Study on surface roughness and residual stress change during cold forging.

Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59–61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions.

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Sacrificial Materials and Release Etchants for Metal MEMS That Reduce or Eliminate Hydrogen-Induced Residual Stress Change

Journal of Microelectromechanical Systems ◽

10.1109/jmems.2021.3069397 ◽

2021 ◽

pp. 1-7

Author(s):

Longchang Ni ◽

Maarten P. de Boer

Keyword(s):

Residual Stress ◽

Stress Change ◽

Sacrificial Materials

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Measuring the Casimir Forces with an Adhered Cantilever: Analysis of Roughness and Background Effects

Universe ◽

10.3390/universe7030064 ◽

2021 ◽

Vol 7 (3) ◽

pp. 64

Author(s):

Ivan A. Soldatenkov ◽

Anastasiya A. Yakovenko ◽

Vitaly B. Svetovoy

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Short Distance ◽

Technological Progress ◽

Experimental Information ◽

Casimir Forces ◽

Raw Data ◽

Micromechanical Devices ◽

Negligible Contribution

Technological progress has made possible precise measurements of the Casimir forces at distances less than 100 nm. It has enabled stronger constraints on the non-Newtonian forces at short separations and improved control of micromechanical devices. Experimental information on the forces below 30 nm is sparse and not precise due to pull-in instability and surface roughness. Recently, a method of adhered cantilever was proposed to measure the forces at small distances, which does not suffer from the pull-in instability. Deviation of the cantilever from a classic shape carries information on the forces acting nearby the adhered end. We calculate the force between a flat cantilever and rough Au plate and demonstrate that the effect of roughness dominates when the bodies approach the contact. Short-distance repulsion operating at the contact is included in the analysis. Deviations from the classic shape due to residual stress, inhomogeneous thickness of the cantilever, and finite compliance of the substrate are analysed. It is found that a realistic residual stress gives a negligible contribution to the shape, while the finite compliance and inhomogeneous thickness give measurable contributions that have to be subtracted from the raw data.

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Influences of Residual Stress, Surface Roughness and Peak-Load on Micro-Cracking: Sensitivity Analysis

Metals ◽

10.3390/met11020320 ◽

2021 ◽

Vol 11 (2) ◽

pp. 320

Author(s):

Jairan Nafar Dastgerdi ◽

Fariborz Sheibanian ◽

Heikki Remes ◽

Hossein Hosseini Toudeshky

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Crack Formation ◽

Peak Load ◽

Crack Size ◽

Effective Parameters ◽

Load Range ◽

Load Effect ◽

Damage Initiation ◽

Load Conditions

This paper provides further understanding of the peak load effect on micro-crack formation and residual stress relaxation. Comprehensive numerical simulations using the finite element method are applied to simultaneously take into account the effect of the surface roughness and residual stresses on the crack formation in sandblasted S690 high-strength steel surface under peak load conditions. A ductile fracture criterion is introduced for the prediction of damage initiation and evolution. This study specifically investigates the influences of compressive peak load, effective parameters on fracture locus, surface roughness, and residual stress on damage mechanism and formed crack size. The results indicate that under peak load conditions, surface roughness has a far more important influence on micro-crack formation than residual stress. Moreover, it is shown that the effect of peak load range on damage formation and crack size is significantly higher than the influence of residual stress. It is found that the crack size develops exponentially with increasing peak load magnitudes.

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Effects of Roughness on Stresses in an Oxide Scale Formed on a Superalloy Substrate

Coatings ◽

10.3390/coatings11040479 ◽

2021 ◽

Vol 11 (4) ◽

pp. 479

Author(s):

Yang Zhao ◽

Fan Sun ◽

Peng Jiang ◽

Yongle Sun

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Residual Stresses ◽

Oxide Scale ◽

Rough Surface ◽

Alumina Scale ◽

Growth Stress ◽

Oxide Growth ◽

Substrate Thickness ◽

Roughness Effect

The effects of surface roughness on the stresses in an alumina scale formed on a Fecralloy substrate are investigated. Spherical indenters were used to create indents with different radii and depths to represent surface roughness and then the roughness effect was studied comprehensively. It was found that the residual stresses in the alumina scale formed around the rough surface are almost constant and they are dominated by the curvature rather than the depth of the roughness. Oxidation changes the surface roughness. The edge of the indent was sharpened after oxidation and the residual stress there was released presumably due to cracking. The residual stresses in the alumina scale decrease with increase in oxidation time, while the substrate thickness has little effect, given that the substrate is thicker than the alumina scale. Furthermore, the effect of roughness on the oxide growth stress is analysed. This work indicates that the surface roughness should be considered for evaluation of stresses in coatings.

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Study on the Effect of Grinding Pressure on Material Removal Behavior Performed on a Self-Designed Passive Grinding Simulator

Applied Sciences ◽

10.3390/app11094128 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4128

Author(s):

Peng-Zhan Liu ◽

Wen-Jun Zou ◽

Jin Peng ◽

Xu-Dong Song ◽

Fu-Ren Xiao

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Service Life ◽

Material Removal ◽

Removal Rate ◽

Grinding Force ◽

Grinding Wheel ◽

Grinding Process ◽

Grinding Temperature ◽

Grinding Efficiency

Passive grinding is a new rail grinding strategy. In this work, the influence of grinding pressure on the removal behaviors of rail material in passive grinding was investigated by using a self-designed passive grinding simulator. Meanwhile, the surface morphology of the rail and grinding wheel were observed, and the grinding force and temperature were measured during the experiment. Results show that the increase of grinding pressure leads to the rise of rail removal rate, i.e., grinding efficiency, surface roughness, residual stress, grinding force and grinding temperature. Inversely, the enhancement of grinding pressure and grinding force will reduce the grinding ratio, which indicates that service life of grinding wheel decreases. The debris presents dissimilar morphology under different grinding pressure, which reflects the distinction in grinding process. Therefore, for rail passive grinding, the appropriate grinding pressure should be selected to balance the grinding quality and the use of grinding wheel.

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Study on the effect mechanisms of pre-stress on residual stress and surface roughness in PSHG

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-016-9033-2 ◽

2016 ◽

Vol 88 (9-12) ◽

pp. 3243-3256 ◽

Cited By ~ 9

Author(s):

Yansheng Deng ◽

Shichao Xiu ◽

Xiaoliang Shi ◽

Cong Sun ◽

Yushi Wang

Keyword(s):

Residual Stress ◽

Surface Roughness

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In Situ Thin Film Stress Measurements – A Path to Understanding the Structure and Morphology of Electron Beam Evaporated ZnS

MRS Proceedings ◽

10.1557/proc-749-w10.8 ◽

2002 ◽

Vol 749 ◽

Author(s):

Vincent Barrioz ◽

Stuart J. C. Irvine ◽

D. Paul

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Electron Beam ◽

Stress Reduction ◽

Float Glass ◽

Film Stress ◽

Intrinsic Stress ◽

Ex Situ ◽

Stress Measurements

ABSTRACTZnS is a material of choice in the optical coating industry for its optical properties and broad transparency range. One of the drawbacks of ZnS is that it develops high compressive intrinsic stress resulting in large residual stress in the deposited layer. This paper concentrates on the evolution of residual stress reduction in ZnS single layers, depending upon their deposition rate or the substrate temperature during deposition (i.e. 22 °C and 133 °C). The substrate preparation is addressed for consideration of layer adhesion. Residual stress of up to − 550 MPa has been observed in amorphous/poor polycrystalline ZnS layers, deposited on CMX and Float glass type substrates, by electron beam evaporation at 22 °C, with a surface roughness between 0.4 and 0.8 nm. At 133 °C, the layer had a surface roughness of 1 nm, the residual stress in the layer decreased to − 150 MPa, developing a wurtzite structure with a (002) preferred orientation. In situ stress measurements, using a novel optical approach with a laser-fibre system, were carried out to identify the various sources of stress. A description of this novel in situ stress monitor and its advantages are outlined. The residual stress values were supported by two ex situ stress techniques. The surface morphology analysis of the ZnS layers was carried out using an atomic force microscope (AFM), and showed that stress reduced layers actually gave rougher surfaces.

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Effect of Surface Machining on the Fatigue Life of Low Alloy Steel for Hydrogen Pressure Vessels

Volume 6: Materials and Fabrication ◽

10.1115/pvp2007-26535 ◽

2007 ◽

Author(s):

Yoru Wada ◽

Ryoji Ishigaki ◽

Yasuhiko Tanaka ◽

Tadao Iwadate ◽

Keizo Ohnishi

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Fatigue Life ◽

Fatigue Damage ◽

Pressure Vessels ◽

Hydrogen Gas ◽

Annealed Specimen ◽

Surface Machining ◽

Hydrogen Fatigue ◽

Effect Of Surface

The effect of surface machining on fatigue life in high pressure hydrogen gas was investigated. The test was conducted under the elastic range under 45MPa gaseous hydrogen environment by the ground specimen which were machined so that the surface roughness to be Rmax = 19μm(Mark: 19s), 26μm(26s) and 93μm(93s) and by the polished specimen which are prepared so that the surface roughness to be Rmax = 1μm(1s), 3.6μm(3.6s) and 10μm(10s). The hydrogen fatigue life of ground specimens was considerably reduced with increasing surface roughness as compared to the fatigue life in air at the same surface condition. On the other hand, for the annealed conditions of the ground specimen, the reduction by hydrogen effect was fairly small. The residual stress for the ground specimen at the surface rises sharply in tension while the residual stress for the annealed specimen was nearly equal to zero. We have shown that the hydrogen fatigue damage can be evaluated by obtaining the information about residual stress on surface, stress concentration by maximum surface roughness and the threshold stress intensity SH above which hydrogen fatigue damage occurs.

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