Function Analyses And Design Of Bra Straps

The brassiere is one of the fundamental underwear for daily life, which is playing the vital role of supporting and protecting women’s breast. The strap, as one of the important components of a brassiere, can basically lift and shape the breast to a desired full curve. Being dressed in fitting brassiere with good comfort, women’s feminine shitsuke can be incisively and vividly shown in public social situations. However, they often encounter the embarrassed situation when the strap slipping off the shoulders if wearing unreasonable designed or discomfortable brassiere. Excessive pressure of strap can cause pains around neck and shoulders, and, a long time compression would even result in such symptoms as dizzy, nausea and so on. The comfortability of wearing brassiere has received public attention from women as well as researchers.Focusing on on the requirable functions analyses of strap, its tensile properties, and functional design for strap, this paper conducted investigative and experimental study in the following five aspects, and concluded some constructive and instructive progresses.(1) Analyses on functional requirements for bra strapFocusing on analyzing the functional reaquirements of bra strap, this paper firstly designed and conducted a questionnaire survey both on internet and via a site visit. The survey covering purchasing preference, wearing habits, washing and caring methods, which was designed to deeply investigate the specific requirements of general functions of bra strap, as well as, to find out the possible influence factors. Combined with the functional characteristics of the strap and wearers’ habits, three aspects of the specific functional requests had been extracted as lifting and shaping function, anti-slipping function, and pressure comfort. Some main factors and their relationships influencing the specific functional requests had been discussed in the aspects of the strap styles, physical properties, usage characteristics and mechanical tensile properties.(2) Foundamental study on tensile properties and fatigue characterization of bra strapThe tensile properties of bra strap and its fatigue characteristics were considered of the highly importance to discuss the general functions of bra strap. The strap’s fatigue phenomenon and its induced problems had attracted women’s concern. However, the study of tensile properties and fatigue characteristics of bra strap had never been documented in previous researches. In this thesis, seven types of strap typically made of polyamide blended with latex were selected as the samples. The stretching-fracture test and the test of repeatedly stretching to a fixed elongation were implemented to get some indicators of tensile property, fracture work and effective elastic point, as well as the elastic recovery rate and the index of plastic deformation of bra strap samples. The analysis of variance and the correlation analysis were combined to discuss the characteristics of tensile properties of bra strap.Basing on the tensile stress-strain curve of the sample strap, and taking a reference of the Meredith method to determine the yield point of fiber, a creative method was designed to determine the effective elastic point of the strap. On the tensile curve of strap, draw a parallel line nearby the line between the origin and the breaking point, and make sure that the parallel line is tangent to the turning segment of the tensile curve of strap. The point of tangency can be considered as the effective elastic point of the strap.Referring to the definition of quantity of progress in physics, the definitions of elastic recovery loss△εn(%) and plastic deformation accumulation△Gn(%) were innovatively proposed to describe the variable characteristics of elastic recovcry and plastic deformation of the strap after repeatedly stretching test. The amount of the elastic recovery loss and the plastic deformation accumulation can respectively character the changing speed of the loss of elastic recovery and the accumulation of plastic deformation. The paired sample tests were applied to prove that the definitions of elastic recovery loss△εn(%) and plastic deformation accumulation△Gn(%) were of statistically significance. By means of correlation analysis, the elastic recovery loss△εn(%) and the plastic deformation accumulation△Gn (%) of the strap were suggested that they could chatacter the fastness and durability of the strap.(3) Lifting and shaping function of bra strapFactorial wearer trial was specially designed to quantitively evaluate the breast lifting and shaping capability of bra strap. Referring to some anthropometric bones and joints, several measurements featuring the breast lifted and shaped effects were sclccted to quantify the lifting and shaping capability of the strap. The width of strap, its connected position onto the bra back and the stretching rate were selected as the controlled factories in the factorial design. Subjective ratings for wearing feelings such as wearing sensation of pressure, lifted and shaped effect of breast, and general comfort were rated in the wearer trial.By means of paired samples test, the anthropometric measurements were compared between the situations naked breast and in bra without strap. The test result indicated that the bra cup and band gave a fundamental support for women’s breast. Paired samples tests were also conducted to compare the measurements difference between the situation in bra without strap and that with strap in different extensions. The result suggested that the strap did have a lifting and shaping function for women’s breast. Multifactor analysis of variance suggested that the stretching rate of the strap was the main factor to cause the significant difference in the measurements featuring breast shape characteristics.The multifactor analysis of variance for the subjective ratings suggested that, in the same wearing conditions, the wider strap could cause more compressive sensation of pressure. The stretching rate of the strap was proved a key factor influencing the wearing sensation of pressure as well as general comfort, and the measurement difference was also proved to be significant between any two adjacent levels by means of multiple tests. Generally, the subjective sensation was more likely to be perceived than the objective measurement was detected with significant difference.(4) Anti-slipping function and wearing stability studyThe slipping problem of strap has aroused general dissatisfactory of the wearers. This paper designed a series of wearing trials to discuss the moving tendency of the strap and its anti-slipping function. The designed controlling variables were the connected position onto bra back of the strap, its widths, and its stretching rates. The initial wearing position on wearer’s shoulder were recorded as the observed variables. The displacement of strap were calculated to rate the movement of strap during the trial. The strap’s length covering body surface was also measured during the process of doing the designated activities. The analysis of variance and multiple tests were combined to discuss how the connected positions of the strap onto bra back effect the moving tendency of strap, and how to develop the new methods to improve the anti-slipping function of the strap. It can be concluded that the connected position onto bra back of the strap designed closer to the central back can effectively prevent the strap slipping off the shoulder. Some valuable suggestions can also be concluded from the analysis as following: the wider strap can cause less length change of the strap itself after finishing the activities; the bigger extension of the strap in daily wearing can improve the wearing stabilization of the strap; the daily basic activities can significantly affect the balanced wearing situation of the strap, then the strap would slip off the shoulder as a result.(5) The relationship between the tensile properties of bra strap and its pressure on bodyThe tensile properties of the strap itself can directly influence the inner stress caused by its elongation. The inner stress of strap by elongation will thereby turn into the compressive pressure on body. Therefore, the study of the relationship between the tensile properties of bra strap and its pressure on body can contribute to analyze the characteristics of pressure variations. In order to eliminate the effects caused by body difference on the pressure measurements, a mannequin was used firstly to get objective pressure measurements. According to the characteristics of bones and joins of human shoulder, five typical points covered by strap on the right side of mannequin were determined as the measuring points. One subject whose figure was very closer to the standard figure was also invited to do the pressure measurement trial. The corresponding pressure at the designed measuring points was analyzed to compare the difference between the mannequin and human body.Basing on the previous study, this paper analyzed the regression relation between the elastic recovery and the pressure on mannequin. But the fitting effects of regression were not satisfacted. The relaxed stress of the strap when it was stretched to a certain elongation was creatively designed as the independent variable to discuss its quantitative relationship with the pressure on mannequin. According to the results of significance test of regression equation and the test of goodness of fit, the significant linear relationship existed between the relaxed stress and pressure measurement. The relaxed stress of the strap had also been proved sensitive to reflect the change in compressive pressure by elongation.