One of the methods used for calculating this characteristic is the tensile test, where a sample is pulled apart by a Tensile Testing machine until it brakes. The effect of elasticity of the specimen and the testing machine is investigated with special attention to relaxation tests. Introduction The construction materials course is an essential part of civil engineering as the strength of all structures and constructions depends on the material used. Tensile and compressive stress are known as direct stress. Tensile Testing specimen before testing Figure 1. In the experiment, a 0. The phenomenology of the tensile test is re-examined with special attention to the influence of strain rate sensitivity of the flow stress.
From the curve, point E is the elastic limit point. It can also be defined as the ultimate stress corresponding to the peak point on the stress strain graph. The materials used are trammel to measure the dimensions of samples, the felt pen, 4 samples of timber with grains parallel to the load and 2 samples of timber with grains perpendicular to the load, high-carbon steel, low-carbon steel and aluminium specimens. It is used to characterize the mechanical properties of the material and has direct implications on the design and construction of the end product. These failures are typical failures for ductile and brittle materials.
Furthermore, the steel sample experienced nearly two times the torque than the cast iron. The tensile tester used in this lab is manufactured by Instron model 5569. It has a maximum load of 2 or 50 kN and a variable pulling rate. When the specimen is stretched and broken, the computer will record down the necessary measurements. The ultimate stress was determined to be 487. During the laboratory a Tinius Olsen Tension Test equipment was used, and the test samples were from low and high carbon steel and timber with grains parallel and perpendicular to the load. We then analyzed the data output from the load and extension gauge.
The error in the ultimate stress as calculated from Equation at a force level of 9848 N was ± 8. For safe design of these components, there ultimate tensile strength and ductility one to be determine before actual use. For shear force, area parallel to force is considered for calculation of stress. Engineering Stress is obtained by dividing the load by the original area of the cross section of the specimen. An engineering stress-strain curve can be constructed from this load-elongation curve by making the required calculations. For the cast iron there is extreme discrepancy with the accepted value, in our experimentation the cast iron was put in the torsion arms tight enough so the iron effectively went through two different tests and only the data from the second test was used, this most likely caused problems. As shown below in the stress strain curve.
Idle cross head can be moved up and down for adjustment. Test equipment and materials The test equipment used during the laboratory is one of the Benchtop Materials Testing Machines made by Tinius Olsen. Further, we will discover how different materials behave under similar loading conditions as well as how material properties differ. These values can be used to find the torque modulus of resiliency for the metals 5 , however, since cast iron is a very brittle material, it is not resilient and has no modulus. Once a specimen is placed on the tensile testing machine, start the machine. Yield Stress: is defined as load at the yield point divided by original cross section area.
Where the line measured out at strain of 0. Percentage Reduction in Area: Youngs Modulus E defined as stress over strain. Referring from the resultant graph, we can see that the obtained graph line is straight until the one point it decrease gradually and be rupture. In this diagram stresses are plotted along the vertical axis and as a result of these stresses, corresponding strains are plotted along the horizontal axis. T Hamburg Tensile Testing Machine Max. The yield point is difficult to detect in many none ferrous alloys.
On the graph point U is the ultimate stress point. If the area is perpendicular to applied force, then stress can be tensile or compressive as per direction of force. More information can be obtained from these graphs by analyzing the elastic portions of each material. The test measures the notch toughness of material under shock loading. Sample calculation is to be included in the Appendix. Following this procedure several conclusion and calculations can be made pertaining to each sample. The topic of this lab is confined to the tensile property of polymers.
The setup of the experiment could be changed to. Of all types of impact tests, the notch bar tests are most extensively used. The first and most important assumption that was confirmed was the brittle tendencies of cast iron and the ductile characteristics of mild steel. Though there was a large amount of error in this experiment a lot was learned about torsion testing. After the specimen breaks the final gauge length is plotted upto failure.
Therefore, the impact test measures the energy necessary to fracture a standard notch bar by applying an sudden load. Machine two different types of attachments: the first is to fix the metal samples, and second is to hold timber samples. Other calculated properties included true fracture strength, percent reduction of area, and percent elongation. Punch marks must be made at 2 inch intervals along each sample. Torsion: Torque applied in a plane perpendicular to the longitudinal axis of a member is called as torsion. After obtaining the readings electronically the values were tabulated into a graph to obtain a tensile testing graph in which the values for Yield.
During a typical tensile experiment, a dog-bone shaped specimen is gripped at its two ends and is pulled to elongate at a determined rate to its breakpoint; a highly ductile polymer may not reach its breakpoint. Try to balance it with the help of concerned handle and note down the value of balancing load. The work load and bearing load are noted. Replace pin in Extensometer and remove Extensometer from specimen. The average reading of Tensile Strength and Yield Strength ranges from 21.