International Journal of Mechanical and Materials Engineering最新文献

Friction stir welding (FSW) of 6-mm-thick plates of AA6061-T651 was carried out using a simple cylindrical pin tool. The impact of welding factors (rotational speed, welding speed) on tensile properties, microhardness, and surface roughness of FSW joints was investigated. Ultimate tensile strength (UTS), yield strength, and % elongation of AA6061-T651 base plate as well as FSW joints were found out using a universal testing machine (UTM). Maximum value of UTS and yield strength were achieved at rotational speed of 1400?rpm and welding speed of 20?mm/min. Minimum surface roughness was reached at rotational speeds of 1400?rpm and welding speed of 20?mm/min. Microstructural evolutions in the friction stir welded (FSWed) joint and microhardness profile were also determined. Maximum hardness of HV 120 was acquired for the stir zone (SZ). Hence, attainment of the maximum tensile strength, microhardness, and minimum surface roughness during FSW is a desired method to improve the service life and suitability of AA6061-T651.

Friction stir welding (FSW) is a solid-state welding technique, which two workpieces join by pressure and large plastic deformation near their melting points. The tool offset, pin offset, and position of dissimilar alloys can highly affect the maximum temperature and heat distribution in FSW process. In current research, the effects of three mentioned variables on the maximum temperature of FSW of AA6061 and AA5086 alloys have been investigated. In this manner, Response Surface Methodology (RSM) as an auxiliary method has been used. The results show that pin offset is the most effective parameter affecting maximum achieved temperature. In all pin and tool offsettings, placing the harder alloy (AA6061) at advancing side results in more maximum temperature increment compared to the case which the harder alloy is at the retreating side.

The machining capability of metal composites is different compared to other materials because of their specific physical and mechanical properties. The aluminum composite A413 reinforced with Alumina powder is one of the materials which causes rapid erosion of the tool if traditional machining methods are employed. In this research, the electrical discharge machining experiments were conducted using the Taguchi method. After analysis of variance (ANOVA) using simultaneous analysis of total normalized quality loss (TNQL), and signal-to-noise ratio (S/N) of outputs, the effect of each parameter such as current intensity, voltage, pulse on-time and pulse off-time have been investigated. These parameters are influential on material removal rates, surface roughness, and tool wear ratio of electric discharge machining in two cases of with alumina powder and without alumina powder in dielectric. The outcomes of this research indicate that the use of Alumina powder 3?g/L in kerosene dielectric averagely reduces the material removal rate by 7.8%, increases the surface roughness by 8.8%, and decreases the tool wear ratio by 1.3%. Also, the results of analysis of total normalized quality loss and signal-to-noise ratio of the experiment have been shown as the first level of voltage (A₁), the first level of current intensity (B₁), the first level of pulse on time (C₁), and the third level of pulse off time (D₃).

Composite material is being used in vehicles for protective structures against blast loading. Limited data is available which compare experimental works and numerical analysis in the open field environment. More data is needed in this area in order to be able to predict and use composite materials safely.

In this work, the response of woven glass/epoxy composite plates under blast loading was investigated, both experimentally and numerically. The plate was manufactured using glass/epoxy woven Cytec 120?°C curing system. The explosive material was Tri-Nitro-Toluen (TNT) with different masses, which are 60, 80, and 100?g. The stand-off distance was also varied, ranging from 300 up to 1000 mm. In the experimental work, a sewing needle pin was put under the plate to record the maximum deformation of the plate during TNT explosion. In the numerical analysis, LS-DYNA was used extensively. The composite plate was modeled as shell elements using MAT54, and the failure criteria was Chang-Chang failure criteria. The explosive TNT material was modeled in two different ways. First, it was modeled using CONWEP and the second was modeled using Smooth Particle Hydrodynamics (SPH). The numerical analysis results were then compared with the experimental data for the case of maximum deformation.

Experimentally, the sewing needle method was able to measure the plate maximum deformation during the explosion. The numerical analysis showed that the SPH model gave better agreement with experimental results compared with CONWEP method. The SPH results were in the range of 8–18% compared to experimental data, while the CONWEP results were in the range of 14–43%.

Albeit its simplicity, sewing needle method was able to measure the maximum deformation for blast loading experimentation. The SPH model was better compared with CONWEP method in analyzing the response of composite plate subjected to blast loading.

The axisymmetric problem in two-dimensional transversely isotropic magneto-thermoelastic (TIMT) solid due to inclined load with Green–Naghdi (GN)-III theory and two temperature (2T) has been studied. The Laplace and Hankel transform has been used to get the expressions of temperature distribution, displacement, and stress components with the horizontal distance in the physical domain. The effect of Green–Naghdi theories of type I, II, and III theories of thermoelasticity has been studied graphically on the resulting quantities. A special case for the magneto-thermoelastic isotropic medium has also been studied.

Presented are experimental results on the effect of concentration, aging, and annealing time on the optical and structural properties of sol gel zinc oxide (ZnO) and Al-doped ZnO thin films. ZnO and ZnO:Al thin films were fabricated on glass substrates using spin coating followed by annealing. XRD confirmed that the films are polycrystalline wurtzite. For low concentration films (0.2 and 0.4 M), grain size increased with aging time up to 72 hours. For high concentration samples (0.6 and 0.8 M), grain size increased only up to 48 hours. Additional aging resulted in a decrease in the grain size. The largest grain sizes were found for 0.4 M at 72 hours and 0.6 M at 48 hours. The band gap tended to decrease with increasing aging time for all concentrations. The smallest band gap for each aging time (24, 48, and 72 hours) was observed for 0.6 M films. These results suggest that higher concentration sol gel near 0.6 M may yield better properties with shorter aging times than 0.2 and 0.4 M films. Annealing data suggests that 350 ^oC is the minimum annealing at 1 hour to achieve high-quality films and higher concentration ZnO films have stronger diffraction peaks. ZnO:Al also exhibits stronger diffraction peaks and a larger blue shift of the band edge with increasing sol gel concentration.

This work aims for a novel thermoelastic analysis methodology based on experimental steady-state temperature data and numerical displacement evaluation. The temperature data was acquired using thermal imaging and used as the input for a boundary element method (BEM) routine to evaluate its consequent thermoelastic displacement. The thermoelastic contribution to the resultant displacement arises in the BEM formulation as a domain integral, which compromises the main benefits of the BEM. To avoid the necessity of domain discretization, the radial integration method (RIM) was applied to convert the thermoelastic domain integral into an equivalent boundary integral. Due to its mathematical development, the resultant formulation from RIM requires the temperature difference to be input as a function. The efficacy of the proposed methodology was verified based on experimental displacement fields obtained via digital image correlation (DIC) analysis. For this purpose, a CNC (computer numerical control) marker was developed to print the speckle pattern instead of preparing the specimen by using manual spray paint or using commercially available pre-painted adhesives. The good agreement observed in the comparison between the numerical and experimental displacements indicates the viability of the proposed methodology.

Functionally graded material shafts are the main part of many modern rotary machines such as turbines and electric motors. The purpose of this study is to present an analytical solution of the elastic-plastic deformation of functionally graded material hollow rotor under a high centrifugal effect and finally determine the maximum allowed angular velocity of a hollow functionally graded material rotating shaft. Introducing non-dimensional parameters, the equilibrium equation has been analytically solved. The results for variable material properties are compared with the homogeneous rotor and the case in which Young’s modulus is the only variable while density and yield stress are considered to be constant. It is shown that material variation has a considerable effect on the stress and strain components and radial displacement. Considering variable density and yield stress causes yielding onset from inner, outer, or simultaneously from both inner and outer rotor shaft radius in contrast to earlier researches that modulus of elasticity was the only variable. The effects of the density on the failure of a functionally graded material elastic fully plastic in a hollow rotating shaft are investigated for the first time in this study with regard to Tresca’s yield criterial. Numerical simulations are used to verify the derived formulations which are in satisfying agreement.