Various Modes Of Failure Research Articles

Modelling and experimentation of failure modes to obtain safe operating range for improved dielectric elastomer actuation performance

Abstract Dielectric elastomers (DEs) possess high energy density, lightweight, and low response time making them suitable material candidatures for electromechanical transducers (ET). Performance enhancement of ET necessitates escalated electrical load making prone to failure and subsequently hindering reliability and life cycle. Existing models towards failure mitigation focus on mechanical and electrical loads individually with constant relative permittivity, whereas DEs undergoes combined loading and stretch-electrostriction in real-time application. This study aims to identify safe design and operating parameters by addressing various modes of failures under combined loads and stretch-electrostriction. Under combined load, pre-strain emerges as a crucial parameter to reduce EMI, while extensive pre-strain leads to diminish thickness which in turn promotes electrical breakdown of elastomer. The optimized design for DEs exhibit substantial failure suppression at a pre-strain value of 1.7 ( λ pre ) under maximum electrical load of 37.66 MV / m ( E max ). The efficacy of optimized parameters for the failure suppression is verified through an in-house fabricated planar actuator. Operation within the identified range of parameters is observed to enhance the reliability and lifespan of DE-actuators, marking a noteworthy advancement in the field of soft robotics.

Analysis of behavior and uniaxial compression failure modes in ungrouted hollow concrete block masonry and their implication in design expressions

In this study, new analytical expressions for the design and revision of ungrouted masonry of hollow concrete blocks under gravitational effects were developed. These expressions can predict the compressive strength and modulus of elasticity for full and face-shell mortar beddings. A trend chart was generated, considering various modes of failure for different strength relationships between blocks and mortar. The study revealed that the main international masonry design codes underestimate the compression resistance of masonry when using weak mortar in combination with full mortar bedding. Results obtained using the Finite Element Method indicated that the optimal compression strength ranges were: 62–70 % for weaker mortar than the block with full mortar bedding; 152 % for block weaker than the mortar with full mortar bedding; and close to 67 % with face-shell bedding mortar.

Estimation of road cut slope stability along the national and state highway of Garhwal Himalaya (India) applying slope mass rating and kinematic analysis

Slope stability assessment of different road cut slopes has been conducted along the National Highway in Garhwal Himalaya, Uttarakhand (NH-34, NH-134, NH-7, NH-107 and a state highway from Dharasu to Tilwara). Slope instability issues in the Himalayan terrain are radically increasing due to high anthropogenic activities and rapid growth of urban centers since past years. Road networks in mountainous areas are the main source of transportation and socio-economic development. In this concerned study, forty (40) road cut slopes have been selected. These sites are selected based on lithology and structure. Diverse slope stability quantification methods along with various modes of failures have been systematically analyzed. The entire region falls under the tectonically active belt or the vicinity of the active fault zones that make the slopes inherently unstable. The Geological Strength Index (GSI) and Rock Mass Rating (RMR) have been applied for determination of slope conditions. Slope mass stability has been evaluated using Slope Mass Rating (SMR) index. The RMR rating ranges from 26 to 87 and the SMR values of forty (40) roads cut slopes range from 10 to 91. The kinematic analysis shows that most of the probable slopes failures are susceptible under planar and wedge failure. This study will definitely help to reduce the loss of life and property and also helps the ongoing constructional processes along the road section.

Influence of process parameters on bead geometry and its effect on mechanical properties of CMT welding of automotive grade steel and aluminium alloy using aluminium based filler wire

This investigation aims to examine the effectiveness of torch position, welding-brazing parameters on the embedded bead profile and load carrying potential of the brazed joint of zinc coated DP600 steel and Al 5052 joined by cold metal transfer (CMT) technique. The base metals were joined at different torch position (−0.6, 0 and 0.6 mm) in lap joint position using Al-based filler wire. At different wire feed rate (WFR) 3, 4 and 5 m/min changes in bead shape and its geometry were observed. The various modes of failure were classified based on effective bonding length (LH–LV) and LH/θ ratio. The best combination of welding-brazing parameters at which the maximum load bearing capacity of 4.1 kN and enhanced bead properties was achieved at 0.6 mm torch position and WFR 5 m/min. The intermetallic compound layers formed during the process affect the tensile properties of weld-brazed joint. The possible intermetallics and the presence of major elements in intermetallic layer were analyzed by energy-dispersive X-ray spectroscopic analysis. Furthermore, in this investigation, it was also observed that the thickness of IMC layer increases with the increasing WFR and heat input up to a critical value of 10 µm.

Influences of true 3D twin flaws on principal stress status and crack occurrence of brittle rock-like samples under uniaxial compression: Insights from experimental and DEM studies

Fracture structures commonly have negative impacts on the strength and safety of rock mass, and various combinations of 2D and 3D flaws make the destruction procedure becomes more complicated. Therefore, laboratory tests based on three types of flawed rocks (symmetric twin flaws with different 2D-3D occurrences) are finished to detect the mechanical, optical and acoustic characteristics of fractured rocks during the uniaxial compression test; PFC3D simulations are conducted for analyzing the deformation features, principal stress distributions, and detailed failure mechanism of the fractured rocks. The main results are as follows: 1) Different combinations of 2D & 3D preset flaws directly influence the results of deformation, stress distribution, and failure developments. 2) Rotation of the intermediate stress axes only appear near the flaw inclination boundary (when the monitoring position moves outwards), while the directions of intermediate principal stress axes remain stable near the flaw strike boundary. 3) Separating cracks by various occurrences helps to construct local failures along different directions, and make some local failures visible and clear; the traditional cracks (short line or thin oval shape) are induced by the uneven deformation in x-o-z planes, and the separated cracks (wide oval or standard disc shape) result from the uneven deformation in y-o-z planes. 4) Surrounding rocks at different positions suffer various modes of failures, the non-ignorable thickness of preset flaw leads to simultaneous Mode I and Mode II failure at the flaw tip, and the mixed Mode II&III failure only occurs in the rocks adjacent to the flaw strike boundary.

Effects of two metal nanoparticles on performance properties of asphalt binder and stone matrix asphalt mixtures containing waste high density polyethelene

Asphalt mixtures has a long history of usage as pavement due to its economic efficiency. Asphalt mixtures have various modes of failure as they go through various temperature profiles and loading stresses over time since they are viscoelastic materials. Three different forms of distress, including rutting, fatigue cracking, and low-temperature cracking, are frequently seen in pavements composed of HMA. Such troubles limit its service life and lead to unsatisfactory service conditions. One of the most popular additive to modify bitumens is polymers. Numerous disadvantages prevent the widespread use of polymers in asphalt concrete (AC) mixture modification for the building of roads. Research on using complimentary materials, including nanomaterials, to counteract the detrimental effects of polymers while improving the performance of the AC combination has recently drawn a lot of interest. Recent years have seen pavement specialists reach the conclusion that modifying asphalt using composite material is the best way to address the issues with binder additives and meet requirement for asphalt mixture. So, in the current research, original asphalt binder was modified using nano-CuO, nano-Al2O3, carbon nano tube (CNT) as a conductive material, and HDPE. To improve their qualities, modifications were made to the additions Nano-CuO (2%, 4% by weight of asphalt binder), Nano-Al2O3 (2%, 4% by weight of bitumen), CNT (1%), and HDPE (3%, 5%). In addition to rheological bitumen testing and storage stability tests, other physical binder tests were conducted, including ones for penetration grade, softening point, and ductility. Additionally, tests for dynamic creep, four-point beam fatigue (FPBF), indirect tensile strength (ITS), Hamburg wheel tracking (HWT) and resilient modulus (Mr) were conducted to examine the impact of compound-modified binders on the performance of stone matrix asphalt (SMA) mixtures. According to the results, adding nano-CuO and nano-Al2O3 lowered the penetration grade and raised the softening point. The combination of combind modifiers has the highest performance against rutting and fatigue distress, according to the findings of MSCR and LAS tests. The addition of Nano-CuO and Nano-Al2O3, CNT, and HDPE increased the ITS, MR, rutting resistance, and fatigue characteristics of asphalt mixes, according to the findings of mixtures tests. The mixture, which included all three additions, exhibited the most favorable qualities overall.

Failure characterisation of sandwich beams using integrated acoustic emission and digital image correlation techniques

The paper presents the experimental study of the failure behaviour of sandwich beams subjected to bending. The samples examined are sandwich beams made of polyethylene terephthalate foam core and glass fibre-reinforced polymer laminate face sheets. In a series of experiments, it has been proposed to integrate diagnostic techniques with acoustic emission and digital image correlation to accurately track the cracking process on the surface as well as in the entire volume of the beam. The research programme carried out allowed observing various modes of failure in composite specimens. The results obtained showed that the integration of acoustic and optical diagnostic techniques provided complementary results and can be used successfully for failure monitoring in sandwich beams.

The Role of Dissipated Energy and Stiffness in Enhancing the Fatigue Life of Asphalt Concrete under Environmental Influence

Variation of environmental conditions exhibits various modes of failure of asphalt concrete pavement. Under cold environment, the flexible pavement experience cracking and disintegration, while under hot environment, the pavement practices rutting. Both environmental conditions can enhance the fatigue life of the flexible pavement. In the present work, the role of the change in the dissipated energy, and flexural stiffness of asphalt concrete on its fatigue life under environmental influence have been investigated. Asphalt concrete mixtures were prepared with its optimum asphalt binder requirements, and then compacted into a slab mold by laboratory roller to a target density. Beam specimens were obtained from the prepared slab samples and tested for fatigue life using three levels of constant strain of (750, 400, and 250) microstrain under dynamic flexural stresses. The specimens were tested at (5, 20, and 30) ℃ environment levels. It was noticed that specimens practicing cold environment exhibit shorter fatigue life as compared with those tested at hot environment. However, the flexural stiffness of the beam specimens decline as the testing temperature rises. Such behavior was further supported with the variation in the dissipated energy among testing environment. It was concluded that higher testing environment declines the flexural stiffness, increases the fatigue life, and changes the mode of failure of asphalt concrete from brittle to plastic mode.

Post-fire strength of austenitic stainless-steel T-stubs with four bolts per row

For connections made with carbon-steel, the behaviour of the T-stub component is well understood and documented in the Eurocodes and is applied to T-stubs with two or four bolts per row. Researchers have investigated the application of the same Eurocodes guidance to T-stubs made with stainless-steel and having two and four bolts per row. However, there is very little information or studies on the post-fire behaviour of stainless-steel T-stubs and none found for those with four bolts per row. This study is aimed at providing a fundamental understanding of the post-fire behaviour of this connection component. Finite element analyses were carried out on 190 specimens with different parameters including temperature, T-stub flange thickness, width and strength, bolt diameter and grade, bolts spacing and edge distance. The results indicated four failure modes that are possible for the post-fire austenitic stainless-steel T-stub with four bolts per row. In all specimens, no circular yield patterns were recorded but only beam patterns occur at the web-flange intersection and at the bolt locations. A design approach for calculating the post-fire plastic resistance is proposed by introducing new and simplified formulas for determining the effective length of the plastic hinges for the various modes of failure. The accuracy of the design approach was validated using finite element modelling and experimental data from the literature.

Outcomes of Total Hip Replacement for Failed Hemiarthroplasty.

Our study aims to analyze the outcomes of conversion total hip replacement (THR) done for failed hemiarthroplasty. We retrospectively analyzed 104 consecutive patients who underwent conversion THR for failed hemiarthroplasty between January 2012 and December 2018. The patient's records were analyzed for demographic information, index surgery details, preoperative functional status, and perioperative complications. Patients were analyzed according to the various modes of failure of hemiarthroplasty. The radiographs were analyzed for any progressive osteolysis, cup migration and stem subsidence. All the patients were evaluated using the modified Harris hip score (HHS) for clinical outcome. Complications, revision or reoperation in the follow-up period was recorded. A total of 73 patients were included in the study for final analysis after exclusion criteria. The average follow-up was 48.2 ± 29.6months. There was a significant improvement in mean HHS from 38.5 ± 9.1 preoperatively to 80.9 ± 4.3 at the last follow-up (p < 0.05). The different modes of failure had no statistically significantdifference in the postoperative Harriship score (p = 0.393). None of the patients had progressive radiolucent lines more than 2mm or significant subsidence in the final follow-up compared to the initial postoperative radiograph. There was one deep infection, one patient had grade 2 heterotopic ossification, intraoperative calcar fracture was fixed with cerclage wiring in 11 patients, and postoperative periprosthetic fracture in two patients was treated with plate osteosynthesis. There were no neurovascular complications or dislocation during the follow-up. Conversion THR for failed hemiarthroplasty is a challenging procedure and results in good functional outcome and provides reliable pain relief. Conversion THA for septic loosening by two stage revision have comparable postoperative outcomes like THA for aseptic loosening. Caution is required owing to high incidence of peri-prosthetic fracture during conversion THA. Dislocation rate is negligible even with smaller head provided the prosthesis is implanted in the proper orientation and adequate soft tissue balancing is achieved.

Time-Variant System Reliability Analysis of Concrete Sewer Pipes under Corrosion Considering Multiple Failure Modes

This paper presents a framework for time-variant system reliability analysis of concrete sewer pipes considering multiple modes of failure. Sewer pipelines are among critical infrastructure systems, designed to collect and transport wastewater away from communities. Such pipes are typically subjected to corrosion and subsequent damage because of continuous contact with corrosive materials. Corrosion is here modeled in terms of the reduction in the pipe wall thickness. In the proposed framework, prevailing uncertainties in the characteristics of wastewater fluid, geometric properties of fluid cross section, and corrosion-related parameters of concrete are quantified as random variables. Next, various modes of failure under bending, shear, excessive cracking, and cover loss are formulated as multiple limit-state functions. This leads to a general system reliability problem defined as a series system of parallel subsystems, i.e., cut sets. Further, by introducing the corrosion model into the limit-state functions, a time-variant system reliability problem is established in which the integration domain is conditioned to the corrosion level at each point in time. By integrating over the conditional probabilities through a rejection sampling method, the failure probability is computed given the corrosion level over the desired time span. The results show that the failure probability increases sharply with time and corrosion level. For instance, the failure probability exceeds 80% for pipes over 50 years and at corrosion levels of over 40%. Moreover, the sensitivity analysis shows that the acid-consumption capacity of the pipe material, the pH-related factor, and the proportion of S2− dissolved highly influence the failure probability. The maximum effects of these parameters occur within 0%–10% corrosion. The results of this study can be used to evaluate the failure probability of sewer pipes given their age and current corrosion level.

Probabilistic stability analysis of anchored cantilever sheet pile walls using fuzzy set theory

Ensuring the safety and stability of waterfront retaining structures is of utmost importance. However, uncertainties may lead to imprecise analysis and inadequate or uneconomical design. Fuzzy set theory is one of the computationally efficient methods of evaluating the effects of uncertainties on systems and has a great potential of making probability-based stability analysis of sheet piles considerably less cumbersome. This paper analyzes the effects of uncertainty on the stability of anchored cantilever sheet pile walls in the sand using the fuzzy set theory and genetic algorithm. The uncertain variables include soil properties as well as structural and geometrical parameters. Different levels of uncertainty are assigned to the governing parameters using the triangular fuzzy membership functions and the α-cut method. To generate the fuzzy responses for wall stability, a search for extreme (minimum and maximum) safety factors is carried using evolutionary algorithm at various cut levels. The proposed method is used in this study to investigate the effects of uncertainty in soil and wall parameters on overturning, sliding, and flexural stabilities, as well as the overall wall stability. In addition, the effects of changes in water level, anchor tensile force and wall section modulus on the probability of different failure modes were determined. Results confirm the previous findings in the literature on significant impact of uncertainty in these parameters on the wall stability. Conducting a sensitivity analysis, it was found that the uncertainty in water level is an effective factor on all failure modes. Reduction of the water level leads to a decrease in the probability of flexural failure, while it increases the probability of overturning and sliding failures. The provided diagrams are also useful for probability-based design against various modes of failure, in engineering practice. The results emphasize the robustness of the presented fuzzy approach to account for the uncertainties of input variables in the sheet pile wall design procedure.

EXPERIMENTAL INVESTIGATION AND COMPARATIVE EVALUATION OF PUSH-OUT BOND STRENGTH FIBER POST CEMENTED WITH DIFFERENT ADHESIVE RESIN CEMENTS: AN IN-VITRO STUDY

This article present an experimental investigation of push-out bond strength of fiber post that are cemented with various adhesive resin cements. Various modes of failure are also studied and discussed herein. Three resins namely Fluorocore 2+, Rely-X U200 and G-Cem are used in this study. The study is carried out on forth five single rooted teeth randomly divided into three groups. The teeth specimens were prepared by chemo-mechanical procedure and cemented with various adhesive resin cement. These teeth are further sliced at coronal, middle and apical levels for experimental testing of bond strength. These samples further tested on universal spring testing machine until the post was dislodged. Using Chi square, Mann Whitney U and Kruskal Wallis test, the obtained results were analyzed with significance level of p = 0.05. Bond strength of Fluorocore 2+ showed highest as compared to others. Rely-X U200 and G-Cem showed insignificant variation in bond strength at coronal, middle and apical levels.

Failure Analysis – An Overview with Case Study

Failure analysis is an important tool to determine the physical root causes of problems. The process is critical, based upon many different technical disciplines and uses a variety of observation, inspection, and laboratory techniques. It relies on collecting failed components for subsequent examination of the cause or causes of failure using a wide array of methods, especially microscopy and spectroscopy [1]. One of the important parameter in performing a failure analysis is properly observing each and every factor related to failed component and provide unbiased conclusion and corrective action. The objective of failure analysis is to identify whether component or product has failed in service or during manufacturing or during production processing. In any case, one must determine the cause of failure to prevent future occurrence, and/or to improve the performance of the device, component or structure.&#x0D; This paper briefly introduces the basics of failure analysis, various modes of failure and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. In addition, this paper also covers a typical case study to explain the process methodology in detail.

An Overview of Slope Failure in Mining Operations

The primary aim of every twenty-first century mining operation is to extract as much ore as possible in a safe and economical manner. Failure in mine excavation occurs when the shear stress acting on the rock is greater than the shear strength of the rock mass. The stability of rock slopes in open-pit mine and quarry operations is extremely important from both economic and safety points of view because unstable slopes can result in the loss of human life and damage to properties. This paper presents an overview of several case studies of slope failure in mining operations and explains various modes of failure in rock slopes, as well as factors that influence the stability of slope walls. With the aim of enforcing the importance of monitoring and evaluating slope stability in mining, both linear equilibrium and numerical modeling techniques were reviewed to elaborate their importance in designing stable slopes. In addition, the process of slope failure was discussed, and key signs of failure were indicated. In an effort to prevent mines from experiencing the hazards of slope failure, this study reports previous work performed in determining slope failure and the current state-of-the-art models, which entail the integration of analytical methods with artificial intelligence techniques. This innovation would help overcome the drawbacks of conventional prediction techniques that are cumbersome and ambiguous.

Experimental and numerical studies on the low‐velocity impact response of carbon fiber‐reinforced polymer anisogrid cylindrical shells

AbstractThis work presents the experimental and finite element (FE) simulations to investigate the behavior of both unstiffened and anisogrid composite cylindrical shells subjected to low‐velocity axial impact. Impact damage has been an epidemic problem for composite structures. Even subjected to a low‐velocity impact, thin‐walled composite structures may sacrifice its load‐carrying capacity considerably due to various modes of failure. A low cost, reliable and innovative manufacturing process is proposed for the production of anisogrid cylindrical lattice structures. Initially, test coupons are fabricated as per American Society for Testing of Materials (ASTM) standards and inspected using infrared (IR) thermography to find the imperfections incurred during fabrication. The test coupons without defects were only taken into account for material characterization. FE simulations were carried out on both the unstiffened and anisogrid shells using LS‐DYNA® for a series of low‐velocity impacts. Also these shell structures were subjected to impact loading experimentally for the validation of the numerical results. The results of these studies indicate that the anisogrid model presented in this work possesses a great load‐carrying capacity than an unstiffened shell under dynamic loading conditions, also the weight of the structure has been reduced up to 51.27%. Numerical simulation results are in good agreement with the experimental data, having less than 11.56% of maximum deviation on the energy absorption value.

Failure Mode and Cost Effect Analysis of a Model Bone Crushing Hammer

Critical investigation of strength properties of materials is required in Engineering practice to ensure an enhanced service life. Globally, industrialists are struggling to increase cost savings from lost production due to the failure of machine, while customers are concerned about the safety and reliability of the products. Hammer mills are prone to various modes of failure like chemical failure, erosive failure, abrasive failure and fatigue failure. The effect of these failure modes is always detrimental to the operation of the machine and its efficiency. Hence, forensic investigation is essential to determine the failure modes and their effects on hammer mills for bone crushing. Field investigation was carried out to monitor the hammer mill in operation for 12 months with a production of 20 bags per hour. The total production per day for 8 hours is expected to be 160 bags at a given speed. Thus, the cost of machine downtime on production is huge. The Pareto method was used to determine the effect of downtime on revenue and production for a period of one year. The hours of failure were between 1 to 2 hours per day. The loss in revenue was calculated using the variation of number of failure with time, as obtained from hammer mill. The outcome showed that hammers investigated failed as a result of abrasive wear, fatigue, impact, and chemical wear, respectively. The cost of downtime was found to be $ 37,745,809,920.00 CAD for the period of study. Based on findings, wide ranging factors are required to evaluate the performance of the hammer mill for improved productivity and efficiency. These are proper material selection, design and appropriate operational parameters. However, there is need for optimisation of the hammer material via heat treatment methods as this will reduce the yearly cost of production, downtime of the milling machine for bone crushing as well as improvement in productivity.

Experimental investigation of the impact resistance on KEVLARXP S308® fabric impacted with truncated ogive projectile subjected to pre-tension

Aramid fabrics made of polymeric chains have wide use in ballistic applications due to their low density, high strength, and their excellent resistive behavior to high strain rate loading like terminal ballistic impact. The response of the aramid yarns depends on yarn architecture, the shape of impacting projectile, and the boundary conditions fabric is subjected to. This work is focused on studying the ballistic response of KEVLARXP S308® manufactured by DuPont. The fabric has a unique +45°/−45° layer sequence with interlaced stitches and would be impacted by a truncated ogive projectile at different levels of fabric pre-tension. A new experimental setup is designed to induce circumferential pre-tension to the fabric and record the fabric's contact force response on impact. The fabric's terminal ballistic parameters like ballistic limit, peak force, time duration, and energy absorption were examined. The ballistic parameters were studied for three different levels of pre-tension, 100 N, 200 N, and 300 N. For each of the pre-tension, the SEM micrograph images were studied for range V30 to V70, and various modes of failure like fibrillation, yarn pull-out, yarn bowing, yarn shearing were analyzed at and near the ballistic limit for both the layers in the fabric. The study findings indicate that the presence of stitches in the fabric restricts the mobility of the yarns in the transverse direction up to a certain extent, and leads to a decrease in the ballistic limit velocity for higher pre-tension value. The analysis of change in peaks of the force-deflection curves in increasing values of impact energy showed the increased strain energy transfer from +45° layer to +45° layer.

Ballistic efficiency of Corchorus fiber and aramid reinforced epoxy composite for armor material application

In the present work, an experimental study on multi-layered armor system (MAS) ofCorchorusfibrealso known as jute (in mat form) along withkevlar, reinforced with and without epoxy matrix had been studied. The efficiency of the composites was tested against the ballistic impact of 9 × 19 mm projectile in accordance with NIJ0101.06. Energy absorption (Eabs), stopping velocity (V0), ballistic limit (V50), and back face signature (BFS) were considered for the performance evaluation. Among all the combinations, 15 K + 20 J without resin were able to stop the bullet of velocity up to 400.2 m/s with observed BFS as 21.78 mm. The combination of 15 K + 20 J with resin was able to stop the bullet of velocity up to 480 m/s with observed BFS as 13.19 mm. The addition of resin reduces the BFS up to 53.66% and increases the V0 & Eabs by 37.66% and 61.14%. The addition of the jute layer had significantly contributed to energy absorption, resulting in the reduction of BFS up to 31.26%. Macro photography and scanning electron microscope analysis had been studied to understand the energy dissipation and various modes of failure. The analytical and ballistic test results have exhibited the potential application of jute for armour material applications.

Failure Modes in Microfabricated Ion Trap Devices for Quantum Information Science

Abstract Trapped ion systems are one of the leading technology platforms for quantum computing. This article describes the construction and operation of ion trap devices and the various modes of failure that have been observed. Examples of failure in either the rendering or use of packaged trap chips are presented, including electrode shorts and opens, detached bond wires, and RF breakdown damage.