Sharif Digital Repository

The application of sensor system is becoming more commonplace in improving productivity and reliability. Although measuring force signal have been widely used for monitoring of metal machining process that their application to stone cutting has not been well investigated. In this paper, the effect of machining parameter on force signal and tool wear was investigated. The result indicate that increasing of the depth of cut and spindle speed will increase the force and tool wear while increasing feed rate will increase force and decrease tool wear  

Recently, receptance coupling substructure analysis (RCSA) is used for stability prediction of machine tools through its dynamic response determination. A major challenge is the proper modelling of the substructures joints and determination of their parameters. In this paper, a new approach for predicting tool tip FRF is presented. First, inverse RCSA formulation is extended so that the holder FRFs can be identified directly through experimental modal tests. The great advantage of this formulation is its implementation in arbitrary point numbers along joint length. Therefore, in comparison with previous inverse RCSA approaches, a more realistic joint model can be considered. In addition, due... 

Free, forced, and self-excited vibrations are the three main types of machine tool vibrations. Self-excited vibration is the most important type of destructive vibration in machining. The most important factor in increasing the chipping rate, stability, and tool life is decreasing this type of destructive vibration. In this paper, we aim to introduce a method to control the self-excited vibrations by the means of the combining a vibration absorber as a passive controlling method and a classical active controller such as PID or compensator or the other classical methods. Utilizing the SIMULINK toolbox of MATLAB software, first, we designed and added the vibration absorber to the model... 

This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the... 

In high speed machining of hard materials, tools with chamfered edge and materials resistant to diffusion wear are commonly used. In this paper, the influence of cutting edge geometry on the chip removal process is studied through numerical simulation of cutting with sharp, chamfered or blunt edges and with carbide and CBN tools. The analysis is based on the use of ALE finite element method for continuous chip formation process. Simulations include cutting with tools of different chamfer angles and cutting speeds. The study shows that a region of trapped material zone is formed under the chamfer and acts as the effective cutting edge of the tool, in accordance with experimental observations.... 

In some tasks, a rigid robot manipulator handles a long, slender, and flexible tool, which usually has not been equipped with vibration measuring devices. This situation makes a different tool tip position control problem. In this paper, a new method will be presented for simultaneous tip position and vibration suppression control of a flexible tool on a rigid-link 3-DOF robot. This approach uses fuzzy logic rule-based controllers without using any sensors and actuators on the tool or a priori knowledge about the tool. Numerical simulation of robot and tool set has been accomplished and results support the fact that designed fuzzy controllers perform remarkably well in reducing vibrations... 

This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the... 

One of the major challenges in the manufacturing parts, especially metals, is turning with good/excellent surface quality, which has a significant effect on the fatigue strength of the industrial components. Selecting incorrect or unsuitable values of machining parameters leads to vibration instability in the cutting tool and as a result, excessive roughness is created on the product’s surface. Therefore, one of the ways to reduce the roughness factor and increase the product fatigue life is to control the relative slip and vibration between the cutting tool and the workpiece. To achieve this goal, the authors attempted to investigate the simultaneous effects of tool overhang and cutting... 

Inaccuracies in workpiece location lead to errors in position and orientation of machined features on the workpiece, and strongly affect the assemblability and the quality of the product. The accurate positioning of workpiece on a fixture is influenced by rigid body displacements and rotations of the workpiece due to several errors (e.g. geometric radial and position errors in locators and manufacturing tolerances of the workpiece). In this paper, an efficient approach is introduced for analysis and compensation errors in the workpiece-fixture-cutting tool system. A new mathematical formulation of workpiece-fixture modelling is proposed to establish the relationship between the locating... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system... 

In this paper, bifurcation analysis is performed for the nonlinear milling process under sub-harmonic resonance and regenerative chatter, with tool wear and process damping effects. Multiple-scales approach is used to construct analytical approximate solutions for non-autonomous parametrically excited equations of the system with time delay terms. The new bifurcation parameters are the detuning parameter (deviation of the tooth passing frequency from three times of the chatter frequency), damping ratio (affected by process damping) and tool wear width. Jump phenomenon and multi-values responses are observed in the first order solution under sub-harmonic resonance condition. Periodic,... 

Ultrasonic-assisted machining is an advanced method which could improve the process of machining. Besides, simulation modeling process is a method to help the researchers analyze different aspects of the process with more details in a shorter time. Simulation of ultrasonic-assisted machining is also a field of research that is of interest to researchers working in the field of machining processes. In recent years, a variety of papers have been published where cutting forces, chip formation, tool wear and temperature, and microstructure changes were simulated. That being the case, a review paper is required to represent the advances implemented by researchers in the simulation of... 

ARX algorithms are a class of symmetric-key algorithms constructed by Addition, Rotation, and XOR. To evaluate the resistance of an ARX cipher against differential and impossible-differential cryptanalysis, the recent automated methods employ constraint satisfaction solvers to search for optimal characteristics or impossible differentials. The main difficulty in formulating this search is finding the differential models of the non-linear operations. While an efficient bit-vector differential model was obtained for the modular addition with two variable inputs, no differential model for the modular addition by a constant has been proposed so far, preventing ARX ciphers including this... 

In this paper, a new method is proposed to determine parameters of some types of fractional order models to represent a system dynamics using its step response. The model structure is assumed to have rational commensurateorder as α = M/N . By this assumption infinite terms of the model step response is converted into finite terms limited to N. The proposed method is practically applicable on all fractional order model structures due to the order approximation imposed by the limited precisions in available computational tools