Selective laser melting is a promising metallic additive manufacturing process with many potential applications in a variety of industries. Through a gracious donation made by Lawrence Livermore National Laboratory, California Polytechnic State University received and installed an SLM 125 HL selective laser melting machine in February 2017. As part of the initial setup effort, a preliminary machine verification study was conducted to evaluate the general print quality of the machine with default parameter settings. Coincidentally, the as-printed microstructure of SLM components was evaluated through nil strength fracture surface examination, an alternative to conventional polish-and-etch metallography. A diverse set of components were printed on the SLM 125 HL to determine the procedural best practices and inherent constraints. Additionally, the mode and mechanism of failure for a defective Lawrence Livermore National Laboratory component fabricated at their facility was investigated. From these studies, extensive documentation in the form of standard operating procedures, guidelines, templates, and summary reports was generated with the intent of facilitating future selective laser melting research at Cal Poly and strengthening the learning of students interfacing with the novel technology.

The work described here has been carried out to obtain a better understanding of the tooth root cracking failure mode of timing belts. Previous work has demonstrated the close dependence of this on the tooth deflections of fully meshed teeth, generated by torque transmission, but has not considered the additional distortions generated in the partially meshed conditions at entry to and exit from a pulley groove. Approximate compatibility and constitutive equations are combined with a rigorous consideration of tooth equilibrium in partial meshing to show how bending moments are generated at both exit from a driven pulley and entry to a driving pulley. Experimentally determined belt lives correlate very well with a combined measure of fully meshed tooth strain and strain due to bending at entry or exit. The analysis also shows that this strain measure reduces with increasing belt tooth stiffness, confirming the importance of a high tooth stiffness for a long belt life. Tooth force variations through the partial meshing cycle have also been predicted and compared with measurements obtained from a special strain gauge instrumented pulley. A greater pulley rotation than is predicted is required for a belt tooth to seat in a pulley groove. There is room for improvement in the modelling

No / Internet of Things (IoT)-based smart agriculture systems are increasingly being used to improve agricultural yield. IoT devices used for agricultural monitoring are often deployed in outdoor environments in remote areas. Due to the exposure to harsh environments and the nature of deployment, sensors and other devices are susceptible to an increased rate of failure, which can take a system to unsafe and dangerous states. Failure of a smart agriculture system can cause significant harm to nature and people and reduce agricultural production. To address the concerns associated with the failure of the system, it is necessary to understand how the failures of the components of a system can contribute to causing the overall system failure. This paper adopts Fault Tree Analysis, a widely used framework for failure behaviour analysis in other safety-critical domains, to demonstrate the qualitative failure analysis of smart irrigation systems based on the components’ failure.

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Yes / The rapid proliferation of internet-connected devices in public and private spaces offers humanity numerous conveniences, including many safety benefits. However, unlocking the full potential of the Internet of Things (IoT) would require the assurance that IoT devices and applications do not pose any safety hazards to the stakeholders. While numerous efforts have been made to address security-related challenges in the IoT environment, safety issues have yet to receive similar attention. The safety attribute of IoT systems has been one of the system’s vital non-functional properties and a remarkable attribute of its dependability. IoT systems are susceptible to safety breaches due to a variety of factors, such as hardware failures, misconfigurations, conflicting interactions of devices, human error, and deliberate attacks. Maintaining safety requirements is challenging due to the complexity, autonomy, and heterogeneity of the IoT environment. This article explores safety challenges across the IoT architecture and some application domains and highlights the importance of safety attributes, requirements, and mechanisms in IoT design. By analysing these issues, we can protect people from hazards that could negatively impact their health, safety, and the environment. / The full text will be available at the end of the publisher's embargo: 11th Feb 2025

Manually diagnosing recurrent faults in software systems can be an inefficient use of time for engineers. Manual diagnosis of faults is commonly performed by inspecting system logs during the failure time. The DevOps engineers in Pipedrive, a SaaS business offering a sales CRM platform, have developed a simple regular-expression-based service for automatically classifying failed deployments. However, such a solution is not scalable, and a more sophisticated solution isrequired. In this thesis, log mining was used to automatically diagnose Pipedrive's failed deployments based on the deployment logs. Multiple log parsing and machine learning algorithms were compared based on the resulting log mining pipeline's F1 score. A proof of concept log mining pipeline was created that consisted of log parsing with the Drain algorithm, transforming the log files into event count vectors and finally training a random forest machine learning model to classify the deployment logs. The pipeline gave an F1 score of 0.75 when classifying testing data and a lower score of 0.65 when classifying the evaluation dataset.

No description available.

Die bruchmechanische Analyse des Bruches einer Königswelle zeigt, dass der Ermüdungsriss von einer Fehlstelle ausging und durch die Betriebsbeanspruchung gewachsen ist. Die errechneten Lebensdauerwerte decken sich mit den tatsächlich erreichten. / The fracture mechanics analysis of the rupture of an upright shaft shows that the fatigue crack originated from a defect was able to grow with the operational stress. The calculated and actual lifetime are the same.

Avec l’évolution des technologies vers la haute intégration, il devient de plus en plus difficile de localiser les défaillances fonctionnelles situées dans la partie logique des circuits intégrés. En effet, la résolution spatiale fournie par les techniques actuelles n'est pas suffisante. Pour répondre à cette problématique, cette thèse propose une nouvelle approche qui combine le diagnostic ATPG et les techniques optiques. Cette méthode a fait ses preuves sur de nombreux cas d'analyses pour l'amélioration des rendements de production. La méthode utilisant les techniques optiques statiques et dynamiques, une contribution à l'amélioration de l'utilisation de ces techniques a également été apportée par cette thèse. / Nowadays, with the increasing complexity of new VLSI circuits, currents techniques used for functional logic failure localization reach their limits . To overcome these limitations, a new methodology has been established. This methodology, combines ATPG diagnostic and opticals techniques in order to improve accuracy of fault isolation and defect localization. This work contributes also to improve the use of dynamics and statics opticals techniques.

Esta Dissertação, submetida à Escola Politécnica da Universidade de São Paulo, tem como objetivo a caracterização de fratura por fadiga em componentes mecânicos. Esse estudo foi motivado por dois casos de falha: barras estabilizadoras de truques de trem para transporte de minério, e engrenagens de redutores de grande porte, aplicados em turbogeradores em usinas de cogeração. Foi apresentada uma revisão da literatura sobre nucleação e propagação de trincas de fadiga, sobre fadiga de contato e por flexão de dentes, os dois principais modos de falha de engrenagens, e sobre a dinâmica do truque de trem. As amostras coletadas de barras falhadas foram caracterizadas e suas superfícies de fratura foram examinadas. A trinca de fadiga iniciou-se em uma das dobras do rebaixo, em local com dano por corrosão, que favoreceram sua nucleação. Uma análise por elementos finitos foi realizada para analisar as tensões residuais devido ao processo de dobra da barra e conformação do rebaixo e as tensões devido à operação, num caso crítico de warp tracionando a barra. Os resultados mostraram que localmente a tensão de escoamento do material foi superada, especialmente nas regiões de pequeno raio de curvatura devido ao rebaixo. Para o caso das engrenagens, foi feita uma análise de confiabilidade por distribuição de Weibull com base nos tempos de vida dos componentes falhados e do restante fabricado. Do resultado inferiu-se que as falhas consistiram na \"mortalidade infantil\" dos componentes. Havia apenas uma amostra de engrenagem falhada disponível para análise, a qual foi detalhadamente caracterizada e cuja superfície de fratura foi minuciosamente estudada, a fim de determinar o modo e o mecanismo de falha, o início da trinca e, com isso, a causa da falha. Pôde-se concluir que a engrenagem falhou devido a fadiga por flexão de dente devido a um desalinhamento na montagem. Determinadas as causas das falhas, podem-se sugerir soluções, aumentando assim a confiabilidade dos componentes. As sugestões podem dizer respeito ao próprio projeto, à seleção de materiais, aos processos de fabricação, ao tratamento térmico, à montagem, ou ao sistema de lubrificação. / This Dissertation, submitted to the Escola Politécnica da Universidade de São Paulo, aims to characterize fatigue fracture in mechanical components. This study was motivated by two cases of failure: frame brace of train bogies for ore transportation, and gears of large transmission systems, applied to turbogenerators in cogeneration power plants. A literature review was presented on nucleation and propagation of fatigue cracks, contact and tooth bending fatigue, which are the two main modes of failure of gears, and train bogie dynamics. Samples collected of failed bars were characterized and their fracture surfaces were examined. The fatigue crack initiated at one of the bends of the \"fillister\", where corrosion damage took place - both of which favoured the nucleation. A finite element analysis was performed to analyze the residual stresses due to the bending process of the bar and the forming of the \"fillister\" and the stresses due to operation, in a critical case of warp tensioning the bar. The results showed that locally the yield stress of the material was exceeded, especially in the regions of small radius of curvature due to the \"fillister\". For the case of the gears, a reliability analysis was performed by Weibull distribution based on the lifetimes of the failed components and the remainder manufactured. From the result it was inferred that the failures consisted of the \"infant mortality\" of the components. Only one failed gear sample was available for the analysis, which was thoroughly characterised and whose fracture surface was minutely studied, in order to determine the mode and mechanism of failure, crack initiation and, hence, cause of failure. It was concluded that the gear failed due to tooth bending fatigue due to misalignment in the assembly. Having determined the causes of failures, solutions can be suggested, thus increasing the reliability of the components. Suggestions may concern the design itself, materials selection, manufacturing processes, heat treatment, assembly, or lubrication system.