Testing of Metallic Materials PDF

Testing of Metallic Materials Metal Testing Once a heat-treatment process has been carried out, the material must be tested to ensure that the desired qualities have been achieved. Some of the properties tested for are: Hardness Tensile strength Fatigue strength Impact resistance. Note: Testing is c...

Testing of Metallic Materials Metal Testing Once a heat-treatment process has been carried out, the material must be tested to ensure that the desired qualities have been achieved. Some of the properties tested for are: Hardness Tensile strength Fatigue strength Impact resistance. Note: Testing is carried out with a test piece consisting of the same material and thickness of the component which was heat-treated along with the component. Image by IABG Dresden via Wikipedia Commons Licence IABG Fatigue test of the Airbus A380 Wing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 65 of 229 Hardness Testing Since the strength of most metals varies with hardness, it is often required to measure the hardness of a metal. The two most widely used methods of hardness measurement are the Brinell and Rockwell methods. Brinell Hardness Tester The Brinell hardness tester uses a hydraulic force to impress a spherical penetrator into the surface of a sample. This force is hydraulically applied by a hand pump and read on a pressure gauge. When the sample is removed from the tester, the diameter of the impression is measured with a special calibrated microscope. The diameter of the impression is then converted into a Brinell number by using a chart furnished with the tester. Aviation Australia Brinell hardness tester 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 66 of 229 Brinell hardness tester Relevant Youtube link: Brinell hardness testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 67 of 229 Rockwell Hardness Tester The Rockwell hardness tester gives the same information as the Brinell tester, except that it measures the depth to which the penetrator sinks into the material rather than the diameter of the impression. A minor load is applied and the machine is zeroed. A major load is then applied and the dial on the tester indicates the depth the penetrator sinks into the metal. Instead of indicating the depth of penetration in thousandths of an inch, it indicates it in Rockwell numbers on either a red or a black scale. Rockwell testers use three types of penetrators and three major loads that may be applied during the test. Benchtop Rockwell hardness tester Relevant Youtube link: Rockwell testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 68 of 229 Rockwell hardness tester Tensile Strength Testing Tensile strength of a ferrous metal is tested by applying a longitudinal load to a sample of material and plotting the load against the resulting elongations on a graph. Tensile testing Relevant Youtube link: Tensile test 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 69 of 229 Tensile testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 70 of 229 Fatigue Strength Testing Fatigue strength testing establishes the stress level at which structural failure will occur. A specially shaped test piece is gripped at one end, while at the other end a ball race is fitted. A load is suspended from the ball race and the test piece is then rotated from the end at which it is held by an electric motor. Under the action of the overhung load, it is stressed in tension and compression once every revolution. The number of cycles completed is measured to determine fatigue failure. This number of cycles is then classified as fatigue life. Fatigue strength testing - The Wohler Cantilever bending fatigue machine 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 71 of 229 Airframe Fatigue Testing Aircraft are subjected to fatigue tests. The purpose of an airframe fatigue test is to provide key data that help design engineers identify the likelihood and causes of premature fatigue damage or wear on the airplane's structure and structural components. Aircraft are subjected to fatigue strength tests to determine fatigue life of components, which helps with the development of maintenance programs. An F35 Lighting II multirole combat aircraft fatigue test is shown. Airframe fatigue testing - F35 at British Aerospace Relevant Youtube link: Boeing 787 fatigue testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 72 of 229 Impact Resistance Testing Two tests, the Charpy and Izod impact tests, are used to measure the impact resistance (or impact strength) of a metal. Both are mechanical tests in which a pendulum hammer (swinging through a fixed distance) fractures a standard-size notched piece of material with one blow. The main difference between the Izod impact test and the Charpy impact test is that each one uses a different beam configuration (cantilevered configuration vs a three-point beam configuration). Impact resistance testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 73 of 229 Izod and Charpy testing Relevant Youtube link: Izod impact testing 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 74 of 229 Charpy V-notch (CVN) Technique By far the most common impact testing method used today for metals is the Charpy V-notch impact test. In this technique, the specimen is in the shape of a bar of square cross section with a V-notch. The load is applied as an impact below from a weighted pendulum hammer that is released from an initial height. The pendulum with a knife edge strikes and fractures the specimen at the notch. The pendulum continues its swing, rising to a maximum final height, which is lower than the initial height. The energy necessary to fracture the test piece is directly calculated from the difference in initial and final heights of the swinging pendulum. Charpy V-Notch test Relevant Youtube link: Charpy impact test 2022-05-18 B-06a Materials and Hardware CASA Part 66 - Training Materials Only Page 75 of 229