He was assessed and given the rank of first-class engineer.
Tips
memory
评 (to evaluate/comment) + 定 (to determine/fix) = to evaluate and arrive at a determination.
usage
评定 implies a formal evaluation with a definitive outcome. Compare with 评价 (píngjiā, to evaluate/comment on, more general) and 评估 (pínggū, to assess, often for value or risk).