Types of Failures and Analyzing Failures.

TYPES OF FAILURES AND ANALYZING FAILURES

TYPES OF FAILURES :

1. Mechanical Failure

Mechanical failure arises from applied external forces which, when they exceed the yield strength of the material, cause the product to deform, crack, or break into pieces. The force may have been applied in tension, compression, and impact for a short or a long period of time at varying temperatures and humidity conditions.

2. Thermal Failure

Thermal failures occur from exposing products to an extremely hot or extremely cold environment. At abnormally high temperatures the product may warp, twist, melt, or even burn. Plastics tend to get brittle at low temperatures. Even the slightest amount of load may cause the product to crack or even shatter.

3. Chemical Failure

Very few plastics are totally impervious to all chemicals. Failure occurring from exposing the products to certain chemicals is quite common. Residual or molded-in stress, high temperatures, and external loading tend to aggravate the problem. Figure 7 illustrates failure of a product from chemical attack.

4. Environmental Failure

Plastics exposed to outdoor environments are susceptible to many types of detrimental factors. Ultraviolet rays, humidity, microorganisms, ozone, heat, and pollution are major environmental factors that seriously affect plastics. The effect can be a mere loss of color, slight crazing and cracking, or complete breakdown of the polymer structure. A typical product failure arising from weathering effects is shown in

ANALYZING FAILURES :

The first step in analyzing any type of failure is to determine the cause of the failure. Before proceeding with elaborate tests, some basic information regarding the product must be gathered.

If the product is returned from the field, the district manager or consumer should be asked for basic information such as the date of purchase, date of installation, date when the first failure encountered, geographic location, types of chemicals used with or around the product, and whether the product was used indoors or outdoors. This information is vital if one is to analyze the defective product proficiently. For example, if the report from the field indicates a certain type of chemical was used with the product, one can easily check the chemical compatibility of the product or go one step further and simulate the actual-use condition with that chemical.

Recordkeeping also simplifies the task of failure analysis. A simple date code or cavity identification number will enhance the traceability. Many types of checklists to help analyze the failures have been developed. Ten basic methods are employed to analyze product failure,

1. Visual examination

2. Identification analysis

3. Stress analysis

4. Heat reversion technique

5. Microtoming (microstructural analysis)

6. Mechanical testing

7. Thermal analysis

8. Nondestructive testing (NDT) techniques

9. Fractography

10. Simulation testing

By zeroing in on the type of failure, one can easily select the appropriate method of failure analysis.

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................FIZA ENGINEER..............

SK NAJMUL (munna)

Hi. I’m a Mechanical Engineer, are I’m Designer of Blog Magic. I’m Creative Website, Web Designer, Auto Cad 3D and Interaction Designer, Industrial Machine Designer, Web Developer, Business Enthusiast, CNC, Writer and Photo editing and some time research an Mechanical subjects, Inspired to make things looks better.