# Determination of Reliability of Selected Case
## 1 Introduction  
In general, the quality of furniture is defined as a system of sets of aesthetic, functional, technical, material, technological, ecological, and other properties. The specific composition of this system of the set is dynamic, because it is possible to adjust this set for different ways of evaluating furniture, and individual elements can have different relevance. The more elements the set has and the more precisely the relevance of individual elements is determined, the more accurately the quality of the furniture will be evaluated in terms of the level of the given requirements. From an objective point of view, the product is of high quality only if all elements of the set meet the agreed parameters. Each element in the set has an importance (relevance) that corresponds to the degree of the required quality. It is necessary to realize that even with the most objective determination of the relevance of individual elements, it is not possible to achieve complete agreement with the consumer's opinion because each consumer understands the quality of the product from his/her point of view [1]. Nevertheless, in several studies investigating the determinants of customers' choices when purchasing furniture [2; 3; 4; 5; 6; 7], authors indicate a set of properties that receive the highest priority. Among those desirable features of furniture items, furniture durability which includes also their reliability is listed. In the work [8], it is pointed out how essential the strength and durability features are to meet the requirements of the contemporary furniture market. At the same time, it highlights that the failure in furniture is often attributed to its joints, which are the weakest link in the structure. Therefore, theengineering data on the strength of furniture joints have key importance for designing and redesigning the products in the furniture industry to meet product strength and durability [9]. Thus, it is crucial for the manufacturers to be able to evaluate the reliability of both the joints and the whole furniture items they produce [10]. Reliability is the property (ability) of furniture to perform the required functions in a specified time while maintaining the operating parameters given by the technical conditions; it is expressed by partial properties, such as failure-free service life and repairaibility. From the point of view of reliability, furniture construction is considered a multi-component system. In a multi-component system generally, we find the reliability of each component, each of which may be treated as a system itself, and then knowing the structure of the system and using probability concepts, the reliability of the complete system may be evaluated [1,11]. According to [12], the reliability indicators can be divided into five directions according to the theoretical approach and application goals:  
* Probabilistic reliability analysis (PRA);
* Phenomenological theory of reliability;
* Interference theory of reliability (ITER);
* Synthesis of fracture mechanics and reliability;
* Corrected theory of reliability. There is no universal practical procedure for estimating the reliability of a complex mechanical structure. Mathematical theories of reliability are in a state of development, and the preparation of specific documents for the quantification of reliability is insufficient [12]. Regardless of the reliability estimation method, it is necessary to obtain data from two areas, the area of operational load and the area of properties of the used material. In addition, it is necessary to choose a suitable hypothesis (model) that would combine the data from these two areas. In this way, operational load characteristics and material characteristics will be brought into context, while the desired reliability (lifetime, strength) will be the result.