Fatemeh FaghihKhorasani, Mohammad Zaman Kabir, Mehdi AhmadiNajafabad and Khosrow Ghavami
The purpose of this paper is to provide a method to predict the situation of a loaded element in the compressive stress curve to prevent failure of crucial elements in…
Abstract
Purpose
The purpose of this paper is to provide a method to predict the situation of a loaded element in the compressive stress curve to prevent failure of crucial elements in load-bearing masonry walls and to propose a material model to simulate a compressive element successfully in Abaqus software to study the structural safety by using non-linear finite element analysis.
Design/methodology/approach
A Weibull distribution function was rewritten to relate between failure probability function and axial strain during uniaxial compressive loading. Weibull distribution parameters (shape and scale parameters) were defined by detected acoustic emission (AE) events with a linear regression. It was shown that the shape parameter of Weibull distribution was able to illustrate the effects of the added fibers on increasing or decreasing the specimens’ brittleness. Since both Weibull function and compressive stress are functions of compressive strain, a relation between compressive stress and normalized cumulative AE hits was calculated when the compressive strain was available. By suggested procedures, it was possible to monitor pretested plain or random distributed short fibers reinforced adobe elements (with AE sensor and strain detector) in a masonry building under uniaxial compression loading to predict the situation of element in the compressive stress‒strain curve, hence predicting the time to element collapse by an AE sensor and a strain detector. In the predicted compressive stress‒strain curve, the peak stress and its corresponding strain, the stress and strain point with maximum elastic modulus and the maximum elastic modulus were predicted successfully. With a proposed material model, it was illustrated that the needed parameters for simulating a specimen in Abaqus software with concrete damage plasticity were peak stress and its corresponding strain, the stress and strain point with maximum elastic modulus and the maximum elastic modulus.
Findings
The AE cumulative hits versus strain plots corresponding to the stress‒strain curves can be divided into four stages: inactivity period, discontinuous growth period, continuous growth period and constant period, which can predict the densifying, linear, non-linear and residual stress part of the stress‒strain relationship. By supposing that the relation between cumulative AE hits and compressive strain complies with a Weibull distribution function, a linear analysis was conducted to calibrate the parameters of Weibull distribution by AE cumulative hits for predicting the failure probability as a function of compressive strain. Parameters of m and θ were able to predict the brittleness of the plain and tire fibers reinforced adobe elements successfully. The calibrated failure probability function showed sufficient representation of the cumulative AE hit curve. A mathematical model for the stress–strain relationship prediction of the specimens after detecting the first AE hit was developed by the relationship between compressive stress versus the Weibull failure probability function, which was validated against the experimental data and gave good predictions for both plain and short fibers reinforced adobe specimens. Then, the authors were able to monitor and predict the situation of an element in the compressive stress‒strain curve, hence predicting the time to its collapse for pretested plain or random distributed short fibers reinforced adobe (with AE sensor and strain detector) in a masonry building under uniaxial compression loading by an AE sensor and a strain detector. The proposed model was successfully able to predict the main mechanical properties of different adobe specimens which are necessary for material modeling with concrete damage plasticity in Abaqus. These properties include peak compressive strength and its corresponding axial strain, the compressive strength and its corresponding axial strain at the point with maximum compressive Young’s modulus and the maximum compressive Young’s modulus.
Research limitations/implications
The authors were not able to decide about the effects of the specimens’ shape, as only cubic specimens were chosen; by testing different shape and different size specimens, the authors would be able to generalize the results.
Practical implications
The paper includes implications for monitoring techniques and predicting the time to the collapse of pretested elements (with AE sensor and strain detector) in a masonry structure.
Originality/value
This paper proposes a new method to monitor and predict the situation of a loaded element in the compressive stress‒strain curve, hence predicting the time to its collapse for pretested plain or random distributed short fibers reinforced adobe (with AE sensor and strain detector) in a masonry building under uniaxial compression load by an AE sensor and a strain detector.
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Lothar Wagner, Mansour Mhaede, Manfred Wollmann, Igor Altenberger and Yuji Sano
The purpose of this paper is to investigate the influence of mechanical surface treatments on the surface layer properties and the fatigue performance of the aircraft alloys Al…
Abstract
Purpose
The purpose of this paper is to investigate the influence of mechanical surface treatments on the surface layer properties and the fatigue performance of the aircraft alloys Al 7075‐T73 and Ti‐6Al‐4V
Design/methodology/approach
Laser peening without coating (LPwC), shot peening (SP), ultrasonic shot peening (USP) and ball burnishing (BB) were applied and the resulting changes in surface roughness and residual stress‐depth profiles were evaluated. Fatigue performance of both alloys was tested in rotating beam loading (R=−1) on hourglass‐shaped specimens and the results were compared with the electrolytically polished (EP) reference conditions.
Findings
All studied mechanical surface treatments led to pronounced increases in fully reversed fatigue lives and fatigue strengths in both Al 7075‐T73 and Ti‐6Al‐4V.
Originality/value
To the authors' knowledge, this is the first paper that compares fatigue performance of a wide variety of mechanically surface treated conditions in two aircraft alloys.
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Ch. Alk. Apostolopoulos and C.A. Rodopoulos
Seismic loading can induce significant deformations to steel reinforcement. The recent approach suggested by Eurocode 8 indicates that steel reinforcement shall sustain repeated…
Abstract
Purpose
Seismic loading can induce significant deformations to steel reinforcement. The recent approach suggested by Eurocode 8 indicates that steel reinforcement shall sustain repeated loading well within its elastic region, excluding by definition seismic loading. This paper aims to examine the behaviour of S500s steel reinforcement at strain ranges representing strains corresponding to small/medium earthquakes while significant attention has been paid to cases where the reinforcement has been corroded as this is most representative to aged buildings. The work concludes that the complex behaviour of steel reinforcement under low cycle fatigue conditions can be successfully treated via the use of the viscous stress. The latter is found to be independent to corrosion exposure while it holds the merits of ductility exhaustion on which most degradation models are based.
Design/methodology/approach
This paper establishes a relationship between the cumulative effect of low cycle fatigue and that of the viscous stress.
Findings
The work identifies that the viscous stress follows an exponential growth behaviour which terminates at a plateau. The plateau value is found to be independent to corrosion exposure and strain rate and hence providing a strong potential for being a characteristic indicator of the behaviour of steel reinforcement under realistic inelastic loading.
Research limitations/implications
The study is limited to S500s grade steel. Further study on different steel grades is necessary to increase the potential of viscous stress.
Originality/value
The significance of this paper is the introduction of viscous stress in an area where traditional approaches of cumulative damage are based on a large number of empirical parameters and assumptions.
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Fuad M. Khoshnaw and Nazhad A. Hussain
The purpose of the paper is to characterize the fatigue behavior, such as fatigue strength, and stress intensity factor values of aluminum alloy type 2024‐T3, using only a round…
Abstract
Purpose
The purpose of the paper is to characterize the fatigue behavior, such as fatigue strength, and stress intensity factor values of aluminum alloy type 2024‐T3, using only a round specimen. The aim in this study is to interrelate the fatigue behavior directly with the microstructure, as an attempt to reduce other parameters that might be associated in using different specimen geometries.
Design/methodology/approach
For this purpose, round specimens were machined from 2024‐T3, and the fatigue behavior was studied with various heat treatments. Two different temperatures were selected; 160 and 200°C, at different times. From stress‐number of cycles diagram, the fatigue strength is determined for the selected specimens. Moreover, the linear elastic fracture mechanic approach was used to determine threshold stress intensity factor, crack growth rate, and fracture toughness. A replica method is used for following and calculating the crack depth in round specimens. Moreover, theoretical equations and approaches have been carried out to evaluate the effect of specimen geometry (correction factor) on the results.
Findings
The results showed that the specimen aged at 160°C for five h develops greatest values of fatigue limit, ultimate strength, yield strength, and hardness. Moreover, the specimen aged at 200°C for 15 h develops greatest threshold stress intensity factor and fracture toughness.
Practical implications
The heat treatment does not have a strong influence on crack growth rate. Generally, the specimens, which develop greatest values of strength values, and HB, had lowest Kth, and KIC values and vice versa.
Originality/value
The LEFM approaches can be used even on round specimens to follow the crack growth rate instead of plates. A specific equation as a correction factor of geometry effect has been determined for round specimen.
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Iñigo Flores Ituarte, Sergei Chekurov, Jukka Tuomi, Julien Etienne Mascolo, Alessandro Zanella, Patrick Springer and Jouni Partanen
Additive manufacturing requires a systemic approach to help industry on technology applicability research. Towards this end, the purpose of this research is to help manufacturing…
Abstract
Purpose
Additive manufacturing requires a systemic approach to help industry on technology applicability research. Towards this end, the purpose of this research is to help manufacturing business leaders decide whether digitalised manufacturing based on additive manufacturing are suitable for engineering applications and help them plan technology transfer decisions.
Design/methodology/approach
The methodology is based on case study research and action research, involving a mix of quantitative and qualitative research methods. The empirical part involved the study of the fatigue life of industrial component manufactured by laser sintering as well as a combination of quantitative and qualitative methods to define a strategic decision-making.
Findings
Laser-sintered plastic materials are suitable in end use automotive applications, especially when there are multiple product variations. Fatigue life of the tested coupling meets the design requirements. Additionally, production of mechanical parts can be substituted by additive methods while digitalising the manufacturing process to gain productivity, especially when there is a need for mass-customisation.
Research limitations/implications
This research relies on a single case study research. The application used is unique and its technical empirical data cannot be transferred directly to other applications.
Practical implications
Industry practitioners can use this research to shed light on technology transferability challenges considering technical feasibility of additive polymer materials, economic aspects as well as strategic implications for implementing digitalised manufacturing methods based on additive manufacturing.
Originality/value
This research presents a combined study of technical and strategic factors for additive manufacturing transferability using an industrial mass-customisation case as an example. In addition, a new cost comparison model is presented including the impact of geometry variations.
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Youssef L. Nashed, Fouad Zahran, Mohamed Adel Youssef, Manal G. Mohamed and Azza M. Mazrouaa
The purpose of this study is to examine how well reinforced concrete structures can be shielded against concrete carbonation using anti-carbonation coatings based on synthetic…
Abstract
Purpose
The purpose of this study is to examine how well reinforced concrete structures can be shielded against concrete carbonation using anti-carbonation coatings based on synthetic polymer.
Design/methodology/approach
Applying free radical polymerization, an acrylate terpolymer emulsion that a surfactant had stabilized was created. A thermogravimetric analysis, minimum film-forming temperature, Fourier transform infrared spectroscopy and particle size distribution are used to characterize the prepared eco-friendly water base acrylate terpolymer emulsion. Using three different percentages of the acrylate terpolymer emulsion produced, 35%, 45% and 55%, the anti-carbonation coating was formed. Tensile strength, tensile strain, elongation, crack-bridging ability, carbon dioxide permeability, chloride ion diffusion, average pull-off adhesion strength, water vapor transmission, gloss, wet scrub resistance, QUV/weathering and storage stability are the characteristics of the anti-carbonation coating.
Findings
The formulated acrylate terpolymer emulsion enhances anti-carbonation coating performance in CO2 permeability, Cl-diffusion, crack bridging, pull-off adhesion strength and water vapor transmission. The formed coating based on the formulated acrylate terpolymer emulsion performed better than its commercial counterpart.
Practical implications
To protect the steel embedded in concrete from corrosion and increase the life span of concrete, the surface of cement is treated with an anti-carbonation coating based on synthetic acrylate terpolymer emulsion.
Social implications
In addition to saving lives from building collapse, it maintains the infrastructure for the long run.
Originality/value
The anti-carbonation coating, which is based on the synthetic acrylate terpolymer emulsion, is environmentally benign and stops the entry of carbon dioxide and chlorides, which are the main causes of steel corrosion in concrete.
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Nikos P. Andrianopoulos and Aggelos Pikrakis
The purpose of this paper is to study mutual interaction between von Mises equivalent and hydrostatic stresses at the crack tip area of an elastoplastic material in order to…
Abstract
Purpose
The purpose of this paper is to study mutual interaction between von Mises equivalent and hydrostatic stresses at the crack tip area of an elastoplastic material in order to obtain critical conditions for crack propagation under fatigue loading.
Design/methodology/approach
A5083-H111 aluminum alloy is used to obtain a Chaboche-type constitutive equation, which is introduced in a commercial finite elements package to evaluate stress distribution at crack tip area. A simplified three-dimensional (generalized plane strain) grid is used, resulting in fast and accurate results. Numerical simulations are performed to connect crack propagation rate with various combinations of fatigue stress amplitude, initial crack length and number of loading cycles. Distance between characteristic points of stresses distribution in the crack tip area are compared to experimental fatigue crack growth rates in order to assess the validity of the present approach.
Findings
It is found that saturation of plastic strains, i.e. maximization of von Mises equivalent stress, is a prerequisite for hydrostatic stress to take a critical-maximum value, outside the plastically saturated zone. At the point of maximum hydrostatic stress brittle fracture is initiated, driving to separation of the ligament up to crack tip, without formation of new plastic strains. The length of this ligament is defined as crack propagation step, showing good agreement with experimental data.
Originality/value
The present approach seems to constitute a reasonable and adequate method for the description of fatigue crack propagation in terms of continuum mechanics, not necessitating microscopic considerations or empirical criteria lacking theoretical or physical basis. In addition, it liberates from the notion of stress intensity factors, strongly disputed beyond linear elasticity. Improved constitutive equations and numerical models are expected to drive in a complete fatigue failure criterion similar to those of static loading.
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Konstantinos F. Koulouris and Charis Apostolopoulos
As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete (RC) structures which are located on coastal areas. This phenomenon combined with…
Abstract
Purpose
As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete (RC) structures which are located on coastal areas. This phenomenon combined with repeated loads, as earthquake events, negatively affects their service life. Moreover, microstructure of steel reinforcing bars has significant impact either on their corrosion resistance or on their fatigue life.
Design/methodology/approach
In the present manuscript an effort has been made to investigate the effect of corrosive factor on fatigue response for two types of steel reinforcement; Tempcore steel reinforcing bars and a new generation dual phase (DP) steel reinforcement.
Findings
The findings of this experimental study showed that DP steel reinforcement led to better results regarding its capacity to bear repeated loads to satisfactory degree after corrosion, although this type of steel has less stringent mechanical properties.
Originality/value
Additionally, a fatigue damage material indicator is proposed as a parameter that could rank material quality and its suitability for a certain application. The results of this investigation showed that the fatigue damage indicator can be used as an appropriate index in order to evaluate the overall performance of materials, in terms of strength and ductility capacity.
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Dibakor Boruah, Xiang Zhang and Matthew Doré
The purpose of this paper is to develop a simple analytical model for predicting the through-thickness distribution of residual stresses in a cold spray (CS) deposit-substrate…
Abstract
Purpose
The purpose of this paper is to develop a simple analytical model for predicting the through-thickness distribution of residual stresses in a cold spray (CS) deposit-substrate assembly.
Design/methodology/approach
Layer-by-layer build-up of residual stresses induced by both the peening dominant and thermal mismatch dominant CS processes, taking into account the force and moment equilibrium requirements. The proposed model has been validated with the neutron diffraction measurements, taken from the published literature for different combinations of deposit-substrate assemblies comprising Cu, Mg, Ti, Al and Al alloys.
Findings
Through a parametric study, the influence of geometrical variables (number of layers, substrate height and individual layer height) on the through-thickness residual stress distribution and magnitude are elucidated. Both the number of deposited layers and substrate height affect residual stress magnitude, whereas the individual layer height has little effect. A good agreement has been achieved between the experimentally measured stress distributions and predictions by the proposed model.
Originality/value
The proposed model provides a more thorough explanation of residual stress development mechanisms by the CS process along with mathematical representation. Comparing to existing analytical and finite element methods, it provides a quicker estimation of the residual stress distribution and magnitude. This paper provides comparisons and contrast of the two different residual stress mechanisms: the peening dominant and the thermal mismatch dominant. The proposed model allows parametric studies of geometric variables, and can potentially contribute to CS process optimisation aiming at residual stress control.
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Rhys Jones, Neil Matthews, Daren Peng and Nicholas Orchowski
The purpose of this paper is to describe the results of a combined numerical and experimental study into the ability of supersonic particle deposition (SPD) to restore the load…
Abstract
Purpose
The purpose of this paper is to describe the results of a combined numerical and experimental study into the ability of supersonic particle deposition (SPD) to restore the load carrying capacity of rib stiffened wing planks with simulated stress corrosion cracking (SCC).
Design/methodology/approach
In this context the experimental results reveal that SCC can result in a dramatic reduction in the load carrying capacity of the structure and catastrophic failure via cracking that tears the length of the structure through buckling. A combined numerical and experimental study then reveals how this reduction, in the load carrying capacity can be overcome by using SPD.
Findings
This paper is the first to show that SPD can be used to restore the load carrying capacity of rib stiffened structures with SCC. It also shows that SPD repairs can be designed to have only a minimal effect on the local stiffness and hence on the load path. However, care should be taken to ensure that the design is such that premature failure of the SPD does not occur.
Originality/value
This is the first paper to show that a thin layer of SPD deposited 7,075 aluminium alloy powder on either side of the SCC-simulated stiffener has the potential to restore the load carrying capability of a rib stiffened structure. As such it represents an important first step into establishing the potential for SPD to restore the buckling strength of rib stiffened wing panels containing SCC.