The Effect of Deformation on Mechanical Properties and Shakedown on Railroad Wheels

2014 ◽  
Author(s):  
Steven L. Dedmon ◽  
Takashi Fujimura ◽  
Daniel Stone
Keyword(s):  
Mechanical Properties ◽  
Rolling Contact ◽  
Effect Of Temperature ◽  
Plastic Deformations ◽  
Rail Head ◽  
Class D ◽  
Shakedown Theory ◽  
Freight Car ◽  
Class C ◽  
Railroad Wheels

Plastic deformations alter the mechanical properties of many metals and alloys. Class C and Class D wheel steels such as are used in North American freight car service are particularly affected by plastic deformations occurring during rolling contact between the wheel tread and rail head. This investigation determines the effect plastic deformations have on the mechanical properties of Class C and D wheel steels and how those changes could relate to shakedown theory. The effect of temperature is also discussed.

Effect of temperature on the performance of railroad wheels

2017 ◽  
Vol 231 (7) ◽  
pp. 786-793
Author(s):  
Steven L Dedmon
Keyword(s):  
Contact Forces ◽  
Rolling Contact ◽  
Effect Of Temperature ◽  
Railroad Wheel ◽  
Cold Temperatures ◽  
Thermal Cracks ◽  
The World ◽  
Freight Car ◽  
The Many ◽  
Railroad Wheels

Sliding and tread brake heating are known to alter microstructures and properties and show causal relationships with shelling and spalling. Temperature can also affect the performance of wheels in other ways: rolling contact forces depend on the size of the contact patch, which is affected by the elastic modulus, which in turn is affected by the tread temperature. Temperature differences from the rim to the remaining portion of the wheel may cause distortions, which may result in unfavorable contact between the wheel and the rail. Cold temperatures affect the fracture toughness and, in the presence of water, may cause wedging, which will accelerate the shelling process. Oxidation within a crack can also cause wedging, resulting in the propagation of thermal cracks. Changes in the residual stress due to brake heating can also affect shakedown. This study considers the many ways of how temperature can affect the performance of the railroad wheel of a freight car. Most of the author’s observations relate to the freight car service in North America and may not be applicable to other types of service in other parts of the world.

Effect of Temperature on Hardening and Residual Stress Development During Wheel/Rail Rolling Contact

2016 ◽  
Author(s):  
Steven Dedmon ◽  
Takanori Kato ◽  
James Pilch
Keyword(s):  
Thermal Effects ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Rolling Contact ◽  
Effect Of Temperature ◽  
Thermal Cracks ◽  
Field Investigations ◽  
Hardening Mechanisms ◽  
Railroad Wheels ◽  
The Relationship

Brake heating of Railroad Wheels has been known to accelerate shelling, soften the wheel tread and contribute to stress reversal which is a requisite for generating thermal cracks. The effect brake heating has on shakedown has been investigated to a lesser extent, yet even here brake heating can be very important. This research combines field investigations and laboratory work in an attempt to quantify the thermal effects on wheel performance, especially as it relates to sub-surface shelling, microstructural changes and hardening mechanisms. Cyclic tensile tests were conducted at three temperatures to show the relationship between deformation at elevated temperatures and hardening response. Ductility measurements from both monotonic and cyclic tests were used to estimate residual stresses.

Effect of nickel on formation of transition layer during liquid-phase aluminizing of titanium

2020 ◽  
pp. 313-317
Author(s):  
A.I. Kovtunov ◽  
Yu.Yu. Khokhlov ◽  
S.V. Myamin
Keyword(s):  
Mechanical Properties ◽  
Liquid Phase ◽  
Intermetallic Layer ◽  
Reaction Diffusion ◽  
Strength Properties ◽  
Effect Of Temperature ◽  
Nickel Concentration ◽  
Aluminum Melt ◽  
Titanium Aluminum ◽  
Titanium Foam

Titanium—aluminum, titanium—foam aluminum composites and bimetals obtained by liquid-phase methods, are increasingly used in industry. At the liquid-phase methods as result of the reaction diffusion of titanium and aluminum is formed transitional intermetallic layer at the phase boundary of the composite, which reduces the mechanical properties of titanium and composite. To reduce the growth rate of the intermetallic layer between the layers of the composite and increase its mechanical properties, it is proposed to alloy aluminum melt with nickel. The studies of the interaction of titanium and molten aluminum alloyed with nickel made it possible to establish the effect of temperature and aluminizing time on the thickness, chemical and phase compositions of the transition intermetallic layer. The tests showed the effect of the temperature of the aluminum melt, the nickel concentration on the strength properties of titanium—aluminum bimetal.

scholarly journals Symmetric Nature of Stress Distribution in the Elastic-Plastic Range of Pinus L. Pine Wood Samples Determined Experimentally and Using the Finite Element Method (FEM)

Symmetry ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 39
Author(s):  
Łukasz Warguła ◽  
Dominik Wojtkowiak ◽  
Mateusz Kukla ◽  
Krzysztof Talaśka
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Stress Distribution ◽  
Moisture Content ◽  
Tool Geometry ◽  
Wood Fibers ◽  
Data Set ◽  
Plastic Deformations ◽  
Pine Wood ◽  
Elastic Plastic

This article presents the results of experimental research on the mechanical properties of pine wood (Pinus L. Sp. Pl. 1000. 1753). In the course of the research process, stress-strain curves were determined for cases of tensile, compression and shear of standardized shapes samples. The collected data set was used to determine several material constants such as: modulus of elasticity, shear modulus or yield point. The aim of the research was to determine the material properties necessary to develop the model used in the finite element analysis (FEM), which demonstrates the symmetrical nature of the stress distribution in the sample. This model will be used to analyze the process of grinding wood base materials in terms of the peak cutting force estimation and the tool geometry influence determination. The main purpose of the developed model will be to determine the maximum stress value necessary to estimate the destructive force for the tested wood sample. The tests were carried out for timber of around 8.74% and 19.9% moisture content (MC). Significant differences were found between the mechanical properties of wood depending on moisture content and the direction of the applied force depending on the arrangement of wood fibers. Unlike other studies in the literature, this one relates to all three stress states (tensile, compression and shear) in all significant directions (anatomical). To verify the usability of the determined mechanical parameters of wood, all three strength tests (tensile, compression and shear) were mapped in the FEM analysis. The accuracy of the model in determining the maximum destructive force of the material is equal to the average 8% (for tensile testing 14%, compression 2.5%, shear 6.5%), while the average coverage of the FEM characteristic with the results of the strength test in the field of elastic-plastic deformations with the adopted ±15% error overlap on average by about 77%. The analyses were performed in the ABAQUS/Standard 2020 program in the field of elastic-plastic deformations. Research with the use of numerical models after extension with a damage model will enable the design of energy-saving and durable grinding machines.

scholarly journals The effect of temperature and drawing ratio on the mechanical properties of polypropylene monofilaments

2014 ◽  
Author(s):  
Hesam Taheri ◽  
João Miguel Nóbrega ◽  
Pieter Samyn ◽  
José Antonio Covas
Keyword(s):  
Mechanical Properties ◽  
Effect Of Temperature ◽  
Drawing Ratio

Effect of Temperature on the Structure and Mechanical Properties of Mechanically Alloyed Al-Nio Composite

2014 ◽  
Vol 59 (1) ◽  
pp. 121-126
Author(s):  
M. Zygmunt-Kiper ◽  
L. Blaz ◽  
M. Sugamata
Keyword(s):  
Mechanical Properties ◽  
Aluminum Oxide ◽  
Aluminum Matrix ◽  
Hot Extrusion ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Mechanically Alloyed ◽  
Structure Morphology ◽  
High Purity Aluminum ◽  
Extrusion Method

Abstract Mechanical alloying of high-purity aluminum and 10 wt.% NiO powders combined with powder vacuum compression and following hot extrusion method was used to produce an Al-NiO composite. Mechanical properties of as-extruded materials as well as the samples annealed at 823 K /6 h, were tested by compression at 293 K - 770 K. High mechanical properties of the material were attributed to the highly refined structure of the samples. It was found that the structure morphology was practically not changed during hot-compression tests. Therefore, the effect of deformation temperature on the hardness of as-deformed samples was very limited. The annealing of samples at 823 K/6 h induced a chemical reaction between NiO-particles and surrounding aluminum matrix. As a result, the development of very fine aluminum oxide and Al3Ni grains was observed.

scholarly journals Effect Of Temperature On The Mechanical Properties Of Fibronectin

2009 ◽  
Vol 96 (3) ◽  
pp. 641a
Author(s):  
Isaac T.S. Li ◽  
Gilbert C. Walker
Keyword(s):  
Mechanical Properties ◽  
Effect Of Temperature

Investigating the Effect of Thermoelectric Processing on Ionic Aggregation in Thermoplastic Ionomers

2017 ◽  
Author(s):  
Prasant Vijayaraghavan ◽  
Vishnu-Baba Sundaresan
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Field ◽  
Thermal Studies ◽  
Effect Of Temperature ◽  
Self Healing ◽  
Polymer Backbone ◽  
Ionic Dissociation ◽  
Dissociation Temperature ◽  
Aggregate Morphology ◽  
Poly Ethylene

Ionomers are a class of polymers which contain a small fraction of charged groups in the polymer backbone. These ionic groups aggregate (termed ionic aggregates) to form temporary cross-links that break apart over the ionic dissociation temperature and re-aggregate on cooling, influencing the mechanical properties of these polymers. In addition to enhanced mechanical properties, some ionomers also exhibit self-healing behavior. The self-healing behavior is a consequence of weakly bonded ionic aggregates breaking apart and re-aggregating after puncture or a ballistic impact. The structure and properties of ionomers have been studied over the last several decades; however, there is a lack of understanding of the influence of an electrostatic field on ionic aggregate morphology. Characterizing the effect of temperature and electric field on the formation and structure of these ionic aggregates will lead to preparation of ionomers with enhanced structural properties. This work focuses on Surlyn 8940 which a poly-ethylene methacryclic acid co-polymer in which a fraction of the carboxylic acid is terminated by sodium. In this work, Surlyn is thermoelectrically processed over its ionic dissociation temperature in the presence of a strong electrostatic field. Thermal studies are performed on the ionomer to study the effect of the thermoelectric processing. It is shown that the application of a thermoelectric field leads to increase in the ionic aggregate order in these materials and reduction in crystal size distribution. Thermal Analysis is performed using a Differential Scanning Calorimeter and the resulting thermogram analysis shows that thermoelectric processing increases the peak temperature and onset temperature of melting by 4 C and 20 C respectively. The peak width at half maximum of the melting endotherm is reduced by 10 C due to thermoelectric processing. This serves as a measure of the increased crystallinity. A parametric study on the effect of field duration and field strength is also performed.

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