Fracture Strength Of Materials Research Articles

Hitting the material rail: An exploration of the comparison between Alloy Steel and AISI 1020

The rail track is a component that directly interfaces with the wheels. Generally, rail tracks serve as the foundation for trains, trams, and similar vehicles, bearing the friction and pressure from the wheels. Rail tracks have the potential for cracking and breaking due to various loads. Many studies have investigated the factors causing rail track fractures. This article employs the Finite Element Analysis (FEA) method using Solidworks research license software. In this simulation, two rail tracks with different materials, AISI 1020 and Alloy Steel, are numerically studied using Solidworks software to determine the most effective material for mitigating the risk of rail track fractures. The fracture risk is then calculated based on the material's fracture strength. The simulation results indicate that the fracture risk of rail tracks using Alloy Steel is lower than that of AISI 1020, thus recommending Alloy Steel as the more suitable material for rail tracks.

Characterization of temperature dependence of fracture behavior of monolithic and laminated ultra‐high temperature ceramic matrix composites

AbstractThe fracture behavior of ultra‐high temperature ceramic matrix composites at high temperature has received increasing attention. However, few studies consider the effect of particle/crack interaction on the high temperature fracture strength of materials. In this work, the effect of particle/crack interaction is introduced into temperature‐dependent fracture strength model of monolithic ultra‐high temperature ceramic matrix composites, which also considers effects of flaw size, grain size, and residual thermal stress. Furthermore, by considering the influence of laminated structure, a theoretical model of the temperature‐dependent fracture strength of laminated ceramic matrix composites is developed. The effect of particle/crack interaction is also included in this model. It should be noted that the predictions of models agree well with the experimental data of both monolithic and laminated materials without using any fitting parameters. The effect of particle/crack interaction is found to have a significant weakening effect on the strength of materials at different temperatures.

The Flexural Strength of Acrylic Resin Repairs Reinforced with Different Nanoparticles

Objective: The purpose of this study is to assess the flexural strength of heat-cure acrylic resins repaired with auto-polymerized acrylic resins modified with 1%, 3% TiO2, Fe2O3, CuO nanoparticles. Materials and Methods: Fifty-six samples (65x10x2.5 mm) were prepared with heat-cure acrylic resins and divided into 7 groups (8 samples each) to make repair procedure: Specimens were repaired with unmodified (control group) and 1%, 3% TiO2, Fe2O3, CuO added auto-polymerized acrylic resins. For 3-point flexural test, the force was loaded at 5 mm/min crosshead speed directly to the middle part of the repaired acrylic resin with a Universal Testing Machine. Data were analyzed statistically by ANOVA followed by Tukey test (p < 0.05). Results: Control group showed lower strength values than the other groups. 1% TiO2 nanoparticle added group showed significantly higher flexural strength values than 3% added groups and control group (p < 0.05). The highest strength value was measured in 1% TiO2 group. Conclusion: Acrylic resins reinforced with 1% TiO2 developed higher strength than resins reinforced with 3 % TiO2, Fe2O3, CuO nanoparticles. Adding 1% nanoparticles to resins could improve the fracture strength of materials.

Residual Stress Analysis in Deep Rolling Process on Gas Tungsten Arc Weld of Stainless Steel AISI 316L

Because of the general problem of the welding workpiece such as fatigue fracture caused by tensile residual stress lead to initial and propagation crack in the fusion zone. Thus, the mechanical surface treatment of deep rolling on Gas Tungsten Arc Welded (GTAW) surfaces of AISI 316L was studied. Deep rolling (DR) is a cold working process to induce compressive residual stress in the surface layer of the workpiece resulting in hardening deformation which increased surface hardness, and smooth surface that inhibit crack growth and improve fracture strength of materials. The present study focuses on compressive residual stress at the surface of stainless steel AISI 316L butt welded joint of GTAW. The three parameters of DR process were used; pressure 150 bar, rolling speed 400 mm/min, and step over 1.0 mm. The residual stresses analysis by X-ray diffraction with sin2Ψ method at 0, 5, 10, and 20 mm from the center of the welded bead. The results showed that the DR process on the welded of GTAW induce the minimum compressive residual stress-408.6 MPa and maximum-498.1 MPa in longitudinal direction. The results of transverse residual stress in minimum and maximum are 43.7 MPa and-34.8 MPa respectively. The FWHM of DR both longitudinal and transverse direction were increased in the same trend. Furthermore, the microhardness after DR treatment on workpiece surface layer higher than GTAW average 0.4 times.

THE EFFECT OF WELDING CURRENT ON AISI 1045 STRENGTH AND CORROSION RATE

Shielded Metal Arc Welding (SMAW) was widely used in industry for joining AISI 1045 steel because this method was simple, in-expensive, and the device is portable. This researched aimed to analyze the effect of variations in welding current towards material strength and corrosion rate of AISI 1045. Welding current that been used as variations in this study are 100, 110, and 120 Ampere. This research was conducted using tensile test on the weld area and immersion around the weld area in NaCl solution with 0.4% concentration. From the research that conducted, it is known that increasing in welding current made the yield strength, tensile strength, and fracture strength of material also increased. This phenomenon also happened for elongation of material in weld area. With increasing the welding current then the elongation of material also increasing. Another aspect that researched in this paper is the effect of welding current toward corrosion rate of material. From the result, it was known that increasing welding current made corrosion rate of material became faster.

A novel evaluation of fracture toughness for random fibrous material

In this study, we perform three-point-bending tests for 3-dimensional random fibrous (3D RF) material specimens of two porosities (87% and 83%) with a crack. The crack with two different crack-length-to-specimen-width ratios (0.2 and 0.5) is considered. Using the tensile strength obtained from experiments and a characteristic average fiber spacing parameter from an equivalent orthotropic fiber network model, a simple theoretical model is developed to evaluate the fracture toughness of 3D RF material. This model gives the fracture toughness of 3D RF material, which is in good agreement with that from compact tension test, and better than the results calculated via the American Society for Testing Materials (ASTM) standard for three-point-bending test. This fact not only rationalizes the use of average fiber spacing size in the developed model, but also demonstrates the model efficiency in evaluating the fracture toughness of 3D RF material. Further, considering the temperature effect on the fracture strength of material, this theoretical model can be successfully used to predict fracture toughness of 3D RF materials at elevated temperatures (299 K~1073 K).

Influence of Structural Changes on the Brittle Fracture Strength in Metal Springs of Kamaz Trucks Used in a Northern Environment

To make structural components and vehicle parts reliable, it is necessary to study accumulated structural damage and its influence on the properties of materials, taking into account the operational environment. To discover the relation between structural changes in and brittle fracture strength of materials, we studied the degree and kind of structural damages, impact toughness, and microscale processes of destruction observed in the metal of springs mounted on Kamaz trucks driven in a northern environment. The techniques used in this article include optic and electron microscopy and structural statistical analysis of the microhardness and porosity according to which the structural damage was evaluated. New data are derived about accumulated fatigue damages and their influence on the brittle fracture resistance of the metal in springs used in a cold climate environment. The results can be used to extend the service life of elastic parts of automotive vehicles.

Дослідження впливу неоднорідних пустот на кінцеву міцність інженерних пористих матеріалів

One way to identify porous materials is to use multi-scale analysis, and the relationships currently available for multi-scale analysis are limited to mean stress and strain values. These relationships have a great error in calculating the fracture strength of materials. It should be noted that in multi-scale methods, quantities of normal mean values are usually used to calculate macro properties, while concepts such as fracture and fatigue cannot be explained by such quantities. Since the amount of stress in different portions of porous materials is not the same, this study uses statistics and probability to better understand the stress. For this purpose, the stress histogram of the porous materials is firstly investigated. According to the obtained histogram, the probability density function was calculated for it. Finally, the effect of location uniformity and cavity size on the probability density function of porous materials is investigated.

Failure Analysis on 42CrMo Steel Bolt Fracture

Fracture behaviors of 42CrMo ultrahigh strength steel-based bolt have been experimentally studied including macroscopic and microscopic fracture observation, metallographic test, mechanical property testing, and energy spectrum analysis. The results show that a large amount of structure defects, such as sulfide inclusions, band, and carbon depletion, appear in the fracture origin region and matrix of the bolt. Such defects reduce fatigue strength of materials and easily yields fatigue fracture origin. In addition, sulfide inclusions provide easy access to crack growth, gradually reducing the effective cross section of the bolt accompanying with increasing stress and finally causes fracture when stress exceeds the material fracture strength. The fracture mechanism is also explored based on fracture failure criterion and fatigue crack growth curve.

A generalized weakest-link model for size effect on strength of quasi-brittle materials

The work contributes to the statistical approach to unitedly characterize the random variation and size effect of brittle fracture strength of materials. Current practices rely on the conventional Weibull statistics and more recently on the weakest-link statistical model conforming to the uniform spatial distribution of microcracks. Based on the understanding that the weakest-link postulate is built on the mutual independence of microcracks and is not necessarily bounded to the uniform spatial distribution of microcracks, this work develops a generic weakest-link statistical formulation pertaining to a power-law spatial distribution of mutually non-interactive microcracks to synchronize the random variation and size effect of brittle fracture strength. The formulation encompasses both Weibull statistics and the uniform spatial distribution law-based weakest-link model as its subordinate members. A resultant master curve behavior between a compound parameter and the nominal fracture strength is identified for size scaling of strength and is validated by the strength data of a wide spectrum of quasi-brittle materials including wood, concrete, coal, gamma titanium aluminum alloy, nuclear-grade graphite and aluminum foam on geometrically self-similar specimens under same loading conditions.

An investigation into strain rate dependent constitutive properties of a sandwiched epoxy interface

A composite material fracture strength can significantly depend on the constitutive description of interfaces. A computational model of composite deformation should, therefore, incorporate interface constitutive behavior. However, separating main phase constitutive behavior from interface constitutive behavior in mechanical property measurement experiments is an arduous task. In this work, an epoxy interface is analyzed under quasistatic and dynamic loading conditions to obtain a description of interfacial constitutive response at strain rates from 10−2 to 103s−1. The approach relies on describing interfaces as a confined material phase between two unconfined phases. Dynamic microscale impact tests are used to obtain stress-strain response as a function of strain rate for the analyzed interface. The rate dependent stress-strain response is fitted to the Johnson-Cook constitutive model. Based on the analyses of confinement effects, a power law constitutive model is proposed to predict the interface deformation behavior with a dependence on both strain rate and interface thickness.

Analysis of Stress and Fracture Strength of Zirconia Implants after Cyclic Loading

The aim of this study was to manufacture a new zirconia implant (Y-TZP) and to evaluate the fracture strength and stresses generated after cyclic loading compared to titanium implants. Thirty-three zirconia and titanium implants were fabricated. The stress generated around the implants was observed by photoelastic analysis. The implants were then separated into groups (n = 10): Control (no treatment), mechanical fatigue and thermomechanical fatigue. All groups were submitted to a single cantilever flexure test to measure the material fracture strength. The results (2-way ANOVA, Bonferroni test, p <.05) showed no statistically significant difference in the stresses generated between the zirconia and titanium implants. Titanium implants showed higher fracture strength than the zirconia implants, a property that was not altered by fatigue applied. It was concluded that stress distribution was similar for Zr and Ti and mechanical and thermomechanical fatigue had no influence on the fracture strength of the implants tested.

Effects of microstructures and flaw evolution on the fracture strength of ZrB2–MoSi2 composites under high temperatures

Based on the existing fracture theories and a temperature dependent fracture surface energy model, a temperature dependent fracture strength model for ZrB2–MoSi2 composites is established. The excellent agreement is obtained between the model predictions and experimental data. The model can be used for qualitative even quantitative analysis of the effect of SiO2 size on the strength of hot pressed composites under high temperatures, and to predict the temperature dependent critical flaw size of composites which thus can help us to discover the control mechanisms of material strength under different temperatures. The effects of microstructures and flaw evolution on the strength of ZrB2–MoSi2 under high temperatures are studied in detail using the model. The study shows that the critical flaw causing the failure of the hot pressed composites under high temperatures is related to the largest SiO2 grains. The fracture strength of materials is controlled by the combined effects of temperature, grains and flaws. Both with the increases of temperature and initial flaw size the sensitivities of fracture strength to grain size and flaw size decrease. During preparation of the composites reducing the initial flaw size should be firstly considered. Improving the starting powder purity and sintering method which could reduce the amount, sizes and their dispersion of dispersed phases present in the microstructure, MoSi2 grain size and initial flaw size would result in the greater strength of materials under high temperatures.

A new temperature dependent fracture strength model for the ZrB2–SiC composites

In this paper, based on a temperature dependent fracture surface energy model and the traditional Griffith fracture theories, a new temperature dependent fracture strength model for the ZrB2–SiC composites is developed. The combined effects of temperature, grain size, microflaw size and residual stress on the strength of ZrB2–SiC composites are included in the new model. According to the model, the temperature dependent fracture strength of materials can be easily predicted using some basic material parameters. The model is verified at different temperatures by comparison with experimental data of different ZrB2–SiC composites. Excellent agreement is obtained between predicted and experimental data of fracture strength of ZrB2–SiC composites.

On Modeling Hydrogen-Induced Crack Propagation Under Sustained Load

The failure of hydrogen containment components is generally associated with subcritical cracking. Understanding subcritical crack growth behavior and its dependence on material and environmental variables can lead to methods for designing structural components in a hydrogen environment and will be beneficial in developing materials resistant to hydrogen embrittlement. In order to identify the issues underlying crack propagation and arrest, we present a model for hydrogen-induced stress-controlled crack propagation under sustained loading. The model is based on the assumptions that (I) hydrogen reduces the material fracture strength and (II) crack propagation takes place when the opening stress over the characteristic distance ahead of a crack tip is greater than the local fracture strength. The model is used in a finite-element simulation of crack propagation coupled with simultaneous hydrogen diffusion in a model material through nodal release. The numerical simulations show that the same physics, i.e., diffusion-controlled crack propagation, can explain the existence of both stages I and II in the velocity versus stress intensity factor (V–K) curve.

Fracture analysis for ceramic disk with semi-elliptical crack and pore

Crack resistance is important to exam the structures destroyed under static and dynamic load as well as to the ceramic products under extreme mechanical and thermal load. But in addition to the metallic material, ceramic and ceramic composite materials have been pointed out as low resistance referred to a brittle materials form thermal impact. As destroyed ceramics are impossible to be restored, so the development of high toughness ceramics is required. To get high strength material design variables while keeping light weight, this study derives the modulus of elasticity for ceramic disk with elliptical crack pore and performs fracture behaviors assessment by applying the modulus of elasticity derived and MSST(Maximum Shear Stress Theory) techniques to compare with test data. As a result of assessment of fracture behavior based on the MSST, if stress is greater than fracture strength of material, it showed high probability of occurring of the shear fracture when fracture strength is 38 kgf.

Temperature and Microstructures Dependent Thermal Shock Resistance Models for Ultra-High-Temperature Ceramics Considering Effect of Residual Stress

ABSTRACTBased on the researches on the temperature and microstructures dependent fracture strength and temperature dependent thermal shock resistance, the new thermal shock resistance models for ultra-high-temperature ceramics were proposed. The effect of density on the fracture strength of material was investigated. A damage term was introduced to reveal the effects of uncertain factors on fracture strength. The roles of residual stress and microstructure sizes at different initial thermal shock temperatures in the thermal shock resistance were studied using the models. The study showed that the models can reveal the relationships among the residual stress, microstructure sizes and the temperature dependent thermal shock resistance well. The better thermal shock resistance is found for ultra-high-temperature ceramics having small SiC grains and relatively large micro-cracks around SiC grains. Large enhancement in thermal shock resistance can be achieved through our studies.

Effects of Meso-Structure Characters on Fracture Properties and Fracture Mechanism in Concrete

To understand relationship between the meso-structure of non-homogeneous materials and the fracture properties, two groups of concrete specimens are designed and tested. For the two groups with the same water-cement ratio and coarse aggregate volume ratio, small and large grain size gravels are used respectively. Since both groups of materials are with the same mass ratio of coarse aggregates, the heterogeneity of the gravels distribution in concrete with larger grain size is higher than the other. The results show that the group with smaller aggregate grain size gains higher material fracture strength and fracture energy than another group. Then the concrete with more homogeneous meso-structure will reach higher fracture properties

Micro-Scale Cantilever Testing of Linear Elastic and Elastic-Plastic Materials

t is increasingly a requirement to be able to determine the mechanical properties of materials: (i) at the micro-scale, (ii) that are in the form of surface coatings and (iii) that have nanoscale microstructures. As a consequence micro-scale testing is an important tool that has been developed to aid the evaluation of the mechanical properties of such materials. In this work cantilever beam specimens (typically 2μm by 2μm by 10μm in size) have been prepared by gallium ion milling and then deformed in-situ within a FEI Helios Dual Beam workstation. The latter is achieved using a force probe with a geometry suitable for loading the micro-scale test specimens. Thus force and displacement can be measured together with observing the deformation and fracture of the individual specimens. This paper considers the evaluation of the mechanical properties in particular elastic modulus, yield strength and fracture strength of materials that result in relatively large deflections to the micro-scale cantilever beams. Two materials are considered the first is linear elastic single crystal silicon and the other elastic-plastic nanocrystalline (nc) nickel. The results are discussed with respect to the reproducibility of this method of mechanical testing and the evaluated properties are compared with those derived by alternative procedures.

G030074 き裂を有する異種材料の破壊靭性評価([G03007]材料力学部門一般セッション(7):はく離と異材 )

A method of strength evaluation based on fracture mechanics is important to analyze the fracture strength of material with crack. The heterogeneity of mechanical property in dissimilar materials causes change of fracture behavior. Analysis of mechanical property and fracture strength in dissimilar materials is important to evaluate fracture toughness with accuracy. The purpose of this paper is experimentally to analyze correlation between Young's modulus ratio and fracture toughness in dissimilar materials with a single edge crack. 4 kinds of specimen were used in this experiment. One was homogeneous material, the others were 3 kinds of dissimilar materials. The fracture behavior of dissimilar materials was analyzed by high-speed video camera and digital image correlation method. Then, specimens were bended and displacement near the crack was measured. Fracture toughness was experimentally calculated based on fracture mechanics. The experimental results showed that fracture energy and strain distribution around a crack tip were same values at all specimens. We conclude that relationship between Young's modulus ratio and fracture toughness in dissimilar materials is uncorrelated. Then, the heterogeneity of Young's modulus causes the change of crack opening displacement.