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A Reliability Engineering Concept By: Nicole Panaccio

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1 A Reliability Engineering Concept By: Nicole Panaccio
Life Testing A Reliability Engineering Concept By: Nicole Panaccio

2 Life Testing Overview What is Life Testing?
Life Testing in Organizations How Does Life Testing Work? Who Uses Life Testing? Motorola’s Process Paper Clip Life Testing Summary

3 What is Life Testing? A process done under controlled conditions to determine how and when a product will fail in its intended environment Improves a product’s reliability Finds the weakest and strongest points of a product This test is done before any products enter the market. Once the weakest and strongest points are found, the testing determines how the product will be redesigned to fix the failures found during the testing. Information Found from:

4 Life Testing in Organizations
Design Life Cycle: Have an idea Design it Make a prototype Final definition Design and evaluation implementation Products want to be entered into markets fast. For a product to make it to the market fast, Life Testing or Accelerated Life Testing needs to be implemented. The design cycle helps show that life testing should only be done with a prototype. It takes a shorter time period to make a simple prototype and test that rather than make an entire batch. Making an entire batch will increase costs, and if there is vast amount of failures the entire batch will be useless.

5 Life Testing in Organizations
Life testing design cycle: Idea Design Prototype Prototype is tested for failures Design cycle stops with prototypes Although it is not the entire design cycle used when tested, in the end each step will be followed. The tests done to the prototype will re vamp the finial design.

6 Life Testing in Organizations
Customers believe that quality is inherent is all product Life testing validates this assumption. Specific directions are followed in a uniform fashion Life testing allows a product exist without failures. To find valid data that can help make the product better, failures have to be induced. A consistent set of instructions are performed each time a prototype is tested. At each stage of the process it must be documented what was done and how, so upon completion the product can be redesigned.

7 Three Types of Tests Type of tests performed: Qualitative Tests
ESS (Environmental Stress Screening) Accelerated Life Testing All three of these type will usually be used with different products. A test is done to see what type of test should be used on a particular product.

8 Qualitative Tests Gives the product tested the most failures
Failures produced by high and low stresses To pass the product must live through the entire test without failure ¹ As a prototype the product may not be designed as intended by the blueprints. This test could make a product break or fail if it is tested beyond the means it is intended for. For the test to be effective, it should allow the product to meet what it is expected to meet when put on the market. To test for something it is not going to encounter could be costly and inefficient. As the definition states, it is to be tested for its intended environment. Footnotes: 1.

9 ESS-Environmental Stress Screening
Applies environmental stimulus to products Goal: ¹ To find latent defects and eliminate them To find defects not found with inspection or electrical testing ESS is usually the test that is used on electronic or electromechanical products. Footnotes: 1.

10 Accelerated Life Testing
Similar to Life Testing Testing moves at a faster pace Uses quantitative data End results yield times-to-failure data Times-to-failure: how long it takes till a failure is made Standard Life testing is not used as much any more because it is so time consuming. Accelerated Life testing is a more recent technology. The reason is that it makes the times-to-failure happen faster and can get the product fixed and out on the market. Example: You will not expect a new dishwasher to fail in the first year but if it fails twice in ten years accelerated life testing was successful. It is successful because life testing will fix the failures a product is supposed to encounter but not all.

11 Accelerated Life Testing
Life distributions show how fast a product will fail ¹ Two methods used to get times-to-failure information: Usage rate acceleration Overstress acceleration Footnotes: 1.

12 Usage Rate Acceleration
A test used for products that only operate for small amounts of time ¹ It increases the time to make failures happen quicker than if it were used normally Footnotes: 1.

13 Overstress Acceleration
Backup to usage rate Used if usage rate is not appropriate means ¹ Tests products that are constantly used Uses stress levels that it would not normally encounter Defects that are found in accelerated life testing are found from low and high levels of stress and cold temperatures. Testers also are required to use high humidity, high heat, pressure and vibration. Many other techniques are used. The same basic idea is conveyed, that they need to break the product in turn to make it better. All things done with accelerated life testing is done faster than normal. Footnote: 1.

14 How Does Life Testing Work?
Majority of tests done on small sample 4 to 6 units Begin test with lowest level of the product Failures must be documented as they happen Since such a small sample is tested, the testers do not want to destroy all prototypes. Therefore to test correctly, the least destructive test is performed first and then the stress or whichever method used is increased. Soft failures will not show up if you continue to move on with test. As the test happens and failures are found documentation will help find failures that the tester could have overlooked.

15 How Does Life Testing Work?
Soft failures occur when there is damage made but the product returns to its normal state Hard failures are permanent damages done to the product For More Information go to:

16 Margins and Reliability
The difference between soft and hard failures is the margin for stress ¹ Once the failures are found and fixed, the margins have reached their max Maximized margins increase reliability and the life of the product Footnotes: 1. This figure shows the stress and its number of failures. The curves represent the distribution of failure that is responsible for that limit. This is a good imitation of a large sample instead of 4 to 6 units. The reason is because the failure will be detected and as long as it is detected then it does not matter where. As soon as the curves move toward the operating margin then the failure is considered an out of box failure.

17 Who Uses Life Testing? Motorola
Mission to produce cell phones with “virtually no defects” Use accelerated life testing to accomplish mission Helps to validate their six sigma corporate standard Motorola has their own reliability engineering department. Once that department believes that the product meets and or exceeds customer satisfaction then they will sell to the market.

18 Motorola’s Process Determine environment
Perform life testing in all environments. Four to six weeks of testing is required ¹ Motorola uses accelerated life testing with their products. It is based on Standard rules of life testing. Footnotes: 1.

19 Motorola’s Process Drop Testing ¹ Hot and Cold Temperatures ²
Samples are dropped on different surfaces of the phone multiple times. Hot and Cold Temperatures ² The phones receive extreme temperatures of hot and cold. Testing simultaneously with audio quality and simulated calls Footnotes: 1. 2.

20 Motorola’s Process Electro-Static Discharge ¹ Dust Exposure ²
Zap products with an electric pulse at “discharge” points Dust Exposure ² Products are placed in dust chamber Dust is shaken all over the product and then left to settle The “discharge” points are jolted with thousands of volts of electro static discharges. A discharge gun is used to shoot the charges into the holes of the product. Footnotes: 2.

21 Motorola’s Process Vibration Testing ¹
Horizontal and vertical vibration testing. Placed into vibration table and controlled by tester The tests vary in the extremes of vibrations given During the test it places a call and must be stable throughout the process Footnotes: 1.

22 Motorola’s Process Environmental Aging Tests ¹ Certification Testing ²
Temperature cycling: moving from low to high heat and cold Temperature shock Certification Testing ² Sudden Impact Testing Endurance Testing Package Drop Testing Transport Simulation Footnotes: 2.

23 Motorola Summary Life testing cuts Motorola’s costs
Less return of products that fail for the customer Their design exceeds customer satisfaction with “virtually no defects”

24 Paper Clip Life Testing
Follow these directions to determine how fast a paper clip will break using the life testing methods. ¹ Footnotes: 1. Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona

25 Follow These Steps With one hand, hold the clip by the longer, outer loop. With the thumb and forefinger of the other hand, grasp the smaller, inner loop. Pull the smaller, inner loop out and down 90 degrees so that a right angle is formed as shown. All of this information is from: Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona

26 Follow These Steps With one hand, continue to hold the clip by the longer, outer loop. With the thumb and forefinger of the other hand, grasp the smaller, inner loop. All of this information comes from: Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona

27 Follow These Steps Push the smaller inner loop up and in 90 degrees so that the smaller loop is returned to the original upright position in line with the larger, outer loop as shown. All of this information comes from: Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona

28 Follow These Steps This completes one cycle.
Repeat until the paper clip breaks. Count and record the cycles-to-failure for each clip. For this particular example, the larger size paper clips were demonstrated. Different sized paper clips will give different information. Throughout the life testing cycle of the paper clip be careful to use the same stress each time through. All of this information comes from: Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htm, Tucson, Arizona weibull.com is part of Reliasoft.com who made Weibull ++ 6 for Life Data Analyses which sets the standards for Reliability Life testing.

29 Summary Quality is inherent in most products
Life Testing allows the consumer to have reliable information because it is consistent throughout the testing Some life testing can cause permanent damage, and some aspects of the testing do not Prototypes are used to test because it is cheaper and easier to run tests on samples

30 Summary Life Testing can be done with ease or tremendous detail
Any way it is done it will yield the same information The tester must document what and how they do things Three sources I used:


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