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Open PhD Position metal cutting

Doctoral POSITION (R1): ANALYSIS AND IMPLEMENTATION OF NEW TECHNIQUES FOR MEASURING TEMPERATURES DURING MACHINING PROCESSES

Project description

In all machining operations for chip removal, there is a series of physical magnitudes that determine the life of the cutting tool. Among these magnitudes some are easily controlled during machining (cutting speed, feed, tool, ...), but others must be predicted or measured (cutting and advancing forces, temperature, plastic deformations, vibrations) all these variables influence to a greater or lesser extent in the useful life of the cutting tool and in the quality of the surface finish. It is therefore very interesting to determine empirically and analytically, the type of correlations that are established between the two types of variables and the effect of these in the useful life of the tool. The high performance machining group has extensive experience in the measurement and simulation of these processes, but is still far from being able to predict the useful life of a tool and / or determine the conditions in which it must work to extend its life of work as much as possible without losing profitability / quality during the cutting process.

The technological objective is to i) analyse and implement new temperature measurement techniques and heat fluxes that complement the existing ones using measurement techniques with infrared cameras, pyrometers embedded with optical fiber and thermocouples and ii) the use of the obtained results to establish correlations between the temperature and other mechanical magnitudes, being of special relevance the useful life of the tool and measures of ruggedness of the mechanized piece.

Goals:

1.       To analyse and develop temperature measurement techniques and heat fluxes in the different parts of the cut (tool, chip, piece) during the machining, including measurement techniques with infrared cameras, pyrometers embedded with optical fiber and temopars.

2.       Study and determination of correlations between temperature + heat fluxes and other mechanical magnitudes related to the cutting process (cutting forces, roughness, end of life)

3.       Development of a device to determine the emissivity of different common materials in the world of machining (steels, titanium alloys, hard metals) depending on the temperature.

4.       Development of action protocols to make "Digital Image Correlation" (DIC) with high-speed infrared images in combination with images in the visible range

5.       Development of empirical, analytical and finite element models to describe the oxidation process that occurs in metals and determination of the effect of oxidation on the finish of the machined parts and the useful life of the cutting tools.

Requirements

Applicants will hold a Masters Degree in Mechanical Engineering, Manufacturing Engineering, Material Science or Physics or equivalent.

Other skills and experience (essential or desirable):

·         Experience in mechanical testing (desirable)

·         Experience in CAD and FEA (desirable)

·         Excellent English – writing and speaking (essential)

 

Doctoral POSITION (R1): MODEL OF FINITE ELEMENTS FOR THE MACHINING OF COMPOSITE MATERIALS

Project description

CFRP (carbon fibre) composite materials are used in the manufacture of structural components where the required mechanical properties are very high. They are basically a combination of two components with very different behaviour characteristics before machining: a matrix (epoxy resin generally, which acts as a binder) and a carbon fibre (which gives resistance to the material). The behaviour so differentiated of both materials involves the use of dedicated tools and special cutting conditions: High cutting speed and low forward force. PCD tool are usually used.

The usual problems that appear during machining are the short tool lifetime, the thermal and mechanical degradation of the machined material, the formation of burrs, the roughness, the geometric tolerances, etc.

In order to optimize its machining, one of the strategies to be followed, combined with experimental analyses, is the fine-tuning of numerical models (Finite Elements), which allows analysing the influence of a non-homogeneous material in the areas previously mentioned.

Goals:

1.       To develop a model that is able to define, qualitatively and quantitatively, the forces generated, temperatures, damage of the tool and the machined workpiece in machining.

2.       Development of the basic knowledge of the machining of composite materials.

3.       Development of a device for studying the process of machining of composite materials that allows the monitoring of cutting forces, temperatures ...

4.       Validate the results with experimental or empirical tests.

 

This thesis will be developed in English (documentation, presentation).

Requirements

Applicants will hold a Masters Degree in Mechanical Engineering, Manufacturing Engineering, Material Science or Physics or equivalent.

Other skills and experience (essential or desirable):

·         Experience in Finite Element Modelling (desirable)

·         Excellent English – writing and speaking (essential)

 

Doctoral POSITION (R1): FINISHing OF PARTS MANUFACTURED BY ADDITIVE MANUFACTURING THROUGH MACHINING

Project description

The ASTM F2729-12 standard defines additive manufacturing (AM) as "the process of joining materials to make objects from 3D model data, usually layer by layer, as opposed to subtractive manufacturing methodologies, such as traditional machining". AM techniques represent a set of processes based on the manufacturing of complex parts through the addition of material. Although AM has been used to process materials for more than three decades, it has not been considered an important commercial manufacturing technology until recently mostly due to the lack of manufacturing precision and methodologies to certify AM processes. This is especially valid for AM of metals (AMM), as the main potential consumers of the AMM parts – aeronautics, defence and medicine – are highly demanding for precision and reproducibility.

However, without correct processing and finishing, AMM components can fail in the early stages of evaluation. It is commonly admitted that in order to manufacture parts using AMM it is necessary to carry out a series of subsequent treatments to reduce the internal tension, increase the precision of the piece in required areas and achieve an adequate superficial integrity that guarantees the expected fatigue life. One of the well-accepted methods for post processing of AMM parts is machining, which provides both the accuracy and a good finish where necessary. The challenge of machining of AMM parts lays in the fact that the internal structure and thus the mechanical properties of AMM materials are substantially different from the materials produced by other methods e.g. casting or forging. This makes the existing know-how in machining (machinability, surface integrity…) to a large extend obsolete and necessitates generation of the new knowledge and protocols for machining of AMM parts.

This project is intended to cover this gap and to generate the knowledge relevant for future machining processing of AMM parts.

Goals:

To study different finishing techniques for pieces produced by AMM (mainly conventional chip removal) depending on the type of piece.

To determine differences in machinability rate between AM and conventional materials.

To propose working conditions in each case that would guarantee the level of required surface integrity.

To understand the differences between cutting process of conventional materials and AM manufactured materials..

Requirements

Applicants will hold a Masters Degree in Mechanical Engineering, Manufacturing Engineering, Material Science or Physics or equivalent.

Other skills and experience (essential or desirable):

·         Experience in mechanical testing (desirable)

·         Experience in microstructure analysis (desirable)

·         Excellent English – writing and speaking (essential)

 

DOCTORAL POSITION (R1): EXPERIMENTAL AND NUMERICAL ANALYSIS OF THE EFFECT OF MACHINING STRATEGIES ON THE DISTORTIONS OF AEROESTRUCTURAL PARTS OF ALUMINUM AND TITANIUM ALLOYS

 

Project description

With the aim of reducing fuel consumption and polluting emissions, the construction of aircraft with lighter structural elements is increasingly required. To this end, high-strength and damage-tolerant alloys are used, which make it possible to design parts with thinner thicknesses. Commonly, aluminum alloys are used to manufacture these lightened aero structural parts, due to their high specific resistance, low cost and good manufacturability properties. To a lesser extent, in certain critical components, titanium alloys are also used. However, these structural components are easily distorted during the manufacturing process, mainly as a consequence of the initial residual stresses of the raw material (caused by the rolling or forging processes and heat treatments), the high rate of material removal during machining (up to 90%) and the thermo-mechanical loads generated during this last process. Frequently, the final distortions require correction processes that increase the cost of the component or, in the worst case, lead to rejection of the part.

The general objective of this thesis is to study the effect of machining strategies on the final distortions and develop a predictive numerical model that allows selecting the machining strategy that minimizes distortions. For this purpose, characterization tests of the raw material (mechanical properties and measurement of residual stresses), machining tests of parts with different geometries and cutting strategies, and characterization of the final part (geometric distortions and final residual stresses) will be carried out. These results will be used to develop a finite element model with the ability to predict the final distortions depending on the starting material, machining strategies and cutting conditions.

Requirements

Applicants will hold a Masters Degree in Mechanical Engineering, Manufacturing Engineering, Material Science or Physics or equivalent.

Other skills and experience (essential or desirable)

·         Experience in CAD and FEA (desirable)

·         Experience in computer programming (desirable)

·         Experience in machining (desirable)

·         Excellent English – writing and speaking (essential)

Comments

If you are interested in the positions, write an email to man_rod1@hotmail.com or rodjua@ltu.se

 

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