ABSTRACT Using the reliability index to express a system’s safety, reliability theory is applied to study a structure’s failure probability due to the uncertainty (i.e., randomness) of design and production parameters with (a) variability in working conditions and the environment and (b) direct interaction with the soil, the conventional approach has been based on deterministic design methods. In contrast, using the concept of reliability as a new and useful approach, we develop the industry of design and manufacture of agricultural machinery. In this study, the first-order reliability method (FORM) was used to analyze the reliability of a plow bottom standard. To perform the reliability analysis, the required forces on the standard were determined by simulating the interaction of the plow with the soil using finite element method by Abaqus software. Random variables were considered as longitudinal and vertical forces on the bottom standard, radius of the standard arc, plastic cross-section modulus, and yield stress. The reliability index (β) as a measure of the system’s safety of was determined using reliability analysis whose value was found to be 2.569 for the bottom's standard. Moreover, the failure probability (Pf) of the bottom's standard was calculated as 0.005. In the final step, the results of FORM reliability analysis were compared with the reliability results of the Monte Carlo simulation of the plow bottom’s standard. The results showed that the bottom standard’s probability of failure in the FORM and Monte Carlo methods for the conditions considered—i.e., very compacted soil, plowing depth of 30 cm, and velocity of 3 m s-1—are low and almost low, respectively. Also due to the lack of lateral force FX in the limit state function, the FORM analysis indicated sufficient uncertainty of the bottom standard design; therefore, strengthening or optimizing this part of the moldboard plow chassis seems necessary. پرونده مقاله

Connecting parts through welding as permanent connections can play an important role in various industries. Despite the favorable load-bearing capabilities of joints resulting from welding dissimilar parts, they have some limitations that need to be identified and checked to optimize their use. One of the limitations is the behavior of parts under thermal stresses caused by the welding process. Thus, it is important to consider the welding conditions of the dissimilar parts in the contact area of the electrode and the welding seam, as this can significantly affect the mechanical performance of the welds. The research conducted in this study involved using the electric welding method with non-consumable tungsten electrodes under shielding gas (TIG) to connect aluminum and carbon steel parts. Ansys software was utilized to investigate the effect of thermal stress in the welding process for different joints. To ensure accuracy, parts were welded together practically under similar conditions, and the results obtained were compared with the results of the modeled method. First, the behavior of a steel sheet under the butt and Tee Joint and then the role of various factors on welding performance were investigated by modeling the process for a pipe in different conditions. Finally, due to the significant role of T-shaped joints in various industries, heat distribution, behavior, and stress analysis were investigated. پرونده مقاله