The Material Point Method's founding papers frame their motivation as penetration, impact, and large rotations together — not penetration alone

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Both the Sandia National Laboratories technical report SAND93-7044 (June 1993) and its 1994 journal descendant in Computer Methods in Applied Mechanics and Engineering open with the identical sentence: "A broad class of engineering problems including penetration, impact and large rotations of solid bodies causes severe numerical problems." This is the authors' own stated motivation, quoted verbatim, and it names penetration as one of three coordinate problem classes — alongside impact and large-rotation solid dynamics — rather than as the sole or headline motivation.

This refines rather than overturns the vault's existing account, which compressed the motivation to "penetration problems in solid dynamics." That compression is not wrong, exactly — penetration genuinely is named, first, in the authors' own sentence — but it drops the "broad class" framing and the two problem classes that ride alongside it. "Motivated by a class of problems that includes penetration" is what the primary source says; "motivated primarily by penetration" is a tightening the source itself does not make.