Research and development leading to generation of new knowledge, technology and products has always been at the heart of Zentech’s activities. We have developed many novel algorithms and numerical schemes which facilitate efficient simulation procedures.
Zentech has participated in a number of funded research projects in the aerospace industry to assess the residual life and durability of components under varied thermal, cyclic, time dependent and dynamic loadings.
- In the early 1990s, Zentech participated with the Royal Aerospace Establishment based in Farnborough, UK, to develop focussed 3D finite element meshes at the crack front to determine the energy release rate and simulate crack propagation. This eventually led to development of the Zencrack software.
- In 2000 Zentech participated in a 3 year SBIR funded project with the Air Force Research Laboratory at Wright Patterson Air Force Base, Dayton, Ohio, USA, to further enhance 3D crack propagation in Zencrack by introducing new capabilities including large scale crack advancement and time dependent crack growth prediction.
- In 2011 Zentech participated in the DISPLACE project led by Rolls-Royce plc and introduced crack growth prediction under full cycle loading with combined cyclic and time varying loads. This was a TSB-funded development of 'technology to increase the life and reliability of advanced lightweight Ni-based gas turbine discs'.
Zentech has been continuously incorporating new features into Zencrack including capabilities to assess the durability and damage tolerance of additive manufactured components, adhesive lap joints and cracking due to corrosion.
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 on 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.More information about consultancy services and projects can be found on the consultancy page.
Zentech has close research and development links with the academic community at Brunel University London and its state-of-the-art experimental and computational facilities. Many of our associate expert consultants at Brunel enjoy international acclaim in their respective field of work and can offer specialist services in a wide range of engineering fields.
Examples of publications derived from R&D activities undertaken by Zentech
Thoughts on the Importance of Similitude and Multi-Axial Loads When Assessing the Durability and Damage Tolerance of Adhesively-Bonded Doublers and Repairs
Rhys Jones , Ramesh Chandwani , Chris Timbrell , Anthony J. Kinloch , Darren Peng 
 Centre of Expertise for Structural Mechanics, Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
 ARC Industrial Transformation Training Centre on Surface Engineering for Advanced Materials, Faculty of Science, Engineering and Technology, Swinburne University of Technology, John Street, Hawthorn, VIC 3122, Australia
 Zentech International Limited, 590B Finchley Road, London NW11 7RX, UK
 Department of Mechanical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK
Aerospace 2023, 10(11), 946.
Adhesively bonded doublers and adhesively bonded repairs are extensively used to extend the operational life of metallic aircraft structures. Consequently, this paper focuses on the tools needed to address sustainment issues associated with both adhesively bonded doublers and adhesively bonded repairs to (metallic) aircraft structures, in a fashion that is consistent with the building-block approach mandated in the United States Air Force (USAF) airworthiness certification standard MIL-STD-1530D and also in the United States (US) Joint Services Structural Guidelines JSSG-2006. In this context, it is shown that the effect of biaxial loads on cohesive crack growth in a bonded doubler under both constant amplitude fatigue loads and operational flight loads can be significant. It is also suggested that as a result, for uniaxial tests to replicate the cohesive crack growth seen in adhesively bonded doublers and adhesively bonded repairs under operational flight loads, the magnitude of the applied load spectrum may need to be continuously modified so as to ensure that the crack tip similitude parameter in the laboratory tests reflects that seen in the full-scale aircraft.
A Time Dependent Crack Growth Law For High Temperature Conditions
Chris Timbrell, Ramesh Chandwani, Zentech International Ltd.
Duncan MacLachlan, Steve Williams, Rolls-Royce plc, Derby
NAFEMS European Conference: Multiphysics Simulation, Frankfurt, Germany, Oct 16-17 2012
Alloys, especially nickel based ones used in the aerospace industry, are continuously being improved to provide greater strength against component failure and also to increase resistance against crack propagation. This involves altering their composition and, under controlled conditions, modification of precipitate and grain sizes. At high temperatures under both sustained and cyclic loading conditions, these microstructural changes interact synergistically with time dependent mechanisms such as creep, oxidation and corrosion and affect the crack growth rate (CGR). The individual effects of environmental conditions such as oxidation and corrosion and microstructural evolution of grain size at high temperatures, are generally difficult to evaluate. In addition, thermo-mechanical testing of large numbers of specimens under a variety of conditions can be prohibitively costly. Attempts have been made over the last few decades by a number of investigators to conduct standardised tests under controlled environmental conditions and compare them with the results obtained in neutral environments such as vacuum or inert gas [1-4]. It has been found that these environmental effects interact and their combined effect is generally greater than if they were considered separately. In this paper a time dependent crack growth law, COMET (Creep Oxidation Microstructure Environment Temperature), is described which considers the effect of these combined processes using a temperature dependent parameter based on an Arrhenius equation. Using this time dependent law in conjunction with a fatigue crack growth law, a finite element based implementation has been developed to carry out detailed 3D crack propagation analysis and simulation of a cracked component under the effect of thermo-mechanical loading at high temperatures.
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