Assessing Structural Integrity with Finite Element Analysis (FEA)

We use advanced FEA methods to assess the structural integrity and serviceability of complex engineering systems. This can include:

  • Multi-component systems with surface-to-surface interactions such as metal-to-metal seals;
  • Materials, such as metal, composites, elastomers, cement, rock and soil;
  • Manufacturing methods such as heat treating, cold working and additive manufacturing;
  • Loading scenarios such as multi-axeis, cyclic and thermal effects;
  • High strain conditions such as low-cycle (plastic) fatigue and plastic collapse;
  • Environmental effects on the material properties such as embrittlement, thermal degradation and chemically induced swell; and
  • Time-dependent effects such as fatigue, strain ageing, stress relaxation and creep.

We use the results of the structural integrity and serviceability modelling to:

  • Increase reliability and run-life;
  • Develop safe operating procedures;
  • Identify critical dimensions and tolerances for quality control and inspection programs; and
  • Evaluate the impact of new operating procedures and environments.

Example projects where FEA has been used include:

  • Premium connection integrity in thermal and high pressure, high temperature (HPHT) wells;
  • Well failure investigation and design optimization;
  • Sand control system performance in thermal wells;
  • Structural integrity of flexible pipes (steel tube umbilicals);
  • Offshore platform design;
  • Ship collisions with offshore structures;
  • Ice loading for offshore structures;
  • Collapse of subsea pipelines;
  • Geo-hazard impact on pipelines;
  • Fracture, fault, subsidence impact on well casing;
  • Permafrost thaw impact on well casing; and
  • Piles and foundations.

We primarily use the FEA package SIMULIA ABAQUS from Dassault Systèmes®.

Determining Ultimate and Serviceability Limits

Modeling projects usually define the ultimate limits and serviceability limits of the component. The ultimate limit occurs when there is a complete loss of function of the component, such as:

  • Loss of pressure containment;
  • Structural collapse; and
  • Rupture or burst.

The serviceability limit is reached when some function of the component is impaired. This can include criteria such as:

  • Ovalization or buckling of a pipe that impairs access through the pipe;
  • Opening of gaps in a sand retention screen to allow over-sized sand to pass;
  • Reducing contact stress on a seal surface to below design requirements; and
  • Accumulating excessive plastic strain through load cycles.

Accounting for Uncertainty using Monte Carlo and Response Surface Methods

C-FER Technologies’ FEA simulations account for uncertainty in the model input parameters. We use Monte Carlo simulation techniques to consider a broad range of possible input parameters. These analyses require running the FEA simulation hundreds of times with different parameters to determine how the component behaviour changes. These results are used to estimate the likelihood, or probability, that a specific condition will occur.

If multiple uncertainties need to be considered in an analysis, the number of possible combinations of parameters could require an unmanageable number simulations. In these cases, a response surface methodology can be used to select critical parameter combinations. This can substantially reduce the number of FEA simulations that need to be performed to fully describe the effects of input variability on component behavior. The results of these simulations are expressed as a simplified, multi-variate relationship using a radial basis function, which uses the Euclidean distance between points to perform the interpolation.

The uncertainties that can be assessed with these techniques include:

  • Manufacturing tolerances;
  • Material properties;
  • Operating loads, pressures and temperatures; and
  • Wear, erosion and material degradation.

How FEA is used to Conduct Better Testing Programs

We often integrates FEA into our large-scale testing programs. These analysis are used prior to testing to:

  • Pre-qualify prototype specimens to avoid testing inadequate designs;
  • Design or select specimens to minimize the number of tests that need to be completed;
  • Identify critical measurements that should be made during testing;
  • Design complex test fixtures; and
  • Design safety systems such as energy absorbing devices, specimen constraints and protective barriers.

Examples of how FEA has been used to simplify testing programs include:

  • Enabling the use of shorter pipe segments for deepwater pipeline collapse tests by developing new end cap designs;
  • Simulating high temperature coiled tubing performance at ambient temperature by using different steel grades;
  • Minimizing the number of premium threaded connection specimens to be tested by identifying critical manufacturing tolerance combinations that would impact connection performance; and
  • Making large-scale burst and tensile tests safe by designing efficient and reusable energy absorbing devices.

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