The microstructure and mechanical behavior of modern high temperature alloys
, Pages: 1-20
A.T. Samaei, M.M. Mirsayar and M.R.M. Aliha PDF (2256K)
Abstract: Over the past decades, high entropy alloys (HEAs) have attracted continuously increasing research efforts because of their technological promise for structural applications and their scientific interest as a multi-component alloy exhibiting an overall random solid solution structure with high mixing entropy at high temperature. In this summary, we briefly review the recent studies focused on the structure and mechanical behavior of HEAs, covering the important issues from phase stability to elastic modulus, mechanical strength, hardness and fatigue resistance. Finally, we highlight a few key findings recently reported for HEAs and discuss the outstanding issues yet to be resolved.
Keywords: High Entropy Alloy, Phase Stability, Mechanical Properties, Structure-Property Relation
Improvement the impact damage resistance of composite materials by interleaving Polycaprolactone nanofibers
, Pages: 21-26
H. Saghafi, T. Brugo, G. Minak, and A. Zucchelli PDF (2256K)
Abstract: In this study, the impact response of glass/epoxy laminates interleaved by Polycaprolactone (PCL) nanofibers is considered. PCL is a thermoplastic polymer, which is a good choice for toughening epoxy-based composite. The impact tests were conducted on curved laminates and under 24 and 36J. The results showed that the effect of interleaving on impact parameters such as maximum load is negligible, but on the other hand could decrease damaged area significantly. By inserting 30m of PCL nanofibers between each layer of laminate the damaged area decreased about 27%.
Keywords: Nanofibers, Electrospinning, Impact loading, Interleaving
Experimental and computational study on the effects of wearing neck collar on the carotid blood flow
, Pages: 27-34
Hamidreza Ghasemi Bahraseman, Bahareh Hamzehei, Karim Leilnahari, Arezoo Khosravi and Ehsan Mohseni Languri PDF (2256K)
Abstract: The effect of football neck collar on the right external carotid blood flow was investigated for ten healthy subjects using Echo-Doppler technique and computational fluid dynamics (CFD) approach. Carotid is in charge of blooding head’s parts including the brain and eyes. Hence, the evaluation of affected carotid flow by using neck collars is crucial for an improved ergonomic design. The testings were divided into three main categories; participants without wearing neck collar (Category 1), wearing neck collar (Category 2), and finally wearing neck collar with an embedded gap adjacent to the carotid artery position (Category 3). The experimental and numerical results revealed that wearing the neck collar (Category 2) reduced the average blood carotid flow by 28% compared to the case with no neck collar (Category 1). This average blood carotid flow reduction was improved by 15% when a gap separates the collar from the carotid artery position (Category 3). The results of this paper suggest a new design for the next generation of the neck collar by devising an appropriate gap near to carotid artery. The numerical results were validated and were in a reasonable agreement with the experimental data.
Keywords: Computational fluid dynamic, Echo-Doppler flow, Football neck collar, Carotid artery
Tensile fracture analysis of blunt notched PMMA specimens by means of the Strain Energy Density
, Pages: 35-42
A. Campagnolo and F. Berto PDF (256K)
Abstract: In this paper, a volume criterion based on a simple scalar quantity, the mean value of the strain energy (SED), has been used to assess the static strength of notched components made of Polymethylmethacrylate (PMMA). The local-strain-energy based approach has been applied to a well-documented set of experimental data recently reported in the literature. Data refer to blunt U-notched cylindrical specimens of commercial PMMA subjected to static loads and characterised by a large variability of notch tip radius (from 0.67 mm to 2.20 mm). Critical loads obtained experimentally have been compared with the theoretical ones, estimated by keeping constant the mean value of the strain energy in a well-defined small size volume. In addition, some new tests dealing with V-notched specimens with end holes have been carried out to investigate the effect of the notch opening angle.
Keywords: Polymethylmethacrylate, U-notch, V-notch, Static, Elasticity, Strain energy
Study of free vibration analysis of laminated composite plates with triangular cutouts
, Pages: 43-50
Harsh Kumar Bhardwaj Jyoti Vimal and Avadesh Kumar Sharma PDF (256K)
Abstract: Cutouts are commonly used as access port for mechanical and electrical structures. Most of the structures generally work under severe dynamic loading and different constrained conditions during their service life. This may lead to vibration of the structure. Therefore, it is necessary to predict the vibration responses of laminated composite plates with cutouts precisely with less computational cost and good accuracy of these complex structures. A suitable finite element model is proposed and developed based on first order shear deformation theory using ANSYS parametric design language (APDL) code. The model has been discretized using an appropriate eight nodded element (SHELL 281) from the ANSYS element library. The free vibrations are computed using Block-Lanczos algorithm. The convergence study has been done of the developed model and compared with those available published literature. Effects of different geometric parameters (aspect ratio, thickness ratio, boundary conditions, number of layers, angle of lamina geometry of cutout, cutout side to plate side ratio and distance between cutouts) and material properties on the free vibration responses are discussed in detail. The frequency increases with increase in the number of layers, modulus ratio of plate and angle of lamina. The frequency decreases with increase in aspect ratio, thickness ratio, size of cutout and distance between cutouts. The boundary conditions of the plate play an important role in the free vibrations of the plate with cutouts. The Non-dimensional frequencies are higher for fully clamped boundary condition in comparison to other boundary conditions.
Keywords: Free Vibration, FEM, Composite plate, Triangular cut-out
Time-dependent response of intact intervertebral disc – In Vitro and In-Silico study on the effect of loading mode and rate
, Pages: 51-58
Mohammad Nikkhoo Ya-Wen Kuo, Yu-Chun Hsu, Kinda Khalaf, Mohammad Haghpanahi, Mohamad Parnianpour and Jaw-Lin Wang PDF (256K)
Abstract: The investigation of dynamic response of intervertebral disc is beneficial for the development of new synthetic and engineered tissues for treating diseased or injured disc. There are limited experimental studies on comparing the effect of loading mode and rate on global response of intervertebral disc. In this study, in-vitro experiments were performed using a total of 24 porcine motion segments. The harvested specimens were assigned to prolong and 2 different cyclic loadings. Both disc deformations and water contents were measured to investigate how the mode and rate of loading affect the response of intervertebral disc. In parallel, a backward FE poroelastic model combined with in-vitro experiments were used to find the material properties of intervertebral discs. The experimental result showed that the final disc height loss under creep loading was significantly greater than cyclic groups. Increasing the frequency of cyclic loading decreased the disc height loss. The water content decreased significantly in cyclic loading from those in prolong loading. The backward FE models showed that, the elastic modulus of anulus fibrosus and nucleus pulposus were 2.43 (±0.48) MPa and 1.46 (±0.29) MPa, respectively. The hydraulic permeability was 2.08 (±0.42) ×10-16m4/Ns, and the Poisson’s ratio was 0.21 (±0.03). In conclusion, this study investigated how the loading mode and rate affect porcine intervertebral disc deformation. It is found that dynamic stiffness is greater at higher frequencies which resulted from interactions between the solid phase and fluid flow within the disc.
Keywords: Porcine intervertebral disc, Time-dependent response, Poroelastic FE model, Creep, Cyclic loading, Response surface methodology
Static structural CAE analysis of symmetrical 65Si7 leaf springs in automotive vehicles
, Pages: 59-74
Vinkel Kumar Arora Gian Bhushan and M.L Aggarwal PDF (256K)
Abstract: Leaf springs in vehicles are used to absorb, store and release energy. During this cycle stresses induced in the springs must not exceed design stress, in order to avoid settling or premature failure. Number of experiments are done in order to determine the stresses, load rate and deflection, which involves lot of time and cost. Today, the technologies in leaf springs are changing gradually; therefore new tools are required to keep aligned with worldwide technological requirements. The work presented in this paper provides a CAE solution to static analysis of 65Si7 leaf springs used in light commercial vehicles (LCV’s). A practical model of leaf spring used in LCV has been taken into consideration for this study. It has been experimentally tested for deflection, stress and load rate on a full scale leaf spring testing machine. A static structural CAE analysis of leaf spring has been done under similar loading condition. The CAD model of the leaf spring has been prepared in solid works and analyzed using ANSYS. Using CAE tools, ideal type of contact and meshing elements have been proposed to achieve results closer to the experimental results. The analytical method for static analysis of the leaf springs has also been described. CAE results have been compared with experimental and analytical results for validation.
Keywords: Static Structural analysis, Leaf springs, Computer Aided Engineering (CAE), 65Si7, Load rate
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