Shower´s easy access for elder or people with physical disabilities
IRAITZ MUGICA CATALINA ASIER URKIZU INSAUSTI
Department of Mechanical Engineering School of Engineering
Blekinge Institute of Technology Karlskrona, Sweden
October, 2011
Supervisor: Lic.Sc., Armando León
ACKNOWLEDGEMENTS
We are students of Mechanical Engineering of EHU/UPV, in Donostia-San Sebastian, Spain. We made this project like exchange stundents in BTH, in Karlskrona, Sweden. We take these words to thank the Department of Mechanical Engineering and other exchange students for the help and support that we have received. It has been an excellent experience that has helped us for our professional and personal future.
This work was carried out at the Department of Mechanical Engineering of Blekinge Tekniska Högskola, BTH, in Karlskrona, Sweden under the supervision of Lic.Sc, Armando León.
ABSTRACT
This project has been created to help elder or people with physical disabilities. The help consists on getting easier the access to the shower. To reach our purpose, we realized a really innovative idea. Our idea is based on a door which rotates 90 º with respect to a lateral axis. In that door there is attached a chair to get easier the shower. When the user is in front of the opened door it would be easier for him or her to reach the chair which is added on the door, after that when the door is closed the user would be in the perfect position to get washed in his or her own. A CAD model was developed to make this design and also evaluate its resistence and safety.
KEYWORDS: Easy access shower, Innovation, CAD
CONTENT
ABSTRACT... 3
CONTENT ... 4
NOTATION ... 5
1. INTRODUCTION ... 6
1.1. Background ... 7
1.2. Aim ... 9
2. NEED: To facilitate access to the shower ...10
3. OUR INITIAL IDEAS ... 11
3.1. Our Choice ... 11
4. POSSIBLE SOLUTIONS ... 12
4.1. Lateral driving Mechanism for the chair ... 12
4.2. 180 deegrees rotational door ... 12
4.3. Final Solution: 90 deegrees rotational door ... 14
5. OUR DESIGN: 90 deegrees rotational access door ... 15
5.1. The Chair ... 15
5.2. The Door ... 16
5.3. Join the chair with a door ... 18
6. STRESS ANALYSIS ... 20
6.1. Handmade Calculations ... 20
6.2. Calculations by Inventor ... 29
7. OUR DESIGNED DOOR AT THE BATH-SHOWER ... 32
7.1. The Shower ... 32
7.2. The Bathroom ... 33
CONCLUSIONS ... 35
NOTATION
A Area
B Base of the profile
Fy Force in axis Y
H Height of the profile
Iy Moment of inertia in axis Y Iz Moment of inertia in axis Z My Bending moment in axis Y Mz Bending moment in axis Z
N Safety factor
N Axial force
Ty Shear strength in axis Y Tz Shear strength in axis Z
y Distance between moment and center of gravity of the profile z Distance between moment and center of gravity of the profile
Maximum stress allowed. Von Mises.
Simple stress
y Shear stress in axis Y
z Shear strength in axis Z
1. INTRODUCTION
In Sweden, the quality of life is good, and comparing it with the rest of Europe we could say that is very high. The conservation of nature, environmental protection and energy efficiency are usually priority in the political world and Swedish people see it with good eyes. [1]
These priorities obviously are important, but at the same time the Swedish government tries to solve different problems for its citizens, especially the problems related to physical disabled and elderly people. According to information from the European Union, about 37 million of people in Europe have some type of disability. Of this population, close to 1.2 million are Swedes between 16 and 64 years old, which means a 20.8% of population in this age range in a country that has 9.4 millions of inhabitants.[2]
On the other hand, Sweden has one of the oldest population of the world, just after Italy, Greece and Japan. 1.5 million of people were aged 65 or over, which is 15.96 % of the population.
In 2010, the estimated proportion over-65s were 18.6 % and in 2030, it is likely to be as high as 22.6 %. [3]
If we use all these data we can conclude that the population of Sweden is very adult and the percentage of disabled people is relatively high when it is compared with the total population. For this reason our final project is focused on it. In the first meeting with our coordinators, they gave us the option of the project which was focused to help disabled and elderly people. From years ago, the mechanical engineering section of the BTH focuses its projects for the cause. In the university we could see that they are trying to improve the help for disabled people, such as mechanic doors and spacious bathrooms. After that first meeting we decided that our project was as innovative as possible.
Once focused on the theme, we started thinking about how to help. The first ideas were obtained by comparison between Sweden and Spain in those aids. We present some ideas, but in the end we decided to design a door for the bath that is supplemented with a chair that could be regulated in different heights. So these people may be able to shower in a conventional bath, trying to avoid problems like a being able to slide or the impossibility to get a wheelchair in a bath. Our design had been created to any type of conventional shower, because we had considered the shower plates of the market.
A high percentage of the disabled people in Sweden live in their own home, and the majority of children with disabilities grow up in their homes with their families without any problems. So with this project we want to help to make current problems not be a problem in the future anymore.
1.1 Background
The Word “inventor” comes from the latin verb invenire, invent-, to found. The sentence
“the necessity is the mother of the invention”, discuss essentially, the cadency of recourses which brings us to the invention. Mainly the best recognized inventors during many decades and also of course nowadays, are those which have been able to identify the problems of our society and also have been able to analyze and solve then with exist. In the process of the resolution for this problem it has been necessary to analyze each aspect and also analyze profoundly the causes and effects of each problem, using different investigations made by the inventors. In fact all causes and effects could show us how we can solve all problems in their prime. So we have chosen to analyze diverse problems which affect directly in our society.
Deeping us into our project, first of all we are going to define what is life expectancy, in fact Life expectancy is the expected (in the statistical sense) number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience. The term that is known as life expectancy is most often used in the context of human populations, but is also used in plant or animal ecology; it is calculated by the analysis of life tables (also known as actuarial tables).
Humans live on average 31.88 years in Swaziland and 82.6 years in Japan, although Japan's
[4] recorded life expectancy may have been very slightly increased by counting many infant deaths as stillborn. The oldest confirmed recorded age for any human is 122 years. This is referred to as the "maximum life span", which is the upper boundary of life, the maximum number of years any human is known to have lived.
Life expectancy variation over time
The following information is derived from Encyclopedia Britannica, 1961[5] and other sources, and unless otherwise stated represents estimates of the life expectancies of the population as a whole. In many instances life expectancy varied considerably according to class and gender.
Obviously, life expectancy at birth takes account of infant mortality but not pre-natal mortality (miscarriage or abortion).
Era Life Expectancy at Birth
(years) Comment
Upper Paleolithic 33 At age 15, life expectancy of
39 (age 54)
Neolithic 20
Bronze Age and Iron Age 26
Classical Greece 28
Classical Rome 28 At age 15, life expectancy of
37 (age 52).
Pre-Columbian North
America 25-30
Medieval Islamic
Caliphate 35+
Medieval Britain 30
At age 21, life expectancy of 43 for British aristocrats (age 64)
Early Modern Britain 25-40
Early 20th Century 50-65
Current world average 67.2 2010 est.
In some cases life expectancy may increase with age as the individual survives the higher mortality rates associated with childhood. For instance, the table above listed life expectancy at birth in Medieval Britain at 30. A male member of the English aristocracy at the same period could expect to live, having survived until the age of 21:
1200-1300 A.D.: 43 years (to age 64)
1300-1400 A.D.: 24 years (to age 45) (due to the impact of the Black Death)
1400-1500 A.D.: 48 years (to age 69)
1500-1550 A.D.: 50 years (to age 71).
In general, the available data indicates that longer lifespan became more common recently in human evolution. This increased longevity is attributed by some writers to cultural adaptations rather than genetic evolution; although some research indicates that during the Neolithic Revolution natural selection favored increased longevity. Nevertheless, all researchers acknowledge the effect of cultural adaptations upon life expectancy.
Public health measures are credited with much of the recent increase in life expectancy. During the 20th century, the average lifespan in the United States increased by more than 30 years, of which 25 years can be attributed to advances in public health.
In order to assess the quality of these additional years of life, 'healthy life expectancies' have been calculated for the last 30 years. Since 2001, the World Health Organization publishes statistics called Healthy life expectancy (HALE), defined as the average number of years that a person can expect to live in "full health", excluding the years lived in less than full health due to disease and/or injury. Since 2004, Eurostat publishes annual statistics called Healthy Life Years (HLY) based on reported activity limitations. The United States of America uses similar indicators in the framework of their nationwide health promotion and disease prevention plan
"Healthy People 2010". An increasing number of countries are using health expectancy indicators to monitor the health of their population.
1.2 Aim
It is known that life expectation has increased conspicuously during last years. In fact we reach to the conclusion that there are going to be more old and physically disable people than in the previous years. Although being a good new that the life expectance has increased this leads new problems to our society because it is necessary to guarantee a good living standard to this people who have difficulties in their everyday routine.
In consequence, we focus our project in different aspects in order to help society. We thought that this people need to have more facilities in their life, because they have the same right to live as good as the rest of the population.
2. NEED: To facilitate access to the shower
During our stay in Sweden we had the opportunity to visit a residence where disabled people lives. There we could see and compare that the facilities that they have in Sweden are better than in Spain. Also the financial aid is bigger, so the projects and technologies that they use are better.
In this residence we could see a group of houses, which were designed and complemented by different accesories and specific machines that are significantly useful for disable people in their everyday life. Some accessories are even very specific according to the person’s disability and they are not very easy to find on the market.
In the kitchen for example, the kitchen´s countertop could be placed at the approppriate height of the disabled person through an electronic system and powered by hydraulic pistons. The cupboard doors were false, while the respective internal shelves of the cupboard can go up and down, using the same previous system, making easy the access to plates, goods, etc. The windows can be opened and closed mechanically.
In the bedroom we saw a bridge crane that they used to carry the disables person to bed.
The bed can be reclined electronically and it could accommodate in different positions for the confort of the person, of course.
The bathroom was also a conditioned placed for the person. The sink could be positioned in the approppriate height for the person making easier to use it. The toilet was complemented with armrests. However we did not see any innovation in the shower. The shower was only covered with a curtain and the floor had a slope to allow the water falls to the drain hole.
After seeing one whole house for the help of the disabled people, our idea of improving the access to the shower by complementing the shower’s door with a chair, come up stronger. Then our thesis project was taking shape.
The shower would be covered by screens, being one of them the access door. On the floor we would put a plate to insert the screens and the door and the water couldn’t get out.
Therefore, the aim of the present thesis is to design an easy access to the shower for elderly or people with physical disabilities, that can be affordable and convenient to use at their bathrooms.
3. OUR INITIAL IDEAS
So we started by thinking like an incapacitated person so we tried to feel how a person would feel in our society. We founded many problems in our own routine, and we thought different ways to solve them. We had many different solutions for all different problems we got, but these are the most interesting ideas we had to get our society better:
1. A multifunctional wheelchair which can be positioned vertically or horizontally. It is known that people who use wheelchair are going to pass much time in their chair, so it would be a good idea to have a wheelchair which can be positioned in different ways, because for different activities we need different positions. It won´t be the same position while you are cleaning dishes or while you are relaxing. So it would be a good idea to can adapt their wheelchair in their own without depending of anyone else.
2. An “elevator chair” which can be used to get in or out of the bath. It is difficult to get in a bath for a physically disable person while for the rest is an automatically activity which is so easy. But without any facility a physically disable person couldn´t get in a bath. In consequence we thought that it would be a good idea to invent an elevator which will move the people from outside to inside of the bath.
3. A chair which can be used to get in or out of a conventional shower from the side. For the same reason at the second point this will be a good invention.
4. Stairs which can become in an elevator that could move up and down a wheelchair from the bus. Many times it takes too many time for people to get into a bus, because the ramp many times get blocked and it is usually uncomfortable, so this kind of stairs would became easier to get a bus, it will be faster and more similar to the others.
3.1 Our choice
After discussing this several ideas with our supervisor, Armando Leon, we concluded that the best idea which could be used was the third one. We focus our project in how we could help an physically disable person in his or her diary shower.
Before doing anything we get information about how the standard and commercial showers are, their general characteristics, sizes, etc. Our intention was that our final product could be used by as many people as possible. So we read many articles and this is what we had to take care about when we want to build a shower to an incapacitated person.
4. POSSIBLE SOLUTIONS
Our job now was to think how design an easy access to the bath for everyday life. Ideally the design was simple and cheap, for sale on the market to reach all the people that they need and not a specific and unattainable product.
4.1 Lateral driving Mechanism for the chair
Taking into account that our first idea was to put a machinery out of the conventional bath to move through a mechanism laterally a chair to the extent that the disabled person was inside of the bath and could be cleaned without problems (See Figure 4.1). In the same way the person could leave the bath, doing the same way opposite to the initial. This first idea we thought that was good, because satisfy our set requirements. The person would be self-sufficient and they wouldn’t need any aid; the prototype would be innovative, because would be a product that we didn’t found on the market; a simple prototype, initially the machinery would be built with gears and hydraulic pistons to move the chair laterally. But, still believing that the project could be simple, to can build a machinery inside of the bathroom we thought that it couldn’t be available to all customers, overcoat economically.
Figure 4.1 One of our initial solutions.Sketch on lateral mechanism to access to the shower 4.2 180 degrees rotational door
Our second idea, was instead to use the machinery to move the disabled person inside the conventional bath, by putting a chair on a bath’s door. But this novelty wasn’t the only one,
because the door for comfort and ease of the user, it rotates 180º on a central axis (See Figure 4.2).
This new idea we thought that would be more simply than the previous one, it would be to make an easy access for the user and more important, now could be available to all customers economically.
The operation of this prototype would be as simply than when the chair will be out of the bath (the door would be closed) the user would sit on the chair. When the user will be seated, the door would rotate 180º (the door would continue closed) and then user would be located inside of the bath to be cleaned. In the same way, after to clean, the user would repeat the same action to out of the bath.
Figure 4.2 Second idea on an easy access to the shower. A180 deg rotational door
This idea we would pleased completely and we thought that it was suitable for its ease. But it had a little problem. We wanted our product to be suitable for any bath of any house, and with this product that would not be possible. Taking into account the sizes of the plates for the bath in different catalogs we needed a minimum and maximum of space in the bathroom. Because the minimum distance that we would need, would be a person seated on a wheelchair. It was that we did, we seated on a wheelchair and we took measures, from the back of the chair to the feet, taking in count an upright posture and comfortable. When we took this measures we knew that we
exceeded the maximum measure, i.e., the person when it was seated would create a turning radius bigger than a half of the plate’s size, so we excelled of our measures. This it was a problem, because the size of the plate defines us the maximum permitted.
Rotation Axis
As you can see in figure 4.3, when the door swings, the person who was seated on the chair would crash against the wall.
4.3 Final solution: 90 deg rotational door
Taking into account the parameters that we must fit, we thought in our third and last idea. It was more simply than the second one, but equally valid. Now, the door instead of rotate 180º on a central axis, it works like a conventional door, i.e., it had some hinges in one side of the door turning it 90º.
Figure 4.4 Final solution: A 90 deg rotational door
In this way we would put the chair as close as possible of the side where the hinges would be placed, so we wouldn’t have problems with the space when the user will be seated on the chair.
With this, our aims would be completed, because the project would be innovative, simple, cheap and standard.
5. OUR DESIGN: 90 degrees rotational access door
After all the possible solutions, eventually discarded for the reasons mentioned before, we arrive to the final design. No doubt a difficult task, being a completely new model, invented from beginning to end.
In our final purpose, we have done above all with the help of Solid-Edge program; however, the strength of materials analysis we have done with INVENTOR program, that we did not know anything until now.
5.1 Chair
We started designing the chassis of the chair, without have clear if the thickness of the profiles would be appropriate or not, so that we designed so that after making resistance tests, to be as easy as possible to change the parameters chosen initially.
We started the design with a 60x40x3 profile for the L-shaped profile of the chassis. (When performing analysis with Inventor we decide to change a profile 60x40x1.5)
Figure 5.1 L-shaped profile of the chassis
Following, we design some reinforcement, that we use it to reinforcement the chassis and to combine two L-s. Next we design a rectangular lid, to save get inside water into chassis. To finish with the chassis, we design the tabs with which we combine the chassis and the door.
Figure 5.2 Complete chassis
Before starting to design the shower it-self, to get a shower of standard size, we find a catalog of showers. The catalog we used was the company's Synergy. Of all the models that the operator had in their catalog, we chose the most appropriate in our opinion for our project. Always keeping in mind that the plate from the shower should be, the minimum size to open and close the door once the user was sitting in the chair. So our choice was a shower-dish of 1000x1200.
We could not ensure that our project was preferably performed in a smaller plate, however if the plate exceed those measures did won´t be any kind of problem.
5.2 Door
Once selected measures of the plate, we start with the design of the door. One of the tasks that more work certainly gave us on our project. Not because of its apparent difficulty, but by the multitude of adjusts we did, once the initial prototype. Ultimately, the final door, there is much like the initial prototype, after many changes we chose a simple model but at the same time met all our requirements.
We design some profiles with regular forms in the manufacture of aluminium windows. All the profiles are made by aluminium.
The two pieces that divide the screen door and at the same time are the pieces that support the chassis of the chair are of this type of profile and we call it central bar.
Figure 5.3 Central bar
The vertical piece that it sticks the screen and the hinges is of this type of profile and we call it the big vertical fix.
Figure 5.4 Big vertical fix
The other vertical piece that is located just in the other side of the door is of this type of profile and we call it small vertical fix.
Figure 5.5 Small vertical fix
Horizontal bars, both below and above are the same, are of this type of profile and we call it horizontal fix.
Figure 5.6 Horizontal fix
To finish with the door, we design two hinges like that one to combine the fixed part of the shower with the mobile part.
Figure 5.8 Hinge
Figure 5.7 Complete door
5.3 Join the chair with a door
Once designed the chassis of the chair and the door on the other hand, we needed to figure out how to merge the two sets. To do this, we add four tabs to the chassis at the rear. At the same time, in central bar of the door, we make some holes a little wider than the tabs to enter the tabs. It would be easy to make more holes in central bar at different heights, to put the seat higher or lower.
But we think wheelchairs usually have the same height, so as normally would use it at the same height. Moreover, this type of assembly would be very easy to remove the chair if at any given time, the shower will use someone who has no need for it.
Figure 5.9 Our design
6.STRESS ANALYSIS
Once designed, we did the stress analysis with the help of Inventor. Before we start to do anything in Inventor, we made the necessary calculations by hand. We never obtain the same outcome, by a very simple reason, to make them by hand we simplify things a lot to performon the other hand the computer does not need such simplifications. However, the results often take similar parameters and this is what we seek.
6.1 Handmade calculations:
When we made this handmade calculations, the first thing that we had to make was if the chassis of the chair could support the weight of the person, because otherwise it would be unfeasible placing it at the door. For it, we had to follow these steps:
1- Taking into account the measures of the chassis of the chair and its profile, we calculated their moment of inertia.
2- When we calculated the moment of inertia, we had to calculate the bending moment and the shear strength that it would cause the weight of the person on the tabs that connect the chassis of chair and door.
3- After calculate the bending moment and the shear strength we had to calculate the simple stress and shear stress that must support the chair.
4- We continue using Von Mises’s criteria, calculating the maximum stress that could resist the chair.
5- To finish, checking if the chair supported the weight, with the relation between the yield of the material that the chair was composed and the maximum stress allowed, we
calculated the security factor.
Next, we are going to describe the formulas and criterias that we used to do the calculations.
These equations we are going to use to calculate different areas (Eq. 6.1):
Moment of inertia on a rectangular shape (Eq. 6.2):
3
12
1 B H
I Iz = IZ1 – IZ2
A1 = B1 · H1 A2 = B2 · H2 A = A1 – A2
To calculate shear strength, simple stress and shear stress (Eq. 6.3):
To calculate the maximun stress that could resist, we will use Von Mises`s criteria (Eq. 6.4):
Now, after describe the steps, we are going to specify it:
1- The first thing we are going to describe the profile that we used for the structure of the chassis.
Figure 6.1 L-shaped chassis including forces and distances
The chassis of the chair have L-shaped and its profile is rectangular. The rectangular profile is hollow and its thickness is 3mm. The base is 60mm and it has a 40mm of height.
In this way we can calculate the area of profile:
A T A
T
I Z M I
Y M A N
Z Z Y
Y
Y Y Z
Z
2 2
2 3 Y Z
Acording to equations (Eq. 6.1):
A = A1 – A2
A1 = B1 · H1 = 60mm · 40mm = 2400mm2 A = 2400mm2 – 1836mm2 = 564mm2 A2 = B2 · H2 = 54mm · 34mm = 1836mm2
We continue calculating the moment of inertia. The profile shape is rectangular, so we are going to use the next formula to calculate it, acording to equiation (Eq. 6.2): 3
12
1 B H
I In this case, the only force that supports the chair is the weight of the person. So, we can say that the only force would be in the same direction of the axis Y. In this way, this force it wouldn’t create any moment My, and consequently we wouldn’t have to calculate the moment of inertia in axis Y that would create on the profile. The force only would create a moment in axis Z, so we only have to calculate the moment of inertia in axis Z, i.e., Iz.
The moment of inertia in axis Z we would calculate in this way:
4 3
3 1 1
1 60 40 320000
12 1 12
1 B H mm
IZ
4 3
3 2 2
2 54 34 176868
12 1 12
1 B H mm
IZ
4 2
1 I 143132mm
I
IZ Z Z
2- After calculate de moment of inertia, the next step would be to calculate the bending moment and the shear strength that would create the weight of the person. For that we are going to use formulas of the static.
First, we will propagate the weight of the person. Instead of a point force we are going to use like distribute force. Our purpose would be that the chair could support 1500N (150Kg) of weight. The chassis of the chair consist in two bars of L-shaped, but the calculations we will make in only one bar, so we will use 750N like force.
The base of the chair where the person can sit has 360mm of length, so:
mm N mm
N 2,083 360
750
Figure 6.2 L-shaped chassis with forces
We will use this profile to make the calculations.
N N
T mm mm
T N
FY 0 2,083 360 0 749,88 750
mm N mm
N M
mm mm
mm mm M N
M
165000 6
, 164973
2 0 40 360
360 083
, 2 0
3- After have calculated the bending moment and shear strength that would create the weight of the person on chassis of the chair, we will continue calculating the simple stress and shear stress.
Acording to (Eq. 6.3):
A T A
T
I Z M I
Y M A N
Z Z Y
Y
Y Y Z
Z
In this case as we have explained above, we won’t a bending moment My, because the forces they are in the same direction of the axis Y. We will haven’t any axial force, so N=0. In this way the equation will be as follows:
Z Z
I Y M
Substituting the values obtained:
2
2 2
2 4
0
33 , 564 1
750
05 , 143132 23
20 165000
mm N A
T
mm N mm
N A
T
mm N mm
mm mm
N I
Y M I
Z M I
Y M A N
Z Z
Y Y
Z Z Y
Y Z
Z
4- Then we will calculate the maximum stress that can support the chair, and for that we will use the criteria of Von Mises.
2 2
2 3 Y Z
Substituting the values obtained:
2 2
2
2 2
22 3 23,05 1,33 0 23,165
mm N
Z
Y
5- We will finish calculating the security factor. Then we will check if the chair can support the force made by the weight of the person. For that we will relate the yield of the material that the chair was composed and the maximum stress allowed. In our case the material used has been aluminum.
The yield of aluminum 10 2 98 2 mm
N mm
Kg
The security factor: 4,23
165 , 23
98
2
2
mm N mm
N N
We realizing the results obtained, we conclude that the chair won’t break it for the force suffered, because the security factor may hold more than four times the force that suffered. This lead us to another conclusion, the chair is too safe. For that we thought in reduce the thickness of profile of the chair, because would also be cheaper.
Our initial calculations had made with a thickness of 3mm, and it was too safe, so we decided make more calculation with thickness of 2mm, 1,5mm, and 1mm.
Following the steps of the calculations above, we will make the same with another thicknesses.
Using a thickness of 2 mm
Acording to (Eq. 6.1)
A = A1 – A2
A1 = B1 · H1 = 60mm · 40mm = 2400mm2 A = 2400mm2 – 2016mm2 = 384mm2 A2 = B2 · H2 = 56mm · 36mm = 2016mm2
Acording to (Eq. 6.2)
4 3
3 1 1
1 60 40 320000
12 1 12
1 B H mm
IZ
4 3
3 2 2
2 56 36 217728
12 1 12
1 B H mm
IZ
4 2
1 I 102272mm
I
IZ Z Z
N N
T mm mm
T N
FY 0 2,083 360 0 749,88 750
mm N mm
N M
mm mm
mm mm M N
M
165000 6
, 164973
2 0 40 360
360 083
, 2 0
Acording to (Eq. 6.3)
2
2 2
2 4
0
953 , 384 1
750
267 , 102272 23
20 165000
mm N A
T
mm N mm
N A
T
mm N mm
mm mm
N I
Y M I
Z M I
Y M A N
Z Z
Y Y
Z Z Y
Y Z
Z
Acording to (Eq. 6.4)
2 2
2
2 2
22 3 32,267 1,953 0 32,4488
mm N
Z
Y
= √ 2 + 3·(y2 + z2) = √ 32,2672 + (1,9532 + 02) = 32,4488N/mm2
Security factor: 3,02
4488 , 32
98
2
2
mm N mm
N N
Using a thickness of 1,5 mm
Acording to (Eq. 6.1)
A = A1 – A2
A1 = B1 · H1 = 60mm · 40mm = 2400mm2 A = 2400mm2 – 2109mm2 = 291mm2 A2 = B2 · H2 = 57mm · 37mm = 2109mm2
Acording to (Eq. 6.2)
4 3
3 1 1
1 60 40 320000
12 1 12
1 B H mm
IZ
4 3
3 2 2
2 57 37 240601,75
12 1 12
1 B H mm
IZ
4 2
1 I 79398,25mm I
IZ Z Z
N N
T mm mm
T N
FY 0 2,083 360 0 749,88 750
mm N mm
N M
mm mm
mm mm M N
M
165000 6
, 164973
2 0 40 360
360 083
, 2 0
Acording to (Eq. 6.3)
2
2 2
2 4
0
578 , 291 2
750
56 , 25 41
, 79398
20 165000
mm N A
T
mm N mm
N A
T
mm N mm
mm mm
N I
Y M I
Z M I
Y M A N
Z Z
Y Y
Z Z Y
Y Z
Z
Acording to (Eq. 6.4)
2 2
2
2 2
22 3 41,56 2,578 0 41,8
mm N
Z
Y
Security factor: 2,34
8 , 41
98
2
2
mm N mm N N
Using a thickness of 1 mm
Acording to (Eq. 6.1)
A = A1 – A2
A1 = B1 · H1 = 60mm · 40mm = 2400mm2 A = 2400mm2 – 2204mm2 = 196mm2 A2 = B2 · H2 = 58mm · 38mm = 2204mm2
Acording to (Eq. 6.2)
4 3
3 1 1
1 60 40 320000
12 1 12
1 B H mm
IZ
4 3
3 2 2
2 58 38 265241,67
12 1 12
1 B H mm
IZ
4 2
1 I 54758,33mm I
IZ Z Z
N N
T mm mm
T N
FY 0 2,083 360 0 749,88 750
mm N mm
N M
mm mm
mm mm M N
M
165000 6
, 164973
2 0 40 360
360 083
, 2 0
Acording to (Eq. 6.3)
2
2 2
2 4
0
826 , 196 3
750
265 , 33 60
, 54758
20 165000
mm N A
T
mm N mm
N A
T
mm N mm
mm mm
N I
Y M I
Z M I
Y M A N
Z Z
Y Y
Z Z Y
Y Z
Z
Acording to (Eq. 6.4)
2 2
2
2 2
22 3 60,265 3,826 0 60,628
mm N
Z
Y
Security factor: 1,616
628 , 60
98
2
2
mm N mm
N N
6.2 Calculations by Inventor:
Not knowing the program, we were in difficulties a bit at first, but we managed to adapt to it quickly, since all such programs are very similar.
First of all, not to do again all the designs in Inventor, we design Solid-Edge, Inventor saving them as "Parasolid" and being able to open without any problem in Inventor.
We started with the chassis of the chair to begin assign the material of the profiles in this case all the pieces are welded aluminum. We continue with the restrictions, we put fixed
restrictions on the 4 tabs. Applied loads, a vertical force which would be equivalent to the person on the chair, though, divided into two forces to implement them in the L-s, and apply the gravity taking into account the volume and assigned the same material program calculates the weight and strength placed at the center of gravity. Then we calculate the mesh, and now we have given all the necessary data to the program will ask for the results. The default program calculates more results that we take into account, we only use Von Mises stress, displacement and the safety factor.
A value of 3.44, would be the result of security factor of the chair. Indicating the most critical point.
As we did taking in count only the chair, we did the same with the chair by adding the door.
In fact, this would be the most important, because this set would absorb only the chair, and would be that really we had to consider it.
The process would be the same. In this picture it can see how it is fixed all and how the forces have been applied.
Figure 6.4 Fixed door with forces
The result of security factor would be this and it is placed where would be the most critical point.
Even after obtaining the results, it can see a simulation of the process that exerts forces on each result.
