A streamline solution for rigid laterally loaded piles in permafrost

1989 ◽  
Vol 26 (4) ◽  
pp. 568-574 ◽  
Author(s):  
A. Foriero ◽  
B. Ladanyi
Keyword(s):  
Velocity Field ◽  
Creep Rate ◽  
Secondary Creep ◽  
Laterally Loaded Piles ◽  
Creep Response ◽  
Soil Movement ◽  
State Of Stress ◽  
Bound Theorem ◽  
Laterally Loaded ◽  
Secondary Creep Rate

A streamline solution for the design of laterally loaded rigid piles in permafrost is presented. The proposed method relies on a power law to describe the rate dependence of permafrost creep response. It describes the soil movement with a kinematically admissible velocity field and estimates the overall reaction at a given pile section with the bound theorem for a creeping material. The approach is valid only for a secondary creep rate and a stationary state of stress. Key words: pile, lateral load, velocity field, secondary creep rate.

On Time-Temperature Parameters for Correlation of Creep-Rupture Data in Stainless Steel Weldments

1978 ◽  
Vol 100 (3) ◽  
pp. 319-332 ◽  
Author(s):  
W. E. White ◽  
Iain Le May
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Creep Rate ◽  
Creep Rupture ◽  
Rupture Time ◽  
Function Approach ◽  
Secondary Creep ◽  
Rupture Data ◽  
The Relationship ◽  
Secondary Creep Rate

The Manson-Haferd, Larson-Miller, and Orr-Sherby-Dorn time-temperature parameters were applied to creep-rupture data obtained from testing two batches of austenitic stainless steel weldments. It was found that none of these correlated the data satisfactorily. A new parameter, based on a modification of one proposed originally by Manson and by Goldhoff and Sherby, was found to adequately correlate the data. The Minimum-Commitment, Station-Function Approach of Manson and Ensign was also applied, the results of which supported those obtained from the analysis made using the parameters listed above. Finally, from the relationship between rupture-time and secondary creep-rate, it is suggested that the form of the rupture data may be useful in predicting the physical basis for creep.

scholarly journals Brittle Creep Failure, Critical Behavior, and Time-to-Failure Prediction of Concrete under Uniaxial Compression

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Yingchong Wang ◽  
Na Zhou ◽  
Fuqing Chang ◽  
Shengwang Hao
Keyword(s):  
Creep Rate ◽  
Uniaxial Compression ◽  
Power Law ◽  
Critical Behavior ◽  
Creep Process ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Brittle Creep ◽  
Secondary Creep Rate

Understanding the time-dependent brittle deformation behavior of concrete as a main building material is fundamental for the lifetime prediction and engineering design. Herein, we present the experimental measures of brittle creep failure, critical behavior, and the dependence of time-to-failure, on the secondary creep rate of concrete under sustained uniaxial compression. A complete evolution process of creep failure is achieved. Three typical creep stages are observed, including the primary (decelerating), secondary (steady state creep regime), and tertiary creep (accelerating creep) stages. The time-to-failure shows sample-specificity although all samples exhibit a similar creep process. All specimens exhibit a critical power-law behavior with an exponent of −0.51 ± 0.06, approximately equal to the theoretical value of −1/2. All samples have a long-term secondary stage characterized by a constant strain rate that dominates the lifetime of a sample. The average creep rate expressed by the total creep strain over the lifetime (tf-t0) for each specimen shows a power-law dependence on the secondary creep rate with an exponent of −1. This could provide a clue to the prediction of the time-to-failure of concrete, based on the monitoring of the creep behavior at the steady stage.

Post Creep Microstructures of Ti-6A12Sn4Zrf3Mo Alloy

1977 ◽  
Vol 35 ◽  
pp. 274-275
Author(s):  
S. Fujishiro ◽  
A. W. Sommer
Keyword(s):  
Creep Rate ◽  
Transverse Direction ◽  
Elevated Temperatures ◽  
Rolling Direction ◽  
The Other ◽  
Secondary Creep ◽  
Slip Systems ◽  
Alloy Plate ◽  
Schmid Factor ◽  
Secondary Creep Rate

It has been reported (1,2) that in highly textured titanium alloys the secondary creep rate in the direction normal to major concentration of basal poles at elevated temperatures is much greater than that of the c-direction. This phenomenon can be attributed to two major reasons: the first is that Youngs Modulus in the c-direction is approximately 25% higher than in the a-direc- tion; the second is that if an alpha grain is oriented in the c-direction with respect to the applied stress, the Schmid factor for prismatic planes is zero, and thus the slip on the major slip systems is extremely restricted. In the present study, two sets of creep specimens have been prepared from a highly textured Ti-6A12Sn4Zr6Mo alloy plate; one set is parallel to the rolling direction and the other set is parallel to the long transverse direction (major concentration of c-poles).

Laterally loaded piles in permafrost

1984 ◽  
Vol 21 (3) ◽  
pp. 431-438 ◽  
Author(s):  
J. F. (Derick) Nixon
Keyword(s):  
Numerical Procedure ◽  
Ground Surface ◽  
Surface Displacement ◽  
Field Tests ◽  
Creep Model ◽  
Sustained Load ◽  
Laboratory Model ◽  
Secondary Creep ◽  
Laterally Loaded Piles ◽  
Laterally Loaded

A theory for the design of laterally loaded piles in permafrost is presented. The approach is valid for icy soils or ice, where secondary creep displacements will be responsible for the majority of the soil strain under sustained load. Initially, the paper studies in some detail the response of a short, rigid pile embedded in a nonlinear viscous medium. The concept of a flexible elastic pile in a viscous continuum is then introduced, and a relatively straightforward numerical procedure must be introduced to obtain a solution. Once the limiting or design ground surface displacement rate is established by the designer, the paper shows how a typical chart relating lateral pile load to average ground temperature can be prepared.The available (but limited) data base is reviewed for field pile load tests carried out in the early 1970's in Inuvik, N.W.T. and some laboratory model pile tests carried out in connection with this study. Using available long-term secondary creep data for ice and icy silts, predictions for the lateral creep response of piles can be carried out. Agreement between prediction and observation is certainly encouraging and points the way to further research and field testing in this area. Finally, the paper briefly discusses the resistance of rigid fixed-headed piles to lateral loads, and the resistance of a pile in permafrost to the application of a pure moment. Key words: lateral piles, permafrost, creep, model, field tests.

scholarly journals Lattice continuum and diffusional creep

2016 ◽  
Vol 472 (2188) ◽  
pp. 20160039 ◽  
Author(s):  
Sinisa Dj. Mesarovic
Keyword(s):  
Creep Rate ◽  
Continuum Theory ◽  
Primary Creep ◽  
Diffusional Creep ◽  
Secondary Creep ◽  
Diffusional Flux ◽  
Coupled Diffusion ◽  
Boundary Dissipation ◽  
Definition Of ◽  
Secondary Creep Rate

Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro–Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro–Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate.

Mechanistic Modeling of the Anisotropic Steady State Creep Response of SnAgCu Single Crystal

2015 ◽  
Author(s):  
Subhasis Mukherjee ◽  
Bite Zhou ◽  
Abhijit Dasgupta ◽  
Thomas R. Bieler
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Dislocation Density ◽  
Single Crystal ◽  
Steady State Creep ◽  
Secondary Creep ◽  
Steady State Creep Rate ◽  
Modeling Framework ◽  
Creep Response ◽  
Tier 1

A multiscale modeling framework is proposed in this study to capture the influence of the inherent elastic anisotropy of single crystal Sn and the inherent heterogeneous microstructure of a single crystal SnAgCu (SAC) solder grain on the secondary creep response of the grain. The modeling framework treats the SAC microstructure as having several distinct length scales. The smallest length scale (Tier 0) consists of the Sn BCT lattice. The eutectic Sn-Ag micro-constituent, consisting of nanoscale Ag3Sn IMC particles embedded in the single crystal BCT Sn matrix, is termed Tier 1. The single-crystal SAC microstructure, consisting of Sn dendrites and surrounding eutectic Sn-Ag phase, is termed Tier 2. Dislocation recovery mechanisms, such as Orowan climb and detachment from nanoscale Ag3Sn particles, are found to be the rate controlling mechanisms for creep deformation in the eutectic Sn-Ag phase (Tier 1) of a SAC single crystal. The anisotropic secondary creep rate of eutectic Sn-Ag phase (Tier 1), is then modeled using the above inputs and the saturated dislocation density calculated for dominant glide systems during secondary stage of creep. Saturated dislocation density is estimated as the equilibrium saturation between three competing processes: (1) dislocation generation; (2) dislocation impediment caused by back stress from pinning of dislocations at IMCs; and (3) dislocation recovery due to climb/detachment from IMCs. Secondary creep strain rate of eutectic Sn-Ag phase in three most facile slip systems is calculated and compared against the isotropic prediction. At low stress level secondary steady state creep rate along (110)[001] system is predicted to be ten times the creep rate along (100)[0-11] system. However, at high stress level, secondary steady state creep rate along (110)[001] system is predicted to be ten thousand times the creep rate along (100)[0-11] system. The above predictions are in strong agreement with (1–4) orders of magnitude of anisotropy observed in steady state secondary creep response in SAC305 solder joints tested under identical loading conditions in experiments conducted by several authors. The above model is then combined with Eigen-strain methods and average matrix stress concepts to homogenize the load sharing between the Sn dendrites and the surrounding eutectic Ag-Sn matrix. The resulting steady state creep rates are predicted for a few discrete single crystal SAC305 specimens. Very good agreement is observed between the predicted steady state creep rate and the measured creep rates for two SAC305 single crystal specimens.

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