In order to tackle the development of advanced technologies, the reliability of products has become a significant
matter of concern. It regards with respect to failure avoidance rather than probability of failure [10]. Product failure
occurs when the product is not able to perform its objective functions and does not meet its requirements. Thus,
reliability is a product capability to fulfill intended tasks for a specified performance period. Performance period can
be a function of cycles, distance or time [11]. Its rapid growth results from the introduction of the idea of safety and
risk as nowadays it is expected to produce and sell high reliability products and purchase and operate them safely
without any risk [12,13,14].
Failures are usually attributable to one or a group of failure modes which can result from a chain of causes and
effects such as: a symptom, trouble or operational complaint [15]. They can be categorized into different types and
sources. Considering all product failures two types can emerge: random (or physical) and systematic (or functional).
Random failures result in casual lack of achieving its objectives what may lead to one or more degradation
mechanisms in the hardware, whereas if the product does not perform its intended tasks but no components have
already failed is the example of systematic failure [16]. Failures can be categorized due to intrinsic and extrinsic
causes which result from weakness and/or wear-out or errors, misuse or mishandling [17]. Among them the
following can be distinguished: design faults, material defects, processing and manufacturing deficiencies, lack or
improper quality control, inadequate testing, human errors, improper assembly or installation, off-design or
unintended service conditions, improper operation, lack of protection against over stress and maintenance
deficiencies [4,15,18]. Failures lead to losses in repair cost, warranty claims, customer disappointment, product
recalls, loss of sale, and finally loss of life [19]. To reduce them, variations can be decreased or a product can be designed robust against these variations. Moreover, other uncertainties such as incomplete information regarding the
phenomena, data, model errors, human mistakes and parameter uncertainties have to be taken into account.
Uncertainty encompasses the occurrence of events which are beyond human management capabilities. Any
uncertain variable has a random characteristics which yields a level of error. In the literature there are various
classifications of uncertainties [20,21], however, they are generally categorized as either aleatory and epistemic
uncertainties. The first one concern the underlying, inherent uncertainties such as randomness of a phenomenon,
scattered in life and the load variation within a population when the modeler is not able to foresee the possibility of
their reduction. The latter one refers to the uncertainties due to lack of knowledge, which can be decreased by the
application of additional data or information, better modeling, and parameter estimation methods. It should be
emphasized that in the reliability modeling, it is possible to divide the second kind of uncertainty into statistical
uncertainty and model uncertainty, whereas the first type of uncertainty is called random variation (or physical
uncertainty, noise factor). Statistical uncertainty refers to estimation of model parameters based on the available data
where the observations of the variable may not represent the real situation perfectly, and thus, the recorded data may
be biased. Additionally, different sample data sets usually provide diverse statistical estimates. Model uncertainty
results from the use of one (or more) simplified relationship which is supposed to represent the “real” relationship or
phenomenon of interest. Such an approach results from lack of knowledge or increased availability of data. Another
important kind of uncertainty is related to the uncertainties due to human factors. Such uncertainties result from
human errors and interventions undertaken in the design, manufacturing and operation. For example, they can be
caused by misuse, gross errors and human mistakes [22,23,24]. They can be considered by creating robustness
through product changes or using an extra safety, however, in practice they are primarily subjects to quality
management [10].
เพื่อภาวะการพัฒนาของเทคโนโลยีที่ทันสมัย ความน่าเชื่อถือของผลิตภัณฑ์ได้กลายเป็นสำคัญเรื่องของความกังวล ได้พิจารณาเกี่ยวกับการหลีกเลี่ยงความล้มเหลวมากกว่าความสำเร็จ [10] ความล้มเหลวของผลิตภัณฑ์เกิดขึ้นเมื่อผลิตภัณฑ์ไม่สามารถกระทำฟังก์ชันวัตถุประสงค์ และตอบสนองความต้องการของ ดังนั้นความสามารถในผลิตภัณฑ์เพื่อตอบสนองวัตถุประสงค์งานสำหรับรอบระยะเวลาที่ระบุประสิทธิภาพความน่าเชื่อถือได้ ระยะเวลาประสิทธิภาพสามารถเป็นฟังก์ชันของวงจร ระยะทาง หรือเวลา [11] เติบโตอย่างรวดเร็วเป็นผลจากการแนะนำของความคิดของความปลอดภัย และความเสี่ยงเช่นทุกวันนี้คาดว่าจะผลิต และขายสินค้าความน่าเชื่อถือสูง และซื้อ และมีปลอดภัยไม่ มีความเสี่ยงใด ๆ [12,13,14]มีความล้มเหลวมักจะรวมกลุ่มของโหมดความล้มเหลวซึ่งอาจส่งผลจากห่วงโซ่ของสาเหตุอย่างหนึ่ง และลักษณะพิเศษเช่น: อาการ ปัญหา หรือร้องเรียนการดำเนินงาน [15] สามารถแบ่งเป็นประเภทต่าง ๆ และแหล่งที่มา พิจารณาความล้มเหลวทั้งหมดของผลิตภัณฑ์สองชนิดสามารถเกิด: สุ่ม (หรือทางกายภาพ) และระบบ (หรืองาน)ความผิดพลาดแบบสุ่มทำให้ขาดบรรยากาศของการบรรลุวัตถุประสงค์ที่อาจนำไปสู่การสลายตัว น้อยกลไกในฮาร์ดแวร์ ในขณะที่ถ้าไม่มีทำผลิตภัณฑ์ การตั้งใจทำงานแต่ประกอบไม่ได้แล้วไม่สามารถเป็นตัวอย่างของความล้มเหลวของระบบ [16] ความล้มเหลวสามารถจัดประเภท intrinsic และสึกหรอcauses which result from weakness and/or wear-out or errors, misuse or mishandling [17]. Among them thefollowing can be distinguished: design faults, material defects, processing and manufacturing deficiencies, lack orimproper quality control, inadequate testing, human errors, improper assembly or installation, off-design orunintended service conditions, improper operation, lack of protection against over stress and maintenancedeficiencies [4,15,18]. Failures lead to losses in repair cost, warranty claims, customer disappointment, productrecalls, loss of sale, and finally loss of life [19]. To reduce them, variations can be decreased or a product can be designed robust against these variations. Moreover, other uncertainties such as incomplete information regarding thephenomena, data, model errors, human mistakes and parameter uncertainties have to be taken into account.Uncertainty encompasses the occurrence of events which are beyond human management capabilities. Anyuncertain variable has a random characteristics which yields a level of error. In the literature there are variousclassifications of uncertainties [20,21], however, they are generally categorized as either aleatory and epistemicuncertainties. The first one concern the underlying, inherent uncertainties such as randomness of a phenomenon,scattered in life and the load variation within a population when the modeler is not able to foresee the possibility oftheir reduction. The latter one refers to the uncertainties due to lack of knowledge, which can be decreased by theapplication of additional data or information, better modeling, and parameter estimation methods. It should beemphasized that in the reliability modeling, it is possible to divide the second kind of uncertainty into statisticaluncertainty and model uncertainty, whereas the first type of uncertainty is called random variation (or physicaluncertainty, noise factor). Statistical uncertainty refers to estimation of model parameters based on the available datawhere the observations of the variable may not represent the real situation perfectly, and thus, the recorded data maybe biased. Additionally, different sample data sets usually provide diverse statistical estimates. Model uncertaintyresults from the use of one (or more) simplified relationship which is supposed to represent the “real” relationship orphenomenon of interest. Such an approach results from lack of knowledge or increased availability of data. Anotherimportant kind of uncertainty is related to the uncertainties due to human factors. Such uncertainties result fromhuman errors and interventions undertaken in the design, manufacturing and operation. For example, they can becaused by misuse, gross errors and human mistakes [22,23,24]. They can be considered by creating robustnessthrough product changes or using an extra safety, however, in practice they are primarily subjects to qualitymanagement [10].
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