Characterization of Shot-Peened Surfaces by a Noncontacting Thermoelectric Method

2000 ◽  
Author(s):  
Hector Carreon ◽  
Peter B. Nagy
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Surface Layer ◽  
Dislocation Density ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Cold Work ◽  
Subsurface Layer ◽  
Thermoelectric Method

Abstract Shot peening is widely used in the aerospace and other industries to increase the damage tolerance of metal parts via producing a thin surface layer of compressive residual stress that prevents crack initiation and retards crack growth during service. Nondestructive evaluation of the prevailing compressive residual stress in the shallow subsurface layer is complicated by the adverse effects of shot peening, such as surface roughness and cold work that manifests itself through increased dislocation density and localized texture. Recent research efforts have revealed that conventional ultrasonic and eddy current NDT methods are simply too sensitive to surface roughness to quantitatively assess the subtle variations in mechanical and electrical properties that are caused by shot peening. On the other hand, noncontacting thermoelectric techniques are very unique among all other methods used in nondestructive materials characterization in that they are solely sensitive to intrinsic material variations regardless of the size, shape, and surface quality of the specimen to be tested. Noncontacting thermoelectric methods, based on magnetic detection of local thermoelectric currents around inhomogeneities in metals when a temperature gradient is established throughout the specimen, are especially well suited for the characterization of shot peened surfaces. Experimental evidence suggests that this method can reliably detect and quantitatively assess otherwise hidden variations in material properties within the shallow surface layer of shot peened specimens. The thermoelectric method is sensitive to all three “material” effects of shot peening, namely residual stress, local texture, and increased dislocation density, but it is entirely insensitive to its “geometrical” by-product, i.e., the rough surface topography. Further development of the thermoelectric method is necessary to study the underlying physical phenomena before it can be successfully adapted to practical inspection problems, but the preliminary results presented in this paper are very promising.

scholarly journals Determination of the Optimal Coverage for Heavy-Duty-Axle Gears in Shot Peening

2021 ◽  
Author(s):  
Hongzhi Yan ◽  
Pengfei Zhu ◽  
Zhi Chen ◽  
Hui Zhang ◽  
Yin Zhang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Dislocation Density ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Heavy Duty ◽  
High Coverage ◽  
Service Lifetime ◽  
Maximum Value

Abstract Pitting and wear often appear on heavy-duty-axle gears due to their harsh working conditions, such as high torques, high loads and poor lubrication. Shot peening is a popular surface strengthening method for gears. In order to ensure complete coverage during shot peening, 100%~200% coverage is usually prescribed for most gears. However, it is difficult to effectively improve the contact fatigue and wear resistance of heavy-duty-axle gears. Generally, increasing shot peening coverage can heighten the compressive residual stress for prolonging the service lifetime of gears. Whereas, high coverage levels may cause the deterioration of surface roughness, thus increase the noise and vibration of gears. To address this issue, this paper deals with the determination of optimal coverage for heavy-duty-axle gears by experimental tests. The influence of shot peening coverage on the surface integrity of gears is analyzed in terms of residual stress, microhardness, surface morphology and dislocation density. The results show that the maximum compressive residual stress increases first and then keeps stable with the increase of coverage, and the maximum value is −1172.10 MPa. The microhardness peak increases obviously in the beginning and then slowly rises with the increase of coverage, and the maximum value is 747.5 HV1.0. The surface roughness (Ra) decreases initially and then enhances with the increase of coverage, and the minimum value is 0.99 μm under the coverage of 1000%. The dislocation density increases with the increase of coverage, and the maximum value is 3.70×1016 m-2. Numerous damages (microscalings, spallings) occur on the treated gear tooth flank affecting the residual stress distribution and roughness under high coverage levels. Taking into consideration of service lifetime, working noise and economic efficiency, the coverage of 1000% is the optimal coverage for heavy-duty-axle gears in shot peening.

Characterization of nanocrystalline surface layer induced by shot peening and effect on their fatigue strength.

2004 ◽  
Vol 843 ◽  
Author(s):  
Hideo Mano ◽  
Kondo Satoru ◽  
Akihito Matsumuro ◽  
Toru Imura
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Fatigue Strength ◽  
Vickers Hardness ◽  
Shot Peening ◽  
White Layer ◽  
The Other ◽  
Fatigue Properties ◽  
Nanocrystalline Layer

ABSTRACTThe shot peening process is known to produce a hard layer, known as the white layer” on the surface of coil springs. However, little is known about the fatigue properties of this white-layer.In this study, coil springs with a white-layer were manufactured. The surface of these springs was then examined using micro Vickers hardness, FE-SEM etc. to test fatigue strength of the springs.From the results obtained, a microstructure of the white-layer with grain size of 50–100 nm was observed, with a Vickers hardness rating of 8–10 GPa.Tow category springs were manufactured utilizing a double-peening process. These springs had the same residual stress destruction and surface roughness. Only one difference was observed: one spring had a nanocrystalline layer on the surface, while the other did not. The results of the fatigue test realized an increase in the fatigue life of the nanocrystalline surface layer by 9%.

A Study on the Fatigue Characteristics of Al6061-T651 by Shot Peening Velocity

2006 ◽  
Vol 326-328 ◽  
pp. 1093-1096 ◽  
Author(s):  
Won Jo Park ◽  
Sun Chul Huh ◽  
Sung Ho Park
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Fatigue Life ◽  
Shot Peening ◽  
High Speed ◽  
Compressive Residual Stress ◽  
Velocity Increase ◽  
Fatigue Characteristics ◽  
Height Increase ◽  
Small Steel

Small steel ball is utilized in Shot peening process. Called “shot ball” are shot in high speed on the surface of metal. When the shot ball hit the surface, it makes plastic deformation and bounce off, that increase the fatigue life by compressive residual stress on surface. In this study, the results of observation on the tensile strength, hardness, surface roughness, compressive residual stress and fatigue life of a shot peened Al6061-T651 were obtained. Experimental results show that arc height increase tremendously by shot velocity. Also, it shows that surface roughness, hardness, compressive residual stress and fatigue life increase as shot velocity increase.

Influence of Microshot Peening on Surface Layer Characteristics of Cold Tool Steel

2007 ◽  
Vol 561-565 ◽  
pp. 897-900 ◽  
Author(s):  
Yasunori Harada ◽  
Kenzo Fukaura ◽  
Toshinori Aoki ◽  
Daien Yokoi ◽  
Yasushi Haruna
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Surface Layer ◽  
Fatigue Strength ◽  
Tool Steel ◽  
Compressive Residual Stress ◽  
Heating Furnace ◽  
Cemented Carbide ◽  
Compressed Air ◽  
New Type

Shot peening is a surface treatment and improves the performance of engineering components. More recently, a new type of microshot has been developed to enhance peening effect. In the present study, the influence of microshot peening on the surface layer characteristics of cold tool steel was investigated. In the experiment, the microshot peening apparatus with a heating furnace was produced experimentally. The projective method of the microshot was a compressed air type. The peening microshots of 0.1mm diameter were cemented carbide and the workpiece was commercially cold tool steel SKD11. Surface roughness, compressive residual stress, and hardness in the peened workpiece were measured. The effect of microshot peening on the fatigue strength of cold tool steel was also examined. The use of hard microshot such as cemented carbide was found to cause a significantly enhanced peening effect for cold tool steel.

scholarly journals Small–Scale Experimental Investigation of Fatigue Performance Improvement of Ship Hatch Corner with Shot Peening Treatments by Considering Residual Stress Relaxation

2021 ◽  
Vol 9 (4) ◽  
pp. 419
Author(s):  
Jin Gan ◽  
Zi’ang Gao ◽  
Yiwen Wang ◽  
Zhou Wang ◽  
Weiguo Wu
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Fatigue Life ◽  
Stress Relaxation ◽  
Stress Field ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Fatigue Performance ◽  
Residual Stress Field ◽  
Residual Stress Relaxation

Ship hatch corner is a common structure in a ship and its fatigue problem has always been one of the focuses in ship engineering due to the long–term high–stress concentration state during the ship’s life. For investigating the fatigue life improvement of the ship hatch corner under different shot peening (SP) treatments, a series of fatigue tests, residual stress and surface topography measurements were conducted for SP specimens. Furthermore, the distributions of the surface residual stress are measured with varying numbers of cyclic loads, investigating the residual stress relaxation during cyclic loading. The results show that no matter which SP process parameters are used, the fatigue lives of the shot–peened ship hatch corner specimens are longer than those at unpeened specimens. The relaxation rate of the residual stress mainly depends on the maximum compressive residual stress (σRSmax) and the depth of the maximum compressive residual stress (δmax). The larger the values of σRSmax and δmax, the slower the relaxation rates of the residual stress field. The results imply that the effect of residual stress field and surface roughness should be considered comprehensively to improve the fatigue life of the ship hatch corner with SP treatment. The increase in peening intensity (PI) within a certain range can increase the depth of the compressive residual stress field (CRSF), so the fatigue performance of the ship hatch corner is improved. Once the PI exceeds a certain value, the surface damage caused by the increase in surface roughness will not be offset by the CRSF and the fatigue life cannot be improved optimally. This research provides an approach of fatigue performance enhancement for ship hatch corners in engineering application.

scholarly journals Fatigue Limit of Custom 465 with Surface Strengthening Treatment

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 238 ◽  
Author(s):  
Gang An ◽  
Ren-jing Liu ◽  
Guang-qiang Yin
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Limit ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Subsurface Layer ◽  
Micro Hardness ◽  
Surface Residual Stress ◽  
Surface Strengthening ◽  
The Relationship

In order to study the effect of nitriding or shot peening on the surface modification and fatigue properties of martensitic stainless-steel Custom 465, the residual stress and micro-hardness of the strengthened layer are determined by X-ray and micro-hardness tester, respectively. The up-and-down method is used to measure the rotational bending fatigue strength at 1 × 107 cycles, and the fatigue fracture characteristic is observed by scanning electron microscopy. The relationship between surface residual stress and internal fatigue limit of surface strengthening treatment is discussed. Results show that nitriding or shot peening surface strengthening layer forms a certain depth of compressive residual stress, where in the surface compressive residual stress of the nitrided specimens is greater than the shot peened specimens. The micro-hardness of the nitrided or shot peened surface strengthening layer is significantly improved, where in the surface micro-hardness of nitriding specimens are higher than shot peening specimens. The nitriding or shot peening surface strengthening can significantly improve the fatigue limit of Custom 465, wherein the fatigue limits of nitrided and shot peened surface strengthened specimens are 50.09% and 50.66% higher than that of the un-surface strengthened specimens, respectively. That is, the effect of the two strengthening methods on fatigue limit is not very different. The fracture characteristics show that the fatigue crack of the un-surface strengthened specimens originates from the surface, while the fatigue crack of surface strengthened specimens originates from the subsurface layer under the strengthened layer. The relationship between the internal fatigue limit and the surface residual stress of the surface strengthened specimen can be used as a method for predicting the fatigue limit of the surface strengthened specimens.

The Influence of Shot Peening Process on the Residual Stress and Microstructure in Deformed Surface Layer of S30432 Austenitic Stainless Steel

2013 ◽  
Vol 768-769 ◽  
pp. 550-556 ◽  
Author(s):  
Ke Zhan ◽  
Chuan Hai Jiang ◽  
Henry Pan
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Surface Layer ◽  
Austenitic Stainless Steel ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Diffraction Method ◽  
Micro Structure ◽  
Near Surface ◽  
Deformed Layer

Shot peening is an important surface treatment which can induce compressive residual stress and refine micro-structure in the deformed surface layer. In this paper, the conventional shot peening, dual shot peening and triple shot peening have been applied to S30432 austenitic stainless steel. The residual stress and micro-structure in the deformed layer were investigated by X-ray diffraction method. The results revealed that a compressive residual stress field was induced in the deformed layer for all shot peening conditions. As the shot peening step increased, the compressive residual stresses increased in near surface layer, and then deceased faster in deeper deformed layer. In terms of microstructure, the domain size increased, while the micro-strain decreased with the depth increasing in the deformed layer. Compare with the effect of three different shot peening method, triple shot peenng is more effective to optimize the compressive residual stress, microstructure and micro-hardness of S30432 austenitic stainless steel.

scholarly journals The influence of vibratory shot peening on the selected properties of the surface layer elements made of cast iron

Mechanik ◽  
2019 ◽  
Vol 92 (11) ◽  
pp. 739-741
Author(s):  
Kazimierz Zaleski ◽  
Agnieszka Skoczylas
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Surface Layer ◽  
Cast Iron ◽  
Shot Peening ◽  
Experimental Investigations ◽  
Spheroidal Graphite ◽  
Absolute Value ◽  
Spheroidal Graphite Cast Iron ◽  
Graphite Cast Iron

The results of experimental investigations influence of vibratory shot peening on surface roughness and residual stress of spheroidal graphite cast iron objects were presented. The surfaces before vibratory shot peening were milled using different feed. After vibratory shot peening surface roughness Ra = 0.7÷0.9 μm was obtained and in surface layer compressive residual stress, with the maximum (absolute) value from 170 MPa to 330 MPa at a depth 0.4÷0.7 mm have been formed. For accepted vibratory shot peening condition it was recommended to use time of about 8 minutes.

Comparable Study on Water Cavitation Peening and Traditional Shot Peening of Almen Strips

2010 ◽  
Vol 154-155 ◽  
pp. 1446-1449
Author(s):  
Xiu Juan Zhao ◽  
Jun Wen Wang ◽  
Chun Huan Chen ◽  
Yuan Sun ◽  
Rui Ming Ren ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Sample Surface ◽  
Standoff Distance ◽  
Operating Pressure ◽  
Pressure Sensing ◽  
Wide Range ◽  
Colour Changes

Comparing with conventional mechanical shot peening (SP) technique, water cavitation peening (WCP) experiments of Almen strips were carried out on a self-manufactured equipment. The results show that WCP demonstrates a wide range of standoff distance (SD) that from the nozzle to the surface of the object. By measuring the colour changes of the Fuji pressure sensing film, over 110 MPa impacting pressure was detected, which is resulted from the bubbles blasting on the sample surface when the SD is from 65 to 100 mm under 40 MPa of operating pressure. 600 MPa compressive residual stress achieved on the suface of the Almen strips after WCPed for 32 min. The depth of the zone affected by the compressive residual stress is about 100 µm. The highest residual stress appears in the top surface layer, while in case of SP it appears in the subsurface. Compared to SP, WCP is capable to get rather smoother surface and cause less deformation of the testing sheet, simultaneously.

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