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1

A new approach to job shop-scheduling problem

Mahdavinejad R. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 41, nr 1-2

200-206

EN

Purpose: Ant colony optimization algorithm, not only promote the ability of this proposed algorithm, but also de- creases the total working time because of decreasing in setup times and modifying the working production line. Design/methodology/approach: In this paper, single-processors jobshop scheduling problems are solved by a heuristic algorithm based on the hybrid of priority dispatching rules according to an ant colony optimization algorithm. Findings: The objective function is to minimize the makespan, i.e. total completion time, in which a simultanous presence of various kinds of ferons is allowed. The process of finding the best solution will be improved by using the suitable hybrid of priority dispatching rules. Research limitations/implications: By solving some problems as samples (i.e. Fisher’s & Tomson’s problems), this algorithm is compared with the others. Practical implications: The utilization of one processor instead of multiple one, merging the industrial control network layer into system management layer and omission of processor execution layer in each axis and optimized using of multi-tasking capability of processor. Originality/value: The results show that when the size of the problem becomes larger, the deviation from lower limit increases, but its rate decreases with the size of the problems, so that it reaches to its limit.

2

Optimization of surface roughness parameters in dry turning

Mahdavinejad R. A., Sharifi Bidgoli H.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

571-577

EN

Purpose: The precision of machine tools on one hand and the input setup parameters on the other hand, are strongly influenced in main output machining parameters such as stock removal, toll wear ratio and surface roughnes. Design/methodology/approach: There are a lot of input parameters which are effective in the variations of these output parameters. In CNC machines, the optimization of machining process in order to predict surface roughness is very important. Findings: From this point of view, the combination of adaptive neural fuzzy intelligent system is used to predict the roughness of dried surface machined in turning process. Research limitations/implications: There are some limitations in the properties of various kinds of lubricants. The influence of some undesirable factors in experiments is Another limitation in this research. Practical implications: From this point of view, some samples are machined with various input parameters and then the experimental data is used to create fuzzy rules and their processing via neural networks. So that, the prediction model is created with some experimental data first. Then the results of this model are compared with the real surface roughness. Originality/value: When the cutting speed is increased the machined surface quality is improved.The quality of machined surface is decreased with the feeding rates and the depth of cut.The error of the model is more less than the error of using ordinary equations. The comparison results show that this model is more effective than theoretical calculation methods.

3

EDM process optimization via predicting a controller model

Mahdavinejad R.A.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 3

161-167

EN

Purpose: Electro-discharge machining is an important manufacture technology in machining difficult-to-cut materials and to shape complicated contours and profiles with high material removal rate, low tool wear and good tolerances. Design/methodology/approach: In machining of carbon-based materials such as WC-Co and non-oxide ceramics which are growingly used, the complexity and non-linear nature of EDM is a serious problem. EDM is the best and nearly the only non-conventional method for machining of these kind of materials, but it shows high instability and tendency to arcing, compared with machining of steel. Occurrence of instability phenomenon due to the different input setting up parameters make the modeling of EDM process impossible with conventional methods. To achieve instantaneous data from machining condition, the new method of fuzzy analysis of single machining pulses and computing the magnitude of system condition in the form of a real number between 0 and 1, has been used. Findings: Some tests with WC-Co material are carried out and finally, the results of implementation of control system on a sinking ED machine and an EDM system that has been set with an expert user, has been compared. Practical implications: The optimization and control of EDM process using the neural model predictive control method. A genetic algorithm has also been employed to optimize the input parameters and to create the optimized setting collection of process. Originality/value: The testing results from ED machining of WC-Co confirms the capability of the system of predictive controller model based on neural network with 32.8% efficiency increasing in stock removal rate.

4

Prediction of cannon barrel life

Mahdavinejad R. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 30, nr 1

11-18

EN

Purpose: Calculation of the fatigue life based on attaining a critical defect size for fast fracture is very important. Cannon is one of the most used parts in military industries and analysis of this component is under consideration. Therefore, the prediction of its longevity to say, the number of cannon ball that can be fired till it is broken down should be under consideration. Design/methodology/approach: Obviously the number of the cracks and their sizes dictate the life of the cannon's barrel. Since the life of this component directly depends on the inner micro-cracks after numerous firing, the study of these cracks is very important. From this point of view, the stress analysis on crack tip is carried out via ANSYS software in this research. This research was to demonstrate the large changes in total fatigue life caused by the initial crack number and the residual stress at the cannon bore, the fatigue with several cracks is analyzed in the barrel according to the critical explosion pressure.The research is carried out with one, two, three, four and twenty five cracks. Findings: The methods of testing and analysis are believed to be generally applicable to problems in fatigue life evaluation. This analysis shows that the stress intensity on the tip of the crack is a function of its length and increases with the number of these cracks. Since the cannon barrel life is a convert function of the stress intensity of the cracks, multi-cracks condition passes the most fatigue cycling. The shape function of the cracks is also decreased with the number of the cracks. Originality/value: Characterization of the cracking at a cannon bore is a difficult problem. This analysis shows that the critical cycle life of the cannon barrel occurs at two numbers of the cracks.

5

Optimisation of electro discharge machining parameters

Mahdavinejad R. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 27, nr 2

163-166

EN

Purpose: Electro discharge machining (EDM) is one of the most effective non-conventional machining methods. This method is the best condidate in machining of ceramics and carbide materials. Design/methodology/approach: The complexity and non-linear nature of EDM from one side, and occurrence of instability phenomenon due to the different input setting up parameters especially in machining of carbon-based materials such as non-oxide ceramics, on the other side, make the modeling of EDM process impossible with conventional methods. What is presented in this paper is the optimization and control of EDM process using the neural model predictive control method. Findings: The results of implementation of control system on a sinking ED machine and an EDM system that has been set with an expert user, has been compared. Research limitations/implications: To achieve instantaneous data from machining condition, the new method of fuzzy analysis of single machining pulses and computing the magnitude of system condition in the form of a real number between 0 and 1, has been used. Originality/value: The testing results from ED machining of WC-Co confirms the capability of the system of predictive controller model based on neural network with 32.8% efficiency increasing in stock removal rate.

6

Fatigue study on the cracks of a cannon

Mahdavinejad R. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 27, nr 1

59-62

EN

Purpose: Cannon is one of the most usage parts in military industries and analysis of its pipe is very important. Therefore, the prediction of its longevity to say, the number of cannon ball that can be fired till it is break down should be under consideration. Design/methodology/approach: Since the life of cannon's barrel directly depends on the inner micro-cracks under numerous firing, the study of these cracks are very important. From this point of view, the stress analysis on crack tip is carried out via ANSYS software in this research. Findings: This analysis shows that the stress intensity on the tip of the crack is a function of its length and increases with the number of these cracks. Research limitations/implications: In this research the fatigue with several cracks is analyzed in the barrel according to the explosion pressure in order to find the critical conditions. Originality/value: Since the cannon barrel life is a convert function of the stress intensity of the cracks, multi-cracks condition passes the most fatigue cycling. The shape function of the cracks is also decreased with the number of the cracks.

7

Minimization of heat loss in CNC motors via a dynamic control method

Mahdavinejad R. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 14, nr 1-2

163--170

EN

Purpose: The aim of this paper is to optimize the input current so that it reaches the requested velocity-position condition with the lowest amount of misaligned magnetic field and current converted to heat. Design/methodology/approach: A new control method based on open architecture is introduced. Then the enhanced free running of pulse width modulated (PWM) driver is represented. Findings: The actual requested motor current is reached. Practical implications: The result of this dynamic control method is represented on CNC two axes cutting machine and extended to the other systems. Originality/value: 1. Execution simple and powerful algorithms with sufficient accuracy and speed and also manufacturing a sample one. 2. The current is being controlled by data output of positioning sensors. 3. Regarding to database updating of resistance force versus to the distance of each axis, it is possible to define a periodic control method to determine resistance forces of suspension CNC systems. 4. Reduction in speed error and also increasing in machined surface quality via analysis of linear speed’s error in a system of two axes which are executed by free-running PWM driver circuit with constant and variable reference voltages. 5. Increasing in working efficiency, decreasing in energy loss and long lasting of motor drives.