Strength of Materials Lab
1. Torsion testing apparatus.
A torsion testing machine is a device that uses a torsion beam to apply a twist to a specimen and measure the torque necessary to induce failure. Torsion testing machines are helpful in research, development, and production engineering to determine the ultimate tensile strength (UTS) or elastic modulus of materials. A torsion testing machine consists of a lever arm, a torque cell for holding the sample, and a load cell for measuring the torque. Usually, students turn a twist handle to apply force to drive the gears within the machine. It guides a shaft lengthwise from input to output, which allows for any change in length of the specimen during the tests and easy insertion of samples. An encoder measures any tilt or movement relative to continuous rotation. While this does not calculate the rotation angle directly, it displays the angular displacement on an analog display. In addition, another gauge – measuring torsion forces – is built into one or both sides of the drivetrain.

2. Impact testing apparatus.
Impact testing machines evaluate an object's capacity to withstand high-rate loading and it is commonly used to determine the service life of a part or material. Impact resistance can be among the most challenging qualities to measure. There are two standard kinds of impact test, Charpy and IZOD. Charpy tests are commonly performed on metals, but a few plastics and polymers can also be tested. IZOD tests can be performed on either plastic or metal specimens. A Charpy test specimen is usually a 55 x 10 x 10 millimeter bar. An IZOD specimen is typically a 64 x 12.7 x 3.2-millimetre bar.
(a) Charpy impact testing machine.
The tester is equipped with a falling pendulum hammer, able to break, with a single blow, a sample carved in the middle and positioned on two supports. The test is carried out on a CHARPY sample.
The energy absorbed during the test is checked. The value stands for the impact strength of the material (resilience) are Cast iron frame, Pendulum with hardened knife, Brake device to stop the pendulum, Impact energy 300J with 2J graduation, Falling angle: 140°, Pendulum mass kg 21.3, Impact speed: 5.187 m/s.
(b) IZOD impact testing machine.
The IZOD impact test is an ASTM (American Society for Testing and Materials) standardized method used to determine the impact resistance, or toughness, of a material. When designing a structure or part, it is important for engineers to know the toughness of a material to ensure that their designs not only satisfy the intended application, but are also safe, resilient, and long-lasting. To determine impact resistance (toughness) using an IZOD impact test, a weighted pendulum is dropped from a prescribed height and strikes a notched test specimen. When the specimen breaks, the energy absorbed and the material’s impact resistance can be related back to the potential energy of the pendulum before it is released.
