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The purpose of this paper is to find a practical and effective way to test wearing product lifetime with two SCARA robots.

The paper designs a mathematical model to simulate human motion, calculate the coordinate trajectory, then implement with two SCARA robots.

The two-robot testing platform for wrist band is an effective and precise simulation method and is feasible to deploy in mass production.

The paper introduces a way for apply robots in wearing product lifetime testing which is novel, practical and effective.

The purpose of this paper is to consider the general k level step-stress accelerated life test with the Rayleigh lifetime distribution for units subjected to stress under progressive Type-I censoring.

The parameter of this distribution is assumed to be a log-linear function of the stress, and a tampered failure rate model holds. The progressive Type-I censoring reduces the cost of testing. Due to constrained resources in practice, the test design must be optimized carefully. A numerical study is conducted to illustrate the optimum test design based on several four optimality criteria under the constraint that the total experimental cost does not exceed a pre-specified budget.

This paper compares unconstrained and constrained optimal k level step-stress test. Based on the results of the simulation study, the cost constraint reduces cost and time of the test and it also, in the most cases, increases the efficiency of the test. Also, the T-optimal design is lowest cost and time for testing and it is found more optimal in both conditions.

In this paper, various optimization criteria for selecting the stress durations have been used, and these criteria are compared together. Also, because of affecting the stress durations on the experimental cost, the author optimize under the constraint that the total experimental cost does not exceed a pre-specified budget. The efficiency of the unconstrained test in comparison with constrained test is discussed.

The effects of space environment on friction and wear and on the selection of lubricants and self‐lubricating materials for spacecraft mechanisms are discussed, with special emphasis on the ultrahigh vacuum of space. Experimental studies have demonstrated the feasibility of using selected oils and greases to lubricate lightly loaded ball bearings without replenishment for periods of over one year under the following conditions of operation : speeds of 8,000 rpm, temperatures of 160 to 200°F., and vacuum of 10–8 torr. Over one‐half year of successful operation has been achieved under similar operating conditions with self‐lubricating retainers of reinforced Teflon, provided that the loads were light. Bonded films of molybdenum disulfide have given shorter lifetimes and poor repro‐ducibility. Metal‐to‐metal slip‐ring contacts introduce excessive electrical noise into circuits when operated in vacuum of 10–7 torr. The noise (as well as the friction and wear) can be markedly reduced by providing a small amount of oil vapor, sufficient to maintain a pressure on the order of 10–6 torr, or by incorporating molybdenum disulfide into the brush material.

Acceptance sampling plans are designed to decide about acceptance or rejection of a lot of products on the basis of sample drawn from it. Accelerating the life test helps in obtaining information about the lifetimes of high reliability products quickly. The purpose of this paper is to formulate an optimum time censored acceptance sampling plan based on ramp-stress accelerated life test (ALT) for items having log-logistic life distribution. The log-logistic life distribution has been found appropriate for highly reliable components such as power system components and insulating materials.

The inverse power relationship has been used to model stress-life relationship. It is meant for analyzing data for which the accelerated stress is nonthermal in nature, and frequently used as an accelerating stress for products such as capacitors, transformers, and insulators. The method of maximum likelihood is used for estimating design parameters. The optimal test plan is obtained by minimizing variance of test-statistic that decides on acceptability or rejectibility of lot. The optimal test plan finds optimal sample size, stress rates, sample proportion allocated to each stress and lot acceptability constant such that producer’s risk and consumer’s risk is satisfied.

Asymptotic variance plays a pivotal role in determining the sample size required for a sampling plan for deciding the acceptance/rejection of a lot. The sample size is minimized by optimally designing a ramp-stress ALT so that the asymptotic variance is minimized.

The model suggested is of use to quality control and reliability engineers dealing with highly reliable items.

This article considers Inverse Gaussian distribution as the basic lifetime model for the test units. The unknown model parameters are estimated using the method of moments, the method of maximum likelihood and Bayesian methods. As part of maximum likelihood analysis, this article employs an expectation-maximization algorithm to simplify numerical computation. Subsequently, Bayesian estimates are obtained using the Metropolis–Hastings algorithm. This article then presents the design of optimal censoring schemes using a design criterion that deals with the precision of a particular system lifetime quantile. The optimal censoring schemes are obtained after taking into account budget constraints.

This article first presents classical and Bayesian statistical inference for Progressive Type-I Interval censored data. Subsequently, this article considers the design of optimal Progressive Type-I Interval censoring schemes after incorporating budget constraints.

A real dataset is analyzed to demonstrate the methods developed in this article. The adequacy of the lifetime model is ensured using a simulation-based goodness-of-fit test. Furthermore, the performance of various estimators is studied using a detailed simulation experiment. It is observed that the maximum likelihood estimator relatively outperforms the method of moment estimator. Furthermore, the posterior median fares better among Bayesian estimators even in the absence of any subjective information. Furthermore, it is observed that the budget constraints have real implications on the optimal design of censoring schemes.

The proposed methodology may be used for analyzing any Progressive Type-I Interval Censored data for any lifetime model. The methodology adopted to obtain the optimal censoring schemes may be particularly useful for reliability engineers in real-life applications.

The purpose of this paper is to present a novel reflow profile optimization method using mechanical reliability estimation of micro‐ball grid array (μBGA) solder joints, based on the heating factor, Q_η is introduced, where the coupling effect of reflow temperature and time on the mechanical reliability of μBGA joints is considered.

The method presented is actualized through vibration fatigue tests. First, a two‐parameter Weibull distribution is used to model the collected data of vibration fatigue lifetime for different Q_η. After that, two explicit functions are deduced in a unified mathematic expression form, which give an intuitionistic description of the mean time to failure and reliability of solder joints against induced variable Q_η, thus revealing definitely the effect of Q_η on the mechanical fatigue lifetime of solder joints suffering from cyclic vibration loading. Finally, for a specified reliability goal, how to choose proper Q_η values, based an improved Golden Section Search arithmetic, is discussed.

Numerical analysis and calculation are performed. The results show that the solder joints made at Q_η near 510 have higher mechanical reliability, and those reflowed farther away this optimal value have less reliability.

This paper presents a useful and applicable solution to achieve reflow profile optimization and process control for a quantitative mechanical reliability estimation of μBGA solder joints.

The paper aims to present acceptance sampling plans based on failure‐censored step‐stress accelerated life tests for items having Weibull lives.

The model parameters are estimated by the method of maximum likelihood. Based on asymptotic distribution theory, the sample size and the acceptability constant are determined satisfying the producer's and consumer's risks. The step‐stress accelerated life test is optimized to have a minimum sample size by minimizing the asymptotic variance of test statistic. Two modes of step‐stress accelerated life test are considered, and a comparison between them is made. The proposed sampling plans are compared with the sampling plans based on constant stress accelerated life tests.

Asymptotic variance is a dominating factor in determining the sample size required for a sampling plan to determine the acceptability of a lot. The sample size is minimized by optimally designing a step‐stress accelerated life test so that the asymptotic variance is minimized.

The sampling plans presented in this paper are particularly useful when items to be tested are so reliable and are useful to reliability engineers and life test planners.

The purpose of this paper is to describe the effect of indium alloying on the thermal fatigue endurance of Sn3.8Ag0.7Cu solder in low‐temperature co‐fired ceramic (LTCC) modules with land grid array (LGA) joints and the feasibility of using a recalibrated Engelmaier model to predict the lifetime of LGA joints as determined with a test assembly.

Test assemblies were fabricated and exposed to a temperature cycling test over a temperature range of −40‐125°C. Organic printed wiring board (PWB) material with a low coefficient of thermal expansion was used to reduce the global thermal mismatch of the assembly. The characteristic lifetime, θ, of the test assemblies was determined using direct current resistance measurements. The metallurgy and failure mechanisms of the interconnections were verified using scanning acoustic microscopy, an optical microscope with polarized light, and scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) investigations. Lifetime predictions of the test assemblies were calculated using the recalibrated Engelmaier model.

This work showed that indium alloying increased the characteristic lifetime of LGA joints by 15 percent compared with Sn3.8Ag0.7Cu joints. SEM/EDS analysis showed that alloying changed the composition, size, and distribution of intermetallic compounds within the solder matrix. It was also observed that a solid‐state phase transformation (Cu,Ni)₆Sn₅(→ (Ni,Cu)₃Sn₄ occurred at the Ni/(Cu,Ni)₆Sn₅ interface. Moreover, the results pointed out that individual recalibration curves for ceramic package/PWB assemblies with high (≥ 10 ppm/°C) and low (≈ 3‐4 ppm/°C) global thermal mismatches and different package thicknesses should be determined before the lifetime of LGA‐type assemblies can be predicted accurately using the recalibrated Engelmaier model.

The results proved that indium alloying of LGA joints can be done using In‐containing solder on pre‐tinned pads of an LTCC module, despite the different liquidus temperatures of the In‐containing and Sn3.8Ag0.7Cu solders. The characteristic metallurgical features and enhanced thermal fatigue endurance of the In‐alloyed SnAgCu joints were also determined. Finally, this work demonstrated the problems that exist in predicting the lifetime of ceramic packages with LGA joints using analytical modeling, and proposals for developing the recalibrated Engelmaier model to achieve more accurate results with different ceramic packages/PWB assemblies are given.

This paper presents the defects that occur during the assembly and manufacturing of solder joints in single‐sided insertion‐mount printed wiring boards (PWBs). Each type of defect is discussed, with particular focus on how these defects are related to solderability issues, the mechanisms of failure due to defect‐induced failure accelerators, and the effect of the defect on solder joint reliability.