Finite Element Analysis of ECAP, TCAP, RUE and CGP Processes

A finite element method was applied to study the various severe plastic deformation processes like, Equal Channel Angular Pressing (ECAP), Tubular Channel Angular Pressing (TCAP), Repetitive Upsetting and Extrusion (RUE) and Constrained Groove Pressing (CGP), considering aluminum AA-390 alloy as specimen material for all these processes. FEA simulation was carried out using AFDEX simulation tool. Effect of the various ECAP process parameters like, die corner angle, channel angle, and the coefficient of friction were analyzed. The die corner angles were divided into 2 equal parts for increasing the effectiveness of ECAP process, thereby increasing the channel number from 2 to 3 and further, their influence on ECAP process was investigated. A 3D simulation of TCAP was carried out for die shapes like triangular and trapezoidal, and variation of the generated stress and strain was plotted. In CGP, four cycle operation was carried out; wherein each cycle is composed of corrugating the specimen and subsequent straightening to original dimension. During RUE process, a maximum effective stress of 683.1 MPa was induced in the specimen after processing it for four complete cycles of RUE process; whereas the maximum strain induced during the same condition was 3.715

A comparison of repetitive corrugation and straightening and high-pressure torsion using an Al-Mg-Sc alloy

A comparative study was conducted to evaluate the influence of two different severe plastic deformation (SPD) processes: repetitive corrugation and straightening (RCS) and high-pressure torsion (HPT). Samples of an Al-3Mg-0.25Sc alloy with an initial grain size of ∼150 μm were processed by RCS through 8 passes at room temperature either without any rotation during processing or with a rotation of 90° around the longitudinal axis between each pass. Thin discs of the alloy were also processed for up to 5 turns by HPT at room temperature. The results show that both procedures introduce significant grain refinement with average grain sizes of ∼0.6–0.7 μm after RCS and ∼95 nm after HPT. Measurements of the Vickers microhardness gave values of ∼128 after RCS and ∼156 after HPT. The results demonstrate that processing by HPT is the optimum processing technique in achieving both high strength and microstructural homogeneity

Grain refinement of Al-Si hypoeutectic alloys by Al3Ti1B master alloy and ultrasonic treatment

Al-Si alloys are widely used in automotive and aerospace industries due to their excellent castability, high strength to weight ratio and good corrosion resistance. However, Si poisoning severely limits the degree of grain refinement with the grain size becoming larger as the Si content increases. Generally the effect of Si poisoning is reduced by increasing the amount of master alloy added to the melt during casting. However, an alternative approach is physical grain refinement through the application of an external force (e.g. mechanical or electromagnetic stirring, intensive shearing and ultrasonic irradiation). This work compares the grain refining efficiency of three approaches to the grain refinement of a range of hypoeutectic Al-Si alloys by (i) the addition of Al3Ti1B master alloy, (ii) the application of Ultrasonic Treatment (UT) and (iii) the combined addition of A13Ti1B master alloy and the application of UT

A loaded self-managed exercise programme for patellofemoral pain: A mixed methods feasibility study

© 2019 The Author(s). Background: A novel loaded self-managed exercise programme that includes pain education and self-management strategies may result in better outcomes for people with patellofemoral pain (PFP). However, establishing program feasibility is an essential first step before testing efficacy. The purpose of this study was to evaluate the feasibility and acceptability of conducting a definitive RCT which will evaluate the clinical and cost-effectiveness of a loaded self-managed exercise programme for people with PFP compared with usual physiotherapy. Methods: In a mixed methods, pragmatic, randomised controlled feasibility study, 60 participants with PFP (57% female; mean age 29 years) were recruited from a physiotherapy clinic within a large UK teaching hospital. They were randomly allocated to receive either a loaded self-managed exercise programme (n = 30) or usual physiotherapy (n = 30). Feasibility indicators of process, resources, and management were collected through follow-up of standardised questionnaires six months after recruitment and semi-structured interviews with 20 participants and physiotherapists. Results: Recruitment rate was 5 participants per month; consent rate was 99%; adherence to intervention appointments was 87%; completeness of questionnaire data was 100%; and adherence to intervention delivery was 95%. Three exercise diaries were returned at six months (5%). At six months, 25 questionnaire booklets were returned (9 in the loaded self-managed group, 16 in the usual physiotherapy group), with a total retention rate of 42%. At six months, 56% (5/9) of respondents in the loaded self-managed group and 56% (9/16) in the usual physiotherapy group were classified as 'recovered'. Both groups demonstrated improvements in average pain (VAS), kinesiophobia, pain catastrophizing, general self-efficacy and EQ-5D-5 L from baseline to six months. Conclusion: The results of this feasibility study confirm that it is feasible and acceptable to deliver a loaded self-managed exercise programme to adults with PFP in an NHS physiotherapy outpatient setting. However, between group differences in lost to follow up and poor exercise diary completion mean we are uncertain on some feasibility aspects. These methodological issues need addressing prior to conducting a definitive RCT. Trial registration: ISRCTN 35272486. Registered 19th December 2016

Validation of the Activity Preference Assessment: a tool for quantifying children’s implicit preferences for sedentary and physical activities

Background High levels of sedentary behavior and low physical activity are associated with poor health, and the cognitive determinants of these behaviors in children and adolescents are not well understood. To address this gap, we developed a novel, non-verbal, computer-based assessment to quantify the degree to which youth prefer to be sedentary relative to physically active in their leisure time. Methods The Activity Preference Assessment (APA) uses a forced-choice paradigm to understand implicit decision-making processes when presented with common sedentary and physical activities. The APA bias score ranges from − 100 to + 100, with positive scores indicating a relative preference for sedentary activities, and negative scores representing a preference for physical activities. In 60 children ages 8–17 years, we assessed the validity of this behavioral task against a free-choice play observation, accelerometry-measured activity, anthropometrics and body composition, and cardiorespiratory fitness. We explored neighborhood, family, and individual-level factors that may influence implicit activity preferences. Test-retest reliability was assessed over one week. Results The majority of children (67%) preferred sedentary relative to physical activities. APA bias scores were positively associated with sedentary time during free-choice play. In girls, bias scores were negatively associated with average daily MVPA. APA bias scores were positively associated with body fat and negatively associated with cardiorespiratory fitness. These findings were independent of age, sex, and race/ethnicity. Neighborhood access to physical activity spaces, the number of people in the home, perceived physical self-competence (e.g., coordination, strength), and self-reported depressive symptoms were associated with activity preferences. The intra-class correlation for test-retest reliability was r = 0.59. Conclusions The APA shows promise as a novel tool for quantifying children’s relative preference for sedentary versus physical activities. Implicit bias scores from the APA are clinically meaningful, as shown by significant associations with adiposity and cardiorespiratory fitness. Future longitudinal studies should examine the directionality of the association between preferences and health markers, and the degree to which implicit activity preferences are modifiable. Importantly, the task only takes an average of 10 min to complete, highlighting a potential role as an efficient screening tool for the propensity to be sedentary versus physically active

Effect of a Grain Refiner Cum Modifier on Mechanical Properties of Al-7Si and Al-11Si Alloys

This study evaluates the influence of grain refiners/modifiers on the mechanical properties of the Al-7Si and Al-11Si alloys with an experiment of quantitative and qualitative correlations with the microstructure. Modification of Al-Si alloys with strontium additions and grain refinement with Al-Ti, Al-B and Al-T-B master alloy additions are demonstrated to be efficient on Al-Si alloys. A single master alloy with combined additions of Sr and Ti and/or B was prepared and the microstructure and mechanical properties were studied. The results show that boron rich (Al-3B-Sr and Al-1Ti-3B-Sr) master alloys are more efficient than Ti rich (Al-3Ti-Sr and Al-5Ti-1B-Sr) master alloys considering their combined grain refinement and modification effect on Al-7Si and Al-11Si alloys. However, the presence of Sr does not influence the grain refinement. Similarly, presence of grain refiner does not influence the modification of eutectic Si

Dry sliding wear response of A413 alloy:Influence of intermetallics and test parameters

Intermetallic particles of Al3Ti, TiB2, AlB2 and Al4Sr were added to A413 alloy, and sliding wear tests were carried out under dry sliding conditions at room temperature as well as at high temperatures of 60, 120,and180 1C. The results demonstrate that contacting surfaces at high temperature conditions are susceptible to oxidation and the wear rate of reinforced alloys is reduced. This is due to the formation of glazing layer that offers protection. Moreover,intermetallic particles played an important role as grain modifier/refiner and were responsible for reduced wear and friction

Influence of Combined Addition of Boron and Strontium on High-Temperature Wear Behavior of A356 Alloy

In the present study, the effect of the combined addition of boron (B) and strontium (Sr) on the high-temperature dry sliding wear behavior of A356 alloy has been investigated using a pin-on-disc wear testing machine attached with a furnace. During wear studies, the effect of alloy composition, normal pressure, sliding speed, and sliding distance on A356 alloy at four temperatures, namely, room temperature and 100, 200, and 300°C, have been investigated. Further, the cast alloys and worn surfaces of A356 alloy with and without B and Sr were characterized by scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) microanalysis. Results indicate that the combined addition of B and Sr to A356 alloy has led to improvements in wear properties. This is due to a change in microstructure, improvement in mechanical properties, and the formation of an oxide layer between the mating surfaces during the sliding wear process