Why am I getting the error message below with PLANE223? The same model with PLANE13 doesn't produce this error.
*** ERROR *** CP = 2.344 TIME= 10:47:07
The calculated specific heat at constant strain is negative. Please
verify the input of thermal material quantities for consistency.
PLANE223 is different because it has two way thermal-structural coupling. You may be getting the negative Cv message because your value of Cp is too small. From the numerical values in your input, it appears as though you are using the length unit off mm. The table below from the Coupled Field Guide gives units of length^2 for specific heat, so the MKS value of 460 for specific heat should be multiplied by 1e6 to produce a value of 460e6. This will make the value of Cv very positive.
Theory Manual Equation 11-31
Coupled Field Guide Section 2.6.2 points a through d.