Point Of First Failure Research Articles

Towards the digital factory twin – design guide for creating a 3D factory model

AbstractShorter product lifecycles are also leading to even shorter planning times for the development of production systems. In most companies, the restructuring is carried out within a few weeks during the annual holidays. Digital tools such as simulations or the digital twin are used to avoid delaying the restructuring during this time. However, the introduction of a 3D model of the factory is often the first point of failure for many companies. This article proposes a six-step process model that enables the transition from 2D to 3D design. The process model was evaluated in a research project.

Patient-specific 3D printed plates improve stability of Le Fort 1 osteotomies in vitro

PurposeSelective laser melting used to manufacture patient-specific 3D-printed (PSP) plates is a delicate process, which may introduce weakened areas in the plates, with risk of fracture. This in vitro study's purpose was to test the ability of PSP plates to stabilize Le Fort I osteotomies compared with manually adapted stock plates. The study's objectives were to measure the force needed to compress the osteotomy and evaluate whether the PSP plates would break during compression. Materials and methodsThis controlled in vitro study evaluated the maxillary stability using the clinical data from 7 patients. The virtually planned maxillary reposition was 3D-printed in 2 copies, and the osteotomy gap was fixated by either PSP plates or stock plates. The models were compressed until the Le Fort I osteotomy gap was eliminated. The primary outcome was the force needed to compress the model. The primary predictor variable was a comparison between PSP and stock plates. Secondary outcome measurements were the slope of elastic modulus, yield point, and force needed for 2 mm compression. Statistical testing was performed by Wilcoxon signed-rank test with significance level at P ≤ 0.05. ResultsThe PSP plates performed better than stock plates in all outcome measurements. None of the plates broke during compression despite forces of more than 4000 N. The first point of failure in PSP plates was the first screw cranial to the osteotomy. In comparison, the first point of failure in stock plates was in the plates’ bend at the osteotomy. ConclusionIn this in vitro setup, the Le Fort I osteotomies fixated with PSP plates were more stable than the osteotomies fixated with conventional stock plates. No adverse effects occurred during testing of PSP plates; thus, PSP plates seem to be a safe alternative to stock plates and may even be preferable.

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

BackgroundDouble hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size. MethodsSemitendinosus, gracilis, and quadriceps tendons were harvested from 10 matched pairs of human cadaver lower extremities. Within each pair, a routine hamstring ACL graft (control) consisting of the semitendinosus and gracilis tendons, and an quadriceps augmented hamstrings graft of equal size comprised of the semitendinosus and quadriceps tendons, were prepared. A freeze-clamp mount was used to biomechanically test each graft construct. Tensile failure load, displacement, energy absorbed, and stiffness were determined and statistically compared within each pair and mode of graft failure was established. ResultsNo statistically significant differences were found between the quadriceps augmented hamstrings graft versus standard control grafts. Average values for peak failure load and graft displacement at the point of first failure were nearly identical. All ACL graft constructs failed at the mid-substance. ConclusionsThis study demonstrates no statistical difference in the biomechanical properties of an isolated hamstring ACL autograft versus a quadriceps augmented ACL autograft of equal size at time zero. Clinical relevanceThis is a potentially new and reliable method for quadriceps tendon autograft augmentation of hamstring autograft for ACL reconstruction.

An investigation of the mechanical behavior of three-dimensional low expansion lattice structures fabricated via laser printing

A feasibility study of the fabrication of a specific type of low expansion lattice structure via 3-D laser printing has been conducted. In addition, a detailed baseline understanding of the mechanical response of a specific low thermal expansion lattice geometry has been established. The printed Ti-6Al-4V structures exhibit robust mechanical behaviour and fail via initial buckling followed by strengthening and then fracturing of the struts. Finite element simulation can predict the mechanical behaviour of the printed structures with a good degree of accuracy until the onset of buckling, which is the first point of failure. An analytical model has also been constructed, and homogenization techniques have been implemented to determine the effective stiffness and strength of the lattice structure arranged periodically to be used in sandwich panels. The analytical studies of the lattice structure performance show that the low CTE lattices are suitable for lightweight applications. Additionally, analysis has been performed to optimise the design of a bi-material lattice structure and the optimised design was found to have better performance compared to the bulk material while maintaining a low coefficient of thermal expansion for most cases studied. The techniques used in this paper can serve as a foundation for future studies to optimise and improve such lattice structures.

Margin Elimination Through Timing Error Detection in a Near-Threshold Enabled 32-bit Microcontroller in 40-nm CMOS

This paper presents a near-threshold operating voltage timing error detecting 32-bit microcontroller system. The lightweight in situ error detection and correction technique uses a soft-edge flip-flop combined with in-latch transition detection and a set-dominant error latch to detect data path transitions after the clock edge. Inherent error correction is achieved through time borrowing in soft-edge flip-flops. The technique is implemented in an ARM Cortex M0 microcontroller system in 40-nm CMOS, rendering the microcontroller “timing error aware.” Automatic critical path analysis results in an optimized timing error detection window and sparse flip-flop replacement. An autonomous dynamic voltage scaling (DVS) loop facilitates automatic operation at the point of first failure. The M0 system operates down to 290 mV and achieves 11-18 pJ/cycle core energy consumption in a 5-30 MHz frequency ranges. The architecture profits optimally from ULV operation at frequencies <;10 MHz, where intra-die variations are significant.

Optimisation of recovery protocols for double-base smokeless powder residues analysed by total vaporisation (TV) SPME/GC-MS

The investigation of explosive events requires appropriate evidential protocols to recover and preserve residues from the scene. In this study, a central composite design was used to determine statistically validated optimum recovery parameters for double-base smokeless powder residues on steel, analysed using total vaporisation (TV) SPME/GC-MS. It was found that maximum recovery was obtained using isopropanol-wetted swabs stored under refrigerated conditions, then extracted for 15min into acetone on the same day as sample collection. These parameters were applied to the recovery of post-blast residues deposited on steel witness surfaces following a PVC pipe bomb detonation, resulting in detection of all target components across the majority of samples. Higher overall recoveries were obtained from plates facing the sides of the device, consistent with the point of first failure occurring in the pipe body as observed in previous studies. The methodology employed here may be readily applied to a variety of other explosive compounds, and thus assist in establishing ‘best practice’ procedures for explosive investigations.

Methodology for Wind-Driven Rainwater Intrusion Fragilities for Light-Frame Wood Roof Systems

Light-frame wood buildings represent most of residential structures throughout the United States. Approximately half of the U.S. population lives within 50 miles of the coast with many of those dwellings in the Gulf Coast region or along the eastern seaboard, both of which can be negatively impacted by hurricanes. The majority of damage during a hurricane is the result of wind-driven rainwater entering a building through openings caused by strong wind. To date, wind fragility approaches to examine the probability of damage to a light-frame wood building have focused only on component or subassembly strength, thereby providing information up to the point of first failure of the building envelope. These previous analyses, while valuable, will not allow hurricane engineering research to progress to fully mechanistic loss modeling, which is needed to mitigate losses caused by these events. In this paper a methodology to develop fragility curves and fragility surfaces for the volume of rainwater intrusion is summarized and demonstrated on an example structure. To do this, nonlinear structural analysis, computational fluid dynamics, and reliability theory are combined with particle dynamics for rainwater trajectory modeling, essentially providing the first fragilities of their kind and going beyond first failure of the building envelope. It should be emphasized that it is the methodology that is the focus and some level of calibration is still necessary.

RazorII: In Situ Error Detection and Correction for PVT and SER Tolerance

Traditional adaptive methods that compensate for PVT variations need safety margins and cannot respond to rapid environmental changes. In this paper, we present a design (RazorII) which implements a flip-flop with in situ detection and architectural correction of variation-induced delay errors. Error detection is based on flagging spurious transitions in the state-holding latch node. The RazorII flip-flop naturally detects logic and register SER. We implement a 64-bit processor in 0.13 mum technology which uses RazorII for SER tolerance and dynamic supply adaptation. RazorII based DVS allows elimination of safety margins and operation at the point of first failure of the processor. We tested and measured 32 different dies and obtained 33% energy savings over traditional DVS using RazorII for supply voltage control. We demonstrate SER tolerance on the RazorII processor through radiation experiments.

Effect of substrate surface roughness on mechanical properties of diamond-like carbon coatings

A plasma enhanced chemical vapour deposition (PECVD) amorphous carbon coating was deposited onto 100Cr6 steel substrates having varying degrees of surface roughness. The samples were subsequently evaluated to determine the correlation between substrate roughness and coating performance. The steel substrates were prepared before coating deposition to attain five different levels of roughness: (a) ground; (b) superfinished (SF); (c) polished to 1000 grit; (d) polished to 220 grit and (e) polished to a 1 μm diamond finish. The aim of the investigation was to determine the degree of finish required for good tribological performance and coating adhesion. The mechanical and tribological properties of the samples were assessed by nanoindentation, ramped load scratch testing, and pin on disk wear testing. Nanoindentation testing was used to determine the hardness of the samples and the relative contributions to the system hardness from the substrate and coating were separated using the model of Korsunsky et al. Nanoindentation testing showed that the coating hardness (when separated from the system hardness) was lower for the samples with the SF substrate than the others: the reasons for this are discussed in the light of Raman measurements on the fractions of diamond-like and graphite-like bonding in the coatings. Ramped load scratch testing was used to determine coating adhesion and the scratch test failure mode. With the exception of the samples with the ground substrate finish, studies of the friction coefficient plots during scratch testing showed little variation between the samples, and SEM imaging revealed a common failure mode of severe spallation at the scratch track border. The samples with the ground substrate showed differences in response between scratches parallel and perpendicular to the grinding direction, with scratches parallel to the grinding direction showing more severe spallation. The average critical load to failure, as determined by the point of first failure in the scanning electron microscope, was lower for the coatings on the SF substrate than the coatings on the 220 grit, 1000 grit and 1 micron finished substrates. The critical load to failure for the samples with ground substrates was lower than the other substrate surface finishes. Pin on disk wear testing of the samples against a steel ball revealed that the major effect of the varying substrate roughness was on the wear of the counterface, with rougher substrate finishes generally resulting in higher wear rates of the counterface, although the smoothest substrate finish, the micrometre finish, also resulted in higher wear. The sample whose substrate was superfinished gave least wear of the counterface and this was therefore the optimum finish for the samples when considering their performance in a tribological couple.

A Self-Tuning DVS Processor Using Delay-Error Detection and Correction

In this paper, we present a dynamic voltage scaling (DVS) technique called Razor which incorporates an in situ error detection and correction mechanism to recover from timing errors. We also present the implementation details and silicon measurements results of a 64-bit processor fabricated in 0.18-/spl mu/m technology that uses Razor for supply voltage control. Traditional DVS techniques require significant voltage safety margins to guarantee computational correctness at the worst case combination of process, voltage and temperature conditions, leading to a loss in energy efficiency. In Razor-based DVS, however, the supply voltage is automatically reduced to the point of first failure using the error detection and correction mechanism, thereby eliminating safety margins while still ensuring correct operation. In addition, the supply voltage can be intentionally scaled below the point of first failure of the processor to achieve an optimal tradeoff between energy savings from further voltage reduction and energy overhead from increased error detection and correction activity. We tested and measured savings due to Razor DVS for 33 different dies and obtained an average energy savings of 50% over worst case operating conditions by scaling supply voltage to achieve a 0.1% targeted error rate, at a fixed frequency of 120 MHz.

Impact failure of poly(methyl methacrylate)

AbstractDamage development during instrumented falling weight impact (IFWIM) testing of poly(methyl methacrylate) (PMMA) is recorded using short pulse photography. The first visible damage is cracking on application of the peak force. Finite element analysis predicts the deformation and state of stress throughout the specimen until the first point of failure is reached. A variation in the specimen geometry produces a significant change in initial failure energy, while the maximum tensile stress is approximately constant. The proposed failure criterion is the attainment of a critical time‐dependent value of tensile stress. © 1992 John Wiley &amp; Sons, Inc.