Warm Forming Research Articles

From friends to foes: fungi could be emerging marine sponge pathogens under global change scenarios.

Global change, experienced in the form of ocean warming and pollution by man-made goods and xenobiotics, is rapidly affecting reef ecosystems and could have devastating consequences for marine ecology. Due to their critical role in regulating marine food webs and trophic connections, sponges are an essential model for studying and forecasting the impact of global change on reef ecosystems. Microbes are regarded as major contributors to the health and survival of sponges in marine environments. While most culture-independent studies on sponge microbiome composition to date have focused on prokaryotic diversity, the importance of fungi in holobiont behavior has been largely overlooked. Studies focusing on the biology of sponge fungi are uncommon. Thus, our current understanding is quite limited regarding the interactions and “crosstalk” between sponges and their associated fungi. Anthropogenic activities and climate change may reveal sponge-associated fungi as novel emerging pathogens. Global change scenarios could trigger the expression of fungal virulence genes and unearth new opportunistic pathogens, posing a risk to the health of sponges and severely damaging reef ecosystems. Although ambitious, this hypothesis has not yet been proven. Here we also postulate as a pioneering hypothesis that manipulating sponge-associated fungal communities may be a new strategy to cope with the threats posed to sponge health by pathogens and pollutants. Additionally, we anticipate that sponge-derived fungi might be used as novel sponge health promoters and beneficial members of the resident sponge microbiome in order to increase the sponge's resistance to opportunistic fungal infections under a scenario of global change.

Extension of Process Limits in High‐Strength Aluminum Forming by Local Contact Heating

The aluminum alloy EN AW‐7075 T6 is used in the automotive sector for its favorable strength‐to‐weight ratio. However, the limited cold formability is currently addressed by energy‐ and time‐consuming temperature‐assisted processes. In order to limit the effort to critical forming areas only, the state‐of‐the‐art shows promising results for increasing the blank temperature in the range of warm forming. The design of new processes in an industrial context requires appropriate numerical simulation with inherent complexity due to time‐ and temperature‐dependent effects. Herein, the potential of a newly developed tool setup and process chain with integrated local contact heating of the EN AW‐7075 T6 blank is investigated on the basis of a curved hat profile. A thermomechanically coupled FE model of the process is developed and validated. The influence of the local heating layout is analyzed in experimental forming tests and a corresponding process window is derived. The influence of local heating on the occurring failure mechanisms is discussed based on simulation results. The equivalent plastic strain evolution is successfully used to evaluate the local heating dependent failure behavior. A significant increase in the overall formability of the part is achieved by the proposed process chain.

Warm Aging of Pre-aged AA6013 Sheet and Its Relevance to Room Temperature and Warm Forming Applications—Experimental and Modeling Analyses

AbstractWarm forming has been shown to be an effective way to increase the formability of various aluminum sheet alloys. If applied to precipitation hardenable alloys, aging and/or coarsening may occur during heating and/or forming processes. As such, there is a potential to leverage the warm forming process to artificially age precipitation hardenable alloys. In this study, the aging characteristics of a pre-aged Al-Mg-Si-Cu alloy (designated AA6013-PA and comprising a 4 h, 100 °C pre-aging cycle following solutionization) were examined using: (i) room temperature tensile and (ii) bendability experiments, as well as (iii) elevated temperature tensile and formability experiments in the temperature range of 220-280 °C. In the pre-aged condition, the alloy exhibited very high work hardening, elongation and bendability. It was found that T6-like properties can be obtained with short duration secondary aging of the AA6013-PA starting temper (410 s at 235 °C), followed by a paint bake cycle (30 min at 177 °C). In such heavily aged conditions, the bendability is found to be moderate and consistent with a T6 temper. Bendability of the pre-aged alloy is shown to be enhanced by reducing the extent of aging, which may be beneficial for applications requiring energy absorption during crash, for example. In the pre-aged condition, AA6013 displayed a 55% improvement in room temperature formability, relative to the T6 condition, for near plane-strain loading using a Nakazima punch, although neither temper exhibited formability improvements through warm forming. The aging kinetics of AA6013-PA were determined from mechanical test data and used to calibrate an aging kinetics model. A strong obstacle model was used to relate precipitation state to yield strength, for artificial aging in the range 220-280 °C. The incremental strength increase due to exposure to an automotive paint cure cycle was also modeled and found to yield accurate results. Warm deformation, as well as room temperature deformation, were shown to enhance the paint bake response of the alloy, reducing the time to the peak aged condition by up to 14% for artificial aging at 177 °C.

Deep Drawing Behaviour of Steel–Glass Fibre-Reinforced and Non-Reinforced Polyamide–Steel Sandwich Materials

Thermoplastic-based fibre metal laminates (FMLs) have gained increasing interest in the automotive industry due to their forming potential—especially at higher temperatures—into complex components compared to thermoset-based ones. However, several challenges arise while processing thermoplastic-based FMLs. One the one hand, forming at room temperature (RT) leads to early failure modes, e.g., fracture and delamination. On the other hand, warm forming can extend their forming limits, although further defects arise, such as severe thickness irregularities and wrinkling problems. Therefore, this study focuses on developing different approaches for deep drawing conditions to deliver a promising, feasible, and cost-effective method for deep-drawn FML parts. We also describe the defects experimentally and numerically via the finite element method (FEM). The FMLs based on steel/glass fibre-reinforced polyamide 6 (GF-PA6/steel) are studied under different deep drawing conditions (temperatures, punch, and die dimensions). In addition, mono-materials and sandwich materials without fibre reinforcement are investigated as benchmarks. The results showed that the best deep drawing condition was at a temperature of 200 °C and a die/punch radius ratio of 0.67, with a gap/thickness ratio of ≤2.0. The FEM simulation via Abaqus 6.14 was able to successfully replicate the anisotropic properties and wrinkling of the GF-PA6 core in an FML, resembling the experimental results.

Tribology in Warm and Hot Aluminum Sheet Forming: Transferability of Strip Drawing Tests to Forming Trials

For conventional sheet metal forming at room temperature, numerous tribometers have been developed in the 20th century. At the present state of the art, there are some challenges for tribometry in warm and hot forming processes of high‐strength aluminum (e.g., EN AW‐7075). Especially for nonisothermal processes with heated sheets and cooled dies, the tribological design is a major challenge, which needs to be addressed by investigations with adapted tribometers. Herein, the transferability of friction and wear behavior of three different lubricants and temperatures is investigated. Therefore, tribometer test results are compared with real forming trials in combination with thermomechanical finite element simulations. Both the behavior of different lubricant types and the characteristics of tool lubrication in sheet metal forming are discussed.

The effect of minor addition of Mn in AA7075 Al–Zn–Mg–Cu aluminum alloys on microstructural evolution and mechanical properties in warm forming and paint baking processes

The microstructures and mechanical properties in the peak ageing condition, warm forming process, and paint baking process of two Al–Zn–Mg–Cu aluminum alloys, which possessed the same base compositions but different levels of Mn (0 and 0.24 wt%), have been investigated. The results show that Mn addition can hardly refine the grain size (around 20 μm) in AA7075 aluminum alloy in warm forming and paint baking processes. Mn-free and Mn-containing alloys subjected to all three processes possess nano-precipitates of nearly the same size, indicating that Mn addition does not influence the nano-precipitate evolution in the aluminum matrix. Energy-dispersive X-ray spectroscopy (EDS) mapping results of dispersoids show that dispersoids in Mn-bearing specimens are enriched in Mn and depleted in Zn and Mg. The Zn and Mg expelled from dispersoids in Mn-containing specimens into the aluminum matrix presumably formed Zn- and Mg-rich zones around the dispersoids, which improved the precipitate transformation reation from GPII to η′ phase at the boundaries between aluminum matrix and dispersoids. Although the solid solution strengthening effect triggered by Mn addition might be less effective because of the formation of dispersoids, the slight enhancement of ultimate tensile strength (UTS) in Mn-containing specimens rather than in Mn-free specimens in all states can be attributed to the formation of nano-precipitates around the dispersoids.

The effects of laser-assisted heat treatment on warm formability of dual-phase materials

ABSTRACT In this study, the effects of local heat treatment using a low-power laser on the bending formability of DP800 sheet material were experimentally investigated. In the first step of the study, only the punch contact bending region of sheet metal was locally heated with a constant feed rate (1 mm s−1) and at different laser powers (50, 75, and 100% Watt). In the next step, the sheet material was transferred to the bending die for bending without any cooling process, and into the last stage, the sheet material was formed in different angled V-bending dies (30°, 60°, and 90°). It was observed that in heating up to 75-W power, the hardness decreased to 237 HV due to the dissolution of the martensite in the microstructure of DP material, and the springback value decreased by 39.285% due to the decrease in hardness.

Hydrogen Generation During Thermal Processes of Water Decomposition on the Surface of Nano-ZrO2+3mol.%Y2O3

The study of physicochemical properties of nano-ZrO2+3mol.%Y2O3 was determined. The X-ray diffraction spectrum of the nano-ZrO2 and system nano-ZrO2+3 mol.%Y2O3 compound was drawn by the Ritveld method and the crystal structure was determined at different temperatures (T = 373, 473, 573, 673 K) and under normal conditions. The energy of the arrangement of H2 as a result of the decay of H2O, on the surface of nano-ZrO2+3mol.%Y2O3 was considered. Impacts of adsorption and desorption preparation of ZrO2+3mol.%Y2O3 nanoparticles were considered at diverse (T = 373, 473, 573, 673 K) temperatures. The thought of H2 in warm forms at nano-ZrO2+3mol.%Y2O3 framework expanded. This tells about hydrogen era by water part in close future. Nano-ZrO2 and system nano-ZrO2+3mol.%Y2O3 with the temperature range of T = 373, 473, 573, 673 K have been studied by SEM analysis. These results are promising of hydrogen generation by water splitting in near future. HIGHLIGHTS First innovative research article in this area Importance of the thermal in water splitting for hydrogen generation Design and optimization of water splitting for hydrogen generation Future of hydrogen generation at a large scale economically GRAPHICAL ABSTRACT

Dynamic evolution and driving forces of carbon emission efficiency in China: New evidence based on the RBM-ML model

The globe is being confronted with a tremendous challenge in the form of global warming, which is produced by emissions of carbon dioxide. To accomplish the double-sided objective of reducing carbon emissions while preserving a healthy rate of economic development, it is crucial to evaluate the driving forces of carbon emissions. In this study, the polar coordinate method is employed to improve the traditional Slacks-based Measure (SBM) method and propose a Ray SBM (RSBM). Additionally, the revised approach is paired with the Malmquist-Luenberger (ML) index to determine the carbon emission effectiveness (CFTP) of 30 prefectural regions in China between 2001 and 2019. The evolution features of the CFTP are examined by kernel density and spatial Markov chain. Moreover, according to the findings, CFTP in China has seen a moderate increase, with cutting-edge technological progress serving as the primary driver. The CFTP in eastern China is significantly lower than that in western China, and there is a discernible tendency toward the disparity becoming even wider. In addition, there is obvious club convergence in China's CFTP, which shows certain spatial agglomeration characteristics in the sample period. In accordance with the low-carbon economic theory and literature on CFTP, the variables of industrial structure, energy structure, technological progress, economic growth and environmental regulation are utilized to examine the driving factors for the spatial econometric model, and the corresponding spatial spillover effect is obvious.

Titanium clad plate forming: critical consideration and how different it is from solid titanium forming

Titanium offers exceptional corrosion resistance both in organic & inorganic acid media. Thus, it is a preferred material by various industries such as Oil and Gas refining, Petrochemical (PTA Plant) including Nickel refining by Hydrometallurgy. These equipment are operated at high temperature and pressure, necessitating the use of higher thickness for safety and efficient functioning. Therefore, use of solid titanium is not economical, and often substituted with explosion bonded Ti-Clad steel. Fabrication of certain components of this equipment like Dished heads are required to be made by forming with options of cold, warm or hot forming. Selection of forming method for Ti-clad steel component is often governed by its effect on Clad-Base metal bond integrity and reduction shear strength unlike other commonly used Stainless steel or Ni-based alloy clad material, wherein thickness of the base metal is major deciding factor. In case of Ti-Clad steels both cladding and base metal are not metallurgically compatible as well as differs significantly in their physical properties, forming temperature plays a crucial role. This paper describes the effect of various Dished heads forming methodology on integrity of clad plate. Also, it brings out how the Ti-clad steel forming is critical than the forming of solid Titanium.

Research on warm laser shock sheet micro-forging

This paper introduces warm laser shock sheet micro-forging, which combines the advantages of sheet bulk metal net forming, laser shock dynamic micro forming and warm forming. The influence of AZ31B magnesium alloy on laser energy and forming temperature was investigated by experiment and simulation. The mechanism that warm temperature has better properties than room temperature has been revealed from the aspects of microstructure, stress wave transmission and material flow. The results show that the forming depth of workpiece increases with the increase of laser energy. Forming depth increases with increasing temperature at the same laser energy, but serious ablation occurs on the surface of workpiece at 250 °C, which affects the forming quality of workpiece. EBSD results show that with the increase of forming temperature, the number of twins decreases, the dislocation density decreases and the forming depth increases. The grain refinement after laser shock forming is obvious, and the increase of grain dislocation density promotes the improvement of microhardness, which indicates that laser shock can improve the mechanical properties of materials. The numerical simulation results show that the elastic wave propagates faster than the plastic wave. The stress on the workpiece at 150 °C is less than that at room temperature, but the equivalent plastic strain is higher than that at room temperature. After plastic deformation, the material in the workpiece gradually flows to the cavity. At 150 °C, the material flow inside the workpiece is faster, the filling effect is better and the forming uniformity is better.

Effect of Warm Deformation on Mechanical Properties and Deformation Mechanism of Nano/Ultrafine‐Grained 304 Stainless Steel

To prevent the performance of 304 stainless steel with nano/ultrafine grain from being damaged during cold forming, the deformation temperature is increased to above the Md point, and its mechanical properties and deformation mechanism during warm forming are studied. The significant effects of rolling temperature on the microstructural evolution of nano/ultrafine‐grained 304 stainless steel deformation are characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy, and the relationships between temperature, stacking fault energy (SFE), and deformation mechanisms are discussed. The results show that the tensile strength of 304 austenitic stainless steel decreases with an increase in the tensile temperature from room temperature to 900 °C, and the total elongation decreases first with increasing temperature. The elongation at 400 °C is the worst, only 32%. The dislocation slip becomes the only deformation mechanism due to the high SFE. Then, the total elongation begins to increase, and the highest elongation is 288% at 800 °C, showing superplastic behavior and the deformation mechanism is dynamic recrystallization, and grain boundary sliding.

CAPTURING OF CARBON DI OXIDE AND PREVENTION OF CORROSION IN BIOMASS PRODUCTION

The generation of heat, electricity is being produced through biomass burning process, but it is seen that it has many challenges. The capture and storage of CO2emissions produced from the combustion of biomass and many other industrialization processes is a great deal to the world. Carbon di oxide emission percentage is continuously increasing in the atmosphere, thus this leads to the climate change in the form of global warming. This study analyses the viable and potent method of capturing carbon di oxide, transporting it in an affordable way and finally then safe storage of itself and increase the temperature as well as corrosive resistivity. KEYWORDS: - Pre combustion capture, post combustion capture, biogas, biogas digester,ccs

Study on Ductility Failure of Advanced High Strength Dual Phase Steel DP590 during Warm Forming Based on Extended GTN Model

Under warm forming, the damage parameters of extended GTN model are easily affected by temperature, and the failure of materials under warm forming is less studied by using this model. In this paper, based on the extended GTN model, the damage parameters of DP590 at different temperatures are determined by experiment and numerical simulation, studying the trend of damage parameters changing with temperature. Through the analysis of shear specimens at different angles and temperatures, we studied the changes in shear damage and void damage under different conditions, discussing the influence of shear damage and void damage on competitive fracture failure under warm forming. We modify the damage by using a function based on stress triaxiality, and present a competitive failure equation considering temperature and stress triaxiality. It is found that the extended GTN model can be applied to the failure study of DP590 steel under warm forming.

Experimental investigations of warm incremental sheet forming process on magnesium AZ31 and aluminium 6061 alloy

Aerospace, automobile and biomedical sector focuses on innovative rapid manufacturing processes, which can enable product customization, reduction in cost and manufacturing lead time. Aerospace, automobile and biomedical industries mostly use magnesium AZ31 and aluminium 6061 alloy materials for manufacturing of products because of their lower elastic modulus, excellent corrosion and fatigue resistance. The conventional sheet metal forming processes often require additional tools like punch and die and would not be economically viable to produce the customized structure for applications. An emerging forming technique known as warm incremental sheet forming process is evolved, which is capable of forming intricate, asymmetrical components at elevated temperature with localized deformation method. The characteristics of warm incremental sheet forming process suggest the need for the investigation of magnesium AZ31 and aluminium 6061 alloy materials for wide application of the process. Experimental investigation on the influence of process parameters on warm incremental sheet metal forming of magnesium AZ31 and aluminium 6061 alloy materials using electric heating technique was studied. Experimental results revealed that magnesium AZ31 and aluminium 6061 alloy sheet metal component formed with incremental depth of 0.1 mm, wall angle of 50° and temperature of 300°C showed maximum formability and thickness reduction with minimum geometrical deviation.

Numerical simulation and experimental study of warm hydro-forming of magnesium alloy sheet

The uneven forming temperature during warm hydro-forming of magnesium alloy sheets is one of the main causes of defects in formed parts. In order to completely solve this problem to obtain products with good forming quality, a new warm forming method for magnesium alloy sheet is proposed: the magnesium alloy sheets and forming die are immersed in hot oil to achieve constant temperature forming. In addition, a hot oil warm hydro-forming device for magnesium alloy sheets was designed and developed. This work also carried out the numerical simulations and forming experiments, this study to investigated the effects of forming concave die chamfer, temperature, friction coefficient, hydraulic pressure, and blank holder force on the warm hydro-forming of magnesium alloy sheet. The simulation results are in good agreement with the experimental ones, and the feasibility of warm hydro-forming of magnesium alloy sheet is verified. According to the numerical simulations and forming experiments, the best process window for warm hydro-forming of l mm thick AZ31B magnesium alloy sheet was obtained. The hot oil constant temperature hydraulic forming technology can enrich the forming process of magnesium alloy and provide a new perspective and technical basis for warm forming of other hard-to-deform metal materials.

Effect of Initial Temper on the Warm Forming Characteristics of a High Strength 7000-series Al-Zn-Mg-Cu Alloy

In this work, the formability of a developmental 7000-series copper containing aluminium alloy was assessed at room temperature (RT), 150°C, 175°C and 200°C in pre-aged (PA), peak-aged (T6) and overaged (T76) tempers using Nakazima tests with stereoscopic digital image correlation (DIC) strain measurement. The limit strains were identified using a novel curvature-based approach to detect the formation of an acute neck. The tensile mechanical properties in these warm forming processing routes were characterized with and without a paint bake cycle. Finally, a thermo-mechanical tensile simulator was used to evaluate the constitutive response of the PA and T76 tempers as a function of strain-rate and time at 175°C. Formability results found the selected PA temper to have a good room temperature formability and a mild positive response to the selected warm-forming cycles. The T6 and T76 tempers both exhibited increases in formability in response to warm forming. The PA temper had a significant positive response to short-duration warm forming and subsequent paint baking, with the yield strength increasing from 420 MPa to 512 MPa following this thermal cycle. For the T6 temper, the warm-forming cycle showed a trend characteristic of retrogression and re-aging, with the warm-forming cycle dropping the yield strength from 566 MPa to 534 MPa and the subsequent paint-bake re-aging to 554 MPa. The effect of aging during pre-heating prior to warm forming on the warm constitutive response of the PA and T76 tempers was also investigated. Both tempers exhibited rather different aging responses to short-duration thermal cycles. In the PA temper, this manifested as an increase in at-temperature yield strength and loss of hardening rate. In contrast, the T76 temper exhibited a drop in strength since this temper is already over-aged prior to warm forming. Both the PA and T76 tempers showed comparable at-temperature strain-rate sensitivity.

U-channel forming of an 7075-T6 in warm conditions

The use of high mechanical strength aluminum coupled with the warm forming process makes it possible to replace certain steel parts in vehicles, thus reducing its mass and consequently greenhouse gas emissions. Warm forming of aluminum alloys requires heating the part between 150°C and 250°C to increase formability and reduce springback. In this study, a 7075-T6 alloy U-channel part was warm formed at 200°C in a short enough time to maintain the T6 state of the material. The process consisted of successively performing the heating by contact and stamping steps on the same mechanical press. From a thermomechanical characterization of the alloy in the temperature range between RT and 200°C and several strain rates, numerical simulations of the forming of the U-channel part were carried out using Abaqus. The experimental springbacks reduced with temperature were in agreement with the numerical simulations. An analysis of the conductivity and hardness of the material showed also that the 7075 keeps its T6 state until 10 s of warm forming.

Sheared Edge Formability Characterization of High Strength Aluminum Alloys at Room and Elevated Temperatures using Hole Expansion Tests

High strength 6000- and 7000-series aluminum alloys have significant potential for automotive light weighting due to their high strength-to-weight ratios. Alternate thermal processing routes and warm forming operations with rapid heating to 150 - 300°C are being explored to expand their forming process windows. While the constitutive and formability behavior of these alloys at elevated temperatures is an active area of research, limited data is available on their sheared edge stretchability, particularly under elevated temperature forming conditions. To this end, the influence of cutting clearance on the edge fracture limits of two precipitation hardening alloys, AA6013-T4 and AA7075-T6, and a non-heat treatable AA5182-O were first investigated at room temperature using the conical hole expansion test. A 12% clearance was found to be suitable for the three materials and used to process the hole expansion samples prior to warm forming. Microhardness tests were used to characterize the depth and severity of the shear affected zone (SAZ) for the AA7075-T6 before and after the warm forming cycle. The forming temperature was found to increase the hole expansion ratio by approximately 400%, 150%, and 520% for the AA5182-O, AA6013-T4, and AA7075-T6 respectively relative to the room temperature tests. The edge stretchability during W-temper forming of the AA6013 and AA7075 at room temperature was also assessed. It was observed that W-temper forming negatively influenced the hole expansion of AA6013 by approximately 30% relative to the T4 condition. Conversely, the hole expansion ratio for AA7075 when formed in W-temper increased by over 35% with respect to the T6 temper.

Experimental and numerical investigation of ductile fracture for AA6061-T6 sheets at room and elevated temperatures

Warm forming is largely employed to enhance the poor formability of aluminum alloys at room temperature. The knowledge of the effect of stress state and temperature on the forming limits is an important aspect for the control of warm forming operations. Therefore, the objective of this work is to investigate the influence of temperature on the ductile fracture of AA6061-T6 aluminum alloy sheet metal under different stress states, ranging from shear to biaxial tension. For this purpose, experiments and numerical simulations of uniaxial tensile tests on dog-bone shaped specimen, notched specimens with different radius, specimens with a central hole and shear specimens are conducted at room and elevated temperatures. The hybrid experimental–numerical approach is used to identify the fracture strain and the corresponding stress state parameters (i.e. stress triaxiality and Lode parameter) to derive the fracture loci at room temperature, 150∘C and 200∘C. To accurately model the material behavior, the positive strain rate sensitivity in the flow stress response at elevated temperature is considered and attention is paid to constrain the finite element model by using the real experimental boundary conditions. The strain rate dependence of fracture strain is not considered in this work. A strong dependency of the ductile fracture on the temperature and stress state is evidenced. Also, an extension of Lou’s ductile fracture criterion which includes the impact of temperature on ductile fracture prediction is proposed. The prediction accuracy of the original and extended criteria is evaluated. It is found that Lou’s ductile fracture criterion is well suited to predict accurately ductile fracture at elevated temperatures under isothermal conditions whereas the extended form is very useful to predict ductile fracture initiation under non-isothermal conditions.