Analysis of dynamics and fit of diving suits

. Paper presents research on dynamical behaviour and fit analysis of customised diving suits. Diving suits models are developed using the 3D flattening method, which enables the construction of a garment model directly on the 3D computer body model and separation of discrete 3D surfaces as well as transformation into 2D cutting parts. 3D body scanning of male and female test subjects was performed with the purpose of body measurements analysis in static and dynamic postures and processed body models were used for construction and simulation of diving suits prototypes. All necessary parameters, for 3D simulation were applied on obtained cutting parts, as well as parameters values for mechanical properties of neoprene material. Developed computer diving suits prototypes were used for stretch analysis on areas relevant for body dimensional changes according to dynamic anthropometrics. Garment pressures against the body in static and dynamic conditions was also analysed. Garments patterns for which the computer prototype verification was conducted were used for real prototype production. Real prototypes were also used for stretch and pressure analysis in static and dynamic conditions. Based on the obtained results, correlation analysis between body changes in dynamic positions and dynamic stress, determined on computer and real prototypes, was performed.


Introduction
Diving suit is garment type for special purposes, for which is necessary to satisfy high criteria of comfort, fit and functionality.There are three basic diving activities: scuba diving, spearfishing and free diving and every activity has there one characteristics which condition properties and demands that are to be satisfied [1][2][3].Considering high demands for fit in specific dynamic conditions, we investigated application of computer 3D pattern construction directly on surface of a 3D body model and flattening method for separation and transformation of discrete 3D surfaces into 2D cutting parts [4,5].When using 3D flattening method it is necessary to take in consideration physical and mechanical properties of the material for a real garment.It requires comprehensive approaches to complete computer clothing design and implementation of all necessary properties into the CAD system for clothing construction and simulation [6][7][8][9].In order to verify the proposed method and complete development process and prototype in real conditions of use, we selected female test subject, which is successful and multiple awarded free diver [10] and a male test subject, which is active spear fisher and a successful diving suits manufacturer [11].

3D scanning and body model processing
To achieve high fit of a diving suit and at the same time secure functionality in characteristic dynamic body positions when diving, it is necessary to determine body measurements defining body shape, body curves and body surface segments dimensions.Measurement and analysis of female and male test subjects was performed in basic static position according to ISO 20685:2010 and five selected dynamic body positions, using 3D scanner Vitus Smart and software Anthroscan 3.0.4., Figure 1a.Regarding the problems of tight-fit clothing construction and determining the necessary body measures, application of such technology significantly simplifies the design of such clothing.Larger number of measurement points and curves on target body segments was defined in addition to the usual anthropometric body measures for the conventional clothing construction.Four dynamic postures refer to the mobility of the upper extremities and present the terminal positions of the arms at characteristic body movements when diving.The fifth posture refer to the mobility of the lower extremities, flexion of 90˚ in the hip and knee, wherein we analyse the elongation length on the back line of the leg and the change in length in the area of the knee joint.The scanned body models were processed in terms of closing the surface and creating a single-layered polygonal model, suitable for implementation into a CAD system for construction and simulation of clothing.

3D construction of diving suits models
The complete computer development of the female and male diving suits prototype models was carried out using the 2D/3D CAD system Optitex.In previously conducted research [12], authors analysed construction of female diving suit in detail, for which in this research additional pressure analysis in static and dynamic conditions was performed.Within this research, we developed male diving suit prototype using the same methodology and tested computer prototypes using 3D simulations with applied properties of neoprene material, in order to obtain cutting pattern for real prototype production.

Analysis of dynamic behaviour and fit of developed diving suits prototypes
Computer normal collision pressure analysis of simulated garment prototypes was performed on customized and scanned body models in static position, Figure 3, in measurement points shown in Figure 1b.Additionally, real prototypes pressure was analysed in the same measurement points on test subjects in conditions of use by using Picopress M-1200 measuring equipment of Microlab Electronics.Considering limited possibilities of CAD system and inability for fast and accurate body animation, dynamic analysis was performed on customized parametric body model which enables animation in position D2.Real garments pressure analysis in dynamic conditions was performed in positions D2, D5 and D6 on points CF, CB and GT.Garment stretch on upper back body area was performed regard to previously measured physical and mechanical properties of neoprene material.

Results of garment pressure analysis against the body in static posture
Table 1 shows results of pressure measurement of computer garment prototypes on static body models and real garment prototypes on test subjects, in defined measuring points.Results analysis showed better correlation between garment pressure values measured on scanned body models and real test subjects, which is mostly visible from body areas where parametric body model does not allow precise shape adjustment.This refers to measurement points on head, wrist and ankles (CH, FH, ER, WR i IA).Pressure analysis of female suit also showed significant difference on measurement point CF between scanned and customized body model, which can also be explained with limitations of parametric body model.

Results of pressure and stretch analysis of garment against the body in dynamic postures
Figure 4 presents analysed garment zones on which the measurements of pressure and linear stretch were performed.Measuring of pressure values was performed on measurement points CF and CB on chest line.Values obtained from computer prototype were compared with Picopress measurement results of real male diving suit prototype, Table 2. Measured garment pressure values showed satisfying correlation between simulated and real prototype.Pressure measurement on real diving suit prototype, was additionally performed on lower extremities, on point GT on hip area, in positions D5 and D6, Table 2.  Results of linear stretch analysis of simulated and real male diving suit prototype, in position D2 are presented in Table 3. Stretch analysis was performed on linear dimensions on upper back body area, Figure 5a.Results showed differences between values measured in static and dynamic positions, 17th World Textile Conference AUTEX 2017-Textiles -Shaping the Future IOP Publishing IOP Conf.Series: Materials Science and Engineering 254 (2017) 152007 doi:10.1088/1757-899X/254/15/152007caused by arms movement.Diving suit requires skin-tight fit and elastic properties of neoprene materials enables that fit, but in a combination with precise construction and right scaling of garment pattern to achieve right pressure of garment in static, and functionality in dynamic conditions.Stretch of neoprene material can be seen from differences between linear segment measurement on garment pattern and values measured on garment on body in static condition showed in Table 3.Further analysis leads to data on values of stretch and compression of garment caused by body movement, Figure 5b and 5c., confirming tight fit with the same behaviour that can be observed on naked body dimensions in dynamic postures.In order to verify developed prototypes in all defined dynamic postures, we performed testing in real conditions of use Figure 6.According to the subjective test subjects evaluation, both diving suits have good fit and method is verified as applicable for design and construction of diving suits with high fit and functionality demands.

Conclusion
The purpose of the research was evaluation of the application of the 3D flattening method in the process of computer construction of diving suit according to individual body anthropometric characteristics and to determine if the developed diving suit model is precisely enough for the professional divers to evaluate positively from the aspect of fit and functionality in dynamic body positions.The overall development process of 3D prototype is pretty challenging, from the aspect of method complexity and all of the criteria that need to be fulfilled so that the functional suit model can be realized.Considering the high criteria for functionality, diving suit models are realised in synergy with professional athlete diver and diving suit manufacturer who defined the criteria that need to be satisfied and evaluated the developed prototypes.Based on pressure measurement values of garment against the body in predefined measurement points, good correlation between simulated and real prototype was determined.The application of the research results in the process of cutting pattern development enables achievement of high fit and functionality of tight-fit garment models.

a b Figure 1 .
3D body scanning: a. scanning in one static and five dynamic positions b. position of body points for pressure measurement

123456789017thFigure. 2
Figure. 2 3D construction of male diving suit model, segmentation of 3D surfaces and transformation in 2D cutting parts

Figure. 3
Figure. 3 Normal collision pressure in static position: a) Female prototype, b) Male prototype

Figure. 4
Figure. 4 Dynamic fit analysis: a) clothing pressure against the body, b) Linear stretch according to y (weft) axis

Figure. 5
Figure. 5 Linear stretch analysis: a) measurement positions on block pattern, b) static conditions, c) dynamic conditions

123456789017thFigure. 6
Figure.6 Diving suits evaluation in five dynamics positions: a) female prototype for free diving sport discipline, b) male prototype for spearfishing

Table . 1
Garment pressure values in static conditions measured on virtual prototypes simulated on parametric and scanned body models and on developed real diving suits

Table . 2
Pressure measurements on characteristic points for dynamic postures D2, D5 and D6 measured on virtual and real prototypes

Table . 3
Linear segments dimensions measured on block pattern and on virtual and real prototype in static and dynamic conditions