Proof Test Research Articles

Acoustic emission-based damage characterization of 70 MPa type IV hydrogen composite pressure vessels during hydraulic tests

This paper aims to characterize the damage mechanisms of 70 MPa Type IV hydrogen composite pressure vessels using the acoustic emission (AE) method. First, AE signals were captured during the 0–105 MPa and 0–158 MPa hydraulic tests of two vessels using multi-step loading method. Second, the AE feature parameters in time-domain and frequency-domain such as amplitude, frequency, and energy are studied. A multi-parameter statistical analysis (MPSA) method based on empirical mode decomposition (EMD) and K-means algorithm is performed to cluster AE events for the vessels. Intrinsic mode functions (IMFs) are decomposed by EMD and three IMFs with high frequency are chosen to reconstruct the feature parameters and provide signal pre-processing for K-means clustering analysis. Based on the relationship between AE features and damage modes, three main clusters with separate amplitude, absolute energy, and energy are correlated to matrix cracking, fiber/matrix debonding, and fiber breakage damage mechanisms. Besides, the effectiveness of MPSA method for signal classification is validated by principal component analysis (PCA) and fast Fourier transformation (FFT) method. Finally, the AE feature parameters such as amplitude and counts to peak for the three main damage modes are studied for the hydraulic proof tests and the burst tests to explore the damage evolution behaviors of the vessels with pressure increasing. Results show that AE method can be reliably used to characterize damage evolution mechanisms in composite pressure vessels.

The characteristics of mathematical reasoning and proof test on indonesian high school students

Both reasoning and proof ability have been considered as two sides of the coin on which cannot be separated. The reasoning ability is developed by solving proof tasks on which the students’ abilities in argumentation and justification are needed. However, the test items provided by the teachers tend to be routine problems by which the students’ reasoning ability is limited. This study aims to test the instrument of mathematical reasoning and proof evaluation at the high school level. The instrument had been carried out on 61 high school students in East Java. QUEST was used for analyzing the students’ answers. The result provides a value of INFIT MNSQ as 1,21 (around 1) and standard deviation 0,02 (around 0,0), which imply that the whole test fit with the PCM 1 PL model. The degree of difficulties of the developed high school reasoning and proof assessment instrument varies between −2.0 and +2,0, which imply that the instrument is categorized as good because the required criteria have been satisfied.

BEHAVIOR OF DISPLACEMENT CONCRETE PILE UNDER COMPRESSIVE LOADS

This paper provides the research of displacement precast piles through performing compressive Static Load Tests (SLTs). A total number of 40 piles which contain square solid pile and pipe pile with various pile lengths were tested. It is concluded that, because of the soil layers’ difference among driven locations, the piles with various lengths presents different maximum settlements. Furthermore, it is discovered that the load-settlement curves obtained from the same type of concrete pile are relatively parallel during unloading stages. For the solid pile, the interpretations which are based on Double Tangent and Chin’s method are used for capacity determination, and these results are compare to the designed ultimate capacity. It can be found that the Double Tangent method is conservative, and Chin’s method overestimate the pile capacity. The increase and reduction factors are proposed and then the modified Double Tangent and Chin’s interpretations are determined. Due to most of the SLTs being the Proof Tests (PTs), it is expected that this paper can provide practical information for geotechnical engineers to determine the ultimate bearing capacity of pile foundation from these PT results.

Structural development of ultra-lean-burn preburners for small liquid engines

An ultra-lean-burn preburner has been developed by KARI. This paper describes the general structural design, the results of the finite element analyses (FEA) and the experimental results related to structural issues during the development. Before the fabrication, two burst experiments with the specimens simulating the brazing joints were performed and compared with the FEA results, which increases the reliability of the analyses and the design. Also, 2D FEA of the combustion chamber cooling channel were performed for the first combustion region upstream of the liquid oxygen (LOX) hole and the second region downstream of the hole, where the hottest spot locates downstream of the region between the adjacent LOX holes. Various structural modifications were analyzed by 3D FEA and a screen structure was introduced to reduce the stress over highly stressed regions. During the development, some proof and leakage tests were performed for the head, the chamber with and without flange, and the preburner assembly, of which the burst test was performed. Several firing tests of the assembly were performed to show the operation without any structural failure.

Investigating 10th grade students’ understanding of the structure of deductive proof

Miyazaki, Fujita, and Jones define the structure of deductive proofs as the relational network via deductive reasoning that combines singular and universal propositions. Related to the theory, this research aims to investigate students understanding of the structure of deductive proofs. Researchers conducted a qualitative research to 30 students of 10th grade. The data was collected from geometrical proof test that focused on Sine and Cosine rule. The result of this research showing the lack of students understanding of the structure of deductive proofs. For the future research, researchers wonder whether to apply a flow-chart proof or a table proof to teach mathematical proving can improve students understanding of the structure of deductive proofs.

Structural Integrity Assessment of a Propellant tank in Presence of Welding Residual Stresses

Upper stage of India’s new generation launch vehicle makes use of cryogenic propellants with liquid hydrogen (LH2) and liquid oxygen (LOX) as fuel and oxidizer respectively. The propellants are stored in tanks fabricated of Aluminum alloy and contain various openings. As carrying out proof test at operating environment is not feasible, the tanks are subjected to proof pressure test at room temperature (RT). During the RT proof pressure test of LOX tank, high strains, greater than 8000με, were recorded by gauges at three locations where weld rework had been undertaken. From structural analysis, the maximum welding residual stress at these locations is evaluated to be 95N/mm2. From stress analysis point of view, positive margins were observed with respect to failure of the tank even in presence of these residual stresses.However, since the tank is operating at cryogenic temperature, though there is an increase in the yield and ultimate strengths of the tank material, there is a reduction in ductility (lower percentage elongation). Therefore, evaluation of structural integrity of the hardware from fracture point of view is of paramount importance. A study was undertaken to investigate the influence of residual stresses on integrity of the tank in presence of minimum detectable crack sizes using conventional NDE techniques. The location where maximum strains were observed, post proof test, is considered for fracture evaluation. Directional stresses at location of interest are predicted through detailed finite element analysis. Subsequently, generalized Failure Assessment Diagram was drawn based on Elasto-Plastic fracture mechanics principles and margin against ultimate load ensured. The tank was used in a launch vehicle which was successfully flown in June 2017.

Improving the Impact Resistance Performance of STF Treated Kevlar Fabric Structures

Abstract A continuous increase in the war-conflicts and development in the area of weapons challenges the research community to develop the body armor materials accordingly. The focus is on making the materials light weight and flexible yet improving its impact resistance performance to make the material compatible to use for a longer duration. Application of nano-materials such as nano-fibers, nano-fillers and nano-finishes are turning the concept into reality. Application of shear thickening fluid (STF) has been proved to increase the impact resistance performance of the textile structures to further use it as a body armor material. Present research deals within the same segment where nano-silica based STF was applied on Kevlar woven fabric to make the structure lightweight and flexible while improving its impact resistance performance. It was observed in the earlier studies by the authors that it is difficult to get a fair amount of add-on of STF on Kevlar fabric as it comes with a PTFE coating which hinders its absorbency. Hence, a novel method named as sequential padding is developed in the present study to improve the add-on of STF on Kevlar fabric. Contrary to the conventional process, where Kevlar fabric is treated with STF once using any one pressure, in sequential padding method, the Kevlar fabrics were treated twice using three levels of pressure (0.5, 1 and 2 bar) in various combinations and sequences. STF add-on % and dynamic Impact energy absorption on dynamic impact tester at a fixed velocity of 6 m/s were observed for sequentially padded fabrics and compared with untreated Kevlar fabric and fabrics treated with STF in single step. Low velocity bullet proof tests with 165 m/s were also performed to verify the results It was observed that both add-on% and impact energy absorption of Kevlar fabrics increases significantly with sequential padding process as compared to untreated as well as single step padding process. It was also noted that different combinations and sequences of padding pressures used for STF treatment of Kevlar fabric play a significant role in improving the impact resistance performance. It was noted that impact energy absorption of sequentially padded Kevlar fabric show almost 125% increase in ballistic impact energy absorption (40.62 J) as compared to untreated fabric (18.07 J). Therefore, it is concluded that sequential padding process opens up a new horizon for further improvement in impact performance of body armor materials based on STF treated Kevlar fabrics.

Characterising native hardwood timber bridges in New South Wales, Australia

During the period 1855-1930, in NSW, Australia many larger timber bridges with spans up to 100 m and overall lengths of 500 m were designed and constructed with local timbers. To justify the safety factors of these structures, the early characterisation of Australian timbers undertaken in the late 1800s is compared with contemporary characterisations. In this paper, a historical background to the early characterisation of Australian hardwoods is contextualised and compared with a more contemporary approach to demonstrate how to assess extant timber bridges. The strength of round structural bridge girders can be inferred from their in-service elasticity, and such knowledge can be incorporated both in new designs and in maintaining those extant. As a girder deteriorates, its modulus of rupture against modulus of elasticity vector will follow a predictable path. By interpreting this path the current and predicted carrying capacity of extant heritage-listed timber bridges can be assessed by loading with a low-mass vehicle precluding the need for proof testing.

Study on the Applicability of Dynamic Pile Load Test to Check Integrity during Installation of Extension Plate Attached PHC Piles and Bolts Spliced PHC Piles and the Correct Proof Test of the Transformed-installation PHC Piles

Study on the Applicability of Dynamic Pile Load Test to Check Integrity during Installation of Extension Plate Attached PHC Piles and Bolts Spliced PHC Piles and the Correct Proof Test of the Transformed-installation PHC Piles

Design, Preparation, and Performance of a Planar Ignitor Inserted With PyroMEMS Safe and Arm Device

A planar ignitor-based on low temperature co-fired ceramic (LTCC) and pyrotechnical micro electro mechanical system (PyroMEMS) technologies was designed and prepared in this paper. The planar ignitor is mainly composed of output charge layer, silicon safe and arm (Si-S&A) layer, and LTCC circuit base. Si/Pb3O4, C6H2(NO2)3OK/KClO4, and B/KNO3 were selected as ignition charge, gas charge, and transfer charge, respectively. The ignition circuit and main structure of the planar igniter were made by the LTCC process. Si-S&A was etched from monocrystalline silicon, which does not need environmental force to disarm. Preparation process of main components of planar ignitor that is suitable for mass production was introduced in detail. Simulation of PyroMEMS S&A actuation based on pendulum method was performed to save time for proof test. Finally, experimental verification on PyroMEMS S&A actuation and combustion propagation of B/KNO3 transfer charge were completed successfully. Results show that the idea of a planar ignitor inserted with PyroMEMS S&A device is feasible. [2018-0075]

Assessment of Safety Integrity Level by simulation of Dynamic Bayesian Networks considering test duration

This paper is devoted to model Safety Instrumented Systems (SISs) availability by Dynamic Bayesian Networks (DBNs). The models integrate several parameters but the main concerns of the study are the integration of test duration and test strategy. The proposed DBN are generic and can be reused for assessing performance and testing the effect of some parameters. More attention has been paid to the performance of the proof test, its harmlessness and particularly its duration. The duration increases the model complexity when considering the components availability given the test but it is more realistic. This parameter should be decided carefully to satisfy the Safety Integrity Level (SIL) objectives.

Analysis of spring operated pressure relief valve proof test data: Findings and implications

Ten years of research into spring operated pressure relief valve (SOPRV) proof test data are reviewed. Previously unpublished results are also presented. The principle findings are: proof test data alone are insufficient to properly analyze SOPRV safety behavior; root cause analysis (RCA) of all failed SOPRV is also required; probability of initial failure is a real and concerning phenomenon in both new (not previously installed) as well as used (previously installed) SOPRV but does not affect all SOPRV equally; SOPRV failure rates and safety performances depend on many variables including set pressure, SOPRV design and manufacturing specifics, and end user safety and maintenance practices; certain SOPRV require shorter proof test intervals (2–3 years) to maintain desired safety ratings but others can endure much longer proof test intervals with only small additional safety risks. Understanding all of the parameters which impact SOPRV safety performance and collecting safety performance data (including RCA of failed SOPRV) at the individual facility level are the keys to optimizing commissioning and pre‐installation proof testing and proof test intervals, and potentially to extending turnaround times. © 2018 American Institute of Chemical Engineers Process Saf Prog 37: 467–477, 2018

Proposed through-life management approaches for adhesively bonded repair of primary structures

The inability of current non-destructive inspection (NDI) procedures to confirm bond integrity has greatly limited the application of adhesively bonded repairs to primary aircraft structure, especially in applications where failure of the repair would lead to safety in flight concerns. Given these concerns, applications to primary structure are generally limited to situations where the residual strength of the parent structure in the absence of the repairs can exceed the design limit load by an acceptable factor, most conservatively as high as 1.5, which is the design ultimate strength.This paper proposes technologies and associated strategies that could lead to some relaxation of the current residual strength requirements. This makes possible the wider application of adhesively bonded repairs to primary metallic structure suffering fatigue cracks and composite airframe structure suffering visible impact damage.The detection of weak, and even absent (“Kissing”), adhesive bonds generally requires the application of a significant stress to the region of the adhesive bond which cannot be achieved by conventional NDI – ultrasonic techniques for example. Since it is generally not feasible to stress the actual repair patch, a “Proof Test” has been developed. This test requires the application of shear stress to a bonded repair coupon (BRC) made of the patch material. The BRC is bonded to the parent structure concurrently with the patch. This test can confirm both the initial and through-life structural integrity of the repair bond. However, it must be agreed by the appropriate authority that the BRC is fully representative of the patch system.In addition to the proof test more critical repairs also require through-life structural health monitoring (SHM) with a focus on detecting patch disbonding and a secondary focus in the case of repairs to metals of monitoring crack growth. It is concluded that to detect patch disbonding, a simple approach using resistance strain gauges, or more robustly optical fibre sensors, holds the most promise, at least in the short term. Disbonding is detected from measurements of reductions in strain transfer from the parent structure into the patch, an approach previously demonstrated during full-scale fatigue testing of a repaired F111 wing.Based on use of the Proof Test together with SHM, as appropriate, decision charts are presented for the management of adhesively bonded repairs to fatigue cracks in metallic structure in which the crack is not removed and to composite structure following removal of visual impact damage. A simple approach to the management of stress-reducing reinforcements for metallic components is also presented.

مستوى التفکیر الریاضی وعلاقته بالتحصیل فی الریاضیات لدى طلبة الصف العاشر من مرحلة التعلیم الأساسی فی الأردن

هدفت هذه الدراسة إلى الکشف عن مستوى التفکير الرياضيوعلاقته بالتحصيل في الرياضيات لدى طلبة الصف العاشر من مرحلة التعليم الأساسي في الأردن. ولتحقيق هذا الغرض، تکونت عينة الدراسة من (491) طالبا وطالبة من طلبة الصف العاشر، والذين تم اختيارهم عشوائيا من مدارس حکومية في مدينة عمان. وتکونت أدوات الدراسة من اختبار التحصيل في الرياضيات، واختبار التفکير الرياضي الذي تناول أنماط ومهارات التفکير الرياضي الآتية: الاستقراء، الاستنتاج، البرهان الرياضي، التفکير المنطقي، التعليل والتبرير (السببية)، وحل المسألة الرياضية الکلامية. وقد أشارت نتائج الدراسة إلى الآتي: - کان أداء الطلبة على اختبار التفکير الرياضي الکلي متوسطا ، في حين کان أداء الطلبة على اختبار الاستقراء هو الأعلى ، بينما کان أداء الطلبة على اختبار البرهان الرياضي هو الأدنى ، وکان أداء الطلبة متوسطا في اختبارات : الاستنتاج ، التفکير المنطقي ، وحل المسألة الرياضية الکلامية . في حين کان أداء الطلبة متدنيا في اختبار التعليل والتبرير(السببية) . - عدم وجود فروق ذات دلالة إحصائية بين متوسط علامات الذکور ومتوسط علامات الإناث في اختبار التفکير الرياضي الکلي وفي الاختبارات الفرعية للتفکير الرياضي : الاستقراء ، الاستنتاج ، البرهان الرياضي ، التفکير المنطقي ، التعليل والتبرير(السببية) ، وحل المسألة الرياضية الکلامية . - وجود ارتباط موجب دال إحصائيا بين التفکير الرياضي والتحصيل في الرياضيات لدى طلبة الصف العاشر . The Level of Mathematical Thinking and its Relationship with Mathematics Achievement of Tenth Grade Students in Jordan The purpose of the study was to investigate the level of mathematical thinking and its relationship with mathematics achievement of tenth grade students in Jordan. To achieve this purpose a study sample of (491) male and female students was selected from the tenth grade. The instruments of the study were a mathematics achievement test, and a mathematical thinking test which contained six major categories that covered the following types and skills of mathematical thinking: induction, deduction, mathematical proof, logical thinking, reasoning and rationalization and word problem solving. The results of the study revealed that: - The average performance of the students in mathematical thinking test was median, while the average performance in induction test was the highest, and the lowest performance was in mathematical proof test. - There were no significant differences between means of males and females in mathematical thinking test. - There was a significant positive correlation between the mathematical thinking and the students` achievement in mathematics.

The strengthening of a steel bridge with prestressed CFRP strips

The use of CFRP (carbon fibre reinforced polymer) strips in steel strengthening works has gone through a big development during the past 15 years. However, only in a few studies the effect of prestressing on the behaviour of steel beams strengthened with the CFRP strips has been examined. The paper briefly describes the research on the new CFRP strips prestressing system with special steel anchorages and its first on-site application for a steel bridge strengthening. The bridge proof tests before and after strengthening have been carried out. The results of testing proved the strengthening efficiency, however the final effect was moderate. As a result of strengthening the following effects has been gained: max. 18.3 % reduction of mid-span deflection and max. 13.9 % reduction of stresses in steel beams. The CFRP strengthening slightly improved the overall dynamic performance of the bridge span as well. The tests results showed moderate strengthening effects, mainly due to beams geometrical constraints not allowing to apply more than one 60 x 14 mm strip per beam. Regardless the moderate efficiency of strengthening, the research results clearly revealed that the new strengthening technology could be efficiently applied for steel bridges.

Out-of-plane Proof Testing of Masonry Infill Walls

Proof testing of multiple fired-clay-brick unreinforced masonry (URM) infill walls set within reinforced concrete frames was undertaken using airbags to simulate out-of-plane (OOP) loading. The proof testing was conducted to provide engineers in various research and practitioner roles with verified wall behaviour for the purpose of seismic assessment of buildings. A total of 19 tests were performed in six buildings. It was observed that two-way OOP flexure can substantially improve the OOP load-carrying capacity of tested infill walls compared to one-way vertical OOP flexure and that boundary restraints and presumed ‘arching’ action from the building frame can significantly increase the OOP capacity of URM walls. In addition, the effects of simulated in-plane damage on the OOP capacity of a URM infill wall were investigated, and it was found that the damage reduced the OOP strength by up to 40%. On-site proof testing is demonstrated as a simple and cost-effective way to establish actual wall lateral capacities in cases where boundary conditions cannot be clearly established and existing analytical models predict low lateral capacities.

Qualification of ITER PF6 helium inlet

The Poloidal Field (PF) coils are one of the main sub-systems of the ITER magnets. The PF6 coil is being manufactured by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) as per the Poloidal Field coils cooperation agreement signed between ASIPP and Fusion for Energy (F4E). As one of the critical components, helium inlet locates on the innermost turn and supplies the coil with supercritical helium. During Tokamak operation, the helium inlet will undergo huge cyclic electromagnetic loads and thermal cycling during cooling down and warming up.This paper focus on the main steps of ITER PF6 helium inlet qualification. Helium inlet hole drilling and stainless steel wrapping removal were firstly been carried out. Helium inlet welding with full penetration by automatic welding machine was then performed, followed by leak proof test, non-destructive test, fatigue test and tomography test. At the end, the samples were sectioned for micro and macro inspection. The results show ITER PF6 helium inlet qualification has successfully met the requirements of PF procurement agreement(PA) and was approved by ITER IO.

Additive manufacturing of Ti-45Al-4Nb-C by selective electron beam melting for automotive applications

Selective electron beam melting (SEBM) is shown to be a viable production route for titanium aluminides components. Fully dense and crack free parts can be produced. In the present paper a titanium aluminide alloy Ti-45Al-4Nb-C was investigated and the complete processing chain was developed, i.e. starting from the determination of the processing window, the evaluation of corresponding material properties for cube like specimens and finally the production of turbocharger wheels. The material properties were optimized by adjusting scanning strategy as well as heat treatment with particular consideration of the application to turbocharger wheels. The issue of dimensional accuracy and the feasibility of joining will be discussed and a proof test is performed.

2018/2 Court of Appeal restores burden of proof test in discrimination cases (UK)

2018/2 Court of Appeal restores burden of proof test in discrimination cases (UK)

Quantifying the contribution of competencies toward performance

PurposePerformance management (PM) is an important tool to enhance productivity. However, its Achilles heel is its lack of future orientation. The main reason for this is that PM systems fail to empirically link competencies to results. The purpose of this paper is to address this gap.Design/methodology/approachThis study uses literature review and deductive logic to evolve the concept of “Contribution of Competencies (CC)” and proof tests it quantitatively.FindingsThe impact of a level of competency on the results of a job can be determined by CC. The gap between expected and actual CC can predict future performance, determine the training needs with precision and measure individual efficacy and human capital adequacy of a department/an organization.Research limitations/implicationsThis is single organization research for proof of concept. Multi-organizational research using empirical study linking CC with demonstrated performance can make the concept of CC more robust.Practical implicationsCC helps to: prioritize training for competencies that would impact performance with surgical precision, fix responsibility for failure to perform on individual/organizational factors, compare individual employees across functions, determine interdepartmental/inter-firm human capital efficacy, and evaluate human capital of a firm.Originality/valueEmpirical expression of the nature of relationship between competency levels and results through CC and its byproducts, individual efficacy ratio, and human capital adequacy ratio are original contributions.