Hot sheet metal forming strategies for high-strength aluminum alloys: a review-fundamentals and applications

In the past decade, aluminum alloys have become important structural materials in the automotive industry, thanks to their low density, high strength, high fracture toughness, and good fatigue performance. However, an important limitation of aluminum alloys is their poor formability at room temperature; as a result, numerous studies have been conducted with the aim of developing forming techniques to overcome this and facilitate the forming of more complex-shaped components. Following an overview on the metallurgical background of aluminum alloys, this article reviews recent developments in forming processes for aluminum alloys. The focus is on process variants at room temperature and at higher temperatures and on a new hot forming technique promising considerable improvements in formability. This review summarizes the influence of different process parameters on microstructures and mechanical properties. Particular emphasis is given to process design and to the underlying microstructural phenomena governing the strengthening mechanisms

The association between green space and depressive symptoms in pregnant women: moderating roles of socioeconomic status and physical activity

Background: The current study explored the association between green space and depression in a deprived, multiethnic sample of pregnant women, and examined moderating and mediating variables. Method: 7547 women recruited to the ‘Born in Bradford’ cohort completed a questionnaire during pregnancy. A binary measure of depressive symptoms was calculated using a validated survey. Two green space measures were used: quintiles of residential greenness calculated using the normalised difference vegetation index for three neighbourhood sizes (100, 300 and 500 m to green space buffer zones around participant addresses); access to major green spaces estimated as straight line distance between participant address and nearest green space (>0.5 hectares). Logistic regression analyses examined relationships between green space and depressive symptoms, controlling for ethnicity, demographics, socioeconomic status (SES) and health behaviours. Multiplicative interactions explored variations by ethnic group, SES or activity levels. Mediation analysis assessed indirect effects via physical activity. Results: Pregnant women in the greener quintiles were 18–23% less likely to report depressive symptoms than those in the least green quintile (for within 100 m of green space buffer zone). The green space-depressive symptoms association was significant for women with lower education or who were active. Physical activity partially mediated the association of green space, but explained only a small portion of the direct effect. Conclusions: Higher residential greenness was associated with a reduced likelihood of depressive symptoms. Associations may be stronger for more disadvantaged groups and for those who are already physically active. Improving green space is a promising intervention to reduce risk of depression in disadvantaged groups

Thermodynamic simulation analysis of a multifuel CHP plant basing on the technological diagram of Avedore unit 2

The paper presents the results of a simulative thermodynamic analysis of a multifuel CHP plant basing on the technological diagram of Avedore 2. Calculations have been carried out for the operation of Avedore 2 plant in the district heating mode. Several variants of simulation have been considered, determined by the choice of operation of the respective plants, viz. main boiler fired with natural gas, main and biomass boiler, main boiler and GT plant, joint operation of the main and biomass boiler and GT plant, main boiler (fired with heavy fuel oil or/and wood chips) and biomass boiler and GT plant. For each variants a diagram of iso-fuel curves has been developed, illustrating the variability of useful effects (power output and district heat) at various loads of the CHP steam part. In case of the variant in which the main boiler and GT are in operation with natural gas as fuel the exemplary energy indices were determined

Extrusion foaming of PHBV

This paper reports work on extrusion foaming of poly(3-hydroxybutyrate-co- 3-hydroxyvalerate) with a chemical blowing agent based on sodium bicarbonate and citric acid and calcium carbonate nucleation agent. It includes investigations in the effects of rheological behaviour of the polymer, blowing agent, nucleation agent and processing conditions on the foam density and morphology. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a natural biodegradable polyester with high crystallinity, low melt viscosity and slow crystallisation rate and high sensitivity to the thermal degradation at temperatures above its melting point, making it particularly difficult to control the foaming process. Use of negative gradient temperature profile was found beneficial to minimise the thermal degradation and achieve necessary melt strength to stabilise the cell structure. Solidification of the super-cooled polymer melt occurring at the die was discussed in relation to the selection of the temperature profile and rheological behaviour and solidification of the poly(3-hydroxybutyrate-co-3- hydroxyvalerate) characterised by rotational rheometry. In addition to extrusion foaming conditions, effect of the blowing and nucleation agents on rheology of the polymer, the cell refinement on foam density and morphology were discussed. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was extruded with a twin screw extruder fitted with a strand die yielding up to 60% density reduction with uniform fine cell structure. © 2013 The Author(s)

Prediction of thinning behavior for complex-shaped, lightweight alloy panels formed through a hot stamping process*

This paper provides an overview of hot stamping of light alloys using a method known as HFQ® forming. We present a new method of forming complex shaped automotive components through the use of a hot stamping process for high strength AA6082 alloy. In particular, the component selected for study is a complex automotive door inner component that could not be conventionally formed from such a strong alloy. The forming process is described and the post-formed thickness distribution is presented. An FE simulation is given to demonstrate the potential to predict the forming process and to provide guidance as to the final component thicknesses

The Impact of Antenatal Depression on Perinatal Outcomes in Australian Women

In Australia, there is limited evidence on the impact of antenatal depression on perinatal outcomes. This study investigates the association between maternal depressive symptoms during pregnancy and key perinatal outcomes, including birth weight, gestational age at birth, breastfeeding indicators and postnatal depressive symptoms.A retrospective cohort of mothers (N = 17,564) of all infants born in public health facilities within South Western Sydney Local Health District and Sydney Local Health District in 2014, in the state of New South Wales (NSW), Australia, was enumerated from routinely collected antenatal data to investigate the risk of adverse perinatal outcomes associated with maternal depressive symptoms during pregnancy. Antenatal depressive symptoms were measured using the Edinburgh Postnatal Depression Scale (EPDS). Logistic regression models that adjusted for confounders were conducted to determine associations between antenatal depressive symptoms and low birth weight, early gestational age at birth (<37 weeks), breast feeding indicators and postnatal depressive symptoms.The prevalence of maternal depressive symptoms during pregnancy was 7.0% in the cohort, and was significantly associated with postnatal depressive symptoms [Adjusted Odd Ratios (AOR) = 6.4, 95% CI: 4.8-8.7, P<0.001]. Antenatal depressive symptoms was associated with a higher odds of low birth weight [AOR = 1.7, 95% CI: 1.2-2.3, P = 0.003] and a gestational age at birth of <37 weeks [AOR = 1.3, 95% CI: 1.1-1.7, P = 0.018] compared to women who reported lower EPDS scores in antenatal period. Antenatal depressive symptoms were not strongly associated with non-exclusive breast feeding in the early postnatal period.Maternal depressive symptoms in the antenatal period are strongly associated with postnatal depressive symptoms and adverse perinatal outcomes in Australian infants. Early identification of antenatal and postnatal depressive symptoms, and referral for appropriate management could benefit not only the mother's mental health, but also the infant's health and development