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Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    209-224
Measures: 
  • Citations: 

    0
  • Views: 

    303
  • Downloads: 

    0
Abstract: 

In the present study, the wake flow field of a submarine model was investigated experimentally in a wind tunnel. The experiments were conducted to determine the effect of the location of control surfaces on the wake inflow to the impeller of the submarine. In order to investigate the effect of the location of control surfaces as the most important innovation of the present study, the aforementioned surfaces were installed in three longitudinal positions 𝑋 ⁄ 𝐿 = 0. 89, 0. 92, 0. 95 on the heel of the submarine model, and the wake flow was measured at the position 𝑋 ⁄ 𝐿 = 0. 978 and the Reynolds number 6 × 105 by a five-hole probe and a hotwire anemometer. Finally, the longitudinal position 𝑋 ⁄ 𝐿 = 0. 95 was selected as the optimal location for the stern planes to improve the wake inflow to the impeller in terms of reducing its total area and the least amount of turbulence and non-uniformity. The results obtained during this study showed that arriving of the holder base's wake to the stern area increases the area and average velocity and subsequently reducing the non-uniformity of the wake flow.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    225-233
Measures: 
  • Citations: 

    0
  • Views: 

    319
  • Downloads: 

    0
Abstract: 

Delamination is one of the most common damage modes in laminated composites that can reduce the stiffness and load-bearing capacity of the composite structure, which highlights the importance of studying this phenomenon. For this purpose, the effect of the interface fiber angles on the mode II fracture toughness of plain-woven laminated composites has been investigated in this study. The end notch flexure specimens (ENF) with 24 layers which have 0//0, 0//30, and 30//-30 interface angles are manufactured using the hand layup method, and experimental tests are conducted on them in accordance with ASTM standard under load II mode loading. Experimental results show that the interface fiber angle has a significant effect on the initiation and propagation of delamination toughness, so the load-bearing capacity of the specimens with the non-zero interface fiber angle was the highest value. Moreover, the initiation and propagation value of fracture toughness for specimens with 0//0 interface fiber angle was less than the corresponding values for other samples with non-zero interface angles. In addition, the fracture process zone (FPZ) length was approximately the same for all samples. Taken images of fracture surfaces using scanning electron microscopy (SEM) show that in addition to the separation of fibers from the resin at delamination, other damage mechanisms including fiber breakage and highly deformed matrix play a key role in increasing the fracture toughness of the sample with 0//30 and 30//-30 interface fiber angle.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    235-245
Measures: 
  • Citations: 

    0
  • Views: 

    338
  • Downloads: 

    0
Abstract: 

In this research, the abrasion resistance of the parts manufactured by Additive Manufacturing (AM) has been experimentally analyzed. These days, the AM is widely used in various industries and the Fused Deposition Modelling (FDM) process is one of the most popular methods of fabrication in this field. Although many researches have been done to model mechanical behavior in this field, there are limited studies in wear and its modeling. In this research, to create an exact mathematical relationship between the input variables (layer thickness, raster angle, and raster distance) and the response variable (wear rate), the experimental design using the Central Composite Design (CCD) method has been employed. Moreover, twenty systematic experiments were performed to determine the response and provide a proportional regression model. Using analysis of variance (ANOVA), a mathematical model corresponding to the actual process was obtained, and the validity of the proposed model was confirmed by statistical methods. The results have indicated that the proposed model predicts the wear rate of Acrylonitrile Butadiene Styrene (ABS) parts made by FDM method with the coefficient of determination of 97. 44%. Furthermore, the results of the experimental study and experimental analysis have shown that the raster distance parameter and the effect of its interaction with the raster angle, creates the highest wear rate, and also the second-order effect of layer thickness has the most negative effect on wear rate.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    247-261
Measures: 
  • Citations: 

    0
  • Views: 

    386
  • Downloads: 

    0
Abstract: 

Forming Limit Diagrams (FLDs) are very useful measures for safe forming of sheet metals without failure due to necking or fracture under different loading conditions. This paper uses ductile fracture criteria to predict the formability of low carbon steel sheets to evaluate their accuracy in predicting the FLDs. In addition, the fracture forming limit curves (FFLD) and necking forming limit curves (NFLD) for St12 low-carbon steel have been extracted experimentally and numerically. In the experimental procedure, the Nakazima stretching test was used. In the numerical procedure, by defining six phenomenological ductile fracture criteria in ABAQUS / Explicit finite element software, the failure is predicted and compared with the experimental results. These criteria were calibrated using 6 tests namely as In-plane shear, uniaxial tensile test, circle hole test, notched tension test, plane strain test, and Nakazima stretching test. The results showed that the criteria, which include both the stress triaxiality (η ) and Lode parameter (L), provide a more accurate prediction of failure. Also to predict necking during numerical simulation of Nakazima test and also to extract the NFLD, three criteria of the second derivative of major strain, the second derivative of thickness strain and the second derivative of equivalent plastic strain have been used.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    263-272
Measures: 
  • Citations: 

    0
  • Views: 

    375
  • Downloads: 

    0
Abstract: 

The sandwich panel is a combination of a soft core and two stiffs, high-strength facesheets. In many cases, the connection between the facesheet and the core is considered as a critical point that can damage the integrity of the sandwich structure. In this study, the debonding toughness between the facesheet and the core has been experimentally measured in sandwich beams with grooved cores made of Kevlar 49/polyester facesheets and polyurethane foam core. The values of the strain energy release rate, obtained at the onset of crack growth for the tested specimens, are in the range of 340 J/m2 and increase with the crack growth up to 500 J/m2. One of the innovations of the present study is to investigate the effect of grooving the sandwich panel core on the structure resistance to the growth of interfacial cracks. The results show that by placing the groove inside the core of the sandwich panel, the interfacial crack stops during growth by hitting each groove and requires higher force to restart its growth. This phenomenon increases the resistance of this type of structure against the growth of cracks in the face/core area. In this research, a model based on cohesive zone theory was used to simulate crack growth in the tested specimens. Comparison of loaddisplacement curves obtained from the analysis shows that the proposed model has a good ability to predict the behavior of the structure under similar loading conditions.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    21
  • Issue: 

    4
  • Pages: 

    273-284
Measures: 
  • Citations: 

    0
  • Views: 

    707
  • Downloads: 

    0
Abstract: 

The hands are one of the most complex moveable organs of the human body. Some reasons such as stroke can cause disorder in hand functions. These patients face problems doing their daily routines. The communication between humans and robots leads to the invention of devices for improving the patient’ s ability. This paper aims to design and manufacture a prototype of a portable wearable robot. This robot has been designed to facilitate the daily routines of patients who are not able to extend their hands. Researchers are facing challenges like high cost due to numerous actuators and these sensors are used to control the system. As the number of elements used to build the device increase, the ultimate weight of the device, also, grows, and practically it loses portability. According to the importance of portability of the robot and the need for long-term use by the user, device components with less weight are designed in this work. In the introduced mechanism, a torque is applied to the lowest metacarpophalangeal joints simultaneously by only one electric operator; therefore, fingers are opened. The power transmission system is inspired from the hand tendon with the help of the cable length changes. Because of disturbances and nonlinearity of the system, a sliding mode controller to minimize the error is designed. The results demonstrate that the joint angle converges to the desired angle, and the error tends to zero. Good results, in addition to the affordable price, and suitable weight imply that we can trust the extensibility of this project.

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