The IMRAD structure:
function vs topic

The IMRAD structure accommodates further sub-division along both functional and topical lines.  You may want to incorporate further sub-divisions which detail your analysis of different aspects, stages or functions of the research process.
E.g.: in Methodology

• Subjects
• Equipment
• Procedure

Topic-based sub-headings are useful to separate sections to reflect the specific content of your study.
E.g.: in the Introduction or Discussion it's likely you'll need to break down your report into topical sub-categories.

• Language attitudes
• Language teaching approaches
• Language performance

Click here for a look at other optional procedural headings within the IMRAD structure.