• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.1
• /
• pp.143-150
• /
• 1998

The evaluation of joint fatigue strength of light weight materials for electrical vehicle body has been performed through single lap joint tests with the design parameters such as joint style, adherend, bonding overlap length and bonding thickness. Fatigue strength was evaluated through 5-Hz, tension-tension, load controlled test with the stress ratio zero value. It is experimentally observed that fatigue strength of joint increases for the increase of overlap length. The combinations of Al-Al and Al-FRP adherends show that fatigue strength of joint is hardly changed for the increase of bonding thickness, but FRP-FRP adherend specimen shows that fatigue strength of joint increases after decreases for the increase of bonding thickness. Al-Al adherend specimen has much higher fatigue length than Al-FRP and FRP-FRP adherend specimens. Riveting at adgesive bonded joint gives little effect on fatigue strength.

• Journal of Welding and Joining
• /
• v.32 no.4
• /
• pp.46-54
• /
• 2014

In this study, the effect of bonding temperature and bonding pressure on deformation and tensile properties of diffusion bonded joint of STS304 compact heat exchanger was investigated. The diffusion bonds were prepared at 700, 800 and $900^{\circ}C$ for 30, 60 and 90 min in pressure of 3, 5, and 7 MPa under high vacuum condition. The height deformation of joint decreased and the width deformation of joint increased with increasing bonding pressure at $900^{\circ}C$. The ratio of non-bonded layer and void observed in the joint decreased with increasing bonding temperature and bonding pressure. Three types of the fracture surface were observed after tensile test. The non-bonded layer was observed in diffusion bonded joint preformed at $700^{\circ}C$, the non-bonded layer and void were observed at $800^{\circ}C$. On the other hand, the ductile fracture occurred in diffusion bonded joint preformed at $900^{\circ}C$. Tensile load of joint bonded at $800^{\circ}C$ was proportional to length of bonded layer and tensile load of joint bonded at $900^{\circ}C$ was proportional to minimum width of pattern. The tensile strength of joint was same as base metal.

• Steel and Composite Structures
• /
• v.21 no.1
• /
• pp.1-36
• /
• 2016

In the present study, the nonlinear magneto-electro-mechanical free vibration behavior of rectangular double-bonded sandwich microbeams based on the modified strain gradient theory (MSGT) is investigated. It is noted that the top and bottom sandwich microbeams are considered with boron nitride nanotube reinforced composite face sheets (BNNTRC-SB) with electrical properties and carbon nanotube reinforced composite face sheets (CNTRC-SB) with magnetic fields, respectively, and also the homogenous core is used for both sandwich beams. The connections of every sandwich beam with its surrounding medium and also between them have been carried out by considering Pasternak foundations. To take size effect into account, the MSGT is introduced into the classical Timoshenko beam theory (CT) to develop a size-dependent beam model containing three additional material length scale parameters. For the CNTRC and BNNTRC face sheets of sandwich microbeams, uniform distribution (UD) and functionally graded (FG) distribution patterns of CNTs or BNNTs in four cases FG-X, FG-O, FG-A, and FG-V are employed. It is assumed that the material properties of face sheets for both sandwich beams are varied in the thickness direction and estimated through the extended rule of mixture. On the basis of the Hamilton's principle, the size-dependent nonlinear governing differential equations of motion and associated boundary conditions are derived and then discretized by using generalized differential quadrature method (GDQM). A detailed parametric study is presented to indicate the influences of electric and magnetic fields, slenderness ratio, thickness ratio of both sandwich microbeams, thickness ratio of every sandwich microbeam, dimensionless three material length scale parameters, Winkler spring modulus and various distribution types of face sheets on the first two natural frequencies of double-bonded sandwich microbeams. Furthermore, a comparison between the various beam models on the basis of the CT, modified couple stress theory (MCST), and MSGT is performed. It is illustrated that the thickness ratio of sandwich microbeams plays an important role in the vibrational behavior of the double-bonded sandwich microstructures. Meanwhile, it is concluded that by increasing H/lm, the values of first two natural frequencies tend to decrease for all amounts of the Winkler spring modulus.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.5 no.3
• /
• pp.217-222
• /
• 1981

The stress analysis of two-orthotropic layer, adhesively bonded structures is considered. An orthotropic plate has a through-crack of finite length and is adhesively bounded by a sound orthotropic plate. The problem is resuced to a pair of Fredholm integral equations ofthe second kind. Using a numerical integration scheme to evaluate the intgrals, The integral equations are reduced to a system of algebraic equations. By solving these equations some numerical results for stress intensity factors are presented for various crack lengths.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.141-144
• /
• 2005

Rip-off failure and Debonding failure were commonly reported premature failure modes. The main reasons of premature failure in RC beams bonded with FRP were strengthening length and the reinforcement ratio. in this study, On the basis of premature failure mechanism in RC beams bonded with FRP, premature failure criteria were proposed. Also It was verified that Rip-off failure and Debonding failure occured according to premature failure criteria

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.531-536
• /
• 2003

It is generally known that RC flexural members strengthened by GFRP(Glass Fiber Reinforced Polymers) tend to be failed by premature bond failure near the flexural-shear cracks happened at the mid-span of beams. It is therefore strongly recommended that premature bond failure must be avoided to insure the intended strengthening effects sufficiently. The various methodologies such as increasing bonded length of GFRP and bonding details including U-shape wrappings and epoxy shear-keys are examined in this study. The bonded length of GFRP are calculated based on the assumed bond strengths of epoxy saturating resin. Total six half scale RC beam specimens were constructed and tested to investigate the effectiveness of each methodologies to prevent the bond failure of GFRP. Test results of each specimens are discussed in this paper.

• Journal of Welding and Joining
• /
• v.19 no.3
• /
• pp.342-347
• /
• 2001

Recently, adhesive-bonding technique is wifely used in manufacturing structures. Stress and strain analysis of joints are essential to design adhesive-bonded joints structure. The single-lap adhesive joint is the design dominating the range of adhesive joints. In this study, single-lap specimens with different joint dimensions were used for the tensile-shear test and finite element calculation in of order to investigate the effect of overlap length and adhesive-bonding thickness on adhesive strength and stress distribution of the joints. Consequently, it was found that overlap lap size and thickness can be important parameters of structure joints using adhesive bonding, which is effected on adhesive strength.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.2
• /
• pp.87-93
• /
• 1997

The bonding strength evaluation of light weight materials for electrical vehicle applications has been performed through single lap joint tests in which the design parameters such as fillet, joint style, adherend, bonding overlap length,bonding thickness, and environmental condition(soaking time in $25^{\circ}C$ water) are considered. It is experimentally oberved that lap shear strength of joint increases for higher fillet height, longer overlap length, and thinner bonding layer thickness. Al-Al adherend combination shows much higher lap shear strength than AL-FRP and FRP-FRP adherend combinations. Riveting at adhesive bonded joint of AL-AL adherend combination makes lap shear strength decrease. Effect of soaking time on lap shear strength is negligible.

• Proceedings of the KIEE Conference
• /
• 2001.11b
• /
• pp.213-215
• /
• 2001

This paper describes an improved analysis method for sheath circulating current on three-underground transmission cables using EMTP(Electromagnetic Transient Program). Author studied diversely the sheath circulating current on three-underground cables depending on the various length rate, the phase arrangement, and the grounding resistance of the sheath in the cross-bonded section. It was clear that very large circulating current is generated in cable systems due to unbalanced length rate and phase arrangement in the cross-bonded section. The analysing method for two or more underground cables will be really Improved for cable system utility.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.9
• /
• pp.841-850
• /
• 2008

Strength and failure of composite-to-aluminum rivetted, bonded, and rivet/bonding hybrid single-lap joints were investigated by experiment. A total of 82 joint specimens were tested with 3 different overlap lengths and 2 types of stacking sequence. FM73m adhesive film and NAS9308-4-03 rivet were used for hybrid joints. While failure loads of the bonded and hybrid joints increased as the overlap length increased, failure loads of the rivetted joints were not affected by the overlap length. Effect of the stacking sequence was not remarkable in the simple bonded or rivetted joints. Failure loads of the hybrid joints, however, showed the maximum of 30% difference depending on the stacking sequence. Major failure mode of the bonded and hybrid joints was the delamination of the composite adherend and failure mode of riveted joints was the rivet failure with local bearing.