Weight–strength optimisation of upholstered sofas by product engineering approach including performance tests and finite element method

In this study, it is aimed to make weight–strength optimization of the sofas according to member section sizes by using the product engineering methodology including performance tests, finite element analyses and optimization techniques. Weight is a factor that negatively affects the cost of the product, shipping cost, worker health, operational safety, and constitutes problems in service for users. In addition, it is a matter of the fact that the exporting firms encounter serious cost problems because of the package weight. When the package weight is decreased, it will also provide some significant advantages to workers of company, main dealer, sub dealer and even users such as ease of operation and usage, and functionality. For this purpose; a total of 6 model sofas, 3 different model double sofas, 3 different model triple sofas were tested in the scope of the study. The weights of the sofas were measured and upholstered sofas were tested for obtaining the performance in order to determine the current weight and strength conditions compared with the acceptable design loads required for domestic usage under the conditions specified in the GSA (General Services Administration) standard test method. According to this; for which model will be strengthened, and for which model will be restored to condition of required strength levels were determined. Cyclic Stepped Increasing Loading Method, which has the most accurate representation of real usage conditions, was used in performance tests. 6 performance test were performed which are seat load test, backrest foundation test, backrest frame test, sidethrust arm load test, sidethrust load test on legs, front to back load test for legs. In this phase of the study, a total of 108 seats were tested, including 6 seat models, 6 loading directions with 3 replications. In the second phase of the study, all upholstered sofas were modeled as 1/1 scale with SpaceClaim software in virtual plathform and Finite Element Method (FEM) was used for three-dimensional structural solutions of sofa models by using ANSYS. After determining the current strength and weight condition and verifying by finite element analysis, individual optimization studies were started for each upholstered sofas. In optimization studies, finite element analysis program was utilized, prototypes for optimized upholstered sofas, which were optimized in terms of weight and strength, and determined to meet the strength values required for domestic usage, were produced under the company's production conditions. In the third stage of the study, all upholstered sofas were taken back to the performance tests carried out in the first stage to verify that the virtually optimized seats have sufficient strength in the actual tests. As a result of the product engineering methodology carried out within the scope of the study, an average of 17% reduction in triple sofa models and 18% in double sofa models was achieved. Regardless of the upholstery weights, the weight of the triple sofa models was reduced by an average of 32% and the weight of the double sofa models was reduced by an average of 36% compared to the skeleton part, which is the only part of the project. Consequently, product improvement by optimizing sofa weights and strengths with quantitative data thanks to the study; with the application of product engineering methodology, which includes performance tests and finite element analysis, a process improvement was carried out in the company's R&D and P&D units.