• Journal of Korean Society for Quality Management
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• v.34 no.1
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• pp.20-26
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• 2006

In the fields of mechanical reliability application, "zero" or "zero or one" failure tests are most commonly used for demonstrating reliability of a product since they reduce test duration and/or sample size compared to other test methods that guarantees the same reliability of a product with a given confidence level or consumer's risk. The test duration of the "zero or one" failure test is longer than that of "zero" failure test but it has advantage of smaller producer's risk. In this paper a two-stage test is developed that compromises the "zero" and "zero or one" failure tests. The properties of the proposed two-stage test are investigated and the three test methods are compared using a numerical example.

• Journal of Korean Society for Quality Management
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• v.39 no.1
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• pp.71-77
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• 2011

In the fields of reliability application, the most commonly used test methods for reliability qualification are zero failure tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. An economic zero failure test plan is developed that minimizes the total cost related to perform a life test to guarantee a specified reliability of a product with a given confidence level and a numerical example is provided to illustrate the use of the proposed test method.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.220-224
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• 2014

A Bayesian zero-failure reliability demonstration test method for products with Weibull lifetime distribution is presented. Inverted gamma prior distribution for the scale parameter of the Weibull distribution is used to design the Bayesian test plan and selecting a prior distribution using a prior test information is discussed. A test procedure with zero-failure acceptance criterion is developed that guarantee specified reliability of a product with given confidence level. An example is provided to illustrate the use of the developed Bayesian reliability demonstration test method.

• Journal of Applied Reliability
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• v.13 no.1
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• pp.1-10
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• 2013

A Bayesian zero-failure reliability demonstration test method for products with exponential lifetime distribution is presented. Beta prior distribution for reliability of a product is used to design the Bayesian test plan and selecting a prior distribution using a prior test information is discussed. A test procedure with zero-failure acceptance criterion is developed that guarantees specified reliability of a product with given confidence level. An example is provided to illustrate the use of the developed Bayesian reliability demonstration test method.

• Journal of Korean Society for Quality Management
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• v.49 no.3
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• pp.341-358
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• 2021

Purpose: After product development, a Reliability Demonstration Test(RDT) is performed to confirm that the target life has been achieved. In the RDT, there are cases where the test equipment cannot accommodate all samples. Therefore, this study considers a test method to most economically demonstrate the target life of the product at a certain confidence level when the sample size is larger than the capacity of the test equipment. Methods: If the sample size is larger than the capacity of the test equipment, test equipments may be added or the test time of individual samples may be increased. So the test method is designed to cover this situation with limited capacity. A zero-failure test method is applied as a test method to RDT. To minimize the cost, the test cost is defined and the cost function is obtained. Finally, we obtain the optimal test plan. Results: A zero-failure test method is designed when the sample size is larger than the capacity of the test equipment, and the expected total cost is derived. In addition, the process of calculating the appropriate sample size, test time, and number of test equipment is illustrated through an example, and the effects of model parameters to the optimal solutions are investigated numerically. Conclusion: In this paper, we study a zero-failure RDT with test equipment that has limited capacity. The expected total cost is derived and the optimal sample size, test time, and number of test equipment are determined to minimize the expected total cost. We also studied numerical examples and for further studies, we can relax some restrictions in the test model and optimize the test method.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.262-266
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• 2014

In this paper, we consider the problem of determining the confidence level in zero-failure reliability sampling plans when the life distribution is Weibull distribution with a shape parameter m and a scale parameter ${\eta}$. We introduce zero-failure reliability sampling plans for Weibull distribution and investigate some characteristics of zero-failure reliability sampling plans. Finally, We propose new guideline for determining the confidence level in zero-failure reliability sampling plans for assuring $B_x-life$.

• Journal of Applied Reliability
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• v.12 no.1
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• pp.47-56
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• 2012

Reliability demonstration tests with zero-failure acceptance criterion are most commonly used in the field of reliability application since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. For products with lognormal lifetime distribution, an economic zero-failure test plan is developed that minimizes the total cost related to perform a life test to guarantee a specified reliability of a product with a given confidence level. A numerical example is provided to illustrate the use of the proposed test plan.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.170-175
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• 2015

Reliability demonstration tests (RDT's) are widely employed in design verification and process validation stages of industry. New mixed attribute-variable RDT plans that compromise demerits of the corresponding zero and zero or one failure plans which are common in practice are developed for the exponential distribution. The proposed mixed plans are compared with the typical RDT plans in terms of probability of acceptance and expected test termination time. A numerical example is provided to illustrate the mixed plans and a procedure to extend these plans to the Weibull distribution with known shape parameter is also presented.

• Journal of Applied Reliability
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• v.14 no.1
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• pp.53-57
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• 2014

In the fields of reliability application, the most commonly used test methods for reliability demonstration are zero-failure acceptance tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. For products with lognormal lifetime distribution, the value of scale parameter is usually assumed to be known in designing reliability demonstration tests. It is important to select correct values of scale parameters to guarantee the specified reliability with given confidence level exactly. The effect of using wrong values of scale parameters in designing reliability demonstration test for products with lognormal lifetime distribution is examined and selecting proper values of scale parameters for conservative reliability demonstration is discussed.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.225-234
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• 2011

In the fields of reliability application, the most commonly used test methods for reliability qualification are zero-failure acceptance tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. Usually values of shape parameters are assumed to be known in designing reliability qualification tests for Weibull lifetime distribution. It is important to select correct values of shape parameters to guarantee the specified reliability with given confidence level exactly. The effect of using wrong values of shape parameters in designing reliability qualification test for products with Weibull lifetime distribution is examined and selecting proper values of shape parameters for conservative reliability qualification is discussed.