Automatic Debugging by Using Soft Constraints

研究成果の概要 (和文) : ソフトウェアの自動デバッグ方式の構築を目的として、プログラムの誤り特定手法に関する研究を行った。そのためのアプローチとして制約の概念を採用した。具体的には、入力、プログラム、事後条件から制約充足問題を構成した上で、違反の原因となった制約を特定し、プログラム中の対応する部分を誤り箇所の候補として提示するようにした。本研究では特に柔らかい制約を用いた自動デバッグ方式を構築し、Ｃ言語を対象とする自動デバッグツールを開発した。研究成果の概要 (英文) : We studied automatic software debugging by focusing on the localization of faults in programs. For this purpose, we adopted the notion of constraints. Specifically, we construct constraint satisfaction problems from inputs, programs, and post-conditions, and then localize constraints that cause the violations to indicate the corresponding program parts as candidates of the faults. We particularly constructed soft constraint-based methods for automatic debugging, and developed an automatic debugging tool for C programs

Automated Debugging with Soft Constraints (Fostering Joint International Research)

研究成果の概要 (和文) : ソフトウェアの自動デバッグ方式の構築を目的として，プログラムの不具合箇所発見・可視化方式を研究開発した．本方式は，不具合箇所を含みうるパスの部分をさらに分類して複数段階の柔らかい制約で符号化することで，不具合箇所候補のランキングを行う．また，複数段階の柔らかい制約を制約階層として扱う制約解消アルゴリズムを構築した．本アルゴリズムは，外部のＳＭＴソルバを用いて通常の制約問題を繰り返し生成し解消することで，制約階層を解消する．研究成果の概要 (英文) : To construct a technology for automated software debugging, we studied a method for localizing and visualizing faults in programs. The method performs the ranking of candidates for faults by encoding possibly faulty program paths with multi-level soft constraints. We also constructed an algorithm for solving multi-level soft constraints as constraint hierarchies. The algorithm solves constraint hierarchies by repeatedly generating and solving ordinary constraint problems by using an external SMT solver

Off-Fault Plasticity and Earthquake Rupture Dynamics: 2. Effects of Fluid Saturation

We present an analysis of inelastic off-fault response in fluid-saturated material during earthquake shear rupture. The analysis is conducted for 2-D plane strain deformation using an explicit dynamic finite element formulation. Along the fault, linear slip-weakening behavior is specified, and the off-fault material is described using an elastic-plastic description of the Drucker-Prager form, which characterizes the brittle behavior of rocks under compressive stress when the primary mode of inelastic deformation is frictional sliding of fissure surfaces, microcracking and granular flow. In this part (part 1), pore pressure changes were neglected in materials bordering the fault. In part 2, we more fully address the effects of fluid saturation. During the rapid stressing by a propagating rupture, the associated undrained response of the surrounding fluid-saturated material may be either strengthened or weakened against inelastic deformation. We consider poroelastoplastic materials with and without plastic dilation. During nondilatant undrained response near a propagating rupture, large increases in pore pressure on the compressional side of the fault decrease the effective normal stress and weaken the material, and decreases in pore pressure on the extensional side strengthen the material. Positive plastic dilatancy reduces pore pressure, universally strengthening the material. Dilatantly strengthened undrained deformation has a diffusive instability on a long enough timescale when the underlying drained deformation is unstable. Neglecting this instability on the short timescale of plastic straining, we show that undrained deformation is notably more resistant to shear localization than predicted by neglect of pore pressure changes.Earth and Planetary SciencesEngineering and Applied Science

Mechanical Behavior of a Ni-based Crystalline and a Zr-based Amorphous Materials Subjected to Surface Severe Plastic Deformation

A surface-treatment process, surface-severe-plastic deformation (S2PD), is developed and applied on both crystalline and amorphous materials to introduce the plastic deformation in the near-surface layer. A S2PD-processed crystalline component is expected to have enhanced fatigue properties because the refined grains in the near-surface layer and the coarse grains in the interior have good resistance to the crack initiation and propagation, respectively. The near-surface structures of the processed specimens were characterized by means of the optical microscopy, scanning-electron microscopy (SEM), X-ray diffraction (XRD), and transmission-electron microscopy (TEM). Mechanical properties, such as the microhardness, yield strength, and four-point-bend fatigue, were systematically investigated. It is shown that the S2PD process has the capability of simultaneously creating (a) a work-hardened surface layer, (b) a nanocrystalline (nc) surface layer, (c) a surface region with compressive-residual stresses, and (d) a grainsize gradient with a nc surface and a coarse-grained interior for the polycrystalline superalloy. Improved fatigue properties were found after the process. However, excessive treatments deteriorate the fatigue properties, and the possible reasons are discussed. For the amorphous material, thermal properties of the processed near-surface layer were characterized by means of the differential-scanning calorimetry (DSC). Effects of the treatment on the microhardness were studied by the nanoindentation. After the treatment, the plastic-flow deformation in the unconstrained sample edge was observed. In the sub-surface layer, the impact-induced shear-band operations generate the extrusion and intrusion marks on the side face. DSC shows that the free volumes of the deformed BMG have increased, and possible crystallization may occur during the process. XRD and high-energy synchrotron diffraction techniques were used to inspect the possible crystalline phase. A nanoindentation test shows that on the side surface, the hardness increases and, then, decreases with the distance from the processed surface. Four-point-bending-fatigue behavior has been studied and related to the modified surface structure and the compressive-residual stress induced by the process

Strain Localization in Pyroxenite by Reaction-Enhanced Softening in the Shallow Subcontinental Lithospheric Mantle

We report structural evidence of ductile strain localization in mantle pyroxenite from the spinel to plagioclase websterite transition in the Ronda Peridotite (southern Spain). Mapping shows that, in this domain, small-scale shear zones occurring at the base of the lithospheric section are systematically located within thin pyroxenite layers, suggesting that the pyroxenite was locally weaker than the host peridotite. Strain localization is associated with a sudden decrease of grain size and increasing volume fractions of plagioclase and amphibole as a result of a spinel to plagioclase phase transformation reaction during decompression. This reaction also fostered hydrogen extraction (‘dehydroxylation') from clinopyroxene producing effective fluid saturation that catalyzed the synkinematic net-transfer reaction. This reaction produced fine-grained olivine and plagioclase, allowing the onset of grain-size sensitive creep and further strain localization in these pyroxenite bands. The strain localization in the pyroxenites is thus explained by their more fertile composition, which allowed earlier onset of the phase transition reactions. Geothermobarometry undertaken on compositionally zoned constituent minerals suggests that this positive feedback between reactions and deformation is associated with cooling from at least 1000°C to 700°C and decompression from 1·0 to 0·5 GP

Intergranular stress corrosion cracking of ion irradiated 304L stainless steel in PWR environment

IASCC is irradiation – assisted enhancement of intergranular stress corrosion cracking susceptibility of austenitic stainless steel. It is a complex degrading phenomenon which can have a significant influence on maintenance time and cost of PWRs’ core internals and hence, is an issue of concern. Recent studies have proposed using ion irradiation (to be specific, proton irradiation) as an alternative of neutron irradiation to improve the current understanding of the mechanism. The objective of this study was to investigate the cracking susceptibility of irradiated SA 304L and factors contributing to cracking, using two different ion irradiations; iron and proton irradiations. Both resulted in generation of point defects in the microstructure and thereby causing hardening of the SA 304L. Material (unirradiated and iron irradiated) showed no susceptibility to intergranular cracking on subjection to SSRT with a strain rate of 5 × 10-8 s-1 up to 4 % plastic strain in inert environment. But, irradiation (iron and proton) was found to increase intergranular cracking severity of material on subjection to SSRT in simulated PWR primary water environment at 340 °C. Correlation between the cracking susceptibility and degree of localization was studied. Impact of iron irradiation on bulk oxidation of SA 304L was studied as well by conducting an oxidation test for 360 h in simulated PWR environment at 340 °C. The findings of this study indicate that the intergranular cracking of 304L stainless steel in PWR environment can be studied using Fe irradiation despite its small penetration depth in material. Furthermore, it has been shown that the cracking was similar in both iron and proton irradiated samples despite different degrees of localization. Lastly, on establishing iron irradiation as a successful tool, it was used to study the impact of surface finish and strain paths on intergranular cracking susceptibility of the material

Multiscale Biomechanics and Tribology of Inorganic and Organic Systems

This open access book gathers authoritative contributions concerning multiscale problems in biomechanics, geomechanics, materials science and tribology. It is written in memory of Sergey Grigorievich Psakhie to feature various aspects of his multifaceted research interests, ranging from theoretical physics, computer modeling of materials and material characterization at the atomic scale, to applications in space industry, medicine and geotectonics, and including organizational, psychological and philosophical aspects of scientific research and teaching as well. This book covers new advances relating to orthopedic implants, concerning the physiological, tribological and materials aspects of their behavior; medical and geological applications of permeable fluid-saturated materials; earthquake dynamics together with aspects relating to their managed and gentle release; lubrication, wear and material transfer in natural and artificial joints; material research in manufacturing processes; hard-soft matter interaction, including adhesive and capillary effects; using nanostructures for influencing living cells and for cancer treatment; manufacturing of surfaces with desired properties; self-organization of hierarchical structures during plastic deformation and thermal treatment; mechanics of composites and coatings; and many more. Covering established knowledge as well as new models and methods, this book provides readers with a comprehensive overview of the field, yet also with extensive details on each single topic

Superalloy Metallurgy a Gleeble Study of Environmental Fracture in Inconel 601

At temperatures above 0.5 Tm and in aggressive atmospheres predicting alloy performance is particularly challenging. Nickel alloys used in regimes where microstructure and properties are altered dynamically present unique requirements. Exposure may alter properties with unexpected early failure. The Gleeble is a valuable tool for investigation and simulation of thermo-mechanical properties of an alloy in various regimes up to the threshold of melting. In this study, four regimes of temperature and strain rate were simulated in an argon atmosphere to both investigate and document normal and abnormal failure modes. Commercial Inconel 601 was tested in selected regimes and in two treatments (as received and strain aged). Next two exposed conditions (TEOS and Hydride) were tested. Slow strain-rate and high temperature produced brittle intergranular fracture. Exposure at elevated temperature to process gases reduced both strength and ductility in both TEOS and Hydride. TEOS exposure reduced reduction in area in the alloy significantly more than the Hydride exposure