Blow Forming Research Articles

Improving the Prediction of Part Thickness in Superplastic Forming Process of Ti–6Al–4V Alloy Using an Appropriate Constitutive Equation

Superplastic alloys, such as Ti–6Al–4V, are a group of polycrystalline materials which can undergo large elongation in special conditions. By this specific characteristic, superplastic forming can be carried out to manufacture products with complicated shapes. Superplastic forming, in comparison with other similar processes, has a good capability to produce parts with uniform thickness; however, in superplastic blow forming, the final part does not have a uniform thickness distribution, and the prediction of the part thickness has a great significance to the process designers. Numerical methods are used to predict thickness distribution in final part and to improve it by suggesting a precise pressure–time diagram. In this regard, the constitutive equation plays a significant role in predicting the process performance. In the present study, superplastic blow forming has been simulated for a cone-shaped part via using commercial finite element code Abaqus and implementation of a proper constitutive equation by user subroutine UMAT. The constitutive equation considers grain growth hardening effects in addition to strain rate effect. A new method is also proposed to predict pressure–time diagram when UMAT subroutine is used. The effects of the process parameters on this diagram have also been investigated. Comparison between the findings of this research and those conducted by other researchers revealed that considering grain growth hardening has a significant role in the improvement of the accuracy of thickness distribution predictions.

EFFECT OF WIND LOAD ON TALL BUILDINGS IN DIFFERENT TERRAIN CATEGORY

Wind is a perceptible natural motion of air relative to earth surface ,especially in the form of air current blowing in a particular direction. The major harmful aspect which concern to civil engineering structures is that, it will load any and every object that comes in its way. Wind blows with less speed in rough terrain and higher speed in smooth terrain . This paper presents displacement accour in different storey due to wind in different terrain category. Three models are analyse using ETABS 2015 package. Present works provides a good source of information about variation in deflection as height of model changes and percentage change in deflection of same model in different terrain category.

Coarse-grained superplasticity and gas blow forming of commercial AZ31 magnesium alloy sheet

Superplasticity of commercial AZ31 magnesium alloy sheet has been investigated at strain rate range of 0·7 × 10−3–1·4 × 10−1 s−1 and temperature range of 523–673 K. Hot uniaxial and equi-biaxial tensile tests are carried out. The maximum elongation of 362% has been obtained at the temperature of 673 K and strain rate of 0·7 × 10−3 s−1. The calculation of activation energy Q and examination of microstructures show that the deformation mechanism of commercial AZ31 magnesium alloy is dissimilar at different conditions. With the decreasing of temperature and increasing of strain rate, the deformation mechanism is converted from grain boundary sliding controlled by grain boundary diffusion to the mix of grain boundary sliding and plastic or/and creep deformation controlled by lattice diffusion. In the free bulging tests, the hemisphere has been formed successfully and for the components, the failure reason is the growing and connecting of the cavities.

Modified male die rapid gas blow forming of fine-grained Mg alloy AZ31B thin sheet

Gas blow forming of a commercial, fine-grained, 0.6-mm-thick Mg alloy AZ31B thin sheets under high strain rates to decrease the forming time was investigated in the present work. An innovative male die rapid gas blow forming method was developed. Using this new method and stepwise pressurization profiles, alloy sheets were successfully deformed to form shallow rectangular pans. Deformation characteristics of rapid gas blow forming were discussed. Results indicated that the proposed process significantly reduces the forming time and that a shallow rectangular pan may be formed under a maximum average strain rate of approximately 10−2 s−1. A 10-mm-high rectangular pan was formed in <109 s. Sheet thinning was improved by modified male die forming. The fillet radius of the rectangular pan was found to be one of the key factors that influence the rapid gas blow forming time. Strain-enhanced grain growth was the major growth mechanism during rapid gas blow forming. Grain growth and cavitation were not serious problems during rapid gas blow forming.

A study on tensile shear strength of IN 718 welded joint

It is well known that nickel-based superalloys are suitable for the high-temperature applications, like turbine blades and discs in aircraft engines and power generation plants. Due to the high cost of manufacturing and repairing with difficulty using conventional mechanical processing, the joining of superalloys has been of a major concern to the aerospace and nuclear industries. Fusion welding is one of the desirable methods and has been investigated with a major problem of the formation of hot cracks, while as other solid state welding technologies, like diffusion bonding or brazing, normally require long bonding times with extra heat treatments. Present work studies the tensile shear strength of welded specimens of Inconel® alloy 718 with electron beam welding, laser beam welding, diffusion bonding and hot isostatic pressing. The purpose was to determine the optimum welding method for overlap bonding of Inconel® alloy 718 for superplastic blow forming.

Superplastic Forming of Friction Stir Welded AA6061-T6 Alloy Sheet with Various Tool Rotation Speed

This study attempts to investigate the superplastic forming (SPF) of friction stir welded (FSW) AA6061-T6 alloy sheet at various tool rotation speeds in the range of 500 to 2000 rpm. The effect of FSW on SPF free blow forming of AA6061-T6, pole height, pole thickness, equivalent strain rate, and equivalent flow stress were investigated at constant pressure and constant temperature. Using the Cheng model the pole thickness, the equivalent strain rate, and equivalent flow stress were determined from superplastic free blow forming experiment. The finite element modeling and simulation is performed over the SPF of FSW specimens using selective superplasticity method. Experimental results indicate that tool rotation speed is the critical parameter during friction stir welding that has a greater influence on SPF. The theoretical modeling results exhibit that the SPF of friction stir welding can be practically applied to determine pole thickness, strain rate, flow stress, and strain rate sensitivity index. The finite element modeling results were found to be fairly agreeing with the experimental results. Hence, superplasticity can be significantly enhanced by friction stir welding by varying the FSW tool rotation speed.

Progress in aerodynamic and aeroacoustic integration of CROR propulsion systems

AbstractContra-Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as an economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the past five years, DLR’s Institute of Aerodynamics and Flow Technology has performed a number of numerical studies investigating important aspects relating to engine-airframe integration of CROR engines. In this article an overview of coupled aerodynamic and aeroacoustic simulations investigating representative pusher-configuration CROR engines will be given, focusing on the impact on aerodynamic performance and aeroacoustics caused by the presence of a pylon, the potential for noise reduction by employing trailing-edge blowing at the pylon trailing edge as well as the performance and noise variations caused by different senses of rotation of the rotors. It is shown that the interaction with the pylon strongly impacts blade performance and front rotor noise emissions but that the use of active flow control in the form of pylon trailing-edge blowing can alleviate these adverse installation effects to a notable extent.

Numerical Shape Optimization in Industrial Glass Blowing

Industrial glass blowing is an essential stage of manufacturing hollow glass containers, e.g., bottles, jars. A glass preform is brought into a mold and inflated with compressed air until it reaches the mold shape. A simulation model for blowing glass containers based on finite element methods, which adopts a level set method to track the glass–air interfaces, has previously been developed [Giannopapa and Groot, 2007, “A Computer Simulation Model for the Blow–Blow Forming Process of Glass Containers,” Paper No. PVP2007-26408, pp. 79–86; Giannopapa, C. G., 2008, “Development of a Computer Simulation Model for Blowing Glass Containers,” ASME J. Manuf. Sci. Eng., 130(4), p. 041003; Giannopapa and Groot, 2011, “Modeling the Blow–Blow Forming Process in Glass Container Manufacturing: A Comparison Between Computations and Experiments,” ASME J. Fluids Eng., 133(2), p. 021103]. A considerable challenge in glass blowing is the inverse problem: to determine an optimal preform from the desired container shape. In previous work of the authors [Groot et al., 2009, “Numerical Optimisation of Blowing Glass Parison Shapes,” ASME Paper No. PVP2009-77946; Groot et al., 2011, “Development of a Numerical Optimization Method for Blowing Glass Parison Shapes,” ASME J. Manuf. Sci. Eng., 133(1), p. 011010] a numerical method was introduced for optimizing the shape of the preform. The optimization method described the shape of the preform by parametric curves, e.g., Bezier-curves or splines, and employed a modified Levenberg–Marquardt algorithm to find the optimal positions of the control points of the curves. A combined finite difference and Broyden method was used to compute the Jacobian of the residual with respect to changes in the positions of the control points. The objective of this paper is to perform an error analysis of the optimization method previously introduced and to improve its accuracy and performance. The improved optimization method is applied to modeled containers of industrial relevance, which shows its usefulness for practical applications.

Superplastic Blow Forming of Aerospace Components

Many metals, such as titanium and superalloys, are used for a wide range of aerospace applications, which include aircraft gas turbine engine and space launcher propulsion engine. In order to manufacture a stiffened extension with superplastic blow forming at elevated temperature, the structural integrity of the joint part was investigated since the welded or bonded joint of internal channels should maintain its strength during superplastic blow forming process. Various types of joint methods were performed in order to investigate microstructural and mechanical properties of the bonded specimen at elevated temperature. In this paper, the possibility of manufacturing combustion chamber and other aerospace components with superplastic blow forming of titanium and superalloy was demonstrated. An innovative manufacturing method to produce complex configuration from titanium multi-sheets by superplastic forming with low hydrostatic pressure was presented. The result also shows that the manufacturing method with superplastic blow forming of multi-sheets of IN718 alloy has been successfully demonstrated for near net shape forming of subscale nozzle extension cone with internal channels.

Everyday Aggression Takes Many Forms

Aggression can take a variety of forms; people hurt one another in a variety of ways. This article summarizes a research program that has examined several questions regarding how people harm one another in their day-to-day lives. The evidence shows that (a) the people that we interact with most frequently (e.g., family members, friends, romantic partners) are the most likely to make us angry; (b) we can hurt people by direct (e.g., physical or verbal attack) or nondirect action (e.g., spreading rumors, giving someone the silent treatment); and (c) the way we hurt people depends on our relationship with them. Whether the harm takes the form of words or blows, aggression is harmful to individuals and to relationships.

FEM Study of Superplastic-Like Forming of Ti-6Al-4V Alloy

A superplastic-like forming (SPLF) process involving the use of hot drawing along with blow forming is studied here. The hot drawing stage helps in enhancing the formability and in fast forming the metal sheet into a hollow shape with desired amount of material draw-in. During the blow forming stage, gas pressure was applied onto the pre-formed part to complete the forming process at a targeted strain rate. Ti-6Al-4V sheets have been successfully formed by this process at 800 °C in 16 min. In this paper, finite element modeling (FEM) was used to demonstrate the effects of each stage (hot drawing and blow forming) during SPLF. A plasticity model based on tensile test data was adopted as a material model for simulation. The pressure cycle which was predicted from the simulation has been used in the process to maintain the sheet forming at an average strain rate (e.g. 10-3, 5×10-4 and 10-4 s-1. Experimental measurements, i.e. material draw-in and thickness distribution, were used to compare and validate the results from simulations. The validated simulations have shown the capability of the model to be used for the forming process. The influences of varying process parameters, such as drawing stroke, blank-holder force, friction coefficient and pressure cycle, were investigated by the simulations. It was found that the punch geometry and drawing stroke played significant roles on the thickness uniformity of the final part, from which an optimized hot-drawing system that could result in minimum thinning has been designed by FEM.

Combinatorial development of bulk metallic glasses

The identification of multicomponent alloys out of a vast compositional space is a daunting task, especially for bulk metallic glasses composed of three or more elements. Despite an increasing theoretical understanding of glass formation, bulk metallic glasses are predominantly developed through a sequential and time-consuming trial-and-error approach. Even for binary systems, accurate quantum mechanical approaches are still many orders of magnitude away from being able to simulate the relatively slow kinetics of glass formation. Here, we present a high-throughput strategy where ∼3,000 alloy compositions are fabricated simultaneously and characterized for thermoplastic formability through parallel blow forming. Using this approach, we identified the composition with the highest thermoplastic formability in the glass-forming system Mg-Cu-Y. The method provides a versatile toolbox for unveiling complex correlations of material properties and glass formation, and should facilitate a drastic increase in the discovery rate of metallic glasses.

Formability and Grain Size of AZ31 Sheet in Gas Blow Forming Process

Initial microstructural effect on mechanical properties and high temperature formability was investigated by experiments such as uniaxial tensile test at room temperature and 400°C and biaxial gas blow forming at 400°C. To observe distinct microstructural effect, three types of AZ31 alloy sheets which have different average grain size as 16.41μm (type-A), 11.02μm (type-B), and 7.58μm (type-C) were investigated. Among the three types of AZ31 alloy sheets, Type-A and Type-B was the partially hardened specimens containing twins (AZ31-H) and Type-C was fully annealed specimen with equiaxed grains (AZ31-O). At room temperature tensile test, initial microstructural features such as twin density, dislocation density, and grain size affected mechanical properties. However at 400°C tensile test and gas blow forming, only initial grain size affected mechanical properties due to the fact that the original microstructures of AZ31-H alloy sheets evolved into recrystallized microstructures with equiaxed grains. Accordingly, AZ31-H magnesium alloys, which have improved mechanical properties at room temperature, could not affect superplastic formability and mechanical properties of post-superplastic formed microstructures.

Blow Forming of Steel and IN718 for Propulsion Components

Blow forming technology has been used to produce glass and plastic components with easy and simple process. In order to apply this technology to metallic system, relatively high formability of material and elevated temperature are required. Since the blow forming temperature is quite high for metallic system, the main difficulty is to obtain adequate mold material which can sustain pressure difference between inside and outside of the tool. The present study demonstrates blow forming process with IN718 and steel can be applied to manufacturing of combustion chamber in liquid propellant rocket engine with complex shape. The result shows that the developed technology to process design of high temperature blow forming by the finite element method can be applied for near net shape forming of a combustion chamber of liquid rocket engine and a cone-shaped chamber extension part with cooling channels.

Process optimization and microstructural development during superplastic-like forming of AA5083

An advanced sheet forming process was utilized by combining hot drawing and blow forming to establish a fast forming technology. As a continuation of the development in superplastic-like forming, this study dealt with the process optimization and evaluation of post-forming properties. Aluminum alloy 5083 (AA5083) parts with near-net shape were successfully fabricated at 400 °C. Thickness uniformity has been improved by optimizing the mechanical preforming (hot drawing) and adopting a strain-rate-control gas forming (blow forming). Fairly uniform microstructure can be achieved with this forming process. To investigate the microstructural information, the annealed and hot deformed samples were characterized using electron backscatter diffraction technique. Fine grains with high-angle grain boundaries occurred near the elongated grains during hot drawing stage as a result of dynamic recrystallization. Subgrain structure was also examined by characterizing the distribution of grain boundary misorientation angles. Grain growth and subgrain boundary migration were two main microstructural features observed during the gas forming stage.

High Strain Rate Blow Formability of Newly Developed Al-Mg-High-Mn Alloy

Blow forming accompanied with superplasticity makes possible the forming of complex parts, which cannot be formed by cold press forming. The conventional superplastic AA5083 alloy ‘ALNOVI-1’ developed by the Furukawa-Sky Aluminum Corp. shows high superplasticity because of its fine grain and is widely used for blow forming. However, for mass production of components, an Al-Mg alloy with finer-sized grains is needed. In this research, the newly developed high Mn version of the Al-Mg alloy ‘ALNOVI-U’ is used, and this material possesses grains finer than those of the conventional AA5083 alloy. The effects of finer grain size on the blow formability at high strain rates over 10-2/s and the properties of the resulting moldings were studied.

Finite Element Simulation for Superplastic Blow Forming of Toroidal Ti-6Al-4V Fuel Tank

In the current study, the finite element simulation for superplastic blow forming of a toroidal Ti-6Al-4V fuel tank is discussed. 3 types of preforms are investigated in order to obtain defect free final shape with desirable thickness distribution. From the simulation result, forming tool is designed so that the hydraulic pressure is not used. The forming test is carried out using forming pressure profile obtained from the simulation, and the validity of the selected perform is investigated in terms of thickness distribution and deformed shape.

Characteristics of the GBS – SDC Transition during Bi-Axial Forming of AA5083

Thermomechanical processing to enable superplasticity in AA5083 materials includes cold working followed by heating prior to hot blow forming. Upon heating for forming at 450°C, a B-type ({110}) rolling texture is replaced by a near-random texture with a weak superimposed cube orientation parallel to the sheet normal. The presence of refined grains 7 – 8μm in size reflects the predominance of particle-stimulated nucleation of recrystallization prior to forming. The subsequent evolution of microstructure, texture and cavitation behaviour during biaxial deformation in the solute drag creep (SDC) and grain boundary sliding (GBS) regimes will be presented.

A Study on Failure of Welded Lap Joints in Alloy 718

It is well known that alloy 718 shows excellent mechanical strength and corrosion resistance and this alloy is now successfully utilized for aerospace and oil industry application. In order to design and manufacture components to satisfy the design requirements of the applied system, it is necessary to consider formability and weldability of the material. This paper provides experimental results of lap shear strength of welded specimens of alloy 718 with EBW(Electron Beam Welding) and LBW(Laser Beam Welding) and Brazing. The purpose is to determine the optimum welding method for overlap welding of alloy 718 for blow forming.

결정립 성장을 고려한 초소성 성형공정의 유한요소해석-II. AZ31 합금의초소성 거동

The aim of this study was to predict the results of superplastic forming on magnesium alloy, by considering the grain growth using numerical simulations. Superplastic behavior of AZ31 alloy was investigated through a set of uniaxial tensile tests that cover the forming temperatures ranges from 375 to . All the material parameters in the model, which consists of a constitutive equation and a grain growth equation, were determined. The model was used in the finite element analysis for uniaxial tensile tests and superplastic blow forming, through a user-subroutine available within ABAQUS. From this study, the effect of grain growth during forming was evaluated. The results show that it is essential to include the effect of grain growth in predicting the behavior during superplastic forming of this magnesium alloy.