Test Data Compression Research Articles

Application of the VPSC Model to the Description of the Stress–Strain Response and Texture Evolution in AZ31 Mg for Various Strain Paths

Accurate description of the mechanical response of AZ31 Mg requires consideration of its strong anisotropy both at the single crystal and polycrystal levels, and its evolution with accumulated plastic deformation. In this paper, a self-consistent mean field crystal plasticity model, viscoplastic self-consistent (VPSC), is used for modeling the room-temperature deformation of AZ31 Mg. A step-by-step procedure to calibrate the material parameters based on simple tensile and compressive mechanical test data is outlined. It is shown that the model predicts with great accuracy both the macroscopic stress–strain response and the evolving texture for these strain paths used for calibration. The stress–strain response and texture evolution for loading paths that were not used for calibration, including off-axis uniaxial loadings and simple shear, are also well described. In particular, VPSC model predicts that for uniaxial tension along the through-thickness direction, the stress–strain curve should have a sigmoidal shape.

A DfT Architecture and Tool Flow for 3-D SICs With Test Data Compression, Embedded Cores, and Multiple Towers

This paper proposes a design-for-test architecture for efficient testing of 3-D ICs. The DfT architecture supports multiple dies, test data compression, and embedded cores. Commercial EDA tools are used to implement the DfT architecture.

An Investigation on the Fabric Type Dependency of the Crack Damage Thresholds in Brittle Rocks

Fabric-guided micro-fracturing phenomenon in brittle rocks and its effect on crack damage thresholds remains subject to continuing research. The available fabric in rocks can act as a motivator for nucleation and/or extension and interaction of micro-fractures in a preferred orientation, or as a suppressor for growth of micro-cracks in a given direction by different mechanisms such as compliance (stiffness contrast) or preferred orientation of minerals and their boundaries. While anisotropy of brittle rocks in terms of their mechanical strengths can play a significant role in the stability of underground openings, the understanding of the dependency of crack initiation (CI) and crack propagation (CD) thresholds on the available fabric in rocks can improve predictions of the extension and density of micro-fracturing in different directions in the walls of underground openings. To better understand the fabric-guided micro-fracturing phenomenon, and also to study the effect of fabric types available in brittle rocks on their anisotropic behaviour, four types of brittle rocks with different types of fabric are investigated in terms of crack damage anisotropy in this paper. The rocks that are chosen for this study are limestone from the Cobourg Formation, Queenston shale, Olkiluoto mica gneiss and Lac du Bonnet granite. For each rock type, CI and CD thresholds are identified from the unconfined compressive strength testing data. The mechanical behaviour of the four rock types are investigated at each damage stress level and the contributing factors to the isotropic or anisotropic behaviour of the rocks at different crack damage thresholds are discussed.

SOC Test Compression Scheme Sharing Free Variables in Embedded Deterministic Test Environment

This paper presents a new SOC test compression scheme in Embedded Deterministic Test (EDT) compression environment. Compressed test data is brought over the TAM from the tester to the cores in SOC and decompressed in the cores. The proposed scheme allows cores tested at the same time to share some test channels. By sharing free variables in these channels across test cubes of different cores decompressed at the same time, high encoding efficiency is achieved. Moreover, no excess control data is required in this scheme. The ability to reuse excess free variables eliminates the need for high precision in matching the number of test channels with the number of care bits for every core. Experimental results obtained for some SOC designs illustrate effectiveness of the proposed test application scheme.

Development and evaluation of a finite element model of the THOR for occupant protection of spaceflight crewmembers

New vehicles are currently being developed to transport humans to space. During the landing phases, crewmembers may be exposed to spinal and frontal loading. To reduce the risk of injuries during these common impact scenarios, the National Aeronautics and Space Administration (NASA) is developing new safety standards for spaceflight. The Test Device for Human Occupant Restraint (THOR) advanced multi-directional anthropomorphic test device (ATD), with the National Highway Traffic Safety Administration modification kit, has been chosen to evaluate occupant spacecraft safety because of its improved biofidelity.NASA tested the THOR ATD at Wright-Patterson Air Force Base (WPAFB) in various impact configurations, including frontal and spinal loading. A computational finite element model (FEM) of the THOR to match these latest modifications was developed in LS-DYNA software. The main goal of this study was to calibrate and validate the THOR FEM for use in future spacecraft safety studies.An optimization-based method was developed to calibrate the material models of the lumbar joints and pelvic flesh. Compression test data were used to calibrate the quasi-static material properties of the pelvic flesh, while whole body THOR ATD kinematic and kinetic responses under spinal and frontal loading conditions were used for dynamic calibration. The performance of the calibrated THOR FEM was evaluated by simulating separate THOR ATD tests with different crash pulses along both spinal and frontal directions. The model response was compared with test data by calculating its correlation score using the CORrelation and Analysis rating system. The biofidelity of the THOR FEM was then evaluated against tests recorded on human volunteers under 3 different frontal and spinal impact pulses.The calibrated THOR FEM responded with high similarity to the THOR ATD in all validation tests. The THOR FEM showed good biofidelity relative to human-volunteer data under spinal loading, but limited biofidelity under frontal loading. This may suggest a need for further improvements in both the THOR ATD and FEM. Overall, results presented in this study provide confidence in the THOR FEM for use in predicting THOR ATD responses for conditions, such as those observed in spacecraft landing, and for use in evaluating THOR ATD biofidelity.

Scan Test Bandwidth Management for Ultralarge-Scale System-on-Chip Architectures

This paper presents several techniques employed to resolve problems surfacing when applying scan bandwidth management to large industrial multicore system-on-chip (SoC) designs with embedded test data compression. These designs pose significant challenges to the channel management scheme, flow, and tools. This paper introduces several test logic architectures that facilitate preemptive test scheduling for SoC circuits with embedded deterministic test-based test data compression. The same solutions allow efficient handling of physical constraints in realistic applications. Finally, state-of-the-art SoC test scheduling algorithms are rearchitected accordingly by making provisions for: 1) setting up time-effective test configurations; 2) optimization of SoC pin partitions; 3) allocation of core-level channels based on scan data volume; and 4) more flexible core-wise usage of automatic test equipment channel resources. A detailed case study is illustrated herein with a variety of experiments allowing one to learn how to tradeoff different architectures and test-related factors.

Parameter estimation approach for particle flow model of rockfill materials using response surface method

Particle flow code (PFC) is widely used to model deformation and stress states of rockfill materials. The accuracy of numerical modeling with PFC is dependent upon the model parameter values. How to accurately determine model parameters remains one of the main challenges. In order to determine model parameters of particle flow model of rockfill materials, some triaxial compression experiments are performed, and the inversion procedure of model parameters based on response surface method is proposed. Parameters of particle flow model of rockfill materials are determined according to the observed data in triaxial compression tests for rockfill materials. The investigation shows that the normal stiffness, tangent stiffness and friction coefficient of rockfill materials will slightly increase with increase of confining pressure in triaxial compression tests. The experiments in laboratory show that the proposed inversion procedure behaves higher computing efficiency and the forecasted stress–strain relations agree well with observed values.

A model for characterizing crack closure effect of rocks

Abstract When there are large amounts of microcracks in the rock, they influence the rock strength and deformation significantly. The crack closure behavior in compression tests and its quantitative characterization are studied in this paper. Firstly, the widely used effective medium theory (EMT) is reviewed, and a method is proposed for characterizing the crack closure behavior of rocks. Secondly, four sets of uniaxial compression test data and four sets of triaxial compression test data are examined, and a negative exponential function is established to represent the relationship between the crack axial strain and the stress. A quantitative model is then proposed to describe the crack closure behavior. Finally, the proposed model is verified using the test results. It is found that the simulated stress–strain curves are in good agreement with the tested ones, indicating that the model can be used to capture the crack closure and the elastic deformation stages of rocks in both uniaxial and triaxial compressions. Variations of the crack closure strain (CCS) with the microcrack damage level and confinement are also discussed. The CCS may be used to estimate the crack density in a rock. By studying the crack closure effect, the amount of microcrack damage in rocks can be identified and possibly quantified.

A New Model for the Dilation of Brittle Rocks Based on Laboratory Compression Test Data with Separate Treatment of Dilatancy Mobilization and Decay

In this study, a new model is presented for the dilation angle of rocks which deform through brittle mechanisms in laboratory compression tests. This model, which is defined by a smaller number of independent parameters than similar models, is shown to fit laboratory test data for a wide variety of rocks (sedimentary rocks, diabase, marble, granites, and quartzite). A detailed investigation of each model parameter is performed, and potential links to geological and geotechnical properties are made. A mechanistic interpretation of the observed dilation angle data is also presented, in the context of the new model. Model parameters for the rock types studied are presented, and recommendations for parameter determination/estimation are made. The key strength of the model is shown to be its flexibility to accommodate a data-poor or data-rich analysis, as well as a simplified or comprehensive implementation. Practical guidance for model modifications is provided.

Static and dynamic mechanical properties of expanded polystyrene

Abstract Expanded polystyrene (EPS) is commonly used in a variety of applications because of its features of light weight, good thermal insulation, moisture resistance, durability, acoustic absorption and low thermal conductivity. It has been increasingly used in building constructions as core material of structural insulated panels (SIP). Some of those structures during their service life may be subjected to dynamic loads such as accidental or hostile explosion loads and windborne debris impacts. Understanding the dynamic material properties of EPS is essential for reliable predictions of the performances of the structural insulated panels with EPS foam core material. This paper presents static and dynamic compressive and tensile test data of EPS with density 13.5 kg/m3 and 28 kg/m3 at different strain rates. The dynamic strength, Young’s modulus and energy absorption capacities of the two EPS foams at different strain rates are obtained and presented in the paper. Based on the testing data, some empirical relations are derived, which can be used to model EPS properties in numerical simulations of dynamic responses of structural insulated panels with EPS foam core subjected to impact and blast loads.

Computing Seeds for LFSR-Based Test Generation From Nontest Cubes

In test data compression methods that are based on the use of a linear-feedback shift register (LFSR), a seed that produces a test for a target fault is computed based on a test cube for the fault. With a given LFSR, a seed may not exist for a given test cube, even though a seed may exist for a different test cube that detects the same fault. This issue is addressed in this brief by computing seeds for LFSR-based test generation without using test cubes. Instead, the procedure described in this brief is based on the use of nontest cubes. A nontest cube for a fault must be avoided in any test or test cube for the fault in order to allow the fault to be detected. Therefore, nontest cubes do not limit the ability of the procedure to compute seeds with a given LFSR. Experimental results demonstrate the advantages that the use of nontest cubes provides, and the associated computational cost.

On System-on-Chip Testing Using Hybrid Test Vector Compression

This paper presents a comprehensive hybrid test vector compression method for very large scale integration (VLSI) circuit testing, targeting specifically embedded cores-based system-on-chips (SoCs). In the proposed approach, a software program is loaded into the on-chip processor memory along with the compressed test data sets. To minimize on-chip storage besides testing time, the test data volume is first reduced by compaction in a hybrid manner before downloading into the processor. The method uses a set of adaptive coding techniques for realizing lossless compression. The compaction program need not to be loaded into the embedded processor, as only the decompression of test data is required for the automatic test equipment (ATE). The developed scheme necessitates minimal hardware overhead, while the on-chip embedded processor can be reused for normal operation on completion of testing. This paper reports results on studies of the problem and demonstrates the feasibility of the suggested methodology with simulation runs on the International Symposium on Circuits and Systems (ISCAS) 85 combinational and ISCAS 89 full-scan sequential benchmark circuits.

A hybrid method for segmented test data compression

This paper presents a hybrid compression method for scan-based testing. Four distinctive compression techniques, i.e. frequency-directed run-length codes (FDR), inverting FDR, option coding technique, and optimal selective Huffman code are selected for compression of a given test set. To lift the potential compression limit, we properly cluster scan cells to classify test data as four subsets respectively, by majorities of 0s, 1s, Xs, and a roughly equal number of 0s and 1s to match specific properties of the compression techniques. Segments are then, respectively, compressed by the technique that fits best to achieve an overall good compression effect. Experimental results for the larger ISCAS’89 benchmark circuits show that up to 69.9% of average compression ratio and significant test application time reduction can be achieved.

Estimation of state and properties of various-scale geomechanical objects using solutions of inverse problems

The authors comment on features of formulation and structure of input data for the inverse problems used in rock mechanics to estimate state and properties of natural and anthropogenic objects at various spatial scales. The article gives examples of using solutions of inverse problems in coal bed degassing monitoring, based on data on changes of pressure in hydraulic props in the overlying bed, and in assessment of deformation parameters of inclusions, based on data of uniaxial compression tests of artificial heterogeneous specimens.

Multi-scale modeling of time-dependent behavior of claystones with a viscoplastic compressible porous matrix

This paper is devoted to multi-scale modeling of time-dependent behavior of claystones using a two-step homogenization procedure. Two materials scales are considered. At the mesoscopic scale, the material is constituted by a clay matrix and embedded mineral grains. At the microscopic scale, the clay matrix is a porous medium composed of a solid phase and spherical pores. The macroscopic plastic criterion of the clay matrix is first determined by a modified secant method (Maghous et al., 2009) considering a pressure sensitive yield function for the solid phase. This criterion is then used as the loading function for the description of viscoplastic deformation of the clay matrix, together with a non-associated viscoplastic potential. At the second step of homogenization, the macroscopic behavior of the claystone is determined by taking into account the effect of mineral grains (quartz and calcite). For this purpose, we propose an extension of the incremental approach initially proposed by (Hill, 1965) to modeling of time-dependent behavior. Therefore, the micromechanical model is able to explicitly account for the effects of pores and mineral grains at two different scales. The numerical algorithm for numerical implementation of the micromechanical model is also presented. The proposed model is finally verified through comparisons between numerical results and experimental data in triaxial compression tests with constant strain rate and in triaxial creep tests.

Evaluation of Static and Dynamic Cushioning Properties of Polyethylene Foam for Determining Its Cushion Curves

A comparison of static and dynamic cushioning properties of polyethylene foam is discussed in this paper. A dynamic factor function is defined and obtained from the analysis on the experimental data from compression and cushion tests. The deformation energy per unit volume is taken into consideration to make an estimate of the maximum strain and dynamic stress data in an impact, and the peak acceleration can be predicted from the compression data corrected for the dynamic effects by the dynamic factor function. Then, the cushion curves at almost every test condition, such as different drop heights or thickness of cushioning material, can be approximated by a specially developed computer code using Matlab. This research can assist in determining the accuracy of cushion curves for all variants of a particular cushioning material from the dynamic factor function and compression test data. This new procedure will greatly simplify the experimental process for determining cushion curves. Copyright © 2014 John Wiley & Sons, Ltd.

Low-Power Test Generation by Merging of Functional Broadside Test Cubes

This paper describes a low-power test generation procedure, which targets the switching activity during the fast functional clock cycles of broadside tests. The procedure is based on merging of test cubes that it extracts from functional broadside tests. The use of test cube merging supports test compaction and it can be used for accommodating the constraints of test data compression. The use of functional broadside tests provides a target for the switching activity of low-power tests, which does not exceed the switching activity that is possible during functional operation, or that the circuit is designed for. The use of test cubes that are extracted from functional broadside tests is a unique feature of this procedure. It ensures that the low-power tests would create functional operation conditions in subcircuits that are defined by the test cubes. Experimental results show that the procedure detects all or almost all the transition faults that are detectable by arbitrary (functional and nonfunctional) broadside tests in benchmark circuits.

Hot deformation behaviour of niobium in temperature range 700–1500°C

Niobium was hot deformed in vacuum in uniaxial compression to a true strain of 0·6 in the temperature range of 700–1500°C and the strain rate range of 10−3–10 s−1. Strain rate sensitivity was calculated from the compression tests data and mapped out in contour plots with the aim to optimise the hot workability of niobium. The domain of hot workability was identified in the temperature range of 1200–1500°C and strain rate range of 10−2–1 s−1. In this domain the strain rate sensitivity was ∼0·15, the stress exponent 7·5 and the activation energy 246 kJ mol−1. Microstructure of the deformed samples showed features of dynamic recrystallisation within the high strain rate sensitivity domain and features of flow instability in the regime of low strain rate sensitivity. Compared to a previous study on Nb–1Zr–0·1C alloy, Nb showed a lower flow stress and an optimum hot working domain at lower temperatures.

Input Test Data Volume Reduction for Skewed-Load Tests by Additional Shifting of Scan-In States

Test data compression methods reduce the input test data volume by allowing compressed tests to be stored on a tester. Additional reductions in the input test data volume can be achieved if each stored test is used for producing several different tests. Skewed-load tests create a unique opportunity to expand a stored test into several different skewed-load tests by continuing to shift the scan-in state for one or more additional clock cycles. This opportunity for test data volume reduction beyond test data compression is introduced in this paper. The paper describes a procedure that starts from a given skewed-load test set. The procedure removes tests from the test set and recovers the fault coverage by applying several tests based on every stored test.

An Improved Method of Determining the Disturbed State Concept Model Parameters

The method of postulate of relatively intact model in the disturbed concept model is reached. Because it is more difficult to assume relatively intact curve by observed experimental data, a method which could automatically calculate the stress strain relation curve of relative intact by triaxial compression test data is raised, so that the determination of material parameters becomes easier, and the improved method is verified by numerical calculation. The results show that this method can effectively determine the stress strain relation curve of relative intact.