ISO 2631-5:2018

Overview

ISO 2631-5:2018 - "Mechanical vibration and shock - Evaluation of human exposure to whole‑body vibration - Part 5" - defines a method to measure and evaluate whole‑body vibration containing multiple shocks for seated individuals. The standard focuses on the prediction of compressive loading to the lumbar vertebral end‑plates caused by repeated vertical shocks and provides requirements for measurement, signal conditioning, spinal response modelling and risk assessment. It applies to unweighted vertical accelerations (0.01 Hz to 80 Hz) with peak values up to 137.3 m/s² (14 g) measured at the seat–occupant interface beneath the ischial tuberosities.

Key topics and technical requirements

• Two exposure regimes: severe (possible loss of seat contact, free‑fall periods; Clause 5 and Annexes C/D) and less severe (no loss of contact; Annexes A/E). Regime selection can be quantified (peak threshold ≈ 9.81 m/s²).
• Measurement location and hardware: accelerations measured at the seat‑occupant interface beneath the ischial tuberosities with specified bandwidth and signal conditioning requirements (see Clause 5).
• Signal conditioning and filtering: band‑limiting and processing rules tailored for multiple‑shock environments; different conditioning for severe versus less severe regimes.
• Spinal response modelling: seat‑to‑lumbar transfer function, calculation of spinal acceleration and compressive stress, and computation of a spinal response dose for injury risk estimation.
• Risk assessment: methods to relate measured exposures and exposure history to the probability of vertebral end‑plate failure; guidance on extrapolating representative measurements to past or future exposure durations.
• Informative annexes: alternative models, relationships between dose and health effects, implementation examples and assessment guidance (Annexes A–E).
• Practical cautions: the method addresses chronic risk from repeated shocks, not acute single‑impact injury. Use caution for very high peak accelerations near physiological limits.

Applications and users

ISO 2631-5:2018 is used to assess the risk of lumbar spine compression injuries from repeated shocks in contexts such as:

• Military and tactical vehicle design and testing (off‑road vehicles, armored vehicles)
• High‑speed marine craft, recreational off‑road vehicles, agricultural and heavy‑plant machinery
• Occupational health assessments for operators exposed to repeated shocks
• Manufacturers of seat systems, restraint systems, vibration measurement instruments and dosemeters Users include ergonomists, vibration specialists, occupational health and safety professionals, vehicle designers, test laboratories and measurement equipment manufacturers.

Related standards

• ISO 2631-1:1997 - Whole‑body vibration: general requirements
• ISO 2041, ISO 5805 - Vibration and shock vocabulary
• ISO 10326-1 - Laboratory method for evaluating vehicle seat vibration

This standard is part of the ISO 2631 series and is essential for robust evaluation of whole‑body vibration and multiple‑shock exposure affecting lumbar spine health.