scholarly journals Ultrasonic monitoring of insulated block joints

2018 ◽  
Vol 233 (3) ◽  
pp. 251-261 ◽  
Author(s):  
JT Stephen ◽  
C Hardwick ◽  
P Beaty ◽  
R Lewis ◽  
MB Marshall
Keyword(s):  
Condition Monitoring ◽  
Polyester Resin ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Reflection Coefficients ◽  
Ultrasonic Technique ◽  
Ultrasonic Monitoring ◽  
Weak Point ◽  
Track System ◽  
Essential Components

Insulated block joints are essential components used in railway tracks. They are divided into circuits and are used for train detection and signalling. However, they also represent a weak point in the track system and have a finite life. Condition monitoring of these components for planning preventative maintenance is currently labour intensive, and can be significantly expensive for the rail operator. In this study, insulated block joints were fatigued via shear load, whilst being condition monitored for degradation using a normally incident ultrasonic technique. Tests were also initially performed on lap-joints and shear specimens to further understand the response of the ultrasonic signal to failure of the adhesive layer under controlled conditions. Dynamic reflection coefficients as well as the applied load were recorded in all tests, and results were compared to failure zones on the specimens. The results showed that the ultrasonic technique was able to determine the onset of failure and de-bonding of the adhesive layer in addition to degradation and wear. The technique was also able to highlight differences in performance between two different liners, pultruded glass reinforced polyester resin and a flexible glass fibre sheet, with the latter showing improved resistance. The outcomes of this study have highlighted the viability of condition monitoring insulated block joints using an ultrasonic approach and have provided a basis for a future field trial.

scholarly journals Compression Shear Properties of Adhesively Bonded Single-Lap Joints of C/C Composite Materials at High Temperatures

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1437 ◽  
Author(s):  
Yanfeng Zhang ◽  
Zhengong Zhou ◽  
Zhiyong Tan
Keyword(s):  
Composite Materials ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Experimental Result ◽  
Shear Stresses ◽  
Test Results ◽  
Adhesively Bonded ◽  
Finite Element Software ◽  
Joint Structure ◽  
Simulation Results

The performance of joint structure is an important aspect of composite material design. In this study, we examined the compression shear bearing capacity of the adhesively bonded single-lap joint structure of high-temperature-resistant composite materials (C/C composite materials). The test pieces were produced in accordance with the appropriate ASTM C1292 standard, which were used for the compression shear test. The failure morphology of the layer was observed by a digital microscopic system and scanning electron microscope. The experimental result shows that the load on the test piece increased nonlinearly until the failure occurred, and most of the adhesive layer exhibited cohesive failures at three temperature points (400, 600, and 800 °C), while the interface failures occurred in a small part of the adhesive layer. A numerical analysis model was established using ABAQUS finite element software. The simulation results were compared with the test results to verify the correctness of the model. On the basis of correctness of the model verified by comparing the simulation results and the test results, the influences of temperature and overlapped length on the joint compression shear performance were studied through the validated simulation method. Numerical results showed that the ultimate load of the joint decreased with increases in temperature and that the distribution trends of the shear stresses in the overlapped length direction were substantially the same for joints of different overlapped lengths.

Ultrasonic Monitoring of Polymer Properties from the Melt to the Solid State: Influence of Chemical/Structural Details

1988 ◽  
Vol 142 ◽  
Author(s):  
L. Piché ◽  
G. Lessard ◽  
F. Massines ◽  
A. Hamel
Keyword(s):  
Molecular Structure ◽  
Glass Transition ◽  
Complex Modulus ◽  
Ultrasonic Technique ◽  
Ultrasonic Monitoring ◽  
Crystalline Polymers ◽  
Polymer Properties ◽  
Wide Range ◽  
Structural Details ◽  
End Use

AbstractAn ultrasonic technique is described for the simultaneous measurement of specific volume, V, sound velocity, v, and attenuation, a, at frequencies between f = 0.5 and f = 15 MHz, in a wide range of temperature (- 150 to + 400°C) and pressure (up to 2 kbars). The results (V,v,a) are translated into a complex modulus, M* = M’ + iM” and analyzed in terms of the thermodynamic state of the material. Typical results for amorphous and semi-crystalline polymers are presented which show that the technique is a probe of the fundamental features of these materials (glass transition, crystallization, melting, molecular structure) which determine processability and end use properties. The method should prove of great interest for quality and process control.

Experimental and Analytical Investigations of the Dynamic Response of Adhesively Bonded Single Lap Joints

2004 ◽  
Vol 126 (1) ◽  
pp. 84-91 ◽  
Author(s):  
A. Vaziri ◽  
H. Nayeb-Hashemi ◽  
H. R. Hamidzadeh
Keyword(s):  
Dynamic Response ◽  
Loss Factor ◽  
Natural Frequencies ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Laser Vibrometer ◽  
Total System ◽  
Adhesive Film ◽  
Single Lap Joints ◽  
Central Void

Dynamic response of single lap joints, subjected to a harmonic peeling load is studied theoretically and experimentally. In the theoretical part, dynamic response of a single lap joint clamped at one end and subjected to a harmonic peeling load at the other end is investigated. Adherents are modeled as Euler-Bernouli beams joined in the lap area by a viscoelastic adhesive layer. Both axial and transverse deformations of adherents are considered in deriving the equations of motion. The effects of adhesive layer thickness, mechanical properties and its loss factor on the dynamic response of the joint are investigated. Furthermore, effects of defects such as a void in the lap area on the dynamic response of the joints are studied. The results showed that frequencies where peak amplitudes occurred were little dependent on the adhesive loss factor. However, peak amplitudes reduced for joints with a higher adhesive loss factor. Furthermore, the results indicated that for the joint geometries and properties investigated the system resonant frequencies were not affected by the presence of a central void covering up to 80% of the overlap length. In the experimental part, single lap joints were fabricated using 6061-T6 Aluminum. Adherents were joined together using Hysol EA 9689 adhesive film. Joints with various central voids were manufactured by removing adhesive film from the desired area of lap joints prior to bonding adherents. Dynamic responses of the joints were investigated using the hammer test technique. The system response was measured using both an accelerometer and a noncontact laser vibrometer. The natural frequencies of the joints obtained by using the laser vibrometer were very close to those obtained theoretically. However, natural frequencies obtained by using an accelerometer depended on the accelerometer location in the system, which was attributed to its mass contribution to the over- all system mass. A central void covering less than 80% of the overlap length had little effect on the system resonance frequencies. This was in agreement with the theoretical results. In contrast total system-damping ratios were a function of the void size. Joints without a void exhibited higher damping.

Simplified stiffness analysis for degraded single lap joints in the space sector – Comparative analytical and finite element analysis

2020 ◽  
Vol 234 (13) ◽  
pp. 1956-1966
Author(s):  
Jannik Zimmermann ◽  
Josef Weiland ◽  
Mohammad Zamaan Sadeghi ◽  
Alexander Schiebahn ◽  
Uwe Reisgen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Ionizing Radiation ◽  
Coefficient Of Thermal Expansion ◽  
Closed Form Solution ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Polymer Chains ◽  
Adhesively Bonded ◽  
European Organization

Considering the aerospace sector, the use of adhesively bonded joints is constantly increasing over the last decades. Due to its lightweight and capability of joining various materials with different coefficient of thermal expansion, this joining technique offers many benefits over conventional methods like rivets, screws and welding. On the other hand, structural adhesives consists of polymer chains that can be severely affected by the environment. An example of such an environmental effect is the interaction of the polymer chains of the adhesive with ionizing radiation in space. Nevertheless in the literature, the influence of ionizing radiation on the mechanical properties of epoxides is covered but not well understood. The present work describes a method of determining the stiffness of an adhesively bonded single lap joint (SLJ) using closed form solution equations. This analytical approach is compared with a numerical model. The mechanical properties of the adhesive in both models is degraded due to irradiation, based on experiments conducted by the European Organization for Nuclear Research (CERN). The results show that the degradation of the mechanical properties of the adhesive layer has a significant influence on the joint stiffness. This effect increases with growing adhesive layer thickness. Comparing the results with a finite element model, it is shown that the developed calculation scheme overestimates the stiffness of the SLJ. This is caused by the neglection of bending stresses within the adherends.

Viscoplastic Analysis of Adhesive Joints

1996 ◽  
Vol 63 (1) ◽  
pp. 21-26 ◽  
Author(s):  
G. K. Hu ◽  
F. Schmit ◽  
D. Baptiste ◽  
D. Franc¸ois
Keyword(s):  
Hydrostatic Stress ◽  
Three Dimensional ◽  
Constant Strain Rate ◽  
Adhesive Layer ◽  
Butt Joint ◽  
Lap Joints ◽  
Experimental Results ◽  
Constitutive Law ◽  
Tensile Creep ◽  
Account Due

The uniaxial constitutive law for an adhesive is studied by constant strain rate tensile, creep and relaxation tests. The S-D effect of the adhesive is taken into account by using the Raghava yielding criterion in a three dimensional constitutive formulation. The obtained constitutive law is then used to analyze a single lap joint and a butt joint by a finite element method. Constant cross head speed tensile and creep loading cases are examined. For a butt joint, the results show that the viscous effect and the influence of the hydrostatic stress must be taken into account due to the variation of the hydrostatic stress and of the loading rate in the adhesive layer as function of its thickness. A comparison with experimental results is also given. A good agreement between viscoplastic calculations and experimental results is obtained for single-lap joints. A reasonable result is obtained for butt joints and the discrepancy is attributed to interfacial debonding.

MECHANICAL BEHAVIOR OF ADHESIVELY-BONDED JOINTS UNDER HIGH LOADING RATES

2021 ◽  
Author(s):  
MEHMET EMIN ERCAN ◽  
FERHAT KADIOGLU
Keyword(s):  
Adhesive Layer ◽  
Experimental Tests ◽  
Lap Joints ◽  
Adhesively Bonded ◽  
Case Scenario ◽  
Worst Case ◽  
Adhesive Film ◽  
Package Program ◽  
Set Up ◽  
Static Conditions

This work aims to investigate the dynamic behavior of adhesively-bonded Single Lap Joints (SLJs) under ballistic conditions. For this purpose, the joints with clamped-clamped boundary conditions were modelled using a Finite Element Method (FEM) via ABAQUS package program. The numerical model is based on the joint subjected to a projectile with a mass of 1.25 gr, a density of 11.3 gr/cm3, and an impacting velocity of 100 m/s. The experimental tests conducted in a specially designed set-up were performed via an air-pressurized gun. 6061 aluminum adherends and an adhesive film were used to manufacture the bonded structure. Curves of the velocity and dynamic load against time were predicted for the joint under the impacting projectile. Failure and stress distributions in the adherend as well as in the adhesive layer were predicted that was validated via the experimental results. The prediction was made according to the worst case scenario that accounts the input data obtained from the quasi-static conditions.

Acoustic Emission on Adhesively Bonded Single-Lap Joints of Composite Laminate during Tensile Test

2014 ◽  
Vol 912-914 ◽  
pp. 441-444
Author(s):  
Yan Rong Pang ◽  
Ran Liu ◽  
Ya Juan Li ◽  
Bo Han Lu ◽  
Xin Kang Xing ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Tensile Test ◽  
Composite Laminate ◽  
Mechanical Response ◽  
Adhesive Layer ◽  
Relative Energy ◽  
Lap Joints ◽  
Adhesively Bonded ◽  
Damage And Failure ◽  
Single Lap Joints

Acoustic emission (AE) was used to monitor the tensile test of composites with adhesive specimens. The mechanical response behavior, damage and failure characteristics, and the corresponding AE characteristics of the composites have been investigated. The results show that the load of the join with defect in the adhesive layer is lower than the join with no defect. The higher AE relative energy and the AE amplitude were obtained in the adhesive specimen with defect in the adhesive layer whereas the variation of the AE relative energy is different from the adhesive specimen with on defect. The characteristics such as AE amplitude distribution, relative energy and cumulative hits are connected with the tensile damage and failure of the adhesively bonded single-lap joints of composite laminate. In the actual AE monitoring, these feature parameters should be considered entirely assess the damage and failure of the composites structures.

Stress analysis of adhesive-bonded lap joints

1974 ◽  
Vol 9 (3) ◽  
pp. 185-196 ◽  
Author(s):  
R D Adams ◽  
N A Peppiatt
Keyword(s):  
Finite Element ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Elastic Behaviour ◽  
Lap Joint ◽  
Linear Elastic ◽  
Rubber Model ◽  
Dimensional Finite Element ◽  
Linear Elastic Behaviour ◽  
Good Agreement

Stresses in a standard metal-to-metal adhesive-bonded lap joint are analysed by a two-dimensional finite-element method and comparisons are made with previous analyses. Particular attention is paid to the stresses at the ends of the adhesive layer. Unlike previous work, which assumes the adhesive to have a square edge, the adhesive spew is treated as a triangular fillet. The highest stresses exist at the adherend corner within the spew. Linear elastic behaviour is assumed throughout. A rubber model is reported which confirms these results physically. Good agreement was also obtained between some practical results and the finite-element predictions.

A Coupled Peel and Shear Stress-Diffusion Model for Adhesively Bonded Single Lap Joints

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Emad Mazhari ◽  
Sayed A. Nassar
Keyword(s):  
Shear Stress ◽  
Diffusion Model ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Fickian Diffusion ◽  
Lap Joint ◽  
Adhesively Bonded ◽  
Single Lap Joints ◽  
Single Lap Joint ◽  
Stress Diffusion

In this study, the Fickian diffusion formulation is extended to the adhesive layer of a single lap joint (SLJ) model, in order to develop a coupled peel and shear stress-diffusion model. Constitutive equations are formulated for shear and peel stresses in terms of adhesive material properties that are time- and location-dependent. Numerical solution is provided for the effect of diffusion on shear and peel stresses distribution. Detailed discussion of the results is presented.

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