Quasi-static methods to evaluate seat strength in rear impacts

Area of Science:

• Automotive Safety Engineering
• Biomechanics
• Vehicle Dynamics

Background:

• For over 50 years, various quasi-static load test procedures have been employed to assess automotive seat performance during rear impacts.
• Evaluating seat performance in rear-end collisions is critical for occupant safety and requires standardized testing methodologies.

Purpose of the Study:

• This study aimed to compare five common test procedures used for evaluating automotive seats under rear impact loading.
• The research also investigated the influence of occupant mass and center of gravity on rear seat loading characteristics.

Main Methods:

• Five distinct seat pull test procedures were analyzed: FMVSS 207, modified FMVSS 207, Quasi-Static Test (QST), body block, and FRED II.
• Data collected included peak force, moment, and seatback angle at peak moment. Occupant loading height was calculated using anthropometric data for body segment weights and positions.

Main Results:

• Significant differences were observed in loading heights and peak force/moment occurrences across the tested procedures.
• The QST and FRED II methods utilized a lower loading height compared to FMVSS 207, leading to different seatback angle responses.
• Variations in occupant center of gravity height (whole body vs. upper torso) were noted, impacting load characteristics.

Conclusions:

• Direct comparison of seat performance data across different rear impact test methods is challenging due to inherent variations in loading conditions.
• Differences in occupant representation (body shape, loading height relative to H-point) cause the seat structure to respond uniquely to each test.
• Standardization or clear understanding of these procedural differences is necessary for accurate seat performance evaluation in rear impacts.