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

Abstract

Digital human models are usually constructed to study human anatomical or topological features and their variance and to optimize the size and shape of various products and tasks. Therefore, most of the researchers focused 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 analyzing 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 have 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, have been used in the past by several authors. The finite element method allows calculating 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, and material properties, as well as boundary conditions. In this paper we present a theoretical background and provide a 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 analyzed that reduces the resulting contact pressure during grasping and provides more uniform pressure distribution while still providing sufficient stability.