Some Problems of Press Forging Lead and Aluminum

1960 ◽  
Vol 82 (3) ◽  
pp. 246-252 ◽  
Author(s):  
A. G. MacDonald ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Work Hardening ◽  
Room Temperature ◽  
Pure Aluminum ◽  
The Body ◽  
Approximate Theory ◽  
Substantial Agreement ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Local Pressures ◽  
Good Agreement

Several press forgings were made and it was found that the experimental mean forging pressures were in substantial agreement with values predicted by theoretical solutions based on an approximate theory. The forging processes were axial symmetric forging of disks between flat dies and forging in closed dies with several edge effects, such as overhanging flash, with and without flash-edge restriction. The materials were commerically pure aluminum and lead and were chosen because of their respective work-hardening and strain-rate effects at room temperature. It was found further that the local pressures measured in the forging were in good agreement with the theory, but that some local plastic flow tends to equalize the pressure in the body of the forging.

scholarly journals Evaluation of Nonlinear Material Behavior for Offshore Structures Subjected to Accidental Actions

2017 ◽  
Author(s):  
Martin Storheim ◽  
Hagbart S. Alsos ◽  
Jørgen Amdahl
Keyword(s):  
Structural Response ◽  
Offshore Structures ◽  
The Body ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Strain Rate Effects ◽  
Nonlinear Structural ◽  
Rate Effects ◽  
High Degree ◽  
Nonlinear Structural Response

Evaluation of the nonlinear structural response of any structure is a challenging task; a range of input parameters are needed, most of which has significant statistical variability and the evaluations require a high degree of craftsmanship. Hence, high demands are set forth both to the analyst and the body in charge of verification of the results. Recent efforts by DNVGL attempts to mitigate this with the second edition of the DNVGL-RP-C208 for determination of nonlinear structural response, in which guidance or requirements are given on many of the challenging aspects. This paper discuss the various challenges and the direction to which the RP-C208 points compared to published research. Parameters affecting the plastic hardening, strain-rate effects and ductile fracture are discussed separately. Then, the combined effect of the range of assumptions is evaluated to assess the resulting level of safety.

A Thermo-Viscoplastic Constitutive Equation Based on Hyperbolic-Shape Thermo-Activated Barriers

1984 ◽  
Vol 106 (4) ◽  
pp. 331-336 ◽  
Author(s):  
Li-Lih Wang
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Present Model ◽  
Strain Rate Effects ◽  
Bcc Metals ◽  
Special Cases ◽  
Wide Range ◽  
Rate Effects ◽  
Simple Parameter ◽  
Good Agreement

A thermo-viscoplastic constitutive equation is proposed on the basis of thermoactivated mechanism with a spectrum of hyperbolic-shape barriers, suitable for a wide range of strain rate and temperature. Relations with other existing models or rate theories, which may be regarded a special cases of present model, are examined. Good agreement with experimental data for both fcc and bcc metals is shown. The activation volume is found dependent on temperature according to an exponential law. A simple parameter, which describes the equivalence between strain rate effects and temperature effects on flow stress, is suggested similar to Zener-Hollomon parameters

scholarly journals Evaluation of Nonlinear Material Behavior for Offshore Structures Subjected to Accidental Actions

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Martin Storheim ◽  
Hagbart S. Alsos ◽  
Jørgen Amdahl
Keyword(s):  
Structural Response ◽  
Offshore Structures ◽  
The Body ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Strain Rate Effects ◽  
Nonlinear Structural ◽  
Rate Effects ◽  
High Degree ◽  
Nonlinear Structural Response

Evaluation of the nonlinear structural response of any structure is a challenging task; a range of input parameters are needed, most of which have significant statistical variability and the evaluations require a high degree of craftsmanship. Hence, high demands are set forth both to the analyst and the body in charge of verification of the results. Recent efforts by DNVGL attempt to mitigate this with the second edition of the DNVGL-RP-C208 for the determination of nonlinear structural response, in which guidance or requirements are given on many of the challenging aspects. This paper discusses the various challenges and the direction to which the RP-C208 points compared to published research. Parameters affecting the plastic hardening, strain-rate effects, and ductile fracture are discussed separately. Then, the combined effect of the range of assumptions is evaluated to assess the resulting level of safety.

scholarly journals Temperature and Strain-Rate Effects on Deformation Mechanisms in Irradiated Stainless Steel

1994 ◽  
Vol 373 ◽  
Author(s):  
J. L. Brimhall ◽  
J. I. Cole ◽  
J. S. Vetrano ◽  
S. M. Bruemmer
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Room Temperature ◽  
Deformation Mode ◽  
Radiation Hardening ◽  
Strain Rates ◽  
Lower Yield ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Higher Temperature

AbstractAnalysis of the deformation microstructures in ion-irradiated stainless steel shows twinning to be the predominant deformation mode at room temperature. Dislocation channelling also occurs under slow strain rate conditions. Stresses required for twinning were calculated by the model of Venables and are compatible with observed yield stresses in neutron-irradiated material if loops are the principal twin source. Computation of the expected radiation hardening from the defect structure, based on a simple model, is consistent with yield strengths measured on neutron-irradiated steels. Lower yield stresses and greater thermal energy at 288°C lessen the probability of twinning and dislocation channeling becomes the primary deformation mode at the higher temperature. However, preliminary results show that some twinning does occur in the irradiated stainless steel even at the higher temperature when higher strain rates are used.

Strain Rate Effects in Low Speed Two-Body Abrasion

1978 ◽  
Vol 100 (2) ◽  
pp. 181-184 ◽  
Author(s):  
J. Larsen-Basse ◽  
P. A. Tanouye
Keyword(s):  
Silicon Carbide ◽  
Flow Stress ◽  
Strain Rate ◽  
True Strain ◽  
Pure Aluminum ◽  
Plastic Work ◽  
Sliding Velocity ◽  
Strain Rate Effects ◽  
Dependent Part ◽  
Rate Effects

Specimens of pure aluminum, copper, and iron were abraded on silicon carbide abrasive papers. The sliding velocity was varied between 0.5 and 82 mm/s and a range of abrasive grit sizes was used. The cutting force is composed of a friction contribution, which accounts for 70–90 percent of the total, and a plastic work contribution. The plastic work contains a velocity-independent and a velocity-dependent contribution. The velocity-independent part is the work to deform the metal plastically to a true strain of approximately 5. The velocity-dependent part is relatively small and is proportional to the logarithm of the velocity. It is caused by the effect of strain rate on the flow stress. No effects of grit size alone on strain rate were found.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

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