How can I eliminate the imaginary part?

Question

How can I eliminate the imaginary part? It is zero, but Mathematica does not seem to simplify it.

expr = (1/
     10020) E^(-(250000/47) (t + 
        3 I Sqrt[167] t)) (5010 E^(250000/47 (t + 3 I Sqrt[167] t)) + 
     10 (501 - I Sqrt[167]) m + 
     I (2505 I + 799 Sqrt[167] + 400 Sqrt[167] n - 400 Sqrt[167] p) + 
     E^(1500000/47 I Sqrt[167] t) (-2505 - 799 I Sqrt[167] + 5010 m + 
        10 I Sqrt[167] m - 400 I Sqrt[167] n + 400 I Sqrt[167] p));
Assuming[{t \[Element] Reals, m \[Element] Reals, n \[Element] Reals, 
  p \[Element] Reals, t > 0, m > 0, n > 0, p > 0}, 
 FullSimplify[ComplexExpand[expr]]]
 

Answer 1

Another option is to run ComplexExpand after expanding it on each part

expr = (1/
     10020) E^(-(250000/47) (t + 
        3 I Sqrt[167] t)) (5010 E^(250000/47 (t + 3 I Sqrt[167] t)) + 
     10 (501 - I Sqrt[167]) m + 
     I (2505 I + 799 Sqrt[167] + 400 Sqrt[167] n - 400 Sqrt[167] p) + 
     E^(1500000/47 I Sqrt[167] t) (-2505 - 799 I Sqrt[167] + 5010 m + 
        10 I Sqrt[167] m - 400 I Sqrt[167] n + 400 I Sqrt[167] p));
Simplify[ComplexExpand[#] & /@ Expand[expr]]

FreeQ[%, I]

Answer 2

ComplexExpand[ReIm[expr], TargetFunctions -> {Re, Im}][[2]] // 
   FullSimplify // N // Chop

returns

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