Badis Haddag

Active vibration control of composite plate with optimal placement of piezoelectric patches

ABSTRACT The active vibration control of a composite plate using discrete piezoelectric patches has been investigated. Based on first order shear deformation theory, a finite element model with the contributions of piezoelectric sensor and actuator patches to the mass and stiffness of the plate was used to derive the state space equation. A global optimization based on LQR performance is developed to find the optimal location of the piezoelectric patches. Genetic algorithm is adopted and implemented to evaluate the optimal configuration. The piezoelectric actuator provides a damping effect on the composite plate by means of LQR control algorithm. A correlation between the patches number and the closed loop damping coefficient is established.

A study of the BTA deep drilling process through a quantitative and qualitative analysis of the chip formation process

This paper deals with the analysis of the cutting process in the BTA (Boring Trepanning Association) deep hole drilling. The process is a major technique of drilling when the machining with a conventional tool is not possible. Poor training and/or poor chips evacuation often cause a temperature rise and excessive wear detrimental to the tool life and the dimensional stability of machined parts. The process is relatively not explored enough, because it is difficult to instrument experimental tests (measurement of forces acting at each insert of the BTA drilling tool, temperature at each cutting edge…). Moreover, the thermomechanical phenomena related to the cut are localized at the end of the BTA drilling head and confined in a zone inaccessible to the observation. Hence, a study of this process based on a scientific approach has been proposed. The evaluation of the chips morphology has been performed. Indeed, it is a good indicator of the stability of the cutting process and it can therefore be a serious help in the selection of optimal cutting parameters. Adequate parameters are proposed to highlight the impact of cutting conditions on the cutting process. Macro and microscopic observations of generated chips under several cutting conditions are performed. Fragmentation and segmentation of chips are some examples of analysed phenomena. In this sense, experimental tests have been conducted. The chips have been sorted according to their morphology and identified according to their origin and then proposed physical parameters are assessed. The quantitative and qualitative analysis of chips allowed identifying the impact of the cutting speed and feed rate on the cutting process.

Analysis of coating performances in machining titanium alloys for aerospace applications

The current study emphasises the role of coating materials in enhancing the wear resistance of the cutting tool and improving the tool-chip contact. The wear mechanisms have been investigated through a series of cutting experiments performed on an instrumented planer machine. Machining tests were conducted on the usual Ti-6Al-4V alloy (workpiece) and cemented carbide tools. Four new coatings were especially designed for the study: 1diamond (thin layer, about 2 to 3 μm) 2diamond+TiB2+CrN/DLC (diamond like carbon, about 3, 5 μm) 3diamond (thick layer, 6 μm) 4TiB2+CrN/DLC (3 μm). The performance of each coating material was analysed and compared in one hand to the uncoated carbide tools and on the other hand to the CBN reinforced carbide tools in terms of cutting forces and tool wear mechanisms.

Some cases of machining large-scale parts: Characterization and modelling of heavy turning, deep drilling and broaching

Machining large-scale parts involves extreme loading at the cutting zone. This paper presents an overview of some cases of machining large-scale parts: heavy turning, deep drilling and broaching processes. It focuses on experimental characterization and modelling methods of these processes. Observed phenomena and/or measured cutting forces are reported. The paper also discusses the predictive ability of the proposed models to reproduce experimental data.