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Department of Mechanical Engineering
Reliability Engineering (GENG 621)
Acceleration Life Test, ALT, of the Steam Iron
Dinesh Raj Goud
1. Problem Statement
3. Steam iron description
4. Development of Test Plan
5. Acceleration Method
6. Stress Level
7. Sample Size
8. Censoring Times
9. Failure Definition
10. Data Collection Method
11. Acceleration Model
12. Data Analysis Method
13. Example Accelerated Test Plan
1. Problem Statement
1.2 Type: Rowenta DW2070 with 300-Hole Stainless Steel Soleplate
An Accelerated Life Test (ALT) is the process of determining the
reliability of a product in a short period of time by accelerating in the use environment. ALTs are
also good for finding dominant failure mechanisms. Thus, an accelerated Life Test (ALT) is a
test method which subjects test units to higher than use stress levels in order to compress the
time to failure of the units. Therefore, the practitioners have tried to accelerate their failures over
the years, so they used the accelerated life testing (ALT) to describe all the practices. In this
project we will use the accelerated life test plan for estimating the reliability of our product
3.Steam iron description
A steam iron which is filled up with water to produce iron of
clothes in order to avoid wrinkles in clothes and fabrics that may not be suitable for traditional
dry ironing. It is preferred to use Distilled water that is to be filled up into a holding tank and
special heating elements heat it up to becomes steam. This hot mist comes out through many
holes in the bottom heating element of the steam iron. As the steam loosens the individual fibers
of the clothes, the steam iron's pressing action smooth’s out wrinkles. An electric iron that emits
steam from channels in the iron face to facilitate the pressing and ironing of clothes, etc., the
steam being produced from water contained within the iron.
3.1 Parts of the Steam Iron
1. Variable steam
3. Spray button
4. Steam shot button
5. Vertical steam
6. Extra-long 3m cord
7. Power indicator light
8. Soft-grip handles
9. Water spout
10. Spray nozzle
11. Stainless steel soleplate
12. Maximum water level
13. Temperature dial
14. Heat indicator light
15. Built-in anti-calc system
16. large water tank
17. Cord storage
4.Development of Test Plan.
Planning an ALT in advance is a critical step toward success in
obtaining valid and accurate information. A feasible and reasonable test plan should include
managerial, logistical, and technical considerations. Managerial considerations deal with
formation of a team, definition of the roles and responsibilities of each team member,
coordination of the team, and other personnel management tasks’.
Logistical tasks are to secure the availability of test facilities such as chambers, functionality
inspection systems, and measuring devices. Technical considerations include determine the
test’s purpose, sample units and size, failure definition, acceleration method, data collection and
analysis method. The purpose of the accelerated life testing (ALT) are usually different, but the
common test purposes are to compare and assess the reliability of materials and components,
determine optimal design alternative, confirm the effectiveness of a design change, evaluate the
relationship between the reliability and stress, discover potential failure modes.
The purpose of acceleration is to yield reliability information
more quickly. Any means that serves this purpose is an acceleration method. There are four
types of acceleration method, which are overstressing, increasing usage rate, changing level of a
control factor, and tightening the failure threshold. The appropriate method to use for a specific
product depends on the purpose of the test and the Unit for our project the Steam iron itself. In
practice, the accelerated life testing often utilizes one or two of the four types of method. We
will choose increase the usage of the Steam iron to see how it survives during a certain time. The
rate of usage to be chosen, which we used to measure the reliability of the steam iron, is a
temperature per time.
The main goal of a quantitative accelerated life testing (ALT) is
to assume the life distribution at a use condition. This will be accomplished by extrapolating the
life data obtained at elevated stress levels. To do this we have to have a model that relates to
accelerating stress such as temperature, humidity. We have to determine the stress level and
type, and we must decide the stress of the steam iron physically when we applied the same
design load on the steam iron. We need to know what kind of Materials the clothes are made it
by, if it is Cotton, polyester, wool and Nylon, all can bear under specific temperature that
associated with it.
The sample size is very important feature of any empirical study
in that the purpose is to make inferences about a population from a sample. In fact, the sample
size used in a study is determined based on the expense of data collection, and the need to have
sufficient statistical power. In a census, data are collected on the entire population; hence the
sample size is equal to the population size. We will choose the sample sizes for example:
1. The water tank.
2. The soleplate.
3. The handle.
Then, we will have to try to make these samples from each category in order to keep their costs
as low as we can by keeping their number smaller than the statistical one but not lower than the
total number of potential failure possibilities, and those number of samples should clarify the
failure mode to be happened by duplicating the probability of failure modes. Then we can move
to the next step.
Censoring occurs when the value of a measurement or
observation is only partially known. This failure type is the result of sudden failure. In fact,
these types of numbers are variables (random) that might make some difficulty with the time.
Obstacles occur some times.
The failure definition is an economic term that encompasses a
situation where, in any given market, the quantity of a product demanded by consumers does not
equate to the quantity supplied by suppliers. This is a direct result of a lack of certain
economically ideal factors, which prevents equilibrium. The purpose of the steam iron is to
remove the wrinkles in the clothes. We try to define the failure mode to get a measurement to
help the designer or manufacture to extract and know the failure units. So, we define the failure
of a steam iron, as a result we can achieve the success of the product. For instance in our goal the
product failure is that the steam iron does not remove the stubborn wrinkles of the clothes well,
or the handle is very weak so it will break easier, or taunt itself another failure is if the
temperature goes up so high it will burn the clothes because the timer does not shut off or due to
the overheating of the steam iron the iron sticks to the clothes an makes a burn spot on the
10. Data Collection Methods
In the Data collection Methods the test units(like the steam iron)
should be monitored continuously during the testing to get the exact failure times, for instance in
a binary state product, the monitoring system detects failure exactly when a steam iron ceases to
function .The life of the unit is the time to catastrophic failure. To monitor a degrading unit, the
system should measure the performance characteristics continuously or very frequently. Doing
so enables generating nearly exact failure times, which yield more accurate estimates. The life
of the steam iron monitored is the time at which a performance characteristic crosses its failure
threshold. This data collection method usually needs an automated data acquisition system and
advanced software. We look and search for the data to check on the steam iron to determine the
time between the failures and the no of the steam iron units of what we measure. The results are
supposed to be lower the cost to might we say that we success in this point.
Acceleration factors show how time-to-fail at a particular operating stress level can be
used to predict the equivalent time to fail at a different operating stress level. A model that
predicts time-to-fail as a function of stress would be even better than a collection of acceleration
12.Data Analysis Method
Analysis of data is a process of inspecting, cleaning, transforming, and
modeling data with the goal of highlighting useful information, suggesting conclusions, and
supporting decision making. Data analysis has multiple views and approaches, encompassing
diverse techniques under a variety of names, in different business, science, and social science
domains. We should have enough information and details as fast as we can to analysis the
customers want and demand as "no customer would expect to get a defective steam iron". After
that we have to analyze that information and data by using software that will give us exact
13.Example of an Accelerated Test Plan
The main objective is to determine exactly the mean number of cycles-to-failure of a
given steam iron. We will see how the soleplate, the water tank, and the hand are reliable after
being accelerated. The following assumptions are considered:
The acceleration stress is assumed to the degree of Temperature that will use to remove stubborn
wrinkles. The Temperature Selector Dial of the Steam iron has index to select the temperature.
For instance the index are symbols for 3 temperature ranges:
A. Accelerated Heat stresses at Low Temperature.
B. Accelerated Heat stresses Medium Temperature.
C. Accelerated Heat stresses High Temperature.
13.1Test condition :
Test stress level
(Temp) High Medium Low
50 100 150
The samples of three kinds of clothes we will try under different temperature fabric from Nylon,
Wool, and Cotton.
Summarizing, the benefit we get from accelerated life testing (ALT) is to know when and
why the product will fail before it occurs (at the design phase). So, we can compete with other
companies in our product which is the steam iron. It is important to identify these defects, which
will lead us to eliminate the failure of the product. After that, we will re-design the product, and
test it and to avoid these problems and produce an effective product(i.e. steam iron) for the