Yield Strength Of Material Research Articles

Microstructure evolution and mechanical properties of TiB2/18Ni300 composite material produced by laser additive manufacturing

As a reinforcing phase, TiB2 exhibits exceptional wettability and stability when mixed with steel matrices, making it an ideal reinforcement for steel matrix composites. In this paper, we add TiB2 for additive manufacturing of 18Ni300 steel for weight reduction and reinforcement. TiB2 reinforced 18Ni300 matrix composites were prepared by laser cladding. SEM, EDS, and XRD were used to observe the joints' interface and fracture characteristics and analyse the substance composition. Tissue analysis was then performed using EBSD and TEM. According to the TEM and XRD results, there is a martensite structure within the cell, and the cell boundary is an austenite structure. After adding TiB2, a reinforcing phase ((Mo, Fe)3B2) is distributed at the boundary of the cell structure. The high hardness of boride increases the microhardness of the composite material. The yield strength, modulus, and elongation of the samples prepared with 18Ni300 powder are lower than that of forged 18Ni300, but the tensile strength reaches 1134 MPa. The addition of TiB2 increases the composite material's yield strength and elastic modulus significantly. This strengthening technique, which employs the addition of ceramic particles to martensitic steel, is currently not widely used. This experiment provides a theoretical basis and process reference for preparing high-stiffness and lightweight ceramic particle reinforced metal matrix composites.

Reliability Index of Simply Supported Beam Based on HL Method

In this paper, reliability of simply supported I-beam is studied under point load at the mid-point of span. Reliability index has been obtained by using Hasofer-Lind method. In the analysis, yield strength of material, depth of the section and load are considered as basic random variables and those are assumed to follow normal distribution. Non-linear limit state surface function has been considered. Derived design point in each case and found the reliability.

Novel bake hardening mechanism for bainite-strengthened complex phase steel

• Yield strength of materials can be greatly improved after pre-strain and baking. • Dislocation as fast channels for carbon diffusion promotes cementite formation. • Carbon clusters gathered at the dislocations act as precursors of cementite. • Cementite precipitation is main reason for increase in strength of bainite steel. In the automobile industry, stamping and paint baking processes are used to strengthen components, and this not only saves costs, but also further reduces the bodyweight of automobiles. In this work, the bake hardening mechanism of the complex phase (CP) steel CP980 was explored by comparing it with that of DP1180, which has a clear bake hardening mechanism and a carbon content similar to that of CP980. By analyzing the bake hardening response and the microstructural changes of the two steels, we found that the bake hardening process of CP980 was divided into three stages. In the first two stages, the carbon atoms diffused into dislocations to form Cottrell atmosphere pinning dislocations, and excess carbon atoms formed carbon clusters or low-temperature carbide pinning dislocations that were similar to DP1180. In the third stage, the dislocation acted as rapid channels for carbon diffusion, and fine cementite gradually formed when the carbon clusters gathered at the dislocations as precursors, resulting in precipitation hardening. This novel bake-hardening (BH) mechanism is crucial for obtaining a comprehensive understanding of the strain-baking behavior of advanced high-strength steals (AHSS).

A computational analysis of a novel therapeutic approach combining an advanced medicinal therapeutic device and a fracture fixation assembly for the treatment of osteoporotic fractures: Effects of physiological loading, interface conditions, and fracture fixation materials.

The occurrence of periprosthetic femoral fractures (PFF) has increased in people with osteoporosis due to decreased bone density, poor bone quality, and stress shielding from prosthetic implants. PFF treatment in the elderly is a genuine concern for orthopaedic surgeons as no effective solution currently exists. Therefore, the goal of this study was to determine whether the design of a novel advanced medicinal therapeutic device (AMTD) manufactured from a polymeric blend in combination with a fracture fixation plate in the femur is capable of withstanding physiological loads without failure during the bone regenerative process. This was achieved by developing a finite element (FE) model of the AMTD together with a fracture fixation assembly, and a femur with an implanted femoral stem. The response of both normal and osteoporotic bone was investigated by implementing their respective material properties in the model. Physiological loading simulating the peak load during standing, walking, and stair climbing was investigated. The results showed that the fixation assembly was the prime load bearing component for this configuration of devices. Within the fixation assembly, the bone screws were found to have the highest stresses in the fixation assembly for all the loading conditions. Whereas the stresses within the AMTD were significantly below the maximum yield strength of the device's polymeric blend material. Furthermore, this study also investigated the performance of different fixation assembly materials and found Ti-6Al-4V to be the optimal material choice from those included in this study.

Theoretical model of yield strength for eutectic colony microstructure materials

Eutectic alloys have a wide range of applications and have been studied in numerous experiments and simulations. However, there is no model available to describe the contribution from the morphology on strength of the eutectic structure. The model for eutectic strengthening σsp = kspf λ−1/2 is derived from the Brown model and Taylor-Orowan's equation. The equation reveals the relationship between yield strength and eutectic features including slip parameter, effective shear modulus, second phase volume fraction and eutectic spacing. The equation predictions agree well with the experimental measurements for both Al-Ce and Fe28Ni18Mn33Al21 alloys. The model may effectively predict the yield strength of eutectic alloys and provide insights for eutectic strengthening.

A Finite-element Method of Solution for Optimization of Frame of Tractor Operated Single Row Maize Cobs Picker

Finite element analysis (FEA) is a computational technique that divides complex structures into small elements and solves them numerically using various partial differential equations. In agriculture, engineers can use numerical simulation based on the FEA technique to study the behaviour of various input products in order to optimise the design of any machine without developing a prototype. The present study focused to design and simulates the frame of tractor operated single row maize cobs picker by employing the FEA technique. A 3D-CAD model of the frame of a tractor-operated single row maize cobs picker was created using the Solid Works software, and a static structural test was performed using the FEA technique in the ANSYS version 15.0 workbench software. A special fixture has been developed to calculate the force required to scrape the pulpy material of the leaves in the Universal Testing Machine. According to the simulation results, maximum deformation was observed as 0.051mm while maximum shear stress and Von Mises equivalent stress were found to be 0.246 MPaPa and 1. 47 MPa, respectively at 250 N scraping forces. Additionally, it was noted that the stress values fall within the material's yield strength. The FEA approach was found to be a scientific and highly effective method for designing and simulating the frame of a tractor-operated single row maize cobs picker.

Theoretical model for yield strength of monocrystalline Ni3Al by simultaneously considering size and strain rate

AbstractTo comprehensively describe the size and strain rate dependent yield strength of monocrystalline ductile materials, a theoretical model was established based on the dislocation nucleation mechanism. Taking Ni3Al as an example, the model firstly fits results of molecular dynamics simulations to extract material dependent parameters. Then, a theoretical surface of yield strength is constructed, which is finally verified by available experimental data. The model is further checked by available third part molecular dynamics and experimental data of monocrystalline copper and gold. It is shown that this model can successfully leap over the huge spatial and temporal scale gaps between molecular dynamics and experimental conditions to get the reliable mechanical properties of monocrystalline Ni3Al, copper and gold.

Finite Element Analysis of Thermal Management Automobile Unit

In order to verify the rationality of the structural design scheme of the battery thermal management unit for a new energy vehicle, this paper uses SolidWorks to establish the geometric model of the device, and conducts harmonic response analysis of the unit according to the vibration test requirements specified in the standard for automotive air conditioners, and obtains the modal frequencies, modal shapes, and structural stress distribution of the unit. The results show that under the specified load, the stress of each part of the structure does not exceed the material yield strength, and the structure as a whole meets the design requirements, achieving the purpose of verification.

Lateral buckling capacity of steel H-piles supporting integral abutment bridges (IABs)

Integral abutment bridges (IABs) have been gaining wide popularity in the United States and neighboring countries due to the rapid increase in maintenance costs associated with conventional bridges. The elimination of expansion joints in IABs allows the thermally induced lateral demand in the superstructure to be transferred to the supporting piles. This paper aims to study the behavior of steel H-piles supporting IABs through a detailed nonlinear finite element analysis that was calibrated and validated against available experimental data. A total of 30 models were established to examine the effect of various parameters (pile size, pile orientation, pile material yield strength, pile equivalent cantilever length, and axial compressive load) on piles supporting jointless bridges subjected to a combined axial load and lateral cyclic displacement amplitude. Local buckling was the dominant failure mode for all the specimens. Furthermore, this paper reiterates the various parameters and assesses their influence through a statistical regression analysis to develop an empirical formula for calculating the lateral buckling capacity. The rationality of the developed formula was examined and tested with existing experimental data, which testified the reliability to be used for future design considerations.

Stochastic analysis of steel frames considering the material, geometrical and loading uncertainties

This paper develops a Stochastic Practical Advanced Analysis Program for stochastic analysis of structural steel frames. The second-order refined plastic-hinge analysis method combined with the technical simulation of Latin Hypercube Sampling is developed to predict the actual ultimate load-carrying capacity of steel frames and investigate the sensitivity of the uncertain input parameters. The input parameters of material properties, geometrical characteristics, and load combinations are considered as independent random variables that may occur in simultaneous randomness. A proposed parallel analytical technique integrates the modified Newton-Raphson and Generalized Displacement Control algorithms to solve the nonlinear inelastic problems to estimate the critical displacement-based system reliability index. The results of the statistical analysis in terms of coefficients of variation and Pearson correlation index show that the yield strength of material is the most sensitive with respect to the behavior of steel frames. The Bayesian Model Averaging is employed to find the most influential structural components on the ultimate structural resistance. The useful results of this research may be used in steel structure design and maintenance in practice.

Removal mechanism of the chemical products layer on single-crystal sapphire surface in magneto-rheological polishing with Fe3O4/SiO2 core-shell abrasives

Chemical reactions will occur on sapphire surface in the magneto-rheological polishing (MRP) process with Fe3O4/SiO2 core–shell abrasives, resulting in a chemical products layer, which is easily removed due to its low hardness. In this paper, the specific mechanical removal mechanism of this chemical products layer was investigated by analyzing scratch morphology and scribing forces obtained from computer simulation and scratching experiment. The results showed that the tangential force plays a major role in the material removal process, the shearing action of abrasives dominates the material removal of the chemical products layer on sapphire surface. During scribing process, the chemical products layer is plastically deformed firstly and then removed when the shear stress exceeds its material yield strength. The materials on both sides of scratch flow outward plastically cause ridges under the continuous extrusion process. The material on the bottom of scratch is destroyed and removed under the continuous severe extrusion and shearing process, resulting in an uneven “jag-like” morphology. Both normal and tangential forces increase fluctuatingly with scribing distance, and the average depth and width of scratch increase with scribing velocity. Therefore, the material removal mechanism of sapphire in MRP process is the combination of chemical reaction of surface material and the synthetic action of plastic deformation and shearing removal of chemical products layer.

Impact Buffering Characteristics of One-Dimensional Elastic-Plastic Composite Granular Chain.

Considering the elastic-plastic deformation, the wave propagations and energy transmissions of the one-dimensional three-segment composite granular chain are studied. The axial symmetry model for elastic-perfectly plastic materials is built by using the finite element method. Six materials with different yield strengths are selected for the adjustable segment. The results show that the repeated loading and unloading behaviors, as well as the wave propagations in the elastic-plastic granular chain, are complex and significantly different from those in the purely elastic granular chain. The yield strength of the granular materials in the adjustable segment has significant effects on energy dissipation and wave velocity, which could be used to design the impact buffer. The studies show that taking lower yield strength for the adjustable part than the non-adjustable part, the energy dissipation could be increased, and the wave velocity could be reduced, then the arrival time of the impact waves could be delayed. These characteristics of the elastic-plastic granular chain could be used to design metamaterials for impact absorbers in impact protection.

A physics-based machine-learning approach for modeling the temperature-dependent yield strengths of medium- or high-entropy alloys

Machine learning is becoming a powerful tool to accurately predict temperature-dependent yield strengths (YS) of structural materials, particularly for multi-principal-element systems. However, successful machine-learning predictions depend on the use of reasonable machine-learning models. Here, we present a comprehensive and up-to-date overview of a bilinear log model for predicting temperature-dependent YS of medium-entropy or high-entropy alloys (MEAs or HEAs). In this model, a break temperature, Tbreak, is introduced, which can guide the design of MEAs or HEAs with attractive high-temperature properties. Unlike assuming black-box structures, our model is based on the underlying physics, incorporated in the form of a priori information. A technique for the unconstrained global optimization is employed to enable the concurrent optimization of model parameters over low- and high-temperature regimes, showing that the break temperature is consistent across the YS and ultimate strength for a variety of HEA compositions. A high-level comparison between YS of MEAs/HEAs and those of Nickel-based superalloys reveals superior strength properties of selected refractory HEAs. For reliable operations, the temperature of a structural component, such as a turbine blade, made from refractory alloys, may need to stay below Tbreak. Once above Tbreak, phase transformations may start taking place, and the alloy may begin losing structural integrity.

Evaluation of strain based ECA method in DNVGL-RP-F108

Pipelines may be subject to strain-controlled external loads exceeding yield strength of materials due to many causes, e.g., soil settlements and ground movement. There are several strain based fracture mechanics assessment methods to determine the maximum tolerable defect sizes in girth welds in pipelines. One of these methods is the DNVGL-RP-F108 procedure which was developed from a joint industry project for assessing reeled pipes and has been used for both offshore and on-shore pipelines. However, as with other methods, it requires the weld strength either even- or over-matching the parent steel which may be difficult to achieve for high strength steels. There are also uncertainties about the adequacy of the DNVGL-RP-F108 guidance addressing the effects of internal pressure and welding-induced residual stresses. In this study, the maximum tolerable defect sizes in the girth welds of an X70 spiral welded pipeline were determined using the DNVGL-RP-F108 approach. The effects of several variables on the assessment results, including weld strength mismatch, stress-strain curve magnitude, internal pressure level, fracture toughness, residual stresses and misalignment, were also investigated. A comprehensive finite element analyses were performed to verify the crack driving force determined by the DNVGL-RP-F108 approach. It was found that the DNVGL-RP-F108 approach can be conservatively applied to girth welds with a weld strength under-match by 5% in all cases, and even by 10% for most cases, for the conditions investigated. It was also revealed that use of this guidance could be unduly conservative for strength over-matching welds.

Influence of Microstructure on the Mechanical and Corrosion Response of a Friction Stir-Extruded WE43 Magnesium Rod

Friction stir extrusion (FSE) was used with WE43 Mg to create a rod with a hybrid microstructure. The rod’s electrochemical corrosion response was characterized in Hank’s balanced salt solution at 37 ± 1 °C. The rod showed refined grains near the edge, while coarse grains were observed at the rod center. A larger fraction of precipitates was observed near the edge possibly hindering grain growth. The refined grains and the presence of a larger fraction of precipitates in the edge regions resulted in higher hardness owing to a confluence of precipitate hardening and solid–solution strengthening. Texture analysis of the rod cross-section exhibited a basal texture, perpendicular to the extrusion direction and populating the rod’s outer surface. In compression, the rod showed a near-base material yield strength (225.6 MPa) and a good combination of compressive strength (357.5 MPa) and ductility (~17.7%). The rod’s electrochemical corrosion response was sensitive to variations in the grain size, texture, and precipitate distribution between the rod core and edge regions. Removal of the edge region resulted in the formation of a more stable and protective film with an increase in the immersion period. The results from the study establish the ability of the FSE process to tailor the rod microstructure thereby influencing the mechanical properties and corrosion rate of Mg alloy.

Reliability analysis of bearing support structure of device for recovering metallic sodium from sodium slag

In a device for recovering metallic sodium from sodium slag, the bearing support structure that supports and drives the rotation of the distillation furnace is one of the key components that cause the failure of the device, and its failure form is insufficient strength. In this paper, under the condition of certain material parameters, the bearing mechanism's loadbearing capacity is analyzed by finite element analysis, and the design and optimization of the bearing mechanism based on the response surface method are carried out to guide the fit between the parts in the device. Then establishing a reliability model, the design results were evaluated for their reliability based on the Six Sigma module, which improves the overall reliability of the device. The results show that the maximum equivalent force of the bearing support structure is about 15.066 MPa, which is much smaller than the default structural steel material yield strength of 235 MPa. The maximum deformation after optimization is about 0.02 mm higher than before, which has little impact on the device. This method has a little guiding meaning for similar assembly reliability analysis.

Cohesive zone model based reliability analysis for a sandwich pipe

A cohesive zone model based reliability analysis for a sandwich pipe (SP) is presented in this paper. The collapse or burst strength of SP is predicted by a cohesive zone model based nonlinear finite element (FE) analysis. The interlayer adhesion is simulated by cohesive zone model in accordance with the maximum shear strength. The bilinear traction separation law is employed in the cohesive zone model. A quadratic stress criterion and an energy-based model are used for simulating the damage initiation and evolution. The validity of the FE analysis is then validated by the comparison between model prediction and experimental results. A first-order reliability method coupled with a response-surface method is then used for reliability estimate dealing with implicit limit state functions corresponding to failure modes of collapse and burst. A sensitivity analysis to investigate the influence of design variables on the reliability of SP is further conducted and the results show that working pressure, yield strength of material, and modelling uncertainties are relatively important design variables in predicting the collapse and burst strength of SP, while initial ovalities of internal and external pipes could be regarded as constants in the reliability analysis for improving the computational efficiency.

Energy analysis of wear sliding friction units

This article deals with the calculation of friction and wear of working surfaces of sliding friction units on the basis of energy theory. Working surfaces have roughness, i.e., protrusions and depressions, which under the influence of load and as a result of slip undergo plastic deformation, as a result of which the roughness of contacting surfaces changes and differs from the initial one, which is called equilibrium roughness. Profilograms of surfaces with equilibrium roughness showed that their protrusions have approximately the same height and large rounding radii, which causes a large contact area of the mating friction surfaces. The intensity of wear of the friction pair depends largely on the normal load on the contact areas. If the contact stress does not exceed the yield strength of the tooth material, the wear of the friction surfaces occurs without seizure, if the yield strength of the material is exceeded, seizure may occur. The process of separation of wear products during meshing operation has a cyclic nature and occurs after a certain number of repeated deformations. The obtained results allow calculating the amount of wear of sliding friction surfaces [1].

Моделирование контактного термического сопротивления при проектировании технологического оборудования

Analysis of the processing equipment structures when designing according to the temperature criterion is a necessary guarantee of ensuring the required performance characteristics. The presence of a significant number of parts in the processing equipment units and mechanisms requires, when designing, the prediction of the heat flow passage through the joints. When simulating contact thermal resistance, the variety of requirements for a joint can be taken into account by introducing a pseudolayer into the contact zone. The paper presents test results of the proposed regression dependence of the temperature change when the heat flow goes through the pseudolayer obtained considering four significant factors: the pseudolayer thickness, the nominal pressure, the material yield strength, and the actual contact zone location. The adequacy of the specified regression dependence was verified experimentally and applying numerical simulation using large-block finite elements. To describe the process of heat transfer in the thermal model elements, the authors determined contact thermal resistances for several conditions for the heat flow propagation: from one finite element to another within one part; from one finite element to another located in an adjacent part; heat flow passing through closed cavities; heat flow propagation into the environment for finite elements located on the outer (free) contour of the part. The experiments showed a good agreement between the experimental data and the simulation results. The application of large-block finite elements based on the proposed contact thermal resistance model allowed bringing the FE simulation technique to engineering use without complex software.

Some exact solutions of the nonlinear evolutionary equation for the spreading of a plastic layer on a plane

The problem of free spreading of a plastic layer between parallel approaching planes of tool bodies [1] is considered, which simulates the technological process of stamping thin-walled structural elements. To describe the specified flow of a thin plastic layer, A. Ilyushin proposed an effective two-dimensional mathematical model averaged over the layer thickness, to which the original three-dimensional problem of the flow of an ideally plastic body leads. The transition to a two-dimensional problem was carried out on the basis of special hypotheses proposed as a result of the analysis of the well-known Prandtl solution in the problem of upsetting a flat, in a vertical section, layer of plastic material [2]. On the contact surfaces, the condition of complete slippage of the material is assumed, and the shear stresses reach a maximum value equal to the shear yield strength of the layer material. Within the framework of this model, A. A. Ilyushin formulated a boundary value problem in a region with a moving boundary with respect to three unknown functions - contact pressure and two flow velocity components.