Anna Dziubińska

Investigation of ignition temperature, time to ignition and chip morphology after the high-speed dry milling of magnesium alloys

Purpose The purpose of this paper is to determine time-to-ignition of magnesium alloy chips and the ignition-preceding stages as well as to examine chip morphology. The tests were conducted according to the following pattern: directly after a milling operation, after ignition using a special test stand located outside the machine tool and after intensive oxidation which prevented ignition. Design/methodology/approach Milling is a machining process widely used in the manufacturing of various parts that are applied, e.g. in the aircraft industry. Milling is used for both roughing and finishing machining. In the dry machining of magnesium alloys, spontaneous ignition can occur; therefore, the analysis of chip temperature in the cutting area is of great significance. Additionally, time-to-ignition and chip morphology are crucial when considering the safety of magnesium alloy machining processes. Findings The experimental results demonstrate the effect of parameters of the milling process on time-to-ignition of chips made of magnesium alloys AZ31 and AZ91HP. The experiments also involved examining the morphology of a selection of chips produced at the maximum cutting velocity vc and feed per tooth fz. In addition, we analysed the morphology of both ignition products and chips subjected to high temperature where ignition did not occur. Practical Implications Based on the time-to-ignition and chip morphology results, it is possible to indicate both safety levels in machining and the efficient range of parameters in the milling of aircraft parts made of magnesium alloys. Originality/value The paper presents a new approach to assessing safety in milling operations. The results of the tests of chip flammability (time-to-ignition) which were run at a special test stand placed outside the machine tool enabled determination of both safety and efficiency range of the milling process.

Forming of flat parts with ribs from magnesium alloy

Purpose – The purpose of this research is working out of a new forming technology of flat parts with ribs from magnesium alloys with the application of a three-slide forging press (TSFP) for the aircraft industry. Design/methodology/approach – New possibilities of forming aviation parts with ribs gives the application of a prototype TSFP. This press consists of three moveable tools and has wider technological possibilities than typical forging machines. It was assumed that this machine (press) application would allow for obtaining ribbed flat forgings from magnesium alloys of good functional and resistance qualities. A characteristic feature of such forgings forming is the working movement of two side tools, which upset the billet in the form of a plate; the result of their action is forming of one or more ribs in the plane central part. It is possible to use the upper punch to form appropriate rib outline. Theoretical research works based on simulations by means of finite element method were conducted fo...

A new technology for producing AZ31 magnesium alloy aircraft brackets with a triangular outline

Purpose This paper aims at working out an innovative technology of aircraft brackets with a rib of a triangular outline manufacturing from magnesium alloy AZ31 based on forging process. Design/methodology/approach Theoretical analysis of the assumed forming process of brackets with a rib of a triangular outline was made on the basis of computer simulations in software Deform 3D, basing on finite-element method. Research works were conducted for a magnesium plate from magnesium AZ31 alloy. Considering calculations, the scope of technological parameters guaranteeing the process proper course and good quality of the product was determined. Theoretical results were verified using a three-slide forging press. Findings The experiment’s results confirmed the effectiveness of the worked-out technology and the rightness of its application at manufacturing of brackets from non-ferrous metals used in the aircraft industry. Practical Implications The main aim of the worked-out method is manufacturing of aircraft brackets from light metals alloys, e.g. magnesium alloys. This technology can be applied for plastic forming of flat parts with ribs of a triangular outline. Manufacturing of aircraft brackets, basing on that worked out by the author’s technology, will allow for the improvement of products’ quality and reduction of their manufacturing costs. Originality/value The originality of this paper is based on the presentation of a new, innovative manufacturing technology of brackets with a rib of a triangular outline. The presented method is a unique one at a national (Poland) and global scale, and its assumptions underwent patent protection.

THE FORMING OF MAGNESIUM ALLOY FORGINGS FOR AIRCRAFT AND AUTOMOTIVE APPLICATIONS

The paper presents the theoretical and technological aspects of forming magnesium alloy parts for aircraft and automotive applications. The main applications of magnesium alloys in the aircraft and automotive industries are discussed. In addition, the forging technology for magnesium alloys is generally described, with a particular emphasis on wrought alloys. A brief outline of the state of the art in the forging of magnesium alloys is given based on a survey of the specialist literature and the results of previous research by the authors.

A new method for producing magnesium alloy twin-rib aircraft brackets

Purpose – The purpose of the present paper is to develop a new technology for producing magnesium alloy twin-rib aircraft brackets by the forging method. Design/methodology/approach – An overall description of magnesium alloys is given, with particular emphasis placed on magnesium wrought alloys that are used in the aircraft industry. Methods for producing ribbed brackets are discussed and the location of these parts in aircraft structure is described. The forging process for producing AZ31 magnesium alloy twin-rib brackets was modelled numerically, and selected results of the simulations performed are presented. The simulation results were then verified under laboratory conditions using a three-slide forging press equipped with three movable working tools. It was assumed that the use of this machine would allow for obtaining twin-rib aircraft brackets with improved both functional and strength properties compared to the production methods used so far. Findings – The results demonstrate that the method de...

Investigation of the Effect of Forging Temperature on the Microstructure of Grade 5 Titanium ELI

The paper reports the experimental results of an investigation of the effect of forging temperature on the microstructure and hardness of Grade 5 titanium ELI. A growing interest in the use of titanium alloys in implantology results from their unique properties. Grade 5 titanium ELI is widely used in medicine for producing a variety of implants and medical tools such as hip, knee and shoulder joints; bone plates; pacemaker casing and its components; screws; nails; dental materials and tools. In the first part of the paper the properties of Grade 5 titanium ELI are described and examples of medical applications of this alloy are given. In a subsequent section of the paper, forging tests performed on this biomaterial in a temperature range from 750°C to 1100°C are described. Following the forging process, the results of the titanium alloy’s microstructure and hardness are reported. The experimental results are used to determine the most suitable forging temperature range for Grade 5 titanium ELI with respect to its microstructure.

A study of a new screw press forging process for producing aircraft drop forgings made of magnesium alloy AZ61A

Purpose The aim of this study was to develop a die forging process for producing aircraft components made of magnesium alloy AZ61A using a screw press. Design/methodology/approach The proposed forging technique was developed based on the results of numerical and experimental research. The required forging temperature was determined by upsetting cylindrical specimens on a screw press in order to examine both plasticity of the alloy and quality of its microstructure. The next stage involved performing numerical simulations of the designed forging processes for producing forgings of a door handle and a bracket, both made of magnesium alloy AZ61A. The numerical modelling was performed using the finite element method-based on simulation programme, Deform 3D. The numerical results revealed that the forgings are free from material overheating and shape defects. In addition to this, the results also helped determine the regions which are most prone to cracking. The final stage of the research involved performing ...

New Method for Forming Brackets with a Triangular Rib

This paper presents the experimental research results concerning a new method of forming of brackets with a triangular rib. The forging process of products with ribs was conducted applying a three-slide forging press (TSFP) on material model in the form of lead plates. During the experiment, the influence of the process particular parameters on the obtained products quality was analyzed. On the basis of the research results the main failure modes of the material during processing were determined. The limiting value of the plate upsetting coefficient depending on its length was given. Considering conducted research works, it was stated that it is possible to form such brackets forgings in TSFP in accordance with the worked out method.

FLOW STRESS MODEL FOR COLD-FORMED 40HM CONSTRUCTIONAL STEEL

The paper presents the results of research undertaken to investigate cold forming process for 40HM constructional steel suitable for heat treatment. In the first part of the paper, mechanical properties of this steel and its industrial applications are described. The second part of the paper presents the results of the analysis of flow curves for two kinds of steel specimens: those that were subjected to annealing and those that did not undergo any heat treatment. It was found that the application of heat treatment had a significant effect on improving the forming conditions for this steel at room temperature. The experimental flow curves obtained in a compression test were described by constitutive equations illustrating the dependence between flow stresses and strain value. In order to determine the equation coefficients, the Generalized Reduced Gradient method implemented in Microsoft Excel was used. Based on the obtained equations, a material model will be developed to perform numerical simulations of cold forming for 40HM steel, using FEM-based software that aids the design of metal forming technologies. Keyword: flow stress, 42CrMo4 constructional steel, cold forming.