Plastic Deformation Failure Research Articles

Simulation of Plastic Deformation Failure of Tillage Tools Based on the Smoothed Particle Hydrodynamics Method

The problems of large deformations, failures, and fractures that agricultural tillage tools may encounter during the cultivation process has long been a concern in the field of agricultural machinery design and manufacturing. It is important to establish a more accurate numerical model to effectively predict tools’ plastic deformation failures and ductile fracture failures. This research develops a numerical model for predicting the plastic deformation failure and ductile fracture failure of agricultural tillage tools using the smoothed particle hydrodynamics (SPH) method and the Johnson–Cook constitutive model. The model uses the Drucker–Prager criterion to describe the elastic–plastic constitutive behavior of the soil, the von Mises criterion to describe the Johnson–Cook constitutive model of the tool, and the coupling condition with the Lennard-Jones repulsive force to describe the interaction between the tool and soil. The numerical results show that the proposed model can effectively simulate the interaction between the tool and soil, as well as the tool’s plastic deformation failure and ductile fracture failure during the agricultural cultivation process. It can also predict the variation trend of the cutting force of the tool. This helps to provide a new approach for the numerical simulation of such problems.

Microscopic mechanism analysis and failure criterion study of glass fiber recycled concrete under three‐dimensional compressive stress state

AbstractThis study aims to address the complex stress state commonly observed in concrete structures in practical engineering, as well as the challenges posed by resource scarcity and environmental pollution. To achieve this, a total of 168 cylinder specimens of glass fiber recycled coarse aggregate concrete (GFRAC) were designed for conventional triaxial compression tests. The analysis of the test results reveals that the application of lateral restraint force induces a shift in the failure mode of GFRAC from longitudinal splitting failure to plastic deformation failure, occurring either in the middle or at the end of the specimen. The lateral constraint force can effectively improve the stress and strain at the peak point of GFRAC and the modulus of elasticity of the specimen. The glass fiber increases the peak stress of the specimen, and the maximum growth rate is 20%. On the contrary, the glass fiber reduces the peak strain, and the maximum reduction is 49.66%. Increasing the replacement rate of recycled coarse aggregate will lead to a decrease in peak stress, with a maximum decrease of 19.17%. Glass fiber (GF) limits the appearance and propagation of cracks by bridging, pulling out or breaking. Finally, three different failure criteria are used to analyze the triaxial compression state of GFRAC from a macro perspective.

Compression behavior and permeability of concrete composed of glass sand and rice husk ash

Using glass sand and rice husk ash as raw materials for concrete production can effectively save resources, protect the environment, and promote waste recycling. In this study, glass sand (20%) and rice husk ash (15%, 30%, 45%) are used to replace natural river sand and cement in concrete, respectively, while ordinary concrete is also considered as a reference. The effects of glass sand and rice husk ash on the performance and structural safety of concrete were evaluated through a series of experiments, including slump test, uniaxial compression test, triaxial compression test and dynamic compression test. The experimental results show that glass sand reduces the slump, uniaxial compressive strength, and triaxial compressive strength of the concrete but improves its dynamic compressive strength and strain rate sensitivity. In addition, the permeability of glass sand concrete is observed to be lower than that of ordinary concrete under high confining pressure. Furthermore, when the replacement rate of rice husk ash is 15%, the experimental results are found to be better than those for other mixtures, except for the uniaxial compressive strength. However, increasing the replacement rate to 30% and 45% fails to meet the strength requirements of structural concrete. Moreover, when subjected to external load, the samples containing rice husk ash exhibits toughness and plastic deformation failure characteristics, which became more obvious with an increase in the rice husk ash replacement rate. Overall, this study provides novel insights into the performance of glass sand and rice husk ash in concrete.

The efficient design of hybrid and metallic sandwich structures under air blast loading

A novel hybrid composite honeycomb sandwich structure (HCHSS) and metallic honeycomb sandwich structure (MHSS) were developed to obtain realistic and blast resistance parameters for the consideration of blast loading. Hybrid composite square honeycomb sandwich structure (HCSHSS) and metallic honeycomb sandwich structure with different cores such as square, hexagonal, octagonal, and circular were modelled to obtain the target protection level (lowest deflection) for the vehicle armour structure. The Johnson-Cook and Donadon failure criteria were incorporated into finite element analysis (FEA) for MHSS and HCSHSS, respectively. For the progressive damage modelling of the HCSHSS, the Donadon criterion was implemented in ABAQUS/Explicit software as a user-defined subroutine. The HCSHSS showed the fibre failure, matrix failure and delamination modes of failure in composite laminates and the plastic deformation failure of the core and metal plates. The HCSHSS was shown to have excellent blast worthiness properties in comparison to the MHSS. The metallic circular honeycomb sandwich structure (MCHSS) was shown to have the minimum deflection of the top and bottom face plates as compared to the square, hexagonal and octagonal honeycomb sandwich structures. A novel HCSHSS has obtained the minimum deflection for both the top and the bottom face plates in comparison to the other MHSS.

Improvement of forging die life by failure mechanism analysis**

Abstract This study analyses the causes of rapid failure at the early stages of hot forging tools. Tool life generally refers to the number of forgings that meet the required geometry, properties and quality produced by a tool. Die failure in hot forging processes are caused by failure modes such as plastic deformation, wear and thermomechanical fatigue. This study focuses on plastic deformation failure. The practical experience was carried out in the upset forge fastener head, having a workpiece material of Ck45 alloy steel and tool made of 56 NiCrMoV7 tool material, which was forged at 950–1150°C, under an 800-ton, horizontal mechanical press. The finite element (FE) software MSC Simufact Forming 16.0 was used to simulate the process. The results showed plastic deformation occurring in the upper and lower dies because the temperature increase progressively reduced the hardness, creating softening effects during the forging process. The optimal forging temperature to form the fastener head was determined to be lower at 1000°C, saving time and cost. The FE method can be efficiently used to enhance the formation and to predict diet life.

Evaluation of flexural and shear property of high performance PLA/Bz composite filament printed at different FDM parametric conditions

In the present work, 14% bronze (Bz) with a particle size of 10-20 μm is used as reinforcement in the PLA matrix to obtain a composite 3D filament. The bonding properties of Bz particles in the PLA matrix are uniform and excellent. The manufactured composite filament is printed under different parameters of the fused deposit model at a matrix angle of 45°. The density, bending and shear properties of the printed specimens were evaluated according to ASTM standards. The nozzle temperature, bed temperature and Layer height were taken as independent parameters. The layer height had an impact on other output parameters. Fracture mechanics are analysed through scanning electron microscopy and 3D optical microscopy. The bending and shearing test specimens present a plastic deformation failure. The push mechanism of the particles has been observed, and most of the fracture surface is subject to wear caused by the Bz particles.

The Microstructure and Microscopic Mechanical Performance of Welded Joint for 9%Ni Steel Using Nickel-Based Filler Metal

Abstract Shielded metal arc butt welded joints for 9%Ni steel using nickel-based filler metal were analyzed by optical microscopy, scanning electron microscope, as well as transmission electron microscopy. The nanoindentation method was used to study the correlation between the structure and micromechanical properties of the fusion welded joint. The results show that there is a microstructural evolution from melted deposit to 9%Ni base steel. A significant coarse lath martensite-bainite mixture has been obtained in 9%Ni steel close to the fusion boundary while the retained austenite distributing in grain boundary of lath martensite has reduced to an undetectable level. In fusion boundary, an intermetallic layer has been observed which corresponds to the epitaxial growth of weld metal. The analysis of stress-strain behavior using nanoindentation shows that the heat-affected zone of coarse grains exhibits ductility loss and quantitative plastic deformation failure. The fusion boundary has the lowest value of yield stress while the coarse grained heat affected zone has the maximum value of yield stress.

Investigation of effects of functionalization on mechanical properties of penta-graphene

Penta-graphene is a new two-dimensional metastable carbon allotrope composed entirely of carbon pentagons with unique electronic and mechanical properties. In this work, molecular dynamics simulations are carried out to investigate the effects of functionalization by hydrogen, epoxide or hydroxyl groups on the mechanical properties and failure mechanism of penta-graphene, as well as the effects of different functionalization coverages. The effects of functionalization on the structural transformation of free-standing penta-graphene triggered by increasing temperature have also been studied. The results indicate that each of the three functional groups considered can effectively tune the mechanical properties and the failure mechanism of penta-graphene. Both the Young's modulus and elastic limit of penta-graphene first decrease sharply and then increase slowly with the increase of the functionalization coverage, while the ultimate elastic strain increases monotonically. Like the pristine penta-graphene, partially functionalized penta-graphene still exhibits a plastic deformation failure behaviour under tensile load, which is caused by the irreversible pentagon-to-polygon structural transformation occurring during tensile loading. Temperature can trigger structural reconstruction for free-standing partially functionalized penta-graphene, and the corresponding critical transition temperature is higher than that of pristine penta-graphene. However, complete functionalization can change the deformation mechanism of penta-graphene from plastic deformation to brittle fracture. For fully functionalized penta-graphene by each of the three functional groups, the structural transformation is not observed when tensile strain is applied or environmental temperature is increased. These findings are expected to provide important guidelines for effectively tuning the mechanical properties of two-dimensional nanomaterials including penta-graphene.

Effects of design parameters on carrying capacity of a double-row tapered roller slewing bearing used in wind turbine

Mechanical model with detailed design parameters of a rotor slewing bearing with the structure type of double-row tapered roller for supporting the rotor of the wind turbine was presented. The internal geometrical relationships of the rotor slewing bearing were established in the Cartesian coordinate system. The elastic contact deformations between each tapered roller and the raceways were expressed through the geometrical transformation. The mechanical model was established using the equilibrium relations in the rotor slewing bearing. The safety factor and the fatigue life which represents, respectively, the ability of resisting the rolling contact plastic deformation failure and the rolling contact fatigue failure of the rotor slewing bearing were obtained based on the solution of the mechanical model. Effects of the detailed design parameters such as axial clearance, contact angle, and roller semi-cone angle on the carrying capacity of the rotor slewing bearing were analyzed. The results show that right amount of small negative axial clearance, increase in contact angle, and decrease in roller semi-cone angle are advantageous for enhancing the carrying capacity of the rotor slewing bearing. This provides the basis for the reasonable value selection of the design parameters of the double-row tapered roller slewing bearing for supporting the rotor of the wind turbine.

Static Behavior Study for Latticed Concrete-Filled Steel Tubular Wind Turbine Tower Joints

Six latticed concrete-filled steel tubular (CFST) wind turbine tower K-shape joints were carried on the static load test, which included the weld intersecting joint and gusset plate joint. The failure mechanism and characteristics on the two kinds of K-shape joints, the deformation development process after joints entered plastic stage and the stress state and distribution of joint intersection area were studied. The results show that the failure mode and mechanical behavior of CFST K-shape joints are greatly different from that of the hollow steel tube K-shape joints because of the existence of core concrete, the failure mode of the weld intersecting joints showed the local buckling of compression web member and that of the gusset plate joints presented as the compression buckling and tension tearing of the gusset plates, while the plastic deformation failure of tower column tube wall in joint area was not appear. It is also shown by test results that the stress distribution of tower column tube wall and gusset plate in joint intersection is extremely non-uniform, individual parts already enter plastic state but some other parts are still in elastic state. According to the failure mode and stress distribution conditions of the two kinds of K-shape joints, some design suggestions are drawn, which can provide reference for the latticed CFST wind turbine tower joints.

Ultimate Strength Research of the Tube-Plate Connection of K-Shape

Based on relevant flow rule, Von Mises yield condition and the virtual displacement principle determined by the updated-Lagrange configuration, nonlinear finite-element analysis of the tube-plate connection of K-shape by ANSYS program is studied in this thesis. In order to study the influence of main pipe to the ultimate strength of the tube-plate connection of K-shape, two geometric parameters are considered, D, diameter of the main pipe; T, thickness of the main pipe .Three typical failure modes, gusset yielding, main pipe excessive plastic deformation failure and branch local buckling are also summarized. A comparison was made between formula result and analysis of finite element stimulation to validate the veracity of the existing formula.

Effect of Working Pressure on Microstructure and Mechanical Properties of Magnetron Sputtered ZrN Coatings

The influence of working pressure on microstructure and mechanical properties of magnetron sputtered ZrN coatings were systemically investigated. The results reveal that a decreased working pressure results in preferred orientation evolution from (111) to (200) and cross-sectional morphologies transition from columnar structure to equiaxed grains. These microstructural changes are considered responsible for an increase in hardness and modulus with decreasing working pressure. Chip spallation and plastic deformation failure modes are observed during scratch testing, and the increased critical loads are attributed to higher hardness and elastic modulus, as well as moderate compressive stress at lower working pressure.

A New Contact Probe without Cleaning Process

To remove dust particles accumulated on pad surfaces or probe tips after they contact each other during semiconductor wafer testing, a cleaning process is required. On the one hand, scrubbing is an efficient method to remove the oxide layer on the surfaces. However, excessive scrubbing degrades the probe’s mechanical properties and leads to the accumulation of excessive dust and plastic deformation failure of the pad surface. Therefore, we have developed a new contact probe that allows only a vertical displacement of the probe tip on the pad surface to minimize the horizontal displacement for scrubbing. This probe is fabricated using a beryllium-copper alloy and is characterized by a two-beam structure. The matrix method is employed to investigate the contact probe structure and the results are compared with the data obtained with a commercial finite element method. Furthermore, electrical contact resistance is measured experimentally and determined theoretically using Holm’s theory. A durability test is conducted to simulate more than 100,000 contacts between the probe tip and the pad; this allows us to examine the probe tip’s endurance and whether the electrical resistance of the contact could be sustained. Our results suggest that the two-beam structural probe ensures a stable electrical contact resistance when the contact force is within specific limits and the horizontal displacement for scrubbing is min

Stability of an expanding circular cavity and the failure of amorphous solids

Recently, the existence and properties of unbounded cavity modes, resulting in extensive plastic deformation failure of two-dimensional sheets of amorphous media, were discussed in the context of the athermal shear-transformation-zones (STZ) theory. These modes pertain to perfect circular symmetry of the cavity and the stress conditions. In this paper we study the shape stability of the expanding circular cavity against perturbations, in both the unbounded and the bounded growth regimes (for the latter the unperturbed theory predicts no catastrophic failure). Since the unperturbed reference state is time dependent, the linear stability theory cannot be cast into standard time-independent eigenvalue analysis. The main results of our study are as follows: (i) sufficiently small perturbations are stable; (ii) larger perturbations within the formal linear decomposition may lead to an instability; this dependence on the magnitude of the perturbations in the linear analysis is a result of the nonstationarity of the growth; and (iii) the stability of the circular cavity is particularly sensitive to perturbations in the effective disorder temperature; in this context we highlight the role of the rate sensitivity of the limiting value of this effective temperature. Finally we point to the consequences of the form of the stress dependence of the rate of STZ transitions. The present analysis indicates the importance of nonlinear effects that were not taken into account yet. Furthermore, the analysis suggests that details of the constitutive relations appearing in the theory can be constrained by the modes of macroscopic failure in these amorphous systems.

A contribution to the theory of mechanical wear

An attempt is made to predict the wear behaviour, particularly of metals, when wear arises from asperity interactions alone. It incorporates the concept of fatigue failure and also of simple plastic deformation failure which is considered as fatigue failure in one cycle of loading. The analysis demonstrates that fatigue mechanisms of wear are not inconsistent with observed behaviour and indicates an approach to a better appreciation of the effects of such factors as material constants and surface topographical features.