GMNA GMN8396 PDF

Material Description. The material defined by this specification is a laminated vibration damping steel (LVDS) consisting of either two similar or dissimilar metal skins of the same or different thickness separated by, and bonded to, a viscoelastic core. The engineering drawing will specify dimensions, tolerances, skin steel and coatings required. Only unexposed (U) applications with low carbon steel have been approved for LVDS applications.

LVDS will have approximately the same density as homogenous or monolithic steel sheets. The elastic modulus, however, is variable depending upon such factors as deformation rate, temperature and vibrational frequency. For analysis purposes, the stiffness of a stamping from LVDS is generally between 50 - 70% of a monolithic sheet at the total specified thickness of the composite sheet.

Laminate Core: The core shall consist of a viscoelastic resin that exhibits adequate bonding, temperature stability, strength and plasticity to provide the required damping and manufacturing performance of the composite. A Material Safety Data Sheet (MSDS) shall be provided along with information on potential toxicity and odor emissions through the resistance welding temperature ranges.

Laminate Skins: Most applications are specified as cold rolled low carbon sheet steel per GMW2. The material may be specified as uncoated, or with an electroplated coating applied to exterior surfaces as specified in GMW11. Hot dip coatings may be available as LVDS but shall not be specified without approval of Materials Engineering.

Material Identification. This specification shall be included in the engineering drawing material callout and the Manufacturing Engineering Metal Part Specification (MPS) Sheet. The materials shall be identified by this specification number, followed by a grade selected from Table 1.

In this table, electrogalvanized materials shall carry an additional designation indicating the coating process ("EG") and the coating weight and type. If the material is to be hot dip coated, the coating process ("HD") shall be used along with the coating weight and type. Only the base metal specifications and grades listed in Table 1 can be used. See Section 7 for examples.

Typical Application. Parts where vibration damping is required such as: dash panels and cowl plenums.