Spot Resistance Welding of St12 and HSLA Steels in Different Thicknesses

, M.Sc. Thesis Sharif University of Technology Farhangdoust, Sajad (Author) ; Kokabi, Amirhosein (Supervisor) ; Ekrami, Aliakbar (Supervisor)

Abstract

High-strength low alloy (HSLA) E275 developed specifically for automotive application. Also St12 Steel is used in autobodies. On the other hand the resistance spot weld of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. The influence of the primary welding parameters affecting the heat input such as; current and time on the morphology, fracture mode, microhardness, and tensile shear load bearing capacity of dissimilar welds between HSLA E275 steel and St12 steel in two different thicknesses (1,2 mm) has been investigated in this study which consisted six group. The...

High-dimensional data analytics for sparse recovery of guided-waves dispersion curves using b-splines

, Article Structural Health Monitoring 2023: Designing SHM for Sustainability, Maintainability, and Reliability - Proceedings of the 14th International Workshop on Structural Health Monitoring ; 2023 , Pages 796-803 ; 978-160595693-0 (ISBN) Momeni, H ; Jeddi, M ; Ebrahimkhanlou, A ; Farhangdoust S ; Guemes A ; Chang F. K ; Sharif University of Technology

DEStech Publications 2023

Abstract

This research presents a technique to recover the dispersion curves of guided-waves by utilizing the inherent sparsity of these signals in the frequency-wavenumber domain. The proposed methodology is a data-driven approach that combines physics-based knowledge with high-dimensional analysis to obtain the dispersion curves of the medium from experimental signals. Initially, a sparse two-dimensional dispersion matrix is constructed using sparse wavenumber analysis. Then, B-splines are fitted to non-zero elements of this matrix to establish an initial estimate of the dispersion curve parameters. These parameters are further optimized using the quasi-Newton algorithm to improve the accuracy of...

Adversarial Attack to Deep Learning Networks via Imperceptible Sparse Perturbation

, M.Sc. Thesis Sharif University of Technology Heshmati, Alireza (Author) ; Ghaemmaghami, Shahrokh (Supervisor) ; Marvasti, Farokh (Supervisor) ; Amini, Sajad (Co-Supervisor)

Abstract

Nowadays, methods based on deep learning networks are the most effective artificial in telligence methods. Although they have achieved success in various fields (such as machine vision and object recognition), practical and experimental cases show the fragility of deep learning networks against perturbations and unwanted changes of the input pattern. All these perturbations must be in a way that the main class of the perturbed input pattern can be rec ognized by human, but the network makes a mistake in recognizing its correct class. This thesis seeks a more accurate evaluation by designing adversarial attacks such that the main class of the adversarial pattern is detectable by human...

Mechanical characteristics improvement of spot-welded dissimilar steels in different thickness

, Article Proc. of the Int. Conf. on Advances in Welding Science and Technology for Construction, Energy and Transportation, AWST 2010, held in Conj. with the 63rd Annual Assembly of IIW 2010, 11 July 2010 through 17 July 2010, Istanbul ; 2010 , Pages 803-810 ; 9786056141911 (ISBN) Farhangdoust, S ; Kokabi, A. H ; Adineh, A ; Mansourzadeh, S. A ; Ghasemzadeh, H ; Ardakani, R. T ; Sharif University of Technology

2010

Abstract

Resistance spot welding of dissimilar materials especially in different thickness is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. And also when the part is under static and dynamic forces the health of spot-welds is crucial. Hence, the influence of welding parameters such as current, time, applied force and hold time on the shear-tensile load has been investigated in this study. Moreover, in this research the case study is one of the most important body parts of the vehicle which is front wheel house, and effect of above-mentioned parameter on the strength of spot-welds has been...

Dynamic response of metal foam FG porous cylindrical micro-shells due to moving loads with strain gradient size-dependency

, Article European Physical Journal Plus ; Volume 134, Issue 5 , 2019 ; 21905444 (ISSN) Sajad Mirjavadi, S ; Forsat, M ; Barati, M. R ; Abdella, G. M ; Mohasel Afshari, B ; Hamouda, A. M. S ; Rabby, S ; Sharif University of Technology

Springer Verlag 2019

Abstract

The dynamic characteristics of functionally graded (FG) metal foam cylindrical micro-scale shells in contact with a moving load will be analyzed thorough this paper accounting for strain-gradient size-dependency. In the material structure of a metal foam, pores can diffuse uniformly or non-uniformly. Based upon Laplace transform, the dynamical governing equations of the first-order micro-shell model can be established in a new domain. In order to go back into the time domain, an inverse Laplace transform will be required. Thus, on can express the time response or dynamic deflection of the micro-shell under moving load. In the presented results, it is easy to see the prominence of...