Browsing by Author "Khan, Muhammad"
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Item Open Access An analysis of methods to achieve robustness towards a lean product development process(Institute of Electrical and Electronics Engineers, 2012-06-18) Cabello, Alan; Flores, Karina; Flores, Myrna; Khan, Muhammad; Al-Ashaab, AhmedSince Taguchi’s introduction to robustness much has been researched about it, particularly into the field of new product development. Despite the attention given to the subject by academia, recent research has found that industry has yet to fully grasp its benefits. Among the main attributed factors, lie the complexity of the proposed statistical tools and a general misconception of the concept and its implementation. Based on Toyota’s Product Development System, the term Conceptual Robustness is broadly defined based on three forms of variation: physical, design and market. Parting from the this definition and as part of the LeanPPD Project, the objective of this paper’s contribution is threefold: 1), to present the state of the art on research in the area of robustness, 2) propose a taxonomy in order to understand the different scopes of available resources and 3) finally identifying the possibilities to achieve conceptual robustness (that of Sobek et al., 1999) with the available resources presented to the industry by academic research.Item Open Access Compatibility and challenges in machine learning approach for structural crack assessment(Sage, 2022-03-11) Omar, Intisar; Khan, Muhammad; Starr, AndrewStructural health monitoring and assessment (SHMA) is exceptionally essential for preserving and sustaining any mechanical structure’s service life. A successful assessment should provide reliable and resolute information to maintain the continuous performance of the structure. This information can effectively determine crack progression and its overall impact on the structural operation. However, the available sensing techniques and methods for performing SHMA generate raw measurements that require significant data processing before making any valuable predictions. Machine learning (ML) algorithms (supervised and unsupervised learning) have been extensively used for such data processing. These algorithms extract damage-sensitive features from the raw data to identify structural conditions and performance. As per the available published literature, the extraction of these features has been quite random and used by academic researchers without a suitability justification. In this paper, a comprehensive literature review is performed to emphasise the influence of damage-sensitive features on ML algorithms. The selection and suitability of these features are critically reviewed while processing raw data obtained from different materials (metals, composites and polymers). It has been found that an accurate crack prediction is only possible if the selection of damage-sensitive features and ML algorithms is performed based on available raw data and structure material type. This paper also highlights the current challenges and limitations during the mentioned sections.Item Open Access Coupled effects of temperature and humidity on fracture toughness of Al–Mg–Si–Mn alloy(MDPI, 2023-05-30) Alqahtani, Ibrahim; Starr, Andrew; Khan, MuhammadThe combined effect of temperature and humidity on the fracture toughness of aluminium alloys has not been extensively studied, and little attention has been paid due to its complexity, understanding of its behaviour, and difficulty in predicting the effect of the combined factors. Therefore, the present study aims to address this knowledge gap and improve the understanding of the interdependencies between the coupled effects of temperature and humidity on the fracture toughness of Al–Mg–Si–Mn alloy, which can have practical implications for the selection and design of materials in coastal environments. Fracture toughness experiments were carried out by simulating the coastal environments, such as localised corrosion, temperature, and humidity, using compact tension specimens. The fracture toughness increased with varying temperatures from 20 to 80 °C and decreased with variable humidity levels between 40% and 90%, revealing Al–Mg–Si–Mn alloy is susceptible to corrosive environments. Using a curve-fitting approach that mapped the micrographs to temperature and humidity conditions, an empirical model was developed, which revealed that the interaction between temperature and humidity was complex and followed a nonlinear interaction supported by microstructure images of SEM and collected empirical data.Item Open Access Degradation mechanisms associated with metal pipes and the effective impact of LDMs and LLMs in water transport and distribution(SAGE, 2022-11-09) Agala, Alaa; Khan, Muhammad; Starr, AndrewThe effective operation of water management systems is contingent upon leak localization and detecti– a common problem that is more acute in large networks. This paper reviews the salient literature in this context and demonstrates the effectiveness of leakage location methods (LLMs) and leakage detection methods (LDMs). Although there is a significant amount of literature that discusses leakage localization and detection technologies, an academic lacuna still exists concerning the linkage between degradation mechanisms and LDMs and do not cover or connect past efforts from the start of a degradation mechanism that leads to changes in the mechanical strength (such as a reduction in fracture toughness) of pipes and results in crack propagation and leakage. This review focuses on these issues in the context of degradation mechanisms and common detection methods.Item Open Access Effect of 3D printing process parameters on damping characteristic of cantilever beams fabricated using material extrusion(MDPI, 2023-01-04) He, Feiyang; Ning, Haoran; Khan, MuhammadThe present paper aims to investigate the process parameters and damping behaviour of the acrylonitrile butadiene styrene (ABS) cantilever beam manufactured using material extrusion (MEX). The research outcome could guide the manufacture of MEX structures to suit specific operating scenarios such as energy absorption and artificially controlled vibration responses. Our research used an experimental approach to examine the interdependencies between process parameters (nozzle size, infill density and pattern) and the damping behaviour (first-order modal damping ratio and loss factor). The impact test was carried out to obtain the damping ratio from the accelerometer. A dynamic mechanical analysis was performed for the loss factor measurement. The paper used statistical analysis to reveal significant dependencies between the process parameters and the damping behaviour. The regression models were also utilised to evaluate the mentioned statistical findings. The multiple third-order polynomials were developed to represent the relation between process parameters and modal damping ratio using stiffness as the mediation variable. The obtained results showed that the infill density affected the damping behaviour significantly. Higher infill density yielded a lower damping ratio. Nozzle size also showed a notable effect on damping. A high damping ratio was observed at a significantly low value of nozzle size. The results were confirmed using the theoretical analysis based on the underlying causes due to porosity in the MEX structure.Item Open Access The effect of printing parameters on crack growth rate of FDM ABS cantilever beam under thermo-mechanical loads(Elsevier, 2022-01-04) He, Feiyang; Alshammari, Yousef Lafi A.; Khan, MuhammadFused deposition modelling (FDM) is the most widely used additive manufacturing (AM) process in the customised and low-volume production industries. Acrylonitrile butadiene styrene (ABS) is the most commonly used thermoplastic printing material for FDM. The fabricated FDM ABS parts commonly work under thermo-mechanical loads in reality. In order to produce the high fatigue performance FDM ABS components, it is significant to investigate the effect of 3D printing parameters on crack growth. Hence, this research evaluated the crack propagation under bending fatigue test for FDM ABS beam in high-temperature conditions with varying printing parameters, including building orientations, nozzle size and layer thickness. The combination of three building orientations (0°, ±45° and 90°), three nozzle sizes (0.4, 0.6 and 0.8 mm) and three layer thickness (0.05, 0.1 and 0.15 mm) were tested under 50 to 70 °C environmental temperature ranges. The research attempted to investigate the relationship between crack growth rate and different printing parameter combinations. The study also attempted to determine the possible parameter combination which achieved the longest fatigue life for the FDM ABS specimen. Preliminary experimental results showed that the specimen with 0° building orientation, 0.8 mm filament width and 0.15 mm layer thickness vibrated for the longest time before the fracture at every different temperature.Item Open Access Effects of printing parameters on the fatigue behaviour of 3D-printed ABS under dynamic thermo-mechanical loads(MDPI, 2021-07-19) He, Feiyang; Khan, MuhammadFused deposition modelling (FDM) is the most widely used additive manufacturing process in customised and low-volume production industries due to its safe, fast, effective operation, freedom of customisation, and cost-effectiveness. Many different thermoplastic polymer materials are used in FDM. Acrylonitrile butadiene styrene (ABS) is one of the most commonly used plastics owing to its low cost, high strength and temperature resistance. The fabricated FDM ABS parts commonly work under thermo-mechanical loads in actual practice. For producing FDM ABS components that show high fatigue performance, the 3D printing parameters must be effectively optimized. Hence, this study evaluated the bending fatigue performance for FDM ABS beams under different thermo-mechanical loading conditions with varying printing parameters, including building orientations, nozzle size, and layer thickness. The combination of three building orientations (0°, ±45°, and 90°), three nozzle sizes (0.4, 0.6, and 0.8 mm) and three-layer thicknesses (0.05, 0.1, and 0.15 mm) were tested at different environmental temperatures ranging from 50 to 70 °C. The study attempted to find the optimal combination of the printing parameters to achieve the best fatigue behaviour of the FDM ABS specimen. The experiential results showed that the specimen with 0° building orientation, 0.8 mm filament width, and 0.15 mm layer thickness vibrated for the longest time before the fracture at each temperature. Both a larger nozzle size and thicker layer height can increase the fatigue life. It was concluded that printing defects significantly decreased the fatigue life of the 3D-printed ABS beam.Item Open Access An empirical torsional spring model for the inclined crack in a 3D-printed acrylonitrile butadiene styrene (ABS) cantilever beam(MDPI, 2023-01-18) Yang, Zhichao; He, Feiyang; Khan, MuhammadThis paper presents an empirical torsional spring model for the inclined crack on a 3D-printed ABS cantilever beam. The work outlined deals mainly with our previous research about an improved torsional spring model (Khan-He model), which can represent the deep vertical (90°) crack in the structure. This study used an experimental approach to investigate the relationships between the crack angle and torsional spring stiffness. ABS cantilever beams with different crack depths (1, 1.3 and 1.6 mm) and angles (30, 45, 60, 75 and 90°) were manufactured by fused deposition modelling (FDM). The impact tests were performed to obtain the dynamic response of cracked beams. The equivalent spring stiffness was calculated based on the specimen’s fundamental frequency. The results suggested that an increased crack incline angle yielded higher fundamental frequency and vibration amplitude, representing higher spring stiffness. The authors then developed an empirical spring stiffness model for inclined cracks based on the test data. These results extended the Khan-He model’s application from vertical to inclined crack prediction in FDM ABS structures.Item Open Access The EUCAMS gear partnership - a model of industry/academic collaboration(British Institute of Non-Destructive Testing, 2011-12-31) Starr, Andrew; Khan, Muhammad; Allen, Brian; Marshall, Mick; Phang, Albert; Badi, Nuri; Chen, Yong Kang; Edwards, Rodger; Sinha, Jyoti; Rzeszucinski, Pawel; Jones, Rhys; Mao, Ken; Shepherd, Duncan; Curran, AlanChallenges in maintenance systems can pose multi-faceted problems, which are difficult to resolve alone. Over a four year period, a partnership evolved a vision for tackling the understanding of fundamentally difficult mechanical failures and their detection, with potential for practical exploitation of the solutions. The partnership assembled a team of researchers and far-sighted project management, to undertake a study of gearbox failures, including finite element modelling, gear testing, and signal analysis. The partnership trained a series of doctoral and postdoctoral staff in running an integrated project, coping with changes in staffing and locations. The final stages of the work will validate the models and signal processing.Item Open Access Evolution of crack analysis in structures using image processing technique: a review(MDPI, 2023-09-12) Azouz, Zakrya; Honarvar Shakibaei Asli, Barmak; Khan, MuhammadStructural health monitoring (SHM) involves the control and analysis of mechanical systems to monitor the variation of geometric features of engineering structures. Damage processing is one of the issues that can be addressed by using several techniques derived from image processing. There are two types of SHM: contact-based and non-contact methods. Sensors, cameras, and accelerometers are examples of contact-based SHM, whereas photogrammetry, infrared thermography, and laser imaging are non-contact SHM techniques. In this research, our focus centres on image processing algorithms to identify the crack and analyze its properties to detect occurred damages. Based on the literature review, several preprocessing approaches were employed including image enhancement, image filtering to remove the noise and blur, and dynamic response measurement to predict the crack propagation.Item Open Access Experimental and theoretical aspects of crack assisted failures of metallic alloys in corrosive environments – a review(Elsevier, 2022-09-08) Alqahtani, Ibrahim; Starr, Andrew; Khan, MuhammadFailure analysis is one of the complex tasks in engineering materials since it involves analyses of the interdependency of factors like environmental conditions, materials properties and loading conditions etc., causing catastrophic failure of engineering components in real-time applications. In recent times, the advances in characterization techniques have led to the precise findings of the cause of the failures in several cases. However, specific failure analysis-based case studies report that the couple load effects of two or more parameters influencing the failures of engineering components are complex to identify. Moreover, it is difficult to formulate a mathematical model involving the interdependency factors to study the failure behaviour of the engineering materials. Especially in aerospace industry, the crack initiation and propagation in metallic alloys are more complex since the various factors like environmental conditions combined with loading parameters cause unpredictable failures. Hence, there is a need to study the effect of environmental conditions combined with different loading systems on the crack propagation of metallic alloys. The review concludes that still a comprehensive analytical modelling approach is required to relate the interdependencies of couple loads such as humidity and temperature of metallic alloys in corrosive environment.Item Open Access Experimental assessment of multiple contact wear using airborne noise under dry and lubricated conditions(SAGE Publications (UK and US), 2017-03-29) Khan, Muhammad; Basit, K.; Khan, S. Z.; Khan, K. A.; Starr, Andrew G.The generation of wear and airborne noise is inevitable in the mechanical contacts of the machine components. This paper addresses the effectiveness of the airborne noise data in estimating the wear on a disc under multi-contact conditions. A pin-on-disc rig was employed to study the role of noise parameters on the evolution of the wear area. When a pin slides on the disc, the airborne noise is generated and subsequently a sound signal is obtained. These signals, for various sets of experiments, were recorded using a digital microphone. A Matlab code was developed and employed to estimate the noise parameters from the recorded sound. Noise parameters including values of voltage RMS, noise counts and amplitudes of dominant frequencies were used to analyse the variation in the disc wear at different time intervals. These parameters were found to be effective in the determination of the wear damage evaluation under different loads without lubrication.Item Open Access Fracture toughness investigation of AL6082-T651 alloy under corrosive environmental conditions(Trans Tech Publications, 2024-04-03) Alqahtani, Ibrahim; Starr, Andrew; Khan, MuhammadThe crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.Item Open Access Interdependence of friction, wear, and noise: a review(Tsinghua University Press and Springer, 2021-04-19) Lontin, Kevin; Khan, MuhammadPhenomena of friction, wear and noise in mechanical contacts are particularly important in the field of tribomechanics but equally complex if one wants to represent their exact relationship with mathematical models. Efforts have been made to describe these phenomena with different approaches in past. These efforts have been compiled in different reviews but most of them treated friction, wear mechanics and acoustic noise separately. However, an in-depth review that provides a critically analysis on their interdependencies is still missing. In this review paper, the interdependencies of friction, wear and noise are analysed in the mechanical contacts at asperitical level. The origin of frictional noise, its dependencies on contact’s mechanical properties, and its performance under different wear conditions are critically reviewed. A discussion on the existing mathematical models of friction and wear is also provided in the last section that leads to uncover the gap in the existing literature. This review concludes that still a comprehensive analytical modelling approach is required to relate the interdependencies of friction, noise, and wear with mathematical expressionsItem Open Access Interdependencies between dynamic response and crack growth in a 3D-printed acrylonitrile butadiene styrene (ABS) cantilever beam under thermo-mechanical loads(MDPI, 2022-02-28) He, Feiyang; Khan, Muhammad; Aldosari, Salem MohammedAcrylonitrile butadiene styrene (ABS) is the most commonly used thermoplastic printing material for fused deposition modelling (FDM). FDM ABS can be used in a variety of complex working environments. Notably, the thermo-mechanical coupled loads under complex operating conditions may lead to cracking and ultimately catastrophic structural failure. Therefore, it is crucial to determine the crack depth and location before a structural fracture occurs. As these parameters affect the dynamic response of the structure, in this study, the fundamental frequency and displacement amplitude response of a cracked 3D-printed ABS cantilever beam in a thermal environment were analytically and experimentally investigated. The existing analytical model, specifically the torsional spring model used to calculate the fundamental frequency change to determine the crack depth and location was enhanced by the proposed Khan-He model. The analytical relationship between the displacement amplitude and crack was established in Khan-He model and validated for the first time for FDM ABS. The results show that a reduced crack depth and location farther from the fixed end correspond to a higher fundamental frequency and displacement amplitude. An elevated ambient temperature decreases the global elastic modulus of the cracked beam and results in a lower fundamental frequency. Moreover, a non-monotonic relationship exists between the displacement amplitude and ambient temperature. The displacement amplitude is more sensitive to the crack change than the fundamental frequency in the initial stages of crack growth.Item Open Access Investigation of the combined influence of temperature and humidity on fatigue crack growth rate in Al6082 alloy in a coastal environment(MDPI, 2023-10-24) Alqahatni, Ibrahim; Starr, Andrew; Khan, MuhammadThe fatigue crack growth rate (FCGR) of aluminium alloys under the combined influence of temperature and humidity remains a relatively unexplored area, receiving limited attention due to its intricate nature and challenges in predicting the combined impact of these factors. The challenge was to investigate and address the specific mechanisms and interactions between temperature and humidity, as in coastal environment conditions, on the FCGR of aluminium alloy. The present study conducts a comprehensive investigation into the combined influence of temperature and humidity on the FCGR of the Al6082 alloy. The fatigue pre-cracked compact tension specimens were corroded for 7 days and then subjected to various temperature and humidity conditions in a thermal chamber for 3 days to simulate coastal environments. The obtained data were analysed to determine the influence of temperature and humidity on the FCGR of the Al6082 alloy. An empirical model was also established to precisely predict fatigue life cycle values under these environmental conditions. The correlation between FCGR and fracture toughness models was also examined. The Al6082 alloy exhibits a 34% increase in the Paris constant C, indicating reduced FCGR resistance due to elevated temperature and humidity levels. At the same time, fatigue, corrosion, moisture-assisted crack propagation, and hydrogen embrittlement lead to a 27% decrease in threshold fracture toughness. The developed model exhibited accurate predictions for fatigue life cycles, and the correlation between fracture toughness and FCGR showed an error of less than 10%, indicating a strong relationship between these parameters.Item Open Access Investigation of the effect of temperature on the wear rate and airborne noise in sliding wear(MDPI, 2022-01-21) Lontin, Kevin; Khan, Muhammad; Alharbi, BanderWhen friction processes occur, wear is generated. The generation of wear also leads to airborne noise. There have been many research studies on wear and its correlation with airborne noise, but most research has focused on experimental aspects, and theoretical models are rare. Furthermore, analytical models do not fully account for the wear and airborne noise generation, especially at an asperitical level. One model was developed that gave a reasonable quantification for the relationship between wear and airborne noise generation at an asperitical level under room temperature. In this paper, the accuracy of the model is assessed at higher temperatures. Two materials were set up on a tribometer (aluminium and iron) at 300 RPM. The samples were tested at two different temperatures (40 and 60 degrees) and two different loads were applied (10 N and 20 N). The model computed the predicted wear and sound pressure, and it was compared with the experimental results. The errors are larger for the wear than when the model was validated at room temperature. However, the increase in the error for the sound pressure was smaller at higher temperatures (approximately 20–30%). This is due to the assumptions that were made in the initial model, which are exacerbated when higher temperatures are applied. For example, flash temperatures were neglected in the original model. However, when initial heat is applied, the effects of flash temperatures could be more significant than when no heat is applied. Further refinements could improve the accuracy of the model to increase its validity in a wider temperature range.Item Open Access Low-velocity impact characterization of fiber-reinforced composites with hygrothermal effect(ASTM, 2018-06-19) Zai, Behzad Ahmed; Khan, Muhammad; Park, M. K.; Shahzad, Majid; Shahzad, M. A.; Salman, Nisar; Khan, Sohaib Zia; Khan, Kamran Ahmed; Shah, AqueelIn this article, low-velocity impact characteristics of UHN125C carbon fiber/epoxy composite, including unidirectional (0°), cross-directional (0°/90°), and quasi-isotropic layups, were experimentally measured. The effect of the fiber orientation angle and stacking sequences on impact force and induced strain were measured via an instrumented drop-weight apparatus with special concern for the moisture absorption effect. Dried specimens were immersed in distilled water for a certain period of time to absorb water for intermediate and saturated moisture content. It was observed that the impulse was reduced with the increase in moisture content; on the other hand, strain increased with moisture, as measured by DBU-120A strain-indicating software (MADSER Corp., El Paso, TX). Impact damage is widely recognized as one of the most detrimental damage forms in composite laminates because it dissipates the incident energy by a combination of matrix damage, fiber fracture, and fiber-matrix debonding. Therefore, it is extremely important to know the impact strength of a structure, especially for applications in industries such as aerospace, ship design, and some other commercial applications. The use of composite materials in engineering applications is increasing rapidly because they have higher strength-to-weight ratios than metals. The strength, stiffness, and, eventually, the life of composite materials are affected more than conventional materials by the presence of moisture and temperature. Thus, it is necessary to analyze the response of composites in a hydrothermal environment.Item Open Access Manufacturing carbon fibres from pitch and polyethylene blend precursors: a review(Elsevier, 2020-06-05) Aldosari, Salem Mohammed; Khan, Muhammad; Rahatekar, Sameer S.Carbon fibres are one of the newer, emerging materials with multiple engineering applications, from automobiles to space vehicles. Carbon fibres have high mechanical strength, are lighter than metals with better chemical resistance. There have been reports on the use of polyethylene and pitch precursors for the production of carbon fibres, but there are few reports of how these blends could be used for carbon fibre preparation. Bearing in mind the myriad of benefits that using carbon fibres could bring, this paper reviews recent advances published in the literature on how mesophase pitch and polyethylene could be suitable precursors for carbon fibres. It also provides an introduction to the development of precursor blends that allow the properties of carbon fibres to be tailored to specific applications, including processing techniques, fibre parameters, fibre properties and fibre structureItem Open Access Mathematical complexities in modelling damage in spur gears(MDPI, 2024-05-16) Oreavbiere, Aselimhe; Khan, MuhammadAnalytical modelling is an effective approach to obtaining a gear dynamic response or vibration pattern for health monitoring and useful life prediction. Many researchers have modelled this response with various fault conditions commonly observed in gears. The outcome of such models provides a good idea about the changes in the dynamic response available between different gear health states. Hence, a catalogue of the responses is currently available, which ought to aid predictions of the health of actual gears by their vibration patterns. However, these analytical models are limited in providing solutions to useful life prediction. This may be because a majority of these models used single fault conditions for modelling and are not valid to predict the remaining life of gears undergoing more than one fault condition. Existing reviews related to gear faults and dynamic modelling can provide an overview of fault modes, methods for modelling and health prediction. However, these reviews are unable to provide the critical similarities and differences in the single-fault dynamic models to ascertain the possibility of developing models under combined fault modes. In this paper, existing analytical models of spur gears are reviewed with their associated challenges to predict the gear health state. Recommendations for establishing more realistic models are made especially in the context of modelling combined faults and their possible impact on gear dynamic response and health prediction.