Finite Element Modelling of Creep Rupture on Grade 91 Steel using Monkman-Grant Ductility based Damage Model

Failure strain is a main parameter used in the ductility exhaustion based damage model in which the accuracy of the prediction is dependent on its input value. The experimental measured has indicated that the value of strain at fracture is extensively scattered, therefore may affect the prediction. This paper presents the result of creep rupture time using a modified creep damage model incorporating Monkman-Grant (MG) failure strain as an alternative to strain at fracture. Both strains at fracture and MG failure strain are separately employed in the damage model to predict the failure time of uniaxial smooth specimen and notched bar with different acuity ratios of 3.0 and 20. The FE model of the specimen is loaded under different stress values and the multiaxial failure strain at each stress level is estimated using Cock and Ashby void growth model. The predicted creep rupture time that is compared to the experimental data (in a range of 40-1000 hours) showing a good agreement within the scatter band of +/- factor of 2. Both approaches using strain at fracture and MG failure strain can be used in predicting the creep failure under uniaxial and multiaxial features. The advantage of using MG strain is that the laboratory creep testing can be interrupted prior to specimen fractured or once the secondary creep deformation occurs. Meanwhile, the determination of strain at fracture needs longer test duration where the test can be stopped only when the specimen broken

Development of smart self-healing coating for the corrosion protection of magnesium alloys: a brief review

The combination of excellent physical qualities and biocompatibility has made magnesium (Mg) alloys a viable light alloy, particularly for automotive, aerospace, and pharmaceutical applications. However, in most environments, Mg alloys are easily corroded, thus preventing their extensive use. Surface protection by coating is an affordable method for preventing corrosive media from contacting Mg substrate. The development of smart self-healing coatings has attracted attention for surface coating of Mg alloys, as it can impede corrosion reactions, repair mechanical damage, and enable the substrate to function normally again. This article briefly reviews the promising approach of smart self-healing coatings, state-of-the-art coatings, and various healing agent encapsulations. Polymerizable healing agents or corrosion inhibitors are encapsulated in containers and embedded in the coating matrices to facilitate autonomous healing mechanisms. This brief explanation and review are expected to give an insight and more opportunities to explore newly designed smart self-healing coatings

Autonomous navigation of mobile robot using kinect sensor

The problem of achieving real time process in depth camera application, in particular when used for indoor mobile robot localization and navigation is far from being solved. Thus, this paper presents autonomous navigation of the mobile robot by using Kinect sensor. By using Microsoft Kinect XBOX 360 as the main sensor, the robot is expected to navigate and avoid obstacles safely. By using depth data, 3D point clouds, filtering and clustering process, the Kinect sensor is expected to be able to differentiate the obstacles and the path in order to navigate safely. Therefore, this research requirement to propose a creation of low-cost autonomous mobile robot that can be navigated safely

Finite Element Modelling of Creep Rupture on Grade 91 Steel using Monkman-Grant Ductility based Damage Model

Failure strain is a main parameter used in the ductility exhaustion based damage model in which the accuracy of the prediction is dependent on its input value. The experimental measured has indicated that the value of strain at fracture is extensively scattered, therefore may affect the prediction. This paper presents the result of creep rupture time using a modified creep damage model incorporating Monkman-Grant (MG) failure strain as an alternative to strain at fracture. Both strains at fracture and MG failure strain are separately employed in the damage model to predict the failure time of uniaxial smooth specimen and notched bar with different acuity ratios of 3.0 and 20. The FE model of the specimen is loaded under different stress values and the multiaxial failure strain at each stress level is estimated using Cock and Ashby void growth model. The predicted creep rupture time that is compared to the experimental data (in a range of 40-1000 hours) showing a good agreement within the scatter band of +/- factor of 2. Both approaches using strain at fracture and MG failure strain can be used in predicting the creep failure under uniaxial and multiaxial features. The advantage of using MG strain is that the laboratory creep testing can be interrupted prior to specimen fractured or once the secondary creep deformation occurs. Meanwhile, the determination of strain at fracture needs longer test duration where the test can be stopped only when the specimen broken

Creep life prediction of P91 steel using omega method

Martensitic P91 steel is desirable for structural components operating at elevated temperatures. It is extensively used in nuclear power plant boilers, pipelines, reactor pressure vessels, and steam generators due to its high creep strength and corrosion resistance. Predicting the P91’s creep rupture life is critical for safe operation. Numerous creep laws have been developed throughout the years to anticipate the deformation, propagation of damage, and rupture of materials subjected to the creep phenomena. The Omega method is one of the most widely used in API RP579 on fitness-for-service purposes. In this study, the creep tests have been performed at 600 °C for 160, 180 and 190 MPa. In order to predict the rupture life, the omega method has been employed, which utilised the initial creep strain rate and creep strain. The experimental data has been compared to available literature data for P91 material. The predicted life was always more significant than the experimental result, and it was strongly linked to the omega value. The result shows that the value omega value of the test data are in line with the available data and the initial creep strain rate increased linearly with increased of stress and temperature. The predicted rupture life values are consistent and close to the experimental results

Applying TRIZ to design and develop roof shield for two-wheeled motorcycle

Online purchasing and food delivery have shown an increase in demand during the pandemic COVID-19. In Malaysia, the most preferred mode of transportation for food delivery is motorcycle. However, the hot weather and rain affect the delivery time. This paper presents the effort to design and develop a roof shield for a motorcycle to tackle the problem of delivery during uncertain weather conditions. A survey was conducted around Pekan and Kuantan, Pahang districts, encompassing a total of 100 respondents, including riders and customers. From respondents’ feedback, the design requirements for the roof shield were derived. Two conceptual designs were sketched based on the TRIZ approach and evaluated using the scoring test matrix. The roof shield is designed so that it is height adjustable and expandable to fit different brands of motorcycles, which have slightly different dimensions. Furthermore, the rotatable roof is developed to improve riding, especially during cornering. The fabricated roof was assembled on the AVETA DY90 and DEMAK EX90 motorcycles. Twenty random riders were chosen to test the roofed motorcycle on the road. The feedback collected from them showed overall satisfaction with the roof shield installed on the motorcycle. They believed that the roof can protect them from the sun’s rays and light rain thereby increasing delivery performance. The suggestion by the rider to further improve the roof is being considered for future design

Rupture Life and Failure Mechanism of Grade 91 Steel Under the Influence of Notch Constraint

Coal-fired power plants must operate at higher temperatures and pressures to achieve maximum efficiency. During operation, components are exposed to the creep environment, which can lead to catastrophic plant failure. In this study, an initiative was taken to evaluate the creep behavior and failure mechanism of Grade 91 steel by conducting creep tests at 873 K and different stress levels. Two types of specimens (smooth and notched) were used to study the effects of uniaxial and multiaxial stress states on creep strength. Notched specimens with different acuities (2.28 and 4.56) were employed. The creep curve of both specimens showed all three stages known as primary, secondary, and tertiary. The secondary stage seems to be dominant in all three. The analysis of the creep life under the influence of net stress showed that the notched specimen had a longer creep life than the smooth specimen at the same stress level, indicating a "notch strengthening" effect. The effects of the representative stress were also evaluated, revealing that the von-Mises stress controls the rupture life. A comparative analysis of multiaxial ductility is made with various void-growth models. The Rice and Tracey model closely matches the experimental data at lower triaxiality, but the Cocks and Ashby and Splinder model overestimates the ductility. The fractography examination of the notched specimen revealed that, in comparison to the area at the root, the area towards the middle of the notch exhibits shallow dimples, indicating less plasticity. Meanwhile, the ruptured surface of smooth specimens shows that ductile dimples predominate

Ultrasensitive electrochemical detection of metal ions using dicarboethoxycalixarene-based sensor

In this paper, we have reported an electrochemical detection of metal ions based on Calixarene-based sensor. In the sensing strategy, 3-aminopropylsilane (APTMS) was initially self-assembled on indium tin oxide (ITO) followed by functionalization of dicarboethoxy-calix [4]arene (EtC4). The morphology and properties of electrodes were characterized by contact angle, atomic force microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The electrochemical response characteristics of the modified electrodes (EtC4/APTMS/ITO) towards analyte ions; Zn(II), Cu(II), and Fe(II) ions were investigated by differential pulse voltammetry (DPV) under optimized conditions. It was found that the response of modified electrode towards the analytes was improved significantly as compared to the ITO electrode and resulted in limit of detections (LOD) of 9.88 pg/L, 8.33 μg/L and 1.15 μg/L, respectively. In addition, the detection limit of simultaneous detection quantification of Cu2 +, Zn2 + and Fe2 + ions could be achieved with the concentration 6.19 ng/L, 3.02 mg/L and 2.79 mg/L, respectively. It is worth to show that dicarboethoxy-calix [4]arene modified electrode is a promising candidate as electrochemical sensors for simultaneous and ultrasensitive heavy metal ions determination

Photocatalytic Nanolithography of Self-Assembled Monolayers and Proteins

Self-assembled monolayers of alkylthiolates on gold and alkylsilanes on silicon dioxide have been patterned photocatalytically on sub-100 nm length-scales using both apertured near-field and apertureless methods. Apertured lithography was carried out by means of an argon ion laser (364 nm) coupled to cantilever-type near-field probes with a thin film of titania deposited over the aperture. Apertureless lithography was carried out with a helium–cadmium laser (325 nm) to excite titanium-coated, contact-mode atomic force microscope (AFM) probes. This latter approach is readily implementable on any commercial AFM system. Photodegradation occurred in both cases through the localized photocatalytic degradation of the monolayer. For alkanethiols, degradation of one thiol exposed the bare substrate, enabling refunctionalization of the bare gold by a second, contrasting thiol. For alkylsilanes, degradation of the adsorbate molecule provided a facile means for protein patterning. Lines were written in a protein-resistant film formed by the adsorption of oligo(ethylene glycol)-functionalized trichlorosilanes on glass, leading to the formation of sub-100 nm adhesive, aldehyde-functionalized regions. These were derivatized with aminobutylnitrilotriacetic acid, and complexed with Ni2+, enabling the binding of histidine-labeled green fluorescent protein, which yielded bright fluorescence from 70-nm-wide lines that could be imaged clearly in a confocal microscope

Facile formation of highly mobile supported lipid bilayers on surface-quaternized pH-responsive polymer brushes

Poly(2-dimethylamino)ethyl methacrylate) (PDMA) brushes are grown from planar substrates via surface atom transfer radical polymerization (ATRP). Quaternization of these brushes is conducted using 1-iodooctadecane in n-hexane, which is a non-solvent for PDMA. Ellipsometry, AFM, and water contact angle measurements show that surface-confined quaternization occurs under these conditions, producing pH-responsive brushes that have a hydrophobic upper surface. Systematic variation of the 1-iodooctadecane concentration and reaction time enables the mean degree of surface quaternization to be optimized. Relatively low degrees of surface quaternization (ca. 10 mol % as judged by XPS) produce brushes that enable the formation of supported lipid bilayers, with the hydrophobic pendent octadecyl groups promoting in situ rupture of lipid vesicles. Control experiments confirm that quaternized PDMA brushes prepared in a good brush solvent (THF) produce non-pH-responsive brushes, presumably because the pendent octadecyl groups form micelle-like physical cross-links throughout the brush layer. Supported lipid bilayers (SLBs) can also be formed on the non-quaternized PDMA precursor brushes, but such structures proved to be unstable to small changes in pH. Thus, surface quaternization of PDMA brushes using 1-iodooctadecane in n-hexane provides the best protocol for the formation of robust SLBs. Fluorescence recovery after photobleaching (FRAP) studies of such SLBs indicate diffusion coefficients (2.8 ± 0.3 μm s–1) and mobile fractions (98 ± 2%) that are comparable to the literature data reported for SLBs prepared directly on planar glass substrates