Showing papers by "Jung-Ju Lee published in 2008"
01 Nov 2008
TL;DR: In this article, two kinds of tactile sensors using the optical fiber sensors are described, one is the tactile sensor using fiber Bragg grating (FBG) sensor, which can detect external force using change of the reflective wavelength.
Abstract: This paper describes two kinds of the tactile sensors using the optical fiber sensors. One is the tactile sensor using fiber Bragg grating (FBG) sensor. Bragg grating inscribed in an optical fiber causes reflect of a spectral component at the Bragg wavelength. This sensor can detect external force using change of the reflective wavelength. The other is the tactile sensor using the microbending optical fiber (MBOF) sensors. The microbending of the optical fiber drives the light transmission loss from the optical fiber. Using the light loss, this sensor can also detect the external force. The structures of these type tactile sensors are very simple. The tactile sensor using FBG sensor consists of an optical fiber which has a Bragg grating and bridge type transducers, and using MBOF sensors is composed of crossed fibers in the silicone rubber. In this paper, we fabricated and evaluated both tactile sensors. The performances of both tactile sensors were verified.
33 citations
TL;DR: In this paper, preliminary research to develop a NiTi linear actuator using a two-way shape memory process is conducted, and the bolts are fractured successfully using both one-way and two way shape memory effects.
Abstract: NiTi can produce a large force per unit volume and operate with a simple mechanism. For these reasons, it has been widely researched for application as an actuator. In this study, preliminary research to develop a NiTi linear actuator using a two-way shape memory process is conducted. Compression tests on a NiTi cylinder to investigate basic compressive properties are performed and recovery stresses to evaluate the actuating capacity are measured. The one-way shape memory process requires compressive loading and unloading but the two-way recovery does not. Hence, a two-way recovery can be utilized more conveniently compared to a one-way process. Additionally, bolt-fracturing tests are performed to confirm the possibility of NiTi actuators. The bolts are fractured successfully using both one-way and two-way shape memory effects.
23 citations
TL;DR: In this paper, a composite/steel interfacial crack was compared with the fracture toughness of the interface, which was measured from bi-material end-notched flexure (ENF) specimens, to predict the failure loads of lap joints, and the results showed that interfacial fracture mechanics characterization of adhesion strength can be a practical engineering tool for predicting the loadbearing capacities of adhesive-bonded joints.
Abstract: The failure in an adhesive-bonded structure starts at the interface, and the interfacial fracture is of interest whenever adhesion between different materials is concerned. One of primary factors limiting the application of adhesive-bonded joints to structural design is the lack of a good evaluation tool for adhesion strength to predict the load-bearing capacity of boned joints. The adhesion strength of composite/steel bonding has been evaluated using interfacial fracture mechanics characterization. The energy release rate of a composite/steel interfacial crack was compared with the fracture toughness of the interface, which was measured from bi-material end notched flexure (ENF) specimens, to predict the failure loads of bi-material lap joints. Fracture toughness, IIc G , was regarded as a property of the interface rather than a property of the adhesive. The results show that interfacial fracture mechanics characterization of adhesion strength can be a practical engineering tool for predicting the load-bearing capacities of adhesive-bonded joints.
5 citations
TL;DR: The program using Abaqus UMAT based on Modified Brinson model is used to analyze SMA, and the martensite fraction, the most important factor which defines SMA motion, is also calculated by Fortran program in UMAT.
Abstract: In this paper, the algorithm of Abaqus UMAT is introduced to analyze the shape memory alloy. The SMA has two main effects which show non-linearity. Due to this, it is hard to analyze SMA using analysis tools and to describe all of two effects. Therefore, in this study, the program using Abaqus UMAT based on Modified Brinson model is used to analyze SMA. The martensite fraction, the most important factor which defines SMA motion, is also calculated by Fortran program in UMAT. In addition, the tensile test of SMA specimen is conducted. The availability of algorithm is proved by comparing analysis to experimental result.
3 citations
01 Jan 2008
TL;DR: In this paper, an interface fracture mechanics approach was introduced to predict the load-bearing capacity of composite metal bonded joints, and the critical energy release rates of double-lap joints showed a good agreement with the measured fracture toughness.
Abstract: Prediction of the load-bearing capacity of an adhesive-bonded Joint is of practical importance for engineers. This paper introduces interface fracture mechanics approach to predict the load-bearing capacity of composite metal bonded joints. The adhesion strength of composite/steel bonding is evaluated in terms of the energy release rate of an interfacial crack and the fracture toughness of the interface. Virtual track closure technique (VCCT) is used to calculate energy release rates, and hi-material end-notched flexure (ENF) specimens are devised to measure the interfacial fracture toughness. Bi-material ENF specimens gave consistent mode II fracture toughness values of the composite/steel interface regardless of the thickness of specimens. The critical energy release rates of double-lap joints showed a good agreement with the measured fracture toughness. Therefore. the energy-based interfacial fracture characterization can be a practical engineering tool for predicting the load-bearing capacity of bonded joints.
1 citations