Failure Analysis Research Articles

An updated perspective on teleonomy.

The analysis of proxy failure given by John et al. provides a good starting point for interdisciplinary discussions. Here, the discussion of teleonomy is extended and updated to include more recent discourse on the topic.

Failure analysis of the suspender fracture in a railway self-anchored suspension bridge: Damage identification, fatigue mechanism and remaining life prediction

A suspender fracture accident was reported in a railway self-anchored suspension bridge, arousing intensive concern to fatigue issue in the suspender end connector area which is exposed to complex stress states and cyclic traffic loads. Some critical issues involving the fatigue mechanism, the damage identification, and the remaining life prediction were investigated on the basis of on-site and lab tests, numerical simulations, and theoretical analyses. It was found that the root of an ear-plate screw with threads becomes the fatigue-prone detail since action of stress concentration and the unexpected cyclic bending. Also, an effective crack identification scheme by the ultrasonic phased array inspection as well as a verified prediction method for remaining life were proposed. Short suspenders in the main span are significantly affected by the cyclic bending, resulting in the extremely lower fatigue life than that of a long or side-span suspender. Suggestions for a classified disposal plan are provided based on fatigue risk for individual suspender.

Load Bearing Capacity and Failure Analysis of Fibrous Plaster Wads

ABSTRACT Fibrous plaster is a culturally significant material used in high-status buildings from the late nineteenth century. Fibrous plaster ceilings are typically suspended using load-bearing fibrous plaster wads, which are attached to roof structure components. Understanding the behaviour of wads is highly significant, with important safety implications emphasised by the partial collapse of the Apollo Theatre ceiling in 2013. This study demonstrates an original, innovative test method for fibrous plaster wads that enables quantification of load capacities, with manufactured specimens representative of historic in situ wads. The methodology is rigorously evaluated for traditional and alternative wad designs, reinforced with hessian scrim or continuous fibre glass (CFG) mat, with and without steel wires in looped (untwisted) or looped-twisted configurations. Tensile tests generated load-displacement characteristics and determined failure modes including cracking of plaster, deformation and tearing of fibrous reinforcement, and if present, plastic failure of a wire. Results demonstrate that hessian performs better than CFG in axial tension and inclusion of a wire increases tensile load capacity and ductility. An industry standard repair wad with hessian and looped-twisted wire can typically support 3 kN. Looped wire performed better in isolation than looped-twisted wire, with higher peak loads and greater ductility, while looped-twisted wire carried a greater load as part of a fibrous plaster composite wad. The test methodology and findings have revealed new insights into the mechanical behaviour of wads which will inform commercial practice and conservation of historic buildings, preserving important heritage and promoting safe longevity.

Solder joint reliability performance study and shear characterization of low-Ag SAC lead-free solders for handheld application

As handheld electronic products move toward smaller and thinner form factor, the demand of high reliability under stringent field usage also increasing. Drop test, based on the JEDEC JESD22-B111A, accompanied with temperature cycling (TC) test, based on JEDEC JESD22-A104F, are two of the most critical board-level reliability tests for handheld makers. In terms of solder joint reliability (SJR), total 7 candidates of LF35-liked lead-free solder alloys are investigated for its drop performance, and TC reliability evaluation. Among 7 solders, leg 4 and 5 exhibit both decent drop and TC behavior, which are likely owing to the silver (Ag) precipitation hardening and bismuth (Bi) solid solution hardening effect respectively. In addition, the shearing mechanical characterization of 7 solder alloys are being studied. Shear strength of leg 4 and 5 shows higher strength value than others. In terms of failure analysis under drop test, three main fracture modes are observed, including via cracking at PCB side, solder/intermetallic compound (IMC) cracking at package side, and Cu trace broken at package side. Furthermore, in terms of failure modes of TC test, solder/IMC cracking at package side are the main fracture modes. In summary, this study provides an overall reliability performance mapping for 7 solders, and list out a table comprising of shear strength, void% analysis, TC reliability, and drop reliability performance for each LF35 solders which lays out potential future solder alloy to meet higher handheld phone drop reliability margin.

Study and Application of Rock Drilling Resistance Characteristics in the Jiyang Depression Formation

In response to the unclear drilling resistance characteristics of rocks in the Ji’yang Depression, low drilling efficiency of PDC drill bits, and difficulties in drill bit selection, this study selected rock samples from different depths in the area for indoor drilling resistance analysis testing. Based on logging data, a prediction model was established for drilling resistance characteristics parameters of the strata in the area, and a graph of drilling resistance characteristic parameters of the rocks in the area was drawn. The study showed that the uniaxial compressive strength of the strata rocks was 50–110 MPa, with a hardness of 500–1300 MPa, a plasticity coefficient ranging from 1 to 2, a rock drillability grade of 8–20, and an abrasiveness index of 5–20. Combining the analysis of on-site drilling bit failures, PDC drill bits adapted to the strata in the area were selected, and the mechanical drilling speed of the selected bits reached 12.58 m/h, successfully drilling through the target layer. The above research results are of guiding significance for understanding the reasons for the difficulty of drilling into the Jiyang Depression strata and for improving mechanical drilling speed and drill bit selection in this area.

Faulty machining and micro-segregation assisted fatigue failure of cylinder head stud of a diesel generator

A detailed failure analysis of cylinder head stud bolt of a four-stroke diesel generator has been presented. The study included optical emission analysis, tensile testing, hardness testing, optical microscopy, SEM, and EDX analyses. The investigation showed that the main mechanism of failure was corrosion-fatigue. Fatigue initiation was assisted by pitting corrosion induced by faulty machining, moisture, and presence of tempered martensite and non-metallic inclusions at the surface. Propagation of the fatigue crack was encouraged by localized corrosion within the tempered martensite, non-metallic inclusions, and Mn/Cr/Mo/Si micro-segregation. Both excessive C and Mn/Cr/Mo/Si micro-segregation caused the formation of mixed microstructure of tempered martensite and fresh martensite with retained austenite. The non-uniform microstructure led to non-uniform hardness distribution and caused localized deformation during cyclic loading and promoted fatigue crack propagation.

Buckling Failure Analysis of Slender Composite Structure with Telescopic Boom and Truss

Buckling Failure Analysis of Slender Composite Structure with Telescopic Boom and Truss

Structural analysis of small-scale 3D printed composite tidal turbine blades

The existing research literature lacks comprehensive investigations into assessing the structural performance of marine renewable energy conversion devices, particularly 3D printed turbine blades, which often rely solely on computational modelling without experimental validation methods and/or established mechanical characterization techniques. This leads to significant uncertainty regarding the performance of 3D printed turbine blades manufactured by additive manufacturing technology. This study aims to fill this gap by proposing a procedure for evaluating the structural integrity of commercial small-scale tidal turbine blade (5 KW) manufactured using fused filament fabrication 3D printing with a linear infill pattern. This is achieved by developing a combined experimental, hydrodynamic, and finite element approach with the view to inspect the micro-mechanical properties of representative volume elements of 3D printed microstructures using homogenization technique. The results of mechanical testing and hydrodynamic modelling are used to create a finite element model of the 3D printed blade, allowing for stress and failure analysis. Findings indicate that while integrating 3D printed materials into blade design via 3D printing technology is feasible, the choice of materials is limited to high stiffness composite filaments. Finally, experimental validation of numerical results, particularly full field strain distribution maps obtained by digital image correlation technique for flexural testing and laboratory-scale 3D printed blade, confirms the accuracy of the finite element results. Finite element-based homogenization techniques provide valuable insights into potential failure modes in 3D printed tidal turbine blades. However, the expedited calculation of orthotropic properties through finite element analysis proves to be a faster mechanical characterization method compared to experimental approaches. The proposed methodology in this study facilitates quicker iterative design of 3D printed blades, thereby reducing the need for repeated experiments and ultimately lowering manufacturing costs.

Fatigue failure analysis of U75V rail material under Ⅰ+Ⅱ mixed-mode loading: Characterization using peridynamics and experimental verification

Fatigue failure behavior of U75V rail material under Ⅰ+Ⅱ mixed-mode loading is analyzed and characterized in this work. A fatigue crack propagation experiment was carried out on U75V rail material under mixed-mode loading for R = 0.1. Then, based on the Ordinary State-Based Peridynamic (OSB PD) theory, bond strain rate and bond energy release rate methods were used to characterize the fatigue failure behavior of the rail material. Finally, the simulation results were compared with experimental results in terms of crack propagation length, path and angle to evaluate the characterization effects of both methods. The conclusions were as follows: under single mode I loading, both methods could accurately characterize the fatigue failure behavior of the rail material. However, compared with the bond strain rate method, the bond energy release rate method could provide a more accurate characterization under I + II mixed-mode loading.

Fracture analysis of hyperelastic membrane using bond-associated non-ordinary state-based peridynamics

In this paper, a non-ordinary state-based peridynamics model (NOSB PD) has been proposed to simulate the large deformation and failure analysis of hyperelastic membranes. To account for the curving horizon of the membrane, a non-local membrane theory has been developed by approximating it as a flat surface and applying the plane stress assumption locally. Thus, the membrane structure is simulated using a single layer of material points, which simplifies implementation, improves efficiency, and avoids volume locking. The Gent model has been employed to simulate the hyperelastic material constitutively, as it has an elegant mathematical framework and can achieve the entire range of stretches. Furthermore, Bond-associate NOSB PD is utilized to overcome zero-energy modes without affecting the material properties. A modification has been addressed to overcome the boundary effect by adding a complementary force density to the boundary nodes. The accuracy of large deformation and incompressibility of the developed models are verified by the corresponding finite element analyses. Finally, the proposed method is demonstrated by presenting some benchmark examples, and the results illustrate the accuracy and efficiency of the proposed method for the large deformation, fracture, and off-plane tearing analyses of hyperelastic membranes.

Research and verification on parameter solution of mixed shock model for common cause failure based on particle swarm algorithm

AbstractMixed shock model is an explicit construction method of failure probability model based on component independent failure, system nonfatal shock, and fatal shock failure, which considers common cause failure (CCF) in redundant system. For aerospace systems, a modified mixed shock model is proposed, which considers several components may fail independently and simultaneously in operation. In order to solve the issue that the parameters of the mixed shock model cannot be solved directly based on the failure probability data, a parameter solving method based on particle swarm optimization (PSO) algorithm is proposed. Additionally, the relationship between the failure probability and the gradient of the parameter change is deduced, and the reduced‐order (RO) solution based on the gradient of the parameter change is proposed to improve the efficiency of the solution. A fitness function construction method based on the relative error of the solution probability and the true probability is proposed to improve the probability solution accuracy of multicomponent failure. The nonlinear inertia factor optimization method combined with fitness change is studied to improve the particle swarm dynamics. The accuracy of the results of different parameters solving sequence and different PSO methods are compared, and the effectiveness of the RO solution is verified. The results of the mixed shock model before and after modification are compared with the different CCF data, which verifies the effectiveness and wide applicability of the modified mixed shock model. The results show that the modified mixed shock model for CCF and its parameter solution method can significantly improve the probability solution accuracy of all components failure, and also provide a new theoretical basis and solution method for the quantitative analysis of multiredundant system failure.

Laser Treated Novel Textures for Adhesion Performance of Aluminum Alloy Joints Exposed to Corrosion

The aim of this study was to investigate novel laser-treated structures designed to improve the adhesion performance and corrosion resistance of AA7075-T6 bonded joints. The spacing, position, and surface area parameters of the laser-treated grooves were investigated to understand their role in adhesion performance even under corrosion conditions. Laser-treated surfaces were analyzed using microscopic, topographic, and chemical methods to determine their scientific contribution to adhesion and corrosion performance. Laser-treated adherends were also bonded to mechanically test their bond strength both before and after exposure to corrosion for varying periods of time. Roughness and therefore surface area have a significant effect on adhesion performance; however, it is worth noting that the best adhesion performance both before and after corrosion exposure was achieved when the required surface area was properly designed and, laser treated according to the salt water exposure directions to inhibit its diffusion into the adhesion interface. The performance of the novel laser-treated structures in terms of adhesion performance under corrosive atmosphere was also supported by failure analysis. The mixed failure mode was significantly shifted to the cohesive failure mode, especially for bonded joints with box-type laser-treated structures.

Investigation on dynamic deformation behavior of 7A75 aluminum alloy over wide strain rates and constitutive model establishment

The aluminum alloy components on automobile often experience high strain rate deformation during accidents. The dynamic deformation behavior and constitutive model are crucial for analysis of vehicle body collisions and failures. In this work, the 7A75 aluminum alloy plate was heat treated according to standard body manufacturing procedures. Quasi-static and dynamic tensile experiments were conducted on the aged 7A75 alloy in a wide strain rate range from 0.001 s−1 to 500 s−1. The dynamic deformation behavior of the alloy was revealed, and the constitutive models were established. It was found that the 7A75 alloy has strong strain rate sensitivity, and its mechanical properties can be significantly improved with the increase of strain rate. As the strain rate increases, the necking instability strain shifts towards higher values, which leads to a larger uniform deformation ability and fracture elongation. This behavior results in a better energy absorption capacity at high strain rates, thus providing a good collision protection property. The constitutive models, including Johnson-Cook (J-C) and Zerilli-Armstrong (Z-A) types, were established and compared. Note that the conventional J-C and Z-A models exhibit severe prediction distortion. Therefore, a modified J-C model incorporating strain rate compensation was introduced, which decrease the errors by 149% and achieves accurate predictions of both dynamic and static deformation behaviors over a wide range of strain rates.

Modelling and Impact Analysis of Combined Dam Failure of Small Tandem Reservoir Groups in Hilly Areas

Numerous small reservoirs in hilly areas play a significant role in flood control and profit-making in the basin, but there is also a risk of dam failure when encountering special circumstances such as excessive flooding, which may cause large losses downstream. In this paper, we take the small reservoirs in Shandong Province as the research object, analyze the hydraulic topology of three types of tandem reservoirs, generalize the shape of the breach by using the transient lateral local one-break to the end, calculate the dam-break flooding process by using the quadratic parabolic method, and simulate the dam-break by using the MIKE21 model based on the principle of the two-dimensional incompressible Reynolds mean stress equation for the incompressible fluid, and analyze the peak flow under various combinations of dam-break flow by setting various combinations of the number of dam-breaks and the timing of dam-break simulation. By setting various combinations of dam failure numbers and timing, we analyzed the changing rules of peak dam failure flow, inundation area and other elements under various combinations, and sought the most unfavorable combinations and parameters such as the timing of dam failure, and the results of the analyses can provide technical support for the assessment of the risk of dam failure in the tandem reservoirs in the hilly area and the risk correspondence.

A comparative analysis of compressive and wear failure of laser-powder bed fused Stainless Steel 316L produced with different hatch spacing in stripe and contour patterns

The selection of hatch spacing is crucial in additive manufacturing processes to produce a defect free Stainless Steel 316L (SS) components, especially in laser powder bed fusion (LPBF) process. Improper selection of hatch spacing could lead to various failure regimes (like vertical cracking, porosity, and un-melted particles) in Stainless Steel 316L (SS) component produced through laser powder bed fusion (LPBF). Further, the failure regimes have a direct impact on the hardness, compression strength, friction, and wear properties of LPBF SS components. The present study has taken substantial efforts to analyse the impact of various hatch spacing (0.08 mm, 0.10 mm. and 0.12 mm) in stripe and contour patterns, in terms of morphology, mechanical, and tribological properties of LPBF SS components. Also, the present study elucidates how variations in hatch spacing influences the features like particle fusion, crack formation, density, hardness, surface roughness, compression, and wear properties. The stripe pattern with low hatch spacing of 0.08 mm showed better particle fusion and high surface roughness; whereas the high hatch spacing has produced voids, un-melted powder particles, and cracks in the stripe and contour pattern. High densities and hardness values were attributed to the stripe patterns with more effective melting and fusing of powder particles. XRD analysis revealed the stable phase compositions across various hatch spacing with a predominant FCC crystal structure. Residual stress distribution was significantly influenced by the hatch spacing for both stripe and contour patterns. Importantly, the low hatch space leads has promoted the tensile residual stress formation and vice versa for the higher hatch spacing. Stripe patterns showed higher compression strengths with buckling and shear mode as a compression failure. The stripe pattern demonstrated a low specific wear rate (SWR) and coefficient of friction (COF) compared to the contour pattern, with respect to the various hatch spacing. Furthermore, the simulated body fluid (SBF) lubrication regime played a significant role in reducing the COF. Patches, groves, furrows, and craters demonstrated the abrasive and adhesive failure for both stripe and contour pattern, which is further detailed in the article.

Large deformation of cable networks with fiber sliding as a second-order cone programming

A new model for irreversible large deformations of fiber networks is developed. The fibers are considered as inextensible cables that slide relative to each other in the frictional junctions. This sliding is constituted by a rate-independent flow rule. The nonsmooth dissipation potential for each sliding system is defined as a product of the yield strength and the absolute value of the fiber sliding. The response of the cable segments is nonsmooth as well, since it shows asymmetry with respect to tension and compression. A principle of minimum incremental potential and a pure complementary energy principle are derived for the equilibrium incremental loading of the network at large deformations. They form a pair of primal and dual second-order cone programming problems with matching sets of displacement-based and force-based variables. These problems can be effectively solved by interior point methods that have many advantages compared to the gradient-based methods or dynamic relaxation. The model is extended by a simple mechanism of fiber pull-out resulting from fiber sliding at the free unconstrained ends. This can be used for the microstructural analysis of failure of needle-punched nonwoven materials.

Wear Failure Analysis of Ball Bearings with Artificial Pits for Gas Turbines

Wear Failure Analysis of Ball Bearings with Artificial Pits for Gas Turbines

In-situ computed tomography and transient dynamic analysis – failure analysis of a single-lap tensile-shear test with clinch points

Clinching is a mechanical joining technology, in which a mainly form-fit joint is created by means of local cold forming. To characterize the load-bearing behavior of such joints, they are typically analyzed destructively, for example by tensile-shear tests in combination with metallographic sections. However, both the initiation and progress of failure can only be described to a limited extent by this method. Furthermore, these tests allow only limited conclusions about clinch points under in-service loading. More purposefully, clinch points can be analyzed nondestructively by combining in-situ computed tomography (CT) and transient dynamic analysis (TDA). The TDA continuously measures the dynamic behavior of the specimen and indicates failure events like crack initiation, which then can be evaluated thoroughly by stopping the test and performing a CT scan. To qualify the TDA for this task, it is necessary to link the observed damage behavior with specific dynamic characteristics. In this work, the complementation of in-situ CT and TDA is investigated by testing a clinched single-lap tensile-shear specimen made of aluminum. The testing procedure is stepwise: at certain displacement levels, the specimen is investigated by in-situ CT and TDA. While the in-situ CT provides the location, extent, and development of the failure phenomena, the TDA uses this information to evaluate the dynamic signal and detect relevant frequency ranges, which indicate damage events. The results demonstrate, that failure initiation and progression can be analyzed efficiently by combining both measuring systems. The TDA reliably detects relevant signal changes in the monitored frequency band. By means of in-situ computed tomography, the corresponding failure phenomena can be described in detail, enhancing the understanding of the load-bearing and deformation behavior of clinch points. The concatenation of characteristic signal changes and observed failure phenomena can henceforth be transferred to analyze complex structures during operation nondestructively by TDA.

Remineralizing pretreatment using Casein phosphopeptide-amorphous calcium phosphate fluoride, self-assembling peptide, and Nanohydroxyapatite gel activation via invisible infrared light on the dentin microhardness and micro shear bond strength to the composite restoration

Different remineralizing pretreatments Casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF), tricalcium phosphate fluoride (TCP-F), self-assembling peptide (SAP) P11-4 and 10% Nanohydroxyapatite (nHA) gel activation via invisible infrared light on the dentin microhardness (MH) and micro shear bond strength (µSBS) of composite restoration. Seventy-five human molar teeth were collected and the dentinal surface of all the samples was exposed to different demineralizing solutions. (n=15) Group 1 (demineralized dentin), Group 2 (CPP ACP), Group 3 (TCP-F), Group 4 (SAP P11-4), Group 5 (nHA gel activation via invisible infrared light). MH assessment was performed using Vickers hardness. Each group of 10 samples was subjected to composite restoration buildup and µSBS were tested. The debonded samples were then observed under a stereo-microscope for failure analysis. ANOVA was conducted, along with Tukey's post hoc analysis, to examine the µSBS of composite and MH of the remineralized surface. nHA gel activation via invisible infrared light pretreated specimens showed the maximum outcomes of surface hardness (331.2 ± 77.3) and bond strength (10.38 ± 2.77). However, Group 4 (SAP P11-4) (148.3 ± 29.2) remineralized dentin displayed minimum scores of MH and µSBS (5.88 ± 1.01). Remineralizing pretreatment nHA gel activation via invisible infrared light and casein phosphopeptide-amorphous calcium phosphate fluoride seem to improve the dentin MH and µSBS of the composite restoration.

Fatigue cracking behavior and life assessment of TC11 titanium alloy in very high cycle regime at two working temperatures

Axial loading fatigue tests were conducted with two stress ratios to investigate fracture surface behavior and associated failure analysis governing crack nucleation of TC11 titanium alloy at two working temperatures, spanning high-cycle and very high-cycle fatigue regimes. Furthermore, scanning electron microscopy, optical microscopy, and electron-backscattered diffraction techniques were employed to analyze the cracking mechanism. The interior failure is attributed to the cleavage of the large equiaxed αp-grains and facet-facet cluster area-fisheye formation. Moreover, the crack growth threshold values and the transition sizes from small to long cracks decrease with temperature rise. In addition, small cracks follow the path that requires minimum energy for propagation as per the microstructural orientation and are governed by maximum shear stress, resulting in the formation of crystallographic facets. Based on the analysis above, the interior fracture mechanism was summarized as related to the microstructure characteristics. Considering the fatigue cracking behavior and microstructural features, a model for predicting crack nucleation life is developed, exhibiting a better consistency between predicted and experimental fatigue lives.