Structural analysis routine for construction hoist components : A novel method for calculation and testing of mast ties

Product development is often conducted through a similar process each time. It contains everything from market analysis and need finding to concept development, production and product launch. Along with technology development, product development processes are also evolving. Computer simulations where products are tested virtually are more frequently used for concept design and evaluating final products. This saves time on prototyping and testing. The increased product knowledge that simulations give, results in that over- and under-dimensioning are avoided which in turn help improve factors as material use and manufacturing. Since simulations always to some degree approximate reality, validation tests are important. All machines must fulfil the safety demands stated by the machinery directive. Based on the machinery directive there are several harmonized, product specific standards. To show that the safety demands are fulfilled, a CE-certification is made. To do so, it must be proven that the product specific standard is satisfied. At Alimak Hek AB, manufacturer of construction hoists in Skellefteå and requestor of this master's thesis project, there is a need for a documented process for how structural strength analysis of new products should be performed to satisfy the standard, and how the analysis should be included in the product development process. It also is of interest to investigate if there are newer tools that would fit these types of applications. This master's thesis treats methodology within structural strength analysis and the result is a work procedure for structural strength analysis of new product developments at Alimak Hek. The work is limited to focus on one sub system of the hoist, the mast ties. In the standard for construction hoists it is stated that these shall be calculated for static structural strength and stability, and that a test shall be performed. A method for FEM calculations of the mast ties is developed. A simplified, general model is used as a first concept model which gives an overview of where the construction is most stressed. Weak points in the construction are analyzed in more detail with a bilinear plastic material model. To fulfil the demands for CE-certification, a standardized test method for mast ties is developed. A test setup is designed, that imitates the real conditions of the mast tie, but where the load can be controlled. Strain gauges are used to compare the FE-model with reality and a method for measuring total deflection of the tie with few error sources is developed. By implementing a standardized test method, new mast tie developments fulfil the standard and can be approved for CE-certification. Control of each other's work within the company is introduced to reduce the risk of human errors. This work also reflects on benefits of updating the product development process with early strength analyzes that can be used in the design work