Journal of Aerospace Mechanics
Year:2015 | Volume:11 | Issue:3 (41) (MANUFACTURING AND PRODUCTION)|Papers Count:8

Deep drawing is one of the frequently applied methods in sheet metal forming. Optimizing the factors involved in this process is one of the most important research fields for decreasing production costs of this method. To reach optimal values of these factors, the effectiveness of each of the factors involved has to be studied by analytical, numerical, an experimental methods. Vast research has been done on the effective factors (friction, punch and die radii, blank-holder force, sheet metal substance, etc.) and the amount of effect each factor has on the deep drawing process, but there hasn't been mentionable research done on the effectiveness of geometrical symmetry and shape of the pieces produced and other effective factors on the whole process. In this article, we have used the FEM and the process simulation method (ABAQUS commercial software) and the Taguchi technique in the design of experiments (DOE) and have finally analyzed the results based on variance (ANOVA), to study the effectiveness of geometrical symmetry and shape of the pieces on the deep drawing process and the possible changes they impose on the other effective factors on the process (mechanical properties of sheet, punch and die radii, friction, blank-holder force).

The forming torque is one of the most important information needed for starting-up a roll-forming line. In this paper the effect of profile geometric parameters on the forming torque is investigated, in roll-forming of symmetric channel section. The parameters which are to be studied include sheet thickness, fold angle, flange width and web width. To end this, the torque is predicted by a neural network algorithm. Finite element simulation has been utilized to train the neural network and the simulation results were validated, comparing with existing experimental results. Then an equation is proposed to determine forming torque. The results show that forming torque is considerably affected by sheet thickness, fold angle and flange width, while the effect of web width is negligible.

In the present paper, a three-dimensional thermo-mechanical model for friction stir welding is presented. Friction stir welding (FSW) is a relatively new welding process that may have significant advantages compared to the fusion processes. Although originally intended for aluminium alloys, reach of FSW has now extended to a variety of materials including steels and polymers. This study aims to numerically explore the thermal histories and temperature distributions in a work piece during a friction stir welding process involving the butt joining of aluminum 6061-T6. In this regard ABAQUS commercial software was utilized. The process is solid state and as such, temperatures experienced near the weld are lower than those experienced during fusion welding and there are no large density changes due to a solid-liquid transformation.

Thermosonic (Sonic-IR) is a novel non-destructive testing technique (NDT) capable of detecting surface defects and fatigue cracks in different materials. The component is excited with high-power ultrasonic vibrations or other external source, causing crack surfaces rub together and generate heat. The dissipation of vibration energy and converting to heat at the faces of the crack causes an increase in temperature in the vicinity of the crack, which is imaged by the IR camera. However, the excitation in a thermosonic test is non-reproducible and can lead to cracks being undetected if sufficient vibrational energy is not applied at the crack location. This problem has caused that thermosonic is not considered as a reliable non-destructive testing technique. So, the investigation of parameters which have significant effects on temperature rise in thermosonic test is important. The vibrational energy dissipated as heat at the defect is directly related to the frequency and amplitude of the vibration. So, in this paper, a finite element modeling has been used to simulate thermosonic and the affection of these parameters on the temperature rise in the crack surfaces during sonic infrared imaging has been studied.

Because of high flexibility of the incremental sheet metal forming, it is used as a Rapid prototyping tool. The formability of the sheet can be defined in terms of four major parameters: sheet thickness, tool path, speed (both rotational and feed rate) and radius of the forming tool. In this paper unlike previous studies, the forming behavior of clad sheet or double-layers is studied in which the two layers are produced by roll bounding. The double-layers sheet have different industrial applications in various industries according to their combined properties such as aerospace, electrical, chemical, automotive and food. The influences of major parameters on the formability during the process are studied such as strength, forming force, tensility and thinning of thickness. In order to study the process parameters, the use FE simulation of the process is used. A comparison between numerical and experimental results is made to assess the suitability of model. The results for both the methods are in good agreement, which indicate that the criteria chosen for determination of the mechanical behavior of the formed sheets has been adequate. The results also show strong potentials of the finite element method for simulation of the incremental sheet forming process, with the aim of estimating the critical parameters in this process.

In this paper, dynamic analysis of doubly curved composite shells under low velocity impact is studied analytically. The governing equations based on the first-order deformation theory (FSDT) are derived for simply supported boundary conditions. The contact force history is predicted using two models of complete and improved spring-mass. Considering the displacement components as the doubly Fourier series, equations of motion shell and impactor are solved analytically. By writing code in Matlab softwar, using Galerkin method, the dynamic response of shell is obtained. In this investigation, the effect of geometrical parameters, such as curvature changes, aspect ratio (curvature length ratio), fiber orientation, mass and velocity of impactor, with constant impact energy, on the impact response of shell is determined by two models.

The elastoviscoplastic behavior of metal matrix composites with various fiber aspect ratios subjected to multi-axial loading is studied by a 3D time-dependent micromechanical model in the presence of interfacial damage. The representative volume element of the composites consists of three phases, fiber, matrix and fiber/matrix interphase. The effects of thermal residual stresses induced from the manufacturing process are included in the analysis. The fiber and interphase are assumed to be elastic, while the matrix exhibits elastic-viscoplastic behavior with isotropic hardening. The Bodner-Partom viscoplatic theory is used to model the time dependent inelastic behavior of the matrix. The Needleman model is employed to analysis interphase damage. While predictions based on undamaged interphase are far from the reality, the predicted thermomechanical behavior including interphase damage and thermal residual stresses demonstrate very good agreement with experimental data.

Electromagnetic forming is a high energy rate forming process which is applied for manufacturing and assembly of many parts that are used in automobile and aerospace industries. In this process, the electromagnetic body forces (Lorentz forces) are used to produce metallic parts. In this article, the influence of important process parameters such as discharge voltage, friction coefficient, clearance between the tube and die, wall thickness and length of tube, on the radial displacement and workpiece thinning were investigated. The output of governing equations in the form of pressure applied on the part by using a subroutine in a Fortran Program. A dynamic analysis using two dimensional axisymmetric models were performed and Johnson-Cook theory was applied to represent the effect of strain rate sensitivity and show the plastic behavior in the deformation process. Finally, the numerical results were compared with the results reported by other researchers and found a good agreement between them.