Showing 5 results for Tensile Strength
R. Tamasgavabari, A. Ebrahimi, S. M. Abbasi, A. Yazdipour ,
Volume 5, Issue 1 (9-2019)
Abstract
In this research, the effect of vibration at the resonant range (75 Hz) on the hardness and tensile strength of AA-5083-H321 aluminum alloy, were welded by gas metal arc welding (GMAW) investigated. Vibration forces were ranged from 850 N to 2200 N, under identical welding parameters. Tensile strength and hardness testing of welded samples were performed. After mechanical tests, the fracture surfaces of welds were examined using scanning electron microscope (SEM) and discussed. The results showed that with increasing vibration force, the tensile strength and fracture strength of the specimens were welded during vibration, were increased by about 3 and 9 percent, respectively, compared to the non-vibrated weld sample. However, no significant change was observed in the hardness of the welded specimens. Mean grains size and heat affected zone of the sample was welded was welded with conventional GMAW, were about 200 μm and 1800 μm, but due to inducing vibration, as vibration force increased from 850 N to N 2200 N, Mean grains size was reduced to about 75 μm and HAZ was reduced from about 1000 μm to 700 μm, that is, about 44 to 61%.
Hamed Tirband, Davood Akbari, Mohammad Golzar,
Volume 7, Issue 1 (8-2021)
Abstract
In this research, tensile strength of ultrasonic welded parts made of thermoset polymer-reinforced glass fiber with surface preparation has been investiagted. In order to elevate the adhesion of two surfaces laser grooving method has been applied. Two type of thermoplastic materials including Plymethyl methacrylate (PMMA) and polypropylene (PP) have been used as interlayers. Influences of main welding parameters were investigated. The results show that the force and compression parameters in these joints have been ineffective parameters and in higher weld welds, the thermosetting resin has started thermal degradation. The pressure considered constant and set at 2 bar, welding time set at 1.6 seconds and holding time considered 3 seconds. The results showed that the minimum tensile strength of welded samples with laser surface preparation method is 1286 N, which is much more than maximum tensile strength of welded samples without any surface preapration. This indicates that laser beam surface preparation is an effective method in improving of the adhesion strength of thermoset polymeric parts.
Mojtaba Vakili-Azghandi, Ali Shirazi,
Volume 7, Issue 1 (8-2021)
Abstract
The results showed that the microhardness and tensile strength of the heat-affected zone as the weakest welding zone in some samples reduced up to 30% compared to the base metal. On the other hand, a decrease in rotational speed, an increase in tool movement speed, and the number of welding passes cause grain refinement and improve mechanical properties. However, the effect of decreasing the rotation speed and increasing the tool movement speed were shown to be more favorable due to less heat production. Accordingly, the hardness in the welded zone with a rotational speed of 600 rpm and a movement of 80 mm/min increased from 90 to 125 HV compared to the base metal, and the hardness reduction in the zones around the welded zone was only 5 Vickers. It was also found that reducing the grain size of the stir zone, while improving the mechanical properties leads to increasing the density of the surface pasive layer, preventing the attack of aggressive chlorine ions and thus reducing the corrosion intensity by 50 times in saline seawater.
Majid Aslani, Mahdi Rafiei,
Volume 7, Issue 2 (1-2022)
Abstract
In this study, in order to modify the weld structure obtained from repair welding of AZ91C magnesium alloy and improvement of tensile strength, input parameters such as current intensity and preheating temperature were optimized for this alloy. T6 heat treatment was separately done befor and after the welding to homogenize the microstructure and improvement of the mentioned properties. Using variance analysis, the accuracy of the models was checked and analyzed. Optical microscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and tensile tests were used to characterize the microstructure and mechanical properties of the repaired parts. The results of microstructural studies showed that the samples 2 (samples that were subjected to T6 heat treatment before and after welding) had continuous precipitates which these precipitates affected the strength due to the interruption of more slip planes and creating stronger barriers in the path of dislocations, resulting the better mechanical properties as compared with samples 1 (samples that were subjected to heat treatment only after welding). Also, by plotting response surface graphs and level diagrams, the highest tensile strength for samples 1 was observed at preheating temperatures of 493 to 513 K and current intensities of 80 to 90 A, and for samples 2 at temperatures of 513 to 553 K and current intensities of 100 to 110 A.
H. Tirband, D. Akbari, M. Sadeh,
Volume 8, Issue 1 (8-2022)
Abstract
Todays, application of composite materials has been increased in various industries due to their special strength properties and also other unique features. One of the important things during making of such materials, is their connection to each other. In this article, the Joining of heat-hardened parts with surface preparation with the help of laser, simple and rough, has been investigated. The main goal is to investigate the better surface adhesion mechanisms of the connection compared to the simple surface, as well as to create practical approaches to increase the adhesion strength of the thermosetting parts. The composites were made of heat-hardened epoxy resin (which hardens after 12 hours at room temperature) and two-dimensional woven glass fibers and were connected by glue after volume heating at a temperature of 180-200 degree Celsius. In this research, the overlapping surface of the part was engraved by laser in circular patterns. The raw parts were prepared by manual polishing and mechanical abrasion. The results show that by examining the effect of surface roughness and composite thickness, the highest value of shear strength is related to the surface roughness compared to other preparation methods. Surface preparation increases the amount of adhesive penetration in the parts and expands the tensile strength. The thickness also has a conditional effect on the strength of the connection.
