International Journal of Advanced Design and Manufacturing Technology
Volume:10 Issue: 2, Jun 2017

For making rivet and bolt connections, making a hole is necessary. While basic S-N graph can be extracted from design documents, analysis of stress can be used for two different approaches. The first approach is the theoretical derivation of analytical relations with simplified assumptions like planar stress or uniform bolt load distribution. The other one is the numerical simulation using robust codes like Abaqus software. By using these two approaches, residual stress distribution around the hole can be extracted in various conditions. In this experiment, an aluminium 2024-T3 plate with 3.2 mm thickness is considered. The stress analysis results and basic S-N graph were combined and discursive S-N graphs were obtained for different cold-expanded bolted holes. These graphs were compared with experimental data in several steps. First, the bolt fastening was considered. In the second step, cold expansion was considered and in the final step, the effects of fastening bolts and nuts and cold expansion was considered simultaneously. At last, a comparison between various steps was drawn. The results of this study showed that this new analytical method on distribution of residual stresses around cold expansion holes is as effectiveness as old methods.

In this paper, an expert system (ES) is developed for manufacturability evaluation of ND:YAG laser in computer based concurrent engineering. The expert system evaluates machining cycle time and cost in less than 30 seconds. Experimental verification and validity of the expert system is carried out. The results of expert system are compared with the results of experimental laser beam machine. Results are presented. The results of the expert system show machining cycle time and cost for expert system is about 10 percent less than the experimental one. In addition material is selected by the expert system. It gives valuable information to help designers and manufacturing engineers to improve design and manufacturing. The expert system links with design feature library, material database and laser beam machine database. The design specification is acquired through a feature based approach. Material database holds attributes of more than 10 types of materials. Laser beam machine database holds attributes of 2 types of laser beam machine and machine parameters. For each design feature, the expert system provides information needed for manufacturability evaluation and estimation of machining cycle time and cost. It can be used for design and manufacturing optimization. The expert system can be used as an advisory system for designers and manufacturing engineers. It can be used as a teaching program for new laser operators in computer based concurrent engineering environment.

Metal Bellows finds wide application in expansion joints, which are used in aerospace, chemical plants, power system, heat exchangers, automotive vehicle parts, piping system, petrochemical plant, refineries, etc. During service they are subjected to various stresses and exposed to different environments, which leads to failure. Hence there is a need for proper design of metal bellow as per the application. The main objective of the paper is to evaluate the stresses generated in the metal bellow and the cycle life working at different working pressures. In this paper, the stresses are calculated using Expansion Joint Manufacturing Association (EJMA) standards and compared with the results obtained using ANYS software for two different materials namely Inconel 625 and Inconel 718 for the pressure values ranging from 20 to 40 bar.

This paper presents a theoretical study on wood plastic composite's (WPCs) flow, based on empirical data provided by a twin screw extruder and experimental data from a rotational rheometer. Four circular extrusion dies were designed and manufactured to produce rod shaped products with various diameters (D) and length-to-diameter ratios (L/D). Also other parameters such as screw speed (N), polymer matrix type, polymer viscosity (m) and percentage of wood content (W) were selected as the process or material factors to investigate the relationship between the flow characteristics and the above mentioned factors. Moreover, frequency sweep experiments were performed on the selected composites using rotational plate rheometer. The results from these experiments have been studied by using power law and Bingham plastic models which are believed as proper models for WPC in the literature. The results show that Bingham plastic model can explain the flow characteristics of this composite much better. Moreover, although the results of a frequency sweep test can give the required values for parameters in the Bingham plastic model, these quantities will be different with those from empirical experiments.

An adaptive robust controller for nonlinear and coupling dynamic of aerial vehicle has been presented. In this paper an adaptive sliding mode controller (ASMC) is integrated to design the attitude control for the inner loops of nonlinear coupling dynamic of Unmanned Aerial Vehicle (UAV) in the presence of parametric uncertainties and disturbances. In the proposed scheme, the adaptation laws can estimate the unknown uncertain parameters and external disturbances, while the sliding mode control is used to ensure the fast response and robustify the control design against unmodeled dynamics with a small control effort.The synthesis of the adaptation laws is based on the positivity and Lyapunov design principle. In comparison with other sliding mode approaches, the approach does not need the upper bound of parametric uncertainty and disturbances. The navigation outer loops of small UAV instead is based on PIDs to control altitude and heading. Simulation results demonstrate that the proposed controller can stabilize the nonlinear system and also it has stronger robustness with respect to the model uncertainties and gust disturbance.

In the present study a procedure is proposed for the development of bone surface models by using point clouds that can be extracted from CT scan images. Since the images are as multiple two dimensional sections, three methods of surface fitting are considered: ruled, skinning and global approximation methods. The required algorithms were discussed in fields of image processing and curve and surface fitting. For the purpose of further exploring the modelling requirements and results, and gaining further insights into the impacts of effective parameters, a computer program was developed. By adopting a detailed case study and analysis approach, three samples of the cattle’s bones were selected and scanned with CT scan. Similar protocols corresponding to the human body bones were used during the scanning process. Subsequently, the surface models of the sample output from the program were transferred to CAD software. Moreover, the samples were scanned with COMET5™scanner after removing the flashes surrounding the bones. It was observed that although the bone surface modelling is feasible within 0.25 and 0.75 mm accuracy range with these algorithms, skinning method works better compared to other two algorithms in terms of processing speed and increasing the ratio of data compaction. The use of control points balance algorithm and smoothing the contours, used in this paper, will greatly improve the performance of the program as well.

Microgrippers can be effectively applied for handling, positioning and assembling of the micro components. In the present study, a new design of a U-shape electrothermal microgripper was fabricated and developed with the voltages correspond between 1 to 10 volts. The microgripper was made of silicone with thickness of 25 microns, and pieces between 460 to 480 microns. The proposed microgripper has a simpler design and more facile fabrication comparing to most reported electrothermal microgripper. The behavior of the microgripper was simulated in COMSOL software to measure the displacement of the arms which hold and heat generations during the voltage changes. The present microgripper has more thermal and voltage tolerance comparing to other electrothermal microgripper. Furthermore, the obtained amount of tip displacement for voltage changes is acceptable. Another simulation method based on a three layer artificial neural network model (ANN) was carried out. Feed forward back propagation algorithm was employed as training algorithm to predict the displacement. The obtained results from both models proved that ANN model had better estimation due to the mean absolute percentage error of 1.024% and determination coefficient of 0.9995. Moreover, they confirm higher capability and accuracy of ANN in prediction of arms displacement compared to FEM.

Nowadays, dieless and flexible sheet forming methods are gaining much interest in prototyping and low production. In this research, a new method is developed to change the cross-sectional area of metal tubes in a longitudinal direction without using special dies. This technique is based on the force applied by a rotary tool to the inside/outside surface wall of a tube. The forming tool is mounted on a CNC milling machine and moves spirally with a specific pitch. In order to study the effects of process parameters on the product quality, a full factorial design of experiments was designed and performed. The input parameters were the feeding depth, forming pitch and tool velocity. Three responses including roughness, minimum thickness and production time were precisely measured for this purpose. The results showed that surface quality and minimum thickness is reduced with increasing the forming pitch and feeding depth. Tool rotational velocity does not have a significant effect on the forming parameters except for production time. Using a multi-objective response optimization, forming pitch of 0.25 mm, feeding depth of 1.25 mm and velocity of 800 mm/min were found to be the best configuration.

Metal bipolar plates are the most important parts of the fuel cells and recently these plates are used instead of graphite ones. In the present study, gas blow forming of a pin-type aluminum 5083 bipolar plate has been studied. After the simulation of the process, the FE model has been validated using experimental results. Then, the effects of parameters including maximum pressure of the gas, pressurization profile and corner radius of the pin on thinning ratio and forming depth of final part have been investigated. Nine experiments were designed using the Taguchi L9 orthogonal array and the experiments were performed using the FE model. The signal to noise (S/N) ratio and the analysis of variance (ANOVA) techniques were carried out to determine the effective parameters and the contribution of each parameter. The maximum pressure of 1.2 MPa, SP2 pressurization profile and corner radius of 0.2 mm lead to the minimum thinning ratio. Also, it was found that to maximize the forming depth, the maximum pressure of 2 MPa, SP1 pressurization profile and corner radius of 0.3 mm should be selected. Also, ANOVA analysis showed that the most significant parameters on thinning ratio and forming depth are corner radius and maximum pressure, respectively.

In this paper the fracture toughness of WC-12Co coatings in optimum particle temperature in high velocity oxy fuel (HVOF) process have been studied by means of Vickers indentation. Multiple linear regression model applying Minitab, were used to determine the relationship and interaction between HVOF parameters and particle temperature. For genetic algorithm optimization, the signal to noise ratio was applied as a functional output of design of experiments. The results of validation test show a good agreement between obtained optimum condition and the results of genetic algorithm. The fracture toughness obtained by Vickers indentation shows the direct effect of particle temperature on coating toughness. The maximum amount of signal-to-noise using the genetic algorithm for velocity and temperature is 53.07 and -64.62, which equals 450.2 m/s and 1702 ºC respectively. The results show that the Fracture toughness of WC-12Co deposited by LPG fuel in smallest level of temperature is MPa(m)1/2 compared to MPa(m)1/2 in highest temperature. The spray watch diagnostic system, micro-hardness test, Vickers indentation, X-Ray diffraction, EDS and scanning electron microscopy have been used for this purpose.

Cold roll forming is a process in which a metal sheet gets a desired section form by passing through a series of rotating rollers. Predicting the amount of the distortion in pre-notched cold formed sections still remains challenging in cold roll forming industry, depending on the shape and position of the holes. This study investigates the influence of variation of the design parameters on the defects of the U-channel sections produced by cold roll forming process with circular pre-notches. To analyze the important parameters in deforming the circular holes during the cold roll forming of U-channel sections, a three-dimensional finite element model has been taken into account. A range of variation for design factors in forming the U-channel sections with pre-notches is set, including radius of circular holes, distance between the holes and the flange edge, hole spacing, sheet thickness, and type of material. Furthermore, using the response surface methodology, a set of tests are designed and modeled employing Finite Element analysis. Afterward, a set of output parameters such as edge buckling, the wave of the holes, the change in hole size, hole spacing, and the distance between the holes and the edge of the flange, are considered. Utilizing Analyses Of Variance (ANOVA), the accuracy of the linear regression models was conducted in this study. The accuracy of the simulated models is examined by comparing the analysis results with the experimental results. Finally, the effect of the important parameters on the defects of the product has been extracted in both the statistical form as well as mathematical functions applying response surface methodology. The results show that as the radius of the hole increases, edge buckling increases. The increase of the hole radius increases the edge wave on the holes. The hole width of the product is bigger and the hole length is smaller than the nominal measuring.