Microstructure based FE Simulation and Validation of Cold Upsetting on Aluminium Composites

Formability of Sintered Al, Al-Cu and Al-Cu-TiC Composites during Cold Upsetting

Changing patterns of psychoactive drug injection are increasing risk The recent increase in the number of people injecting a range of stimulants, particularly the recently emerged psychoactive drugs such as mephedrone, is a concern. Over the past decade, the number of people reporting that amphetamines and amphetamine-type drugs are their main drug of injection has increased three-fold. One in eight now say these are the main drug they inject. People injecting stimulants report higher levels of risk behaviours such as sharing and reusing needles and syringes. Although the number injecting these drugs remains small when compared to those injecting opiates or image and performance enhancing drugs, the higher level of risk behaviours associated with their use can increase harm. 
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\nBacterial infections continue to be a problem A third of people who inject psychoactive drugs report having a recent symptom of a bacterial infection. Outbreaks of infections due to bacteria, such as Clostridium botulinum, continue to occur in this group. Some of these infections are severe and place substantial demands on healthcare. 
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\nHalf of those with hepatitis C remain unaware of their status Hepatitis C remains a major problem among people who inject drugs in the UK, with significant levels of transmission continuing to occur. Two in five of those who inject psychoactive drugs are living with hepatitis C and about half of these infections remain undiagnosed. This underlines the need to identify, and make use of, the opportunities for regularly offering tests to those at risk. 
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\nHepatitis B remains rare, but vaccine uptake has stopped improving Around one in 200 people who have injected psychoactive drugs are living with hepatitis B infection. This low level probably reflects the marked increase in the uptake of the hepatitis B vaccine. Vaccination uptake in this group is no longer increasing and may now be declining. Most of those who have not been vaccinated have been in contact with health services where they could have received a dose of the vaccine. 
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\nHIV levels remain low overall and the uptake of care is good Only around one in 100 people who inject drugs are living with HIV; most of these people will have been diagnosed and be in receipt of care. However, HIV transmission continues among people who inject drugs and the recent outbreak in Scotland is a concern. 
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\nProvision of effective interventions needs to be maintained The provision of effective interventions, such as needle and syringe programmes, opioid substitution therapy and other treatments for drug use, which act to reduce risk and prevent infections, need to be maintained. These interventions need to respond to any changes in patterns of drug use and associated risk. Vaccinations and diagnostic tests for infections need to be routinely and regularly offered to people who inject drugs in line with guidance. Appropriate care pathways and treatments should be available to those testing positive.

Workability Studies in Forming of Sintered Fe-0. 35C Powder Metallurgy Preform During Cold Upsetting

In this work, a new method of selective heating is proposed to increase the deformation behaviour of cylindrical sintered aluminium preforms during the process. Initially, cold upsetting is carried out using 0.5 MN hydraulic press machine at 0.1 s−1 strain rate and the failure locations of the preforms are predicted for various initial relative densities with the aspect ratio of 1 during the deformation process. After the prediction of this failure location, various conditions of selective heating are attempted uniformly on the deformed preforms after a certain stage of deformation before the onset of the failure initiation, using portable gas cartridge at a different temperature and time to assess their consequence on formability behaviour. The detailed experimental results are evaluated for the formability of the selectively heated preforms under different variables such as flow stress, relative density, axial strain, formability stress index and stress ratio parameter. As a result, the initiation of failure and its progression can be delayed by selectively heating the samples before the onset of the failure initiation. Selective heating of the failure location may relieve the accumulated stresses and delay the onset of failure to a later strain level thereby increasing the formability of the metal.

Aluminum-based metal matrix composites with various weight percentages (0, 2.5, 5, 7.5, and 10) of TiO2 reinforcement were synthesized by means of powder metallurgy and their workability behavior under triaxial stress-state conditions was completely studied during cold upsetting. Green cylindrical compacts were made using a 400 kN hydraulic press with suitable punch and die, sintered at (590 ± 10) °C for a period of 3 h, furnace cooled and machined to obtain samples with 0.5 aspect ratio. The cold upset tests were carried out in steps of 10 kN and the results were studied for the workability behavior of the composites. The formability stress index (β) and stress ratio parameters (σz/σeff), (σm/σeff), and (σθ/σeff) were calculated for all composites and correlated with true axial strain (∊ z ). It was observed that the addition of TiO2 to the Al matrix material increases the stress ratio parameters and formability stress index (β).

Complete experimental investigation on the workability behavior of sintered plain carbon steel cylindrical preforms with carbon contents of 0%, 0.35%, 0.75%, and 1.1%, under cold upsetting, has been studied in order to understand the influence of carbon content on the workability process. The abovementioned powder metallurgy sintered preforms with constant initial theoretical density of 84% and aspect ratio of 0.4 were prepared using a suitable die set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1,200°C. Each sintered preform was cold upset under nil/no frictional constraint. Under triaxial stress state condition, densification, axial stress, hoop stress, hydrostatic stress, effective stress, and formability stress index against axial strain relationship were established and presented in this work. Further, attained density is considered to establish formability stress index and various stress ratio parameters’ behavior.

Effect of geometric work-hardening and matrix work-hardening on workability and densification of aluminium–3.5% alumina composite during cold upsetting

A deep drawing process is one of the widely used manufacturing techniques in the automotive industry because of its capability to produce complex shapes with sheet material, often performed using lubricants to ease the forming. Finite Element Methods (FEM) are popularly used at the design stage to predict the formability of the product, the spring-back of the sheet metal product after forming, local thinning/thickening of sheet material and failure of the sheet metal during forming. The performance of the FEM simulations relies on the accuracy of the numerical techniques, material models, contact and friction conditions. Over the past decades, FEM has been largely developed on the aspects of numerical techniques, material and contact algorithms. The coefficient of friction used in the contact formulations is often still the Coulomb friction model, i.e. constant coefficient of friction. The coefficient of friction, however, is generally dependent on the nature of surfaces, material properties as well as the operational and environmental conditions. A friction model has been developed in this research work. This model can be coupled with the FEM simulations in predicting the local coefficient of riction for a deep drawing process. The basic friction mechanisms at the asperity scale taken into account in the model are shearing of the boundary layers, ploughing and shearing of the lubricant film. A contact model has been developed to describe the fully plastic deformation of the surface from a given surface topography, the load at the micro-scale as well as the uniaxial bulk strain. The contact models include the roughness of both the sheet material (for surface deformation) and tool surfaces (for ploughing). A lubrication model has been developed to describe the hydrodynamic flow of the lubricant between the surfaces, taking into account the surface deformation of the sheet as well as the operational conditions like the sliding velocity. The effect of surface lay and lubricant amount applied on the surface is also considered in the model. Further, a deterministic approach for the characterisation of the micro-contacts has been used. This approach is better than traditional statistical methods in terms of geometrical description. The contact model has been further extended to elastic-plastic contact conditions to account for the elastic recovery of the asperities if the sheet surface is subjected to unloading. Experiments have also been carried out to study the shear strength of the boundary layers formed due to the lubricant. It is shown that the shear strength of boundary layers is almost constant if the appropriate contact area is used in the analysis of the experimental data. The coefficient of friction is shown to reduce during the deep drawing processes due to the lubricant pressure generation if the operation conditions and the applied lubricant amount favour hydrodynamic effects. The model shows that the coefficient of friction decreases as the contact pressure increases, which is in accordance with the experiments. The contact model shows that the coefficient of friction is dependent on the surface roughness, bandwidth parameter and surface lay. The coefficient of friction is high for rough, low bandwidth and transversal anisotropic surfaces. The coefficient of friction is low for smooth, high bandwidth and longitudinal anisotropic surfaces. The friction model has been subjected to a validation process with a rotational friction tester. The results of the friction model shows good comparison with the experimental results. The applicability of the developed friction model in a FEM simulation has been demonstrated with a cup drawing FEM simulation which shows the expected evolution of friction conditions during the progression of a deep drawing process.

AZ91E, a magnesium alloy, shows promise in vehicle technology with its lightweight properties and potential for hybrid metal matrix composites. This study focuses on investigating compression properties using statistical analysis and finite element method simulations. However, experimental measurements reveal a density decrease compared to theoretical values, impacting weight optimization and structural integrity in vehicles. Incorporating strengthening agents like ZrO2 and fly ash enhances mechanical properties, though fracture toughness reduces due to grain refinement. Overall, this research provides valuable insights for integrating AZ91E-based composites in the automotive industry to achieve weight reduction and improved performance. As vehicles aim for lighter materials to improve fuel efficiency and reduce emissions, magnesium alloys have emerged as promising candidates for various components. AZ91E, composed mainly of magnesium (Mg), along with aluminum (Al) and zinc (Zn) as primary alloying elements, offers excellent lightweight characteristics. However, the experimental measurements in this study revealed a decrease in density compared to theoretical values, which may have implications for vehicle weight optimization and structural integrity. Decreasing deformation height reduced compressive strength for (H/D = 1 and 1.5) of AZ91E and composites, but composites showed higher compressive strength despite slightly higher density, indicating their superior performance. Analytical equations and ANSYS software provided closely matched results for axial, compressive and hydrostatic stress, while the strength coefficient and the exponent of strain hardening revealed plastic behavior of the samples. Incorporation of FA particles improved the ultimate yield and tensile strengths, as well as the tensile characteristics and hardness with underlying processes for strengthening were discussed. The investigation of AZ91E-ZrO2-fly ash hybrid metal matrix offers valuable insights into potential applications of magnesium alloys in the automotive industry. Understanding the compression attributes and mechanical behavior of these composites, its crucial for their successful integration into vehicle components, where weight reduction and improved performance are essential goals.

Magnesium alloys are highly strain rate sensitive and exhibit good workability in a narrow forging temperature range. Consequently, parts made of these materials are usually forged with low-speed hydraulic presses, using specially designed tool heating systems in order to ensure near-isothermal conditions. This study investigates whether popular magnesium alloys such as Mg-Al-Zn can be forged in forging machines equipped with high-speed forming tools. Experimental upset forging tests on AZ31B, AZ61A and AZ80A specimens were conducted, using a screw press with a ram speed of 0.5 m/s and a die forging hammer with a ram speed at stroke of about 5 m/s. Test specimens were preheated to 350 °C, 410 °C and 450 °C. After the upset forging process, they were air- or water-cooled and then examined for their workability, hardness and grain size. To validate the results, a forging process for a producing handle was designed and modelled by the finite element method. Distributions of strain, temperature and fracture criterion were analysed, and energy and force parameters of the forging process were calculated. After that, experimental tests were performed on AZ31B and AZ61A specimens in order to determine mechanical properties of forged parts and examine their micro- and macrostructure. Results have demonstrated that AZ80A is not suitable for forging with either the screw press or the die forging hammer, that AZ61A can be press- and hammer-forged but to a limited extent, and that AZ31B can be subjected to forging in both forging machines analysed in the study.

Prediction of the interpass temperature of a wire arc additive manufactured wall: FEM simulations and artificial neural network

This paper presents the modeling of a cold forging process for a rotary sleeve. The process of forging a EN 42CrMo4 steel part was first modeled numerically by the finite element method using simulation software DEFORM 3D ver. 11.0. After that, the developed forging process was verified by experimental tests carried out in laboratory conditions with the use of 1:2 scale tools and a material model of aluminum alloy EN AW-6060. Finite element method (FEM) results demonstrated that rotary sleeves could be formed from tubes by cold forging. Results of the experimental tests showed, however, that the material inside the hole of the work piece might not adhere to the surface of the sizing pin. Distributions of strain and stress during the forging process are determined. Geometrical parameters of forged parts obtained in experimental tests are compliant with the dimensions of forged parts simulated by FEM. In addition, experimental forces of the forging process show a high agreement with the forces obtained in FEM simulations.

Workability studies on cold upsetting of Al–Al 2O 3 composite material

Effect of helix angle on residual stress in the spiral welded oil pipelines: Experimental and finite element modeling

The deep drawing process, one of the sheet metal forming methods, is very useful in the industrial field because of its efficiency. The limiting drawing ratio (LDR) is affected by many material and process parameters, such as the strain-hardening exponent, the plastic strain ratio, friction and lubrication, the blank holder force, the presence of drawbeads, the profile radius of the die and punch, etc. In order to verify the finite element method (FEM) simulation results of the LDR, the experimental data are compared with the results of the current simulation. The influences of the process parameters such as the blank holder force, the profile radius of the die, the clearance between the punch and the die, and the friction coefficient on the LDR are also examined. The abductive network was then applied to synthesize the data sets obtained from the numerical simulation. The predicted results of the LDR from the prediction model are in good agreement with the results obtained from the FEM simulation. By employing the predictive model, it can provide valuable references to the prediction of the LDR under a suitable range of process parameters.