The contribution of small punch testing towards the development of materials for aero-engine applications

This paper, invited for presentation at the 33rd Meeting of the Spanish Group on Fracture and Structural Integrity, March 2016 in San Sebastian, Spain, reviews the recent work carried out in the authors’ laboratory, addressing the elucidation of tensile and creep characteristics of materials for aero engine components. Two specific applications of the Small Punch (SP) test assessment technology were identified, the first of these takes on board the unique potential of the SP test for testing small quantities of materials which are either in development or through their directional structure cannot easily be produced in quantities which would allow conventional mechanical testing. This goal also required the development and procurement of new SP test facilities capable of operation up to 1150 °C. The examples given in this paper are TiAl intermetallic alloys and nickel based single crystals, all studied utilising the Code of Practice for SP Creep Testing. The second application illustrates the use of SP testing to assess both the tensile and creep properties of additive layer manufactured (ALM) alloys such as IN718 and Ti-6Al-4V using the Code of Practice for SP Tensile and Fracture Testing. Due to the unavailability of sufficient material to facilitate conventional testing for comparison of materials property data, SP testing is unable to provide absolute data for all of these applications, nevertheless the ranking capabilities of SP testing are demonstrably proven

Phased Array Feed Calibration, Beamforming and Imaging

Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20-Meter Telescope. Formed beams achieved an aperture efficiency of 69% and system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.Comment: 19 pages, 13 figure

Application of the small punch test to determine the fatigue properties of additive manufactured aerospace alloys

Additive layer manufacturing (ALM) processes are becoming increasingly prevalent in the aerospace industry as design engineers look to profit from the numerous advantages that these advanced techniques can offer. However, given the safety critical nature and arduous operating conditions to which these components will be exposed to whilst in service, it is essential that the mechanical properties of such structures are fully understood. Transient microstructures are a typical characteristic of ALM components and resulting from the thermal cycles that occur during the build operation. Those microstructures make any mechanical assessment an involved procedure when assessing the process variables for any given parameter set. A useful mechanical test technique is small-scale testing, in particular, the small punch (SP) test. SP testing is capable of localised sampling of a larger scale component and presents an attractive option to mechanically assess complex parts with representative geometries, that would not be possible using more conventional uniaxial test approaches. This paper will present the recent development of a small-scale testing methodology capable of inducing fatigue damage and a series of novel tests performed on different variants of Ti-6Al-4V

Creep strength and minimum strain rate estimation from Small Punch Creep tests

A new standard is currently being developed under the auspices of ECISS/TC 101 WG1 for the small punch testing technique for the estimation of both tensile and creep properties. Annex G of the new standard is covering the assessment and evaluation of small punch creep (SPC) data. The main challenge for estimating uniaxial creep properties from SPC data is the force to equivalent stress conversion between SPC and uniaxial creep tests. In this work a range of SPC assessment methodologies, benchmarked for the standard, are compared for verifying the best practice used in the standard. The estimated equivalent stresses for SPC are compared to uniaxial creep stresses at equal rupture times, using three alternative models. In-depth analyses are performed on SPC and uniaxial creep data for P92, F92 and 316 L steel tested within an inter-laboratory round robin. The formulation for SPC equivalent creep strain rate in the standard is also assessed

Enantioselection in peptide bond formation

Selectivity in abiotic condensations of amino acids remains controversial and stereochemically little explored. We find that competitive activated couplings of N-acyl derivatives of glycine, alanine, valine, proline and phenylalanine with binary, ternary and quaternary mixtures of amides and esters of the same group of amino acids show little selectivity among the reactants, except with respect to configuration, where a consistent and significant preference for heterochiral outcomes, mostly >80%, is observed. One possible explanation of this selectivity predicts a predisposition to homochiral coupling under conditions that would require the two carboxyl functions to be co-facial in the activated complex

Long-term outcome in pulmonary arterial hypertension patients treated with subcutaneous treprostinil

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Small punch creep testing of P92 steel and weld for inter-laboratory comparison and standardization

The small punch creep (SPC) test is a miniature technique that can provide information on creep properties from in service materials or on local material properties such as heat affected zones in weldments. The code of practice (CoP) for the small punch testing technique is currently being transformed into an EN standard. To qualify the selected test specifications and to quantify inter-laboratory data scatter a round-robin was launched for the standardization effort. SPC and reference uniaxial creep tests are performed on P92 steel at temperatures of 600, 625 and 650°C. In parallel a testing programme on P92 welds have been started in the European Creep Collaborative Committee (ECCC). In this paper the initial test results of both these testing programmes are assessed and compared. The initial results show that the SPC time to rupture data scatter is reasonable and that inter-laboratory results are comparable at all specified force levels and temperatures. From the weld tests on specimens targeted to be positioned in different heat affected zones it can be shown that rupture times are indeed affected but no clear reduction in strength can be determined for the short term SPC test. It is clear that the bi-axial stress state and the different stress evolution during the SPC test in comparison to a uniaxial creep test is a challenge when attempting to formulate load to stress transformation equations. Robust estimates on the uniaxial stresses for P92 are acquired by both new approaches and by isothermal determination of force over stress ratios using the classical CoP methodology. This work aims to aid the development of the new standard and to highlight the usability of the method for remaining life or life extension assessments.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

Treatment of intermittent claudication with beraprost sodium, an orally active prostaglandin I2analogue A double-blinded, randomized, controlled trial

AbstractObjectivesIn the current study, we hypothesized that beraprost would: 1) improve treadmill exercise performance and quality of life; and 2) decrease rates of ischemic events in patients with intermittent claudication.BackgroundPrevious trials with beraprost sodium, an orally active prostaglandin I2analogue, in the treatment of claudication in patients with peripheral arterial disease (PAD) have been inconsistent.MethodsPatients with intermittent claudication (n = 897) were randomized to receive either 40 μg three times a day of beraprost with meals (n = 385) or placebo (n = 377) in a double-blinded manner for one year. The primary efficacy parameter was treadmill-measured maximum walking distance, as assessed at three and six months after randomization. Secondary efficacy parameters included treadmill-measured pain-free walking distance and change in quality of life.ResultsThere was no significant improvement in maximum walking distance in the beraprost group (16.7%) as compared with the placebo group (14.6%, p = NS). Administration of beraprost did not improve the pain-free walking distance (p = NS between treatment groups), and there was no improvement in the quality-of-life measures between the treatment groups. The incidence of critical cardiovascular events was 7.3% in the beraprost group and 11.4% in the placebo group (p = NS). There was a significant reduction in the combination of cardiovascular death and myocardial infarction in the beraprost group (p = 0.01).ConclusionsDespite previous investigations suggesting efficacy, these results indicate that beraprost is not an effective treatment to improve symptoms of intermittent claudication in patients with PAD. The potential benefit of beraprost on critical cardiovascular events would require confirmation in a larger prospective investigation