Applied Mechanics and Materials Vol. 598

Abstract: A wear resistant coating is fabricated on TC11 titanium alloy by laser process using CBN powder as the preset materials. Microstructure, microhardness and wear properties of the coating are characterized by optional microscope (OM), scan electron microscopy (SEM), X-ray diffraction (XRD) and HV-1000 microhardness tester and the effect of different laser powers (1.2kW, 1.6kW, 2.0kW) on the three factors was studied. The experiment results show that the coating microhardness and wear resistance increases firstly and then decreases with the increasing of laser powers when the other parameters are fixed. when the laser power is smaller, the laser energy is smaller, the life of molten pool is shorter, the pores can’t discharge in time induced CBN ceramics can’t formed evenly and the interface bonding strength of coating and substrate was weak; when the laser power is bigger, the laser energy is bigger, the CBN particles can dissolved sufficiently, no crack and pores formed at the coating, but can’t obtain coating reinforced by CBN particles due to the CBN particles dissolved mostly. When the laser power was 1.6kw, the clad coating is smooth and the CBN particles distribute evenly, the microhardness reaches maximum value and the wear resistance is the best. The microhardness was up to 4200HV.

Abstract: the hot extruded AZ31 magnesium alloy which has basal texture was impacted along different direction and different fracture mode appeared. Under different impacted direction, the basal slip, prismatic slip, pyramidal slip, compression twin and tension twin have different critical resolved shearing stress (CRSS) and Schmid factor. Then different deformation modes were activated and resulted to different fracture modes.

Abstract: the microstuctures and orientations changing of hot extrusion AZ31 magnesium alloy were obtained by equal channel angular pressing (ECAP). After the ECAP samples annealed, the dynamic anistropy of AZ31 alloy in different impacting directions were given by dynamic compressing in HSPB system. The results showed that with pression passes increasing, the grains were refined more obviously and {0002}<11-20> texture component increased and concentrated in the center of the pole figure. The maxmium reduction under impacting direction (ID) parelleled to extrusion direction (ED) is larger than that of ID // ND during dynamic compressing, and there was a obvious strain softing in the strain-stress curves. However, the dramatic strain hardening and higher yield strength appeared in the stress-strain figure when ID parelleled to ND. In addition, the reasons for mechanical anistropy of AZ31 alloy were discussed in a way of grains orientationes changing.

Abstract: Prolonged standing at work has been linked to health problems including foot, leg and back pain, varicose veins, circulatory problems, including a possible increased stroke risk. [1]. There are many other potentially very serious health concerns. Worsening of existing coronary heart disease as well as varicose veins and chronic venous insufficiency has been associated with prolonged standing. Pain in the lower limbs and feet are also associated. [2] Studies suggest back pain associated with long surgery is about twice as common in those who stand compared to those medical staff who usually work sitting, even after controlling for age and lifting weights. The main reason is the back position must to be inclinate in the most part of the surgery. The design of orthesis for the lower extremity with chest support represents an alternative to medical staff health problems who standing for long periods on surgical procedure. The surgical orthesis system proposal in this research is positioned on middle side of the leg and is designed such that support the body weight during the surgical procedure. The system can be used for release pressure on ankle, knee and hip joints.

Abstract: The article presents an algorithm to implement the confining pressure at a sample’s boundary when modeling a process of rock cutting with a single cutter under pressure. The dynamic process of cutting is modeled using a discrete element method in which the cutter geometry is presented by rigid walls and the rock sample is approximated as a set of separated spherical particles interacting in accord with a given law. The algorithm unifies two approaches to identify boundary spheres and setting forces that act on them. In the areas with particles of big radii, the plane-parallel beam method (shining lamp) is employed, while in the area of cutting that is made of smaller elements, the boundary is identified using the α-shape algorithm.

Abstract: The construction and kinematic computing of the manipulator of the parallel structure with flexible links are given in the papers [1, 2] («Cable crane» [3]). It is reasonable to use the construction of the manipulator of similar type suggested below under the conditions with the rugged relief of the terrain and expanded service area. The problem of the research of manipulators with flexible links lies in the feedback effect of the lading dynamics on the links dynamics. The non-linearity of the kinematic structure of the manipulator expects the emergence of the feedback effects on the links in the dynamics which can exclude one or several links out of the structure (due to the flexibility of the construction). This makes difficult to use the purely analytical method of problem solving for simulation. The obtaining of the dependences of free and forced oscillations in modes of acceleration, steady motion and deacceleration under the exertion of the perturbation influence on the fixing point in the form of the force, the magnitude and direction of which is known should be considered as the main task of the research for the reviewing system.

Abstract: The reliability of the cutting disc in a sawing process is of vital importance in industry. There exist a lot of reported accidents due to damaged disc usage. In most cases the damage on the disc is not visible. Therefore innovative techniques are required to determine the damages. For this aim an experimental setup is built in Afyon Kocatepe University. Different experiments are performed. While experiments different parameters are measured and calculated. In this paper axial forces produced while the cutting processes are studied. Each experiment is represented by a vector of three dimensional axial forces (F_x, F_y, F_z). Experiments are repeated using four different class of cutting disc (solid, less damaged, much damaged and broken). An Adaptive Neuro Fuzzy Inference System (ANFIS) structure is proposed to classify the deformations that occur on a cutting disc in sawing processes. The results indicate that proposed ANFIS structure is very effective on classification.

Abstract: Generally, most research attempts on the axial-flow fan focus on optimizing rotor blade and tip clearance to enhance its aerodynamic and acoustic performances. Few efforts aim at finding out the appropriate frame rib, which is a supporting and vital part within the air passage and thus has significant influence on the turbulent flow near the blade trailing edge. Therefore, this study intends to investigate the geometrical parameters of the frame rib systematically by using an integrated scheme, which consists of numerical simulation, mockup fabrication, and experimental verification. At first, a high-performance fan (90×90×38 mm³) is constructed to serve as the sample fan for this investigation. Then three geometrical sections (triangle, cylinder, and arc) of frame rib are examined systematically to provide a design guideline on utilizing the appropriate frame rib for enhancing the fan performance.

Abstract: This paper presents synthesis of acoustic-emission (AE) wave propagation in multi-layer materials and simulation of AE wave responses at free surface. In particular, the AE source is modelled as an arbitrary-orientation dislocation over an inclined-to-surface fault within one layer or at the layer-to-layer interface, while the materials are assumed as multi-layer media, each of which is homogeneous, isotropic and linearly elastic. With the use of the integral transformation approach, the three-dimensional wave propagation in the materials is solved in transformed or frequency-wavenumber domain. Subsequently, a closed-form solution for wave responses at free surface is found, which can then be converted in time-space domain. Numerical examples are finally provided for illustration.

Abstract: Exoskeletons are used in rehabilitation, military, industrial applications and rescuing, heavy-weight lifting and civil defense applications as well. This paper presents to design of a lower-extremity exoskeleton assisting walking of a load carrying human. Proposed exoskeleton system is designed to be appropriate mechanism with human lower extremity and it operates synchronously with the human realizes. The aim of exoskeleton actuator system is to provide forces against to external load carried by user during walking, sitting, and standing motions. Thus, it supports human walking and significant portion of external load carrying by the user. Also it makes possible to user spend less energy, less stress and fatigue. Proposed work involves the following design steps: kinematic synthesis of the exoskeleton, mechanical and electro-hydraulic system design.