The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.

Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

Analysis of surface roughness and cutting force components in hard turning with CBN tool: Prediction model and cutting conditions optimization

Hard turning is gaining grounds for machining hardened steels as it has several benefits over grinding. There are several issues, which should be understood and dealt with, to achieve successful performance of the process. Researchers have worked upon several aspects related to hard turning. The present work is an effort to review some of these works and to understand the key issues related to process performance. The review shows that the type of tool material, cutting edge geometry and cutting parameters affect the process efficiencies in terms of tool forces, surface integrities integrity, and white layer. Adequate machine rigidity is a must essential to minimize the process inaccuracies. Also moreover, for finish hard turning, where the depth of cut is less than the nose radius of the tool, the forces deviate from the conventional trends as the radial force component is the maximum and axial force component becomes minimum. The present work finally lists down certain areas that can be taken up for further research in hard turning.

State of the art in hard turning

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

The hard turning process with advanced cutting tool materials has several advantages over grinding such as short cycle time, process flexibility, compatible surface roughness, higher material removal rate and less environment problems without the use of cutting fluid. However, the main concerns of hard turning are the cost of expensive tool materials and the effect of the process on machinability characteristics. The poor selection of the process parameters may cause excessive tool wear and increased work surface roughness. Hence, there is a need to study the machinability aspects in high-hardened components. In this work, an attempt has been made to analyze the influence of cutting speed, feed rate, depth of cut and machining time on machinability characteristics such as machining force, surface roughness and tool wear using response surface methodology (RSM) based second order mathematical models during turning of AISI 4340 high strength low alloy steel using coated carbide inserts. The experiments were planned as per full factorial design (FFD). From the parametric analysis, it is revealed that, the combination of low feed rate, low depth of cut and low machining time with high cutting speed is beneficial for minimizing the machining force and surface roughness. On the other hand, the interaction plots suggest that employing lower cutting speed with lower feed rate can reduce tool wear. Chip morphology study indicates the formation of various types of chips operating under several cutting conditions.

Machinability investigations on hardened AISI 4340 steel using coated carbide insert

Hard machining of hardened bearing steel using cubic boron nitride tool

Characteristics of Rb40 steel superficial layer under ball and roller burnishing

Natural gas transmission and distribution industry is using pipes of different origins to transport hydrocarbons under pressure. The use of poly- meric material such as polyethylene (PE) made it possible to achieve significant profits in construction times and installation costs. However, some catastrophic failures took place for various reasons. The objective of this study is to highlight the various mechanisms of rupture of PE pipes in service and in laboratory con- ditions. It is clear that at least two mechanisms control PE pipe failures based on results cumulated in operating conditions. They are nominally ductile and brittle mechanisms respectively characterizing short and long-term failures. Several laboratory tests are used to extract design data for long-term failure-type predi- ction based on stress and time to failure relationship. It remains difficult to assess the relation between creep and fatigue loadings on the one side. On the other side, the manufacturing process of the test specimens (extruded pipes and compression molded sheets) influences considerably the obtained performance for viscoelastic materials subjected to working conditions. When analyzing different results, it is found that there is a certain correlation between failure times under both constant and fluctuating loading patterns and moreover, fatigue can be used as an accelerating agent of brittle fracture which normally occurs in the long-term span and under low load levels. Brittle-to-ductile transition is studied under fatigue crack propagation mode using an energy criterion. It is found that the approach leads to critical energy rates of 211 and 695 J/m² for brittle and ductile regimes respectively. The brittle fracture damage zone is characterized by a single craze made up by locally drawn fibers and dispersed

Failure Analysis of Polyethylene Gas Pipes

Many investigations have been devoted to mechanical resistance and other general properties of plastic pipes as required by technical standards. However, very few research studies have been involved with internal and external pipe surface qualities in relation to aggressive chemical agents. The aim of this work is to present the effects of an equimolar toluene methanol (TM) mixture on mechanical and morphological properties of HDPE-100 pipe surfaces (or layers). Using optimum machining conditions, four different specimen geometries, representative of either surfaces or layers, are manufactured and subsequently aged in TM environment. Laboratory sorption experiments for inner (IL) and outer (OL) pipe layers show that equilibrium is attained within 4 days. Stress-strain tests indicate that outer and inner pipe envelopes, once separated, behave as if they were dissimilar pipes. Indeed, for the as-received pipe IL, the properties E, σy, σf, and ef exceeded those of the OL by 50%, 11%, 9%, and 6%, respectively. After 7-day exposure to TM mixture, the same trend is conserved with somewhat lower values. Most of filament properties are also in favor of the IL after 1290 days in TM mixture. It is found that E dropped significantly compared to the as-received material (OL = − 35% and IL = − 43%) while ef for OL is cut by almost two thirds. The outer surface is rougher than the inner one due to interaction with the extrusion die. As a result, the TM mixture generally causes PE swelling and narrows the gap between roughness (Rz) values with a more pronounced effect for the external surface. The value of Rz dropped from 7.15 to 2.80 μm after 1290 days, whereas the internal surface showed a slight increase up to 7%. This is explained by the particularities of the extrusion process which cools the external surface rapidly giving rise to different morphologies in pipe layers associated to the plasticizing effect of the solvent. Structural changes imparted by extrusion and TM ageing are characterized via crystallinity and oxidation induction time (OIT). It is concluded that after 1290 days, crystallinity and OIT decreased for IL and OL because of structure degradation such as anti-oxidant depletion and pigment loss. Interestingly, it is concluded that crystallinity evolution coincides with OIT progression according to lifetime and to position crosswise pipe wall.

Mechanical properties and surface roughness assessment of outer and inner HDPE pipe layers after exposure to toluene methanol mixture

As part of a Tempus project involving 9 universities (from Europe and Maghreb), an assembly of a master program with six options (specialties) has been developed. Each engaged university from Maghreb will support a Master option according to regional needs and availability of human and material resources. This paper summarizes the context of cooperation in which the project has evolved and how Badji Mokhtar University of Annaba has contributed to the development of its option. The option Mechanical Production Technologies of UBM Annaba (TsPM-UBMA) is founded with 3 engineering companies (FERROVIAL, SOMEMI and ALEMO) that are interested in the new training project. In addition, TsPM-UBMA is one of the first professionalizing degrees in the field of mechanics. The program structure, consistency with industrial corporate demand, the Joint Teaching Committee, Maghreb and European universities contributions and practical trainings are discussed. Mots clefs : Tempus, UBM Annaba, master, professionnalisant, technologie, production mécanique.

Nassereddine Zeghib

Papers

Hard machining of hardened bearing steel using cubic boron nitride tool

Characteristics of Rb40 steel superficial layer under ball and roller burnishing

Failure Analysis of Polyethylene Gas Pipes

Mechanical properties and surface roughness assessment of outer and inner HDPE pipe layers after exposure to toluene methanol mixture

Technologies de Production Mécanique : Un premier master professionnalisant en mécanique à l'Université d'Annaba