• Earthquakes and Structures
• /
• 제15권2호
• /
• pp.155-164
• /
• 2018

Design of structures subjected to blast loads are usually carried out through nonlinear inelastic dynamic analysis followed by imposing acceptance criteria specified in design codes. In addition to comprehensive aspects of inelastic dynamic analyses, particularly in analysis and design of structures subjected to transient loads, they inherently suffer from convergence and computational cost problems. In this research, a strategy is proposed for design of steel moment resisting frames under far range blast loads. This strategy is inspired from performance based seismic design concepts, which is here developed to blast design. For this purpose, an algorithm is presented to calculate the capacity modification factors of frame members in order to simplify design of these structures subjected to blast loading. The present method provides a simplified design procedure in which the linear dynamic analysis is preformed, instead of the time-consuming nonlinear dynamic analysis. Nonlinear and linear analyses are accomplished in order to establish this design procedure, and consequently the final design procedure is proposed as a strategy requiring only linear structural analysis, while acceptance criteria of nonlinear analysis is implicitly satisfied.

• 한국정밀공학회지
• /
• 제14권8호
• /
• pp.115-121
• /
• 1997

The in-process detection of the tool wear is one of the most important technologies in completely auto- matic operation of machine tool. In this research, using the tools having flank wear, the dynamic compo- nent of cutting forces is considered to be available for identifying the cutting process. In order to investi- gate this relation in detail, the cutting forces in turning of workpiece made of aluminum were measured by dynamometer of piezoelectric type, and the dynamic components of cutting force were analyzed. The fre- quency analysis, probability density analysis and RMS analysis of the dynamic components were carried out independently. Through the experiments, the characteristics of the tool system have a large effect on the dynamic component of cutting forces. As a result, it is shown that the dynamic cutting force was able to detect flank wear accurately.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.1004-1006
• /
• 2014

This study was conducted to improve the understanding of factors affecting an automobile seat cushion in dynamic conditions. When there are two dummies on the seat to measure each places respectively at once, the shape of the transfer function changes because the dummies affect each other as if they are linked with some kind of a spring when under excitation. A simple two-degree-of-freedom linear model is used to define a translational stiffness of dynamic coupling phenomenon. The cushion deflection model was created to find the relation between dynamic coupling and distance. Experimental set-up was made to compare with the two-degree-of-freedom linear model. The dynamic coupling factor could be utilized to improve the dynamic comfort of automobile seats.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
• /
• pp.485-492
• /
• 2001

The dynamic analysis model is developed with the high-speed train (KTX) and a 2-span continuous prestressed concrete box girder bridge with a double track. The analytical results are compared with the dynamic field test results and found to be valid to yield quite accurate dynamic responses. The various trainset models with different number of cars are developed and compared with the results of the regular 20-car trainset model. It is concluded that the reduced trainset models, such as 7-car and 10-car models, cannot exactly produce the dynamic responses of bridges, especially when the train speed is high. Under the coincidence condition of two trains traveling with resonance velocity in the opposite directions, it is found that the impact factor under two-way coincidence is three times larger than that under one-way traffic. Consequently, for the bridge with a double-track it is necessary to check not only the dynamic responses of the bridge with one-way traffic but those with two-way coincidence.