• International Journal of Concrete Structures and Materials
• /
• v.10 no.4
• /
• pp.425-434
• /
• 2016

In this experimental study, six post-tensioned light weight concrete (LWC) continuous one-way slabs were tested in the following manner: the flexural behaviors of the members were compared with the calculations from the existing standards. The test also examined the effect of prestressing in tendons and proper prestress conditions to reduce the deflection and crack width, and to enhance the flexural capacity and ductility of LWC members. Flexural capacity and stress increments in unbonded tendons of the specimens were compared with those of the simply supported normal and the lightweight concrete members. The suggested safety limit from the American Concrete Institute (ACI) regulation on the maximum capacity and the stress incremental in unbonded tendons were also compared with the test results under simple and continuous supporting conditions.

• International Journal of Automotive Technology
• /
• v.6 no.3
• /
• pp.293-303
• /
• 2005

Bonded dissimilar materials are being increasingly used in automobiles, aircraft, rolling stocks, electronic devices and engineering structures. Bonded dissimilar materials have several material advantages over homogeneous materials such as high strength, high reliability, light weight and vibration reduction. Due to their increased use it is necessary to understand how these materials behave under stress conditions. One important area is the analysis of the stress intensity factors for interface cracks emanating from circular holes in bonded dissimilar materials. In this study, the bonded scarf joint is selected for analysis using a model which has comprehensive mixed-mode components. The stress intensity factors were determined by using the boundary element method (BEM) on the interface cracks. Variations of scarf angles and crack lengths emanating from a centered circular hole and an edged semicircular hole in the Al/Epoxy bonded scarf joints of dissimilar materials are computed. From these results, the stress intensity factor calculations are verified. In addition, the relationship between scarf angle variation and the effect by crack length and holes are discussed.

• Journal of Power System Engineering
• /
• v.19 no.1
• /
• pp.50-55
• /
• 2015

This study takes AC8A, which is a representative light weight alloy as matrix, and nickel as reinforcement for its superior properties. The manufacturing method applied in this study required low pressure for the infiltration of the metal matrix into the reinforcement. Porous Ni was applied as preform. The fabrication was conducted under 0.3 MPa at 600, 700 and 750 degrees centigrade, respectively. Intermetallic compounds Al3 generated between Al and Ni were observed in the composites. Microstructure, Vickers' hardness and wear characteristics of the composites were also investigated. The result indicates that the structures of compounds created at 650 degree centigrade were distributed densely; the grain size of the substances and the compounds was increased with the infiltration temperature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1998.04a
• /
• pp.114-121
• /
• 1998

This paper presents the model updating of an equipment panel by using modal test and sensitivity analysis. The equipment panel is one of the major structures of communication satellite, on which broadcasting and communication equipments are mounted. For high rigidity and light weight, the panel was designed as an aluminum honeycomb sandwich panel. In addition, heat pipes were embedded in the panel for thermal control. It is essential to improve the finite element model of a satellite by using modal test in order to verify the satellite is designed with adequate margin under launch environment. In this paper, Young's modulus of aluminum facesheet was selected as a modified parameter by sensitivity analysis. The effect of rotational springs of boundary points was also considered.

• The Journal of Korea Robotics Society
• /
• v.9 no.3
• /
• pp.178-184
• /
• 2014

Tendon driven robot mechanisms have many advantages such as allowing miniaturization and light-weight designs and/or enhancing flexibility in the design of structures. When designing or analyzing tendon driven mechanisms, it is important to determine how the tendons should be connected and whether the designed mechanism is easily controllable. Graph representation is useful to view and analyze such tendon driven mechanisms that are complicatedly interconnected between mechanical elements. In this paper, we propose a method of generalized graph representation that provides us with an intuitive analysis tool not only for tendon driven manipulators, but also various other kinds of mechanical systems which are combined with tendons. This method leads us to easily obtain structure matrix - which is the one of the most important steps in analyzing tendon driven mechanisms.

• International Journal of Contents
• /
• v.11 no.1
• /
• pp.69-72
• /
• 2015

Generally, existing parallel main-memory spatial index structures to avoid the trade-off between query freshness and CPU cost uses light-weight locking techniques. However, still, the lock based methods have some limits such as thrashing which is a well-known problem in lock based methods. In this paper, we propose a distributed index structure for moving objects exploiting the parallelism in multiple machines. The proposed index is a lock free multi-version concurrency technique based on the D-Stream model of Spark Stream. The proposed method exploits the multiversion nature of D-Stream of Spark Streaming.

• Journal of Korea Foundry Society
• /
• v.11 no.1
• /
• pp.63-70
• /
• 1991

Aluminium alloy castings, which can be not only manufactured in larger geometrically complex shapes, but also show good mechanical properties in addition to light weight, have kept their potential use as structures in the field of automotives, industrial machines and aircrafts. The variations of eutectic Si size a great effect on the elongation, impact value, fracture toughness and fatigue crack propagation rate without changes in the tensile strength or yield strength. The cooling curves with the solidification rate between $1.4^{\circ}C\;/min$ and $19.1^{\circ}C\;/min$ were obtained. With the increase of solidification rate, DAS, eutectic Si size and grain size were all decreased, which enhanced the mechanical properties. The tensile strength and yield strength were the most greatly influenced by DAS, and the elongation and impact value by eutectic Si size.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1999.04a
• /
• pp.287-294
• /
• 1999

The tensegrity structure by prestressed cable, which may have large freedom in scale and form and therefore are received much attention from the view points of their light weight and aesthetics, is a very flexible and geometrically unstable structure because the cable material has little initial rigidity. For the stable self-equilibrated state of the usually very deformable structure, the method to find the optimal initial stress by the shape analysis is proposed in this paper. The proposed procedure is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity and used to modified load incremental method adding to Newton-Raphson method with the proposed condition for optimal initial stress. The result of the shape analysis for the tensegrity structure with the radius of 30m is shown the almost approximated shape to architectural shape and the changed procedure of initial stress

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1118-1123
• /
• 2003

Based on the design requirements(size, strength, structure, weight, and etc.) for the rubber-tired AGT vehicle, carbody made of aluminum alloy is designed. The analysis of strength and stiffness is performed in the designed carbody, which results in the modification for optimal shapes and structures. It consists of a under frame, side frame, roof frame, end frame and forehead frame. After the carbody manufactured, tests are performed, which are vertical load test, longitudinal compressive load test, twisting load test, twisting natural frequency measurement, bending natural frequency measurement and 3 points supporting test. Results of them can guarantee a structural safety.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.12 no.6
• /
• pp.8-13
• /
• 2003

CFRP composite has a lot of merits such as mechanical characteristic, light weight and thermal resistance. For these merits CFRP is applied to so many industrial area. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the relationship between the stack thickness and drill diameter is examined from the drilling experiment, which is the drilling of 16, 32, 48p1ies specimen with the ${\phi}8$, ${\phi}10$, ${\phi}12mm$ cemented carbide drill. The results are analyzed with consideration of cutting force, stack thickness and drill diameter.