• 접착 및 계면
• /
• 제7권4호
• /
• pp.13-17
• /
• 2006

The elasto-plastic finite element method (FEM) was used to investigate the effect of off-center recessing location (8 mm length) on the stress distribution in the lap zone of adhesively bonded aluminium double lap joint. The results from simulation showed that the effect of off-cent recessing in bondline of double lap joint in the mid-bondline is not evidently to stress distribution in mid-bondline but the peak stresses both in mid-bondline and in the interface near the adherend side of the joint may increase markedly when an 8 mm length recessing was arranged symmetrical to the point of x =18 mm. When shifting an 8 mm length recess from near left end to the right end of the lap zone, all the highest peak stresses in the mid-bondline occurred under the condition of recess arranged symmetrical to the point of x = 6 mm.

• Corrosion Science and Technology
• /
• 제17권3호
• /
• pp.109-115
• /
• 2018

Electrical Resistance Welding (ERW) on a longitudinal seam-welded pipe has been extensively used in oil and gas pipelines. It is well known that the weld zone commonly suffers from grooving corrosion in ERW pipes. In this paper, the grooving corrosion performances of API X65 grade non-sour service (steel-A) and API X70 grade sour gas resistant (steel-B) steel electrical resistance welding pipelines were evaluated. The microstructure of the bondline is composed of coarse polygonal ferrite grains and several elongated pearlites. The elongated pattern is mainly concentrated in the center of the welded area. The grooving corrosion test and electrochemical polarization test were conducted to study the corrosion behavior of the given materials. A V-shaped corrosion groove was found at the center of the fusion zone in both the steel-A and steel-B ERW pipes, as the corrosion rate of the bondlines is higher than that of the base metal. Furthermore, the higher volume fraction of pearlite at the bondline was responsible for the higher corrosion rate at the bondline of both types of steel.

• Journal of Welding and Joining
• /
• 제18권5호
• /
• pp.84-89
• /
• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• 접착 및 계면
• /
• 제7권4호
• /
• pp.18-23
• /
• 2006

The influence of the notch length on the stress distribution of mid-bondline and adherend was investigated using elasto-plastic finite element method. The results from the simulation showed that peak stress of mid-bondline decreased markedly as adherend with notch in the middle of lap zone, and the stress in the middle of joint with low stress originally increased evidently. All the peak stresses decreased firstly and increased again as the length of notch increased. The relative higher peak stress appeared at the point near the notch of adherend where might be failed previously during the loading procedure.

• 대한기계학회논문집A
• /
• 제25권1호
• /
• pp.115-126
• /
• 2001

In this paper, through a series of comparative experiments, effects of two different cure processing methods, cocure and precure, on the mechanical properties of honeycomb core materials for aircraft applications are considered. Mass of moisture accumulated into the closed cells of the sandwich panel specimen from the measured mass of moisture diffused to the full saturation state into the elements(skin, adhesive layer, Nomex honeycomb), consisting the honeycomb sandwich specimen has been calculated. Water reservoir of 70$\^{C}$ was used to have specimens absorb moisture to see the influence of moisture absorbed into sandwich panel on its mechanical properties. For the repair condition holding for 2 hours at 177$\^{C}$(350℉) temperature, a pressure due to the vapor expansion in each cell of the sandwich panel, which may result in the local separation of the interface between laminated skin and the surface of the honeycomb, has been estimated by vapor pressure-temperature relation from the thermodynamic steam table and compared to the pressure from the ideal gas state equation. The bonding strengths of the laminated skins on the flat surface of the Nomex honeycomb have been compared by the flatwise tension test and climbing drum peel test performed at room temperature for dry, wet and wet-repair specimens, respectively.

• Advances in Computational Design
• /
• 제1권1호
• /
• pp.37-60
• /
• 2016

In this paper an electromechanically coupled isogeometric finite element is utilized to analyse Lamb wave excitation with piezoceramic actuators. An effective actuator design reduces the energy needed for Lamb wave excitation, which is beneficial if a structural health monitoring system should be applied for a structure. For a better understanding of the actuator behavior the piezoeceramics are studied both free and bonded at a structure. The numerical part of the analysis is performed utilizing isogeometric finite elements. To obtain the optimal performance for the numerical analysis the effect of k-refinement of the isogeometric element with respect to the convergence is studied and discussed. The optimal numerical setup with the best convergence rate is proposed and is validated with free piezoeceramic actuators. The validated model is then utilized to study the impact of actuator shape and adhesive bondline effect to the wave amplitude. The study shows that simplified analytical equations do not predict the optimal excitation frequencies for all piezoceramic designs accurately.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 추계학술발표대회 논문집
• /
• pp.73-77
• /
• 2004

Failure predictions of composite single-lap bonded joints were performed considering both of composite adherend failure and bondline failure. An elastic-perfectly plastic model of adhesive and a delamination failure criterion are used. The failure prediction results such as failure mode and strength have very good agreements with the test results of joint specimens with various bonding methods and parameters. The influence of variations in the effective strength (that is, adhesion performance) and plastic behavior of adhesive on the failure characteristics of composite bonded joints are investigated numerically. The numerical results show that optimal joint strength is archived when adhesive and delamination failure occur in the same time.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 추계학술발표대회 논문집
• /
• pp.118-121
• /
• 2002

Polyvinylidene di-fluoride (PVDF) film sensor appeared to be practically useful for the structural health monitoring of composite materials and structures. PVDF film sensors were either attached to or embedded in the graphite/epoxy composite (CFRP) samples to detect the fatigue damage at the bondline of single-lap joints or the tensile failure of unidirectional laminates. PVDF sensors were sensitive enough to detect and determine the crack front in linear location since composites usually produce very energetic acoustic emission (AE). PVDF sensors are extremely cost-effective, as flexible as other plastic films, in low profile as thin as a few tens of microns, and have relatively wide-band response, all of which characteristics are readily utilized for the structural health monitoring of composite structures. Signals due to fatigue damage showed a characteristics of mode II (shear) type failure whereas those from fiber breakage at DEN notches showed that of mode I (tensile) type fracture.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.232-236
• /
• 2004

The fracture characteristics of unidirectional composite single-lap bonded joints were investigated experimentally and numerically. The effects of bonding method, surface roughness, bondline thickness and the existence of fillet on the failure characteristics and strength of bonded single-lap joints were evaluated experimentally. The failure process, failure mode and the behavior of load-displacement curve was apparently different according to bonding method. The failure load of the specimen co-cured without adhesive was definitely superior to other types of specimens but the specimens co-cured with adhesive film had a less strength than secondary bonded specimens. In the secondary bonded specimens, the lower value of surface roughness and existence of fillet improved the strength of specimens. The strain energy release rates calculated by geometric nonlinear finite element analyses and Virtual Crack Closure Technique for the secondary bonded specimens considering the three types of initial cracks - comer crack, edge crack and delamination crack - were consistent with the test results.

• Composites Research
• /
• 제16권5호
• /
• pp.45-53
• /
• 2003

본 논문에서는 이차 본딩으로 접착된 복합재료-복합재료 Single-Lap 조인트 시편에 대해 인장 시험 및 수치해석을 통해 그 파손 특성을 조사하였다. 시편시험에서는 시험 중에 CCD 카메라 및 AE 센서를 이용해 초기 균열의 발생 및 진전양상에 대한 시험적인 관찰을 수행하였다. 시편에 대해 기하비선형 유한요소해석 및 VCCT(Virtual Crack Closure Technique)기법을 이용해 시편의 거동 및 변형율에너지방출률을 계산하고 세 가지 관찰된 초기 균열 모드에 대해 파손강도를 계산하였다. 인장시험에서 초기 균열은 모서리 계면 균열, 측면 계면 균열 및 층간 분리 균열의 세 가지 형태로 최종 파손의 60∼90% 하중에서 발생하였다. 주된 파손 모드는 접착제 계면 파손(adhesive failure) 및 적층판의 첫 번째 및 두 번째의 층간 분리 파손이었다. 두꺼운 접착제 층을 갖는 시편들은 초기균열이 낮은 하중에서 발생하였지만 균열진전에 대한 저항성 및 파손하중은 높게 나타났다. 층간분리파손은 주로 두꺼운 접착제의 경우에 발생하였다. 세 가지 초기 균열 모드에 대해 변형률에너지방출률은 Mode I의 G값이 Mode II의 G값보다 크게 계산되었다. Mode I 및 전체 G값은 측면 계면 균열, 모서리 계면 균열, 층간분리 균열의 순서로 크게 계산되었다.