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Macroscopic images of fracture surfaces of Charpy test specimens of steel R73 were studied, where bright spots in images represent cleavage facets or ductile dimples, respectively, both in special orientations. Within image analysis, they may be taken for the most significant textural element. Being the brightest patches in the image, they can be extracted by thresholding. Their counts and area distribution are closely related to temperature and impact energy.

The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.

It is important to know the impact fracture behaviors in the safety design of the brittle material board. However, the three-dimension analysis for the impact fracture behaviors of the brittle material board is not done over the current. In this research, the impact penetration fracture when the impact body collides with the center of the brittle material board is analyzed by PFC 3 D. It is the general three-dimensional program that uses the Distinct Element Method (DEM). DEM is suitable for the analysis of the fracture behavior of the non-individual body and the break-up body. The analytical results are compared with the experimental one and the validity of analytical results are checked. By this research, it is obvious that the penetration speed and the loss energy increase as the impact velocity, radius and mass of the impact body increase. Moreover, the relations between the parameters of impact body and fracture behavior are clarified.

Attempts have been made to improve the impact resistance of biodegradable thermoplastic polymer, PLA. A ductile biodegradable polymer, PCL, has been used to improve such property of PLA by using blending technique. Details of the impact fracture properties and mechanisms of PLA/PCL blends, however, have not fully been understood yet. Recently, it was also found that LTI can improve the immiscibility between PLA and PCL. In this study, PLA/PCL and PLA/PCL/LTI blends were prepared, and their impact fracture toughness values were measuredto assess the effect of PCL content and LTI addition on the impact resistance. Fracture mechanisms of the polymer blends were also characterized by scanning electron microscopy.

In order to investigate the mechanical behavior of newly developed materials such as bulk amorphous metals, it is essential to use small-size specimens. An instrumented impact testing apparatus was devised which could provide a load-displacement curve on subsize Charpy specimens under impact loading without oscillations. The impact fracture behaviors of Zr-based bulk amorphous metals (BAM) were investigated by using the instrumented impact tester using both V-notched and precracked subsize Charpy specimens. It was found that most of the fracture energy absorbed was used in the process of crack initiation through the development of shear bands.

Impact fracture strength is influenced by the loading direction and the length of a specimen subjected to an impact force. Such characteristic properties of the impact strength is described initially by introducing some examples. Based on the characteristic properties, a problem associated with the evaluation of the impact strength using the dynamic stress intensity factor of a cracked member is highlighted. It implies that further investigation is necessary to evaluate the integrity of cracked structural members subjected to impact loads.

In this study, a bar impact test of low velocity was carried out to gain an insight into the damage mechanism and sequence induced in alumina plates during quasi-static impact conditions. An experimental setup which could measure directly the impact force applied to the specimen and supply a compressive pre-stress to the specimen by utilizing an long bar impact was devised. During the bar impact testing, the influence of the pre-stress applied to the specimen along the impact direction on the fracture behavior was investigated. The measured impact force profiles explained well the damage behavior induced in alumina plates. The application of higher pre-stress to the specimen led to less damage due to the suppression of radial cracks which was caused by the increase in the apparent stiffness of the plate. The observed results showed the following sequence in damage development: The development of cone crack at the impact region, the formation of radial cracks from the rear surface of plate depending on the plate thickness, and the occurrence of crushing or fragmentation within the cone envelope.

The thermally tempered glass has strong resistance for the surface crack, because the residual compressive stress exists near the surface of the glass. On the other hand, it also has the residual tensile stress in the center of the glass. Fracture behavior of the thermally tempered glass depends on the distribution of the residual stress. However, it is very difficult to clarify those relationships by an experiment. In this paper, a thermally tempered glass model using the Extended Distinct Element Method (EDEM) is proposed. Using our proposed model, the impact fracture behavior and the crack velocity are evaluated. As results for the normal glass and tempered glass, it is confirmed that the distribution of residual stresses can be evaluated by the thermally tempered glass model and the thermally tempered glass model is broken to many pieces by the residual tensile stress as well as experimental results. Furthermore, it is found that residual stresses of tempered glass greatly influence the crack velocity.

Resistance to impact fracture and high flexural strength are desirable properties of denture base acrylics. The purpose of this laboratory study was to determine the Izod impact strength, the flexural strength, the flexural modulus, and the yield distance for four premium denture resins. Bar specimens 86 x 11 x 3 mm of Lucitone 199, Fricke Hi-I, ProBase Hot, and Sledgehammer Maxipack were fabricated following the manufacturer's instructions for heat processing. The bars were surface finished using silicon carbide paper to 600 grit. Ten specimens from three lots of each material were made (n=30). Flexural strength, flexural modulus, and yield distance were determined by testing the specimens to failure using a three-point test fixture. Izod impact strength was determined using an Izod tester on un-notched specimens generated from the flexural test (n=60). Analysis of variance (ANOVA) and post-hoc Tukey's test were used for statistical comparison of each property. There were significant differences in the physical properties among the denture acrylics tested. Lucitone 199 demonstrated the highest impact strength, flexural strength, and yield distance (pCitationMeng TR, Latta MA. Physical Properties of Four Acrylic Denture Base Resins. J Contemp Dent Pract 2005 November;(6)4:093-100.

Impact is the largest single cause of the fracture of glass objects, although thermal stresses and simple overloading, including pressure loading, also contribute to glass failures. Impact fractures of glass may be caused by either the glass object contacting a hard surface, such as when champagne glasses are thrown into a stone fireplace, or by a projectile striking the glass, such as a baseball encountering a window or a stone striking an auto windshield. In every instance, the impact fracture of glass appears to occur instantaneously, accompanied by an acoustic outburst of discernible magnitude. For these reasons, many glass impact fractures, particularly those of beverage containers, are attributed erroneously to explosions.

Technique for creation of polycrystalline computer materials is presented. The method considered allows for the obtaining of not only polycrystalline particle packings with various grains sizes but also the creating of materials with the preset value of porosity. Plate impact experiments were performed to compare strength properties of mono- and polycrystalline computer materials and also to investigate influence of the material porosity on the shock wave penetration and spallation processes. The experiments show significant differences in the impact fracture processes between mono- and polycrystalline materials. Smearing the shock waves due to heterogeneity of the granular structure of the polycrystals decreases localization effects, and the fracture occupies larger areas but with the smaller level of injury. Porosity adds significant resistance due to the strong plastic deformation during the pore collapsing. This effect can strongly decrease the penetration distance of the shock wave and even prevent the spallation.

This paper presents an impact fracture analysis of a ceramic plate by the extended distinct element method (EDEM). The EDEM model consists of springs, dampers and sliders between two elements in both the normal and tangential directions. This model has the continuity by introducing the pore-springs, which show the effect of the pore material between elements. The medium composed of the EDEM model becomes gradually discontinuous with the destruction of the pore-springs. The purpose of this study is to confirm usefulness of this method for the analysis of the impact fracture and to examine the effect of the impact velocity on the impact fracture behavior. From numerical results, it is shown that the impact velocity greatly influences in the mode of the impact fracture and the genera-tion of the crack is localized at the collision part with the increase in the impact velocity. It is also found the position of fracture is closely related to the position of the high equivalent stress.

The structure and impact toughness of the pipeline 17Mn1Si steel have been studied. The main attention was paid to the analysis of various conditions of stress concentration under dynamic loadings. The process of strain localization with increasing stress state stiffness at the tip of the concentrator with decreasing testing temperature was investigated. Impact loading diagrams for specimens with various stress concentrator shapes were registered and analyzed.

The impact fracture toughness of several ethylene-propylene block copolymers has been evaluated using the traditional contact notch sharpening technique of tapping and a new non-contact technique based on femtolaser ablation. The fracture toughness values obtained with the specimens notched by the femtolaser ablation technique were always lower than the tapped specimens. The impact fracture toughness values of these block copolymers does not depend only on the ethylene content, but also the molecular weight has a remarkable influence. © 2014 Elsevier Ltd. All rights reserved.

In this paper, the influence of temperature on impact toughness and fracture behavior of alloy steel (AISI Classification 8320) is presented and discussed. Impact toughness decreased with a decrease in test temperature. The extrinsic influence of temperature on impact toughness–fracture resistance relationships is rationalized in light of the conjoint and mutually interactive influences of intrinsic microstructural features, local stress states and macroscopic fracture behavior.

In order to investigate impact fracture behavior of carbons, the following processes were carried out. A high velocity steel sphere accelerated by a two-stage light gas gun was impacted on three kinds of polycrystalline graphites having different maximum particle sizes and a C/C composite. In-site observation of impact fracture was performed by using a high-speed framing camera, taking pictures of those specimens in front, rear and side views. As a result, the following are obtained. In spite of similar density and elastic modulus graphites, the graphites of the biggest and the middle maximum particle size have similarity in little cracks on their front surface, differing from one of the smallest. On the contrary, the graphites of the smallest and the middle maximum particle size have similarity in brittle fracture on their rear surface, differing from one of the biggest. The gushing fine fragments were recognised in all specimens on side view. Their lengths depend on maximum particle size of the specimen.

The impact fracture behavior of molecularly orientated polycarbonate (PC) sheets was investigated. The molecular orientation was achieved via a newly developed equal channel angular extrusion (ECAE) process. Improvement in impact fracture propagation resistance was observed in the ECAE processed PC sheets. The improved impact resistance was found to be directly related to the changes in molecular orientation because of ECAE. The unique characteristics of the ECAE process for polymer extrusion are described. The potential benefits of ECAE in enhancing physical and mechanical properties of the extruded PC sheets are discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2060–2066, 2001

A method based on the measurement of failure time is being developed by the European Structural Integrity Society to determine high rate fracture toughness of polymers. The test method appears reasonably straightforward but produced unacceptably high scatter, due to failure time data scatter. In this work an experimentally based sensitivity study was performed by fracture tests at 1 ms−1 in order to determine the causes of scatter and to seek to improve the test protocol. No single cause of scatter was identified but the quality and repeatability of the notching technique was identified as a major contributor.

The present paper discusses the theoretical modelling of liquid impact damage thresholds as a result of spatial and temporal distributions of transient stresses in elastically deformable brittle materials. The model predicts changes in the response characteristics of brittle materials owing to an idealised representation of a droplet of water impacting a plane surface. The analytical approach used does not include the effect of lateral outflow of water and is therefore only applicable to the first stages of impact where the compressibility of water in the droplet is most significant. The predicted response characteristics are compared with experimental data generated using controlled liquid jet impacts produced by the Cavendish Laboratory’s multiple impact jet apparatus (MIJA). The predicted responses of a selection of infrared transmitting materials compare well with experimental results. The results illustrate the importance of the first stages of liquid impact.

In this paper, dynamic stress intensity factors of bonded dissimilar materials were determined by using caustics methods. Bonding between epoxy resin and polycarbonate composed specimens by epoxy bond. Upper materials of specimens were epoxy resin and polycarbonate. Lower materials were polycarbonate with V notches for all. V notch length was 3mm. As the result of this experiment, dynamic stress intensity factor of bonded materials was larger than non-interface specimen. It is clear that crack tips influenced these interfaces and mechanical properties of upper meterials. In dynamic behavior, each specimens showed a similar tendency up to 300, 600 and 900 μs. Dynamic stress intensity factor increase became less at 300, 600 and 900 μs, and afterwards became moer. Cracks were propagated at t=950 μs for interface next reached interface and became interface crack. Dynamic fracture toughness of bonded materials was larger than non-interface specimen, but time of crack propagated were faster than this.

For the windshield of automobiles, laminated glass with bilayer glass of the same thickness and interlayer polyvinyl butyral is usually used. Recently, asymmetrically laminated glass with thinner inside glass is used in order to reduce the weight without loosing the safety. On the other hand, it is well known that the impact strength of the laminated glass is infulenced by the initial crack occurred after car crashed. In this study, the symmetrically and asymmetrically lamineted glass are impacted through the airbag by the striker shot from a special experimental apparatus. The fracture behavior of the laminated glass without and with three types of the initial crack, are observed and compared. Based on the analysis results of the corresponding discrete element models, the impact fracture mechanism of the lamineted glass is investigated.

A study is made of the problem of the penetration of a wedge-shaped tool in rock. It follows from the solution of the problem in the elastoplastic formulation that the continuation of the axis of the wedge in the elastic region includes a zone in which the rock is subjected to tension perpendicular to the axis. In accordance with the kinetic thermofluctuation theory of strength, this determines the formation and propagation of microcracks oriented along the wedge axis. A computer model is proposed to describe the process of random accumulation of microdefects in a loaded solid body. The model is used to create an algorithm to calculate the formation and development of an incipient crack before the vertex of the wedge. The length of the crack is determined by the properties of the medium and the parameters of the penetrated tool.

A degradação do ABS foi avaliada após envelhecimento térmico (ASTM D794) e fotooxidativo (ASTM G53 e G24). Essas condições foram escolhidas na tentativa de simular as condições a que esse polímero é submetido durante seu ciclo de vida como componente automobilístico. As mudanças ocorridas no ABS envelhecido pelos três métodos, em diferentes tempos, foram caracterizadas por ensaios mecânicos de tração e impacto, pelo índice de fluidez, pelo índice de carbonilas (FT-IR), pelo índice de amarelecimento e por fotografias ampliadas das fraturas de impacto. Os resultados mostraram que cada técnica utilizada fornece uma resposta característica em função do método de envelhecimento utilizado. A aplicação de técnicas de análise multivariada aos resultados permitiu uma visualização da degradação do material em função das técnicas de envelhecimento. The ABS degradation was investigated after thermal- (80°C) and photo-oxidative ageing (ASTM G53 and G24). These conditions were selected to simulate a car interior and the ABS lifetime weatherability. ABS changes were characterised by mechanical properties, melt flow index, carbonyl index (FT-IR), yellowing index and macro-photography of impact fracture. The results showed that each technique gives a characteristically answer for the ageing method. The multivariate analysis provided the degradation view as a function of the ageing method.

Influence of a structure with intergranular grain boundaries on mechanical properties and development of impact and fatigue failure processes were considered on an example of St3 steel. Fractographic studies showed that a brittle component is observed during impact fracture when the presence of knife-like boundaries inside the ferrite grains take place, the rate of growth of fatigue cracks increases.

In this paper, the PVC impact fracture modes and processes were analyzed via the technique of successively increasing impact energies. Force-displacement and microscopic analyses were employed at macroscopic level to study PVC fracture modes. The fracture modes were classified as: ductile, brittle, and mixed. The mixed mode was separated into: semi-ductile and semi-brittle. In the semi-ductile mode, radial cracks were initiated and propagated, but were ultimatley arrested. For the semi-brittle mode, the fracture was characterized by connected radial and circumferential cracks. It was verified that the primary elements which governed the fracture modes and impact resistance of PVC were the crack initiation and propagation processes.