19.03.2026 – “Linear Contact” Is an Oxymoron

📌 In the last days I have been faced with what is commonly called “linear contact”.

🔨 Which is an oxymoron .

🛠️ Because contacts can open, close, slip or stick. And they can change from one state to another one during the analysis, forcing the stiffness matrix [K] to be regenarated, typical situation of a non linear analysis.

❗ This is why “linear contact” is an oxymoron.

⁉️ The only possible condition to have a constant [K] during an analysis with contacts is that the contacts do not change their status, but this would mean a “TIED” contact, which in turn is based on MPC formulations, which in turn is not a real contact.

‼️ As far as I am aware, at least two software are having “linear contacts” as an option: NX Nastran and Optistruct, but I might be wrong.

❓I’m skeptical about results from analyses run with “linear contacts”: there is no shortcuts for high quality calculations, and whenever there is the needing for a contact analysis, well, it must be done properly.

I am dealing with contacts at Chapter 12 of my book 𝐂𝐨𝐦𝐩𝐮𝐭𝐚𝐭𝐢𝐨𝐧𝐚𝐥 𝐒𝐭𝐫𝐮𝐜𝐭𝐮𝐫𝐚𝐥 𝐄𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠