Search results

With the implementation of new emission standards, the thermal–mechanical coupling load of engine pistons becomes more important. In this case, forged steel material with higher fatigue limit and impact resistance has been applied gradually in piston manufacturing. However, new failure problems emerge, and the wear of skirt under boundary lubrication conditions is an essential problem which needs to be solved urgently.

In this research, the abrasion testing machine was used to simulate the wear behavior under different conditions of normal pressure, relative velocity and surface roughness. Besides, the wear morphology was observed by scanning electron microscope. Then, the wear model was established by using test results fitting method, offering a way to conduct qualitative analysis for the wear problem under the same conditions.

The results show that mainly the wear mechanism of the piston skirt under boundary lubricated conditions is adhesive wear and abrasive wear. In addition, the coefficient and wear rate will increase with the increase in the normal load and surface roughness and decrease with the increase in the relative speed. In the wear model, the wear loss is mainly influenced by the normal load, the relative sliding speed and the wear time.

The wear degree of piston skirt was qualitatively obtained in this investigation by factors such as pressure, velocity and so on, and the wear mechanism of forged steel piston skirt under boundary lubrication conditions was also determined. These could provide theoretical support for further optimization of cylinder motion and oil supply system, reduction of friction loss and power loss.

The purpose of this paper is to build a flow stress model and microstructure evolution models which can be used to fulfill the multi-physics prediction of hot forging process, in this way the process design can be virtually verified and optimized. This is especially crucial for micro-alloyed steel forging which microstructure determines the component properties, since the downstream quenching is usually not needed.

First, hot compression tests have been completed; second, experimental data are used to build the flow stress model and models for microstructure evolution; third, programming has been finished to integrate the proposed models into the commercial finite element method (FEM) code; fourth, case study is conducted to simulate multi-stage hot forging process of micro-alloyed steel F38MnV piston; and fifth, simulation results are validated by experiment.

First, simulation results in grain size and phase volume fraction are in well agreement with experimental ones; second, the austenite grain is dramatically refined by the dynamic recrystallization in pre-forging process and static recrystallization in the two intervals has no obvious change during the following final forging and cooling above the Ae3 temperature; third, during the cooling process below the Ae3 temperature, ferrite and pearlite transformation begin from the thin skirt to the thick skirt and piston bottom because of different cooling speeds at different areas.

First, flow stress model, dynamic recrystallization model, static recrystallization model, austenite grain growth model and phase transformation models are established for a micro-alloyed steel; second, the multi-physics FEM simulation of multi-stage hot forging of industrial piston has been conducted and verified by experiment, which show good agreement.

THE Mercedes‐Benz Model DB‐601A aero‐engine is a development of the Daimler‐Benz Aktiengesellschaft of Stuttgart, Germany, a firm which lias been engaged in the manufacture of automotive and aero‐engines for over fifty years. During the first World War the Daimler Motorcn Gesellschaft of Stuttgart produced the famous Mercedes aero‐engines iii three 6‐cylindcr types with ratings of 160 horse‐power, 180 horse‐power, and 260 horse‐power. Equally renowned were the 160 horse‐power and 230 horse‐power 6‐cylindcr aero‐engines built by Benz and Company in Mannheim. After the war, and as a result of the economic and financial crisis which brought almost complete stagnation to the automotive industry in Germany during the early twenties, these two companies were practically forced to combine their activities in order to survive. Accordingly in 1926 a merger was consummated between the Daimler and Benz organizations. Thus came into being the firm of Daimler‐Benz A.G. and their product, the Mercedes‐Benz line of automotive vehicles and aircraft power plants.

THE Rotol airscrew is the modern development of the Gloster‐Hele‐Shaw Beecham unit originally designed by Dr. Hele‐Shaw, developed by the Gloster Aircraft Company, and test flown in various aeroplanes some years ago. It is interesting to recall that this early British airscrew anticipated the present demand for constant‐speed control. The first models, which were arranged either for hydraulic or electric operation, had welded hollow steel or forged aluminium alloy blades; the current types, the constant speed and fully feathering hydraulic models, may be fitted with wooden blades. Unfortunately there are restrictions upon the publication of a description of the feathering airscrew, owing to a number of novel features in connexion with its design and construction, but it has been fully flight‐tested and will soon be on the Open List. However, the following description of the hydraulically operated constant‐speed model covers the latest details available for publication.

AMONG the aeroengine and aircraft parts manufactured by the drop‐forging and drop‐stamping processes are airscrew hubs and shafts, crankshafts, connecting rods, valves, valve‐rockers, camshafts, dashpot pistons, spar brackets, and windmill propellers. In addition a large number of smaller and less important parts are drop stamped to practically finished dimensions.

TO say that the Twenty‐fourth S.B.A.C. Show was an unqualified success is perhaps to gild the lily. True there were disappointments— the delay which kept the TSR‐2 on the ground until well after the Show being one—but on the whole the British industry was well pleased with Farnborough week and if future sales could be related to the number of visitors then the order books would be full for many years to come. The total attendance at the Show was well over 400,000—this figure including just under 300,000 members of the public who paid to enter on the last three days of the Show. Those who argued in favour of allowing a two‐year interval between the 1962 Show and this one seem to be fully vindicated, for these attendance figures are an all‐time record. This augurs well for the future for it would appear that potential customers from overseas are still anxious to attend the Farnborough Show, while the public attendance figures indicate that Britain is still air‐minded to a very healthy degree. It is difficult to pick out any one feature or even one aircraft as being really outstanding at Farnborough, but certainly the range of rear‐engined civil jets (HS. 125, BAC One‐Eleven, Trident and VCIQ) served as a re‐minder that British aeronautical engineering prowess is without parallel, while the number of rotorcraft to be seen in the flying display empha‐sized the growing importance of the helicopter in both civil and military operations. As far as the value of Farnborough is concerned, it is certainly a most useful shop window for British aerospace products, and if few new orders are actually received at Farnborough, a very large number are announced— as our ’Orders and Contracts' column on page 332 bears witness. It is not possible to cover every exhibit displayed at the Farnborough Show but the following report describes a wide cross‐section beginning with the exhibits of the major airframe and engine companies.

131A Aluminium Alloy Sand or Die Castings (suitable for Pistons, etc.).

ONE of the primary considerations in the design of high performance aircraft is the attainment of a high power/weight ratio for the unloaded machine, while at the same time ensuring complete reliability under the most exacting service conditions.

Machine tools have been developed to produce high energy levels at high rates. It has been discovered that metals exhibit hydrodynamic properties, when subjected to these conditions, which facilitate shaping. The principle has been applied to the shaping of steel tungsten, columbium, sintered nickel and other metals. Thin sections may be extruded and forged and the effect on cost reduction is substantial.

In the manufacture of Republic aircraft the use of forged parts has increased from one 12 × 12 in. component in the P47 Thunderbolt to a total of 436 forged units in recent designs.