Applied Mechanics and Materials Vols. 110-116

Abstract: Nowadays Shape Memory Alloys (SMAs) are used as actuators in many applications such as aerospace structures. In sandwich structures, the SMA wires or plates are used in the skins for shape control of the structure or vibration damping. In this paper, bending behavior of sandwich plates with embedded SMA wires in their skins is studied. 3D finite element method is used for construction and analysis of the sandwich plate with a flexible core and two stiff skins. Some important points such as continuity conditions of the displacements, satisfaction of interlaminar transverse shear stresses, the conditions of zero transverse shear stresses on the upper and lower surfaces and in-plane and transverse flexibility of soft core are considered for accurate modeling and analysis of sandwich structures. Solution for bending analysis of sandwich plates under various transverse loads are presented and the effect of many parameters such as plate dimensions, loading conditions, material properties of core, skins and SMA wires are studied. Comparison of the present results in special case with those of the three-dimensional theory of elasticity and some plate theories confirms the accuracy of the proposed model.

Abstract: Industries always face severe crisis by increased scrap rate, so they are continually striving to improve process quality by reducing defective parts and controlling setup procedures for critical processes. This work concentrates on the thermoforming process of a bathtubs factory that consists of four processes: thermoforming, spray, refine and packaging. The main problem in the thermoforming process is the differences in the acrylic sheets thickness. So, this work presents a procedure applied on the thermoforming process to determine the best setup factors such as temperature, time and other independent factors of ovens, which effect on the acrylic sheets thickness. An algorithm was developed called the Best Setup (BS), is used to determine the process setup factors to eliminate the defective parts. BS combines orthogonal experimental design with ANOVA that is a suitable technique for testing the hypothesis about the mean. Also applies an optimization design for variables defined by quality control engineers.

Abstract: In this paper, the effect of load path on thickness distribution and product geometry in the tube hydroforming process is studied by finite element simulation and experimental approach. The pressure path was obtained by using finite element simulation and its validation with experiments. In simulations and experiments, low carbon stainless steel (SS316L) seamless tubes were used. The obtained results indicated that if pressure reaches to maximum faster, bulge value and thinning of the part will be more and wrinkling value will be less.

Abstract: This paper describes a finite element structural analysis model and determines analysis methods appropriate for determining the stability of the mast of a crane. This analysis model allows various analysis approaches to be applied to the conditions affecting the construction of a large gantry crane in order to ensure the stability of the mast of the crane. The finite element method is used as a way to construct an analytical model that can help ensure the stability of the mast in two stages. The model is used in a two-stage analytical process that takes into account the conditions of the model. In this way, the model can be used to judge the stability of the mast. By allowing variation in the analysis approach used for the crane mast, the analysis model may be changed if the conditions of the one-girder gantry crane require. Designers may apply this method for the active analysis of the stability of a crane mast.

Abstract: An Anti-Windup (AW) compensator is applied to the Embedded Cylindrical-Array Magnetic Actuator (ECAMA) to sustain the performance of spindle position regulation for milling machines under actuator saturation. Since ECAMA is a type of Active Magnetic Bearing (AMB), the maximum supplied coil current and the induced magnetic force are both limited by their extrema. Once the magnetic actuator is saturated, the required control input cannot be realized by the actuator as long as the magnitude of control input exceeds the upper limit of the actuator output. In this work, an AW compensator is therefore proposed and employed to compensate the output of PID controller to prevent saturation of ECAMA. By employing commercial software MATLAB/Simulink and signal processing interface, Module DS1104 by dSPACE, the efficacy of the AW compensation is practically verified by intensive experiments.

Abstract: Curvic coupling of mill turret should maintain disk weight and the cutting resistance, which occurs when the machining operation must have a power transmission function. In order to improve machining operation range, distance to the disk must increase as much as possible. But moment is increased by the lack of bearing capacity of the curvic coupling. Increase of moment is the cause of vibration/noise and degradation of machining performance, it not only a stability problem. In this study, a finite element analysis model of the mill turret is designed and considered in the method of equations for finding distance to the disk by structural analysis of Ansys workbench. Through the considered method, critical distance to the disk, and the stability of the curvic coupling are confirmed by increasing each value 10mm from 228.5mm

Abstract: This paper mainly investigate the accuracy of the computed drag on the DLR-F6 Wing-Body configuration, and analyze effect of grid and the turbulence models including the Spalart-Allmaras model, Wilcox’s k-ω model and Menter shear-stress transport model on aerodynamic forces for wing-body configuration. The computed results show that grid refinement has little effect on the pressure distributions, significant effect on drag. The turbulence models have certain effects on the pressure distributions, especially positions of the shock wave. They have obvious effects on drag, particularly friction drag. This study shows that performing the CFD calculation at the same angle-of-attack as experiment resulted in good comparisons with wing surface pressures.

Abstract: Multi-roll stretch forming process is a new flexible manufacturing technique that the general idea of discretizing is put in use in the design of stretch forming machine. In the new process, the metal sheet can be more easily formed, and the flexibility can be much higher, which the traditional process cannot compare with. In this paper, in through extensive numerical simulations of the MRSF stretching process of toroidal saddle parts, A series of finite element simulations have done for the process of forming toroidal saddle parts using different lubricant and two kinds of rollers named damped rollers and ordinary rollers. The results show that the smaller the friction coefficient is, the easier the center of toroidal saddle part is stretched. Damped rollers can increase the stretching force and the ordinary rollers can increase the mobility of sheet metal. Arranging the damped rollers and ordinary rollers at a reasonable position can make the workpiece a more uniform stretching.

Abstract: In this study, 3D finite element models were developed to evaluate the effect of canal diameter on the stress distributions of post and dentin in post-core restored endodontically treated maxillary incisor under various static loads. The results show that the posts with large diameters support more of the load, but cause high stress concentrations at the apical portion of the root, which is not desirable.

Abstract: This paper presents a simplified strain-based fracture mechanics approach to study the effect of pressure induced hoop stress on bi-axially loaded through walled cracked (TWC) pipes subjected to an external bending load in combination with internal pressure. Elastic-plastic finite element analyses are conducted to establish the relation between global strain and Crack tip opening displacement (CTOD). In the finite element model X65 pipeline steel is considered using power-law idealization of stress-strain, and the inelastic deformations, including ductile tearing effects, are accounted for by use of the Gurson–Tvergaard–Needleman model. Several parameters are taken into account, such as crack length, internal pressure and material hardening. Strain based crack driving force equation is used and maximum load criterion is adopted to determine the critical strain from ductile tearing in the cracked pipeline. The results suggest that presence of pressure-induced hoop stresses increases the fracture response in high-hardening materials and their effects are significant due to large plastic-zone size.