312 research outputs found
Theoretical backgrounds of durability analysis by normalized equivalent stress functionals
Generalized durability diagrams and their properties are considered for a material under a multiaxial loading given by an arbitrary function of time. Material strength and durability under such loading are described in terms of durability, safety factor and normalized equivalent stress. Relations between these functionals are analysed. We discuss some material properties including time and load stability, self-degradation (ageing), and monotonic damaging. Phenomenological strength conditions are presented in terms of the normalized equivalent stress. It is shown that the damage based durability analysis is reduced to a particular case of such strength conditions. Examples of the reduction are presented for some known durability models. The approach is applicable to the strength and durability description at creep and impact loading and their combination
The mixed convolved action
A series of stationary principles are developed for dynamical systems by
formulating the concept of mixed convolved action, which is written in terms of
mixed variables, using temporal convolutions and fractional derivatives.
Dynamical systems with discrete and continuous spatial representations are
considered as initial applications. In each case, a single scalar functional
provides the governing differential equations, along with all the pertinent
initial and boundary conditions, as the Euler-Lagrange equations emanating from
the stationarity of this mixed convolved action. Both conservative and
non-conservative processes can be considered within a common framework, thus
resolving a long-standing limitation of variational approaches for dynamical
systems. Several results in fractional calculus also are developed
A Damage Mechanics Approach to Fatigue Assessment in Offshore Structures
This article is intended to describe the development of a fatigue damage model capable of assessing fatigue damage in offshore structures. This is achieved by for mulating a set of damage coupled constitutive and evolution equations which make the for mulation of a unified approach possible under both low and high cycle fatigue damage and consistent with the structural dynamic response of the changing/deteriorating material be haviors. The structural analysis for the whole designed period, say about 30 years, can be carried out with the aid of the proposed analytical procedure, in which the fundamental characteristics of sea wave statistics responsible for the structural dynamic response can be sufficiently considered. An offshore structure subject to complex ocean environment is described by a general stochastic system which embeds a group of stochastic subsystems, each characterizing a duty cycle. An effective analytical method is established by introduc ing the concept of duty strain range with a clear mathematical definition and its analytical solution which covers all possible spectral parameters. The history-dependent damage is also included in the damage model so that the overload effects can be analyzed. It should be pointed out that the whole procedure can be fully computerized such that the practical or engineering significance of varying design variables can be readily highlighted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67255/2/10.1177_105678959300200405.pd
Application of nonlinear hereditary strain theory to description of stress relaxation in metals, and conversion of relaxation data to creep
Critical time of compression of metal rods under creep due to the joint effect of constant loads and elevated temperatures
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