Rolling fatigue of oxynitrided chilled cast iron

Rolling fatigue of oxynitrided chilled cast iron

Thermal shock and t h e r m a l fatigue testing. Yuen, J.L. and Walter, R.J. ASTM J. Test. Eval, Sept. 1991 19, (5), 403-407 A method is described for...

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Thermal shock and t h e r m a l fatigue testing. Yuen, J.L. and Walter, R.J. ASTM J. Test. Eval, Sept. 1991 19, (5), 403-407 A method is described for rapidly screening candidate materials used in severe thermal-shock applications. The method involves electron beam heating of the surface of specimens using a thermal flux equal to that experienced during actual service operation. Two methods of electron beam radiation are described. In one method, the electron beam is swept across a narrow path with the specimen translated across the beam. In the second method, the specimen remained stationary, while the electron beam was repeatedly reetered over s square-shaped area. The similarity of the thermal-shock damage produced on rocket engine turbine blades (MAR-M246) during thermal-shock tests and that produced during engine firings indicates that computer-controlled electron beam radiation can be used for determining the thermal-shock resistance of turbine blade materials. Graphs, photomicrographs. Behaviour of acoustic embleion f o r l o w - s t r e n g t h structural steel during

fatigue and corrosion fatigue. Wang, Z.F., Zhu, Z. and Ke, W. Metall. Trans. A Nov. 1991 22A, (11), 2677-2680

Fatigue tests measured with the acoustic emission (AE) method have been conducted on a low-strength structural etael (SMSOB) in either air or a 3.5% NaCI solution. The results show the relation between the AE count rate and the crack growth rate or stretm intensity factor range. The/ME activity during the fatigue process decreases in solution in comparison with that in air. Furthermore, a model of AE behsviour is proposed, and the difference of AE activity between fatigue and corrosion fatigue (CFi depends upon the efhm~ of both the decrease of plastic zone size and the mstarial embdttlement at the crack tip. Graphs, photomicrographs. 10 refs. Calculating the fatigue strength o f solid cages in w h e e l s e t cylindrical miler ~ . Schulze, E. and Wachter, L. Schmierungstechnik M a y 1991 22, (5), 138-144 (in German) To ensure the long service life and high operating reliability of bearings, a method of celoulating fatigue strength values has been developed. This paper considers the effects of notch action, peak stresses, and permissible cage loads upon critical cage cross sections. The cages consist of brass with steel rivets. Graphs. 5 refs. Infkmnco o f r e a i d u l l stress on fatigue strength of non-load-carrying

fillet weld joints. Matsuoka, K., Takahashi, I., Yoshii, T. and Fujii, E. Quart. J. Japan Welding Soc. Feb. 1991 9, (1), 36-42 (in Japanese)

The influence of plate thickness on the fatigue strength of non-load-carrying fillet weld joints is examined both experimentally and analytically, from the viewpoint of weld residual stresses. In order to control the longitudinal residual stresses (in the direction of the weld line), rib-cruciform joint specimens with various plate widths were prepared. Specimens in which the heat input for each pass was varied were also prepared to control the transverse residual stresses (in the perpendicular direction to the weld line). Using these specimens, both residual-stress measurement and fatigue tests were carried out. It was found that the plate width of the specimen had a great effect on the longitudinal residual stresses and little effect on the transverse residual s t r e e ~ . The transverse residual stresses increased as the heat input decreased. As long as the heat input was constant, the plate width had no effect on the fatigue strength. The heat input significantly influenced the fatigue strength of joints with the same thickness as the main plate. The fatigue strength in the case of a high heat input was much higher than in the case of a low heat input, it is concluded that the fatigue strength of non-loed-cerrying fillet weld joints depends on the transverse residual stresses, and the tensile residual stresses increase as the plate thickness increases and/or the heat input decreases, causing a reduction of fatigue strength. Graphs. 10 refs. Relation b e t w e e n f e t ~ l u e strength and reinforcement shape of simulated

butt.welded Joints. Nisitani, H., Tanaka, H. and Harada, T. Quart. J. Japan Weld. Soc. Feb. 1991 9, (1), 31-36 (in Japanese)

The fatigue limits of simulated butt-welded joints were obtained under reversed bending and the results were discussed based on the critical condition for the existence of a non-propegating crack. It is well known that there is a close connection between the fatigue strength and the flank angle of a welded joint, as pointed out by Newman and Gurney in 1959. However, the relation shows a considerable amount of scatter. According to the results the cause of the scatter can be explained by the critical condition mentioned. Graphs, photomicrographs. 32 refs. Fatigue w i t h i n adhesive bonds. Wassell, G.C., Clark, J.D., Crompton,

J.S. and Dickson, R.F~ Int. J. Adhesion Adhesives Apr. 1991 11, (2), 117-120

The Paris law has been measured for adhesive materials within bonded AI down to crack growth rates of 7-10 mm/cycle, thereby creating the definition of conditions under which negligible crack propagation occurs. To make this measurement, a test method and analytical procedure have been developed that are capable of detecting crack growth rates two orders of magnitudes slower than the traditional double cantilever beam test. Evidence is presented of the verification of the analytical method and for the reproducibility of the technique. Graphs. 12 refs. O b s e n m t o r y o f n e w metedeis. Evolution perspectives f o r the materiels used in civil t r a n s p o r l a t i o n eirerafL Ferran, A. Aerospatiale Report No Ngl-23248/8/XAB 31 Jan. 1991 48 pp (in French) It is shown that, in aeronautics, each material innovation is the cause of reactions in other competitive materials. The evolution of metallic and organic materials is

Int J Fatigue July 1992

considered. Aluminium alloy improvements were made with regard to the fatigue strength, corrosion beheviour, and damage tolerances. Newly developed AI-Li alloys showed a 9% mass gain potential. New AI alloys, new Ti alloys, and new steels are presented. Titanium alloys are discussed. Titanium superplastic forming and diffusion bonding is illustrated. Landing gear steele and structural steel properties are given. The evolution of metallic matrix composites is presented. Atuminium matrix matedal characteristics are given. New mmriels for civil aircraft are presented. A marked evolution towards composite material utilization is emphasized. Rolling fatigue of o x y n i t d d e d chilled cast iron. Fushimi, S, Netsu Shori (J. Japan Soc. Heat Treat.) Jan. 1991 31, (1), 47-53 (in Japanese) Chilled cast iron is widely used for automotive engine camshafts, it faces severe conditions. The effects of oxynitriding on rolling fatigue properties in chilled cast iron are investigated. Two compositions of chilled cast iron, Fe-3.35C-2.3Si-0.8Mn-0.65Cr and Fe-3.4C-2.2Si-0.72Mn-O.6Cr-0.22Mo, and SUJ2 rollers are used in the experiments. Results show that the addition of Mo can improve the rolling fatigue limit by approximately 8% and etabilize the quality. Oxynitriding treatment (570°C/150 min) improves the rolling fatigue limit by approximately 10-20%. Surface peeling causing fatigue failure is initiated in the peadite structure in chilled cast iron. Graphs, photomicrographs. 9 refs. On fatigue beheviour of microalloyed pearlitie steals. Buchholz, H.,

Schaper, M., Schmidt, M. and Just, CI. Materialprufing. Mar. 1991 33, (3), 58-61 (in German)

In many industrial countries a rising consumption of microalloyed pearlitic steels (eg, C45, 38Mn6, 45MnV3, Nb49) for forgings can be noticed. The application of these steels permits a saving in energy, alloying and procedures because the quenching and tempering process is replaced by a controlled cooling (BY treatment). Some results of fatigue tests and crack propagation tests are presented. BY-treated steels showed a similar behaviour compared with quenched and tempered forging steels. Graphs, photomicrographs. 16 refs. Hard and effective testing f o r w e a r and corrosion on hardened surfaces of stainless austenftic steels. Gumpel, P., Kolster, B.H. and van der Jagt,

R. Maschinenmarkt Jan. 1991 97, (4), 40-43 (in German)

A process has been developed that will provide surfaces of 1.4575 auetenitic steel with a surface hardness of 1200 HV. This hardness drops off to the core hardness value of 300 HV within an adjustable depth, such as 33 i~m. The process, aimed at improving the wear resistance, raises the impact strength, corrosion and fatigue resistance, but does not change the tensile strength. The process may allow the substitution of austenitic surface-hardened steels for martensitic stainless steels. Other steels discussed ere 1.4057, 1.4301 and 1.4436. Graphs, photomicrographs. 2 refs. Optimization of locking threaded connections durability of drill pipe strings on the basis o f f r e c t u r e mechanics criteria. Gnip, I.P., Babyuk,

I.S. and Chernov, B.O. Fiziko-ghim. Mekh. Mater. Nov.-Dec. 1990 (6), 105-109 (in Ukrainian)

A method for calculating the durability of the locking threaded connections of drill pipes is proposed that is based on a fracture mechanics approach. The method makes it possible to optimize the assembly of the threaded joints in accordance with the cyclic fracture toughness of specific steels. The possibility of predicting the service life of threaded joints with a fatigue crack and for estimating the crack size for a certain service period is demonstrated. Experimental results are presented for 45 and 40KhN2MA steels. Graphs. 11 refs. DC-IO accident leads to basic r e v i e w of jet engine rotating parts treatment. Hughes, D. Aviation Week & Space Technol. M a y 1991 134, (20), 35-36 The United Airlines/McDonnell Douglas DC-10 accident at Sioux City, Iowa, on 19th July 1989, has precipitated a major re-evaluation of how to process and inspect rotating components in engines. In the accident, the stage-1 Ti fan rotor disc in s General Electric CF0-6D turbofan failed due to a metallurgical defect that went undetected when the ingot from which the disc was forged was made in 1971. A resulting 0.5 in long fatigue crack was missed during an in-eervice inspection in February 1988. Implementation of the report recommendations during the next four years could cause engine manufacturers and suppliers of rotating components to make investments in equipment and engineering and change the fan and compressor disc designs. The history and number of failures since 1962 are summarized. Graphs.

M D e v o l o . pHosoda, m e nT, tOka, N., Hata, M., Minami, K. and Syuku, H. of thermal hardening hot-rolled steel sheets f o r highn g m a u t o m o t i v e parts.

Kobe Res. Dev. Apr. 1991 41, (2), 69-72 (in Japanese)

To manufacture high-strength press-formed parts for automotive use, Cu-beadng hot-rolled steel sheets capable of being thermally hardened were developed. Steel sheets coiled et.a low temperature to suppress the Cu precipitation have good press formebility and are hardened through precipitation by subsequent heating. The asrolled steel sheets with a tensile strength of 600 N mm -2 can be press formed into complex power train parts. After being heated, a strength of more than 800 N ram-2 and a high fatigue strength of the parts are obtained. Graphs, photomicrographs. 2 refs.

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