Showing papers on "Peening published in 1978"

Method of reducing fuel consumption by peening

Abstract: A method of reducing fuel and oil consumption in an internal combustion engine in which the cylinder walls of the engine are peened with glass spheres having a diameter within the range of form about 0.002 inches to about 0.004 inches. The glass spheres form a multiplicity of local depressions and surface compression at the points of impact and are directed against the cylinder walls for a period of time sufficient to form the depressions over the entire surface area without leaving flat portions of the surface between the depressions. In some embodiments the cylinder walls are coated with a lubricating agent such as graphite prior to being peened. After the peening step the walls are lightly honed to produce substantially flat supporting areas between the individual depressions.

Retrofitting fatigue damaged bridges

Abstract: This paper examines continuing laboratory and field studies on ways to retrofit fatigue damaged members. Results of a pilot field study on two bridge structures with known fatigue cracks at the ends of cover plates are reviewed. Fatigue damage members were retrofitted by peening and gas tungsten arc remelting the weld toe. The initial retrofit is summarized and the results of subsequent inspection after 1 1/2 years is reviewed. Also discussed is the retrofitting of several more bridges by peening weld toes on a more extensive scale. In recent years many highway and bridge structures have experienced fatigue damage from out-of-plane displacements. This has resulted in web cracking at the ends of transverse stiffeners and floor beam connection plates which were not welded to tension flanges. Cracking as a result of out-of-plane movement is reviewed and several examples of cracking in a number of bridges is discussed. Nearly all of these fatigue damaged members have been repaired and retrofitted by drilling holes in the web plate at the ends of the horizontal cracks. A series of laboratory studies have been carried out to evaluate the fatigue behavior of stiffeners due to out-of-plane displacement. After fatigue cracking from out-of-plane movement these test beams are retrofitted by drilling holes in the web plate. Subsequently the fatigue damaged girder has been cycled to confirm the adequacy of the retrofitting procedures. These results will be summarized and related to bridges with comparable conditions. /Author/

Effects of sodium chloride and shot peening on corrosion fatigue of AISI 6150 steel

Abstract: Reversed-bending fatigue tests of quenched and tempered AISI 6150 steel were conducted in dry air and in aqueous 3 pct NaCl. The 3 pct NaCl environment drastically reduced fatigue life but two different shot peening treatments were found to improve the corrosion fatigue life over that of unpeened samples. Multiple fatigue crack initiation occurred at very distinct locations in both the unpeened and the peened specimens fatigued in 3 pct NaCl. Fatigue crack propagation from each initiation site occurred first on flat facets normal to the stress axis and then by a more ductile mechanism after the initiation facets had linked. The average size of the corrosion fatigue initiation facets in the peened specimens was much smaller than that of the unpeened specimens; however, the number of initiation sites was greater in the peened specimens. It is believed that the beneficial effect of the shot peening results from significantly reduced early fatigue crack propagation rates in the compressive residual stress layer at the surface.

Investigations on Peen Forming : 1st Report, On the basic features of this process

Abstract: Peen forming has been utilized in the special field of the airplane industry. The authors conceive independently the principle of this process and intend to develop this as a general forming process of sheet metals. Suitable selection of peening conditions such as the diameter or the velocity of a shot enables bulging of a disc and bending of a strip. Successful conditions in these formings depend on the peening energy of a grain of shot and there exist a lower and an upper limit of the energy. When the upper limit is exceeded, the disc sinks and the strip bends in the opposite direction. So, the intended forming cannot be attained. Peening brings about a strengthening through work-handening and a roughening of the products. This process is applied successfully to strong brittle materials which are difficult to form because it has a feature of forming under compressive stresses.

Retrofitting procedures for fatigue-damaged full-scale welded bridge beams

Abstract: Bridge beams on the east and westbound bridges of span No. 1 at Yellow Mill Pond in Bridgeport, Connecticut, were inspected for fatigue cracking and then retrofitted, using either the peening or the gas tungsten arc remelting procedures. The retrofitted beams were then subjected to fatigue strength tests. The results indicated that both procedures could be used to successfully extend the fatigue life and prevent further crack growth. Only details with initial crack depths greater than 1/8 inch did not achieve the desired life increments. For details with very small or no visible crack, the peening procedure appears to provide a reliable and the most economical means of retrofitting fatigue damage; for details with slightly larger cracks (up to 3/16 inch deep) the gas tungsten arc remelt process is preferred.

Shot for shot peening

Abstract: PURPOSE: To treat a stainless steel pipe effectively by distributing Cr carbide in the state of a net in shot to have the efficiency of toughness. CONSTITUTION: This shot is composed of Cr carbide distributing as a net and particles of carbide exhibited in basic martensite and bainite as shown in the table. The high hardness and toughness may be attributed to the metallic composition. The usual white pig iron has an inclination of easy cracking though hard due to the combined constitution of cementite and pearlite. The shot is used to give the effective shot peening of stainless steel pipe or the like. COPYRIGHT: (C)1980,JPO&Japio

Retrofitting fatigue damaged cover-plated bridge members, for presentation at the 1978 annual meeting of the TRB.

Abstract: This paper summarizes the results of laboratory and field studies on post weld treatment of the termination of welded cover plates. Both aswelded and fatigue damaged members were tested in the laboratory to determine ways to improve fatigue strength and to retrofit fatigue damaged bridge members. Three treatments were examined in the laboratory: grinding, peening, and gas tungsten arc remelting. These methods were applied to details prior to fatigue testing and to members which had experienced fatigue crack growth. Grinding the weld toe with a burr provided the least reliable method. Some improvement was noted at the lower stress range levels, but erratic results were apparent. Gas tungsten arc remelting at the weld toe termination was observed to provide the most reliable and consistent method of improving fatigue strength and retrofitting fatigue damaged members. Peening the weld toe was observed to be most effective when dead load remained on the beam during peening or else the minimum stress was low. Also, only very shallow fatigue cracks could be effectively retrofitted. Based on the results of the laboratory investigation, two bridge structures with known fatigue cracks at the ends of cover plates were retrofitted using the gas tungsten arc remelt procedure or peening. The results of a detailed inspection in 1976 revealed that 22 of 40 cover plate ends had fatigue cracks in the beam flange at the toe of the end welds. These cracks varied in size up to 1/2 in. (12 mm) deep. Only those beams

Shot peening material and shot peening for stress corrosion cracking resistance

Abstract: PURPOSE: By increasing the delay breaking strength of, for example, jointing pins (dovetail pins) of rotors and running blades of a steam turbine by use of shot peening materials of more than the Vickers hardness of at least 1000, breaking damage is prevented. CONSTITUTION: The surfaces of dovetail pins 3 inserted into pin holes 6 equipped on a rotor 1 and a blade 2 are shot peened by a shot peening material of more than the Vickers hardness of at least 1000 on the surface. In this method delay breaking strength of the dovetail pins 3 is increased and breaking damage is prevented. COPYRIGHT: (C)1980,JPO&Japio

Apparatus for producing mechanically-worked vapor-deposited bulk alloys

Abstract: The porosity of bulk alloys produced by deposition of the components of the alloy from the vapor phase can be reduced if the surface of the alloy is mechanically worked, preferably by a peening action, during the course of the deposition. Suitable apparatus for mechanically working the surface of the alloy are sets of hammers or flails driven by a suitable means that they strike the surface of the alloy with sufficient force to flatten asperities produced during the course of the deposition and preferably sufficient to remove porosity adjacent to the surface, yet do not at the same time grossly distort the surface of the alloy.