Test Data Compression Research Articles

A microstructure-based constitutive model for cement paste with chemical leaching effect

This work focuses on the study of macroscopic mechanical behavior of cement paste in relation with micro-structural degradation due to chemical leaching. According to experimental evidences, the degradation of cement paste is mainly characterized by a significant increase of porosity due to the dissolution of Portlandite (CH) and the decalcification of calcium silicate hydrates (C–S–H). We shall first establish the explicit relations between macroscopic elastic properties and plastic yield stresses and porosity of cement paste by using analytical homogenization methods. With these relations, the degradation of elastic and plastic properties of cement paste by chemical leaching can be systematically determined. Combining with a specific plastic hardening law, the complete micro-macro constitutive model is formulated to describe the mechanical behavior of cement paste under general loading conditions. The efficiency of the proposed model is assessed through the comparison between numerical results and experimental data in uniaxial and triaxial compression tests performed on both sound and leached samples.

Comparative Assessment on the Hot Deformation Behaviour of 9Cr–1Mo Steel with 1Cr–1Mo Steel

Hot forged 1Cr–1Mo and 9Cr–1Mo steels are being progressively used in the making of the turbine rotors of steam power plants. Forging of these steels requires precise control of processing parameters (i.e. strain, strain rate and temperature) for a defect free product. In line with the above mentioned applications, a comparative study to analyze the hot deformation behavior of both the steels was carried out in the temperature domain of 850–1050 °C with varying strain rate (0.001–0.1 s−1) by compression test data obtained from Gleeble 3800® thermomechanical simulator up to true strain of 0.69. The flow stress behavior of hot compressed specimens was analyzed by using material constants, activation energy and formulated Zener–Hollomon parameter. Critical conditions for dynamic recrystallization (DRX) of both the steels were calculated with the help of a mathematical model developed by Poliak and Jonas. Further, the variations in critical conditions were correlated with the Zener–Hollomon parameter. For both the steels, the current study also focused on the comparison of dynamically recrystallized austenite ( $$X_{DRX}$$ ) volume fraction with respect to true strain by applying the concept of Avrami equation. Finally, to validate the kinetics of DRX and softening mechanism, the microstructural evaluation and characterization have been carried out using optical and electron microscopy.

Origami metamaterial with two-stage programmable compressive strength under quasi-static loading

An origami metamaterial with two-stage programmable compressive strength is proposed by combining the stacked Miura-origami and rhombic honeycomb structure. By adjusting the geometries of the structure, the compressive response of each stage including the compressive strength and the densification strain can be programmed within a certain range. Furthermore, the initial peak force, as an undesired energy-absorbing characteristic, can be programmed to maintain at a low level. The commonly seen fluctuation of crushing resistance on honeycomb structure is also minimized during the second stage deformation. The crushing behaviour of origami metamaterial is investigated under quasi-static loading condition. The programmability of compressive properties is demonstrated for the two stages of the deformation. The analytical model of the two-stage compressive response of the proposed origami metamaterial is firstly developed with friction contribution being taking into consideration during the first deformation stage. The analytical model is then verified with numerical analysis and quasi-static compressive testing data. The programmability of its compressive properties such as the initial peak crushing resistance, mean crushing force for both stages of deformation are then analysed based on the verified analytical model.

Damage propagation and dynamic material properties of aluminosilicate glass

Understanding the damage progression in aluminosilicate glass against impact loading is all-important for the design of a transparent structure. The Edge-on impact (EOI) experiments linked to the ultra-high-speed camera on glass plates are completed to visualize and quantify damage propagation. This followed quasi-static compressive and split-tensile, and dynamic compressive experimentation on aluminosilicate samples to examine failure process, strength, and crack initiation. By incorporating the compression and tensile test data, Johnson-Holmquist ceramic (JH-2) model parameters were estimated for aluminosilicate glass. The compression tests simulated for verification of determined JH-2 constants and finally validated by conducting the EOI simulations on glass plates to the spherical and cylindrical-shaped projectile. The simulated results for damage shape, propagation, and spall effect were collated with experiments and JH-2 model for aluminosilicate glass well predicted the impact/damage response. The high-speed visuals, calculated results, and scan electron microscopic imageries confirmed that damage progression is dependent on the impactor shape.

Padding of LFSR Seeds for Reduced Input Test Data Volume

In a commonly used test data compression method, the on-chip decompression logic is based on a linear-feedback shift-register ( $LFSR$ ), and compressed tests consist of seeds for the $LFSR$ . A seed can be modified and used for applying several different tests. This reduces the input test data volume further than the basic test data compression method. In this context, this article introduces a new approach for applying several different tests based on every seed. The new approach pads a seed in different ways to obtain new seeds for LFSR s with more bits, all of which can be implemented by a single programmable LFSR . The advantage of using LFSR s with more bits is that they are effective in detecting more target faults, thus supporting test compaction together with a reduction in the input test data volume. The experimental results for benchmark circuits demonstrate these points.

An empirical relation for parameter mi in the Hoek–Brown criterion of anisotropic intact rocks with consideration of the minor principal stress and stress-to-weak-plane angle

The parameter mi accounts for the anisotropy of rock strength, and the accurate determination of mi is a primary requirement of the Hoek–Brown (H–B) strength criterion. In this study, a relation for mi as a bivariate, second-order, polynomial function of the minor principal stress (σ3) and the angle (β) between the major principal stress and weak plane is developed. First, the possible contribution of σ3 and β to mi is systematically investigated based on substantial uniaxial and triaxial compression test data of various rock types collected from the available literature. This investigation allows mi to be described in terms of σ3 and β. A self-defined fitting function is adopted to formulate the functional relationship among these metrics. Using this relation, the H–B strength criterion is modified, and its performance is evaluated in two examples. The examples illustrate the improved ability of the modified criterion to determine the strength of metamorphic and sedimentary rocks. The applicability of this criterion to additional rock types warrants further study.

Three-dimensional discrete element simulation of the runaway vehicle deceleration process on the arrester bed of truck escape ramps.

Due to imperfect design norms and guidelines for China's truck escape ramp, previous studies have not been able to reflect the effect of wheel subsidence process on the deceleration of runaway vehicles. A discrete element method was used to establish an aggregate discrete element and a wheel discrete element. The three-dimensional discrete element model for an aggregate-wheel combination was established based on a particle flow code in three dimensions on a software platform using the "FISH" language. The microscopic parameters of the aggregate discrete element particles and wheel discrete element particles were calibrated using a simulated static triaxial compression test and real vehicle test data, respectively. Four sets of numerical simulation tests were designed for analyzing the influence of the aggregate diameter, grade of the arrester bed, truckload, and entry speed on the wheel subsidence depth and stopping distance of runaway vehicles. The results indicate that the smaller the aggregate diameter and entry speed and the greater the truckload and grade of the arrester bed, the more easily the wheel falls into the gravel aggregate, the better the deceleration effect, and the smaller the stopping distance. As the wheel subsidence depth increases, the speed at the unit stopping distance decreases more quickly. The maximum subsidence depth mainly depends on the truckload. The research results can provide a theoretical basis for the design of the arrester bed length and the thickness of the aggregate pavement in a truck escape ramp.

Experimental investigation of the unconfined compressive strength characteristics of masonry mortars

Mortar plays a major role on the strength and durability characteristics of masonry structures. While the mortar is in confined state in masonry, generally the unconfined compressive strength is assessed for quality control and strength assessment of masonry. Subsequently there are several testing methods available across different standards to determine the unconfined compressive strength of masonry mortars. Therefore this paper presents the outcome of the experimental programme conducted to empirically correlate the unconfined compressive strengths of masonry mortars determined through various testing methods. The compressive strength data of mortars were developed through testing of mortar cubes (50 mm and 70 mm), prisms (160 mm × 40 mm × 40 mm), cylinders (100 mm dia × 200 mm) and slates extracted from masonry joints (50 mm × 50 mm × 10 mm). Consequently to develop a comprehensive database to correlate the mortar compressive strengths determined through different testing methods, following variables were considered (1) mortar types (2) water to cement ratio (w/c) (3) age of testing and (4) curing conditions. Subsequently from the compressive test data obtained from the testing programme, strength correlations between different testing methods were established and presented. Furthermore simplified analytical stress-strain relationship for masonry mortars under unconfined compression is also proposed. The verification of the proposed analytical model was carried out using the experimental data obtained and the proposed simplified analytical model showed good agreement with the experimental data.

3D numerical investigation of the coupled interaction behavior between mechanized twin tunnels and groundwater – A case study: Shiraz metro line 2

Mechanized tunneling method using Tunnel Boring Machine (TBM) is being extensively employed in urban areas, especially when excavation takes place underneath the groundwater table. In this study, three-dimensional coupled Finite Element Analyses (FEA) have been performed to investigate the interaction mechanism between mechanized twin tunnels construction of Shiraz metro (line 2) and groundwater. Firstly, two soil constitutive models (Mohr-Coulomb and Modified Cam-Clay model) of Shiraz lean clay are validated against drained triaxial compression test data. Varying the permeability of the grout layer within the specified range, the base numerical model is then calibrated by the field data of ground surface settlements. Parametric studies are conducted subsequently to evaluate the effects of influencing factors involved in the coupled FEA of twin tunnels, including the drainage boundary condition of the grout layer, the position of groundwater level, and the rest interval between excavations of twin tunnels. The numerical results indicate that the ground surface settlements and internal forces of existing segmental lining are greatly influenced by the drainage condition of the grout layer. Also highlighted is the marked effect of the drainage condition of the grout layer in the numerical prediction of the interaction behavior between mechanized twin tunnels and groundwater in different cases of the groundwater level and the rest interval between excavations of twin tunnels.

Hybrid encoding for test data compression

Main disputes of digital integrated circuits testing are increasing test data volume and test power. The proposed encoding schemes are a combination of nine coded and selective pattern compression, Alternate Variable Run length code to reduce test data volume. The test cubes are divided into multiples of 8, 16, 32, and 64 blocks to upsurge the relationship among the successive test patterns which offers enriched test data reduction. The test data blocks are encoded with two methods in order to reduce test data volume. In the first method, the test sets are encoded using nine coded with selective pattern coding to expand the test data density. In the second method, the test sets are encoded using nine coded with Alternate variable run length laterally with selective pattern coding to improve the test data compression. Investigational results show that the proposed first and second approaches offer a maximum of 76% and 83% of compression ratio respectively for ISCAS’89 benchmark circuits.

Evaluation of optimum foam density for effective design of blast absorbers

A first-of-its-kind look-up matrix for determining ideal foam density against a spectrum of blast loads is developed to design an efficient foam-based blast absorber. A numerical study is carried out based on the principle of maximum blast energy absorption at minimum transmitted force. The model used in this study is developed using quasi-static compression test data. Comprehensive shock tube experiments are carried out on sandwich samples and the numerical model is validated against experimental results. This validated model is then applied to evaluate the performance of sandwich panels with varying foam densities under a range of blast loads.

An Efficient VLSI Test Data Compression Scheme for Circular Scan Architecture Based on Modified Ant Colony Meta-heuristic

A new test data compression scheme for circular scan architecture is proposed in this paper. A stochastic heuristic based bio-inspired optimization approach namely ant colony algorithm (ACO) is applied after modification and customization to improve compression efficiency. In circular scan architecture, test data compression is achieved by updating the conflicting bits between the most recently captured response and test vector to be applied next. The quantity of conflicting bits also manifests the Hamming distance between the most recently captured response and the next test vector. A significant reduction in test data volume and test application time is achieved by reducing Hamming distance. The problem is renovated as a traveling salesman problem (TSP). The test vectors are presumed as cities and Hamming distance between a pair of test vectors is treated as intercity distance and a modified ACO algorithm in combination with mutation operator is applied here to resolve this combinatorial optimization problem. The experimental results confirm the efficacy of this approach. An average improvement of 6.36% in compression ratio and 4.77% in test application time is achieved. The exhibited technique sustains an optimal level of performance without incurring any extra DFT (design for testability) cost.

Design of Injection Mold from Plastic Material

This paper deals with the use of plastics for making injection molds. Mold production times reduced by 90% and costs cut by up to 75% are some of the benefits of prototype molds from plastic materials. Today, materials with melt temperatures above 300 °C are used for plastic molds. They include ABS, PE, PP and PA. In this study, testing of high-temperature resin from Formlabs was performed. Compression and tensile test data are compared with the datasheet values and with virtual simulations. The tests were carried out at different temperatures. Based on their results, one can identify a suitable molding process with molds from this material.

Microstructure and high temperature mechanical properties of wire arc additively deposited Stellite 6 alloy

In this work, wire arc additive deposition of Stellite 6 alloy was carried out using cold metal transfer (CMT) process and the microstructural features, microhardness, and high temperature mechanical properties were studied. The as-deposited multi-layer wall was free of any defects. High temperature compression test samples were extracted parallel to the build direction, and the tensile samples were prepared along parallel and perpendicular orientation to the build direction. The hot compression test data was used to predict the flow behavior of the additively deposited alloy using an Arrhenius type equation at a strain of 0.6. The flow behavior of the additively deposited Stellite 6 alloy was similar to the conventional Co-based alloys in spite of the layer-by-layer macrostructure and microstructural variations. Microstructure, hardness, and phase analysis studies were carried out for the deformed samples after hot compression. The high temperature tensile properties were found to be anisotropic and location-specific, which were correlated with the columnar dendritic microstructure, alignment of the layer interfaces and variation in the secondary dendrite arm spacing due to repeated thermal cycles and difference in the cooling rate.

Hot deformation behavior and constitutive modelling of low carbon micro-alloyed steel YQ450NQR1 during isothermal compression

In this paper, the flow stress curves of YQ450NQR1 low carbon (wt. 0.12%) vanadium micro-alloyed YQ450NQR1 steel are obtained by conducting isothermal compression tests using Gleeble-1500 thermal simulation machine covering the temperature range of 1143K-1433K. To better describe the complex and abrupt deformation during the hot rolling process of the “Z-shaped” YQ450NQR1 products used for train beams, three deformation strain rates (1s−1, 10 s−1 and 30s−1) are selected to study the hot deformation behavior. On this basis, a constitutive model considering deformation activation energy is established from the experimental stress-strain data. The model is further validated against multiple sets of hot compression test data and shows a good accuracy between predicted and tested flow stress with a correlation coefficient of 0.988 and an average error of 8.4%, which indicates the accuracy and reliability of the constitutive model for YQ450NQR1 steel.

A micro-mechanics-based elastoplastic friction-damage model for brittle rocks and its application in deformation analysis of the left bank slope of Jinping I hydropower station

This study develops a micro-mechanics-based elastoplastic damage model within the framework of irreversible thermodynamics. In the model, damage is related to growth of micro-cracks, while plastic deformation is induced by frictional sliding along those cracks. The damage criterion and functions of thermodynamic force are used to describe the damage evolution of rocks and determine whether they are damaged. Time-dependent deformation of rock is also taken into account by considering subcritical growth of micro-cracks. For engineering application, the proposed model is implemented in the standard finite element code Abaqus as a user-defined material model (UMAT) by using a specific local integration algorithm. The accuracy of the proposed model is assessed by comparing numerical results with experimental data in conventional triaxial compression tests and triaxial creep tests. The proposed model is then used for simulating the displacement field, damage and plastic zones of the left bank high slope. The predicted results are in a good consistency with field monitored data.

Failure Criteria for Isotropic Rocks Using a Smooth Approximation of Modified Mohr–Coulomb Failure Function

It is reported that strength of rocks is a function of three-dimensional (3D) stress state as observed from the large sets of experimental results under the true-triaxial condition. Triaxial compression test data in general is readily available for rocks, but in practice true-triaxial facilities are seldom used. This creates a requirement for 3D failure criterion, which can be used to predict the true-triaxial strength using simple triaxial compression test data. We have proposed three criteria by altering the deviatoric function of modified Mohr–Coulomb criterion (Singh et al. in Int J Rock Mech Min Sci 48(4):546–555, 2011). The proposed criteria represent the behaviour of rock from lower to very high confining pressures. The criteria have unique yield surfaces. The yield surface changes its shape with the change in the mean stress. It is observed beyond certain value of the mean stress; the yield surfaces converge to von-Mises yield surface which means the shape of the yield surface is independent of pressure beyond the certain value of mean normal stress. The criteria require three parameters that can be easily calculated from the triaxial compression test results. The proposed criteria also satisfy the Drucker stability postulate, hence could be adopted as a plastic potential function. For the assessment of the criteria, true-triaxial data from twelve rocks are considered. Results of the criteria are compared with the modified Mohr–Coulomb criteria both 2D and 3D proposed by Singh et al. (Int J Rock Mech Min Sci 48(4):546–555, 2011). Performance of the new failure criteria for the considered rocks are observed to be better than the modified Mohr–Coulomb criteria (2D and 3D).

Visco-hyperelastic constitutive modeling of the dynamic mechanical behavior of HTPB casting explosive and its polymer binder

A new visco-hyperelastic constitutive model is developed to describe the dynamic compressive behavior of polymer-bonded explosive (60 wt% RDX, 16 wt% aluminum, and 24 wt% HTPB) and its polymer binder. The constitutive relationship comprises two parts: a component with a strain-energy function to characterize large deformation and a viscoelastic model to describe dynamic viscoelastic behavior. The hyperelastic model parameters are curve-fitted using quasi-static compressive test data under a strain rate of $$0.0001\,\hbox {s}^{-1}$$. The time–temperature superposition principle master modulus curves are studied using relaxation tests at different temperatures, and their compressive relaxation time and modules are obtained by fitting the master modulus curves. To obtain the rational dynamic compressive results, a modified split-Hopkinson compressive bar setup is designed such that the specimens are in dynamic stress equilibrium and deformed homogeneously at nearly constant strain rates. A comparison of the constitutive relationship with the experimental results revealed a good agreement and demonstrates its potential to describe the dynamic mechanical behavior of the PBX and its polymer binder.

LFSR-Based Test Generation for Reduced Fail Data Volume

Fail data is collected on a tester to allow defect diagnosis to be carried out. The high volume of fail data that some faulty units produce, and the test application time, motivated the development of procedures for terminating the fail data collection process before it stores the entire fail data for a faulty unit. A procedure for modifying a test set to reduce the fail data volume it produces was developed to complement these approaches, but without considering the constraints of a test data compression method. This article describes a procedure for modifying a stored test set to reduce the fail data volume under a test data compression method where a linear-feedback shift-register is used for on-chip decompression. The constraints of the test data compression method affect the procedure in several important ways. The experimental results for benchmark circuits demonstrate the ability of the procedure to reduce the fail data volume by modifying a stored test set.

Microstructure and High Temperature Mechanical Properties of Wire Arc Additively Deposited Stellite 6 Alloy

In this work, wire arc additive deposition of Stellite 6 alloy was carried out using the cold metal transfer (CMT) process and the microstructural features, microhardness, and high temperature mechanical properties were studied. The as-deposited multi-layer wall was free of any defects. High temperature compression test samples were extracted parallel to the build direction, and the tensile samples were prepared along parallel and perpendicular orientation to the build direction. The hot compression test data was used to predict the flow behavior of the additively deposited alloy using an Arrhenius type equation at a strain of 0.6. The flow behavior of the additively deposited Stellite 6 alloy was similar to the conventional Co-based alloys in spite of the layer-by-layer macrostructure and microstructural variations. Microstructure, hardness, and phase analysis studies were carried out for the deformed samples after hot compression. The high temperature tensile properties were found to be anisotropic and location-specific, which were correlated with the columnar dendritic microstructure, alignment of the layer interfaces and variation in the secondary dendrite arm spacing due to repeated thermal cycles and difference in the cooling rate.