Lab 0 - Lab 0 Writing the Laboratory Report CEE 300/TAM...

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Lab 0: Writing the Laboratory Report CEE 300/TAM 324 Section: AB5 September 2, 2016 1
(1) ABSTRACT A tensile test was performed on an annealed specimen of AISI 4340 steel. Using an Instron Model 4483 and extensometer, ultimate and fracture strengths of the specimen were calculated. The annealing process allowed for the specimen to experience a slightly longer elastic deformation than the original alloy steel specimen by increasing its ductility. This procedure proved that the Instron Model 4483 is a reliable source for measurements and testing. 1. INTRODUCTION 1.1 Tension Tests A tension test is utilized to collect data for the stresses and strains a particular specimen experiences in order to learn more about the material properties of that specimen. This is important to understand the capabilities and strengths of these materials in order to determine how, where and when these materials will work as ideally as possible. In a tension test, a uniaxial tensile load is applied, increasing gradually until the point of failure. 1.2 Engineering Stress By utilizing the Instron Model 4483, the process of calculating a specimen’s engineering stress is simplified. Stress refers to load or force per unit area. The following equation for engineering stress can be used: σ = F A 0 where σ represents the engineering stress, F is the loading applied by the machine, and A o represents the initial cross-sectional area of the specimen. The ultimate strength, σ u , of a specimen is solved using the maximum load applied whereas the fracture strength, σ f , is found using the load applied at the point when the specimen fails. 1.3 Engineering Strain 2
(2) (3) Another parameter measured in a tension test is the engineering strain which occurs because of the application of a stress. Strain refers to the elongation of a specimen divided by the original length of the specimen. The equation for this parameter is defined below: ε = l i l o l o = Δl l o where ε is the engineering strain, Δ l represents the elongation or change in length of the specimen, l i is the instantaneous length and l o is the initial length. This parameter is unitless, therefore it often exists as a percentage. If the measured strain goes away following the removal of the load or applied stress, the strain is called “elastic.” However, if the strain removes, the strain is called “plastic.” 1.4 Hooke’s Law

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