Statistical models in engineering , Statistical models in engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Statistical Models in Engineering

Design verification and validation in product lifecycle

Dimension reduction method for reliability-based robust design optimization

Inverse analysis method using MPP-based dimension reduction for reliability-based design optimization of nonlinear and multi-dimensional systems

This paper presents the eigenvector dimension reduction (EDR) method for probability analysis that makes a significant improvement based on univariate dimension reduction (DR) method. It has been acknowledged that the DR method is accurate and efficient for assessing statistical moments of mildly nonlinear system responses in engineering applications. However, the recent investigation on the DR method has found difficulties of instability and inaccuracy for highly nonlinear system responses while maintaining reasonable efficiency. The EDR method integrates the DR method with three new technical components: (1) eigenvector sampling, (2) one-dimensional response approximation, and (3) a stabilized Pearson system. First, 2N+1 and 4N+1 eigenvector sampling schemes are proposed to resolve correlated and asymmetric random input variables. The eigenvector samples are chosen along the eigenvectors of the covariance matrix of random parameters. Second, the stepwise moving least squares (SMLS) method is proposed to accurately construct approximate system responses along the eigenvectors with the response values at the eigenvector samples. Then, statistical moments of the responses are estimated through recursive numerical integrations. Third, the stabilized Pearson system is proposed to predict probability density functions (PDFs) of the responses while eliminating singular behavior of the original Pearson system. Results for some numerical and engineering examples indicate that the EDR method is a very accurate, efficient, and stable probability analysis method in estimating PDFs, component reliabilities, and qualities of system responses.

Eigenvector dimension reduction (EDR) method for sensitivity-free probability analysis

Study of an assembly tolerance allocation model based on Monte Carlo simulation

The use of a quasi-naturalistic riding method to investigate bicyclists’ behaviors when motorists pass

Analyses and Measurements on Bending Performance of Gas-Assisted Injection Molded Parts

The wear properties and wear mechanism of Stellite No. 6 powder cladded over AISI 1020 low carbon steel have been investigated. The wear resistance of specimens with laser surface cladding overlapping by different amounts (20%, 30% and 50%) was measured using a dry-sand rubber-wheel abrasion test and a block-on-ring wear test at room temperature. Wear tests were also performed at different temperatures (50 °C, 150 °C, 250 °C and 400 °C) with an Schwingung reibung verschleis (SRV) oscillation friction wear tester under 25 N and 50 N loads. The specimen with 50% overlapping showed the lowest initial wear, together with the highest surface hardness and a smoother surface than the others. The specimen with 50% overlapping also suffered the lowest total weight loss. Weight loss increased with increasing test temperature up to 150 °C, and then decreased with further increases in temperature owing to transfer of material. The average friction coefficient was about the same for all the overlapping ratios at 50 °C. At 150 °C it had a slightly higher value. The wear mechanism was studied by observing worn surfaces through scanning electron microscopy which showed that the surface polish, plastic deformation and ploughing caused by abrasive wear were very significant at 50 °C. Microcracking, fatigue delamination and brittle fracture could also be observed at temperatures above 250 °C.

Wear behaviour of cobalt-based alloys in laser surface cladding

The solid lubricants Ag and BaF 2 -CaF 2 eutectic with bond coat Cr 3 C 2 -(Ni-Al) were successfully coated onto AISI 1020 low carbon steel by laser surface cladding via the pre-placing method. The frictional and wear properties of single- and multiple-component lubricants were evaluated at various temperatures (50, 300 and 550°C) with a Schwingung Reibung Verschleiβ (SRV) oscillation friction wear tester under different loads (10, 20 and 30 N). Scanning electron microscopy was used to characterize the wear mechanisms of the worn surfaces of specimens. The results showed that the specimens underwent a loss and that the diameter of their counterpart balls increased with increasing test temperature. The friction coefficient decreased with increasing load. The wear mechanism was studied by observing worn surfaces using scanning electron microscopy which showed that the abrasive wear due to the ploughing of wear debris was significant. The specimen D, which contained 15wt.% Ag and 15wt.% BaF 2 -CaF 2 eutectic in a metal-bonded Ni-Al and Cr 3 C 2 matrix, has the best frictional and wear performance at 300 and 550°C.

Ming-Chang Jeng

Papers

Study of an assembly tolerance allocation model based on Monte Carlo simulation

The use of a quasi-naturalistic riding method to investigate bicyclists’ behaviors when motorists pass

Analyses and Measurements on Bending Performance of Gas-Assisted Injection Molded Parts

Wear behaviour of cobalt-based alloys in laser surface cladding

Wear behaviour of solid lubricants Ag and BaF2-CaF2 obtained by laser surface cladding