Davood Afshari, M. Sedighi, M.R. Karimi and Z. Barsoum
The purpose of this paper is to predict residual stresses in resistance spot weld of 2 mm thick aluminum 6061-T6 sheets. The joint use of finite element analysis and artificial…
Abstract
Purpose
The purpose of this paper is to predict residual stresses in resistance spot weld of 2 mm thick aluminum 6061-T6 sheets. The joint use of finite element analysis and artificial neural networks can eliminate the high costs of residual stresses measuring tests and significantly shorten the time it takes to arrive at a solution.
Design/methodology/approach
Finite element method and artificial neural network have been used to predict the residual stresses. Different spot welding parameters such as the welding current, the welding time and the electrode force have been used for the simulation purposes in a thermal-electrical-structural coupled finite element model. To validate the numerical results, a series of experiments have been performed, and residual stresses have been measured. The results obtained from the finite element analysis have been used to build up a back-propagation artificial neural network model for residual stresses prediction.
Findings
The results revealed that the neural network model created in this study can accurately predict residual stresses produced in resistance spot weld. Using a combination of these two developed models, the residual stresses can be predicted in terms of spot weld parameters with high speed and accuracy.
Practical implications
The paper includes implication for aircraft and automobile industries to predict residual stresses. Residual stresses can lower the strength and fatigue life of the spot-welded joints and determine the performance quality of the structure.
Originality/value
This paper presents an approach to reduce the high costs and long times of residual stresses measuring tests.
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Imad Barsoum, Hamda Almansoori, Aaesha Ahmed Almazrouei and Ebru Gunister
The main aim of this study is to determine the fracture toughness and accordingly to predict the fracture initiation, crack propagation and mode of crack extension accurately in…
Abstract
Purpose
The main aim of this study is to determine the fracture toughness and accordingly to predict the fracture initiation, crack propagation and mode of crack extension accurately in polypropylene subsea pipes subjected to internal pressure.
Design/methodology/approach
Tensile test was performed following the ISO 527–1 standard. An elastic-plastic constitutive model was developed based on the tensile test results, and it is implemented in the FEA model to describe the constitutive behaviour of the polypropylene material. Three-point bend tests with linear-elastic fracture mechanics (LEFM) approach were conducted following ISO-13586 standard, from which the average fracture toughness of the polypropylene pipe material in crack-opening mode was found as KIc = 3.3 MPa√m. A numerical model of the experiments is developed based on the extended finite element method (XFEM), which showed markedly good agreement with the experimental results.
Findings
The validated XFEM modelling approach is utilised to illustrate its capabilities in predicting fracture initiation and crack propagation in a polypropylene subsea pipe subjected to an internal pressure containing a semi-elliptical surface crack, which agrees well with existing analytical solutions. The XFEM model is capable of predicting the crack initiation and propagation in the polypropylene pipe up to the event of leakage.
Originality/value
The methodology proposed herein can be utilised to assess the structural integrity and resistance to fracture of subsea plastic pipes subjected to operational loads (e.g. internal pressure).
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Anoop Vasu, Jerry Chung, Cory Padfield and Ravi Desai
The brake reaction test performed on a rear axle assembly revealed that the brake flange weld could not sustain the load needed to pass the minimum requirement of the test…
Abstract
Purpose
The brake reaction test performed on a rear axle assembly revealed that the brake flange weld could not sustain the load needed to pass the minimum requirement of the test. Evaluation of the failure mode indicated that the fracture of the weld originated at the root of the weld and cracked through the fusion zone of the weld instead of cracking through base material (toe failure). The paper aims to discuss these issues.
Design/methodology/approach
A computational methodology is presented to quantify the critical parameters to prevent throat failure. The torsion dominated loading created high in-plane shear stress on the weld which can contribute significantly to the premature failure.
Findings
The failure through the fusion zone, often termed as weld throat/root failure, was not accounted for during the design phase by numerical simulation which led to the wrong conclusion that the design will pass the test requirement. Although weld sizing and weld penetration depth can explain such unexpected failure modes, fatigue life of this particular failure was still over-predicted using the Master SN curve formulation of structural stress approach which is well established for Mode I type of failure. Accounting for the shear component in the structural stress approach led to good correlation with the test specimen. Weld throat depth is a significant parameter contributing to throat failure.
Practical implications
The failure of the weld joining the brake flange and the tube of an axle is a high severity failure mode which can result in loss of vehicle control and injury or death and hence the failure should be prevented at any cost.
Originality/value
Most of the previous work of welded components relates to Mode I loading. There is very few research performed to discuss the Mode III loading and failure. This research illustrates the importance of considering the throat failure mode and quantifies the weld parameters to prevent such failures in design applications.
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Mayur Pratap Singh, Pavan Kumar Meena, Kanwer Singh Arora, Rajneesh Kumar and Dinesh Kumar Shukla
This paper aims to measure peak temperatures and cooling rates for distinct locations of thermocouples in the butt weld joint of mild steel plates. For experimental measurement of…
Abstract
Purpose
This paper aims to measure peak temperatures and cooling rates for distinct locations of thermocouples in the butt weld joint of mild steel plates. For experimental measurement of peak temperatures, K-type thermocouples coupled with a data acquisition system were used at predetermined locations. Thereafter, Rosenthal’s analytical models for thin two-dimensional (2D) and thick three-dimensional (3D) plates were adopted to predict peak temperatures for different thermocouple positions. A finite element model (FEM) based on an advanced prescribed temperature approach was adopted to predict time-temperature history for predetermined locations of thermocouples.
Design/methodology/approach
Comparing experimental and Rosenthal analytical models (2D and 3D) findings show that predicted and measured peak temperatures are in close agreement, while cooling rates predicted by analytical models (2D, 3D) show significant variation from measured values. On the other hand, 3D FEM simulation predicted peak temperatures and cooling rates for different thermocouple positions are close to experimental findings.
Findings
The inclusion of filler metal during simulation of welding rightly replicates the real welding situation and improves outcomes of the analysis.
Originality/value
The present study is an original contribution to the field of welding technology.
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Qing Liu, Chengjun Wang, Chenchen Shang and Jiabao Li
The purpose of this study is to reduce the residual stress in welded workpieces, optimize the vibratory stress relief treatment process through the use of a vibration generator…
Abstract
Purpose
The purpose of this study is to reduce the residual stress in welded workpieces, optimize the vibratory stress relief treatment process through the use of a vibration generator and enhance the durability and longevity of the workpiece by developing a vibratory stress relief robot that incorporates a multi-manipulator system.
Design/methodology/approach
The multi-manipulator combination work is designed so that each manipulator is deployed according to the requirements of vibration stress relief work. Each manipulator works independently and coordinates with others to achieve multi-dimensional vibratory stress relief of the workpiece. A two-degree-of-freedom mobile platform is designed to enable the transverse and longitudinal movement of the manipulator, expanding the working space of the robot. A small electromagnetic superharmonic vibration generator is designed to produce directional vibrations in any orientation. This design addresses the technical challenge of traditional vibration generators being bulky and unable to achieve directional vibrations.
Findings
The residual stress relief experiment demonstrates that the residual stress of the workpiece is reduced by approximately 73% through three-degree-of-freedom vibration. The multi-dimensional vibration effectively enhances the relief effect of residual stress, which is beneficial for improving the strength and service life of the workpiece.
Originality/value
A new multi-manipulator robot is proposed to alleviate the residual stress generated by workpiece welding by integrating vibratory stress relief with robotics. It is beneficial to reduce material and energy consumption while enhancing the strength and service life of the workpiece.
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Felice Rubino, Giacomo Canale and Prabhakar Sathujoda
Electron-beam welding has been widely used in industry to join different titanium alloys (Ti-6Al-4V) components. During welding production defects, such as porosity, lack of…
Abstract
Purpose
Electron-beam welding has been widely used in industry to join different titanium alloys (Ti-6Al-4V) components. During welding production defects, such as porosity, lack of penetration or thinning are often observed. High-cycle fatigue (HCF) tests have been performed on welded specimens to understand the effect of weld defects on fatigue capabilities. The fatigue life of different types of “defective” welds has been compared against a non-welded reference specimen.
Design/methodology/approach
The results of the experimental campaign have been correlated with finite elements models.
Findings
It is concluded the geometry produced by the weld process, e.g. toe radius and under-bead shape, and the related stress raisers play a relevant role on fatigue capabilities of welds. This conclusion is valid only for a Ti-6Al-4V T-joint weld and only for flaw initiation. Knock down in materials properties has not been considered.
Originality/value
There is a lack of HCF fatigue data for welds of this geometry and material in the open literature. The paper is of relevance for industrial application and practical interest, although a lot more validation tests are required to draw a final conclusion.
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Babak Lotfi and Bengt Ake Sunden
This study aims to computational numerical simulations to clarify and explore the influences of periodic cellular lattice (PCL) morphological parameters – such as lattice…
Abstract
Purpose
This study aims to computational numerical simulations to clarify and explore the influences of periodic cellular lattice (PCL) morphological parameters – such as lattice structure topology (simple cubic, body-centered cubic, z-reinforced body-centered cubic [BCCZ], face-centered cubic and z-reinforced face-centered cubic [FCCZ] lattice structures) and porosity value ( ) – on the thermal-hydraulic characteristics of the novel trussed fin-and-elliptical tube heat exchanger (FETHX), which has led to a deeper understanding of the superior heat transfer enhancement ability of the PCL structure.
Design/methodology/approach
A three-dimensional computational fluid dynamics (CFD) model is proposed in this paper to provide better understanding of the fluid flow and heat transfer behavior of the PCL structures in the trussed FETHXs associated with different structure topologies and high-porosities. The flow governing equations of the trussed FETHX are solved by the CFD software ANSYS CFX® and use the Menter SST turbulence model to accurately predict flow characteristics in the fluid flow region.
Findings
The thermal-hydraulic performance benchmarks analysis – such as field synergy performance and performance evaluation criteria – conducted during this research successfully identified demonstrates that if the high porosity of all PCL structures decrease to 92%, the best thermal-hydraulic performance is provided. Overall, according to the obtained outcomes, the trussed FETHX with the advantages of using BCCZ lattice structure at 92% porosity presents good thermal-hydraulic performance enhancement among all the investigated PCL structures.
Originality/value
To the best of the authors’ knowledge, this paper is one of the first in the literature that provides thorough thermal-hydraulic characteristics of a novel trussed FETHX with high-porosity PCL structures.
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Sheng Chen, Suming Xie, Tao Li and Jian Wang
This study aims to extend the application of the quality category approach in rapid fatigue assessment of complex welded structures containing defects under arbitrary loadings…
Abstract
Purpose
This study aims to extend the application of the quality category approach in rapid fatigue assessment of complex welded structures containing defects under arbitrary loadings, following the investigation of their core data and fatigue assessment procedures based on fracture mechanics.
Design/methodology/approach
The analysis methods and procedures for calculating equivalent sizes of semi-elliptic cracks and initial sizes of through-width cracks at the weld toe were developed based on the life equivalence principle. Different stress concentration solutions, i.e. 2D-Mk and 3D-Mk solutions, and different bending ratios were considered. Then, approximate equations were proposed to calculate the crack size under combined stress. In addition, a procedure for calculating the fatigue life by interpolation was proposed and applied to engineering examples.
Findings
The fatigue lives of fillet and butt weld joints obtained with the 3D-Mk solution for large L/B are longer than those obtained with the 2D-Mk solution. The results of the fatigue life of the brake unit bracket show that the average error between the proposed approximation equations and the quality category approach is 1.6%.
Originality/value
The quality category and equivalent size curves of different stress concentration solutions under combined membrane and bending stresses are newly added, which further expands the application of the quality category approach. When the proposed fatigue life calculation methods are employed, the remaining life can be quickly derived in addition to the qualitative conclusion on the safety of the structure. These provide the necessary conditions to perform a rapid fatigue assessment adapted to engineering purposes.
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The emergence of smart wearables using clothing as a technology platform is a significant milestone with considerable implications for industrial convergence, creating new value…
Abstract
Purpose
The emergence of smart wearables using clothing as a technology platform is a significant milestone with considerable implications for industrial convergence, creating new value for fashion. This paper aimed to present a premeditated prototype to integrate a human activity recognition (HAR) system into outdoor clothing.
Design/methodology/approach
For the development of wearable HAR (WHAR) clothing, this paper explored three subject areas: fashion design related to the structural feature of the clothing platform, electronics related to wearable circuits and modules design and graphic user interface design related to smartphone application development.
Findings
For WHAR functions in outdoor terrains, the coexistence of accelerometer–gyroscope sensing and distance-sensing could be practical to surpass the technological limitation of activity and posture recognition with gyro sensors highly depending on the changes of acceleration and angles.
Research limitations/implications
Through the vital sign check and physical activity–change recognition function, this study's WHAR system allows users to check their health by themselves and avoid overwork. A quick rescue is possible manually and automatically in a dangerous situation by notifying others. Thus, it can help protect users' health and safety (life).
Originality/value
This study designed the modularization of HAR functions generally installed in indoor medical spaces. Through the approach, smart clothing–embracing WHAR systems optimized for health and safety care for outdoor environments was pursued to diversify expensive roles of clothing for technological applications.
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Jianxin Xu, Delei Du, Jian Song, Dongming Li and Yana Li
Notched fatigue life curves of welded joints were established and compared with International Institute of Welding (IIW) standards to verify the metal fatigue performance of…
Abstract
Purpose
Notched fatigue life curves of welded joints were established and compared with International Institute of Welding (IIW) standards to verify the metal fatigue performance of welded joints treated with pneumatic impact (PIT).
Design/methodology/approach
This paper was based on the notched stress method, and this approach not only allows for the assessment of fatigue failure of welded structures with toes and roots but also for the assessment of fatigue strength of joints with localized post-treatments. The paper summarizes the nominal stress data of weld and pneumatic impact treated (PIT) steel joints of different strengths, fits the nominal stress curves of the joints without the use of strength and obtains the stress concentration factor of the joints through the establishment of the finite element (FE) method. Notched fatigue life curves for welded joints were established and compared with IIW standards.
Findings
Notched stress concentration data obtained by the FE method was more reliable. The slope of the fatigue life curve of welded joints treated with pneumatic impact (PIT) increases by at least 2.5%, and the stress concentration factor decreases by 20%.
Originality/value
In the fatigue study of notched systems, there were fewer studies on fatigue life assessment of joints processed by high frequency mechanical impact. The purpose of this paper was to analyze the fatigue test data of typical strength steel welded joints and fit fatigue life curves, and the research content provides an important reference for improving the safety and fatigue failure assessment of heavy steel structures.