Test Cubes Research Articles

Process development and impact of intrinsic heat treatment on the mechanical performance of selective laser melted AISI 4140

The low alloy steel AISI 4140 (German grade 42CrMo4) is one of the most frequently used Quench & Tempering (Q&T) steels with a wide range of applicability. Until now, commercially available iron powders for additive manufacturing can be summed up by their low amount of carbon. Fusion welding of Q&T steels often leads to cracks due to brittle martensitic transformation and the associated volume change. Therefore, the selection of appropriate process parameters in laser powder bed fusion (LPBF) plays a key role for the final material properties and is achieved through utilization of a new process development strategy and evaluation of microstructural features of test cubes. In this work tensile specimens were successfully produced with optimal process parameters and mechanical tests of additively built samples indicate mechanical performance comparable with a 450 °C tempered state of conventionally cast material. By correlating the measured mechanical properties of LPBF samples to those of a conventional Q&T state, an estimation of the intrinsic heat treatment during LPBF was carried out using an inverse transient Hollomon–Jaffe approach. This analysis indicates that a rapid reheating rate of 103 − 105 °C/s to ≈700–800 °C of the previous built layers is the determinant for the low hardness found in the LPBF process of AISI 4140. This is also in accordance with the finely dispersed carbide precipitates in the as built condition. Furthermore, the effect of bed pre-heating on the final material tempering state was found to be negligible. This shows the importance of a balanced match between LPBF process parameters and subsequent application demands as well as necessary postprocessing steps.

Preventing early age chloride migration into low-carbon concrete

The use of substituting cementitious materials (SCMs) to produce low-carbon concrete is escalating. This contributes to reducing the anthropogenic emission of CO2, and to reduce harmful temperature gradients during cement hydration in massive structures. Mature low-carbon concretes are known to perform well on both strength and durability. However, the maturity process is slow compared to that of standard concrete. Structures made from low-carbon concrete are subject to penetration of agents like chloride at early age, accelerating degrading processes. Chloride penetration is a major problem especially to infrastructure, due to seawater proximity and the use of de-icing agents. Solutions for reducing penetration of harmful substances are called for, especially at early age in the life of structures made from concrete with high cement substitution. This paper reports from investigations on the use of hydrophobic paint utilized as surface treatment, to reduce the penetration of water-soluble agents like chlorides into low-carbon concrete at low maturity. The test specimens are mainly core cylinders, drilled from larger elements subsequent to exposure of NaCl-solution under ambient temperature conditions. Some tests have also been executed on standard test cubes, partly submerged in NaCl-solution and exposed to repeated freezing-thawing cycles to simulate the conditions in the splash-zone of marine structures. The results indicate a potential for reducing chloride penetration with efficiency up to 90%, depending on the exposure regime and the maturity level of the concrete and the hydrophobic paint.

LFSR Reseeding-Oriented Low-Power Test-Compression Architecture for Scan Designs

Massive test data volume and excessive test power consumption have become two strict challenges for very large scale integrated circuit testing. In BIST architecture, the unspecified bits are randomly filled by LFSR reseeding-based test compression scheme, which produces enormous switching activities during circuit testing, thereby causing high test power consumption for scan design. To solve the above thorny problem, LFSR reseeding-oriented low-power test-compression architecture is developed, and an optimized encoding algorithm is involved in conjunction with any LFSR-reseeding scheme to effectively reduce test storage and power consumption, it includes test cube-based block processing, dividing into hold partition sets and updating hold partition sets. The main contributions is to decrease logic transitions in scan chains and reduce specified bit in test cubes generated via LFSR reseeding. Experimental results demonstrate that the proposed scheme achieves a high test compression efficiency than the existing methods while significantly reduces test power consumption with acceptable area overhead for most Benchmark circuits.

Test Data Compression with Alternating Equal-Run-Length Coding

This paper presents a new X-filling algorithm for test power reduction and a novel encoding technique for test data compression in scan-based VLSI testing. The proposed encoding technique focuses on replacing redundant runs of the equal-run-length vector with a shorter codeword. The effectiveness of this compression method depends on a number of repeated runs occur in the fully specified test set. In order to maximize the repeated runs with equal run length, the unspecified bits in the test cubes are filled with the proposed technique called alternating equal-run-length (AERL) filling. The resultant test data are compressed using the proposed alternating equal-run-length coding to reduce the test data volume. Efficient decompression architecture is also presented to decode the original data with lesser area overhead and power. Experimental results obtained from larger ISCAS'89 benchmark circuits show the efficiency of the proposed work. The AERL achieves up to 82.05 % of compression ratio as well as up to 39.81% and 93.20 % of peak and average-power transitions in scan-in mode during IC testing.

Two-stage low power test data compression for digital VLSI circuits

In this paper, we present a hybrid X-filling and two-stage test data compression (TS-TDC) techniques for digital VLSI circuits to reduce the test power and test data volume respectively. The proposed hybrid X-filling combines adjacent filling and modified 4m filling technique to reduce the switching activities of the scan cells. It divides the unspecified bits present in the test cubes by multiples of 4 to increase the correlation between the consecutive test patterns which in turn provides better run length for test data reduction. The filled test cubes are encoded with two stage test data compression in order to reduce test data volume. In the first stage, the completely specified test sets are encoded using Alternative Statistical Run Length (ASRL) coding to enhance the test data compression. The compressed ASRL test set is encoded further using Run Length based Huffman Coding (RLHC) since ASRL codewords contain the maximum run length of oneâ;;s. Experimental results show that the proposed hybrid filling provides the scan-in average and peak-power transition reduction of 88% and 29% respectively against original test sets. The two-stage test data compression scheme achieves a maximum of 86% and an average of 76% compression ratio for ISCAS’89 benchmark circuits.

BASIC EMOTIONS, EXECUTIVE FUNCTIONS AND SOCIAL COGNITION IN PATIENTS AFTER STROKE

Alterations in executive functions (EF) constitute a common cognitive sequel, affecting up to 75% of patients with stroke. Previous investigations have found alterations in tasks of Theory of Mind (ToM) and empathy. Numerous studies have described alterations in the facial recognition of basic emotions (FRBE). However, there is little evidence on the presence of alterations in FRBE and social cognition, and their relationship with EF in this type of patients. We included 24 patients from Santa Catalina Neurorehabilitación Clínica with diagnosis of lobar ischemic stroke with an evolution time of 3 - 12 months. Patients with aphasia, visual perception deficit, fluctuations in the state of consciousness, or psychiatric antecedents were excluded. 17 patients completed these requirements and were able to complete the neurocognitive assessments and social cognition tasks. Control group: For the FRBE tests, 23 subjects were included, without neurological diseases. Instruments: General Diagnostic Battery: California Verbal Learning Test, Semantic Verbal Fluency, Boston Vocabulary, Complex King Figure, Symbols and Digits Test, Analogies, Matrices, Vocabulary, Digits and Adult Intelligence Scale Cubes Design WAIS III. Executive Function Tests: Wisconsin Card Sorting Test, Trail Making Test, FCR Copy Strategy, Reverse digits, phonological fluency. Tests of Social Cognition: Theory of the Mind (TOM): Reading of the Mind in the Eyes (RME), Faux Pas (FP), False belief (FB) of first and second order. Making of social decisions: Game of Dice Task (GDT). FRBE Battery: 60 photographs were selected based on the work of Calder et al. Three tasks were assembled, of 60 sheets each for basic emotion: joy, sadness, anger, disgust, fear and surprise. 92% of the patients presented alterations in at least two of the three tasks of FRBE. 75% showed alterations in TOM tasks. 42% showed alterations in GDT. 85% of the patients showed alterations in at least two EF tasks. Although the heterogeneity locations of the ischemias, most of the patients presented alterations in FRBE, TOM and EF. Disturbance for both the comprehension and expression of emotional and affective states are very frequent in this population, causing socially inadequate responses, deteriorating their rehabilitation process and quality of life.

Potential use of recycled construction and demolition waste aggregates for non- structural concrete applications

Promoting recycled aggregates from construction and demolition (C&D) waste for producing concrete will reduce the demand on conventional aggregates and it is an alternative to effectively manage C&D waste. Application of recycled C&D aggregates as a substitute to conventional aggregates in low strength concretes is the best way to initiate this in the industry. Therefore, this study focused on investigating the strength properties and the influence of time on the behaviour of strength gaining of concrete elements made by mixing the conventional aggregates and recycled C&D aggregates. The grade of the concrete was 25. The research methodology involved replacing the conventional coarse aggregates partially with 0 %, 20 %, 40 % and 60 % recycled C&D aggregates in concrete mixtures. Test cubes were cast for each percentage of the materials and other conditions were kept as constants. The test cubes were then subjected to compressive strength test under three test series. The test series were focused on different curing periods of the specimens as 7, 28 and 90 days to determine the behaviour of strength gaining with time. The conclusion drawn from the study is that it is feasible to substitute up to 40 % of coarse aggregates by recycled C&D aggregates in conventional low-intermediate strength concrete applications with the specified mix design.

Prognosis of fatigue and impact induced damage in concrete using embedded piezo-transducers

Concrete structures are often subjected to a wide array of load conditions, such as fatigue and impact, and the consequent damages. Recently, smart materials, in particular the piezoelectric materials, have received high attention from the point of view of structural health monitoring (SHM). In this connection, the electro-mechanical impedance (EMI) is one of the latest and most effective techniques. The technique harnesses the piezoelectric property of lead-zirconate-titanate (PZT) patches to sense any incipient damage. In the research covered in the paper, embedded PZT patches are employed to monitor the accumulating damage in plain cement concrete subjected to fatigue and impact type loadings. Concrete specimens (150 mm cubes and 100φ × 200 mm cylinders) of grade M-25 are cast with embedded concrete vibration sensors (CVS). The impact loading is simulated by a free falling iron-ball of mass 5 kg dropped from variable heights of 2 m, 2.5 m and 3 m above the top surface of the test cubes. For fatigue tests, a 4000 kN cyclic compression testing machine is used to apply the fatigue load in a sinusoidal form. The admittance signatures from the embedded PZT patches for impact and fatigue tests are acquired using an LCR meter. These signatures are used to determine the PZT-identified equivalent system properties (damping, stiffness and mass) of the specimens at varying damage states. For impact tests, strain history during the impact process is acquired in addition to the admittance signatures. The results for impact tests show an increase in the maximum strain induced in the patch with the number of impacts, while the equivalent damping computed from the admittance signature is found to decrease with increasing damage. For fatigue tests, the equivalent damping is again found to decrease with increasing damage, finally undergoing a phenomenal increase near the failure. Based on these measurements, separate relationships have been developed for impact and fatigue induced damages linking the PZT-identified damping with remaining life.

A Longitudinal Study of Neurocognition in Dementia with Lewy Bodies Compared to Alzheimer's Disease.

There are relatively few longitudinal studies on the differences in cognitive decline between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), and the majority of existing studies have suboptimal designs. We investigated the differences in cognitive decline in AD compared to DLB over 4 years and cognitive domain predictors of progression. In a longitudinal study, 266 patients with first-time diagnosis of mild dementia were included and followed annually. The patients were tested annually with neuropsychological tests and screening instruments [MMSE (Mini-Mental Status Examination), Clinical Dementia Rating (CDR), the second edition of California Verbal Learning Test (CVLT-II), Trail Making Test A & B (TMT A & B), Stroop test, Controlled Oral Word Associations Test (COWAT) animal naming, Boston Naming Test, Visual Object and Space Perception Battery (VOSP) Cubes and Silhouettes]. Longitudinal analyses were performed with linear mixed effects (LME) models and Cox regression. Both specific neuropsychological tests and cognitive domains were analyzed. This study sample comprised 119 AD and 67 DLB patients. In TMT A, the DLB patients had a faster decline over 4 years than patients with AD (p = 0.013). No other longitudinal differences in specific neuropsychological tests were found. Higher executive domain scores at baseline were associated with a longer time to reach severe dementia (CDR = 3) or death for the total sample (p = 0.032). High or low visuospatial function at baseline was not found to be associated with cognitive decline (MMSE) or progression of dementia severity (CDR) over time. Over 4 years, patients with DLB had a faster decline in TMT A than patients with AD, but this should be interpreted cautiously. Beyond this, there was little support for faster decline in DLB patients neuropsychologically than in AD patients.

Preliminary study of tin slag concrete mixture

The study focuses on practices to facilitate tin smelting industry to reduce radioactive waste product (Tin Slag) by diluting its radioactivity to a safe level and turning it to a safer infrastructural building product. In the process the concrete mix which include Portland cement, sand, tin slag, water and plasticizer are used to produce interlocking brick pavements, piles and other infrastructural products. The mixing method follows DOE (UK) standard method of mixing targeted at in selected compressive strength suitable for its function and durability. A batching machine is used in the mixing and six test cubes are produced for the test. The testing equipment used are a compressional machine, ultrasonic measurement and a Geiger Muller counter to evaluate of the concrete mix to find the lowest emission of radiation surface dose without compromising the strength of concrete mix. The result obtained indicated the radioactivity of tin slag in the mixing process has reduced to background level that is 0.5μSv/h while the strength and workability of the concrete has not been severely affected. In conclusion, the concrete mix with tin slag has shown the potential it can be turned into a safe beneficial infrastructural product with good strength.

Estimation of corrosion resistance of modifying concrete in a solution of sulfuric acid

This study presents the test results of 8 concrete series in 5% sulfuric acid solution for 28, 56 and 180 days. Each series was made using two mixtures based on CEM II/A-S 32.5 and CEM III/A 32.5 cements. Modification of the properties of concrete was obtained by the introduction of superplasticizer, silica fume, complex of structure modifier and hydrophobic admixture. The water-binder ratio varied from 0.27 to 0.63, the compressive strength was 26 to 83 MPa, and water absorption from 3.4 to 8.4 %. Samples of test cubes (10x10x10 cm) and test beam (16x4x4 cm) were prepared to immersion in the acid solution. The assessment of corrosion resistance was carried out on the weight loss and strength of concrete in relation to the initial value of 28 days. The obtained results showed that the surface layer of concrete in all samples was destroyed after 28 days of exposure. The deterioration of the corrosion resistance of modified concrete in relation to ordinary concrete without additives was observed regardless of the type of cement. An exception was a series of concrete, which had a water-binder ratio of 0.27–0.28 and a compressive strength of 77–83 MPa.

The influence of recycled concrete aggregate on the properties of concrete

Use of Recycled Coarse Aggregate (RCA) in concrete can be described in terms of environmental protection and economy. This paper deals with the mechanical properties of concrete compressive strength, splitting tensile strength, modulus of elasticity, and modulus of rupture. Three kinds of concrete mixtures were tested, concrete made with Natural Coarse Aggregate (NCA) as a control concrete and two types of concrete made with recycled coarse aggregate (50% and 100% replacement level of coarse recycled aggregate). These kinds of concrete were made with different targets of compressive strength of concrete f ’c (35MPa) and (70 MPa). Fifty specimens were tested of the fresh and hardened properties of concrete. The waste concrete from laboratory test cubes was crushed to produce the Recycled Coarse Aggregate used in recycled concrete. A comparative between the experimental results of the properties for fresh and hardened concrete is presented in the paper. Recycled aggregate concrete (RCA) had a satisfactory performance despite the replacement ratios. It was found using the size of Recycled Coarse Aggregate (RCA) of (5-14) mm has quite similar in performance with the same size of Natural Coarse Aggregate (NCA), it is necessary to use high quality of recycled concrete (with low levels of impurities). Recycled aggregate as an alternative to natural aggregates -seems quite successful.

Asymmetry dual-LFSR reseeding for low power BIST

Growing test data volume and excessive test power consumption are two of the major concerns for the industry when testing large integrated circuits. LFSR-decompressor-based compression methods have been widely adopted to reduce test data volume because they can provide high compression ratio. These techniques have been enhanced to address the need for low power as well as low test data volume. The key idea behind these methods is to generate seeds for LFSR reseeding such that the don’t-cares in test cubes are filled with proper values to reduce the transition count. This paper presents a LFSR reseeding approach adopting dual-LFSR to effectively reduce the amount of test data while keeping the scan-in power as low. Two LFSRs are used to jointly generate test patterns for a given test set to increase the correlation between neighboring bits and thus to reduce the transition count. Experimental results on the ISCAS’89 benchmarks demonstrate that our proposed approach can achieve a better compression ratio than the existing related dual-LFSR scheme while keeping a roughly equal shifting power reduction.

Surface topography investigations on nickel alloy 625 fabricated via laser powder bed fusion

Laser powder bed fusion as an additive manufacturing process produces complex surface topography at multiple scales through rapid heating, melting, directional cooling, and solidification that are often governed by laser path and layer-to-layer scanning strategies and influenced by process parameters such as power, scan velocity, hatch distance, and resultant energy density. Investigations on manufactured surfaces, as-built and after applying electropolishing, are performed using stylus profilometry, digital optical microscopy, and scanning electron microscopy techniques to reveal the complex surface texture of the nickel alloy 625 test cubes that are produced by following an experimental design. Surface texture is further explored using image processing together with machine learning-based algorithms. Measurement uncertainty is also discussed briefly. The results reveal a complex nature of laser powder bed fusion created surface topography and textures as exposed with electropolishing that may further lead to a quantitative understanding of such textures and their formations influenced by different scanning strategies and process parameters.

Optimal Don’t Care Filling for Minimizing Peak Toggles During At-Speed Stuck-At Testing

Due to the increase in manufacturing/environmental uncertainties in the nanometer regime, testing digital chips under different operating conditions becomes mandatory. Traditionally, stuck-at tests were applied at slow speed to detect structural defects and transition fault tests were applied at-speed to detect delay defects. Recently, it was shown that certain cell-internal defects can only be detected using at-speed stuck-at testing . Stuck-at test patterns are power hungry, thereby causing excessive voltage droop on the power grid, delaying the test response, and finally leading to false delay failures on the tester. This motivates the need for peak power minimization during at-speed stuck-at testing. In this article, we use input toggle minimization as a means to minimize a circuit’s power dissipation during at-speed stuck-at testing under the Combinational State Preservation scan (CSP-scan) Design-For-Testability (DFT) scheme. For circuits whose test sets are dominated by don’t cares, this article maps the problem of optimal X-filling for peak input toggle minimization to a variant of the interval coloring problem and proposes a Dynamic Programming (DP) algorithm (DP-fill) for the same along with a theoretical proof for its optimality. For circuits whose test sets are not dominated by don’t cares, we propose a max scatter Hamiltonian path algorithm, which ensures that the ordering is done such that the don’t cares are evenly distributed in the final ordering of test cubes, thereby leading to better input toggle savings than DP-fill. The proposed algorithms, when experimented on ITC99 benchmarks, produced peak power savings of up to 48% over the best-known algorithms in literature. We have also pruned the solutions thus obtained using Greedy and Simulated Annealing strategies with iterative 1-bit neighborhood to validate our idea of optimal input toggle minimization as an effective technique for minimizing peak power dissipation during at-speed stuck-at testing.

Performance of Anthill Soil Replaced Concrete in Sulfate Solutions

Durability of concrete is defined as its ability to resist any form of deterioration, allowing it to retain its original form and quality after it has been exposed to the environment of its intended use. Sulfate attack causes concrete to lose its compressive strength through the decomposition of the products of hydration of cement. Pozzolanic reactions from Supplementary Cementitious Materials (SCMs) help in resisting the sodium sulfate (Na2SO4) attack. This work investigated the potential use of Anthill Soil (AHS) to improve the performance of concrete in sulfate aggressive environments. An AHS replacement of 30% (per cent) by the weight of cement was used to make concrete test bars and cubes. The 0% replacement also referred to as the control was used as the point of reference from which all performances were measured. The specimens were immersed in 5% Na2SO4, 5% magnesium sulfate (MgSO4), and 5% mixed solution of Na2SO4 and MgSO4. Elongation measurements were taken over a period of 9 months, whereas compressive strength tests, which were used to work out the Strength Deterioration Factors (SDFs) and visual observations for surface deterioration were carried out at 9 months. From the results, AHS specimens that were immersed in the Na2SO4, MgSO4 and mixed Na2SO4 and MgSO4 solutions performed poorly in elongation compared with the control specimens, but had lower SDFs in the Na2SO4 and mixed solutions of Na2SO4 and MgSO4. The surface deterioration of AHS specimens in the MgSO4 solution was worse than that of the control specimens but was similar to that of the control in the mixed sulfate solution of Na2SO4 and MgSO4. The SDF results highlight the potential of using AHS with an advantage in Na2SO4 and mixed Na2SO4 and MgSO4 environments.

Performance of Anthill Soil Replaced Concrete in Sulfate Solutions

Durability of concrete is defined as its ability to resist any form of deterioration, allowing it to retain its original form and quality after it has been exposed to the environment of its intended use. Sulfate attack causes concrete to lose its compressive strength through the decomposition of the products of hydration of cement. Pozzolanic reactions from Supplementary Cementitious Materials (SCMs) help in resisting the sodium sulfate (Na2SO4) attack. This work investigated the potential use of Anthill Soil (AHS) to improve the performance of concrete in sulfate aggressive environments. An AHS replacement of 30% (per cent) by the weight of cement was used to make concrete test bars and cubes. The 0% replacement also referred to as the control was used as the point of reference from which all performances were measured. The specimens were immersed in 5% Na2SO4, 5% magnesium sulfate (MgSO4), and 5% mixed solution of Na2SO4 and MgSO4. Elongation measurements were taken over a period of 9 months, whereas compressive strength tests, which were used to work out the Strength Deterioration Factors (SDFs) and visual observations for surface deterioration were carried out at 9 months. From the results, AHS specimens that were immersed in the Na2SO4, MgSO4 and mixed Na2SO4 and MgSO4 solutions performed poorly in elongation compared with the control specimens, but had lower SDFs in the Na2SO4 and mixed solutions of Na2SO4 and MgSO4. The surface deterioration of AHS specimens in the MgSO4 solution was worse than that of the control specimens but was similar to that of the control in the mixed sulfate solution of Na2SO4 and MgSO4. The SDF results highlight the potential of using AHS with an advantage in Na2SO4 and mixed Na2SO4 and MgSO4 environments.

The Experiment Study of the Special Shaped Anchor Bearing Capacity

The partial stress concentration effect in traditional anchor is serious, leading to overall failure of anchors. Therefore, experiential method had been applied to explore the relationship between bolt bearing capacity, anchor thorn layer, strength of mortar and the block size, through improving the bearing capacity of anchor with the anchor thorn. From the test, below conclusions had been drown: firstly, the special shaped anchor bearing capacity has a linear relation with the early stress of cement mortar at the early stage, while after reaching a certain intensity, the relation would change to be nonlinear, meaning greater mortar strength doesn’t represent better function. Secondly, based on the experiment results, we can conclude that under the condition of single anchor thorn, the bearing capacity of anchor increases with the size of the test cube, representing that given a certain level of anchor thorn stress, the anchor bearing capacity is positively related to the thickness of the cement mortar.

Star-EDT: Deterministic On-Chip Scheme Using Compressed Test Patterns

This paper presents Star-EDT—a novel deterministic test compression scheme. The proposed solution seamlessly integrates with EDT-based compression and takes advantage of two key observations: 1) there exist clusters of test vectors that can detect many random-resistant faults with a cluster comprising a parent pattern and its derivatives obtained through simple transformations and 2) a significant majority of specified positions of ATPG-produced test cubes are typically clustered within a single or, at most, a few scan chains. The Star-EDT approach elevates compression ratios to values typically unachievable through conventional reseeding-based solutions. Experimental results obtained for large industrial designs, including those with a new class of test points aware of ATPG-induced conflicts, illustrate feasibility of the proposed deterministic test scheme and are reported herein. In particular, they confirm that the Star-EDT can act as a valuable form of deterministic BIST.

Computation of Seeds for LFSR -Based n -Detection Test Generation

This article describes a new procedure that generates seeds for LFSR -based test generation when the goal is to produce an n -detection test set. The procedure does not use test cubes in order to avoid the situation where a seed does not exist for a given test cube with a given LFSR . Instead, the procedure starts from a set of seeds that produces a one-detection test set. It modifies seeds to obtain new seeds such that the tests they produce increase the numbers of detections of target faults. The modification procedure also increases the number of faults that each additional seed detects. Experimental results are presented to demonstrate the effectiveness of the procedure.