Showing papers on "Peening published in 1993"

Method of and apparatus for water-jet peening

Abstract: A water jet peening method in which a pressurized water jet flow containing cavities is jetted through a nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with the velocity increasing orifice portion to impinge against a surface of a metallic material immersed in water and to cause the cavities to collapse at the surface of the metallic member, and a tensile plastic deformation is caused in a surface layer of the metallic material by a local high pressure generated by the impingement and the collapse so that a residual tensile stress in the surface of the metallic member is reduced In this method, the nozzle is vibrated so that vibration-induced cavities are formed in the vicinity of a nozzle wall surface, and the vibration-induced cavities are caused to impinge against the surface of the metallic member by the pressurized water jet flow containing cavities It is thereby possible to promote the generation of cavities even in a case where pure water existing in a nuclear reactor and scant of nuclei from which cavities will be generated is used in peening of an internal structual member of the reactor

An improved method for the deposition of corrosion-resistant aluminium coatings for aerospace applications

Abstract: The gradual reduction in the use of electroplated cadmium as a corrosion barrier for aircraft parts has led to the development of ion- vapour-deposited (IVD) aluminium as an alternative. The most common IVD technique is the McDonnell Douglas “Ivadize” process, but the morphology of such aluminium coatings is usually open and columnar. Consequently, a post-deposition shot peen is used to densify the structure. This has led to very poor control over the thickness and uniformity of the coating, and precision parts cannot be coated by such techniques. The use of multimagnetron ion plating can guarantee close control over the coating dimensions by the precise deposition of fully dense aluminium films which do not require peening. To further improve the properties of the films, a series of aluminium alloys have been deposited to provide enhancement of the corrosion and tribological properties of the films.

Ultrasonic impact peening treatment of welds and its effect on fatigue resistance in air and seawater

Abstract: Welding residual stresses and stress concentrations are main factors which determine the load carrying capacity of welded structures under multicyclic loading conditions as typically experienced by ships and offshore structures. Ultrasonic Impact Peening Treatment has been introduced to improve fatigue performance . This local treatment of the weld toe is carried out by means of specially developed equipment consisting of a magnetoconstriction convertor, an ultrasonic wave transmitter and a special tool with holder. The tool tip using either a single 16mm ball element or multiple needles, vibrates at 27 KHz with maximum axial amplitudes up to 30 microns. The tool holder isolates the operator from the vibration and there is little audible sound during the treatment. The process introduced compressive residual stresses (up to 900 MPa at and near the surface) into areas of high stress concentration. It reduces stress concentration associated with weld local geometry and creates plastic deformation strain hardening in a surface layer (up to 0.7mm in depth).

Spacer for rotary peening apparatus

Abstract: The invention relates to a spacer for a rotary peening apparatus having a hub and a plurality of peening flaps that are spaced about and retained by the generally cylindrical peripheral surface of the hub Each peening flap includes several peening rivets attached to a distal end of the peening flap The spacer of the present invention positions the peening flaps at at least two locations inward of one of the hub ends of the hub, which enables the rotary peening apparatus to impart a uniform surface finish to a surface

Peening processing method for coil spring

Abstract: PURPOSE:To improve durability of a compression coil spring. CONSTITUTION:First, ordinary shot peening, wherein a shot is projected on a compression coil spring (a) while said spring (a) is rotated in a free state around an axis is carried out as shown in Fig A. Secondly, straight peening, wherein shot peening is performed while the compression coil spring is rotated around an axis in a state that the compression coil spring (a) is compressed by a jig 3 so that a twist stress, exceeds a specified value is carried out as shown in Fig B. By means of the first ordinary shot peening, an approximately uniform residual stress is exerted on the whole of the spring and by means of the second straight peening, a residual force is further exerted on a necessary part, such as the outside diameter side of the coil, for reinforcement.

Fatigue endurance of welded joints, residual stresses and fatigue improvement treatments

Abstract: A method of calculating the effect of residual stresses on the cyclic endurance of welded joints, which makes it possible to estimate with an accuracy sufficient to practice the role of residual stresses in the fatigue process in relation to the type of weld, mechanical properties of base metal and external loading parameters was developed. A new ultrasonic impact peening treatment is introduced. The fatigue improvement treatment is based on the introduction of compressive residual stresses into areas of high stress concentration, reduction in stress concentration associated with welds local geometry and plastic deformation strengthening of surface metal layer. A quantitative assessment of effectiveness of fatigue improvement treatments was developed. This paper briefly describes the assessment. Comparison of the calculated values with the experimental data indicates satisfactory agreement (difference does not exceed 10%).

Shot-peened gear failure due to operation in a misaligned condition

Abstract: Historv This paper discusses a unique failure mode discovered in case carburized and shot-peened gears. This type of failure is caused by an overload due to excessive misalignment, combined with the residual compressive stresses that result from carburizing and peening. This results in a reduction of the residual A failure of a T56-A-15 propeller gearbox occurred 24 January 1992 on a United States Coast Guard HC130H aircraft, while flying near Cold Bay, Alaska. A gear had broken-up, sending pieces through the gearbox case. The failure resulted in the propeller compr&sive stresses. These gears are made of alloy steel and are case carburized and shot-peened, which increases the residual compressive stress at the surface, resulting in infinite fatigue life. Failures of the gears attributed to fatigue warranted an investigation to determine the cause of the fatigue. Finite element analysis techniques were used to analyze gear stress profiles under various misaligned conditions. One loading scenario placed bending loads on the gear teeth that resulted in highly compressive stresses in the gear tooth root. These compressive stresses, combined with the residual compressive stresses from manufacturing, caused localized yielding of the material at the surface of the gear tooth root. The severe loading while in the misaligned condition was sufficient enough to produce fatigue crack initiation sites. This yielded material, with reduced residual compressive stress, will allow fatigue initiation sites to propagate when subsequently run in normal operating conditions. w

The Suitable Region of High-Speed Submerged Water-Jets for Cutting and Peening

Abstract: In order to establish techniques of cutting, drilling, peening and flushing by high-speed submerged water-jets, we systematically observe the eroded surface on aluminum-alloy test-pieces in relation to the aspects of cavitating jets, especially for the impinging jet through lucite-test-pieces, for several types of nozzles. The impulsive pressures induced by the impinging jets are also measured by means of pressure-sensitive film. It is concluded that the erosion characteristics are quite different in two regions differentiated by the standoff distance. Cylindrical, small and deep pits occur in one of the regions, while small lots of plastic deformations occur in the other region. The former is suitable for cutting, while the latter is for peening.

Theoretical Analysis of the Effect of Residual Stresses in Welded Structures on the Improvement of Fatigue Strength

Abstract: A theoretical analysis of the effect of residual stresses on the fatigue strength of butt welded joints was developed by using Linear Elastic Fracture Mechanics (LEFM), superposition principle of fracture mechanics and finite element approaches. Various configurations of residual stresses in butt welded joints was considered and corresponding residual stress intensity factors were calculated by using Bueckner's and Kanazawa's weight functions for an edge and a central through-thickness crack in finite plate respectively and Newman-Raju's empirical equation was used for surface crack. Fatigue strength of butt welds subjected to various stress-induced treatments was calculated by using Paris' law with the effective range of mess intensity factor for zero-to-tensile loading (R=0) and compared with the available experimental data. Compressive residual stresses introduced on the surface of the welded joints by various surface treatment methods such as single and multiple point hammer peening, steel shot peened, glass peened, suess peened (loaded and peened) or tensile preloading improved fatigue life and fatigue strength of welded joints. The improvement is due to the early stage of crack propagation only up to the crack length corresponding to the depth of compressive residual stress field. It is also found that the effect of the low level of compressive residual stress (less than 62 MPa) in terms of the fatigue strength improvement is of the same order as the effect of the post-weld thermal stress relieving process. The contribution of hardness of the treated material to the improvement of fatigue strength is obvious at high level of induced compressive residual stresses. This was shown by comparison of the model with the available experimental data.

Base blade prodn. method for circular saws, grinding and cutting off disks - involves stacking blade disks and traversing lance with radial shot peening nozzle along peripheral slits to peen bottom of slit in direction parallel to disk plane

Abstract: The base blade (2) for a circular saw etc. is made from a disk (4) which has around the circumference radial slits (12) with a root hole (14). To prevent the formation of cracks, the slit (12) is shot peened around the surface (18) normal to the plane of the disk in a direction parallel to the plane of the disk. This is accomplished by stacking a number of disks (4) with the slits aligned. A lance (24) with a radial shot peening nozzle (32) is positioned concentric to the root hole (14) and traversed through the stack whilst being rotated about its axis (26). USE/ADVANTAGE - Simple, quick and economical circular saw prodn. ensuring uniform quality and high resistance to cracking.

Evaluation of surface modifications in high strength steel

Abstract: This paper reports on the application of micromagnetic inspection techniques to the evaluation of the surface condition of shot peened, high strength HP9430 steel. It is shown from the results that the modification of the surface condition resulting from different shot peening intensities can be detected from the amplitude of the micromagnetic signals emitted from the surface under alternating magnetic field excitation. It is further demonstrated that the production of residual stresses in the surface of a steel, as a result of shot peening, causes a broadening of the range of critical field strengths for domain wall activation. Consequently the spectrum of activation fields obtained on a plot of micromagnetic activity versus magnetic field strength can be used as an indication of the shot peened condition of the material.

Post-treatment of spring

Abstract: PURPOSE:To enhance both the durability and sag resistance of a spring. CONSTITUTION:A formed spring is subjected to shot peening in an atmosphere at 100-300 deg.C under stress produced at the time of use. When this stress peening is carried out in a warm state, higher residual stress can be formed and the fatigue strength of the spring, that is, the durability is enhanced. The superimposed action of the impartment of stress and lonnealing is also obtd. and the fatigue deformation preventiveness of the spring, that is, the sag resistance is also enhanced.

Ccd solid-state image pickup device

Abstract: PURPOSE: To provide a CCD capable of measuring the two-dimensional video of very weak light by remarkably suppressing the generation of dark current even if the CCD is exposed for an extremely long time. CONSTITUTION: By forming barrier layers B1, B2 and B3... on the parts of the channel layer 9 areas under each of transfer electrode G1, G2 and G3... and impressing peening voltage on all the transfer electrodes G1, G2 G3... groups at the time of an imaging, signal electric charge generated by receiving light is integrated into the potential well group corresponding to a pixel generated in the channel layer 9 areas where the barrier layers B1, B2, B3... are not formed. At the time of an electric charge transfer, by defining an 'L' level as peening voltage and impressing a two-phase clock where an 'H' level is made prescribed voltage which is higher than peening voltage on the transfer electrodes G1, G2 and G3... groups, the signal electric charge integrated into each two adjacent potential wells is mixed, it is separated every mixture signal and electric change transfer is made to be performed. COPYRIGHT: (C)1994,JPO

Production of plated titanium alloy parts

Abstract: PURPOSE:To provide a producing method for plated titanium alloy parts CONSTITUTION:(1) This is a producing method for plated titanium allay parts constituted of a primary stage in which titanium alloy parts are subjected to preliminary treatment for time in which pitting does not occur by a warmed soln of hydrochloric acid, a secondary stage in which specified plating is executed immediately after the removal of smuts produced in the primary stage and a third stage in which baking treatment is executed for a long time at a low temp in a vacuum After the three stages, the surface of the plating layer is subjected to glass bead peening or shot peening

An aspect of internal fatigue limit for metals with aid of strength appraisal on hardered steels

Abstract: An aspect of the intermal fatigue limit for metals was proposed with the aid ofappraisal of the fatigue behaviour of shot peened, nitrided or carbonitrided steels. The inter-nal fatigue limit of metals seems to be 1.35 times of surface one. Based on this aspect, the fa-tigue strength of surface hardened steels was analysed.

Manufacture of sliding member

Abstract: PURPOSE:To provide a method for manufacturing a sliding member securing fatigue strength while the wear resistance of the sliding part of a block 32 is improved. CONSTITUTION:A driving belt 3 wound around a driving pulley and a follower pulley in a belt type continuously variable transmission of a CVT system is constituted of a hoop 30 and a block 32. As for the block 32, an iron-based material (an SUP6 improved material) having austenite generating working strain induced transformation is used as a base metal. Then, the sliding part of the block 32 is subjected to a peening working, and its surface is martensitized by the relevant transformation to regulate its Hv to >=600. Furthermore, the martensitized sliding part is coated with a chromium plating layer 35 (5 to 10mum thickness) with 700 to 800 Hv by an electroplating method. At the time of the sliding, the plastic deformation in the surface area of the base metal of the block 32 is suppressed, by which the peeling resistance of the chromium plating layer 35 can be improved.

Increasing surface hardness and residual stress results in the enhancement of strength of carburized gear teeth

Abstract: An experimental formula has been proposed for the estimation of bending fatigue strength of carburized gears. The derivation of the formula is briefly reviewed first, and the effectiveness of the formula is examined based on the comparison with many test results including shot peened gears. Except for some cases, the formula is verified to be effective for the approximate estimation of the fatigue strength. The formula also shows a way of enhancing fatigue strength by increasing surface hardness and residual stress. The enhancement of the strength is demonstrated quantitatively. The strength is enhanced about 300MPa by appropriate shot peening. And it can be improved still more by electropolishing. 25 refs.

A continuous shot peening system and method for shot peening a plurality of tubes

Abstract: A shot peening system (15) for peening the tubes (7) of a steam generator (1) continuously generates a shot stream and withdraws the shot stream dispensing nozzle (31) into a vacuum chamber (165) in an end effector (33) while repositioning the nozzle (31) for peening the next tube (7). A load tank (61) forms an air lock for recycling shot recovered and cleaned by a vacuum system (37, 39) to a pressurized peen tank (57) which feeds the recycled shot to a feed valve (53) for mixing with a flow of compressed air to generate the shot stream. The pressure on the shot in the peen tank (57) and the pressure of the compressed gas supplied to the feed valve (53) are independently regulated to adjust the concentration of shot in the shot stream. The feed valve (53) is constructed for ease of assembly and repair, and directs flow of a purge gas across the shot feed orifice (121) and into a purge line (99) which cycles shot and debris purged from the feed valve (53) to the shot cleaning equipment (87, 287, 41) on the vacuum side.

Method for treating an iron plate and plate obtained by this method

Abstract: Method for treating an iron plate (2) made of forged aluminium alloy, the oblong outer face (1) of which has undergone an emery abrasion operation along its longitudinal direction. According to the invention, brushing of the entire outer face (1) of the plate is also carried out along its longitudinal direction, using at least one cylindrical brush (4) rotationally mounted along an axis parallel to the plane of the plate, the said brush used comprising bristles (6) made of a sufficiently hard material to produce "multistrand" hammering (peening) of the outer face (1) of the plate, capable of forming a plurality of microscopic, longitudinal furrows (7) in the said face.