Monitoring Time-Dependent Deformation in Small Volumes

1991 ◽  
Vol 239 ◽  
Author(s):  
T P Weihs ◽  
J B Pethica
Keyword(s):  
Strain Rate ◽  
Strain Energy ◽  
Contact Stiffness ◽  
Effective Strain ◽  
Applied Pressure ◽  
Time Dependent ◽  
Atomic Diffusion ◽  
Continuous Measure ◽  
Plastic Strains ◽  
Monitoring Time

ABSTRACTTime-dependent deformation (TDD) in small volumes was monitored using an alternating (AC) force technique and a Nanoindenter. The AC technique provides a continuous measure of contact stiffness during an indentation. By holding the force constant and monitoring the stiffness, the applied pressure and an effective strain rate were measured. Reasonable strain rate sensitivities were obtained for permanent indentations involving significant plastic strains. Time-dependent recovery due to residual strain energy is also reported. For reversible, elastic indentations, TDD was seen when the applied force was held constant. The deformation is attributed to atomic diffusion.

Improving the Long-Term Performance of Elastomeric Seals by Material Behavior Design

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ryan B. Sefkow ◽  
Nicholas J. Maciejewski ◽  
Barney E. Klamecki
Keyword(s):  
Energy Density ◽  
Contact Pressure ◽  
Strain Energy ◽  
Applied Pressure ◽  
Material Behavior ◽  
Time Dependent ◽  
Ring Section ◽  
Stiff Material ◽  
Elastomeric Seals

Previously it was shown that including smaller inset regions of less stiff material in the larger O-ring section at locations of high stress results in lower strain energy density in the section. This lower energy content is expected to lead to improved long-term seal performance due to less permanent material deformation and so less loss of seal-housing contact pressure. The shape of the inset region, the time-dependent change in material properties, and hence change in seal behavior over time in use were not considered. In this research experimental and numerical simulation studies were conducted to characterize the time-dependent performance of O-ring section designs with small inset regions of different mechanical behaviors than the larger surrounding section. Seal performance in terms of the rate of loss of contact pressure of modified designs and a baseline elastic, one-material design was calculated in finite element models using experimentally measured time-dependent material behavior. The elastic strain energy fields in O-ring sections were calculated under applied pressure and applied displacement loadings. The highest stress, strain, and strain energy regions in O-rings are near seal-gland surface contacts with significantly lower stress in regions of applied pressure. If the size of the modified region of the seal is comparable to the size of the highest energy density region, the shape of the inset is not a major factor in determining overall seal section behavior. The rate of loss of seal-housing contact pressure over time was less for the modified design O-ring sections compared with the baseline seal design. The time-dependent performance of elastomeric seals can be improved by designing seals based on variation of mechanical behavior of the seal over the seal section. Improvement in retention of sealing contact pressure is expected for seal designs with less stiff material in regions of high strain energy density.

Thermoelastic Constitutive Equations for Chemically Hardening Materials

1974 ◽  
Vol 41 (3) ◽  
pp. 652-657 ◽  
Author(s):  
Bernard W. Shaffer ◽  
Myron Levitsky
Keyword(s):  
Bulk Modulus ◽  
Strain Rate ◽  
Chemical Reaction ◽  
Constitutive Equations ◽  
Strain Energy ◽  
Elastic Solid ◽  
Time Dependent ◽  
Component Model ◽  
Two Component ◽  
Potential Applications

Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

scholarly journals Determination of time-dependent strengths of salt pillars based on strain energy principle

2019 ◽  
Vol 29 (2) ◽  
pp. 273-279 ◽  
Author(s):  
Prapasiri Junthong ◽  
Supattra Khamrat ◽  
Suratwadee Sartkaew ◽  
Kittitep Fuenkajorn
Keyword(s):  
Strain Energy ◽  
Time Dependent ◽  
Energy Principle

Influence of Loading History on Delamination in Multilayered Beam with Creep

2021 ◽  
Vol 1046 ◽  
pp. 23-28
Author(s):  
Victor Iliev Rizov
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Time Dependent ◽  
External Loading ◽  
Loading History ◽  
Multilayered Beam

The present paper deals with an analytical study of the time-dependent delamination in a multilayered inhomogeneous cantilever beam with considering of the loading history. The multilayered beam exhibits creep behaviour that is treated by using a non-linear stress-strain-time relationship. The material properties are continuously distributed along the thickness and length of the layers. The external loading is applied in steps in order to describe the loading history. The analysis reveals that during each step of the loading, the strain energy release rate increases with time. The influences of crack length and location on the time-dependent strain energy release rate are also investigated.

Simulation of Influence of Friction Coefficient on Extrusion of TC4 Alloy

2013 ◽  
Vol 470 ◽  
pp. 244-249
Author(s):  
Chang Dong Liu ◽  
Yi Du Zhang
Keyword(s):  
Friction Coefficient ◽  
Strain Rate ◽  
Effective Strain ◽  
High Stress ◽  
Extrusion Process ◽  
Extrusion Pressure ◽  
Tc4 Alloy ◽  
Stress Zone ◽  
D Model ◽  
High Stress Zone

Based on Simufact11.0, a 3-D model of T profile extrusion is established and the extrusion process of TC4 is investigated using finite volumemethod(FVM) of Euler mesh description. Effects of different friction coefficients on the effective stress, extrusion pressure, effective strain and effective strain rate have been studied. The study shows that there is a high-stress zone at a certain distance from the entrance of the forming area and a high strain rate zone around that area. With the increase of friction coefficient, the value of the stress increased and the deformation is more uneven. The track of extrusion pressure shows that extrusion increase with the increase of friction coefficient.

Effective atomic diffusion coefficient dependence on applied pressure during spark plasma sintering

Materialia ◽  
2019 ◽  
Vol 6 ◽  
pp. 100334 ◽  
Author(s):  
X.X. Li ◽  
C. Yang ◽  
T. Chen ◽  
Z.Q. Fu ◽  
Y.Y. Li ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Spark Plasma Sintering ◽  
Applied Pressure ◽  
Atomic Diffusion ◽  
Plasma Sintering ◽  
Spark Plasma

Comparison of Two Complete Solutions in an Axisymmetric Extrusion With Experiment

1969 ◽  
Vol 91 (3) ◽  
pp. 543-548 ◽  
Author(s):  
A. H. Shabaik ◽  
E. G. Thomsen
Keyword(s):  
Strain Rate ◽  
Effective Strain ◽  
Cone Angle ◽  
Low Friction ◽  
First Approximation ◽  
Strain And Strain Rate ◽  
Conical Die ◽  
Stream Lines ◽  
Half Cone ◽  
Half Cone Angle

An upper-bound and a potential solution to a forward extrusion problem were compared with experimental results obtained by the visioplasticity method. The process consisted of extruding a 2-in-dia billet of preforged lead through a conical die having a half-cone angle of 45 deg under the condition of relatively low friction. The comparison was made for steady state stream lines, velocities, strain rate components, effective strain and strain rate, grid distortion, and stress distribution. It was found that the curves were generally of similar shape and that some differences existed in magnitude only. It is suggested that the theoretical solutions can be used to advantage to a first approximation in predicting all important variables.

The Creep of Thick Tubes Under Internal Pressure

1957 ◽  
Vol 24 (3) ◽  
pp. 464-466
Author(s):  
C. D. Weir
Keyword(s):  
Internal Pressure ◽  
Strain Rate ◽  
Shear Strain ◽  
Rate Equation ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Stress Deviator ◽  
Constant Density ◽  
Creep Stress ◽  
Shear Strain Energy

Abstract Using the usually accepted assumption that the strain rate of a material undergoing creep is given by the product of the stress deviator and a function of the shear-strain energy, and assuming constant density, equations are derived for the creep stresses in a thick-walled tube under internal pressure for a generalized form of the shear strain-energy function. It is shown that these reduce to previously published equations on the substitution of a power law stress-strain rate equation. The nonisothermal case is considered also and creep-stress equations are obtained in a similarly generalized form.

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