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RISS 인기검색어
- 검색키워드
- 저자 : Abolfazl Darvizeh (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Abolfazl Darvizeh,Mansour Darvizeh,Reza Ansari,Ata Meshkinzar 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10
In this paper, the energy absorption characteristics of grooved circular tubes are investigated under quasi-static loading condition. Forexperiments, thick-walled tubes with circumferential grooves are prepared. The grooves divide the thick-walled tube into several shorterthin-walled portions. Specimens are subjected to axial crushing load to observe the effect of distribution of circular grooves on the deformationmechanism and energy absorption capacity. Geometrical parameters of the specimens are designed utilizing the Taguchimethod to cover a reasonably wide range of groove length-to-wall thickness ratios. An analytical approach based on the concept of energydissipation through the plastic hinges is applied. Taking the effect of strain hardening into account, the obtained analytical results arein good agreement with the experimental ones. The agreement between analytical and experimental results may indicate the validity ofthe proposed analytical approach. Desirable mechanism of deformation observed justifies the pre-forming method for obtaining favorableenergy absorption characteristics.
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Analytical and experimental studies for deformation of circular plates subjected to blast loading
Hashem Gharababaei,Abolfazl Darvizeh,Mansour Darvizeh 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.9
In this paper, experimental responses of the clamped mild steel, copper, and aluminum circular plates subjected to blast loading are investigated. Extensive experimental results concerning variations of central deflection are presented. Approximate energy analysis is used for the analytical modeling of the mid-point deflection thickness ratio of the circular plates. The essence of the model is to describe the deformation profile, which depends on the distribution of impulsive load. By using the present modeling, one can show how the midpoint deflection varies with the variations of the important parameters. The results obtained from the present model show very good agreement with the experimental data.
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Effect of Nanoclay Addition on the Hygrothermal Durability of Glass/Epoxy and Fiber Metal Laminates
Moslem Najafi,Abolfazl Darvizeh,Reza Ansari 한국섬유공학회 2018 Fibers and polymers Vol.19 No.9
This article investigated the effect of adding montmorillonite nanoclay on the hygrothermal durability of glass/ epoxy (GE) composites and fiber metal laminates (FMLs). Experimental results indicated that the addition of nanoclay to both GE composites and FMLs increases water absorption, but reduces diffusivity as compared with the neat specimens. The flexural strength, flexural stiffness and impact properties of GE composites were negatively affected by hygrothermal aging and decreased by 24.76 %, 18.98 %, and 9.53 %, respectively, while these values for the aged FMLs were only 10.05 %, 4.40 %, and 4.14 %, respectively. It was also found that the addition of nanoclay can enhance the flexural and impact properties of both laminate types especially GE composites in both the pristine and post-aging conditions. The GE composites filled with 3 % nanoclay exhibited the enhancement of 10.73 %, 8.03 %, and 6.95 % in flexural strength, flexural stiffness and impact strength over neat GE composites, whereas these values were found to be only 1.35 %, 0.50 %, and 0.51 % in FMLs with 3 % nanoclay. In addition, the aged GE specimens with 3 wt.% nanoclay showed 13.45 %, 16.20 %, and 7.23 % loss in flexural strength, flexural stiffness and impact strength, respectively, while these values for aged FMLs contain 3 wt.% nanoclay were 8.63 % and 3.82 %, and 1.13 %, respectively.
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Investigation of mechanical surface treatment effect on the properties of titanium thin film
Ehsan Bazzaz,Abolfazl Darvizeh,Majid Alitavoli,Mehdi Yarmohammad Tooski Techno-Press 2024 Advances in nano research Vol.17 No.1
Using the mechanical treatments for mechanical properties improvement was rarely in the development scope before. This research approves through analytical ways that surface impacts can improve the quality of the surface significantly. This fact is approved for deposited titanium on silicone substrate. The new algorithm called minimum resultant error method (MREM) which is a direct combination of nanoindentation, FEM and dimensional analysis through a reverse method is utilized to extract the mechanical characteristics of the coating surface before and after impact. This method is extended to the time dependent behavior of the material to obtain strain rate coefficient. To implement this new approach, a new analysis technic is developed to define the residual stress field caused by surface impact as initial condition for nanoindentation. Analyzing the model in micro and macro scale at the same time was one of the main resolved challenges in this study. The result was obtaining of the constants of Johnson-Cook constitutive equation. Comparing the characteristics of the coating surface before and after impact shows high improvement in yield stress (34%), Elastic modulus (7.75%) and strain hardening coefficient (2.8%). The main achievement is that the strength improvement in titanium thin layer is much higher than bulk titanium. The yield strength shows 41.7% improvement for coated titanium comparing with 24% for bulk material. The rate of enhancement is about 6 times when it comes to the Young's modulus.
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Masir, Amin Nouroozi,Darvizeh, Abolfazl,Zajkani, Asghar Techno-Press 2018 Advances in materials research Vol.7 No.3
The mechanism of biological materials structure is very complex and has optimal properties compared to engineering materials. Top Neck mollusks shells, as an example of biological materials, have hierarchical structure, which 95 percent of its structure is Aragonite and 5 percent organic materials. This article detected mechanical properties of the Top Neck mollusks shell as a Nano composite using Nano-indentation method in different situations. Research findings indicate that mechanical properties of the Top Neck mollusks shell including elastic modulus and hardness are higher than a fresh one preserved in -50 centigrade and also a Top Neck mollusks shell preserved in environmental conditions. Nano-indentation test results are so close in range, overall, that hardness degree is 3900 to 5200 MPa and elastic modulus is 70 to 85 GPa.
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