Plastic Deformation, in regards to Transportable Moisture Limit (TML) testing, is a term used during the Flow Table Test (FTT) procedure stated in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code). Plastic deformation is a process in which enough stress is placed on a material to cause a material to change its size or shape in a way that is not reversible. In other words, the changes are permanent; even when the stress is removed, the material will not go back to its original shape. Plastic deformation is also known as plasticity.
- The impacting action of the flow table causes the grains to rearrange themselves to produce compaction of the mass. As a result, the fixed volume of moisture contained in the material at any given level increases as a percentage of the total volume. A flow state is considered to have been reached when the moisture content and compaction of the sample produce a level of saturation such that plastic deformation occurs (In certain conditions, the diameter of the cone may increase before the flow moisture point is reached, due to low friction between the grains rather than to plastic flow. This must not be mistaken for a flow state.). At this stage, the moulded sides of the sample may deform, giving a convex or concave profile..
- International Maritime Organisation, International Maritime Solid Bulk Cargoes Code, 2013 Edition, London: International Maritime Organization.