R&D

Our main software, Zencrack, has achieved many milestones since its beginnings in 1990, including the development of a true-3D fatigue crack propagation facility. This full non-planar crack growth prediction capability was available from the earliest release of the software but was significantly enhanced through a 3-year (2000-2003) SBIR funded project with Wright Patterson Research Station at Dayton, Ohio. One feature introduced to the software as part of this project was time dependent crack growth predicition. This capability was further enhanced during a subsequent Rolls-Royce led project, DISPLACE (2011).

Zentech also supports independent university R&D activities by providing reduced rate licensing of Zencrack for academic use. Many researchers are using Zencrack to assist with their fracture mechanics analyses, e.g.:

  • studying the effect and application of patch repairs for welded structures
  • studying the toughness characteristics of interfacial cracks in materials with thin surface coatings
  • studying non-planar crack growth for comparison with test specimens.

Zentech has always recognised the benefit of consultancy services - to the ongoing development of successful software; only through regular application to real-world problems can our programs evolve and continue to be relevant.

Our consultancy services on a range of commercially important applications include:

  • forensic analyses to determine the cause of failure of components
  • damage tolerance assessment in aircraft engine components
  • modelling defects starting from sub-surface inclusions in a spherical roller thrust bearing assembly
  • fatigue analysis of riser hang-off structure for an offshore field development.

DISPLACE Project

Example
DISPLACE was a Technology Strategy Board UK Government-funded development (2011) of 'technology to increase the life & reliability of advanced lightweight Ni-based gas turbine discs'.

"The work carried out by Zentech for this project will provide new and enhanced capabilities within the Zencrack software. A significant enhancement will be made to the combined fatigue and time dependent analysis capability for full flight cycle analysis. This includes enhancement in the options for time dependent crack growth laws and the addition of an option for including the effect of minor cycles during the fatigue crack growth calculations. The complex interaction between stress and temperature time histories is treated in a thorough manner with industry-standard options included to define the method of association of temperature with fatigue cycles during evaluation of crack growth rates. Although the framework of this project addresses a specific aerospace requirement, the capabilities introduced in Zencrack are general and can be applied to other industry areas where thermo-mechanical fatigue and high temperature crack growth present significant problems." (Reference: TP/8/MAT/6/I/Q1525K)



WPAFB SBIR Project

Example
"The objective of this SBIR was to incorporate new features in the fracture mechanics software, Zencrack, including cyclic and time-dependent load spectra, residual stress distributions, generalized Willenborg retardation, user-defined crack fronts (e.g. for transition from semi-elliptic to through cracks) and automatic large 3-D crack growth. Zencrack was also interfaced to ANSYS in addition to enhanced interfaces to ABAQUS and MSC.MARC. Zencrack models crack fronts by replacing solid elements in finite element (FE) meshes by detailed regions of crack-blocks. The CTOD method was added to the existing 3-D J-integral facility to compute stress intensity factors (SIF) and direction of crack propagation under mixed mode LEFM loading. Numerical crack growth integration algorithms were developed for superposition load systems (e.g. static residual stresses and cyclic loading). New 3-D meshing features to minimize element distortion were developed including large crack-blocks with transition elements at crack block tied surfaces, mesh ‘relaxation’, crack-block boundary shifting and boundary flipping of through cracks. Fatigue and time-dependent crack growth data can now be specified as a function of stress ratio and temperature using Paris Law segment data, tabular data or in a Zencrack user subroutine. Validation of the software was conducted by benchmarking against AFGROW software, data and theoretical solutions." (Reference: AFRL-ML-WP-TR-2004-4014)