Showing papers on "Peening published in 1989"

Laser peening system and method

Abstract: A laser peening apparatus and method for peening a workpiece utilizing a laser beam is described. The system includes a foil aligned with a surface of the workpiece to be peened and lasing the aligned foil surface. The foil absorbs energy from the beam and a portion of the foil vaporizes, which creates a hot plasma within the foil. The plasma creates a shock wave which passes through the foil and peens the workpiece surface.

Method and apparatus for producing turbine blade roots

Abstract: A method and apparatus for producing turbine blade roots (23) utilize an electro-discharge machining apparatus (10) to machine critical portions of the blade root (23) and a peening apparatus (25) for peening of the machined portions. The electro-discharge machining of the blade root leaves recast layers (22) on the surface of the blade root (23), and high residual tensile stresses are found in the surface of the blade root (23), which could lead to crack propagation. Peening of the machined surfaces leaves compressive residual stresses near the surface and reduces the recast layers (22). The resulting blade root (23) meets the same specifications for durability and tolerances as a blade root machined using the conventional transfer line type cutting process, but at a fraction of the cost.

The Effect of Shot Peening on the Bending Strength of Carburized Gear Teeth

Abstract: The quantitative effects of hardness and residual stress produced by shot peening on the bending strength of carburized spur gears of m=5 are investigated. The residual stress of every test tooth is measured by an X-ray diffraction method. The intensity of shot peening has little effect on the fatigue strength. The mean strength is about 1200 MPa, which is about 1.3 times that of carburized gears without shot peening. When a tooth surface is electropolished and a higher compressive residual stress is applied to the fillet, the fatigue strength is still 250 MPa higher than that of the shot-peened gears. In this study, the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress, and an experimental formula is proposed to estimate the fatigue strength.

Peening shot curving

Abstract: A method of shaping planar parts which have an elastic and plastic range for making components which are curved two dimensionally around two axes under utilization of a high pressure peening shot beam comprises the steps of tension positioning the part to obtain through elastic deformation to obtain the desired contour; peening the surface of the part to be deformed by running a beam of shot along track lines which are essentially lines of equal strain in the parts to be made; controlling the peening shot beam energy such that more central parts receive shot at a higher energy than more peripheral parts of said part; repeating the aforementioned steps on the other side of the part; and separately peening shot treating at least some of thicker edge parts, so as to obtain plastic deformation.

Rotor type shot peening device

Abstract: PURPOSE:To attain the uniformity of a workpiece in its quality with a peening effect stabilized by providing a control means for driving a driving means controlling a speed of a rotor in accordance with a ball size of shot in a manner wherein each kinetic energy is almost the same in case of projecting the shot supplied by a supply means CONSTITUTION:A selecting means selects a shot in accordance with a ball size, thereafter supply means 33, 35 supply a shot to rotors 15, 17 different in accordance with the ball size Next a control means controls driving a driving means of the rotors 15, 17 and their rotary speeds in a manner wherein kinetic energy is almost equally generated in case of projecting the supplied shot In this way, a workpiece 5 can attain the uniformity of its quality by enabling a peening effect to be stabilized Further a relation between the ball size and the rotary speed is exchanged after the predetermined time by opening and closing valves SVI to SVIV of an exchange mechanism mutually between the different rotors In this way, only one rotor is prevented from always rotating at a high speed

High-strength coil spring and method of producing same

Abstract: TITLE OF THE INVENTION HIGH-STRENGTH COIL SPRING AND METHOD OF PRODUCING SAME ABSTRACT OF THE DISCLOSURE The present invention relates to a high-strength coil spring useful for an engine and other high-strength springs requiring a high fatigue-resistance and a method of producing the same. In general, a higher tensile strength is desired for spring materials but it has been known that if a tensile strength exceeds a certain limit, a toughness and a fatigue resistance are contrarily reduced. In addition, a coil spring has been used after forming and then being subjected to a quenching treatment followed by being subjected to a shot peening treatment to add a compressive residual stress to a surface thereof but an effective shot peening treatment gives a surface roughness Rmax of 6 to 20 µm, so that not only it has been impossible to remove surface defects having a surface rough-ness of 6 to 20 µm or less but also impressions due to the shot peening have covered the surface defects to be turned into injured portions and fatigue nuclei in many cases. In view of the above description, the present invention has found a high-strength coil spring with high fatigue resistance using a clean steel wire, such as chromium-vanadium steel wire and chromium-silicon steel wire, by forming it in the shape of a spring, quenching and tempering at lower temperatures to heighten the tensile strength, and being subjected to a shot peening treatment followed by being subjected to an electrolytic polishing treatment, which does not exert a bad influence on fatigue resistance, to remove surface defects and a method of producing the same.

Fatigue Crack Growth Retardation in an Al Alloy 2024 in a Residual Compressive Stress Field

Abstract: The contribution of residual compressive stresses induced by shot peening to the improvement in fatigue life of Al 2024 is assessed. Shot peening results in an increase in dislocation density and in compressive residual stresses at the surface. Propagation rates of small surface cracks were measured in the electrolytically polished (reference) and shot peened conditions, and were found to be drastically reduced after shot peening. A minimum in propagation rates for shot peened specimens is found where the cracks propagate through the region of maximum residual compressive stresses. Comparison of these results with those of other materials indicates that the effect of residual compressive stresses on fatigue life in Al 2024 is far more pronounced than has been previously thought.

Microstructural Characterization of Heat-Treated Cold Worked Steels and Fatigued Shot-Peened Aluminium by X-Ray Diffraction Profile Analysis

Abstract: The purpose of our studies was to link macroscopic mechanical properties (hardness, strength...) with X-ray diffraction profile analysis characteristics, and also to improve the understanding of the plastic deformation process using the profile analysis method We firstly studied a low-alloyed carbon steel (with 0.35%C and 1% Cr) quenched and tempered at different temperatures. By recording the diffraction peaks of the {110}, {220}, {211} and {422} planes with a position sensitive detector, we have shown a good relation between X-ray diffraction profile analysis parameters, such as peak width (ds), coherent diffraction domain size (D) and average distortion factor e1, and macroscopic mechanical properties (hardness, tensile strength) Secondly, we tried to characterize the influence of the plastic deformation ratio on microstructural state of a Nickel alloyed steel (with 9%Ni) by X-ray diffraction. This plastic deformation was imposed either by simple traction (0.36% to 10% of strain) or by torsion (5% to 150% of equivalent strain). The relations found between those parameters were different accordingto the kind of imposed plastic deformation The third example concerned Aluminium (2024 alloy) which was shot-peened and then fatigued. The variation of the distortion factor e1 measured at the surface, versus the number of cycles allows to point out three stages: a softening during the first cycles, a stabilization and then a final hardening announcing the fracture.

The Effect of Temperature and Time on the Stress Relaxation of Shot Peened Nickel Based Superalloy IN100

Abstract: We present in this text an experimental study and a theoretical modelisation of the heat stability of the shot peening residual stresses of the turbine blades in nickel alloy IN100 with the shot peening parameters. We have used the X-ray diffraction for analysing the superficial stresses and the incremental hole drilling method for analysing the stresses in depth. The results obtained have allowed us to propose an optimal shot peening treatment which differs approximately from that which is actually brought into play.

Nondestructive characterization of shot peened surface states by the magnetic barkhausen noise method

Abstract: SUMMARY The residual stress state of shot peened steel sheets has been measured with X-ray, mechanical, and micromagnetic methods. The results show that macro- and microstresses, the work hardening depth and the homogeneity of shot peened states can be determined by the micromagnetic quantities. The procedure to get quantitative results is outlined briefly.

Welding method for austenitic stainless steel welding structure

Abstract: PURPOSE:To form a good multilayer weld zone having no directional fatigue strength by executing peening on the surface of a welded welding metal and making the effective depth of the peening more than the penetration depth of the welding time adjoining the welding metal. CONSTITUTION:Peening is executed on the surface of the welding metal 2 of the multilayer weld zone 1 of an austenitic stainless steel welding structure. A deformation is therefore given to the surface layer of the welding metal 2 and the dendrite of the welding metal subjected to peening becomes discontinuous by attaining at least one part of the depth of the layer causing the deformation to more than the penetration depth of the welding time by adjoining the welding metal. Or the developing direction of the dendrite is scattered and refined by developing it in different direction from the dendrite developing direction.

Shot peening time setting method

Abstract: PURPOSE:To perform uniform shot peening of works having various shapes by detecting a time interval during which the level of an optical detection signal exceeds over a reference value within single rotation of a measuring work and employing the duration of light irradiation until the accumulated value of that time interval exceeds over a reference value as a shot peening time. CONSTITUTION:Measuring works 20, 21 having same shapes as that of an actually processed work and provided with photo-receptors 22, 23 at portions corresponding to those portions of the work where peening is applied are rotated, and light is projected onto the measuring work through a light irradiating means 13 arranged at a position corresponding to the position of a shot projecting means with respect to the work. Time interval when the level of a light detection signal exceeds over a reference value within single rotation of the measuring work is detected based on the light detection signal. The time interval is accumulated and the duration of light irradiation until the accumulated time interval exceeds over a reference value is calculated and employed as the processing time of the work.

Modelling of the Shot Peening Residual Stress Relaxation in Steel Structure Under Cyclic Loading

Abstract: With the help of a new description on the material cyclic softening law [1] and the elastoplastic calculation method proposed by Zarka et al [2], a theoretical model is developped for calculating shot peening residual stress relaxation under cyclic loadings. This model can take into account the modification of material mechanical properties due to shot peening, material cyclic softening and real local loading conditions. An application of this model on a shot peened plate in the steel SEA4135 subjected to a repeated plane bending is presented. The calculated results can well predict the experimental ones obtained by X-ray diffractometer.

Fatigue with Residual Stresses due to Shot Peening: Effects and Evolution

Abstract: Prestressing by shot peening prolongs the life of components under mechanical stress. It should be possible to predict this improvement by calculation, in order to optimize the shot peening parameters and the shape of the components, and so reduce costs whilst increasing resistance.

Method for preventing creep embrittlement of apparatus used in creep temperature range

Abstract: PURPOSE:To effectively prevent creep embrittlement or rupture of the title apparatus and to enable partial repair which is effective for obstructing the creep proceeding by successively subjecting the metal surface of the apparatus to shot blasting, thermal spraying with an Ni alloy and thermal spraying with ceramic. CONSTITUTION:The metal surface of the apparatus used in the creep temp. range is subjected to shot blasting or blasting with a blasting material to produce cleaning and peening effects on the metal surface in a first stage. An Ni alloy or cermet is thermally sprayed on the treated surface to form an underlayer in a second staged and then ceramic is thermally sprayed to form a finishing layer in a third stage. By this method, the temp. of the metal surface can be reduced without changing the operation conditions of the apparatus, creep embrittlement or rupture and proceeding can be prevented and the apparatus can be partially repaired during use.

A Theoretical Prediction of Residual Stresses Introduced by Shot Peening

Abstract: Shot peening has a significant influence on the fatigue behaviour of treated components. The treatment generates superficial compressive stresses. Theoretical prediction of the stress profile against depth will make easier the choice of the shot peening parameters. We use the model derived by Zarkaetal [1] which lies upon elastic calculations and local geometrical constructions.

Steel for carburizing-shot peening

Abstract: PURPOSE: To manufacture the steel having improved fatigue resistance by incorporating specific ratios of C, Si, Mn, S, Cr, Nb, Al, N and P into Fe. CONSTITUTION: A steel contg., by weight, 0.10 to 0.25% C, 0.50 to 3.0% Si, 1.00 to 3.0% Mn, 0.01 to 0.20% S, 0.50 to 1.50% Cr, 0.020 to 0.120% Nb, 0.02 to 0.10% Al, 0.010 to 0.025% N and ≤0.01% P, contg., at need, 0.005 to 0.10% Ti, furthermore contg. ≤4.0% Ni, ≤1.0% Mo, ≤0.1% V and ≤1.0% Cu and the balance Fe with inevitable impurities is prepd. In this way, the steel for carburizing-shot peening provided with excellent fatigue resistance can be obtd. COPYRIGHT: (C)1990,JPO&Japio

Residual Stress State After Roll-Peening of Sintered Fe-Cu Material

Abstract: The parameters of roll-peening with line contact are optimized with regard to the enhancement of the fatigue strength. The residual stress depth distribution after rollpeening is determined by X-ray with sintered Fe Cu 25 specimens. The change in the macro and micro residual stresses in the two phases in the roll direction and transverse direction are investigated with two stress horizons as a function of the number of stress cycles.

Manufacture of steam turbine blade root section

Abstract: PURPOSE: To prevent the damage of turbine blade roots caused by the progress or growth of cracks by peening the machined portions of the turbine blade roots electro-discharge machined into the desired shape, and reducing recast sections on the surface and residual tensile stress. CONSTITUTION: When a blank blade root 14 is electro-discharge machined into the desired blade root shape by a wire electrode 15, recast layers 22 are formed on the surface layer by the heat of electro-discharge machining, and residual tensile stress is generated on the surface of a blade root 23. Steel shots 24 are shot to the surface of the blade root 23 by a peening device 25 at the peening strength of about 4-6A for peening. The damage of the blade roots 23 caused by the progress or growth of cracks is prevented, and durability can be improved.

A fracture mechanics approach to partial coverage in shot-peened components

Abstract: This investigation examines the effect of incomplete coverage upon the fatigue life of v-notched cylindrical specimens made of medium carbon steel (En8). Room temperature rotating bending fatigue tests conducted on the different partially peened specimens, at different stress levels, generally revealed a life improvement. This improvement is however governed, amongst other factors, by the ratio between the area covered by the plastic indentations and the total surface area of the component. The work was supported by three-dimensional finite element analysis of circumferentially cracked notched and un-notched cylindrical components. The resulting theoretical stress intensity factors (KI) were subsequently used in the evaluation of fatigue crack growth rate data at the different stress levels examined.

An X-Ray Study on the Residual Stress of Shot-Peened Steels

Abstract: Although shot peening treatment is widely applied to the machine parts for the purpose to produce compressive residual stresses in order to improve mechanical properties, detailed relation between the shot peening condition and the residual stress distribution near the surface layers is not clarified yet. The aim of the present study is to find out the precise effect of shot peening condition on the fatigue life through the control of residulal stress distribution near the surface layers of Ni-Cr-Mo steel plates which are used for various kinds of gears or other machine parts. The residual stress near the surface layers of shot peened specimen followed by grinding was measured by the use of X-ray diffraction method. The residual stress distribution across the thickness direction was also measured removing the surface layers by electrolytical polishing.

Production of plain bearings with overlays

Abstract: A process is described for the production of bearings for sustaining high loads, the bearings having indentations (14, 32) filled with soft overlay alloy (13, 33). The indentations are produced by peening or embossing. The peening is preferably performed with rounded ceramic shot of 0.25 to 0.5mm diameter. Indentations should preferably be between 0.01 and 0.05mm deep. In one embodiment a bearing is described having alloy comprising a steel-backed (10) aluminium-based bearing alloy (11) having a composition of, for example, Al-Sn20-Cul and a soft Pb-SnlO overlay (13) there also being an interlayer of 3 to 5 um of nickel (12) between the bearing alloy and the overlay. Bearing surfaces having a continuous overlay or a composite surface comprising randomly-shaped areas of bearing alloy and overlay may be produced.

The Effect of Substructure in Surface Strengthened Layer on the Fatigue Strength of α-brass

Abstract: The fatigue strength of α-brass tends to increase after shot peening The surface residual compressive stress will not relax when shot peened specimens are tested under cyclic stress This is because the substructures of surface strengthened layer are rather stable in fatigue process Deformation twin, planar defect and residual stress which are introduced into surface layer by shot peening have been analysed by transmission election microscope and x-ray stress analyser, thus the relationship among fatigue strength, substructure and residual stress could be studies attentively