http://srg.northwestern.edu/Publications%20Library/Journals/2009_3DModelingSubsurfaceFatigueCrack__ShotPeenedGearSteels.pdf

3D modeling of subsurface fatigue crack nucleation potency of primary inclusions in heat treated and shot peened martensitic gear steels

In the cold spray process, deposition of particles takes place through intensive plastic deformation upon impact in a solid state at the temperatures well below their melting point. The high particle impact velocity causes high local stresses which lead to deforming the particles and the substrate plastically in the proximity of the particle–substrate interface. As a result, high residual stresses are introduced in cold spray coatings due to the peening effect of the particles collisions with the substrate. In this study, a powder based on the chemical composition of IN 718 was cold-sprayed on IN 718 substrates by using nitrogen gas for an application as a repair tool for aero engine components. The magnitude of the residual stress and its distribution through the thickness were measured by using the hole-drilling and the bending methods. Residual stress was also estimated by using an approach based on the physical process parameters. Mainly compressive residual stresses were observed in cold-sprayed IN 718 coatings. Accumulation of residual stresses in the coatings is highly affected by peening during deposition and it decreases with increase in thickness. It has been observed that the adhesion-strengths of cold-sprayed IN 718 coatings are highly influenced by coating thickness and residual stress states of the coating/substrate system. In the presence of residual stresses in the coatings, adhesion-strength decreases with increasing coating thickness. The energy-release-rate criterion has been used to predict adhesion-strength with increasing coating thickness. Predicted bond-strength values are close to the measured adhesion-strength values and decrease with increase in coating thickness.

Influence of coating thickness on residual stress and adhesion-strength of cold-sprayed Inconel 718 coatings

Effect of micro ploughing during fine particle peening process on the microstructure of metallic materials

In a toroidal continuously variable transmission, a primary oil pump is driven by an engine, whereas a secondary oil pump is driven in response to rotation of a road wheel. A hydraulic servo mechanism is connected to a trunnion to create an offset of the trunnion from a neutral position for a tilting motion of the power roller. Also provided is a hydraulic system that supplies the hydraulic pressure discharged from the secondary pump to the hydraulic servo mechanism to prevent the offset of the trunnion in the trunnion-axis direction, corresponding to an upshift, occurring owing to rotation of the road wheel in a stopped state of the engine. A modulated hydraulic pressure, which is constantly produced by the hydraulic system during operation of the engine, acts to hold the secondary pump at either of an inoperative state and an unloaded condition during the operation of the engine.

Toroidal continuously variable transmission

A toroidal type continuously variable transmission includes an input disk mounted on an input shaft; an output disk mounted on an output shaft; and a pair of power roller bearings each of which includes an inner race, an outer race, and a plurality of rolling elements. The inner races are engaged with the input and output disks to transmit the power of the input shaft to the output shaft. The inner races, outer races, input disk and output disk are made of case hardening steel, and are each subjected to a heat treatment in which carburizing or carbonitriding, hardening and tempering are performed sequentially, and then to shot peening, and finished by grinding of a predetermined grinding portion.

Toroidal type continuously variable transmission parts having increased life

Simplified theoretical formulae based on shot peening parameters and materials properties have been developed to predict the maximum and the peak depth of the compressive residual stress produced by shot peening. These formulae are based on the motion equation for a shot and the analytical model proposed by Li, who utilized the Hertz theory of elastic contact and a simplified elasto-plastic theory. Experimental verifications were carried out under various shot peening conditions. Shots were made of cast steel, fused Zirconia, and glass, each having its own range in diameter. Actual residual stress distributions were measured by the X-ray diffraction method. The maximum and peak depth of the compressive residual stress predicted by the proposed formulae agreed well with the experimental values in a wide variety of shot peening conditions.

Theoretical Prediction of Residual Stress Produced by Shot Peening and Experimental Verification for Carburized Steel

The shot velocity in two pneumatic shot-peening machines has been examined by means of experiment and theory. The shot velocity was measured under various operating conditions by a high-speed shutter TV camera. As a result, the shot velocity over the usual range of shot diameter D, shot density p, and air-pressure p was related by the formula, V=K·Dα·ρβ·(p+pb)γ, where Pb is atmospheric pressure. α and β are almost independent of the shot-peening machine, and α a 0.36, β a 0.48, K and γ are dependent on the shot-peening machine. On the other hand, the theoretical consideration based on hydrodynamics tied to the derivation of the formula, V=K·D-0.44·ρ-0.44·(p+pb)0.43 for the suction type machine, and almost the same formula for the direct-pressure type. The theoretically derived formula coincided well with the experimentally induced formula.

Measurement and Analysis of Shot Velocity in Pneumatic Shot Peening.

PROBLEM TO BE SOLVED: To provide a planetary roller mechanism capable of preventing macro slip properly without increasing normal force into a contact part excessively. SOLUTION: Since a recessed part 26 is formed at a position opposing to an outer peripheral face 33 of a pinion roller 23 on an inner peripheral face 32 of a ring roller 22, length Lr (=L1+L2) of the contact part 28 of each pinion roller 23 and the ring roller 22 in the direction vertical to the direction of tangential line and the direction of normal line of the contact part 28 is set to be shorter than length Ls of the contact part 27 of a sun roller 21 and each pinion roller 23 in the direction vertical to the direction of tangential line and the direction of normal line of the contact part 27. Consequently, an area of the contact part 28 can be reduced, a surface pressure of the contact part 28 can be increased, and difference between the surface pressure of the contact part 27 and the surface pressure of the contact part 28 can be reduced. COPYRIGHT: (C)2007,JPO&INPIT

Planetary roller mechanism

A brightening chemical polishing solution for a hardened steel article (e.g., a carburized and quenched gear) comprises hydrofluoric acid having a molar concentration of from 0.2 to 2 mol/l, hydrogen peroxide having a molar concentration of from 0.4 to 4 mol/l, and water, a molar ratio of the hydrofluoric acid to the hydrogen peroxide being from 1:1.5 to 1:2.8. The steel article is quench hardened and is chemically polished in the solution. A shot-peening is additionally performed, prior to the polishing.

Kazuyoshi Ogawa

Papers

Theoretical Prediction of Residual Stress Produced by Shot Peening and Experimental Verification for Carburized Steel

Measurement and Analysis of Shot Velocity in Pneumatic Shot Peening.

Planetary roller mechanism

Brightening chemical polishing solution for hardened steel article and method of chemically polishing said article in the solution

Theoretical Prediction of Residual Stress Produced by Shot Peening for Hardened Steel