Nie udalo sie połączyć z bazą! EJPAU .
Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.

Volume 8
Issue 3
Topic:
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
. , EJPAU 8(3), #38.
Available Online: http://www.ejpau.media.pl/volume8/issue3/art-38.html


 

ABSTRACT

This work is a contribution to virtual design of the healthy sleep parameters. This study method can be expanded to virtual models of sitting postures, namely in solving the question of chairs comfort (seat and backrest). Further studies and their scope in the area of healthy laying and healthy sitting (especially in schools and offices) may facilitate development of design-constructional solutions for the corresponding furniture and thus cover wider area of upholstered furniture.

Key words: .

INTRODUCTION

The general model of human life, which was established in the previous century, exists until today and is characterised by the division of the 24-hour rhythm of activity into three basic parts: 8 hours of sleep, 8 hours of work and 8 hours of leisure time.

So, at least one third of our life is spent in sleep. That is why good sleep is indispensable for good health. Quality of sleep determines quality of life. Psychophysical and physical aspects of good sleep are very important for the overall proper development and restoration of the body [13]. Healthy and appropriate sleep requires consideration of at least three factors: sleeping process, conditions and habits, and the equipment which enables and facilitates sleeping process.

From the physiological and psychological point of view, sleep is influenced by two groups of factors [4, 7]. The first marks the biorhythm, the phenomenon in the human organism which by means of its "inner clock" determines the time for sleep.

The system of physiological control causes that this periodicity (sleep – work – leisure) is controlled by chemical and neural processes [4]. Two nerve structures situated in the brain stem are believed to be involved in the control processes and they oppose each other: one of them stimulates, while the other – inhibits. If the stimulatory system prevails, a person is usually well rested and if the inhibitory system takes the upper hand – he or she feels tired and sleepy. This feeling occurs every evening and precedes sleep in a natural way.

However, there is also a whole series of external factors which might have bigger influence on sleeping conditions than the biorhythm, such as: illumination, noise, temperature, moisture and, above all, a bed system which consists of a bed structure, mattress, cover and pillow.

Primary role of the lying furniture is to satisfy human needs in rest and sleep and to entirely recover the body by supported lying under minimal energy consumption [6]. This goal is also achievable with the mattress conforming to specific anthropometrical and physiological-hygienic conditions.

Physiologically and above all, a bed must be a good bodily support, designed so as to ensure utmost muscular relaxation and enable proper and the least tiring bodily position. Upholstered parts of the bed have their specific functions too, determined by their shape, colour, upholstery texture and, most importantly, by their constructional parts. Consequently, a bed is important from two aspects [7]:

The closer a body is to supine position the more body weight is released and the more intense is the resting phase. Each of the above aspects implies product's (bed) construction, desing and dimensions. Irrespective of its purpose there are four stages of its use:

A complete and maximal relaxation of muscles occurs only when optimal matching of the form of the upholstered furniture and the shape of the user’s figure is possible allowing the natural shape and course of the line of the spinal column (Fig. 1).

Fig. 1. Proper, desirable system of the spinal column for the position of a lying person

To date research in the interaction between a human body and a bed has revealed various roles of this piece of furniture [7, 12, 14, 15, 16]. Some of them are:

According to many investigations, any mattress with the dedicated function of sleep should fulfil the following three basic requirements:

Unfortunately, the furniture market is still full of articles which do not meet ergonomic and functional requirements. The manufacturers of lying furniture usually highlight the quality of their products by pointing out certain technical advantages (e.g. winter and summer sides of mattresses). However such statements are frequently unconfirmed and are used exclusively for commercial purposes [13]. The incorrect design of mattresses intended for sleeping stems from the mistakes in the process of determining the rigidity of springy layers. At the present time, the majority of designers focus all their attention on intuitive modelling only of the covering systems (in the case of various kinds of foamy synthetic materials, primarily, polyurethane and latex foams), whereas the problem lies in the careless selection of spring rigidity and padding materials.

The most apparent results of sleep deprivation include psychological disorders taking the form of hallucinations and other psychotic symptoms, i.e. associated with psychosis. One or several nights spent on a badly designed mattress may result in such afflictions as [17:

Bedsores constitute a serious problem, especially for senior and disabled persons. As shown in Figure 2, bedsores develop most commonly in the area of the backbone and, therefore, the improvement of this dysfunction of mattresses should be one of the most important determinants when designing these articles.

Fig. 2. Frequency and place of occurrence of bedsores [17]

Bearing in mind ineffective, intuitive methods of the process of designing of spring systems of upholstered furniture and the absence of technical recommendations essential for rational designing of this type of furniture, the authors decided to elaborate parameters of an anthropo-technical model useful in the testing of furniture with the sleep function.

ANTHROPO-TECHNICAL MODELS

An anthropo-technical system is created as a result of bonds developed in the process of utilisation between a technical means and a human being. The man treated as an integral element of this system is spatially, functionally and in terms of time attached to the technical means. The anthropo-technical system is not just a simple combination of a man and a technical means but it rather develops in the result of his purposeful impact on the technical means [21].

As a result of performed investigations [1], so far researchers succeeded in developing a set of accurate and objective anthropometric and statistical data characterising the population of adult people in different body positions. The collected data offers detailed information concerning dimensional relationships and dimensions of the human body which provide an essential data base for designers of human phantoms and mattresses. The authors maintain that designing process should be conducted on the basis of the dimensional model of a female body, which is quite understandable bearing in mind dimorphic changes concerning differences in the body structure of men and women. Slight differences in the structure of the female body – in the case of utilisation of mattresses – cause a more complex state of loads. The only exception is the case when a longer mattress is designed. In this case, the designers should use statistical information of the man’s body. Differences in the body structure of men and women are estimated at about 8% and they stabilise at the age of 16 to 18 (these differences become smaller in older people).

The schematic dimensional diagram of a woman’s body aged 31 – 60 [3] is shown in Figure 3, while Table 1 presents individual dimensional values (the determined values of the height and weight were used for further numerical analyses).

Fig. 3. Anthropometric model of the woman‘s body [3]

Table 1 The dimensional values of a woman’s body aged 31 – 60 [3]

No

Standing

1

body length

cm

165.2

2

eye height

cm

155.1

3

acromial height

cm

135.2

4

elbow height

cm

101.8

5

hip height

cm

93.2

6

fist height

cm

74.1

No

Sitting

7

crown-buttock height

cm

86.5

8

eye-buttock height

cm

76.4

9

shoulder-buttock height

cm

56.5

10

elbow-buttock height

cm

23

11

thigh-buttock height

cm

14.5

12

popliteal height

cm

43.4

No

Widths

13

head breadth

cm

14.7

14

shoulder width

cm

42.4

15

elbow width

cm

47.2

16

hipbreadth sitting

cm

41.4

No

Depths

17

head depth

cm

18.7

18

elbow-fist depth

cm

32.1

19

arm-fist depth

cm

68.8

20

stomach depth

cm

29.3

21

breast depth

cm

31

22

buttock popliteal length

cm

49.9

23

buttock-knee length

cm

61.3

No

Hand

24

hand length

cm

17.9

25

hand breadth with thumb

cm

9.3

26

hand breadth without thumb

cm

8.1

27

thumb breadth

cm

2.1

28

forefinger tip breadth

cm

1.6

29

hand depth

cm

2.7

No

Foot

30

feet length

cm

24.5

31

feet breadth

cm

9.4

No

Weight

32

body Weight

kg

70.5

No

Circumference

33

Head

cm

55.1

34

neck base

cm

44.7

35

Breast

cm

101.3

36

Waist

cm

86.3

37

Hips

cm

106.6

Results of anthropometric measurements are interpreted according to the so called limiting measures. These measures take into consideration the statistical distribution of selected dimensions in the examined population and are expressed numerically with the assistance of the position parameters of the statistical distribution, the so called centiles. Properly designed articles should be suitable for the highest number of users, i.e. to approximately 95% of the population. That is why threshold values are quoted: the so called values of the bottom centile C5, top centile - C95 and the medial value C50. The minimum length of the mattress should be suitable for 95% of users, which means that it must be limited by the dimension of the tallest user represented by the C95 centile.

The input data most frequently used for the calculation of forces and moments in bones in anthropo-technical systems are the weights of the body sections shown in Figure 2.

DATA FOR MODELLING

When designing the anthropo-technical phantom to be used for testing of upholstered furniture, the following data were to be applied:

– Height – 1653 mm,
– Weight – 70.5 kg [3],
– Mean density of the phantom:

– Linear elasticity modulus E

When designing the phantom, the author decided to apply the principle whereby the human body is divided into seven equal sections, bearing in mind the appropriate solution of the problem of connection of individual bones (joints).

DESCRIPTION OF INVESTIGATIONS AND ANALYSIS OF RESULTS

The simulation of the deformation distribution occurring in the system man – upholstered furniture, as exemplified by loads of mattresses intended for sleeping, was carried out with the assistance of the ALGOR program realising the algorithm of the finite element method. For this purpose, numerical models of the following two types of upholstered systems were developed:

In both cases, the authors employed the model of a cylindrical spring 125 mm high and 60 mm in diameter and the designed panels were 2062.6 mm long and 964.4 mm wide (32 x 15 springs). The simplified model was used, which reduced the geometry of springs to a cuboids with the base 60 x 60 mm and the height of 125 mm (Fig. 4.). The distance between individual springs was 4.6 mm, In the case of the system without foam, strands connecting neighbouring springs were used. The characteristics of the materials were defined on the basis of strength studies performed earlier; every time rigidity k [N/m] and the linear elasticity modulus E [MPa] were determined on a series of 10 samples (spring E = 0,0132 MPa, polyurethane foam E = 0,0118 MPa).

In addition, the performed numerical calculations also utilised the distribution of forces published by the Natural Chemical Products Company Ltd. derived from investigations on the value of pressures exerted by a lying woman of 60 kg weight using a sensor matt and computer software ‘Force Sensitive Application’. The map of pressures (Fig. 5) was subjected to a numerical analysis with the assistance of the IMAQTM Vision Builder program and the area of individual contours was determined (Fig. 6 and 7), which allowed recalculating pressure values for the required weight of 70.5 kg (Tab. 1). Next the map was divided into squares measuring 60x60 mm corresponding to the course of lines of the panel network of the upholstery system. Then, the surface and the centre of the area of individual contours were determined again but only within the confines of elementary squares and the response of supports in all four corners was calculated. In this way, values of forces affecting individual panel nodes were obtained. Models of spring systems were loaded in accordance with pressures derived from the above-mentioned map of pressures and a numerical analysis was carried out.

Table 2 Wright proportions of individual body segments in the total body weight (NASA 1989).
Weight of the segment = total body weight x coefficient

Part of body

Coefficient

Head

0.051618

Neck

0.012900

Ashamed

0.306310

Stoma

0.029330

Pelvis

0.144300

Torso

0.479930

Arm

0.024050

Forearm

0.017010

Hand

0.006210

Haunch

0.042700

Thigh

0.078600

Calf

0.047390

Foot

0.011840

Fig. 4. Simplified model of the panel made up of springs together with a layer of polyurethane foam

Fig. 5. Map of pressures derived from the system of measurements of pressure distribution of the Force Sensitive Applications

Fig. 6. Example of the measurement of the contour surface, determination of the spectrum borders

Fig. 7. Example of the measurement of the contour surface, area and surface value

Fig. 8. Distribution of relocations on the mattress with the A and B system

Figure 8 shows the effect of the performed numerical analysis of the relocation in the spring system together with the layer of the polyurethane foam, this figure presents the relocation in the spring system connected with strands. Small differences in the relocation values and more apparent – in the distribution of pressures on the system surface are noticeable. Figure 9 presents a diagram illustrating differences in the relocation values on the longitudinal cross section in the symmetry axis of the distribution of pressures, while Figure 10 – the same differences in the most heavily loaded cross section of the system.

Fig. 9. Relocations on the mattress recorded under the body load along its longitudinal axis

Fig. 10. Relocations of the mattress recorded under the load of hips

CONCLUSION

The presented attempt of the numerical deformation modelling of elastic models of upholstered furniture allows developing a catalogue of parameters essential for the elaboration of anthropo-technical phantoms intended for the testing of upholstered furniture (or mattresses and other types of upholstered furniture).

Many studies [6, 7, 10, 11, 13] have confirmed that sleeping habits, bed construction, environmental conditions and other aspects influence quality of speep (especially in elderly and ill population). These findings have pointed out the importance of a multidisciplinary approach to the bed-sleeping system. All to date bias approaches could not yield comprehensive and acceptable results, particularly because of high complexity of this issue. It can be concluded that a bed construction must be such as to:

The studies in the area of bed systems and body load upon the bed surface must be continued, particularly with simulation on more anthropo-tehnical models (subjects) of different anthropometric dimensions, gender, age and other characteristics [19]. A 5th percentile of users must also be taken into account (handicapped, diseased and newborns). Better cooperation with medical professionals is necessary (radiologists, psychologists, orthopedists, etc.) in order to achieve a virtually optimal design-constructional-technological bed system, suited to every individual. Bed manufacturers must find here their own interest, as this may help identify some specific problems, significant in the very design and construction of this product. In addition to increasing the number of study subjects, virtual models must include other constructional types of beds too, e.g. biobeds, waterbeds, airbeds and other types of fillings. By their comparison it would be possible to get a valuable picture of what is the best for sleeping and relaxation.

If we think of all the time we spend in bed we realize how significant must be the effects of its poor construction and design our health and physical condition. In the light of the modern living culture and rather high scientific, technical and economic state of social development, the furniture for sleep and rest should be of appropriate quality, functionality and design. In particular, it must fulfull its basic function i.e. help you feel comfortable, cozy and secure.

This work is a contribution to virtual design of the healthy sleep parameters. This study method can be expanded to virtual models of sitting postures, namely in solving the question of chairs comfort (seat and backrest). Further studies and their scope in the area of healthy laying and healthy sitting (especially in schools and offices) may facilitate development of design-constructional solutions for the corresponding furniture and thus cover wider area of upholstered furniture.

REFERENCES

  1. Batogowska A., Malinowski A., 1997. Ergonomia dla każdego [Ergonomic for all]. Sorus Poznań [in Polish].

  2. Brezigar D., 1985. Study of some factors determining quality and usability of mattresses; Doctoral Thesis. Faculty of Forestry, Zagreb.

  3. Dirken T., et. al., 2004. Ontwerprelevante maten van volwassen Nederlanders. Delft University Press.

  4. Grandjean E., 1978. Ergonomia mieszkania [Float ergonomic]. Arkady Warszawa [in Polish].

  5. Grbac I., 1984. Research into the durability and elasticity of different mattress structures, Master’s Thesis. Faculty of Forestry, Zagreb.

  6. Grbac I., 1985. Rationalization of the bed construction. Bilten ZIDI 13, 2, 143-153.

  7. Grbac I., 1988. Research into the quality of mattress and its structural upgrade, Doctoral Thesis. University of Zagreb, Faculty of Forestry, Zagreb.

  8. Grbac I., Bogner A., Dziegielewski S., 1997. Investigation into the quality of sleep on various types of beds and mattresses. 11 Ses. Nauk. Badania dla meblarstwa, Poznań, 29-37.

  9. Grbac I., Dalbelo-Bašić B., 1994. Data analysis of thermal conductivity and moisture permeability in mattres, ITI 94, Proc. 16th Int. Conf. Information Technology Interfaces. Pula 14-17 June, 217-222.

  10. Grbac I., Dalbelo-Bašić B., 1994. Thermal conductivity and moisture permeability in mattres. Drvna Ind. 45(4), 130-134.

  11. Grbac I., Dalbelo-Bašić B., 1996. Comparasion of thermo-physiological properties of diferent mattress structures, Proc. 18th Int. Conf. Information Technology Interfaces. Pula, 18-21 June, 113-118.

  12. Grbac I., Dziegielewski S., Bogner A., 1997. Investigation of thermal and physiological properties of different mattress types. 11 Ses. Nauk. Badania dla meblarstwa, Poznań, 22-28.

  13. Grbac I., Ivelić Ž, Markovac Ž., 2000. Usage and abusage of terminology for furniture assigned for sleeping, Int. conf. Ecological, biological and medical furniture – fact and misconceptions. Zagreb, October 13th, University of Zagreb, Faculty of Forestry (Croatia), UFI-Paris, Zagreb, 83-92.

  14. Grbac I., Ljuljka B., 1985. Study of the man-bed interaction. Conf. on the occasion of the 125th anniversary of teaching in forestry in Croatia, Bilten ZIDI, 13, 6, 51-91.

  15. Grbac I., Ljuljka B., Dalbelo-Bašić B., Tkalec S., 1994. Study of thermal conductivity and moisture permeability of the bed. Professional Conf. on the role of science in the economic system of wood processing in Croatia. Novi Vinodolski 11-12 May, 68-71.

  16. Kapica L., Smardzewski J., Grbac I., 1999. Deformation of multiple-layer sponges at spring constructions, Int. Conf. Furniture construction and quality – a step forward to customer protection. Zagreb, October 15th, University of Zagreb, Faculty of Forestry (Croatia), UFI-Paris, Zagreb, 89-96.

  17. Krutul R., 2004. Odleżyny. [Excortiation]. Ogólnopol. Przegl. Med., 4, 38–42 [in Polish].

  18. Levinson S. F., 1995. Sonoelastic determination of human skeletal muscle elasticity. University of Rochester Scholl of Medicine and Dentistry, Department of Orthopedics.

  19. Mijović B., Grbac I., Domljan D., 2004. Furniture design by means of digital anthropometry. Int. Conf. Trends in design, construction and technology of wooden products. October 15th, Grbac I. (ed.), Zagreb, University of Zagreb, Faculy of Forestry, UFI-Paris, 1-6.

  20. Muftić O., Miličić D., 2002. Issues in physiological anthropology related to design. Int. Conf. Furniture, human, design. Zagreb, October 18th, University of Zagreb, Faculty of Forestry (Croatia), UFI-Paris, Zagreb, 41-50.

  21. Winkler T., 2005. Komputerowo wspo.magane projektowanie systemów antropotechnicznych [Computer Aided Design anthropotechnical systems]. WN-T Warsaw [in Polish].



Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.


Nie udalo sie połączyć z bazą!