Sharif Digital Repository

Numerous advantages of application of tailor welded blanks (TWBs) in automobile industry, namely reduction of weight, fuel consumption and air pollution, have made the manufacturers eager to investigate in this field. On the other hand, while experiments generally provide valuable information in regard with mechanical behaviors, but utilization of simulation methods has extended vastly due to time and cost saving issues. One challenging issue in numerically analyzing the forming behavior of transversely welded TWBs, welded by laser welding methods, has been the presence of weld zone. While some researchers believe that during simulation, the weld zone can be neglected due to its minority and... 

In the present study, a special heat treatment cycle (step quenching) was used to produce a dual-phase (DP) microstructure in low carbon steel. By producing this DP microstructure, the mechanical properties of the investigated steel such as yield stress, tensile strength, and Vickers hardness were increased 14, 55, and 38%, respectively. In order to investigate the effect of heat treatment on formability of the steel, Nakazima forming test was applied and subsequently finite element base modeling was used to predict the outcome on forming limit diagrams. The results show that the DP microstructure also has a positive effect on formability. The results of finite element simulations are in a... 

In order to analyze the flow behavior and workability of Ni–42Cu in cast and wrought conditions, hot deformation tests were performed at temperatures and strain rates within the ranges of 900–1150 °C and 0.001–1 s−1, respectively. Tensile tests showed a “hot ductility trough” at 950 °C for both alloys. The drop in hot ductility was more considerable in the cast alloy because of the sluggish dynamic recrystallization. The hot ductility drop and grain boundary cracking, particularly in the cast alloy, were attributed to the segregation of detrimental atoms to the boundaries. It was shown that the hot ductility of the wrought alloy could be improved with increasing strain rate. It was... 

The effects of sheet thickness and frictional condition between the punch and sheet on formability is predicted and compared with the experimental results of the Erichsen test as a stretch-forming process. The material and geometrical nonlinearity are considered. A hypoelastic-plastic model is used and strain-field stabilization is taken into account using the Assumed Strain Finite-Element Method. By considering the contact problem and applying the nonlinear finite-element method, the force and dome height for aluminum and steel sheets are computed and compared with the experimental results. The Oyane criterion is used to access the formability of the sheet. A good agreement was found... 

This article presents a crystal plasticity methodology to evaluate the AA1050 sheet formability. In order to determine the orientation distribution of the crystals, initial texture of the material is measured through X-ray diffraction technique. Also, the stress-strain behavior of the material is determined by performing tensile test. In order to simulate the path-dependent crystal plasticity behavior of body-centered cubic crystal structures, a UMAT subroutine that employs the rate-dependent crystal plasticity model along with the power law hardening was developed previously by the authors and linked to the finite element software ABAQUS. This subroutine was further developed to simulate... 

In this study, the mechanical properties, formability and forming limit diagrams (FLDs) of the tailor-welded blanks (TWBs) produced by friction stir welding (FSW) were analyzed experimentally. At first, the suitable FSW parameters were achieved. The formability and FLDs of TWBs were evaluated for sheets with the same or different thicknesses and compared to the base metal sheet. This study was performed on low carbon steel (St14) sheets with a lot of applications in automobile industries. The welded zone properties were evaluated by some experiments. The tensile test, micro hardness testing, and metallographic studies were done. The effect of welding seam directions on formability and FLD... 

In this article, we investigated the effect of martensite morphology on the mechanical properties and formability of dual phase steels. At first, three heat treatment cycles were subjected to a low-carbon steel to produce ferrite–martensite microstructure with martensite morphology of blocky-shaped, continuous, and fibrous. Tensile tests were then carried out so as to study mechanical properties, particularly the strength and strain hardening behavior of dual phase steels. In order to study the formability of dual phase samples, Forming Limit Diagram was obtained experimentally and numerically. Experimental forming limit diagram was obtained using Nakazima forming test, while Finite Element... 

In this article, we investigated the effect of martensite morphology on the mechanical properties and formability of dual phase steels. At first, three heat treatment cycles were subjected to a low-carbon steel to produce ferrite–martensite microstructure with martensite morphology of blocky-shaped, continuous, and fibrous. Tensile tests were then carried out so as to study mechanical properties, particularly the strength and strain hardening behavior of dual phase steels. In order to study the formability of dual phase samples, Forming Limit Diagram was obtained experimentally and numerically. Experimental forming limit diagram was obtained using Nakazima forming test, while Finite Element... 

Failure in sheet metal forming can occur by necking, fracture or wrinkling. By using a forming limit diagram (FLD) as a powerful tool to prevent sheets metal failures in the forming process, provides parameters controlling throughout forming. There are different developed methods for predicting FLDs, which estimate sheet metal forming strains limits. Assessment of FLD estimation reveals that there is a dependency between the effect of several factors containing normal stress, shear stress, sheet thickness, mechanical properties, metallurgical properties, yield function, strain path, and bending with formability. In this research, the effects of bending via two finite element models are... 

Recently, isogeometric methodology has been successfully implemented in one-step inverse analysis of sheet metal stamping processes. However, these models are not capable of analyzing forming processes which require severe deformation and/or several forming stages. This paper presents a multi-step inverse isogeometric methodology to enhance the precision of one-step models in predictions of the initial blank, strain distributions, and drawability of the formed parts. This methodology deals with the minimization of potential energy, deformation theory of plasticity, and considering membrane elements. The presented methodology utilizes the NURBS basis functions to create the final, middle, and... 

Dual phase steels (DPS)s have a microstructure consisting of a hard second phase called Martensite in the soft Ferrite matrix. In recent years, there has been interest in dual-phase steels, because the application of these materials has made significant usage; particularly in the automotive sector Composite microstructure of (DPS)s exhibit interesting characteristic mechanical properties such as continuous yielding, low yield stress to tensile strength ratios(YS/UTS), and relatively high formability; which offer advantages compared with conventional high strength low alloy steels(HSLAS). The research dealt with the characterization of damage in (DPS)s. In this study by review the mechanisms... 

Metal forming processes are widely used in industrial productions, automobile bodies, food industries, oil refineries, and liquid and gas transmission systems. Analyzing these processes is very important to reduce wastes and optimize the processes. Study of some main factors such as physical and mechanical properties of material and its formability, die geometry, die material, lubrication and pressing speed has been the topic of many research projects. In this paper, forming limit diagrams (FLDs) for LC and ULC steels and the effect of different parameters like the work-hardening exponent, n, and the plastic strain ratio, r, on these diagrams have been evaluated and simulated using... 

Isolation and characterization of circulating tumor cells (CTCs) found in blood samples of cancer patients have been considered as a reliable source for cancer prognosis and diagnosis. A new continuous microfluidic platform has been designed in this investigation for simultaneous capture and characterization of CTCs based on their deformability. The deformability-based chip (D-Chip) consists of two sections of separation and characterization where slanted weirs with a gap of 7 μm were considered. Although sometimes CTCs and leukocytes have the same size, the deformability differs in such a way that can be exploited for enrichment purposes. MCF7 and MDA-MB-231 cell lines were used for the...