i have problem in IMPACT load on beam , whatever is there i mentioned below

i have load (kips) vs time (sec)

at time =0 , load=0 

at time =0.006 , load=5.9

at time 0.056 , load=0

i use funtion editor by linear eqution Y=aX+b

i could not accurate result because of interpolations in ANSYS is differance then the MATHEMATICS. like

As per ANSYS

                    Time      Force 

                     0            0