The distance or change in distance between two nodes can be obtained with one of the following approaches. 1) *DEFINE_CURVE_FUNCTION can be employed as follows. – Define a curve function that calculates the current distance between two nodes n1 and n2 as: SQRT((CX(n2)-CX(n1))**2.+(CY(n2)-CY(n1))**2.+(CZ(n2)-CZ(n1))**2.) – Define a curve function that calculates the initial (at t=0) distance between the two nodes as: SQRT((CX(n2)-DX(n2)-CX(n1)+DX(n1))**2.+(CY(n2)-DY(n2)-CY(n1)+DY(n1))**2.+ (CZ(n2)-DZ(n2)-CZ(n1)+DZ(n2))**2.) – Given the above two functions, define a curve function that calculates the change in distance. Assuming the curve id is 1 and 2 for the first and second curve function respectively, the change in distance can be calculated with the curve function: LC1-LC2 The curve function value with respect to the time is written in the output file CURVOUT (*DATABASE_CURVOUT). 2) If a discrete spring element (*ELEMENT_DISCRETE, *SECTION_DISCRETE) is defined between the two nodes, the change in length of the spring is available in the output file DEFORC (*DATABASE_DEFORC). 3) In LS-PrePost, the length or change in length between two nodes can be plotted with respect to the time using Element Tools > Measure > Dist N2N. The output time interval will be that of the binary database d3plot.