The structural integrity laboratory offers a wide range of equipment for studying the mechanical behaviour of components and material samples, using destructive and non-destructive methods.

The laboratory allows examination of the conditions and parameters that affect material strength and durability due to stress, fatigue, fracture and corrosion. It is important that materials are tested to determine how they behave throughout their lifecycle. The laboratory contains state-of-the-art modern testing equipment, and is used for education and industry-led research.

The loading of specimens and components is possible under unaxial tension-compression, bending and rotating bend arrangements. A pipe pressure-temperature rig is available and used for testing and verification of composite pipeline repair systems.

A range of inspection, non-destructive testing equipment and structural health monitoring systems are used for crack and stress measurement. The laboratory specialises in the testing of non‑standard specimens and components, development of fatigue design rules, acceptance testing and inspection reliability trials. Industrial-scale samples can be tested in the laboratory.

Key facts

  • Fully-equipped workshop and lab technicians for industry led research, teaching and project support.
  • A range of servo-hydraulic materials and fatigue testing facilities as standard test machines or as test rigs built about full or large-scale components.
  • Strain gauges: which link to P3 strain indicator and recording system, which can be linked to a computer for analysis.
  • Fully automated software's for performing KIC and JIC fracture toughness testing and analysis according to standard test methods.
  • Compliance measurements in fracture mechanics tests using calibrated clip gauges.
  • Digital image correlation (DIC) measurements. 

Servo hydraulic fatigue testing machines - these can be configured for industrial bespoke research requirements and all use the latest 8600 Instron controllers:

  • 1 x 2.5 MN (dynamic capacity) - four post high-stiffness Instron test machines with various gripping arrangements;
  • 1 x 1MN – arranged horizontally or vertically;
  • 1 x 500kN – a versatile general purpose test machine with top mounted actuator and load cell;
  • 2 x 100kN – used for testing small standard samples (e.g. compact tension test specimens).

Various jacks: for building test rigs.

Charpy impact test machine: with 300J capacity for quick, inexpensive testing of material notch toughness.

Corrosion testing: we can simulate sea conditions, e.g. temperature and salt content, to test for corrosion and crack propagation.

Environmental chamber: this is used to test the effects of specified environmental conditions on materials, specifically fracture toughness. Operating temperatures range from -70°C to +400ºC.

Hopkinson Bar facility: the tri-function Hopkinson Bar is able to test material specimens in compression, tension, torsion and combined loadings. It achieves strain rates of up to 5000/sec in tension and 10000/sec in compression. The bar can be configured as a direct impact bar for measuring low impedance foams and similar materials. The bar is supported with finite element (FE) modelling to develop novel specimen grips, pulse modifiers and to assist the development of FE material models.

Pipeline repair rig: the pipeline is used to study structural health monitoring purposes and to research crack propagation, initiation, inspection and repairs.

Non-destructive testing (NDT) - the methods used are:

  • Acoustic emission (AE) - utilises the sound waves produced when a material undergoes stress (internal change), as a result of an external force;
  • Alternating current potential drop (ACPD) - an electrical potential method used for sizing cracks in electrically conducting materials;
  • Alternating current field measurement (ACFM) - an electromagnetic technique for detection and measurement of surface breaking cracks;
  • Magnetic particle inspection (MPI) - a process for detecting surface cracks in metal;
  • Direct current potential drop (DCPD) - used to determine electrical conductivity and resistivity due to materials with cracks;
  • Strain gauging - used to measure applied or residual stress (through centre hole drilling).
Structural Integrity Lab
Structural Integrity Laboratory staff

Summary of applications

Cranfield has worked with a number of industrial partners to test and research structural integrity such as Centrica, Petronas, RWE, E.ON, EDF and Dong Energy, among others.

Some of our areas of expertise and research include:

  • Fatigue and fracture mechanics analysis – methods of assessment to test fitness-for-purpose, damage tolerance and evaluation of repair strategies;
  • Structural reliability analysis – providing design optimisation by systematic quantification of uncertainties and calibrating design standards;
  • Design of structures and components – design, analysis and performance assessment of structures and structural details; testing and characterisation of new materials; engineering for installation, manufacturing and large-scale production;
  • Composite materials – determine the properties of new materials to optimise design and manufacturing;
  • Corrosion analysis – with a focus on modern materials such as very thick plates where combined effect of fatigue and corrosion assessment is required;
  • Requalification of structures – extending the service life of installations by improving structural integrity.

Take a virtual 360° tour of our Structural Integrity Laboratory below.

Using the facility

The Structural Integrity Laboratory has been used to test and research structures and components, in the following sectors:

  • Offshore oil and gas structures;
  • Offshore wind structures;
  • Marine renewable energy structures;
  • Pipelines (oil and gas, and carbon capture and storage);
  • Aerospace;
  • Automotive;
  • All large scale industrial testing.