Considerable effort has been made to model, predict, and mitigate wear as it has significant global impact on the environment, economy, and energy consumption. This work proposes generalized foundation-based wear models and a simulation procedure for single material and multimaterial composites subject to rotary or linear abrasive sliding wear. For the first time, experimental calibration of foundation parameters and asymmetry effects are included. An iterative wear simulation procedure is outlined that considers implicit boundary conditions to better reflect the response of the whole sample and counter-body system compared to existing models. Key features such as surface profile, corresponding contact pressure evolution, and material loss can be predicted. For calibration and validation, both rotary and linear wear tests are conducted on purpose-built tribometers. In particular, an experimental calibration procedure for foundation parameters is developed based on a Levenberg–Marquardt optimization algorithm. This procedure is valid for specific counter-body and wear systems using experimentally measured steady-state worn surface profiles. The calibrated foundation model is validated by a set of rotary wear tests on different bimaterial composite samples. The established efficient and accurate wear simulation framework is well suited for future design and optimization purposes.
Purpose: We intended to study the effect of thoracic endovascular aortic repair (TEVAR) and optimal medical treatment (OMT) on type B intramural hematoma (BIMH). Methods: We searched PubMed, EMbase, Cochrane Library, and China National Knowledge Infrastructure databases that compared TEVAR and OMT in patients with BIMH. Two authors independently assessed the risk of bias using the Newcastle-Ottawa Scale. The rate ratio (RR) and 95% confidence interval were used to calculate the outcome. The primary endpoints were aortic-related death and regression/resolution. Secondary endpoints were all-cause death, progression to dissection, and secondary intervention. Results: Eight observational studies were included in the analysis. TEVAR reduced aorticrelated death (RR 0.22, 95% CI 0.08-0.56, P = 0.002, I² = 24%) and promoted hematoma regression/resolution (RR 1.48, 95% CI 1.05-2.10, P <0.05, I² = 71%) compared to OMT. Moreover, TEVAR was associated with a reduction in progression to dissection (RR 0.32, 95% CI 0.13-0.81, P <0.02, I² = 39%) and secondary intervention (RR 0.18, 95% CI 0.09-0.37, P <0.00001, I² = 38%) compared to OMT. However, all-cause death has no significant difference between the two groups (RR 0.45, 95% CI 0.17-1.19, P = 0.11, I² = 58%). Conclusions: The results of this meta-analysis suggested that TEVAR is an effective treatment for BIMH, which can delay the progression of intramural hematoma and promotes regression/resolution. More research about indications of TEVAR is still needed.
Purpose
Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM.
Design/methodology/approach
A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens.
Findings
Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures.
Originality/value
This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.
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The high-pressure water jet is utilized to perform impact test on coated surfaces with different hardness. The decoating effect is measured and the surface roughness change can be tested by White-light Interferometer (WLI). Also the microstructure of surface damage after impact test is analyzed. The result shows that when utilizing high-pressure water jet to clean the coating, it’s a better choice to start at the place where the coating is broken. The gap will be enlarged rapidly and the decoating velocity will increase linearly. Otherwise, the impact of water jet will cause surface damages and generate holes of particular shape. This kind of hole is flat in the middle, then forming a sunken district and apophysis successively along the radius outwards.
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