Effect of cerium and barium additions and superheating melt treatment on the morphology and hardness of al-mg2si-cu composite

Aluminium-based alloy, reinforced with particulate Mg2Si phase has been widely accepted to replace Al-Si alloy due to its improved properties in producing engineering products especially for automotive and aerospace applications. However, in as-cast Al-based reinforced with Mg2Si composite, the particles formed are coarse with large skeleton shapes and eutectic Al-Mg2Si phase which are also present in flake-like form. These phases are known to have detrimental effect on the mechanical properties of the composite. The present research is therefore aimed to investigate the effect of elements addition and superheating melt treatment in order to modify the undesired structures and phases in Al-Mg2Si-Cu metal matrix composite. The elements addition were Ce (0.3-1.0 wt.%) and Ba (0.1-1.0 wt.%). Meanwhile, superheating above the melting temperature of Al-Mg2Si-Cu composite was carried out at three different temperatures (850°C, 900°C and 950°C) and three different holding times (15, 30 and 45 minutes) to further modify the microstructures. The samples were produced by melting commercial Al-Mg-Si ingot and pouring into a ceramic mould and the transformation temperatures were determined by computer aided cooling curve thermal analysis (CACCTA). The phase and microstructural changes were characterized using optical microscopy, field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness test (ASTM E92) was performed in order to investigate the effect of morphology modification on the hardness of the composite. Both approaches, namely, elements addition and melt superheating with varying parameters were found to refine not only Mg2SiP reinforcement particles but also eutectic Al-Mg2Si phase. Various morphologies of the phases were observed, particularly, coarse skeleton of Mg2SiP has been transformed to finer polygonal structure. Likewise, flake-like morphology of Mg2SiE has transformed to rod and fibrous-like form while the needle-like intermetallic ß has transformed to a phase. The optimum concentrations to achieve the adequate refinement effect were found to be 0.8wt% Ce and 0.2wt% Ba. While, the optimum parameter for the melt superheating was 950°C and underwent 15 minutes holding melt duration. The modified composite with addition of optimum concentration of Ce and Ba were observed to increase in hardness property from 61.32Hv to 74.3Hv and 67.95Hv for Ce and Ba, respectively. Whereas, for the composite modified by melt superheating, the hardness improved from 61.32Hv to 70.22Hv

Design and analysis of mesh size subjected to wheel rim convergence using finite element method

This paper discusses the effect of meshing size on wheel rim. It is not known that every design needs to consider the optimum result of the design, in reality the simulation cannot generates the optimal analysis due to several factors. One of the influencing factors in the simulation is the mesh size when simulating the wheel rim design. It is known that each mesh size gives different results, therefore it is necessary to do a calibration using finite element method from the benchmarking literature studies that have discussed this case before. Authors designed a vehicle wheel using Fusion360 and ran the simulating static analysis using ANSYS. The material used is steel and the boundary conditions of its design is angular velocity and load. The wheel designs were given different mesh sizes and resulted in stress (von-Mises) and displacement, since the results were analyzed for mesh convergence. For the convergence result, wheel rim has a von-Mises stress for 10 mm, 15 mm, and 20 mm size mesh is 164.38 MPa, 128.68 MPa, and 131.08 MPa, and the displacement is 0.16117 mm, 0.15592 mm, 0.15286 mm. The simulation made stress ratio for 1.174, 0.919, 0.936 and displacement ratio for 0.989, 0.957, 0.938. Through the use of different mesh sizes, different results can be proven, this is necessary to determine the convergence of the mesh used in the simulation. This paper proves that 10, 15, 20 mm size mesh convergence, with error ratio of displacement is 0.011, 0.043, 0.062 and the error ratio of stress is -0.174, 0.081, 0.064 to the benchmarking studies literature

Microstructural characterization, mechanical and tribological properties of ZC71 hybrid composite reinforced with SiC and MWCNT

In the present study, the influences of different SiC addition, MWCNTs and various SiC particle sizes on the structural, mechanical and tribological properties of ZC71 alloys were studied. The results revealed that the proper amount/size of SiC particles with the addition of MWCNTs had a considerable effect on the microstructural alteration, and mechanical and tribological properties of the ZC71 alloy. The Vickers hardness values of the ZC71 alloy improved with the addition of MWCNT and SiC. The UTS (216 MPa) and El.% (6.95 %) were achieved in the ZC71-5%SiC(15µm)-0.5%MWCNT. The cast ZC71 alloy showed brittle fracture with some quasi-cleavage characterizations. However, by adding 5% SiC (15 µm) and 0.5% MWCNT, the fracture mode changed to ductile fracture. The wear results showed that the ZC71-5%SiC-0.5%MWCNT hybrid composite had the highest wear resistance with the lowest friction coefficient and wear rate. Examination on the worn surface of the ZC71-5%SiC-0.5%MWCNT hybrid composite showed mild abrasion as the governing wear mechanism

Field dependent-shear stress prediction of magnetorheological fluid using an optimum extreme learning machine model

Extreme learning machine (ELM) application to model the shear stress of magnetorheological (MR) fluids has superiority over the existing methods, such as Herschel-Bulkley. Although the shear stress has been successfully predicted, the hidden node numbers are too high reaching up to 10,000 that will hinder the application of the models. Furthermore, the existing works have tried to determine the hidden node number only by trial and error method. Therefore, this paper aims to reduce the hidden node number by employing the particle swarm optimization (PSO) considering the accuracy and the hidden node numbers. The ELM based-shear stress model was firstly defined by treating the magnetic field and shear rate as the inputs and shear stress as output. The objective function optimization method was then formulated to minimize the normalized error and the hidden node numbers. Finally, the proposed methods were tested at various ELM activation functions and samples. The results have shown that the platform has successfully reduced the hidden node numbers from 10,000 to 571 while maintaining the error of less than 1%. In summary, the proposed objective function for PSO optimization has successfully built the optimum shear stress model automatically

Design of crashworthy attenuator structures as a part of vehicle safety against impact: Application of waste aluminum can-based material

The impact attenuator is an essential system in both race cars and urban vehicles. The structure of an impact attenuator serves as a safety barrier between the impacted surface and the driver in an accident. Attenuator materials tend to have a high price, thus, alternative materials were explored in the current work, i.e., used cans from food and beverage containers. The study deployed a nonlinear finite element algorithm to calculate a series of impacts on the attenuator structures. The thickness of the cans and velocity of the impact were considered as the main parameters. Analysis results concluded that the attenuator's average energy was 16000 J for a can thickness of 1 mm. This value is more than two times the 0.5 mm thick used cans. The attenuator's new design was then matched with an attenuator regulation, and the results surpassed the standard value of 7350 J

Loss factor behavior of thermally aged magnetorheological elastomers

Polymer composites have been widely used as damping materials in various applications due to the ability of reducing the vibrations. However, the environmental and surrounding thermal exposure towards polymer composites have affected their mechanical properties and lifecycle. Therefore, this paper presents the effect of material-temperature dependence on the loss factor and phase shift angle characteristics. Two types of unageing and aging silicone-rubber-based magne-torheological elastomer (SR-MRE) with different concentrations of carbonyl iron particles (CIPs), 30 and 60 wt%, are utilized in this study. The morphological, magnetic, and rheological properties related to the loss factor and phase shift angle are characterized using a low-vacuum scanning electron microscopy, and vibrating sample magnetometer and rheometer, respectively. The morphological analysis of SR-MRE consisting of 30 wt% CIPs revealed a smoother surface area when compared to 60 wt% CIPs after thermal aging due to the improvement of CIPs dispersion in the presence of heat. Nevertheless, the rheological analysis demonstrated inimitable rheological properties due to different in-rubber structures, shear deformation condition, as well as the influence of magnetic field. No significant changes of loss factor occurred at a low CIPs concentration, whilst the loss factor increased at a higher CIPs concentration. On that basis, it has been determined that the pro-posed changes of the polymer chain network due to the long-term temperature exposure of different concentrations of CIPs might explain the unique rheological properties of the unaged and aged SR-MRE. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Skim Pensyarah Lantikan Baru [SLB2111]; Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [RP/CPS/2020/006]; Universiti Teknologi Malaysia, Collaborative Research Grant (CRG) [08G79]; Universiti Teknologi Malaysia, Professional Development Research University (PDRU) [05E21]05E21; RP/CPS/2020/006, SLB2111; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Universiti Teknologi Malaysia, UTM: 08G7

Numerical estimation of the torsional stiffness characteristics on urban Shell Eco-Marathon (SEM) vehicle design

Shell Eco-Marathon (SEM) is an international competition among university students that involves designing, building, and driving energy-efficient cars. The car frame is the most crucial aspect influencing the strength of the car. This research aims to obtain maximum torsional strength with variations in the material and thickness of the frame. Calculation and testing are done using the simulation method to obtain a strong car frame. This simulation method is calculated by a series of finite element analyses. Then, data from the simulation method are obtained in the form of deformation and safety factors. By comparing the moment received with its deformation, torsional stiffness is then obtained. Furthermore, the torsional stiffness is divided by the weight to produce a value ratio. It is known that the factor which has the most significant influence on the difference in torsional stiffness of each variation is the shear modulus of the material used. In contrast, the weight of the chassis is influenced by the density of the material and the thickness of the chassis. Additionally, the safety factor of each variation is strongly influenced by the strength of the chassis structure itself. The results of this study will demonstrate the car frame design with the best performance

Field-dependent viscoelastic properties of graphite-based magnetorheological grease

This paper highlights the effect of graphite on the dynamic viscoelastic properties of magnetorheological grease (MRG). Two types of MRG namely MRG and graphite-MRG, GMRG with 0 wt.% and 10 wt. % of graphite respectively was synthesized by using a mechanical stirrer. The rheological properties of both sample at various magnetic field strength from 0 to 0.603 T was analyzed via rheometer under oscillatory mode with strain ranging from 0.001 to 1% with fixed frequency at 1 Hz for strain sweep and frequency ranging from 0.1 to 80 Hz at a constant strain of 0.01 % for frequency sweep. Based on the result obtained, the value of storage and loss modulus are dependent on the graphite content. A high value of storage modulus was achieved in the GMRG sample at all applied magnetic field strengths within all frequency ranges. These phenomena related to the contribution of graphite to forming the chain structure with CIPs and offered a more stable and stronger structure as compared with MRG. Moreover, the reduction in the value of loss modulus in GMRG was noticed compared to MRG at on-state conditions reflected by the stable structure obtained by GMRG. Lastly, both samples displayed a strong solid-like (elastic) behavior due to the high value of storage modulus, G’ acquired compared to loss modulus, G’’ at all frequency ranges. Therefore, the utilization of graphite in MRG can be used in wide applications such as brake and seismic dampers

Design and dynamic stiffness evaluation of magnetorheological elastomer bushing using FEMM and dynamic testing machine

This research presents a simulation study on electromagnetic behaviour of magnetic flux density distribution in a magnetorheological elastomer (MRE) bushing. The design concept of MRE bushing is based on the design of the bushing used in the conventional car, only the natural rubber is being replaced by the MRE compound. Furthermore, the electromagnetic simulations were conducted by using Finite Element Method Magnetics (FEMM) software where the main aim is for more magnetic flux density in the MRE, which indicates better performances for MRE bushing in this study. The best configuration of the MRE bushing for this study is using single coil, magnetic material for all parts except for coil bobbin, and the thickness of ring plate of 4 mm, which yield the highest magnetic flux density of 0.205 T. By using this configuration, the dynamic stiffness of this MRE bushing is ranging from 2259.13 N/mm to 2671.06 N/mm with the applied currents of 0.5 A to 2.5 A and frequencies from 1 Hz to 15 Hz. All in all, the optimized configurations improve the performance of MRE bushing remarkably

Enhancement of the rheological properties of magnetorheological foam via different constraint volumes foaming approach

The potential of magnetorheological (MR) foam, a recently developed porous smart material, has grown rapidly in recent years. The ability of MR foam to change its properties continuously, actively, and reversibly in response to a controlled external magnetic stimulus is one of its advantages for applications in advanced technology industries. However, its ability to store energy is still relatively low. This study attempts to address this drawback by highlighting a method to improve this ability by enhancing the material's storage modulus by introducing constrained foaming during the fabrication process. MR foam containing 75 wt% carbonyl iron particles (CIPs) was prepared in situ using two foaming approaches: free and constrained foaming. The effect of constraint foaming on the storage modulus enhancement was further investigated by reducing the mold length by 25 % and 50 %. The rheological properties of the fabricated MR foam samples were then examined using a rheometer in both the absence and presence of magnetic fields in an oscillatory shear mode. Thus, this study showed that constraint foaming has successfully improved the properties, especially regarding storage modulus and MR effect. When the mold volume was further reduced by 50 %, the storage modulus increased by about 50 % compared to a free-foaming MR foam at off-state conditions. Meanwhile, the results portrayed a higher storage modulus value under a 0.659 T magnetic field. This positive enhancement was believed to be due to a more compact CIP distribution. Hence, constraint volume MR foams were able to form stronger chain-like structures. The micrograph analysis by digital microscope revealed that the pore size decreased as the mold length was reduced. A shorter mold resulted in a more compact distribution of magnetic particles. As a result, MR foam with constrained foaming, especially at 50 % mold length, has a higher storage modulus. Overall, using constrained foaming to fabricate MR foam could improve the structure and mechanical properties of MR foam for a wide range of smart devices. © 2023 The AuthorsCIPs, (0.23, 0.43g/ml, 18,22,26,27,33,34); Grantová Agentura České Republiky, GA ČR, (23-07244S); Ministry of Higher Education, Malaysia, MOHE, (FRGS/1/2022/TK10/UTM/02/75); Japan International Cooperation Agency, JICA, (R.K130000.7343.4B696