Tensile Shear Fracture Research Articles

Investigation of Tensile Properties and In Situ Analysis of Fracture Behavior in High-Porosity Open-Cell Nickel Foam.

Nickel foam offers excellent conductivity, a high surface area, and lightweight structure, making it ideal for applications, like battery electrodes, catalysts, and filtration systems. Its durability and corrosion resistance further enhance its performance in various industries. However, few studies focus on the tensile anisotropy of nickel foam and its tensile fracture process. In this study, the anisotropic tensile behavior of nickel foam with varying relative densities has been investigated, along with its tensile fracture behavior using in situ techniques. The tensile properties of nickel foams show strong anisotropy due to the flattening process in the production process. The results show that the tensile properties, including the yield strength, tensile strength, and elastic modulus, increase with the increasing relative density, while the elongation percentage has no relationship with the relative density. The experiment data on tensile strength are in agreement with Gibson's formula and Liu's formula. In situ tensile tests are conducted to explore the microscopic fracture mechanism of nickel foam. The results show that the struts of nickel foam are tensile fractures or shear fractures near the joints, and the fracture process of struts is clearly recorded and analyzed. This study is significant as it provides critical insights into the anisotropic tensile behavior of nickel foam and fracture mechanism, enabling the optimization of production processes and broadening its potential applications.

Disturbance shear fracturing process and failure precursors of intermittent structural planes with different connectivity under true triaxial condition

The mechanisms, processes, and precursors of shear failure in rock structural planes under three-dimensional geostress and excavation disturbances are unclear, which poses challenges for disaster prediction and warning in underground rock engineering. Therefore, this study self-developed a new separation rolling-sliding shear device for rock structural plane under true triaxial condition, and proposed a true triaxial shear testing method to simulate the damage of rock structural plane induced by the three-dimensional geostress redistribution during engineering excavation and subsequent dynamic disturbance further triggering failure. True triaxial disturbance shear tests were conducted on intermittent structural planes with different connectivity. With connectivity increasing, disturbance shear strength and failure surface roughness of structural planes gradually decreases. An improved simplex acoustic emission spatial localization method was proposed to reveal disturbance shear fracturing evolution. During disturbance shear fracturing process, micro-tensile cracks dominate, and the proportion of micro-shear cracks continues to increase, showing a mixed tensile-shear fracture mechanism. Approaching to disturbance shear failure, the acoustic emission fractal dimension decreases rapidly then increases to the maximum value, the b-value decreases rapidly to less than 1, the rapid increase in LgN/b exceeds 3, and the low-frequency and high-amplitude dense fracture signal appears abundantly, which can be used as disturbance failure precursors of intermittent structural planes.

Experimental behavior and fracture prediction of a novel high-strength and high-toughness steel subjected to tension and shear loading tests

In this study, laboratory testing and numerical simulation methods are used to investigate the mechanical behavior and perform fracture prediction of a novel high-strength and high-toughness steel with a negative Poisson's ratio (NPR) effect under combined tensile-shear loading conditions. A test device capable of meeting different tensile-shear combination test angles is designed and manufactured, wherein the mechanical experiments on the NPR (Negative Poisson's Ratio) steel specimens are carried out at various testing angles. Q235 steel and MG400 steel are used as experimental control groups. The results show that the mechanical deformation of NPR steel is significantly better than that of Q235 steel and MG400 steel. Its tensile-shear test curve has no yield plateau and it has quasi-ideal elastic-plastic mechanical properties. The loading direction gradually changes from tension-dominated to shear-dominated as the tension-shear angle increases, and the strength and deformation of the specimens show a decreasing trend. Based on the laboratory test results, a finite element numerical model of NPR steel is established. A series of numerical simulations are carried out under the conditions of different tension and shear angles and the average stress triaxiality and fracture strain data are obtained. The fracture data of NPR steel are fitted using the Johnson-Cook fracture criterion, and the Johnson-Cook fracture parameters under the tensile-shear test conditions of NPR steel are thus obtained. The numerical simulation verifies that the fracture model can accurately predict the tensile-shear fracture behavior of NPR steel.

Optimization investigation of parameters for spot-welding of AA2014 and AISI316 dissimilar alloys

The objective of the research was to determine the exact process parameters required for spot-welding AA2014 and AISI316 alloys. The main focus was on achieving particular welding results, including nugget diameter, hardness, and tensile shear fracture load (TSFL). The central composite rotatable design model within the framework of a Response Surface Methodology (RSM) optimization approach, the study sought to intensify key spot weld process factors. The mechanical characteristics and nugget diameter of the welded joints were analyzed by carefully examining these factors to determine their significant effects. The investigation yielded crucial insights, revealing that the highest strength of welded joints, characterized by a nugget diameter of 5.982 mm, hardness of 149.6 VHN, and TSFL of 2.355 KN, was achieved at 3.4 kgf, when accompanied by 60 W power and a 2.5s duration. Notably, power emerged as the predominant factor driving the spot-welding process. Furthermore, microhardness and TSFL displayed direct correlations with power, while nugget diameter exhibited an inverse relationship. Moreover, rigorous statistical analyses, including F-tests and ANOVA, provided robust validation, indicating that the observed values fell comfortably within a 99.5% confidence interval for hardness, nugget diameter, and TSFL. These meticulously derived conclusions represent a significant stride towards establishing more standardized and efficient spot-welding protocols, particularly beneficial for the manufacturing sectors dealing with mild steel and aluminium materials.

Joining of Al-Alloy Tubes by Carbon Steel Tubes using MPW Technique

Background/ Objectives: Joining aluminum alloys with low carbon steel (DC01) through fusion welding is a challenging task due to the occurrence of solidification defects like porosity, alloy segregation, and hot cracking. However, these issues can be addressed by employing solid-state welding techniques like explosive welding and MPW (magnetic pulse welding). MPW is a cost-effective and high-speed solid state welding method that involves creating joints in an overlap configuration. Methods: The MPW technique was employed to join dissimilar aluminum alloy AL 7075T6 hollow tube and DC01 steel rod in this study. A central composite design model was created to analyze the relationship between key MPW process parameters, including stand-off distance (SoD), overlap length, and discharge energy, and the bonding strength of the joints. Experimental setups were established and correlate with tensile-shear fracture load and interface hardness of the joints with the MPW process parameters. Findings: It is understood that the maximum TSFL of 2.404 kN was obtained under the welding condition of 23kJ discharge energy, 2.25 mm Stand-off distance, 8.5 mm overlap length, which is the optimum MP welding state for AA 7075 T6 with DC01 and confirmed by RSM. In addition, the cultivated connection can be aptly leveraged to anticipate the TSFL of MPW joints with a 95% confidence level. Novelty: The parametric mathematic samples were developed for forecasting TSFL of joints. The MPW parameters were optimized to enhance TSFL of joints. Aluminium alloys with low carbon steel joints were developed using MPW for cars and ships applications without fusion welding defects. Keywords: Magnetic Pulse Welding, Dissimilar Joint, (RSM) Response Surface Methodology, Tensile Shear-Fracture Load

Effect of loading rate on energy and acoustic emission characteristics of tensile fracture and shear fracture for red sandstone

To understand the influences of loading rates (LRs) on the energy and acoustic emission (AE) characteristics during tensile fracture and shear fracture, a series of pure mode I and pure mode II fracture tests were carried out under different LRs using the semi-circular bending (SCB) and single-notched shear-box (SNSB) sandstone specimens. The AE technique is employed to obtain the acoustic signal generated from rock fracture. Results show that: (1) The mode I fracture toughness KIC and mode II fracture toughness KIIC increase logarithmically with the increase of LRs, and the ratio of KIIC to KIC changes in the range of 2.1–2.3 at different LRs; (2) The cumulative AE energy (EAEI and EAEII) increases with LRs in a power function relationship under two loading modes, and the ratio of EUAEII and EUAEI (the released AE energy per unit fracture area) at different LRs varies from 38 to 46; (3) The cumulative input energy (ECII and ECI) increases logarithmically with the increase of LRs, and the ratio of EUII to EUI (the total released energy per unit fracture area) at different LRs ranges from 49 to 54. The LR has a significant effect on the RA-AF distribution characteristics. The quantitative analysis shows that the proportion of shear cracks increases but the proportion of tensile cracks decreases with LRs under two loading modes. Finally, the relationship between fracture toughness and tensile strength of red sandstone is discussed.

Enhanced Mechanical Properties of Ti/Mg Laminated Composites Using a Differential Temperature Rolling Process under a Protective Atmosphere.

Addressing the issue of low bonding strength in Ti/Mg laminated composites due to interfacial oxidation, this study employs a differential temperature rolling method using longitudinal induction heating to fabricate Ti/Mg composite plates. The entire process is conducted under an argon gas protective atmosphere, which prevents interfacial oxidation while achieving uniform deformation. The effects of reduction on the mechanical properties and microstructure of the composite plates are thoroughly investigated. Results indicate that as the reduction increases, the bonding strength gradually increases, mainly attributed to the increased mechanical interlocking area and a broader element diffusion layer. This corresponds to a transition from a brittle to a ductile fracture at the microscopic tensile-shear fracture surface. When the reduction reaches 47.5%, the Ti/Mg interfacial strength reaches 63 MPa, which is approximately a 20% improvement compared to the bonded strength with previous oxidation at the interface. Notably, at a low reduction of 17.5%, the bonding strength is significantly enhanced by about one time. Additionally, it was found that a strong bonded interface at a high reduction is beneficial in hindering the propagation of interfacial cracks during tensile testing, enhancing the ability of the Ti/Mg composite plates to resist interfacial delamination.

The Effect of a Coating Sprayed Using Supersonic Flame Coating Technology on the Mechanical Properties and Interface Structure of a Thick Steel/Aluminum Composite Plate during Hot Rolling

Given the characteristics of a thick steel/aluminum composite plate, such as its large thickness and the significant differences between its components, it is difficult to prepare using direct rolling. Instead, a thick steel/coating/aluminum composite plate may be successfully prepared by combining supersonic flame coating technology with a hot rolling composite process. In this study, the interface shear strength test, SEM, EDS, and other detection methods were applied to investigate the effects of the reduction rate and coating thickness on the interface structure and mechanical properties. The results show that under the condition of single-pass direct rolling, the micro-interface of steel/aluminum is improved with an increase in the reduction rate, but the bonding strength of the interface remains poor. After adding the coating, the thickness of the diffusion layer and the shear strength increase significantly. When the coating thickness is reduced to 0.1 mm, the deformation coordination and shear strength of the composite plate are further enhanced under the combined action of mechanical interlocking and metallurgical bonding. The tensile shear fracture is mainly located at the steel/coating interface. The interfacial shear strength reaches 66 MPa, which exceeds the requirements of the US military standard MIL-J-24445A (SH) for steel/aluminum shear strength. The research results thus support the use of this new method for the simple and efficient production of thick steel/aluminum composite plates.

Bonded particle model for dilated polyhedron considering fracture modes and its application to lateral resistance of ballast bed in cold regions

Considering the spatial arrangement characteristics of bonded irregular particle systems, this paper first constructs irregular dilated polyhedron elements based on the Voronoi cutting algorithm and Minkowski Sum theory. Subsequently, by extending the traditional sphere-based BPM (Bonded Particle Model) to irregular particle elements, a novel dilated polyhedron bonding-breaking model considering different fracture modes is developed under arbitrary contact modes. A collision example between two bonded square particles and a rigid plate is adopted to verify the stability of the model. Later, the difference between the tensile-shear fracture mode and the mixed fracture mode with damage process for contact bond is compared by the discrete element simulations of the tension-fracture behavior between two bonded square particles and the uniaxial compression simulation of frozen ballast aggregate. Finally, the influence of section size on the lateral resistance of the ballast bed structure at low temperatures is discussed using the dilated polyhedron BPM. The results showed that the developed dilated polyhedron BPM considering different fracture modes can realize mechanical behaviours between bonded irregular particles. Compared with the tensile-shear fracture mode, the mixed fracture mode not only considers the combined effect of normal and tangential stress on the bond but also realizes the damage deformation and stiffness attenuation of the bond, which can achieve the “delayed” fracture effect. Meanwhile, the model also shows good reliability in analyzing large-scale engineering problems, such as the mechanical performance of low-temperature ballast beds. The research effectively develops the bonding and breaking model of irregular elements and provides a new perspective for the contact-bond-fracture behavior simulation of irregular granular materials.

Study on strengthening and toughening Al/CFRP hybrid composites with biomimetic interface

The biomimetic interface of Al/CFRP hybrid composite material was obtained by combining laser surface treatment and hot-pressing process. The experimental results showed that the tensile shear strength and fracture energy of the biomimetic interface were 44.5 MPa and 1652 J/m2, which were 224% and 72.6% higher than those of the untreated interface. The new C-O-Al chemical bond was formed at the biomimetic interface, which replaced the van der Waals force and improved the interface strength. The transition layer of the biomimetic interface can effectively delay the transmission of cracks at the interface. The finite element results showed that the stress distribution of biomimetic interface was uniform and stress concentration was not obvious. The strengthening and toughening effect of the interface is mainly due to the pinning effect of mechanical interlocking of the interface and the behavior of crack deflection of the transition layer.

Effect of laser pre-treatment on adhesive joint performance and evaluation of interfacial strain distribution using mechanoluminescence

ABSTRACT In this study, factors that improve bonded joints structural response through laser surface pre-treatment on aluminum surfaces were investigated. Specifically, the focus was put on analyzing the laser treatment conditions, formation of the interface structure, and behavior of interface strength at the adhesive interface. The results revealed a specific range of laser treatment conditions in which tensile shear strength and fracture mode are stable. Although laser-treated adhesive joints showed cohesive failure similar to that observed in sandblasting or chemical treatment during the double cantilever beam test, the fracture toughness value was improved by a factor of 2 and 1.5, respectively. The laser-induced microstructure on the aluminum interface contributed to the improvement of fracture toughness. Furthermore, observation of the adhesive layer using a microscopic mechanoluminescence measurement system revealed that changes in the 3D structure of the interface significantly altered the stress luminescence pattern reflecting strain. As a result, direct visualization of interface strengthening via laser processing was achieved.

Macro-meso fatigue fracture and instability of rock-backfill composite structure under increasing-amplitude cyclic loading

The rock-backfill composite structure (RBCS) material in mine stopes is often subjected to stress disturbance. In order to reveal the fracture and instability mechanism of the RBCS exposed to disturbed stresses, a series of multi-stage cyclic loading tests were conducted on RBCS specimens with various cement-tailing ratios (c/t). The results indicate that deformation characteristics, stiffness degradation, damage propagation and failure mode of the RBCS were greatly influenced by the c/t. The volume dilatancy increases as well as the secant modulus (Es) increases and then decreases with decreasing c/t, i.e., from 1:4 to 1:12. For a sample with c/t of 1:4 and 1:8, the damage displays two-phase increasing pattern. However, for a sample with c/t of 1:10 and 1:12, inverted S-shaped damage accumulation pattern is found. As the c/t decreased, failure mode of RBCS specimens transformed from mixed tensile-shear failure to dominant tensile failure. Post-test CT imaging reveals obvious fracture evolution pattern that was characterized by shear fracture within the backfill, a circular tensile fracture along the rock-backfill interface, and tensile-shear fracture within the surrounding rock. It is noteworthy that complicated crack network is prone to forming for RBCS specimens with the c/t of 1:4 and 1:8. It is found that the use of "flexible CTB" with relatively low c/t is beneficial to improve the overall stability of the mine stopes.

Effect of tool rotational speed on friction stir spot welds of AZ31B Mg alloy to AISI 304 stainless steel

Abstract AZ31B Mg alloy were welded to AISI 304 stainless steel (which is a very challenging task because of their huge different chemical and physical features) by friction stir spot welding (FSSW) at different tool rotation speeds (700, 1000, and 1300 rpm) while keeping other conditions the same. Welds were evaluated and compared by examining their cross-sectional geometry, XRD pattern, tensile shear strength, fracture way and area. From cross-sections of welds, it was obtained that joining area expanded when speed was enhanced and the weld made through 1300 rpm had the largest one. Therefore, weld fabricated with the highest speed of 1300 rpm displayed the biggest tensile shear load of 3741 N while that manufactured with the lowest speed of 700 rpm possessed the lowest of 2430 N. All welds showed tensile shear type fracture and fracture occurred from the hooking regions where joining took place. From the fracture joint region, the weld of 700 rpm had the smallest joined area, whereas that of 1300 rpm showed the biggest. Higher speed produced a stronger joint, which agreed with a bigger bonding area and broken joint region. Also, joint became more ductile with increasing speed. Some phases were detected in joints.

Development characteristic and main controlling factors of the Ordovician karst caves in the Keping area, Tarim Basin

This research endeavors to characterize the primary factors that influence the formation of Ordovician karst caves in the Keping area of China. A 3D digital model of the cave structure and fracture sets was generated using an Unmanned Aerial Vehicle (UAV). The characterization of fracture and cavity development involved the examination of thin sections, fluid inclusion testing, and the analysis of C and O isotopes. Key parameters controlling karst development were identified through the application of multiple linear regressions and statistical analysis. The Ordovician limestone karst cave exhibited four distinct fracture sets. Set 1 consisted of partially filled fractures with a sub-horizontal orientation and a striking direction of SEE, interpreted to have formed during the Middle-Late Caledonian orogeny. Set 2 comprised inclined tensile-shear fractures with a striking direction of NEE, likely formed during the Early Hercynian orogeny. Set 3 included fully filled conjugate shear fractures with variable orientations, which developed during the Indo-Yanshanian orogeny. Set 4 comprised high-angle shear fractures with striking directions of NNE 20–40° and NEE 60–80°, formed during the Himalayan orogeny. Two stages of cave filling deposition were identified. Stage I coincided with the Middle-Late Caledonian Set 1 fractures and can be attributed to the circulation of freshwater fluid. Stage II occurred concurrently with the Early Hercynian Set 2 fractures and can be attributed to deep hydrothermal fluid circulation. The karst caves are interconnected and aligned along a fault zone. The Ordovician limestone possesses high permeability, which facilitates karst development. The lithologies in the Aksu area play a crucial role in cavity formation and dissolution. The development of cavities is influenced by the combined patterns of the fracture system, with larger fault and fracture zones resulting in larger cave sizes. As one moves away from the fault zone, limestone dissolution decreases, resulting in less pronounced karst development.

Deformation law and bonding mechanism of 45 carbon steel/316L stainless steel cladding tubes fabricated by three-roll skew rolling bonding process

Realizing the continuous forming and metallurgical bonding in bimetallic cladding tubes with high-strength and corrosion-resistance is the key bottleneck to be solved urgently. In this study, 45 carbon steel/316L stainless steel (CS/SS) cladding tubes were fabricated by the three-roll skew rolling bonding process under different radial reduction rates. The deformation law, interfacial microstructure characteristics, and deformation mechanism were analyzed. With the increase of the radial reduction rates from 11.7 % to 19.3 %, the 45 CS/316L SS cladding tubes were elongated along with the diameter and wall thickness decrease. Besides, the wall thickness ratio between 45 CS and 316L SS was unchanged due to the coordinated deformation. Tensile shear fracture locations of CS/SS cladding tubes were on the 45 CS matrix, and the average diffusion distances in the longitudinal section and the cross section were consistent, proving that uniform metallurgical bonding was achieved. Besides, average decarburized layer thickness decreased and average diffusion distances increased with the increase of radial reduction rates. Furthermore, spherical and fibrous Mn-Si-Cr-O oxides, generated in the insulation heating process, were dispersed near the bonding interface. The refined grains were formed close to the interface, and deformation twins were formed away from the interface on the 316L SS side, whereas only elongated ferrite grains evolved due to the decarburization adjacent to the interface on the 45 CS side. Therefore, the interfacial bonding mechanism was illustrated as three stages, namely the insulation heating stage, the skew rolling bonding stage, and the air cooling stage. The three-roll skew rolling bonding process provides a high-efficiency method to prepare CS/SS cladding tubes with uniform metallurgical bonding, which adopts axial forming and contributes to breaking through the product length size limit.

Phase field method of multi-mode fracture propagation in transversely isotropic brittle rock

A phase field model (PFM) for simulating multi-mode brittle fractures in transversely isotropic rock is proposed. In the model, we employ a novel decomposition form of strain energy consisting of tensile, tensile–shear and compressive–shear components to improve the fracture driving force, and the positive–negative decomposition forms of elastic energy are considered as an approximate extension of the spectral decomposition method for transversely isotropic materials. We also introduce the tensor form of the critical energy release rate and Lamé constants, which breaks through the limitations of traditional PFMs that cannot well reproduce fracture anisotropy and multi-mode brittle fracture in transversely isotropic rock, i.e. the tensile, shear, and mixed-mode fractures. A new mixed phase field model is established, which is solved in COMSOL by employing a staggered scheme to solve the phase field, displacement field, and historical field independently. Subsequently, the accuracy and effectiveness of the proposed model are comprehensively verified by a series of 2D and 3D numerical examples. The results show that the proposed model agrees well with the existing model in capturing tensile and tensile–shear fractures. Compressive–shear fractures can be additionally captured well in the compressive state.

Typical fracture modes of metal cylindrical shells under internal explosive loading

The competition and coupling of various fracture modes, including tensile fracture, shear fracture and spallation, exist in explosively-driven metal shells. However, the fracture mechanisms and influencing factors of different fracture modes are still unclear. In this study, three typical fracture modes of explosively-driven metal shells–tensile fracture, tensile-shear fracture and shear fracture are numerically revealed by using both the maximum principal strain and the Johnson-Cook cumulative-damage failure criterion. The selection of failure criteria is explained in detail. The fracture strain and fragment morphology are in good agreement with the experimental results. Combined with failure criterion, the numerical results are analyzed from the perspective of pressure, stress and strain. It is found that the formation of different fracture modes depends on the competition between the shear failure formed in the inner surface of the shell and the tensile micro-cracks formed in the middle of the shell. To further investigate the influencing factors of different fracture modes, three dimensionless parameters affecting the fracture modes are proposed based on dimensional analysis. In addition, by analyzing 29 sets of experimental data, we propose the dimensionless equations that can control different fracture modes. And the distribution diagrams of three typical fracture modes (tensile, tensile-shear and shear fracture) of explosively-driven metal shells are determined. Furthermore, we propose a parameter that can effectively distinguish adiabatic shear fracture from non-adiabatic shear fracture.

Numerical simulation study on shear resistance of anchorage joints considering tensile–shear fracture criterion of 2G-NPR bolt

2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has significant effects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under different tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verified by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.

Breaking behavior and stress distribution of T12A hard steel core penetrating ceramic/aluminum alloy lightweight composite armor

The armor-piercing incendiary (API) round inflicts significant damage to light armor. This article conducts penetration experiments on lightweight ceramic composite armor using 12.7 mm API rounds. The Rosin-Rammer distribution model is used to analyze the macroscopic fragmentation characteristics of the core, and the SEM is used to analyze the fracture surface of the bullet core after fragmentation at the microscopic level. Numerical simulations are also used to verify and expand the material parameters. The experimental results show that as the penetration velocity increases, the average feature size of the core decreases, indicating an increase in the degree of fragmentation of the core. The fragments generated by the fragmentation can be almost completely restored. The main fracture form is the brittle crushing fracture of the head of the projectile, while the tail and body of the projectile are basically intact, and the fracture surface is mainly a 45° shear fracture and radial platform-like tensile fracture.At the microscopic level, SEM images show that the material fracture mainly occurs in the form of radial cleavage shear fracture and river patterned tensile-shear fracture. The numerical simulation results show that as the penetration velocity increases, the energy dissipation of the core continuously increases. The main energy dissipation process of the core during penetration occurs during the contact with the ceramic cone, accounting for 66.48 % of the total energy loss, while the mass of the core remains almost unchanged during the interaction with the aluminum alloy.In addition, the experiment is verifiedusing different working conditions at different angles, confirming that the "unequal tearing" of the aluminum alloy backing plate is caused by the inclination of the penetration angle. It was also found that the penetration efficiency and destructive capability of the API round are significantly reduced when there is an angled penetration.

Research on the anti-penetration behavior and failure mode analysis of different ceramics

The principal objective of this study is to investigate the anti-penetration performance of ceramic composite armor and to explore the impact of ceramic structural and performance parameters on this ability. We conducted both experimental and numerical simulations on four types of ceramics widely used in this field—B4C, SiC, Si3N4, and Al2O3, using them as the faceplate, and Kevlar fiber board as the backing, to ascertain the influence of the ceramic's structure and performance parameters on its anti-penetration properties. Given the context where Kevlar fiber serves as the backing, an extensive damage analysis was carried out from both macro and micro perspectives, focusing on the projectile-ceramic-fiber interplay. We deployed the LS-Dyna finite element software to simulate the penetration behavior of these ceramics, and a high level of agreement was observed with experimental results, thus validating the relevance of the parameters used. The results indicate that the principal failure modes of the projectile core and ceramics include tensile shear and compressive shear, leading to fractures. The backing's main failure mode consists of tensile fracture and shear fracture. As the hardness of the ceramics increases, there is a slight decrease in their anti-penetration performance, suggesting that this performance may not be significantly related to hardness as a single variable. Conversely, an increase in fracture toughness and a decrease in brittleness can lead to enhanced anti-penetration performance. Utilizing numerical simulations, an assortment of the four ceramics was tested. When the harder ceramics are placed at the forefront and those with higher toughness at the rear, the energy absorption per unit area increases to a certain extent. Following a comparative analysis of different ceramic combinations, when B4C is combined with SiC, Al2O3, and Si3N4, placing B4C in the front layer increased energy absorption efficiency per unit area by 28.27%, 7.78%, and 18.96% respectively, compared to when it was placed at the back. Furthermore, the combinations of Al2O3 with Si3N4 and SiC respectively resulted in an enhanced energy absorption capability per unit area by 5.96% and 1.72%. A dual-layer ceramic structure with high hardness and high fracture toughness can significantly improve the anti-penetration efficiency of the composite armor.