A transformerwood notch redirects force through the remaining material and veneer layout. Compare transitions and loading states to select the notch that delivers conductor space with a supported mechanical response. [1]
Calculation basis. Project-specific values and gates in the illustrative screens below are assumptions; cited catalogue values retain their source test conditions.
Locate the actual contact forces and restraints. A notch close to a load introduction point may experience local bearing and bending, while a remote notch may primarily affect the axial path. Start the comparison with those mechanisms rather than a generic net-area limit.
Compare changes without mixing their causes
| Comparison | Variable kept visible | Damage observation |
|---|---|---|
| Sharp versus smoother transition | Remaining geometry and contact position | Crack origin at the transition or another feature |
| Different veneer orientations | Same notch and loading arrangement | Splitting relative to grain and layers |
| Different notch depths | Force path and local section | Whether the limiting region moves |
| Changed machining route | Same intended profile | Effect of local separation or torn material |
In an illustrative axial calculation, a 5 kN force through a 250 mm² net section gives 20 MPa average nominal stress. The same number for two notch shapes does not establish the same peak stress or failure load. It excludes concentration, directional stiffness, local contact and bond behaviour.
An isotropic metal notch chart cannot supply those missing properties for a veneer laminate. A numerical model can help locate likely regions, but its directional material description and contact assumptions need supporting evidence.
Watch where damage begins
In representative load tests, record displacement and inspect the notch region as well as the eventual fracture. A crack that begins at a machined layer opening has a different cause from splitting initiated by an otherwise sound transition under transverse loading.
Include the relevant oil and temperature state, and identify which face and layer direction the fixture loads. A test on a plain block in the strongest direction can miss the tensile or shear condition around the actual cutout.
Use qualification sections to verify the intended notch profile and local bond condition. The examination method should preserve the difference between existing damage and separation introduced while preparing the section.
Increasing the transition radius can remove a sharp feature while reducing clearance or moving contact onto a different surface. Evaluate the resulting load path and assembly envelope together. Likewise, thickening the block may increase net area without correcting a poorly supported bearing surface.
Keep the crack-initiation map with the geometry comparison. If the critical region moves after a design change, the next inspection and validation must follow it. Accepting the revised support solely because its net area increased would leave that new mechanism unevaluated.
The useful design outcome is a notch and layup combination tested for its intended loading and state. Its range should identify which depth, transition and machining changes remain represented, so subsequent conductor-clearance edits receive the mechanical check they require.
Separate net-section stress from notch concentration
Match the material identity and relevant test direction before comparing densified-wood evidence [2].
The assumed 5 kN load over 250 mm² gives 20 MPa nominal stress. Assume two hypothetical direction-aware elastic models give concentration factors 2.5 and 1.5 under the same reference stress. Their local screens are 50 MPa and 30 MPa. Against an assumed 40 MPa local allocation, the first fails and the second passes. Replace those assumed factors and allocation with applicable material, geometry and damage evidence; the input factors are not validated results.
References
- Röchling Industrial, Lignostone L I/2-E3-HQ (P2R), Technical Data Sheet, version 2.0, released 20 September 2023.
- IEC, IEC 61061-2:1992, Specification for non-impregnated, densified laminated wood for electrical purposes — Part 2: Methods of test.