Fracture toughness and fatigue and engineering materials

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1. FRACTURE TOUGHNESS & FATIGUE & ENGINEERING MATERIALS

2. Chapter 4 4.1 Impact Testing 4.2 Destructive Testing 4.3 Fatigue Testing

3. What is fracture toughness? fracture toughness  is a property which describes the ability of a material containing a crack to resist  fracture , and is one of the most important properties of any material for many design applications.

4. What is fatigue? In  materials  science,  fatigue  is the weakening of a  material caused by repeatedly applied loads. It is the progressive and localised structural damage that occurs when a  material  is subjected to cyclic loading.

5. 4.1 Impact testing Is a high strain rate   test  which determines the amount of energy absorbed by a material during fracture.

6. Two Types of Impact Testing Charpy Impact Testing IZOD Impact Testing

7. Charpy Impact Test The apparatus consists of a pendulum of known mass and length that is dropped from a known height to impact a notched specimen of material . The Charpy Impact Test was invented in 1900 by  Georges Augustin Albert Charpy  (1865-1945 ). Charpy impact test are on conducted on machines that are capable of measuring less than 1 ft. lb. to 300 ft. lb.  at temperatures ranging from -320°F to over 2000°F

8. V-notch: 2mm deep, with 45° angle and 0.25mm radius along the base

9. IZOD Impact Testing   IZOD Impact Testing  can be done up to 240 foot-pounds. on standard single notch and type-X3 specimens . The test is similar to the  Charpy impact test  but uses a different arrangement of the specimen under test .  The Izod impact test differs from the Charpy impact test in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration.

10. 4.2 Destructive testing Destructive testing  is the method of identifying the point of an applications  failure.

11. Benefits of Destructive Testing (DT) Verifies properties of a material Determines quality of welds Helps you to reduce failures, accidents and costs Ensures compliance with regulations

12. 4.3 Fatigue testing The definition of fatigue testing can be thought of as simply applying cyclic loading to your test specimen to understand how it will perform under similar conditions in actual use. The load application can either be a repeated application of a fixed load or simulation of in-service loads. The load application may be repeated millions of times and up to several hundred times per second. 

13. Why do a fatigue test? In many applications, materials are subjected to vibrating or oscillating forces. The behavior of materials under such load conditions differs from the behavior under a static load. Because the material is subjected to repeated load cycles (fatigue) in actual use, designers are faced with predicting fatigue life, which is defined as the total number of cycles to failure under specified loading conditions. Fatigue testing gives much better data to predict the in-service life of materials.

14. End of Slides (play sample video.)