A novel hierarchical clustering algorithm for the analysis of 3D anthropometric data of the human head

In recent years, the use of 3D anthropometry for product design has become more appealing because of advances in mesh parameterisation, multivariate analyses and clustering algorithms. The purpose of this study was to introduce a new method for the clustering of 3D head scans. A novel hierarchical algorithm was developed, in which a squared Euclidean metric was used to assess the head shape similarity of participants. A linkage criterion based on the centroid distance was implemented, while clusters were created one after another in an enhanced manner. As a result, 95.0% of the studied sample was classified inside one of the four computed clusters. Compared to conventional hierarchical techniques, our method could classify a higher ratio of individuals into a smaller number of clusters, while still satisfying the same variation requirements within each cluster. The proposed method can provide meaningful information about the head shape variation within a population, and should encourage ergonomists to use 3D anthropometric data during the design process of head and facial gear

3D digital headform models of Australian cyclists

Traditional 1D anthropometric data have been the primary source of information used by ergonomists for the dimensioning of head and facial gear. Although these data are simple to use and understand, they only provide univariate measures of key dimensions. 3D anthropometric data, however, describe the complete shape characteristics of the head surface, but are complicated to interpret due to the abundance of information they contain. Consequently, current headform standards based on 1D measurements may not adequately represent the actual head shape variations of the intended user groups. The purpose of this study was to introduce a set of new digital headform models representative of the adult cyclists' community in Australia. Four models were generated based on an Australian 3D anthropometric database of head shapes and a modified hierarchical clustering algorithm. Considerable shape differences were identified between our models and the current headforms from the Australian standard. We conclude that the design of head and facial gear based on current standards might not be favorable for optimal fitting results

Improving fit of bicycle helmet liners using 3D anthropometric data

3D anthropometry has provided much-needed information about the size and shape of the head, which can be used to improve the fit of protective helmets. In this study, a new 3D head scan sizing method was implemented in a reverse engineering approach for bicycle helmet liner dimensioning. The inside liner of a commercially available helmet was modified to improve the fit for a selected size group of 30 participants. The fit of the standard and new liner were assessed and compared, using the Helmet Fit Index (HFI). The HFI scores showed a significant improvement of overall fit (Difference: 11.32 ± 7.82 (μ ± SD), p < 0.0005) and for each of five defined regions of the liner inside surface. The presented methodology for dimensioning helmet liners based on 3D anthropometry proved effective, resulting in improved fit for the end users

Finite Element Bicycle Helmet Models Development

AbstractImpact attenuation performance of three different range of commercial bicycle helmet were investigated in lateral drop impact test in accordance to AS/NZS 2063:2008, Australian/New Zealand Standard for bicycle helmet using numerical simulation and and experimental impact test. The aim of this research is to develop a simulation model of drop impact test, which to be used in further investigations of user-centred design approach of bicycle helmet. Three commercial bicycle helmet models were used in this study. All helmets and J headform were scanned using Flexscan 3D scanning equipment. Post-scan processing jobs of scanned geometry models such as helmet liner, shell and headform were conducted in Geomagic Studio 12. The experimental impact test is carried out using 2-wire drop test facility in accordance to the AS/NZS 2063:2008, Australian Standard for bicycle helmet. A few samples were cut from the liner of each helmet to determine the density of Expanded Polystyrene (EPS). Headform peak linear acceleration, impact duration and impact speed of each helmet were measured and recorded from the drop test. The scanned geometry models were imported into Abaqus. A drop impact simulation was developed based on the density and impact speed data obtained from the physical test. Inner liner of bicycle helmet, made from Expanded Polystyrene (EPS), was modeled using crushable foam properties, while headform and anvil were modeled as rigid bodies. Peak linear accelerations and impact duration of the headform on each helmet at three different impact locations of helmet were recorded. A robust correlation study using peak linear acceleration score, impact duration score and Pearson correlation coefficient between the data from physical test and numerical model was conducted. Good correlation scores (>80%) were achieved between the numerical model and experimental impact test in terms of headform peak linear acceleration and impact duration score, suggesting that the simulation model is in good correlation with those from physical test

The helmet fit index - an intelligent tool for fit assessment and design customization

Helmet safety benefits are reduced if the headgear is poorly fitted on the wearer's head. At present, there are no industry standards available to assess objectively how a specific protective helmet fits a particular person. A proper fit is typically defined as a small and uniform distance between the helmet liner and the wearer's head shape, with a broad coverage of the head area. This paper presents a novel method to investigate and compare fitting accuracy of helmets based on 3D anthropometry, reverse engineering techniques and computational analysis. The Helmet Fit Index (HFI) that provides a fit score on a scale from 0 (excessively poor fit) to 100 (perfect fit) was compared with subjective fit assessments of surveyed cyclists. Results in this study showed that quantitative (HFI) and qualitative (participants' feelings) data were related when comparing three commercially available bicycle helmets. Findings also demonstrated that females and Asian people have lower fit scores than males and Caucasians, respectively. The HFI could provide detailed understanding of helmet efficiency regarding fit and could be used during helmet design and development phases

A design framework for the mass customisation of custom-fit bicycle helmet models

Mass customisation (MC) can provide significant benefits to the customers. For example, custom-fit design approaches can improve the users’ perceived comfort of products where the fit is an important feature. MC can also bring major value to the producers, where for instance, premium prices can be implemented to the products. Research show that MC can bring competitive advantages especially when the system is new. It is therefore surprising that MC of helmets has not been studied more extensively, especially given the advances in 3D scanning, computational analyses, parametric design, and additive manufacturing techniques. The purpose of this study was to present a novel MC framework for the design of custom-fit bicycle helmet models. In the proposed design framework, we first categorized a subset of the Australian population into four groups of individuals based on their similar head shapes. New customers were then classified inside one of these groups. The customisation took place inside these groups to ensure that only small variations of the helmet liner were implemented. During the design process, the inside surfaces of a generic helmet model was modified to match the customer's head shape. We demonstrated that all the customized models created complied with the relevant drop impact test standard if their liner thickness was between the worst and best case helmets of each group. Fit accuracy was verified using an objective evaluation method. Future work should include detailed description of the manufacturing methods engaged in our MC framework

Identification of performance requirements for user-centered design of running shoes

This research aims to identify design attributes of a new generation running shoe by relating key performance parameters to the requirements of a specific user group. This paper considers the first phase of the research, comprising user group profiling, as well as the selection and subjective quantification of appropriate performance variables for targeted user groups. Three user groups have been defined, with the key functional performance attributes identified and prioritised for each. Using this information it has been possible to form the basis of a functional design specification for a shoe that should be best suited to the needs of runners within the target user group

Histoires de la souffrance sociale

Fréquemment ignorée par les contemporains, souvent inaperçue par la recherche, l’histoire de la souffrance sociale concerne à la fois les individus et les groupes. Elle relève de l’expérience douloureuse que les hommes et les femmes peuvent faire du monde social. L’histoire de ceux qui souffrent car ils se battent contre eux-mêmes, leur milieu, leur destinée familiale, la place sociale qui leur est faite ou encore les rets de la fatalité a trop longtemps été négligée. Depuis peu, cependant, se multiplient les propos sur la souffrance sociale, devenue « symptôme » du malaise des sociétés contemporaines, expression de l’ exclusion des sans domicile, des sans travail, des sans ressources. Nombreux sont les mots qui expriment la résignation, mais certains se présentent comme des sortes de cri, où se mêlent le désespoir, le renoncement et la haine de l’autre ou d’un système social. Entre la résignation silencieuse et la révolte, toute la gamme des attitudes s’avère ouverte. Fruit d’un travail collectif, le présent ouvrage n’entend pas relever d’un dolorisme ambiant, souvent méprisant, mais s’attache à explorer un certain nombre de pistes et s’interroge sur les seuils de l’ acceptable. Objets difficilement saisissables, à l’intersection de l’individu et du collectif, du social et du psychisme, les souffrances sociales sont analysées, du xviie au xxe siècle, à partir de quatre grandes approches : la première s’intéresse aux stigmates et figurations, la deuxième aux figures et expressions, la troisième aux trajectoires et aux mécanismes, la dernière à certaines manifestations et situations. Entreprise pluridisciplinaire à laquelle historiens, historiens de l’art et sociologues ont collaboré, ces Histoires de la souffrance sociale, entendent apporter une contribution à un débat essentiel en lui redonnant une perspective historique pour mieux comprendre les attentes et les espoirs des hommes et des femmes du passé comme ceux d’ aujourd’hui