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1 – 10 of over 1000Qingyang Liu, Ziyang Zhang, Denizhan Yavas, Wen Shen and Dazhong Wu
Understanding the effect of process parameters on interfaces and interfacial bonding between two materials during multi-material additive manufacturing (MMAM) is crucial to the…
Abstract
Purpose
Understanding the effect of process parameters on interfaces and interfacial bonding between two materials during multi-material additive manufacturing (MMAM) is crucial to the fabrication of high-quality and strong multi-material structures. The purpose of this paper is to conduct an experimental and statistical study to investigate the effect of process parameters of soft and hard materials on the flexural behavior of multi-material structures fabricated via material extrusion-based MMAM.
Design/methodology/approach
Sandwich beam samples composed of a soft core and hard shells are fabricated via MMAM under different printing conditions. A design of experiments is conducted to investigate the effect of the print speed and nozzle temperature on the flexural behavior of soft-hard sandwich beams. Analysis of variance and logistic regression analysis are used to analyze the significance of each process parameter. The interfacial morphology of the samples after the flexural tests is characterized. Thermal distributions during the MMAM process are captured to understand the effect of process parameters on the flexural behavior based on inter-bonding formation mechanisms.
Findings
Experimental results show that the soft-hard sandwich beams exhibited two different failure modes, including shell failure and interfacial failure. A transition of failure modes from interfacial failure to shell failure is observed as the nozzle temperatures increase. The samples that fail because of interfacial cracking exhibit a pure adhesive failure because of weak interfacial fracture properties. The samples that fail because of shell cracking exhibit a mixed adhesive and cohesive failure. The flexural strength and modulus are affected by the nozzle temperature for the hard material and the print speeds for both hard and soft materials significantly.
Originality/value
This paper first investigates the effect of process parameters for soft and hard materials on the flexural behavior of additively manufactured multi-material structures. Especially, the ranges of the selected process parameters are distinct, and the effect of all possible combinations of the process parameters on the flexural behavior is characterized through a full factorial design of experiments. The experimental results and conclusions of this paper provide guidance for future research on improving the interfacial bonding and understanding the failure mechanism of multi-material structures fabricated by MMAM.
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Piyush Suresh Mundada, Che-Hao Yang and Roland K. Chen
The purpose of this study is to propose the use of a pre-deposition heating system for fused filament fabrication (FFF) as a means to enhance interlayer bonding by elevating the…
Abstract
Purpose
The purpose of this study is to propose the use of a pre-deposition heating system for fused filament fabrication (FFF) as a means to enhance interlayer bonding by elevating the substrate temperature. The effects of the heating on thermal profile at the bonding interface and the mechanical properties of three-dimensional printed parts are investigated.
Design/methodology/approach
A 12-W laser head is integrated to a commercial printer as the pre-deposition heating system. The laser beam heats up substate before the deposition of a fresh filament. Effects of laser powers are investigated and the thermal profile is measured with thermocouple, infrared camera and finite element model. The correlation between the temperature at the bonding interface and the bonding quality is investigated by conducting tensile testing and neck width measurement with microscope.
Findings
The pre-deposition heating system is proven to be effective in enhancing the inter-layer strength in FFF parts. Tensile testing of specimens along build direction (Z) shows an increase of around 50% in ultimate strength. A linear relationship is observed between the pre-deposition temperature at bond interface and bonding strength. It is evident that elevating the pre-deposition temperature promotes interlayer polymer diffusion as shown by the increased neck width between layers.
Originality/value
Thermocouples that are sandwiched between layers are used to achieve accurate measurement of the interfacial temperature. The temperature profiles under pre-deposition heating are analyzed and correlated to the interlayer bonding strengths.
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Yanhui Liu, Lingjie Zhu, Lei Zhou and Yongjiu Li
This paper aims to explore the influence of the reinforcement included either glass beads (GBs) or carbon fiber (CF) on the reinforced polyamide 12 (PA12) composite samples…
Abstract
Purpose
This paper aims to explore the influence of the reinforcement included either glass beads (GBs) or carbon fiber (CF) on the reinforced polyamide 12 (PA12) composite samples prepared by selective laser sintering (SLS).
Design/methodology/approach
In this paper, the microstructure and mechanical properties are investigated, and the results are compared with those obtained for non-reinforced pure PA12 samples prepared by SLS.
Findings
The tensile fracture surface of the non-reinforced pure PA12 sample presents strong micro-deformation within the crack origination zone between the melted PA12 matrix and the un-melted PA12 particle cores. As a result, the pure PA12 sample exhibits the greatest maximum elongation. The maximum tensile strength is obtained for the CF reinforced sample because of the strengthening effect of CF and the relatively good bonding between CFs and the PA12 matrix. The minimum tensile strength is obtained for the GB reinforced PA12 sample because of the relatively weak bonding between GBs and the PA12 matrix.
Originality/value
These results demonstrate that the characteristics of the interfaces between the reinforcement and the PA12 matrix have an important influence on the fracture mechanisms and mechanical properties of PA12 composites fabricated by SLS.
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Dongsheng Wang, Xiaohan Sun, Yingchang Jiang, Xueting Chang and Xin Yonglei
Stainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms…
Abstract
Purpose
Stainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms areas, because of their excellent anticorrosion performance and relatively lower production costs. However, the properties of SCBS, including the mechanical strength, weldability and the anticorrosion behavior, have a direct relation with the manufacturing process and can affect their practical applications. This paper aims to review the application and the properties requirements of SCBS in marine environments to promote the application of this new material in more fields.
Design/methodology/approach
In this paper, the manufacturing process, welding and corrosion-resistant properties of SCBS were introduced systematically by reviewing the related literatures, and some results of the authors’ research group were also introduced briefly.
Findings
Different preparation methods, such as rolling composite, casting rolling composite, explosive composite, laser cladding and plasma arc cladding, as well as the process parameters, including the vacuum degree, rolling temperature, rolling reduction ratio, volume ratios of liquid to solid, explosive ratio and the heat treatment, influenced a lot on the properties of the SCBS through changing the interface microstructures. Otherwise, the variations in rolling temperature, pass, reduction and the grain size of clad steel also brought the dissimilarities of the mechanical properties, microhardness, bonding strength and toughness. Another two new processes, clad teeming method and interlayer explosive welding, deserve more attention because of their excellent microstructure control ability. The superior corrosion resistance of SCBS can alleviate the corrosion problem in the marine environment and prolong the service life of the equipment, but the phenomenon of galvanic corrosion should be noted as much as possible. The high dilution rate, welding process specifications and heat treatment can weaken the intergranular corrosion resistance in the weld area.
Originality/value
This paper summarizes the application of SCBS in marine environments and provides an overview and reference for the research of stainless-clad bimetallic steel.
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Tie-Lin Chen, Wenbin Tao, Wenjun Zhu and Mozhen Zhou
Near-surface mounted (NSM) fiber-reinforced polymer (FRP) rod is extensively applied in reinforced concrete (RC) structures. The mechanical performances of NSM FRP-strengthened RC…
Abstract
Purpose
Near-surface mounted (NSM) fiber-reinforced polymer (FRP) rod is extensively applied in reinforced concrete (RC) structures. The mechanical performances of NSM FRP-strengthened RC structures depend on the bond behavior between NSM reinforcement and concrete. This behavior is typically studied by performing pull-out tests; however, the failure behavior, which is crucial to the local debonding process, is not yet sufficiently understood.
Design/methodology/approach
In this study, a three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure process in pull-out tests of NSM FRP rod in concrete. The smeared crack model is used to capture the cohesion failures in the adhesive or concrete. The interfacial constitutive model is applied to simulate the adhesion failures on the FRP-adhesive and concrete-adhesive contact interfaces.
Findings
The present method is first validated by two simple examples and then applied to a practical NSM FRP system. This work studied in detail the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone. The developed method provides a practical and convenient tool applicable for further investigations on the debonding mechanism for the NSM FRP rod in concrete.
Originality/value
A three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure in NSM FRP-strengthened RC structures. The smeared crack model and the interfacial constitutive model are introduced to develop a convenient approach to analyze the failures in adhesive, concrete and related interfaces. The developed numerical method is applicable for studying the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone in detail.
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The purpose of this study is to demonstrate that isothermal intermetallic growth data for gold ball bonds can be non-parabolic with explanations of why deviation from parabolic…
Abstract
Purpose
The purpose of this study is to demonstrate that isothermal intermetallic growth data for gold ball bonds can be non-parabolic with explanations of why deviation from parabolic kinetics may occur.
Design/methodology/approach
Intermetallic thickness measurements were made at the centre of cross-sectioned ball bonds that were isothermally annealed at 175°C. Intermetallic growth kinetics were modelled with a power law expression(x(t) − x0)2 = α1tα2. The parameters of the power law model were obtained by transformation of the response and explanatory variables followed by data fitting using simple linear regression (SLR).
Findings
Ball bonds made with 4 N (99.99%Au) and 3 N (99.9%Au) gold wires exhibited two consecutive time regimes of intermetallic growth denoted Regime I and Regime II. Regime I was characterised by reactive diffusion between the gold wire and the aluminium alloy bond pad, during which Al was completely consumed in the formation of Au–Al intermetallics with non-parabolic kinetics. In Regime II, the absence of a free supply of Al to sustain intermetallic growth led to the conclusion that thickening of intermetallics was caused by phase transformation of Au8Al3 to Au4Al. Ball bonds made with 2 N (99%Au) wire also exhibited non-parabolic kinetics in Regime I and negligible intermetallic thickening in Regime II.
Research limitations/implications
The analysis of intermetallic growth is limited to total intermetallic growth at a single temperature (175°C).
Originality/value
The value of this study lies in showing that the assumption that only parabolic intermetallic growth is observed in isothermally aged gold ball bonds is incorrect. Furthermore there is no need to assume parabolic growth kinetics because with an appropriate data transformation, followed by fitting the data to a power law model using SLR and with the use of statistical diagnostics, both the suitability of the kinetic model and the nature of the growth kinetics (parabolic or non-parabolic) can be determined.
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K. Md Nasir, N.H. Ramli Sulong, M.R. Johan and A.M. Afifi
This study aims to discuss the modification and/or improvement of intumescent coating system by incorporating waterborne resin with an appropriate combination of flame-retardant…
Abstract
Purpose
This study aims to discuss the modification and/or improvement of intumescent coating system by incorporating waterborne resin with an appropriate combination of flame-retardant additives and four different fillers, namely, TiO2, Al(OH)3, Mg(OH)2 and CaCO3.
Design/methodology/approach
Coating mixtures are characterized using the Bunsen burner, thermogravimetric analysis, limiting oxygen index, scanning electron microscope, static immersion bath, Fourier transform infrared and adhesion tester.
Findings
Results show that the combination of coating with CaCO3 filler significantly improved fire protection performance because of its thick char layer and the equilibrium temperature being 264°C. Char layer showed a uniform dense foam structure on micrograph and this formulation had adhesion strength of 2.13 MPa, which indicates effectiveness of the interface adhesion on substrate. Conversely, the combination of coating with Al(OH)3 exhibited highest oxygen index of 35 per cent, which resulted in excellent flammability resistance.
Research limitations/implications
This paper discusses only the effect of mineral fillers on properties of intumescent coatings.
Practical implications
In the modern design of building infrastructure, fire safety is significant for the protection of human life and assets. The application of intumescent coating in buildings is currently practiced because of its effect on material flammability during a fire.
Originality/value
The analysis method to evaluate the performance of water-borne resin with different fillers is formulated, and it could be applied in all kinds of coatings and mixtures to be used as an effective fire protection system for steel constructions.
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Hong Yuan, Jun Han, Huaqiang Lu, Junhui Li and Lan Zeng
Due to its inexpensive production costs, low stress concentration and maintenance-friendliness, the adhesive bonded pipe joint is frequently utilized for pipe connection. However…
Abstract
Purpose
Due to its inexpensive production costs, low stress concentration and maintenance-friendliness, the adhesive bonded pipe joint is frequently utilized for pipe connection. However, further theoretical analysis is needed to understand the debonding failure mechanism of such bonded pipe joints under axial tension.
Design/methodology/approach
In this study, based on the bi-linear cohesive zone model, the integrated closed-form solutions were derived by considering the axial stiffness ratio and failure stage to determine the relative interfacial slip, interfacial shear stress and relationship of tension–displacement in the bonded pipe joint.
Findings
Additionally, solutions for the critical bonded length and the ultimate load capacity were put forth. Besides, the numerical study was conducted to verify the theoretical solutions regarding the load–displacement relationship. The interfacial shear stress distribution at different failure stages was presented to understand the interfacial shear stress transmission and debonding process. The effect of bonded length on the ultimate load and ductility of pipe joints was also discussed.
Originality/value
The findings in this study can give a reference for the design of bonded pipe joints in their actual engineering applications.
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Ao Zhang, Jian Zhang, Mingjun Zhang, Junyi Liu and Ping Peng
This paper aims to investigate the effect and mechanism of O atom single doping, Ce and O atoms co-doping on the interfacial microscopic behavior of brazed Ni-Cr/diamond.
Abstract
Purpose
This paper aims to investigate the effect and mechanism of O atom single doping, Ce and O atoms co-doping on the interfacial microscopic behavior of brazed Ni-Cr/diamond.
Design/methodology/approach
Using first-principles calculations, the embedding energy, work of separation, interfacial energy and electronic structures of Ni-Cr-O/diamond and Ni-Cr-O-Ce/diamond interface models were calculated. Then, the effect of Ce and O co-doping was experimentally verified through brazed diamond with CeO2-added Ni-Cr filler alloy.
Findings
The results show that O single-doping reduces the interfacial bonding strength between Ni-Cr filler alloy and diamond but enhances its interfacial stability to some extent. However, the Ce and O co-doping simultaneously enhances the interfacial bonding strength and stability between Ni-Cr filler alloy and diamond. The in-situ formed Ce-O oxide at interface impedes the direct contact between diamond and Ni-Cr filler alloy, which weakens the catalytic effect of Ni element on diamond graphitization. It is experimentally found that the fine rod-shaped Cr3C2 and Cr7C3 carbides are generated on diamond surface brazed with CeO2-added Ni-Cr filler alloy. After grinding, the brazed diamond grits, brazed with CeO2-added Ni-Cr filler alloy, present few fracture and the percentage of intact diamond reaches 67.8%. Compared to pure Ni-Cr filler alloy, the brazed diamond with CeO2-added Ni-Cr filler alloy exhibit the better wear resistance and the slighter thermal damage.
Originality/value
Using first-principles calculations, the effect of Ce and O atoms co-doping on the brazed diamond with Ni-Cr filler alloy is investigated, and the calculation results are verified experimentally. Through the first-principles calculations, the interface behavior and reaction mechanism between diamond and filler alloy can be well disclosed, and the composition of filler alloy can be optimized, which will be beneficial for synergistically realizing the enhanced interface bonding and reduced thermal damage of brazed diamond.
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M. Grujicic, R. Yavari, J.S. Snipes, S. Ramaswami and R.S. Barsoum
The purpose of this paper is to address the problems of interaction of tensile stress-waves with polyurea/fused-silica and fused-silica/polyurea interfaces, and the potential for…
Abstract
Purpose
The purpose of this paper is to address the problems of interaction of tensile stress-waves with polyurea/fused-silica and fused-silica/polyurea interfaces, and the potential for the accompanying interfacial decohesion.
Design/methodology/approach
The problems are investigated using all-atom non-equilibrium molecular-dynamics methods and tools. Before these methods/tools are employed, previously determined material constitutive relations for polyurea and fused-silica are used, within an acoustic-impedance-matching procedure, to predict the outcome of the interactions of stress-waves with the material-interfaces in question. These predictions pertain solely to the stress-wave/interface interaction aspects resulting in the formation of transmitted and reflected stress- or release-waves, but do not contain any information regarding potential interfacial decohesion. Direct molecular-level simulations confirmed some of these predictions, but also provided direct evidence of the nature and the extent of interfacial decohesion. To properly model the initial state of interfacial cohesion and its degradation during stress-wave-loading, reactive forcefield potentials are utilized.
Findings
Direct molecular-level simulations of the polyurea/fused-silica interfacial regions prior to loading revealed local changes in the bonding structure, suggesting the formation of an interphase. This interphase was subsequently found to greatly affect the polyurea/fused-silica decohesion strength.
Originality/value
To the authors’ knowledge, the present work is the first public-domain report of the use of the non-equilibrium molecular dynamics and reactive force-field potentials to study the problem of interfacial decohesion caused by the interaction of tensile waves with material interfaces.
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