Two methods of photoelasticity and finite element were employed to analyze contact stresses in bolted joints. Samples were made up of photoelastic materials. Photos were taken when samples were loaded with polariscope. Finite element models were analyzed using ANSYS 5.6 sofware. To verify the model, finite element results were compared with those of the experimental ones. The comparison led to an acceptable agreement between the two, with a correlation coefficient (R2) of 0.99. After a validation of the finite element model, the effect of number of engaged threads and different moduli of elasticity of bolt and nut were investigated, using ANSYS software. According to the results obtained, increasing the number of engaged threads in bolted joints resulted in a decrease of load concentration percentage in the first thread, and then smoother load distribution was observed to be accomplished. Of course, the behavior of load distribution in “bolt and nut” is not the same as in “body and stud” arrangement, but in either cases, when the number of engaged threads passed 20, this didn’t affect stress distribution. For body and stud, the most uniform load is obtained when the Young’s modulus ratio of body and stud is in the range of 0.5-1, while this value for nut and bolt is observed to be about 0.1.
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