scholarly journals Predicting the Effects of Grain Size on Machining-Induced Residual Stresses in Steels

2014 ◽  
Vol 996 ◽  
pp. 634-639 ◽  
Author(s):  
Mohamed N.A. Nasr
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Residual Stresses ◽  
Finite Element Modelling ◽  
Material Strength ◽  
Grain Size Effect ◽  
Inverse Relation ◽  
Lower Yield ◽  
Element Modelling ◽  
Lower Yield Strength

The current study examines the effect of grain size on machining-induced residual stresses (RS), during turning, using finite element modelling. Based on the well-known inverse relation between grain size and material strength, the grain size effect was simulated via changing the workpiece yield strength. This was also done at different strain hardening rates. The model was validated using four materials. Larger grain size (lower yield strength) resulted in higher surface tensile RS. This is attributed to the surface layer being subjected to higher compressive plastic deformation, as well as higher workpiece temperatures, which both contribute to higher tensile RS.

A work-hardening model of the lower yield strength of discontinuously yielding alloys: Ni3Al and mild steel

1989 ◽  
Vol 4 (3) ◽  
pp. 470-472 ◽  
Author(s):  
E. M. Schulson
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Mild Steel ◽  
Work Hardening ◽  
Lower Yield ◽  
Hardening Model ◽  
Lower Yield Strength ◽  
Work Hardening Model ◽  
Lüders Bands

The lower yield strengths of Ni3Al and mild steel and their respective relationships to (grain size)−0.8 and (grain size)−0.5 are explained in terms of work hardening within Lüders bands.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

An Investigation of Adaptive Rubber Bearings

2016 ◽  
Author(s):  
C. S. Tsai ◽  
Hui-Chen Su ◽  
Wen-Chun Huang
Keyword(s):  
Yield Strength ◽  
Lower Yield ◽  
Passive Devices ◽  
Major Benefit ◽  
Lead Rubber Bearings ◽  
Lower Yield Strength ◽  
Multiple Levels ◽  
Materials Used ◽  
Rubber Bearings ◽  
Stiffness And Damping

Proposed in this study are several innovative seismic isolators composed of rubber materials that are called adaptive rubber bearings based on their adaptive characteristics. The materials used in the proposed isolators are free of lead commonly found in lead rubber bearings. The lead material results in a heavy environmental burden as well as lower yield strength and damping due to rising temperature during earthquakes, and thus causes larger displacements than we would expect. The designed mechanisms in the proposed isolators enable these devices to be manufactured relatively easily. They also provide extremely high damping to bearings, which is strongly desired by engineers in practice. The proposed rubber bearings are completely passive devices yet possess adaptive stiffness and adaptive high damping. The change in stiffness and damping is predictable and can be calculated at specifiable and controllable displacement amplitudes. The major benefit of the adaptive characteristics of seismic isolators is that a given system can be optimized separately for multiple performance objects at multiple levels of earthquakes. In this study, mathematical formulations are derived to explain the mechanisms of the proposed devices. Experimental results of high velocity cyclical loadings are also provided to verify the advanced concepts of the proposed devices.

Mechanical Properties and Morphologies of PP/Co-PP/Talc Composites for Microwave Application

2012 ◽  
Vol 626 ◽  
pp. 711-715 ◽  
Author(s):  
J. Piwsawang ◽  
T. Jinkarn ◽  
Chiravoot Pechyen
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Filler Loading ◽  
Lower Yield ◽  
Elongation At Break ◽  
Compression Load ◽  
Microwave Application ◽  
Lower Yield Strength ◽  
Morphology Development ◽  
Internal Mixer

Unmodified talc fillers were compounded with polypropylene (PP) and copolymer polyethylene (Co-PP) separately in a Brabender plasticorder internal mixer at 180 °C and 50 rpm in order to obtain composites, which contain 040 phr (per 100 part of resin) of filler at 40 phr intervals. The morphology development and the mechanical properties of the composites with reference to filler loading were investigated. In terms of mechanical properties, Youngs modulus and maximum compression load increased, whereas yield strength and elongation at break decreased with the increase in filler loading of PP/Co-PP/Talc composites. The PP/Co-PP exhibited lower yield strength and youngs modulus, and higher elongation at break than talc composites (data not show here). Scanning electron microscopy (SEM) was used to examine the structure of the fracture surface to justify the variation of the measured mechanical properties.

scholarly journals Experimental study of zone of yield strength on corroded construction steel specimens for reuse

2019 ◽  
Vol 279 ◽  
pp. 02009
Author(s):  
Antonio Shopov ◽  
Borislav Bonev
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Experimental Study ◽  
Yield Strength ◽  
Structural Changes ◽  
Steel Structures ◽  
Strain Diagram ◽  
Lower Yield ◽  
Structural Element ◽  
Lower Yield Strength

Zone of yield strength is a part of stress-strain diagram on steel. In this zone is located an upper and lower yield strength points. These points are important for calculation and design of steel structures elements. When a structural element is corroded, its mechanical properties are changed i.e. changes the geometric characteristics, superficial defects appear and leads to structural changes of material. The facts unambiguously determine that in order to decide whether or not the corrosion element can be reuse, it is necessary to study the material and to determine the new values at the yield strength points. In order to legally make the necessary calculation in sizing and to judge for its reuse. The report studies a zone of yield strength on steel elements with corrosion. Experimental data was obtained, then processed using the stochastic method of processing empirically obtained data, and it was determined with sufficient probability the values to be used for calculation and design in practice.

Influence of Inhomogeneous Deformation on Tensile Behavior of Sheets Processed Through Constrained Groove Pressing

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Sunil Kumar ◽  
S. Venkatachalam ◽  
Hariharan Krishnaswamy ◽  
Ravi Kumar Digavalli ◽  
H. S. N. Murthy
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Strain Distribution ◽  
Fe Simulation ◽  
Total Elongation ◽  
Image Correlation ◽  
Lower Yield ◽  
Standard Specimens ◽  
Lower Yield Strength ◽  
Miniature Specimens

Constrained groove pressing (CGP) is a severe plastic deformation technique to produce the ultra-fine grained sheet. The inhomogeneous strain distribution and geometry variation induce differential mechanical properties in the processed sheet. The improved mechanical properties of CGP sheets is due to the composite effect of weak and strong regions formed by geometric and strain inhomogeneities. Weaker regions exhibit large strain, lower yield strength, and higher strain hardening compared to stronger regions. The estimation of mechanical properties is influenced by these defects leading to the difference in the mechanical properties along different orientations. Experimental investigation revealed that the commonly used tensile samples cut perpendicular to the groove orientation exhibit variation in thickness along the gauge length affecting the results from tensile tests. To further understand the effect of geometric variation, a typical CGP specimen was reverse engineered and finite element (FE) simulation was performed using the actual geometry of the CGP processed specimen. The strain distribution from FE simulation was validated experimentally using the digital image correlation data. Based on the numerical and experimental studies, miniature specimens were designed to eliminate the geometric effects from the standard parallel specimen. Miniature parallel specimens showed lower yield strength and total elongation compared to the standard specimens. However, the statistical scatter of total elongation of the miniature specimens was much less than that of the standard specimens, indicating better repeatability. Probably this is the first study to quantify the contribution of composite geometric effect in the mechanical properties of CGP.

DETERMINING RESIDUAL STRESSES IN WELDED CONNECTIONS OF ORTHOTROPIC STEEL BRIDGE DECKS WITH A HOLE-DRILLING TECHNIQUE

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Wim Nagy ◽  
Philippe Van Bogaert ◽  
Hans De Backer
Keyword(s):  
Yield Strength ◽  
Residual Stresses ◽  
Experimental Test ◽  
Bridge Decks ◽  
Hole Drilling ◽  
Material Strength ◽  
Steel Bridge ◽  
Test Setup ◽  
Deck Plate ◽  
Drilling Technique

Manufacturing processes such as welding operations cause residual stresses that are present in most civil structures. They cause plastic deformations without any external loads and are therefore often overlooked during design. Nevertheless, residual stresses can have profound influences on material strength and fatigue life. This is also true for orthotropic steel bridge decks, which have many complex welding details. Because little is known about the distribution of residual stresses due to welding, a semi-destructive experimental test setup is developed for a stiffener-to-deck plate connection on an orthotropic steel bridge deck. In particular, the hole-drilling technique is used. With this experimental test setup, a clear distribution of the residuals stresses becomes visible. Residual stresses up to the yield strength can be found near the weld and up to 50% of the yield strength elsewhere. However, more research is needed to verify why the sign of the stresses is opposite to the expected stresses in the literature.

Stress Measurement Using a Bilayer Metal-Ceramic Strip

1992 ◽  
Vol 264 ◽  
Author(s):  
Shukla Kapur ◽  
Philip L. Flaltz
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Finite Element Modelling ◽  
Stress Measurement ◽  
Second Phase ◽  
Thermal Expansion Mismatch ◽  
Element Modelling ◽  
Metal Ceramic ◽  
Stress Asymmetry

AbstractResidual stresses that develop in metal/ceramic bonded systems due to thermal expansion mismatch have been calculated using finite element modelling and measured experimentally using a simple bilayer strip. Bending in the strip occurs during cooling due to the stress asymmetry. Residual stresses are calculated by measuring the deflection of the strip and the temperature at which the strip is flat. Various compositions of both copper and nickel pastes, with and without glass and other second phase additions were evaluated on glass-ceramic. The effects of further processes, e.g. thermal cycling, brazing and plating, are also reported in this work.

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