MATERIALS: DEFECTIVE

Fire & Forensic

Defects

There is no such thing as a perfect crystalline structure, with all of its atoms (of a given type) arranged into a precisely matched form and lattice. Indeed, all crystalline structures not only have defects, but these contribute to the mechanical properties (in particular of metals).

It is very much the case therefore, that ‘defects’ are not only present but at times absolutely desirable and intentionally used to manipulate the mechanical properties of a material.

For example, the adding of alloying elements into a metal is a common way of introducing deliberate crystalline defects.

When assessing crystalline defects we typically talk of three classes:

  1. Point Defects – these are spaces created by a missing atom, or an atom that has been irregularly placed into the lattice structure. Examples include lattice vacancies, self-interstitial atoms, substitution impurity atoms, and interstitial impurity atoms.
  2. Linear Defects (also known as ‘dislocations’) – these are groups of atoms placed into irregular positions.
  3. Planar Defects – these are interfaces between homogeneous regions of the crystal material. They include grain boundaries, stacking faults and external surfaces.

Plastic deformation of a material will occur by the movement of linear defects within it, but it is worth considering that millions of such dislocations will result from the operations such as rolling and extruding (plastic forming). Defects of the regular lattice structure will disrupt the motion of dislocation, causing slip or plastic deformation to become more difficult. While such defects lead to ever more dislocations and from that increased strength to the material, it should be remembered that not all defects are desirable and both in production and later use, the monitoring and assessment of defect progression is a highly specialised science.

Our material scientists frequently consult on the positive and negative results from defects, and for damages or failures of metallic components and machine parts. Our strength in material sciences, and history in consistently resolving metal related claims are well applied to heavy industry and multi-modal shipping related incidents. We are also experts in materials testing, and the use of various laboratory techniques and instruments to do so.

AMA experts can assist at the material design and assessment phase, through to production and post production reviews. We can decipher the seeming complexities of design, specification and other product documents, determining the suitability of selected materials and providing guidance on suitable alternatives or workarounds when needed.

When materials are obtained, we can ensure they are as ordered and described, and of a suitable material strength for the intended use. We can conduct detailed macro and micro inspections by all means, including materials testing and microscopy in a laboratory.

Case Study: Lithium Battery Fires

A major provider of vehicular remote tracking systems suffered a series of high-profile fires in their devices, leading to multi-million pound claims to the provider.

We were initially instructed only after lab assessment of the suspect Li-ion batteries had already occurred. Even so, by careful assessment of the contracted technical specifications, factory production and QA reports, third-party device and component inspection reports, plus various supporting laboratory test results, our experts were able to trace the specific issues back to decisions made by the  production plants in China at the manufacturing stage, these had introduced quality defects which later manifested themselves as fires.

This provided the client with a means to pass these very large claims on to their production partner, who we showed had demonstrably failed to meet the agreed and contracted standards.

 
AMA Provided: –

  • Material scientists (battery experts)
  • Mechanical engineers (QA experts)

Why not give us a call now to see how we could help you

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