جستجوی مقالات مرتبط با کلیدواژه « نمودار حد شکل دهی » در نشریات گروه « مواد و متالورژی »

Ferrite - martensite dual-phase (DP) steels are a subset of advanced high strength steels which can be produced by applying heat treatment on low-carbon steels. The strength and toughness of DP steels are greater than those in ferrite – pearlite steels with the same chemical composition. In this study, mechanical properties and forming limit diagram of ferrite – pearlite and DP steels with the same chemical composition were investigated and compared. For this purpose, inter-critical quenching heat treatment was applied on a low-carbon steel with ferrite – pearlite microstructure to produce ferrite – continuous martensite DP steel. Tensile and hardness tests were used to determine the mechanical properties, and Nakazima test was used to determine the formability of ferrite – pearlite and DP steels. Forming limit diagram of steels was also simulated using finite element method in macro scale, and compared with experimental results. The results of mechanical tests showed that the yield stress, tensile strength and hardness of produced DP steel were increased 65, 91, and 87% respectively, in comparison to the same mechanical properties of ferrite – pearlite steel. Based on Experimental and simulation results of Nakazima test, the formability of DP steel is better than ferrite – pearlite steel. There was good agreement between simulation and experimental results.

Forming limit diagram (FLD) is an effective tool to evaluate the limiting strain in various conditions. In this study the formability of tantalum has been investigated and led to forming limit diagram of tantalum. For this propose three groups of tests has been carried out on the tantalum. At first، Erichsen test has been performed on sheets of tantalum to obtain the forming limit diagram (FLD). Then for evaluating the result of Erichsen test، compression test has been carried out. The obtained FLD of Erichsen test presented a good conformity with the FLD from compression test. In addition، the strain-hardening exponent، n، for tantalum has been obtained from tensile test. The n value from results of tensile test is close to the minimum point of forming limit diagram that indicate the strain-hardening exponent.

Forming limit diagrams (FLDs) are very powerful tool for prediction of the formability of sheet metals. However, it has been shown that FLD diagrams are valid only for proportional loadings during which the ratio between the principal stresses remains constant throughout the forming process. Therefore, forming limit stress diagrams (FLSDs), which are independent of the straining path, have been developed. In this work, the forming limit diagram for aluminum alloy 3105 was first obtained experimentally using the Nakazima out-of-plane test. The forming limit stress diagram was then calculated by the application of plasticity theory. In addition, the FLDs and FLSDs for AA3105 were simulated using ABAUUS finite element software through the application of a ductile fracture criterion. The results showed that the diagrams obtained by the application of the ductile fracture criterion are relatively in good agreements with the experimental results, and hence, can be successfully used for the prediction of forming limit diagrams of the aluminum alloys.