3 an Audi TT and a side impact test for LSD wing doors
4 Introduction Impact Testing, ASTM E23 and IS/ BS Standard The impact test is a method for evaluating the toughness and notch sensitivity of engineering materials. It is usually used to test the toughness of metals, but similar tests are used for polymers, ceramics and composites.
6 Low yield strength Large plastic energy = Ductile ( เหนียว ) High yield strength Elastic energy = Brittle ( เปราะ ) Toughness =? Brittle Ductile
7 Notch sensitivity = ? The extent to which the sensitivity of a material to fracture is increased by the presence of a surface defect, such as a notch, a crack, or a scratch. Low notch sensitivity is usually associated with ductile materials. High notch sensitivity is usually associated with brittle materials.
8 แรงกระแทกที่เกิดระหว่างใช้งานซึ่งจะ กระทำอย่างรวดเร็ว (A suddenly applied stress) เรียกว่า Dynamic load อาทิ การกระแทกของเสาเข็ม, ปั้นจั่น, ใบพัด, รอยเชื่อม Metal industry sectors include Oil and Gas, Aerospace, Power Generation, Automotive, and Nuclear.
9 Effects of the notch effects: Stress concentration around the notch causes plastic deformation to occur in this area. The decrease in area caused by the notch increases the stress to a value above the yield stress for the material, while the rest of the specimen may still be at a stress below the yield stress. This plastic hinge which develops at the notch reduces the total amount of plastic deformation in the test specimen. The plastic deformation at the notch is constrained by the surrounding material and this increases the tensile stress in the plastic zone. The degree of constraint depends on the severity of the notch (depth and sharpness). The increased tensile stress encourages fracture and reduces the work done by plastic deformation before fracture occurs.
10 The Charpy Impact Test was invented by Georges Augustin Albert Charpy (1865-1945). The Charpy impact test continues to be used as an economical quality control method to determine the notch sensitivity and impact toughness of engineering materials.
15 รูปแสดงการทดสอบแรงกระแทก Energy held at lifted angle E1= WR(1-cos ) Energy held at swing angle E2= WR(1-cos )
16 The notched test specimen is broken by the impact of a heavy pendulum or hammer, falling at a predetermined velocity through a fixed distance. The test measures the energy absorbed by the fractured specimen. http://www.steeluniversity.org