Showing papers on "Shot peening published in 1984"

Wood-like molded product of synthetic resin

Abstract: The present invention relates to wood-like molded products of synthetic resin which are manufactured by mixing a synthetic resin material with a fine aggregate of cellulose base such as wood meal, chaffs, begasse and in which the internal residual stress which may cause deformation (for example, warping and twisting) of the products at the time or after molding is eliminated in advance to prevent chronological deformation. More particularly, it relates to a method of eliminating said residual stress by subjecting the molded products containing cellulose-base aggregate, especially the resinous skin layer thereof, to re-heating, curing and sanding or jetting treatments (sand blasting, shot peening, grit blasting) under predetermined conditions.

Roller contact fatigue study of austempered ductile iron

Abstract: Contact fatigue properties of austempered nodular iron transformed at 230 °C to Rc 45-47 were evaluated using roller contact fatigue tests. At a given load, contact fatigue life of the austempered iron was 35 to 45 pct lower than carburized steel. Shot peening, performed using 1.168-mm diameter Rc 45-55 cast steel balls to Almen strip intensity of 0.006 to 0.008 C, was not beneficial. An increase in the surface compressive residual stress introduced by shot peening was accompanied by surface roughening which lowered the fatigue life by detrimentally influencing the EHD film thickness. Stress induced white etching areas well known to develop in high carbon martensite were found to develop in bainitic microstructure also.

The fatigue of an aluminium alloy produced by fretting on a shot peened surface

Abstract: An Al-4.2%Cu-0.7%Mg-0.7%Si age hardening alloy (2014A) has been shot peened and subjected to plain and fretting fatigue. The shot peening improves both plain and fretting fatigue strengths, and in particular the fretting fatigue strength of the alloy in the fully aged condition is increased by 130%. The improvement in fretting fatigue properties is largely due to the residual compressive stresses induced into the surface by the shot peening process. Surface roughening also has a small beneficial effect but work hardening of the surface does not influence the fretting fatigue properties.

Improvement of the fatigue life for offshore welded connections

Abstract: The advantages provided by using high strength structural (HSS) steels for offshore construction might be limited by the fatigue resistance properties of the welded connections. Since fatigue crack propagation characteristics are not significantly different between low and high strength structural steels, the best way to improve the fatigue resistance of welded joints in HSS steels is to introduce a longer initiation period. For this purpose, we developed two complementary procedures: an improved weld procedure, and a global post weld improvement technique. The overall geometry of the fillet weld is controlled to obtain the best stress flow and the lowest stress concentration in the weld toe region. Furthermore the weld toe run is done at the beginning of the welding. This improved weld procedure gives smaller global and local stress concentrations. The second step to improve the fatigue resistance of such welded joints is post weld shot peening. Such a technique has the advantage of being a “global treatment”, not only localized at the weld toe. The compressive residual stress field induced by shot peening has been studied at the surface of the specimen and in depth. By measuring the initial stress field (prior to fatigue testing) and the redistribution of these residual stresses during fatigue, optimum parameters of shot peening (ALMEN intensity, shot diameter, coverage rate, etc) may be chosen. Fatigue tests were carried out on 30 mm thick T shape welded joints. Comparative results between as-welded and shot peened specimens show the efficiency of the improved weld procedure and of shot peening in improving the fatigue resistance of welded structures.

Simultaneous spray deposition and peening of metals (SSP)

Abstract: A new process, simultaneous spray peening (SSP), is described which comprises the spray deposition of metals together with simultaneous shot peening. This combined incremental operation allows either thick or thin deposits to be made in ferrous or non-ferrous metals. The deposits are hot worked and densified during the process so improving their properties compared with more conventional spray deposits. An additional advantage is that the inherent residual tensile stresses of spray deposition are counter-balanced by the compressive stresses caused by peening. By control of the simultaneous peening operation it is shown that the residual stresses in SSP deposits can be maintained at any required positive or negative level. Examples and structures are shown of SSP products made from gas-atomized melts, by arc spray, and by plasma spray.

Powder solidifying method

Abstract: PURPOSE:To perform high density sintering by enhancing the degree of freedom of a shape, by a method wherein the surface of a metal powder green compact or the preliminarily sintered body thereof is subjected to pore sealing by a physical means and, after the treated one is further coated with a vitreous substance, the formed matter is pressed by a hot hydrostatic press. CONSTITUTION:The surface of a metal powder green compact or the preliminarily sintered body thereof is subjected to pore sealing by a physical means such as hammering, shot blast or shot peening. If necessary, the treated surface is further coated with a virtreous substance by a proper means. The obtained matter is strongly pressed under heating by a hot hydrostatic press. Because the surface fine pores of the sintered body are entirely sealed, internal vacuum spaces are perfectly lost by external pressure and a good sintered body is obtained while the necessity of discretion due to the shape of hydrostatic pressure is eliminated to enhance the degree of freedom due to a shape.

Electromagnetic connection device

Abstract: PURPOSE:To stabilize the torque due to elimination of any camber as well as increase in hardness of the friction surface by applying processes such as liquid honing, shot peening and the like to the friction surface of at least either one of rotor or armature CONSTITUTION:Such processes as liquid honing, shot peening and the like are applied to friction surfaces 3b, 5c of a rotor 3 and an armature 5 to effect hardening work Namely, when honing process and the like are applied, traces due to lathe machining on the friction surfaces 3b, 5c are eliminated and said surfaces not only turn aventurine-like but also hardened due to hardening work Thus, frictional torque is enhanced, and fine tears and the like are prevented at the time of connection, and further stabilized transmission torque can be obtained Besides the above, any chamber produced on sides of a rib of the armature 5 due to processing disappears, and stable torque can be obtained

Shot-peening surface-finishing

Abstract: PURPOSE:To obtain a finished surface like a mirror by jetting-out the ultrafine shot grains having the hardness lower than the quenching hardness onto the surface of a material to be worked which has been already polishing-worked. CONSTITUTION:The surface of a hardening-processed workpiece is super-polishing-finished, and the surface roughness is reduced to 1mu or less, and the ultrafine shot-grains having a hardness of HR 35-40 lower than the hardness of the workpiece and a having a grain diameter of 40-50mu are jetted-out, and then the edge having an acute angle which is formed by scratching the surface is crushed down, roughness of the surface is improved, and the surface is finished like a mirror. Therefore, the service life can be prolonged ten times or more in comparison with the material which is only hardened and tempered.

Manufacture of rear axle housing

Abstract: PURPOSE:To increase fatigue strength of a rear axle housing by removing unevenness due to mold deviation, burrs, traces of welding correction, traces of grinding etc. caused in manufacturing a rear axle housing made of cast steel by blasting work. CONSTITUTION:After casting a rear axle housing as a cast steel product M, the gate 2 is ground by a grinder 3 or acute angled part 2a is ground by welding correction. Then, blasting work by shot peening is performed on the whole body of the rear axle housing 1. Shot peening is performed by blasting about 0.3-4mm. steel shots at blasting speed of 10-50m/sec. Compressive stress is caused on the surface of the rear axle housing by spot peening and internal tensile stress is cancelled by this and concentration of stress is prevented. Consequently, fatigue strength is increased.

Treatment in weld zone of nickel alloy

Abstract: PURPOSE:To improve the corrosion resistance in the weld zone of an Ni alloy contg. Cr by subjecting the weld zone thereof to strong plastic working then heating the weld zone so as to form a fine granular structure by a primary recrystallization. CONSTITUTION:The respective surfaces in the weld metal and weld heat affected zone of a weldment made of an Ni alloy contg. Cr are sujbected to strong plastic working and thereafter the strong-plastically worked parts are heated to form the fine granular structure by a primary recrystallization, whereby the corrosion resistance in the weld zone is improved while a mechanical property such as high temp. strength is maintained. The above-mentioned weldment is preferably formed of a welding base metal produced by subjecting the same to an immunization treatment for >=10hr at 650-850 deg.C to deposit thoroughly Cr carbide and to decrease intergranular corrosion. The above-mentioned strong plastic working is accomplished adequately by shot peening or wire peening and the heating in the strong-plastically worked parts is acoomplished preferably at 700-850 deg.C by high frequency induction heating, laser beam heating or IR heating.

Track bushing of track

Abstract: PURPOSE:To give high wear resistance to a track bushing without increasing manufacturing cost of the bushing, by making the bushing into a dual structure made of an external and internal pipes. CONSTITUTION:A track bushing 1 is made into a dual structure made of an external pipe 2 and an internal pipe 3. The external pipe 2 is made of low-carbon alloy steel having 0.5-0.8% carbon content to give wear resistance to the pipe 2, and hardness of the pipe 2 is made into HRC58 or more by applying hardening and tempering to the same. On the other hand, although the wear resistance is not required for the internal pipe 3, fatigue strength for crack resistance is necessary. Then low-carbon alloy steel having 0.5-0.48% carbon content is selected for the internal pipe 3. Hardness is made into HRC35-50 through hardening and tempering. Then compressive residual stress of -30--60kg/mm. is made to generate on the surface of an inner diametral surface of each of the pipes by applying shot peening to the surface.

Working for bearing of connecting rod

Abstract: PURPOSE:To obtain the superior fitting state by increasing the diameter of a fitting surface in a bearing fitting part of a connecting rod body, taking account of the final finish dimension in shot peening, when a bearing is fitted after applying shot peening onto said bearing fitting part. CONSTITUTION:A connecting rod body 1 is equipped with a cylindrical bearing 2 for the penetration of a piston pin at one edge and a half-divided cylindrical bearing 3 for the penetration of a crank pin at the other edge. The connecting rod body 1 divided into two parts at the above-described bearing 3 part and joined by a bolt 5. Before the above-described both bearings 2 and 3 are fitted onto the connecting rod body 1, shot peening is applied onto the bearing fitting surface of the connecting rod body 1, and the surface is roughened. In this case, the diameter of the cylindrical surface of the connecting rod body 1 is spread by a necessary dimension beforehand, taking account of the final finish dimension in shot peening. Therefore, the superior fitting state between the connecting rod body 1 and the above-described both bearings 2 and 3 is formed, and generation of fretting corrosion is prevented.

Eddy-current type hardness measurement

Abstract: PURPOSE:To measure the hardness of a shot peening applied on the inner surface of a stainless steel pipe or the like in non-destructive manner by synchronously detecting the output of an amplifier in which a positive feed circuit is composed of a measuring coil and a dummy coil. CONSTITUTION:A measuring coil Zs is arranged on a stainless steel pipe 1 and a feedback amplifier 3 has a positive feedback circuit made up of the coil Zs and a dummy coil Z1. An alternating current is fed to the measuring coil Zs through an oscillator 4 and the feedback amplifier 3 to generate an eddy current in the steel pipe 1. As the steel pipe 1 undergoes a shot peening, electric characteristics thereof changes causing a change in the eddy current value. The change portion turns to an impedance change of the measuring coil Zs as reaction. The change is detected with a synchronous detector 6 and the output signal thereof is recorded on a recorder 7 to measure the depth of the shot peening.

Cylinder head for diesel engine

Abstract: PURPOSE:To protect the inter-valve section from crack while improving withstandability against thermal fatigue, by applying shot peening onto the surface of inter-vane section of cylinder head for Diesel engine thereby providing compression residual stress. CONSTITUTION:The lower face 8 of inter-valve section 5 to be formed between the suction port 2 and exhaust port 3 of cylinder head 1 for Diesel engine is recessed slightly to shorten the distance between a water hole 7. Said recess is made at the portion between the lines 9, 10 and after casting of the cylinder head 1, shot peening is applied onto the surface 8 of said inter-valve section 5. Shot peening is performed with arc height in the range of 0.22-0.35mm. and masked such that shot beads will not be dispersed to other portions.

Surface treatment of ferrous metallic parts

Abstract: PURPOSE:To prevent the generation of the blown-out matter after mechanical removal of the infiltrated matter, by subjecting porous ferrous parts to a surface treatment by a nitriding treatment with a salt bath then heating the same to a specific temp. to blow out forcibly the infiltrated matter and removing mechanically the same. CONSTITUTION:A hard nitride layer is formed by a nitriding method with a salt bath on porous metallic parts such as ferrous sintered parts in order to improve the wear resistance thereof. Since the salt in the bath used in this case is infiltrated into the inside of the porous material, the parts are heated for 30- 60min at 200-300 deg.C to blow out forcibly the infiltrated matter onto the surface. The blown-out matter is thoroughly removed by shot blasting or shot peening. The generation of the succeeding blow-out is thoroughly prevented by such treatment, and the surface hardness of the sintered parts is further improved by a peening effect as a secondary effect.