IPC JEDEC 9704a Test Fixture Deflection Commissioning Verification Procedure
IPC JEDEC 9704A fixture commissioning mandates high-speed triaxial strain gauge verification to prevent transient flexure damage to BGAs and capacitors.
Mohr Circle Strain
Geometrical Deformation Representation
A graphical construction displays the maximum and minimum normal strains acting on an element at a point subjected to a state of plane strain. The mohr circle strain provides a convenient coordinate transformation method to calculate values at any orientation from known directional components. This analytical tool defines the principal strains as the extreme horizontal intercepts on a two-dimensional plot.
It governs the shear strain magnitude relative to the normal strains through the radius of the circle itself.
Analytical Transformation Procedure
Practitioners plot the normal strain along the abscissa and the halved engineering shear strain along the ordinate for a specific stress state. The construction relies on the center point calculated from the average of the normal components. Rotating the radial line by twice the physical angle identifies the strain state at a new orientation within the material.
This procedure reveals the state where shear strain vanishes and normal strain reaches a peak. Orthogonal axes ensure the visual representation remains consistent with the tensor nature of the underlying physical field.
Measurement Boundary Condition
Experimental optical methods such as digital image correlation or resistance strain gauge arrays provide the input data required for this graphical model. The reliance on infinitesimal strain assumptions limits the application of the approach to materials undergoing elastic deformation within stable linear regimes. Large displacement geometries introduce errors that necessitate more complex numerical tensors for accurate representation.
The circle remains a valid analytical constraint only when the material behaves as a continuum.