scholarly journals Propagation of Non-Linear Lamb Waves in Adhesive Joint with Micro-Cracks Distributing Randomly

2020 ◽  
Vol 10 (3) ◽  
pp. 741 ◽  
Author(s):  
Xiaoyang Li ◽  
Guoshuang Shui ◽  
Youxuan Zhao ◽  
Yue-Sheng Wang
Keyword(s):  
Adhesive Joint ◽  
Lamb Waves ◽  
Damage Zone ◽  
Adhesive Layer ◽  
Propagation Distance ◽  
Element Model ◽  
Matching Condition ◽  
Simulation Method ◽  
Micro Cracks ◽  
Non Linear

With the advantages of uniform stress transfer and weight reduction, adhesive joints are widely used in engineering. The propagation of non-linear Lamb waves in an adhesive joint with micro-cracks distributing in a random way is systematically investigated by using the numerical simulation method in this paper. A finite element model of the tri-layer adhesive structure with micro-cracks distributing randomly is established, and the Lamb wave mode pair with a matching condition of the phase velocity is chosen to examine the interaction of the micro-cracks with Lamb waves. The results show that the micro-cracks within the adhesive layer will lead to the generation of second harmonics. We also find that the Acoustic Non-linearity Parameters (ANP) increase with the propagation distance in the micro-crack damage zone and the density of the micro-cracks. However, ANPs are less concerned with the friction coefficients of the surface of micro-cracks. This numerical research reveals that non-linear Lamb waves can be employed to effectively characterize the micro-cracks related damages within an adhesive joint.

Effect of Bond Thickness on the Fracture Toughness of Adhesive Joints

2004 ◽  
Vol 126 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Deok-Bo Lee ◽  
Toru Ikeda ◽  
Noriyuki Miyazaki ◽  
Nak-Sam Choi
Keyword(s):  
Fracture Toughness ◽  
Adhesive Joint ◽  
Damage Zone ◽  
Crack Tip ◽  
Adhesive Layer ◽  
Compact Tension ◽  
Optical Microscope ◽  
Adhesive Joints ◽  
Adhesive Layers ◽  
Modified Epoxy

The effect of bond thickness on the fracture toughness of adhesive joints was investigated from a microstructural perspective, using compact tension (CT) adhesive-joint specimens with different bond thicknesses. The adhesive material was a rubber-modified epoxy resin with 12.5 wt% carboxy-terminated butadiene acrylonitrile (CTBN) elastomer. The shapes of the rubber particles dispersed in adhesive layers of damaged and undamaged specimens were observed with an optical microscope. The damage was distributed along the interfaces between the adhesive layer and the two adherends. The results show that the primary causes of variations in the fracture toughness of an adhesive joint with the bond thickness are not only a damage zone around a crack tip but also the combination of a damage zone around a crack tip and additional damage zones along the interfaces.

scholarly journals Evaluation of Moisture and Decay Models for a New Design Framework for Decay Prediction of Wood

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 721
Author(s):  
Jonas Niklewski ◽  
Philip Bester van Niekerk ◽  
Christian Brischke ◽  
Eva Frühwald Hansson
Keyword(s):  
Service Life ◽  
Wood Decay ◽  
Element Model ◽  
Digital Design ◽  
Design Guideline ◽  
Digital Performance ◽  
Detail Design ◽  
Non Linear ◽  
Service Life Design ◽  
Life Design

Performance-based, service-life design of wood has been the focus of much research in recent decades. Previous works have been synthesized in various factorized design frameworks presented in the form of technical reports. Factorization does not consider the non-linear dependency between decay-influencing effects, such as between detail design and climate variables. The CLICKdesign project is a joint European effort targeting digital, performance-based specification for service-life design (SLD) of wood. This study evaluates the feasibility of using a semi-empirical moisture model (SMM) as a basis for a digital SLD framework. The performance of the SMM is assessed by comparison against a finite element model (FEM). In addition, two different wood decay models (a logistic, LM, and simplified logistic model (SLM)) are compared. While discrepancies between the SMM and FEM were detected particularly at high wood moisture content, the overall performance of the SMM was deemed sufficient for the application. The main source of uncertainty instead stems from the choice of wood decay model. Based on the results, a new method based on pre-calculated time series, empirical equations, and interpolation is proposed for predicting the service life of wood. The method is fast and simple yet able to deal with non-linear effects between weather variables and the design of details. As such, it can easily be implemented as part of a digital design guideline to provide decision support for architects and engineers, with less uncertainty than existing factorized guidelines.

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

2013 ◽  
Vol 558 ◽  
pp. 489-500 ◽  
Author(s):  
Patrick Norman ◽  
Claire Davis ◽  
Cédric Rosalie ◽  
Nik Rajic
Keyword(s):  
Wave Field ◽  
Lamb Waves ◽  
Base Material ◽  
Adhesive Layer ◽  
Scattered Wave ◽  
Phase Lag ◽  
Wave Fields ◽  
Surface Mount ◽  
Frequency Regime ◽  
Fibre Bragg Gratings

The application of Lamb waves to damage and/or defect detection in structures is typicallyconfined to lower frequencies in regimes where only the lower order modes propagate in order to simplifyinterpretation of the scattered wave-fields. Operation at higher frequencies offers the potentialto extend the sensitivity and diagnostic capability of this technique, however there are technical challengesassociated with the measurement and interpretation of this data. Recent work by the authorshas demonstrated the ability of fibre Bragg gratings (FBGs) to measure wave-fields at frequencies inexcess of 2 MHz [1]. However, when this work was extended to other thinner plate specimens it wasfound that at these higher frequencies, the cyanoacrylate adhesive (M-Bond 200) used to attach theFBG sensors to the plate was significantly affecting the propagation of the waves. Laser vibrometrywas used to characterise the wave-field in the region surrounding the adhesive and it was found that theself-adhesive retro-reflective tape applied to aid with this measurement was also affecting the wavefieldin the higher frequency regime. This paper reports on an experimental study into the influence ofboth of these materials on the propagating wave-field. Three different lengths of retro-reflective tapewere placed in the path of Lamb waves propagating in an aluminium plate and laser vibrometry wasused to measure the wave-field upstream and downstream of the tape for a range of different excitationfrequencies. The same experiment was conducted using small footprint cyanoacrylate film samplesof different thickness. The results show that both of these surface-mount materials attenuate, diffractand scatter the incoming waves as well as introducing a phase lag. The degree of influence of thesurface layer appears to be a function of its material properties, the frequency of the incoming waveand the thickness and footprint of the surface layer relative to the base material thickness. Althoughfurther work is required to characterise the relative influence of each of these variables, investigationsto date show that for the measurement of Lamb Waves on thin structures, careful considerationshould be given to the thickness and footprint of the adhesive layer and sensor, particularly in the highfrequency regime, so as to minimise their effect on the measurement.

Adhesive Layer Effects on PZT-induced Lamb Waves at Elevated Temperatures

2010 ◽  
Vol 9 (3) ◽  
pp. 247-256 ◽  
Author(s):  
Sungwon Ha ◽  
Kuldeep Lonkar ◽  
Amrita Mittal ◽  
Fu-Kuo Chang
Keyword(s):  
Elevated Temperatures ◽  
Lamb Waves ◽  
Adhesive Layer

Reelability Assessment of Adhesively Bonded Mechanically Lined Pipe

2021 ◽  
Author(s):  
Grégory Alexandre Toguyeni ◽  
Jens Fernandez-Vega ◽  
Richard Jones ◽  
Martin Gallegillo ◽  
Joachim Banse
Keyword(s):  
Finite Element ◽  
Adhesive Layer ◽  
Element Model ◽  
Curing Temperature ◽  
Sensitivity Analyses ◽  
Adhesively Bonded ◽  
Element Analysis ◽  
Physical Test ◽  
Weld Overlay ◽  
Outer Pipe

Abstract A solution to prevent liner wrinkling in Mechanically Lined Pipes (MLP) with a standard 3.0mm thick liner during reeling, without the use of pressurisation, has been developed in the form of the GluBi® lined pipe. The liner being adhesively bonded to the outer pipe, its integrity is maintained despite the global plastic strain applied by the installation method. This new linepipe product has been qualified for offshore use through testing accompanied by a detailed Finite Element Analysis programme to fully capture the pipe and adhesive behaviours under and range of temperatures and loading conditions. The objective of this analysis program was to investigate the reelability of the GluBi® pipe. The instalability was defined as the capability of the pipe to tolerate cyclic plastic deformation representative of a typical pipeline installation by reeling without the formation of wrinkling of the CRA liner, and to maintain the integrity of the adhesive layer, particularly near the weld overlay at the pipe ends. Important areas of the GluBi® pipe design are the pipe extremities, particularly the transition between the liner and the weld overlay length. A detailed Finite Element model of the pipe was created. It captured all stages of the pipe manufacturing: pipe lining, hydrostatic expansion, adhesive curing, overlay weld deposition and reeling simulation. The pipe modelled was 312.1mm OD × 19.7mm WT SMLS 450 with a nominal 3.0mm thick Alloy 625 liner. An important validation work was performed to obtain a precise material response of the adhesive layer between liner and outer pipe. The adhesive mechanical properties were thus assessed in shearing and peeling over a range of temperatures covering all possible manufacturing and installation conditions. The model's elements and adhesive property modelling were validated against physical test results. Sensitivity analyses were done on the adhesive curing temperature, the geometry of the adhesive transition between the liner and the overlay weld at the pipe ends and on the liner thickness. The model was subjected to reeling simulation corresponding to Subsea 7's reel-lay vessels. The liner's integrity post reeling was assessed according to a range of acceptance criteria. These studies made it possible to establish parameter ranges for the safe installation of the linepipe.

scholarly journals Analysis of Vertical Stiffness of Air Spring Based on Finite Element Method

2018 ◽  
Vol 153 ◽  
pp. 06006
Author(s):  
Jiatong Ye ◽  
Hua Huang ◽  
Chenchen He ◽  
Guangyuan Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Element Simulation ◽  
Element Model ◽  
Simulation Method ◽  
Bench Test ◽  
Air Spring ◽  
Vertical Stiffness ◽  
Element Simulation ◽  
Element Method

In this paper, a finite element model of membrane air spring in the vehicle is established, and its vertical stiffness characteristics under a certain inflation pressure are analysed. The result of finite element simulation method is compared with the result of the air spring bench test. The accuracy and reliability of the finite element simulation method in nonlinear analysis of air spring system are verified. In addition, according to the finite element method, the influence of the installation of the air spring limit sleeve on its stiffness is verified.

Study on the critical loosening condition toward a new design guideline for bolted joints

2018 ◽  
Vol 233 (9) ◽  
pp. 3302-3316 ◽  
Author(s):  
Hao Gong ◽  
Jianhua Liu ◽  
Xiaoyu Ding
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Simulation Method ◽  
Bolted Joints ◽  
Design Guideline ◽  
Factors Affecting ◽  
Dimensional Finite Element ◽  
Frictional Coefficients ◽  
Three Dimensional Finite Element ◽  
Fit Tolerance

An understanding of conditions that trigger the loosening of bolted joints is essential to ensure joint reliability. In this study, a three-dimensional finite element model of a typical bolted joint is developed, and a new simulation method is proposed to quantitatively identify the critical transverse force for initiating loosening. This force is used to evaluate the anti-loosening capacity of bolted joints. Using the proposed simulation method, the effects of factors affecting critical loosening are systematically studied. It is found that the preload, frictional coefficients at the thread and the bearing surfaces, clamped length, and fit tolerance mainly affected loosening. When the preload and friction coefficients are increased, and the clamped length and fit tolerance are reduced, loosening is inhibited. Experiments are performed to demonstrate the reliability of the results. Finally, a suggestion is proposed to improve the design guideline VDI 2230 for bolted joints, which considers the requirement of avoiding loosening under vibrational loading.

Efficient Simulation Method to Predict Green Water Loads on Superstructures

2015 ◽  
Author(s):  
Lasse Theilen ◽  
Ole Detlefsen ◽  
Moustafa Abdel-Maksoud ◽  
Michael Bohm
Keyword(s):  
Simulation Method ◽  
Computational Effort ◽  
Numerical Prediction ◽  
Green Water ◽  
Impact Loads ◽  
Operational Conditions ◽  
Efficient Simulation ◽  
Non Linear ◽  
Linear Behaviour

The numerical prediction of green water loads on super-structures is challenging due to the high number of required calculations to identify the critical operational conditions in the seaway which lead to overcoming seawater on deck. Further, the simulation of the non-linear behaviour of water on the deck and the prediction of impact loads require high computational effort. This paper presents an efficient three-step approach to simulate green water loads. The application of the developed procedure will be demonstrated on a mega yacht geometry.

The Dynamic Behavior of a Rolling Element Auxiliary Bearing Following Rotor Impact

2001 ◽  
Vol 124 (2) ◽  
pp. 406-413 ◽  
Author(s):  
M. O. T. Cole ◽  
P. S. Keogh ◽  
C. R. Burrows
Keyword(s):  
Dynamic Behavior ◽  
Angular Acceleration ◽  
Element Model ◽  
Magnetic Bearing ◽  
Rolling Element Bearing ◽  
Linear Matrix ◽  
Rolling Element ◽  
Non Linear ◽  
In Series ◽  
Inner Race

The dynamic behavior of a rolling element bearing under auxiliary operation in rotor/magnetic bearing systems is analyzed. When contact with the rotor occurs, the inner race experiences high impact forces and rapid angular acceleration. A finite element model is used to account for flexibility of the inner race in series with non-linear ball stiffnesses arising from the ball-race contact zones. The dynamic conditions during rotor/inner race contact, including ball/race creep, are deduced from a non-linear matrix equation. The influences of bearing parameters are considered together with implications for energy dissipation in the bearing.

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