International Journal of Material Forming最新文献

Deep rolling has advantages to modify local residual stresses in AA2024 sheets. A previous study about deep rolling for tailoring residual stresses [1] is extended in order to examine the homogeneity of the residual stress field. For the experimental residual stress analysis, the incremental hole drilling method with electronic speckle pattern interferometry is used with two different drill diameters. A numerical evaluation scheme is applied to simulation results of an existing process model with the aim of mimicking the experimental analysis technique. The volume under the deep rolled surface is classified in three sections based on the history of the process. Comparisons between experimental and simulative results yield a number of observations: Deeper evaluation with higher driller diameter does not come at a price of higher in-plane averaging of spatial gradients. Simulating a number of paths lower than those of the experiments shows similar homogeneity of the simulatively and experimentally analyzed stress field. Stretching the evaluation scheme from cylindrical volumes to cubic volumes shows very good qualitative agreement and validates the choice of classification.

The complete parameterization of complex anisotropic material models for forming simulation of tubes presents significant challenges due to the inherent limitations of tube material testing. Furthermore, the impact of anisotropic material behavior on the hydroforming process, along with the relevance of specific parameters, remains inadequately understood. This study aims to investigate how selected parameters within elastic-visco-plastic anisotropic material models influence hydroforming simulations. Sensitivity analyses are conducted across three distinct characteristic hydroforming geometries, employing a zone-based approach to enable systematic comparison of parameter sensitivities and their correlation with the underlying hydroforming geometries. The results reveal substantial variations in sensitivity driven by differences in plastic strains, diverse strain or stress states, and interactions between neighboring zones. For accurate material modeling of E235 carbon steel tubes in hydroforming applications, determining the true stress–strain curve is basically important. Additionally, experimental quantification of strain rate sensitivity (p), uniaxial yield stress ({sigma}_{90}), and biaxial yield stress ({sigma}_{b}) is essential for ensuring simulation precision.    

Single point incremental forming (SPIF), which is a method that can be controlled by CNC processes without the need for a mold, as in traditional sheet metal forming, reduces costs and is suitable for low production series. In this study, the thickness change, surface roughness, and spring-back behaviours of AA5754-H22 alloy, which is widely used in many industries, especially in aviation and automotive, after forming with the SPIF method, were experimentally investigated. The geometric shape used in the study is hexagonal. The study was carried out using the parameters of increment (0.25, 0.5 mm), feed rate (500, 1000 mm/min), spindle speed (1000, 1500 rpm), tool diameter (6, 10 mm), wall angle (50, 55°), lubricant (machine oil, sunflower oil). The results were analysed after the experiments were conducted using an L16 orthogonal experimental design with the Taguchi method, and variance analysis was performed. As a result of the experiments, it was determined that the most important parameter affecting the wall thickness was the wall angle with a rate of 95.33%, the most important parameter affecting the surface quality was the tool diameter with a rate of 70% and the most important parameter affecting the spring-back was the wall angle with a rate of 52.76%. From here, it was understood that the parameters affecting the spring-back were in a wider range. In addition, when all the results were taken into consideration, it could be said that the most effective parameter was the wall angle.

The aims of present work are to apply the Bressan-Barlat mathematical model to predict the FLC curve and the proposed new equations of r-values to accurately predict the Lankford and the equal biaxial stress coefficients of anisotropy in sheet metal forming operations, using the non-associated Barlat´s Yld 2000-2d plastic potential. The Forming Limit Curve by shear stress fracture, FLC-S, was predicted employing Bressan-Barlat critical shear stress criterion combined with the non-associated Barlat´s Yld 2000-2D plastic potential. The predicted coefficients of anisotropy were calculated and validated by the new Bressan´s anisotropy equations in conjunction with the Lankford and equal biaxial stress material anisotropy parameters, r-values, and the non-associated Barlat´s Yld 2000-2d plastic potential. New Barlat´s coefficients of anisotropy a_i were defined and calibrated from material experimental data of r-values for specimens under simple uniaxial tension and equal biaxial stress tests. The examined distinct metal alloys were the highly anisotropic AISI 439 steel sheets and AA 6016-T4 aluminium sheets presented in the ESAFORM 2021 cup drawing benchmark articles obtained from published literature. In the results analysis and discussion, the new coefficients of anisotropy of the Barlat´s non-associated plastic flow rule were calculated and validated by plotting on the same graph the predicted r-value and s-value curves and experimental data for the anisotropic steel sheets. Correlation analyses have revealed that the Barlat´s yield criterion and the plastic flow stress potential were not coincident. Prediction of FLC-S of AISI 439 steel was quite good, when using the Bressan-Barlat shear stress fracture criterion combined with the non-associated Barlat´s Yld 2000-2d plastic stress potential. For both AISI 439 and AA 6014-T4, the non-associated Barlat´s Yld 2000-2d flow rule, calibrated by 7 r-values, provided a better fit to the experimental Lankford and equal biaxial coefficients of anisotropy. Exponent m = 10 was excellent and improved prediction accuracy over m = 8 for the AA 6014-T4.

Multi-pass compression deformation experiments for a high-strength container steel have been conducted on the DIL805A/D thermal expansion instrument. The true stress- plastic strain curves of experimental steel were plotted. Three typical flow stress models are used to predict the flow stress of the first pass deformation, and Model-1 flow stress model with the highest fitting accuracy is selected as the basic model form. Also, high precision static recrystallization volume fraction model and austenite grain size model have been established. The genetic algorithm is used to optimize the parameters in Model-1 model according to the second pass flow stress data. The relationships between static recrystallization volume fraction, the initial austenite grain size, the dislocation density before deformation, the deformation temperature, the strain rate and the model parameters are established through the Support Vector Machine (SVM) algorithm. The established flow stress model not only has high accuracy but also conforms to physical metallurgical principles under multi-pass steel deformation conditions according to a maximum plastic strain of 0.25. The research results can provide an important theoretical guidance for the load distribution of the rolling mill for the production of high-strength container plate.

Robo-forming is a flexible version of Incremental Sheet Forming (ISF) that utilizes industrial robots to guide the forming tool along a desired trajectory on a blank surface. ISF is particularly suitable for rapid prototyping and low-volume production; however, the process is limited by a critical wall angle, beyond which the material fails by necking. Geometric shapes that exceed this critical wall angle have to be formed in multiple stages, adhering to the maximum limit of wall angle in each of the intermediate stages. Since the final outcome depends upon the intermediate shapes formed, it is essential to optimize the design of pre-form shape(s). The existing methods for multi-stage forming rely heavily on intuition and other heuristics for preform design. The current work proposes a frequency decomposition based approach using Fourier transform to generate preforms. The proposed multi-stage methodology presents a more standardized, algorithmic approach, ensuring an effective and reliable methodology that can be applied to any new complex shape. Experimental results demonstrate that the forming depth of the target geometries has improved significantly up to (235%) for the human cranial implant shape (a freeform shape) and by (155%) and (173%), respectively, for hemispherical and elliptical components compared to the case without preform, ensuring successful forming of the components without fracture.

Research results for the production of strips from a platinum‒rhodium alloy for the manufacture of spinneret feeders are presented. Using the author’s software, an analysis of the process of rolling strips of the investigated alloy with a thickness of 1 mm from a forged workpiece with a thickness of 28 mm, which is currently used in industrial conditions, was carried out. The number of rolling passes and the number of annealing steps decreased. Experiments for the process of cold sheet rolling of strips from the platinum‒rhodium alloy were carried out. The proposed compression mode was tested under industrial conditions, and it was found that for the studied process of cold sheet rolling of a platinum‒rhodium alloy, it is possible to increase the unit degree of deformation to 0.3–0.4 mm, which leads to a decrease in the fractional deformation, a decrease in the number of anneals and passes in the absence of strip destruction.

Galvanized steel has been widely used in industrial fields such as automobiles, ships, and household appliances. Due to its anti-corrosion properties, galvanized steel samples have lower corrosion rates and toughness losses. Therefore, using galvanized steel sheets is an effective way to improve the quality of welded joints. Nowadays aluminum alloy is gradually replacing steel as the raw material for industrial products due to its lightweight and corrosion-resistant properties, aluminum alloys have disadvantages in terms of cost and mechanical properties. Multi-material structures in industrial products (especially in automotive components) to fully utilize the advantages of steel and aluminum alloys. There are many ways to achieve steel/aluminum dissimilar metal connections. Due to the high welding temperature and poor welding environment, a high volume fraction of Al-Fe-Si intermetallic compounds precipitates at the welding interface, resulting in higher hardness at the welded joint and strong local corrosion. High-speed impact welding can effectively avoid these problems. At low welding temperature and high impact speed, minimal metal melting occurs at the interface while the base material deforms in solid state, forming a characteristic wavy bond morphology. Therefore, the coating will affect the morphology and component content of the welding interface during the impact joining process. In this paper, the effects of Zn coating on the welding interface will be investigated and the joint interface formation process will be clarified by using a method that combines numerical simulation and experiment, in order to instruct the processing design.

The Single Point Incremental Forming (SPIF) technique has received considerable recognition for its improved formability, versatile process capabilities, and diminished forming forces. Nevertheless, its widespread industrial adoption remains limited due to challenges in accurately predicting fracture during forming. This study addresses these challenges by examining the formability and damage mechanisms of a ferritic steel matrix composite reinforced with TiB₂ ceramic particles. By leveraging advanced materials and computational methods, our research focuses on optimizing the SPIF process for these composites, renowned for their exceptional mechanical properties. We analyze three critical process parameters—blank thickness, forming tool diameter, and wall angle of the cone—to evaluate their influences on deformation mechanics and process performance. Numerical simulations generate response surfaces to optimize forming parameters, focusing on punch force, equivalent plastic strain, Von Mises stress, and final forming depth. Employing a desirability function approach, we tackle this multi-objective optimization, providing a robust framework for parameter selection. This study demonstrates the potential of TiB₂-reinforced steel matrix composites in advanced forming applications and highlights the optimal SPIF conditions for achieving superior formability while minimizing damage. The findings offer valuable insights for industries working with innovative composite materials and advancing manufacturing efficiency.