Improving ergonomic value of product interface materials using numerical digital human models

Abstract

Digital human models are usually constructed to study the human anatomical or topological features and its variance and to optimize the size and shape of various products and tasks. Therefore, most of the researchers focussed on developing accurate three-dimensional digital human models based on surface mesh using various methods and techniques. However, such models do not allow biomechanical and ergonomic analyses of product interface materials that are in direct contact with the user. Based on manual testing using various materials and analysing the subjective response of users, researchers have shown that product interface material has an important impact on the overall product safety, comfort and even performance. Basic ergonomic and biomechanical guidelines regarding the material choice were provided based on the findings, however detailed material choice and even material parameter determination has not been studied, evaluated, and discussed due to the complex biomechanical systems and lack of appropriate digital human models. To overcome these limitations, numerical methods, especially the finite element method has been already used in the past by several authors. Finite element method allows calculating of various results in terms of internal stresses and contact pressure, deformations, and displacements, however it requires accurate development of numerical digital human models that accurately represent the anatomical, topological, material properties and boundary conditions. In this paper we present theoretical background and provide methodology for successful development of numerical digital human models that can be used for biomechanical analyses and product material ergonomic improvement. This is presented with a case study of the development of a numerical digital human finger model for ergonomic improvement of the biomechanical response of a product handle deformable interface material. Based on the developed numerical model, a novel deformable interface material is analysed that reduces the resulting contact pressure during grasping and provides more uniform pressure distribution while still providing sufficient stability.