This paper deals with the statistical fracture mechanical method for the optimal design of forest machine components. The problem of optimal design includes the choice of the objective function and independent design variables and establishment of the system limits. The objective function is determined as the mean total cost that includes the initial cost and the cost of failure according to the failure probability. A quasi-brittle fracture occurs under the influence of the stationary random process of loading. Analytical equations of reliability function estimation are obtained. The algorithm of the random search method includes an interval reduction with regard to zone and functional constraints. The approach to the optimal design problem solution can be applied to obtain optimal geometrical sizes and permissible limit defect values of machine components.

The purpose of this paper is to present the catastrophe theory method for the optimal design of machine components. A brief description of the cusp catastrophe is presented in the introduction. The statement of optimal design problem is given in the second part of the paper. A single criterion design is presented; the reliability function is used as the objective function. The last part is devoted to probability approach. Manage variables are viewed as stochastic quantities, analytical and statistical linearization methods are used for the reliability function evaluation.

Current standards in the field of self-propelled machinery for forestry require equipping tractor cabins with roll-over protective structures (ROPS). It is necessary to reduce the risk of operator’s injuries caused by tractor rollovers or falling trees. This article deals with the way of increasing the energy absorption capacity of forest machine cabin roll-over protective structure. The ability to absorb certain amount of potential energy during deformation is the one of basic requirements to cabin of a forest machine. The risk of injures to the operator is reduced by using energy-absorbing cab support in the construction of roll-over protective structure. The protective effect is attained by plastic strain of cab support elements, that provides operator’s protection during an accidental roll-over. The article presents the design of the cab support, describes its functional principle in the event of an emergency

This paper deals with the statistical catastrophe theory method for the optimal design of machine components. A short introduction to the catastrophe theory is presented, the statement of optimal design problem is given in the first part of the paper. A single criterion design is presented; the reliability function is used as the objective function. The last part is focused on probability approach. Manage variables are viewed as random stationary processes, statistical linearization method and Pearson moment method are used for the reliability function evaluation.

One of the requirements to the cabin of a forestry machine is the ability to absorb a certain amount of energy during deformation in the event of a rollover. The paper presents a method for increasing energy absorption of protective structure of a forestry machine cabin, enabling to reduce the risk of injuries to the operators in the event of an emergency. This is achieved by introducing into the structure of the protective frame of a cab energy-absorbing mounts in which the energy is absorbed due to plastic deformation of their elements in the event of a rollover of forestry machine. The article presents the design of the mount, describes the principle of its operation in the event of an emergency, and theoretical and experimental studies of the deformable mount. As the result of theoretical and experimental investigations the geometric parameters of the energy-absorbing mount are determined.