Effect Of Material Strength Research Articles

Behavior of high strength concrete encased steel composite stub columns with C130 concrete and S690 steel

This paper presents an experimental program that studies the structural behaviour of high strength Concrete Encased Steel (CES) composite columns. The structural performance under compression, including the damage pattern, load-carrying capacity, post-peak ductility, and load-displacement response is experimentally investigated. A total of 14 specimens were tested under concentric compression. The parameters studied in this program include concrete compressive strength, steel yield strength, stirrup spacing, incorporation of steel fiber, as well as the shape of the structural steel section. To evaluate the material compatibility between high strength concrete and high strength steel, two concrete grades (C90, C130) and two steel grades (S500, S690) were used to prepare the test specimens. In addition, 0.5% volume fraction of steel fiber was added in concrete mix to minimize the inherent brittleness of high strength concrete. The comparison between test results and analytical predictions reveals the inability of existing design codes to estimate high strength CES columns, unless steel fiber and dense reinforcement are used in combination. The effect of material strength, steel fibers, volumetric ratios of hoop reinforcement, and shape of steel section on both strength and ductility of CES columns was assessed through a comprehensive parametric study. The analysis of test results demonstrates that steel contribution ratio plays a dominant role in the ductility, whereas increasing hoop reinforcement ratio and adding steel fiber has negligible effect. Finally, a simplified formula is proposed to evaluate ductility of high strength CES columns.

Investigation of target property effects on crater populations in long lava flows: A study in the Cerberus region, Mars, with implications for magma source identification

Young volcanism on Mars is exemplified within the Cerberus region, which enables examination of relatively pristine lava flow surfaces. In this investigation, we derived model ages within the circum-Cerberus channelized lavas for sites proximal, medial, and distal to the lava flow sources, finding that these ages decrease with increasing distance from the inferred source. Investigating multiple possible explanations for this downstream decrease in model ages, we conclude that the most likely cause is changes in the rheological properties of the lava during emplacement. Analogous terrestrial lava flows exhibit rheological changes along their length during emplacement, supporting the hypothesis that target properties affect crater size frequency distributions (CSFDs) on extraterrestrial bodies. Using scaling methods, we investigated how possible material property changes in the Cerberus channelized lavas affected CSFDs. To derive a single model age for each channel, we arithmetically size-scaled the distal and proximal crater sizes. We also used pi-group scaling to estimate the effect of material strength and porosity on the final CSFDs. We infer that the Athabasca, Grjótá, and Marte Valles lavas underwent minor, moderate, and major rheological changes, respectively, to account for the progressively larger age discrepancies along their respective flow lengths. The arithmetic size-scaling yields relative lava emplacement ages, from oldest to youngest, respectively, as Grjótá, Marte, and Athabasca. This lack of a consistent progressive directional emplacement (east-to-west or west-to-east) of lava model ages implies that the magma source was spatially distributed beneath the Cerberus region, although magma contributions from the two bordering volcanic provinces cannot be ruled out. The results of this study support the findings of previous lunar and martian studies that inferred target property changes affected CSFDs, which may have some bearing on age dating of young lava surfaces across the inner Solar System.

Development of an interfacial heat transfer coefficient model for the hot and warm aluminium stamping processes under different initial blank temperature conditions

Different initial blank temperatures, or forming temperatures, are applied in hot and warm aluminium stamping processes depending on the component being formed and the desired post-form properties. An initial blank temperature dependent interfacial heat transfer coefficient is therefore an essential boundary condition in such non-isothermal forming processes for obtaining precise temperature fields from the formed components in finite element simulations. This precision is crucial for the optimisation of the processing window and tool design, to subsequently achieve the desired cooling rates and post-form strength of the aluminium components being formed. The IHTC between a 7075 aluminium alloy and tungsten carbide cobalt coated cast-iron was found to approximately increase linearly with increasing initial blank temperature in the present research. The effect of the initial blank temperature was identified as a combination of two mechanisms; the effects of material strength and thermal conductivity. The IHTC was found to decrease with increasing strength of the blank when the contact pressure was lower than a threshold value, while a larger thermal conductivity of the aluminium blank increased the IHTC values. Furthermore, an initial blank temperature-dependent model was developed to predict the IHTC at different initial blank temperatures, which was subsequently verified by the results of non-isothermal forming tests.

Numerical evaluation of core concrete quality on the response of concrete jacketed columns

Reinforced concrete jacketing is one of the most frequently used methods for strengthening of reinforced concrete (RC) columns. A large number of experimental studies have been carried out to investigate the effectiveness of repair and strengthening techniques and interface treatment on the response of concrete jacketed columns. However, the effects of potential damage in existing column and quality of core concrete on the response of jacketed RC columns have not been investigated. One of the main goals of this study is to examine how the material properties of the existing column affect the overall response of the jacketed RC columns. Two computer models were developed and nonlinear analyses were performed to determine the moment-curvature relationships and axial load-moment interaction diagrams of concrete jacketed RC cross sections. The effects of material strength and magnitude of axial loads were investigated. It is determined that the strength of core concrete has no effect on the response of concrete jacketed RC columns under lower axial loads while it increases the strength and reduces the ductility under higher axial load levels

Investigating the impact of tool inertia on machinability of a β-titanium alloy using tool deflection and acoustic emission

Finding sustainable ways of machining exotic materials is gaining more and more importance in the manufacturing industry. Application of advanced measuring instruments for quantifying performance measures is a crucial requirement for making machining processes viable. The presented work aims to ameliorate machining of a high-strength β-titanium alloy using information from measurements of key responses, such as cutting energy consumption, tool deflection, and tool damage. Acoustic emission data and tool’s acceleration data are utilized to work out the magnitudes of energy consumed and deflection undergone by the tool, respectively. The article focuses on quantifying the effects of tool’s inertia, strength of work material, and two cutting parameters on the aforementioned responses. A total of 54 continuous cutting experiments are performed in which a fixed volume of material per experimental run is removed. Tool deflection method helped to determine the significant effects of varying tool inertia, work material strength, and cutting speed on the machining process. Likewise, acoustic emission method highlighted the strong effects of material strength and cutting speed caused on the cutting energy consumption. The effect of feed rate is found to be significant regarding tool wear only. Finally, the tool wear data are tested for correlation against the corresponding data sets of the other two responses. It is found that both tool deflection and cutting energy possess strong uphill relationships with tool wear.

A modified phase-field model for quantitative simulation of crack propagation in single-phase and multi-phase materials

A quantitative phase-field model based on the regularized formulation of Griffith’s theory is presented for crack propagation in homogenous and heterogeneous brittle materials. This model utilizes correction parameters in the total free energy functional and mechanical equilibrium equation in the diffusive crack area to ensure that the maximum stress in front of the crack tip is equal to the stress predicted by classical fracture mechanics. Also, unlike other phase-field models, the effect of material strength on crack nucleation and propagation was considered independent of the regularization parameter. The accuracy of the model was benchmarked in two ways. First, the stress and strain fields around the crack tip in single-phase ZrB2 were compared with the analytical solutions in classical linear elastic fracture mechanics. Second, the crack path and force–displacement responses were examined against experimental results for concrete in the form of fracture of L-shaped plate and wedge splitting tests. To demonstrate the capability of the model in multi-phase materials, crack propagation was simulated for laminates composed of alternating layers of ZrB2 and carbon. The results showed that the proposed modifications in the phase-field model were necessary to predict crack deflection along carbon layers similar to the experimental observations.

A Novel Micromechanics Approach for Understanding of Fatigue in Nodular Cast Iron

Nodular cast iron (NCI) experiences failure under static loading in manner of nucleation, growth, and coalescence of voids. Under cyclic loading, materials with elastic-plastic behaviour show an increase in porosity with each cycle which is called void ratchetting. A number of finite element studies in literature proved this mechanism by means of a few cyles with unit cell models. In the present study, low cycle fatigue (LCF) in nodular cast iron is investigated using the cell models for void ratchetting till final failure. The cyclic necking due to plastic strain accumulation is observed as mechanism in the final stage. The proposed methodology uses only input parameters defining the elastic-plastic material behavior and geometrical features of the microstructure. The strain-life curves extracted from the simulations are compared with experimental data collected from the literature. From the comparison, it is confirmed that void ratchetting is the relevant mechanism of LCF in NCI. The effects of material strength, temperature and load sequencing on the fatigue behaviour are studied.

Effect of material strength and species of gas impurity on inhibition of hydrogen-induced fracture by gas impurities

Effect of material strength and species of gas impurity on inhibition of hydrogen-induced fracture by gas impurities

Hydrocode modeling of the spallation process during hypervelocity impacts: Implications for the ejection of Martian meteorites

Hypervelocity ejection of material by impact spallation is considered a plausible mechanism for material exchange between two planetary bodies. We have modeled the spallation process during vertical impacts over a range of impact velocities from 6 to 21 km/s using both grid- and particle-based hydrocode models. The Tillotson equations of state, which are able to treat the nonlinear dependence of density on pressure and thermal pressure in strongly shocked matter, were used to study the hydrodynamic–thermodynamic response after impacts. The effects of material strength and gravitational acceleration were not considered. A two-dimensional time-dependent pressure field within a 1.5-fold projectile radius from the impact point was investigated in cylindrical coordinates to address the generation of spalled material. A resolution test was also performed to reject ejected materials with peak pressures that were too low due to artificial viscosity. The relationship between ejection velocity veject and peak pressure Ppeak was also derived. Our approach shows that “late-stage acceleration” in an ejecta curtain occurs due to the compressible nature of the ejecta, resulting in an ejection velocity that can be higher than the ideal maximum of the resultant particle velocity after passage of a shock wave. We also calculate the ejecta mass that can escape from a planet like Mars (i.e., veject > 5 km/s) that matches the petrographic constraints from Martian meteorites, and which occurs when Ppeak = 30–50 GPa. Although the mass of such ejecta is limited to 0.1–1 wt% of the projectile mass in vertical impacts, this is sufficient for spallation to have been a plausible mechanism for the ejection of Martian meteorites. Finally, we propose that impact spallation is a plausible mechanism for the generation of tektites.

SPH calculations of Mars-scale collisions: The role of the equation of state, material rheologies, and numerical effects

We model large-scale ( ≈ 2000 km) impacts on a Mars-like planet using a Smoothed Particle Hydrodynamics code. The effects of material strength and of using different Equations of State on the post-impact material and temperature distributions are investigated. The properties of the ejected material in terms of escaping and disc mass are analysed as well. We also study potential numerical effects in the context of density discontinuities and rigid body rotation. We find that in the large-scale collision regime considered here (with impact velocities of 4 km/s), the effect of material strength is substantial for the post-impact distribution of the temperature and the impactor material, while the influence of the Equation of State is more subtle and present only at very high temperatures.

Investigation on the weld damage behavior of steel beam-to-column connection

A large number of steel moment frames fractured at the welds of beam-to-column connections in earthquake. As the weld damage behavior is a crucial factor for aseismic performance of steel frame connections, 20 local welded connections representing beam-to-column connections were tested under monotonic and cyclic loads to study the weld damage behavior in this paper. The failure modes and deformation curves were recorded; the effects of material strength, load types, and beam geometries on the connection damage behavior were analyzed. Three damage evolution models were calibrated, the relation between weld damage and macro connection performance was established. The results indicate weld cracking and plate buckling are the main causes of the connection damage; the range of cyclic loads is the key factor affecting the weld damage level; the plastic strain based damage model illustrate the damage process with good accuracy. This study provide technical basis for the damage evaluation and fracture prevention of the welded steel beam-to-column connections.

Observations on Impacts of Deformable Conical Projectiles at 60 Degree Target Obliquity

Conical aluminium projectiles of apex angle 34 degrees were made to impact thin aluminium targets inclined at an angle of 60 degrees at low subordnance velocities where material strength effects are still valid. Thin targets of thickness 1.5mm and 2mm underwent failure by reverse petalling as the projectiles penetrated the targets. Projectiles underwent ricochet while impacting 2.5mm targets causing severe dents and visible contact marks on the target. While the projectile nose tips were separated in the 1.5mm and 2mm cases, the projectiles impacting 2.5mm targets underwent substantial nose deformation. Numerical simulation performed using ABAQUS/Explicit was able to capture the projectile deformation and target deformation quite well phenomenologically.

Eulerian Hydrocode Estimates of Richtmyer-Meshkov Instability Growth and Arrest

Following previous experimental evidence of growth and arrest of Richtmyer-Meshkov instabilities in copper, we have used the CTH shock physics code to study and calibrate the effects of material strength at high strain rates. Highly resolved one and two-dimensional simulations were performed using the Johnson-Cook (JC), Mechanical Threshold Stress (MTS), and Preston-Tonks-Wallace (PTW) strength models. The one-dimensional simulations utilized a prescribed homogeneous deformation strain path covering strain rates observed in previous hydrodynamic instability experiments. Spall was modeled using a nominal threshold pressure model (PFRAC) and we use the Mie-Gruneisen equation of state to estimate the volumetric response of the experiments. Our results show good qualitative and quantitative agreement between numerical estimates and prior experiments in the strain rate regimes of interest.

Effects of Material Strength on Structural Performance of Damaged RC Buildings

The first defect was related with concrete for RC buildings that damaged after an earthquake. In this study, effects of concrete class on structural performance of reinforced concrete building have been investigated. Celtiksuyu School building that has collapsed after 2003 Bingol earthquake was selected to obtain realistic results. Calculations have been made for each concrete class which was selected as C8, C16, C20, C25 and C30. Pushover analyses were used for both direction of selected building. As a result, structural behaviour of RC buildings with different concrete classes is compared and evaluated according to analysis results in detail. The displacement and internal forces obtained from results of analysis is investigated comparatively. The results show that base shear of building was increased according to increasing concrete strength. The increasing in base shear has been increased the amount of peak displacement in the structure. As a result, it can say that concrete strength was not too defective. The main issue is manufacturing of concrete has not been made under proper conditions. The reason for this is lack of control, workmanship and material defects.

Instability growth for magnetized liner inertial fusion seeded by electro-thermal, electro-choric, and material strength effects

A critical limitation of magnetically imploded systems such as magnetized liner inertial fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is the magneto-Rayleigh-Taylor (MRT) instability which primarily disrupts the outer surface of the liner. MagLIF-relevant experiments have showed large amplitude multi-mode MRT instability growth growing from surface roughness [McBride et al., Phys. Rev. Lett. 109, 135004 (2012)], which is only reproduced by 3D simulations using our MHD code Gorgon when an artificially azimuthally correlated initialisation is added. We have shown that the missing azimuthal correlation could be provided by a combination of the electro-thermal instability (ETI) and an “electro-choric” instability (ECI); describing, respectively, the tendency of current to correlate azimuthally early in time due to temperature dependent Ohmic heating; and an amplification of the ETI driven by density dependent resistivity around vapourisation. We developed and implemented a material strength model in Gorgon to improve simulation of the solid phase of liner implosions which, when applied to simulations exhibiting the ETI and ECI, gave a significant increase in wavelength and amplitude. Full circumference simulations of the MRT instability provided a significant improvement on previous randomly initialised results and approached agreement with experiment.

Evaluation of Compressive Chord Plastification of Circular Hollow Section X-joint Truss Connection

원형강관구조 접합부는 재료의 발전과 접합부의 복잡한 국부 거동 때문에 지속적인 연구되고 있다. 이 연구는 지강관에 압축력이 작용하는 원형강관 X-이음 트러스접합부의 주강관 소성화변형과 접합부 강도에 재료강도와 주강관벽세장비가 미치는 영향을 파악하는 것을 목적으로 한다. 이를 위하여 재료강도와 주강관벽세장비를 변수로 하여 다양한 원형강관 X-이음 트러스접합부에 대하여 범용 유한요소해석 프로그램인 ANSYS Mechanical APDL을 사용하여 정밀유한요소해석을 수행하였다. 해석결과를 토대로 현행 건축구조기준에서 제시하는 주강관소성화 한계상태의 접합부 설계강도를 검토하였다. 결론적으로 원형강관 X-이음 트러스접합부 설계에서 고려해야 할 사항을 제시하였다. The researches on circular hollow section(CHS) connections have been conducted continuously because of development of material properties and complex local behavior of the connections. The purpose of this study is that the effects of material strength and chord wall slenderness on chord plastification and strength of CHS X-joint truss connection under compression on branch member were evaluated. To this end, finite element analyses were performed for various connections, using ANSYS Mechanical APDL program. Based on the analysis results, the design strength of the connections according to chord plastification limit state in KBC were examined. Finally, special considerations for CHS X-joint connection design were suggested.

Numerical Simulation and Parameters Analysis for Roll Forming of Martensitic Steel MS980

Circle-to-square roll forming process of martensitic steel MS980 was studied. A 3D elastic-plastic roll forming finite element model was established with ABAQUS and the influence of material and process parameters was investigated. Four material with different strengths include MS980, Fe360D, DP590, MS1500 were compared to study the effect of material strength. The result shows that as the material strength increase, the fillet radius of formed square tube decrease, corner thickness increase significantly, and the edge convexity is worse. Rolled compression amount distribution is an important parameter in roll forming process. Three distribution schemes were proposed, which were parabola distribution, decline distribution and equal distribution. The result shows that the equal distribution scheme can get good square shape and uniform force on each pass.

Temporal peculiarities of brittle fracture of rocks and concrete

When we want to compare the strength of two materials, we compare the table values of quasistatic strength. However results of some experiments show that the strength ratio of the materials can change with increase in rate of loading. Such of material strength at different strain rates is studied in this paper. It is shown that one material can have a lower dynamic strength for a higher static strength compared to the other material. Tests of two different materials, tests of mortar and concrete, and tests of concrete with different water content are considered. It is shown that load-carrying capacity of materials and the substitution effect of material strength in a wide range of loading rates can be predicted by the incubation time criterion.

Seismic performance evaluation of unreinforced masonry school buildings in Turkey

In this study a seismic performance assessment of school buildings, which have been built in accordance with template unreinforced masonry school projects in Turkey, has been conducted. For this purpose, the most widely used three template projects have been selected. The seismic performances of these buildings have been evaluated for various earthquake levels. This evaluation has been carried out in compliance with the Turkish earthquake code entered into force in 2007. The effects of material strength and plan features on the performance of masonry school structures have been investigated within the scope of this study. It has been concluded that school buildings with template design are far from satisfying the required performance criteria. For spectral acceleration of 0.80 g, which is expected in a 475 year period in the seismic Zone 1, the average exceedance ratio for life safety performance limit is more than 80% considering different material strengths. Upon evaluation of the results a building capacity index is proposed for rapid seismic assessment of masonry school buildings.

鉄道車輪鋼のシェリング損傷に及ぼす材料強度の影響

鉄道車輪鋼のシェリング損傷に及ぼす材料強度の影響