Threshold stress criterion in new wheel/rail interaction for limiting rail damage under heavy axle loadsKumar, S. and Singh, S. P. J. Eng. Ind. (Trans. ASME) Aug. 1992 114 (3) 284–288

1993 ◽  
Vol 15 (5) ◽  
pp. 442-442
Keyword(s):  
Threshold Stress ◽  
Stress Criterion ◽  
Trans Asme

Threshold Stress Criterion in New Wheel/Rail Interaction for Limiting Rail Damage Under Heavy Axle Loads

1992 ◽  
Vol 114 (3) ◽  
pp. 284-288 ◽  
Author(s):  
S. Kumar ◽  
S. P. Singh
Keyword(s):  
Threshold Stress ◽  
Rolling Friction ◽  
Contact Stresses ◽  
Rolling Contact ◽  
Internal Damage ◽  
Stress Criterion ◽  
Plasticity Region ◽  
Proper Design ◽  
Axle Loads ◽  
Qualitative Discussion

This paper presents a qualitative discussion of the effects of increasing new (initial) wheel-rail contact stresses on the degree of damage to the rail due to heavy axle loads. The importance and need of heavy axle loads and its relationship to rail damage as a result of the increasing wheel-rail contact stresses is discussed. Various mechanisms of energy absorption/losses due to free rolling and modes of rail damage are presented. These modes include surface and internal damage due to wear, contact shear, plasticity, fatigue, shelling, crack formation, etc. The concept of threshold stress observed in free rolling friction much earlier by Drutowski is discussed and analyzed. It is believed by the authors that the threshold stress is s material property. This concept of threshold stress, based on sharply increased rates of wear in free rolling contact, is then presented and analyzed. Considerations of increased plasticity-region development, due to increasing contact stresses and their relationship to increased rates of wear seen in experiments, is utilized to determine an upper bound of contact stresses for new wheel and rail under heavy axle load conditions. It is indicated that new wheel-rail profiles, which will achieve contact stresses below the threshold stress, will enable the U.S. railroads to carry heavy axle loads without serious future damage to the rails. It is concluded that a satisfactory solution for maintaining rail integrity under heavy axle loads is possible with proper design accompanied with laboratory experimentation for the new steels as they may be used in the rails.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

Design options for self-cleansing storm sewers

1996 ◽  
Vol 33 (9) ◽  
pp. 215-220 ◽  
Author(s):  
Chandramouli Nalluri ◽  
Aminuddin Ab. Ghani
Keyword(s):  
Cohesive Sediments ◽  
Stress Criterion ◽  
Sediment Bed ◽  
Sediment Size ◽  
Codes Of Practice ◽  
Design Charts ◽  
Design Options ◽  
Minimum Velocity ◽  
Limited Depth ◽  
Storm Sewers

A list of available codes of practice for self-cleansing sewers is presented and a review of appraisals of minimum velocity criterion is summarised. Comparisons of newly developed “minimum velocity” criteria and “minimum shear stress” criterion are presented. Some design charts are also given. These charts are applicable to non-cohesive sediments (typically storm sewers). It appears that sediment size and concentration need to be taken into account, and that a limited depth of sediment bed is recommended for large pipes (diameters > 1000 mm) to maximise their transport capacity.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

scholarly journals Application of the Point Stress Criterion to Assess the Bond Strength of a Single-Lap Joint

2014 ◽  
Vol 46 (4) ◽  
pp. 518-525
Author(s):  
K. S. Sajikumar ◽  
N. Asok Kumar ◽  
B. Nageswara Rao
Keyword(s):  
Bond Strength ◽  
Lap Joint ◽  
Stress Criterion ◽  
Single Lap Joint

The Effects of Material Strength, Stress Ratio, and Compressive Overload on the Threshold Behavior of a SAE1045 Steel

1985 ◽  
Vol 107 (1) ◽  
pp. 19-25 ◽  
Author(s):  
M. T. Yu ◽  
T. H. Topper
Keyword(s):  
Mechanical Properties ◽  
Growth Rate ◽  
Threshold Stress ◽  
Stress Ratio ◽  
Peak Load ◽  
Load Level ◽  
Material Strength ◽  
Threshold Stress Intensity ◽  
Threshold Behavior ◽  
Rate Behavior

The fatigue crack growth rate behavior of a SAE1045 steel in the as received condition and four different quenched and tempered conditions was studied as a function of stress ratio and peak compressive overload. The threshold stress intensity behavior of the quenched and tempered conditions was not sensitive to changes of monotonic mechanical properties. The threshold decreased linearly with increasing positive stress ratio and compressive peak load level. As received ferritic-pearlitic SAE1045 steel was much more sensitive to stress ratio and compressive peak load than any of the quenched and tempered conditions studied.

Brittle Fracture Analysis of a Dissimilar Metal Weld

2013 ◽  
Author(s):  
A. Blouin ◽  
S. Chapuliot ◽  
S. Marie ◽  
J. M. Bergheau ◽  
C. Niclaeys
Keyword(s):  
Brittle Fracture ◽  
Weld Joint ◽  
Threshold Stress ◽  
Base Alloy ◽  
Welding Process ◽  
Loading Conditions ◽  
Brittle To Ductile Transition ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

One important part of the integrity demonstration of large ferritic components is based on the demonstration that they could never undergo brittle fracture. Connections between a ferritic component and an austenitic piping (Dissimilar Metal Weld — DMW) have to respect these rules, in particular the Heat Affected Zone (HAZ) created by the welding process and which encounters a brittle-to-ductile transition. Within that frame, the case considered in this article is a Ni base alloy narrow gap weld joint between a ferritic pipe (A533 steel) and an austenitic pipe (316L stainless steel). The aim of the present study is to show that in the same loading conditions, the weld joint is less sensitive to the brittle fracture than the surrounding ferritic part of the component. That is to say that the demonstration should be focused on the ferritic base metal which is the weakest material. The bases of this study rely on a stress-based criterion developed by Chapuliot et al., using a threshold stress (σth) below which the cleavage cannot occur. This threshold stress can be used to define the brittle crack occurrence probability, which means it is possible to determine the highest loading conditions without any brittle fracture risk.

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