Asphaltmix, asphalt compression test, and steel tension
Theyield point and ultimate stress of 1018 steel were determined inuniaxial tension. The specimen without an edge had a length of 11.25inches and a width of 0.323 inches. That without an edge had a lengthof 11.25 inches and a width of 0.467 inches. In the force-chartgraph, the range between 0 – 1000 exhibit a nonlinear response to theapplied force. The range between the 1000-1500 exhibits a linearresponse to the applied force.
Thisbehavior implies that the sample was very compliant at moderatestress levels, and sufficiently stiff at high-stress levels. There isno structural or chemical premise why steel should exhibit anincreasing modulus with increasing stress. Therefore, a possibleexplanation is realigning and rotating the test fixture in the lowstress or low force region (Smith, 255). The test fixture and thespecimen are under the same applied force. Under these conditions ofthe experiment, the most compliant member will be dominant in thestress-strain behavior. The test fixture seems very compliant duringrealignment and rotation the fixture seems to be very stiff becauseof its large cross section at greater force levels. In the subsequentregion, the stress-strain behavior is dominated by the sample. Atgreat forces, deformation of the specimen was the dominant response.
Asthe specimen is loaded beyond the yielding point and then the load isrelaxed to zero, the material does not regain its initial dimensionscompletely, that is,the length and the diameter change permanently. Apermanent strain is observed.
Onthe application of the ultimate tensile stress, all further plasticdeformation is concentrated in the “necking” region and rapidfracture follows (Smith, 255).
Sincethe tensile test is completely standardized and well established, itmay be stated that it is a fast method of obtaining the desiredmechanical characteristics of materials.
Smith,W.F., Principles of Materials Science and Engineering- 2nd Edition,McGraw Hill, 1990, p 255.