The Challenge

Offshore structures operate in one of the harshest engineering environments imaginable. Ageing assets, cyclic loading, corrosion, and fabrication defects all contribute to a common and critical challenge, crack initiation and growth in primary load‑bearing components.

At Andymus Consulting, we support operators and asset owners in answering one fundamental question:

Is the structure still fit for service – and if so, under what conditions?

A key part of this capability comes from the work of Abdulla Toma, whose experience spans finite element modelling of offshore jacket structures, fatigue, compliance evaluation, and repair justification. If you need assistance from the team at Andymys Consulting, please contact us to discuss your requirements.

In this case study, assessment and repair approach and assessment will be detailed to tackle an oil rig, with large crack. The crack was discovered in one of the main leg joints during routine inspection.

Engineering Objective

The objective of this work was to:

1. Assess the structural integrity of the cracked joint.
2. Assess the risk
3. Propose and engineer repair
4. Assess adequacy of the repaired joint

Modelling Approach

Following methodology was followed to reinstate the cracked joint and make the platform fit for service again:

1. Performed SACS structural analysis of the platform (as built condition) for the operating conditions.
2. Using boundary nodes deflections (BND) from the SACS model, FEA analysis of local model of the jacket leg (no crack) was conducted. Stress distribution in the joint are used as reference in the subsequent FEA analysis.
3. Using BND from the SACS model, performed FEA analysis of local model of the cracked jacket leg (the crack was explicitly modelled.
4. Localised stresses around the crack from FEA were used to run subsequent crack growth analysis.
5. Based on stress assessment and crack growth rate, the following repair strategy was proposed:
   1. Cut the diagonal/horizontal brace that is directly responsible for the main load path through the crack.
   2. Reconnect the brace to the jacket leg by-passing the cracked node with clamping arrangement.
   3. Grout the leg section, above and below the crack. To model the grouted leg accurately, advanced FE analysis techniques, like contact and geometric non-linearity are used.
   4. The repair approach restores structural capacity, divert load path from crack, avoid introducing new stress concentrations, and maintain constructability under offshore constraints
6. For the jacket with the proposed repair, SACS structural analysis were conducted and the boundary conditions deflection at the boundary nodes were used in subsequent FEA analysis.
7. Run FEA analysis using boundary nodes deflections from SACS to assess the repaired joint.
   1. The jacket leg section, which is filled with grout, is modelled with solid elements. The rest of the modelled jacket members were modelled with shell elements.
   2. The crack (void) in the jacket is simulated with very soft material, which is fully bonded to the steel, to help with convergence for contact analysis.
   3. The grout is modelled explicitly within the jacket leg.
   4. Frictional contact is simulated between the jacket leg shell and the grout assuming perfect contact condition.
8. Run FEA analysis using boundary nodes deflections from SACS to design/ assess the clamping arrangement of the member reconnection.

Understanding Offshore Jacket Behaviour through Advanced Modelling

Offshore jacket structures are highly redundant but complex systems. Load paths are three‑dimensional, boundary conditions are non‑linear, and local stress concentrations often govern structural integrity.

Abdulla’s work focuses on developing engineering‑grade finite element models that realistically capture:

• Global load distribution through jacket legs, braces, and joints using joint deflections from global SACS analysis of the platform.
  • Boundary conditions representative of real foundation and pile soil interaction and behaviour.
  • Combined effects of wave loading, gravity, operational loads, and cyclic fatigue loads.
• Local stress intensification at weld toes and tubular intersections.

Crack Assessment: Moving Beyond Detection to Engineering Decisions

Cracks in offshore structures are not, by themselves, a reason for shutdown. The real question is what the crack means for structural integrity, remaining life, and risk to asset and human life.

Abdulla’s approach bridges inspection data and engineering decision‑making by:

• Translating scan data results into engineering crack representations through use of FEA explicitly modelling the cracks and defects.
• Evaluating crack driving forces under realistic operational load cases
• Assessing fracture and fatigue behaviour using recognised fitness‑for‑service frameworks
• Differentiating between monitor, repair, and operate‑as‑is outcomes

This enables asset owners to move from “we’ve found a crack” to “we understand the consequences”.

Compliance Assessment: Aligning Analysis with Codes and Standards

Regulatory and internal compliance requirements are a critical part of offshore asset management. Crack assessments must align not only with physics – but also with recognised codes and industry practice.

Abdulla’s work supports compliance pathways by:

• Demonstrating structural adequacy against applicable offshore and fracture standards
  • API RP 2A Planning, Designing, and Constructing Fixed Offshore Platforms— Working Stress Design
  • API 579‑1 Fitness-For-Service
  • ASME FFS‑1 FFS-1 – Fitness-for-Service
  • DNV rules and standards for offshore units
• Providing traceable assumptions, load cases, and safety factors.
• Supporting regulatory submissions and independent verification processes
• Ensuring engineering judgement is anchored in defensible analysis

This combination of technical depth and compliance awareness is essential when decisions carry operational, financial, and safety consequences.

Engineering‑Led Repair Design and Justification

When a repair is required, the objective is not simply to “fix the crack”, but to:

• Restore structural capacity
• Avoid introducing new stress concentrations
• Maintain constructability under offshore constraints

Through integrated modelling and assessment, Abdulla contributes to repair strategies that are proportionate, targeted, and technically justified, including:

• Evaluation of load redistribution post‑repair
• Assessment of residual stresses and fatigue implications
• Support for repair effectiveness and inspection planning

This ensures repairs are engineered solutions, not reactive interventions.

Engineering‑Led Repair Design and Justification

When a repair is required, the objective is not simply to “fix the crack”, but to:

• Restore structural capacity
• Avoid introducing new stress concentrations
• Maintain constructability under offshore constraints

Through integrated modelling and assessment, Abdulla contributes to repair strategies that are proportionate, targeted, and technically justified, including:

• Evaluation of load redistribution post‑repair
• Assessment of residual stresses and fatigue implications
• Support for repair effectiveness and inspection planning

This ensures repairs are engineered solutions, not reactive interventions.

Fitness‑For‑Service: Enabling Safe and Informed Continued Operation

At the heart of this work is Fitness‑For‑Service (FFS) – providing asset owners with a clear, defensible answer to whether a structure can continue operating safely.

By linking inspection, analysis, compliance, and repair assessment, Abdulla helps deliver:

• Clear FFS conclusions grounded in mechanics, not assumptions
• Confidence for operators, regulators, and stakeholders
• Reduced unnecessary conservatism without increased risk
• Improved decision‑making over inspection intervals and asset life

Practical Engineering for Asset‑Critical Decisions

What distinguishes this work is its practical focus. Offshore integrity assessments are not academic exercises – they directly inform shutdown decisions, repair campaigns, and long‑term asset strategies.

Through his experience in offshore jacket modelling and crack assessment, Abdulla Toma strengthens Andymus Consulting’s capability to support high‑consequence engineering decisions with clarity, rigour, and confidence.

The post Advanced Finite Element Modelling of cracked leg of oil rig platform appeared first on Andymus Consulting.

Eliminating numerical instability to enable accurate thermo‑mechanical brake design

This case study is the summary of Abdulla Toma‘s Masters Thesis work on braking performed at RMIT Melbourne. It demonstrates how advanced non‑linear and thermo‑mechanical finite element modelling was used to eliminate numerical instability in automotive brake simulations. The result is design‑grade insight suitable for safety‑critical components – reducing reliance on physical testing and enabling earlier, more confident engineering decisions.

The Challenge

During braking, large amounts of kinetic energy are converted into heat through friction between the brake drum and shoe. This creates extreme mechanical and thermal loading, making accurate performance prediction essential at the design stage.

Conventional drum brake design methods rely on simplified analytical equations that assume rigid components, uniform pressure, and constant friction. These assumptions lead to poor prediction of brake effectiveness, durability, and thermal limits.

Physical testing improves realism but is slow, costly, and unsuitable for early design iteration. Earlier finite element studies attempted to bridge this gap, but many reported unexplained numerical instability, undermining confidence in simulation results.

Working on high‑load or thermal‑critical components where numerical instability is a risk?
Talk to us about design‑grade non‑linear and thermo‑mechanical FEA – before costly testing and late‑stage redesigns. Please reach out to Andymus Consulting to discuss how we can help.

Engineering Objective

The objective of this work was to deliver a validated, design‑ready finite element framework that:

• Predicts realistic contact pressure and brake factor
• Captures thermal–mechanical coupling effect during braking
• Eliminates artificial numerical fluctuation
• Supports design optimisation before prototyping

Modelling Approach

A progressive modelling strategy was implemented in ABAQUS, moving deliberately from problem reproduction model to robust solution.

1. Preliminary Mechanical Model

A 3D mechanical FEA model of a single‑shoe drum brake was developed to reproduce the instability reported in literature. This model confirmed the issue was structural in nature rather than a solver artefact.

2. Root Cause Investigation

Detailed interrogation showed instability was driven by geometric discretisation errors, including first‑order elements on curved surfaces and mismatched contact meshes. As the drum rotated, the effective contact diameter changed numerically, forcing oscillation in pressure and brake factor.

Key Innovation

Two production‑grade modelling techniques were developed to permanently remove this instability.

Advanced Model 1 – Geometric & Increment Control

Stability was achieved by enforcing geometric consistency at the contact interface and synchronising rotational increments with mesh topology. This produced smooth, physically realistic pressure distributions suitable for short‑duration events.

Advanced Model 2 – Surface Multi‑Point Constraint (SMPC)

To model realistic manufacturing clearance, a second‑order shell surface was introduced and tied to the corresponding drum surface via a surface multi‑point constraint. This enabled accurate contact prediction even with initial gaps.

Coupled Thermo‑Mechanical Analysis

With mechanical stability proven, fully coupled thermo‑mechanical simulations were executed. These captured frictional heat generation and distribution, temperature‑dependent material response, thermal expansion, and stress redistribution during sustained braking.

Key Results

Contact Pressure

The advanced models eliminated artificial fluctuation and produced stable pressure fields aligned with theory and test evidence.

Brake Factor

Brake factor remained stable under rotation. Thermal expansion reduced effectiveness over time, while temperature‑dependent friction partially offset this reduction.

Temperature & Stress

Peak temperature aligned with pressure concentration. More uniform pressure reduced both thermal and structural extremes.

Design Insights

This work generated actionable design guidance:

• Small, intentional clearance reduces peak pressure and temperature
• An optimal gap exists, governed by geometry and material stiffness
• Softer friction materials promote more uniform contact
• Shoe stiffness dominates system response more than drum stiffness

Business Value

This case study shows how advanced simulation replaces trial‑and‑error design. For Andymus Consulting clients, it enables faster decisions, reduced testing cost, and higher confidence in safety‑critical components.

Where This Capability Applies

This work draws on deep expertise in contact mechanics, numerical stability control, and production‑grade non‑linear FEA using ABAQUS.

• Automotive and heavy‑vehicle braking systems
• Off‑highway and industrial equipment
• Rail braking applications
• Any system involving high‑load frictional contact with thermal coupling

Need confidence in high‑load, high‑temperature component design?

Andymus Consulting combines advanced simulation with real‑world engineering judgement to help you make better design decisions earlier.

Talk to us about advanced FEA and design optimisation.

The post Advanced Finite Element Modelling of Automotive Drum Brake Systems appeared first on Andymus Consulting.

This case study is based on doctoral research undertaken at the University of Greenwich (UK) in collaboration with HIsmelt Corporation Pty Ltd and Rio Tinto Technology. The work developed an integrated simulation framework to predict refractory wear, freeze layer formation, and cooling feasibility in high‑temperature direct smelting processes.

The Challenge

Direct smelting furnaces operate under extreme thermal and chemical conditions, where small design decisions can have major consequences for safety, availability, and campaign life.

Key challenges included:

• Predicting refractory wear under highly variable operating conditions
• Understanding whether freeze layers would protect or destabilise the furnace lining
• Evaluating the feasibility of water‑cooled elements close to molten slag
• Making design decisions with limited empirical data and high risk exposure

At the time, industry lacked a predictive, physics‑based modelling framework capable of addressing these issues in an integrated way.

The Approach

This work developed a tightly coupled multiphysics simulation framework combining:

• Computational Fluid Dynamics (CFD)
• Solidification and phase‑change modelling
• Free‑surface and multiphase flow
• Explicit refractory wear mechanisms

The models were implemented using a finite‑volume, unstructured mesh CFD framework (PHYSICA) and applied directly to industrial smelt reduction vessels, rather than simplified academic geometries.

A key innovation was treating refractory wear as a dynamic, evolving system, rather than a static boundary condition.

What Was Modelled

The modelling framework was applied across several real‑world scenarios, including:

• Freeze layer formation on water‑cooled furnace elements
• Accretion growth (“Elephant Trunks”) on solids injection lances
• Refractory wear in pilot‑scale smelt reduction vessels
• Laboratory validation using induction furnace and rotary slag tests

Each model was validated against measured plant or test‑scale data, ensuring results were grounded in operational reality.

Key Technical Insights

The research delivered several insights with direct engineering relevance:

• Refractory wear is driven primarily by temperature excursions, not steady operation
• Freeze layers form naturally once thermal equilibrium is reached
• Water‑cooled designs can be viable when freeze layer behaviour is explicitly considered
• Cooling strategies must be evaluated as system‑level interactions, not isolated components

This shifted decision‑making from “Can this be cooled?” to “Under what operating envelope is cooling self‑stabilising?”

Outcomes & Impact

The modelling framework provided:

• A defensible basis for evaluating water‑cooled stave designs
• Improved understanding of refractory life‑limiting mechanisms
• Reduced reliance on conservative over‑design
• A structured way to link process variability to asset degradation

The work bridged the gap between advanced simulation and practical industrial decision‑making in high‑risk environments.

Why This Matters Today

This case study underpins how Andymus Consulting approaches complex engineering and operational problems:

• Simulation as a decision support capability, not just analysis
• Explicit treatment of degradation, uncertainty, and time‑dependence
• Integration of physics, materials, and operations
• Translation of complex modelling into clear, defensible decisions

These principles are now applied across resources, energy, infrastructure, and advanced SME advisory engagements.

Key Takeaway

The real value of simulation lies in predicting how systems evolve over time — not just how they perform at a single point.

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Reference

An PDF download of the thesis for this research is available from the Univeristy of Greenwich.

The work was performed by Andrew Campbell, under the supervision of Prof Koulis Pericleous and Prof Mark Cross in collaboration of Chris Cross who supported from the Office of the Chief Technologist, Rio Tinto Technology.

The post Modelling Freeze Layer Formation and Refractory Wear in Direct Smelting Processes appeared first on Andymus Consulting.