Repeat procedure for additional specimens 19. Replace pin in Extensometer and remove Extensometer from specimen. These properties can be used for design and analysis of engineering structures, and for developing new Materials that better suit a specified use. The measurement of point depends on the sensitivity of the equipment used since some materials do not show a sharp line deviation from the straight line. This behavior suggests that the sample was very compliant at low stress levels, and very stiff at high stress levels.
The theory behind tensile testing is to measure the stress-strain response of the material. In the experiment, a 0. Addition error in these stress resulted form errors in determining the force and errors in the dimensions. The first and most obvious data were the qualitative observations. While both approaches are common, the second approach produces the largest range of starting points for the 0.
The first and most important assumption that was confirmed was the brittle tendencies of cast iron and the ductile characteristics of mild steel. At the end of the video a graph of vertical load versus vertical deflection shows how mild steel behaves under tension. However, since both E and φ were predicted, and contain error associated with that prediction, there must also be error in calculated strain at zero stress. More information can be obtained from these graphs by analyzing the elastic portions of each material. While the fixture appears very compliant during realignment and rotation, the fixture appears very stiff due to its large cross section at higher force levels. It can also be defined as the ultimate stress corresponding to the peak point on the stress strain graph. The average reading of Tensile Strength and Yield Strength ranges from 21.
However since the standard deviation is less than the corresponding distribution width, and alternate approach is to use three times the standard deviation as the appropriate error term. This can be confirmed by analyzing the domain in which the two metals twist, that is that the steel twist nearly ten times more than cast iron. Of all types of impact tests, the notch bar tests are most extensively used. Furthermore, the steel sample experienced nearly two times the torque than the cast iron. When the specimen is stretched and broken, the computer will record down the necessary measurements. Polar moment of inertia: The geometric rigidity of the X-sec is termed as polar moment of inertia.
On the other hand cast iron is a brittle material, brittle materials failure under significantly smaller shear forces than those of ductile materials, a brittle material also deforms much less under torsion. The region of fixture realignment and rotation creates some difficulties in determining the yield point by the 0. As the body is loaded beyond this limit i. Remember, that the text fixture and the sample are under the same applied force. It is denoted by double head arrow. This machine can test different types of materials and it is provided with software which gives the opportunity to users to fully control the system.
During plastic deformation, at larger extensions strain hardening cannot compensate for the decrease in section and thus the load passes through a maximum and then begins to decrease. T Hamburg Tensile Testing Machine Max. Figure 1 shows a tensile testing machine similar to the one used in this lab. The Tinius Olson Torsion Machine is interesting piece of equipment. The two materials tested, cast iron and mild steel, have opposing characteristics. It is hydraulically operates a pump, oil in oil sump, load dial indicator and central buttons.
That error can be approximated according to: where the standard deviation of the predicted intercept was 3. Data is recorded until specimen reaches. The tension test is one of the laboratories which help students develop their knowledge in this course by practice. The region of minimum cross section had dimensions 6. Impact strengths are generally lower as compared to strengths achieved under slowly applied loads. Idle cross head can be moved up and down for adjustment. From the tests, results were obtained; Tensile strength, Impact strength, and hardness were calculated.
In addition to this, also yield stress, tensile strength and percentage elongation and reduction of area will be calculated, only for the standard steel sample. Yield Stress: is defined as load at the yield point divided by original cross section area. The stress up to this point can be also be known as proportional limit stress. Stress strain curve is a behavior of material when it is subjected to load. It provides the extreme forces needed to understand the properties of materials.