An Analytical Theory of the Creep Deformation of Materials

1953 ◽  
Vol 20 (2) ◽  
pp. 245-252
Author(s):  
Yoh-Han Pao ◽  
Joseph Marin
Keyword(s):  
Creep Strain ◽  
Creep Deformation ◽  
Elastic Strain ◽  
Transient Creep ◽  
Analytical Theory ◽  
Simultaneous Action ◽  
Creep Recovery ◽  
The Past ◽  
Short Time ◽  
Transient Creep Strain

Abstract This paper reports on the formulation of an analytical theory of creep. This theory is proposed for an idealized material and may be applied to those materials whose behavior conforms to that of this ideal material. The theory takes into account the initial elastic strain, the transient creep strain, and the minimum rate creep strain. Unlike previous theories, this theory is capable of representing the simultaneous action of creep and creep recovery and may be used for conditions of varying as well as constant stresses. In this respect the theory is more general than those presented in the past. The new theory is of particular importance in the design of many new military and domestic applications where high temperatures over short periods of time make the initial short-time creep strains of importance.

scholarly journals Effects of transient creep strain on post-tensioned concrete slabs in fire

2017 ◽  
Vol 69 (7) ◽  
pp. 337-346 ◽  
Author(s):  
Ya Wei ◽  
Francis T. K. Au ◽  
Jing Li ◽  
Neil C. M. Tsang
Keyword(s):  
Creep Strain ◽  
Transient Creep ◽  
Concrete Slabs ◽  
In Fire ◽  
Transient Creep Strain ◽  
Post Tensioned

Tensile Properties and Creep Behavior of Compositional Modified Orthorhombic Ti2AlNb Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 1549-1552 ◽  
Author(s):  
Yong Mao ◽  
Masuo Hagiwara
Keyword(s):  
Tensile Properties ◽  
Creep Strain ◽  
Room Temperature ◽  
Transient Creep ◽  
Steady State Creep ◽  
Plasma Arc ◽  
Steady State Creep Rate ◽  
Arc Melting ◽  
Cr Addition ◽  
Transient Creep Strain

Several beta stabilizing elements such as Mo, Cr, W, V and Fe have been added to Ti- 22Al-27Nb alloy for substituting a portion of Nb in order to further improve the tensile properties and creep resistances of orthorhombic Ti2AlNb-based alloys. Six compositional modified alloys Ti- 22Al-19.2Nb-2Cr, Ti-22Al-12.5Nb-2W-2Cr, Ti-22Al-10.8Nb-2Mo-2Cr, Ti-22Al-16Nb-2Cr-2V, Ti-22Al-11Nb-2Mo-1Fe, Ti-22Al-16.3Nb-2V-1Fe were prepared by plasma arc melting. The phase constitutions of these alloys were found to be B2+O or B2+O+α2 phases. The tensile properties were investigated at room temperature, and the creep behaviors were investigated under 650oC/310MPa and 650 to 750oC/200MPa. The results showed that Mo+Fe and W+Cr addition improved effectively the 0.2% yield strength and creep resistance. Ti-22Al-11Nb-2Mo-1Fe alloy exhibited the lower transient creep strain and steady-state creep rate, and longer 1% creep-strain lifetime than Ti-22Al-27Nb alloy at 650 to 700oC creep. The dislocation-controlled creep deformation mechanism was suggested to the creep behaviors of the Mo+Fe-modified alloy.

Interaction diagrams and failure criteria for RC columns subjected to high temperature

2020 ◽  
Vol 11 (3) ◽  
pp. 347-378
Author(s):  
Khaled Ahmed Mahmoud
Keyword(s):  
Creep Strain ◽  
Elevated Temperatures ◽  
Failure Criteria ◽  
Transient Creep ◽  
Limit Strain ◽  
Experimental Results ◽  
Content Type ◽  
Proposed Model ◽  
Ultimate Limit ◽  
Transient Creep Strain

Purpose Previous works in constructing interaction diagrams have only focused on incorporating transient creep strain implicitly in the ultimate limit strain. The present paper aims to use different approaches to define concrete ultimate limit strain (failure strain) envelops at high temperatures for preloaded and unloaded, confined and unconfined, columns during heating are proposed. These approaches are chosen to understand the effect of using different techniques to determine transient creep strain on the resulted Nu–Mu diagrams. Design/methodology/approach Transient creep strain is included within the concrete ultimate limit strain relationships, implicitly and explicitly, by four different ways, and accordingly, four different failure criteria are suggested. To define the concrete ultimate limit strain, studies are conducted to evaluate the compression strain corresponding to the maximal flexural capacity at elevated temperatures. In the analysis, the thermal and structural analyses are decoupled and, based on the resulted ultimate limit strain, the Nu – Mu diagrams are constructed at different fire exposures. Findings The validity of the proposed model is established by comparing its predictions with experimental results found in the literature. Finally, comparative calculations regarding interaction diagrams obtained by the proposed model and by other methods found in the literature are performed. It was found that the proposed model predictions agree well with experimental results. It was also found that the suggested approaches, which include simplifications, reasonably predicted the exact column capacity. Originality/value The model.

World Economy: Prospects and Barriers for Recovery

2012 ◽  
pp. 61-83 ◽  
Author(s):  
M. Ershov
Keyword(s):  
World Economy ◽  
Western World ◽  
Short Time Period ◽  
Market Segments ◽  
Junk Bonds ◽  
The Past ◽  
Time Period ◽  
The Us ◽  
Global Liquidity ◽  
Short Time

According to the latest forecasts, it will take 10 years for the world economy to get back to “decent shape”. Some more critical estimates suggest that the whole western world will have a “colossal mess” within the next 5–10 years. Regulators of some major countries significantly and over a short time‑period changed their forecasts for the worse which means that uncertainty in the outlook for the future persists. Indeed, the intensive anti‑crisis measures have reduced the severity of the past problems, however the problems themselves have not disappeared. Moreover, some of them have become more intense — the eurocrisis, excessive debts, global liquidity glut against the backdrop of its deficit in some of market segments. As was the case prior to the crisis, derivatives and high‑risk operations with “junk” bonds grow; budget problems — “fiscal cliff” in the US — and other problems worsen. All of the above forces the regulators to take unprecedented (in their scope and nature) steps. Will they be able to tackle the problems which emerge?

Creep Deformation of Particle-Strengthened Metal-Matrix Composites

1989 ◽  
Vol 111 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Z. G. Zhu ◽  
G. J. Weng
Keyword(s):  
Constitutive Equation ◽  
Metal Matrix Composites ◽  
Creep Strain ◽  
Creep Deformation ◽  
Creep Resistance ◽  
Metal Matrix ◽  
Order Approximation ◽  
Stress Redistribution ◽  
Matrix Composites ◽  
The Matrix

A multiaxial theory of creep deformation for particle-strengthened metal-matrix composites is derived. This derivation is based on the observation that there are two major sources of creep resistance in such a system. The first, or metallurgical effect, arises from the increased difficulty of dislocation motion in the presence of particles and is accounted for by a size- and concentration dependent constitutive equation for the matrix. The second, or mechanics effect, is due to the continuous transfer of stress from the ductile matrix to the hard particles and the corresponding stress redistribution is also incorporated in the derivation. Both power-law creep and exponential creep in the matrix, each involving the transient as well as the steady state, are considered. The constitutive equations thus derived can provide the development of creep strain of the composite under a combined stress. The multiaxial theory is also simplified to a uniaxial one, whose explicit stress-creep strain-time relations at a given concentration of particles are also given by a first- and second-order approximation. The uniaxial theory is used to predict the creep deformation of an oxide-strengthened cobalt, and the results are in reasonably good agreement with the experiment. Finally, it is demonstrated that a simple metallurgical approach without considering the stress redistribution between the two constituent phases, or a simple mechanics approach without using a modified constitutive equation for the metal matrix, may each underestimate the creep resistance of the composite, and, therefore, it is important that both factors be considered in the formulation of such a theory.

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