kamran khan - Academia.edu (original) (raw)

Papers by kamran khan

Journal of Materials Science

Polymers, 2021

Thermomechanical modeling of epoxy/graphene oxide under quasi-static and dynamic loading requires... more Thermomechanical modeling of epoxy/graphene oxide under quasi-static and dynamic loading requires thermo-mechanical properties such as Young’s modulus, Poisson’s ratio, thermal conductivity, and frequency-temperature dependent viscoelastic properties. In this study, the effects of different graphene oxide (GO) concentrations (0.05, 0.1, and 0.2 wt%) within an epoxy matrix on several mechanical and thermal properties were investigated. The distribution of GO fillers in the epoxy was investigated using transmission electron microscopy (TEM). The digital image correlation (DIC) technique was employed during the tensile testing to determine Young’s modulus and Poisson’s ratio. Analytical models were used to predict Young’s modulus and thermal conductivity, with an error of less than 13% and 9%, respectively. Frequency–temperature dependent phenomenological models were proposed to predict the storage moduli and loss tangent, with a reasonable agreement with experimental data. A relativel...

Sensors, 2020

Accurate damage detection in engineering structures is a critical part of structural health monit... more Accurate damage detection in engineering structures is a critical part of structural health monitoring. A variety of non-destructive inspection methods has been employed to detect the presence and severity of the damage. In this research, machine learning (ML) algorithms are used to assess the dynamic response of the system. It can predict the damage severity, damage location, and fundamental behaviour of the system. Fatigue damage data of aluminium and ABS under coupled mechanical loads at different temperatures are used to train the model. The model shows that natural frequency and temperature appear to be the most important predictive features for aluminium. It appears to be dominated by natural frequency and tip amplitude for ABS. The results also show that the position of the crack along the specimen appears to be of little importance for either material, allowing simultaneous prediction of location and damage severity.

Applied Sciences, 2021

The effect of temperature on structural response is a concern in engineering applications. The li... more The effect of temperature on structural response is a concern in engineering applications. The literature has highlighted that applied temperature loads change the system vibration behaviour. However, there is limited information available about temperature impacting the dynamic response. This paper investigated the heating rates effects on modal parameters for both with crack and without crack conditions in a cantilever beam. A beam subjected to three heating rates was considered: 2, 5, and 8 °C/min. The first one was assumed as a slow heating rate while the others were assumed as moderate and high, respectively. This controlled rate of heating was achieved by using a proportional-integral-derivative (PID) temperature controller. The results showed that heating at different rates has little impact on modal parameters. While this effect is minimal at lower temperatures and more evident at higher temperatures. The results of temperature ramped at 2, 5, and 8 °C/min were compared with...

Advanced Engineering Materials, 2021

The advancements in additive manufacturing (AM) technology make the fabrication of complex archit... more The advancements in additive manufacturing (AM) technology make the fabrication of complex architected materials and structures at multiple length scales possible to explore a new family of metamaterial. A metamaterial is an artificially engineered material to have a property not found in conventional materials. [1] Historically, the term "metamaterials" were limited to electromagnetism field, but, recently, it has been extended to photonic, phononic, and mechanical systems to design architected engineered materials that exhibit properties not usually found in conventional materials. [2] Mechanical metamaterials refer to a sort of metamaterials that designed artificial structural materials with counterintuitive mechanical properties derived from their tailored internal microstructure rather than the composition of base material. [3] The unusual properties include negative Poisson's ratio, negative modulus of elasticity, and negative compressibility. [4,5] Examples of mechanical metamaterials include acoustic metamaterials, auxetic materials, pentamode metamaterials, and micropolar metamaterials. The concept of metamaterials combined with AM opens new design avenues for the fabrication of complex microstructures over a wide range of length scales. [6-8] Auxetic mechanical metamaterials are recognized by a negative Poisson's ratio; i.e., materials will contract (expand) in the transverse direction when compressed uniaxially (stretched). Auxetic mechanical metamaterials are of interest because of their enhanced mechanical properties, such as increased indentation resistance, [9] shear modulus, [10] and fracture toughness. [11] They have a great potential in engineering applications, such as cellular materials with superior damping and acoustic properties, [12] piezoelectric metamaterials, [13] piezocomposites, [14] auxetic fasteners, [15] bioprostheses, [16] tissue engineering, [17] and mechanically tunable, elastically reversible, and transformable topological mechanical metamaterials. [18,19] The negative Poisson's ratio of auxetic material depends on the topology of auxetic building blocks and scaleindependent. [20,21] Several natural materials exhibit negative Poisson's ratio, such as silicates, [22] cubic elemental metals, [23] zeolites, [24] natural layered ceramics, [25] and monolithic ferroelectric polycrystalline ceramics. [26] Love [27] was the first to report the negative Poisson's ratio of naturally occurring cubic crystals of

Engineering Reports, 2021

Structural health monitoring (SHM) using self-sensing cement-based materials has been reported be... more Structural health monitoring (SHM) using self-sensing cement-based materials has been reported before, where nano-fillers have been incorporated in cementitious matrices as functional sensing elements. A percolation threshold is always required in order for conductive nano-fillers modified concrete to be useful for SHM. Nonetheless, the best pressure/strain sensitivity results achieved for any self-sensing cementitious matrix are <0.01 MPa −1. In this work, we introduce for the first-time novel partially reduced graphene oxide based electronic textile (e-textile) embedded in plain and as well as in polymer-binder-modified cementitious matrix for SHM applications. These e-textile embedded cementitious composites are independent of any percolation threshold due to the interconnected fabric inside the host matrix. The piezo-resistive response was measured by applying direct and cyclic compressive loads (ranging from 0.10 to 3.90 MPa). A pressure sensitivity of 1.50 MPa −1 and an ultra-high gauge factor of 2000 was obtained for the system of the self-sensing cementitious structure with embedded e-textiles. The sensitivity of this new system with embedded e-textile is an order of magnitude higher than the state-of-the-art nanoparticle based self-sensing cementitious composites. The composites showed mechanical stability and functional durability over long-term cyclic compression tests of 1000 cycles. Additionally, a two time-constant model was used to validate the experimental results on decay response of the e-textile embedded composites.

Journal of Materials Research and Technology, 2020

This work presents the application of both uniaxial and bi-axial in-plane loads to unidirectional... more This work presents the application of both uniaxial and bi-axial in-plane loads to unidirectional carbon fiber reinforced polymer laminates using a newly developed Arcan fixture, which is a reliable experimental setup to obtain a uniform shear stress field in a butterfly specimen. The setup can be used for both damage model validation and parameters identification at various fiber orientations while using the same specimens. A sequential damage study was completed to highlight the influence of diffused damage induced in pure shear on the fiber direction tensile behavior of the laminate. This was accomplished by applying load on the specimens in two steps: (i) the pure shear step and then unloading at approximately 70% of the shear failure strength, (ii) in the tensile step until final failure. A clear drop in the tensile behavior of the laminate was observed by the diffused damage induced in the first loading step of pure shear. The experimental study is also supplemented with numerical simulations using a nonlinear elasto-plastic coupled damage constitutive law by employing Puck's failure theory for mesodamage activation. In addition to the damage pattern, the non-linear mechanical behavior in shear is predicted and found in good correspondence with the experimental results.

Journal of Intelligent Material Systems and Structures, 2021

Architected piezoelectric materials with controlled porosity are of interest for applications suc... more Architected piezoelectric materials with controlled porosity are of interest for applications such as hydrophones, miniature accelerometers, vibratory sensors, and contact microphones. Current analytical modeling approach cannot be readily applied to design architected periodic piezoelectric foams with tunable properties while exhibiting elastic anisotropy and piezoelectric activity. This study presents micromechanical-finite element (FE) models to characterize the electromechanical properties of architected piezoelectric foams. The microstructure with zero-dimension (3-0 foam, spherical porosity) and one-dimensional (3-1 foam, cylindrical porosity) connectivity were considered to analyze the effect of porosity connectivity on the performance of piezoelectric foam. 3D FE models of the 3-0 and 3-1 foams were developed and using the intrinsic symmetry of porous structures simplified mixed boundary conditions (MBCs) equivalent to periodic boundary conditions (PBC) were proposed. The pr...

Polymers, 2019

Acrylonitrile butadiene styrene (ABS) offers good mechanical properties and is effective in use t... more Acrylonitrile butadiene styrene (ABS) offers good mechanical properties and is effective in use to make polymeric structures for industrial applications. It is one of the most common raw material used for printing structures with fused deposition modeling (FDM). However, most of its properties and behavior are known under quasi-static loading conditions. These are suitable to design ABS structures for applications that are operated under static or dead loads. Still, comprehensive research is required to determine the properties and behavior of ABS structures under dynamic loads, especially in the presence of temperature more than the ambient. The presented research was an effort mainly to provide any evidence about the structural behavior and damage resistance of ABS material if operated under dynamic load conditions coupled with relatively high-temperature values. A non-prismatic fixed-free cantilever ABS beam was used in this study. The beam specimens were manufactured with a 3D p...

Journal of Sound and Vibration, 2019

This paper investigates the interdependencies of crack depth and crack location on the dynamic re... more This paper investigates the interdependencies of crack depth and crack location on the dynamic response of a cantilever beam under thermo-mechanical loads. Temperature can influence the stiffness of the structure, thus, the change in stiffness can lead to variation in frequency, damping and amplitude response. These variations are used as key parameters to quantify damage of Aluminum 2024 specimen under thermo-mechanical loads. Experiments are performed on cantilever beams at non-heating (room temperature) and elevated temperature, i.e., 50°C, 100°C, 150°C and 200°C. This study considers a cantilever beam having various initially seeded crack depth and locations. The analytical, numerical and experimental results for all configurations are found in good agreement. Dynamic response formulation is presented experimentally on beam for the first time under thermo-mechanical loads. Using available experimental data, a novel tool is formulated for in-situ damage assessment in the metallic structures. This tool can quantify and locate damage using the dynamic response and temperature including the diagnosis of subsurface cracking. The obtained results demonstrate the possibility to diagnose the crack growth at any instant within the operational condition under thermo-mechanical loads.

Journal of Engineering Mechanics, 2019

This study presents the finite-element based micromechanical modeling approach to obtain the elec... more This study presents the finite-element based micromechanical modeling approach to obtain the electromechanical properties of the piezoelectric metamaterial based on honeycomb (HC) cellular networks. The symmetry of the periodic structure was employed to derive mixed boundary conditions (MBCs) analogous to PBCs. Three classes of hexagonal HC cellular networks, namely, conventional HC (CHC), a re-entrant HC (RE) and a semi-re-entrant HC (SRE) were considered. The representative volume elements (RVEs) of these three classes of cellular materials were created, and finite element analyses were carried out in order to analyze the effect of orientation of the ligament on their effective electromechanical properties and their suitability in specific engineering applications. The longitudinally poled piezoelectric HC cellular networks showed an enhanced behavior as compared to the monolithic piezoelectric materials. Moreover, longitudinally poled HC cellular networks demonstrated that, as compared to the bulk constituent, their hydrostatic figure of merit increased and their and acoustic impedance decreased by one order of magnitude, respectively, indicating their applicability for the design on hydrophones. Moreover, results showed that cellular metamaterial with tunable electromechanical characteristics and variety of auxetic behaviors such as negative, positive or zero Poisson's ratios could be

Measurement, 2019

Failure in gears, transmission shafts and drivetrains is very critical in machineries such as air... more Failure in gears, transmission shafts and drivetrains is very critical in machineries such as aircrafts and helicopters. Real time condition monitoring of these components, using predictive maintenance techniques is hence a proactive task. For effective power transmission and maximum service life, gears are required to remain in prefect alignment but this task is just beyond the bounds of possibility. These components are flexible, thus even if perfect alignment is achieved, random dynamic forces can cause shafts to bend causing gear misalignments. This paper investigates the change in energy levels and statistical parameters including Kurtosis and Skewness of gear mesh vibration and airborne sound signals when subjected to lateral and angular shaft misalignments. Novel regression models are proposed after validation that can be used to predict the degree and type of shaft misalignment, provided the relative change in signal RMS from an aligned condition to any misaligned condition is known.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2019

This article presents a literature review of published methods for damage identification and pred... more This article presents a literature review of published methods for damage identification and prediction in mechanical structures. It discusses ways which can identify and predict structural damage from dynamic response parameters such as natural frequencies, mode shapes, and vibration amplitudes. There are many structural applications in which dynamic loads are coupled with thermal loads. Hence, a review on those methods, which have discussed structural damage under coupled loads, is also presented. Structural health monitoring with other techniques such as elastic wave propagation, wavelet transform, modal parameter, and artificial intelligence are also discussed. The published research is critically analyzed and the role of dynamic response parameters in structural health monitoring is discussed. The conclusion highlights the research gaps and future research direction.

Journal of Composite Materials, 2019

Highly conductive composites have found applications in thermal management, and the effective the... more Highly conductive composites have found applications in thermal management, and the effective thermal conductivity plays a vital role in understanding the thermo-mechanical behavior of advanced composites. Experimental studies show that when highly conductive inclusions embedded in a polymeric matrix the particle forms conductive chain that drastically increase the effective thermal conductivity of two-phase particulate composites. In this study, we introduce a random network three dimensional (3D) percolation model which closely represent the experimentally observed scenario of the formation of the conductive chain by spherical particles. The prediction of the effective thermal conductivity obtained from percolation models is compared with the conventional micromechanical models of particulate composites having the cubical arrangement, the hexagonal arrangement and the random distribution of the spheres. In addition to that, the capabilities of predicting the effective thermal cond...

Journal of Testing and Evaluation, 2019

In this paper, a methodology is proposed which can be used to predict the crack growth and fatigu... more In this paper, a methodology is proposed which can be used to predict the crack growth and fatigue life of a cantilever beam made of Acrylonitrile Butadiene Styrene (ABS) manufactured with fused deposition modeling Three beam configurations based on length (L=110 mm, L =130 mm, and L=150 mm) are considered. Empirical relationships are formulated between the natural frequency and the crack growth. The analytical and experimental results are found in good agreement for all configurations. Using the experimental data, global relation is formulated for the crack depth prediction. This global relation is useful for an in-situ crack depth prediction with an error of less than10%. Later a residual fatigue life of these specimens is compared with metallic structure (Aluminum 1050) of similar configuration available in the literature. It is found out that the ABS material has more residual fatigue life compared to the metallic structure at the same frequency drop. Based on remaining fatigue life, ABS material can be a potential material to manufacture machine components under cyclic loads.

Journal of Reinforced Plastics and Composites, 2016

Thermal conductivity is one of the key material properties to understand the effective thermo-mec... more Thermal conductivity is one of the key material properties to understand the effective thermo-mechanical behavior of advanced composites. Experimental studies show that when highly conductive inclusions are embedded in a less thermally conductive matrix, the effective thermal conductivity of the composite changes drastically with the increase of volume fraction ( Vf) of the inclusions. This study presents a theoretical model to predict the effective thermal conductivity of two-phase particulate composites containing highly conductive inclusions in a polymeric matrix. The probabilistic approach presented by Tsao (1961) has been modified and extended for predicting the effective thermal conductivity of two-phase composites. The expression for the effective thermal conductivity of a unit cube of two-phase composite is derived implicitly in terms of distribution function, Vf and thermal conductivity of the constituents. Different distribution functions of the inclusions are proposed and...

Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, 2017

Design of piping system requires a systematic consideration of various factors as addressed by th... more Design of piping system requires a systematic consideration of various factors as addressed by the codes and standards. This research paper aims to provide a method for flexibility analysis of a selected area of process piping at an industrial plant. Analysis is done for the purpose of accommodating a spare heat exchanger in the process layout. The analysis follows a systematic procedure, with preparation of a tentative model of the system on CAESAR II software followed by insertion of different pipe supports. The selection and location of these supports is based on the results obtained from displacement, stress, reaction and equipment nozzle analysis of the piping system. The design is in accordance with ASME B31.3, which is the standard code for process piping. The proposed method can be adapted for piping configuration of any industrial plant. With the provision of a systematic procedure, the method ensures time saving and efficient flexibility analysis of any piping system.

Journal of Composite Materials, 2016

This study introduces a unit cell-based finite element micromechanical model that accounts for co... more This study introduces a unit cell-based finite element micromechanical model that accounts for correct post cure fabric geometry, in situ material properties and void content within the composite to accurately predict the effective elastic orthotropic properties of 8-harness satin weave glass fiber-reinforced phenolic composites. The micromechanical model utilizes a correct post cure internal architecture of weave, which was obtained through X-ray microtomography tests. Moreover, it utilizes an analytical expression to update the input material properties to account for in situ effects of resin distribution within yarn (the yarn volume fraction) and void content on yarn and matrix properties. This is generally not considered in modeling approaches available in literature and in particular, it has not been demonstrated before for finite element micromechanics models of 8-harness satin weave composites. The unit cell method is used to obtain the effective responses by applying periodi...

Nuclear Medicine Communications, 2009

Objective To find an easy tool to detect dyshormonogenesis. Methods In this study, the standard p... more Objective To find an easy tool to detect dyshormonogenesis. Methods In this study, the standard perchlorate discharge test was modified by using a c-camera instead of a c-probe to detect this rare abnormality. Results By using this technique two cases of dyshormonogenesis were identified. Conclusion The gamma-camera-based perchlorate discharge test is an easy, reliable, convenient, and feasible procedure where thyroid uptake probe is not available.