Search

Magnetorheological (MR) grease is one of the smart materials that owing excellent properties that can be altered and changed significantly with the presence of a magnetic field. However, thermal stability of MR grease is one of the crucial issues that restricted the efficiency of MR grease in MR applications since the induced heat to the material would affect the resultant properties of the material. In this study, the thermal behavior of MR grease with 1wt.% of cobalt-ferrite (CoFe2O4) were analyzed. The CoFe2O4 particles was synthesized via co-precipitation method. The synthesized particles were characterized in terms of morphological by using field Emission scanning electron microscope (FESEM) and magnetic properties by Vibrating Sample Magnetometer (VSM). Then, the synthesized particles were mixed with grease and carbonyl iron particles (CIPs) by using a mechanical stirrer. The thermal properties of the MR grease samples in terms of conductivity were tested by using KD2Pro. Additionally, rheometer was used to examine the MR effect of MR grease under magnetic field sweep at different applied temperatures. The results showed that the synthesized particles formed in polygonal shape with 68.9 emu/g meanwhile CIPs are in spherical shape with 125 emu/g of magnetic saturation, Ms. Moreover, the thermal conductivity of MR grease increased as the temperature increased, particularly with presence of CoFe2O4 due to the Brownian motion by 178.69%, at 65°C. The storage modulus of the MR grease samples also showed an increasing trend with the addition of CoFe2O4 and with the magnetic field intensity increased, although the induced temperature also increased. [ABSTRACT FROM AUTHOR]

This study used magnetorheological (MR) foam which consist of carbonyl iron particles (CIPs) that were incorporated into a polyurethane foam. The polyurethane was fabricated using two different compositions of CIPs which were 35 and 55 wt.% to investigate the magnetostriction effect with different concentrations of magnetic particles. The magnetostriction of MR foams with influence of temperatures were investigated by using shear oscillatory rheometer that equipped with the temperature's controller applied at a specific temperature, with magnetic fields ranging from 0 to 0.7T. Based on previous research, MR foam has been found to expand in the presence and strength of magnetic fields. However, the magnetostriction of MR foams under different operating temperatures are not yet discovered since it causes changes in its behavior and performance. Therefore, the purpose of this study is to analyze the magnetostriction of MR foams at different operating temperatures between 25 to 50°C, with 5°C increment. The finding revealed that the mag-netostriction has slightly decreased at temperatures between 25 to 40°C. Nevertheless, at temperature between 40 to 50°C, the magnetostriction some-how increased for both MR foam samples. In fact, the magnetostriction for MR foam with 55 wt.% concentration of CIPs achieved higher compared to MR foam with 35 wt.% concentration of CIPs, by about 26.56% particularly at 25°C. Prior to the application of MR foam in sensors and actuators that would experience induced of heat during the operating system, it is crucial to understand the behaviors of MR foam as well as the magnetostriction under different operating temperatures. [ABSTRACT FROM AUTHOR]

A novel type of magnetorheological (MR) foam that provides unique porous structure with embedded magnetic particles somehow could response to magnetic field stimuli continuously, actively and reversibly. Its low density and controllable properties have rendered MR foam to be a new potential smart material for advance applications such as smart actuators or sensors technology. Unfortunately, the rheological properties in terms of stiffness or known as storage modulus of MR foam is still rather limited, in the range of below than 1 MPa to withstand frequencies with high amplitude displacement during the operational system. Therefore, the aim of this research is to enhance the rheological properties of MR foam in terms of storage modulus by adding silica nanoparticles as an additive. In this study, MR foams were fabricated with different compositions of silica nano-particles in the range of 0 to 5 wt.%, with 1 wt.% increment. The rheological testing was carried out using modular compact rheometer (MCR) under different frequency inputs in the range of 1 to 10 Hz, with the absence and presence of magnetic field at 0 T and 0.8 T, respectively. The finding has revealed that the storage modulus of MR foam has significantly increased up to ∼273% during the off-state condition and further increased to ∼346% at the on-state condition, indicating higher stiffness of MR foam with silica nanoparticles as compared to non-additive MR foam. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) material is a smart material composed of one of the magnetic particles of carbonyl iron (CIP) in a non-magnetic medium that can be controlled via magnetic fields. One of the groups of MR materials is MR plastomer (MRP) which consists of CIPs in the low-crosslinking polymer network such as plastomer, and it is introduced to compromise the limitations in MR fluid and MR elastomer. Somehow, the new modern approach particularly machine learning needs to be highlighted to acquire accuracy in the prediction trend of the MRP's properties, including viscosity. In fact, the approach may reduce time and work consuming in the development process of MRP. Therefore, using an artificial neural network (ANN) as one of the machine learning approaches is an effective medium for forecasting the behavior of the material and resolving constitutive model concerns. [ABSTRACT FROM AUTHOR]

Different fabrication process would result to different properties of material. This is due to the properties of porous materials are highly dependent on its structure. In this study, magnetorheological (MR) foam was prepared via two fabrication processes, namely open mould system and constraint volume mould system which was also known as open-mould (O-MRFoam) and closed-mould system (C-MRFoam), respectively. The characteristics and properties of the fabricated MR foam were presented in this paper. The characteristics of MR foam such as morphological and rheological behavior in terms of storage modulus and linear viscoelastic (LVE) region were experimentally investigated. It can be seen that the properties of MR foam were affected by different fabrication processes. In terms of morphological observation, the average area of pores decreases by 39% when a constraint volume mould system was implied to the fabrication process of the MR foam. It is believed that the distribution of magnetic particles become more compact resulting to more bubble nucleation during the foaming process. As a result, the storage modulus of MR foam was successfully enhanced along with the decrement of the size of pores. Therefore, the results obtained from this study would widen the potential MR foam especially for the use of applications with controllable stiffness. [ABSTRACT FROM AUTHOR]

MR foam is a magnetically permeable solid material that composed of micron-sized magnetic particles known as carbonyl iron (CIPs) that are embedded in a porous absorbent matrix of foam. There are two types of methods to fabricate MR foams known as ex situ and in situ methods. In particular, the methods related to the location of CIPs in the structure of MR foams such that in situ MR foam contained of CIPs in the struts of foam. Meanwhile, ex situ MR foam contained of CIPs in the pores of foam rather than in the struts structure. Correspondingly, resultant magnetostriction of each type of MR foam would be different as magnetic responsiveness of MR foams towards the applied magnetic fields would be differ as well. Therefore, three MR foams were fabricated via three methods particularly, ex situ, in situ, and hybrid as a combination of ex situ and in situ methods. Then, the samples underwent the magnetostriction test at various magnetic fields from 0 to 0.8 T using a rheometer that equipped with electromagnetic device. The results show that the hybrid MR foam exhibited the highest magnetostriction, about 36.74%, followed by ex situ- and in situ MR foams. It is attributed to the CIPs that were located in the struts and pores of MR foam which result in a stronger magnetic force between the particles, and towards the applied magnetic fields. [ABSTRACT FROM AUTHOR]

In this study, a simple and low-cost approach to additively manufacture (3D print) Inconel 718 by using a desktop fused filament fabrication (FFF) 3D printer via a 3-step printing-debinding-sintering stage is presented. Inconel 718 filament containing high metal loading (86% by mass) was 3D printed by varying the nozzle temperatures from 210°C to 300°C. As-printed samples were successfully fabricated through all nozzle temperatures without any clogging issues. Debinding and sintering results generally exhibit an increasing trend of densification levels with increasing nozzle temperatures, with the highest relative density of 85% achieved with a nozzle temperature of 290°C. These results show significant promise in the additive manufacturing of metallic materials with high quality just by using the widely available and accessible desktop FFF 3D printers. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) has emerged as a viable economical additive manufacturing technique (AM) to fabricate metallic components using low-cost desktop 3D printers via a simple 3-step printing-debinding-sintering stages. In this study, 316L stainless steel (SS) filament containing 83.5 wt.% metal loading and 16.5 wt.% PLA as the polymer binder was used as the raw material for 3D printing. The nozzle temperature is varied between 190°C and 225°C to observe the printability of the filament 316L SS and the resulting densification level of the sintered part. Sintering was performed under atmospheric condition at 1260 °C by adding sintering carbon to prevent oxidation on the 3D printed samples. Based on the results, the highest relative density obtained was 75.8% at a nozzle temperature of 200°C. Thus, this study shows that FFF is a simple, feasible and more accessible approach of AM technology to fabricate metallic parts. [ABSTRACT FROM AUTHOR]

Studies on smart materials called Magnetorheological (MR) materials has attracted interest from numerous researchers due to its properties that can be manipulated through applications of magnetic fields. Owing to its wide potential application in various field, improvement on its properties in terms of rheology, tribology, thermal stability as well as electrical conductivity need to be optimized for a material to be possibly applied in real applications. Graphite on other hand is a carbon-allotrope that has been utilized in MR materials which acts as a filler or additives and was reported to significantly improves the distinct properties in different types of MR materials. Therefore, this paper has summarized and discussed the effect of graphite's addition on the properties of several types of MR materials especially on its electrical conductivity, thermal stability, tribological as well as rheological properties to provides an insight view of graphite as a future potential additives and filler in MR materials for upcoming research. [ABSTRACT FROM AUTHOR]

In this study, silicon carbide (SiC) is introduced as a reinforcing additive of magnetorheological elastomer (MRE) to be added in silicone rubber matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were set at 70% by weight, and two types of MRE samples were produced based on with/out plasticized matrix. The hardness of the MRE samples was determined using a Durometer Shore A. The rheological test of MRE samples in terms of storage modulus was investigated using a rheometer during a magnetic field sweep. The results showed that the hardness of the MRE with SiC was reduced by 13% in plasticized MRE. Interestingly, plasticized MRE with SiC produced a 284% MR effect compared to a 69% MR effect in a non-plasticized matrix. As a result, the incorporation of SiC in plasticized MRE has been shown to resolve the aligning issues in anisotropic MRE that degrade the performance of MRE application devices and systems. [ABSTRACT FROM AUTHOR]

In the development of magnetorheological elastomers (MRE) for long-lasting mechanical elements, durability has emerged as a critical factor. It is necessary to determine the material's ability to withstand changes in property levels caused by actual service circumstances. Similarly, the degradation process of MRE in viscoelastic materials is controlled by a variety of damage mechanisms that result in material deterioration. MRE durability research has revealed an astonishingly consistent trend, but more research is required. As a result, this research advances our understanding of MRE microscopic durability under shear loads at constant strain, a phenomenon known as stress relaxation. Isotropic MRE samples based on silicone rubber (SR) were prepared by incorporating 70 wt% of magnetic particles. The rheological and shear stress relaxation behavior of MRE samples in oscillatory shear mode was tested using a rheometer. In the stress relaxation durability test, the angular frequency effect was used. At 31.4 rad/s, the damping property (loss factor) and shear stress showed an increased pattern. During the first 12,000 seconds of the test, both parameters gradually decreased. However, at 6.28 rad/s, both damping and stress showed only a minor decrease. The sheared MRE sample was then examined using a field emission scanning electron microscope (FESEM), with particular focus on the formation of shear bands, which occurred as early as 12,000 s into the test. As a result, a clear and predictive picture of stress relaxation in the generic shear band will provide insights for dealing with and processing such material in real-time practice, thereby contributing to the long-term development goal of domestic technology development, research, and innovation. [ABSTRACT FROM AUTHOR]

Environmental effects like rain and temperature as well as the continuous heating phenomenon during device operation are the common factors that will degrade the mechanical and rheological performance of composite rubber materials like Magnetorheological elastomer (MRE) over the time. In this study, the morphological, and rheological properties of the unaged and aged MRE is examined. Two types of silicone rubber based MRE with 30 wt% of CIPs is investigated under the influence of continuous thermal ageing of 100°C for 3 days. Their morphological and rheological properties under the influence of frequency and magnetic field were evaluated using the low vacuum scanning electron (LV-SEM) and rheometer equipped with electromagnetic device. The results revealed that the storage modulus of aged MRE increased with the increment of frequency as compared to unaged MRE. While the MR effect of aged MRE decreased as compared to an unaged MRE. This finding not only provide a better understanding on the influence of thermal ageing phenomenon towards the rheological properties of the MRE but also can be used as an important information for the future device application in MRE. [ABSTRACT FROM AUTHOR]