The Lab was organized in 1989 to promote development of methods of assessment of structural reliability, mostly in ship and marine applications. Through a certain period, the lab worked in cooperation with SPb Marine Technical University and Maritime Research Institute, which allowed carrying out co-operative experimental works on cyclic behavior and failure of structural steels and alloys, on crack propagation in structural steels, etc. Lately, only occasional experimental studies were feasible, in cooperation with University of Rostock, Technical University Hamburg-Harburg (Germany) and SPb Polytechnic University. The mechanical properties of virgin and fatigued microstructures were examined; the fatigue behavior of welded structures has been analyzed based on test results. Lately, the two groups were formed: one, engaged in development of analytical and numerical methods for modeling deformation and fracture of inhomogeneous media with inclusions, pores, cavities and cracks; the work of another is focused on fatigue mechanics of materials and structures, with emphasis on welded ship and marine structures.
The prime objective of the group work is developing new efficient computational means for studying deformation and fracture of a medium with multiple structural elements, complicated processes at their interfaces, inclusions, pores and cracks. It is reached on the basis of modern analytical and computational achievements of solid and fracture mechanics. The methods employed include: hypersingular boundary integral equations, asymptotic analysis of singular fields near points of stress concentration, complex variable boundary element method, quadrature rules for singular multi-wedge boundary elements, dual reciprocity method, fast Fourier transform, numerical simulation and inverse analysis of seismic effects, and, recently, fast multipole method. Numerical realization of the methods is performed on conventional laptops. The developed codes serve for evaluation of local fields at various levels of structure; for obtaining macroscopic effective properties; and for solving particular practical problems of rock mechanics, mechanics of polymers and steel constructions.
• New singular and hypersingular boundary integral equations (BIE) for solving 2D and 3D problems of potential and elasticity theories involving multiple structural elements with
complicated contact interaction, inclusions, pores, and growing cracks. Highly efficient analytical recurrent quadrature rules for boundary elements (straight, circular-arc,
ordinary and singular), used when solving these BIE numerically. The complex variable (CV) form of the boundary element method (BEM) based on the derived equations and quadrature rules.
• New method for evaluation of effective properties of a medium, based on solving doubly-(in 2D) or triply (in 3D) periodic problems by using the suggested BIE. Obtaining data on effective properties of regular structures with a) deterministic properties and b) with random perturbation of structural elements.
• Theoretical rationale and extension of non-local fracture criteria of Novozhilov-Neuber type to the problems concerning with field concentration at common apexes of grains and structural blocks, fracture under compressive stresses, and influence of pore pressure and thermal loading.
• A stable and accurate method for automatic tracing curvilinear trajectory of a crack, propagating under the extended fracture criteria. The method provides convergence at smooth portions of a crack path, as well as at kink points, including the points of branch-ing and bifurcation.
• A new step-wise method for tracing irreversible deformations at the contacts of structural elements under a prescribed loading path of external loads.
• Development of the theory and efficient numerical method for finding asymptotic behav-iour of physical fields at the common apexes of interacting structural elements. Working out special multi-wedge boundary elements, accounting for the asymptotics. Implementa-tion of the special elements into computer codes of the CV-BEM. Studying the field con-centration, crack nucleation and propagation near a multi-wedge poin
• Development of the theory and efficient computational methods for numerical simulation of seis-mic and aseismic events accompanying fracture nucleation and propagation.
• New efficient methods combining the CV-BEM and dual reciprocity method for solving unsteady thermal, and coupled transient thermo- and poro-elastic problems.
• Development of the theory and computational methods for numerical modeling of hydraulic frac-tures.
• Numerical realization of all the suggested methods in the form of highly efficient com-puter codes for conventional laptops.
The main results have been presented at International Congresses, Symposia and Conference as Key-Note lectures and session talks. The methods and codes developed are systematically used in Russia, France and South Africa for solving problems of mining, material science, civil and mechanical engineering.
The group has scientific contacts and collaborates with the following foreign universities and research centers: Aberystwyth University, Liverpool University (UK); Berkeley University, New Mexico University, University of Minnesota, University of North Dakota, University of Oklahoma (USA); Institute of Mine Seismology (South Africa - Australia); INERIS (France); Rzeszow Technical University (Poland); SINTEF (Norway).
Research works of the group are aimed at the development of advanced fatigue models which would include the damage accumulation and crack extension mechanisms within a combined or unified approach. The method employed is numerical modeling of cyclic behavior of polycrystalline material considering for stochastic macro and microplasticity of material elements, including crack extensions due to the damage accumulation and influence of stress field (stress intensity factors). The modeling is based on results of systematical experimental analysis of elastic-plastic cyclic (and irregular) behavior and fatigue failure of structural steels and alloys, carried out in the SPb Marine Technical University, partly within the frames of a cooperative program.
Also, the efforts are focused on development of modified methods of fatigue analysis and design of welded structures for a required life, methods of in-service condition assessment of structures, etc., with particular emphasis on marine technology.
• New stochastic models of elastic-plastic behavior of a polycrystalline media, which allow considering localized
accumulation of fatigue damage in material and in critical locations of structural details under variable loading.
• A concept of load-history sensitive cyclic stress-strain curve aimed at application in the inelastic strain energy approach for fatigue.
• New stochastic models of fatigue crack initiation and propagation in which the process is uniformly controlled by the combined, damage accumulation and failure of structural bonds influenced by the stress field.
• Advanced approaches in assessment of fatigue crack growth based on fatigue damage ac-cumulation allowing for analysis of through-thickness crack in welded joints and in plate and shell elements of structures until complete failure, far beyond the limits of LEFM.
The methods developed were applied in solution of particular practical problems for a Marine Design Bureau, St.Petersburg, for Hyundai HI Co., American Bureau of Shipping and in development of a personnel training courses on Fatigue and Fracture for engineers engaged in testing of materials, and on Fatigue Design of Ship Structures for the Lloyd's Register, UK.
The group maintains research contacts (alas, fading contacts) and worked with following foreign universities and research centers: Ship Structures Committee of the US Coast Guard, En-gineering Integrity Society, Sheffield (UK), Ruhr-Westphalia Technische Hochschule (Ger-many), Lloyd's Register of Shipping (UK), Institute of Advanced Mechanics, University of Clermont-Ferrand, France, Leoben Mountain University, Austria.
List of reports, papers and books where research works of the group are published counts over 200. To exemplify these, a brief list of the recent publications is given in the below: